Enhancing geopolymer composites with citric acid-treated jute and coir fibers: A sustainable approach to enhance mechanical and physical properties

• Citric acid-treated jute and coir fibers enhanced geopolymer composite strength. • Strength nearly doubled in the JCT-1.5 composite. • Treated fibers enhanced durability. • Eco-friendly treatment supports sustainable construction. This study investigates the influence of the use of short jute and coir fibers untreated and treated with 5 wt.% of citric acid on the fly ash-based geopolymer matrix to improve mechanical properties, workability and durability. The citric acid treatment was done in order to alter the surface of the fibers, providing better fiber-matrix interface. Mechanical testing exhibited significant improvements, especially for composites with treated fibers. The fibers with 1 wt.% of treated fibers (JCT-1) had the highest compressive strength which was 90.9% higher compared to the Control (JC-0) and 10.7% higher compared to the untreated fiber version (JCUT-1). For flexural strength the strength of JCT-1.5 composite (1.5 wt.% treated fibers) obtained was 8.62 MPa, which is almost double of Control and about 10% higher than its untreated counterpart.Citric acid treatment also decreased the hydrophilicity of fibers resulting in low level of water absorption (up to 35% reduction) and improved sulfate resistance, confirming the enhanced durability performance. Workability was also improved; the flow value of the JCT-1.5 mix was 45% while that of the untreated equivalent was 40%, which showed the dispersion and the reduced water demand. Overall, citric acid-treated natural fibers significantly improved the strength, workability and durability of the geopolymer composites. This approach provides a sustainable and cost-effective pathway towards the development of high-performance construction materials that can be used for lightweight structural components, prefabricated panels and environmentally friendly alternatives to cement-based products.