Effect of the Addition of Aggregates Derived from Used Tires on the Mechanical Behavior of Clay

The study of the shear strength parameters of mixtures comprising tire-derived aggregates (TDA) and clay was the main objective of this experimental work. The tests were performed using the direct shear box. First, the test was performed on specimens comprising only clay in its natural state and then on mixtures consisting of clay and TDA in increasing contents. A total of four samples (natural clay and natural clay with 2, 4, and 6% tire-derived aggregates)) were made and tested at three normal stress levels (100, 200, and 300 kPa). Then, Mohr-Coulomb failure envelopes were drawn to determine the internal friction angle and cohesion for all mixes. The results were compared to find the optimum TDA content and to study the stress-strain behavior of the mixtures. It was observed that mixing TDA up to 6% by weight with clay significantly changes the shear strength, and the internal friction angle increases from 27.47 to 59.39º (an increase of 46.25%). However, the cohesion significantly decreases from 45 to 26 kPa (a decrease of 57.77%). On the other hand, it was observed that increasing the TDA content reduces the density and increases the shear strength of the mixtures. Also, the addition of TDA increases the mixture consolidation and deformation level at failure.