Enhancing mechanical properties of rubberized cement mortar through Polydopamine surface modification: a sustainable approach to waste tire recycling

The incorporation of waste tire rubber particles as concrete aggregate presents a sustainable solution to mitigate environmental challenges. This study developed hydrophilic rubber particles through polydopamine (PDA) surface modification inspired by mussel adhesion mechanisms. Rubber particles were treated with dopamine hydrochloride (1–3 g/L) under varying durations (1–12 h), with optimal conditions identified as 2 g/L for 6 h. The results demonstrated significant hydrophilicity enhancement: water contact angle decreased from 134.0° to 72.7° (45.75 % reduction), while activation index decreased by 66.6 %. FTIR analysis confirmed successful PDA deposition through emerging -OH and C-N functional groups. In cement mortars with 30 % modified rubber replacement, 28-day compressive strength showed 88.1 % improvement compared to untreated counterparts and flexural strength increased by 31.3 %. Microstructural analysis revealed 42.7 % porosity reduction and 60 % decrease in harmful pores (>200 nm). The PDA coating facilitated denser interfacial transition zones through Ca²⁺-catechol interactions, reducing interfacial cracks from 8μm to complete bonding. This green modification method enables high-value recycling of 30 % waste tire content while maintaining a high compressive strength providing an eco-efficient pathway for sustainable materials.