Effects of amorphous nano-silica additions on mechanical and durability performance of SCC mixtures

TLDR: In this article, two different types of nano-silica were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD) but produced in two different processes (filmed powder silica and precipitated silica in colloidal suspension).

Abstract: In the recent years the application of nanotechnology in building materials has increased exponentially. One of the most referred and used nano-materials is amorphous silica with particles size in the nano-range, even though its application and effect in concrete has not been fully understood yet. It has been reported that nano-silica (nS) addition increases the compressive strength and reduces the overall permeability of hardened concrete due to the pozzolanic properties which are resulting in finer hydrated phases (C-S-H gel) and densified microstructure (nano-filler and anti leaching effects). These effects enhance the durability of concrete structures such as bridges, quays or off-shore oil facilities in marine environments. In this study two different types of nano-silica were applied in self-compacting concrete (SCC), both having similar particle size distributions (PSD) but produced in two different processes (filmed powder silica and precipitated silica in colloidal suspension). The influence of nanosilica on SCC was investigated with respect to the properties of concrete in the fresh state (workability) and hardened state (mechanical properties and durability). Additionally, the densification of microstructure of the hardened concrete was verified by SEM and EDS analyses. The obtained results demonstrate that an efficient use of nano-silica in SCC can improve its mechanical propelties and durability. Considering the reactivity of the two nano-silica studied, colloidal type shown more reactivity at early age, which influenced all the final SCC properties.