Electrical Resistivity of King Concrete Repair Products

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Any concrete repair involving a cathodic protection system (impressed current or galvanic anodes) requires the use of repair materials exhibiting low electrical resistivity. In general, normal Portland cement concrete exhibits an electrical resistivity of 15,000 Ω∙cm (ohm∙cm) and a concrete repair material is considered to have a low electrical resistivity when it exhibits a resistivity below this value. The use of a low resistivity concrete repair material is desired in a cathodic protection system as it helps promote ion flow, which is invariably the key mechanism involved in any cathodic protection system. Increased use of cathodic protection systems has lead to requests for data related to electrical resistivity values for concrete repair materials. Therefore, a study was undertaken to determine which King Concrete Repair Products displayed low resistivity characteristics.

The King Concrete Repair Products tested for electrical resistivity can be seen in Table 1, with an accompanying description of each product. Several samples of each King Concrete Repair Product were tested for electrical resistivity, and sample sizes varied depending on the product. It should be noted that the shotcrete core samples tested for electrical resistivity were taken from a shotcrete panel in order to simulate the job-site conditions of shot in place shotcrete. Each sample tested for electrical resistivity was moist cured in laboratory conditions for a minimum of 28 days, and the resistivity values shown represent testing that was performed at a minimum of 28 days after casting. The electrical resistivity testing was performed by a third party organization that specializes in cathodic protection systems using a proprietary test method. The results of the electrical resistivity testing for each King Concrete Repair Product can be seen in Table 2.

After performing this study, it is apparent that several King Concrete Repair Products are acceptable for use in conjunction with a cathodic protection system. King Concrete Repair Products containing silica fume such as MS Shotcrete or MS Concrete mixes will exhibit much higher resistivity values and should be approved by the manufacturer of the cathodic protection system before using.

This report is intended for use as a guide only. Please consult the Technical Services Department of King Packaged Materials Company for further information regarding material selection for a specific application.

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KING's Engineering Services Team offers a variety of specification documents. E-Mail engineeringservices@kpmindustries.com to request these resources.

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