Resistivity, Penetrability and Porosity of Concrete: A Tripartite Relationship

Abstract

Abstract Demands for using electrical resistivity techniques (surface and bulk resistivity) as an alternative to the rapid chloride penetrability test (RCPT) have been growing, for example by a number of transportation agencies in North America, to give an indication of the relative penetrability of concrete. While resistivity measurements may reflect the quality of pore structure in the cementitious matrix, their accuracy might be affected by a multitude of parameters including the concentration of ionic species in the pore solution, particularly when supplementary cementitious materials (SCMs) are incorporated in the binder. Hence, a systematic investigation on the resistivity of concrete and its corresponding physical penetrability is warranted. The main objective of this study was to establish a tripartite relationship (nomogram) to correlate surface resistivity with penetrability (migration coefficient) and porosity of concrete using a wide range of concrete mixtures, taking into account the effect of key mixture design parameters (water-to-binder ratio, air-entrainment, SCMs, and type of cement). Relationships between surface and bulk resistivity as well as migration coefficient and porosity of concrete were also established. In addition, a penetrability classification of concrete based on the corresponding ranges of surface resistivity, migration coefficient, and porosity has been proposed. The efficacy/practicality of the proposed classification was evaluated by comparing the predicted migration coefficient and porosity, based on surface resistivity of concrete, to the measured ones for field cores extracted from concrete pavement in Winnipeg, Canada. For newly constructed and aging pavement, the nomogram and penetrability classification provided reasonable assessment for the condition of field concrete.