Factors that Influence Electrical Resistivity Measurements in Cementitious Systems

Abstract

The electrical resistivity of cement-based materials can be used in quality control or service life prediction as an indicator of the fluid transport properties of these materials. Although electrical tests have the advantage of being easy and rapid to perform, several key factors can influence the results: (a) specimen geometry, (b) specimen temperature, and (c) sample storage and conditioning. This paper addresses these issues and compares the measurements from several commercially available testing devices. First, the role of sample geometry is explained with the use of three common geometries: surface, uniaxial, and embedded electrodes. If the geometry is properly accounted for, measurements from different test geometries result in electrical resistivity values that are similar. Second, the role of sample temperature is discussed for both pore solution and uniaxial tests on cylinders. Third, the paper examines the importance of sample curing, storage, and conditioning. Sample storage and conditioning influence both the degree of hydration and the degree of saturation. The role of sample volume to solution volume is discussed, as this ratio may influence alkali leaching and pore solution conduction. This paper is intended to identify factors that influence the results of rapid electrical test measurements and to help identify areas of future research that are needed so that robust specifications and standard test methods can be developed. Standardization will enable electrical tests to provide rapid, accurate, repeatable measurements of concrete's electrical properties.

Early Detection of Joint Distress in Portland Cement Concrete Pavements

“…Furthermore, it is worth mentioning that specific values of resistivity are dependent on a large number of factors that are independent to each pavement, including solution in the pores, degree of saturation, and temperature (Spragg, Bu, Snyder, Bentz, & Weiss, 2013;Spragg, Villani, et al, 2013). As such, specific ranges of resistivity values that will lead to premature deterioration are difficult to establish.…”

“…There has been previous research that has studied the impact of the degree of saturation on electrical resistivity measurements (Spragg, 2013;Spragg, Villani, et al, 2013;Weiss, Snyder, Bullard, & Bentz, 2012). These studies have utilized a correction, or a saturation function, that would allow for the resistivity at any level of saturation to be corrected to a comparative measurement at a saturated state .…”

Saturation of Air Entrained Voids and Its Implication on the Transport of Ionic Species in Concrete

“…This solution was chosen instead of lime water to reduce the effect of alkali leaching on the measurements of electrical resistance Spragg et al, 2013). The equipment used for the uniaxial bulk resistance testing is a Miller-400D digital resistance meter, operating at voltage of 12 V and a frequency of 82.2 Hz, with an accuracy of ±0.01 Ω.…”

Increased Use of Fly Ash in Hydraulic Cement Concrete (HCC) for Pavement Layers and Transportation Structures

“…Instead, an extrapolation from the pore solution resistivity vs. degree of hydration (DOH) curve was performed. These two parameters are linearly related after a certain degree of hydration (Spragg et al, 2013). Estimating the DOH at the different ages mentioned above, it was then possible to calculate the pore solution resistivity, and thus, normalize the results in Figure 4.2.…”

“…Assuming that the sample has homogeneous semi-infinite geometry, the mortar resistivity is described by Equation 3.3 (Spragg et al, 2013):…”