Bio-inspired functionalization of crumb rubber using polydopamine to enhance the performance of rubberized mortars

Abstract

This paper explores a biomolecule, dopamine, to functionalize crumb rubber (CR) to enhance the performance of cement mortars made with the CR. This is inspired by marine mussels, which can attach to various substrates underwater using the adhesive protein L-3,4-dihydroxyphenylalanine in its byssus. Dopamine is a mimic of the adhesive protein of mussel. At pH = 8.5, dopamine can spontaneously self-polymerize on the CR surface through the oxidation and the subsequent cross-linking of the catechol structure to form uniform polydopamine (PDA) film. This can enhance the wettability of the CR, leading to higher fluidities of the produced mortar. More importantly, the PDA film can chelate with Ca2+, promoting the formation of a denser interface transition zone between the CR and the cement paste and accelerating the hydration of the cement. As a result, the compressive strengths of the produced mortars were improved by 1–24 % at 3d, 13–52 % at 7d, and 37–68 % at 28d. The capillary water absorptions of mortars were also reduced by 28.6–41.8 %, significantly enhancing the durability of the mortar.