1、Designation: C1231/C1231M 10a C1231/C1231M 12Standard 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 origin
2、al 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 unb
3、onded 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 strengthlev
4、el. 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 be
5、low 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 t
6、hetwo 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 applica
7、bility 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 St
8、andards: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 Specim
9、ensD2000 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 usi
10、ng 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 of ASTM Committee C09 on Concrete and Concrete Aggregatesand is the direct
11、responsibility of Subcommittee C09.61 on Testingfor Strength.Current edition approved Oct. 1, 2010Nov. 15, 2012. Published November 2010December 2012. Originally approved in 1993. Last previous edition approved in 2010 asC1231/C1231M10.10a. DOI: 10.1520/C1231_C1231M-10a.10.1520/C1231_C1231M-12.2 Sec
12、tion on Safety Precautions, Manual of Aggregate and Concrete Testing, Annual Book of ASTM Standards, Vol. 04.02.3 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to th
13、e standards 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 ac
14、curately, 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 Harb
15、or 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
16、the 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. Thi
17、s may 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 insidediamet
18、er 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 Shore A durometer hardness is 6 5. Table 1 provides requiremen
19、ts for 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
20、manufacturers 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 ofuse
21、s to 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(See (Note 1 and Fig. 1). Each retainer (upper and lower) includes a (retaining) ring that is welded to or manufactured integrallywith a
22、 base plate. The height of the retaining ring shall be 25 6 3 mm 1.0 6 0.1 in. The inside diameter of the retaining ringshall not be less than 102 % or greater than 107 % of the diameter of the cylinder. The thickness of the retaining ring shall be atleast 12 mm 0.47 in. for 150 mm 6 in. diameter re
23、tainers and at least 9 mm 0.35 in. for 100 mm 4 in. diameter retainers.The surface of the base plate that contacts the bearing block of the testing machine shall be plane to within 0.05 mm 0.002 in.The thickness of the base plate shall be at least 12 mm 0.47 in. for 150 mm 6 in. retainers and at lea
24、st 8 mm 0.3 in. for 100mm 4 in. retainers. The bearing surfaces of the retainers shall not have gouges, grooves, protrusions, or indentations greater than0.25 mm 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 a
25、cceptable.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 (approximately(Note 2 equival
26、ent to ). 18 in. in 12 in. 3 mm in 300 mm). No individual diameter of a cylinder may differfrom any other diameter by more than 2 %.TABLE 1 Requirements for Use of Polychloroprene(Neoprene)PadsCompressive Strength,A psiMPaShore ADurometerHardnessQualificationTests RequiredMaximumReusesBLess than 150
27、0 10 Not permitted1 500 to 6 000 10 to 40 50 None 1001500 to 6000 10 to 40 50 None 1002 500 to 7 000 17 to 50 60 None 1002500 to 7000 17 to 50 60 None 1004 000 to 7 000 28 to 50 70 None 1004000 to 7000 28 to 50 70 None 1007 000 to 12 000 50 to 80 70 Required 507000 to 12,000 50 to 80 70 Required 50G
28、reater than 12,000 80 Not permittedACompressive strength of concrete at age of testing 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 122NOTE 2One metho
29、d 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 the end of the cylinder on a plane surface and supportthe try square on that
30、 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.6.2 Depressions under a straight edge measured with a round wire gage across any diameter shall not exceed 0.20 in. 5 mm.If cylinder ends do not meet this tolerance, the cylinder sh
31、all 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,provided the caps meet the requirements of Section 5. Pad hardness shall be in accordanc
32、e with Table 1. (See (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 addition to the test requirements for verification of specified compressive strength.
33、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 bottomsurface that exceed 38 in. 10 mm in length regardless of depth. Insert pad
34、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 or caps on the cylinder and place the cylinder on the lower bearing block of th
35、e 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 brought to bear on the upper retaining ring, rotate itsmovable portion gently b
36、y 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 is vertical within a tolerance ofdoes not depart from verticalby more than 0.5 18(Note 5 in. in 12 in. 3.2 mm in 300 mm ) an
37、d that the ends of the cylinder are centered within the retainingrings. If the cylinder alignment does not meet these requirements, release the load, check compliance with 6.1, and carefullyrecenter the specimen. Reapply load and recheck specimen centering and alignment. A pause in load application
38、to check cylinderalignment 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.7.4 Complete the load application, testing, calculation, and reporting of results in accordance with Test Method C39/C39M (see(Notes 56 and 67).FIG. 1 Example of Retain
39、ing Ring and Base PlateC1231/C1231M 123NOTE 6Some users have reported damage to testing machines from the sudden release of energy stored in the elastomeric pads.NOTE 7Occasionally, unbonded capped cylinders may develop early cracking, but continue to carry increasing load. For this reason Test Meth
40、odC39/C39M requires cylinders to be loaded until it is certain that they have been compressed beyond their ultimate capacity.8. Qualification of Unbonded Capping Systems and Verification of Reuse of Pads8.1 Table 1 specifies the conditions under which polychloroprene (neoprene) unbonded pads must be
41、 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 unbonded
42、 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 or capped
43、 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 accordance
44、 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 strengths
45、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 composition or
46、 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 those in T
47、able 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 8Pad life depends on the hardness and type of pad material, the strength
48、 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, provided
49、 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 grinding 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 stren
