Influence of Recycled Asphalt Aggregate Size on the Compressive Strength and Permeability of Pervious Concrete: A Sustainable Strategy for C&D Waste Valorization

Urban centers like Lipa City, Batangas, face persistent flooding due to inadequate stormwater management and increasing impermeable surfaces. Pervious concrete offers a functional solution for water infiltration, but its production often relies on virgin aggregates. This study addresses the opportunity in construction and demolition (C&D) waste by utilizing Recycled Asphalt Pavement (RAP) as a coarse aggregate. The research investigates the challenge of balancing structural integrity with hydraulic performance by evaluating how varying RAP aggregate sizes influence the compressive strength and permeability of the resulting concrete. Pervious concrete samples were prepared using three distinct RAP aggregate size fractions: Small (4.5–9.5 mm), Medium (9.5–19 mm), and Large (19–25 mm). These were compared against a control mix of commercial-grade pervious concrete. Compressive strength was tested following ASTM C39 standards, while hydraulic performance was evaluated via falling head permeability tests. Statistical significance was determined using one-way ANOVA and linear regression models to quantify the relationships between aggregate size and mechanical properties. The findings revealed a significant trade-off between strength and infiltration capacity. A strong inverse correlation was found between aggregate size and compressive strength (R = -0.87), with the Small RAP (2.83 MPa) outperforming the Large RAP (1.38 MPa). Conversely, permeability showed a strong direct correlation with aggregate size (R = 0.95), where Large RAP achieved an exceptionally high infiltration rate of 5.983 cm/s compared to just 0.062 cm/s for the CG control. ANOVA results confirmed these differences were statistically significant (p < 0.05), with aggregate size explaining approximately 92.5% of the variance in permeability. This research demonstrates that while RAP pervious concrete generally exhibits lower compressive strength than commercial alternatives, it provides vastly superior permeability. This makes it a highly viable, eco-friendly material for low-load infrastructure such as sidewalks and parking lots. By repurposing RAP, the study presents a scalable framework for reducing C&D waste sent to landfills while simultaneously strengthening urban climate resilience.