The effect of cement and zeolite on undrained shear strength of the expansive clay

Expansive soils can be problematic in that they impose significant economic damages on the construction projects worldwide due to their high volume change in wet-dry conditions. Annually, many structures have been constructed on expansive soils such that nearly 60 percent of them undergo minor damage such as different kinds of fissure while 10 percent face severe unrehabilitatable damages. In this research, the cement and zeolite have been used as the base and supplementary cementitious stabilizers, respectively, and the undrained behavior of the treated expansive clay has been investigated. Hence, 6, 8, 10, and 12 percent of cement and 10, 30, 50, 70, and 90 percent of zeolite replacement were employed to cast the specimens. In the following, using the unconfined compression strength (UCS) and unconsolidated undrained triaxial (UU) tests, it can be stated that the best geotechnical performance such as maximum UCS, deviator stress in UU tests, secant modulus of elasticity (E50), cohesion, and internal fraction were obtained at 12% cement addition and 30% zeolite replacement after 28 days of curing. In both tests, increase in the cement content led to the increment in the failure strength of the samples. Based on the analysis of the results, it can be stated that the best geotechnical characteristics such as UCS, maximum deviational stress in triaxial test, secant modulus of elasticity (E50), and cohesion and internal friction angle were derived from the specimen stabilized with 12 percent of cement and 30 percent zeolite replacement cured in 28 days. With the above said, it can be noted that the optimum amount of zeolite replacement was 30%. Cement increment led to the enhancement of mechanical performance. Increase in zeolite replacement reduced the brittleness of the samples. In addition, increase in the curing time improved the mechanical behavior of the stabilized samples. The microscopic view justified the improvement of the stabilized samples.