Concrete Admix

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  • Topic: Concrete, Construction aggregate, Compressive strength
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Designation: C 494/C 494M – 99ae1

Standard Specification for

Chemical Admixtures for Concrete1
This standard is issued under the fixed designation C 494/C 494M; 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 (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense.

e1 NOTE—Range value in 12.2.2 was editorially corrected July 2001.

1. Scope 1.1 This specification covers materials for use as chemical admixtures to be added to hydraulic-cement concrete mixtures in the field for the purpose or purposes indicated for the seven types as follows: 1.1.1 Type A—Water-reducing admixtures, 1.1.2 Type B—Retarding admixtures, 1.1.3 Type C—Accelerating admixtures, 1.1.4 Type D—Water-reducing and retarding admixtures, 1.1.5 Type E—Water-reducing and accelerating admixtures, 1.1.6 Type F—Water-reducing, high range admixtures, and 1.1.7 Type G—Water-reducing, high range, and retarding admixtures. 1.2 This specification stipulates tests of an admixture with suitable concreting materials as described in 11.1-11.3 or with cement, pozzolan, aggregates, and an air-entraining admixture proposed for specific work (11.4). Unless specified otherwise by the purchaser, the tests shall be made using concreting materials as described in 11.1-11.3. NOTE 1—It is recommended that, whenever practicable, tests be made using the cement, pozzolan, aggregates, air-entraining admixture, and the mixture proportions, batching sequence, and other physical conditions proposed for the specific work (11.4) because the specific effects produced by chemical admixtures may vary with the properties and proportions of the other ingredients of the concrete. For instance, Types F and G admixtures may exhibit much higher water reduction in concrete mixtures having higher cement factors than that listed in 12.1.1. Mixtures having a high range water reduction generally display a higher rate of slump loss. When high-range admixtures are used to impart increased workability (6 to 8-in. slump [150 to 200–mm]), the effect may be of limited duration, reverting to the original slump in 30 to 60 min depending on factors normally affecting rate of slump loss. The use of chemical admixtures to produce high-slump (flowing) concrete is covered by Specification C 1017. NOTE 2—The purchaser should ensure that the admixture supplied for use in the work is equivalent in composition to the admixture subjected to test under this specification (see Section 6, Uniformity and Equivalence). NOTE 3—Admixtures that contain relatively large amounts of chloride may accelerate corrosion of prestressing steel. Compliance with the 1 This specification is under the jurisdiction of ASTM Committee C09 on Concrete Aggregates and is the direct responsibility of Subcommittee C9.23 on Chemical Admixtures. Current edition approved Oct. 10, 1999. Published December 1999. Originally published as C 494 – 62. Last previous edition C 494 – 99.

requirements of this specification does not constitute assurance of acceptibility of the admixture for use in prestressed concrete.

1.3 This specification provides for three levels of testing. 1.3.1 Level 1—During the initial approval stage, proof of compliance with the performance requirements defined in Table 1 demonstrates that the admixture meets the requirements of this specification. Uniformity and equivalence tests of Section 6 shall be carried out to provide results against which later comparisons can be made. 1.3.2 Level 2—Limited retesting is described in 5.2, 5.2.1 and 5.2.2. Proof of compliance with the requirements of Table 1 demonstrates continued conformity of the admixture with the requirements of the specification. 1.3.3 Level 3—For acceptance of a lot or for measuring uniformity within...
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