Study on Behavior of Copper Slag and Lime–Treated Clay under Static and Dynamic Loading

Abstract

This paper presents the results of a laboratory study on evaluating the behavior of highly expansive clay that was treated with copper slag and lime under static and cyclic loading. The copper slag, obtained as a by-product from the smelting and refinery process of copper, was used as a stabilization agent in this study. In order to stimulate the pozzolanic activity of the copper slag, hydrated lime powder was used as a supplementary additive. Comprehensive laboratory tests including Atterberg limits, free swell, California bearing ratio (CBR), and unconfined compressive strength (UCS) tests were carried out to study the behavior of the clay treated with different proportions of copper slag and lime in the admixture content. Morphological change of soil after the stabilization was analyzed using the X-ray diffraction test. The optimum quantity of admixture was decided based on the CBR and UCS test results. Based on the strength criterion, the optimum stabilizer content that resulted in maximum strength improvement was found, i.e., copper (Cu) slag and lime at a 1∶1 proportion forming 12.5% admixture content by weight. The results of X-ray diffraction (XRD) test indicated substantial changes in the soil structure over the curing period. The stabilized soil samples were also subjected to dynamic loading to determine their dynamic properties. The study shows that the use of copper slag and lime for stabilizing expansive soil not only improves its static properties by reducing swelling and increasing the shear strength, but also increases its dynamic properties. Further, the behavior of the stabilized soil under fatigue load was analyzed by measuring the resilient modulus. The results have shown that the clay soil when stabilized with 12.5% admixture (Cu slag + lime at 1∶1) resulted in an increase in dynamic shear modulus of about 30%, a decrease in damping ratio of about 56%, and increase in resilient modulus of about 104%, proving the enhanced dynamic behavior of the soil.