Influential Mechanisms and Potential Applications of Nano-Silicas in Cement Composites

Nanosilicas have been known as super-pozzolanic materials and compared to silica fume, these materials have higher purity of silica and finer particles. However, in contrast to silica fume, nanosilicas are produced by various methods, leading to different morphologies and agglomeration statuses in their initial form. On the other hand, due to several mechanisms such as the bridging effect of calcium ions between particles, double layer compression at a high ionic concentration, and dehydration of silica surfaces, nanosilica particles are destabilized in the pore solution environment of cement mixtures. Thus, the behavior of these materials is different from that of silica fume. In this research, considering the recent studies, a comprehensive investigation has been carried out on the influence of nanosilicas on the mechanical, durability and microstructural characteristics of cement composites. This study investigates the mechanisms that influence the performance of nanosilica in cement-based materials. Based on these mechanisms, several applications have been suggested and discussed. Some of these applications include viscosity-modifying agent in self-compacting concrete, enhancing the cohesion of cement composites, increasing the adhesion capacity of repair mortars and shotcrete to the substrate surface, accelerating the cement hydration, developing low-alkali cements and fast early-strength cements.