Bond-slip behavior between ultra-high-performance concrete and carbon fiber reinforced polymer bars using a pull-out test and numerical modelling

Abstract

In the present study, the impact of carbon nanotube (CNT) on the bonding behavior of carbon fiber reinforced polymer (CFRP) and steel rebars in carbon nanotube reinforced ultra-high-performance concrete was studied numerically and experimentally. The finite element (FE) analyses, was used to numerical modelling of the pull-out tests. Mechanical properties of the samples, were extracted from the experimental tests performed on standard samples with different quantities of CNT. In order to consider more realistic assumptions, the interaction and bond between concrete and rebar was simulated using cohesive zone modelling method, whose parameters were obtained by model-updating between the FE models and the experimental pull-out test results. The three-dimensional FE model was validated with the experimental pull-out tests. Then, the effect of the diameter and material of rebar as well as the contents of CNT on the pull-out behavior of bar and UHPC were considered. The results show that for 0.02 wt% CNT the maximum pull-out stress of CFRP rebar with a diameter of 12 mm and 16 mm increased by 176% and 407% compared to the control sample (UHPC without CNT), respectively; also, this increase for steel rebars was 5.7 times and 1.7 times, respectively.