Epoxy coated reinforcement (ECR) has been used in Florida from the 1970s to 1990s but has been discontinued due to the observation of severe corrosion in some ECR bridges after short service times. Corrosion projections have been made in earlier investigations based on corrosion initiation and propagation concepts but did not consider the presence of structural cracks. The current research in progress reexamines Florida ECR bridges after an additional decade of service, to determine if corrosion propagation took place as projected for bridges with high permeability concrete. The corrosion condition of ECR in cracked concrete locations is examined to aid in improving corrosion projection for those conditions. Field survey and laboratory examinations confirmed expectations of active corrosion in bridges with high permeability concrete. In bridges with low permeability concrete, little to no corrosion was observed with one exception. In that case, significant local corrosion was observed at near tide level locations that had relatively wide structural cracks. That corrosion was present despite large concrete cover, high quality concrete, and short service time.
Epoxy coated steel reinforcement (ECR) was used for corrosion control in Florida DOT (FDOT) marine reinforced concrete bridges from the late 1970?s up to the early 1990?s. The use of ECR for new FDOT structures was discontinued upon mounting evidence of severe corrosion in some of the existing bridges. Earlier investigations assessed the corrosion condition of 20 FDOT ECR bridges after ~5-12 years of service1. A model of the corrosion mechanism of ECR in marine concrete was developed2. Corrosion was viewed as resulting from the presence of coating production imperfections (within allowable limits at the time of construction) then aggravated by fabrication, handling, and a severe construction yard environment which promoted coating-metal disbondment3-5. Disbondment was found to become more extended after only a few years of service in the marine structures. Penetration of chloride ions to the rebar level resulted in severe undercoating corrosion, aggravated by extended macrocell formation with cathodes elsewhere in the rebar assembly6-7. Durability prognosis evaluations were formulated based on the research findings and application of an initiation-propagation deterioration model1,4,8. Based on measured concrete permeability properties, the model projected development of corrosion after about one more decade of service in some additional FDOT ECR bridges (a group designated as Category A here), and a lesser likelihood of early corrosion in other bridges with lower concrete permeability (Category B). Several Florida ECR bridges are now at the age of expected corrosion propagation. The present investigation examines the corrosion condition of those structures one decade after the initial projections, to validate and modify those, including introducing allowance for the possible effect of thin structural cracks on early corrosion in low permeability concrete9. A recent paper9 detailed initial findings confirming expectations of corrosion development in two Category A bridges (Vaca Cut and Snake Creek) and little to no corrosion in one Category B bridge (Sunshine Skyway). Additional sites have been investigated since for a present total of three Category A bridges and three Category B bridges.
