Electrochemical reactions for steel beams strengthened with CFRP sheets

This paper presents the effect of electrochemical reactions on the physical and chemical responses of steel beams strengthened with carbon fiber reinforced polymer (CFRP) sheets. An accelerated corrosion protocol is used to deteriorate the strengthened beams. An emphasis is placed on the electric potential, mass loss, corrosion current density, corrosion rate, flexural capacity, interfacial strain development, failure mode, and infrared spectroscopy of the beams. Corrosion damage is dispersed with increasing electrochemical reaction time; however, premature CFRP-debonding is not observed. The presence of surface rust tends to impede the flow of electric current and the diffusion of iron ions is reduced, thereby decreasing the rate of corrosion. The consequence of corrosion damage results in a decrease in load-carrying capacity of the strengthened beams along with two phases, such as initiation-propagation and steady-state. The electrochemical effect alters the pattern of CFRP-debonding from discrete-discontinuous to smooth progression. Infrared spectroscopy illustrates that the functional group of the CFRP system changes from a chemistry standpoint as the degree of corrosion augments. Design recommendations are proposed to facilitate the use of CFRP-strengthening for steel members subjected to corrosive service environments.