Exploiting porous clay brick waste-derived recycled sand and recycled powder as crack inducers for developing eco-friendly high-ductility cementitious composites

Due to the porous nature of clay brick waste, achieving efficient resource utilization presents significant challenges. This study employed porous clay brick waste-derived recycled sand and recycled powder as crack inducers to develop eco-friendly high-ductility cementitious composites (HDCC). The findings reveal that recycled powder contained a substantial amount of SiO 2 crystalline phases and some amorphous components, exhibiting good filling effect and moderate pozzolanic activity. Substituting recycled powder for cement and slag inhibited hydration reactions and reduced hydration product formation, particularly at high replacement levels, leading to increased flaws and micro-cracks in the HDCC. The HDCC strength decreased with increasing recycled powder content, yet remained relatively high even at a 70% replacement level. Moderate incorporation of recycled powder enhanced tensile strength and strain while increasing crack numbers, whereas high-volume addition diminished tensile performance of HDCC. Porous recycled sand incorporation provided effective internal curing and improved HDCC strength and ductility; meanwhile, incorporating recycled sand introduced numerous uniformly distributed micro-pores, promoting uniform crack initiation and propagation within the HDCC. Even at 100% replacement of silica sand, recycled sand-incorporated HDCC exhibited better tensile performance compared to the reference HDCC. Combining recycled sand with recycled powder could produce fully recycled HDCC that met diverse strength and ductility requirements. The tensile strengths of HDCC-Reference, 100SS-C30S30, and 100SS-C70S70 were 11.62 MPa, 12.18 MPa and 8.49 MPa, with corresponding tensile strains of 5.67%, 6.07% and 6.53%.