Adoption of Resistivity Tests for Concrete Acceptance

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Title: Adoption of Resistivity Tests for Concrete Acceptance

Author(s): Robert Douglas Hooton and Gita Charmchi

Publication: Special Publication

Volume: 303

Issue:

Appears on pages(s): 269-280

Keywords: electrical resistivity; durability; indicator test; chloride resistance

Date: 6/1/2015

Abstract:
For concrete in severe environments, measurement of its resistance to fluid ingress is fundamental to evaluating its potential durability. As a rapid index of concrete’s resistance to fluid penetration there is interest in standardization of a bulk electrical resistivity test. In this study, tests were conducted on a range of concrete mixtures using a bulk resistivity test as well as the ASTM C1202 coulomb test and the Nordtest NT492 rapid migration test. With the objective of development of a performance-based standard for bulk resistivity, rather than specifying the details of the equipment to be used, a verification cell using precision resistors was used to determine the accuracy of results obtained using three different commercially available resistivity test devices. In addition, the influence of conductive coupling gels or water on the resistivity values were evaluated. The results from the verification cell tests demonstrate that all three commercially available test devices are accurate within 4.5% at low resistivity levels (39 ohm-m) and within 1.0% at higher resistivity levels (390 ohm-m). As well, use of water soaked sponges to couple the concrete to the electrodes gave essentially the same results as when a conductive gel was used. For the concretes tested, exponential relationships were obtained between bulk resistivity and either ASTM C1202 coulomb results (r2 = 0.992) or Nordtest NT492 migration results (r2 = 0.86).