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Civil MDC

Guide for Maintenance of Concrete Bridge Members (ACI 345.1R-06) 2

Guide for Maintenance of Concrete Bridge Members (ACI 345.1R-06)

Description

Bridges represent a substantial investment of public fundsand are expected to function for many years. United States design specifications typically require a 75- or 100-year designlife, and European specifications require a 120-year design life. Neglecting or delaying bridge maintenance can result inreduced service life and increased life-cycle costs due torepair, rehabilitation, or replacement at an early age. Another consequence of neglecting maintenance is that the condition ofthe bridge can become life-threatening to the public.

When exposed to sufficiently aggressive environmental conditions, structural concrete members will eventually deteriorate and lose strength. Aggressive environmental conditions for bridges involve cycles of freezing and thawing, and cycles of wetting and drying, with or without the presence of chloride. Corrosion of reinforcing steel spalls the cover concrete, reduces the cross-sectional area of there inforcing steel, and therefore, its strength. The time required for deterioration to occur varies considerably, depending on the severity of the exposure conditions and thecharacteristics of the structural concrete. It is believed thatcontinuous and systematic maintenance of a bridge willextend its service life and reduce its overall operating cost.

Bridge deterioration usually occurs slowly at first and isoften overlooked. In later stages of deterioration, however,sudden catastrophic events can occur, demanding immediateaction. Progressive deterioration can be retarded and some-times avoided if proper systematic preventive maintenanceis practiced (Carter and Kaufman 1990). Concrete bridgemaintenance involves relatively inexpensive, repeatableactivities that either prevent or minimize concrete life ofbridge elements or are minor repairs that extend the serviceof the structural concrete members.


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