A Low-Carbon, Recycled Powder-Based Binder: Engineering Properties, Carbon Sequestration Potential, and Recycling

To improve the high-value utilization of recycled concrete powder (RCP) and its carbon sequestration potential, this study developed a low-carbon recycled powder-based binder (LCRPB) incorporating RCP, silica fume (SF), granulated blast-furnace slag (GBFS), and fly ash (FA). A five-factor, five-level orthogonal design was used to evaluate workability, mechanical properties, hydration behavior, wet carbonation performance, and post-carbonation reusability. The water-to-binder ratio showed the greatest relative influence on flowability and compressive strength, whereas RCP content had a greater influence on 28-day flexural strength and wet carbonation behavior. At favorable dosage levels, 2% SF, 7.5% GBFS, and 10% FA increased the 28-day compressive strength by 17.43%, 12.43%, and 11.83%, respectively. Wet carbonation showed the highest efficiency at a liquid-to-solid ratio of 5 and a CO₂ flow rate of 3 L/min, with CaCO₃ identified as the main carbonation product. The carbonated powder retained reuse potential. Matrix analysis identified a balanced formulation of W/B = 0.40, 0% SF, 7.5% GBFS, 10% FA, and 10% RCP. The selected formulation reduced the material-related carbon footprint by 26.6% relative to the 100% OPC reference.