Reuse of recycled plastic in the construction industry is a novel approach instead of landfilling. However, the utilization of recycled plastic aggregates (RPA) aggravated the majority of concrete properties. In previous investigations, different techniques such as surface treatment of RPAs were utilized to reduce the negative influence of the RPAs on the concrete performance. Research regarding the improvement of RPA self-compacting concrete (SCC) properties by the addition of nano-silica particles (NS) is scarce. Therefore, the current study aims to experimentally investigate the properties of the SCC-incorporated RPAs modified with NS. The experimental program contained sixteen different mixtures which were subdivided into three stages. In the first stage, the effect of NS addition on the performance of SCC mixtures was evaluated. Moreover, the effect of different percentages of RPAs was investigated in the second phase. In the third stage, the optimum percentage of NS particles found in the first stage was utilized to improve the performance of SCC mixtures which aggravated in the second stage. The total binder content for all mixtures was 500 kg/m3 which contained 70 % of cement, 20 % of ground granulated blast furnace slag (GGBFS) and 10 % silica fume. In the first stage the cement was replaced by 1 %, 2 %, and 3 % NS particles, while, in the second stage, the natural fine aggregate (NFA) was replaced by RPAs at six volume fractions (5 %, 10 %, 15 %, 20 %, 30 %, and 40 %). The fresh behaviour of all SCC mixtures was investigated to assess the flowability, filling ability, passing ability, and cohesiveness of the mixtures. The mechanical behaviour was evaluated for compressive strength, splitting tensile strength, modulus of elasticity, flexural strength, and stress–strain behaviour. Moreover, the microstructure characteristics were investigated to illustrate the modifications that occurred in the microstructure scale. The results indicated that the addition of an optimum percentage of NS particles can significantly restore most properties of RPASCC which were degraded due to the addition of RPAs. This technique can help the construction industry to safely use the RPAs in the SCC mixtures without concern about their negative impact on concrete performance.
