Title: Estimation of Diffusion Coefficients for Chloride Ion Penetration into Structural Concrete

Author(s): Arvind K. Suryavanshi, R. Narayan Swamy, and George E. Cardew

Publication: Materials Journal

Volume: 99

Issue: 5

Appears on pages(s): 441-449

Keywords: chloride diffusion; concrete; concrete durability; corrosion of steel

DOI: 10.14359/12322

Date: 9/1/2002

Abstract:
The objective of the present study is to identify a simple, reliable, and rational method for evaluating chloride ion diffusion coefficients for civil engineering applications. To make the conclusions of the study relevant to field concrete structures, the chloride penetration data used to estimate the diffusion coefficients were generated using fairly large-sized reinforced concrete slabs subjected to long-term cyclic exposure to a chloride environment. Furthermore, to make the study comprehensive, the parameters influencing the microstructure of the concrete such as water-to-binder ratio (w/b) and supplementary mineral admixtures were included. The simplified linear error-function-based method (SLEM) and Newton-Raphson method estimated almost identical values of diffusion coefficients irrespective of the w/b and the type of mineral admixture in the mixture, while the least square fit method estimated consistently lower diffusion coefficients. On the other hand, the values of diffusion coefficients estimated by the graphical method showed a mixed trend of higher and lower values compared with those estimated by the other three methods. Nevertheless, all four methods employed to evaluate the chloride ion diffusion were unanimous in estimating lower diffusion coefficients for the concrete slabs having mineral admixtures compared to the control concrete slab, and the slab cast with concrete of w/ b = 0.45.