Granulated blast furnace slag (GBFS) is utilized to overcome or to limit the expansion of an expansive soil sample. GBFS is added to sample in proportions of 10%-20% by weight. The test studies of swelling-shrinkage and basic physico-mechanical characteristics of soil samples are taken

so as to determine the improvement effects. Compared with unmodified sample

the free swelling ratio

liquid limit and plastic index decrease obviously; and the particle size gradation

strength characteristics and hydrated properties of the treated expansive soil are improved by a wide range. After improvement

clay content decreases

while silt content increases. The change of dry density with water content decreases and the hydrated property of modified soil is enhanced. It is shown that adding GBFS can successfully improve the expansive soil.