Sustainability Evaluation of Using Waste Rubber in Treating Soft Clay Subgrades for Road Embankments

Large amounts of waste rubber tires are disposed to dumping areas along different cities around the world. They are exposed to burning processes which causing air pollutions. The evaporated Carbon Dioxide (CO2) and others affect the environment and people's health. To overcome these disposals, it can be grinded into powder and re-used in different industries such as roads constructions. Many studies investigated the possibility of using such materials in stabilizing weak materials. Some studies investigated it in treating subgrade soils and others for asphalt layers. This study investigates the effect of using the grinding rubber with Portland cement in improving the soft clay subgrade embankments. Rubber percentages 2.00%, 5.00%, 7.00%, 9.00%, 11.00% and 13.00% and Portland cement percentages 2.00%, 4.00% and 6.00% are used in this study. Soil characteristics; plasticity, strength, and density were investigated through conducting Atterberg Limits, direct shear, California Bearing Ratio and compaction tests to evaluate the behavior of the improved soils. Results indicated that increasing rubber powder in stabilizing the soft clay causes the maximum dry density and the optimum moisture content to be decreased. Using the rubber powder as a stabilizing agent for the soft clay subgrade has low effect on the soil strength and bearing capacity. Using rubber powder and cement together in the stabilization processes lead to moderate improvements in soil strength, bearing capacity and plasticity. The optimum percentages of rubber and cement that lead to significant improvement on soil strength are 4.00% rubber and 6.00% cement.