Long-term behavior of aramid fiber reinforced plastic (AFRP) tendons

The recent advancements in the fields of materials science and composites have resulted in the development of high-strength, corrosion-resistant fiber reinforced plastic (FRP) tendons that could potentially replace steel tendons in prestressed or post-tensioned concrete structures, particularly in areas where corrosion is a problem. The more common types of FRPs used in construction are made from high-strength filaments of glass, carbon, or aramid placed in a resin matrix. Each combination of fiber and resin presents a unique advantage for a particular application. In this paper, the behavior of aramid fiber reinforced plastic (AFRP) tendons will be examined. Test results of relaxation, creep, and fatigue behavior of 10-mm-(3/ 8-in.)-diameter AFRP tendons under simulated field conditions are presented. Twelve specimens were tested in air at temperatures of -30, 25, and 60 C, and 24 specimens were tested in alkaline, acidic, and salt solutions at temperatures of 25 and 60 C to evaluate the relaxation behavior. In addition, 45 specimens were tested in tension-tension fatigue to investigate the effect of repeated loading on the mechanical properties of the tendon, such as the elastic modulus E, Poisson's ratio V, and the residual tensile strength P_r. A preliminary investigation of the creep behavior was also conducted at room temperature in air, alkaline solution, and acidic solution. The fatigue and creep performance of the AFRP tendons tested in this study was very good. The relaxation losses were higher in solutions, as compared with those specimens tested in air. In particular, the losses in acidic solutions were the highest.