United States Department of Transportation
i
Corrosion characteristics of unprotected post-tensioning strands under stress : [summary].
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2014-05-01
[PDF-1.06 MB]
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Abstract:Post tensioned concrete is used in many Florida
transportation structures, many of which are
exposed to fresh or salt water. The steel strands
that supply the tension are encased in a plastic
duct which is later filled with grout, so the strands
are generally well protected from the elements.
However, during construction, strands may
reside in the pipe for a while before tensioning
or grouting. During this time, the strands are
vulnerable to corrosion. Florida Department of
Transportation (FDOT) guidelines specify sealing
the duct to exclude moisture or other harmful
agents from reaching the steel strand. However,
if moisture is sealed in the duct or the duct is
inadequately sealed, corrosion can result. Ideally,
ducts are grouted within hours of stressing, but
there are circumstances that can delay grouting
for days or, rarely, weeks. If damaged, strand
failure can be immediate, or it can mature over
time to produce delayed failure.
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