High-temperature pullout behavior of a bond-type anchorage system for CFRP strand tendon

The bonding performance of sand-coated CFRP (carbon fiber reinforced polymer) strand tendon-UHPC (ultra-high performance concrete) interface under elevated temperature ranging of 25∼210 °C was experimentally investigated in the present study. Effects of target temperature, bond length and anchoring method on the bonding performance of CFRP strand tendon-UHPC interface were identified and quantified. The difference between high-temperature bond-slip behaviors of sand-coated CFRP strand tendon-UHPC and ribbed CFRP tendon-UHPC interfaces was also uncovered. Theoretical models were developed for determining average bond strength of CFRP tendon-UHPC interface and critical bond length of CFRP strand tendon under high temperature. The obtained results indicated that debonding of sand coating layer from core region of tendon was the dominant failure mode for all test bond-type anchorage systems. The average bond strength of CFRP strand tendon-UHPC interface significantly decreased by 82.4–94 % under glass transition temperature T_g of tendon (210 °C). The bearing capacity of the bond-type anchorage system for CFRP strand tendon under temperature below 100 °C can be greatly improved by applying the dispersion anchoring method, while the benefit diminished as temperature increased to 210 °C. The sand coated CFRP strand tendon-UHPC interface has lower average bond strength than the ribbed CFRP tendon-UHPC interface under both ambient and high temperatures.