Surface Modification of End-of-Life Rubber for Impact-Resistant Cement Composites

Incorporating end-of-life tire rubber in cement-based composites improves shock absorbance and flexural toughness while reducing waste generation and improving resource utilization. However, including rubber in cement-based composites reduces compressive strength, which can limit its application. In this study, we propose a two-step novel chemical treatment process to recycle scrap tire rubber into Portland cement-based composites that improve compressive strength while maintaining impact resistance. The first step encompassed a chlorination process, whereas the second step entailed amine grafting and functionalizing it using hydroxyl and sulfonate groups. The treatment induced hydrophilicity on the surface of the rubber, as observed from contact angle decreasing to 77° from 119°. The compressive strength of the mortar samples containing 10% rubber by volume increased by 24% when treated rubber was used instead of untreated rubber, without any statistically significant change in the impact resistance. Further, the treatment method did not affect the early-age hydration kinetics. The results indicate that the end-of-life rubber treatment method can thus be used for manufacturing impact-resistant concrete for crash barriers and blast-proof structures.