Effect of freeze-thaw cycling on the mechanical properties of lime-stabilized expansive clays

In cold regions, earth structures such as embankments and roads are exposed to periodic freeze-thaw (F-T). This study was conducted to investigate the impact of F-T cycles on the mechanical properties of two types of plastic soils, stabilized with lime. Two types of clayey soils (high plasticity-bentonite and low plasticity-kaolinite), both untreated and lime-treated (with a curing time of up to 300 days), were tested. Durability was assessed as the influence of F-T cycles on the unconfined compressive strength (UCS), direct shear strength, porosity and volume changes of these soils. The results indicate that the volume of the treated soils increased during the first F-T cycles, after which this increase became less pronounced. The UCS increased significantly when the curing time was extended from 3 to 28 and then to 300 days. After subjecting the materials to F-T action, the damage (crack formation) caused by the formation of ice lenses in the pores of lime-stabilized soil samples was found to have a more significant effect in bentonite soil than in kaolinite soil. Both direct shear strength parameters presented some alterations with the increased number of F-T cycles (the friction angle increased slightly and the cohesion decreased). The F-T effects on the direct shear strength were mainly reflected in cohesion, thus affecting the durability of the stabilized soil.