Effect of cement treatment on geotechnical properties of some Washington State soils

This study presents experimental results on the use of Portland cement in the modification and stabilization of soils in the state of Washington, USA. Cement was added in percentages of 2.5, 5, 7.5, and 10%, by dry weight of the soils. Laboratory tests to determine the drying rate of the soil, Atterberg limits, compaction characteristics, unconfined compressive strength, and consolidated-undrained triaxial behaviour were performed. Results of the investigation showed significant improvement in drying rate, workability, unconfined compressive strength, and shear strength. The improvement is dependent on the type of soil. Results of undrained triaxial tests showed that while cement treatment improved shear strength significantly, the type of failure behavior varied greatly. Non-treated, 5%, and 10% cement treated soils displayed ductile, planar, and splitting type of failure, respectively. Treated soils with 10% cement content split during failure with rapid rise in pore pressures equaling confining pressures resulting in effective pressure at failure near zero. Therefore, while increased strength is achieved by cement treatment, high percentages of cement should be used with caution in field applications.