SEDL / STP / STP169A-EB / STP49904S

Chemical Admixtures

Foster, Bruce
Chief, National Bureau of Standards, Washington, D. C.

Pages: 9    Published: Jan 1966

Download this paper for $25 PDF (196K)          View License Agreement
Abstract

Although concrete admixtures are chemicals in a literal sense, by convention in concrete technology, the term “chemical admixture” is restricted to water-soluble substances other than air-entraining agents. Most chemical admixtures react chemically with the cement in concrete. This discussion will be confined to set-controlling and water-reducing admixtures. Chemical admixtures of other types are classified and described in a recent report of the American Concrete Inst. [1]. A water-reducing admixture is defined as one that reduces the quantity of mixing water required to produce concrete of a given consistency; a retarding admixture as one that retards the setting of concrete; an accelerating admixture as one that accelerates the setting and early strength development of concrete; a water-reducing and retarding admixture as one that reduces the quantity of mixing water required to produce concrete of a given consistency and retards the setting of concrete; and a water-reducing and accelerating admixture as one that reduces the quantity of mixing water required to produce concrete of a given consistency and accelerates the setting and early strength development of concrete. These five types of admixtures are referred to in ASTM Specifications for Chemical Admixtures for Concrete (C 494 - 63 T) as Types A, B, C, D, and E, respectively.