Effect of Partial Substitution of Highly Reactive Mineral Additions by Nanosilica in Cement Pastes

The phenomena involved in portland cement hydration and interactions with nanosilica are very complex and not yet fully understood. In addition, few papers have currently proposed to investigate the microstructure and mechanical properties of ternary mixtures using portland cement, colloidal nanosilica, and highly reactive mineral additions. This article investigates, for the first time, the behavior of different highly reactive mineral additions (silica fume and metakaolin) when partially replaced by colloidal nanosilica in the microstructure and hydration of cementitious materials. For the study of the cementitious material microstructures, a Langavant calorimeter, compressive strength, X-ray diffraction, thermogravimetry, infrared spectroscopy, and mercury intrusion porosimetry were used. The pastes with a 1% substitution of highly reactive mineral additions by nanosilica showed higher compressive strength and more refined porosity than the pastes with only silica fume or metakaolin. The results show that nanosilica appears to have better synergism with metakaolin than with silica fume.