Spatial variability of chloride and its influence on thickness of concrete cover: A two-dimensional mesoscopic numerical research

Abstract This paper mainly studied the spatial variability of the chloride caused by the inhomogeneous mesoscopic structure of the concrete in a numerical simulation approach. To conduct the research, a method to generate the random aggregate structure (RAS) based on elliptical and polygonal aggregates was firstly proposed. Secondly, the governing equation of the chloride diffusion process was numerically solved by the finite element method. Several important issues in this method, e.g, how to explicitly consider the ITZ in the meso-scale model, were discussed. The design method of the concrete cover with the consideration of the spatial variability was proposed as well. The effects of several key parameters related to the mesoscopic structure of the concrete on the degree of the spatial variability of the chloride were comprehensively studied. Based on the results and discussion, the following conclusions were drawn: (1) the influence of the spatial variability of the chloride on the thickness of the concrete cover is significant enough that cannot be neglected in practice even after the consideration of construction error; (2) the degree of the spatial variability of the chloride is not sensitive to the mesoscopic material structure of the concrete; (3) the rebars have a limited influence on the degree of the spatial variability of the chloride provided that the size of the aggregate is comparable to the diameter of the rebar. Finally, a general result on the spatial variability of the chloride was also provided to help design the proper thickness of the concrete cover.

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