NOVEMBER 2015 V. V. 37 No. 11
Sustainability & Resilience Resilience 29 The
Challenge of Predicting the Shear Strength of Very Very Thick Slabs
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Get Certified Since 1980, ACI has tested over 400,000 concrete technicians, inspectors, supervisors, and craftsmen in 20 different certification programs. When you have a need for qualified concrete professionals— specify ACI Certification.
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CCRL LAB TOUR The Cement and Concrete Reference Laboratory offers performance examinations for the ACI Concrete Strength Testing Technician and ACI Aggregate Testing Technician – Level 1 certification programs.
To schedule your lab for CCRL inspection, and to arrange for performance testing, contact Jan Prowell at +1.240.436.4800.
Upcoming tour locations are: November and December 2015 Northern California Southern California January 2016 Eastern Canada Northern California Southern California
Ci
Concrete international The Magazine of the Concrete Community
NOVEMBER 2015 V. 37 No. 11 SUSTAINABILITY & RESILIENCE
29
The Challenge of Predicting the Shear Strength of Very Thick Slabs
Results support recommendation to use at least minimum shear reinforcement by Michael P. Collins, Evan C. Bentz, Phillip T. Quach, and Giorgio T. Proestos
38
Quality Control for Concrete Durability
A case study provides comparisons of work performed under performance and prescriptive specications by Odd E. Gjørv
45
Condition Assessment of Launch Pad 39B
Ensuring the historic site at the John F. Kennedy Space Center will continue to make history by Richard E. Weyers, Alberto A. Sagüés, and Jerzy Z. Zemajtis
ALSO FEATURING
15
Knowledge to Practice: ACI Foundation
Memorial fellowship created to honor ACI’s Dan Falconer
25 20
Awards at The ACI Concrete Convention and Exposition – Fall 2015
Recipients to be honored at the Opening Session in Denver, CO
25
Notable Concrete in Denver
Some examples of recent precast construction in the region
68
Concrete Q&A
Designing Anchors and Their Attachments for Tensile Loading
46 www.concreteinternational.com | Ci | NOVEMBER 2015
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November
Ci Concrete international PUBLISHER
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EDITORINCHIEF Rex C. Donahey, PE (
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At the University of Toronto, laboratory staff and research assistants partici pated in a project to construct and load to failure a specimen representing a strip cut from a 13 ft (4 m) thick slab. Engineers from around the globe were invited to provide predictions of the shear response of such thick slabs. For more on the research, see the article on p. 29.
GRAPHIC DESIGNERS Gail L. Tatum (Senior Designer ), Susan K. Esper, Ryan M. Jay, Aimee M. Kahaian
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President’s Memo
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Concordancies
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n this month’s President’s Memo, guest author Johan L. Silfwerbrand calls for a common strategy toward meeting the numerous challenges faced by our industry. He concludes that working “on a common concrete code would be one of the most important parts” of that strategy (see p. 7). In the interim, it remains worthwhile to compare existing codes against each other, using data from numerical models and/or laboratory tests as benchmarks. This month’s CI includes such an assessment, conducted by a team of researchers at the University of Toronto and focused on the shear capacity of thick, slab-type elements (see p. 29). This work provides strong evidence that the ACI 318 Code overestimates the contribution provided by plain concrete in resisting shear forces in slab-type elements. Further, because it allows that contribution to increase with concrete strength up to a 10,000 psi (69 MPa) limit, the Code may be inadvertently encouraging the use of high-strength concrete in lieu of shear reinforcement. In many cases, the elements are mass concrete placements, and the heat of hydration of high-strength mixtures could force the use of external and internal cooling, easily negating any savings in shear reinforcement. The research also shows the signicant benet of using minimum reinforcement in the form of headed deformed bars. Of course, deep elements with top mats of reinforcing bars will already contain bars (standees) that effectively act as shear reinforcement but probably don’t meet the Code’s anchorage requirements. Additional study of standees might provide value to the industry—even if it’s little more than conrmation that existing elements are not totally dependent on the shear capacity of the concrete alone. Rex C. Donahey
Board of Direction P
D
Sharon L. Wood
Dean A. Browning JoAnn P. Browning Cesar A. Constantino Alejandro Durán-Herrera Augusto H. Holmberg Kimberly Kayler
P P B M
James K. Wight Anne M. Ellis William E. Rushing Jr.
V P
E V P
Michael J. Schneider Khaled W. Awad
T A C
Cary S. Kopczynski Kevin A. MacDonald Fred Meyer Michael M. Sprinkel Roberto Stark David M. Suchorski
Ronald Burg
E A C P C C
CHAIR
CHAIR
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Trey Hamilton III
Frances T. Grifth
George R. Wargo
SECRETARY
STAFF LIAISON
STAFF LIAISON
Matthew R. Senecal
Kathryn A. Amelio
John W. Nehasil
Michael C. Brown JoAnn P. Browning Catherine E. French Fred R. Goodwin Larry Kahn Neven Krstulovic-Opara Kimberly E. Kurtis Tracy D. Marcotte Jan Olek Michael S. Stenko Andrew W. Taylor Eldon G. Tipping
Cesar A. Constantino Alejandro Durán-Herrera Joe Hug Antonio Nanni Ronald L. O’Kane William D. Palmer Jr. Lawrence L. Sutter Lawrence H. Taber Scott Tarr Ronald Vaughn David W. Whitmore
Khaled W. Awad Roger J. Becker William Ciggelakis Alejandro Durán-Herrera J. Mitchell Englestead Brian Green Augusto H. Holmberg Joe Hug Warren E. McPherson Jr. Thomas L. Rozsits Xiomara Sapon Michael M. Sprinkel Pericles C. Stivaros David M. Suchorski Janet White
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February 2-5, 2016
Visit ACI’s World of Concrete booth –Central Hall 4213– Learn more about ACI’s publications, education, and certication. Other features: • • • •
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President's
Memo International Cooperation is the Goal
M
y rst experience with ACI was at the Spring Convention in 1989 in Atlanta, GA. I was in the United States as a post-doc and had the pleasure of spending 6 months in Austin, TX, and UrbanaChampaign, IL. My supervisor Sven Sahlin introduced me to his friends Jim Jirsa and Mete Sozen and they introduced me to ACI. Since then I have tried to attend every second convention Guest author and I think the reception you Johan L. Silfwerbrand, FACI experience when you arrive as a European to ACI is very positive and rather different from the conditions at various conferences elsewhere. I am thinking not only of the ofcial recognition given to international attendees at the Opening Session and the invitation to the President’s Reception but also the welcome from kind individuals. ACI is almost like a very big family. During my rst conventions, everyone seemed to be astonished that I had made the long trip from Sweden to North America for such a short visit, but more recently, the astonishment has vanished concurrently with the decreasing air ticket prices. However, the journey is still very long; you just pay less for every hour you spend in the air. Another difference between ACI conventions and most international conferences is ACI’s focus on committee meetings. Having xed dates for committee meetings at least twice a year facilitates ongoing activities within each committee, and the travel throughout the United States and Canada required of members does not seem to impair the efciency. In many other volunteer organizations, the process of nding meeting days is very time-consuming and often slows a committee’s progress. Compared to European concrete organizations, I also think that ACI is much better at attracting students and young professionals. Young professionals play important roles as Committee Secretaries or even Chairs, Speakers, and Session Moderators. Personally, I am engaged in the work of both ACI and b (the International Federation of Structural Concrete). I know
that efforts are being made to improve the cooperation between these two important international concrete organizations but wish that the progress could be faster. During my time as the President of the Swedish Concrete Association, I was very happy to sign an International Partner Agreement with ACI. We could develop the cooperation further, and any apprehension that the larger society would overshadow the smaller one has been shown to be completely groundless. In Europe, b paved the way for the current Eurocode 2 that successfully has replaced the national concrete codes in the member states to facilitate trade between the countries.
“…the reception you experience when you arrive as a European to ACI is very positive…” Being a faculty member at a university with international ambitions and many incoming students, I am pleased that today we can illustrate the hour-long lectures with examples from Eurocode 2 and not just the old Swedish code. Recently, b released MC 2010, which will form the basis for the next version of Eurocode 2 that may be launched in 2020 or 2025. Simultaneously, ACI has released a new version of ACI 318. When are we going to make one document that could be used across the entire globe? A concrete structure should not be designed differently due only to the fact that Europe is using French units and the United States is using British units. You may argue that it is benecial to have two competitive codes because the competition may lead to improvements of both. However, I think that in the long run we can neither handle the challenges from global warming, sustainable energy production, clean water, urbanization, and an aging population, nor the competition from other construction materials without a common strategy where the work on a common concrete code would be one of the most important parts. Johan L. Silfwerbrand, is a Professor with the KTH Royal Institute of Technology, Stockholm, Sweden www.concreteinternational.com | Ci | NOVEMBER 2015
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are the foundation of our success. To provide additional exposure to ACI Sustaining Members, Concrete International includes a 1/3-page member profile and a listing of all Sustaining Member organizations. All Sustaining Members receive the 1/3-page profile section on a rotating basis. ACS Manufacturing Corporation
Kleinfelder
Advanced Construction Technology
Kryton International Inc.
Services American Society of Concrete Contractors
Lafarge North America Lithko Contracting, Inc. Mapei
Ash Grove Cement Co.
Mason Construction, Ltd.
Ashford Formula
Meadow Burke
Baker Concrete Construction, Inc.
W. R. Meadows, Inc.
Barrier-1 Inc.
Metromont Corporation
BASF Corporation
MTL
Bauman Landscape & Construction
Multiquip Inc.
BCS
Municipal Testing
Braun Intertec Corporation
North S.Tarr Concrete Consulting PC
Buzzi Unicem USA
Oztec Industries, Inc.
Cantera Concrete Company
Pacific Structures
CHRYSO, Inc.
Penetron International Ltd.
Concrete Reinforcing Steel Institute
Portland Cement Association
Construction Forms, Inc.
Precast/Prestressed Concrete Institute
CTLGroup
Saudi Building Code National
Dayton Superior
Committee
Ductilcrete Slab Systems, LLC
Sika Corp.
The Euclid Chemical Co.
S.K. Ghosh Associates, Inc.
Fibercon International, Inc.
STRUCTURAL
Future Tech Consultants
Structural Services, Inc.
W.R. Grace & Co.
Tekna Chem
Headwaters Resources, Inc.
Triad Engineering, Inc.
Holcim (US) Inc.
TWC Concrete Services
Keystone Structural Concrete
Wacker Neuson
Since its establishment in 1996, ACTS has become a regional reference in construction consultancy services and a pioneer in achieving technological advancements in the materials and geo-engineering fields. Its operations cover the whole MENA region through its branches and activities in Lebanon, Qatar and KSA. The company has witnessed a rapid expansion in its service offerings through six separate, yet complementary divisions: Consultancy, Geotechnical Engineering, Material Testing, Technical Standards and Solutions, Certification and Training & Conferences. ACTS’ fully equipped and modern labs, well-trained staff and customer centric services have been awarded with high caliber accreditations as the company became the first consulting firm in the Middle East, in its field, to obtain the ISO 9001, ISO 14001, ISO 17025 and OHSAS 18001 certifications. ACTS is also the local sponsoring group of the American Concrete Institute (ACI) for its certification programs in the Middle East. The company provides a large array of training programs in asphalt and concrete technologies and prepares trainees to become ACI Certified. Additionally, being the representative of IHS, ASTM, BSI, IEEE and other global standards development organizations, ACTS has become the region’s one-stop provider of international codes and standards. For more information about ACTS, please visit their website at www.acts-int.com .
To learn more about our sustaining members, visit our website at www.concrete.org/sustainingmembers
Dayton Superior Corporation is a leading provider of accessories, chemicals, forming, shoring and paving product solutions within the nonresidential concrete construction industry. Serving the industry for over ninety years, the company’s portfolio includes over 17,000 standard, in stock SKUs, 13 U.S. manufacturing facilities and a network of 15 distribution centers located in the U.S., Canada, Latin America, Australia and China, allowing Dayton Superior to serve customers as a single source provider of world class products and services. Dayton Superior products are found on many of the world’s most prominent civil infrastructure, institutional and commercial construction projects. The company’s commitment to Perform with Precision is illustrated by the 2014 opening of the Dayton Superior Innovation Center. Here, Dayton Superior is able to assess, evaluate, rapid prototype and launch new products at an industry leading pace – transforming industry productivity through innovation and creating a competitive advantage for our customers. For more information about Dayton Superior Co., please visit their website at www.daytonsuperior.com or call +1.888.977.9600.
TEKNACHEM was founded Modern Technology Laboratories (MTL) is a limited liability company thanks to the willingness of a group registered in Saudi Arabia. MTL is of technicians and chemists that ISO 17025 certified and accredited by gained a solid experience from SASO and iAS. It is the regional leader in primary companies in the cement and advanced and value-added construction concrete industry. materials testing and engineered These professionals have been in solutions. Through highly trained and this sector since 1965. TEKNACHEM qualified personnel and state-of-the-art is the result of the fusion of a group of equipment, MTL provides superior experts with significant technical testing and innovative technical knowledge, which is the result of its solutions that help its clients execute success worldwide. A highly qualified quality construction projects on time sales engineering staff operates on site and with least cost. offering a wide range of products and What sets MTL apart from other technical assistance. independent laboratories in the region TEKNACHEM responds to its is its unique capabilities to develop customers’ needs through its facilities engineered solutions for challenging and ability to listen, that guarantees a construction projects. MTL’s customers customized production in line with get both reliable and accurate the clients’ requirements such as: type independent testing and value-added of application, aggregates to use, engineering services and solutions weather conditions, implementation tailored to the specific challenges of constraints. their particular project. Its customer service offers complete MTL has been providing technical assistance through the “Istituto solutions and testing services for many Italiano per il Calcestruzzo”, an landmark projects in Saudi Arabia association focused on concrete’s such as the Haram and Mataaf Expansupport, research and training. Tekna sion Projects in Makkah, the Madinah Chem is presently operating in Algeria Haram Expansion Project, the King with headquarters in Sidi-Bel Abbes, Abdullah Financial District in Riyadh, in partnership with the Hasnaoui the King Abdul-Aziz Airport in Group, while in North Africa is Jeddah, the North and South Jeddah creating new opportunities in Tunisia Water Treatment Plants, the Makkah and Morocco. Tower, Lamar and Kingdom Tower Tall Tekna Chem is also in Spain with buildings, Al-Haramain High Speed Tekna Chem Química and is creating a Rail Project, Aljamaraat Bridge, etc. network of manufacturing facilities in Russia and South America. To learn more about MTL, please visit their website at For more information about TEKNACHEM, please visit their http://www.mtl-me.com or call +(966).2.6774340. website at www.teknachem.it or www.tekna-group.com .
On the
Move Simpson Gumpertz & Heger has recently promoted the following individuals to the indicated positions: ACI member Pedro J. Sifre, Senior Principal, has more than 30 years of experience as a structural engineer. His experience includes new design and renovation of structures for a variety of building types, including institutional, high-rise, industrial, and residential buildings; Wen H. Tong, Senior Principal, has over 30 years of experience in seismic structural dynamic analysis and evaluation of seismic capacities of building structures and equipment for commercial nuclear power plants, DOE facilities, reneries, and hospitals; Kevin Poulin, Principal, has 20 years of experience as a structural designer of projects that range from renovation of existing buildings and design of new buildings to structural peer reviews and feasibility studies; John M. Porter, Associate Principal, has 16 years of structural engineering experience designing new structures and assessing existing structures. His work includes performing condition assessments of existing structures, developing rehabilitation programs to repair deterioration and distress, and helping owners prioritize future repair and maintenance needs; and ACI member Mauro J. Scali, Director of Petrography, is a licensed geologist and concrete petrographer with more than 30 years of experience in the evaluation, testing, and repair of concrete, masonry, stone, and stucco. He is a member of ACI Committees 201, Durability of Concrete; 232, Fly Ash in Concrete; and 233, Ground Slag in Concrete. Dewberry promoted ACI member David Hieber to Senior Associate. He has more than 15 years of experience in the analysis, design, and management of highway bridges, pedestrian bridges, retaining walls, and other associated highway structures. Hieber received his bachelor’s and master’s degrees in civil engineering from the Virginia Polytechnic Institute and State University, Blacksburg, VA, and the University of Washington, Seattle, WA, respectively. He is a member of the Engineering Consultant Leadership Committee of Virginia Transportation Construction Alliance and the American Council of Engineering Companies of
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Hieber
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Metropolitan Washington. Hieber also serves as the President of the American Society of Highway Engineers-Potomac Chapter. Additionally, he serves as an Adjunct Professor in the Department of Civil, Environmental, and Infrastructure at George Mason University, Fairfax, VA. Hieber is a member of ACI Committee 341, Earthquake-Resistant Concrete Bridges, and Joint ACI-ASCE Committee 343, Concrete Bridge Design. Avanti International appointed Britt N. Babcock to Vice President of Sales to further develop a growing portfolio of customers and partners nationwide. Babcock comes with a wealth of experience within the industry, having spent the last 4 years as Avanti’s Geotechnical Market Director focusing on mining, tunneling, subways, and soil stabilization.
Honors and Awards The National Ready Mixed Concrete Association (NRMCA) Research, Engineering and Standards (RES) Committee established the Richard D. Gaynor Award in honor of Gaynor, who was the Executive Vice President of NRMCA and the National Aggregates Association (NAA). Gaynor Award recipients are selected for their lifetime contributions to the ready mixed industry in the technical eld. The 2015 Gaynor Award recipient is ACI Honorary Member Nicholas J. Carino, a Concrete Technology Consultant based in Cleveland, OH, and an afliated Consultant with Wiss, Janney, Elstner Associates, Inc. He received his BS, MS, and PhD from Cornell University, Ithaca, NY. Carino was an Assistant Professor at The University of Texas at Austin, Austin, TX. He retired from the National Institute of Standards and Technology (NIST) in 2004, where he held the position of Research Structural Engineer. He received several awards and recognitions from NIST for his contributions during his 25-year career. He is a four-time recipient of the ACI Wason Medal for Materials Research and has received numerous other ACI and ASTM awards for his technical contributions to the industry. Carino is a Fellow of ASTM International and a Life Member of the American Society of Civil Engineers (ASCE). Carino is an active member of various ACI committees.
News New ACI/ICRI Guide to Benet the Repair Industry construction considerations; and quality assurance. An invaluable new resource for concrete industry The Guide’s Project Examples illustrate the use of the Code professionals—“Guide to the Code for Evaluation, Repair, and for concrete building repair, rehabilitation, or strengthening Rehabilitation of Concrete Buildings”—has been published projects from inception through completion. These real-world jointly by ACI and the International Concrete Repair Institute examples are based on actual projects and demonstrate how (ICRI). Available as a printed and digital book, the guide ACI 562 could be used when repairs are designed. These provides assistance and examples to professionals engaged in examples cover several types of projects, including: the repair of concrete buildings. The guide has been developed Typical parking garage repairs; to serve as a companion to “Code Requirements for Evaluation, Typical façade repairs; Repair, and Rehabilitation of Concrete Buildings” (ACI 562-13). Repair of historic structure for adaptive reuse; The primary purpose of this Guide is to help licensed Strengthening of a two-way at slab; and design professionals interpret and properly use the ACI 562 Strengthening of double-tee stems for shear. code. Although specically developed for licensed design Funding to develop the “Guide to the Code for Evaluation, professionals, the guide will also provide insight into the use Repair, and Rehabilitation of Concrete Buildings” was and benets of ACI 562 for contractors, material manufacturers, provided by ACI, ICRI, and the Strategic Development building owners, and building ofcials. The Guide is separated Council (SDC). Vision 2020, a document prepared in part by into two main components: Chapter Guides and Project SDC, formulated a set of goals for improving the efciency, Examples. These two components work together to provide safety, and quality of concrete repair and protection activities. additional information pertaining to how to interpret the The new Guide solidies the Vision 2020 goals by providing performance requirements in ACI 562 and how the requirements the tools to execute concrete repair and protection, thereby may be applied to a broad range of projects. The Chapter Guides follow the organization of ACI 562, broken down by the corresponding sections. They include particular insight into how the chapters and sections of the Code t within the whole of the project. Where Voided slab design, analysis, applicable, owcharts are provided to project examples. illustrate how to navigate the various provisions. Project Examples are Comprehensive guide providing design included to illustrate how specic considerations and state-of-the-art practices. provisions within each chapter of ACI 562 are incorporated into the $49.95 Non-member/$34.95 Member design process. In some instances, Use code CI-15 and save 15% at www.crsi-webstore.org . additional limited-scope examples within the Chapter Guides better illustrate a point that is not covered by the Project Examples. 24/7 continuing education. The Chapter Guides contain information on several topics related to use of the Distance e-learning makes professional code, including applicability of ACI 562; development easy and convenient. selection of the building code for the repair design; preliminary evaluations to Visit www.crsi-learning.org for a list of topics. determine a compliance method for meeting the code requirements; strength Get FREE technical and informational downloads at www.crsi.org! reduction factors and load combinations both during and after the repair; require933 North Plum Grove Road, Schaumburg, IL 60173 ments for evaluation, determination of p: 847.517.1200 • f: 847.517.1206 • e:
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News extending the useful life of existing installations—a key factor in producing a sustainable environment. Order the “Guide to the Code for Evaluation, Repair, and Rehabilitation of Concrete Buildings” at www.concrete.org. Key ACI Sta Promotions ACI announced staff promotions aimed at increasing alignment and ow from ACI’s technical documents to educational products. Michael L. Tholen has been named the Tholen Senecal Hiltz Institute’s new Managing Director of Engineering and highest honor, acknowledging recipients Professional Development; Matthew R. Senecal has been named as Manager, Engineering; and Claire A. Hiltz has been for their body of work within the industry and their service to ASCC. The named Manager of Professional Development. Tholen will coordinate the efforts and resources of both the award was presented by Michael J. Schneider, ACI Vice President and Engineering and the Professional Development Departments. Senior Vice President and Chief People He will continue the supervisory and coordination aspects of Ofcer, Baker Concrete Construction. his previous position in the Professional Development Baker served on the ASCC Board and Department and act in a similar role for the Engineering has made signicant donations of time Department. He will oversee the Engineering staff in both Baker and monies to both ASCC and its departments to allow better interdepartmental coordination education and research foundation. and align staffs’ strengths with project requirements. Tholen received his BS in architectural engineering and his In 2001, he was the rst concrete contractor to serve as ACI President, emphasizing education of contractors and students MS and PhD in civil engineering from the University of and providing them opportunities within the Institute during Kansas, Lawrence, KS. Previously at ACI, he was the his term in ofce. Engineering Editor of Concrete International and, most In 1991, Baker made a strong statement to his peers and to recently, Managing Director of Professional Development. the construction industry in general, by ofcially naming ACI’s Engineering Department will be under the direction safety as Baker’s number-one value. “Dan has inuenced of Matthew R. Senecal, Manager, Engineering. Senecal thousands of people and had a profound impact on concrete received his BS in civil engineering from the University of Notre Dame, South Bend, IN, and his MS in civil engineering contracting,” said Bev Garnant, ASCC Executive Director. “It is our great pleasure to present him the ASCC Lifetime from the University of Kansas. He worked as a Civil and Achievement Award.” Structural Engineer for 14 years before joining the ACI Engineering Department in 2004, where he most recently ASTM Sustainability Committee Forms New served as Senior Engineer. Subcommittee on Water Use and Conservation As ACI’s new Manager of Professional Development, ASTM Subcommittee E60.07, Water Use and Conservation, Claire A. Hiltz will coordinate and implement programs will develop standards to support sustainability and the necessary to increase the effectiveness and productivity of sustainable development of water-related products and ACI Professional Development. Hiltz was previously Course processes. These standards will benet regulators, designers, Developer, Professional Development. Hiltz received her environmentalists, and many others seeking to address water bachelor’s of business administration (BBA) from the use and conservation issues. University of Wisconsin, Oshkosh, WI, and her MS in Michael Schmeida, Chair of ASTM Committee E60, education in instructional design and technology from Purdue Sustainability, says the new subcommittee will address a wide University, West Lafayette, IN. range of issues related to the environmental, social, economic, and other attributes of water. The subcommittee will acquire, Baker Honored with ASCC Lifetime promote, and disseminate high-quality technical knowledge to Achievement Award stimulate research in and the development of specications ACI Honorary Member Dan Baker, CEO, Baker Concrete associated with water use. Construction, Monroe, OH, received a Lifetime Achievement “Water sustainability is a major, growing concern for all Award from the American Society of Concrete Contractors aspects of society: business, public health, food, and more,” (ASCC) on September 24, 2015, at its Annual Conference in Schmeida said. “The time for this subcommittee has come.” Dallas, TX. The Lifetime Achievement Award is ASCC’s 12
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News Rick Layton, an active ASTM member, has been appointed Chair of E60.07. Layton is afliated with many organizations dedicated to water standards and code development. Already, he has overseen the creation of major water-related standards dealing with residential wastewater, rainwater quality, and building-water stewardship and reclamation. ASTM welcomes participation in the development of its standards. Become a member at www.astm.org/JOIN.
Bank of America Plaza, Los Angeles, CA; BG Group Place, Houston, TX; Canopy Airport Parking, Denver, CO; Charles Square Garage, Charles Hotel, Cambridge, MA; Forest Home Garage, Cornell University, Ithaca, NY; Silver Spring Metro Plaza, Metro Washington, DC; and Westpark Corporate Center, Tysons, VA. “Cars are getting smarter, people are getting smarter, and parking garages are getting smarter,” explained Paul Wessel, Parking Garages Achieve Green Executive Director of the GPC, an afliate of the International Garage Certication Parking Institute. “The greening of parking facilities transforms The Green Parking Council (GPC) announced the rst seven them into enablers of sustainable mobility. Certied Green parking facilities in the United States to achieve Green Garage Garages offer signicant benets for drivers, tenants, building Certication, a comprehensive sustainability standard for existing owners, property managers, and society overall.” and new parking facilities evaluating 48 elements of garage Launched in 2015, Green Garage Certication recognizes parking facility management practices that maximize perforoperation, programs, structure, and technology. New Green Garages include corporate, university, airport, and hotel facilities. mance while minimizing waste, programs that encourage The rst parking facilities to achieve Green Garage mobility options and choice, and efcient and sustainable Certication are: technology and structure design. Sustainable garages frequently • • • • • • •
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News employ energy-efcient lighting and ventilation systems, guidance systems that help drivers nd parking faster, idlereduction technologies, electric vehicle charging stations, car sharing, bicycle parking, and storm-water management practices. Green Garage Certication is a program of the nonprot Green Parking Council. For copies of Green Garage Certica tion at a Glance, the Elements of Green Garage Certication, the free Green Garage Certication Program Guide, and to purchase the Green Garage Certication Standard, visit www.greenparkingcouncil.org/certication.
The winning teams’ designs are based on a 100-year planning horizon and focus on maximizing the Mississippi River’s natural and sustainable land-building potential while taking into account the needs of navigation and other industries, ood control, and sustainable community development—a challenge raised by the state of Louisiana’s master planning process. While each of the winning teams offered a different vision, all three identied three major themes as critical to sustaining the Mississippi River Delta today and into the future: A clear focus on a sustainable delta through using the Global Design Competition Presents 100-Year natural forces of the Mississippi River; Maximum integration of navigation, ood control, and Visions for Restoring Louisiana’s Eroding Coast The international Changing Course design competition has restoration, including consideration of ideas for a better announced the winning teams and their 100-year visions for and more sustainable navigation channel; and restoring and sustaining the Mississippi River Delta. The Consideration of a gradual transition of industry and winning teams—comprising some of the world’s top engineers, communities into more protected and resilient communities, coastal scientists, planners, and designers —are Baird & over time. Associates, Moffatt & Nichol, and Studio Misi-Ziibi. For more information, visit www.changingcourse.us. •
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ACI Strategic Advancement Award To showcase the contributions and signicant eorts that have helped
further the ACI Strategic Plan, the American Concrete Institute presents the ACI Strategic Advancement Award. This newest ACI award recognizes individuals or organizations that provide support in the implementation of membership and customer satisfaction; the quality of ACI programs, products, and services; and global credibility and impact. Nomination forms will be available following the 2015 ACI Concrete Convention and Exposition in Denver, with presentation of the award taking place in 2017. For further information contact Diane Pociask, ACI Awards Coordinator, at
[email protected].
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Knowledge to Practice:
Memorial Fellowship Created to Honor ACI’s Dan Falconer The ACI Foundation is honoring the late Dan Falconer with the formation of the Daniel W. Falconer Memorial Fellowship. Dan served as ACI’s Managing Director of Engineering for more than 17 years. Dan was a Fellow of ACI, given this distinction for his outstanding contributions to the production and use of concrete materials, products, and structures through education, research, and development. “Dan had an incredible gift of taking a controversial technical issue and breaking it down into practical elements that would develop consensus,” Randall W. Poston, past Chair of ACI Committee 318, said. “This came from his years of practicing structural engineering before joining ACI. He knew with continued resolve and steadfast guidance, committee members would eventually come together and ‘do the right thing.’ In large measure, the reorganization of the ACI 318-14 Structural Concrete Building Code was Dan’s vision of simplifying the use of the code for practitioners.” ACI has agreed to contribute a dollar-for-dollar match for donations made by individuals and companies. To learn more or to donate online, visit www.acifoundation.org. The award is for graduate students studying in the eld of structural engineering with an emphasis in reinforced concrete design. Preference will be given to applicants conducting research pertaining to ACI codes or specications. The fellow ship includes an optional summer internship in the ACI Engineering Department.
Visit the ACI Foundation at The Concrete Convention & Exposition – Fall 2015 Stop by the ACI Foundation booth in the ACI Pavilion during The ACI Concrete Convention and Exposition in Denver, CO. Talk with Ann Daugherty, Foundation Director, about how you can further concrete innovation and research or help fund scholarships for future leaders.
Concrete Research Council (CRC) Calls for Proposals In August, the CRC opened its call for research proposals that advance the knowledge and sustainable aspects of concrete materials, construction, and structures. Details include: Maximum funding is $50,000 per project (increased from $10,000), and CRC will fund up to two worthy projects; The proposal submission due date is December 1, 2015. Proposals submitted after the due date will be returned without review; and Projects will be awarded soon after The Concrete Convention and Exposition – Spring 2016. •
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An ACI Foundation memorial fellowship will honor the late Dan Falconer (center), shown here at a reception after a Technical Activities Committee meeting at ACI headquarters in Farmington Hills, MI
Updated information, proposal requirements, and submittal deadlines are located on the CRC website: www.concreteresearchcouncil.org . For additional questions, or to submit proposals, e-mail Ann Daugherty, Director, ACI Foundation, ann.daugherty@ acifoundation.org.
New Research Products from CRC Co-funded Research The ACI Foundation, through CRC initiatives, has partnered with other industry entities to leverage its research funds: CRC 67, Improved Procedures for the Design of Slender Structural Concrete Columns—funded by the Precast/ Prestressed Concrete Institute with support from the ACI Foundation, the Portland Cement Association, and the Concrete Reinforcing Steel Institute; Ryan W. Jenkins and Robert J. Frosch, FACI, Purdue University; CRC 87, Dening Structurally Acceptable Properties of High-Strength Steel Bars through Material and Column Testing (Part 1, Material Testing Report)—funded by the Charles Pankow Foundation, the ACI Foundation, and in-kind materials support by various entities; Chase M. Slavin and Wassim M. Ghannoum, The University of Texas at Austin; and CRC 88, Proposed Specication for Deformed Steel Bars with Controlled Ductile Properties for Concrete Reinforcement—funded by the Charles Pankow Foundation and the ACI Foundation; Conrad Paulson and Scott K. Graham, Wiss, Janney, Elstner Associates, Inc. A complete list of CRC co-funded projects is available at www.concreteresearchcouncil.org/Home/Projects. •
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Chapter
Reports New Jersey Chapter – ACI Awards Student Chapter $20,000 Grant for Ready Mixed 90-Minute Rule Research
college presented their research at the ACI Fall 2014 Convention in Washington, DC. To learn more about the New Jersey Chapter – ACI, visit www.njaci.com.
The New Jersey Chapter – ACI announced the $20,000 award to the New Jersey Institute of Technology (NJIT) Student Chapter – ACI for the research proposal “Evaluation Iraq Chapter – ACI Announce Winners of Student Project Competition of the 90-Minute Rule as an Acceptance Criteria Considering Current Concrete Mix Design Technology and Mix Constituents.” The winners of the rst student project competition hosted Every year, a substantial amount of ready mixed concrete by the Iraq Chapter – ACI were announced in August. The is returned to concrete plants for disposal. One of the main competition was open to undergraduate students from several reasons is strict enforcement of the 90-minute time limit Iraqi universities. A maximum of two students were allowed specied in ASTM C94/C94M, “Standard Specication for to submit a project focused on concrete design, material, and/ Ready-Mixed Concrete.” or construction. The projects were reported in paper form and The Principal Investigator is ACI member Mohamed included a problem statement/statement of research signicance, Mahgoub, Associate Professor in the Department of Engineering a conclusion, and a list of references. The goal of the contest Technology at NJIT, and the Co-Principal Investigator is was to prepare students for participation in international Nakul Ramanna, Assistant to the Chair and Concrete Laboratory competitions hosted by ACI. The winners received a certicate Manager in the John A. Reif Jr. Department of Civil Engineering. and recognition during special ceremonies held in Basrah, The proposed research aims to gain better understanding of Bagdad, and Erbil. how elapsed time affects the quality of a concrete load. To The rst-place winner was “Prediction of Compressive meet the goal, a large number of concrete batches will be Strength of Fiber Reinforced Concrete Using Articial Neural tested under different weather conditions and elapsed times. Network” by Hussein Sadiq Latief and Alkarar Taha Yaseen The research results would greatly benet concrete suppliers, of the University of Basrah, College of Engineering; Alaa C. engineers, and inspectors in the concrete industry. Galeb, Supervisor. The second-place winner was “Producing The 1-year research project began in August 2015, with Sustainable Accelerated Hardening Cementitious Materials” commitments from the National Ready Mixed Concrete by Rana Hameed Faisal of the University of Technology, Association (NRMCA), Silvi Group, Sika Corp., and County Building and Construction Engineering Department; Maan S. Hassan and Ziyad Majeed, Supervisors. The third-place Concrete. Eric Miller, Silvi South Plaineld Manager; David Jaramillo, Silvi Quality Control Manager; and Nicholas winner was “Comparison between ACI 318 and EC2: for Denicoli, County Concrete Quality Control Manager, will Beams, Slabs, and Columns” by Bahar Abdul Rahman Hassan participate in the research effort. of the University of Salahaddin – Hawler, College of Engineering; Last year, the College of New Jersey received a similar Salahaddin Abdul Rahman, Supervisor. grant from the New Jersey Chapter – ACI. Students from the
Winners of the first student project competition sponsored by the Iraq Chapter – ACI were (from top left): Hussein Sadiq Latief, Alkarar Taha Yaseen , and Rana H ameed Faisal, and (bottom left): Bahar Abdul Rahman Hassan
Members of the NJIT Student Chapter – ACI
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Chapter Reports To learn more about the Iraq Chapter – ACI, visit www.aci-iraq.com.
India Chapter – ACI to host 2nd Biennial R.N. Raikar International Conference in December The 2nd Biennial R.N. Raikar International Conference & BanthiaBasheere International Symposium on advances in science and concrete technology will be held at the Lalit Mumbai Hotel, Mumbai, India, December 18-19, 2015. The conference mission is to introduce participants to cutting-edge technologies in the eld of R.N. Raikar concrete and concrete construction and to The meeting of the Arizona Chapter – ACI in August featured the facilitate technology transfer in appropriate Dodge Construction Forecast areas. A number of national and international experts will Cliff Brewis, Vice President of Operations at Dodge Data & present, including Nemkumar Banthia, FACI, from the Analytics, presented. Brewis is part of the management team Canadian Academy of Engineering, and P.A. Muhammed responsible for the news gathering operations at Dodge. In Basheer, FACI, from the Irish Academy of Engineering, who addition, Brewis has been with Dodge for over 30 years in will act as co-facilitators of the event. sales, planning, and operations. Last year’s forecast called for The India Chapter – ACI is fully geared up for this a 4% gain over the previous year, although the market fell conference, which was named after former chapter ofcer short with approximately 3.4% growth in 2014-2015. He R.N. Raikar, who was involved with the chapter from its expects to see the same rate of growth for next year. Brewis inception in 1979 until his death in 2008. has spoken to chapter members before and he spends valuable The Chapter is in its 36th year and is dedicated to sharing time bringing a presentation suited for those working in the and exchanging activities, knowledge, and information in the Arizona market. “We appreciate the thoroughness of his data,” eld of concrete. The Chapter has more than 2000 members said Britt. throughout India, who actively participate in all the chapter Specic segments for this coming year are in education and programs. To learn more about the India Chapter – ACI, visit public works. It is expected that money will ow for water www.icaci.com. works, as this has been one of the largest growing areas in construction. Schools are beginning to see growth, with higher Arizona Chapter – ACI Presented Market education seeing more investments to fund new campuses. Forecast During Opening Meeting Hotel and hospital building is also expected to rise. Elderly In August, the Arizona Chapter – ACI welcomed approxicare for the retired population in Arizona will see a steady mately 60 attendees to its annual Market Forecast to kick off increase, but the concern is how to properly fund those needs. its 2015-2016 membership meetings. The luncheon was held Another area of concern is the highway sector. Transportation at the DoubleTree Suites Hotel in Phoenix, AZ. The group funding is declining until solid funding into the future is represented concrete suppliers, product representatives, established; this market will remain slow. concrete contractors, general contractors, engineers, and “Arizona was hit extremely hard when the housing bubble testing labs. The chapter hosts eight lunch meetings throughout burst, and we lost many good, long-standing companies in our the year with the Market Forecast as the rst topic. industry when that happened. Investing in our future begins “We like to start our year off with a market forecast with concrete because we make the foundation of all that rises because we feel it gives an overview of what to expect in the from the desert. Arizona hopefully will have learned a coming year,” explains Beth Britt, Executive Director of the valuable lesson in this last recession, and appreciate slow, Arizona Chapter – ACI. “Our meeting topics try to focus on steady, healthy growth, so we can stay one of the best places current local market issues, and sometimes knowing which to call home,” said Britt. sector of the market will be strong helps us all prepare To learn more about the Arizona Chapter – ACI, visit accordingly. Of course, we all know working in this industry www.azaci.org. is anything but predictable.” www.concreteinternational.com | Ci | NOVEMBER 2015
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Chapter Reports
The annual battering ram contest at Kennesaw State University
through which all may coordinate their efforts to improve the nished product known as concrete, to study problems of Members of the Georgia Chapter – ACI and guests at the recent common concern in that eld and make recommendations awards banquet thereon.” Wilson remembers taking his rst Concrete Field Technician Certication exam from this organization in 1984, long before ACI’s current Field Tech Grade I Certication Georgia Chapter – ACI Celebrates 50-Year was created. Anniversary In 1971, CAB rst published standard minimum specications The Georgia Chapter – ACI is celebrating its 50-year for ready mixed concrete for use in Georgia, thought by many anniversary this year. Sadly, however, with the recent passing to be a forerunner to ACI 301. In 1979, they revised this of many of our older members and longtime Georgia specication to reect changes in the 1977 ACI 318 Code. Chapter – ACI Secretary LaGrit “Sam” Morris in 2013, The last published revision was completed in 1987 to match records and personal accounts of the Chapter’s history are updates in the 1983 ACI 318 Code. Current building codes in scarce. Much of what follows is pieced together from the recollections of Wayne Wilson, Certication Activities Chair, Georgia now reference current ACI codes and standards. CAB no longer exists today as an organization but the rich Georgia Chapter – ACI. history and original incorporation objective of supporting and The Georgia Chapter – ACI was rst incorporated as the Atlanta Chapter of ACI in 1965 and later changed its name to promoting quality concrete in Georgia is alive and well. The Georgia Chapter – ACI holds monthly lunch meetings so the Georgia Chapter in 1990. The rst Chapter President was Robert A. Shoolbred, followed by numerous Georgia Industry professionals can network and listen to a variety of concreterelated topics. The Chapter hosts an annual summer seminar, greats like Virgil D. Skipper (1967 and 1974), Eugene Boeke the Virgil D. Skipper Memorial Seminar, which highlights a (1976), Donald Lathrup (1978), Donald E. Dixon (1983), topic of interest. The summer seminar is most popular with Robert Terpening (1989), Robert Kuhlman (1990), Melvyn Galinat (1991), and a host of others over the years. As best as the local engineering community because of its four professional development hours (PDHs) and has included recent Wilson can tell, because the chapter still has the original felt hands-on programs on decorative concrete, precast, and ready banner, the Georgia Chapter has been named an Excellent mixed concrete batching and inspection. Chapter by ACI every year since 1991. The Georgia Chapter – ACI has held an annual Georgia The Chapter works at promoting the proper use of concrete Concrete Projects awards program every year since 1978. The in Georgia. On March 4, 1970, the Chapter, along with the Georgia Chapter – ACI Dan R. Brown Awards, named in Georgia Concrete and Products Association and Local Chapters of AIA, AGC, CSI, and ACEC, incorporated a sister memory of long-time member Dan Brown in 2005, has grown over the years to an annual banquet that includes more than organization called the Concrete Advisory Board of Georgia 200 attendees, 15 to 25 project entries, and a keynote address (CAB). The following general purpose statement comes from from the ACI President. The Chapter hosted ACI Fall conventions their original incorporation papers: “…[the] objective [is] to in 1997 and 2007. Wilson was part of the Convention promote and encourage constructive cooperation among the Committee in 2007 and he is sure many will remember participating organizations by providing an instrument 18
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Chapter Reports the unbelievable Concrete Mixer at the Georgia Aquarium. The Robert Kuhlman ($5000) and LaGrit “Sam” Morris ($2500) Memorial Scholarships are awarded each fall to Georgia college students enrolled in a concrete-related program. The Student Chapter at Kennesaw State University, Kennesaw, GA, is very active and holds an annual Battering Ram competition to test the students’ concrete design and fabrication abilities. ACI certication is very strong in Georgia, as the Chapter hosts more than 500 certication exam sessions annually in almost all of ACI Field Tech, Lab Tech, Craftsman, and Inspector Programs. Wilson is the Certication Committee Chairman and can attest to the number of dedicated people involved in ACI Certication and what it means to the quality of concrete produced in Georgia. To learn more about the Georgia Chapter – ACI, visit www.aci-ga.org. The 2015 Georgia Chapter – ACI President, Angela San Martin, and the rest of the Board of Directors would like to thank all of the Georgia members for a memorable rst 50 years and look forward to another prosperous 50.
Philippines Chapter – ACI Reaches Record of 435 Student Members The Philippines Chapter – ACI Student Chapter at the Technological Institute of the Philippines in Quezon City (TIPQC) announced that they now have 435 students enrolled as members of ACI. In early September, the Philippines Chapter – ACI hosted a free seminar at Eulogio “Amang” Rodriguez Institute of Science and Technology (EARIST) in Manilla. The seminar theme, “Bridging the Gap Between Concrete Knowledge and Practice,” served as an induction for the student chapter at EARIST, a state university with a small population of engineering students. “Giving a free seminar is a way we help the universities and engineering students learn all about concrete practice,” explained Ellen Chua, Vice President of the Philippines Chapter – ACI. “We are still receiving more requests for seminars and interest in forming an ACI student chapter from state and private universities all over the Philippines.”
Officers of the Philippines Chapter – ACI and the Student Chapter at the Technological Institute of the Philippines in Quezon City (TIPQC)
DELIVERING SUSTAINABLE SOLUTIONS
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Awards at The ACI Concrete Convention and Exposition – Fall 2015 Recipients to be honored at the Opening Session in Denver, CO
S
everal annual awards of ACI and the ACI Foundation will be presented during the Opening Session of The ACI Concrete Convention and Exposition, on November 8, 2015, at the Sheraton Denver Downtown Hotel in Denver, CO. These awards and the recipients include: ACI Distinguished Achievement Award to Castle Rock Construction Company; Arthur J. Boase Award to Andrew W. Taylor; Robert E. Philleo Award to Ramón L. Carrasquillo; Jean-Claude Roumain Innovation in Concrete Award to Fred R. Goodwin; ACI Concrete Sustainability Award to Julie K. Buffenbarger; ACI Young Professional Essay Contest Award to Shane M. Maxemow; and ACI Commemorative Lecturer in the series honoring Katharine and Bryant Mather to Kenneth C. Hover. Three of these awards are administered by councils of the ACI Foundation. The Concrete Research Council presents the Arthur J. Boase and Robert E. Philleo Awards, and the Strategic Development Council established the Jean-Claude Roumain Innovation in Concrete Award.
smoothness specication was instituted, going from a prole index (PI) to an international ride index (IRI). Believing that an optimized aggregate blend would help with the smoothness of concrete roads, the optimized mixture became a positive factor in the production of smoother and more durable concrete pavements. CRCC has shared its experiences with many contractors across the country in the hopes of improving the industry. CRCC has won 14 national paving awards since 2007. Some of its more notable projects include US 287; I-70 and Central Park Design Build in Denver, CO; Pena Boulevard; Broadway in Downtown Denver; and I-76 in Greeley, CO. CRCC also received a Rocky Mountain Chapter – ACI Award for Excellence for Transportation in 2012 for Outbound Pena Boulevard. Recently, CRCC worked with the city of Brush, CO, to design and place its rst concrete road in a traditional asphalt setting: Hospital Road, considered “the gateway to the city.” CRCC is currently working on the connector from Boulder to Denver, US 36 Design Build project. The project consists of 1.3 million yd2 (1.086 million m2) of 10 in. (254 mm) dowelled concrete paving, with several features including bridges, a concrete barrier wall, a concrete bike path, and enhanced drainage. ACI Distinguished Achievement Award “for providing leadership in the advancement of the CRCC believes concrete is the best investment in our infrastructure and will continue to promote its use to stretch concrete industry through innovation, information sharing, and concrete promotion” the taxpayers’ investment in the future. CRCC is a member of Castle Rock Construction Company (CRCC) has been the American Concrete Paving Association (ACPA) both involved in concrete paving in Colorado for over 35 years. locally and nationally, and is also a member of the Colorado Originally part of the Irving F. Jensen Company, Sioux City, IA, Contractors Association. CRCC moved to Colorado in the early 1980s and was a strong advocate for developing a concrete paving market, which was Arthur J. Boase Award “for his active and dedicated contributions through almost nonexistent. CRCC has worked with agencies to research and committee work to the advancement of seismic develop specications, such as the Colorado Department of performance of reinforced concrete structures and to the Transportation (CDOT) Smoothness Specication and the development of design guides through application of the CDOT Optimized Aggregate Blend Specication, to enhance results of structural concrete research” the durability and quality of concrete paving. In 2011, a new •
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Castle Rock Construction Company
Andrew W. Taylor, FACI, is an Associate at KPFF
Taylor
Carrasquillo
Goodwin
and ASTM International. International. He is a licensed professional engineer in Texas and Puerto Rico. He received his BS in civil engineering from the University of Puerto Rico, Mayaguez, PR, in 1975, and his MS and PhD in civil engineering from Cornell University, Ithaca, NY, in 1978 and 1980, respectively.
Consulting Engineers, Seattle, WA. WA. He has 29 years of experience in structural engineering research and practice, including 7 years with the Building and Fire Research Laboratory at the National Institute of Standards and Technology, Gaithersburg, MD. In 2001, Taylor received the ACI Structural Research Award, and in 2007 was named a Jean-Claude Roumain Innovation in Fellow of ACI. Concrete Award He is a Chair of ACI Subcommittee 318-H, Seismic “for over 30 years of leadership in the construction Provisions, and a member of ACI Committee 318, Structural chemicals industry, including cement manufacture, R&D and Concrete Building Code. He is a member of the ACI Technical technical support of grouts, adhesives, coatings, shotcrete, Activities Committee (TAC) (TAC) and serves as a liaison between stucco, ooring, ooring, and concrete concrete repair repair materials; and for for TAC and Committee 318. Taylor is a consulting member and championing improvement in the concrete and concrete repair past Chair of 374, Performance-Based Performance-Based Seismic Design of industry” Concrete Buildings, and a past member of 341, EarthquakeFred R. Goodwin, FACI, is a Fellow Scientist in the Resistant Concrete Bridges. Product Development group of BASF Construction Chemicals, Taylor Taylor has extensive research experience in experimental Beachwood, OH. and theoretical investigations of the seismic behavior of He received his BS in chemistry from Northwest Missouri reinforced concrete structures. His specialties include structural State University, University, Maryville, MO, in 1977. He has over 30 vibrations, performance-based seismic design of concrete years of experience in the construction chemicals industry, industry, structures, seismic base isolation, and seismic damping systems. including cement manufacture, research, development, and He received his BSCE and MSCE degrees in 1983 and technical support of grouts, adhesives, coatings, shotcrete, 1985, respectively, from the University of Washington, stucco, ooring, and concrete repair materials. In 2011, he Seattle, WA, and his PhD from the University of Texas at was named a Fellow of ACI and also received the ACI Delmar Austin, Austin, Austin, TX, in 1990. Bloem Distinguished Service Award. Taylor Taylor is also a member of the American Society of Civil He is currently Chair of ACI Committee 515, Protective Engineers (ASCE), and a licensed professional and structural Systems for Concrete, and the Technical Repair and Rehabiliengineer in Washington. tation TAC TAC Subcommittee. He is also a lso a member of the ACI T echnical Activities Committee (TAC); (T AC); and ACI Committees Robert E. Philleo Award 351, Foundations for Equipment and Machinery; 364, “for his contributions through education, research, and Rehabilitation (past Chair); 546, Repair of Concrete; 562, consulting to the advancement of concrete technology” Evaluation, Repair, and Rehabilitation of Concrete Buildings; Ramón L. Carrasquillo, FACI, is the Founder and 563, Specications for Repair of Structural Concrete in President of Carrasquillo Associates, Austin, TX—a forensic Buildings; Committee on Nominations; TAC TAC Concrete engineering engineering consulting rm. Terminology Committee; Technical Committee Manual Task Carrasquillo was named a Fellow of ACI in 1993, and is Group; TAC Awards Task Group; and E706, Concrete Repair currently Chair of the ACI Construction Liaison Committee Education; and Subcommittee 563-I, Proprietary Grouts/ and the International Conferences Committee. Committee. He is a Concrete, of which he is a past Chair. member of ACI Committees 201, Durability of Concrete; Goodwin has been with BASF and its predecessors for 211, Proportioning Concrete Mixtures; 232, Fly Ash in 26 years and is an active member of the International Concrete Concrete; 233, Ground Slag in Concrete; 234, Silica Fume Repair Institute (ICRI), ASTM International, NACE Internain Concrete; and 301, Specications for Concrete; and tional, Strategic Development Council (SDC), and SSPC. Subcommittee 318-S, Spanish Translation. He is also a member of the American Society of Civil Engineers (ASCE) He is a Fellow of ICRI, an Honorary Member of ASTM www.concreteinternatio www.concreteinternational.com nal.com | Ci | NOVEMBER 2015
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Committees C1 and C9, and current Chair of the ICRI Technical Technical Activities Committee; ASTM C09.41, Cement Based Grouts; and SSPC 8.3, Commercial Floor Coatings. He is also a guest Lecturer for the Grouting Fundamentals short course (Colorado School of Mines) and was awarded the Journal of Protective Protective Coatings Coatings and Linings Linings Editors Award in 2006, 2010, and 2012. He received the BASF President’s Award in 1990, 2003, and 2005; and the BASF DAVIS Innovation Challenge Award in 2011 and Innovent in 2014. He is a NACE Corrosion Technologist, holds ve patents, was named as a Top 25 Innovative Thinker by Technology Publishing in 2013, and frequently speaks at industry events.
ACI Concrete Sustainability Sustainability Award “in recognition of her leadership in concrete sustainability, her guidance as Chair of ACI Committee 130, Sustainability, and her tireless efforts as Co-Chair of many ACI sustainability forums” Julie K. Buffenbarger, FACI, serves as a Construction
Specialist for LafargeHolcim. Her role is to promote cement, supplementary cementitious materials, aggregates, specialty concrete mixtures, sustainable and resilient design, and
ACI A CI University Award Awa rd
building practice initiatives initiatives through technical technical education, promotion promotion,, and speci specicati cation on with with owners, owners, archit architects, ects, engineers, engineers, and design agencies. Her additional industry experience includes concrete construction admixture marketing and research with Master Builders, Inc., Cleveland, OH. Buffenbarger has authored over 35 publications on cementitious materials, concrete sustainability, sustainability, durability and resilience, and concrete admixtures in concrete. She was Co-Editor of ACI SP-269, Concrete: The Sustainable Material Choice , in 2010. Buffenbarger is Chair of ACI Committee 130, Sustainability of Concrete; Secretary of 234, Silica Fume in Concrete; and a member of the ACI Publications Committee; 132, Responsi bility in Concrete Conc rete Construction; Constr uction; 232, Fly Ash in Concrete; Concre te; and C601-E, Concrete Construction Sustainability Assessor. Since 2009, she has served as Co-Chair of ACI’s Concrete Sustainability Forum for numerous fall conventions, including inclu ding Denver, CO. Buffenbarger Buffenbarger previously served as Secretary on ACI Subcommittee 301-H, Tilt-Up Construction and Architectural Concrete, and was a member of the Committee on Nominations, Board Advisory Committee on Sustainable Development, and Awards Awards for Papers Subcommittee SC2, Wason Medal for Materials Research. She volunteered as a Convention Mentor from 2009-2011 2009-2011 and was named a Fellow of ACI in 2011. Buffenbarger Buffenbarger is Chair of the Concrete Joint Sustainability Initiative (CJSI) and an active member of the National Ready Mixed Concrete Association (NRMCA) and the Portland Cement Association (PCA) technical committees relating to sustainability. She received her BS in chemistry and her MS in synthetic organic chemistry from Bowling Green State University, University, Bowling Green, OH, in 1987 and 1993, respectively. respectively. She is also an accredited ac credited LEED AP building design and construction professional.
ACI Young Young Professional Essay Contest Award Award Shane M. Maxemow is a Structural Engineer at Robert
The ACI award for University Student Activities identies the universities that qualify for excellent
or outstanding status, based on points received for their participation in select ACI-related activities/ programs. To receive an ocial entry form or if you have any
questions, please e-mail Diane Pociask at
[email protected]. diane.pociask@concrete .org. Forms must be completed and submitted by January 31, 2016. 22
NOVEMBER 2015 | Ci | www.concreteinternational.com
Silman, Washington, Washington, DC, working on a wide range of projects from the Smithsonian Castle to Mt. Vernon. Previously he was employed with the civil engineering rm Bayside Engineering, Engineering, where he did roadway and drainage design, and the structural rm BillerReinhart Structural Group, where he designed and restored structures from concrete bridges to carbon ber structures. Maxemow received his BS and master’s degrees in civil engineering in 2012 from the University of South Florida, Tampa, FL. He was the past Governing Board Vice-Chair Vice-Chair and Emerging Professionals Co-Chair for the Green Building Council, Tampa Tampa Bay Chapter; and also the Founding Chair of the Young Young Members Committee for the Florida Structural Engineering Association. Maxemow was the recipient of the Suncoast Chapter – ACI Scholarship, 2011; U.S. Green Building Council National Scholarship, 2009; and the Public Works Academy Scholarship, 2008-2010.
Buffenbarger
Maxemow
Hover
Stringer
Harn
ACI Commemorative Lecturer Lecturer Kenneth C. Hover, FACI, is Professor of civil and
environmental engineering (CEE) at Cornell University, University, Ithaca, NY, NY, where his teaching and research focus on concrete materials, design, and construction. He served as a Captain in the U.S. Army Combat Engineers, and was Project Engineer and Project Manager for Dugan and Meyers Construction Co., Cincinnati, OH, working on buildings, interstate bridges, and water treatment plants. Joining THP Structural Engineers in Cincinnati, he became a Partner and Manager engaged in the design and repair of buildings and industrial facilities. Hover’s PhD studies at Cornell were funded by the Exxon Fellowship, designed to bring experienced professionals to engineering programs at U.S. universities. He teaches reinforced and prestressed concrete design, concrete materials, and construction management. In addition to his technical courses, Hover lectures on management skills, leadership, and professional ethics. His research interests interests include freezingand-thawing durability, durability, mixture proportions and ingredients, behavior and testing of fresh fresh concrete, and the impact of construction operations and construction environment on concrete quality. He is a Fellow and Past President of ACI, Past President of the Greater Miami Valley Chapter – ACI, and a member of ACI Committees 301, Specications for Concrete; 305, Hot Weather Concreting; 306, Cold Weather Concreting; and ACI Subcommittee 318-A, General, Concrete, and Construction. He holds the Outstanding Educator Award from the American College Personnel Association (ACPA) and has received ACI’s Kelly, Philleo, Anderson, and Structural Research Awards and the ASCE Materials Division Best Basic Research Paper Award. He holds the top teaching awards in CEE (Chi Epsilon Award), the College of Engineering (Tau Beta Pi Award), and Cornell University (The Stephen A. Weiss Presidential Fellowship), plus the Senior Class of 2015 Award as one of the top 1% of Professors at the University. In 2006, he was named one of the “Ten Most Inuential People in the Concrete Construction Industry.” Hover received his bachelor’s and master’s degrees in civil engineering from the University of Cincinnati, Cincinnati, OH, and his PhD in structural engineering from Cornell University, University, Ithaca, NY NY.. He is a licensed professional engineer in Ohio and New York.
2015 T.Y. Lin Award The winners winne rs of ASCE’s 2015 T.Y. T.Y. Lin Award—Stuart J. Stringer and Robert E. Harn—will be recognized at a t the Opening Session in Denver, CO. Their paper “Seismic Stability of Marine Piers Built with Prestressed Concrete Piles,” was published by ACI in SP-295, Recent Advances Prestressed Concrete Concrete Piles in Marine Marine in the Design of Prestressed Structures , in October 2013. ACI member Stuart J. Stringer is an Engineer at Moffatt & Nichol, Seattle, WA. He specializes in the seismic design and analysis of waterfront, marine, and bridge structures. stru ctures. He has been b een published publishe d in several seve ral peer-reviewed peer-reviewe d journals, conference proceedings, proceeding s, and research reports for agencies such as the Transportation Transportation Research Board of the National Academies and the Federal Highway Administration. Administration. He completed his graduate-level research on the seismic design of prestressed prestress ed concrete concr ete pile-supported pile-s upported piers pie rs and wharves wha rves at the University of Washington, Seattle, WA. Stringer is experienced in the analysis and design of new and retrot waterfront, marine, and bridge projects, including reinforced, rei nforced, precast, and prestressed pres tressed concrete, steel, and timber structures. He received his BSCE in civil and environmental engineering and his MSCE in structural engineering from the University of Washington. Robert E. Harn is a Project Manager at BergerABAM,
Federal Way, WA. He oversaw the team responsible for the seismic upgrade of the Port of San Diego’s Broadway Pier, one of the rst to use seismic isolation for a pier. The project received the ASCE/COPRI 2013 Project Excellence Award at the Ports 2013 Conference. Harn has been a member of ASCE since 1975. He served as a member on the ASCE/COPRI Volunteer Committee that developed the recently published ASCE 61-14 document, “Seismic Design of Piers and Wharves.” In addition to the T.Y. Lin award paper, Harn has authored and coauthored 16 papers, 12 of which were presented at the ASCE Ports Conferences.
www.concreteinternation www.concreteinternational.com al.com | Ci | NOVEMBER 2015
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[email protected] www.concreteseminars.com 24
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Topics ACI 318-14 Building Code Requirements for Structural Concrete ACI/PCA 318-11 Building Code Requirements for Structural Concrete ACI/PCA Simplified Design of Concrete Buildings of Moderate Size and Height Anchorage to Concrete Basics of Concrete Materials and Testing Code Requirements for Nuclear Safety-Related Concrete Structures Concrete Repair Basics Construction of Concrete Slabs-on-Ground Design of Concrete Slabs-on-Ground Environmental Engineering Concrete—Design and Details Physical Tester—Basics of Cement Testing Portland Cement Concrete Overlays: State of the Technology Reinforced Concrete Design Repair of Concrete Bridges, Parking Decks, and Other Transportation Structures Repair of Concrete Workshop Seismic and Wind Design Considerations for Concrete Buildings Seismic Design of Liquid-Containing Concrete Structures Troubleshooting Concrete Construction Troubleshooting Concrete Floor Problems Troubleshooting Concrete Forming and Shoring
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Notable Concrete in Denver Some examples of recent precast construction in the region
A
s ACI prepares to meet for The Concrete Convention and Exposition, November 8-12, 2015, at the Sheraton Denver Downtown Hotel, in Denver, CO, here are a few samples of nearby projects:
precast products went into the building. The architectural concrete wall panels were cast with thin brick, and the surrounding colored concrete was lightly acid-etched. Project credits: Fentress Architects, Architect; Martin/ Martin, Structural Engineer; Stresscon Corporation, Precast
Circle Point 11030 Circle Point Road, Westminster, CO 80020
The Circle Point ofce building is a total precast solution with a distinctive kinked oor plate. The total gross area is 340,000 ft2 (31,600 m2), with about 68,000 ft 2 (6300 m2) per oor. The precast oor and roof components include double tees and prestressed beams. The lateral force-resisting system is made up of four shafts; cast-in-place topping on the oor double tees serve as the diaphragms. At the roof level, the double tees are connected to act as a diaphragm without topping. The exterior walls, made up of highly accented architectural precast panels, are part of the gravity-load system. This complex building enclosure is made up of architectural precast concrete and a glass curtain wall system. The architectural precast concrete includes two integral colors, a stone liner, and multiple lines of reveal work. The lower spandrel panels use a dark tan stone liner and an acid-etched nish. The second, third, and roof line spandrel panels are two-tone, adding a lighter buff concrete, plus dramatic relief from multiple reveals. Column panels are single-color, with a color change above the rst story. Multiple horizontal reveals in the columns play off those in the spandrel panels. Project credits: Pahl Architecture, PC, Architect; Jirsa+Hedrick and Associates, Structural Engineer; Stresscon Corporation, Precast Supplier; and PCL Construction, General Contractor.
Denver Health Employee Parking Garage 601 Acoma Street, Denver, CO 80204
The Denver Health Employee Parking Garage provides 228,000 ft2 (21,200 m2) of parking in ve stories. The structure has an open interior created by double tees that span between “spread walls” and K-frames, which also resist lateral loads. Altogether, 927 pieces of architectural and structural
Circle Point (photo courtesy of Fred Fuhrmeister) www.concreteinternational.com | Ci | NOVEMBER 2015
25
Supplier; and Hensel Phelps Construction Company, General Contractor.
1st Bank Center 11450 Broomeld Lane, Broomeld, CO 80020
Denver Health Employee Parking Garage (photo courtesy of Fred Fuhrmeister)
The 1st Bank Center was built to accommodate events including concerts, rodeos, and community functions. The Center contains 6000 seats, 25 suites, 900 club seats, a 200-seat restaurant, two club lounges, and separate basketball and hockey facilities. Precast, prestressed concrete used in the structure include 581 pieces of single-leg risers, triple risers, walls, beams, and stairs. The precast concrete was installed using two hydraulic cranes operating inside the building to coordinate with the roof steel erection. The 1st Bank Center hosts about 130 events each year. While owned by the city and county of Broomeld, CO, the site is managed by Peak Entertainment, a partnership of AEG Live and Kroenke Sports & Entertainment. Project credits: Sink, Combs and Dethlefs, Architect; Martin/Martin, Structural Engineer; Stresscon Corporation, Precast Supplier; and Saunders Construction, General Contractor.
Golden Park-N-Ride 605 Johnson Road, Golden, CO 80401
1st Bank Center (photo courtesy of Fred Fuhrmeister)
The Golden Regional Transportation Department (RTD) parking structure serves as the western terminus of the W-Line of the RTD Light Rail System. Keeping the theme of the Jefferson County Judicial Center, the architectural precast concrete maintains the colors, acid-etching, and exposed aggregate textures of the campus. At the south end of the structure, the precast framing creates a tunnel for the light rail train to pass through to reach the boarding platform. The 250,000 ft2 (23,000 m2) parking structure includes three levels designed to accommodate more than 800 vehicles. The structure is congured four bays deep with the two center bays as a single-leaf ramp. Precast framing components include tees, beams, and columns, with K-frames and hammerhead shear walls for lateral stability, and a load-bearing architectural exterior. Project credits: IBI Group, Architect; Martin/Martin, Structural Engineer; Stresscon Corporation, Precast Supplier; and Hyder Construction, General Contractor.
Santa Fe and C-470 Flyover South Santa Fe Drive (US 85) at C-470 Westbound, Littleton, CO 80120
Golden Park-N-Ride (photo courtesy of William Towns)
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The Colorado Department of Transportation (CDOT) added the yover ramp at Santa Fe Drive and C-470 to reduce congestion on Santa Fe Drive and ease southbound trafc merging onto eastbound C-470. Precast concrete was used for the main structural elements of this $23.3 million project (funded by CDOT, Douglas County, and a federal stimulus grant). The 1713 ft (522 m) elevated structure is made up of 36 curved tub sections (822 ft [250 m] radius) and straight trapezoidal U-girders, supported by precast pier caps, topped
Santa Fe and C-470 Flyover (photo courtesy of EnCon Colorado)
with precast, prestressed deck panels. Over 200 deck panels were cast directly on the U-girders in the plant to create torsionally rigid sections. The yover opened 4 months ahead of schedule and under budget, largely due to the use of the precast, prestressed concrete. Erection was done at night to minimize disruption to the public. EnCon Colorado, which produced the precast, received the Award of Excellence for Bridge Construction in the 44th Annual Awards of the Rocky Mountain Chapter – ACI. Project credits: Wilson & Company, Structural Engineer; EnCon Colorado, Precast Supplier; and Edward Kraemer and Sons, General Contractor. Starz Encore (photo courtesy of Barber Architecture)
Starz Encore 8900 Liberty Circle, Englewood, CO 80112
The cut-stone appearance of the precast structural panels used on the lower levels of this more than 300,000 ft2 (28,000 m2) building reect the granite design on a nearby structure. The design was produced by creating individually sculpted formliners, and panels were turned to create more diversity in the appearance. The structure is three bays wide, framed with 10 ft (3 m) precast twin tees. To create the entablature at front and rear entries, round columns were cast with horizontal
joints to emulate historically correct Roman/Tuscan columns. The project provided many challenges: matching the color, texture, and shape, while hiding joints between panels to replicate the look of stone blocks; designing and erecting the two entablatures; and delivering and erecting precast panels weighing up to 70,000 lb (31,700 kg) each. Project credits: Barber Architecture, Architect; S.A. Miro, Inc., Structural Engineer; and Rocky Mountain Prestress, Precast Supplier.
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NOVEMBER 2015 | Ci | www.concreteinternational.com
The Challenge of Predicting the Shear Strength of Very Thick Slabs Results support recommendation to use at least minimum shear reinforcement
by Michael P. Collins, Evan C. Bentz, Phillip T. Quach, and Giorgio T. Proestos
M
any large structures, such as those shown in Fig. 1, incorporate very thick slabs, the shear capacity of which must be evaluated. However, there can be very large differences in the shear-strength estimates for such slabs given by the procedures in different codes, such as ACI 3181 or AASHTO LRFD,2 and few experiments are available to guide engineers as to which approach will give more accurate results. To provide a benchmark against which the accuracy of shear-strength prediction procedures for thick slabs could be measured, it was decided to construct and load to failure a specimen representing a strip cut from a 13 ft (4 m) thick slab (Fig. 2). Apart from its considerable self-weight, the specimen was loaded by an off-center point load, P , dividing the 62 ft 4 in. (19 m) simple span into shear spans, a, of 39 ft 4 in. (12.0 m) and 23 ft (7.0 m) on the east and west sides of the load. The east shear span contained no shear reinforcement, and the shorter west shear span contained about the minimum shear reinforcement per the ACI 318 Code. To assess the ability of the profession to accurately estimate the shear response of such thick slabs, engineers were invited to provide predictions as to the magnitude of P required to cause failure of the specimen, the location where rst failure would occur, the magnitude P required to cause failure if both shear spans had contained minimum shear reinforcement, and the load-deformation response for the actual specimen. This article presents a summary of the results and compares the results with predictions provided by the 66 entries, as well as values calculated based on a number of codes of practice.
17ft 6in. (5.33 m) (a)
6 m thick slab 4m thick wall
(b) Fig. 1: Examples of very thick slabs: (a) mat foundation for a high-rise building; and (b) intake structure for hydroelectric powerhouse (Note: 1 m = 3 ft)
Specimen Design The specimen, shown in Fig. 2, was designed so that it would fail rst in the long east shear span (the span not containing shear reinforcement). The specimen’s effective
Ci
The loading to failure of the east span is shown in a movie, available at www.concrete.org/CIvideo1
www.concreteinternational.com | Ci | NOVEMBER 2015
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depth, d , was 151.2 in. (3.84 m), so the shear span-depth ratio, a/d , of the east shear span was 3.12, while that of the west shear span was 1.82. Thus, while direct strut action might increase the shear strength of the west shear span, it f = 40 MPa = 5800 psi would not increase that of the east. To b = 250 mm = 9.84 in. Bar Area f h = 4000 mm = 157.5 in. t the large specimen into the available 30M 700 mm 1.085 in. 573 MPa 83.1 ksi d = 3840 mm = 151.2 in. max aggregate = 14 mm = 0.55 in. 20M 300 mm 0.465 in. 522 MPa 75.7 ksi laboratory space, reductions in the overall depth of the specimen were required near each end. The highP strength longitudinal tension reinforcement consisted of nine bars with a total yield strength of 812 kip (3610 kN), giving the section a exural capacity of about 9670 kip-ft (13,100 kN∙m). Thus, the magnitude of P which, in addition to self-weight, would cause exural failure of the specimen, was predicted to be about 615 kip (2730 kN). Figure 3 summarizes the calculations involved in predicting the value of P Fig. 2: Details of the specimen (Note: 1 mm = 0.04 in.; 1 m = 3 ft) that would cause a shear failure in the east shear span. Equations (1a) and (1b) are the traditional “basic expression” for V c for normalweight and normal-strength concrete—still used in ACI 318-14.1 In M , kNm using the equation, the term Vd / M is limited to no more than 0 2000 4000 6000 8000 unity. The ACI 318 Code expression was derived3 based on Failure V = 215 + 24.4 Vd /M ≤ 240 kip ≥ 227 kip 250 ACI 318-14 (Eq. (1)) the correct assumption that the failure shear stress will decrease as the stress in the exural tension reinforcement P =563 kip b = 9.84 in. =2505 kN increases 1000 ´
c
y
2
2
2
2
. n m i m 2 . 0 1 4 5 8 1 3 = = d d
c
w
U.S. customary units
200
2 . 1 5 1 =
d
150
) 1 ( t f 6 2 . 3 1 = x
p i k ,
800 ) 2 ( t f 9 6 . 9 1 =
x w =
V
P
100
0.656%
SI units ) 3 ( t f 2 1 . 6 2 =
600 N k ,
x
V
=150.6 kip = 670 kN V c =
130.4 kip 1 + 1500εx
εx = 566x103 C S A + A AS HT O ( E q. ( 2) )
50
P
self-weight
0 0
400
/(0.9d ) V + M
Failure
1000
2000
200
x 23 ft 0 in.
3000 4000 M , kip-ft
39 ft 4 in.
5000
6000
0 7000
Fig. 3: Shear strength predictions based on ACI 318-14 (Eq. (1)) and CSA/AASHTO Standards (Eq. (2)) (Note: 1 in. = 25 mm; 1 ft = 0.30 m)
30
(1a)
. n i
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(1b)
As shown in Fig. 3, for this section with a relatively small amount of longitudinal reinforcement, the predicted ACI shear strength decreases from 240 to 227 kip (1070 to 1010 kN) as the magnitude of the moment increases. Note that the simplied version of this ACI equation permits the failure shear stress to be taken as 2 , which results in a predicted shear strength of 227 kip (1010 kN). Shear failure of a slab with no shear reinforcement involves a exural crack starting on the exural tension face and becoming inclined toward the applied load as it spreads toward the exural compression face. Because the shear failure surface involves a length along the member about equal to d , sections closer than d to the face of the support or the face of the load will not be critical.3 In Fig. 3, three sections along the east shear span are checked: Section 1, a distance d from the face of the support; Section 2, halfway along the east shear span; and Section 3, a distance d from the face of the load. As P is increased, the moments and shears at these three sections increase from the self-weight values to the
failure values. It can be seen that Section 1 has the smallest increment of shear to cause failure; based on the ACI 318 requirements, the magnitude of P at shear failure was predicted to be 563 kip (2505 kN). Thus, the ACI Code would predict that the east shear span would fail in shear near Section 1 when the point load was at 92% of the exural failure value. In a discussion to the 1962 ACI-ASCE shear report,3 which proposed the ACI basic expression for V c, Moe suggested that the reason members with higher stress in the exural tension reinforcement fail at lower shear stress is that they have wider exural cracks and these wider cracks are not able to transmit such high shear stress. Flexural crack width is a function not only of tensile strain in the longitudinal reinforcement but also of spacing of the cracks. What was not appreciated at the time is that large members have their widest exural cracks close to the middepth of the member because that is where the largest crack spacing occurs. Along the span of a slab, the crack spacing near middepth varies between about 0.5d and 0.8d , so thicker slabs have more widely spaced cracks. For two slabs, one twice as thick as the other, with the same strain in the exural tension reinforcement, the thicker slab will have crack widths near middepth about twice as wide as those of the thinner slab. Because of their wider cracks, thicker slabs will fail at lower shear stresses, a phenomenon referred to as the size effect in shear. This size effect is predicted by the Modied Compression Field Theory (MCFT), 4 which forms the basis of the shear provisions of the AASHTO LRFD standard, the Canadian CSA A23.3-14 standard,5 and the resource for future European standards, “ b Model Code for Concrete Structures 2010.”6 In ACI 318 format and U.S. Customary units, an appropriate MCFT expression for V c that clearly identies the strain effect and the size effect is given by
(670 kN). This value is 24% and 27% of the exural failure and the ACI predicted shear failure values of P , respectively. For the MCFT-based method (ignoring the detrimental effect of the large spacing of the shear reinforcement), the predicted shear capacity of the west shear span is V c + V s = 193 + 109 = 302 kip (1340 kN), where V s is given by Eq. (3) (3) Note that when the distance between the loading plate and the support plate is less than 2d , the critical section is taken3 halfway along the shear span. Also note that this predicted shear capacity for the west shear span is about 3.5 times the MCFT predicted shear capacity of the critical east shear span. As previously discussed, it is assumed that the specied minimum quantity of appropriately spaced shear reinforcement will eliminate the size effect in shear, causing a large increase in V c. The spacing, s, of the shear reinforcement in the west shear span was 59 in. (1500 mm). While this is only 0.39d , it considerably exceeded the traditional 24 in. (610 mm) maximum spacing limit.1 The CSA code5 allows this spacing limit to be exceeded if s x in Eq. (2) is set equal to ( s − 12) in. Changing s x from 12 to 47 in. (305 to 1190 mm) reduces the predicted shear capacity of the west shear span to 129 + 115 = 244 kip (1084 kN), which is still about 2.9 times the predicted shear capacity of the east shear span. So for very thick slabs, even widely spaced minimum shear reinforcement is predicted to greatly increase shear capacity. The point load required to fail the west shear span is thus predicted to be 334 kip (1485 kN), which is 2.22 times the load predicted to fail the east shear span.
Loading until First Failure (2) where ε x is the calculated longitudinal strain at middepth of the member; and s x is the effective longitudinal spacing of the exural cracks at middepth of the member. If the member has at least minimum shear reinforcement satisfying traditional spacing limits, s x can be taken equal to 12 in. (about 300 mm) and the size effect is eliminated. If the member has no shear reinforcement and the maximum specied aggregate size, a g , is at least 1 in. (25 mm), then s x is taken as 0.75d . For smaller maximum aggregate sizes, s x is taken as 1.25d /(0.65 + a g ), which for the large test specimen is 1.25 × 151.2/(0.65 + 0.55), or 157.5 in. (4 m). The value of ε x can be taken as one-half the strain in the exural tension reinforcement, where the tension force in this reinforcement is taken as M /(0.9d ) + V . The resulting shear-moment interaction diagram shown in Fig. 3 was calculated by assuming values of ε x and then calculating the corresponding values of V and M . The interaction line is labeled CSA + AASHTO because very similar values for the line would have been obtained if the shear provisions of either of these two codes had been used. Note that Eq. (2) predicts a shear failure in the east span when P equals only 150.6 kip
The behavior of the specimen during loading until rst failure is summarized in Fig. 4. Flexural cracking rst occurred under the point load when P reached 45 kip (198 kN), corresponding to a bending moment in the specimen of 1400 kip-ft (1900 kN∙m) and a tensile stress in the concrete of 360 psi (2.48 MPa). At several load stages during the experiment, the magnitude of P was reduced signicantly so that cracks could be safely marked and crack widths measured and labeled. Figure 4(a) shows the specimen after P had reached 84.4 kip (375 kN). In the east shear span at the level of the exural tension reinforcement, seven cracks can be seen. The average spacing of these cracks is 28.5 in. (724 mm) and the average crack width is 0.06 mm (0.003 in.). Two of these seven cracks extend up past the middepth of the member and the spacing between these two cracks equals 93.3 in. (2320 mm), which is 0.60d . Near middepth, these two cracks have an average width about three times greater than the average crack width near the exural tension face. As P was increased to 141 kip (625 kN), the crack further from the load developed into a potential exure-shear failure crack (Fig. 4(b)). As P was further increased, a exural crack originating about 18 ft (5.5 m) from the east support began to spread upward www.concreteinternational.com | Ci | NOVEMBER 2015
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the nominal shear strength provided by shear reinforcement, V s, as
(a)
(4) Ignoring the detrimental effect of the large spacing of the shear reinforcement, the ACI predicted shear capacity of the west shear span is V c + V s = 240 + 90 = 330 kip (1470 kN). At the critical section halfway along the short west shear span, the shear due to self-weight is 33 kip (146 kN), leaving 297 kip (1320 kN) to resist the shear due to P . Thus, the ACI Code-predicted point load to cause a failure in the west shear span is 470 kip (2090 kN), which is 83% of the ACI-predicted load to cause failure of the east shear span. The ACI expressions predict failure in the wrong shear span because for very thick slabs, they greatly underestimate the increase in shear capacity caused by adding minimum shear reinforcement.
(b)
(c)
(d)
Predictions from Engineers Fig. 4: Diagonal cracking of east span: (a) Load Stage 2 at P = 84.4 kip (375 kN), crack widths at middepth = 0.15 mm (0.006 in.); (b) Load Stage 4 at P = 141 kip (625 kN), crack widths at middepth = 0.75 mm (0.030 in.); (c) Load Stage 5 at failure load P = 154.1 kip (685 kN), spacing between three cracks at middepth = 0.60d and 0.68d , crack widths at middepth up to 3 mm (0.118 in.), deflection under load = 12 mm (0.47 in.); and (d) Load Stage 6 when reloaded maximum P = 97 kip (433 kN), crack widths opened up to 35 mm (1.4 in.)
and crossed the middepth with a slope of about 45 degrees and as this crack propagated toward the point load, the force applied by the displacementcontrolled ram decreased from the peak load of 154.1 kip (685 kN) to less than 112 kip (500 kN) (refer to Fig. 4(c)). The applied load was reduced to zero for the weekend, after which the damaged specimen was reloaded. During this loading, P reached a maximum of only 97.4 kip (433 kN), the cracks spread and widened, and P fell to just 3 kip (13 kN) (Fig. 4(d)). Thus, the magnitude of the point load required to cause shear failure of this strip from a 13 ft (4 m) thick slab occurred when the point load was 1.02 times the load predicted by the MCFT based method and 0.27 times the load predicted by the ACI basic expression 32
for the shear strength of members not containing shear reinforcement. Note that at the peak load, the maximum shear force resisted at the section 18 ft (5.5 m) from the support was only 22.0 + 56.8 = 78.8 kip (350 kN). This corresponds to a nominal shear stress (V /(bwd )) at failure of only 53 psi (0.365 MPa). In comparison, Eq. (1) predicts that the shear stress at failure will be 161 psi (1.11 MPa), which is three times the experimental failure stress. The traditional ACI simplied equation suggests that at shear failure the nominal shear stress will be 2 , which is 152 psi (1.05 MPa), or 2.9 times the experimental value. Perhaps of equal concern, the ACI 318 Code calculations predict that failure should occur rst in the west shear span. The ACI 318 Code denes
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Figure 5 compares the experimental result from the east shear span with the 66 predictions made by engineers who responded to the challenge of predicting the failure load of the very thick slab. By coincidence, 33 of the predictions came from engineers in industry and 33 came from engineers in academia. A total of 26 predictions came from Europe, 23 from the United States, 14 from Canada, and one each from Australia, Brazil, and Mexico. Also shown on the plot are the predictions based on provisions in six different codes.1,2,5-8 Given the large range of values shown in the gure and the almost uniform distribution of predicted values across the entire range, it is evident that predicting the shear strength of very thick slabs not containing shear reinforcement was a challenging task for the profession. The upper red zone in the gure identies very unconser vative predictions, where the ratio of predicted failure load to observed failure load ranges from 1.5 to 5.5. The yellow band in Fig. 5, on the other hand, indicates the “gold standard” prediction range of ±10% from the observed
strength. It can be seen that based on this measure, eight of the representing linear elastic response predictions. The steeper line is appropriate for an uncracked specimen (moment of predictions from industry, ve from academia, and three predictions based on codes were excellent. While 20% of the inertia, I , based on the gross section moment of inertia, I g ), while the second line with the much lower slope would be entries were very accurate, the concern is that 44% of the entries and two of the codes were in the red zone and thus appropriate if the member is fully cracked ( I based on the cracked moment of inertia, I cr , which is taken as 0.335 I g ) and made very unconservative predictions. Engineers were challenged to predict not only the magnitude shear deformations are negligible. Note that in the rst case, of P required to fail the thick slab strip but also the deection, the predicted deection at the location of the point load due to self-weight of the specimen equals about 0.04 in. (1 mm), Δ, at the location of the load when the load was 25, 50, 75, and 100% of the predicted failure load. A total of 36 of the while for the lower stiffness, this self-weight deection is entries—13 from industry and 23 from academia—submitted about three times greater. It can be seen that predicting the predictions for the load-deformation response. Figure 6 load-deformation response of a very thick slab is very compares these predictions with the experimentally determined challenging. As one would expect, the deformations measured response. Also shown on the gure are two straight lines prior to cracking closely followed the linear elastic prediction for the uncracked member. At rst cracking, there was a substantial loss of member stiffness, after which the loaddeformation response followed an approximately straight line at a slope that was only about 15% of the slope for the uncracked member. The yellow zone around the observed response loading line indicates deections at a given load that were within ±20% of the experimental values. Five of the predictions lie within this “zone of excellence”; two stay well below the zone, indicating underestimates of stiffness; and 18 stay above, indicating overestimates of stiffness, while the remaining 11 intersect the zone typically because calculated initial post-cracking stiffnesses were too high. Only three of 400
684 kip 1.54 in.
435 kip 0.37 in.
472 kip 1.04 in.
848 kip 0.94 in.
Δ=
2
723 kip 5.50 in.
2
402 kip 1.44 in.
300
p i k ,
P
, d a o l t n i o p d e i l p p A
258 kip 1.46 in.
200 Prague Toronto
P exp = 154 kip = 685 kN Δexp = 0.47 in. = 12 mm P
100
Observed Failure Brescia
Δ Prague (Cervenka) Predicon Experimental
0 0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
Displacement under point load, Δ, in. American
Fig. 5: Comparison of predictions of point load to cause first failure with test result
Canadian
European
Other
University
Industry
Fig. 6: Predicted and observed load-deformation response for initial test (failure in east span) (Note: 1 kip = 4.45 kN; 1 in. = 25 mm) www.concreteinternational.com | Ci | NOVEMBER 2015
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the load-deformation predictions met the demanding requirements that the predicted failure load is within ±10% of the experimental value and the four predicted deformations are within ±20% of the experimental values. These predictions were submitted by Červenka and Sajdlova from a consulting rm in Prague, Czech Republic; Conforti and Facconi of the University of Brescia, Brescia, Italy; and Bentz from the University of Toronto. The rst two predictions were made using nonlinear nite element models, while the third used a
650
Failure of the West Shear Span
600 P exp = 486 kip = 2162 kN
550
Δ exp = 1.55 in. = 39.3 mm
500
11 10
450 p i k ,
P
, d a o l t n i o p d e i l p p A
9
400 350 2
300
Δ=
2
8
3
250 7 Experimental
200 150 P
Observed Failure
100 50 0
newly developed version of the sectional analysis program Response-2000.9 With respect to location of failure, Červenka and Sajdlova submitted the most accurate prediction, shown as an insert in Fig. 6, of where the failure would occur and what the specimen would look like as failure progressed. Six of the entries predicted that rst failure of the specimen would be a shear failure in the shorter west shear span while two predicted a exural failure under the load. Because of this, these eight entries predicted that adding minimum shear reinforcement to the east shear span would not increase the failure load of the specimen.
Δ
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7
Displacement under point load, Δ, in.
Fig. 7: Load-deformation response of repaired specimen (Note: 1 kip = 4.45 kN; 1 in. = 25 mm)
To determine the shear capacity of the shorter west shear span, the failed east end of the specimen was repaired by strapping that shear span with four pairs of 1.375 in. (36 mm) diameter Dywidag threadbars and post-tensioning each bar to about 30 tons (270 kN). The load-deection response of the repaired specimen is shown in Fig. 7. It can be seen that at low loads, the deformations of the repaired but cracked member closely matched the predictions of the elastic equation using E c I cr , where E c is the elastic modulus for the concrete. However, at higher loads, the stiffness of the member reduced substantially so that at failure the deformation was about 1.8 times the predicted elastic value for the cracked specimen. The conditions of the specimen at 81% of failure load and at failure are shown in Fig. 8(a) and (b). When the point load reached 486 kip (2162 kN), the concrete at the west end of the loading plate crushed (refer to inset illustration in Fig. 7), causing the load to reduce to about 10% of its peak value. The zone of crushed concrete corresponded closely to what Mihaylov et al.10 dene as the critical loading zone (CLZ). For short shear spans, the CLZ is predicted to carry a large portion of the shear.11 Note that the shear force required to fail the shorter west shear span with minimum shear reinforcement was 33 + 307 = 340 kip (1511 kN), which is 340/78.8 = 4.3 times the magnitude of the failure shear of the longer east shear span with no shear reinforcement.
West Shear Span Predictions (a)
(b)
Fig. 8: Diagonal cracking of west span (east span repaired with external reinforcement): (a) Load Stage 9 at P = 394 kip (1750 kN), diagonal crack widths up to 4.0 mm (0.157 in.); and (b) Load Stage 11 at failure load, P = 486 kip (2162 kN)
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Figure 9 compares the experimental value of the point load required to fail the west shear span with the 44 predictions made by engineers who responded to the challenge of predicting the failure load of the specimen if the east shear span had also contained shear reinforcement. Again note that the red zone indicates very unconservative predictions and the yellow band identies excellent predictions within ±10% of the experimental value. Comparing Fig. 9 to Fig. 5, it can be seen that while 29 of the 66 entries were in the red zone for the east shear
span without shear reinforcement, for the west shear span, only one of the 44 entries was in the red zone. Further, for the west shear span, 66% of the predictions were conservative while for the east shear span, only 24% were conservative. For the west shear span, 10 of the predictions (ve from industry, four from academia, and the ACI value) were within 10% of the experimental value. There are two CSA predictions shown in Fig. 9—one based on sectional analysis (Eq. (2) and (3)) and the second on a strut-and-tie analysis. For thick slabs with a/d less than about 2, the use of strut-and-tie models1,2,5 often gives higher and more accurate estimates of failure loads.11 For this specimen, the strut-and-tie estimate of failure was only 11% higher than the sectional value, indicating that strut action, while signicant, is not yet as dominant as it would be for a somewhat shorter shear span.
Only two entries predicted the failure loads of both the east shear span and the west shear span within 10% of the experimental values. These entries were from Červenka Consulting and from SNC-Lavalin Hydro in collaboration with École Polytechique de Montréal, Canada. Both groups used their own nonlinear nite element programs. Of these two excellent entries, the load-deformation prediction from Červenka Consulting was more accurate and hence they were chosen as the overall winners of the prediction competition.
Traditional-Sized Specimen The ACI basic expression for the shear strength of members without shear reinforcement (Eq. (1)) was developed3 using experiments on beams that were only about 1 ft (0.30 m) deep. To provide a direct comparison with such a beam, a companion beam—about 1 ft in overall depth—was cast on April 27, 2015, along with the 13 ft (4 m) deep specimen. The small specimen was loaded to failure on August 4, 2015, by which time the concrete strength had reached 6500 psi (45 MPa). The small specimen had a d of 10.4 in. (264 mm) and a span of 65 in. (1650 mm) and was loaded by a central point load. The a/d of 3.12 for the small specimen was selected to be the same as for east span of the large specimen. Also, the percentage of longitudinal reinforcement for the two specimens M ,
0
5
10
15
kNm 20
ACI 318-14 (Eq. (1))
12
C S A + A A S H T O ( E q . ( 2 ) )
bw = 6.89 in.
10
. n i 4 . 0 1
25
30
Failure V = 11.5 kip = 51.2 kN
50 Failure V exp = 10.7 kip = 47.4 kN
Failure V = 9.7 kip = 43.1 kN
40
=
8
d
As = 0.456 in.2 w = 0.649% f y = 66.4 ksi f c ' = 6500 psi ag = 0.55 in.
p i k ,
V
6
P exp = 21.3 kip
30
1.5 in.
) 3 ( . n i 1.5 in. 4 . 1 2 =
V
1.5 in.
x = 21.4 in. 65 in.
20
V /
4
N k ,
M
=
x
10
2
self-weight
0 0
Fig. 9: Comparison of predictions of point load to cause failure of west shear span with test result
50
100
150 M , kip-ft
200
250
0 300
Fig. 10: Comparison of strength predictions with experimental result for the small specimen (Note: 1 in. = 25 mm; 1 in. 2 = 645 mm2; 1 ksi = 6.9 MPa; 1 psi = 0.0069 MPa) www.concreteinternational.com | Ci | NOVEMBER 2015
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a factor of 14.5, the shear stress at failure decreased by a was very similar. However, the d of the large specimen was factor of 2.8 and the crack widths near failure increased by a 14.5 times d of the small specimen. factor of about 3.8. For the small specimen, both Eq. (1) and The shear capacities of the small specimen at different (2) gave excellent predictions, which were within ±10% of the values of bending moment as predicted by Eq. (1) and (2) are experimental result. shown in Fig. 10. The most signicant difference between the two predicted interaction lines is that Eq. (2) predicts a more Summary and Recommendations signicant reduction in shear strength as moment increases. To investigate the ability of current design procedures to Because for this small specimen self-weight shears are predict the shear strength of very thick slabs, a specimen negligible, the section d from the face of the loading plate is representing a strip cut from a 13 ft (4 m) thick slab was predicted to be critical. In the experiment, failure occurred constructed and loaded to failure under an off-center point when the applied point load reached 21.3 kip (94.8 kN), load. Prior to loading of the specimen, engineers were invited corresponding to a shear force of 10.7 kip (47.4 kN). The to predict the magnitude of the point loads required to fail the failure cracks for the two specimens were similar, but the two shear spans. The shear strength of the longer shear span crack in the small specimen was proportionally somewhat (with no shear reinforcement) of the very thick slab was closer to the load point. This time, the three cracks crossing dangerously overestimated by many engineers—44% of the middepth on the failure side of the specimen were spaced at 66 entries predicted failure loads that were more than 1.5 times 0.50d and 0.78d . For the small specimen, the nominal shear the experimental value and 12% of the entries predicted stress at failure was 149 psi (1.03 MPa) or 1.85 , and the failure loads that were more than 3 times the experimental maximum crack width just prior to failure was 0.20 mm value. The prediction per the basic equation in ACI 318-14, (0.008 in.). In contrast, the nominal shear stress at failure which does not account for the size effect, was 3.7 times the for the large specimen was only 53 psi (0.365 MPa) or 0.70 , and the maximum crack width measured just prior to experimental value. Although not detailed herein, it should failure was 0.75 mm (0.030 in.). Thus, as the size increased by also be noted that predictions made per Eurocode 2,7 which also underestimates the size effect, indicated a failure load that was 2.0 times the experimental value. It is concluded that these two traditional shear design procedures can seriously overestimate the strength of very thick slabs in long shear spans not containing shear reinforcement. The second and more positive conclusion is that, as shown by 20% of the entries and three of the codes, excellent estimates of failure load for such shear spans can be made. The engineers who developed the basic ACI expression for shear strength, Eq. (1),3 intended that engineers should account for the detrimental effects of moment when designing for shear. Unfortunately, this expression, which was based on tests of small, heavily reinforced beams, seriously underestiACI’s Online Career Center brings mates the inuence of moment and neglects the inuence of together great job opportunities and member size on shear stress at failure. Slabs, in contrast, great candidates. usually have low reinforcement ratios and can be very thick. With this combination of variables, Eq. (1) can be very This job search engine is specifically unconservative—as the experiment in this paper demonstrates. targeted to the concrete industry. As shown in this project and in the research of Sherwood • Easy online job management et al.,12 the addition of minimum shear reinforcement to a • Resume searching access very thick slab can more than triple the shear strength of the • Company awareness slab. ACI 318-14, however, suggests that adding minimum • FREE Student Internships shear reinforcement will increase the shear strength by a factor of only 1.38, irrespective of the thickness of the slab. Don’t miss this unique opportunity to Traditionally, the thickness of slabs has been chosen so that be seen by an exclusive audience of shear reinforcement is not required because placing shear the industry’s best and brightest! reinforcement was regarded as expensive and the predicted Visit www.concrete.org . benets of including it were small. The ability to use large headed bars as shear reinforcement and space the bars further apart than 24 in. (600 mm) signicantly reduces placing costs. More importantly, the addition of this shear reinforcement will totally transform the shear behavior of the slab. For very
r e t n e C r e e r a C s ’ I C A
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thick slabs with shear spans long enough to negate direct strut action, safe designs can be ensured by providing at least minimum shear reinforcement.
Size on Beam-Shear Strength of Thick Slabs,” ACI Structural Journal , V. 104, No. 2, Mar.-Apr. 2007, pp. 180-190. Selected for reader interest by the editors.
Acknowledgments This project would not have been possible without the assistance of many experienced engineers, technicians, and research assistants. The 95 engineers from 17 different countries who took the ti me and had the courage to answer the challenge of predicting the shear capacity of the very thick slab made it possible to evaluate the current state of the art. Headed Reinforcement Corporation (HRC) was kind enough to donate the headed reinforcement and the couplers, while Dufferin Construction, an operating division of Holcim Canada, generously donated the large quantity of concrete. In addition, Aluma Systems supplied and erected the formwork, Amherst Group did the concrete pumping, and Ontario Cutting and Coring assisted with the demolition of the tested specimen. The enthusiasm and skill of the laboratory staff and of the research assistants made it possible to complete this complex project in the limited time available. Many of them are shown in the cover photograph. Finally, the long-term support of the Natural Sciences and Engineering Research Council of Canada (NSERC) is greatly appreciated.
References 1. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary,” American Concrete Institute, Farmington Hills, MI, 2014, 519 pp. 2. “AASHTO LRFD Bridge Design Specications and Commentary,” sixth edition, American Association of State Highway Transportation Ofcials, Washington, DC, 2012, 1264 pp. 3. ACI-ASCE Committee 326, “Shear and Diagonal Tension,” ACI Journal Proceedings, V. 59, No. 1, 2, and 3, Jan., Feb., and Mar. 1962, pp. 1-30, 277-334, and 352-396, respectively, and discussion and closure, Oct. 1962, pp. 1323-1349. 4. Vecchio, F.J., and Collins, M.P., “The Modied Compression-Field Theory for Reinforced Concrete Elements Subjected to Shear,” ACI Journal Proceedings, V. 83, No. 2, Mar.-Apr. 1986, pp. 219-231. 5. “CSA A23.3-14 - Design of Concrete Structures,” Canadian Standards Association, Mississauga, ON, Canada, 2014, 290 pp. 6. “ b Model Code for Concrete Structures 2010 (MC2010),” International Federation for Structural Concrete ( b), Ernst & Sohn, Lausanne, Switzerland, 2013, 402 pp. 7. EN 1992-1-1:2004, “Eurocode 2: Design of concrete structures — Part 1-1: General rules and rules for buildings,” European Committee for Standardization, CEN, Brussels, Belgium, 2004, 225 pp. 8. “AS 3600-2009: Concrete Structures,” Standards Australia, Sydney, Australia, 2009, 206 pp. 9. Response-2000, available for download at www.ecf.utoronto. ca/~bentz/r2k.htm. 10. Mihaylov, B.I.; Bentz, E.C.; and Collins, M.P., “Two-Parameter Kinematic Theory for Shear Behavior of Deep Beams,” ACI Structural Journal , V. 110, No. 3, May-June 2013, pp. 447-455. 11. Uzel, A.; Podgorniak, B.; Bentz, E.C.; and Collins, M.P., “Design of Large Footings for One-Way Shear,” ACI Structural Journal , V. 108, No. 2, Mar.-Apr. 2011, pp. 131-138. 12. Sherwood, E.G.; Bentz, E.C.; and Collins, M.P., “Effect of Aggregate
ACI Honorary Member and Professor Michael P. Collins teaches structural engineering at the University of Toronto, Toronto, ON, Canada. He is a member and former Chair of Joint ACI-ASCE Committee 445, Shear and Torsion, and a former member of ACI Committee 318, Structural Concrete Building Code. At Toronto, he has led a long-term research project aimed at developing rational but simple shear design procedures for both reinforced and prestressed concrete structures. The results of this work have inuenced design
provisions for buildings, bridges, nuclear containment structures, and oshore concrete platforms. As a consulting engineer, Collins
has been involved in a number of failure investigations and in evaluating and strengthening concrete structures in distress. Evan C. Bentz, FACI, is an Associate Professor of civil engineering at the University of Toronto. He received his bachelor’s degree from the University of Waterloo, Waterloo, ON, Canada, in 1994, and his PhD from the University of Toronto in 2 000. He is the author of the sectional analysis program Response, is Chair of ACI Committee 365, Service Life Prediction, and a member of Joint ACI-ASCE Committee 445, Shear and Torsion. He has received four teaching awards and two awards for technical papers. Phillip T. Quach is completing his Masters of Applied Science degree at the University of Toronto and the tests in this paper will form part of his MASc thesis. He received his bachelor’s degree in civil engineering from the University of Toronto in 2013. During his professional experience year, he worked in the structural engineering group at Golder Associates Ltd., Toronto. Giorgio T. Proestos is a joint PhD candidate at the University of Toronto and the Institute for Advanced Study of Pavia, Italy (IUSS). In 2012, he received his BASc in engineering science, with a structural engineering specialty, from the University of Toronto, and his MASc in civil engineering in 2014.
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Quality Control for Concrete Durability A case study provides comparisons of work performed under performance and prescriptive specifications
by Odd E. Gjørv
I
n 2005, a new development project began in the Tjuvholmen to be fullled for a 100-year service life according to thencurrent European concrete standards. To obtain greater neighborhood in the harbor region of Oslo, Norway. This project comprises a number of business and apartment durability and service life of the structures, the owner would have preferred having all contracts based on the DURACON buildings built on concrete substructures positioned in seawater (Fig. 1). The substructures, for which the highest (Durability Design of Concrete Structures) Model. 1,2 This model provides for probability-based durability design, possible durability and service life were required, were performance-based concrete quality control, quality assurance nished by 2010. with documentation of achieved construction quality, and In shallow water, the structures typically include a solid condition assessment during operation of concrete structures concrete bottom slab on the sea bed. The slab is surrounded in severe environments (Fig. 4). While application of the by concrete walls partly protected by riprap or wooden DURACON Model became an option in the nal contract, the cladding and partly exposed to the tides. In deeper water, some structures include an open concrete deck on columns of contract still required documentation of the achieved construction quality based on the DURACON procedures. driven steel pipes lled with concrete, while other structures The project was carried out by two different contractors. comprise four large concrete caissons extending as much as One of them (Contractor A) applied the DURACON Model as 20 m (66 ft) below the surface. Three of these caissons a basis for the contract. This contractor was in charge of the provide up to four levels of parking (Fig. 2). The caissons rst four parts of the project, mainly including the solid were prefabricated in dry docks, oated into position, and concrete bottom slabs with perimeter concrete walls exposed submerged (Fig. 3). to the tidal and splash zones. The experience obtained from For all concrete substructures, the owner and developer of the durability design and concrete quality assurance of these the project required a service life of 300 years, which meant that the highest possible durability and long-term performance concrete structures has been reported in a previous article.3 The other contractor (Contractor B) applied the prescriptivewere needed. As a minimum, all durability requirements had
Fig. 1: The new city development on Tjuvholmen in the Oslo harbor (photo courtesy of Terje Løchen)
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Fig. 2: Large, prefabricated concrete caissons shown in rendering provide up to four levels of submerged parking
based durability requirements according to the then-current European concrete standards but with some additional requirements and protective measures as a basis for the contract. Contractor B was in charge of the last four parts of the project. These structures mainly included the four large caissons prefabricated in dry docks at two different construction sites. In addition, a number of open concrete decks were also included, partly as prefabricated elements, but mostly produced on site. Because documentation based on the DURACON procedures was required to determine the achieved construction quality of all concrete structures, the project created a unique opportunity for comparing the results obtained through the use of performance and prescriptive specications. Further results and experience from the durability design and concrete quality control of the project’s concrete structures are described and discussed in more detail elsewhere.2 Specied Durability For design according to the DURACON Model, the overall durability requirement is based on the specication of a given “service period” before the probability for onset of steel corrosion exceeds a certain upper level. In accordance with current standards for reliability of structures, a probability of 10% is adopted for this level. To calculate the probability of corrosion, durability analyses are carried out, providing a basis for selecting proper combinations of concrete quality and concrete cover which would meet the required service period for the given environment. Procedures and input for durability design are described and discussed in more detail elsewhere,1,2 but it should be noted that in the DURACON Model, the concrete quality is characterized by the chloride diffusivity ( D) according to the rapid chloride migration (RCM) method. 4 The RCM method does not require pre-curing of the concrete and so can be carried out very rapidly, independent of concrete age. Because the method provides a very strongly accelerated test, the results can be considered only as a simple relative index. However, the results vary with the density and permeability of the concrete as well as the ion mobility in the pore solution of the concrete, so they do reect a concrete mixture’s resistance to chloride ingress and thus its general durability properties. Using the 28-day chloride diffusivity ( D28) as an input parameter for durability design can be compared to using the 28-day compressive strength as an input parameter for structural design—both parameters are actually relatively simple indexes that can be used to establish that a concrete mixture is t for purpose. However, it should be noted that the 28-day chloride diffusivity is a much more sensitive concrete quality parameter than the 28-day compressive strength. Performance-based durability requirements (Contractor A)
Because the current procedures for probability-based durability design according to the DURACON Model are not considered valid for a service period of more than 150 years,
the overall durability requirement to the concrete structures in the rst four parts of the project (Contractor A) was based on a probability of corrosion as low as possible and not exceeding 10% for a service period of up 150 years. To further ensure
(a)
(b) Fig. 3: Large concrete caissons were: (a) prefabricated in dry docks; and (b) moved into position and submerged in water up to 20 m (66 ft) deep
Fig. 4: The DURACON Model includes concrete quality control and quality assurance measures, documentation of achieved construction quality, and condition assessment during operation of concrete structures in severe environments1,2 www.concreteinternational.com | Ci | NOVEMBER 2015
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the durability of the structures, some additional protective Prescriptive-based durability requirements measures were applied. For the rst concrete structure (Contractor B) constructed by Contractor A, provisions were provided for For all the concrete substructures in the last four parts of future cathodic protection in combination with embedded the project (Contractor B), the durability requirements were probes for chloride control. For the other three structures, the primarily based on the prescriptive durability requirements additional protective measure was based on a partial replaceaccording to the then-current European concrete standards for ment of plain carbon steel reinforcing bars with EN 1.4301/ a 100-year service life. These provisions included a maximum AISI 304 stainless steel bars. water-binder ratio (w/b) of 0.40 and a minimum binder To select a proper combination of concrete quality and content of 330 kg/m3 (556 lb/yd3). Provisions also included concrete cover, an initial durability analysis was carried out. nominal concrete covers for the permanently submerged parts Because the concrete quality in the durability design was and the tidal/splash zones of 60 and 70 mm (2.4 and 2.8 in.), based on the RCM diffusivity, current experience with the respectively. To further increase the durability, however, the RCM diffusivity of different types of concrete had to be nominal concrete cover for the permanently submerged slabs 2 reviewed. On this basis, a concrete with blast-furnace of the caissons was increased from 60 to 80 mm (2.4 to 3.1 in.), slag cement with 70% slag (CEM III/B 42.5 LH HS) in while for all external walls with tidal and splash exposure, it combination with 10% silica fume was adopted. This was increased from 70 to 90 mm (2.8 to 3.5 in.). For the mixture typically provides a D28 of 2.0 × 10 –12 m2/s. A submerged parts of the structures, cathodic protection in the nominal concrete cover of 100 ± 10 mm (4 ± 0.4 in.) was form of sacricial anodes was also applied, while above also adopted, while all the other input parameters needed for water, provisions were made for future installation of cathodic the durability design were based on current experience for protection in combination with embedded instrumentation for the local marine environment. As a result, a probability for future chloride control. corrosion of less than 0.3% after a 150-year service would be attained for the most exposed parts of the structures. Concrete Quality Control Therefore, the aforementioned values for the D28 and the As a basis for the performance-based concrete quality nominal concrete cover were adopted as intended values for control, ongoing control of both the chloride diffusivity the rst concrete substructure. Resistance to freezing was (RCM) of the concrete and the concrete cover were carried also required, and to reduce the risk for early-age cracking out throughout concrete construction. For all the concrete of the 100 mm (4 in.) concrete cover, synthetic bers were structures for which the probability-based durability design required in the mixture. was applied, the specication called for a D28 of 2.0 10 –12 m2/s While provisions for future cathodic protection were or less, while for all the other concrete structures that were applied as an additional protective measure for all exposed only based on prescriptive durability requirements, the D28 walls of the rst concrete substructure, no additional protective value had to be determined for the given concrete of each new measure for the continuously submerged bottom slab was concrete structure before concrete construction started. considered necessary due to the very low oxygen availability. Although the RCM method is a very rapid test method For the second concrete structure, which consisted of an which provides data on the chloride diffusivity within a few open concrete deck on columns of driven steel pipes lled days, this is not good enough for the regular quality control with concrete, the additional protective measure was based on during concrete construction. Based on the DURACON partial replacement of plain carbon steel reinforcing bars with procedures, therefore, a calibration curve relating the chloride stainless steel bars. Because this protective measure very soon diffusivity and the electrical resistivity of the given concrete proved to be a simple and robust technical solution and even mixture must be established before concrete construction proved to be economically competitive, a partial use of starts (Fig. 5). Then, the D28 value is indirectly controlled by stainless steel was adopted for the most exposed sections of regular nondestructive testing of the electrical resistivity of the remaining parts of the project. the concrete during concrete construction. All of the quality When plain carbon steel was replaced by stainless steel in control measurements of the electrical resistivity were made the outer layer of the reinforcing bar system, the effective on compressive strength test specimens (immediately before concrete cover to the carbon steel reinforcement increased to the specimens were tested for strength) using the four-electrode more than 150 mm (6 in.). As a consequence, the nominal (Wenner) method. concrete cover to the stainless steel bars could be reduced to Because the specied concrete covers were substantial and 85 ± 10 mm (3.3 ± 0.4 in.) while still maintaining a very low the reinforcement system was mostly highly congested, it probability of corrosion. At the same time, the addition of was very difcult to measure the cover thickness accurately bers to the concrete for these parts of the structures was no using conventional cover meters. The use of stainless steel longer considered necessary. For all the solid bottom slabs, reinforcement further complicated the quality control however, plain carbon steel with a nominal concrete cover of measurements. While sophisticated scanning equipment for 100 ± 10 mm (4 ± 0.4 in.) and concrete with synthetic bers control of thick concrete covers does exist,2 a more pragmatic were still applied. approach, based on manual readings of the cover depth on ×
40
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Table 1: Probabilities of corrosion based on regular quality control measurements of the 28-day chloride diffusivity and concrete cover (Contractor A)
Fig. 5: Typical calibration curve for an indirect control of the 28-day chloride diffusivity (RCM) based on electrical resistivity measurements
protruding bars in all construction joints during concrete construction, was applied. If the quantity of such control measurements was sufcient to produce reliable statistical data, this simple approach was considered adequate for the regular quality control and quality assurance during concrete construction.
Achieved Construction Quality Upon completion of the concrete construction of each new structure, all data from the regular concrete quality control tests were incorporated as new input parameters for durability analyses used for documenting the achieved construction quality. Because the control of the 28-day chloride diffusivity was only carried out on small and separately produced concrete specimens cured in the laboratory for 28 days, the values may be quite different from that obtained on the construction site. Therefore, some additional documentation of achieved chloride diffusivity on the construction site and the long-term diffusivity of the various types of concrete are also required according to the DURACON approach. As a basis for the documentation, it should be noted that the achieved construction quality is characterized and quantied in the form of the obtained corrosion probability for the required service period of 150 years. Compliance with durability requirements
For all concrete substructures in the rst four parts of the project (Contractor A), a probability of corrosion as low as possible and not exceeding 10% for a 150-year service period was specied. To show compliance, a new durability analysis had to be carried out upon completion of each new concrete structure. These analyses were carried out with input parameters based on the achieved average values and standard deviations of both the 28-day chloride diffusivity and the concrete cover from the regular quality control. All of the other previously assumed input parameters were kept the same. Hence, this documentation primarily reects the results obtained from the regular control of concrete quality and concrete cover during concrete construction, including the scatter and variability
Part of project
Bottom slab, %
External walls, %
Open deck, %
1
0.24
2.1
0.13
2
0.92
0.02
NA
3
0.64
0.002
NA
4
0.01
<0.001
NA
observed. For all the structures where a given value of the 28-day chloride diffusivity had been specied, any unacceptable deviation from this value could be detected and corrected for during concrete construction. For the rst concrete substructure in Part 1 of the project, delivered concrete was somewhat retarded compared to the intended type of concrete. Thus, the obtained average 28-day chloride diffusivities of 3.0 and 5.0 × 10 –12 m2/s for the bottom slab and the external walls of this structure, respectively, were higher than the specied maximum value of 2.0 × 10 –12 m2/s. However, because this concrete showed a very rapid further reduction of chloride diffusivity over time, it was accepted for the project. For all the external walls in the rst concrete structure where a nominal concrete cover of 100 mm (4 in.) was specied, an average concrete cover of 102 mm (4.02 in.) with a standard deviation of 8 mm (0.3 in.) was obtained. For one of the sections in these walls, however, the quality control tests revealed a distinct deviation. For this particular section, an average concrete cover of only 74 mm (2.9 in.) with a standard deviation of 8 mm (0.3 in.) was observed, and as a consequence, the contractor was required to apply an additional protective surface coating on this particular section of the wall. For this rst concrete structure as a whole, however, as well as the open concrete deck with stainless steel in the second structure of Part 1 of the project, the probabilities of corrosion were signicantly below the specied 10% (refer to Table 1). The specied durability was also achieved with very good margins for all of the additional concrete structures in Parts 2 to 4 of the project. For the concrete substructures in Parts 5 to 8 of the project, which were only based on prescriptive durability requirements (Contractor B), it was not possible to provide any documentation of compliance with the durability specication. Because a performance-based concrete quality control program was also carried out for all these structures, however, documentation of the achieved construction quality in the form of corrosion probability after 150 years could also be calculated (Table 2). The durability analyses were based on the average values and standard deviations of both the 28-day chloride diffusivity and the concrete cover from the regular quality control evaluation of each structure. www.concreteinternational.com | Ci | NOVEMBER 2015
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Table 2: Probabilities of corrosion based on regular control measurements of the 28-day chloride Part of the project
Bottom slab, %
External walls, %
Open deck, %
5
15
3
6
6
*
11 to 13
NA
7
14
1.3
NA
8
NA
NA
4.5
No quality control measurements for the bottom slab were carried out
*
The generally higher corrosion probabilities obtained for all the concrete substructures in Parts 5 to 8 (Table 2) com pared to that in Parts 1 to 4 of the project (Table 1) may be ascribed to several sources. For all the concrete structures in Parts 1 to 4, the concrete was based on a blast-furnace slag cement with 70% slag (CEM III/B 42.5 LH HS) in combination with 10% silica fume, while all the concrete structures in Parts 5 to 8 were produced with concrete based on y ash cements in combination with 5% silica fume. For most of these structures, a y ash cement with 30% y ash (CEM II/B-V 32.5 N) was applied, but some structures comprised a y ash cement with 20% y ash (CEM II/A-V 42.5 N). It is well known that blast-furnace slag cements generally give both very low chloride diffusivities and a very rapid reduction of chloride diffusivity, even at low curing temperatures, while y ash cements generally give both higher chloride diffusivities and a very slow reduction of chloride diffusivity, particularly at low curing temperatures. For all the external walls in Parts 2 to 4 of the project, stainless steel was also used, while the much higher probabilities for the bottom slabs in Table 2 compared to that of the bottom slabs in Table 1 primarily reect the different concrete covers of 80 and 100 mm (3 and 4 in.), respectively. Although the mixture compositions of the various types of concrete applied to the structures in Parts 5 to 8 of the project were basically the same, the 28-day chloride diffusivities obtained at the different construction sites were quite different from one construction site to the other. Thus, for one of the construction sites, the diffusivity varied from 6.4 to 8.9 × 10 –12 m2/s, while for another construction site, it typically varied from 12.1 to 16.7 × 10 –12 m2/s. In-place quality
For documentation of the achieved in-place quality during the construction period, a number of concrete cores were removed from each concrete structure and tested for chloride diffusivity at different ages up to 1 year (Fig. 6). As part of this testing, a number of concrete cores removed from corresponding dummy elements were also included. Upon removal, all of these cores were wrapped in plastic and sent to the laboratory for testing as soon as possible. Based on the achieved chloride diffusivities after 1 year of site curing combined with the achieved site data on concrete cover as 42
NOVEMBER 2015 | Ci | www.concreteinternational.com
Fig. 6: Typical development of chloride diffusivity (RCM) on the construction site and in the laboratory for up to 1 year
Table 3: Probabilities of corrosion based on in-place data collected during the first year Part of project
Bottom slab, %
External walls, %
Open deck, %
1
<0.001
<0.001
0.02
2
<0.001
<0.001
NA
3
<0.001
<0.001
NA
4
<0.001
<0.001
NA
5
70
25
35
6
*
30
NA
7
20
0.6
NA
8
NA
NA
1.2
No quality control measurements for the bottom slab were carried out
*
new input parameters, new durability analyses were carried out for each concrete structure. Also, all the other previously assumed input parameters to the analyses during durability design were kept the same. The typical values of achieved in-place quality expressed as corrosion probability after a 150-year service period are shown in Table 3. For all concrete substructures in Parts 1 to 4 of the project (Contractor A), Table 3 shows very low corrosion probabilities compared to that in Parts 5 to 8 (Contractor B). Also, a high variation of corrosion probability was obtained for the open concrete decks. The generally slow development of chloride diffusivity for concrete based on y ash cements has already been pointed out. In particular, this was true for those structures produced during the winter seasons at low curing temperatures. For marine concrete construction, this may have some implications for an early-age exposure of the concrete to seawater before the concrete has gained sufcient maturity and density.2 For the concrete structure in Part 6, it should be noted that the in-place data on achieved chloride diffusivity were based only on concrete cores from the separately produced dummy element. Thus, the obtained probability of 30% for the external walls of this structure is not very representative. For
one of the external walls of this structure, a severe segregation of the self-consolidating concrete during concrete construction took place. Therefore, separate investigations based on extensive concrete coring of this particular wall were later on carried out. The investigations clearly demonstrated that the durability properties of this segregated concrete were distinctly reduced. However, it was not possible to provide any documentation of increased w/b of the segregated concrete beyond what was specied as a basis for the contract. Also, because the in-place compressive strength of the segregated concrete was just high enough to be acceptable according to the current concrete standard, the owner had to accept the reduced durability properties in this particular structure according to the applied durability specications in the contract.
Table 4: Probabilities of corrosion based on laboratory-produced specimens, water cured in the laboratory for 1 year Part of project
Bottom slab, %
External walls, %
Open deck, %
1
<0.001
<0.001
0.002
2
<0.001
<0.001
NA
3
<0.001
<0.001
NA
4
<0.001
<0.001
NA
5
0.04
0.01
0.01
6
*
0.05
NA
7
0.5
0.01
NA
8
NA
NA
0.5
No quality control measurements for the bottom slab were carried out
*
Potential quality
For most types of binder system, the development of clearly resulted in improved workmanship with reduced chloride diffusivity tends to plateau after about 1 year of water scatter and variability of achieved construction quality. curing at 20°C (68°F) in the laboratory. To provide informaIn contrast, where a prescriptive-based durability specica tion about the potential construction quality of the various tion was applied as basis for the contract, it was not possible structures, the chloride diffusivity was also tested on a number to provide any documentation of compliance to the durability of separately produced and water-cured specimens in the specication. Also, the achieved construction quality of the laboratory for up to 1 year, as shown in Fig. 6. These chloride various concrete structures typically showed a higher scatter diffusivities combined with the achieved site data on concrete and variability. cover were used as new input parameters for further durability analyses. As with the previous analyses, all the other origiReferences nally assumed input parameters were kept the same. Typically 1. NAHE, “Durable Concrete Harbor Structures - Part 1: Recommended achieved values of the potential construction quality of the Specications for New Concrete Harbor Structures, Part 2: Practical various concrete structures are shown in Table 4. Guidelines for Durability Design and Concrete Quality Assurance,” For all structures, the potential construction quality was Norwegian Association for Harbor Engineers (NAHE), TEKNA, Oslo, extremely good. The corrosion probability was hardly Norway, 2004. (in Norwegian) detectable for structures in Parts 1 to 4 of the project (Con2. Gjørv, O.E., Durability Design of Concrete Structures in Severe tractor A) and very low for the concrete structures in Parts 5 to Environments, second edition, CRC Press, Boca Raton, FL, 2014, 254 pp. 8 of the project (Contractor B). 3. Gjørv, O.E., “Durability Design and Quality Assurance of Concrete The results demonstrate that the concrete based on highInfrastructure,” Concrete International , V. 32, No. 9, Sept. 2010, pp. 29-36. volume y ash cements could reach quite a good potential 4. AASHTO TP 64-03, “Predicting Chloride Penetration of Hydraulic construction quality given good curing conditions. Cement Concrete by the Rapid Migration Procedure,” American Association of State Highway and Transportation Ofcials, Washington, DC, 2003.
Concluding Remarks
For all the concrete structures where a performance-based durability specication was applied as basis to the contract, the durability requirements were achieved with very good margins. For the owner and developer of the project, it was very important to receive a documentation of compliance to the durability specication before the structures were formally handed over from the contractor, because this may have implications both for the future operation and expected service life of the structures. Also, it was observed that the performance-based durability specication distinctly claried the responsibility of the contractor for the quality of the construction process. During concrete construction, any unacceptable deviations from the performance-based requirements for concrete quality and concrete cover could be detected and corrected. The required documentation of compliance to the durability specication
Selected for reader interest by the editors.
Odd E. Gjørv , FACI, is Professor Emeritus and former Head of the Department of Building Materials at the Norwegian University of Science and Technology, Trondheim, Norway. He is former General Secretary of the Norwegian Academy of Technical Sciences and has served on several ACI committees, including 201, Durability of Concrete; 222, Corrosion of Metals in Concrete; and 357, Oshore and Marine Concrete
Structures. He has received several international awards.
www.concreteinternational.com | Ci | NOVEMBER 2015
43
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Condition Assessment of Launch Pad 39B Ensuring the historic site at the John F. Kennedy Space Center will continue to make history
by Richard E. Weyers, Alberto A. Sagüés, and Jerzy Z. Zemajtis
S
tarting in 1963 and ending in 1966, the U.S. National Aeronautics and Space Administration (NASA) constructed Launch Complex 39 on Florida’s Merritt Island. Launch Complex 39 has played a major role in the history of NASA’s John F. Kennedy Space Center, as it served as the launch facility for NASA’s Apollo, Skylab, and Space Shuttle programs. The complex includes the Vehicle Assembly Building (VAB), Launch Pads 39A and 39B, and a connecting crawlerway used for the transport of launch vehicles from the VAB to the launch pads. The rst launch from Pad 39A—Saturn V/ Apollo 4 (a test ight)—was on November 9, 1967. The rst launch from Pad 39B—Saturn/Apollo 10—was on May 18, 1969. The last shuttle mission—STS-135—began from Pad 39A with the liftoff of the Shuttle Atlantis on July 8, 2011. The last liftoff from Pad 39B was on October 28, 2009, when the rst stage of an Ares 1-X was launched as a test ight for NASA’s Constellation program. This program was canceled shortly after the initial test ight, but has since been replaced with the Space Launch System (SLS)—an advanced heavy-lift launch vehicle designed to facilitate human exploration beyond earth’s orbit. Pad 39A is now leased to Spacex, which will use it to launch its Falcon Heavy rockets. NASA intends to use Pad 39B to launch the SLS. To inform the decision-making process for modications needed to accommodate the rst SLS launch in 2017, we assessed the reinforced concrete portions of Pad 39B in 2010. The 1964 plans and material specications were reviewed, followed by on-site measurements of cover depths, corrosion potentials, concrete resistivity, and corrosion current density. Finally, we used a durability forecast model, focused on corrosion issues, to support our evaluation and conclusions. The measurements and our conclusions are summarized in this article.
Components and Exposures For this assessment, Launch Pad 39B (Fig. 1) was separated into four components: 1) the crawler pad, comprising two sections, east and west, separated by the ame trench over which the launch vehicle was centered; 2) the pipe tunnels, which are within the crawler pad sections and carry the launch water to the umes and then to the holding ponds; 3) the high-pressure gas bays open to the environment and located on the east side of Pad 39B; and 4) the catacombs, which support the crawler pad on the east and west side of the ame trench. The exterior catacombs are completely soil covered; thus, the only access is through the interior walkways. The east and west catacombs consist of 18 cells each with access through the south end through partial wall openings. In general, each cell is about 40 x 20 ft (12.2 x 6.1 m) in plan
Fig. 1: Launch Pad 39B includes concrete catacombs below the crawler pad (photo courtesy of Jerzy Zemajtis) www.concreteinternational.com | Ci | NOVEMBER 2015
45
and 40 ft in height, with 2.5 ft (0.8 m) thick reinforced through the pipe tunnels to the umes and into the catch basins, concrete walls and a 3 ft (0.9 m) thick ceiling (crawler pad). where it is treated prior to being released to the environment. Launch Pad 39B is about 1/4 mile (0.4 km) west of the The crawler pads, pipe tunnels, and the high-pressure gas Atlantic Ocean, so its surface is exposed to chloride and bays are exposed to windblown ocean water and carbon sulfate ions present in ocean water. Also, below-grade dioxide (CO2), particularly the high-pressure gas bays, which components at or below the water table are exposed to the are open and face the Atlantic Ocean. The catacombs are ionic composition of the groundwater, and the water table closed with the lower walls exposed to groundwater and the elevation raises and falls with the ocean tide. ceilings exposed to launch water. The crawler pads and pipe During launches, the ame trench (Fig. 2) is ooded with tunnels are directly exposed to the launch water. As shown in water to reduce vibration and noise. The pH of this water was Table 1, the catacomb groundwater ionic content is signicantly lowered by residuals from the solid rocket boosters used in the lower than seawater. The level of chloride, sulfate, and shuttle and Ares launches. Following liftoff, the water ows magnesium are relatively low enough not to be aggressive agents to steel-reinforced concrete. In contrast, the neutral pH could be mildly aggressive to noncarbonated portland cement concrete that has a pH of 13. The launch water in the holding pond is the result of the mixing of the various water streams owing off the launch pad through the piping tunnels into the holding pond. The ignition exhaust of the solid rocket boosters increased the chloride content of the holding pond water to about one order of magnitude higher than that of the groundwater, but to a level still much lower than that of seawater. However, the pH of 2 of the holding pond water is very low, making it a very aggressive concrete corrosive agent. The pH of the launch water was measured on the launch pads immediately after a launch. The range of the 12 measurements was 1 to 6. Even considering the relative short contact periods and small number of exposures, the launch water would corrode the concrete surfaces of the crawler pad and pipe tunnels from an extremely corrosive agent at a pH of 1 to a mildly corrosive agent at a pH of 6.
Concrete
Fig. 2: Crawler pad at the launch location. During a launch, the flame trench (foreground) was flooded with water (photo courtesy of Jerzy Zemajtis)
Table 1: Catacomb groundwater and holding pond water test results Analyte/pH
Catacomb
Holding pond
Seawater
Chloride, ppm
150 to 450
1500
20,000
Sulfate, ppm
27 to 120
110
2700
Magnesium, ppm
1.4 to 13.5
18
1400
pH
7.4 to 8.6
2.0
7.5 to 8.4
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The original concrete specication for Pad 39B called for concrete with a compressive strength of 3000 psi (20.7 MPa) and Type II portland cement for mass concrete and Type I otherwise. Coarse aggregate was either maximum 3/4 or 1-1/2 in. (19.0 or 37.5 mm) crushed stone or a blend of crushed stone and uncrushed gravel. Fine aggregate was either natural sand or a blend of natural sand and manufactured sand. Some portions of the structure were intentionally air-entrained and others only contained entrapped air. However, the records available did not show which structure components were to be air-entrained concrete. Test concrete cores were taken in triplicate from the high-pressure gas bays (HPGB), east and west catacomb walls (ECW and WCW), and the west catacomb ceiling (WCC). As shown in Table 2, the concrete density, moisture uptake, and compressive strength were relatively uniform. The average moisture uptake of about 3% by mass or about 6.5% by volume indicated that sufcient void space was open to oxygen penetration to support steel corrosion. Additionally, one core each was taken for petrographic analysis from ECW, WCW, ECC, and WCC. The ECC core was taken over a visible crack in the ceiling. The coarse
Table 2: Average concrete core test results Moisture Density as
uptake, % by
Compressive
Component
rec’d, lb/ft3
mass
strength, psi
HPGB
130.9
3.07
3970
ECW
133.9
3.49
3540
WCW
136.5
3.12
4880
WCC
134.0
2.52
3840
Average
133.8
3.07
4050
Coefficient of variation, %
1.8
16.3
16.0
Note: 1 lb/ft = 16 kg/m ; 1 psi = 0.007 MPa 3
3
aggregate was crushed limestone and the ne aggregate was natural quartz sand. The general quality of the concrete was good and consistent with the original material specications. No deleterious chemical reactions were observed in the hardened cement paste, in the aggregates, or between the aggregates and the cement paste. The aggregates were uniformly distributed within the cement paste and the bond
between the cement paste and aggregate was good. The cement paste was hard to moderately hard and the water absorption was moderate to moderately low. The ECC concrete samples had air contents ranging from 4 to 6%, whereas the other three samples had entrapped air contents of 2 to 3%. Per phenolphthalein pH indicator, the ECC core taken over a visible crack showed carbonation in a V-shape to a depth of 0.9 in. (23 mm). The WCC core was carbonated to a depth of 0.22 in. (6 mm). The carbonation depth of the ECW and WCW cores varied from 0.3 to 1.3 in. (8 to 33 mm).
Reinforcing Steel Two reinforcing steel bar sections each were removed from ECW and WCW and one from HPGB. Tests per ASTM A615/ A615M1 indicated average yield strength at 0.2% offset, ultimate strength, and elongation of 50,800 psi (350 MPa), 87,100 psi (601 MPa), and 27%, respectively, complying with specications for Grade 40 reinforcing steel. 1
Corrosion Survey Tools Corrosion of reinforcement forms expansive corrosion products that most noticeably cause damage in the form of
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concrete spalls, subsequent reinforcing steel section loss, and chloride content of the concrete at the reinforcement depth reduction in structural capacity. Steel is initially prevented and of the extent to which carbonation penetration approaches from corrosion by a thin surface passive lm that forms due to the reinforcement location. the high pH of the pore water. The lm breaks down, however, The onset of corrosion initiation can be inferred to some if chloride ions permeating from the concrete exterior reach extent from nondestructive readings of the electrode potential the steel surface and build up to a threshold concentration difference between the steel and the surrounding concrete, as 3 3 2-4 value C T (typically about 1 lb/yd [0.59 kg/m ] or greater). measured with a Cu/CuSO4 electrode (CSE). As indicated by Corrosion also occurs, even in the absence of chlorides, if the ASTM C8765, highly negative potential values (for example, concrete pore water pH at the steel depth decreases to values less than −350 mV SCE) suggest a high probability that active below about 11. Such a decrease may take place via carbonation, corrosion has already started at the location sampled, while whereby atmospheric CO2 slowly reacts with the cement values more positive than −200 mV SCE may represent a low hydration products, resulting in a decreased pH front progressing probability. However, the interpretation of corrosion potentials inward from the external surface. In older structures such as for steel in concrete must include a knowledge of the moisture Pad 39B, built with what is considered today as highcontent of the cover concrete and the concrete at the steel depth. permeability concrete, chloride and carbonation ingress may After corrosion initiates, it propagates at a rate that varies act synergistically to initiate corrosion. For example, some of with availability of oxygen, moisture, and the extent of the chloride ions that had already penetrated the concrete may electrochemical coupling that may exist with other parts of the have been chemically bound and hence not available to break reinforcement assembly. Those conditions may be assessed by down the steel passive lm. However, on subsequent arrival in-place measurement of the electric resistivity of the concrete of the low-pH carbonation front, the salts may decompose and with a Wenner array probe.6 Steel corrosion in concrete is release the formerly bound chloride ions, thus accelerating usually revealed by low resistivity values (for example, less corrosion initiation. Assessments of the likelihood of corrosion than 10,000 ohm·cm). Additionally, a direct estimate of the in a structure thus usually include measurements of the rate of corrosion can be made with polarization resistance measurements using a 3LP device.6 The result of such a measurement is a value for the corrosion rate, expressed in terms of a nominal corrosion current density iCORR. Values of iCORR greater than 1 mA/ft2 are usually considered to be indicative of actively progressing corrosion, with values between 1 and 10 mA/ft2 indicating a moderate pace and values greater than 10 mA/ft2 indicating a severe pace, respectively.6 Contrary to direct corrosion observation, indirect assessment methods are each subject to uncertainty and their results should be interpreted as a whole rather than relying on ndings of a single technique. The corrosion survey for Launch Pad 39B consisted of visual examination of reinforcement locally exposed by removing the concrete cover, and measurements of potential, corrosion current density, concrete resistivity, relative humidity (RH) and temperature, carbonation penetration, and chloride concentration of the concrete. Carbonation depth was determined using a phenolphthalein solution.
Evaluation
Fig. 3: After determination of corrosion potentials and rates, we removed spalled concrete and visually inspected the reinforcing bars (photo courtesy of Jerzy Zemajtis)
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A total of six catacomb cell wall sections (about 2% of approximately 120,000 ft2 [11,148 m2] of catacomb wall area) and six ceiling sections (about 5% of about 25,000 ft2 [2323 m2] of catacomb ceiling surface area) were surveyed. Based on visual and sounding surveys, about 3.5% of the total catacomb wall survey areas (about 70 ft2 [6.5 m2]) were damaged (spalls plus delaminations). To aid in the assessment of the indirect steel corrosion measurements, reinforcing steel was exposed at eight locations (ve in the WCC and three in the ECC) to visually examine its corrosion (refer to Fig. 3). Prior to exposure, corrosion potentials and rates were determined at the same eight locations.
As shown in Table 3, corrosion products (red rust) were thus demonstrated that sufcient quantity of the concrete pore observed even at potentials less negative than −200 mV, and system is open to allow transport of oxygen to the bar depth. between −200 and −350 mV. The measured corrosion rates For the 36 chloride contents determined for the ECW and were between 1 and 10 mA/ft2, except for one measurement of WCW (18 per each wall), the average and range of the 23.4 mA/ft2. As noted previously, such values would suggest chlorides at the depth of 4.5 in. (114 mm), assumed to be intense corrosion activity. However, direct observations background chloride, were 0.51 and 0.40 to 0.72 lb/yd3 (0.30 showed only very little to moderate corrosion for the locations and 0.24 to 0.43 kg/m3), respectively. Background chloride with corrosion rates between 1 and 10 mA/ft2, and only concentration for concretes in Florida with crushed limestone moderate corrosion for the 23.4 mA/ft2 location. In considering and natural sand is typically 0.1 to 0.2 lb/yd3 (0.06 to 0.12 kg/m3). these discrepancies, it is noted that when carbonation- and Thus, the catacomb aggregate, most likely the sand, contained chloride-induced corrosion of reinforcing steel in concrete about 0.3 to 0.5 lb/yd 3 (0.18 to 0.30 kg/m3) of chloride. Of the occur in concert, interpretation of corrosion potentials and 18 chloride sample locations, only one showed typical rates need to include consideration of the inuence of decrease in chloride content with depth—0 to 5 ft elevation carbonation, as carbonation reduces the concrete pH and for ECW. The remaining 17 locations had lower surface inuences the concrete moisture content. chloride, which then increased and remained relatively Carbonation can affect corrosion potential and rates by constant with depth. drying of the concrete and blocking the pores with carbonation The pH of concrete pore water is normally in the range of products. Anodes and cathodes of carbonation-induced 12 to above 13. A pH of 9 was measured at depths of 0.12 to corrosion cells are very close together, promoting mixed 1.5 in. (3 to 38 mm). Thus, the pH of the concrete increased potential readings, while the removal of hydroxyl and calcium from 9 to more than 12 at depths beyond the measured 9 pH ions across the carbonation front can lead to a junction value. As noted earlier, this pH decrease can free formerly potential superimposed on the corrosion potential, complicating bound background chloride into the concrete pores, as a wave the interpretation of the results. Thus, more extensive chloride of increased free chloride in front of the carbonation front. concentration, carbonation depth, and reinforcing concrete Thus, the measured corrosion rates can be seen as a result of cover depth measurements were conducted to further identify the released free chlorides and reduction in pH of the concrete the extent of corrosion activity. pore water. The estimated depth of release of bound to free chlorides is generally at 1.5 in. (38 mm) for the ECW and Chloride Content 2.2 in. (56 mm) for the WCW. Also, results of concrete cover Catacomb walls and carbonation depth measurements indicate that a portion Chloride content as a function of depth, concrete cover of the reinforcing steel is embedded in concrete with a depth, depth of carbonation at a pH of 9.0 (as revealed by a reduced pH and free chlorides. Thus, the observed corrosion phenolphthalein indicator), and RH and temperature measure- can be viewed as the result of the synergistic relationship ments were taken at three elevation ranges: 0 to 5 ft (0 to 1.5 m), between free chloride and carbonation attack.3 This phenomenon, 7 to 12 ft (2.1 to 3.7 m), and 20 to 25 ft (6.1 to 7.6 m), for the not often reported in U.S. literature, could be expected to entire length of the selected cell walls. Zero elevation was occur in structures such as these considered herein, built with marked at the intersection of the concrete wall and oor. The relatively high water-cement ratio ( w/c) concrete and low average and range of six RH and temperature measurements cement content concrete. at the depth of the reinforcement at the selected locations within the wall sample areas for the east catacomb Table 3: were 98% and 94% to 99%, and 67°F Corrosion potentials, rates, and visible corrosion (19.4°C) and 66 to 68°F (18.8 to 20°C), respectively. For the west Corrosion 3LP device catacomb, the average and range of six potential (CSE), corrosion rate, RH and temperature measurements at mV Location mA/ft Corrosion on reinforcing bar the depth of the reinforcing steel were WCC −278 2.4 Very little on ribs 96% and 90% to 99%, and 68°F (20°C) ECC −400 1.6 Very little on ribs and 66 to 75°F (18.8 to 24°C), respecWCC 2.1 Very little on and between ribs −398 tively. Thus, the RH and temperature are WCC −280 4.1 Little on and between ribs sufcient to support corrosion of the reinforcing steel. Even though the RH WCC −250 2.1 Little on and between ribs values are very high, the concrete ECC −191 4.0 Little on and between ribs moisture uptake of water showed that WCC −390 23.4 Moderate on and between ribs 6.5% of the volume of the concrete ECC 5.7 Moderate uniform over entire surface −210 voids were not lled with water and 2
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Fig. 4: The catacomb ceiling slabs exhibited surface e fflorescence and stalactites at cracks (photo courtesy of Jerzy Zemajtis)
Fig. 5: Corrosion rates on catacomb ceilings at epoxy-injected crack locations were measured after grinding off sections of the epoxy (photo courtesy of Jerzy Zemajtis)
Crawler pads/catacomb ceiling
was measured on a core taken from each of the three catacomb The catacomb ceiling slabs support the crawler pads. The cell ceilings in the east and west catacombs. In addition, a system conguration over the catacomb ceiling slab is a layer pH indicator measured the range of pH change with depth in of lightweight concrete, a sand drainage layer, and the the eld. concrete-lled steel-grate crawler pad. The catacomb ceiling 7 The measured corrosion rates ranged from 1.6 to 29 mA/ft2 had previously cracked from structural overload conditions. at crack locations and 1.7 to 31.5 mA/ft2 at noncrack locations. Drains and piping had been installed to drain the launch Although the corrosion rates were highly variable, they water through the sand layer. In addition, cracks in the indicate an advanced state of active corrosion in localized catacomb ceiling slabs had been sealed by epoxy injection. areas. Based on the range of the concrete depths and carbonation However, water was leaking through some of the epoxydepths, it appears that portions of the reinforcing steel are injected cracks and cracks that were either not sealed or have embedded in concrete that has a pH of less than 12, which formed post-repair. Eforescence and/or stalactites had would result in the release of bound chlorides. Although the formed at leaking crack locations (Fig. 4). Three crawler pads were removed to assess the top surface chloride content as a function of depth was not determined, it is reasonable to state, as in the walls, that the ceiling active of the catacomb ceilings. The sand layer was saturated due to corrosion is the result of a combination of a reduced pore plugged drains that prevented water from getting to the water pH coupled with a release of bound chlorides. piping. The water outlet was through open cracks in the The surveyed ceiling areas exhibited neither spalls nor catacomb ceiling slabs. Carbonation depth measured at two delaminations. An area in one of the surveyed cell ceilings locations was less than 0.15 in. (4 mm). The chloride content at the two locations at a depth of 0.25 in. (6 mm) was 0.25 and had been patched where the concrete cover depth was excessively low—less than 1 in. (25 mm). 0.5 lb/yd3 (0.15 and 0.3 kg/m3) greater than the background 3 3 chloride of about 0.7 lb/yd (0.4 kg/m ), which was relatively High-pressure gas bays constant to a depth of 4.25 in. (108 mm). The ranges of cover As previously noted, the open conditions of the HPGB depths were highly variable for the three exposed top surfaces of the catacomb slabs, 2.2 to 8 in. (56 to 203 mm), 4.5 to 4.8 in. allowed for exposure to windblown chlorides, CO2, and wetting and drying conditions. Delaminations and exposed (114 to 122 mm), and 5.6 to 6.3 in. (142 to 160 mm). The reinforcing steel existed in a number of relatively large areas saturated concrete conditions would account for the low comprising about 30% of the surface. Chloride content at a carbonation penetration. The chloride at the bar depths remained in the bound state and thus not free to initiate corrosion. depth of 0.25 in. (6 mm) ranged from 1.55 to 2.67 lb/yd 3 Corrosion testing of the catacomb ceiling included carbon- (0.92 to 1.58 kg/m3). The chloride content then decreased with depth and then increased to 1.84 and 2.53 lb/yd3 (1.09 and ation depth, cover depth, and corrosion rate. Corrosion rates 1.50 kg/m3) at a depth of 1.5 in. (38 mm). The chloride were measured at epoxy-injection crack locations and at content at 4.25 in. (108 mm) was about 0.7 lb/yd3 (0.4 kg/m3). noncrack locations within three catacomb cells in the east The range of cover depths within the three bays of measured and west catacombs. The epoxy was removed by grinding prior to the corrosion rate measurements (Fig. 5). Carbonation chloride was 1.0 to 1.4 in. (25 to 36 mm). Thus, the observed 50
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corrosion damage, exposed reinforcing steel, and delaminations were a combination of windblown chloride ingress, carbonation, and relatively low concrete cover. Pipe tunnel walls
Spalling of cover concrete and delaminations were observed where the concrete cover was less than 0.75 in. (19 mm). The pH of the concrete was 11 from the surface to about 8 in. (203 mm) depth. In addition, acid attack of the cement paste and limestone aggregate had occurred. The limestone aggregate aided in buffering the acidic launch water, thus reducing the depth of acid attack of the cement paste to a shallow surface depth.
Modeling
where P cum( z , z av,σ z ) is the cumulative normal distribution of variable z that has an average value of z av and a standard deviation σ z . For this case, the distribution was truncated at a value of xm = 0.5 in. (13 mm), as during the survey only one cover depth was measured at value of less than 0.5 in. The fraction of elements having values within an interval of ∆k of k is given by f k (k ) = P (k ,k av,σk )∆k
(6)
where P ( z , z av,σ z ) is a normal probability distribution, same terminology as for P cum. Dividing the interval k = 0 to k = k av + 3σk into small equal segments ∆k centered on k 1, k 2, k i, the fraction of all elements that have spalled by time t s is then given by
The purpose of modeling was to estimate future spalling damage for the catacomb walls and ceilings considering the f (t s) = ∑ [ P cum( x(k i,t s), xav,σ x)· P (k i,k av,σk )∆k ] (7) i selected test locations as a representative sample of the whole. The corrosion model followed the sequence of time events of Equation (7) therefore projects the amount of corrosion-related corrosion initiation plus a propagation period from initiation damage as a function of structure age. For example, for every to spalling of the cover concrete, treating the structure as 1000 ft2 (93 m2) of external structure surface, it is projected consisting of a number of independently evolving elements that a total of 1000 f (t s) ft2 of surface repairs will be needed 8 with statistically distributed corrosion parameters. by age t s. The model is based on the assumption that due to release of chlorides on decrease of the pH due to carbonation, corrosion initiates at some unknown advance distance d , ahead of the carbonation front as measured by a phenolphthalein pH indicator. For a given element at a concrete cover depth x, the time to corrosion initiation t i may be expressed as3,9
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x = kt i1/2 + d
(1)
t i = (( x – d )/k )2
(2)
where k is the carbonation coefcient. With the addition of the propagation period t p, the time to spalling t s is expressed as t s = t i + t p = (( x – d )/k )2 + k p x
■ ■
Or how you solved a constructibility issue… Or any topic related to design and construction.
(3)
where k p is a coefcient indicating that the length of the propagation stage is proportional to the local cover depth x assuming that the reinforcing bar diameter is about the same throughout the structure. 8 Equation (3) is a quadratic equation for which the positive solution is x(k ,t s) = d – k 2k p/2 + (k 4k p2/4 – dk 2k p + k 2t s)1/2
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(4)
Thus, the element that spalls at time t s has a cover depth x given in Eq. (4). Any element having a cover depth less than x and the same value of k would have spalled before the t s value. Therefore, the fraction of elements having the same value of k , that spalled by the time t s, may be expressed as f x( x(k ,t s)) = P cum( x(k ,t s), xav,σ x)
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Table 4:
average cover xav (about 1/3 to 1/2) for all three elevation zones. That large dispersion in the cover values implies Elevation * * −0.5 −0.5 * * a high incidence of low-cover spots, σ x , in. σk , mm·year xav , in. k av , mm·year Components regime, ft even when the average is relatively 2.5 2.06 0.76 large. The nearly linear increase in Walls 9.5 2.24 0.90 2.84 1.36 damage is characteristic of such cases 22.5 2.93 0.98 where the slowly rising end of a broad Ceilings — 1.72 0.37 2.88 1.4 distribution of value is involved. 8 The * Assigned globally, refer to the text projected damage for walls at age 40 years (the time of the survey) is important because it may serve as the basis for validation or calibration of the model. The observed amount of damaged area in the surveyed walls, noted earlier, was approximately 3.5% of the total wall surveyed area. The alternative with d = 5 mm (0.2 in.) projects the closest value to observation—about 4% at 40 years, suggesting that d values of 10 and 20 mm (0.4 and 0.8 in.) may be overly conservative. The base case gives a gradual and nearly linear future damage projection, Fig. 6: Corrosion damage trend projections for walls and ceilings for alternative choices of with about twice more damage in the the advance parameter d . Projections with d = 5 mm (0.2 in.) were closest to observations for next 40 years than that observed at the walls. (Note: 1 mm = 0.04 in.) present. That relatively slow rate of progression (about 0.12% per year) is Modeled cases and input parameters a consequence of the assumed broad distribution of cover The relevant parameters for the catacomb walls and the based on sampling of 2% of the walls. We recommended more ceilings are listed in Table 4. Carbonation coefcients and extensive cover surveys if there was a need to reduce uncertheir variability were obtained from the surveyed carbonation tainty in forecasting future deterioration. depths and the nominal structure age at the time of the surveys The damage projection for the ceilings (adopting also (40 years). There was little differentiation between the k results d = 5 mm as a base case estimate) includes a rapid rise after for walls and ceilings, but the latter exhibited signicantly an initial slow rate period. This shape reects the distinctly lower reinforcement cover as a group, so separate damage narrower relative distribution of ceiling reinforcement covers projections were calculated for walls and ceilings. Reinforcing compared to that for the walls (Table 4). Thus, even though bar cover at the walls was found to change systematically with the average cover in the ceilings is only about 2/3 that of the elevation, so the walls were divided into three elevation walls, the narrower distribution in the former implies fewer regimes, centered at 2.5, 9.5, and 22.5 ft (0.76, 2.9, and 6.9 m) instances of very low cover values than in the latter, with elevations, corresponding to 17%, 28%, and 55% of the total consequently lower amount of projected damage at early ages, wall surface, respectively. ECW and WCW results were treated including 3.7% for the 40-year age at the time of the survey. as one group. Parameter k p was globally assigned a value of Conversely, the faster rise (0.34% per year) starting at about 8,10 0.197 year/mm per prior ndings. The value of the advance present age is a consequence of the low average cover in the distance d was not known precisely but examination of ceilings. Thus, the projected damage there for the next 40 years chloride concentration proles and carbonation patterns is substantially greater than for the rst 40 years. Comparison suggested that d may be somewhere between 5 and 20 mm between projected and observed present damage for the (0.2 and 0.8 in.). Hence, alternative damage projections were ceilings is uncertain. There was little documented corrosion d made globally parametrizing over that range. damage at the ceilings, but some of the half-cell potential The resulting damage projections are shown in Fig. 6, where values were suggestive of corrosion in progress. Extensive the results for the three wall elevation zones were combined cracking of some ceiling areas may also be corrosion related. as a weighted average for simplicity, given that the differentiation among elevation regimes was relatively moderate. Implementation The shape of the damage function for the walls reects the The condition assessment was based on extending the large value of σ x (cover standard deviation) relative to the service life of Launch Pad 39B an additional 40 years. The Parameters used for model damage projections
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options for extending the service life include patching the present damaged areas with portland cement concrete (and continuing to do so as needed), installing an impressed current cathodic protection system, re-alkalization of the concrete, or applying a sprayed zinc system at localized spalled and delamination areas and inspecting the structure every 2 years. Based on the modeling results, the owner decided to employ the sprayed zinc option.
Conclusions The primary deterioration mechanism of Launch Pad 39B is the corrosion of the reinforcing steel from carbonationreleased chlorides present in the concrete mixture at the time of construction. The reinforcing steel cover depth measurements for the walls indicated a wide variability from wall to wall in the catacombs. The relatively large variability resulted in a steady projected corrosion damage in the walls from the present to about twice the value in 40 years. The ceiling damage rate projections are greater than the wall damage rate estimates. The estimated distance in front of the carbonation front, where corrosion initiates, has a relatively large impact on the increase in estimated corrosion damage. A selection of d = 5 mm (0.2 in.) was a better estimate than greater assumed values. Modeling results were used to provide input in selecting repair and rehabilitation options along with other criteria as required by additional service life and budget constraints. Acknowledgments The authors acknowledge CTLGroup, Skokie, IL, who performed on-site corrosion-related testing and the laboratory testing of the concrete and reinforcing steel specimens. Appreciation is extended to Steve Laux, John Schmitt, and Nick Pontillo of Jones Edmunds & Associates for their assistance in procuring historical documents, site history, and guidance, and to Rod Powers for his technical review of the report from which this article was derived.
References 1. ASTM A615/A615M, “Standard Specication for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement,” ASTM International, West Conshohocken, PA. 2. Angst, U.; Elsener, B.; Larsen, C.K.; and Vennesland, Ø., “Critical Chloride Content in Reinforced Concrete – A Review,” Cement and Concrete Research, V. 39, No. 12, 2009, pp. 1122-1138. 3. Broomeld, J.P., Corrosion of Steel in Concrete: Understanding, Investigation and Repair , second edition, Taylor and Francis, 2007, 296 pp. 4. Brown, M.C., “Corrosion Protection Service Life of Epoxy Coated Reinforcing Steel in Virginia Bridge Decks,” dissertation in Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, May 2002, 269 pp. 5. ASTM C876, “Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete,” ASTM International, West Conshohocken, PA, 1991. 6. Balakkumarun, S.S.G., “Corrosion Testing and Modeling of Chloride-Induced Corrosion Deterioration of Concrete Bridge Decks,”
dissertation in Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, Mar. 2012, 229 pp. 7. Launch Pad 39B Infrastructure Study, PCN 98656, Center Operations Directorate, John F. Kennedy Space Center, NASA, KSC-TA-9122, Mar. 25, 2008, 185 pp. 8. Sagüés, A.A., “Modeling the Effects of Corrosion on the Lifetime of Extended Reinforced Concrete Structures,” Corrosion , V. 59, No. 10, Oct. 2003, pp. 854-866. 9. Bertolini, L.; Elsener, B.; Pedeferri, P.; and Polder, R.B., Corrosion of Steel in Concrete, John Wiley & Sons, Inc., New York, 2004, 392 pp. 10. Williamson, G.S.; Weyers, R.E.; Brown, M.C.; Ramniceanu, A.; and Sprinkel, M.M., “Validation of Probability-Based Chloride-Induced Corrosion Service-Life Model,” ACI Materials Journal , V. 105, No. 4, July-Aug. 2008, pp. 375-380. Received and reviewed under Institute publication policies.
Richard E. Weyers, FACI, is the Virginia Tech Charles E. Via Jr. Professor Emeritus, Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA. He has over 40 years of consulting and teaching experience in concrete durability, corrosion of steel in concrete, and service life modeling. He is a member of ACI Committees 222, Corrosion of Metals in Concrete; 345, Concrete Bridge Construction, Maintenance, and Repair; and 365, Service Life Prediction. He received his BS, MS, and PhD in civil engineering from the Pennsylvania State University, State College, PA. ACI member Alberto A. Sagüés is a distinguished university professor, Civil and Environmental Engineering, University of South Florida, Tampa, FL. He is also a Fellow of NACE International. For the last three decades he has conducted research in the area of corrosion and durability of infrastructure engineering materials. He received his PhD from Case Western Reserve University, Cleveland, OH. Jerzy Z. Zemajtis is Senior E ngineer, ACI, Farmington Hills, MI. He has over 20 years of design, research, and consulting experience in areas of bridges, concrete durability, service life modeling, and corrosion protection planning. He received his BS and MS in civil engineering from Gdańsk University of Technology, Gdańsk, Poland, and his
PhD in civil engineering from Virginia Tech. At the time o f Launch Pad 39B investigation, he was Senior Engineer at CTLGroup, Skokie, IL.
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Industry
Focus nonprot company that provides vital assistance to U.S. military veterans and their families. The triathlon took place on June 6, 2015, and featured 24 teams sponsored by Ozinga Bros., Inc., partnered with area creative agency businesses in north Texas. Each team comprised represenCultivate, Inc., to develop an advertising campaign titled tatives from their company, matched up with a combat “Born to Build.” The developers hope to honor construction veteran. The triathlon featured two dozen challenges that workers by celebrating their hard work, perseverance, and included balloon launches, archery, and chipping golf balls sacrice of recognizing their specialized knowledge and at targets. As the team with the most points at the end of the experience. Part of the campaign includes a video game for event, Bob Moore Construction’s team “Bob Moore Bubbas” children: Super Nano Trucks is an iOS gaming app targeted earned possession of the Chris Kyle Trophy for the next for ages 3 to 8 and modeled after Ozinga Bros.’ real concrete year. While the tone of the Texas Redneck Triathlon is production method. Children learn how different amounts of light-hearted, it serves a serious purpose in raising funds. stone, sand, cement, and water are combined to create large-scale construction projects. Additional features include a This year’s Redneck Triathlon raised almost $100,000 for Boot Campaign. CB radio to interact with six different construction workers, awards for completing safety challenges, and authentic factory Western Waterproong Company Celebrating dials used to create concrete.
Ozinga Bros. “Born to Build” Campaign and Super Nano Trucks Gaming App
100th Anniversary
CTLGroup-Qatar Grand Opening Ceremony in Doha CTLGroup announced the opening of its new laboratory in Doha, Qatar. CTLGroup-Qatar conducts a wide range of testing services for concrete, cementitious materials, aggregates, building systems, soils, and asphalt. CTLGroup’s President and CEO Brent Nixon, and Chief Operating Ofcer Tim Tonyan, along with more than 60 stakeholders, attended the May 28, 2015, grand opening ceremony in Doha.
Bob Moore Construction Wins Chris Kyle Trophy at Fundraising Competition for Boot Campaign Bob Moore Construction’s team received the Chris Kyle Trophy for winning the third annual “Redneck Triathlon,” a private fundraising event sponsored by Boot Campaign, a
Owned and operated by third-generation Bishop family members, Western Waterproong Company recently celebrated its 100th anniversary with a cocktail reception and gala at the historic St. Louis Union Station, St. Louis, MO. To mark the occasion, Western unveiled its new name, logo, and tagline. The Western Construction Group and its 30+ branches and member companies, which had been doing business under their original names (Western Waterproong, Company, Brisk Waterproong, Peoria Roong, Western Facades, and Harry S. Peterson Co.), will be known as Western Specialty Contractors – Condence Through Performance. Western’s new logo is an evolution of the former logo, keeping the Western name and a refreshed water drop icon with an updated blue color. A website and video highlighting the 100th anniversary and rebranding efforts have also been developed.
E-Z Drill Expands Manufacturing Plant
Errata for ACI Publications
Available Online Under the menu for “Publications” at www.concrete.org , document errata can be searched by document number or keywords. Call ACI Member Services at +1.248.848.3700 for more information.
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E-Z Drill’s new factory expansion increases its production capacity by adding more than 7500 ft2 (700 m2) of oor space, roughly 20% more room, to its 36,355 ft 2 (3400 m2) factory in Perry, OK. The expansion will house an ofce and a new shipping and receiving area, as well as make room for E-Z Drill’s growing welding department.
Cind-R-Lite Brings a Sustainable Masonry Alternative to Las Vegas Cind-R-Lite Block Company is bringing innovative technologies to the Las Vegas, NV, building market by partnering with CarbonCure. Cind-R-Lite is now equipped to provide designers with greener masonry that makes use of captured carbon dioxide. It is using recycled carbon dioxide as an ingredient to make greener concrete products.
Products &
Practice Hydropad Wash Rack System Hydro Engineering’s Hydropad systems are used to efciently wash vehicles, equipment, or hardware. The systems are platforms engineered to capture efuent and divert it to a Hydrokleen water ltration system and send ltered water back out to the Hydroblaster washing system for nearly 100% water efciency. Hydropad portable wash racks are also designed for maneuverability as well as safe set-up and tear-down. Weight load capacities can reach anywhere from 2 to 70 tons (1.8 to 63 tonnes) of equipment. A single Hydropad’s dimensions are 8 x 20 ft (2.4 x 6.1 m), and they can be linked together to accommodate a variety of needs. Hydropads can include optional side wall panels to capture overspray. These panels range in size from up to 6 ft (1.8 m) outdoors to 12 ft (3.7 m) high indoors and can be congured to be included on one side of the Hydropad or on all sides. —Hydro Engineering, Inc., www.hydroblaster.com
RDS-15 Mobile Crusher IROCK Crushers’ RDS-15 Horizontal Impact Crushing Plant is a compact crushing and screening system that provides increased efciency and the precision to produce a uniform product. While it can process a variety of materials, the RDS-15 is ideal for processing materials such as reclaimed asphalt pavement. Powered by a 350-hp Caterpillar ® C-9 ACERT Tier 3 engine, the unit can process up to 350 tons (317 tonnes) per hour. The entire plant is self-contained and includes an on-board power supply and three electrical outlets for powering optional auxiliary conveyors. An electronic hydraulic clutch reduces power loss and increases fuel efciency. The unit’s closed circuit design gives operators the option of recirculating material requiring further sizing. —IROCK Crushers, www.irockcrushers.com
BM-TSM Tilt Switch BinMaster tilt switch, used for high-level detection of powders and bulk solids, mounts on the top of the bin and activates an alarm when material rises and tilts the switching mechanism 15 degrees. The shaft of the tilt switch is custom-made in lengths from 1 to 8 ft (0.3 to 2.4 m), depending on the distance from the top of the bin that an alert should be activated. The BM-TSM is available with either a paddle or sphere mounted at the end of the shaft and can be used in material with a bulk density of at least 15 lb/ft3 (240 kg/m3). This switch can be used as an alternative to a topmounted rotary level indicator and is suitable for a variety of solid materials. The mechanical design is rugged and operates reliably in a wide range of temperatures and is tough enough to withstand the harshness of granules and lump solid materials. A protective boot protects the tilt mechanism and ensures long operational life. —BinMaster, www.binmaster.com
Hilti Breaker TE 1000-AVR The Hilti Breaker TE 1000-AVR features HiDrive technology which helps deliver 19 ft-lb (26 J) of impact energy for outstanding demolition performance and productivity. It can be used for a variety of applications, including light to medium demolition of concrete slabs and foundations and tamping earthwork. TE 1000-AVR also features a Power Reduction Switch for up to 30% less impact for precision work. A switched reluctance motor helps provide stable performance with power uctuations from generators or extension cords. The TE-SP Wave Chisel helps to avoid excessive leveraging to unstick chisels on tough jobs. Its new wave design produces up to a 30% increase in speed during concrete demolition by reducing friction between the chisel body and base material, leaving a wider opening for fast debris removal. —Hilti, Inc., www.us.hilti.com www.concreteinternational.com | Ci | NOVEMBER 2015
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Products & Practice
Bosch GLM 30, 35, and 40 Laser Measures Bosch GLM 30, 35, and 40 measures extend the pocketsize GLM 15 with more features a nd greater accuracy. These laser measures provide greater range of 100, 120, and 135 ft (30, 37, and 41 m), repectively, with accuracy of 1/16 in. (2 mm). A simple keypad provides users the option to select length, area, volume, and indirect measurements. The user is instantly measuring in real time as soon as the laser measure is turned on. The measurements change instantaneously as the user moves farther or closer to the target. Easy computation of area comes with just two clicks of the button; volume with three clicks. Backlighting allows users to see information in dark areas. The GLM 40 provides all the functionality of the GLM 30 and GLM 35, plus the ability to store up to 10 measurements. The unit also comes with target cards, a hand strap, and a pouch. —Bosch, www.boschtools.com
BV30 Vibrating Screed Atlas Copco’s BV30 screed weighs 28 lb (13 kg) and is available with ve blade sizes, ranging from 6 to 14 ft (2 to 4 m) long. The variety of blade sizes provides contractors the exibility to use the screed on both small- and large-scale jobs. The screed is equipped with a V-shaped, rigid bottom plate that prevents the blade from twisting to ensure stable and consistent leveling. This single-beam vibrating screed provides a height-adjustable, foldable handle for easy operation and transportation. It can be maneuvered by one user and consolidate concrete up to 5 in. (127 mm) deep. —Atlas Copco, www.atlascopco.com
C860 Volumetric Mixers Cemen Tech’s C860 Volumetric Mixers feature a new electronic control panel. The panel allows users in the eld to track the exact ow of admixtures and water. All of the information is displayed on digital readouts, including the total volume of concrete produced during each placement. The GPS Tracking Solution provides tracking of the mixer’s location and will alert managers when and where a mixer stops, as well as how many times the mixer runs each day. —Cemen Tech, www.cementech.com
Pecal Universal Formwork Systems Frank’s Pecal® is an easy-to-use formwork system for the fast and economical construction of ground beams, pile caps, and box-outs. Additionally, Pecal can be used for forming ribbed slabs as well as for providing weather and dust protection. It consists of a special steel grid with varying bar diameters and a heat shrunk polyethylene lm. Pecal is mainly used as lost formwork, but can also be reused in certain applications. —Frank, www.maxfrank.com 56
NOVEMBER 2015 | Ci | www.concreteinternational.com
Products & Practice
Topcon Android app for LN-100 Layout Navigator Topcon Positioning Group released an app designed to drive the LN-100 Layout Navigator system: MAGNET® Construct. The app is built to provide productivity with LN-100W hardware. MAGNET Construct provides optional connectivity with MAGNET Enterprise for real-time data exchange from active project sites to and from the ofce within a user’s private company account. MAGNET Construct is available for Android users to download for free on the Google Play store. —Topcon Positioning Group, www.topconpositioning.com
Design Loads on Structures during Construction (37-14) Prepared by the Design Loads on Structures during Construction Standards Committee of the Codes and Standards Activities Division of the Structural Engineering Institute of American Society of Civil Engineers (ASCE), Design Loads on Structures during Construction, ASCE/SEI 37-14 , describes the minimum design requirements for construction loads, load combinations, and load factors affecting buildings and other structures that are under construction. It addresses partially completed structures as well as temporary support and access structures used during construction. The loads specied are suitable for use either with strength design criteria, such as ultimate strength design and load and resistance factor design, or with allowable stress design criteria. The loads are applicable to all conventional construction methods. Topics include: load factors and load combinations; dead and live loads; construction loads; lateral earth pressure; and environmental loads. — ASCE Publications, www.asce.org/publications Price: $80; 48 pp.; ISBN: 9780784413098
b Bulletin 75: Polymer-Duct Systems for Internal Bonded Post-Tensioning b Bulletin 75 updates and amends b Bulletin 7, “Corrugated plastic ducts for internal bonded post-tensioning,” a technical report published in 2000. The updated bulletin includes new information on the design and detailing of concrete structures containing tendons with polymer ducts. The recommendation provides detailed test specications for polymer materials, duct compo nents, and duct systems. The report contains recommendations for approval testing and attestations of conformity for polymer-duct systems. — b, www.b-international.org
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Product
Showcase Reinforcement Anchoring System for Overhead GFRC Panels for Subway Station Retrot CINTEC America will supply a new anchoring system for glass ber-reinforced concrete (GFRC) ceiling panels for the New York City (NYC) Metropolitan Transportation Authority (MTA) subway station platforms at the 168th and 181st Street stations. On-site testing validated the strength and effectiveness of the anchors, which now support the over 2000 lb (900 kg) ceiling panels rmly in place. CINTEC anchors are typically stainless steel in various grades. They are installed in oversized holes drilled in the structure. The anchor body and a surrounding fabric sock is inserted in each hole, and the socks are lled with a micro-cement grout. —CINTEC America, http://cintec.com
Kodi Klip K-Klips Kodi Klip® K-Klips for reinforcing bar fastening are molded from recycled polycarbonate resin, a type of thermoplastic known for high-impact strength and heat resistance. K-Klips won’t crack, break, or deform. In addition, K-Klips can’t rust, won’t degrade, and won’t scratch or damage epoxy-coated steel, or ber-reinforced polymer bars. They are ideal for marine or other harsh applications because they don’t corrode or abrade. K-Klips are color-coded by size, making them easy to distinguish and inspect. They rmly grip any cross, parallel, or vertical reinforcing bar connection joint, and they work on form spacers, cage assemblies, and high-density mats. The uniform holding strength provided at every reinforcing bar fastening joint eliminates unwanted motion and produces stronger reinforcing bar grids and mats. —Kodi Klip, http://kodiklip.com
MCI Coating for Rebar Cortec’s MCI® (Migratory Corrosion Inhibitor) Coating for Rebar is a water-based, environmentally friendly product that provides corrosion protection for bars in outside storage as well as corrosion resistance for embedded reinforcing bars. The coating can be used for long-term indoor protection (up to 5 years) and short- to medium-term (6 to 24 months) unsheltered outdoor protection. Cortec’s patented MCI technology also protects reinforcing bars in concrete. It is dilutable with water and does not affect concrete adhesion to reinforcing bars. —Cortec Corporation, www.cortecvci.com
ITW Red Head Tapcon+ Screw Anchor ITW Red Head® Tapcon+ concrete screw anchor is an IBC-compliant product approved for use in cracked and uncracked concrete and seismic zones. It can be used for applications such as drywall, railings, racking and conveyor systems, and steel column base plates. Tapcon+ uses patented Advanced Threadform Technology™ to tap and engage the concrete, as well as Blue ClimaSeal® for corrosion protection. The induction hardened tip also bites into concrete. Three anchor diameters are available: 1/4, 3/8, and 1/2 in. (6, 10, and 13 mm), ranging in length from 2-1/4 to 6 in. (57 to 152 mm). —ITW Red Head, www.itwredhead.com 58
NOVEMBER 2015 | Ci | www.concreteinternational.com
Product Showcase
CFS Fibers Steel ber manufacturer Concrete Fiber Solutions (CFS) products meet ASTM and ANSI/SDI standards. Available in multiple sizes to accommodate projects from light commercial to heavy industrial, CFS’ slit-sheet bers provide temperature and shrinkage reinforcement. CFS manufactures two reinforcing steel bers: CFS 100-2 and CFS 150-5. CFS 100-2 is an ASTM A820/A820M Type II ber, engineered for heavy industrial work and special design projects. The bers measure 1 in. (25 mm) in length with an aspect ratio of 43. They are designed to ensure no bers appear at a slab surface. CFS 100-2 bers are sold including design services—a computerized calculation to assess load conditions for each project. CFS 150-5 is an ASTM A820/A820M Type V ber designed for commercial, light industrial work, and composite steel decks. The bers measure 1.5 in. (38 mm) in length with an aspect ratio of 38. —Concrete Fiber Solutions, www.concretebersolutions.com
DiamondShield Glass Fiber Mesh BASF Corporation’s DiamondShield™ is a mesh engineered to provide crack suppression and isolation in stucco wall systems. It is a balanced, open-grid, triaxial glass ber mesh for use with BASF acrylic base coats as an overlay. Diamond Shield is applied over new or existing stucco (portland cement plaster) systems and distributes stress across three directions, which improves the tensile and exural strength of stucco. The result is greater crack resistance properties for improved building aesthetics. —BASF Corporation, www.basf.com
Burke Lockable Dowel and Double Shear Dowel Meadow Burke’s Burke Lockable Dowel and the Burke Double Shear Dowel are being used in the construction of the Dallas Cowboys training complex in Frisco, TX. The complex, which was named “The Star,” will serve as the Dallas Cowboys headquarters and will include a 12,000 seat arena with an indoor practice eld, two outdoor practice elds, ofce buildings, restaurants, retail sites, and a hotel. The Burke Lockable Dowel helps to eliminate pour strips in large placements and post-tensioned construction. With a smooth dowel in a rectangular slot, the Burke Lockable Dowel allows contraction movement in two directions while also carrying the gravity loads once the concrete has reached its designed com pressive strength. The Burke Double Shear Dowel is being used in the construction as a connection for beams. —Meadow Burke, http://meadowburke.com
Grove Products Horseshoe Shims Grove Products, Inc., announced the new 3/16 x 1-1/2 x 2 in. (5 x 38 x 51 mm) horseshoe shim available in orange. Shaped to t around a bolt or anchor, Grove Shims are easy to use for levelling and aligning dead loads. The U-shaped shims are sized to t around a 1/2 in. (13 mm) bolt or anchor point. The shims are also available in a noncombustible form. —Grove Products, Inc., www.groveproductsinc.com www.concreteinternational.com | Ci | NOVEMBER 2015
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Calls for
Papers Symposium on Concrete Pipe and Box Culverts
these events. Critical information will be imparted to those Meeting: ASTM International Symposium on Concrete who will lead tomorrow’s bridge design and construction, Pipe and Box Culverts, December 7, 2016, in Orlando, FL; including practicing engineers, government ofcials, and sponsored by ASTM Committee C13, Concrete Pipe. academics. An ACI special publication will be published. Solicited: Papers are invited on design and installation— Requirements: 1) presentation/paper title; 2) author/ new design methods, including a comparison of direct versus speaker name(s), title, organization, and contact information; indirect methods, innovations in installation methods and and 3) an abstract of 200 words. equipment and comparison of innovations with historical Deadlines: Abstracts are due by November 30, 2015; nal practices; history and development of concrete pipe and papers are due by April 30, 2016. ASTM Committee C13 standards—history of concrete pipe Send to: Yail Jimmy Kim, University of Colorado, Denver, production and manufacturing methodology, development and
[email protected]; Sri Sritharan, Iowa State University, evolution of specications and specifying concrete pipe
[email protected]; and Devin Harris, University of Virginia, products; innovative case histories of successful installation
[email protected]. and uses of concrete pipe; and new technology—new design methods, unique applications, and the use of new materials History of Concrete and admixtures, such as y ash or high-strength concrete. Meeting: Technical session on “History of Concrete” at Requirements: To participate in the symposium, The ACI Concrete Convention and Exposition, October 23-27, presenters/authors must submit the online abstract submittal 2016, in Philadelphia, PA; sponsored by ACI Committee 120, form and attach a 250- to 300-word preliminary abstract. History of Concrete. Visit www.astm.org/C13CFP1216 for abstract submittal. Solicited: Based on the history of cement production in Deadline: Abstracts are due by November 23, 2015. Pennsylvania’s Lehigh Valley, presentations on cement Contact: Additional technical information is available powders such as lime mortars, natural cement, “early” from symposium Co-Chairs John J. Meyer, Wales, WI, masonry, or portland cement are sought; however, presentations +1.262.565.7795; and Josh Beakley, American Concrete Pipe on other topics related to the history of design, construction, Association, Irving, TX, +1.972.506.7216. cementitious powders, and concrete practices would also be considered. Presentations will be 15 to 20 minutes in length. Evaluation and Response of Bridges Subjected Any type of physical artifact is also encouraged. to Non-Conventional Live or Extreme Loads Requirements: 1) presentation title; 2) author/speaker Meeting: Technical session on “Evaluation and Response name(s), title, organization, and contact information; and 3) a of Bridges Subjected to Non-Conventional or Extreme Loads” one-page abstract. at The ACI Concrete Convention and Exposition, October 23-27, Deadline: Abstracts are due by January 15, 2016. 2016, in Philadelphia, PA; sponsored by ACI Committee 345, Send to: Ryan Scott, Essroc Italcementi Group, Concrete Bridge Construction, Maintenance, and Repair, and
[email protected]. cosponsored by ACI Committees 341, Earthquake-Resistant Concrete Bridges; 342, Evaluation of Concrete Bridges and ACI Young Professional Essay Contest Bridge Elements; and Joint ACI-ASCE Committee 343, Event: ACI Committee S806, Young Professional Activities Concrete Bridge Design. (YPA), promotes participation of young professionals in the Solicited: The special session will emphasize the perforACI community through an essay contest. mance of constructed bridges and their elements when Solicited: Entries are invited on the theme of how young subjected to nonconventional live or extreme loads such as professionals have been engaged with ACI and how that has tsunami, landslide, impacts, and nonstandard vehicular trafc. given them an edge in the workplace. An application form Presentations will include a variety of technical aspects such can be found at http://www.concrete.org/Portals/0/Files/PDF/ as the failure mechanisms and characteristics of constructed Young_Professionals_Essay_Contest_Application.pdf. concrete bridge members, seismic energy dissipation, perforRequirements: 1) the essay must be kept to two pages in mance monitoring and evaluation, alternative design length, typed in 12-point font, with 1 in. margins, on letterapproaches, damage assessment, and structural rehabilitation. size (8.5 x 11 in.) paper; 2) any references should be cited Both experimental and analytical investigations are of interest. correctly and the reference list shall be part of the two-page The session will highlight recent research ndings and provide document; and 3) all applicants must have been in a concretean opportunity to discuss present challenges and technical or construction-related industry for less than 8 years. Years issues associated with the integrity of structures subjected to spent as a full-time student studying a construction-related 60
NOVEMBER 2015 | Ci | www.concreteinternational.com
Calls for Papers eld do not count toward these 8 years. Current students and faculty members are not eligible. Deadline: Essays are due by January 31, 2016. Send to: Kathy Rockwell, Young Professional Essay Contest, ACI, 38800 Country Club Drive, Farmington Hills, MI 48331, or e-mail:
[email protected].
Symposium on Computational Design Issues in Concrete Structures Meeting: Mini-symposium on “Computational Design Issues
in Concrete, Steel and Composite Structures” as part of the 2016 International Conference on Advances in Computational Design (ICACD16), August 28-September 1, 2016, Jeju Island, Korea; organized by Thomas Kang, Seoul National University. Solicited: The title of the mini-symposium is “Computational Design Issues on Concrete, Steel and Composite Structures,” which is a part of ICACD16. ICACD16 is held jointly with several other international conferences under the umbrella of the 2016 World Congress on Advances in Civil, Environmental,
and Materials Research at the International Convention Center Jeju, located on the southern coast of Jeju Island (a UNESCO World Natural Heritage and New Seven Wonders of Nature site). Those who have interests in computational or computeraided design issues for concrete structures are invited to submit abstracts. Requirements: Instructions on preparing proceeding papers/abstracts are available at http://acem16.com. Deadline: Abstracts are due by March 30, 2016. Contact: Thomas Kang, Co-Chair, ICACD16, e-mail:
[email protected].
Calls for Papers: Submission Guidelines Calls for papers should be submitted no l ater than 3 months prior to the deadline for abstracts. Please send meeting information, papers/presentations being solicited, abstract re quirements, and dea dline, along with full contact information to: Keith A. Tosolt, Managing Editor, Concrete International , 38800 Country Club Drive, Farmington Hills, MI 48331; e-mail: Keith.Tosolt@ concrete.org. Visit www.callforpapers.concrete.org for more information.
ACI PHYSICAL TESTING OF CEMENT TRAINING VIDEO (EDPTCT13) To supplement on-the-job training, ACI has developed the ACI Physical Testing of Cement Training Video as a resource for new testers and a refresher for experienced testers. The following tests are included: ASTM C109 – Compressive Strength ASTM C151 – Autoclave Expansion ASTM C185 – Air Content ASTM C187 – Normal Consistency
ASTM C191 – Vicat Time of Setting ASTM C204 – Blaine Fineness ASTM C266 – Gillmore Time of Setting ASTM C1437 – Flow of Mortar
Additionally, the video includes a review of safety, equipment, and the laboratory environment. Each chapter reviews the equipment specific to the ASTM test, the test procedure to follow, and the calculation of the result. Helpful tips are provided throughout to improve the technicians’ knowledge and technique. Check out a preview clip on YouTube; search for “ACI testing cement training preview.“
Details can be found at www.concrete.org; search the bookstore for “EDPTCT13.“
www.concreteinternational.com | Ci | NOVEMBER 2015
61
Bookshelf Publications Order Form
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EXP. DATE
Meetings NOVEMBER 2015
9-13 - 16th International Symposium for the Interaction
11-15 - Building Innovation 2016 Conference & Expo, Washington, DC www.nibs.org/?page=conference2016
of the Effects of Munitions with Structures, Destin, FL
http://reg.conferences.dce.u.edu/isiems/1183
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18-19 - Greenbuild International Conference & Expo,
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Washington, DC www.greenbuildexpo.com
27-29 - Advances in Cement and Concrete Technology in Africa 2016, Dar es
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www.middleeastconcrete.com JANUARY/FEBRUARY
24-25 - 2015 International Concrete Sustainability Conference, Dubai, UAE
31-5 - 2016 Mason Contractors Association of America
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1 - International Concrete Polishing & Staining Conference,
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4-5 - International Conference on Construction Materials and Structures 2015, Bandung, Indonesia
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See the events calendar at www.concreteinternational.com for more listings
3-5 - The Precast Show 2016, Nashville, TN http://precast.org/theprecastshow
THE CONCRETE CONVENTION AND EXPOSITION: FUTURE DATES 2015 — November 8-12, Sheraton, Denver, CO 2016 — April 17-21, Hyatt & Frontier Airlines Center, Milwaukee, WI 2016 — October 23-27, Marriott Philadelphia, Philadelphia, PA 2017 — March 26-30, Detroit Marriott at the Renaissance Center, Detroit, MI For additional information, contact: Event Services, ACI, 38800 Country Club Drive, Farmington Hills, MI 48331 Telephone: +1.248.848.3795 • E-mail:
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63
Public
Discussion ACI draft standards open for public discussion that are being processed through ACI’s ANSI-approved standardization procedures can be found at www.concrete.org/discussion. These are not yet ofcial ACI standards.
Document number
Title
Open for discussion
CT
Concrete Terminology
11/1/2015
Discussion closes 12/15/2015
Proposed Standard “Concrete Terminology” The ACI Technical Activities Committee (TAC) approved processing the subject document through ACI’s Standardization Procedure in August 2014, as did the ACI Standards Board in October 2015. Therefore, this draft document is open for public discussion from November 1, 2015, until December 15, 2015. The document appears on the ACI website, www.concrete.org/discussion. Pertinent discussion will be available on ACI’s website and announced in a future issue of Concrete International if received no later than December 15, 2015. Comments should be e-mailed to
[email protected].
Formwork for Concrete Completely revised and updated; still the formwork reference of choice
re te for Conc rk o Ed ition w 8 rm o F
al An ACI Manu
th
The 8th Edition, authored by David W. Johnston, North Carolina State University, is a major revision of the document to bring it up-to-date with “Guide to Formwork for Concrete (ACI 347R-14).” Revisions include referencing current standards and practices, removing outdated or irrelevant material, adding content on new developments in formwork technology and practice, and updating the look and layout of the document.
• An ACI best-selling document
SP-4 (14 )
• Allowable strength design and load and resistance factor design examples • Updated to current standards
• Chapter problems for classroom study • 500 modern color photographs • 150 color illustrations • Includes ACI 347R-14
Formwork for Concrete, 8th Edition, 2014, 512 pp. Order Code: SP48TH, $249.50 (ACI members $149.00)
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NOVEMBER 2015 | Ci | www.concreteinternational.com
Sinopsis en español Control de calidad de la durabilidad del hormigón Gjørv, Odd E., Concrete International , V. 37, N.° 11, noviembre de 2015, págs. 38-43
En 2010 se terminó un nuevo complejo compuesto por una serie de edificios comerciales y de apartamentos en la zona portuaria de Oslo, Noruega. El complejo se construyó sobre subestructuras de hormigón colocadas hasta 20 metros (66 pies) de profundidad en agua marina. El proyecto lo llevaron a cabo dos contratistas distintos. Para alcanzar la vida útil especificada de 300 años, el primer contratista aplicó el modelo DURACON (siglas en inglés de Durability Design of Concrete Structures, diseño de durabilidad de estructuras de hormigón) para seleccionar el grosor de la cubierta, las proporciones de la mezcla de hormigón y los materiales de refuerzo; y el segundo contratista siguió los requisitos normativos de durabilidad especificados en las normas europeas sobre hormigón vigentes en ese momento con algunos requisitos y medidas de protección adicionales. Se compara el rendimiento de los dos contratistas. Evaluación del estado de la rampa de lanzamiento 39B Weyers, R.E.; Sagüés, A.A.; y Zemajtis, J.Z., Concrete International , V. 37, N.º 11, noviembre de 2015, págs. 45-53
El reto de predecir la resistencia al corte de losas muy gruesas Collins, M.P.; Bentz, E.C.; Quach, P.T.; and Proestos, G.T., Concrete International , V. 37, N.º 11, noviembre de 2015, págs. 29-37
Para investigar la resistencia al corte de losas muy gruesas, se construyó una muestra que representaba una línea de corte en una losa de 4 metros (13 pies) de grosor y se aplicó una carga en un punto descentrado para provocar el fallo. Antes de la prueba, se invitó a los ingenieros a compartir sus predicciones en cuanto a la magnitud de la carga requerida para provocar el fallo de la muestra, el punto en el que se produciría el primer fallo y la magnitud de la carga requerida para provocar el fallo si los tramos de corte hubieran contenido armadura de corte mínima, así como la respuesta a la deformación de la carga de la muestra real. Estas predicciones, además de las predicciones de resistencia basadas en los códigos de diseño de Norteamérica y Europa, se compararon con los result ados experimentales. La conclusión fue que muchas de las predicciones eran muy poco conservadoras, incluidas las predicciones de resistencia basadas en los requisitos del código ACI 318, lo que insta a los autores a recomendar el uso de, al menos, la armadura de corte mínima en losas muy gruesas.
Después de 40 años de servicio, se ha llevado a cabo una investigación detallada del estado de la rampa de lanzamiento 39B del Centro Espacial John F. Kennedy. Se identificaron las condiciones de exposición medioambiental del hormigón y se desarrolló una investigación tras una visita inicial. Se evaluaron el hormigón y el acero reforzado mediante el uso de mediciones de resistencia del hormigón, potencial de corrosión, tasa de corrosión, contenido en cloruro y profundidad de la carbonatación. Los resultados demostraron que la corrosión del acero reforzado estaba causada por los cloruros liberados en la carbonatación del hormigón. También se desarrolló un modelo de deterioro de la vida útil y se proyectaron las tasas de deterioro para futuros requisitos de mantenimiento.
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Concrete
Q&A Designing Anchors and Their Attachments for Tensile Loading
Q.
We use anchor bolts to fasten elevator equipment (controllers, guide rail brackets, machines, and buffer stands) to the building elevator shaft or hoistway walls, machine room oors, and pit oors. For seismic applications, where the seismic load is 100% of the total factored load, are we allowed to use the requirement D.3.3.4.3(c) in ACI 318-111 to design the anchor bolts as long as we follow the requirements in D.3.3.4.4? I just want to conrm that anchor bolts used to fasten elevator equipment do not have to follow D.3.3.4.3(a) as long as the design follows D.3.3.4.3(c) and D.3.3.4.4.
A.
A short answer to your question is YES. First, the tensile component of the strength-level earthquake force exceeds 20% of the total factored anchor tensile force associated with the same load combination. So, Section D.3.3.4.2 of ACI 318-11 indicates that Section D.3.3.4.3 is to be used for determining anchor design tensile strength. According to Section D.3.3.4.3: “Anchors and their attachments shall satisfy one of options (a) through (d).” So, using only option (c) meets this requirement. When using D.3.3.4.3(c), you are designing the anchor or group of anchors “for the maximum tension that can be transmitted to the anchors by a non-yielding attachment.” It means that, for example, if your design load from ASCE/ SEI 7-102 is 10 kip (44.5 kN) in tension, but the non-yielding attachment is actually able to take a nominal load of 20 kip (89 kN), then the anchorage needs to be designed for the 20 kip load. You are also calculating the anchor design tensile strength (to resist earthquake forces) using Section D.3.3.4.4 of ACI 318-11. This section requires you to consider items (a) through (e) (where ϕ is in accordance with Questions in this column were asked by users of ACI documents and have been answered by ACI staff or by a member or members of ACI technical committees. The answers do not represent the ofcial position of an ACI committee. Only a published committee document represents the formal consensus of the committee and the Institute. We invite comment on any of the questions and answers published in this column. Write to the Editor, Concrete International , 38800 Country Club Drive, Farmington Hills, MI 48331; contact us by fax at +1.248.848.3701; or e-mail
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D.4.3 or D.4.4) for the failure modes provided in Table D.4.1.1, included herein for reference, with an assumption that concrete is cracked unless it can be demonstrated that it remains uncracked. Because concrete does not fail in a ductile manner when failing in tension, the intent of the Code is to force the tension failure to occur away from the anchorage in the event of a seismic force overload. References 1. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-11) and Commentary,” American Concrete Institute, Farmington Hills, MI, 2011, 503 pp. 2. “Minimum Design Loads for Buildings and Other Structures (ASCE/SEI 7-10),” American Society of Civil Engineers, Reston, VA, 2013, 636 pp.
Fall 2015 | Denver The Concrete Convention nd Exposition
Thank you to our Exhibitors and Sponsors!
The Concrete Convention and Exposition November 8-12, 2015 • Sheraton Denver Downtown Hotel, Denver, CO
Sponsors Aspen Rocky Mountain Chapter – ACI Colorado Ready Mixed Concrete Association Aggregate Industries Baker Concrete Construction Holcim (US) Inc.
Vail BASF Corporation Euclid Chemical Company GCC of America Grace Construction Products Mountain Cement
CEMEX DRP Petrography Eastern Pennsylvania & Deleware Chapter – ACI Greater Michigan Chapter – ACI GH Phipps Construction Companies Kumar & Associates, Inc. LaFarge North America Northern California/Western Nevada Chapter – ACI Restruction Corporation Salt River Materials Group Trinity Expanded Shale & Clay
Loveland
Breckenridge Bestway Concrete Company CTL/Thompson, Inc. Martin/Martin Martin Marietta Metro Mix, LLC PCA Rocky Mountain and Northwest Region
Winter Park AMSYSCO, Inc. Carolinas Chapter – ACI
Arizona Chapter – ACI Arkansas Chapter – ACI Castle Rock Construction Company of Colorado Central Texas Chapter – ACI Concrete Industry Board, New York City Chapter – ACI CR Minerals Georgia Chapter – ACI Illinois Chapter – ACI Intermountain Chapter – ACI Interstate Highway Construction Kansas Chapter – ACI Las Vegas Chapter – ACI
Lillard & Clark Louisiana Chapter – ACI Maryland Chapter – ACI National Capital Chapter – ACI New Jersey Chapter – ACI New Mexico Chapter – ACI Northeast Texas Chapter – ACI Ontario Chapter – ACI Pittsburgh Area Chapter – ACI San Diego International Chapter – ACI Southern California Chapter – ACI The Concrete Industry Board
Eldora Bates Engineering, Inc. Boral Materials Technologies SDG, Inc. Consulting Structural Engineers
Beer Garden DRP Consulting, Inc. Fall Line Testing and Inspection, LCC Intelligent Concrete Rocky Mountain Chapter – ACI
Exhibitors ADAPT Corporation Aggregate Industries ASTM International Aslan FRP/Hughes Brothers ATENA – Cervenka Consulting Baker Concrete Construction BASF Corporation Burgess Pigment Company Buzzi Unicem USA Colorado Ready Mixed Concrete Ass. Composite Rebar Technologies Concrete Décor Magazine Concrete Sealants, Inc. Construction Materials Engineering Council, Inc Decon USA Inc. ELE International ERICO Euclid Chemical Company
FORNEY LP GCC of America, Inc. Germann Instruments, Inc. Giatec Scientific Inc. Grace Construction Products Headed Reinforcement Corp. (HRC) Holcim Huber Engineered Materials ITW Buildex/Red Head/Ramset Kerneos Kryton Myers Associates Inc. Nomaco Olson Engineering, Inc Premier CPG Primekss Rabine Proceq USA QuakeWrap Inc.
Salt River Materials Group (SRMG) Sensors & Software Inc. S-FRAME Software / Red Seat Software Sika Corporation Silica Fume Association Solidia Technologies Stonemont Solutions, Inc Structural Group Trimble Construction Logistics Trinity Expanded Shale & Clay UCT/Radarview uGRIDD Vector Corrosion Technologies Wacker Neuson Xypex Chemical Corporation Zircon *Sponsors and Exhibitors listed as of 10/9/15
Visit the exhibit hall in Denver to learn more about these companies. A complete listing is available online at www.aciconvention.org as well as in The Concrete Convention App.
