Effect of Temperature Fluctuation and Severe Environments on Durability of CFRP Strands

This paper will present the results from an experimental study to examine the effect of severe environmental conditions on the performance of carbon fiber–reinforced polymer (CFRP) prestressed concrete members. Six 4.8 m (16 ft) long decked bulb-T beams will be prestressed with CFRP strands and will be loaded at three different temperatures: hot, ambient, and cold. Subsequently, four of the CFRP-prestressed beams along with five unbonded stressed CFRP specimens will be subjected to 300 freeze–thaw cycles following ASTM C666. Residual strength after freeze–thaw exposure will be assessed by testing the prestressed beams to failure under a flexural loading configuration and the CFRP specimens through a uniaxial tensile test setup. The results show that due to the difference in the coefficient of thermal expansions for concrete and CFRP, the temperature change caused a fluctuation in the level of the prestressing force in the CFRP-prestressed beams. This fluctuation in the prestressing force should be estimated and implemented in the design of CFRP-prestressed beams that are exposed to temperature fluctuations during service, such as bridge beams. In addition, exposing the CFRP-prestressed beams to freeze–thaw cycles resulted in a reduction in their flexural strength of approximately 7.5%. The reduction in the strength was triggered by the deterioration in the concrete strength and a change in the mode of failure. However, the mechanical properties of CFRP strands were not adversely affected.