Influence of Size and Quantity of Shredded Rubber Tires in Modifying the Geotechnical Properties of Weak Clays

Every year, millions of scrap tires are either discarded in huge piles across the landscape or dumped in landfills in large volumes all over the world. These tire piles cause environmental pollution while posing fire and health hazards. Being volumetric goods in comparison to other wastes, they occupy large volumes in landfills. Rainwater tends to accumulate in the stockpiled tires, which, then become a breeding ground for mosquitoes that carry dangerous diseases, such as encephalitis. Several states in the United States have, therefore, banned the disposal of used tires in the land. Shredded rubber has been used in a variety of applications in geotechnical engineering including in highway pavements and backfills of retaining walls, but mostly as individual material. In this study, kaolinite and montmorillonite were modified using different sizes and quantities of shredded rubber tires and used to evaluate the improvement in geotechnical properties. Five different sizes and five different proportions of shredded rubber tires were mixed with the clay minerals. Laboratory experiments were carried out to evaluate the changes in density, permeability and unconfined compressive strength of such modified soil with shredded tires. The results showed that for kaolinite, the maximum dry density decreased as the percentage of shredded rubber tire in the mixture was greater than 4% by dry weight. In Montmorillonite, the maximum dry density of the modified soil increased till 2 to 4% of shredded rubber tire was added to the soil. The highest strength was observed at 4% shredded rubber tire content in kaolinite and at 5% shredded rubber tire content in montmorillonite. Permeability increased when smaller sized shredded rubber tire was added to kaolinite. In montmorillonite, permeability values sharply increased up to 2% shredded rubber tire content and thereafter, showed a linear increase in permeability for all sizes of shredded rubber tire used. From this study, it is concluded that shredded rubber can be effectively used to improve the compaction and strength characteristics of weak soils.