Influence of Cement Treatment on Unconfined Compressive Strength and Compressibility of Lean Clay with Medium Plasticity

Abstract

This study presents the experimental results on the use of cement in modification and stabilization of medium plastic clays. Samples of lean clay were mixed with Portland cement in percentages of 5 and 10 % by dry weight of the soils that had water contents of 40 and 60 %. The curing time of the samples varied between 7 and 28 days. The effects of cement addition on the workability, unconfined compressive strength (UCS) and compressibility of lean clay were examined. The plasticity index showed a steady decrease for all samples leading to higher workability especially in higher cement contents. The results of UCS tests demonstrated that UCS increased up to five times by the addition of 10 % cement to the soil at the end of 28 days. Specimens with lower water content had higher peak strengths. Samples exhibited ductile, semi-brittle, and brittle type of failures depending on their water and cement contents. Brittleness index was used to quantify the mechanical behavior of the soil and the brittleness index increased distinctively as a result of cement treatment. Deformability index was proposed as an alternative to evaluate the deformation behavior of specimens. Moreover, a relationship to determine the UCS development with curing time was proposed. The results of consolidation tests indicated that the compression index decreased and preconsolidation pressure increased by increasing the cement content. The preconsolidation pressure values were found to be related to the UCS values by a ratio of 1.4 for the cement-treated clay.