Effect of Addition of Granular Tire on the Swelling Behaviour and CBR Value of Expansive Soils

Abstract

The deposits of expansive soils exist throughout India and in areas where expansive soils predominate, mitigation efforts usually focus on reducing the swell potential of the soil to eliminate the detrimental effects due to excessive heave and swell pressures on typical engineering structures such as road pavement layers, building foundations, and retaining structures. Early studies investigated the use of the granular waste tire rubber (GWTR) as an alternative geometrical in civil engineering applications. Currently, a very small percentage of waste tire rubber generated in India is beneficially used for civil engineering projects. Beneficial use of GWTR in civil engineering applications is desirable not only from a sustainable point of view but also since GWTR is a relatively light-weight material, which makes it ideal for use in embankment fills and retaining wall backfills. It shall be pertinent to mention here that during our studies in original soil samples granular tire pieces were added in incremental % of 5% every time and CBR values were unaffected while on the addition of lime in incremental % of lime in equal increments of 2% along with the granular tires changed the scenario altogether. In this study, the effect of scrap tire rubber on the compaction, one-dimensional swell- consolidation response and CBR value of an expansive soil from Jhansi, U.P. was investigated systematically in the laboratory. The granulated tire was mixed in 15%, 20% and 25% by weight of expansive soil. The optimum water contents of the soil and expansive soil rubber (ESR) mixture were approximately the same. The addition of different percentage rubber by weight to the soil decreased the maximum dry unit weight of the expansive soil rubber (ESR) mixture due to the lower specific gravity of the rubber material. All specimens were prepared at the same optimum moisture contents and different maximum dry densities obtained from Heavy compaction tests. Typical swell-consolidation test results for the materials tested had shown that the compression and recompression indices increased by 35% and 23%, respectively, with the addition of granulated tire rubber. In contrast, both the swell percent and the swelling pressure were significantly reduced for the ESR mixture due to the addition of waste tire rubber, by weight, to the natural soil. CBR test results had shown a significant drop in CBR value due to the addition of granulated tire but at 20% granular tire the CBR value was approximately equal to the CBR value of raw expansive soil. As there was no improvement in CBR value due to the addition of granular tire so to improve CBR value lime is added in 4%, 6% and 8% by weight of ESR mixture containing 20% granular tire. Test results had shown a continuous increase in CBR value with the increase in lime content.