Durability of AR glass fiber reinforced plastic bars

Since the development of reinforced concrete over a century ago, engineers have constantly struggled with the corrosion problem of steel reinforcement. The new advances in the field of materials science have resulted in the development of fiber reinforced plastic (FRP) materials that could potentially be used as bars in reinforced concrete structures. The attractive features of this type of bars include high strength, light weight, and resistance to electrochemical corrosion. E-glass is the most widely used fiber material in FRPs; however, studies have shown that this type of fiber is susceptible to degradation in alkaline environments (i.e.; concrete). This paper presents the results of a durability study on FRP bars made from an alternative glass fiber, alkali resistant (AR) glass, that could potentially improve the durability of FRP bars. A total of 160 bar samples were tested after exposure to corrosive solutions at temperatures of 25°C and 60°C. These solutions were designed to simulate accelerated exposure to adverse conditions in the field. Test variables included two matrix materials (polyester and vinyl ester), seven chemical solutions, and ultraviolet radiation. Moisture absorption by bars and associated changes in the mechanical properties were the focus of this study. In addition, ten reinforced concrete beams were tested in flexure until failure, to examine the effects of exposure to concrete and deicing salts. Test results indicated that significant loss of strength could result from exposure of AR glass FRP bars to simulated aggressive field conditions. An analytical study based on diffusion models and Pick's law was also conducted to predict the loss of strength. In the Fickian range of diffusion, the models predicted the loss of strength with a reasonable accuracy.