Sustainable mortars containing fly ash, glass powder and blast-furnace and lead-smelter slag

The aim of this study was to develop sustainable concrete using waste products to reduce both the carbon dioxide emissions associated with concrete production and the extraction of non-renewable natural resources. The development of the new sustainable concrete involved the replacement of cement with industrial by-products (fly ash, glass powder and ground granulated blast-furnace slag (GGBS)) and the replacement of natural river sand (NS) with waste-based sand (lead-smelter slag (LSS)). Twenty-four batches of mortar mixes were produced and tests were performed to determine the flowability, compressive strength and direct tensile strength of each batch. Microstructural analysis was undertaken to explain the experimentally obtained properties of the mortars. The compressive and tensile strengths of waste-based mortars containing LSS were found to be similar to those of mortars containing NS. Mortars with 80% replacement of cement with GGBS and 100% replacement of NS with LSS showed minimal strength reduction (4%) compared with the conventional mortar. The strength reductions of the waste-based mortars compared with the conventional mortar increased at 90% and 100% cement replacement levels, but remained limited to approximately 20% (at 90% GGBS) and 30% (at 100% GGBS). The findings of this study are promising and point to the potential development of new structural-grade mortars using full or near-full replacement of cement with industrial by-products and full replacement of NS with waste-based sand.