1、Designation:C494/C494M17Standard Specification forChemical Admixtures for Concrete1This standard is issued under the fixed designation C494/C494M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in p
2、arentheses 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 U.S.Department of Defense.1.Scope*1.1 This specification covers materials for use as chemicaladmixtur
3、es to be added to hydraulic-cement concrete mixturesin the field for the purpose or purposes indicated for the eighttypes as follows:1.1.1 Type AWater-reducing admixtures,1.1.2 Type BRetarding admixtures,1.1.3 Type CAccelerating admixtures,1.1.4 Type DWater-reducing and retarding admixtures,1.1.5 Ty
4、pe EWater-reducing and accelerating admixtures,1.1.6 Type FWater-reducing,high range admixtures,1.1.7 Type GWater-reducing,high range,and retardingadmixtures,and1.1.8 Type SSpecific performance admixtures.1.2 This specification stipulates tests of an admixture withsuitable concreting materials as de
5、scribed in 11.1 11.3 or withcement,pozzolan,aggregates,and an air-entraining admixtureproposed for specific work(11.4).Unless specified otherwiseby the purchaser,the tests shall be made using concretingmaterials as described in 11.1 11.3.NOTE1It is recommended that,whenever practicable,tests be made
6、using the cement,pozzolan,aggregates,air-entraining admixture,and themixture proportions,batching sequence,and other physical conditionsproposed for the specific work(11.4)because the specific effects producedby chemical admixtures may vary with the properties and proportions ofthe other ingredients
7、 of the concrete.For instance,Types F and Gadmixtures may exhibit much higher water reduction in concrete mixtureshaving higher cement factors than that listed in 12.1.1.Mixtures having a high range water reduction generally display ahigher rate of slump loss.When high-range admixtures are used to i
8、mpartincreased workability(6 to 8-in.slump 150 to 200mm),the effect maybe of limited duration,reverting to the original slump in 30 to 60 mindepending on factors normally affecting rate of slump loss.The use ofchemical admixtures to produce high-slump(flowing)concrete is coveredby Specification C101
9、7/C1017M.NOTE2The purchaser should ensure that the admixture supplied foruse in the work is equivalent in composition to the admixture subjected totest under this specification(see Section 6,Uniformity and Equivalence).NOTE3Admixtures that contain relatively large amounts of chloridemay accelerate c
10、orrosion of prestressing steel.Compliance with therequirements of this specification does not constitute assurance of accept-ability of the admixture for use in prestressed concrete.1.3 This specification provides for three levels of testing.1.3.1 Level 1During the initial approval stage,proof ofcom
11、pliance with the performance requirements defined inTable 1 demonstrates that the admixture meets the require-ments of this specification.Admixtures(except for Types B,C,E,and S)shall qualify for provisional compliance when thephysical requirements and any of the alternative compressivestrength requ
12、irements in Table 1 are met.If subsequent testresults at six months or one year fail to meet the standardrequirement of 100%of reference strength,the compliance ofthe admixture to this standard is withdrawn and all users of theadmixture shall be notified immediately.Uniformity andequivalence tests o
13、f Section 6 shall be carried out to provideresults against which later comparisons can be made(see Note4).NOTE4Allowing for provisional compliance while retaining longerterm compressive strength requirements promotes more rapid qualificationof new materials,but also provides assurance that new admix
14、turetechnologies will not exhibit unexpected longer term performance.Thealternative compressive strength requirements in Table 1 are based onstatistical analysis of 103 Specification C494/C494M evaluation tests.Thealternative requirements correspond to a 99%probability of passingsubsequent test age
15、requirements.21.3.2 Level 2Limited retesting is described in 5.2 5.2.2.Proof of compliance with the requirements of Table 1 demon-strates continued conformity of the admixture with the require-ments of the specification.1.3.3 Level 3For acceptance of a lot or for measuringuniformity within or betwee
16、n lots,when specified by thepurchaser,the uniformity and equivalence tests of Section 6shall be used.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1This specification is under the jurisdiction of ASTM Committee C09 onConcrete and Concret
