Effect of alkali exposure on durability performance of GFRP bars: experimental and statistical analysis

India’s extensive coastline poses significant durability challenges for marine infrastructure owing to corrosion of steel reinforcement, resulting in high maintenance and rehabilitation costs. Glass-fibre-reinforced polymer (GFRP) bars present a promising alternative. However, their durability in highly alkaline concrete environments remains a concern and requires further investigation. The influence of alkaline exposure on the tensile strength retention and bond performance of GFRP bars of different diameters (8, 10 and 12 mm) was examined in this study. Specimens were conditioned in simulated alkaline solutions for 28 days and 45 days and tested in accordance with ASTM D7205. The results showed a reduction in tensile strength exceeding 30% after 45 days of exposure, accompanied by microstructural degradation observed through scanning electron microscopy analysis. Pull-out tests conducted after 90 and 180 days revealed minimal bond degradation (3–4%), noticeable only after prolonged exposure. Regression analysis identified bar diameter and exposure duration as key parameters influencing durability performance. Predictive models were developed, which are applicable for bar diameters of 8–15 mm and exposure durations up to 250 days under accelerated conditions. The findings support durability-based design and highlight the potential of GFRP bars for sustainable coastal infrastructure, contributing to UN Sustainable Development Goals.