Synergistic effects of bagasse ash and silica fume on strength and durability properties of sustainable cement mortars

Abstract The global use of supplementary cementing materials as partial replacements for cement aims to reduce greenhouse gas emissions. This study explores the use of sugarcane bagasse ash an agro-industrial by-product, combined with silica fume, as a sustainable binder system for structural retrofitting applications, particularly in fabric-reinforced cementitious matrix (FRCM) technologies. Cement was partially replaced with 5% to 30% bagasse ash, combined with either 5% or 10% silica fume in the cementitious binders. Initially, all mortar mixes exhibited a reduction in compressive strength, due to delayed pozzolanic activity. The mechanical and durability properties of the blended mortars were assessed through compressive strength, acid resistance, rapid chloride permeability, and capillary absorption tests. Results showed an initial reduction in early-age compressive strength due to delayed pozzolanic activity. However, at 56 and 90 days, strength improved by up to 15%, with the optimal performance observed in the mix containing 10% SBA and 10% SF, surpassing the control mix. Acid exposure tests using 1% sulphuric acid solution revealed strength loss ranging from 25% to 37%, with the control mix exhibiting the highest deterioration. Water absorption decreased with increasing bagasse ash content, indicating improved impermeability and enhanced long-term durability. Chloride penetration resistance also significantly improved due to pozzolanic reactions, which densified the pore structure and reduced permeability. Additionally, statistical analysis was performed to develop predictive models for the mechanical and durability properties of the cementitious binders, highlighting the strong correlation between experimental and predicted results. These findings emphasize the effectiveness of bagasse ash and silica fume as sustainable binders for enhancing both the performance and durability of cement-based binders, offering a viable strategy for reducing the environmental impact of construction practices.