Influence of mineral admixture on the hardening process of mortar with a focus on strength and permeability

The compressive strength and the electrical resistivity of mortar specimens using mineral admixture (fly ash and ground granulated blast-furnace slag) were measured to evaluate the influence of mineral admixture on the mortar hardening process. Comparing the changes in compressive strength and electrical resistivity of mortar using the mineral admixture was compared, compressive strength tended to start increasing from a relatively early stage, while electrical resistivity tended to increase after a slight delay. The formation factor variation shows that the increase in electrical resistivity is due to changes in the pore structure, such as tortuosity, rather than changes in the pore solution concentration. Then, the apparent diffusion coefficient of chloride ion was estimated from electrical resistivity. The diffusion coefficient of mortar using blast-furnace slag tended to fall below that of ordinary Portland cement at 7days, and then gradually improved. Until l4days, the diffusion coefficient of mortar using fly ash exceeds that of ordinary Portland cement mortar, but declines below the latter after 9ldays. This study shows that the periods of the surge in permeability and compressive strength differ, and that these features vary depending on the type of mineral admixture used.