Compaction Characteristics, Unconfined Compressive Strengths, and Coefficients of Permeability of Fine-Grained Soils Mixed with Crumb-Rubber Tire

In this study, five different weak soils were mixed with five different sizes of crumb rubber in six different proportions and used to understand the influence of the size and quantity of crumb rubber on the compaction characteristics, unconfined compressive strength, and coefficient of permeability of the soils. The maximum dry unit weight increased with the addition of crumb rubber, with the greatest increase found to occur when 2–4% crumb rubber of any size was added to the soil. An increase in the size of the crumb rubber mixed with kaolinite corresponded to an increase in the maximum dry unit weight. However, the opposite trend was observed when montmorillonite was mixed with crumb rubber. The unconfined compressive strength also increased when crumb rubber was mixed with soil, with the highest strengths also corresponding to the addition of 2–4% of crumb rubber. In all fine-grained soils except those containing montmorillonite, increasing the size of the crumb rubber used resulted in a reduction in the unconfined compressive strength. Moreover, the addition of crumb rubber caused an increase in the permeability of the mixtures. In kaolinite, an increase in the size of the crumb rubber led to a reduction in permeability. The permeability of the mixtures of montmorillonite with crumb rubber dropped as larger-sized crumb rubber was added. However, the coefficient of permeability with the addition of any crumb rubber was always greater than that of the parent soil.