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Slip-forming is a continuous
construction technique that operates around the
clock forming concrete with the use of moving formwork.
Significant time savings can result using this system.
The system uses a shallow form, purpose built to
the concrete profile required, that is continuously
lifted using an hydraulic jacking system.
The form shutter is supported by the slip form rig
that also lifts as the pour progresses. |
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Slip-form rig being prepared |
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The
lifting rate (or speed) of rig is determined by
the slip-form technician and is based on speed
of the placement of the concrete and reinforcement
as well as the setting time of the concrete.
Careful monitoring of the position of the slip
form allows the hydraulic jacking system to control
of the plumb of the finished concrete.
The design of the slip form allows for any twisting
to be countered.
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Openings
with varying wall thicknesses and cross-sections
can be accommodated and all contribute to
an acceptable lifting rate.
The slip-form rig typically comprises three
levels of working:
1) Upper reinforcement deck
2) Working deck
3) Lower rubbing up deck |
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1) Upper Reinforcement Deck |
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The reinforcement deck is the uppermost
deck on the slip-form rig and facilitates
the fixing of the reinforcement.
Some slip-form rigs combine the reinforcement
deck with the middle working deck. |
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The working deck is the main deck of the slip-form
rig. Typically this deck will support the hydraulic
jacking system and provides the working platform
from which to place and compact concrete.
It is important that the concrete is placed in even
layers around the formwork shutters. The control
of the concrete quality, supply and setting rate
is vitally important for slip form operations. |
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The rubbing up deck is located under the working
deck and provides access to the faces of the poured
concrete as they emerge from the underside of the
shutters.
The concrete is made good from this deck to provide
a smooth surface finish. |
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