Designation:C39/C39M–12
Standard Test Method for
Compressive Strength of Cylindrical Concrete Specimens1 This standard is issued under thefixed designation C39/C39M;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1.Scope*
1.1This test method covers determination of compressive strength of cylindrical concrete specimens such as molded cylinders and drilled cores.It is limited to concrete having a density in excess of800kg/m3[50lb/ft3].
1.2The values stated in either SI units or inch-pound units are to be regarded separately as standard.The inch-pound units are shown in brackets.The values stated in each system may not be exact equivalents;therefore,each system shall be used independently of the other.Combining values from the two systems may result in non-conformance with the standard. 1.3This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.(Warning—Means should be provided to contain concrete fragments during sudden rupture of specimens.Tendency for sudden rupture increases with increasing concrete strength and it is more likely when the testing machine is relativelyflexible.The safety precautions given in the Manual of Aggregate and Concrete Testing are recommended.)
1.4The text of this standard references notes which provide explanatory material.These notes shall not be considered as requirements of the standard.
2.Referenced Documents
2.1ASTM Standards:2
C31/C31M Practice for Making and Curing Concrete Test Specimens in the Field
C42/C42M Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C617Practice for Capping Cylindrical Concrete Specimens C670Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
C873Test Method for Compressive Strength of Concrete Cylinders Cast in Place in Cylindrical Molds
C1077Practice for Agencies Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Testing Agency Evaluation
C1231/C1231M Practice for Use of Unbonded Caps in Determination of Compressive Strength of Hardened Con-crete Cylinders
E4Practices for Force Verification of Testing Machines
E74Practice of Calibration of Force-Measuring Instru-ments for Verifying the Force Indication of Testing Ma-chines
Manual of Aggregate and Concrete Testing
3.Summary of Test Method
3.1This test method consists of applying a compressive axial load to molded cylinders or cores at a rate which is within a prescribed range until failure occurs.The compressive strength of the specimen is calculated by dividing the maxi-mum load attained during the test by the cross-sectional area of the specimen.
4.Significance and Use
4.1Care must be exercised in the interpretation of the significance of compressive strength determinations by this test method since strength is not a fundamental or intrinsic property of concrete made from given materials.Values obtained will depend on the size and shape of the specimen,batching,mixing
1This test method is under the jurisdiction of ASTM Committee C09on
Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee
C09.61on Testing for Strength.
Current edition approved Feb.1,2012.Published March2012.Originally
approved in1921.Last previous edition approved in2011as C39/C39M–11a.DOI:
10.1520/C0039_C0039M-12.
2For referenced ASTM standards,visit the ASTM website,,or
contact ASTM Customer Service at For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on
centeringthe ASTM website.
*A Summary of Changes section appears at the end of this standard. Copyright.C ASTM International.100Barr Harbor Dr.P.O.box C-700West Conshohocken,Pennsylvania.19428-2959,United States
procedures,the methods of sampling,molding,and fabrication and the age,temperature,and moisture conditions during curing.
4.2This test method is used to determine compressive strength of cylindrical specimens prepared and cured in accor-dance with Practices C31/C31M,C192/C192M,C617,and C1231/C1231M and Test Methods C42/C42M and C873. 4.3The results of this test method are used as a basis for quality control of concrete proportioning,mixing,and placing operations;determination of compliance with specifications; control for evaluating effectiveness of admixtures;and similar uses.
4.4The individual who tests concrete cylinders for accep-tance testing shall meet the concrete laboratory technician requirements of Practice C1077,including an examination requiring performance demonstration that is evaluated by an independent examiner.
N OTE1—Certification equivalent to the minimum guidelines for ACI Concrete Laboratory Technician,Level I or ACI Concrete Strength Testing Technician will satisfy this requirement.
5.Apparatus
5.1Testing Machine—The testing machine shall be of a type having sufficient capacity and capable of providing the rates of loading prescribed in7.5.
5.1.1Verify calibration of the testing machines in accor-dance with Practices E4,except that the verified loading range shall be as required in5.3.Verification is required under the following conditions:
5.1.1.1At least annually,but not to exceed13months, 5.1.1.2On original installation or immediately after reloca-tion,
5.1.1.3Immediately after making repairs or adjustments that affect the operation of the force applying system or the values displayed on the load indicating system,except for zero adjustments that compensate for the mass of bearing blocks or specimen,or both,or
5.1.1.4Whenever there is reason to suspect the accuracy of the indicated loads.
5.1.2Design—The design of the machine must include the following features:
5.1.2.1The machine must be power operated and must apply the load continuously rather than intermittently,and without shock.If it has only one loading rate(meeting the requirements of7.5),it must be provided with a supplemental means for loading at a rate suitable for verification.This supplemental means of loading may be power or hand oper-ated.
5.1.2.2The space provided for test specimens shall be large enough to accommodate,in a readable po
sition,an elastic calibration device which is of sufficient capacity to cover the potential loading range of the testing machine and which complies with the requirements of Practice E74.
N OTE2—The types of elastic calibration devices most generally avail-able and most commonly used for this purpose are the circular proving ring or load cell.
5.1.3Accuracy—The accuracy of the testing machine shall be in accordance with the following provisions:
5.1.3.1The percentage of error for the loads within the proposed range of use of the testing machine shall not exceed 61.0%of the indicated load.
5.1.3.2The accuracy of the testing machine shall be verified by applyingfive test loads in four approximately equal increments in ascending order.The difference between any two successive test loads shall not exceed one third of the differ-ence between the maximum and minimum test loads.
5.1.3.3The test load as indicated by the testing machine and the applied load computed from the readings of the verification device shall be recorded at each test point.Calculate the error, E,and the percentage of error,E p,for each point from these data as follows:
E5A2B(1)
E p5100~A2B!/B
where:
A=load,kN[lbf]indicated by the machine being verified, and
B=applied load,kN[lbf]as determined by the calibrating device.
5.1.3.4The report on the verification of a testing machine shall state within what loading range it was found to conform to specification requirements rather than reporting a blanket acceptance or rejection.In no case shall the loading range be stated as including loads below the value which is100times the smallest change of load estimable on the load-indicating mechanism of the testing machine or loads within that portion of the range below10%of the maximum range capacity. 5.1.3.5In no case shall the loading range be stated as including loads outside the range of loads applied during the verification test.
5.1.3.6The indicated load of a testing machine shall not be corrected either by calculation or by the use of a calibration diagram to obtain values within the required permissible variation.
5.2The testing machine shall be equipped with two steel bearing blocks with hardened faces(Note3),one of which is a spherically seated block that will bear on the upper surface of the specimen,and the other a solid block on which the specimen shall rest.Bearing faces of the blocks shall have a minimum dimension at least3%greater than the diameter of the specimen to be tested.Except for the concentric circles described below,the bearing faces shall not depart from a plane by more than0.02mm[0.001in.]in any150mm[6in.]of blocks150mm[6in.]in diameter or larger,or by more than 0.02mm[0.001in.]in the diameter of any smaller block;and new blocks shall be manufactured within one half of this tolerance.When the diameter of the bearing face of the spherically seated block exceeds the diameter of the specimen by more than13mm[0.5in.],concentric circles not more than 0.8mm[0.03in.]deep and not more than1mm[0.04in.]wide shall be inscribed to facilitate proper centering.
N OTE3—It is desirable that the bearing faces of blocks used for compression testing of concrete have a Rockwell hardness of not less than 55HRC.
5.2.1Bottom bearing blocks shall conform to the following
requirements:
5.2.1.1The bottom bearing block is specified for the pur-pose of providing a readily machinable surface for mainte-nance of the specified surface conditions(Note4).The top and bottom surfaces shall be parallel to each other.If the testing machine is so designed that the platen itself is readily main-tained in the specified surface condition,a bottom block is not required.Its least horizontal dimension shall be at least3% greater than the diameter of the specimen to be tested. Concentric circles as described in5.2are optional on the bottom block.
N OTE4—The block may be fastened to the platen of the testing machine.
5.2.1.2Final centering must be made with reference to the upper spherical block.When the lower bearing block is used to assist in centering the specimen,the center of the concentric rings,when provided,or the center of the block itself must be directly below the center of the spherical head.Provision shall be made on the platen of the machine to assure such a position.
5.2.1.3The bottom bearing block shall be at least25mm[1 in.]thick when new,and at least22.5mm[0.9in.]thick after any resurfacing operations.
5.2.2The spherically seated bearing block shall conform to the following requirements:
5.2.2.1The maximum diameter of the bearing face of the suspended spherically seated block shall not exceed the values given below:
Diameter of Maximum Diameter
Test Specimens,of Bearing Face,
mm[in.]mm[in.]
50[2]105[4]
75[3]130[5]
100[4]165[6.5]
150[6]255[10]
200[8]280[11]
N OTE5—Square bearing faces are permissible,provided the diameter of the largest possible inscribed circle does not exceed the above diameter.
5.2.2.2The center of the sphere shall coincide with the surface of the bearing face within a tolerance of65%of the radius of the sphere.The diameter of the sphere shall be at least 75%of the diameter of the specimen to be tested.
5.2.2.3The ball and the socket shall be designed so that the steel in the contact area does not permanently deform when loaded to the capacity of the testing machine.
N OTE6—The preferred contact area is in the form of a ring(described as“preferred bearing area”)as shown on Fig.1.
5.2.2.4At least every six months,or as specified by the manufacturer of the testing machine,clean and lubricate the curved surfaces of the socket and of the spherical portion of the machine.The lubricant shall be a petroleum-type oil such as conventional motor oil or as specified by the manufacturer of the testing machine.
N OTE7—To ensure uniform seating,the spherically seated head is designed to tilt freely as it comes into contact with the top of the specimen. After contact,further rotation is undesirable.Friction between the socket and the spherical portion of the head provides restraint against further rotation during loading.Petroleum-type oil such as conventional motor oil has been shown to permit the necessary frict
ion to develop.Pressure-type greases can reduce the desired friction and permit undesired rotation of the spherical head and should not be used unless recommended by the manufacturer of the testing machine.
5.2.2.5If the radius of the sphere is smaller than the radius of the largest specimen to be tested,the portion of the bearing face extending beyond the sphere shall have a thickness not less than the difference between the radius of the sphere and radius of the specimen.The least dimension of the bearing face shall be at least as great as the diameter of the sphere(see Fig.
1).
5.2.2.6The movable portion of the bearing block shall be held closely in the spherical seat,but the design shall be such that the bearing face can be rotated freely and tilted at least4°in any direction.
5.2.2.7If the ball portion of the upper bearing block is a two-piece design composed of a spherical portion and a bearing plate,a mechanical means shall be provided to ensure that the spherical portion isfixed and centered on the bearing plate.
5.3Load Indication:
5.3.1If the load of a compression machine used in concrete testing is registered on a dial,the dial shall be provided with a graduated scale that is readable to at least the nearest0.1%of the full scale load(Note8).The dial shall be readable within 1%of the indicated load at any given load level within the loading range.In no case shall the loading range of a dial be considered to include loads below the value that is100times the smallest change of load that can be read on the scale.The scale shall be provided with a graduation line equal to zero and so numbered.The dial pointer shall be of sufficient length to reach the graduation marks;the width of the end of the pointer shall not exceed the clear distance between the smallest graduations.Each dial shall be equipped with a zero adjust-ment located outside the dialcase and easily accessible from the front of the machine while observing the zero mark and dial pointer.Each dial shall be equipped with a suitable device that at all times,until reset,will indicate to within1%accuracy the maximum load applied to the
specimen.
N OTE—Provision shall be made for holding the ball in the socket and for holding the entire unit in the testing machine.
FIG.1Schematic Sketch of a Typical Spherical Bearing
Block
N OTE8—Readability is considered to be0.5mm[0.02in.]along the arc described by the end of the pointer.Also,one half of a scale interval is readable with reasonable certainty when the spacing on the load indicating mechanism is between1mm[0.04in.]and2mm[0.06in.].When the spacing is between2and3mm[0.06and0.12in.],one third of a scale interval is readable with reasonable certainty.When the spacing is3mm [0.12in.]or more,one fourth of a scale interval is readable with reasonable certainty.
5.3.2If the testing machine load is indicated in digital form, the numerical display must be large enough to be easily read. The numerical increment must be equal to or less than0.10% of the full scale load of a given loading range.In no case shall the verified loading range include loads less than the minimum numerical increment multiplied by100.The accuracy of the indicated load must be within1.0%for any value displayed within the verified loading range.Provision must be made for adjusting to indicate true zero at zero load.There shall be provided a maximum load indicator that at all times until reset will indicate within1%system accuracy the maximum load applied to the specimen.
5.4Documentation of the calibration and maintenance of the testing machine shall be in accordance with Practice C1077.
6.Specimens
6.1Specimens shall not be tested if any individual diameter of a cylinder differs from any other diameter of the same cylinder by more than2%.
N OTE9—This may occur when single use molds are damaged or deformed during shipment,whenflexible single use molds are deformed during molding,or when a core drill deflects or shifts during drilling. 6.2Prior to testing,neither end of test specimens shall depart from perpendicularity
to the axis by more than0.5°(approximately equivalent to1mm in100mm[0.12in.in12 in.]).The ends of compression test specimens that are not plane within0.050mm[0.002in.]shall be sawed or ground to meet that tolerance,or capped in accordance with either Practice C617or,when permitted,Practice C1231/C1231M.The diam-eter used for calculating the cross-sectional area of the test specimen shall be determined to the nearest0.25mm[0.01in.] by averaging two diameters measured at right angles to each other at about midheight of the specimen.
6.3The number of individual cylinders measured for deter-mination of average diameter is not prohibited from being reduced to one for each ten specimens or three specimens per day,whichever is greater,if all cylinders are known to have been made from a single lot of reusable or single-use molds which consistently produce specimens with average diameters within a range of0.5mm[0.02in.].When the average diameters do not fall within the range of0.5mm[0.02in.]or when the cylinders are not made from a single lot of molds, each cylinder tested must be measured and the value used in calculation of the unit compressive strength of that specimen. When the diameters are measured at the reduced frequency,the cross-sectional areas of all cylinders tested on that day shall be computed from the average of the diameters of the three or more cylinders representing the group tested that day.
6.4If the purchaser of the testing services requests measure-ment of density of test specimens,determi
ne the mass of specimens before capping.Remove any surface moisture with a towel and measure the mass of the specimen using a balance or scale that is accurate to within0.3%of the mass being measured.Measure the length of the specimen to the nearest1 mm[0.05in.]at three locations spaced evenly around the circumference.Compute the average length and record to the nearest1mm[0.05in.].Alternatively,determine the cylinder density by weighing the cylinder in air and then submerged under water at23.062.0°C[73.563.5°F],and computing the volume according to8.3.1.
6.5When density determination is not required and the length to diameter ratio is less than1.8or more than2.2, measure the length of the specimen to the nearest0.05D.
7.Procedure
7.1Compression tests of moist-cured specimens shall be made as soon as practicable after removal from moist storage.
7.2Test specimens shall be kept moist by any convenient method during the period between removal from moist storage and testing.They shall be tested in the moist condition.
7.3All test specimens for a given test age shall be broken within the permissible time tolerances prescribed as follows: Test Age Permissible Tolerance
24h60.5h or2.1%
3days2h or2.8%
7days6h or3.6%
28days20h or3.0%
90days2days2.2%
7.4Placing the Specimen—Place the plain(lower)bearing block,with its hardened face up,on the table or platen of the testing machine directly under the spherically seated(upper) bearing block.Wipe clean the bearing faces of the upper and lower bearing blocks and of the test specimen and place the test specimen on the lower bearing block.Carefully align the axis of the specimen with the center of thrust of the spherically seated block.
7.4.1Zero Verification and Block Seating—Prior to testing the specimen,verify that the load indicator is set to zero.In cases where the indicator is not properly set to zero,adjust the indicator(Note10).After placing the specimen in the machine but prior to applying the load on the specimen,tilt the movable portion of the spherically seated block gently by hand so that the bearing face appears to be parallel to
the top of the test specimen.
N OTE10—The technique used to verify and adjust load indicator to zero will vary depending on the machine manufacturer.Consult your owner’s manual or compression machine calibrator for the proper tech-nique.
7.5Rate of Loading—Apply the load continuously and without shock.
7.5.1The load shall be applied at a rate of movement(platen to crosshead measurement)corresponding to a stress rate on the specimen of0.2560.05MPa/s[3567psi/s](See Note 11).The designated rate of movement shall be maintained at least during the latter half of the anticipated loading phase. N OTE11—For a screw-driven or displacement-controlled testing ma-chine,preliminary testing will be necessary to establish the required rate of movement to achieve the specified stress rate.The required rate
of
movement will depend on the size of the test specimen,the elastic modulus of the concrete,and the stiffness of the testing machine.
7.5.2During application of the first half of the anticipated loading phase,a higher rate of loading shall be permitted.The higher loading rate shall be applied in a controlled manner so that the specimen is not subjected to shock loading.
7.5.3Make no adjustment in the rate of movement (platen to crosshead)as the ultimate load is being approached and the stress rate decreases due to cracking in the specimen.
7.6Apply the compressive load until the load indicator shows that the load is decreasing steadily and the specimen displays a well-defined fracture pattern (Types 1to 4in Fig.2).For a testing machine equipped with a specimen break detector,automatic shut-off of the testing machine is prohibited until the load has dropped to a value that is less than 95%of the peak load.When testing with unbonded caps,a corner fracture similar to a Type 5or 6pattern shown in Fig.2may occur before the ultimate capa
city of the specimen has been attained.Continue compressing the specimen until the user is certain that the ultimate capacity has been attained.Record the maximum load carried by the specimen during the test,and note the type of fracture pattern according to Fig.2.If the fracture pattern is not one of the typical patterns shown in Fig.
2,sketch and describe briefly the fracture pattern.If the measured strength is lower than expected,examine the frac-tured concrete and note the presence of large air voids,evidence of segregation,whether fractures pass predominantly around or through the coarse aggregate particles,and verify end preparations were in accordance with Practice C617or Practice C1231/C1231M .8.Calculation
8.1Calculate the compressive strength of the specimen by dividing the maximum load carried by the specimen during the test by the average cross-sectional area determined as de-scribed in Section 6and express the result to the nearest 0.1MPa [10psi].
8.2If the specimen length to diameter ratio is 1.75or less,correct the result obtained in 8.1by multiplying by the appropriate correction factor shown in the following table Note 12:
L/D: 1.75 1.50 1.25 1.00Factor:
0.98
0.96
0.93
0.87
Use interpolation to determine correction factors for L/D values between those given in the
table.
FIG.2Schematic of Typical Fracture
Patterns
版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。
发表评论