Performance of Nano-Modified Cement Pastes and Mortars in Caron's Lake Water

Abstract

Nanomaterials (NMs) are gaining widespread attention to be used in construction sector so as to exhibit enhanced performance in terms of smart functions and sustainable features. The understanding of complex structure of cement based materials at nano-level will definitely result in a new generation of stronger and more durable concrete; with high range of newly introduced properties. This work aims to study the effect of nano-silica (NS) on hydration characteristics, mechanical, microstructure and durability of OPC-slag-NS cement pastes and mortars subjected to Caron's Lake water. The hydration characteristics were followed by estimation of setting times, chemically combined water, free lime, total chloride and sulphate contents, as well as bulk density, compressive and flexural strengths. The hydration process and durability of cement pastes were monitored using SEM and XRD. The results of these investigations indicate that, NS improves the compressive and flexural strengths of cement specimens subjected to Caron's Lake water up to 12 months. The accumulation of additional hydration products within the pore system enhances the densification of cement paste matrix to form closed structure with narrow pores. NS decrease the accessibility of SO 4 2-and Cl-to penetration into the pore system to form ettringite and chloroaluminate hydrate, hence the total sulfate and total chloride contents decrease with NS content. Mortars containing 4 mass, % NS possess higher values of compressive and flexural strengths than those of the other mortars containing NS. Partial inhibition of chloroaluminate formation and the fine closed microstructure of composite cement containing NS caused an increase of compressive and flexural strengths.