Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

How can it be determined that an admixture will serve its intended purpose?

Q. How can it be determined that an admixture will serve its intended purpose?


A. The best way is to test it with the concrete materials to be used in the work and carefully measure the properties of interest in similar mixtures with and without recommended dosages of the proposed admixture, but at similar slump and air content. Concrete and ambient temperatures should also be representative of job conditions. ASTM C233 and C260 describe such tests and provide specifications for air-entraining admixtures. ASTM C494 and C1017 do the same for chemical admixtures for water reduction, retardation, and acceleration.

When time or other conditions do not permit proper testing, the service record of the admixture with similar materials, especially the cementitious materials, should be thoroughly investigated. If the work has started, job tests have some value, but they rarely have the control and precision of laboratory work. Moreover, laboratory tests made well in advance of construction allow time for strength tests at later ages as well as for tests of other properties of the hardened concrete, such as resistance to freezing and thawing and chloride penetration.


References: SP-1(02); ACI CT-23; E4-12; ACI 212.3R-16; SP-288; ASTM C260; ASTM C494; ASTM C1017

Topics in Concrete: Admixture; Quality Assurance; Testing of Concrete; Specifications

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