Geotechnical behaviour of clay soil mixed with rubber waste

In recent years, many engineering researchers have used waste rubbers for the purpose of soil improvement because of its geotechnical and environmental benefits. Rubber wastes extracted from tire waste and can exist in various forms. Three different forms of rubber including granular, fiber and chips were used in this study for evaluating the shear strength of the clay soil mixed with rubber wastes. Different tests including compaction, uniaxial, direct shear, and triaxial tests were employed for evaluating the geotechnical parameters of the mix, as well as microstructural studies by optical microscopy and binocular examination, for a better understanding of the underlying mechanisms. Rubber content, size, and form were the parameters investigated in this study. The results are suggestive of the increase in the strength and shear strain of the mixture by increasing the rubber size. According to the results, the strength of the mixture containing crumb rubber increased by 10–25% as compared to the mixture containing rubber powder under various confined stresses. Further, it was found that rubber fibers offered a higher strength than the other forms of rubber. The limited drop in the strength after the peak is also significant regarding the soil–rubber waste mixture. The separate study of strength under optimum moisture content and saturation conditions shows that this parameter demonstrates different behaviors under each of the conditions. The volume changes of the soil mix specimens are suggestive of a contraction in the mix. Given the reduced maximum dry density of the mix specimens and the favorable shear strength of the mix, using the waste rubber for various geotechnical engineering applications, such as filler material, is recommended.