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.
Highlights
Published: 15 July 2021For civil engineering infrastructure located in a severe natural environment, the chloride diffusion coefficient is one of the important parameters to access the durability and design of reinforced concrete [1,2,3]
Used the electro-migration method to measure chloride diffusivity of concrete with various aggregate contents, and a simple analytical solution based on the single spherical aggregate model was proposed to quantitatively analyze the coupled influence of dilution effect and tortuosity effect of aggregate and the interface transition zone (ITZ) effect [9]
The mesostructure of concrete can be assumed to be composed of a cluster of elliptical aggregates which formed by the specified gradation, an ITZ with a uniform thickness wrapped by the surface of aggregate, and bulk cement paste
Summary
For civil engineering infrastructure located in a severe natural environment, the chloride diffusion coefficient is one of the important parameters to access the durability and design of reinforced concrete [1,2,3]. Used the electro-migration method to measure chloride diffusivity of concrete with various aggregate contents, and a simple analytical solution based on the single spherical aggregate model was proposed to quantitatively analyze the coupled influence of dilution effect and tortuosity effect of aggregate and the ITZ effect [9]. Based on the composite sphere model, an analytical approach was obtained to study the chloride diffusion coefficient. When considering the influence of aggregate shape, the differential effective medium theory was adopted to derive an analytical approximation for the chloride diffusivity of concrete by Zheng et al [19]. Materials 2021, 14, 3957 an analytical solution for predicting the chloride diffusion coefficient of concrete with consideration of the aggregate shape effect needs to be proposed. The effect of aggregate shape on chloride diffusivity is evaluated
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