Durability of glass fiber-reinforced polymer bars in water and simulated concrete pore solution

Abstract

In this study, the durability of glass fiber-reinforced polymer (GFRP) bars in alkaline environments was studied. The GFRP bars were immersed in distilled water and alkaline solutions of various pH values at temperatures of 21 °C, 40 °C, and 60 °C. The water absorption and interlaminar shear strength of the GFRP bars were measured concerning conditioning time. The equilibrium water absorption of the GFRP bars in an alkaline solution of pH 13.0 was one order of magnitude higher than that of GFRP bars in distilled water and an alkaline solution of pH 10.0. Compared with samples conditioned in distilled water or the alkaline solution of pH 10.0, those aged in the alkaline solution of pH 13.0 showed a greater reduction in interlaminar shear strength. This reduction increased with increasing environmental temperature and conditioning time. Scanning electron microscopy images showed that the deterioration of GFRP bars aged in the alkaline solution of pH 13.0 was mainly caused by interfacial debonding between glass fibers and resin matrices. Equations were proposed for predicting the long-term interlaminar shear strength of GFRP bars as a function of water absorption and adopted to predict the interlaminar shear strength of GFRP bars in fields. The prediction results roughly match the measurement results.