Slipform construction technique is an alternative for conventional formwork system which helps in continuous vertical and horizontal construction. The slipform helps to conduct continuous pouring of the concrete to the moving formwork. The process stops only when the required length of casting is completed.
The features and advantages of slipform construction technique is explained in the below section.
Development of Slipform Construction
The property of cement and concrete to gain sufficient strength to stay in shape once cast within the initial setting time of 30 minutes lead to the development of slip form construction technique. Engineers took this property to develop a moving formwork system so that the concrete can be poured continuously.
The height of the formwork is designed such a way that, during the pouring of the upper level formwork, the concrete poured in the below formwork would have gained initial setting. The concrete exposed when the formwork moves up will remain firm.
Components of Slipform
The slipform system is designed with varied features. Generally, it consist of yoke legs. Yoke legs are employed to lift and sustain the weight of the entire structure, so that it behaves as a single unit. Yoke legs are also used to connect with the beams, scaffoldings and working platforms to serve the supporting purpose.
To the yoke legs, walk-away brackets are connected. These walkway brackets will enable proper placement of the concrete.
The whole slipform assembly is lifted by means of strand rods and lifting jacks. These primary components are located at equal intervals so that the uniform and good distribution of weight is performed. In some construction, lifting process are supported by means of hydraulic pump components.
Features of Slipform Construction
The slipform construction technique is a rapid and a economic construction method compared to the conventional formwork technique. This helps to achieve huge cost saving. The technique is best suitable for large building structures and bridges. When small structures are concerned, the projects with identical geometry can be easily completed by slipform construction.
Continuous movement of formwork in upward direction is performed in slip form technique. The movement is facilitated by hydraulic jacks and jack rods. In the construction of vertical structures, the rate of rising the formwork upwards will be almost in the rate of 300mm per hour. These rise with the help of the supports from other permanent parts of the building.
The technique of slipform construction will vary based on the type of structure constructed. Based on this the frameworks required to support the system will vary.
1. Construction of Regular core high rise structures
The slipform construction technique used in high rise building construction will be performed by vertically extruding the reinforced concrete section. Regular shaped core structures and buildings are easily constructed by this method.
2. Slipform Technique for Chimney Construction
The slipform technique used for the construction of large chimneys, cooling towers and piers are called as tapered slipform. This technique is used for constructing vertical structures with varying wall thickness, or shapes or diameters.
3. Construction of Steel Tanks
Slipform construction technique helps to construct the large volume cisterns in industries and factories in a cost effective way.
4. Construction of Water Towers
The slipform technique helps to construct the walls of water tanks uniformly with better quality. Tanks of thousands of litres are easily constructed by this method.
Advantages of Slipform Construction Technique
- Non-stop Method of Construction
- Increase rate of construction
- Increase the productivity
- Provide more working space
- Creates safe work environment for the workers
- Employs less accessory equipment
- Increase flexibility in construction
- Reduced Labor costs
- Scaffolding and temporary works in construction is reduced
- Uniform wall sections and layouts are obtained
Disadvantages of Slipform Construction Technique
- High –cost for initial setup
- Requires Specialized workers and expertise
- Need sophisticated Equipment
- Dimensional Accuracy can go low in certain conditions