Effect of curing temperature on solidification/stabilization of zinc-contaminated slurry-like mud

Chemical solidification/stabilization (S/S) enables the efficient utilization of heavy metal-contaminated slurry-like mud (MS) as engineering fill, but the safe and sustainable application depends strongly on curing temperature and binder composition. This study investigates the effects of curing temperature (20–50 °C) on the unconfined compressive strength (UCS), toxic leaching, chemical speciation and pH of solidified/stabilized zinc-contaminated MS (SSZM), considering different initial Zn concentrations (0–4000 mg kg –1 ) and binder compositions (ordinary Portland cement, OPC, or an OPC-GGBS blend, OG). Isothermal calorimetry, XRD, FTIR and SEM-EDS were performed to relate hydration kinetics, phase assemblage and microstructure to Zn inhibition and its mitigation by heat curing. Zn was found to markedly retard early hydration by poisoning Ca(OH) 2 /C-(A)-S-H nucleation and depleting pore alkalinity, resulting in extended induction periods, reduced cumulative heat and suppressed strength at 20 °C. Heat curing effectively mitigates these barriers and kinetically reactivates strength development by accelerating hydration and promoting pozzolanic reactions, despite the consumption of pore alkalinity. However, improved immobilization efficiency suggests a transition from pH-controlled precipitation to encapsulation/incorporation within the C-(A)-S-H gels. OG-SSZM, with a higher alkalinity demand for depolymerization and slower early hydration at 20 °C, is more susceptible to Zn-induced hydration inhibition than OPC-SSZM, but achieves greater recovery in strength and Zn immobilization at elevated temperatures. These findings highlight the crucial role of early heat curing in enhancing the performance of cementitious systems incorporating GGBS for the treatment of Zn-contaminated MS. • Curing temperature effects on SSZM strength and Zn leachability are quantified. • Heat curing increases UCS and reduces Zn leaching, with faster Zn fixation. • Heat curing reactivates hydration kinetics, partially mitigating Zn retardation. • OG-SSZM shows greater strength recovery under heat curing than OPC-SSZM. • Curing temperature effects in large-volume MS treatment should gain more attention.