Failure analysis of clay soil-rubber waste mixture as a sustainable construction material

Rubber waste (RW) causes serious environmental problems in human societies; however, it has valuable engineering properties, particularly recruited as an additive to construction materials. Hence, the reuse of such wastes is of both geotechnical and environmental importance. In this study, the behavior of clay soil (CS) mixed with RW was evaluated using the unconfined compressive strength (UCS) test. Accordingly, the effect of three rubber shapes, two rubber sizes, and four rubber contents on the UCS, failure modes/mechanisms, strength, modulus of elasticity, failure strains, post-peak loss of strength, and test repeatability were investigated. The findings revealed that, among the three rubber shapes, namely, granular, chips, and fibers, the granular rubber with a larger size than other shapes could more effectively improve the geotechnical properties of CS and produce more repeatable results. Moreover, the CS-RW mixtures showed failure modes/mechanisms different from pure CS ones, depending on the shape of the RW. The RW could also change the CS failure behavior from brittle to ductile. Some practical correlations were further proposed to estimate the strength of CS-RW mixtures. According to the study results, it is recommended to apply granular RW, as a suitable construction material in geotechnical projects in the role of fillers, in view of its failure mode, strength, and low weight along with other positive properties of CS-RW mixtures.