Relationship between water absorption and porosity in concrete with limestone powder addition

摘要

Abstract In this work, the effect of limestone powder addition on the capillary water absorption of concrete was studied using the sorptivity coefficient to characterize the water absorption rate. MIP and SEM analyses were used to investigate the underlying microscopic mechanisms that affect the water absorption performance. The results indicate that adding less than 10?wt% limestone powder decreases the initial and second sorptivity coefficients due to densification of microstructure, which is confirmed by SEM images. An increased fineness of limestone powder also contributes to a decreased sorptivity coefficient. MIP analysis demonstrates that adding appropriate limestone powder reduces the total porosity and refines the pore structure. Variation of the second sorptivity coefficient with porosity suggests that a critical porosity for depercolation occurs at 0.09, below which the sorptivity coefficient decreases sharply due to the depercolation of the pore network. Based on the percolation theory, three water transport regimes, that is, subcritical, critical, and supercritical regimes, are identified with increasing porosity. The sorptivity coefficient in each regime is predicted based on the pore structure characteristics coupled with the percolation theory.