Absorption of Aramid Prestressing Rods in Aggressive Solutions

Fiber-reinforced plastic (FRP) reinforcing bars are not prone to classical electrochemical corrosion. However, this material may suffer from other degradation mechanisms when exposed to moisture, alkaline, or acid solutions for a long period of time. In the present study, the absorption characteristic of aramid fiber-reinforced plastic (AFRP) prestressing rods with epoxy matrix was investigated in terms of weight gain or loss by immersing the rods in water, alkaline, and acid solutions for more than a year. The results showed that the weight of the 8 mm diameter AFRP rods immersed in water increased in weight marginally. The weight of the rods immersed in an alkaline or acid solution increased significantly. A scanning electron microscope photograph showed the penetration zone at the cross section of the rods when immersed in three different solutions. An electron probe microscope analyzer examination is useful to detect the presence of the ion Na+ from the NaOH solution where the rods were immersed. A Simplified Diffusion Model can predict the depth of penetration and was verified by a scanning electron microscope measurement.