Co-utilization of coal-based solid waste and crop straw for porous aggregate: Preparation, performance, and mechanism

The accumulation of coal gangue (CG), fly ash (FA) and the burning of corn straw (CS) cause severe environmental issues. The study was carried out to prepare CG-FA-CS porous aggregate (CFCA) by sintering. The physical properties of CFCA were tested, XRD, FTIR, SEM, TEM, and MIP were used to characterize the microstructure and pore structure of CFCA. Furthermore, the skeleton and pore structure formation mechanisms of CFCA were revealed. Results showed that the maximum cylinder compressive strength of CFCA is 5.89 MPa, and the minimum thermal conductivity of CFCA is 0.086 W/(m & sdot;K). The main crystal phase of CFCA is anorthite (CaAl2Si2O8), and the secondary crystal phase is mullite (Al6Si2O13). Moreover, crystal phase accumulates to form the skeleton structure, providing the strength of aggregate. The pore volume of medium pores (103-104 nm) of CFCA accounted for the largest percentage, which accounted for 66.65 %-92.29 % of the total pore volume. The CFCA prepared in this study exhibits a multi-type pore structure. The study provides a feasible way for the comprehensive utilization of solid waste, which can also reduce the environmental problems caused by exploitation of natural resources.