ABSTRACT
Mixtures of two different soil types and shredded scrap tire containing 0%-100% shredded tire, by weight, at 10% intervals, were tested for moisture-density relationships, permeability, shear strength parameters, unconfined compressive strength, and consolidation behavior. The soils used included a non-plastic silt (ML) and a low plasticity clay (CL). For each soil type, three different size ranges of shredded tire (7mm-13mm, 13mm-25mm, 25mm-38mm) were used to prepare mixtures. The results indicate that the density of soil-tire mixtures decreases and permeability increases with increasing shredded tire content for both soils and all three shredded tire sizes. The dry density values of soil-tire mixtures are reduced to 2/3 of the density values for soils alone (a requirement for lightweight fill) with the addition of 60% shredded tire of any of the three size ranges used. At 60% tire content, the permeability increases by 5-6 orders of magnitude for silt and 6-7 orders of magnitude for clay, the increase being greater for larger sizes. The addition of all three shredded tire sizes improves the friction angle of both silt and clay but has little to no effect on soil cohesion. Unconfined compressive strength deceases with increasing shredded tire content for both soils and all three shredded tire sizes. The chemical analyses of pure tire material, and of the leachate from soil-tire mixtures, indicate the presence of minor amounts of Zn, Fe, and Mn but their concentrations are less than the maximum allowable contaminant levels as specified by the U.S. Environmental Protection Agency. Based on the preliminary data, it is believed that soil-tire mixtures can be used in engineering applications where reduction in density or improvement in the drainage characteristics of low permeability soils is desired. Such applications may include development of football fields and playgrounds in areas of silty and clayey soils, reconstruction of unstable slopes where a light-weight permeable soil may be desirable, and as a general lightweight structural fill.
