Effect of waste rubber on compressive strength, pore distribution and micromorphology properties of cement soil

The disposal of the increasing number of waste rubber tire has become one of the primary problems in global environment. The waste rubber can be recycled by adding it to cement soil (CS) mixtures as a solution instead of dumping or combusting it, which presents an effective avenue for lessening significantly this problem. In this research, waste rubberized cement soil (WRCS) mixtures with different rubber particle contents and sizes are utilized. Subsequently, the effects of waste rubber particle size and content on strength, failure mode, pore distribution of WRCS specimens are systematically evaluated by using laboratory tests such as compressive strength, pore structure and nuclear magnetic resonance (NMR). As well as micromorphology characteristics by scanning electron microscopy (SEM) tests. Results indicate that for WRCS with particle size of 4 mm, the compressive strength tends to decrease as increasing rubber particle content. Conversely, an opposite trend is observed for WRCS with particle sizes of 0.15 mm and 0.106 mm. Compared to CS specimens, specimens with various rubber particle contents exhibit significantly higher air content, average bubble chord length, and bubble spacing factor, while a notable decrease is observed for specific surface area of pores. Notably, rubber particles with various sizes can play a very superior role in preventing crack propagation in the WRCS mixture system. Moreover, the bonding interaction between rubber particles and CS components is weak for 4 mm WRCS specimen, whereas it is relatively stronger for 0.106 mm rubber particles.