Influence of Shrinkage-Reducing Admixtures on Moisture Absorption in Cementitious Materials at Early Ages

The water-absorption behavior of cement pastes (w/c=0.30) containing varying concentrations (i.e., 0, 0.2, and 5%) of a shrinkage-reducing admixture (SRA) was measured. Moisture ingress was monitored using X-ray absorption. A decrease in both the depth of water penetration and the rate of water absorption was observed with increasing specimen maturity and admixture concentration. This agrees with theoretical considerations that suggest water sorption is a function of the surface tension and the viscosity of the fluid ingressing into the pores. The Boltzmann-Matano method was successfully employed to determine the moisture content dependent moisture diffusivity of the material, which exhibited a dependence on both the pore structure (specimen maturity) and the SRA concentration.