An Ecological Cement Mortar Produced by Using Nanosilica and High Content of Metallurgical Waste Slag: Rheological, Mechanical, and Chemical Durability Study

Abstract

This study investigates the possibility of using a high content of ground granulated blast furnace slag (GGBS) with a fixed content of nanosilica (NS) to produce a sustainable cement mortar that can reduce carbon emissions. The synergistic effects of GGBS and NS on the rheological and thixotropic behavior of cement pastes, their chemical durability, and the mechanical properties of mortars were investigated. Cement paste blends and mortars incorporating GGBS were investigated, with and without the addition of NS. The results show that the rheological behavior and the thixotropic characteristics of studied cement pastes were significantly changed in the presence of NS. In phase 1, the GGBS-based cement pastes exhibited shear-thinning behavior, leading to a decrease in viscosity. Gradually, the shear rate increased to the level observed at rest (in phase 2). Using 66% GGBS with 2% NS can produce an ecological mortar with a compressive strength exceeding 55 MPa at 28 days. Moreover, stress-strain curves can show acceptable mechanical behavior of GGBS-based mortar with 66% cement substitution. Incorporating a considerable quantity of GGBS, about 66%, can lead to acceptable results in the two aggressive media (nitric acid [HNO3] and hydrogen chloride [HCl]) looking at their chemical and mechanical resistance.