A sustainable low-carbon pervious concrete using modified coal gangue aggregates based on ITZ enhancement

An eco-friendly low-carbon coal gangue pervious concrete (CGPC) was prepared with coal gangue aggregates (CGAs) and solid waste-based sulfoaluminate cement (WSAC) as binders, which provided an effective approach for the high-value massive utilization of coal gangue and a sustainable solution of pervious concrete. In this study, an innovative slurry wrapping process based on WSAC was employed for the modification of raw CGAs (RCGA) and self-ignited CGAs (SCGA). The basic performance, frost resistance, environmental impact and economic analysis of CGPC were investigated and the mechanism by which SCGA-based CGPCs obtains high performance is expounded from the perspective of interface structure and bonding strength between aggregates and matrix. The results showed that the compressive strength and density of CGPC decreased with the increase of replacement level, while the water permeability and connected porosity improved to a certain extent, and SCGA-based CGPCs had more remarkable compressive strength and freeze-thaw cycle resistance than that of RCGA-based at the same replacement level. Moreover, the compressive strength and freezing resistance of CGPC prepared via slurry wrapping process modified CGAs were significantly enhanced. The higher binding strength of SCGA-matrix is mainly attributed to the dense “shell layer” structure with low water-binder ratio and the enhanced compact structure formed by the self-extension growth of ettringite (AFt) in micropores distributed on the SCGA surface. The leaching concentration of heavy metals is far below the specification limit. The production cost and CO2 emissions are 50.6% and 57% lower than those of traditional pervious concrete, which fully certified the environmental friendliness and practicability of CGPC. This research is of great significance in saving resources, reducing costs, and alleviating the environmental burden of coal gangue.