Formwork is a term used for the process of making a temporary mold in which concrete is poured and formed. Traditional formwork is fabricated using timber, but can also be constructed from steel, glass fiber reinforced plastic, and other materials.
It must be capable of carrying all dead and live weights other than its own weight.
Here we will learn about formwork, types of formwork & it’s important in construction!
Introduction to formwork:
When the concrete is set, the formwork is removed, and a concrete mass achieves the shape of the inner face of the formwork.
Required properties of formwork:
- It must be strong and resist the pressure or the weight of concrete.
- It must be rigid enough to retain the shape without undergoing deformation.
- Also, it must economical in terms of the total cost.
- They must be sufficiently watertight to avoid leakage at the joints.
Types of Formwork:
Classification based on materials:
1. Timber Formwork:
Timber formwork is one of the most used in the construction industry, fabricated on-site using timber, they are further classified as follows:
It’s commonly available material and has excellent strength, weight and cost factor.
The use of plywood in concrete formworks has improved the quantity of finished concrete.
Advantages of timber formwork:
- Timber can be easily cut to any required shape.
- Timber is light in weight and can be easily handled.
- Timber has good thermal resistance which prevents concrete damage in cold areas.
- Timber formwork can be easily dismantled.
Disadvantages of timber formwork:
- These formworks cannot be used for a very long time, have restricted reuse.
- If the wooden is dry, it should absorb moisture from the moist concrete which may weaken the resulting concrete member.
- Wood with excessive moisture content material, moist concrete will shrink which results in leakage of cup open joints and grout.
The initial cost of steel formworks are higher than that of wood formworks but it can be reused more often.
In the long tenure, it is economical.
Steel or aluminium or magnesium is the most commonly used steel formworks.
Advantage of Steel Formwork:
- These formworks are very strong and capable of carrying loads.
- They are easy to fix.
- It has a similar shape and surface.
- It can be used in greater numbers.
- They are more durable than wood formwork.
Disadvantages of steel formwork:
- They are more expensive than wood.
- As a result of excessive weight, handling is difficult.
- They have limited size and shape.
Plastic formwork is an impermeable surface which usually gives the concrete a smooth finish.
This type of formworks can be reinforced or un-reinforced.
It is lighter but less durable than steel formworks.
Advantages of plastic formwork:
- It is lighter in weight.
- It can be simply cut and nailed with woodworking.
- Damage on the formwork may be simply eliminated.
- They are very helpful for complex-shapes and special features.
Disadvantages of plastic construction:
- It’s costly.
- Their load carrying capacity is low.
- Heat damage to plastics.
Classification based on shape:
Column formwork is made from timber or metal panels.
The box is fixed in position by steel column clamps or fastening yoke, supported by wooden props.
Beam formwork has an open-drawn section and it is not close at the top to provide more support to the structures for restraint on the sides.
Slab formworks normally requires a large area of formworks from beam to beam.
Timber and metal struts can be used for vertical support.
Flexible props are essential for levelling.
7.Wall construction formwork:
Wall construction formwork is extremely low as compared to the other concrete because the actual forces are very low against it.
The panel on both sides has been put in position, the tie is used as a spacer.
Wall support systems are usually sloped at satisfactory intervals.
Formwork construction steps:
In construction of formworks, usually involves the following operations as follows:
- Propping and centering: Built to resist various types of dead and living loads.
- Shuttering: Firmly built and effectively hung both horizontally and vertically to maintain its proper shape.
- Provision of camber: To counteract the effect of deflection, it is desirable to place upward camber in horizontal members of the concrete structure (especially long spanned members).
- Cleaning and surface treatment: The joints in the formworks should have been tightened to remove the leakage of cement grout and t unwanted contaminants from the work surface.
Important of formwork:
Time Management: Good formworks system helps to reduce the floor-to-floor construction cycle time and indirect costs of the project.
Safety: Modern system of forworks provide solutions against all superimposed loads, thus ensures the structural safety.
Besides, they provide proper accessibility and work platform provisions into the system to ensure the safety of the workers.
Quality: The surface finishing of any concrete depends on quality and type of formworks.
The improved surface finish provided by the aluminium formworks excludes the need for plastering for any RCC surface.
Project Planning: Proper knowledge of formwork management facilitates timely utilization and impact of formworks resources, effective set movement, minimizing sluggishness, maximizing reappearance and minimizing costs.
It also helps maintaining time and cost contribution to the tendering process.
Human resources: Special skill sets are required for all levels of personnel involved in formworks.
Therefore proper skill assessment, training and effectiveness tracking are continuous mandatory requirements to maximize labour productivity.
Capital Management: Substantial amount of formworks material owned by any construction company falls under the asset category and goes from one project to another.
Therefore, accounting, physical verification, loss mitigation need to be practiced carefully to avoid unnecessary substantial cost effects.
- The material used to fabricate the formworks should meet the specification.
- The formwork is fixed firmly and correctly.
- The development space needs to be protected to prevent vandalism of the formworks.
- Warning signs need to be positioned within the area where the formwork is mounted to stop the entry of those that may damage the formworks.
- The formworks have to be inspected earlier than pouring concrete.
Also read: Slip Formwork & RCC Framed Structure
The formwork should be made from good quality of material and it should be properly constructed.
The type of material used depends on the nature of construction, availability, and material cost.