Abstract: In order to reduce cement usage by effectively utilizing the cementitious activity of industrial solid waste, we added three types of industrial waste in combination (red mud, calcium carbide slag, and phosphogypsum) to partially replace cement as curing agent to prepare solidified soil specimens. We designed two proportions (10% and 20%) of total curing admixture, in which the industrial waste combination substituted different amounts (35%, 45%, and 55%) of cement; and in the meantime, we set pure cement-solidified soil as control group. Through tests, we investigated variations in the strength, electrical resistivity, impermeability, and pH value of leachate of the solidified soil specimens with varied mix ratio. Furthermore, we employed the SEM, FTIR, and XRD spectra to unveil the microscopic mechanism of solidifying soil specimens with industrial waste in combination with cement. Findings indicate an optimal substitution rate of industrial waste for cement. When the total curing agent content is 10% or 20% and the industrial waste percentage is below 45%, mechanical properties surpass those of pure cement-solidified soil. However, when industrial waste percentage reaches 55%, mechanical strength falls below that of pure cement solidified soil. Moreover, higher total curing agent content and aging duration lead to increased strength. The non-destructive resistivity testing method accurately predicts strength. The pH value of leachate decreases over time and remains lower than that of pure cement-solidified soil, consistently remaining below the corrosivity threshold at different dosing levels and aging stages. Solidified soil specimens with both industrial waste and cement demonstrates enhanced impermeability compared to the pure cement-solidified ones. Microscopic analyses reveal the formation of hydration products including calcium aluminate, hydrated calcium silicate, and calcium carbonate in the solidified soil. Incorporating ternary industrial waste generates more cementitious materials, resulting in a denser structure.

Key words: ternary industrial waste, cement-solidified soil, microscopic mechanism, curing agent, strength, electrical resistivity, impermeability, pH value of leachate