Investigating the effect of waste rubber in granular form on strength behavior of Tehran clay

Abstract

Worn tires, as lightweight materials, can play a significant role in retaining walls and embankments in most geotechnical projects, particularly in seismic zones. Such tires are also regarded as one of the many different types of wastes in the environment. In this study, the geotechnical properties of Tehran clay and granular rubber mixtures, produced from these tires, were investigated. To this end, granular rubber in both ground and granulated rubber sizes from zero to 50% rubber content in the mixtures was used. To analyze characteristics of granular rubber in clay-rubber mixtures, various experiments were also performed including direct shear test, uniaxial compaction test, compaction tests, as well as microstructural examinations by means of optical microscopy and binocular imaging. According to the study results, an increase in rubber percentage could lead to a decline in maximum dry density (MDD). Moreover, with reference to strength tests, optimal content of granular rubber in clay-rubber mixtures was 10% and rubber content of more than 40% and up to 50% had little effect on deformations and shear strength of such mixtures. Another positive feature of this mixture was post-peak stress drop in different contents of waste rubber in the mixture, causing samples to fail slowly and gradually and tires change types of failure of pure Tehran clay to a ductile behavior. At high percentages of the rubber, strength properties of both types were also close to each other and converged. Due to a reduction in MDD of clayey soil together with appropriate strength, it was concluded that the given mixtures with up to 50% rubber content could be utilized to lighten consumables, especially filler materials in this area.