Mechanical and environmental properties of limestone calcined coal gangue based cementitious materials

Abstract

The cement industry is one of the major sources of global carbon dioxide (CO₂) emissions, and sustainable solutions are urgently needed to reduce its environmental impact. This study focuses on the synergistic effects of thermally activated coal gangue powder (ACGP) and limestone powder (LSP) in enhancing the mechanical properties and microstructure of composite cementitious materials. Experimental techniques such as thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), hydration heat tests and scanning electron microscopy (SEM) were used to systematically study the thermal activation mechanism of ACGP and its effects on cementitious properties. The results show that ACGP achieves optimal pozzolanic activity when calcined at 700 °C for 1 h. Using a mix proportion of 70 % cement, 20 % ACGP and 10 % LSP, the limestone calcined coal gangue based cementitious materials achieved a 28-day compressive strength of 44.14 MPa, which is 19.8 % higher than the group without LSP and comparable to ordinary Portland cement (OPC). Compared to OPC, this mixture reduces CO₂ emissions by 18.5 % and production costs by 13 %, while also outperforming limestone calcined clay cement (LC3). These findings demonstrate that the limestone calcined coal gangue based cementitious materials is an environmentally friendly and cost-effective alternative to traditional cement, providing essential technical support for sustainable construction practices.