Utilization of coal gangue sand in structural concrete as fine aggregate towards sustainable production

Aiming to utilize coal gangue sand in structural concrete, this paper investigated the mechanical and environmental properties of the coal gangue sand concrete-filled steel tube (GSCFST) and reinforced gangue sand concrete (RGSC) stub columns. Axial compressive tests were conducted to study the effect of gangue sand replacement rate (rGS) on the mechanical performance and environmental impact of the stub columns. The results show that the failure patterns of GSCFST and RGSC are similar regardless of rGS. The reduction in the rigidity and ultimate bearing capacity of GSCFST is less than that of RGSC. When the replacement rate is 100%, the rigidity and ultimate bearing capacity of RGSC are reduced by 29.2% and 11.4% respectively, whilst those of GSCFST are 8.2% and 5.1% respectively. The ductility coefficient of RGSC shows no significant change under different gangue sand replacement rate. In contrast, the ductility of GSCFST is in an increasing trend with the increase of rGS, resulting from the stronger restraining effect of the steel tube on the core concrete of which compressive strength decreases with the increase in the replacement rate. Based on the tested results, a constitutive relationship of gangue sand concrete is used for numerical modelling. A design method of the ultimate bearing capacity for RGSC and GSCFSF is proposed by considering rGS. The predicted values differ from the tested and simulated values in the range of ± 10% and ± 6% for RGSC and GSCFST, respectively. The whole life cycle assessment (LCA) showed that rGS is positively correlated with willingness-to-pay (WTP) and negatively correlated with the axial strength of the two types of stub columns. The material strength and section diameter show the most positive effects on the mechanical-environmental (M-E) performance efficiency factor (kM-E). The kM-E of GSCFST is greater than that of RGSC under the same rGS.