Effect of raw coal gangue coarse aggregates on mechanical properties and compressive stress–strain response of concrete.

Raw coal gangue (RCG) as one of the solid wastes can result in serious ecological and environmental pollution. Utilization of RCG as coarse aggregates in concrete can mitigate the demand for natural aggregates in engineering construction to a certain extent. This study aims to assess the impact of utilizing raw coal gangue aggregates (RCGAs) on the mechanical behaviors and compressive stress–strain responses of concrete. For this purpose, a total of 90 concrete specimens were prepared, varying in RCGA replacement ratios of 0, 30%, 50%, 70%, and 100% and water‐to‐cement (w/c) ratios of 0.37 and 0.47. The slump, compressive and splitting tensile strengths in cubes, and complete compressive stress–strain curves of RCGA concrete were obtained and discussed. Results indicated that as RCGA was incorporated, the peak stress and elastic modulus of concretes with 0.37 and 0.47 w/c ratios decreased by 26%–51% and 23%–57%, respectively. In addition, the crack development and microstructural characteristics of RCGA concrete were analyzed by digital image correlation and scanning electron microscopy (SEM), respectively. The SEM analysis indicated that the interface transition zone between RCGAs and mortar was relatively thick and loose compared to that between coarse natural aggregates and mortar, indicating the poor mechanical properties of RCGA concrete. Finally, based on the test data, a normalized stress–strain model for RCGA concrete was proposed, taking into account the influence of RCGA replacement. [ABSTRACT FROM AUTHOR]