Cathodic Protection of Corroded Prestressing Tendon by CFRP 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. Cathodic Protection is a reduction or elimination of corrosion by making the metal a cathode by impressing a DC current. A new development in repair and rehabilitation of RC structures is the use of carbon fiber reinforced polymers (CFRP) which provide a barrier layer that is expected to impede further corrosion of steel and prevents dislodging of concrete cover. Another important advantage of CFRP could be active protection of structures using CFRP wraps as anode and the steel rebar as cathode. The present work investigates protection of the strand achieved by using surface bonded carbon FRP. The electrically conductive carbon fibre is used as anode while the prestressing tendon is used as cathode in the present active protection. To initiate initial corrosion in the specimens, impressed current was passed through the strand. Then, carbon FRP sheets have been adhesively bonded by using conductive epoxy to the block specimens. Specimens were exposed to highly corrosive environment for specified time. It is observed that the active protection technique is very effective in retarding the corrosion of strand.