On the long term response of concrete with a shrinkage reducing admixture

Shrinkage reducing admixtures (SRAs) have a significant potential in structural concrete mix design due to their ability to reduce the shrinkage deformations in concrete. The research presented here deals with the evaluation of the drying shrinkage behavior of concrete incorporating a glycol-based SRA over a period of one year. The dosage used was 1.5% of the cement weight. A 22% reduction of drying shrinkage is obtained in specimens maintained at 50% r.h. and 20°C after curing them for 28 days. An important secondary effect of the incorporation of the SRA that has also been studied, over a period of one year, is the reduction of the compressive strength, with values that are consistently lower than those of a similar concrete without the SRA, under a range of curing conditions. On the other hand, the influence of the SRA on the splitting-tensile strength and the elastic modulus do not seem to be as significant, especially at later ages. Under dry conditions, the reduction in compressive strength due to the incorporation of SRA is smaller when compared to the behavior under moist curing.