1、Designation: C1231/C1231M 12C1231/C1231M 13Standard Practice forUse of Unbonded Caps in Determination of CompressiveStrength of Hardened Concrete Cylinders1This standard is issued under the fixed designation C1231/C1231M; the number immediately following the designation indicates theyear of original
2、 adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers requirements for a capping system using unbon
3、ded caps for testing concrete cylinders molded inaccordance with Practice C31/C31M or C192/C192M. Unbonded neoprene caps of a defined hardness are permitted to be usedfor testing for a specified maximum number of reuses without qualification testing up to a certain concrete compressive strengthlevel
4、. Above that strength, level neoprene caps will require qualification testing. Qualification testing is required for all elastomericmaterials other than neoprene regardless of the concrete strength.1.2 Unbonded caps are not to be used for acceptance testing of concrete with compressive strength belo
5、w 1500 psi 10 MPaor above 12 000 psi 80 MPa.1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
6、two systems may result in non-conformance with the standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicabi
7、lity of regulatorylimitations prior to use. (WarningConcrete cylinders tested with unbonded caps rupture more violently than comparablecylinders tested with bonded caps. The safety precautions given in the Manual of Aggregate and Concrete Testing arerecommended.2)2. Referenced Documents2.1 ASTM Stan
8、dards:3C31/C31M Practice for Making and Curing Concrete Test Specimens in the FieldC39/C39M Test Method for Compressive Strength of Cylindrical Concrete SpecimensC192/C192M Practice for Making and Curing Concrete Test Specimens in the LaboratoryC617 Practice for Capping Cylindrical Concrete Specimen
9、sD2000 Classification System for Rubber Products in Automotive Applications3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 pad, nan unbonded elastomeric pad.3.1.2 unbonded cap, na metal retainer and an elastomeric pad.4. Significance and Use4.1 This practice provides for using
10、 an unbonded capping system in testing hardened concrete cylinders made in accordancewith Practices C31/C31M or C192/C192M in lieu of the capping systems described in Practice C617.1 This practice is under the jurisdiction ofASTM Committee C09 on Concrete and ConcreteAggregates and is the direct res
11、ponsibility of Subcommittee C09.61 on Testingfor Strength.Current edition approved Nov. 15, 2012Dec. 15, 2013. Published December 2012January 2014. Originally approved in 1993. Last previous edition approved in 20102012as C1231/C1231M10a.12. DOI: 10.1520/C1231_C1231M-12.10.1520/C1231_C1231M-13.2 Sec
12、tion on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol. 04.02.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the s
13、tandards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accur
14、ately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor
15、Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 The elastomeric pads deform in initial loading to conform to the contour of the ends of the cylinder and are restrained fromexcessive lateral spreading by plates and metal rings to provide a uniform distribution of load from the
16、 bearing blocks of the testingmachine to the ends of the concrete or mortar cylinders.5. Materials and Apparatus5.1 Materials and equipment necessary to produce ends of the reference cylinders that conform to planeness requirements ofTest Method C39/C39M and the requirements of Practice C617. This m
17、ay include grinding equipment or capping materials andequipment to produce neat cement paste, high strength gypsum plaster, or sulfur mortar caps.5.2 Elastomeric Pads:5.2.1 Pads shall be 12 6 116 in. 136 2 mm thick and the diameter shall not be more than 116 in. 2 mm smaller than the insidediameter
18、of the retaining ring.5.2.2 Pads shall be made from polychloroprene (neoprene) meeting the requirements of Classification D2000 as follows:Shore ADurometerClassification D2000Line Call-Out50 M2BC51460 M2BC61470 M2BC714The tolerance on ShoreAdurometer hardness is 6 5. Table 1 provides requirements fo
19、r use of caps made from material meetingthe requirements of Classification D2000, above.5.2.3 Other elastomeric materials that meet the performance requirements of qualification tests in Section 8 are permitted.5.2.4 Elastomeric pads shall be supplied with the following information:5.2.4.1 The manuf
20、acturers or suppliers name,5.2.4.2 The Shore A hardness, and5.2.4.3 The applicable range of concrete compressive strength from Table 1 or from qualification testing.5.2.5 The user shall maintain a record indicating the date the pads are placed in service, the pad durometer, and the number ofuses to
21、which they have been subjected.5.3 Retainers, are a pair of metal fixtures used to provide support for and alignment of the neoprene pads and the cylinder ends(Note 1 and Fig. 1). Each retainer (upper and lower) includes a (retaining) ring that is welded to or manufactured integrally witha base plat
22、e. The height of the retaining ring shall be 25 6 3 mm 1.0 6 0.1 in. The inside diameter of the retaining ring shallnot be less than 102 % or greater than 107 % of the diameter of the cylinder. The thickness of the retaining ring shall be at least12 mm 0.47 in. for 150 mm 6 in. diameter retainers an
23、d at least 9 mm 0.35 in. for 100 mm 4 in. diameter retainers. Thesurface of the base plate that contacts the bearing block of the testing machine shall be plane to within 0.05 mm 0.002 in. Thethickness of the base plate shall be at least 12 mm 0.47 in. for 150 mm 6 in. retainers and at least 8 mm 0.
24、3 in. for 100 mm4 in. retainers. The bearing surfaces of the retainers shall not have gouges, grooves, protrusions, or indentations greater than 0.25mm 0.010 in. deep or greater than 32 mm2 0.05 in.2 in surface area.NOTE 1Retainers made from steel and some aluminum alloys have been found acceptable.
25、6. Test Specimens6.1 The specimens shall be either 6 by 12 in. 150 by 300 mm or 4 by 8 in. 100 by 200 mm cylinders made in accordancewith Practices C31/C31M or C192/C192M. Neither end of a cylinder shall depart from perpendicularity to the axis by more than0.5 (Note 2). No individual diameter of a c
26、ylinder may differ from any other diameter by more than 2 %.NOTE 2One method of measuring the perpendicularly of ends of cylinders is to place a try square across any diameter and measure the departureof the longer blade from an element of the cylindrical surface. An alternative method is to place t
27、he end of the cylinder on a plane surface and supportthe try square on that surface. A deviation from perpendicularity of 0.5 is equal to a slope of approximately 1 mm in 100 mm 18 in. in 12 in.TABLE 1 Requirements for Use of Polychloroprene(Neoprene)PadsCompressive Strength,A psiMPaShore ADurometer
28、HardnessQualificationTests RequiredMaximumReusesBLess than 1500 10 Not permitted1500 to 6000 10 to 40 50 None 1002500 to 7000 17 to 50 60 None 1004000 to 7000 28 to 50 70 None 1007000 to 12,000 50 to 80 70 Required 50Greater than 12,000 80 Not permittedACompressive strength of concrete at age of tes
29、ting as specified in ContractDocuments. For acceptance testing, it is the specified compressive strength fc .B Maximum number of reuses will be less if pads wear, crack or split. See 7.2.C1231/C1231M 1326.2 Depressions under a straight edge measured with a round wire gage across any diameter shall n
30、ot exceed 0.20 in. 5 mm.If cylinder ends do not meet this tolerance, the cylinder shall not be tested unless irregularities are corrected by sawing or grinding.7. Procedure7.1 Unbonded caps are permitted to be used on one or both ends of a cylinder in lieu of a cap or caps meeting Practice C617,prov
31、ided the caps meet the requirements of Section 5. Pad hardness shall be in accordance with Table 1. (Note 3)NOTE 3The specified strength in the contract documents is for various stages of construction. This may include strength test requirements forformwork removal or release of prestress in additio
32、n to the test requirements for verification of specified compressive strength. Therefore, pad selectionis based on the strength requirement for the designated stage of construction.7.2 Examine both sides of pads for excessive wear or damage. Replace pads that have cracks or splits in their top or bo
33、ttomsurface that exceed 38 in. 10 mm in length regardless of depth. Insert pad in the retainer before it is placed on the cylinder (Note4).NOTE 4Some manufacturers recommend dusting the pads and the ends of the cylinders with corn starch or talcum powder prior to testing.7.3 Center the unbonded cap
34、or caps on the cylinder and place the cylinder on the lower bearing block of the testing machine.Carefully align the axis of the cylinder with the center of thrust of the testing machine by centering the upper retaining ring onthe spherically seated bearing block. As the spherically seated block is
35、brought to bear on the upper retaining ring, rotate itsmovable portion gently by hand so that uniform seating is obtained. After application of load, but before reaching 10 % of theanticipated specimen strength, check to see that the axis of the cylinder does not depart from vertical by more than 0.
36、5 (Note 5)and that the ends of the cylinder are centered within the retaining rings. If the cylinder alignment does not meet these requirements,release the load, check compliance with 6.1, and carefully recenter the specimen. Reapply load and recheck specimen centeringand alignment. A pause in load
37、application to check cylinder alignment is permissible.NOTE 5An angle of 0.5 is equal to a slope of approximately 1 mm in 100 mm 18 in. in 12 in.7.3 Complete the load application, testing, calculation, and reporting of results in accordance with Test Method C39/C39M(Notes 65 and 76).NOTE 5Some users
38、 have reported damage to testing machines from the sudden release of energy stored in the elastomeric pads.NOTE 6Occasionally, unbonded capped cylinders may develop early cracking, but continue to carry increasing load. For this reason Test MethodC39/C39M requires cylinders to be loaded until it is
39、certain that they have been compressed beyond their ultimate capacity.FIG. 1 Example of Retaining Ring and Base PlateC1231/C1231M 1338. Qualification of Unbonded Capping Systems and Verification of Reuse of Pads8.1 Table 1 specifies the conditions under which polychloroprene (neoprene) unbonded pads
40、 must be qualified under this sectiondepending on the concrete strength and the Shore A hardness. Unbonded pads made of other elastomeric materials must bequalified using the procedures in this section.8.2 When qualification tests are required they must be made by either the supplier or user of the
41、unbonded pads. The user ofthe pads must retain a copy of the current qualification test report to demonstrate compliance with this practice. See X1.1.8.3 The compressive strength of molded cylinders tested with unbonded caps shall be compared with that of companioncylinders tested with ends ground o
42、r capped to meet requirements of Test Method C39/C39M and Practice C617.8.4 To be acceptable, tests must demonstrate that at a 95 % confidence level (= 0.05), the average strength obtained usingunbonded caps is not less than 98 % of the average strength of companion cylinders capped or ground in acc
43、ordance with 8.3.8.4.1 When required, qualification tests in accordance with 8.5 shall be made on initial use of an unbonded cap at both thehighest and lowest strength levels anticipated to establish an acceptable range of cylinder strength for use. In practice individualcylinders shall not have str
44、engths more than 10 % greater than the high strength level or more than 10 % less than the low strengthlevel qualified or specified in Table 1. Qualification tests shall be repeated whenever there is a change in the design or dimensionsof the retaining rings, or when there is a change in pad composi
45、tion or thickness, or the Shore A hardness changes by more thanfive units. Initial qualification tests shall include verification that after the specified maximum number of reuses the pads meet therequirements of 8.4.8.4.2 When tests are made to establish a permissible number of reuses exceeding tho
46、se in Table 1, only those tests or reuseswhich are within 2000 psi 14 MPa of the highest strength level to be qualified will be included in the reuse count. Laboratoriesmust maintain records of the number of times pads are reused.NOTE 7Pad life depends on the hardness and type of pad material, the s
47、trength of the concrete, the difference between the outside diameter of thecylinder and the inside diameter of the retaining ring, the unevenness and roughness of the ends of the cylinder, and other factors. Based on availableinformation, scuffing or abrasion of the perimeter of the pad is normal, p
48、rovided it does not reduce the thickness of the pad around the perimeter.8.5 Specimen Preparation for Qualification and Pad Reuse Testing:8.5.1 Pairs of individual cylinders shall be made from a sample of concrete and cured as nearly alike as possible: one cylinderper pair is to be tested after grin
49、ding or capping in accordance with 8.3 and the other is to be tested using the unbonded cap system.8.5.2 A minimum of 10 pairs of cylinders shall be made at both the highest and lowest strength levels desired or anticipated(Note 98). The “strength level” is the average of the strengths of the 20 or more cylinders whose strengths are within a range of1000 psi 7 MPa (Note 109). More than one pair of cylinders can be made from a single concrete sample, but cylinders must comefrom a minimum of
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