Predicting chloride ingression in concrete containing different SCMs based on chloride binding and electrical resistivity

Document Type

Article

Publication Date

2-2-2024

Department

Department of Civil, Environmental, and Geospatial Engineering; College of Forest Resources and Environmental Science

Abstract

The durability performance of reinforced concrete is significantly impacted by the diffusion of chloride. However, accurately predicting chloride ingression in concrete remains challenging due to the complexity and variance in concrete composition and permeable properties. This study aims to investigate the influence of chloride binding on chloride diffusion under rapid chloride migration (RCM) test conditions. Specifically, class C fly ash (CFA), class F fly ash (FFA) and slag cement (SC) are used to partially replace ordinary Portland cement (OPC) for the preparation of paste and concrete samples. The chloride binding isotherms of different binder types are studied by the equilibrium-binding test method and thermodynamic modeling. Results show that with the increase of replacement ratio, SC continuously increases the binding capacity while both CFA and FFA first increase and then reduce the chloride binding. Thermodynamic modeling and X-Ray diffusion analysis confirmed that for aluminum rich SCMs (e.g., fly ash), an optimum replacement ratio exists with the highest chloride binding capacity. Afterwards, modified Nernst-Plank equation with constant and non-constant diffusion coefficients are adopted to simulate the chloride ingression in concrete under RCM test condition. The predicted chloride depth and non-steady state migration coefficient Dnssm are then compared to the NT build 492 test results. Results show that the consideration of non-linear binding significantly improves the prediction accuracy with a higher coefficient of determination R2. In summary, this paper presents a comprehensive investigation into the intricate relationship between chloride binding, saturated electrical resistivity, and chloride diffusion within concrete, particularly in the presence of different SCMs.

Publication Title

Construction and Building Materials

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