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

The recent advancements in the fields of materials science and composites h ave resulted in the development of high-strength, corrosion-resistant fiber reinforced plastic (FRP) tendons that could potentially replace steel tend ons in prestressed or post-tensioned concrete structures, particularly in a reas where corrosion is a problem. The more common types of FRPs used in co nstruction are made from high-strength filaments of glass,giass, carbon or aramid placed in a resin matrix. Each combination of fiber and resin presen ts a unique advantage for a particular application. In this paper, the beha vior of aramid fiber reinforced plastic (AFRP) tendons will be examined. Te st results of relaxation, creep, and fatigue behavior of 10-mm-(3/8-in.)-di ameter AFRP tendons under simulated field conditions are presented. Twelve specimens were tested in air at temperatures of -30, 25, and 60 C, and 24 s pecimens were tested in alkaline, acidic, and salt solutions at temperature s of 25 and 60 C to evaluate the relaxation behavior In addition, 45 specim ens were tested in tension-tension fatigue to investigate the effect of rep eated loading on the mechanical properties of the tendon, such as the elast ic modulus E, Poisson's ratio v, and the residual tensile strength P-r. A p reliminary investigation of the creep behavior was also conducted at room t emperature in air, alkaline solution, and acidic solution. The fatigue and creep performance of the AFRP tendons tested in this study was very good. T he relaxation losses were higher in solutions, as compared with those speci mens tested in air. In particular the losses in acidic solutions were the h ighest.