Durability against cyclic wetting-drying of cement-stabilized loess subgrade for railway in tropical semi-arid regions

This research investigates the effect of soaking times, number of wetting-drying (W-D) cycles, saturation levels, sample dimensions, and cement contents on the durability performance of cement-stabilized loess for railway subgrade. To imitate the extreme environment in tropical semi-arid regions, the samples were soaked in water and dried in an oven to create the cyclic W-D state. Microstructure tests were used to confirm the cement hydration reaction in the cemented loess sample after the cyclic W-D. The soaking time was observed as the key factor controlling the depth of water infiltration and degree of saturation of W-D samples. At the same soaking time, the small sample reached a higher saturation level than the large sample. Increasing the amount of cement enhanced stability by strengthening cementation bonds and improving water retention capacity. The increase in cement content not only enhanced the strength but also improved the water resistance and reduced the weight loss of soil samples. The unconfined compressive strength (UCS) in high cement content samples increased notably during 6–12 cycles of W-D due to the cement hydration, as proved by the microstructure tested results. The correlation of the UCS after cyclic W-D of the sample with a diameter of 50 mm and that of 101.6 mm was proposed. The durability index was suggested to facilitate the design of cement-stabilized loess mixes effectively while extending the service life. The results could provide valuable guidance for sustainably designing cement-stabilized loess as a subgrade for railway and other geotechnical structures in tropical semi-arid regions.