Manual on Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements (2006) / Chapter Skim
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Pages 26-36
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From page 26... ...
Patches usually have a short service life because they do not address the cause of the problem (i.e., corrosion of the reinforcing bars)
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is initiated and sustained when sufficient amounts of chloride ions, oxygen, and moisture are present at the reinforcing bar surface. Therefore, minimizing or eliminating access of one or some of these elements is required to prevent, stop, or retard the corrosion process in concrete.
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. In the late 1980s, a Strategic Highway Research Program (SHRP)
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The test structures were exposed to a very corrosive environment, and the adjacent sound concrete was heavily contaminated with chloride ions. As with nitrites, there are several advantages and disadvantages for the amine-based corrosion inhibitors, as listed below.
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. A study by the Virginia Transportation Research Council found that the service life of LMC overlays applied on several bridge structures in the state of Virginia was about 20 years [62]
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Membranes Membranes are elastic materials applied to bridge decks and are normally used in conjunction with HMA overlays. The main reason for employing a membrane is to provide a waterproof barrier to prevent the intrusion of chloride ions into the concrete deck.
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Sealers and Surface Coatings Concrete sealers and surface coatings are used to prevent chloride ions from diffusing into the concrete. Measures that prevent water from entering the concrete will also minimize chloride intrusion.
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• Surface friction: The surface should exhibit acceptable frictional characteristics after it is sealed. Penetrating sealers, surface sealers, or coatings may be applied to protect superstructure elements.
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. As a result of extensive government and private industry research in the development of cathodic protection systems for reinforced concrete structures, the Federal Highway Administration has stated that cathodic protection is the only rehabilitation technique that has proven to stop corrosion in salt-contaminated bridge decks regardless of the chloride content in concrete [66]
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From page 35... ...
In addition, the structure must be conventionally reinforced and have an expected remaining service life of 5 to 10 years. Chloride extraction is accomplished by applying an anode and electrolyte to the structure's surface and passing direct current between the anode and the reinforcing bars, where the reinforcement acts as a cathode.
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From page 36... ...
. Sohanghpurwala verified the effectiveness of electrochemical chloride extraction on bridge superstructure and substructure elements and on slabs in the laboratory [78]
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