Evolution of freeze–thaw properties of cement–lime solidified contaminated soil

Cement–based stabilization/solidification (S/S) is an effective, yet economic remediation technology to immobilize heavy metals in contaminated soils. In the present study, by using cement quicklime to solidify and stabilize the hexavalent chromium contaminated soil pretreated with FeSO4 ⋅ 7H2O, the unconfined compressive strength, toxic leaching, nuclear magnetic resonance tests were carried out on the solidified soil after different cycles of freezing and thawing, the evolution rule and action mechanism of the engineering characteristics of the solidified soil polluted by hexavalent chromium were explored. According to the test results, the strength of solidified soil will decrease with the increase of the cycle of freezing and thawing times. The strength at 900 mg kg−1 was logarithmically correlated with the times of freezing and thawing, and the strength at 1800 mg kg−1 was linearly correlated with the times of freezing and thawing; After solidification treatment, the toxicity leaching of solidified soil is linearly related to porosity, which can meet the identification standard of hazardous waste. With the increase of cycle of freezing and thawing times, the pore size of 1∼1.8μm and 1.8∼ 70μm is positively correlated with porosity, and the effect of large pore size on porosity is more stable; The strength of solidified soil mainly depends on the small pore size of < 0.014μm and 0.014 ∼0.1μm. The pore size of < 0.014μm and 0.014 ∼0.1μm have a high correlation with the leaching concentration and the small pore size of < 0.014μm and 0.014 ∼0.1μm has the most significant effect on improving the strength of solidified soil and reducing the leaching concentration. Based on this study, it can provide the corresponding reference for the foundation treatment in the seasonally frozen area, which has important theoretical value and practical engineering application significance.