مشخصات پژوهش

This paper aims to find a proper admixture of the cemented sand-gravel (CSG) material for constructing a hardfill embankment located in cold weather. To this end, the compaction, strength, permeability of the cemented sand-gravel mixtures with cement contents of 5, 7.5, 10, and 12.5% are experimentally studied. Besides, the freeze–thaw durability of native grains of the soil and stabilizing soil is examined. According to the test results, even though the compaction specifications of all mixtures do not considerably depend on the cement content, however the cement content in the mixture significantly influences the compressive strength, stiffness, and permeability of mixtures. The soil aggregates inherently have high water absorption and are thus severely fractured after 50 cycles of freeze–thaw. After stabilizing the soil grains with cement, the freeze–thaw durability of the cemented soil mixture is considerably improved, and the weight loss of all mixtures becomes less than 5% after 12 cycles of freeze–thaw. However, the freeze–thaw cycles reduce the mixture strength up to 40% in comparison with the intact mixture. The analysis of scanning electron microscope images implies that four factors including disintegration of the calcium-silicate-hydration complex, imposing new porosity, releasing interlayered water, and establishing the secondary ettringite are the main reasons for strength reduction of the cemented sand-gravel mixtures after encountering the freeze–thaw cycles which have not been observed in the previous researches.