Formwork refers to the temporary or permanent mould into which concrete or other material is poured.
Fresh concrete mix is plastic in nature, so we provide a basic shape or mould into which concrete can be poured and allowed to harden and take shape.
We require formwork in form of scaffoldings, shuttering or falsework to provide the ‘mould’ for concrete such that on hardening it takes the shape of the mould, e.g. slab.
In the construction of the building, the wooden formwork for slab provided at the base, supported by bamboo or another vertical member until towards the floor or ground level is known as formworks.
These formworks can be removed on a permanent setting of the concrete of slab.
Required properties of formwork:
1) Strong and enough to resist the pressure or the weight of concrete
2) Rigid enough to retain the shape without undue deformation
3) Economical in terms of the total cost of the forms
4) Sufficiently watertight to avoid leakage at the joints types of formwork timber.
Different Types of Formwork in Construction:
Depending upon materials:
1) Timber Formwork:
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.
2) Steel Formwork:
The initial cost of steel formwork is higher than that of wood formwork, 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.
3) Plastic Formwork:
They have 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.
Depending upon shape:
A) Column formwork:
This formwork is made commonly either timber or metal panels.
The box is fixed in position by steel column clamps or fastening yoke, supported by wooden props.
B) Beam Formwork:
This 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.
C) Slab Formwork:
This 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.
D) Wall construction:
This 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 by the unions.
The tie is used as a spacer.
Wall support systems are usually sloped at satisfactory intervals.
When concrete is placed in a wall formwork, the pressure exerted by the fresh concrete occurs spontaneously on opposite sides of the formworks.
The economical solution to this problem is to use troops on either side of the formworks as it prevents separation from the use of steel rods called tie rods passing through concrete to connect the two soldiers.
Types of a tie: 1. Non-Recoverable ties 2. Recoverable ties
The supports needed to be maintained overhang and also provide lateral support to the sides.
Generally, metal and timber formworks are used.
Formwork construction steps:
It usually involves the following operations:
Propping and centring: 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 to remove unwanted contaminants from the work surface.
Important of formwork:
Time Management: Good formworks system helps to reduce the floor-to-floor construction cycle time, also saves indirect costs of the project.
Safety: Modern formwork systems provide solutions designed 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 is used by 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 in incorrect time and cost contribution to the tendering process.
Human resources: Special skill sets are required for all levels of personnel involved in formwork activities.
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 practised carefully to avoid unnecessary substantial cost effects.
Frequently Asked Questions:
What is formwork in construction?
Formwork is a term used for the process of making a temporary mold in which concrete is poured and formed.
What are the types of formwork?
1) Timber Formwork.
2) Steel Formwork.
3) Plastic Formwork.
What is the purpose of formwork?
Formwork serves as a mould for concrete structural components until a mould is provided by clay, other structural components, etc.
What is the difference between formwork and shuttering?
Both formwork and shuttering completes the same task, with the main difference being the material used to complete the work.
When should formwork be removed?
1. Walls and columns can be removed after approximately 24–48 hours.
2. Slabs, with props left under them, can usually be removed after 3-4 days.
3. Soffits, with props left under them, can be removed after one week.
4. Props supporting slabs less than 15 feet can be removed after one week.
Conclusion for formwork:
The formwork should be made from good quality of material and should be properly constructed.
The type of material used depends on the nature of construction, availability, and material cost.
In the production of floor slabs, we can use plywood as shuttering instead of wooden planks.