New insights into water dynamics of Portland cement paste with nano-additives using quasielastic neutron scattering.

Early-age hydration kinetics of Portland cement with nano-additives such as nano-silica (NS) was examined using quasielastic neutron scattering (QENS). Cement pastes with different ratios of Portland cement to NS were prepared. The concentration of the NS played a major role in controlling the free and bound water during the hydration of the cement paste. Additionally, the effects of metakaolin (MK) with NS in Portland cements revealed that MK acts as a retarder by decreasing the bounding water capacity during the early age of hydration. An increase in the concentration of NS affected the degree of hydration by reducing the amount of free and mobile water in the gel pores when compared to Portland cement paste. Here, we show that the concentration of NS governs the early-age hydration process in Portland cements. [ABSTRACT FROM AUTHOR]