Synergistic effects of recycled rubber and polypropylene fibers in mortars: Experimental characterization and nonlinear predictive modeling

Abstract

This study has examined the combined influence of recycled rubber aggregates (RRA) and polypropylene (PP) fibers on the mechanical and durability properties of mortar composites. Nine mortar mixtures have been prepared with RRA contents of 0%, 10%, 20%, and 30% (by sand mass) and PP fiber volumes of 0%, 0.5%, and 1% (by binder mass). Results have shown that increasing RRA content has reduced compressive strength; however, the inclusion of PP fibers has significantly mitigated this loss. Durability parameters such as dynamic modulus, porosity, ultrasonic pulse velocity, and capillary absorption have also measured. A nonlinear empirical model has been developed to predict compressive strength based on RRA and PP content. The model has been validated using two-way ANOVA and Leave-One-Out cross-validation, achieving excellent agreement with experimental results (𝑅􀬶 􀵐0.98). Additionally, a simplified environmental analysis has indicated potential CO₂ emission reductions through partial replacement of natural sand with RRA. Overall, the study has demonstrated that rubberized and fiber-reinforced mortars have offered a sustainable alternative in construction, combining improved durability and environmental benefits without excessively compromising mechanical performance.