Enhancing mechanical properties and microstructure of cadmium-contaminated dredged sludge through CPCS stabilization

Industrial emissions and water pollution cause cadmium (Cd) contamination in dredged sludge (DS), posing a significant environmental threat, while conventional stabilizers often fail to efficiently and stably immobilize Cd. This study introduces a novel stabilizer (CPCS) to evaluate its efficacy in immobilizing Cd in contaminated DS. A comprehensive set of tests, including UCS, toxicity leaching, scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM-EDS), and mercury intrusion porosimetry (MIP), was conducted to evaluate the effects of CPCS, calcium sulfoaluminate (CSA), and ordinary Portland cement (OPC) on the mechanical properties and microstructural characteristics of cadmium-contaminated DS. The results indicate that Cd significantly weakens unconfined compressive strength (UCS), but increasing the stabilizer dosage effectively improves the UCS of the solidified body. Compared to commercial CSA and OPC, CPCS exhibits a superior UCS of 2046.62 kPa and enhanced performance, with a lower Cd 2+ leaching concentration of 0.019 mg/L. Pore structure analysis confirmed that CPCS-solidified Cd-contaminated DS developed smaller pores and a denser microstructure. Furthermore, fractal analysis revealed that the CPCS-solidified bodies possessed a higher fractal dimension, indicating increased pore surface roughness and stronger internal bonding. The main findings of this study highlight an effective approach for achieving early strength development and rapid stabilization of Cd-contaminated DS, particularly in practical engineering applications.