Synergistic effects of recycled plastic aggregate and nano-silica on the elevated temperature and durability performance of self-compacting concrete

Abstract

A new approach to reusing plastic waste in construction is by incorporating recycled plastic aggregates (RPA) in concrete. However, this technique negatively affects concrete properties. Previous studies have treated RPAs to mitigate this issue, but none have investigated enhancing the properties of self-compacting concrete (SCC) made with RPAs through the addition of nano-silica (NS) particles. This study aims to explore the properties of SCC with RPAs modified by NS. Sixteen mixtures were tested in three stages: evaluating the impact of NS on SCC performance, examining various RPA percentages, and using the optimal NS percentage to improve negatively affected SCC mixtures. NS particles replaced cement at 1%, 2%, and 3% in the first stage, while RPAs replaced natural fine aggregate (NFA) at fractions of 5%, 10%, 15%, 20%, 30%, and 40% in the second stage. Compressive strength was assessed over different periods and at elevated temperatures. Durability performance, including water absorption, acid attack, electrical resistivity, chloride permeability, and bulk electrical conductivity, was extensively studied. The results revealed that the addition of the optimal NS percentage effectively restored the most degraded properties of SCCs, making it a safe and effective technique for utilizing RPAs in SCC mixtures without compromising concrete performance.