Durability and Performance Retention of GFRP Bars in Concrete Subjected to 16 Years of Marine Exposure

The use of glass fiber–reinforced polymer (GFRP) as internal reinforcement in concrete structures has seen increased application in recent years. However, the long-term durability of GFRP bars embedded in concrete, particularly those exposed to harsh environments, remains inadequately understood. This study assessed the long-term performance of GFRP bars subjected to a marine environment for 16 years. Two exposure zones were considered: the tidal zone and the underground zone. Two types of GFRP bars were studied, namely ribbed and sand-coated bars. Experimental tests were conducted on retrieved GFRP-reinforced concrete specimens to evaluate their tensile, elastic modulus, and bond properties over intervals of 2, 7, 10, 13, and 16 years. The tensile strength retention of the GFRP bars in both conditions revealed a rapid decline in the initial 2 years, with average retention rates ranging from 65% to 91% over the entire exposure period. In contrast, the elastic modulus of the GFRP bars remained largely unaffected by the exposure conditions. The bond strength of the GFRP-concrete specimens fluctuated throughout the exposure period; however, after 16 years, the bond strength loss was found to be <10%, regardless of the exposure zone. The findings of this study are significant in supporting the use of GFRP bars in marine infrastructure, especially in hot and humid environments such as those prevalent in the Middle East.