Environment-assisted subcritical crack growth in CFRP externally bonded concrete systems

The nation's current state of infrastructure is at an increasing rate of disrepair with new methods of cost-effective rehabilitation being considered over timely and costly reconstruction. Externally bonding carbon fiber-reinforced polymer plates to the tension side of a flexural beam has been one such method that has proven effective and reliable due to the outstanding performance and various advantages in CFRP materials. Gaps in long-term durability studies have been the major reason why this strengthening technique has not seen more success. It is fundamental and crucial that the mechanism of the bond interface between concrete and the strengthening material be thoroughly tested and understood. It is the intention of this study to further increase the knowledge and understanding of the long-term durability of the concrete/adhesive interface while being exposed to various aggressive environments in such externally bonded systems. Firstly, a systematical and comprehensive literature review regarding the use of CFRPs as external reinforcement, the effects of various aggressive environments on the materials being tested, and the application of linear elastic fracture mechanics is presented. An experimental study is conducted using the Boeing wedge test with a digital image correlation technique used to analyze the subcritical crack growth along the concrete/adhesive interface. Results show that subcritical cracking does exist along this interface and its effects can be significant. A theoretical study is conducted to predict the long term debonding behavior by deriving an analytical model based on Euler-Bernoulli beam theory and linear elastic fracture mechanics representing the Boeing wedge test specimen as a double-cantilever beam extending off of a Winkler elastic foundation. A finite element analysis of the test set-up is conducted as verification of the analytical model. Results of this study can and should be included in the long-term durability section to be used as an indicator of maintenance in all future infrastructure rehabilitation plans made at the federal, regional, and state levels. (Published By University of Alabama Libraries