Electrical Resistivity Testing of Concrete Cylinders: Bias, Precision, and Use in Process Control

Electrical resistivity is increasingly used as a test method to assess the transport properties of concrete. This paper describes an interlaboratory study that was conducted to determine precision and bias for resistivity measurements made in surface and bulk configurations of concrete cylinders. Tests were performed following AASHTO T 358-22 and AASHTO T 402-23. A verification device is introduced with a known resistivity (and impedance) to aid in determining the bias associated with resistivity measurements. However, this device can also be used as a training tool and as a tool to evaluate the qualifications of those new to performing the test. Concrete cylinders were prepared, cured, and conditioned using three methods: immersed in simulated pore solution, sealed, and immersed in lime solution. The samples were tested to determine the precision in the resistivity measurements of the samples for the different curing conditions. The paper discusses how resistivity testing can be used for quality control testing as well as quality acceptance. The results were used to develop precision and bias statements for resistivity measurements, which have been adopted in the latest American Association of State Highway and Transportation Officials (AASTHO) standards.