Lowering the cost of corrosion in reinforced concrete bridge decks: Design, management and user cost

Reinforcing bar corrosion in concrete bridge decks causes damage to the deck surface. Correcting such damage is costly, and temporarily interrupts traffic generating user cost. The objective of this research is to examine whether improved corrosion management (CM) can reduce the social cost (direct expenditures and user cost) of reinforcing bar corrosion in bridge decks and how such saving can be achieved. This objective is achieved through the development of a theoretical framework and illustrative analyses of CM scenarios of reinforced concrete bridge deck designs.; A constrained optimization (CO) theoretical framework was developed to explore the problem of CM by examining the interaction among various design and CM alternatives that achieve an output requirement. The CO framework includes both direct and user cost when optimizing design and CM inputs in achieving an output requirement at minimum cost.; The research analyzes deck in moderately corrosive environment and salt loading conditions. Three design options were examined: decks with both top and bottom reinforcing mat plain carbon, epoxy coated or stainless clad steel (concrete quality is excluded from the analysis). We find the cheapest option among those that achieve the service requirement by minimizing the life cycle cost (LCC) of the options (equivalent to minimizing the annualized value).; The research contributed to the analysis method of CM of reinforced concrete bridge decks by (1) applying constrained optimization. This framework provided analytical insight into the interactions and tradeoffs between initial design and CM. Also, (2) our analysis included not only direct cost, but also user costs due to slowed traffic flow, caused by worsening deck conditions, and congestion, caused by CM activities requiring lane closure. Furthermore, the results of the research show that (3) user costs are more significant in determining the LCC then direct costs. The analysis verified (4) the significance of the corrosion resistance of reinforcing bar in concrete on the LCC. The analysis suggests that (5) it is worth to repair the epoxy coating before concrete pouring; (6) inspection is money well spent; (7) deferred maintenance increases LCC; and (8) decks with plain carbon steel reinforcing benefit most from CM.