Research on Properties of Coal Gangue Coarse Aggregate Cured by CO2

The disadvantage of coal gangue coarse aggregate (CGCA) such as high crushing index, high water absorption and poor interface adhesion with concrete matrix limit its application in civil engineering.Improving the performance of CGCA is the premise of increasing its application rate. CO2 curing is to improve the structure of cement paste by the reaction of CO2 with cement hydration product Ca(OH)2, which can reduce energy consumption and improve the properties of aggregate. In this work, the effects of curing temperature (20°C/ 40°C), CO2 concentration (65%/ 95%) and curing time (2 h/ 4 h/ 6 h) on the apparent density, water absorption, crushing index and firmness of CGCA wrapped by cement-based materials and cement + epoxy resin materials were studied. And the chemical composition and interface transition zone morphology were analyzed. Moreover, the carbon fixation rate of CGCA after CO2 curing was measured. A high strength shell is formed on the surface of the wrapped CGCA by CO2 curing, and the CGCA performance is improved. Increasing the curing temperature, CO2 concentration and curing time, the apparent density can be increased by 0.04%—3.24%, and the water absorption can be reduced by 6.51%—14.29%. The crushing index and firmness index of wrapped CGCA can be improved from grade II to grade I aggregate standard. After CO2 curing, the carbon fixation rate can reach up to 20.07%, which improves the aggregate performance and reduces the CO2 emission. Due to the high content of Ca(OH)2 in the cement wrapped layer, the interface is tightly bonded after CO2 curing, and the microstructure is more compact. Therefore, the improvement effect of cement wrapping is the most significant. As a comparison, the improvement effect of cement + 5% silica fume is weak, and the improvement of cement + 10% fly ash and cement + epoxy resin is the worst. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.