Valorization of construction and demolition waste as reinforcing nanofiller for polymer composites

Plastics represents one of the largest global waste streams, with recycling limited by their heterogeneous composition and degraded properties. Simultaneously, construction and demolition activities generate significant amounts of fine fraction waste without reasonable utilization objectives. This study investigated the potential of combining heterogeneous plastic waste and construction and demolition waste (CDW) powder into high-value nanocomposites at various filler loadings (1, 2.5, and 5 wt%), aiming to enhance the mechanical performance of recycled plastics. Virgin polypropylene matrix and commercial nanoclay were used as reference materials. The CDW powder exhibited comparable overall performance to commercial nanoclay in elastic modulus (+ 12%) and even outperformed it in terms of tensile strength (+ 3% vs. +0.4%). Statistical analysis using two-way ANOVA (n = 12, α = 0.05) confirmed that both filler type and loading level significantly affected tensile strength of composites (p < 0.0001), while elastic modulus was primarily influenced by the filler loading. Furthermore, a theoretical model predicting interfacial adhesin between polymer matrix and reinforcing fillers supported these results, indicating stronger polymer-particle adhesion with CDW particles compared to nanoclay. These findings demonstrate that nanoreinforcement is an effective strategy to valorize recycled plastics by improving their mechanical performance and establish CDW-origin filler as a competitive alternative to conventional virgin fillers in the polymer industry.