This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C42/C42M − 16
American Association State Highway and Transportation Officials Standard AASHTO No.: T24
Standard Test Method for
Obtaining and Testing Drilled Cores and Sawed Beams of Concrete 1 This standard is issued under the fixed designation C42/C42M; the number immediately following the designation indicates the year of original origin al adoption or, in the case of revis revision, ion, the year of last revision. revision. A number in paren parenthese thesess indicates the year of last reappr reapproval. oval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Sco Scope* pe* 1.1 This test method covers obtaining, obtaining, prepa preparing, ring, and testing cor cores es dri drilled lled from con concre crete te for len length gth or com compre pressi ssive ve strength or splitting tensile strength determinations. This test method is not applicable to cores from shotcrete. NOTE 1—Test 1—Test Metho Method d C1604/C1604M is applicable for obtain obtaining, ing, preparing, and testin preparing, testing g cores from shotc shotcrete. rete. NOTE 2— 2—Appendix Appendix X1 provides recommendations for obtaining and testing sawed beams for flexural performance.
1.2 The values stated in either SI units or inch-pound inch-pound units are to be regarded separately as standard. The values stated in each system may not be exa exact ct equ equiva ivalen lents; ts; the theref refore ore,, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.3 The text of this standard standard references references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. 1.4 This sta standa ndard rd does not pur purpor portt to add addre ress ss the saf safety ety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Referenc Referenced ed Documents Documents 2.1 ASTM Standards:2 C39/C39M Test C39/C39M Test Method for Compressive Strength of Cylindrical Concrete Specim Specimens ens
1
Thiss tes Thi testt met method hod is und under er the jur jurisd isdict iction ion of ASTM Com Commit mittee tee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.61 on Testing for Strength. Current Curre nt editi edition on approv approved ed Oct. 1, 2016. Published Published Octob October er 2016. Originally Originally approved in 1921. Last previous edition approved in 2013 as C42/C42M – 13. DOI: 10.1520/C0042_C0042M-16. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at
[email protected]. For Annual Book of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
C78/C78M Test Method for Flexural Strength of Concrete C78/C78M (Using Simple Beam with Third-Point Loading) C174/C174M Test C174/C174M Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete Cores C496/C496M Test C496/C496M Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens C617/C617M Pra Practic cticee for Cap Cappin ping g Cyli Cylindr ndrical ical Con Concre crete te Specimens C642 Test Metho Method d for Densit Density y, Abso Absorption rption,, and Voids in Hardened Concrete C670 Practice C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials C823/C823M Pra Practic cticee for Exa Examin minatio ation n and Samp Sampling ling of Hardened Harden ed Concr Concrete ete in Constr Construction uctionss C1231/C1231M Pr Pract actice ice fo forr Us Usee of Un Unbo bond nded ed Cap Capss in Determination Determi nation of Compr Compressive essive Strength of Harde Hardened ned Cylindrical lindric al Concr Concrete ete Specim Specimens ens C1542/C1542M Test C1542/C1542M Test Method for Measuring Length of Concrete Cores C1604/C1604M Test Met Method hod for Obt Obtain aining ing and Test esting ing Drilled Cores of Shotcrete 3. Signi Significanc ficancee and Use 3.1 This test method provides provides standardized standardized procedures procedures for obtaining and testing specimens to determine the compressive, splitting tensile, and flexural strength of in-place concrete. 3.2 Genera Generally lly,, test spe specim cimens ens are obt obtain ained ed whe when n dou doubt bt exists exi sts abo about ut the in-place in-place con concre crete te qua quality lity due eith either er to low strength test results during construction or signs of distress in the structure. Another use of this method is to provide strength information infor mation on older struc structures. tures. 3.3 Co 3.3 Conc ncre rete te str stren engt gth h is af affe fect cted ed by th thee lo locat catio ion n of th thee concrete in a structural element, with the concrete at the bottom tendi ten ding ng to be str stron onge gerr th than an th thee co conc ncre rete te at th thee to top. p. Co Core re streng str ength th is als also o af affect fected ed by cor coree ori orient entatio ation n rel relativ ativee to the hori ho rizo zont ntal al pl plan anee of th thee co conc ncre rete te as pl place aced, d, wi with th str stren engt gth h tending to be lower when measured parallel to the horizontal
*A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C42/C42M − 16 plane.3 Th Thes esee fa facto ctors rs sh shall all be co cons nsid ider ered ed in plan planni ning ng th thee locatio loca tions ns for obt obtain aining ing con concre crete te sam sample pless and in compar comparing ing strength test results. 3.4 The strength strength of con concre crete te mea measur sured ed by tes tests ts of cores is affec af fected ted by the amo amount unt and dis distri tribut bution ion of moi moistu sture re in the specimen at the time of test. There is no standard procedure to condition a specimen that will ensure that, at the time of test, it will be in the identical moisture condition as concrete in the structure. structu re. The moistu moisture re condi conditionin tioning g proce procedures dures in this test method are intended to provide reproducible moisture conditions that minimize within-laboratory and between-laboratory variati var iations ons and to red reduce uce the ef effec fects ts of moi moistu sture re int introd roduce uced d during specimen preparation. 3.5 3. 5 Th Thee me measu asure red d co comp mpre ress ssiv ivee st stre reng ngth th of a co core re wi will ll generally be less than that of a corres generally correspond ponding ing properly molded and cured standard cylinder tested at the same age. For a given concrete, however, there is no unique relationship between the strengths of these two types of specimens (see Note 3) 3). The relationship is affected by many factors such as the strength level of the concrete, the in-place temperature and moisture histor his tories ies,, th thee de degr gree ee of con conso solid lidati ation on,, bat batchch-toto-ba batch tch variability, the strength-gain characteristics of the concrete, the cond co ndit itio ion n of th thee co cori ring ng ap appa para ratu tus, s, an and d th thee ca care re us used ed in removing cores. NOTE 3—A procedure is available for estimating the equivalent cylinder strength from a measured core strength.4 NOTE 4—In the absence of core strength requirements of an applicable building buildi ng code or of other contractual contractual or legal documents documents that may govern the project, the specifier of tests should establish in the project specifications the acceptance criteria for core strengths. An example of acceptance criteri crit eriaa for core str streng ength th is pro provid vided ed in ACI 318 318,,5 which are used to evaluate cores taken to investigate low strength test results of standardcured cylinder during construction. According to ACI 318, the concrete represented by the cores is considered structurally adequate if the average strength of three cores is at least 85 % of the specified strength and no single core strength is less than 75 % of the specified strength.
3.6 The “specifier “specifier of the tests” referenced referenced in this test method method is th thee in indi divi vidu dual al re resp spon onsi sibl blee fo forr an anal alys ysis is or re revi view ew an and d acceptance of core test results. NOTE 5—For investigation of low strength test results, ACI 318 defines the specifier of the tests as the licensed design professional.
3.7 The apparent apparent compressive compressive strength of concrete concrete as measured by a core is affected by the length-diameter ratio (L/D) of the core as tested and this must be considered in preparing core specimens and evaluating test results. 4. Appar Apparatus atus Core Drill, for obt 4.1 Core obtaini aining ng cyl cylind indrica ricall cor coree spe specime cimens ns with diamond impregnated bits attached to a core barrel.
4.2 Saw, for trimming ends of cores. The saw shall have a diamond or silicon-carbide cutting edge and shall be capable of cutting cores without introducing cracks or dislodging aggregate particl particles. es. 4.3 Balance, accurate to at least 5 g [0.01 lb]. 5. Sampl Sampling ing 5.1 General: 5.1.1 Sample Sampless of hardened concrete concrete for use in the preparapreparation tio n of str streng ength th test specimen specimenss sha shall ll not be tak taken en unt until il the concrete is strong enough to permit sample removal without disturbing the bond between the mortar and the coarse aggregate (see Note 6 and Note 7) 7). When preparing strength test specimens specim ens from samples of harden hardened ed concr concrete, ete, sample sampless that have been damaged during removal shall not be used unless the damaged portion(s) are removed and the lengths of resulting test spe specime cimens ns sat satisfy isfy the min minimu imum m len length gth-di -diame ameter ter rat ratio io requirement in 7.2 in 7.2.. Samples of defective or damaged concrete that cannot be tested shall be reported along with the reason thatt pro tha prohib hibits its use of the sam sample ple for preparin preparing g str streng ength th tes testt specimens. NOTE 6—Practice 6—Practice C823/C823M C823/C823M provides provides guidance on the development of a sampling plan for concrete in constructions. NOTE 7—It is not possible to specify a minimum age when concrete is strong enough to withstand damage during removal, because the strength at any age dep depend endss on the cur curing ing history history and str streng ength th gra grade de of the concrete. If time permits, the concrete should not be removed before it is 14 days old. If this is not practicable, removal of concrete can proceed if the cut surfaces do not display erosion of the mortar and the exposed coarse aggregate particles are embedded firmly in the mortar. In-place test methods may be used to estimate the level of strength development prior to attem attempting pting removal of concr concrete ete samp samples. les.
5.1.2 Except as provided provided in 5.1.3 in 5.1.3,, cores containing embedded reinforcement, excluding fibers, or other embedded objects shall not be used for determining strength of concrete. 5.1.3 5.1 .3 If it is not possible possible to pre prepar paree a tes testt spe specim cimen en that meets mee ts the req requir uiremen ements ts of 7.1 and 7.2 and and th that at is fr free ee of embedded reinforcement or other metal, the specifier of the tests is permitted to allow testing of cores with embedded metal (see Note (see Note 8). 8). If a core tested for strength contains embedded metal, the size, shape, and location of the metal within the core shall be documented in the test report. NOTE 8—The presence of steel reinforcement, other than fibers, or other embedded metal in a core can affect the measured strength.6,7 There are insufficient data to derive reliable correction factors that can be applied to the measured strength to account for embedded reinforcement perpendicular to the core axis. If testing of cores containing embedded reinforcement is permitted, engineering judgment is required to assess the significance of the results. The specifier of the tests should not permit a core to be tested for strength if bar reinforcement, reinforcement, or other elongated embedded embedded metal object, is oriented close to parallel to the core axis.
5.2 Core Drilling— When When a core will be tested to measure concrete concr ete strength, the core shall be drilled perpendicular perpendicular to the 3 Neville, A., “Core Tests: Easy to Perform, Not Easy to Interpret,” Concrete International, Vol 23, No. 11, November 2001, pp. 59–68. 4 “Guide for Obtain Obtaining ing Cores and Interpr Interpreting eting Compressive Compressive Stren Strength gth Resul Results,” ts,” ACI 214.4R, American Concrete Institute, P.O. Box 9094, Farmington Hills, MI 48333, www.concrete.org. 5 “Building Code Requirements for Structural Concrete and Commentary,” ACI 318, American American Concre Concrete te Insti Institute, tute, P.O. P.O. Box 9094, Farmin Farmington gton Hills, MI 48333, www.concrete.org.
6
Gaynor, Gayno r, R. D., “Effect “Effect of Horizo Horizontal ntal Reinforcing Reinforcing Steel on the Strength of Molded Cylind Molded Cylinders, ers,”” Proble Problems ms and Pract Practices ices in Journal of the American Concrete Institute, Proceedings, Vol 62, No. 7, July 1965, pp. 837–840. 7 Concrete Concr ete Socie Society ty Working Party, “Concrete Core Testin esting g for Stren Strength,” gth,” Concrete Society Technical Report No. 11, The Concrete Society, England, May 1976.
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C42/C42M − 16 surface and at least 150 mm [6 in.] away from formed joints or obvious edges of a unit of deposit (see Note 9). 9). This minimum distance does not apply to the formed boundaries of structural members. Record the approximate angle between the longitudinal axis of the drilled core and the horizontal plane of the concre con crete te as pla placed ced.. A spe specim cimen en dri drilled lled per perpen pendic dicular ular to a vertical surface, or perpendicular to a sloping surface, shall be taken from near the middle of a unit of deposit when possible. If cores are obtained for purposes other than determination of strength, drill cores in accordance with the instructions provided by the specifier of the tests. Record the date core was drilled. If known, record the date when concrete was placed. NOTE 9—The 9—The intent is to avoid drilling cores in non-r non-repres epresentativ entativee concrete that may exist near formed joints or the boundary of a unit of placement.
Slab Remova Removal— l— Remov 5.3 Slab R emovee a sl slab ab su sufffic icien ientl tly y lar large ge to secure the desired test specimens without the inclusion of any concrete concre te that has been cracked, spalled, undercut, undercut, or other otherwise wise damaged.
DRILLED CORES 6. Meas Measuring uring the Length of Drilled Cores Cores 6.1 Cores for determining the thickness of pavements, slabs, walls or other structural elements shall have a diameter of at least lea st 94 mm [3 [3.7 .70 0 in in.] .] wh when en th thee len lengt gths hs of su such ch co core ress ar aree stipula stip ulated ted to be mea measur sured ed in acco accorda rdance nce with Test Test Met Method hod C174/C174M.. When core length for determ C174/C174M determining ining the thickn thickness ess of a member is not required to be measur measured ed in accord accordance ance with Test Method C174/C174M Method C174/C174M,, core diameter shall be as directed by specifier of tests. 6.2 For cores that are not intended for determining structural dimensions, measure the longest and shortest lengths on the cut surface along lines parallel to the core axis. Record the average length to the nearest 5 mm [ 1 ⁄ 4 in.]. 7. Cores for Compressive Compressive Strength Strength 7.1 Diameter: 7.1.1 7.1 .1 Except as pro provid vided ed in 7.1.2, 7.1.2, th thee di diam amete eterr of co core re specimens specime ns for the determ determination ination of compr compressive essive strength shall be at least 94 mm [3.70 in.] or at least two times the nominal maximum size of the coarse aggregate, whichever is larger. 7.1.2 7.1 .2 If limi limited ted mem member ber thickness thickness makes it imp imposs ossible ible to obtain cores with length-diameter ratio (L/D) of at least 1.0 or if clear distance between reinforcement is limited, core diameters less than 94 mm [3.70 in.] are not prohibited. If a core diameter less than 94 mm [3.70 in.] is used, report the reason. NOTE 10—The compressive strengths of nominal 50-mm [2-in.] diameter cores are known to be somewhat lower and more variable than those of nomi nominal nal 100-m 100-mm m [4-in. [4-in.]] diame diameter ter cores. In additi addition, on, smaller diameter cores cor es app appear ear to be mor moree sen sensit sitive ive to the ef effec fectt of the len length gth-di -diame ameter ter ratio.8
7.2 Length 7.2.1 Except as provid provided ed in 7.2.2 in 7.2.2,, the preferred length of the capped or ground specimen is between 1.9 and 2.1 times the 8
Bartlett, F. M., and MacGregor, J. G., “Effect of Core Diameter on Concrete Core Strengths,” ACI Materials Journal, Vol 91, No. 5, September–October 1994, pp. 460–470.
diameter. If the ratio of the length to the diameter (L/D) of the core exceeds 2.1, reduce the length of the core so that the ratio of the capped or ground specimen is between 1.9 and 2.1. Core specim spe cimens ens wit with h len length gth-di -diame ameter ter rat ratios ios equ equal al to or less than 1.75 require corrections corrections to the measur measured ed compr compressive essive strength (see 7.9.1 (see 7.9.1)). A strength correction correction factor is not required for L/D greaterr than 1.75. A core having greate having a maximum length length of less than 95 % of its diameter before capping or a length less than its diameter after capping, trimming, or end grinding shall not be tested. 7.2.2 7.2 .2 If the com compre pressiv ssivee str streng engths ths of cor cores es are to be com com-pared par ed with spe specifi cified ed str streng engths ths bas based ed on sta standa ndard rd con concre crete te cubes, cores shall be tested with L/D, after end preparation, in the range of 1.0 1.00 0 to 1.0 1.05 5 unl unless ess otherwise otherwise directed directed by the specifier of the tests. If the strengths of cores with L/D =1 are to be compared with specified concrete cube strength, do not apply the correction factor in 7.9.1 7.9.1.. 7.3 Moisture Conditioning— Test Test cores after moisture conditioning as specified in this test method or as directed by the specifier specifi er of the tests. The moistu moisture re condi conditionin tioning g proce procedures dures speci sp ecifie fied d in th this is tes testt me meth thod od ar aree in inten tende ded d to pr pres eser erve ve th thee moistu moi sture re of the dri drilled lled core and to pro provid videe a rep reprod roducib ucible le moistu moi sture re con conditi dition on that min minimiz imizes es the ef effec fects ts of moi moistu sture re gradients introduced by wetting during drilling and specimen preparation. 7.3.1 7.3 .1 Aft After er cor cores es hav havee bee been n dri drilled lled,, wip wipee of offf sur surfac facee dri drill ll water wat er and allo allow w rem remaini aining ng sur surfac facee moi moistu sture re to eva evapor porate. ate. When surfaces appear dry, but not later than 1 h after drilling, place cores in separate plastic bags or nonabsorbent containers and seal to prevent moisture loss. Maintain cores at ambient temperature, and protect cores from exposure to direct sunlight. Tra rans nspo port rt th thee co core ress to th thee te testi sting ng lab labor orato atory ry as so soon on as possible. Keep cores in the sealed plastic bags or nonabsorbent containers at all times except during end preparation and for a maximum time of 2 h to permit capping before testing. 7.3.2 7.3 .2 If water is use used d dur during ing sawing sawing or grinding grinding of cor coree ends, complete these operations as soon as possible, but no later lat er th than an 2 da days ys af afte terr dr drill illin ing g of co core ress un unles lesss sti stipu pulat lated ed othe ot herw rwis isee by th thee sp spec ecifi ifier er of tes tests ts.. Af After ter co comp mplet letin ing g en end d preparation, wipe off surface moisture, allow the surfaces to dry, and place the cores in sealed plastic bags or nonabsorbent containers. contai ners. Minimize the durat duration ion of expos exposure ure to water during end preparation. 7.3.3 Allow the cores cores to remain in the sealed plastic plastic bags or nonabs non absorb orbent ent con contain tainers ers for at leas leastt 5 day dayss aft after er last being wetted and before testing, unless stipulated otherwise by the specifier of tests. NOTE 11—The waiting period of at least 5 days is intended to reduce moisture gradients introduced when the core is drilled or wetted during sawing sawin g or grind grinding. ing.
7.3.4 Whe 7.3.4 When n dir directi ection on is giv given en to tes testt cor cores es in a moi moistu sture re condition condi tion other than achieved by condi conditionin tioning g accord according ing to 7.3.1,, 7.3.2 7.3.1 7.3.2,, and and 7.3.3 7.3.3,, report the alternative procedure. Sawing of End Ends— s— The 7.4 Sawing T he en ends ds of co core re sp speci ecime mens ns to be tested in compression shall be flat, and perpendicular to the longitudinal axis in accordance with Test Method C39/C39M C39/C39M.. If necessary, saw the ends of cores that will be capped so that prior to capping, the following requirements are met:
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C42/C42M − 16 7.4.1 Projec Projections, tions, if any, any, shall not extend more than 5 mm [0.2 in.] above the end surfaces. 7.4.2 The end surfaces shall not depart from perpendicularperpendicularity to the longitudinal axis by a slope of more than 1:8 d [or 1:0.3d ] where d is is the average core diameter in mm [or inches]. Calculated ed Densit Density— y— If 7.5 Calculat I f th thee co core re wi will ll be te test sted ed fo forr strength, measure the mass of the core just before capping or just before testing if bonded caps are not used. Divide the mass by the volume of the core calculated from the average diameter and length determined in 7.7 in 7.7.. Record the calculated density to 3 the nearest 20 kg/m [1 lb/ft3]. NOTE 12—The intent of 7.5 7.5 is to obtain an approximate density of the specimen, which can provide additional insight on measured strength. For example, a lower than expected density can be an indication of a batching error, that there is too much air in the concrete, or that the concrete was not con consol solida idated ted pro proper perly ly,, all of whi which ch can af affec fectt the com compre pressi ssive ve streng str ength. th. Because Because the moi moistu sture re con content tent of the cor coree is not kno known wn and because the calculated volume is approximate, the calculated density is not intend intended ed for evaluating compliance compliance with specified density requirements. Separate cores should be taken for this purpose, and the specifier of the tes tests ts sho should uld ind indica icate te the pro proced cedure ure for mea measur suring ing den densit sity; y; for example, examp le, Test Metho Method d C642 could could be spe specifi cified ed for nor normal mal wei weight ght concrete.
7.6 Capping— If If the ends of the cores do not conform to the perpendicularity requirements of Test Method C39/C39M Method C39/C39M,, they shall be sawed or ground to meet those requirements or capped with bonded caps in accordance with Practice C617/C617M Practice C617/C617M.. If thee en th ends ds of th thee co core ress do no nott co conf nfor orm m to th thee pl plan anen enes esss requirements of Test Method C39/C39M C39/C39M,, they shall be sawed or ground to meet those requirements or capped with bonded caps in accordance with Practice C617/C617M or tested with unbonded caps in accordance with Practice C1231/C1231M Practice C1231/C1231M.. If cores are capped in accordance with Practice C617/C617M Practice C617/C617M,, the capping device shall accommodate actual core diameters and produce caps that are concentric with the core ends. Measure core lengths to the nearest 1 mm [0.05 in.] before capping. If unbonded caps are used, the gap between the core and retaining rings rin gs sha shall ll con confor form m to the req requir uiremen ements ts of Pra Practic cticee C1231/ C1231M.. C1231M NOTE 13—T 13—To sat satisf isfy y the max maximu imum m gap lim limit it in Pra Practic cticee C1231/ C1231M the inner diameter of the retaining rings cannot exceed 107 % of C1231M the the average core diameter. Smaller diameter retaining rings may be needed for tes testin ting g cor cores es wit with h dia diamet meters ers sm smalle allerr tha than n sta standa ndard rd cyl cylind inders ers.. For example if the core diameter is 95 mm [3.75 in.], the inside diameter of the retaining rings cannot exceed 102 mm [4.01 in.].
7.7 Measurement— If If the core will be tested with bonded caps, determine the average length before and after capping, and an d us usee th thee len lengt gth h af after ter cap cappi ping ng to co comp mput utee th thee le leng ngth th-diameter ratio (L/D). If the core will be tested with unbonded caps or with ground ends, determine the average length of the prepared core before testing. Determine the average length of the core to the nearest 1 mm [0.05 in.] using the jaw caliper procedure of Test Method C1542/C1542M Method C1542/C1542M or or the procedure in Test Method C174/C174M Method C174/C174M.. Determine the average diameter by averaging two measurements taken at right angles to each other at the mid-h mid-height eight of the core. Report the average core diameter to th thee ne near ares estt 0. 0.2 2 mm [0 [0.0 .01 1 in in.] .] if th thee di difffe fere renc ncee in co core re diamete diam eters rs doe doess not exc exceed eed 2 % of thei theirr ave averag rage, e, oth otherw erwise ise
report to the nearest 1 mm [0.05 in.]. Do not test a core if the difference between the largest and smallest diameter exceeds 5 % of their average. 7.8 Testing— Test the spe specime cimens ns in acco accorda rdance nce wit with h Test Method C39/C39M. C39/C39M. Test Test the spe specim cimens ens wit within hin 7 day dayss aft after er coring, corin g, unless specified other otherwise. wise. 7.9 Calculation— Calcul C alculate ate th thee co comp mpres ressiv sivee str streng ength th of each specimen using the computed cross-sectional area based on the average diameter of the specimen. 7.9.1 If the ratio of length length to diameter (L/D) (L/D) of the specimen specimen is 1.75 or less, correct the result obtained in 7.9 in 7.9 by by multiplying by the app approp ropria riate te cor correc rection tion factor sho shown wn in the fol follow lowing ing table (see Note (see Note 14) 14): Ratio of Length to Diameter (L/D)
Strength Correction Factor
1 .7 5 1 .5 0 1 .2 5 1 .0 0
0 .9 8 0 .9 6 0 .9 3 0 .8 7
Use int interp erpola olatio tion n to det determ ermine ine cor correc rection tion fac factor torss for L/D values not given in the table. NOTE 14—Correc 14—Correction tion factors depend on variou variouss condit conditions ions such as moisture condition, strength level, and elastic modulus. Aver Average age values for correc cor rectio tions ns due to len length gth-di -diame ameter ter rat ratio io are giv given en in the tab table. le. These correction factors apply to low-density concrete having a density between 1600 and 1920 kg/m3 [100 and 120 lb/ft3] and to normal density concrete. They are applicable to both dry and wet concrete for strengths between 14 MPa and 42 MPa [2000 psi and 6000 psi]. For strengths above 70 MPa [10 000 psi], test data on cores show that the correction factors may be larger than the values listed above.9
7.10 Report— Report Report the results as required by Test Method C39/C39M with C39/C39M with the addition of the following information: 7.10.1 7.10. 1 Length of core core as drilled to the nearest 5 mm [1 ⁄ 4 in.], 7.10.2 7.1 0.2 If the cor coree diam diamete eterr is less than 94 mm [3.70 in.], in.], provide reason for using the smaller diameter. 7.10.3 7.10. 3 Length of test specimen before before and after capping or end preparation to the nearest 1 mm [0.05 in.], and average diameter of core to the nearest 0.2 mm [0.01 in.] or 1 mm [0.05 in.], 7.10.4 7.10. 4 Compre Compressive ssive strength strength to the nearest 0.1 MPa [10 psi] when the diameter is measured to the neares nearestt 0.2 mm [0.01 in.] and an d to th thee ne near ares estt 0. 0.5 5 MP MPaa [5 [50 0 ps psi] i] wh when en th thee di diam amete eterr is measured to the nearest 1 mm [0.05 in.], after correction for length-diame length -diameter ter ratio when requir required, ed, 7.10.5 7.10. 5 Directio Direction n of application of the load on the specimen with respect to the horizontal plane of the concrete as placed, 7.10.6 7.10. 6 The moisture conditioning conditioning history: history: 7.10 7. 10.6 .6.1 .1 Th Thee da date te an and d tim timee co core re wa wass ob obta tain ined ed an and d fir first st placed in sealed bag or nonabsorbent container, 7.10.6.2 7.10. 6.2 If water was used during end preparation, preparation, the date and time end preparation was completed and core placed in sealed bag or nonabsorbent container, 7.10.7 7.10. 7 Date concrete was placed, placed, if know known, n, 7.10.8 7.10. 8 The date and time when tested, 7.10.9 7.10. 9 Nomina Nominall maximum size of concrete aggregate. aggregate. 9
Bartlett, F. M., and MacGregor, J. G, “Effect of Core Length-to-Diameter Ratio on Concrete Core Strengths,” ACI Materials Journal, Vol 91, No. 4, July-August 1994, pp. 339–348.
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C42/C42M − 16 7.10.10 7.10.1 0 The calculated calculated density density to the nearest nearest 20 kg/m3 [1 lb/ft3]. 7.10.11 7.10. 11 The location, location, shape, and size of embedded metal, if the specifier of the tests permits testing cores with embedded metal. 7.10.1 7.1 0.12 2 If app applica licable ble,, des descri criptio ption n of def defect ectss in cor cores es tha thatt could not be tested, and 7.10.13 7.10. 13 If any deviation from from this test method was required, describe the deviation and explain why it was necessary. 7.11 Precision:10 7.11.1 7.1 1.1 The single-operator single-operator coeff coefficient of variati variation on on cores hass be ha been en fo foun und d to be 3. 3.2 2 % 11 for a ran range ge of com compre pressi ssive ve strength between 32.0 MPa [4500 psi] and 48.3 MPa [7000 psi]. psi ]. The Theref refore ore,, res results ults of two pro proper perly ly con conduc ducted ted test testss of singl sin glee co core ress by th thee sam samee op oper erat ator or on th thee sa same me sa samp mple le of material should not differ from each other by more than 9 % 11 of their average. 7.11.2 The multi-laboratory coefficient coefficient of variation on on cores 11 hass be ha been en fo foun und d to be 4. 4.7 7 % for a ran range ge of com compre pressi ssive ve strength between 32.0 MPa [4500 psi] and 48.3 MPa [7000 psi]. psi ]. The Theref refore ore,, res results ults of two pro proper perly ly con conduc ducted ted test testss on cores cor es sam sampled pled from the sam samee har harden dened ed con concre crete te (wh (where ere a single test is defined as the average of two observations (cores), each made on separate adjacent drilled 100 mm [4 in.] diameter cores), and tested by two different laboratories should not differ from each other by more than 13 % 11 of their average. 7.12 Bias— Since Since the there re is no acce accepte pted d ref refere erence nce mat materia eriall suitable for determining the bias for the procedure in this test method, no statement on bias is being made. 8. Cores for Splitting Tensile Tensile Strength Test Specimens— The 8.1 Test The spe specime cimens ns sha shall ll con confor form m to the dimensional requirements in 7.1 in 7.1,, 7.2 7.2,, 7.4.1 7.4.1,, and and 7.4.2 7.4.2.. Ends are not to be capped.
8.2 Moisture Condition ion the spe specime cimens ns as Moisture Cond Conditionin itioning— g— Condit described in 7.3 7.3,, or as directed by the specifier of tests. Bearing Surfac Surfaces— es— The 8.3 Bearing T he lin linee of co cont ntact act be betw twee een n th thee specimen and each bearing strip shall be straight and free of any projections or depressions higher or deeper than 0.2 mm [0.01 in.]. When the line of contact is not straight or contains project pro jection ionss or dep depres ressio sions ns hav having ing hei height ghtss or dep depths ths gre greater ater than 0.2 mm [0.01 in.], grind or cap the specimen so as to produce bearing lines meeting these requirements. Do not test specimens with projections or depressions greater than 2.0 mm [0.1 in.]. When capping is employed, the caps shall be as thin as practicable and shall be formed of high-strength gypsum paste. NOTE 15— 15—Fig. Fig. 1 illustrates 1 illustrates a device suitable for applying caps to the bearing surfa bearing surfaces ces of core specimens. specimens.
8.4 Testing— Test the spe specime cimens ns in acc accord ordanc ancee with Test Test Method C496/C496M.. Method C496/C496M
FIG. 1 Suitab Suitable le Capping Device for Splitting Splitting Tensile Tensile Strength Test
8.5 Calculation and Report— Calculate Calculate the splitting tensile strength streng th and rep report ort the res results ults as req requir uired ed in Test Met Method hod C496/C496M.. When C496/C496M When gr grin indi ding ng or ca capp ppin ing g of th thee be bear arin ing g surfaces is required, measure the diameter between the finished surfaces. surfa ces. Indicate that the specimen was a core and provide the moisture conditioning history as in 7.10.6 7.10.6.. 8.6 Precision:12 8.6.1 The within labor laboratory atory single single-oper -operator ator coef coeffficient of variati var iation on for spl splitti itting ng ten tensile sile str streng ength th of cor cores es bet betwee ween n 3.6 MPa [520 psi] and 4.1 MPa [590 psi] has been found to be 5.3 %.11 Therefore, results of two properly conducted tests by
10
Bollin, Bolli n, G. E., “Development “Development of Preci Precision sion and Bias Statements Statements for Testing Testing Drilled Cores in Accor Drilled Accordance dance with ASTM C42,” ASTM Journal of Cement, Concrete, and Aggregates, Vol 15, No. 1, 1993. 11 These The se num number berss rep repres resent ent,, res respec pectiv tively ely,, the (1s %) and (d2 (d2ss %) %) lim limits its as described in Practice C670 Practice C670..
12
Steele, G.W., “Portland Cement Concrete Core Proficiency Sample Program,” Strategic Highw Strategic Highway ay Resea Research rch Progra Program, m, SHRP SHRP-P-63 -P-636, 6, Nation National al Rese Research arch Counc Council, il, Washington, D.C., 1993.
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C42/C42M − 16 the same operator in the same laboratory on the same sample of material should not differ by more than 14.9 % 11 of their average. 8.6.2 The multi-laboratory multi-laboratory coeff coefficient of variati variation on for splitting tensile strength of cores between 3.6 MPa [520 psi] and 4.1 MPa [590 psi] has been found to be 15.0 %. 11 Therefore, results of two properly conducted tests on the same sample of material mate rial of har harden dened ed con concre crete te and tes tested ted by two dif differ ferent ent laboratories should not differ from each other by more than 42.3 %11 of their average.
8.7 Bias— Since Since ther theree is no acce accepte pted d ref refere erence nce mate materia riall suitable for determining the bias for the procedure in this test method, no statement on bias is being made. 9. Keywo Keywords rds 9.1 compressive strength; concrete concrete coring; concrete sawing; concrete strength; flexural strength; splitting tensile strength
APPENDIX (Nonmandatory Information) X1. SA SAWED WED BEAMS FOR FLEXURA FLEXURAL L TESTING
X1.1 Gene General ral X1.1.1 There are insuf X1.1.1 insuffficient data on the effects effects of variou variouss variables that could affect the measured flexural performance of saw sawed ed bea beams. ms. Con Consid siderab erable le res resour ources ces are nec necessa essary ry to provide the data necessary to develop a definitive test method and an d th thee acc accom ompa pany nyin ing g pr prec ecisi ision on da data. ta. Un Until til th that at da data ta ar aree generated, genera ted, the follow following ing gener general al recomm recommendati endations ons are provided for obtaining and testing sawed beams. X1.1.2 Testing beams sawed from X1.1.2 from existing concrete concrete is not a preferred prefer red method of assessing the in-pla in-place ce flexur flexural al streng strength th becausee of the dif becaus diffficulty in obtain obtaining ing the corre correct ct geomet geometry ry and because of the risk of damage to the specimens by the sawing process, proces s, subse subsequent quent handling, and incor incorrect rect moistu moisture re conditioning. If in-place flexural strength needs to be assessed, the splitting tensile strength can be measured on cores in accordance dan ce with Sect Section ion 8 and publi published shed relatio relationship nshipss between flexural strength and splitting tensile strength can be applied.13 If it is necessary to test sawed beams, the specifier of tests should provide instructions on the size of the beams, dimensional sio nal tolerance tolerances, s, and how bea beams ms are to be ori orient ented ed in the testing apparatus. X1.2 Test Specimens X1.2.1 Dimensions— A beam specimen for the determination of flexural strength should have a square cross section. The cross section can be 100 by 100 mm [4 by 4 in.] if the nominal maximum aggregate size is 25 mm [1 in.] or less; otherwise the cros cr osss se sect ctio ion n sh sho oul uld d be 150 by 15 150 0 mm [6 by 6 in in.] .].. Cross-sectional dimensions should be within 6 2 % of these nominal dimensions. If the depth of the beam is controlled by the depth of the structural element, the specifier of tests needs to specify the beam dimensions. The test specimen should be at least 50 mm [2 in.] longer than three times the nominal depth.
When beams are required for measuring properties other than flexural strength, such as toughness, beam dimensions should conform to the requirements of the applicable test method. X1.2.2 Sawing and Inspection— Beams Beams should be cut with water-cooled masonry saws. Test specimens can be damaged if sawing is not done carefully. Ensure that an adequate supply of water is used to keep the saw blade cool. The sawed surfaces need to be paralle parallell and squar squaree within the limits provided by the specifier of tests. Mark the specimen so that its orientation in the structure can be identified. Check the sawn surface for the presence of cracks, which can be seen by surface drying the specimen and looking for dark lines that indicate water filled cracks.. Do not test a beam if there is a crack in the loading span cracks or if there is a chip on the face that will be loaded in tension. Take care in handling sawed beam specimens to avoid chipping or cracking. Specimens may be rejected by the specifier of tests if they do not conform to the dimensional tolerances or they do not con confor form m to con contact tact req requir uiremen ements ts (at loa load d and sup suppor portt points) when placed in the loading apparatus. X1.3 Moisture Conditioning X1.3.1 The surfaces X1.3.1 surfaces of saw sawed ed spe specim cimens ens need to be protected tect ed fro from m dry drying ing by cov coveri ering ng them with wet bur burlap lap and plastic sheeting during transportation and storage. Relatively small amounts of drying of the surface of flexural specimens can ca n in indu duce ce ten tensil silee st stre ress sses es in th thee ex extre treme me fib fiber erss th that at wi will ll markedly marked ly reduc reducee the measur measured ed flexur flexural al streng strength. th. Specim Specimens ens should be tested within 7 days of sawing or as required by the spec sp ecifi ifier er of te tests sts.. Su Subm bmer erge ge th thee tes testt sp speci ecimen menss in lim limeesaturated water at 23.0 6 2.0 °C [73.5 6 3.5 °F] for at least 40 h imm immedi ediatel ately y bef before ore test testing ing.. Test the spe specim cimens ens pro prompt mptly ly after removal from water storage. During the period between removal from water storage and testing, keep the specimens moist by covering with a wet blanket of burlap or other suitable absorbent fabric.
13
See for examp example le Rapha Raphael, el, J., “T “Tensil ensilee Stren Strength gth of Concr Concrete,” ete,” Journal of the American Concrete Institute, Vol 81, No. 2, March–April 1984, pp. 158–165 and “Referee “Refe ree Testin esting g of Harde Hardened ned Portla Portland nd Cemen Cementt Concre Concrete te Pavem Pavement—P ent—Percen ercentt Within Wit hin Limi Limits ts Revi Revision sion,” ,” Engi Engineer neering ing Brie Brieff No. 34A, Fede Federal ral Aviat viation ion Administration, http://www.faa http://www.faa.gov/airports/engineering/engineering_briefs/media/ .gov/airports/engineering/engineering_briefs/media/ EB_34a.pdf.
X1.4 Testing X1.4.1 Test the specimens in accordance with the applicable provisions of Test Method C78/C78M C78/C78M except except that the orientation ti on of th thee be beam am in th thee te test stin ing g ap appa para ratu tuss sh shou ould ld be in
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C42/C42M − 16 accordance accorda nce with the req requir uiremen ements ts of the spe specifi cifier er of test tests. s. Ideally Ide ally,, the ten tensile sile sur surfac facee dur during ing the tes testt sho should uld be ten tensile sile surface as loaded in the structure. This will typically require the tensile surface to be a cut surface, and the measured flexural strength may be less than the true flexural strength. On the other hand, it may be preferable for the uncut surface to be the tensile surface if it meets dimensional tolerances. Therefore, the specifier of tests needs to state which surface of the beam will be the tensile surface for testing. The location of the tensile surf su rface ace wi with th re resp spec ectt to th thee po posit sitio ion n of th that at su surf rface ace in th thee concrete as placed is to be noted and reported.
X1.5 Repo Report rt X1.5.1 The test res X1.5.1 results ults should should be rep report orted ed in acco accorda rdance nce with the applicable provisions of Test Method C78/C78M Method C78/C78M.. X1.5.2 The test report should include the following inforX1.5.2 information: X1.5.2.1 X1.5. 2.1 The moisture condition condition at the time of testing. X1.5.2.2 X1.5.2 .2 The ori orienta entatio tion n of the tens tensile ile sur surfac facee fac facee wit with h respect to the position of that surface in the structure.
SUMMARY OF CHANGES Committ Com mittee ee C09 has ide identi ntified fied the loca locatio tion n of sele selected cted changes changes to this test meth method od sin since ce the last issu issue, e, C42/C42M – 13, that may impact the use of this test method. (Approved October 1, 2016.) (1) Revised 7.6, 7.7, 7.10.3, and 7.10.4. ASTM International International takes no positi position on respecting the validi validity ty of any patent rights assert asserted ed in connec connection tion with any item mentio mentioned ned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible respon sible technical technical committee, which you may attend. If you feel that your comments have not receiv received ed a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below. This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address addr ess or at 610610-832832-9585 9585 (pho (phone), ne), 610610-832832-9555 9555 (fax (fax), ), or serv service@ ice@astm astm.org .org (e-m (e-mail) ail);; or thro through ugh the ASTM webs website ite (www.astm. (www .astm.org). org). Permission Permission rights to photocopy the standa standard rd may also be secure secured d from the Copyri Copyright ght Clearance Center, Center, 222 Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/
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