Enhancement effects of CO2 curing on biochar modified construction solid waste: Mechanical properties, microstructure, and carbon sequestration evaluation

The proper disposal of construction solid waste has long been a subject of widespread concern. In this study, rice husk biochar was incorporated into construction solid waste to form a composite system, which was subsequently subjected to carbonation curing under different CO 2 concentrations. The mechanical properties of specimen were evaluated through unconfined compressive strength (UCS) and triaxial compression tests, while its microstructural characteristics, phase composition, pore structure, and carbon sequestration capacity were investigated using SEM, XRD, EDS, FTIR, MIP, and TGA analyses. The results reveal that: (1) CO 2 curing significantly enhances the UCS, E 50 , and peak deviatoric stress of specimen, with the most pronounced improvement observed at a CO 2 concentration of 40 %. (2) The carbonation reaction generates CaCO 3 , which effectively fills the mesopores and macropores of specimen, increases the proportion of gel pores. (3) CO 2 curing remarkably improves the relative carbon sequestration of specimen, reaching a maximum value of 3.4 % at 60 % CO 2 concentration.