Beneficial Use of Waste Tire Rubber for Swelling Potential Mitigation in Expansive Soils

Abstract

Approximately 290 million tires are disposed of annually in the United States (EPA 2003). Although markets now exist for about 80% of the US waste tires, it is estimated that about 27 million waste tires still need to be disposed of in landfills (RMA 2004). Waste tire rubber has been used in several applications such as highway backfill, subgrade and embankments; as drainage, landscaping, and sorptive materials; as well as in alternative methods for energy generation (Humphrey et al. 1993; Ahmed and Lovell 1993; Edil 2005). While waste tire rubber has been used to modify the mechanical properties of coarse-grained soils (Edil and Bosscher 1994; Feng and Sutter 2000; Lee et al. 1999), just a limited number of studies have addressed the stabilization of fine-grained soils with rubber (Edil and Bosscher 1994; Ahmed and Lovell 1993; Tatlisoz et al. 1997). None of these studies have tested mixtures of rubber with highly expansive clays, such as the ones widely encountered in Colorado and other western US states. In this study, the effect of adding small particles of waste tire rubber on the swelling potential of an expansive soil from Colorado was evaluated. The index properties and compaction parameters of the rubber, expansive soil, and expansive soil-rubber (ESR) mixture tested were determined. One-dimensional swell-consolidation tests were performed to assess the feasibility of using small particles of waste tire rubber as a mechanical additive to mitigate the swelling potential of the expansive soil. While the ESR mixture is more compressible than the untreated soil, both the swell percent and the swelling pressure are significantly reduced by the addition of rubber to the expansive soil.