Active Protection of Reinforced Concrete Structures by FRP Sheets

Abstract

Reinforced concrete is one of the most commonly used construction materials in civil engineering but its durability problems have been obsessing people. The worst of these problems is caused by corrosion of steel in concrete, inducing the early deterioration of concrete infrastructures. Structural deterioration of reinforced concrete structures affected by corrosion is a gradual process consisting of a few different phases during service life, including corrosion initiation, concrete cracking, excessive deflection and final collapse due to loss of structural strength.

A large number of reinforced concrete structures that have been damaged due to corrosion of steel reinforcements are rehabilitated with fiber reinforced polymer (FRP) composites. FRP offers superior performance such as resistance to corrosion, high stiffness-to-weight ratio, high tensile strength, light weight, high durability and easy installation etc. The present work investigates the progression of corrosion of steel in concrete after it has been treated with surface bonded FRP. Study is carried out with accelerated corrosion through impressed current to get quick results.

The present work also investigates active protection of the steel embedded in concrete that is treated with surface bonded carbon FRP. The electrically conductive carbon fiber is used as anode while the reinforcing bar is used as cathode in the present active protection. Anodic current was passed through the reinforcement in specimens to initiate cracking in concrete. Carbon FRP sheets have been adhesively bonded to the specimens. Specimens were exposed to highly corrosive environment for specified times. The active protection technique is very effective in retarding the corrosion of steel. However, Active (cathodic) protection is one of the efficient technologies that have proven to stop corrosion in existing reinforced concrete structures, regardless of the amount of chloride content in the concrete. This thesis investigates carbon FRP (CFRP) composites for active protection of RC structures by using non destructive monitoring techniques.