Soil Modification Utilizing Cement
Authors:Joseph Cardillo, Alexander Duong, Yonathan Sahle, John Thurlo
Mentor:Binod Tiwari, Associate Professor Civil and Environmental Engineering Department, California State University Fullerton
Soil modification causes multiple positive changes to the existing soil, including an increase of the bearing capacity, reduction of settlement of the soil, and limits potential liquefaction. Cement has been widely used as a soil modifier; research has been conducted into different soils to determine the optimum cement contents for modifying those particular soils. Properties of the modified soil depend on the type of soil. For this project two soil types were used, kaolin clay, and a 50%-50% kaolin sand mix. Tests were conducted by adding 0, 2, 4, 6, 8, 10, 12, 15, and 20% cements on the soils. The soil cement mixes were subjected to standard proctor compaction, triaxial, unconfined compression, direct shear and direct simple shear tests following ASTM standards. Test results showed that the addition of cement to both soils causes an increase in the undrained shear strength, while causing a decrease in the dry unit weight of the soil. Curing of the soil cement mixtures has proven to be the most important aspect of using cement as a soil modifier; if the soil is not allowed to cure the addition of cement has little to no influence on the engineering properties of the soil. Extended curing periods are sometimes beneficial, for the compressive strength; longer curing periods increases the compressive strength, but for other tests such as Atterberg limits longer curing periods do not make any significant difference. Adding 10% cement and curing the cement-modified soil for 14 days gave the optimum benefit in this study.