Optimization of Aspect Ratio of Waste Tire Shreds in Sand-Shred Mixtures Using CBR Tests

The advantage of optimizing aspect ratio (length to width) of waste tire shreds on California Bearing Ratio (CBR) of sand-tire shred mixtures is investigated in this paper. The mixtures were composed of a relatively uniform sand and tire shreds with 2-, 3-, and 4-cm widths and various lengths. Shred contents of 15, 30, and 50 % by volume were mixed with sand at two sand matrix unit weights of 15.5 kN/m3 and 16.8 kN/m3. The results show that the influencing parameters on CBR of the mixtures are sand matrix unit weight, shred content, shred width, and aspect ratios of tire shreds. The variation of aspect ratios can increase CBR up to 850%. The average value for the influence of the shred aspect ratio on CBR was about 161%. For a given shred width, there is only a certain length giving the greatest CBR for sand-tire shred mixtures, regardless of shred contents and compaction effort. This is the main objective sought in this paper.