This paper presents mechanical, microstructural, and physical characterization of glass fiber-reinforced polymer ͑GFRP͒ bars exposed to concrete environment. GFRP bars were embedded in concrete and exposed to tap water at 23, 40, and 50°C to accelerate the effect of the concrete environment. The measured tensile strengths of the bars before and after exposure were considered as a measure of the durability performance of the specimens and were used for long-term properties prediction based on the Arrhenius theory. In addition, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy were used to characterize the aging effect on the GFRP reinforcing bars. The results showed that the durability of mortar-wrapped GFRP bars and exposed to tap water was less affected by accelerated aging than the bars exposed to simulated pore-water solution. These results confirmed that the concerns about the durability of GFRP bars in concrete, based on simulated laboratory studies in alkaline solutions, do not properly correspond to the actual service life in concrete environments.

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The research undertaken during the last two decades has shown that one of the potential solutions to the steel-corrosion-related problems in concrete is the use of fiber-reinforced composite (FRP) reinforcement as a replacement for traditional steel bars. Glass FRP (GFRP) reinforcement is gaining more popularity in construction of bridges and in other concrete structures because of its low cost compared to Carbon FRP reinforcement. The durability of these materials, especially under severe environmental conditions, is now recognized as the most critical topic of research. The lack of data on durability of the GFRP reinforcements is a major obstacle to their acceptance on a broader scale in civil engineering. This paper summarizes the most significant research work published on the durability of FRP bars in the past two decades. A comprehensive review of the literature on the durability of FRP bars indicates a significant increase in the number of studies in this area in the last decade. The durability tests conducted by the authors and others on the latest generation of GFRP bars subjected to stresses higher than the design limits, combined with aggressive mediums at elevated temperatures, have concluded that the strength reduction factors adopted by current codes and guidelines are conservative. These factors were based on limited test results that were carried out on the early generations of the GFRP products, which have now substantially changed.

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