Computer Simulation of Apparent Diffusion in Decks with Concrete Overlays

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Title: Computer Simulation of Apparent Diffusion in Decks with Concrete Overlays

Author(s): P. C. Hoffman and R. E. Weyers

Publication: Special Publication

Volume: 151

Issue:

Appears on pages(s): 197-220

Keywords: bridge decks; chlorides; computer simulation; diffusion; latex-modified concretes; microsilica; resurfacing; service life; slump; Structural Research

Date: 7/1/1994

Abstract:
A computer simulation study of the penetration of chloride through concrete bridge decks with overlays was undertaken. The chloride transport was modeled as apparent diffusion. The apparent diffusion approach was based on the analyses of chloride concentrations obtained from field measurements. Part of the field data included untreated concrete decks and decks overlaid with latex-modified concrete, low-slump dense concrete, or microsilica concrete. The overlay field data was limited in number and repair details. In particular, the overlay data base did not include three significant details: the amount of original deck material removed, the thickness of the overlay placed, and the resistance to chloride penetration of the overlay material versus the original deck material. Consequently, a computer simulation was used to investigate the impact these three repair details have on enhancing the service life of a deck repaired with an overlay. Quality of material was defined by the apparent diffusion constant, a measure of the resistance to chloride penetration. The ranges for apparent diffusion constants were estimated from the overlay data base. Service life was defined as the time required to reach a critical chloride threshold level.