INVESTIGATATION AND COMPARISON OF COMPRESSIVE STRENGTH OF CLAY SOILS STABILIZED BY CEMENT, LIME AND CBR PLUS

Different types of stabilizers have been used for improving the properties of clay soils. Selection of the appropriate stabilizer depends on the soil type, environmental conditions, costs and the required strength. In this research, the effects of three different stabilizers on the compressive strength of two types of clay soils have been investigated. Cement, lime and CBR PLUS nano polymer, in different proportions, have been added to two types of clay soils, one with low plasticity index, and one with a high plasticity index, and the engineering properties of plasticity index and compressive strength have been evaluated. The compressive strength has been evaluated in wet and moist curing conditions in different ages of 1, 7 and 28 days. It is shown that, for the soil with low plasticity index, cement has the highest effect on the reduction of plasticity index, and, for the soil with high plasticity index, CBR PLUS, has the highest effect. Results also show that, for achieving high compressive strength in moist and wet curing condition, cement is the best stabilizer for the soil with low plasticity index. The compressive strength of the cement stabilized soil after 28 days of wet conditioning is found to be about 6 times higher than that of the lime and CBR PLUS stabilized soil. Also, for the soil with high plasticity index, CBR PLUS has the highest effect on the compressive strength in moist curing conditions, and in wet curing condition, the effect of cement is higher than lime and CBR PLUS. However, the difference between the compressive strength of cement stabilized soil in wet curing condition with lime and CBR PLUS stabilized soil is much lower than that for the low plasticity soil. For all the soils and stabilizers, the compressive strength of the moist curing condition is higher than those of wet conditioned. The effect of curing age on the compressive strength is found to be the same for the stabilizers, for which, the compressive strength of 28 days conditioned specimens is approximately twice those of 1 day conditioned specimens. It is also found that the ratio of compressive strength in moist curing condition to that in wet curing condition depends on the soil type, amount and type of stabilizer. The wet curing condition of high plasticity clay has minor effect on the compressive strength of the soil stabilized by lime, and for the soil with low plasticity index the lowest effect is on the soil stabilized by cement. For the CBR PLUS, the effect of wet curing on he reduction of compressive strength depends on the amount of stabilizer. The most economical stabilizer of the soil with low plasticity index is found to be cement, and that for the soil with high plasticity index is lime. Cost analysis show that CBR PLUS is not economical solution for clay stabilization.