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Researchers:
John Breen
Sharon Wood
Graduate Students:
Sean Maclean
Gregory Turco
Sponsor: Texas Department of Transportation
(TxDOT), FHWA, DOT
Project Summary
Emulsifiable oils are used in
post-tensioned construction to provide temporary protection for
strands in tendons during the period between stressing and grouting
of the tendons. It has been common practice in the past to flush
tendons with water to remove the emulsifiable oil prior to grouting.
Compressed air is generally used to remove any remaining water in
the ducts, and it has been assumed that any remaining water will
be ejected from ducts by the advancing grout flow during the grouting
process. Recently, significant voids, pockets of water, and corroded
strands were discovered in grouted post-tensioned tendons of numerous
U.S. bridges. Because it is not certain that water from flushing
is completely removed with the compressed air or during grouting,
the recent discovery of corrosion in grout voids in tendons strongly
suggests that the practice of using water to flush emulsifiable
oils from tendons should not be continued. Leaving emulsifiable
oils in post-tensioned tendons before the tendons are grouted will
most certainly affect bond strength of the tendons. In addition,
it is already known that emulsifiable oils affect friction losses
in tendons during post-tensioning. The proposed research program
will identify oils or other products that will provide temporary
corrosion protection in post-tensioned tendons, investigate how
these oils affect friction losses during post-tensioning, determine
the impact emulsifiable oils have on bond strength of multi-strand
tendons, and examine how flexural capacity is affected by the expected
loss in bond strength.
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