Nondestructive Evaluation of Epoxy-coated Reinforcing Bars in Concrete Using Bi-electrode Half-cell Potential Techniques

Nondestructive Evaluation of Epoxy-coated Reinforcing Bars in Concrete Using Bi-electrode Half-cell Potential Techniques
Author: Stephen R. Sharp
Publisher:
Total Pages: 30
Release: 2006
Genre: Epoxy coatings
ISBN:

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This study evaluated two half-cell mapping methods for nondestructive evaluation of epoxy-coated rebar (ECR) in concrete: the semi-fixed bi-electrode and the moving bi-electrode methods. These methods were expected to provide early detection of corrosion-related damage and ensure adequate time for repair. The techniques were evaluated by comparing the half-cell measurements using the two half-cell mapping techniques and measurements using the standard half-cell technique. The study found that in concrete specimens the response of both bi-electrode techniques was similar to that of the standard half-cell technique. Each technique was sensitive enough to distinguish between ponded and unponded regions along the Type I test beams. Although additional research is required to determine exactly how sensitive either bi-electrode technique is for assessing corrosion of ECR in concrete, it is clear that the use of any nondestructive tool for condition surveys of bridge decks would benefit VDOT and Virginia. The author recommends that the Type I test beams used in this study continue to be ponded until corrosion is initiated to aid in understanding the benefit of using the two bi-electrode methods during the various stages of corrosion. In addition, the Virginia Department of Transportation's Structure & Bridge Division should identify two structures that are beginning to show signs of corrosion, one bridge with ECR and the other with bare bar, to be used in a field study to determine if either bi-electrode method would benefit VDOT as a condition survey tool.

Corrosion Evaluation of Epoxy-coated, Metallic-clad and Solid Metallic Reinforcing Bars in Concrete

Corrosion Evaluation of Epoxy-coated, Metallic-clad and Solid Metallic Reinforcing Bars in Concrete
Author: David B. McDonald
Publisher:
Total Pages: 146
Release: 1998
Genre: Epoxy coatings
ISBN:

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This report describes the work conducted from 1993 to 1998 to develop cost-effective "new breeds" of organic, inorganic, ceramic and metallic coatings, as well as metallic alloys that can be utilized on or as reinforcement for embedment in portland cement concrete. As part of the study, 12 different bar types were tested in concrete: black bars, 3 bendable and 3 nonbendable epoxies, Type 304 and Type 316 stainless steel, copper-clad, galvanized and spray metallic-clad reinforcing. Measurements of macrocell voltages, half-cell potentials, electrochemical impedance spectroscopy, linear polarization and mat-to-mat resistances were used in conjunction with visual observations to determine the effectiveness of each system.

The Electrochemistry and Characteristics of Embeddable Reference Electrodes for Concrete

The Electrochemistry and Characteristics of Embeddable Reference Electrodes for Concrete
Author: R Myrdal
Publisher: Woodhead Publishing
Total Pages: 39
Release: 2014-01-23
Genre: Technology & Engineering
ISBN: 1845692551

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Using reference electrodes to monitor the electrochemical potential of steel reinforcement in concrete is a well established technique for assessing the severity of corrosion and for controlling cathodic protection systems. This report gives a state-of-the-art overview of the electrochemical and physical characteristics and performance of embeddable reference electrodes for concrete, and the method used for installing them. The report first reviews electrochemical potential and reference electrodes in general. It then assesses the different types of reference electrodes for concrete. Finally, it considers key issues such as location and quality control which need to be considered when installing reference electrodes in steel-reinforced concrete structures. Provides a state-of-the-art overview of the electrochemical and physical characteristics and performance of embeddable reference electrodes for concrete Considers key issues such as location and quality control

An Evaluation of the Performance of Epoxy-coated Reinforcing Steel in Concrete Exposure Specimens

An Evaluation of the Performance of Epoxy-coated Reinforcing Steel in Concrete Exposure Specimens
Author:
Publisher:
Total Pages:
Release: 1998
Genre: Concrete bridges
ISBN:

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The application of a mineral admixture or a combination of a mineral admixture with corrosion inhibitor are the methods used for the corrosion protection for reinforced concrete bridges. The results of a 1.5-year study on evaluation of three concretes with fly ash, slag cement (SC), and silica fume (SF) and one concrete with silica fume and a corrosion inhibitor (SFD) are presented. The specimens were built to simulate four exposure conditions typical for concrete bridges located in the coastal region or inland where deicing salts are used. The exposure conditions were horizontal, vertical, tidal, and immersed zones. The specimens were kept inside the laboratory and were exposed to weekly ponding cycles of 6% sodium chloride solution by weight. In addition, cover depth measurements from 21 bridge decks and chloride data from 3 bridge decks were used, together with laboratory data, in modeling the service lives of investigated corrosion protection methods. The methods used to assess the condition of the specimens included chloride concentration measurements, corrosion potentials, and corrosion rates (3LP). Additionally, visual observations were performed for identification of rust stains and cracking on concrete surfaces. The results of chloride testing indicate that the amount of chlorides present at the bar level is more than sufficient to initiate corrosion. Chloride and rapid permeability data demonstrate that for low permeable (LP) concretes there appears to be significant difference both in a rate of chloride ingress and in the diffusion coefficients in comparison to the controls. Corrosion potentials agree with corrosion rates and suggest the possibility of an active corrosion process development on control specimens during indoor exposure. The structural cracks that were observed in some specimens appeared to have no influence on the corrosion development on the bars in the vicinity of the these cracks. It was concluded that the silicone and duct tape protection was adequate. The cracking, other than structural, appeared to be related to the reinforcing steel corrosion, except the cracks in the horizontal zone of the specimen with slag cement which were probably caused by the subsidence cracking. The least number of cracks was observed on the SF and SFD specimens. Modeling the time as a function of probability of the end of functional service life (EFSL) was presented. It has been shown that the distributions of surface concentrations of chloride ions (C0) and diffusion constants (Dc) are key elements in the model. Model predictions show that the LP concretes provide much better level of protection against moisture and chlorides than the A4 concrete alone. Application of a corrosion inhibitor causes an elevation of the chloride threshold resulting in an additional increase in time to EFSL. Recommendations are to continue monitoring until cracking has occurred in all specimens to a greater extent to better estimate the service lives of LP concretes than is presently known in the construction of concrete bridge components in Virginia. The specimens with LP concretes and one control (continuous reinforcement in the legs) should be taken to the Hampton Road North 1 Tunnel Island and placed in the brackish water to a depth of the immersed zone at low tide for further exposure to chloride. The other control (non-continuous reinforcement in the legs) should remain in an outdoor exposure in Southwest Virginia like the Civil Engineering Materials Research Laboratory in Blacksburg, Virginia. Also more field studies are needed to better estimate distributions of surface chloride concentration and diffusion coefficient of Virginia bridge decks, and to confirm predicted times to EFSL for LP concretes.

Corrosion Evaluation of Epoxy-coated Reinforcing Bars in Concrete Containing Rheocrete 222+ Corrosion Inhibitor for Concrete Reinforcing Steel Institute and Master Builders Technology

Corrosion Evaluation of Epoxy-coated Reinforcing Bars in Concrete Containing Rheocrete 222+ Corrosion Inhibitor for Concrete Reinforcing Steel Institute and Master Builders Technology
Author: David B. McDonald
Publisher:
Total Pages: 38
Release: 1999
Genre: Corrosion resistant materials
ISBN:

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