Electrically driven chloride ion transport in blended binder concretes: Insights from experiments and numerical simulations

Citation

Aguayo, M.; Yang, P.; Vance, K.; Sant, G.; Neithalath, N. Cement and Concrete Research 2014, 66, 1-10.

Abstract

Chloride ion transport driven by electrical potential gradients is discussed in concretes wherein OPC is partially replaced by limestone or a combination of limestone and fly ash/metakaolin at replacement levels of 20% or 35% (volume-basis). The ternary formulations demonstrate non-steady state Cl migration (NSSM) coefficients that are comparable to or lower than those of the control OPC concretes, with metakaolin blends showing markedly better performance. A pore structure factor extracted through electrical conductivity measurements before the NSSM test is correlated with Cl penetration depths after the migration test. The transport of all ionic species (Cl, OH, Na+, K+) is modeled using an explicit finite element framework via the coupled Poisson–Nernst–Planck (PNP) equation with suitable consideration of: (a) concentration (depth)-dependent diffusion coefficients, (b) pore-structure factor, and (c) Cl binding. With informed inputs of material properties, the simulations are able to reliably capture Cl penetration behaviors in plain and blended binder formulations.