Multiscale Degradation Behavior and Moisture State-Dependent Mechanisms of Solidified Slurry Under Engineering Service Conditions

Industrial solid waste-based composite binders offer an effective approach to soft soil stabilization and beneficial reuse of industrial solid wastes, but their long-term degradation mechanisms in complex in-service environments remain unclear. This study investigated the degradation behavior of slurry solidified with industrial solid waste-based binders under a simulated in-service environment, combining macroscale mechanical tests, carbonation degree characterization, TG-DTG, XRD, SEM, and molecular dynamics simulation to elucidate multiscale degradation mechanisms. The simulated condition significantly accelerated mechanical property deterioration and carbonation progression. Microstructural analyses revealed low calcium hydroxide (CH) content with only slight changes over time, whereas CaCO3 content increased, chemically bound water decreased, and the local Ca/Si ratio declined. These findings indicate that, beyond decomposition of hydration products such as AFt (ettringite), decalcification of calcium silicate hydrate (C-S-H) gel may be an important carbonation-related degradation pathway. Molecular dynamics simulations showed higher CO2 mobility in dry C-S-H pores, while wet pores strengthened short-range associations between CO2 molecules and Ca sites. These simulation results suggest a hypothetical moisture state-dependent transport-association mechanism: dry conditions may facilitate CO2 transport, whereas wet pores may provide more favorable local interfacial conditions for subsequent carbonation-related processes. This study provides a multiscale understanding of the deterioration of industrial solid waste-based solidified slurry under in-service conditions.