Producing high-quality recycled aggregate concrete: a novel biomimetic strengthening strategy

Using high-volume construction and demolition (C&D) waste for concrete production is an environmentally sustainable approach. However, the use of C&D waste often adversely affects concrete performance. This study proposed a novel biomimetic strengthening method for recycled aggregates (RAs) treated with dopamine (DA) hydrochloride and investigated its effects on the mechanical properties and durability of recycled aggregate concrete (RAC) to produce high-quality precast concrete. The results show that using an appropriate amount of DA hydrochloride solution to enhance RA significantly improved the interface compactness of RAC due to the strong adhesion ability of polydopamine (PDA), which promotes cement hydration around RA. Furthermore, PDA increases the hydration degree of cement by promoting the dissolution of aluminate phase (C 3 A and C 4 AF) in cement clinker and the formation of AFt. When the biomimetic strengthening time of RA was 18 h, the new matrix around the RA had the highest hydration degree, and its interfacial transition zone width was 16.67% smaller than that of the untreated sample. Compared to RAC containing untreated RA, RAC containing RA by biomimetic enhancement for 18 h showed an increase in 28-d compressive strength by 1.59–18.02% and a decrease of 5.22–71.90% in sorptivity coefficient.