Rodney G. Powers

Corrosion of Epoxy-Coated Rebar in Marine Bridges Part 1: A 30-Year Perspective

Abstract The corrosion performance over a nearly 30-year service period of epoxy-coated rebar (ECR) in Florida marine bridges is presented. Severe ECR corrosion was noted earlier in several of those bridges, built with relatively high permeability concrete. Corrosion development took place later in some other structures with less permeable concrete, with instances where the corrosion was associated with preexisting cracks. Corrosion was found to be associated with coating imperfections and coating disbondment. Laboratory experiments and modeling indicated that macrocell coupling with remote cathodes was an aggravating factor. Quantitative damage functions relating the observed deterioration with service time of the affected bridges are presented. A predictive corrosion initiation-propagation model was developed and the model output is compared with the field results to identify suitable parameters for forecasting future rehabilitation needs. The prognosis for future corrosion development is discussed, wit...

Corrosion performance of concrete cylinder piles

Abstract Posttensioned concrete cylinder piles produced using a centrifugally cast, vibrated, roller-compacted process have shown promising corrosion resistance in marine environments. Three bridges in the Florida panhandle with ∼40 years in aggressive marine service and one newly constructed marine bridge utilizing concrete cylinder piles were examined. The older marine bridges showed minimal corrosion distress despite a low design concrete cover over the steel hoop reinforcement (2 cm to 4 cm). Typical concrete distress included minor rust staining (not necessarily indicating corrosion of reinforcement steel) and thin longitudinal cracks (likely caused by mechanical damage from pile driving). Chloride ion diffusivity was low, in the order of 1 × 10−9 cm2/s. Other measured parameters such as concrete resistivity, porosity, and water absorption indicate low permeability. Chloride analysis of cracked and uncracked concrete cores from the older bridges in this study did not show pronounced preferential chlo...

SPRAYED-ZINC SACRIFICIAL ANODES FOR REINFORCED CONCRETE IN MARINE SERVICE

Abstract The use of sacrificial anodes consisting of sprayed zinc on the surface of concrete containing corroding reinforcing steel bars was examined infield tests and laboratory experiments. The a...

Corrosion of Epoxy-Coated Rebar in Marine Bridges—Part 2: Corrosion in Cracked Concrete

Abstract The extent of corrosion of epoxy-coated rebar (ECR) in marine bridges was found to be generally correlated with concrete chloride diffusivity, DApp, with significant corrosion observed for...

Localized cathodic protection of simulated prestressed concrete pilings in seawater

Abstract Corrosion-induced deterioration of prestressed concrete pilings in seawater has been established as the predominant failure mode for bridge substructures in coastal Florida waters. A technology involving localized impressed-current cathodic protection (CP) of the splash-zone region in association with conductive rubber anodes was developed to mitigate this deterioration. A series of experiments involving cathodic polarization of simulated prestressed concrete piling specimens partially immersed in seawater was performed. Variables included the concrete mix design, specimen cross section, anode dimensions, and water level. An interactive aspect of CP-operating parameters in association with water level was identified as important if excessively negative potentials and possible tendon embrittlement were to be avoided. The data were evaluated with regard to the interdependence between depolarization magnitude, potential, and concrete relative humidity. Results were reviewed within the context of CP ...

Abating corrosion in highway structures due to sea or deicing salts

Corrosion of steel reinforcing bars in concrete bridge structures due to the intrusion of chloride ions from seawater or de-icing salts affects many structures in the nations highway system. Over the past decade cathodic protection has evolved as a promising technology for arresting corrosion. The development of materials, equipment, and methods for applying cathodic protection is in a dynamic state. Through cooperative efforts with academia, industry, and the engineering community, the Florida Deparment of Transportation has developed several innovative corrosion protection systems which incorporate technologies from a wide variety of specialty areas including telemetry, photovoltaics, polymers, and specialty components developed as part of the national defense program. This paper provides an overview of corrosion and cathodic protection technology and focuses on the potential for adaptation of existing technologies into preservation of highway bridge structures.