Electrical resistivity of partially-saturated alkali-activated slag containing sodium nitrite admixture

Abstract

Electrical resistivity is a key durability indicator for evaluating the mass transport properties of cementitious materials particularly in partially-saturated states. In this work, the electrical resistivity of alkali-activated slag (AAS) with and without incorporation of sodium nitrite admixture, over a broad range of relative humidity (RH), is analyzed and compared to ordinary Portland cement (OPC) pastes. The van Genuchten equation and Archie equation are used to model the dependency of electrical resistivity of AAS on RH, degree of saturation, and pore structure parameters. The results show that at relatively high RH conditions (>58%), the electrical conductivity of AAS is significantly affected by the pore structure and conductivity of pore solution. At relatively low RH (<58%) conditions, the electrical conductivity of AAS is dominantly governed by the amount of adsorption water of reacted phases. Besides, the incorporation of sodium nitrite has multiple effects on the resistivity of AAS and OPC pastes, including provision of extra conductive ions in pore solution, pore structure refinement, and improvement of the water-binding capacity of reacted phases.