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Ducts
In everyday life the term “Duct” is used for any pipe, tube, or channel by
which a fluid or other substance (like electric
power line, telephone cables, or other conductors) is conducted or
conveyed.
In context of prestressing
(particulary post tensioning) this duct
is normally formed by spiral-wound corrugated sheet metal, corrugated plastic
tubing, metal pipe, or plastic pipe. This duct forms a conduit to accommodate
post-tensioned element ( like strands etc) and provides an annular space for
grout. This is called as “Prestressing duct”.
Sheathing
The term "Sheath" means a case for a blade (or knife).
The word is used to mean any covering that is applied like or resembles in appearance or
function the sheath of a blade.
"Sheathing" means the material used to sheathe (to case or
cover).
In
context of prestressing (particulary post tensioning) Sheathing is used as a general term for the duct materialsurrounding
the prestressing element to provide corrosion protection or conduit
for installation which also provides an annular space for grout.
Sheathing is a material encasing prestressing steel to prevent
bonding of the prestressing steel with the surrounding concrete.,
provide corrosion protection & contain the corrosion-inhibiting
coating.
Thus
even though literal meanings of “Duct” and “Sheathing” are different from each
other, they mean the same thing in context of prestressing.
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(Transverse & Longitudinal ducts/sheathing) |
References:
1. Prestress Manual by Dept of Transportation, California
2. "What is Post Tensioning?" by Evaluation and certification Service, LLC
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