Utilization of Nano-Silica to improve properties of BOF Slag- Cement

摘要

Basic oxygen furnace (BOF) slag is a by-product of the pig iron refining. This paper presents an experimental study on the utilization of nano-silica to improve the setting properties and mechanical strength of pastes and mortars, made from ordinary Portland cement (OPC) by addition of BOF slag. For this reason, some mixtures including different amounts of BOF slag with/without nano-silica were prepared. Initial and final setting times of fresh pastes and compressive and flexural strengths of 3, 7, 28 and 90 days of age hardened mortars were measured. The results have indicated that addition of nano-silica reduces setting time of the pastes and increases mechanical strength of mortars containing large amounts of BOF slag. Microstructural and mineralogical evaluations of hydrated products revealed nano-silica reacts with Ca (OH)2 through a pozzolanic reaction and then, the amount of C–S–H increases. So, this leads to a higher densification of the matrix, which improves the strength and durability of cementitious mixtures containing BOF slag.