While designing formwork for RCC Consruction, following points must be considered to achieve a good formwork.
- How formwork can be erected and de-shuttered fast.
- How good concrete quality and surface finish can be achieved.
- What is the optimum stock of formwork required for the size of work force, the specified time schedule and flow of materials.
- What is the overall cost savings that can be achieved using the right type of formwork.
- How SAFETY can be improved for the site personnel.
In order to successfully carry out its function, formwork must achieve a balance of following requirements:
- Containment
- Strength
- Resistance To Leakage
- Accuracy
- Ease Of Handling
- Finish And Reuse Potential
- Access For Concrete Placement
- Economy
Containment
Formwork must be capable of shaping and supporting the fluid concrete until it cures.
Strength
Formwork must be capable of safely withstanding without distortion or danger the dead weight of the fluid concrete is placed on it, labour weight, equipment weight and any environmental loadings.
Resistance to leakage
All joints in form work must be either close fitting of covered with form tape to make them grout tight. If grout leakage occurs the concrete Will leak at that point. Leakages cause honeycombing of the surface.
Accuracy
Formwork must be accurately set out so that the resulting concrete product is in a right place and is of correct shape and dimensions.
Ease of handling
Form panels and units should be designed so that their maximum size does not exceed that which can be easily handled by hand or mechanical means. In addition, all formwork must also be designed and constructed to include facilities for adjustments, leveling, easing and striking without damage to the form work or concrete.
Finish and reuse potential
The form face material must be selected to be capable of consistently imparting the desired concrete finish (smooth, textured, featured or exposed aggregate etc.) At the same time it should also achieve the required number of reuse.
Access for concrete placement
Any formwork arrangement must be provide access for placing of the concrete. The extent of this provision will be dependent on the ease of carrying out the concrete operations.
Economy
All the formwork is very expensive. On average about 35% of the total cost of any finished concrete unit or element can be attributed to its formwork; of this just over 40% can be taken for material for formwork and 60% for labour. The formwork designer must therefore not only consider the maximum number of times that any form can be reused, but also produce a design that will minimize the time taken for erection and striking.