Analytical Solution for Chloride Diffusivity of Concrete with Aggregate Shape Effect

Abstract

In view of the key role of chloride diffusivity in evaluating concrete durability, it is very important to determine this parameter accurately by an effective approach. This paper establishes an analytical solution for chloride diffusivity of concrete that can consider the aggregate shape. In this approach, the aggregate shape is simulated as an ellipse and the equivalent model is applied to calculate the chloride diffusivity of equivalent aggregate composed of interface transition zone (ITZ) and aggregate. With resort to this model, at the meso scale, the concrete can be reduced from the original three-phase composition to the two-phase one (i.e., equivalent aggregates and cement paste). Based on the mesostructure of concrete that consisted of randomly dispersed equivalent elliptical aggregates and cement paste, the generalized Maxwell’s approach is formed to determine the chloride diffusivity of concrete. The corresponding chloride diffusion test is conducted and the thickness of ITZ is reasonably determined as 0.04 mm by SEM test. By comparing with the experimental data, the accuracy of the analytical solution is confirmed. Finally, the impact of aggregate shape on chloride diffusivity is discussed. The analytical results show that the chloride diffusivity has a reduction with the increase of aggregate content or decrease of aspect ratio.

Two-Dimensional Microstructure-Based Model for Evaluating the Permeability Coefficient of Heterogeneous Construction Materials

“…It has been found in previous studies that the shape of ITZ is related to many factors, such as aggregate type, particle size, water−cement ratio, etc. [34,35]. Considering that the ITZ only accounts for a small percentage of the total volume of the specimen, in this study, the ITZ was considered to be uniformly wrapped around the exterior of the coarse aggregates.…”

Experimental Investigation and Numerical Model for Chloride Diffusivity of Long-Age Fly Ash Cement Slurry

“…Similarly, Damrongwiriyanupap et al [22] established an analytical method to predict the diffusivity of fly ash cement paste based on the porosity evolution. Based on generalized Maxwell's approach, the analytical methods were proposed to predict the chloride diffusivity of fly ash concrete [23,24]. Although the empirical formula and the analytical method are very convenient to use for the engineers and the calculated results seem to be in good agreement with the test values, the universality of these methods still need to be verified.…”