Strength and Deformability of FRP-Jacketed Large-Size Concrete Cylinders after Exposure to Long-Term Actual Environmental Effects

This study focuses on the compressive behavior of large-sized concrete cylinders externally jacketed with carbon or glass fiber-reinforced polymer (FRP: CFRP or GFRP) sheets after prolonged exposure to natural outdoor environmental conditions. Two primary objectives were pursued: first, to experimentally investigate the effects of these conditions on the compressive behavior of the specimens, and second, to evaluate the conservatism of four widely used technical documents. Seven concrete cylinders (250 mm diameter, 500 mm height) were produced in 2003, six of which were jacketed with CFRP or GFRP sheets, while one was left unconfined as a reference specimen. These cylinders were exposed to wet-dry cycles, freeze-Thaw cycles, temperature variations, and ultraviolet radiation in Sariyer, Istanbul, Türkiye, for 18 years. In 2021, monotonic compression tests were conducted, yielding axial and lateral stress-strain relationships. CFRP and GFRP jackets increased strength by 2.93 and 1.77 times and axial strain capacity by 19.19 and 8.58 times compared with the aged unconfined specimen. Moreover, the predictions made by technical documents for the strength and axial deformation capacity of these cylindrical specimens were generally found to be conservative. The experimental enhancement ratios and predictions show that the FRP jacketing system, which is exposed to external environmental conditions for 18 years, still remains effective.