Microstructural analysis on the variation of resilient modulus of lime modified soil under freezing–thawing action

Subgrade soil is sometimes modified with lime to improve strength. In this study, lime modified soil (LMS) specimens are subjected to freezing–thawing cycles, the mechanical properties and microstructure of the specimens are investigated by resilient modulus test and scanning electron microscope test. The variation in pore microstructure is investigated by image analysis. The results indicate that the number and area of micropores are reduced due to phase change and expansion of water in the soil under freezing–thawing cycles, and the micropores are subsequently coalesced into macropores. The variations in porosity and resilient modulus are correlated. The largest effect to the microstructure and resilient modulus of LMS is observed after the first freezing–thawing cycle. The main reason for the attenuation in resilient modulus of LMS is attributed to the increase in porosity, decrease in bond strength among soil particles and increase in the number of narrow and long cracks in soil.