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Deterioration of
reinforced concrete caused by corrosion of the carbon
steel reinforcing bars (rebar) is a worldwide problem.
The corrosion product, rust, occupies a greater volume
than the original steel bar and this creates a pressure
which causes cracking and subsequent spalling of the
surrounding concrete.
Corrosion of
carbon steel rebar is greatly accelerated when chlorides
are present in the concrete. In some parts of the world,
chlorides may be incorporated into the original mix due
to their presence in the sand, aggregate or water. Most
often, chlorides penetrate through the cover when the
external surfaces of the concrete are exposed to
seawater, marine atmospheres or de-icing salts.
 Several methods
are currently employed in an attempt to reduce the
corrosion of carbon steel rebar. These include:
-
Chloride
Extraction – Chemical sprayed on bridge surface to
extract chloride from the bridge deck.
Requires lane closures and cannot stop the
accumulation of chloride over time.
-
Remove
and replace the top 2-3 inches of concrete – Results
in lengthy lane closures and does not address the
chloride that is deeper in the concrete.
-
Cathodic
Protection
-
Increase
Concrete Cove
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Concrete
Coatings/Sealers
 None of these
methods have been proven effective.
The use of
reinforcing materials that have inherently good
corrosion resistance, thus minimizing the need for
maintenance and monitoring of the structure is becoming
more and more essential. Stainless Steel rebar is such a
material. It is being used as a long-term solution in
concrete reinforcing across the USA, Europe, Canada, and
Australia. |
