Performance enhancement of waste-derived super-sulfated cement using carbonated recycled concrete fines

This study investigates the performance enhancement of super-sulfated cement (SSC) derived from arsenic-containing bio-oxidation waste (BW) through the incorporation of carbonated recycled concrete fines (CRCF).The findings revealed that the addition of 5 wt% CRCF yields optimal per-formance, with compressive strengths reaching approximately 1.83 MPa, 12.59 MPa, and 42.81 MPa at 1, 3, and 28 days, respectively. These values represented significant increases of 408.3%, 10.0%, and 14.3% compared to the reference sample. The improvement was attributed to the synergistic ef-fects of ultrafine CRCF particles acting as fillers and nucleation sites, together with the high reactiv-ity of silica gels, which promoted the formation of additional hydration gels. Microstructural analysis confirmed that CRCF addition refined pore structure, enhanced the stiffness of C–S–H gels. Fur-thermore, CRCF acted as a net CO2 sink (0.268 kg CO2·kg-1), leading to a reduction in the carbon footprint of SSC. These findings demonstrate that CRCF effectively overcomes the early-strength limitation of BW-derived SSC, while reducing emissions. In addition, the feasibility of applying CRCF-modified SSC in cemented paste backfill (CPB) is highlighted, given the high cement-related carbon footprint of conventional CPB. When 5 wt% CRCF-modified SSC was employed in CPB, its 3-day compressive strength attains over 70% of that of OPC, while the 28-day strength was compa-rable. The proposed binder thus provides a sustainable pathway for BW valorization, combining waste utilization, carbon sequestration, and improved engineering performance.