Inquiry into bond behavior of CFRP sheets to concrete exposed to elevated temperatures – Experimental & analytical evaluation

Abstract

Efficiency of strengthening with Fiber Reinforced Polymer (FRP) relies on bond properties of FRP to concrete. Exposing concrete to elevated temperatures would reduce its strength. This research is, therefore, aimed at investigating the bond behavior of carbon FRP sheets to heated concrete. To do so, concrete blocks were initially heated up to 300, 400 and 500 °C and then strengthened with FRP sheets. A total of 16 single lap shear tests were carried out. Two-dimensional Digital Image Correlation (2D-DIC) was utilized to measure full-field displacements. Analytical studies were performed as well to evaluate the effective bond length, strain and bond shear stresses. Experimental results showed that exposing concrete to elevated temperatures prior to FRP installation, significantly increased the anchorage resistance. Surprisingly, between 30 and 100% increase in maximum load was experienced for different temperatures. Moreover, slip and effective bond length increased as the preparation temperature increased, contributing to an increased anchorage resistance. Although heating concrete to elevated temperatures would reduce the concrete strength, experimental and analytical results demonstrated that bond properties of FRP-to-concrete improved considerably.