Surface treatment with nano-silica and magnesium potassium phosphate cement co-action for enhancing recycled aggregate concrete

In this study, surface treatment, using blended materials of nano-silica (NS) and magnesium potassium phosphate cement (MKPC) slurries containing four dosages of NS, was applied to recycled aggregate (RA) with distinct RA maintenance schemes to enhance the RA concrete (RAC) performance and control NS dosage for economy. The results imply that the NS + MKPC slurry can efficiently bolster the bonding with RA and the new interfacial transition zone (ITZ), contributing to a distinct enhancement of RAC's macro-properties. Besides, the optimal NS dosage and RA maintenance scheme revealed by the simplified linear weighted sum optimization method were 3% and no pre-curing procedure, respectively. On the basis of the aforementioned optimal conditions, the modified RAC (C-3-N) achieved enhanced compressive strength by 40.75%, split tensile strength by 46.26%, and chloride ion penetration resistance by 65.93% in comparison with the untreated RAC0. Moreover, the advantages observed in C-3-N were attributed to the exceptional microstructural characteristics in both the NS + MKPC slurry and the new ITZ. This study establishes the potential to augment the efficacy of nanomaterials in reinforcing RAC and enhance the economic viability and practicability of RAC applications. Simultaneously, these advancements contribute to fostering sustainable development within the construction industry and yielding environmental benefits.