Effect of freeze-thaw cycles on concrete reinforced with basalt-fiber reinforced polymers (BFRP) bars

This paper examines the performance of concrete beams internally reinforced with basalt fiber-reinforced polymers (BFRP) bars after being subjected to freeze-thaw (FT) cycles. Prior to beam testing, pullout specimens were tested after being exposed to 100 and 200 FT cycles and to a freezing temperature of −20 °C. The pullout test results showed that FT cycles had a slight effect on the bond strength of the BFRP bars. Both unconditioned and conditioned specimens showed similar bond stress-slip relationships and comparable bond strengths. Exposing the pullout specimens to low temperature resulted in a decrease of 10% in their bond strength. In the beam tests, half of the beams were subjected to 200 FT cycles prior to testing whereas the remaining beams were tested at room temperature. The test parameters included the reinforcement ratio, the shear span-to-depth ratios, a/d, and the environmental conditioning. It was observed that conditioning changed the mode of failure of some of the tested beams as compared to that of their unconditioned counterparts. The effect of conditioning on the failure mode was less pronounced in the over-reinforced beams with a/d > 2.5. Conditioning under- and over-reinforced beams with a/d = 2.5 resulted in reductions of 7.4 and 13.4%, respectively, in their load carrying capacities. FT conditioning had a slight effect on the ductility of the tested beams regardless of their a/d ratio or their internal reinforcement.