Durability assessment of GFRP bars exposed to combined accelerated aging in alkaline solution and a constant load

Abstract

Employing fiber-reinforced polymer (FRP) bars as reinforcement in reinforced concrete (RC) elements is a promising approach to solve the issues associated with steel corrosion in RC elements owing to the high corrosion resistance of FRP bars. Although a number of studies on the durability of glass FRP (GFRP) bars in the alkaline environment are available, most of which ignored the influence of sustained loads. This paper presents an experimental program on tensile tests on GFRP bars made of three distinct matrix resins (i.e. epoxy, vinyl ester and polyester), after exposure to combined alkaline solution immersion, an elevated temperature and a constant load. A novel level device was developed, and a prescriptive constant axial stress was imposed on GFRP bars, and the bars with or without a sustained load were exposed to an alkaline solution and an elevated temperature of 60 °C. The main parameters investigated in the present study included aging times, constant stress levels, exposure conditions and types of resin matrices of the GFRP bars. The residual tensile properties of the GFRP bars were tested and presented. The microscopy method was adopted to check the internal defects in the GFRP bars with or without exposures. Test results show that three months of exposure in alkali and loading could lead to more than 40% strength decreases of the GFRP bars. Compared with GFRP bars after exposure to alkaline solution solely, the presence of the constant tensile load only leads to small further detrimental effect in tensile properties of GFRP bars.