Synergistic impact of supplementary cementitious materials (silica fume and fly ash) and nylon fiber on properties of recycled brick aggregate concrete

Rising CO₂ emissions from the cement industry and the increasing construction and demolition waste (CDW), including brick chips in developing countries due to rapid urbanization, cause significant environmental concerns. Therefore, sustainable methods are essential for cement production and CDW management. Use of supplementary cementitious materials (SCMs), such as silica fume (SF) and fly ash (FA), helps to reduce CO₂ emissions. Using recycled brick concrete aggregate (RBCA) from CDW promotes sustainable resource conservation Additionally,ductility of concrete can be enhanced by incorporating nylon fiber (NF). This research investigates the use of SF, FA, and nylon fiber (NF) to enhance the properties of RBCA concrete. The effects of cement replacement by SF (10% and 20%), cement replacement by FA (10%, 20%, and 30%) with varying NF content (0.1%, 0.2%, 0.35%, and 0.5% volume fraction) on RBCA concrete was examined. The maximum compressive strength (33.8 MPa) was found with 10% SF and 0.2% NF at 90 days, with an improvement of 10.8% and 24.0% over clay brick chips (CBC) and RBCA concrete, respectively. Tensile and flexural strengths improved by 11.6% and 8.2% over RBCA concrete. However, the maximum tensile and flexural strengths were achieved with 20% SF and 0.5% NF, showing 4.7% and 2.6% improvements over CBC concrete. The recommended doses is 10% SF and 0.2% NF, considering the maximum compressive and considerable tensile and flexural strength. Thus, incorporating SF, FA, and NF into RBCA concrete improves its mechanical performance, making it a sustainable option for concrete production and resource conservation.