Durability of FRP rods for concrete structures

Over the last two decades fiber-reinforced polymer (FRP) rods have emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. The application of FRP rods in new or damaged structures requires the development of design equations that must take into account the mechanical properties and the durability properties of FRP products. Concerns still remain about the structural behavior of FRP materials under severe environmental and load conditions for long-time exposures. In the case of glass FRP rods, it is the high pH of the pore water solution created during the hydration of the concrete that may cause the chemical attack of the fibers. In this study, an effort was made to develop an experimental protocol to study the effects of accelerated aging on FRP rods. The physico-mechanical properties of five types of carbon and glass FRP rods were investigated. FRP specimens were subjected to alkaline simulated concrete pore solution and environmental agents including freeze-thaw, high relative humidity, high temperature and ultraviolet (UV) radiations. Mechanical and physical tests were used to measure the retained properties and to observe the causes of damage and strength reduction. The experimental data showed that resin properties may strongly influence the durability of FRP reinforcement, environmental combined cycles did not take to significant damage of conditioned rod-specimens, GFRP rods are sensitive to alkaline attack when resin does not provide adequate protection to fibers.