Extending the Season for Concrete Construction and Repair. Phase II - Defining Engineering Parameters

Abstract : The Phase I study, conducted prior to the work reported herein, developed the tools to design, mix, place, and cure concrete in cold weather made with various combinations of commercial admixtures. The admixtures helped to protect concrete and maintain productivity, even when the temperature of concrete falls to 5 C soon after mixing. Phase II addressed the effect of high doses of the chemical admixtures studied in Phase I. The primary finding from Phase I that led to this study was that admixtures, when used in moderate dosages, seemed improve the freeze thaw durability of concrete. Phase II found what appears to be a maximum dosage after which freeze thaw durability becomes a concern. That is because cement hydration can only create a finite amount of space to absorb these chemicals. Thus, for freeze protection, admixture dosages should be designed according to water content as specified in Phase I, while, for freeze thaw durability, admixture dosages should be dictated by cement content. When using both considerations, the freeze-protection limit for enhanced freeze thaw durable concrete can be lower than the 5 C limit set in Phase I.