Directly enforced CO2 mineralization towards upgrading reuse of silty muck for low-carbon construction materials manufacture

The poor engineering performance and lack of high-efficiency treatment technologies of silty muck (SM) in the coastal zones of China post a great challenge for its reuses, and the continual and rapid accumulation of muck residues has raised great threats to the environments. In this work, a directly enforced CO₂ mineralization (DECM) to compress-molded SM blocks was developed to fabricate sustainable fired-free construction materials. The sand-to-muck (S/M) ratio and molding pressure were controlled to optimize the manufacture parameters based on the physical and mechanical properties of the directly enforced CO₂ mineralized silty muck (DECM-SM) blocks. The pore structure and minerals of selected DECM-SM samples were characterized by MIP, XCT, XRD, TG and SEM. The e-CO₂ emissions and costs of DECM-SM production were estimated. The results show that DECM can substantially improve the compressive strength of the muck specimens. Under the optimal conditions of S/M ratio of 1:1 and molding pressure of 5 MPa, the DECM-SM production possesses the lowest e-CO₂ emissions of 63 kg e-CO₂/m³ and cost of 76 CNY/m³, much lower than those of commercial blocks. The direct use of DECM-SM blocks for a two-story building construction reduces e-CO₂ emissions by an average of 81 % and material costs by 83 %. Our findings not only deepen the understanding of carbonate binder formation in compacted soils, but also provide a sustainable solution towards upcycling low-quality muck for value-added material manufacture with low e-CO₂ emissions and costs.