Abstract
Modeling approach for mesoscopic model of concrete depicting mass transportation and physicochemical reaction is important since there is growing demand for accuracy and computational efficiency of numerical simulation. Mesoscopic numerical simulation considering binder, aggregate, and interfacial transition zone (ITZ) generally produces huge number of DOFs, which is inapplicable for full structure. In this paper, a two-dimensional multiscale approach describing three-phase structure of concrete was discussed numerically. An effective approach generating random aggregate in polygon based on checking centroid distance and intersection of line segment was introduced. Moreover, ITZ elements were built by parallel expanding the edge of aggregates on inner side. By combining mesoscopic model including full-graded aggregate and macroscopic model, cases related to diffusivity and width of ITZ, volume fraction, and grade of aggregate were studied regarding the consideration of multiscale compensation. Result clearly showed that larger analysis model in multiscale model expanded the diffusion space of chloride ion and decreased chloride content in front of rebar. Finally, this paper addressed some noteworthy conclusions about the chloride distribution and rebar corrosion regarding the configuration of rebar diameter, concrete cover, and exposure period.
Highlights
Corrosion of rebar induced by chloride ion could significantly deteriorate the serviceability of concrete structures [1]. e protective film of rebar was depassivated by chloride ion penetrated from surface of concrete and corrosion of rebar initiates once the chloride content on surface of rebar reaches a certain thresholding value, defined as critical chloride content
In the view of mesoscopic numerical simulation, concrete was recognized as the heterogeneous composite of three phases, including cement paste, aggregate, and interfacial transition zone (ITZ) [2]
ITZ was identified as a fine cement paste zone enclosing aggregate and rebar, providing higher water-to-cement ratio, higher porosity, and lower cement content compared with normal bulk cement paste regions
Summary
Corrosion of rebar induced by chloride ion could significantly deteriorate the serviceability of concrete structures [1]. e protective film of rebar was depassivated by chloride ion penetrated from surface of concrete and corrosion of rebar initiates once the chloride content on surface of rebar reaches a certain thresholding value, defined as critical chloride content. In the view of mesoscopic numerical simulation, concrete was recognized as the heterogeneous composite of three phases, including cement paste, aggregate, and interfacial transition zone (ITZ) [2]. Mortar plus smaller aggregates embedding coarse aggregate was discretized into finite elements by free meshing [20, 24] or uniform background grid [25,26,27] Another major factor for durability of reinforced concrete structures is corrosion of steel rebar. By means of the multiscale numerical simulation tool, the influence of ITZ on diffusion of chloride ion within concrete in mesoscale was studied in detail, where ITZ was modeled as an individual phase in FE model for chloride diffusion in concrete. The corrosion of rebar in straight edge of concrete induced by diffusion of chloride ion was calculated to study the time evolution of corrosion process
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