Sustainable utilization of clay minerals-rich engineering muck via alkali activation: Optimization of pore structure by thermal treatment

Engineering muck (EM) in South China is a typical construction waste, which has a low utilization rate. After the thermal treatment, this study prepares the EM-based geopolymers and evaluates the CO2 emission. The calcined EM and the geopolymers were characterized through thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and nuclear magnetic resonance (NMR) spectroscopy. The results showed that when the thermal treatment temperature was 850 °C, the dissolution of aluminum (Al) and silicon (Si) was adequate, significantly enhancing the reactivity of geopolymerization and thus forming a geopolymer with dense structures and excellent mechanical properties. Notably, the compressive strength at 7 days for the geopolymer exceeded 50 MPa, and the cumulative pore volume and pore size distribution were both minimal. In addition, an environmental implication analysis revealed that the recycled geopolymers could reduce carbon emissions by approximately 11–65 kg CO2/t when compared to conventional concretes, contributing towards low-carbon goals. The findings of this study propose a more environmentally friendly strategy for the treatment of the EM, contributing to the advancement of sustainable solid waste utilization.