The Effect of Water-Reducing Admixtures and Set-Retarding Admixtures on the Properties of Hardened Concrete

Abstract

Concrete as an engineering material is judged, in the last analysis, by its properties in the hardened state. It is in this state that the effects of imposed load and environment are controlled by the properties of the concrete. It is shown that specific water-reducing admixtures and set retarders permit concrete to be made with properties superior to those attainable in untreated concrete. Such enhancement of properties can usually be achieved simultaneously with economy of materials and labor. In consideration of strength and its parameters, data are given herein to exemplify the fact that certain admixtures, when properly used, are beneficial to the resultant concrete. For example, acceleration of strength development at early ages can be accomplished even under conditions dictating the use of retarders to delay setting time. Not only can this be accomplished without adverse effects, but in some cases economies are possible while maintaining slrength requirements. With respect to weathering and environmental conditions, as affecting durability, it is shown that admixtures permit improvement of resistance to cyclic freezing and thawing and reductions in volume change and permeability.