Durability of concrete-embedded GFRP bars after 20 years of tidal zone exposure: Correlation with accelerated aging tests

The application of non-metallic glass fiber-reinforced polymer (GFRP) bars as embedded reinforcement in reinforced concrete (RC) has been of great interest among researchers and practicing engineers alike, owing to its properties such as high strength-to-weight ratio and corrosion resistance. This study investigated the long-term performance of ribbed (RB) and sand-coated (SC) GFRP bars embedded in concrete columns exposed to harsh seawater conditions for approximately 20 years. The bars extracted from the concrete elements were tested to evaluate strength retention based on ASTM standard transverse and interlaminar shear strength tests. After the long-term field exposure, the ribbed and sand-coated GFRP bars exhibited 82.5 % and 79.4 % transverse shear strength retention, and 84.4 % and 78.1 % interlaminar shear strength retention, respectively, which corresponds to approximately 5 months of exposure in the accelerated solution specified by ACI 440.3R-12 guide. Scanning electron microscopy analyses revealed the extent of damage in the fibers, the matrix, and their interface, which validated the degradation in the mechanical strength of the exposed GFRP bars. Finally, correlations between long-term and accelerated exposure test conditions were developed to predict transverse and interlaminar shear strength in the field based on laboratory conditioning investigations.