Standard Test Method for Determination of Bulk Resistivity Index of Mortar Cubes using Bulk Electrical Resistivity Measurements

Abstract

5.1 The electrical resistivity of a mortar specimen represents the opposition to the transport of ions in the pore solution of the mortar under an applied electric field. A higher resistivity is indicative of a lower rate of transport such as permeability. The measured electrical resistivity depends upon the pore volume, the pore structure (that is, pore size distribution and connectivity), the pore solution composition, the degree of saturation of the mortar specimen, and the specimen’s temperature. Mortar mixture characteristics that are known to affect electrical resistivity, as well as resistance to fluid penetration, include water-cementitious materials ratio, supplementary cementitious material content, the presence of polymeric admixtures, air-entrainment, aggregate type, aggregate volume fraction, degree of consolidation, curing method, and age. Note 1: The bulk resistivity values of mortar cubes should not be considered to be indicative of the potential bulk resistivity of concrete. 5.2 The bulk resistivity index is a relative indicator of the change in porosity, pore size distribution, pore connectivity, and pore solution composition for a mixture containing supplementary cementitious materials, compared to that of a control cement mixture. Note 2: The bulk resistivity index provides an indicator of the reduction in the rate of fluid ingress provided by a supplementary cementitious material. 5.3 This test method is performed on mortar mixtures prepared in accordance with the procedure given in Practice C305, then cast and cured according in accordance with Test Method C109/C109M, immediately prior to testing for compressive strength. 5.4 This test method can also be used to assess the changes in pore structure after different times and temperatures of curing.