California Bearing Ratio of a Sub-Base Material Modified With Tire Buffings and Cement Addition

Proper management of waste tires is a major environmental problem in many regions of the world. Instead of disposal in landfills, waste tires can be used in some engineering applications, thereby reducing their potential impact on the environment. The goal of this study was to assess the use of crushed rock mixed with tire buffings (a by-product of re-treading tires) and cement as sub-base materials for road construction. We prepared various mixtures of crushed rock containing 0, 5, 10, and 15 % tire buffings and 0, 1, 3, and 5 % cement by weight, and determined their California Bearing Ratio (CBR) values at different water contents. The performance of the sub-base gravel was investigated with the inclusion of tire buffings only, cement only, and tire buffings and cement together. The test results indicate that the CBR value of sub-base material decreases with the addition of tire buffings with no cement, and increases with the addition of cement with no tire buffings. In certain cases, small amounts of cement additions to the gravel with tire buffings increase the CBR values of the sub-base gravel, and thereby may result in a substantial decrease in design thickness of a pavement. The CBR values of the specimens with 3 % cement and 5 % tire buffings, 5 % cement and 5, 10, and 15 % tire buffings were found to be greater than the CBR value of the clean sub-base gravel.