Improved Understanding of Concrete Compressive Strength Utilizing Cement Paste Testing

Abstract

Abstract This article provides information for use of cement paste (mixture of water, cementitious materials, and possibly admixtures but no coarse or fine aggregates) in compressive strength testing to improve understanding of concrete. Cement paste testing has potential value because test cylinders can be produced much more easily than concrete. Results from almost 5,000 data points showed that cement paste strength trends were linear with respect to water to cementitious ratio, especially at earlier test days. Cement paste variability was greater than concrete variability in some cases. Cement paste strengths at later ages were disproportionately stronger than concrete and became less useful. Cement paste helped diagnose behaviors seen in concrete. Portland-limestone cement paste strength was always greater than ordinary portland cement paste within a group of several cements. In some cases, cement paste results showed that concrete with portland-limestone cement performed better than ordinary portland cement because of a better paste system. In other cases, cement paste results were able to provide strong evidence that concrete with portland-limestone cement performed better because of paste-aggregate bond improvements relative to ordinary portland cement mixtures. In a third set of cases, cement paste results showed that portland-limestone cement improved paste strength, but this improvement did not translate to concrete strength.