Using Twist-off Method for Measuring CFRP/Concrete Adhesion when Exposed to Cyclic Temperature Changes, Wet-Dry and Freeze-Thaw

Abstract

Materials such as fiber-reinforced plastics (FRPs) are lightweight, strong, and for the most part, non-corrodible. Hence, the use of FRPs as retrofitting materials for concrete represents a viable, durable alternative to conventional practice using reinforcing steel. This paper addresses the magnitude of the residual shear bond strengths between rigid and flexible carbon fiber reinforced plastic (CFRP) sheets and substrate concrete, after being subjected to cyclic temperature changes, wet-dry and freeze-thaw, by means of a Twist-off method. In the experimental investigation, the shear bond strength of a number of CFRP/concrete specimens was monitored. These results were then used to make comparisons between the behaviors of the two types of CFRPs. Analysis of the results indicated that while 180 freeze-thaw cycles destroy the shear bond strength of rigid and flexible CFRP completely, the same number of wetting and drying and temperature change cycles can reduce these bonds by up to about 30 and 20%, respectively. The results also showed that despite the insignificant flexible CFRP failure, the failure in the rigid CFRP material was noticeable.