Study on moisture loss and drying shrinkage behaviour of mortar with mineral admixture based on pore structure

Abstract

The moisture loss and drying shrinkage behavior of mortar with mineral admixture such as blast-furnace slag and fly ash are investigated focusing on the microstructure affected by curing temperature. The curing at high temperature greatly accelerates the hydration reaction of the mortar with mineral admixture to make pore structure denser and leads to smaller moisture loss than that of mortar without mineral admixture. The moisture loss is almost proportional to the accumulated volume of pores whose radii are larger than the radius at the liquid/vapour interface based on the Kelvin equation and BET theory of absorbed water. When the shrinkage is assumed to be induced only by the capillary tension, the estimated shrinkage shows different tendency from experimental one. It suggests that the other shrinkage driving forces that have been believed to be dominant under severe drying conditions should be taken into account even under normal drying condition (RH=60% at 20 degree).