The harden process requires time and includes an expenditure up to 20 to 25% of the cost of the structure or more than that; the temporary design structures are made of economic expenditure.
While the removing process of the framework is known as stripping that can also be used later; the unusable are called panel forms and the non-useable are called stationary forms. The most commonly used material for formwork is Timber.
This article is a short knowledge for people about formwork, the different types of formwork and the basic needs to complete a formwork properly. Formwork comes in several types such as:
1. Traditional timber framework
2. Engineering Formwork System
3. Re-usable plastic formwork
4. Permanent Insulated Formwork systems
5. Stay-In-Place structural formwork systems
6. Flexible formwork
Requirements of Formwork: It is stated above that framework varies as per material and material is the main ingredient for every framework, but for any kind of chosen material the three common principles of quality, safety and economy should be the same. While the quality of material ensures safety and also considerably helps to achieve the economy; any kind of failure in framework can cause of the loss of life and tragic financial loss. To avoid the loss the following guidelines should be followed from start to framing materials and for the associated components:
1. Strength: The strength of material must be sufficient to strong the forces expected and this is the important for both the structural design and safety aspect.
2. Stiffness: the structural movement under load should be small and sure; these deformities and separations are the necessary part of the whole deviations in the formed concrete surface. While planning the formwork system, a designer must take decisions upon the total acceptable variations and the extend workmanship errors and structural deformity. The material stiffness and the workmanship accuracy must be stable to ensure the stability of the total deviations to keep the tolerances.
3. Impact Resistance: The forms are made to make sure that the damaged form that is useless does not make falling debris and to make sure this important safety quality, materials displaying ductile failure are far above than those fail in a hasty and brittle manner.
4. Durability: The framework must be durable either it will affect the economy and the achievement quality concrete product at every reuse of the formwork; formwork is always pre made and used out in the open. When the matter of re-uses came the thing is dependable on its reaction of materials and components with weather and the framing, components and formface materials should be strong in any environment. Material durability is important for both the achievement of good quality concrete surface finishes and safe formwork structures.
5. Weight: While the assembling process in formwork, both the members and components are shifted into position by hand that will be applicable after the complete framework which are heavy and need a crane to do the shifting work. So the framing members, formwork components and formface materials must be keep in size so that they must be carried and lifted by the worker or the crane etc.
6. Accuracy: Every construction process is dependable on a lot of money so the work of lifting and cutting of materials must be done within a minimum amount of money and consistency of size of materials, plywood sheets and framing members is very important.
7. Compatibility: The framework materials should be fitted with either the fluid concrete or the strong concrete and at the formface, the elements of the form materials must not react with the wet cement or concrete.
8. Insulation: Some materials react with the environment if it’s become extra hot or cold, so the protection for the materials is must; if the mix becomes frozen and the chemical bondage damages then the concrete has to be placed at low temperatures, heat the mixing water etc. The placing of the fluid concrete for all forms can cause some damage with the crushed rock aggregate and the proper steps has to be taken to stop it.