Manufacturing of prestressed glass fiber reinforced polymer rebars and effect of fiber pretension on durability of rebars after conditioning in alkaline solution

Applying specific amount of fiber pretension during the manufacturing process of the composite rebars would potentially enhance their performance and durability. In this study, five sets of lab-scale prestressed glass fiber/vinyl-ester composite rebars were fabricated. Each set was manufactured using unique amount of fiber pretension. A set of unprestressed composite rebar was prepared as well. The effect of fiber pretension on the microstructure, tensile properties and long-term durability of rebars was investigated. In addition, the performance of the prestressed composite rebars was compared to composite rebars currently available in the market. An improvement in fiber alignment and a reduction in void content were observed within the pretensioned rebars. The composite rebars fabricated with pretension of 30 MPa showed the maximum increase in tensile properties. The guaranteed tensile strength and average tensile modulus were improved by 7.5% and 2.6%, respectively, compared to the unprestressed counterpart. The prestressed rebars showed relatively less surface degradation and lower moisture absorption after conditioning in alkaline solution at 60°C for 90 days. After conditioning, the tensile properties of the prestressed composite rebars showed superiority over the unprestressed rebar. Comparing to composite rebars available in the market, the prestressed composite rebars prepared in this study showed high performance in both short-term and long-term use.