Slip formwork is a method of construction in which concrete is poured on top of a continuously moving formwork. As the concrete is poured, the formwork is lifted vertically at a speed that allows the concrete to harden before it is free from the formwork at the bottom.
Slip formwork is an advanced method for building large towers or bridges.
Here we will learn about slip formwork, types of slip form & much more.
Introduction to slip formwork:
Slip forming, continuous pouring, continuous forming or slip forming is a construction technique during which concrete is poured into a continuously moving form.
It is used for tall constructions as well as horizontal constructions such as roadways.
Slip forming allows continuous, non-interruption, cast-in-place flawless concrete structures with superior efficiency characteristics to piecewise construction using discrete form components.
Components of Slip Formwork:
Sheathing or vertical forms:
Vertical forms can be wood staves, metal, plywood, glass-fibre reinforced plastic or a combination of this materials.
The function of vertical forms is to shape the concrete.
Wales is also an important component of vertical slip forms supports and holds vertical forms in place.
This transmits the lifting force from the yoke to the vertical forms and other elements of the form.
It also supports various platforms and scaffolding.
Yokes is the component of vertical slip formwork supports the wales at regular interval with their legs.
It transmits the lifting forces from the jacks to the wales and resists the lateral force of plastic concrete within the form.
Jacks is installed on the yoke’s beam, it mounts on the jack rod which provides the necessary force to lift the entire slip form system.
Various platforms, decks and scaffolds complete the slip form system, provides spacee for storage of concrete, reinforcing steel and embedding.
In short, they serve as a work area for placing and finishing
These are climbed up by Jacks.
Types of slip formwork:
1.Vertical slip form system:
The vertical slip form depends on the quick setting properties of the concrete that is required between the initial strength gain and the ability to work.
Placing the concrete into the formwork requires sufficient work to be done practically, it is sufficiently strong to develop the initial strength so that the form slips freshly onto the concrete without any disturbance.
While the concreting process, hydraulic lifters extend the formwork for the entire horizontal projection of a given structure in a continuous sliding motion upward.
Work platforms are permanently attached to the top of the vertical slip form & they are suspended from inside and outside, they are light in weight.
In vertical slip form there is no need to erect and destroy expensive scaffolding.
2.Cantilever Jump Form Method:
In the cantilever jump form slip formwork method, the lifting device is synchronized by electric motors.
This system is that climbers are independent of cranes and attached to a large area of formwork at story height.
In this system, shuttering has already been completed, which is part of the structure between individual levels of climbers.
The cantilever jump form system gives maximum protection, providing a complete self-climbing formwork system that is independent of cranes for walls, columns, supports and floor beers.
For precast floors, cantilever support is easy to install.
3.Egg shape slip form system:
Egg-shape slip formwork is based on the jump form principle that can be adapted to any geometric shape.
If this system circumference changes, the cantilever plate on the periphery is removed or extended, individual curvature adjustment can be obtained by adjusting the axis and vertical circumferential slope.
The system can be adjusted independently on each side of the wall as well as products of optimal working condition, it also shows clear savings in time and personnel costs.
4.Conical formwork system:
Conical formwork is a system by which it is possible to construct structures of varying wall thicknesses and tapering walls.
It is also possible to construct structures whose formwork changes geometrically from angular to circular.
The conical formwork is made up of cantilever plates and overlapping plates, which are fastened to steel yoke frames.
The cantilever plate and overlapping plates automatically adjust the formwork geometry.
It features integrated scaffolding systems consisting of horizontal work platforms that provide an optimal and safe working area for labour, engineers and supervisors.
Uses of Slip Formwork:
- Slip formwork is widely used for constructing large towers or bridges.
- It is also used for constructing silos and grain elevators.
- The technique of slip formwork construction are also been applied for road construction.
It is a construction method in which concrete is poured into a continuously moving form.
The formation of slip formwork depends on the quick-setting properties of the concrete as it requires a balance between quick-setting capacity and working capacity.