Mechanical properties, durability, and carbon emissions of concrete with coal gangue coarse aggregate, fine aggregate and mineral admixtures in coal mining environment
Qiang Song, Yuxin Yang, Shipeng Xu, Changsha Liu, Jie Liu, Jiuwen Bao, Shanbin Xue
Abstract
Coal gangue (CG) represents one of the largest categories of industrial solid waste, and the direct application of CG from mining sites as a construction material presents substantial environmental and economic benefits. However, traditional coal gangue applications remain limited. To optimize its usage while ensuring requisite performance, this study explores the synergistic effects of untreated coal gangue coarse aggregate (CGCA), fine aggregate (CGFA), and mineral admixture (CGMA) on the mechanical properties, durability, and carbon emissions of concrete, focusing on conditions typical of coal mining regions. The results indicate that, at replacement rates of 25% for CGCA, 20% for CGFA, and 2.5% for CGMA, concrete designed to achieve C30 grade attains a compressive strength of 30.8 MPa. The inclusion of CG improves concrete’s sulfate resistance within the initial 90 days, it proves less effective against freeze-thaw cycles and chloride ion penetration. A balanced mixture of CGCA, CGFA and CGMA increases the formation of hydration products and reduces porosity. Under strength-compliant conditions, untreated CG lowers raw material carbon emissions by approximately 8% relative to ordinary Portland cement. This study contributes valuable insights into the environmentally sustainable, large-scale application of CG in construction and mine backfill in managing mining areas.