Multiple Corrosion-Protection Systems for Reinforced-Concrete Bridge Components: Laboratory Tests

Abstract

Techniques for making epoxy-coated reinforcement more corrosion resistant, including epoxies with increased adhesion to the steel; concrete with a decreased water cement ratio; concrete containing calcium nitrite or one of two organic corrosion inhibitors; bars with a primer coating containing microencapsulated calcium nitrite applied prior to epoxy application; and bars coated with zinc prior to epoxy application are compared based on the chloride content required to initiate corrosion and corrosion losses using the southern exposure and cracked beam tests. The coatings on all bars are penetrated prior to testing to simulate damage in the field. The results indicate that, even when damaged, conventional epoxy coatings result in much higher concrete chloride contents at corrosion initiation and much lower corrosion losses than exhibited by conventional reinforcement. A reduced water-cement ratio, corrosion inhibitors, and the primer coating containing microencapsulated calcium nitrite provide protection in uncracked but less or no protection in cracked concrete. The bars coated with zinc prior to epoxy application exhibit relatively high corrosion rates because of preferential losses to the zinc, and no improvement in corrosion performance is observed for epoxies with increased adhesion.