Synergistic Enhancement of Mechanical Strength and Permeability in Hybrid Fiber-Reinforced Pervious Concrete: Experimental Characterization and Multiscale Pore Structure Analysis

Pervious concrete has emerged as a sustainable solution for stormwater management and urban flood mitigation. However, its practical application is constrained by the inherent trade-off between mechanical strength and permeability. This study investigates the synergistic effects of incorporating carbon fibers (CF), polypropylene fibers (PPF), and their hybrid combinations on the mechanical properties, pore structure, and permeability of pervious concrete. Six types of fiber-reinforced pervious concrete mixtures were prepared using a paste-wrapped aggregate method. Compressive strength, flexural strength, and splitting tensile strength were evaluated. Two-dimensional and three-dimensional pore features were extracted and analyzed based on computed tomography (CT) imaging, followed by numerical seepage simulations to assess flow characteristics and key hydraulic parameters. Results showed that fiber incorporation significantly improved the fundamental mechanical properties of pervious concrete but reduced its permeability. However, hybrid fiber reinforcement at equal dosage effectively mitigated this trade-off. Multiscale pore analysis based on CT imaging revealed that the hybrid mixture achieved the highest effective porosity (22.4%) and the lowest viscous resistance coefficient (1.43×109 Pa·s), with a strong linear correlation identified between continuous porosity and permeability. Numerical simulations confirmed a Darcy-to-non-Darcy flow transition at a gradient of 1,000 Pa/m and identified the hybrid mixture as having the optimal hydraulic performance. These findings suggest a novel mix design strategy with promising applications in sustainable pavement systems and sponge city infrastructure.