Variability Analysis of the Bulk Resistivity Measured Using Concrete Cylinders

Abstract

Prepared in cooperation with the Indiana Department of Transportation and Federal Highway Administration. Abstract. Many agencies are interested in using a rapid test method for measuring the electrical properties of concrete (i.e., the resistivity or conductivity) since the electrical properties can be related to fluid transport (e.g., ion diffusion). The advantage of electrical testing is that it is relatively easy to perform and the test method is relatively fast (less than a minute). Over the last century, many studies have investigated different approaches for measuring electrical properties. This paper describes the variability associated with measuring the bulk resistivity along the longitudinal axis of a cylinder after placing electrod es on either end. A multi-laboratory evaluation was performed using ten laboratories. Data from this evaluation provided variability data for twelve concrete mixtures at testing ages of 28, 56, and 91 days. Information on the variability is important in the development of precision and bias statements for standard test methods. In addition, this work discusses how the resistivity results obtained from this test can be correlated with surface resistivity measurements made using the Wenner probe. A linear agreement was noticed between the Wenner test and the measurement through the cylinder, but with a factor confirmed by previous research by Morris et al. (1996). Additionally, the effect of electrode resistance was discussed and for high resistivity concrete such as that used in much of the transportation infrastructure, this effect appears to be negligible; however, it can be accounted for easily. 17.

Correlation Between Bulk and Surface Resistivity of Concrete

“…It is also observed from Table 4 that theoretical geometric correction factor (2.63) closely matches with average ratios at 28, 56, 91 and 161 days for all cementitious mixtures. Recent study conducted by Spragg et al (2012) also showed similar trend of results for comparison of surface and bulk resistivity at different ages. This relationship of ratio between surface and bulk resistivity actually represents an adjustment factor due to geometric size difference for measurement of electrical resistivity on different sizes of specimens.…”

“…This test can be performed by utilizing conductive medium and needs to be remembered that surface finish needs to be flat as much as possible for proper contact pressure and sponges were used between sample and plates to obtain better contact. Recently, Spragg et al (2012) analyzed variability studies on 12 different cementitious mixtures for BR and SR and correlation was established at testing ages of 28, 56 and 91 days. Additionally, the effect of electrode resistance was discussed.…”

Estimation of Ice Content in Mortar Based on Electrical Measurements under Freeze-Thaw Cycle

“…In this test, we adopted end to end AC two point test and referred to the setup of Spragg et al (2011), as shown in Fig. 2(a).…”

“…Resistance of mortar was calculated based on the method applied by Spragg et al (2011). Since high external pressure was used in this test, there is not much difference between top and bottom sponge resistance and…”

“…Recently, using electrical measurements to investigate the micro-characteristics of cement-based materials has attracted more interest because of its high efficiency and easy application (Spragg et al 2012). It seems also quite promising to use this method to study the frost damage of concrete, especially for the ice formation process (Perron and Beaudoin 2002;Sato and Beaudoin 2011).…”