+)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))), *
MCP Application Notes:
*
*
*
1. Character(s) preceded & followed by these symbols ( . -) or ( + ,) are super- or subscripted, respectively. * EXAMPLES: 42m .3- = 42 cubic meters * CO+2, = carbon dioxide *
*
*
*
*
* * *
2. All table notes (letters and numbers) have been enclosed in square * brackets in both the table and below the table. The same is * true for footnotes. * * * *
.))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))-
ACI 350R-89
Environmental Engineering Concrete Structures
Reported by ACI Committee 350
Frank Klein, Chairman; Robert Little, Chairman, editorial subcommittee; Anand B. Gogate, Secretary; James P. Archibald; Jon B. Ardahl; Paul A. Beckmann, Jr.; Reginald H. Benton; Patrick J. Creegan; Ashok K. Dhingra; Donald R. Dressler; Donald L. Dube; Anthony L. Felder; Timothy J. Fowler;* Gerard B. Hasselwander; Dov Kaminetzky; David A. Kleveter; Nicholas A. Legatos; Glenn E. Noble; Predrag L. Popovic; Satish K. Sachdev; Harold N. Schneider; Sudhakar P. Verma; Roger H. Wood. (* Chairman when ACI 350R-83 was developed.)
This report presents recommendations for structural design, materials, and construction of concrete tanks, reservoirs, and other structures commonly used in water containment, industrial and domestic water, and wastewater treatment works, where dense, impermeable concrete with high resistance to chemical attack is required. Special emphasis is placed on a structural design that minimizes the possibility of cracking and accommodates vibrating equipment and other special loads. Design and spacing of joints are considered. Proportioning of concrete, placement, curing, and protection against chemicals are also described. Information on seismic design is included.
Keywords: admixtures; aggregates; cements; chemical attack; coatings; concrete construction; concrete durability; concrete finishing (fresh concrete); concretes; cracking (fracturing); crack width and spacing; curing; deflection; earthquake resistant structures; environmental engineering; finishes; floors; formwork (construction); foundations; joint sealers; joints (junctions); live loads; mix proportioning; patching; permeability; placing; protective coatings; quality control; reinforced concrete; reservoirs; sanitary engineering; sewage treatment; stresses; structural design; tanks (containers); temperature; torque; vibration; volume change; wastewater treatment; water-cement ratio; water supply; water treatment.
This report supercedes ACI 350R-83. This report was submitted to letter ballot of the committee and was approved in accordance with ACI balloting procedures. Copyright (c) 1989, American Concrete Institute. All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed, written, or oral, or recording for sound or visual
reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.
ACI Committee Reports, Guides, Standard Practices, and Commentaries are intended for guidance in designing, planning, executing, or inspecting construction and in preparing specifications. Reference to these documents shall not be made in the Project Documents. If items found in these documents are desired to be part of the Project Documents they should be phrased in mandatory language and incorporated into the Project Documents.
CONTENTS
Chapter 1--Special requirements for environmental engineering concrete structures 1.1--Introduction 1.2--Design and analysis 1.3--Watertightness 1.4--Durability Chapter 2--Structural design considerations 2.1--Introduction 2.2--Principal types of structures 2.3--Load conditions 2.4--Types of foundations 2.5--Structural considerations 2.6--Structural design 2.7--Reinforcement splices 2.8--Joints 2.9--Impact, vibration, torque, and seismic loads Chapter 3--Materials, mixture proportioning, and testing 3.1--Cementitious materials 3.2--Admixtures 3.3--Water 3.4--Aggregates 3.5--Mix proportioning 3.6--Evaluation and acceptance Chapter 4--Construction 4.1--Concrete 4.2--Placement of concrete 4.3--Joints 4.4--Formwork 4.5--Finishes for exposed surfaces 4.6--Curing 4.7--Leakage testing
Chapter 5--Protection against chemicals 5.1--Resistance of concrete and reinforcing steel 5.2--Need for protection 5.3--Types of protection 5.4--Recommended coatings 5.5--Selection of protection system 5.6--Safety precautions 5.7--Chemicals used in treatment plants Chapter 6--References 6.1--Recommended references 6.2--Cited references 6.3--Additional references Discussion
CHAPTER 1--SPECIAL REQUIREMENTS FOR ENVIRONMENTAL ENGINEERING CONCRETE STRUCTURES 1.1--Introduction Environmental engineering concrete structures pose some problems uncommon in other uses of concrete. In all structures, strength and stability are of paramount importance. In environmental engineering concrete structures, serviceability, in terms of limited deflections and cracking, durability, and low permeability demand equal consideration. In these structures, concrete that will be in contact with water or wastewater should: a. Be extremely dense and impermeable to minimize contamination of water supplies or the environment. b. Provide maximum resistance to natural or processing chemicals. c. Provide smooth surfaces to minimize flow resistance. Concrete is particularly suited to environmental engineering structures. It will not warp or undergo significant dimensional change under service conditions and, when properly designed and placed, is nearly impermeable and extremely resistant to corrosion. Because of the stringent service requirements of environmental engineering concrete structures, they should be designed and constructed with great care. The quality of concrete is of great importance, and close quality control should be performed during construction to obtain impervious concrete. 1.1.1 Scope--This report is concerned with conventionally reinforced environmental engineering concrete structures. The recommendations apply to cast-in-place and precast concrete construction of tanks, reservoirs, cast-in-place sewers, manholes, wet-wells, flumes, junction chambers, pump stations, and other similar structures and appurtenances. The purpose of this report is to recommend methods of design and construction
permitting the production of structural concrete that will satisfy not only the usual structural requirements but also those mentioned in Section 1.1(a), (b) and (c). Emphasis is given to the special steps necessary to maximize corrosion resistance and imperviousness of concrete and to the special loading conditions of environmental engineering concrete structures. Recommendations for prestressed concrete are beyond the scope of this report. Specific recommendations for circular prestressed concrete tanks are contained in ACI 344R.
1.2--Design and analysis Design loads on environmental engineering concrete structures are determined from the depth and unit weight of the retained liquid and/or solids, the external soil pressure, and the equipment to be installed. Compared to the accurately known liquid and dead loads, the superimposed design live loads in tanks and reservoirs generally are small. As discussed in Section 2.9, special care is required when designing for impact and dynamic loads caused by mechanical equipment. Design analysis must be accurate to obtain a true picture of the distribution of stresses in the structure and to resist cracking in areas of maximum stress. Soil bearing strength and consolidation information is of great importance to minimize differential settlements that could cause cracking. Environmental engineering concrete structures should be designed to minimize leakage. Accordingly, a design method should be used that will eliminate wide cracks and other potential sources of leakage. Design methods may be based on strength or working stress theories. In environmental engineering concrete structures, service load performance is of paramount importance. Many current design aids are based on the strength design method. For strength design of environmental engineering concrete structures, this report includes the concept of environmental durability coefficients. These coefficients provide conservative service load stresses using Grade 40 and Grade 60 steel and crack control similar to that historically obtained with working stress design.
1.3--Watertightness Environmental engineering concrete structures for the containment, treatment, or transmission of water, wastewater, or other fluids should be designed and constructed to be essentially watertight, with minimal loss of contained volume under normal service conditions (see Section 4.7 of this report for leakage testing). In many industrial applications the United States Environmental Protection Agency will require containment and leak detection systems. 1.3.1 The ability of a structure to retain liquids will be reasonably assured if: a. The concrete mixture is well proportioned and the concrete
is well consolidated without segregation. b. Crack width is minimized. c. Joints are properly spaced, sized, designed, and constructed. d. Impervious protective coatings or barriers are used where required. e. Adequate reinforcing steel is provided.
Usually it is more economical and dependable to resist liquid permeation through the use of quality concrete, proper design of joint details, and adequate reinforcement rather than by means of an impervious protective barrier or coating. Minimum permeability of the concrete will be obtained by using water-cement ratios as low as possible consistent with satisfactory workability and good compaction. Impermeability increases with the age of concrete and is improved by extended periods of moist curing. Surface treatment is important, and surface troweling and use of smooth forms give good impermeability. Air entrainment reduces segregation and bleeding, increases workability, and provides resistance to the effects of freeze-thaw cycles. Because of this, use of an air-entraining agent results in better compacted concrete and permits use of a lower water-cement ratio. Other admixtures, such as water reducing agents, and pozzolans are useful when they lead to increased workability and compaction with lower water-cement ratios. Pozzolans also reduce permeability. Cracking can be kept to a minimum by proper design, reinforcement distribution, and spacing of joints. Cracking caused by drying shrinkage can also be minimized by the proper use of shrinkage-compensating concrete, but for the design to be successful, the engineer must recognize the characteristics and properties of shrinkage-compensating concrete as described in ACI 223. Some shrinkage will always occur in normal concrete, and joints and reinforcement should be designed to control the effects of shrinkage. Joint design should also consider movement resulting from thermal dimensional changes and differential settlements. Joints permitting movement along predetermined control planes that should form a barrier to the passage of fluids should include waterstops. Good placement operations, adequate consolidation, and proper curing also are essential to control of cracking in environmental engineering concrete structures. Additional information on cracking is contained in ACI 224R.
1.4--Durability Durability of concrete in an environmental engineering concrete structure is the resistance of the structure to the deteriorating effects of its environment. In particular, the concrete should be resistant to the action of chemicals, alternate wetting and drying, freezing and thawing cycles, and exposure to the elements. Air entrainment should be used in freezing and thawing exposures. Resistance to chemical attack can be improved by using
good quality concrete with types of cement that improve chemical resistance and provide a smooth surface finish. Care should also be taken to provide adequate cover for the reinforcement and to use fittings and embedded items that do not corrode and cause damage to the concrete. The filling and patching of tie holes, as recommended in Section 4.5.4.1 of this report, is necessary to insure long-term durability of the concrete. Improved workability, lower water-cement ratios, corrosion resistance, and increased resistance to sulfate attack may be derived from the proper use of a good quality fly ash in the mix. The use of a moderately sulfate-resistant cement such as Type II, V, or certain Type K cements, as referred to in Section 3.1.2, V should also be considered when sulfate-resistant concrete is required. Most environmental engineering concrete structures will be exposed to the elements, and adequate provisions should be made to avoid damage due to floods, rain, snow, and freezing and thawing. In some cases, adequate durability can be obtained only by use of special protective barriers (see Chapter 5). Structures subject to movement of liquids should be resistant to erosion. Additional information on durability is contained in ACI 201.2R.
CHAPTER 2--STRUCTURAL DESIGN CONSIDERATIONS 2.1--Introduction The design of environmental engineering concrete structures should be executed in four consecutive or overlapping phases as follows: 1. 2. 3. 4.
Functional design Physical plant layout Hydraulic design Structural design
Authoritative texts and several ASCE manuals of engineering practice[1-3] will be helpful in the first three phases of design, most of which can be performed before undertaking the fourth phase. However, structural advice should be provided during all phases of the design and construction of the work. Except as otherwise indicated in this report, structural design should conform with ACI 318. For the structural design of circular or rectangular reinforced concrete tanks, several helpful publications[4-6] of the Portland Cement Association are available. Circular prestressed tanks are addressed in ACI 344R. The recommendations in the publications just cited may require adjustments to conform with ACI 318 and this report, and with the applicable local building code.
2.2--Principal types of structures Environmental engineering installations generally are water or wastewater treatment facilities composed of a number of separate units as shown below:
Water treatment plants Intake structures Screen chambers Rapid mix chambers Flocculating basins Settling tanks Conduits Chlorination facilities Clarifiers
Filters Filter pipe galleries Clear wells Pumping stations Service reservoirs Chemical storage Office building and laboratory
Industrial and domestic wastewater treatment plants Grit chambers Primary settling tanks Final settling tanks Digesters Thickeners Aeration basins Sludge holding tanks Trickling filters Screening facilities Chlorine contact chambers
Pump and blower stations Gas holders Sludge dewatering Sludge disposal facilities Chemical storage Office building and laboratory Tertiary filters Composting facilities Channels and tunnels
The previously listed structures generally may be classified as follows: Water or liquid-containing structures, tanks, and basins Conduits, interconnecting channels, and cast-in-place sewers Machine and equipment foundations Protective housing, floors, storage rooms, walkways, and stairs
2.3--Load conditions 2.3.1 Dead load--Many references are available for estimating dead loads. ANSI A58.1 is a recommended reference for dead loads. 2.3.2 Live load--The following are conservative values for live loads that should be considered in structural design: Raw sewage
63 lb/ft .3-
Grit excavated from grit chamber
110 lb/ft .3- (1760 kg/m .3-)
Digested sludge, aerobic
65 lb/ft .3-
(1040 kg/m .3-)
Digested sludge, anaerobic
70 lb/ft .3-
(1120 kg/m .3-)
Thickened or dewatered sludge depending on moisture content
(1010 kg/m .3-)
60 to 85 lb/ft .3(960 to 1360 kg/m .3-)
ANSI A58.1 is the recommended reference for other live loads. ANSI A58.1 and local building codes set forth minimum requirements. Actual weights of equipment should be obtained from manufacturers. If the weights given by various manufacturers differ, the heaviest should be used for structural design.
Live loads on catwalks, stairs, and office and laboratory floors should be a minimum of 100 lb/ft² (4790 Pa). In heavy equipment rooms, where the machines may be taken apart and stored on the floor, it is advisable to design the slabs and beams for a minimum live load of 300 lb/ft² (14,400 Pa). Actual weights of machines and other equipment, including their concrete support bases, should be used for designing floor beams, including the effect of moving loads. Live loads should include the weights of large-diameter piping and valves taking into account the size, number, and spacing of piping, including current loads and allowing for planned expansion. In evaluating live loads for closed tanks the engineer should consider the internal pressures or vacuums that occur under normal operation for serviceability checks of deflection. The maximum/minimum settings for the pressure relief valves and vacuum relief valves should be used as the service live load for the design of reinforcement. Care should be taken to insure that vents and relief valves do not plug, freeze, or corrode shut. In cold climates, this may require heating cables on vents and valves. Goose-neck relief valves may require antifreeze. The live load for the roofs of buried tanks should include the earth cover as well as a surface live load of at least 100 lb/ft² (4790 Pa). Depending on the use of the roof area, a greater surface design live load may be required. Pattern loading effects can be very extreme for buried roofs. One bay may be bare (no earth or surface live load), while adjacent bays are subject to full earth and surface live load. These effects are particularly significant in flat slab roof systems. The construction drawings should indicate any restrictions on the placing, type, or weight of equipment to be employed, and the sequence for earth cover. In electrical control rooms, it is best to estimate the foundation area and weight of the equipment. The weight of any unit should be assumed as being applied anywhere in the control room, since the equipment may be shifted from its original location to other locations, or more equipment may be added later. An assumed 250 lb/ft² (12,000 Pa) live load will, in most cases, cover the normal equipment load. The live loads in Table 2.3.2 may be used for chemical storage buildings. Table 2.3.2 -- Weights of chemicals for structrual design )))))))))))))))))))))))))))))0)))))))))))))))))))))))))))))))))))))))))0))))))))))))))))))))))))))))))))
Chemical
*Shipping
and storage data
*Weight, *except
*
lb/ft.3-, as stated
)))))))))))))))))))))))))))))3)))))))))))))))))))))))))))))))))))))))))3))))))))))))))))))))))))))))))))
Activated carbon*
*Bags
35 lb (15.9 kg) (3 x 21 x 39 in.) x 533 x 991 mm); drums 5 lb *(2.27 kg). 25 lb (11.3 kg); bulk
*Powder
*(76.2
*kg/m.3-)
*
*
*
Activated silica* Alum, liquid*
Aluminum ammonium sulfate*
*
8 to 28 (128 to 449 average 12 (192 *kg/m.3-) *
--
*About
11.6 lb/gal. (1390 g/1)
*
*
*Manufactured
near site because high cost precludes distant *shipment; 6000 to 8000 gal. (22,700 *to 30,300 1), steel tank cars; 2000 *to 4000 gal. (7570 to 15,100 1), *rubber lined steel tank trucks
*At
*freight
*gravity
*
*
*
*
*Fiber
60 F (15.6 C) specific 1.285; *10.7 lb/gal. (1280 g/1) * * *
drums, kegs 100 to 400 lb (45.4 *60 to 70 (961 to 1120 kg/m .3-) *to 181 kg); bags 100 lb (45.4 kg); bulk * *
*
Aluminum chloride solution Aluminum potassium sulfate*
Aluminum sulfate
Ammonia, anhydrous NH +3,
Ammonia, aqua
Ammonia silicofluoride
Ammonium sulfate*
Barium carbonate
*
*Carboys;
rubber-lined tank trucks
*Specific
*
*
*Bags
100 lb (45.4 kg); 250 lb (113 bbl 350 lb (159 kg); drums 100 lb *(45.4 kg), 350 lb (159 kg); bulk
*60
*kg);
*
*
*
*Bags
100 lb (45.4 kg); 200 lb (90.7 *kg); bbl 325 lb (147 kg), 400 lb (181 *kg); drums 25 lb (11.3 kg), 100 lb *(45.4 kg), 250 lb (113 kg); bulk
*60
*
*
*Steel
cylinders 50 lb (22.7 kg), 100 *lb (45.4 kg), 150 lb (68.0 kg); tank *car, 50,000 lb (22,680 kg)
*Specific
*
*
*Carboys
5 gal. (18.9 1) 10 gal. *(37.9 1); drums 375 lb (170 kg), 750 lb *(340 kg); 8000 gal. (30,300 1) tank car
*At
*
*
gravity 1.15 to 1.16
to 70 (961 to 1120 kg/m .3-)
*
to 75 (961 to 1200 kg/m .3-) is lighter). To *calculate hopper capacities *use 60 (961 kg/m .3-) *(powder
*is
gravity of liquid 0.68 at )28 F ()33.3 C)
*
60 F (15.6 C) specific is 0.8974
*gravity *
*Pkgs
4 to 26.5 lb (1.81 to 12. kg); kegs *70 to 80 (1120 to 1280 kg/m .3-) *100 lb (45.4 kg); bbl or drums 400 lb * *(181 kg) * *
*
*Boxes
25 lb (11.3 kg); kegs 100 lb *(45.4 kg); bags 100 lb (45.4 kg); bbl *300 lb (136 kg), 400 lb (181 kg);
*bulk
*
*
*Boxes
*52
25 lb (11.3 kg); kegs 100 lb *(45.4 kg); bags 200 lb (90.7 kg)
60 (961 kg/m .3-)
* *
to 78 (833 to 1250 kg/m .3-)
*
)))))))))))))))))))))))))))))2)))))))))))))))))))))))))))))))))))))))))2))))))))))))))))))))))) )) *Bags
50 lb (22.7 kg), 100 lb (45.4 kg); *bulk
*Powder
*
Bromine
Calcium carbonate
*
*
*Glass
bottles 6.5 lb (2.95 kg); *earthenware bottles
*Specific
*
*
*Bags
50 lb (22.7 kg); drums; bulk
Calcium hypochlorite
Calcium oxide
Carbon dioxide
Chlorinated copperas*
Chlorinated lime
Copper sulfate*
* *
*
*Bags
*20
50 lb (22.7 kg); bbl 100 lb (45.4 *kg); bulk; store in dry place
*Powder
*
to 50 (320 to 801 kg/m .3-) To hopper capacity use 40 *(641 kg/m.3-)
*
*
*Bbl
415 Tb (188 kg); cans 5 lb (2.27 *kg), 15 lb (6.8 kg), 100 lb (45.4 kg), *300 lb (136 kg); drums 800 lb (363 kg); *store dry and cool; avoid contact with *organic matter
*Granules
*
*
*Moistureproof
bags 100 lb (45.4 kg); *wood bbl, bulk; C/L; store dry, max 60 *days; keep container closed
*55
*
*
*Steel
cylinders for compressed gas, 150 *lb (68.0 kg); dry ice delivered as *required and evaporated on site in large *steel cylinders
*
*
*
*See
chlorine and ferrous sulfate as *reagents needed
*
*
*
*calculate
68 to 80 (1090 to kg/m.3-) powder 32 to 50 *(513 to 801 kg/m .3-) *1280 * *
to 70 (881 to 1120 kg/m .3-). calculate hopper capacity *use 60 (961 kg/m .3-) *To
--
* * *
--
*
*Drums
100 lb (45.4 kg); 300 lb (136 kg), *45 to 50 (751 to 801 kg/m .3-) *800 lb (363 kg); store cool and dry * *
*Steel
cylinders 100 lb (45.4 kg), 150 lb *Specific gravity with respect *(68.0 kg); ton containers, 15 ton *to air 2.49 *(13.6 t) containers; 16 (14.5 t) 30 * *(27.2 t), 55 (49.9 t) ton tank cars * *
*
*Bags
*Crystal
100 lb (45.4 kg); bbl 450 lb (204 *kg); drums * *
Diatomaceous earth
gravity 3.119 26 (3120 g/1)
35 to 60 (561 to 961 granules 100 to 115 *(1600 to 1840 kg/m .3-)
*
Chlorine*
*lb/gal.
*kg/m.3-);
*
Calcium hydroxide
Bentonite
45 to 60 (721 to 961 *kg/m.3-); granules 65 to 75 *(1040 to 1200 kg/m .3-)
*Bags * * *
75 to 90 (1200 to kg/m.3-); powder 60 to 68 *(961 to 1090 kg/m .3-) *1440 *
50 lb (22.7 kg) bulk
*Natural
5 to 18 (80.1 to 288 calcined 6 to 3 (96.1 *to 48.1 kg/m .3-); flux calcined *10 to 25 (160 to 400 kg/m .3-) *kg/m.3-);
)))))))))))))))))))))))))))))2)))))))))))))))))))))))))))))))))))))))))2))))))))))))))))))))))))))))))))
)))))))))))))))))))))))))))))0)))))))))))))))))))))))))))))))))))))))))0))))))))))))))))))))))))))))))))
Chemical
*Shipping
and storage data
*Weight, *except
*
lb/ft.3-, as stated
)))))))))))))))))))))))))))))3)))))))))))))))))))))))))))))))))))))))))3))))))))))))))))))))))))))))))))
Disodium phosphate
Dolomitic hydrated lime
*Bags
100 lb (45.4 kg) kegs 125 lb (56.7 drums 25 lb (11.3 kg), 100 lb (45.4 *kg), 125 lb (56.7 kg), 325 lb (147 kg), *350 lb (159 kg)
*Crystal
*kg)
*to
*
*
*Bags
50 lb (22.7 kg) bbl; bulk
*
to 50 (481 to 801 kg/m .3-). calculate hopper capacity *use 40 (641 kg/m .3-)
*
*
*Bags
*Pebble
50 lb (22.7 kg), 60 lb (27.2 kg); *bbl, bulk
* *
*
*Solution--carboys
5 gal. (18.9 1), 13 *gal. (49.2 1), truck, tank car; crystal *--keg 100 lb (45.4 kg), 400 lb (181 kg), *450 lb (204 kg); drums 150 lb (68.0 kg), *350 lb (159 kg), 630 lb (286 kg)
*Solution
*
*
* *
Ferric sulfate*
Hydrofluoric acid*
Polyelectrolyte or polymer
Potassium permanganate
Sodium aluminate
Sodium bicarbonate
*
100 lb (45.4 kg); drums 400 lb (181 *63 to 66 (1010 to 1060 kg/m .3-) *kg); bulk * *
*Kegs
5 gal. (18.9 1); pitch-lined drums, *30 percent is 10.5 lb/gal. *50 gal. (189 1); rubber-lined bbl 420 lb *(1260 g/1) *(191 kg) * *
*
*Drums
steel 20 gal. (75.7 1), 30 gal. *(114 1); 100 gal. (379 1); bulk
*
*
*
*Available
*Dry
dry and in solution form. *Various containers used
Sodium chloride
* *
*
*USP
25 lb (11.3 kg), 110 lb (49.9 kg), *125 lb (56.7 kg); steel keg; tech 25 lb *(11.3 kg), 110 lb (49.9 kg), 600 lb *(272 kg);
*steel
*
*
*Ground
bags 50 lb (22.7 kg), 100 lb *(45.4 kg); liquid in drums
*High
*
*
*Bags
110 lb (45.4 kg) and drums
*Bags
Sodium hypochlorite
Sodium silicate
* *
purity 50 (801 kg/m .3-); 60 (961 kg/m .3-)
*standard *59
to 62 (945 to 993 kg/m .3-)
100 lb (45.4 kg) bbl 100 lb (45.4 drums 25 lb (11.3 kg), 100 lb *(45.4 kg); bulk
*Dense
*kg),
*40
*
*
*Bags
*Rock
100 lb (45.4 kg); bbl, drums 25 lb *(11.3 kg); bulk
*Bags
65 (1040 kg/m .3-); medium (641 kg/m .3-) light 30 (481 *kg/m.3-) 50 to 60 (801 to 961 crystal 58 to 70 (929 *to 1120 kg/m .3-) *kg/m.3-); *
*Drums
100 lb (45.4 kg)
*65
to 75 (1040 to 1200 kg/m .3-)
*
*
65 to 100 (1040 to 1600 granules crystal 90 *to 106 (1440 to 1700 kg/m .3-)
*
*
*kg),
Sodium hydroxide
drum 86 to 102 (1380 to kg/m.3-)
*Bags
*
Sodium hexametaphosphate
*1630
100 lb (45.4 kg) drums 100 lb (45.4 *70 to 80 (1120 to 1280 kg/m .3-) 400 lb (181 kg) *
*
Sodium fluoride
*kg/m.3-);
*
*
Sodium chlorite
*
7.5 to 88 (120 to 1410 liquid 62 to 92 (990 *to 1475 kg/m .3-)
*kg),
Sodium carbonate
*
*Bags
*
Sodium bisulfate
11.2 to 12.4 lb (5.08 5.62 kg); crystal 60 to 64, *(961 to 1030 kg/m .3-) anhydrous * 45 to 60 (721 to 961 kg/m .3-) *to
100 lb (45.4 kg); drums 400 lb (181 *70 to 72 (1120 to 1150 kg/m .3-) *kg) 425 lb (193 kg); bulk *
*
Fluosilicic acid*
*kg/m.3-);
*Bags *
Ferrous sulfate*
*30
60 to 65 (961 to 1040 ground 50 to 75 *(801 to 1200 kg/m .3-); lump *50 to 65 (801 to 1040 kg/m .3-); *powder 37 to 65 (593 to 1040 *kg/m.3-); avg 60 (961 kg/m .3-)
*
Ferric chloride
*
*To
*
Dolomitic lime
hydrate 80 to 90 (1280 1440 kg/m .3-); anhydrous 53 *to 62 (849 to 993 kg/m .3-)
100 lb (45.4 kg) drums 25 lb (11.3 125 lb (56.7 kg), 375 lb (170 kg)
*Powder
*kg/m.3-);
*Bag
100 lb (45.4 kg); drums 100 lb (45.4 *Glass 64 to 100 (1030 to 1600 *kg) 300 lb (136 kg), 320 lb 145 kg) *kg/m.3-); powder and granular * *44 to 60 (705 to 961 kg/m .3-) *
*
*Drums
25 lb (11.3 kg), 50 lb (22.7 kg), *350 lb (159 kg), 400 lb (181 kg) 700 lb *(318 kg); bulk solution
*Pellets
*
*
60 to 70 (961 to 1120 flakes 46 to 62 (737 *to 993 kg/m .3-) *kg/m.3-);
*Carboys
5 gal. (18.9 l) 13 gal. (49.2 l); *bulk 15 percent 10.2 lb per *drums 30 gal. (114 l); *gal. (1220 g/l) *
*
*Drums
*Specific
1 gal. (3.79 l), 5 gal. (18.9 l), *55 gal. (208 l); bulk *
gravity 1.39 11.6 lb gal.; Specific gravity 1.41 *11.73 lb/gal. *per
*
Sodium silicofluoride
*
*Bags
100 lb (45.4 kg); drums 25 lb (11.3 *Granular 85 to 105 (1360 to 1680 *kg), 125 lb (56.7 kg), 375 lb (170 kg) *kg/m.3-); powder-granular 60 to * *96 (961 to 1540 kg/m .3-) *
Sodium sulfate
*Bags,
*
bbl, drums, kegs
*
Sodium thiosulfate
*Bags, *Steel *(68.0
bbl, drums, kegs
Tetrasodium pyrophosphate
Trisodium phosphate
*53
to 60 (849 to 961 kg/m .3-)
*
cylinders 100 lb (45.4 kg), 150 lb * kg), 200 lb (90.7 kg) *
*
Sulfuric acid*
to 100 (1120 to 1600 kg/m .3-)
*
*
Sulfur dioxide
*70
*
*Bottle,
carboys 5 gal. (18.9 l), 13 gal. *Specific gravity 1.81 15.1 *(49.2 l); drums 55 gal. 9208 l), 110 gal. *lb/gal. *(416 l); bulk * *
*
*Bags
100 lb (45.4 kg), 200 lb (97.7 *kg); bbl 350 lb (159 kg); drums 25 lb *(11.3 kg), 300 lb (136 kg), 350 lb (159 *kg); kegs 125 lb (56.7 kg)
*Crystal
*
*
50 to 70 (801 to 1120 powder 46 to 66 (737 *to 1060 kg/m .3-) *kg/m.3-); *
*Bags
100 lb (45.4 kg), 200 lb (90.7 kg); *Crystal 55 to 60 (881 to 961 *bbl 325 lb (147 kg), 400 lb (181 kg); *kg/m.3-); monohydrate 65 *kegs 125 lb (56.7 kg) *(1040 kg/m .3-)
)))))))))))))))))))))))))))))2)))))))))))))))))))))))))))))))))))))))))2))))))))))))))))))))))))))))))))))
* Aggressive action on concrete. Special provisions, such as curbs or barriers, should be made to isolate and prevent spreading of spilled or leaking chemicals. The structural engineer should decide what is a reasonable stacking height when designing slabs, beams, and other supporting members. It is recommended that the specific live load, including machines, equipment, piping loads, and bases for which each part of the floor is designed, be indicated on the drawings and posted in the area in which it applies.
2.4--Types of foundations Structures covering large areas may rest on various soils or rock. The foundation may be: a. b. c. d.
Entirely on granular soil Entirely on cohesive soil Entirely on rock On any combination of the above
The type of foundation may be: a. b. c. d.
Piles Caissons Raft Spread or continuous footings
If the foundation of a structure rests entirely on only one kind of soil or rock, the design of the foundation and of the structure itself is not difficult. Design problems are more complicated when the structure rests on more than one kind of soil. Most environmental engineering concrete structures, being water or liquid-containing tanks and reservoirs, cannot tolerate much differential settlement that causes cracks and leakage. Therefore, designers of environmental engineering concrete structures should carefully minimize differential settlement of the foundations and the structures. If necessary, slabs may span between grade beams, foundation walls, and piers. In general, structures should be designed to minimize differential settlement
or designed to accommodate settlement as beams on elastic supports. Adjacent structures with different loading and function may have to be separated physically by expansion joints and/or double wall construction. Design of foundations on granular or other elastic or compressible soils should take into account not only the variations in compressibility of soil materials and the different thicknesses of the soil layers but also the variations in loading caused by alternately filling and draining adjoining tanks, basins, or reservoirs. Soil conditions should be explored with test borings, and soil samples should be analyzed to determine soil resistivity and sulfate content. A minimum of four test borings should be made for the first 10,000 ft² (929 m²) of plant area and at least two additional borings for every additional 10,000 ft² (929 m²). In addition, it may be desirable to locate extra test borings at major concentrated load locations, such as center column foundations of large diameter clarifiers or heavy equipment foundations. Investigations by, and consultation with, a geotechnical engineer is recommended. In cases of irregular rock foundations or unusual bearing strata, additional test borings may be required. It is important to observe and record the elevation of the groundwater table and any periodic and seasonal variations. The maximum and minimum elevation of the groundwater table in the plant area should be determined using the 100 year flood and drought criteria in each case. A high water table may exert uplift on the structures, may lift and damage foundation slabs, and may reduce the bearing capacity of the soil. If the structures are on piles, the use of uplift piles should be considered. Additional substructure considerations are included in Section 2.5.
2.5--Structural considerations Large reinforced concrete reservoirs on compressible soil may be considered as beams or girders on elastic supports. Sidewalls of rectangular tanks and reservoirs can be designed either as cantilever walls fixed at the bottom or as walls supported at two or more edges. Circular tanks normally resist the pressure of their contents by ring tension. Elevation of the groundwater table and flood water conditions are basic design considerations, and these loads should be considered in the same manner as internal liquid loads. The groundwater elevation may be artificially raised locally by leaks from nearby tanks or pipes. Walls supporting both interior water loads and exterior earth loads should be designed to support both the full effect of the interior water pressure and the full effect of the maximum exterior earth pressure without considering that one load could minimize the effect of the other. Should the reservoir space remain sealed, the surrounding walls and the bottom of the structure must withstand combined lateral or vertical water and soil pressures, and the structure as a whole must resist flotation. The soil reaction on an elastic slab is quite different from the soil reaction on a more rigid slab. Walls cantilevered from a
flexible slab on yielding compressible soils present a problem of mutual influence of soil and structure. Spanning a bottom mat between parallel sidewalls is not always a simple task. Increasing the thickness of the mat counteracts uplift with increased concrete weight and reduces required reinforcement. However, this approach has economic limitations. Inverted beams or crosswalls over the mat could reduce mat spans to permit economically acceptable thicknesses. All water-containing structures should be assumed to be empty for buoyancy and external pressure stress calculations. The effect of possible alternate gravity tank loads and uplift should be investigated. In some cases, uplift on the bottom mat could be limited by: (1) standpipes that automatically would bleed water into the tank when a certain groundwater elevation is exceeded; (2) installing automatic pressure relief systems in the base slab or sidewalls where applicable; or (3) lowering the groundwater table with perforated drain pipes and collection systems. Depending on soil conditions, uplift piles or drilled anchors also may be used in appropriate soil/rock conditions to resist uplift pressures. When none of these methods is practical, the use of an alarm system may be considered. The alarm system should alert the operator when a dangerous groundwater elevation is reached so that action may be taken immediately to start filling the tanks to balance the uplift. At least two independent alarm systems should be provided and tested at frequent intervals. Tanks below grade normally are tested for water-tightness before backfilling, and where appropriate, this condition should be considered in the structural design. Large-diameter tanks expand and contract appreciably as they are filled and drained. The connection between wall and footing should either permit these movements or be strong enough to resist them without cracking. When the wall is not interconnected to other structures or tanks and free to move, the joint detail at both the floor and roof should be carefully designed and constructed. The analysis of rectangular wall panels supported at three or four sides is explained in detail in References 6 and 7, which contain tabulated coefficients for design. When the wall panels are rectangular and the dimensional ratios exceed those given in the coefficient tables, the tables still may be of some use. The end regions of the rectangular wall panel can be designed based on the coefficients for the closest aspect ratio in the table. Determine end moments at wall intersections. The remaining middle portion of the wall is then designed as a one-way span or cantilever. As an alternative, an elastic analysis can be used. Vertically reinforced walls supported at top and bottom also are used frequently. These are particularly advantageous when a rectangular tank is relatively narrow or when the tank is supported on piles. It may be desirable to design the side wall of a tank for two conditions: as a cantilever wall and as one supported at top and bottom. The reason for the double design is that such sidewalls, when the tank is constructed in an excavated area, will often be backfilled before the top support is
constructed. It should be noted that expansion joints in tank floors will eliminate the continuity between the opposite walls. Therefore, the designer should carefully investigate sliding, including the reduction of friction due to buoyancy from leakage. Reinforced concrete walls at least 10 ft (3.0 m) high that are in contact with liquids should have a minimum thickness of 12 in. (305 mm). Usually, the minimum thickness of any minor structural member in environmental engineering concrete structures is 6 in. (152 mm). A minimum of 8 in. (203 mm) will be required where a 2 in. (51 mm) concrete cover is desired. However, when waterstops are used and the positioning of reinforcement might adversely affect proper placement, a greater thickness should be considered. It should be noted that the shear key problem discussed in Section 2.8.4 is particularly severe in thin walls. For crack control, it is preferable to use a large number of small-diameter bars for main reinforcement rather than an equal area of larger bars. Maximum bar spacing should not exceed 12 in. (305 mm). Section 10.6.4 of ACI 318R provides guidance for limiting bar sizes. The amount of shrinkage and temperature reinforcement that should be provided is a function of the distance between the joints that will dissipate shrinkage and temperature stresses in the direction of the reinforcement. In addition, the amount of shrinkage and temperature reinforcement is a function of the particular concrete mix and other properties, the amount of aggregate, the member thickness, its reinforcement, and the environmental conditions of the site. These factors have been considered in applying the analysis method developed by Vetter[8] to environmental engineering concrete structures, and the recommendations contained in the remainder of this section are based on this work.[9] Shrinkage and temperature reinforcement should not be less than the ratios given in Fig. 2.5 except when shrinkage-compensating concrete is used.
Contraction and construction joint spacings of up to 75 ft (22.9 m) have been used successfully with shrinkage-compensating concrete and 0.3 percent reinforcement. When shrinkage-compensating concrete is used, construction details should be developed in accordance with ACI 223 recommendations. Consideration may be given to reducing the amount of shrinkage and temperature reinforcement shown in Figure 2.5 when details are developed in accordance with ACI 223 recommendations and non-shrinkage compensating concrete is used. Concrete sections 24 in. (610 mm) or thicker may have the minimum temperature and shrinkage reinforcement at each face based on a 12 in. (305 mm) thickness. Temperature and shrinkage reinforcement should be spaced not greater than 12 in. (305 mm) on center, divided equally between the two surfaces of the concrete section. The reinforcement in the bottom of base slabs in contact with soil may be reduced to 50 percent of the value given in Fig. 2.5. Minimum concrete protective covering of reinforcement should be as shown in Table 2.5. Table 2.5--Minimum concrete cover for reinforcement )))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
Slabs and joists: Top and bottom bars for dry conditions: #14 and #18 bars 1-1/2 in. #11 bars and smaller 3/4 in. Formed concrete surfaces exposed to earth, water, or weather, and over or in contact with sewage and for bottoms bearing on work mat, or slabs supporting earth cover: #5 bars and smaller 1-1/2 in. #6 through #18 bars 2 in. )))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
Beams and columns: For dry conditions: Stirrups, spirals, and ties 1-1/2 in. Principal reinforcement 2 in. Exposed to earth, water, sewage, or weather: Stirrups and ties 2 in. Principal reinforcement 2-1/2 in. )))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
Walls: For dry conditions: #11 bars and smaller 3/4 in. #14 and #18 bars 1-1/2 in. Formed concrete surfaces exposed to earth, water, sewage, weather, or in contact with ground: Circular tanks with ring tension 2 in. All others 2 in. )))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
Footings and base slabs: At formed surfaces and bottoms bearing on concrete work mat At unformed surfaces and bottoms in contact with earth Top of footings--same as slabs Over top of piles
2 in. 3 in.
2 in.
)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
Environmental engineering concrete structures necessarily cover large areas, and the covering of filter beds and tanks may pose problems. In roof design the engineer should take into consideration exposure to a humid, possibly corrosive, interior atmosphere and should allow for movement joints in walls. The latter can be accomplished by carrying the joints through the roof. Supports designed to permit sliding of concrete on concrete frequently result in problems such as spalling of the supporting ledges on beams, walls, and slabs and are not recommended. Superstructures of environmental engineering structures, other than tanks, are not discussed in detail because they are frequently similar to conventional structures. In some facilities, the gases generated may be toxic and also present an explosion hazard. Additional ventilation, pressure venting, gas alarms, and provision for explosion venting may be required. Where buildings or equipment rooms are located over the tops of tanks or digesters, the tanks may require gas-proofing by means of liners and/or the installation of gas detection equipment.
2.6--Structural design 2.6.1 General--ACI 318 contains general requirements for reinforced concrete building structures that are also valid for environmental engineering concrete structures. The design engineer should establish the design criteria for a specific concrete structure within the limitations of the ACI or local building codes based on the special requirements of environmental engineering structures. Environmental engineering concrete structures generally belong to the category of structures for which minimal cracking is a paramount requisite. Leakage into potable water or out of contaminated water facilities must be avoided to protect the public health. Therefore, experienced designers of environmental engineering structures have established somewhat more conservative allowable stresses for such reinforced concrete structures. The strain of the reinforcing bars under stress will be transferred to the adjoining concrete. Low stress in reinforcement at service loads will tend to minimize the amount of cracking. The structural design recommendations herein are to be regarded as minimum provisions for general use. Any special structural features, unusual loading combinations, or unusual exposure conditions may require special design precautions more conservative than the minimum provisions. In particular, the designer should consider the structural effects of joint spacings and details, and construction sequences. Special design considerations regarding details and specifications should be given to the possible hazardous and corrosive effect of oxygen, ozone, hydrogen sulfide, and methane gases in closed tanks. This is especially important when habitable spaces are located above the tank. 2.6.2 Design requirements--Reinforced environmental engineering concrete structures must be designed for both strength and
serviceability. 2.6.3 Methods--Two methods of structural design for reinforced concrete sections generally are accepted in practice, and both are applicable to environmental engineering concrete structures. These methods are presently described in detail in ACI 318. They are (1) strength design, using factored loads U, specified steel and concrete strengths f +y, and f' +c,, and capacity reduction factor N; and (2) working stress design (alternate design method, ACI 318, Appendix B), using service loads and reduced allowable working stresses. 2.6.4 Special limitations--Both methods require special limitations for application to environmental structures to assure resistance to leakage of liquids and long life under conditions of exposure in environmental service. For additional design information when using concrete made with shrinkage-compensating cement, see Chapter 3 of ACI 223. 2.6.5 Strength design--The load factors prescribed in ACI 318 may be directly applied to environmental engineering concrete structures with one adjustment. The load factors for both the lateral earth pressure H and the lateral liquid pressure F should be taken as 1.7. The factored load combinations for total factored design load U, as prescribed in ACI 318, should be increased by sanitary durability coefficients for environmental engineering concrete structures as follows: a. In calculations for reinforcement in flexure, the required strength should be 1.3 U. b. In calculations for reinforcement in direct tension, including hoop tension, the required strength should be 1.65 U. c. "The required design strength for reinforcement in diagonal tension (shear) should be calculated by applying a sanitary durability coefficient of 1.3 times the excess shear. Excess shear is defined as the difference between the factored shear force at the section, V +u,, and the shear strength provided by the concrete, NV+c,. Thus NV+s, $ 1.3 (V +u, ) N V+c,), where NV+s, is the design capacity of the shear reinforcement." d. In calculations for the compressive region of flexure and compressive axial loads, and for all loads carried by concrete, the required strength should be 1.00 U. e. For factors to be used in seismic design, refer to ACI 318. As noted previously, the durability coefficients were developed from crack width calculation methods. 2.6.6 Serviceability for normal sanitary exposures* (* Normal sanitary exposures are defined as liquid retention [watertight], exposure to liquids more alkaline than pH of 5, or exposure to sulfate solutions of less than 1500 ppm. *) Except as provided in this section, serviceability requirements of ACI 318 to control calculated deflections and crack width are applicable to environmental engineering concrete structures. For
flexural reinforcement located in one layer, the quantity Z should not exceed 115 kips/in. Z values were established for cover equal to or less than 2 in. (51 mm) and should be based on this value when the cover exceeds 2 in. Additional cover may be regarded as added protection.[10,11] The Z factor and crack width are a function of the concrete cover and overall thickness of a flexural member and are valid only for one-way flexural members. The designer should use the basic Gergley-Lutz equation, as recommended in the Commentary to Section 10.6.4 of ACI 318, for one-way flexural members. For members subject to direct tension (hoop tension), a sanitary durability coefficient of 1.65 may be used for all grades of reinforcing.[10,11] The factor Z has no direct bearing for this state of stress. The reinforcement for a two-way flexural member (e.g., slabs and walls) may be proportioned in each direction based on Section 2.6.5 since reliable crack-width equations for such members are not available in the literature at this time.[11,12] For design by the working stress method of Section 2.6.7, deformed bars or wire should be spaced so that the quantity Z does not exceed 115 kips/in., as shown in Fig. 2.6.7(a), 2.6.7(b), and 2.6.7(c), and the spacing should not exceed 12 in. (305 mm).
In all other flexural members, bar spacing should be limited so that calculated Z values do not exceed 115 kips per in. Deformed bar or wire spacings should not exceed 12 in. (305 mm). Preferably bar sizes should not exceed #11. For severe environmental exposures,* structural design should conform to Section 2.6.6 with the quantity Z which does not exceed 95 kips/in., and surface or other protection or barrier should be provided suitable for the particular conditions of exposure.
(* Severe sanitary exposures are conditions in which the limits defining normal sanitary exposures are exceeded. *) 2.6.7 Alternate design method, ACI 318, Appendix B (working stress design)--Except as noted below, the alternate design method should be in accordance with ACI 318, Appendix B. Recommended concrete and steel stresses for design at service loads are presented in Tables 2.6.7(a) and 2.6.7(b). Table 2.6.7(a)--Recommended allowable stresses* for concrete in environmental engineering concrete structures that must be water tight and resistant to chemicals )))))))))))))))))))))))))))))))))))))))))))))))))0))))))))))))))) *
Description
*
Recommended value, psi
)))))))))))))))))))))))))))))))))))))))))))))))))3))))))))))))))) *29,000,000
Modulus of elasticity ratio
n
*))))))))))))))) *W.1.5 -33 %f' +c, *
Flexure: Extreme fiber stress in compression f +c, Extreme fiber stress in tension in plain concrete footings and walls
* *0.45 %f'+c, * *1.6 %f' +c, *
Shear: Ç (as a measure of diagonal tension at d from face of support) Beams with no web reinforcement Joists with no web reinforcement Members with web reinforcement or properly combined bent bars and vertical stirrups Slabs and footings (peripheral shear)
* * * *1.1 %f' +c, *1.2 %f' +c, * *5 %f'+c, *2 %f'+c, *
Bearing: On full area On one-third area or less
* *0.25 %f'+c,
*0.375 %f'+c,
)))))))))))))))))))))))))))))))))))))))))))))))))2)))))))))))))))
*Recommended working stresses shown above are in terms of f' +c, for all strengths of concrete. For minimum recommended f' +c, see Section 3.5.1. Other requirements should conform to Appendix B (alternate design method) of ACI 318. Table 2.6.7(b)--Recommended maximum stresses at service load for recommended maximum 12-in. (305 mm) spacing of reinforcing bars in environmental engineering concrete structures ))))))))))))))))))0)))))))))))))))))))))))))))0)))))))))))))))))))))))))))
Sanitary structure * exposure condition* and maximum Z * value 3 * *
Bar sizes
* * * *
Maximum stress at service load, psi (kPa) Grade 60 Grade 40
))))))))))))))))))3)))))))))))))))))))))))))))3)))))))))))))))))))))))))))
All sizes
* *
Members in direct tension
* *
20,000 (138,000)
14,000 (96,000)
))))))))))))))))))3)))))))))))))))))))))))))))3)))))))))))))))))))))))))))
Flexural members * Severe exposure *
* *
22,000
20,000
*
#3, #4, #5
(Maximum Z = 95)
*
(152,000)
(138,000)
/)))))))))))))))))))))))))))3)))))))))))))))))))))))))))
Flexural members Normal sanitary * (Maximum Z = 115) *
*
*
* *
27,000 (186,000)
20,000 (138,000)
))))))))))))))))))3)))))))))))))))))))))))))))3)))))))))))))))))))))))))))
Flexural members Severe exposure * (Maximum Z = 95) #6, #7**, #8**
*
*
*
* *
18,000 (124,000)
18,000 (124,000)
/)))))))))))))))))))))))))))3)))))))))))))))))))))))))))
Flexural members Normal sanitary * (Maximum Z = 115) *
*
*
* *
22,000 (152,000)
20,000 (138,000)
))))))))))))))))))3)))))))))))))))))))))))))))3)))))))))))))))))))))))))))
Flexural members Severe exposure *(Maximum Z = 95) *
*
*
* *
17,000 (117,000)
17,000 (117,000)
#9**, #10**, #11** .)))))))))))))))))))))))))))2))))))))))))))))))))))))))) * Flexural members * 21,000 20,000 * Normal sanitary * (145,000) (138,000) * (Maximum Z = 115) * ))))))))))))))))))2)))))))))))))))))))))))))))2)))))))))))))))))))))))))))
* Normal sanitary exposure is defined as liquid retention (watertight) exposure to liquids with pH > 5 or exposure to sulfate solutions of less than 1500 ppm. Severe sanitary exposures are conditions in which the limits defining normal sanitary exposure are exceeded. 3 The Z values referred to are defined in ACI 318. Derivations for crack control formulas are in the commentary to ACI 318R.
** Bar sizes #7 through #11, in Grade 40, have been deleted from ASTM A 615. These stresses are for a maximum bar spacing of 12 in. and have been established to control crack widths for concrete surfaces exposed to conditions encountered in environmental engineering concrete structures. The stresses for 12 in. bar spacings should not exceed 27,000 psi (186 KPa) for Grade 60 reinforcement nor 20,000 psi (137 KPa) for Grade 40 reinforcement. Fig. 2.6.7(a), 2.6.7(b), and 2.6.7(c) are presented for lesser bar spacings and a broader range of Z values. Development lengths and anchorages should conform to the requirements of ACI 318.
2.7--Reinforcement splices Splices in reinforcement should conform to the requirements of ACI 318. In circular tanks designed for ring tension, the location of splices should be staggered. Adjacent hoop reinforcing splices should be staggered horizontally (center of lap to center of lap) by not less than one lap length nor 3 ft and should not coincide in vertical arrays more frequently than every third bar. It should be noted that due to the unusually thick slabs found
in some liquid-retaining structures, the slab top bar mats may require "top bar" lap lengths. Top bar requirements are set forth in ACI 318.
2.8--Joints 2.8.1 Volume changes--Volume changes in concrete generally are caused by expansion or contraction in response to changes in creep, shrinkage, temperature, or moisture content. Temperature variations, being daily and seasonal, are somewhat more regular and predictable than moisture changes. Contraction due to evaporation of excess water begins during or after the curing period, depending on the quality of the moisture and temperature controls. Shrinkage may continue for several years, as is shown in Fig. 2.8.1, unless water is added to the hardened concrete for extended periods.
However, in environmental engineering concrete structures designed to contain liquids, the shrinkage may be halted when the structures are placed in use and even reversed during hot, humid weather. To provide for volume changes in a manner that will minimize damage to the concrete, movement joints and reinforcement should be provided for in the structure by the design engineer. All joints should be shown on the engineering drawings. Additional guidance on joints is contained in ACI 504R. Shrinkage-compensating concrete can be used to reduce shrinkage cracking in environmental engineering concrete structures, but this committee is not yet in a position to recommend detailed requirements for its use. Additional detailed information on shrinkage-compensating concrete is contained in ACI 223. It should be noted that additional care and control should be exercised during design and construction. 2.8.2 Movement joints 2.8.2.1 Expansion joints--Expansion joints are movement
joints used to allow for expansion and contraction of concrete during the curing period and during service to permit dimensional changes in concrete due to load, to separate or isolate areas or members that could be affected by such dimensional changes, and to allow relative movements or displacements due to expansion, contraction, differential foundation movement, or applied loads. Expansion joints also can function as contraction joints or construction joints. In general, expansion joints should be provided near abrupt changes in the structure configuration. As stated in the foreword of the Federal Construction Council Technical Report No. 65 (National Academy of Sciences), "Many factors affect the amount of temperature-induced movement that takes place in a building, and also the extent to which this movement can take place before serious damage will occur or extensive maintenance will be required. Because of the complexity of this problem, no one has yet established nationally acceptable procedures for precisely determining the size and location of expansion joints."[14] Historically, in environmental engineering concrete structures, the spacing of expansion joints has been conservative and much influenced by the restraints inherent in the geometry of tanks and buildings, with spacings varying from 50 to 250 ft for walls and superstructures. Base slabs with frequent construction joints have been built, without expansion joints, up to 600 ft in length. In general, expansion joint spacing preferably should not be spaced greater than 120 ft (36.6 m). When the spacing of expansion joints exceeds 150 ft (46 m), a special investigation should be made for the reinforcement requirements and the expansion joint details. The restraint exerted on the base slab by the soil should also be investigated. It is often desirable to locate expansion joints at abrupt changes in the structure configuration but when so placed, the joint details must be designed to transfer the shear caused by differential deflection of the elements on each side of the joint or, if shear transfer is not provided for, to accommodate the distortion in the joint details caused by the differential deflection such as in the waterstop. The recommendations of the preceding paragraph are for normal environmental engineering concrete structures partially filled with a liquid. When tanks or other structures will remain empty for long periods of time, particularly in hot climates, closer spacings should be used. In this respect, particular attention should be paid to conditions during construction. Many satisfactory expansion joint details have been devised and used, some of which are illustrated in Fig. 2.8.2.1.
Other suggested details are found in Fig. 8, 11, and 12 of the ACI 504R. All expansion joints should include some type of compressible preformed filler and a joint sealant or compression seal at the liquid face. If the member must be watertight, a suitable waterstop, made of rubber, neoprene, or plastic, should be included to act as the primary barrier to leakage. Waterstops, preformed joint filler, and joint sealant should be selected to allow for the movement anticipated. Reinforcement should terminate 2 in. (51 mm) from the face of the joint. 2.8.2.2 Rubber waterstops permit the greatest joint movement and last indefinitely when kept in a dark and humid environment. Polyvinyl chloride waterstops permit somewhat less movement than rubber and are less sensitive to light and drying out. Polyvinyl chloride may be spliced by applying heat. The minimum thickness of either type should be 3/8 in. (9.5 mm), and they should be at least 9 in. (230 mm) wide for expansion joints and 6 in. (150 mm) wide for other types of joints to provide adequate embedment in the concrete.[15] In any event, the engineer should verify that the water stop is chemically compatible with the liquid it must contain. The preformed joint filler has the twofold task of serving as a form for the second placement of concrete and preserving the space into which the concrete may expand. An ideal joint filler will permit compression to one-half its original width and will reexpand to fill the joint when the adjacent members contract. Cork, neoprene, rubber, foam, and other materials conforming to ASTM D 994, D 1056, D 1751, and D 1752 are satisfactory joint fillers. 2.8.2.3 Sealants should be recommended by the manufacturer for the intended service. Only a few nonsag sealants have been recommended for submerged service. For other services, nonsag and self-leveling sealants may be used. Water treatment plants and reservoirs require sealants approved for potable water. In addition to taste, odor, and toxicity concerns, the sealant should be resistant to chlorinated water. Consideration should be given to the effects of prolonged exposure to chlorine at normal drinking water concentrations, as well as short-term exposure to chlorine at the high concentrations required for disinfection. Sealants intended for use should be approved by agencies having jurisdiction over the specific project or resource. 2.8.2.4 Contraction joints--Some designers use contraction joints as a type of movement joint to dissipate shrinkage stresses. Where used, a contraction joint should be located at intervals not exceeding 30 ft (9.1 m) unless additional reinforcement is provided, as recommended in Fig. 2.5. Two types of contraction joints known as "full" and "partial" contraction joints are in common use. In full contraction joints, all reinforcement is terminated 2 in. (51 mm) clear of the joint. The abutting ends of the concrete are coated with a bond breaker (see Fig. 2.8.2.4).
Waterstops, which may be metal, plastic, or rubber, should be used for watertightness. Where necessary to insure equal deflection of each side of the joint, a method of transferring stress such as smooth dowels, should be provided. A sealant usually is provided along the exposed perimeter of the joint to exclude water or foreign matter. It may be desirable to pass tension forces through the joint to tie portions of the structure together. In this case a partial contraction joint may be used. This joint is similar to the full contraction joint; however, in order to weaken the joint and assure crack formation, not more than 50 percent of the reinforcement is passed through the joint. Inserts which reduce the cross section of the concrete and form a weakened plane have been used to form partial contraction joints in slabs and paving. If the insert is removable, the resultant void should be filled with sealant. It is desirable to use reduced spacing for partial contraction joints. This spacing should be approximately 2/3 that of the full contraction joint. If splices are used at partial contraction joints, they should be positioned as shown in Fig. 2.8.2.4. Contraction joints may not be required when using shrinkage-compensating concrete. Typical contraction joint details are shown in Fig. 2.8.2.4. 2.8.2.5 Additional reinforcement at joints--Movement joints, particularly expansion joints, should have the concrete ends reinforced to resist spalling and/or splitting of the concrete due to inadvertent contact with the concrete on the other side of the joint. The reinforcement should not be smaller than #3 bars spaced 12 in. on center, should be along each face of the joint, and should be anchored back along the normal concrete reinforcement. 2.8.3 Construction joints--Construction joints, which should not be taken as movement joints unless designed in accordance
with Section 2.8.2.4, should be located so as to least impair the strength of the structure, to provide logical separations between segments of the structure, and to facilitate construction. Additional construction joints, or revised locations of joints, may be proposed by the contractor but should be subject to approval of the designer. Before placing new concrete against it, the surface of the joint should be prepared to insure a good bond, unless designed as a contraction joint (Section 2.8.2.4). All reinforcement should be continued across or through construction joints, unless designed as in Section 2.8.2.4. Where the joint must be watertight, a waterstop should be used. 2.8.4 Shear keys for movement joints--In some instances, shear keys have proved troublesome in practice. Failure of the key can result in leakage due to bypassing of the waterstop. When shear keys are used, special precautions should be taken to avoid this problem. A number of techniques have been used, including shear transfer with dowels and steel waterstops, relocation of the waterstop, and redesign to avoid the necessity of shear transfer. 2.9--Impact, vibration, torque, and seismic loads To maintain the watertightness of a structure, it is essential that cracking and crack widths be kept to a minimum. Accordingly, special care is needed in designing for impact and vibration, either of which can initiate or propagate cracks. In particular, the effect of vibration is cumulative and cracks will continue to develop and grow with time. It is, therefore, important that corrective action to reduce the vibration be taken as early as possible in structures where vibrations have caused cracking. 2.9.1 Impact--Impact loads are occasionally encountered in environmental engineering concrete structures. When they are present, a conservative design approach is recommended to keep cracking to a minimum. Design for impact should be as thorough as possible. However, where a complete shock analysis is not practical, appropriate impact factors should be used and design should be based on the stresses recommended in Section 2.6. An appropriate impact allowance, frequently in the range of 25 percent of the weight, is used for heavy machines. 2.9.2 Vibration--Most of the mechanical equipment associated with environmental engineering structures, such as scrapers, clarifiers, certain types of flocculators, and rotating vacuum screens, is basically slow-moving and will not cause structural vibrations. For such equipment, a separate design for dynamic loading is unnecessary. Other commonly used machines, such as centrifugal pumps, fans, centrifuges, blowers, generator engines, and compressors, have much higher rotational speeds and require special considerations in the design of their support structures and foundations. Usually, the value of such machines is so much more than the cost of the foundation that it is imprudent to economize on foundation costs and run the risk of shortened machine life, increased maintenance costs, and breakdowns. In environmental engineering structures, the machines that most often cause vibration problems are forced-draft fans and centrifuges used for dewatering clarifier sludge or digester sludge. These are very sensitive machines and need carefully designed foundations with no critical resonant vibration.
Chemical mixers may also serve as the source of significant dynamic loads. The supports of such mixers are particularly prone to vibration. The key to successful dynamic design is to insure that the natural frequency of the machinery support structure is significantly different from the frequency of the disturbing force. If the two frequencies approach each other, resonant vibrations will be set up in the support structure. To minimize resonant vibrations, the ratio of the natural frequency of the structure to the frequency of the disturbing force should be kept out of the range from 0.5 to 1.5. As discussed later in this section, it is preferable to maintain a frequency ratio above 1.5. For spread foundations, the safe-bearing load frequently is assumed as one-half of the permissible safe load for statically loaded foundations at the same location and on the same soil or rock.[16,17] Some equipment manufacturers recommend minimum foundation/equipment mass ratios, generally in the range of four to six. Adherence to this rule has not always proved satisfactory,[18] and to insure that the equipment will not be in resonance with the foundation, it is recommended that the natural frequency of the foundation system be calculated. For natural frequency calculations, follow the method recommended in Reference 16. For pile-supported foundations, follow the recommendations found in References 19 through 21. Often the machine foundation is insulated or entirely separated from the floors and other parts of the structure, minimizing transmission of vibration to other areas of the building. If the anticipated vibration is of a frequency and amplitude that can be transmitted through the ground, the equipment foundation also should be insulated from the ground by shock-absorbing supports. More detailed information on the dynamic design of foundations can be found in Reference 22. If the machine is not supported directly on a solid foundation but on columns and beams, it is the natural frequency of the support members that is of primary importance. Needless to say, the strength of these members also must be within acceptable limits. The natural frequency of a structure should be calculated for the vertical direction and for the two principal horizontal directions. To combine the effect of several masses, such as those due to the machine and the structure, the natural frequency can be calculated using the following formula:
where F+N, F+1, F+2, F+3, F+4,
= = = = =
combined natural frequency natural frequency due to Mass natural frequency due to Mass natural frequency due to Mass natural frequency due to Mass
1 2 3 4
The individual frequencies, in cycles per min, can be calculated using the expressions given in Table 2.9.2(a), in which D is the immediate deflection due to the mass being considered. Table 2.9.2(a)--Natural frequencies of beams ))))))))))))))))))))))))))))))))))))))))))))))))))))0))))))))))))))))))))))))))) * *
Natural frequency, cycles per minute
)))))))))))))))0))))))))))))))))))0)))))))))))))))))3)))))))))))0)))))))))))))))
End condition *
*
* Where D
)))))))0)))))))1
*
*
End 1
* End 2 * *
Load
*Position of *deflection D
*
Where D * is is * *deflection, * deflection, in. mm * *
)))))))3)))))))3))))))))))))))))))3)))))))))))))))))3)))))))))))3)))))))))))))))
Fixed
*
*
* Free
*
*
*
Uniform
*
*
233
*
1174
*End 2
*
))))
*
))))
*
*
%D
*
%D
)))))))3)))))))3))))))))))))))))))3)))))))))))))))))3)))))))))))3)))))))))))))))
Pin
* Pin
Fixed
or * * Fixed *
*
Uniform
*
*
233
*
1174
*Midspan *
* *
)))
* *
))))
%D
%D
)))))))3)))))))3))))))))))))))))))3)))))))))))))))))3)))))))))))3)))))))))))))))
Fixed
Fixed
Pin
* Fixed * or * *
*
* Free
*
Concentrated (any position)
* *
* *
* *
*
*
188
*
947
*
*
)))
*
)))
%D
*
%D
or
*
*Under Load
*
*
*
*
*
*
* Pin
*
*
*
*
)))))))2)))))))2))))))))))))))))))2)))))))))))))))))2)))))))))))2)))))))))))))))
Gravity should be assumed to act in the direction of vibration, and in lieu of a comprehensive analysis, D can be calculated using the method outlined in Section 9.5.2.3 of ACI 318.
The preceding equations provide a simple method of computing the natural frequency of a structure from its static deflection. For the case of a concentrated load only, Table 2.9.2(b) relates the static deflection of a structure supporting an item of equipment to the natural frequency of that structure as calculated using the equations. A similar table can be developed for structures in which the uniform loads or other loads are significant. As stated, the ratio of natural frequency of the structure to frequency of the machinery or other disturbing force should be either less than 0.5 or greater than 1.5, preferably the latter. Table 2.9.2(b) shows recommended maximum structural deflections for given equipment operating speeds.
Table 2.9.2(b)--Recommended maximum structural deflection for given equipment operating speeds )))))))))))))))))))0))))))))))))))))))))))0))))))))))))))))))))))))))))
Recommended minimum natural * frequency of * Operating speed *structure, cycles per of machinery, min from formula * cycles per min (Hz) * (Hz) *
* * *Maximum
static deflection of structure due to dead *load and machinery load, in. (mm) * *
)))))))))))))))))))3))))))))))))))))))))))3))))))))))))))))))))))))))))
400 (6.67) 600 (10.0) 800 (13.3) 1000 (16.7) 1200 (20.0) 2000 (33.3) 2400 (40.0)
* * * * * * *
600 (10.0) 900 (15.0) 1200 (20.0) 1500 (25.0) 1800 (30.0) 3000 (50.0) 3600 (60.0)
* * * * * * *
0.10 (2.54) 0.044 (1.12) 0.025 (0.635) 0.016 (0.406) 0.011 (0.279) 0.0040 (0.102) 0.0027 (0.069)
)))))))))))))))))))2))))))))))))))))))))))2))))))))))))))))))))))))))))
Theoretically, the natural frequency of the structure also could be lower than the operating rotation of the machine and thus avoid resonant vibration. In this case, the natural frequency of the support should be at least 50 percent below the operating frequency of the machinery. A disadvantage is that the machine would pass through the critical cycle at startup and shutdown. It is not likely that the short coincidence of time would cause damage to the machine, but generally it is preferable to keep the deflection low and the natural frequency of the structure well above operating speed. It is also possible that the machine will be operated at a lower speed for some time, and this lower speed could coincide with, or be close to, the critical frequency of resonant vibration. If the machinery is installed on an upper floor, the use of vibration isolators is recommended, but this should not be considered a substitute for dynamic structural design, since all isolators transmit some vibration. A more complete discussion of dynamic analysis methods is given in References 23 through 26. 2.9.3 Torque--In some cases, it may be necessary to consider torque in the design of the structure. Large circular clarifiers frequently fall into this category. Most clarifiers support the entire mechanism on a center column. The diameters of clarifiers are steadily increasing, and there are now clarifiers of 500 ft (152 m) diameter in operation. These clarifiers have cantilever scrapers close to 250 ft (76 m) in length. Stalling torques of up to 5,000,000 lb-ft (6,780,000 N-m) are specified, and the foundation must be able to resist this load. There have been cases where the center column has sheared off from the foundation. Often, a limit switch is included in the mechanism to prevent overload of the structure. In a few types of clarifiers, the radial scrapers are supported on a center column but driven by a carriage that rides on the periphery of the clarifier. With this type, horizontal reactions occur at both the center column and the periphery, and there is no torque.
The sludge accumulation, which produces the specified stalling torque, is assumed to be a triangular horizontal load on the cantilever arms, the maximum being at the center and tapering off to zero at the circumference. This corresponds with the probable pattern of the sludge accumulation. From the viewpoint of the foundation, the load distribution of the steel structure is immaterial. However, the magnitude of the stalling torque is important, and the foundation and the center column usually are designed to resist a torque of 50 percent in excess of the stalling torque. The resisting earth friction and passive earth pressure have small lever arms about the center of the torque, and it is possible, if the foundation is small or in loose fills or slippery silts, for the clarifier drive mechanism to start turning the center column foundation. However, the concrete center column may be keyed and doweled into the clarifier base slab to resist this torque. The torque resistance of the foundation can be increased by the use of batter piles at the periphery of the foundation. Increasing the friction by increasing the foundation weight and/or increasing the area of the foundation to give a bigger lever arm also will provide greater torque resistance. 2.9.4 Design of tanks to resist seismic loads--In design of tanks to resist seismic loads, the hydrodynamic mass of the contained fluid should be considered in the seismic load determination. This applies to both open and enclosed tanks and all sizes and shapes, e.g., square, rectangular, and circular. Hydrodynamic pressures should include both impulsive and convective components. Impulsive pressures are developed by accelerations of the tank walls acting against the mass of the contained liquid. Convective pressures are those produced by oscillations (sloshing) of the liquid within the tanks. In addition to the preceding, the tanks should also be designed to include seismic effects of external earth pressures and dead loads of the structure. Methodology for developing hydrodynamic pressures has been developed by G. W. Housner and is contained in Reference 27. Additional information on seismic-induced loadings of environmental facilities is contained in Reference 28. Other rational methods for determining the seismic resistance of tanks, such as the energy method described in References 29 and 30, may be used. Seismic action can induce large horizontal and overturning forces on environmental engineering concrete structures. Special provisions may be required when joints at the base of tanks are required to resist high shear forces and tension loads and, at the same time, fulfill the movement requirements outlined in Section 2.8.
CHAPTER 3--MATERIALS, MIXTURE PROPORTIONING, AND TESTING Selection and storage of materials and mixture proportioning for environmental engineering concrete structures should be in conformance with ACI 301, except as specifically recommended in this report. 3.1--Cementitious materials 3.1.1 Cement--Except for the limitations of Sections 3.1.2 and 3.1.3, cement should conform to one of the following specifications. 1. Portland cement ASTM C 150, Types I, IA, II, IIA, III, IIIA, or V. 2. Blended hydraulic cement ASTM C 595 Types I(PM), I(SM), IP, and their air-entrained modifications, as denoted by Suffix A. 3. Expansive hydraulic cement ASTM C 845, Type E-IK.
If air-entrained concrete is required, an air-entraining admixture as noted in Section 3.2 should be used. These different cements should not be used interchangeably in the same element or portion of the work. Additional guidance on cement may be found in ACI 225R. 3.1.2 Sulfate-resistant cement--The C +3,A content of the cementitious material should not exceed 8 percent in any concrete exposed to moderate sulfate attack (150 to 1000 ppm). Portland blast furnace slag cement (ASTM C 595), Types IS (MS) or IS-A (MS), also may be used for such exposures as well as portland pozzolan cement (ASTM C 595), Types IP or IPA, provided the pozzolan content does not exceed 25 percent by weight of the cementitious materials. For severe sulfate exposure (1000 ppm or more), a cementitious material with not more than 5 percent C +3,A should be used. If this type is not available, a cement with a C +3,A content between 5 and 8 percent may be used with a 10 percent reduction in water-cement ratio. Alternatively, substituting a pozzolan such as fly ash for cement by weight so that the total C +3,A content of the resulting cement plus pozzolan is not greater than 5 percent may be done. In this case, the pozzolan should not exceed 25 percent by weight of the cement plus pozzolan. Higher alkali could be permitted if a suitable fly ash or other pozzolan, or ground granulated blast-furnace slag, can be used as an inhibitor of the reaction. Some expansive hydraulic cements (shrinkage-compensating) made with Type II or Type V portland cement clinker and adequately sulfated can provide adequate sulfate resistance. (See Section 2.5.7 of ACI 223.) 3.1.3 Low alkali cement--Where aggregates are alkali reactive, a cement containing less than 0.60 percent alkalies should be used. 3.1.4 Pozzolans--Pozzolans should conform to ASTM C 618 and
should have a pozzolans are not exceed 25 avoid erratic
loss on ignition of less than 3 percent. Not all beneficial to sulfate resistance. Pozzolans should percent by weight of the cement plus pozzolans to absorption of admixtures.
3.2--Admixtures An air-entraining admixture should conform to ASTM C 260. It has been found that this type of admixture has a number of beneficial effects, in addition to improving resistance to the effect of freeze-thaw cycles. These include improved workability (with constant slump), less bleeding, better paste structure, and less shrinkage. As a result, their use contributes to a dense watertight structure, and they should be used in all concrete covered by Section 3.5.1. If chemical admixtures are used, they should meet the requirements of ASTM C 494. Pozzolans should meet the requirements of ASTM C 618. The use of all admixtures should be in accordance with ACI 212.2R and should be acceptable to the engineer. The use of water-reducing admixtures is recommended. Additional guidance may be found in ACI 226R. Admixtures intended for use with shrinkage-compensating cement should be used only with the prior knowledge and approval of the cement manufacturer. 3.2.1 Chloride content--The maximum water-soluble chloride ion content, expressed as a percent of the cement, contributed from all ingredients of the concrete mix, including water, aggregates, cementitious materials, and admixtures, should not exceed 0.06 percent for prestressed concrete or 0.10 percent for all other concrete. If the structure is exposed to chloride, the maximum water-soluble chloride content should be 0.10 percent similarly expressed and measured. Only those admixtures expressly stated by the manufacturer as being chloride-free should be used. Determination of water-soluble chloride ion content should be in accordance with Federal Highway Administration Report No. FHWA-RD-77-85, "Sampling & Testing for Chloride Ion in Concrete." No calcium chloride or admixture containing chloride from other than incidental impurities should be used.
3.3--Water Mixing water should be potable, except that fresh nonpotable water may be used if mortar cubes made with the water in question have 7- and 28-day strengths equal to at least 90 percent of the strength of similar specimens made with potable water when tested in accordance with ASTM C 109.
3.4--Aggregates 3.4.1 Aggregates for watertight, chemical resistant concrete--Fine aggregates should conform to the provisions of ASTM C 33. Coarse aggregates should be sized to be as large as practical, consistent with the placing constraints, as required by the
engineer and as described in ASTM C 33, and should conform to all quality requirements noted therein. The nominal maximum size of coarse aggregate should not be larger than one-fifth of the narrowest dimension between sides of the forms, one-third of the depth of slabs, or three-fourths of the minimum clear spacing between reinforcing bars. These limitations may be waived if, in the judgment of the engineer, workability and methods of consolidation are such that the concrete can be placed without honeycomb or void. 3.4.2 Aggregates for ordinary structural concrete--In general, aggregates for all concrete other than that referred to in Sections 3.4.1 and 3.5.1 should be in accordance with Section 2.4 of ACI 301. For further information, refer to ACI 221R.
3.5--Mix proportioning 3.5.1 Watertight, chemical resistant concrete--All concrete that must be watertight and resistant to freeze-thaw cycles and to naturally occurring or commonly used chemicals should be air entrained. All materials should be proportioned to produce a well-graded mixture of high density and maximum workability, with a minimum specified 28 day compressive strength of 3500 psi (24 Mpa) where the concrete is not exposed to severe and frequent freezing and thawing, or 4000 psi (28 MPa) where the concrete is exposed to severe and frequent freezing and thawing, except where special structural or other considerations require concrete of greater strength. The concrete should be proportioned in accordance with ACI 211.1, subject to the following requirements. 1. Type of cement: See Section 3.1. 2. Maximum water-cement ratio: 0.45. If a pozzolan is used in the concrete, the maximum water-cement plus pozzolan ratio should be 0.45. 3. Minimum cementitious materials content: )))))))))))))))))))))))))))))))))))))0)))))))))))))))))))))))))))
Coarse aggregate size no.
*
lb/yd .3-
)))))))))))))))))))))))))))))))))))))3)))))))))))))))))))))))))))
467 57 67
[ 1-1/2 in. [ 1 in. [3/4 in.
(38.1 mm) maximum] * (25.4 mm) maximum] * (19 mm) maximum] *
517 (307 kg/m .3-) 536 (318 kg/m .3-) 564 (335 kg/m .3-)
)))))))))))))))))))))))))))))))))))))2)))))))))))))))))))))))))))
Concrete mixtures with less cement than shown in the preceding table may be used when it is demonstrated to the engineer that the proposed mixtures will produce concrete that will meet the other requirements of Section 3.5.1 and will have acceptable durability, impermeability, workability, compactability, and finishability, as listed in Section 1.1. 4. Air content (as determined in accordance with ASTM C 173 or C 231): 5-1/2 ± 1 percent for coarse aggregate size No. 467; 6 ± 1 percent for coarse aggregate size No. 57 or No. 67. 5. Slump (as determined in accordance with ASTM C 143), measured at the point of placement into the structure: 1 in. (25
mm) minimum; 3 in. (75 mm) maximum for footings, caissons, substructure walls; 4 in. (100 mm) maximum for slabs, beams reinforced walls, columns. Note: Because of the high slump loss associated with shrinkage-compensating cement-concrete, it requires higher slumps at the batch plant than those just given. (See Section 4.3 of ACI 223.) These slump numbers do not apply when an acceptable high-range water reducer is used. 3.5.2 Ordinary structural concrete--In general, all concrete other than that referred to in Section 3.5.1 should be proportioned in accordance with Chapter 3 of ACI 301 and ACI 211.1. 3.5.3 for the testing ACI 301
Acceptance of proportions--The contractor should furnish engineer's review mixture proportions prepared by a laboratory acceptable to the engineer, in accordance with and ACI 318.
3.6--Evaluation and acceptance 3.6.1--During construction, 7 day compressive strength tests should be used to supplement the 28-day tests by comparing the average relative 7- and 28-day strengths as determined by the laboratory. At least two test cylinders should be made for testing at each age during each concreting operation for each 100 yd .3- (76.45 m .3-) of concrete or fraction thereof. All test cylinders should be cured under laboratory conditions, except that the engineer may require an equal number of field control cylinders cured under job conditions. For details, see ASTM C 31, C 39, C 172, and ACI 214. 3.6.2--If the concrete fails to meet the specified 28-day strength, the engineer may order tests on the hardened concrete, as described in Section 17.3 of ACI 301. If the concrete is cored and the cores fail to meet the requirements of Section 17.3.2.3 of ACI 301 or Section 4.7.4.4 of ACI 318, the engineer should have the right to reject the concrete, change the mix proportions, or both, at the expense of the contractor. CHAPTER 4--CONSTRUCTION Construction of environmental engineering concrete structures generally should be in conformance with ACI 301, particularly Chapters 4 through 13, except as specifically recommended in this report.
4.1--Concrete 4.1.1 Concrete mixture design--In addition to the mixture design parameters established pursuant to structural characteristics, chemical resistance, and durability requirements, the concrete mixtures should be suitable for the placing systems to be employed. Generally, well-proportioned mixtures leaning toward the coarse range in coarse-to-fine proportioning with good cohesive qualities will be able to be placed well with all placing
systems. Loose, sandy, or bleeding mixes should be avoided. Mix proportions should be prepared in accordance with ACI 301 and ACI 211.1. 4.1.2 Mixing concrete--Because uniformity is particularly important in obtaining watertight concrete, the concrete materials should be mixed sufficiently to produce concrete uniform in color and consistency with the required slump and air content. Concrete may be either ready-mixed or mixed at the job site, as recommended in Chapter 7 of ACI 301.
4.2--Placement of concrete Detailed recommendations for acceptable placing practices to obtain durable and watertight concrete, which is absolutely necessary in environmental engineering concrete structures, are given in ACI 304R. The contractor should provide for the continuation of concrete placements in the event of plant or equipment breakdowns. Backup concrete placing equipment should be available for use within 30 min in the event the primary placing equipment breaks down. An alternate concrete source with acceptable materials and mixtures on hand will assure the continuation of concrete placements without unplanned and frequently unacceptable, irregular construction joints. To prevent segregation, the concrete should be deposited in approximately 12 to 24 in. (305 to 610 mm) deep horizontal layers as near as possible to its final position (see ACI 309R). It should not be allowed to drop freely more than 4 ft (1.2 m) or through a cage of reinforcing steel (see Section 4.2.3). 4.2.1 Buckets--Bottom-dump buckets may be used for transporting mixed concrete to the desired location. Particular care should be taken to avoid jarring or bumping that may cause segregation. 4.2.2 Chutes--Chutes used to transport concrete should be of metal, except aluminum, or wood with metal lining and should have a slope not exceeding one vertical to two horizontal and not less than one vertical to three horizontal so that the concrete will travel fast enough to keep the chute clean but slow enough to avoid segregation of materials. The end of each chute should be provided with a baffle to help prevent segregation, or the concrete should be discharged through a drop chute, tremie, or elephant trunk directly into the form. 4.2.3 Drop chutes, elephant trunks, and tremies--Drop chutes, elephant trunks, and/or tremies should be used in walls and columns to prevent free-fall of the concrete and to allow the concrete to be placed through the cage of reinforcing steel. They should be moved at short intervals to prevent stacking of concrete. Vibrators should not be used to move the mass of concrete through the forms. Tremies should be used to place concrete under water and to avoid segregation. 4.2.4 Pumping--Pumping equipment should be a suitable type with adequate pumping capacity for the required slump and maximum size aggregate to be used. Pumplines should not contain aluminum. Loss of slump in pumping from pump hopper to point of placement should not exceed 1-1/2 in. (38.1 mm).
4.2.5 Conveying--Concrete conveying equipment should be designed specifically to place concrete without segregation. Conveyor systems should not impair the strength, slump, or air content of the concrete placed. The placement system should be capable of delivering concrete continuously over the entire placement area without delays for equipment relocation. 4.2.6 Back-up placement systems--Alternate placing equipment should be immediately available for use in the event that the primary placing equipment or system breaks down during a placement. Such equipment should be able to commence placing operations with 30 min notice to avoid cold joints in the structural element being placed. Provisions should be made for the use of retarders. 4.2.7 Portholes in wall and column forms--Limitations -Temporary openings or portholes in wall or column forms may be used to limit the free-fall of the concrete to less than 4 ft (1.2 m) and should be so located to facilitate the placing and consolidation of the concrete. The ports should be spaced no more than 6 to 8 ft (1.8 to 2.4 m) apart to limit the horizontal flow of concrete and to prevent segregation. 4.2.8 Placing in forms--Sections of walls between joints should be placed continuously to produce a monolithic unit. At least 48 hr should elapse between casting of adjoining units. Placing of concrete in beams or slabs should not begin until the concrete previously placed in walls or columns has attained initial set. As soon as possible after concrete has been deposited, it should be consolidated in an acceptable manner to work the concrete around the reinforcement and inserts and to prevent formation of voids. Each horizontal layer should be consolidated by the use of acceptable mechanical vibratory equipment. The vibrator should extend into the underlying layer to bond the two layers together. To avoid excessive pressure on the forms, the vibrator should penetrate no more than 2 ft (610 mm) into the underlying layer. The use of vibrators to move concrete horizontally within the forms should not be allowed. Mechanical high frequency vibrators with a minimum frequency of 8000 revolutions per min are preferred for consolidation of the concrete within the forms. The concrete should be vibrated in accordance with the recommendations contained in ACI 309R. Vibration should be continued until the escape of large bubbles at the surface stops and before the onset of any segregation. Vibrators attached to the forms provide an excellent means of vibrating high walls and columns. The forms must be designed to allow for the full liquid head pressure produced by the use of form vibrators. For more information on vibration and consolidation of concrete, refer to ACI 309R. 4.2.9 Temperature limitations 4.2.9.1 Cold weather--Unless the temperature is at least 40 F (4.4 C) and rising, water and/or aggregates should be heated so that the temperature of the concrete, when placed, is not less than 55 F (13 C). Provision should be made for maintaining the concrete moist and at a minimum temperature of not less than 50 F
(10 C) for a period of at least 7 days. Insulated tarpaulins and blankets may be used to cover concrete slabs or draped over and around walls, columns, and beams to retain the heat generated by hydration of the cement. Forms may be insulated or heated. Atmospheric steam curing may be utilized to accelerate curing and strength gain. Detailed recommendations are given in ACI 306R. Because of potential dangers, form removal should be governed by attainment of adequate strength in the field-placed concrete. 4.2.9.2 Hot weather--When the ambient temperature is 90 F (32 C) or above, special precautions should be taken during batching, mixing, placing, and curing. Aggregate and cement should be kept cool. The use of a set-retarding admixture may be beneficial, particularly with shrinkage-compensating concrete. Sometimes it is desirable to cool the mixing water by the use of liquid nitrogen, by refrigeration, or by replacing part of the water with shaved or crushed ice. Wall forms should be removed as soon as the concrete has hardened sufficiently to prevent damage to the concrete. Curing should be commenced immediately with water and burlap covers or with the application of a nonstaining, nontoxic white-pigmented curing compound acceptable to the engineer. Curing of concrete slabs should be started as soon as possible, when finishing has been completed and/or the water sheen has disappeared. If liquid membrane-curing is used (see Section 4.6), the compound should be nonstaining, nontoxic, and white-pigmented. Detailed recommendations are given in ACI 305R.
4.3--Joints 4.3.1 Construction joints--Vertical construction joints should be prepared and bonded as provided in Chapter 6 of ACI 301. This practice also may be used for horizontal joints. When the wall height exceeds 8 ft, new concrete should be placed on a layer of cement mortar evenly spread over the previously placed concrete. This mortar should be a mixture of cement, sand, and water in the same proportions used in the concrete but with all coarse aggregate omitted. 4.3.2 Movement joints--Concrete surfaces must be clean and dry; free from grease, oil, bitumen, or curing compound; and should be primed according to the recommendation of the manufacturer of the sealant. When a joint sealant is used, it should be investigated for compatibility with the liquid being retained. For detailed recommendations on sealants, see ACI 504R. 4.3.3 Waterstops 4.3.3.1 Steel--Steel waterstops have been used successfully in construction joints. This type of waterstop is usually a 6 x 1/4 in. (152 x 6 mm) steel plate embedded 3 in. (76 mm) into the concrete on each side of the joint. To facilitate bonding to the concrete, the surfaces of steel waterstops should be free of all mud, oil, loose rust, or other material that would inhibit bond.
Splices should be made by butt-welding the ends of the plates together. 4.3.3.2 Flexible waterstops--Waterstops fabricated of rubber, vinyl, metal, or other acceptable material should be of shapes and patterns to accomplish the required function. Where movement is anticipated as in expansion joints, a bulb or U-shaped center section with "tear-away" closure should be provided of such size and pattern as required to accommodate anticipated movement. When a flexible-type waterstop is used, all portions including ends and edges should be firmly tied and/or fixed in position to prevent movement during placement of the concrete. See Fig. 12 and 16 of ACI 504R for installation recommendations.
4.4--Formwork 4.4.1 General--Formwork should be designed, fabricated, erected, used, and removed in accordance with the recommendations and guidelines of ACI 347 and SP-4. 4.4.2 Form design--Formwork should be designed so that all components and members of the structure will be cast to the correct dimensions, shape, alignment, elevation, and position, without excessive deflection. Formwork also should be designed to be erected, supported, braced, and maintained so that it will support safely all vertical and lateral loads that might be applied until such loads can be supported by the concrete structure. The form panels for liquid-containing structures and conduits should be constructed in the largest size consistent with the lifting equipment available to handle them. Form surfaces should be constructed of sheet steel, smooth-dressed wood or plastic-faced plywood, or fiberglass. Assemblies should provide for ease of stripping with minimum damage to the formed surfaces. Vertical or lateral loads should be carried to the ground by the formwork and shoring system or by the in-place construction that has adequate capacity for that purpose. Formwork and falsework vertical and lateral loads should also include live loads, wind loads, and construction loads, together with appropriate safety factors and load multipliers as recommended by ACI 347. All formwork should be mortar tight. Tie systems should provide for positive pressure at all joints to preclude grout leakage. 4.4.3 Form ties--Form tie assemblies for environmental engineering concrete structures should permit tightening of the forms and should leave no metal or other material within 1-1/2 in. (38 mm) of the surface. The assembly should provide cone-shaped depressions at the forms at the surface at least 1 in. in diameter and 1-1/2 in. deep to allow filling and patching.
Ties should be tight fitting, or tie holes in forms should be sealed to prevent leakage where ties penetrate the form.
When a portion of single rod ties are to remain in a liquid-retaining structure, the portion that is to remain should be provided with a tightly fitted washer at midpoint. Multi-rod ties do not require washers. Through ties that are to be entirely removed from the structure should be tapered over the portion that passes through the concrete. The large end of tapered ties should be on the liquid side of the wall. The contractor should be required to demonstrate the methods and materials to be used to fill the void thus formed. 4.4.4 Form coating or release agents--Form surfaces that will be in contact with concrete should be coated with an effective bond-breaking form coating in accordance with Section 4.4 of ACI 347. For water treatment plants, the form coating should be nontoxic after a specified period, usually 30 days. 4.4.5 Inspection before concreting--Prior to placing concrete, forms should be inspected for cleanliness, accuracy of alignment, and reinforcing steel clearances. Inspection ports should be provided if, in the opinion of the inspector, they are necessary to clean and inspect properly the interior of the formed element. 4.4.6 Removal of forms--Removal of forms should be in accordance with ACI 347-78 (Reaffirmed 1984). In hot, dry climates, wood forms remaining in place may not provide adequate curing and should be kept wet or removed or loosened so that the concrete surfaces can be kept moist or coated with a curing membrane. In cold weather, removal of formwork should be deferred and insulated until concrete has attained adequate strength, or formwork should be replaced with insulation blankets to avoid thermal shock and consequent crazing of the concrete surface. 4.4.7 Reshoring--Reshoring, if permitted, should be in accordance with ACI 347-78 (Reaffirmed 1984).
4.5--Finishes for exposed surfaces 4.5.1 Finishing unformed surfaces--Detailed recommendations are given in Section 6.4.4 and Chapter 7 of ACI 302.1R. Concrete should be spread evenly ahead of the strike-off and worked as little as possible during early finishing operations. Any water brought to the surface by the strike-off or rough floating should be allowed to evaporate. If the amount of water or laitance is excessive, it should be removed before the surface is floated or troweled again. If a smooth surface is required, final troweling should be delayed as long as possible. Generally, the proper time for final troweling is after the surface water has disappeared and when the surface cannot be dented easily with the finger. Final troweling should be only as required to produce the specified finish and close any surface cracks that may have developed. 4.5.2 Nonslip finish--All exposed floor areas, sidewalks, and steps subject to foot traffic and likely to be wet should have a nonslip finish, as described in Section 7.11 of ACI 302.1R. 4.5.3 Finishing formed surfaces--Requirements vary from merely removing fins and repairing obvious imperfections to finishing,
which involves grinding, rubbing, floating, or brushing. Such work should be done as soon as forms can be removed. If surfaces are to be finished by grinding, chipping, bushhammering, or sandblasting, the concrete must first be cured thoroughly. Chapter 10 of ACI 301 adequately covers these and other types of concrete finishes. 4.5.4 Repair of surface defects--Repair of surface defects should be in accordance with Chapter 9 of ACI 301 and with ACI 309.2R. 4.5.4.1 Tie holes--After being thoroughly cleaned and dampened, the tie holes should be grouted solid with a nonmetallic, nonshrinking grout. The tie hole should be filled from the large end of the cone-shaped hole and packed solid by rodding. The use of rubber or plastic plugs wedged deep in the wall prior to filling with grout is recommended. The grout material and the entire tiehole filling process should be acceptable to the engineer prior to the start of the work. 4.5.4.2 Patching minor defects--Surfaces to be patched or repaired after removal of forms should be corrected by acceptable methods and not by plastering over them. Patching of defective areas should be done as soon as the forms can be removed and before curing compound is applied. A good patch well-bonded to adjacent concrete is essential. Nonshrink, nonstaining grout should be used where appearance is important. Curing requirements for patches should be the same as for the mass of the concrete. 4.5.4.3 Honeycombed areas--Honeycombed sections may result from improper placement and inadequate vibration. Whether patching of honeycombed areas is permissible depends on the extent and depth of the defective concrete and its location. If patching is allowed, all unsound material should be chipped out back to sound, solid concrete and inspected prior to the start of filling and patching operations.
4.6--Curing Proper curing of fresh concrete requires that moisture be retained to promote additional hydration of cement during the curing period and to prevent formation of surface cracks due to rapid loss of water while the concrete is plastic. Detailed recommendations are given in ACI 308. When surfaces are cured with membrane curing compound, all finishing operations, except grinding, chipping, bushhammering, and sandblasting, should be completed prior to application of the membrane. Curing should commence as soon as possible following initial set or completion of surface finishing, and as soon as marring of the concrete surface will not occur. Various methods commonly used include sprinkling, ponding, using moisture retaining covers, or applying a liquid membrane-forming curing compound seal coat to form a thin water-impervious membrane. Leaving wall forms in place provides an excellent means of
retaining moisture. However, in hot, dry weather, the dry forms tend to absorb moisture from the concrete and inhibit dissipation of the heat of hydration. Therefore, in hot, dry weather, the forms should be kept moist or removed as soon as the concrete has hardened sufficiently to prevent damage to the concrete. Moist or membrane curing should be commenced immediately after removal of the forms. The membrane curing compound should cover the entire surface to be cured with a uniform film that will remain in place without gaps or omissions for the full duration of the curing period. Exposed steel, keyways, or concrete to be surfaced should be protected from the curing compound unless tests show that satisfactory adherence of the surface is obtained. Membrane curing compounds should conform to ASTM C 309 and should have a minimum of 18 percent solids, be nonyellowing, and have a unit moisture loss of less than 0.039 gm/cm² maximum at 72 hr. Rate of application of curing compounds should follow manufacturer's recommendation or be in the range of 150 to 200 ft²/gal. [See Section 2.3.3 of ACI 308-81 (Revised 1986)]. Polyethylene film for curing concrete should conform to ASTM C 171. Curing compounds used in water treatment plant construction must be nontoxic and free of taste and odor.
4.7--Leakage testing It is normal practice to test liquid-retaining structures for water tightness. The leakage test should be performed while the tank walls are exposed so that leaks can be easily found and repaired. Thus, leakage tests usually are performed prior to backfilling or cladding the tank. For potable water facilities, the leakage test is often done in conjunction with the disinfection in order to save water. The acceptance leakage criteria and method of test should be specified in the construction contract. Tanks generally are filled to full overflow level. If the structure has dried out, the water should be left standing for a period to allow for absorption. Tanks are usually considered acceptable if: a. There is no visible leakage or visible damp areas, and b. The volume of leakage in a given time period (after correcting for evaporation losses) is less than a specified amount. Acceptable leakage volumes will vary depending on the specific application. Leakage rates of 1/10 of 1 percent of the tank volume in any 24 hr period (after absorption and stabilization) would be generally acceptable for a water reservoir where the consequences of leakage would not be significant.
CHAPTER 5--PROTECTION AGAINST CHEMICALS 5.1--Resistance of concrete and reinforcing steel Concrete made with the proper type of cement, which has been properly proportioned, batched, mixed, placed, consolidated, and
cured, will be dense, strong, watertight, and resistant to most chemical attack; therefore, under ordinary service conditions, quality concrete does not require protection against chemical deterioration or corrosion. Likewise, reinforcement embedded in quality concrete normally is well-protected against corrosive chemicals. Quality concrete, properly air entrained, is also resistant to freeze-thaw deterioration, which in many locations may be more severe than chemical action.
5.2--Need for protection The corrosive conditions that require concrete surface protection can range from comparatively mild to very severe, depending on the chemicals used and the domestic and industrial wastes encountered. The type of protection employed against chemical attack will also vary according to the kind and concentration of the chemical, frequency of contact, and physical conditions such as temperature, pressure, mechanical wear or abrasion, and freeze-thaw cycles. Where conditions exist that may be expected to deteriorate, remove, or otherwise destroy the concrete immediately around the reinforcing steel, direct protection of the reinforcing steel, such as epoxy coating as specified in ASTM A 775, may be desirable.
5.3--Types of protection Many types of protective coatings or barriers will prevent contact with the concrete surfaces. To be successful, such coatings should exhibit good adhesion to the concrete and be completely impervious. Among these are various coatings of thermoplastic and thermosetting types, ceramics, chemical-resistant mortars, sheet or linear materials, and composite barriers. If conditions are severe enough to deteriorate good-quality concrete, it is difficult to provide complete and lasting protection, even with the best of these types of protection. Consideration should be given to neutralizing severely aggressive liquid wastes. When special protection is required for the reinforcing bars, epoxy-coated bars are preferable. Specifications for such coatings should be patterned upon ASTM A 775.
5.4--Recommended coatings 5.4.1 Water treatment plants--In general, normal concentrations of the chemicals used in water treatment plants for coagulation, taste and color control, and disinfection do not affect concrete, except for liquid alum, which requires a continuous, inert barrier, such as PVC or rubber, at least 20 mils (0.508 mm) in
thickness. 5.4.2 Domestic sewage plants--Concrete in domestic sewage treatment plants seldom requires special protection, although the mechanical equipment in such environments generally is provided with a protective coating of coal-tar-based paint or some type of epoxy due to its much greater susceptibility to damage from mildly corrosive conditions. In exceptional cases, for example, where hydrogen sulfide evolves in a stagnant, unventilated environment that is difficult or uneconomical to correct or clean regularly, a coating such as that normally provided for metal may be necessary. Care should be exercised in using such coatings, and they should be fully tested to insure their suitability for the proposed application. 5.4.3 Industrial wastewater treatment plants--Industrial wastewater treatment may at times involve acid waste with pH as low as 1.0. The type of protection generally used is chemical-resistant mortar, acid proof brick or tile, thick bituminous coatings, epoxies, and heavy sheets or liners of rubber or plastic. 5.4.4 Protection of floors in treatment plants--Concrete floors, where occasional spillage of acids may occur, should be protected with vinyl lacquer, epoxy, chlorinated rubber, or phenolic coatings.
5.5--Selection of protection system Each project should be considered individually because various materials and techniques used from time to time cause new problems of chemical attack. Detailed recommendations are given in ACI 515.1R. Manufacturers of protective materials should be consulted for information on the best preparation of concrete surfaces and the proper mixing and application of their coating products. It is important that the surfaces be clean, dry, and sound in order to obtain proper coverage and bond. Generally, muriatic acid washing and/or sandblasting are recommended for cleaning.
5.6--Safety precautions The toxicity of any product should be investigated. When applying coatings, the need for ventilation should be checked. Required protective equipment such as gloves, goggles, and masks should also be checked before application.
5.7--Chemicals used in treatment plants Chemicals sometimes encountered in water and wastewater treatment were previously listed in Table 2.3.2. Some type of protection may be required where some of these materials contact concrete surfaces. Table 2.5.2 of ACI 515.1R provides additional information on the effect of chemicals on concrete. Group 1
These chemicals are not considered harmful to concrete but are listed because in some instances treatment is desired to prevent staining or the absorption of liquid into the concrete which may react with other chemicals in the future. Activated carbon (except when agitated, then in Group 3) Activated silica (except when agitated, then in Group 3) Calcium hydroxide Calcium oxide Potassium permanganate Sodium bicarbonate* Sodium carbonate Sodium fluoride Sodium hydroxide (except over 20 percent concentration, then in Group 3) Sodium silicate Sodium siliconfluoride Trisodium phosphate (* Caution with respect to alkali-reactive aggregate.)
Group 2 Concrete exposed to the chemicals listed in this group should be made with sulfate-resistant cement (see Section 3.1) or should be given a protective coating, as described in Section 5.4. Copper sulfate Ferric sulfate
Group 3 Concrete should be protected against these chemicals with a protective coating, as described in Section 5.4. Activated carbon (when not agitated, then in Group 1) Activated silica (when not agitated, then in Group 1) Alum, liquid Aluminum ammonium sulfate Aluminum chloride solution Aluminum potassium sulfate Aluminum sulfate Ammonium sulfate Calcium hypochloride Chlorine Ferric chloride Fluosilicic acid Sodium bisulfite Sodium hydroxide (except less than 20 percent concentration, then in Group 1) Sulfuric acid
CHAPTER 6--REFERENCES 6.1--Recommended references The documents of the various standards-producing organizations referred to in this document are listed below with their serial
designation, including year of adoption or revision. The documents listed were the latest effort at the time this document was revised. Since some of these documents are revised frequently, generally in minor detail only, the user of this document should check directly with the sponsoring group if it is desired to refer to the latest revision. American Association of State Highway and Transportation Officials (AASHTO) T 260-84 Sampling and Testing for Total Chloride Ion in Concrete and Concrete Raw Materials
American Concrete Institute (ACI) 201.2R-77 (Reapp 1982)
Guide to Durable Concrete
211.1-81 (Revised 1985)
Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete
212.2R-81 (Revised 1986) Guide for Use of Admixtures in Concrete 214-77 (Reapp 1983)
Recommended Practice for Evaluation of Strength Test Results of Concrete
221R-84
Guide for use of Normal Weight Aggregate in Concrete
223-83
Standard Practice for the Use of Shrinkage-Compensating Concrete
224R-80 (Revised 1984)
Control of Cracking in Concrete Structures
224.1R-84
Causes, Evaluations, and Repair of Cracks in Concrete Structures
225R-85
Guide to the Selection and Use of Hydraulic Cements
301-84 (Revised 1988)
Specifications for Structural Concrete for Buildings
302.1R-80
Guide for Concrete Floor and Slab Construction
304R-85
Guide for Measuring, Mixing, Transporting, and Placing Concrete
305R-77 (Revised 1982)
Hot Weather Concreting
306R-88
Cold Weather Concreting
308-81 (Revised 1986)
Standard Practice for Curing Concrete
309R-87
Guide for Consolidation of Concrete
309.2R-82
Identification and Control of Consolidation-Related Surface Defects in
Formed Concrete 318-83 (Revised 1986)
Building Code Requirements for Reinforced Concrete
318R-83 (Supp 1986)
Commentary on Building Code Requirements for Reinforced Concrete
344R-70 (Reapp 1981)
Design and Construction of Circular Prestressed Concrete Structures
347-78 (Reapp 1984)
Recommended Practice for Concrete Formwork
504R-77
Guide to Joint Sealants for Concrete Structures
515.1R-79 (Revised 1985) Guide to the Use of Waterproofing, Dampproofing, Protective, and Decorative Barrier Systems for Concrete SP-4
Formwork for Concrete, 4th Edition, 1981, Revised 2nd Printing
American National Standards Institute (ANSI) A58.1-1982
American National Standard Minimum Design Loads for Buildings and Other Structures
ASTM A 615-86
Standard Specification for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement
A 616-86
Standard Specification for Rail-Steel Deformed and Plain Bars for Concrete Reinforcement
A 617-86
Standard Specification for Axle-Steel Deformed and Plain Bars for Concrete Reinforcement
A 706-86
Standard Specification for Low-Alloy Steel Deformed Bars for Concrete Reinforcement
A 767-85
Standard Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement
A 775-86
Standard Specification for Epoxy-Coated Reinforcing Steel Bars
C 31-87
Standard Practices for Making and Curing Concrete Test Specimens in the Field
C 33-86
Standard Specification for Concrete Aggregates
C 39-86
Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens
C 109-86
Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube Specimens)
C 143-78
Standard Test Method for Slump of Portland Cement Concrete
C 150-86
Standard Specification for Portland Cement
C 171-69 (Reapp 1986)
Standard Specification for Sheet Materials for Curing Concrete
C 172-82
Standard Method of Sampling Freshly Mixed Concrete
C 173-78
Standard Test Method for Air Content of Freshly Mixed Concrete by the Volumetric Method
C 231-82
Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method
C 260-86
Standard Specification for Air-Entraining Admixtures for Concrete
C 309-81
Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete
C 494-86
Standard Specification for Chemical Admixtures for Concrete
C 595-86
Standard Specification for Blended Hydraulic Cements
C 618-85
Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete
C 806-75
Standard Test Method for Restrained Expansions of Expansive Cement Mortar
C 845-80
Standard Specification for Expansive Hydraulic Cement
C 878-80
Standard Test Method for Restrained Expansion of Shrinkage-Compensating Concrete
D 994-71 (Reapp 1982)
Standard Specification for Preformed Expansion Joint Filler for Concrete (Bituminous Type)
D 1056-85
Standard Specification for Flexible
Cellular Materials--Sponge or Expanded Rubber D 1751-83
Standard Specification for Preformed Expansion Joint Fillers for Concrete Paving and Structural Construction (Nonextruding and Resilient Bituminous Types)
D 1752-84
Standard Specification for Preformed Sponge Rubber and Cork Expansion Joint Fillers for Concrete Paving and Structural Construction
The previously mentioned publications may be obtained from the following organizations: American Association of State Highway and Transportation Officials (AASHTO) 444 N. Capitol Street NW, Suite 225 Washington, DC 20001 American Concrete Institute (ACI) P. O. Box 19150 Detroit, MI 48219-0150 American National Standards Institute (ANSI) 1430 Broadway New York, NY 10018 ASTM 1916 Race St. Philadelphia, PA 19103 6.2--Cited references [1] "Water Treatment Plant Design," Manual of Engineering Practice No. 19, American Society of Civil Engineers, New York, 1969, 353 pp. [2] "Wastewater Treatment Plant Design," Manual of Engineering Practice No. 36, American Society of Civil Engineers, New York, 1977, 574 pp. [3] "Design and Construction of Sanitary and Storm Sewers," Manual of Engineering Practice No. 37, American Society of Civil Engineers, New York, 1969, 332 pp. [4] "Underground Concrete Tanks," Information Sheet No. IS071D, Portland Cement Association, Skokie, 1973, 4 pp. [5] "Circular Concrete Tanks Without Prestressing," Information Sheet No. IS072D, Portland Cement Association, Skokie, 1942, 32 pp. [6] "Rectangular Concrete Tanks," Information Sheet No. IS003.03D, Portland Cement Association, Skokie, 1969 (Revised 1981), 16 pp.
[7] Moody, W. T., "Moments and Reactions for Rectangular Plates," Engineering Monograph No. 27, U.S. Bureau of Reclamation, Denver, 1960 (Revised 1963), 74 pp. [8] Vetter, C. P., "Stresses in Reinforced Concrete Due to Volume Changes," Transactions, ASCE, V. 98, 1933, pp. 1039-1053. [9] Klein, Frank; Hoffman, Edward S.; and Rice, Paul F., "Application of Strength Design Methods to Sanitary Structures," Concrete International: Design & Construction, V. 3, No. 4, Apr. 1981, pp. 35-40. [10] Gogate, Anand B., "Structural Design Considerations for Settling Tanks and Similar Structures," ACI Journal, Proceedings V. 65, No. 12, Dec. 1968, pp. 1017-1020. [11] Gogate, Anand B., "Structural Design of Reinforced Concrete Sanitary Structures--Past, Present, and Future," Concrete International: Design & Construction, V. 3, No. 4, Apr. 1981, pp. 24-28. [12] Gogate, Anand B., "An Analysis of ACI Committee 350's Recommended Design Standards," Concrete International: Design & Construction, V. 6, No. 10, Oct. 1984, pp. 17-19. [13] Troxell, G. E.; Raphael, J. M.; and Davis, R. E., "Long-Time Creep and Shrinkage Tests of Plain and Reinforced Concrete," Proceedings, ASTM, V. 58, 1958, pp. 1101-1120. [14] "Expansion Joints in Buildings," Technical Report No. 65, Federal Construction Council, National Academy of Sciences, National Research Council, Washington, D.C., 1974, 43 pp. [15] Allen, E. A., and Higginson, E. C., "Waterstops in Articulated Concrete Construction," ACI Journal, Proceedings V. 52, No. 1, Sept. 1955, pp. 83-91. Also, Discussion, Part 2, Dec. 1956, pp. 1149-1152. [16] Whitman, Robert V., and Richart, Frank E., "Design Procedures for Dynamically Loaded Foundations," Proceedings, ASCE, V. 93, SM6, Nov. 1967, pp. 169-193. [17] Irish, K., and Walker, W. P., Foundations for Reciprocating Machines, Concrete Publications Ltd., London, 1969, 103 pp. [18] Karabinis, A. Harry, and Fowler, Timothy J., "Design Considerations for Dynamically Loaded Equipment Foundations," Foundations for Equipment & Machinery, SP-78, American Concrete Institute, Detroit, 1982, pp. 61-78. [19] Novak, Milos, "Vertical Vibration of Floating Piles," Proceedings, ASCE, V. 103, EM1, Feb. 1977, pp. 153-168. [20] Novak, Milos, and Howell, John F., "Torsional Vibration of Pile Foundations," Proceedings, ASCE, V. 103, GT4, Apr. 1977, pp. 272-285. [21] Singh, Jogeshwar P.; Donovan, Neville C.; and Jobsis, Adrianus C., "Design of Machine Foundations on Piles," Proceedings, ASCE, V. 102, GT8, Aug. 1977, pp. 863-877.
[22] Barkan, D. D., Dynamics of Bases and Foundations, McGraw-Hill Book Co., New York, 1962, 496 pp. [23] Biggs, J. M., Introduction to Structural Dynamics, McGraw-Hill Book Co., New York, 1964, 341 pp. [24] Church, A. H., Mechanical Vibrations, John Wiley & Sons, New York, 1963, 432 pp. [25] Skipp, B. O., Editor, Vibration in Civil Engineering, Butterworths, London, 1966, 298 pp. [26] Major, A., Vibration Analysis and Design of Foundations for Machines and Turbines, Collets, London, 1962, 828 pp. [27] Housner, G. W., "The Dynamic Behavior of Water Tanks," Bulletin, Seismic Society of America, V. 53, No. 2, Feb. 1963, pp. 381-387. [28] Ballantyne, D. B.; Pinkham, C. W.; and Weinberger, L. W., "Seismic Induced Loadings on Sanitary Facilities," ASCE Specialty Conference on Lifeline Earthquake Engineering (Oakland, Aug. 1981), American Society of Civil Engineers, New York, 1981. [29] Housner, George W., "Limit Design of Structures to Resist Earthquakes," Proceedings, World Conference on Earthquake Engineering, University of California, Berkeley, 1956, pp. 5-1--5-13. [30] Medearis, Kenneth, "Energy Absorption of Structures under Cyclic Loading," Proceedings, ASCE, V. 90, ST1, Feb. 1964, pp. 61-69. [31] Stark, David, "Longtime Study of Concrete Durability in Sulfate Soils," George Verbeck Symposium on Sulfate Resistance of Concrete, SP-77, American Concrete Institute, Detroit, 1982, pp. 21-40. [32] Lamond, Joseph F., "Twenty-Five Years' Experience Using Fly Ash in Concrete," Fly Ash, Silica Fume, Slag and Other Mineral By-Products in Concrete, SP-79, American Concrete Institute, Detroit, 1983, pp. 47-69.
6.3 Additional references 1. Biczok, Imre, Concrete Corrosion and Concrete Protection, 5th Edition, Chemical Publishing Co., New York, 1967, 543 pp. 2. "Code of Practice for the Design of Concrete Structures for Retaining Aqueous Liquids," (BS8007:1987), British Standards Institution, London, 1987. 3. Critchell, Peter L., Joints and Cracks in Concrete, Contractors Record Ltd., London, 1958, 232 pp. 4. Davies, John Duncan, and Long, John Edward, "Behavior of Square Tanks on Elastic Foundations," Proceedings, ASCE, V. 94, EM3, June 1968, pp. 753-772. 5. Manning, G. P., Concrete Reservoirs and Tanks, Concrete
Publications Ltd., London, 1967, 384 pp. 6. Kleinlogel, Adolf, Influences on Concrete, translated from the German by F. S. Morgenroth, Frederick Ungar Publishing Co., New York, 1950, 281 pp. 7. Concrete Manual, 8th Edition, U.S. Bureau of Reclamation, Denver, 1975, 627 pp. 8. "Concrete for Massive Structures," Information Sheet No. IS0W128T, Portland Cement Association, Skokie, 1987, 24 pp. 9. "Concrete for Wastewater Treatment Works," Information Sheet No. IS182W, Portland Cement Association, Skokie, 1976, 15 pp. 10. "Concrete for Water Treatment Works," Publication No. PA069W, Portland Cement Association, Skokie, 1963, 24 pp. 11. "Effect of Various Substances on Concrete and Protective Treatments," Information Sheet No. IS001T, Portland Cement Association, Skokie, 1986, 24 pp. 12. "Volume Changes of Concrete," Information Sheet No. IS018T, Portland Cement Association, Skokie, 1969, 4 pp. 13. "Design of Circular Domes," Information Sheet No. IS076D, Portland Cement Association, Skokie, 1942, 8 pp. THE FOLLOWING DISCUSSIONS, WHICH WERE PUBLISHED IN THE MARCH-APRIL 1990 ACI Structural Journal (PP. 338-339), ARE NOT PART OF THE REPORT ACI 350R-89, BUT ARE PROVIDED AS ADDITIONAL INFORMATION TO THE READER.
Environmental Engineering Concrete Structures.
Report by ACI Committee 350
Discussion by Himat Solanki and Committee 350
By HIMAT SOLANKI Member American Concrete Institute, Senior Design Engineer, Sarasota, Florida ACI Committee 350 should be congratulated for its fine work in preparing the proposed report. The report should facilitate the design of environmental engineering concrete structures. However, the discusser has some questions regarding Section 2.4--Structural Design. This section does not address the design criteria that are required for the design of the structures. In this section, the committee states in Section 2.6.1--General: "ACI 318 contains general requirements. . . [for] environmental engineering concrete structures." This statement may not be true in all cases, because neither ACI Committees 350 nor 318 address adequately several design parameters[33-45] such as the minimum reinforcement ratio to control the cracks where the structure
requires a leakproof condition; loading conditions/combination where an impact due to tornado-tossed objects hit on the structure and the effective ratio of reinforcement; temperature gradient (i.e., temperature of liquid in the structure versus the outside temperature); pressure gradient with respect to time (pressure increases/decreases in the structure in a timely manner); and tensile strength of concrete, etc., in the crack widths and crack spacing computations of the structures. Also Fig. 2.6.7 (a), (b), and (c) are primarily developed from the Gergley-Lutz equation for one-way flexural members. These figures cannot be applied to environmental engineering concrete structures because the figures do not take into account the previously mentioned parameters. The discusser had an opportunity to review and design an environmental engineering concrete structure (sewage treatment plant). The consideration of the previously mentioned parameters was given to the design, and it was found that secondary-type crack widths and spacings were developed so far. REFERENCES [33] Langhout, M. S., "Dikwandige betonconstructies; scheurwijdtebeheersing en minimum wapeningspercentage; afstudeerverslag," TU Delft, 1988. [34] Henning, W., and Rostasy, F. S., "Zwang und Oberflachenbewehrung dicker wande," Beton und Stahlbetonbau (Berlin), No. 4, Apr. 1985, pp. 108-113, and No. 5, May 1985, pp. 134-136. [35] Braam, C. R., and Langhout, M. S., "Berkening van de Scheurwijdte bij dikwandige betonconstructies," PT/Civiele Technik (The Netherlands), No. 3, 1988. [36] Jaccoud, J.-P., "Armature minimale pour le controle de la fissuration des Structures en beton," These No. 666, EPFL-IBAP, Lausanne, 1987. [37] Jaccoud, J.-P. et al.. "Armature minimale pour le controle de la fissuration," Rapports d'essais, EPFL-IBAP, Lausanne, May 1984, Sept. 1985, and July 1986. [38] Konig, Geri, "Restraint, Crack-Width Control and Minimum Reinforcement in Thick Concrete Members," Darmstadt Concrete (Darmstadt), V. 1, 1986, pp. 9-22. [39] Helmus, Manfred, "Experimental Approach to the Minimum Reinforcement in Thick Concrete Elements," Darmstadt Concrete (Darmstadt), V. 2, 1987, pp. 115-122. [40] Schiessl, P., "Beschrankung der Rissbreiten bei Zwangsbeanspruchung," Betonwerk & Fertigteil-Technik (Wiesbaden), No. 6, 1976, pp. 269-274. [41] Dimitriev and Birulin "Opening of Cracks in Prestressed Concrete Members," Beton i Zhelezobeton (Moscow), V. 16, May 1970, pp. 18-22. (in Russian) [42] Holmberg, Ake, and Lindgren, Sten, "Cracks in Concrete
Walls," Document D7:1972, National Swedish Building Research, Stockholm, 1972, 70 pp. [43] "Les fissurations des betons," Annales, Institut Technique du Batiment et des Travaux Publics (Paris), serie Beton No. 202, Oct. 1981, 99 pp. [44] Clarke, J. L., "Compartement des elements en beton precontraint sous l'effect de gradients de tempartures cycliques," seminaire effets cyclique et transitoires dans les structures, Saint-Remy-les-chevreuse, Oct. 1979. [45] Breugel, Van K., "Kan het scheurgedrag van cirkelvormige constructies worden voorspeld?," Cement ('s-Hertogenbosch). V. 40, No. 1, Jan. 1988, pp. 47-51. COMMITTEE CLOSURE The committee thanks Mr. Solanki for his helpful comments and corrections, which have been carefully reviewed and answered as follows. Mr. Solanki had essentially six comments that were related to his belief that Section 2.6--Structural Design does not address the design criteria that are required for the design of the structures. In the same vein, he questions the committee's statement in Section 2.6.1 of the report which says, "ACI 318 contains general requirements for reinforced concrete building structures that are also for environmental engineering concrete structures. The design engineer should establish the design criteria for a specific concrete structure within the limitations of the ACI or local building codes based on the special requirements of environmental engineering structures." Mr. Solanki believes that "these statements may not be true in all cases because neither ACI Committees 350 nor 318 address adequately several design parameters," including a. Minimum reinforcement ratio to control the cracks where the structure requires a leakproof condition. b. Loading conditions where an impact due to tornado-tossed objects hit the structure. c. The effective ratio of reinforcement to withstand loading conditions where an impact due to tornado-tossed objects hit the structure. d. Temperature gradient (i.e., of liquid in the structure versus the outside). e. Pressure gradient with respect to time (pressure increases or decreases in the structure in a timely manner). f. Tensile strength of concrete, etc., in crack widths and crack spacing computations of the structure. g. Also, "Fig. 2.6.7 (a), (b), and (c) are primarily developed from the Gergely-Lutz equation for one-way flexural members. These figures cannot be applied to the environmental engineering concrete structures because the figures do not take into account the previously mentioned parameters."
In answer to Mr. Solanki's general objection, the committee believes that the report was not intended to be a workbook of design aids or a handbook of design. The tables and curves are intended to be illustrative of the committee's recommendations. The design engineer should consider devising appropriate design aids for the various grades of steel and values of concrete strength, concrete cover, bar sizes and sanitary exposure. It is the committee's opinion that Section 10.6 in the Commentary to ACI 318, and the figures and text of Section 2.6 in ACI 350, do address and illustrate the design criteria referred to by Mr. Solanki (Points a and b previously mentioned). They do, however, require some effort by the designer to develop a complete design criteria for each project. In answer to Points b and c of Mr. Solanki's comments, the committee has not found it necessary to design most environmental engineering concrete structures, such as tanks, for tornado loads caused by flying objects. The buildings in treatment plants would ordinarily be designed to resist wind loads and seismic loads set by local codes, ACI 318, or ANSI. We do not understand Mr. Solanki's concern over temperature gradients. Temperature gradients in environmental engineering concrete structures are limited in their effects on the structure by details of design, including reinforcement, which limit deterioration of the structure. Examples of structures affected by temperature gradients are sludge digestion tanks and blower buildings, with their galleries. The temperature gradients in sludge digestion tanks are not extreme, and their effects are limited by details of design, including reinforcement and insulation. The effects of high temperature in blower buildings and air main galleries are also dealt with by details of design, including expansion joints and expansion couplings. Mr. Solanki's concern with regard to "pressure gradients" has not been a problem. The committee does not understand his concern. Changes in pressure usually do occur associated with basically slow moving equipment and do not cause serious structural vibrations or impact loads. In response to Mr. Solanki's comment concerning the Gergley/Lutz equation governing one-way flexural members but not two-way slabs, Section 13.4, ACI 318-83, states, "Area of reinforcement in each direction for two-way slab systems shall be determined from moments at critical sections but shall not be less than required by Section 7.12" (shrinkage and temperature reinforcement).
