Extraction and analysis of bond-slip characteristics in deteriorated FRP-to-concrete joints using a mechanics based approach

Adhesively bonding fiber-reinforced polymer (FRP) composites to reinforced concrete members is a simple and highly effective method to restore strength, increase loading capacities, and extend the service life of structures.With growing demand and wider applications of these strengthening systems, it is their durability that has recently received significant attention from the research community, largely in the form of laboratory testing of deteriorated FRP-to-concrete joints. To develop generalized deterioration factors, a database of shear tests has been collected to quantitatively assess the change in bond characteristics across a number of environmental conditions. It has been identified that a major shortcoming of existing test data is that reporting of the full-range load-displacement behavior is very limited. To supplement existing data, an experimental study is devised to further assess the deterioration of carbon FRP bonded systems under three aqueous conditions. The investigation consists of continually immersing specimens in water, a 5% salt solution, and, for the first time, a sulfuric acid solution of pH 4.0 to simulate the pooling of acid rain. Results show that sulfuric acid attack is most detrimental to the durability of the bond. Then, using a mechanics-based numerical model, bond properties are extracted from the present results as well those in published literature, to determine conservative deterioration factors for the change in bond characteristics with environmental exposure