Effect of freeze-thaw cycles on mechanical strength of lime-treated fine-grained soils

Lime treatment is a widely-used technique for the stabilization and improvement of fine-grained soils in earthworks for transportation. In cold regions, lime treatment can be considered as an appropriate method to improve freeze-thaw resistance of fine-grained soils. The effectiveness of treatment can depend on soil nature, lime dosage and curing time. In the present work, three soils (silt of low plasticity, clay of low plasticity, and silt of high plasticity) were treated at three lime contents (lower, equal and higher than the lime fixation point) at four curing periods (7, 28, 90 and 365 days). The mechanical strength was determined from unconfined compression test performed on specimens having a diameter of 100 mm and a height of 100 mm. Freeze-thaw cycles were applied by varying the specimen temperature between −20 °C and 20 °C, the specimens being beforehand saturated. The mechanical strength of specimen subjected to ten freeze-thaw cycles was compared to those maintained in laboratory temperature (20 °C). Results showed that freeze-thaw cycles significantly decrease the mechanical strength of sample. This decrease can be explained by damage induced by ice lenses formation/thawing during freeze-thaw cycles, as illustrated by the observation at X-ray computed tomography. Interestingly, lime treatment mitigates this damage and increase the soil freeze-thaw resistance. The treatment appears more efficient for lower plasticity soil, a higher lime content, and a longer curing time. This conclusion seems depend on the specimen preparation procedure.