Synergistic Use of Industrial and Agricultural Byproducts in Pavement and Structural Engineering: Comparative Mechanical and Environmental Outcomes

The construction sector is under increasing pressure to reduce carbon emissions while maintaining high-performance standards in pavement and structural materials. This study examines the synergistic potential of combining industrial byproducts—fly ash, ground granulated blast-furnace slag (GGBFS), and steel slag—with agricultural residues such as rice husk ash (RHA), bagasse ash, and palm oil fuel ash to create sustainable, performance-optimized construction materials. Comprehensive characterization using XRF, XRD, SEM, and pozzolanic activity indices, along with factorial mix designs, mechanical testing, durability evaluations, and cradle-to-gate life cycle analysis, was conducted for both structural concretes (M30–M50) and pavement applications. Results demonstrate that hybrid mixes consistently outperform standalone industrialor agricultural-only systems, achieving superior long-term compressive and flexural strengths, enhanced fatigue and rutting resistance, and improved durability against chloride ingress, sulfate attack, and freeze–thaw degradation. Life cycle analysis further reveals that hybrid systems reduce embodied carbon by 25–45% while maintaining or enhancing engineering performance. The study establishes hybrid industrial–agricultural by-product blends as a technically robust and environmentally responsible pathway for circular, low-carbon infrastructure, offering a reproducible framework for sustainable mix design and material optimization.