Synergistic utilization of recycle cement powder and glass powder to prepare low-carbon and environmentally friendly mortar: Mechanical properties, microstructure, and environmental assessment

The discarded cement pastes and glass generated as by-products during the process of building demolition. The open accumulation of waste cement pastes and glass causes resource wastage and environmental pollution, which urgently needs resource utilization. In this study, composite supplementary cementitious materials (RCG), which are formulated by mixing recycled cement paste and glass powder, are utilized to partially substitute conventional cement in the preparation of environmentally friendly mortar. The influence of RCG content on the compressive strength, microstructure and nanomechanical properties of mortar is systematically studied. Additionally, the corresponding ecological benefit was assessed. The results indicate that incorporating an optimal proportion of RCG (10 %–20 %) enhances the mechanical properties of the mortar. Compared with the control specimen, the compressive strength of RCG20 specimen increased by 5.79 % at 28 days. However, the strength of specimens decreased with further increase of RCG content. The addition of 20 %RCG can effectively improve the compactness of mortar specimens, optimize the pore structure, and increase the C-S-H content, especially for high-density C-S-H. Compared with conventional mortar, RCG-containing mortar has lower CO₂ emission and cost. This study highlights the potential for resource recovery from construction waste, contributing to the sustainable development of cement-based materials.