Sustainable Geopolymer Concrete for Pavements: Performance Evaluation of Recycled Concrete Aggregates in Fly Ash-Based Mixtures

This study investigates the feasibility of incorporating recycled concrete aggregates (RCA) into fly ash-based geopolymer concrete for sustainable pavement applications. The research evaluates RCA’s physical and mechanical properties compared to virgin coarse aggregates (VCA) and assesses the performance of geopolymer concrete mixtures with up to 40% RCA replacement. Aggregate characterization revealed that RCA exhibited higher water absorption (4.39%), crushing value (20.9%), impact value (28.2%), and abrasion value (26.1%) compared to VCA, yet these values remained within acceptable limits for pavement applications. Geopolymer concrete specimens were tested for compressive strength, water absorption, abrasion resistance, and chloride ion permeability. Results indicated that increasing RCA content led to a gradual decrease in compressive strength, from 40.16 MPa to 33.52 MPa, while water absorption increased from 5.2% to 6.8%. Abrasion resistance declined as RCA content rose, and chloride ion penetrability increased from 1687 to 2196 coulombs. However, mixtures with up to 20% RCA replacement met the strength and durability criteria required for pavement construction. This study demonstrates the potential for utilizing RCA in geopolymer concrete pavements, offering a sustainable solution for waste management and resource conservation in the construction industry.