Evolution and Prediction of Tensile Properties for Ductile Hybrid FRP Bars in a Simulated Concrete Environment

Hybrid fiber-reinforced polymer (HFRP) bars possessing high tensile ductility and excellent corrosion resistance are an attractive alternative to steel bars. However, the effect of long-term embedment of HFRP bars in concrete on the tensile ductility of bars must be investigated. This study exposes a series of ductile carbon/glass-HFRP bars to a simulated ordinary concrete environment for 3 and 6 months. The accelerated aging method was conducted at 60 degrees C to accelerate the diffusion of moisture and hydroxyl ions into the carbon/glass-HFRP bars, which could rapidly aggravate the degradation of the HFRP bars. Moisture absorption tests, scanning electron microscopy, and Fourier-transform infrared spectroscopy were performed to reveal the degradation mechanisms of the fiber, matrix, and fiber/matrix interfaces in the exposed samples. The tensile ductility of the samples after exposure was lower than that of the samples before exposure. The tensile strength retention of the exposed samples depended on the volume fraction of carbon fibers and the total volume fraction of the fibers, which could be considered in the prediction model of tensile strength retention of the exposed carbon/glass-HFRP bars.