The relationship between the apparent diffusion coefficient and surface electrical resistivity of fly ash concrete

Abstract

Electrical resistivity shows promise in predicting the mass transport of ions in concrete. This could be of great value because of the low cost, speed, and convenience of performing electrical resistivity measurements. This study uses the Nernst-Einstein equation to correlate the apparent iodide diffusion coefficient (Dic) of fly ash–cement paste and the surface electrical resistivity (ρsr) of fly ash concrete of the same age. This relationship is investigated at three different ages for 19 different fly ash sources at 20% and 40% fly ash replacement to the cement. A factor K which shows the correlation between ρsr and Dic is calculated using the Nernst-Einstein equation, and the relationship is evaluated with a regression analysis. While different K factors were found to relate ρsr and Dic, it was not possible to only use one K factor to relate Dic and ρsr for 20% or 40% replacement of fly ash for the materials and mixtures investigated. Despite there not being a single relationship, this work suggests a practical approach to use the ρsr in a specification to obtain a Dic of the desired value or lower.