A Comprehensive Review on Reclaimed Asphalt Pavement and Rice Husk Ash in Pervious Concrete

Abstract

Pervious concrete has emerged as a sustainable pavement material due to its ability to facilitate rapid stormwater infiltration, mitigate surface runoff, and promote groundwater recharge. However, its broader application is constrained by inherently low mechanical strength and the environmental burden associated with the extensive use of natural aggregates and Portland cement. To address these challenges, the incorporation of Reclaimed Asphalt Pavement (RAP) and Rice Husk Ash (RHA) has emerged as a resource-efficient and sustainable alternative. RAP, derived from recycled asphalt layers, enhances porosity and hydraulic conductivity through increased void connectivity; however, it compromises mechanical performance due to aged bitumen coatings, adhered fines, and the formation of weak interfacial transition zones (ITZ). In contrast, RHA, a silica-rich agricultural by-product, exhibits high pozzolanic reactivity, promoting the formation of additional calcium silicate hydrate (C-S-H) gel, which improves matrix densification, interfacial bonding, and long-term strength development. These competing mechanisms define the critical balance between permeability and mechanical integrity in RAP-RHA-modified pervious concrete systems. This review presents a critical synthesis of the physical, mechanical, hydraulic, and durability performance of pervious concrete incorporating RAP and RHA, with particular emphasis on pore structure evolution and ITZ behavior. Despite extensive research on their individual utilization, a mechanistic understanding of their coupled interaction-specifically the interplay between RAP-induced void architecture and RHA-driven pozzolanic densification remains underdeveloped. Accordingly, this study identifies key research gaps and establishes a mechanistically grounded framework for optimizing RAP-RHA blended systems. By explicitly linking microstructural evolution to macro-scale performance, the study provides a pathway for designing high-performance, sustainable pervious concrete with an optimized strength-permeability balance, advancing the development of resilient and environmentally responsive pavement infrastructure.