Over the last decade fiber-reinforced polymer (FRP) reinforcement consisting of glass, carbon, or aramid fibers embedded in a resin such as vinyl ester, epoxy, or polyester has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. Another application of FRP rods in construction was developed to retrofit and repair reinforced concrete (RC) and masonry structures, using a recently developed technology known as near surface mounted (NSM) rods. 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. The mechanical properties measurement requires special test methods developed for FRP products, since it is known that the mechanical properties are related to the direction and content of fibers. Technical codes and standards were developed in Japan, Canada and U.S.A. in order to assure the structural safety, as it regards the recent applications of these materials in civil engineering. Several concerns are still related to the structural behavior under severe environmental and load conditions for long-time exposures. For the case of glass FRP rods, is the high pH of the pore water solution (pH=12.5-13) created during the hydration of the concrete.

In this study an effective tensile test method is described for a mechanical characterization of FRP rods. Several FRP specimens with different sizes and surface characteristics were tested to validate the proposed procedure. An effort has also been made to develop an experimental protocol to study the effects of accelerated ageing on FRP rods. The physico-mechanical properties of six types of commercial carbon and glass FRP rods were investigated; the rods were subjected to alkaline solution exposure, and environmental agents, including freeze-thaw, high relative humidity, high temperature and ultraviolet (UV) radiations exposure. The mechanical properties were investigated by performing tensile and short beam tests. A further investigation was carried out at a micro-level using SEM microscopy. SEM images of conditioned specimens were analyzed and presented in this study. The sorption behavior was observed by means of simple gravimetric measurements in order to study the diffusion of the alkaline solution, since the penetration of the aggressive agents, producing micro cracking in the polymeric matrix, brings to fibers damage caused by chemical attack. The experimental data showed the effectiveness of the proposed tensile test method and the influence of aggressive agents on durability of the tested FRP rods. A complete protocol in order to investigate mechanical properties and long-term behavior of FRP rods is presented. Based on experimental results, design recommendations and important aspects related to durability are furnished in order to help manufacturers and designers.