Mechanical properties of concrete with coarse spontaneous combustion gangue aggregate (SCGA): Experimental investigation and prediction methodology

•Effects of SCGA replacement ratio on mechanical properties of concrete.•Effects of particle size distribution of SCGA on mechanical properties of concrete.•Proposed models for predicting the mechanical properties of SCGA concrete. Spontaneous combustion gangue aggregates (SCGAs) have inferior qualities compared with natural aggregates (NAs). The aim of this study is to investigate the effects of the replacement (rSCGA) ratio and particle size distribution of coarse SCGAs on the mechanical properties of concrete, as well as to propose prediction methods for coarse SCGA concrete. Slump values were obtained to evaluate the effect of coarse SCGAs on the workability of fresh concrete; the compressive strength, tensile splitting strength, and elastic modulus on different days were measured to investigate the effect of coarse SCGAs on the mechanical properties of hardened concrete. Scanning electron microscopy analysis was conducted to reveal the mechanical mechanisms of coarse SCGA concrete. The results indicated that coarse SCGAs significantly affected the mechanical properties of concrete, and for an SCGA replacement ratio of 100%, reductions of 19.4%, 36.1%, and 32.2% were obtained in the compressive strength, tensile splitting strength, and elastic modulus, respectively; while the effect of particle size distribution of coarse SCGAs on the concrete properties was limited. The mechanical properties of coarse SCGA concrete at different rSCGA ratios can be reasonably estimated using the weighted density and weighted water absorption of aggregates used in the concrete mixtures.