Formwork is Construction is the use of support structure, temporary works built for carrying out the construction of the building. Simply stated ” A Mould into which wet concrete mix can be poured and compacted, set to the inner profile of the shuttering box ” Basically formwork is used for the process of creating temporary mould into which concrete is poured and formed.
Formwork for Concrete Construction, ROOF, Slab
Formwork can be made using molds out of steel, wood, aluminum and/or prefabricated forms. Indian style Traditional formwork is fabricated using timber material, but it can also be constructed from steel, glass fiber reinforced plastics and other materials to strong. It is a vertical or horizontal arrangement made to keep concrete in right position until it gains strength & shape of the structure. Type of formwork in concrete construction RCC is purely depending based on used material for construction and structural components.
Formworks can also be named based on their type of structural member construction such as slab formwork, beam formwork, column formwork etc. it is a temporary structure but highly loaded for a few hours during the concrete placement. The form design, shuttering should be such that it can be erected and disassembled efficiently in order to maximize productivity. But, these are temporary RCC structures that are necessary to support concrete until it reaches a particular level of strength. safety is main important factor while placing. These are Temporary structures required to safely support concrete until it reaches adequate strength. Safety should be the overriding priority of contractors and designers responsible for implementing temporary structures.
Types of load that structures support are:
Dead loads – permanent; including self-weight, floor covering, suspended ceiling, partitions, etc.
Live loads – not permanent; the location is not fixed; including furniture, equipment, and occupants of buildings
Wind load (exerts a pressure or suction on the exterior of a building)
Earthquake loads (the effects of ground motion are simulated by a system of horizontal forces)
Shuttering is the most popular type of formwork and is normally constructed on site using timber and plywood. construct strong enough to withstand all types load bearing capacity. rigidly constructed and efficiently propped and braced both horizontally and vertically, the construction of formwork should permit removal of various parts in desired sequences without damage to the concrete.
Shuttering definition stated that is a vertical temporary arrangement, to bring concrete in the desired shape. Which used for columns, footings, retaining walls is called as Shuttering.
Forms mold the concrete to the desired size and control stability its position and alignment condition. But formwork is more than a mold, safety is important. it is a temporary structure that must supports its own weight, plus the freshly placed concrete, plus construction live loads, dead loads. quality and safety, the economy is basic object in form building. Before starting must sacrificing quality or safety. Size, shape, and alignment of slabs,plinth beams, and other concrete structural elements depend on accurate construction of the forms. Safe and Cost-effective or economical. High Quality is the primary objective for frameworks.
Material which used for formwork should be cheap,budget friendly easily available and should be suitable for reuse option. The formwork should be set accurately to the desired line and levels should have plane surface. It is used when the labour costs are lower than the cost of producing re-usable formwork from materials such as steel or plastic. for economical wise, Steel forms are used in situation where large numbers of re-use of the same forms are necessary. as well Fibre glass made of precast concrete and aluminium are used in cast-in-situ construction such as slabs or members involving curved surfaces. The formwork design aims at designing a form that is strong enough to handle the calculated loads safely and stiff enough to maintain its shape under full load.
Formwork Failure Reasons:
Improper Stripping inline
Unstable soil conditions
Inadequate Control of Concrete Placement
lack of Attention to formwork
Strong enough to take heavy loads, with stand all external loads. strong to carry the full load and external side pressure from freshly placed concrete,
together with construction
Deflections should be minimum range
Formwork material should not warp or get distorted when exposed to the elements
Light in weight
Joints should be stiff and strong. Lateral deformation is minimum leak.
It Should be partially waterproofing, so that it should not absorb water from concrete
Swelling and Shrinkage should be minimum
Formwork for beams, columns are varied. for beam it takes the form of three-sided box, it supported and propped in the correct stable position to the structure desired level. for column, it just a vertical mold of the desired shape. as means it keeping the formwork material thickness to minimum horizontal steel or timber clamps. always columns formwork can be used to provide support for beam formwork. for both removal time for the formwork will vary with air temperature, humidity and consequent concrete curing rate.
Formworks can be grouped into three types
- Elementary type of formwork.
- Standard formworks.
- Special formwork.
Material for Formwork Construction. Among the material that can be used for construction of shuttering
3) Glass Reinforced Plastic
Timber material is cant be used for long. it can only be reused for 5 or 6 times only. Timber with high moisture content, wet concrete will shrink cup leading to open joints and leakage of grout. Timber can be used for long, have limited for re-use. Timber used for shuttering for exposed concrete work should have smooth and even surface on all faces which come in contact with concrete. Timber is Most common material used for bracing the member, hence called as the traditional formwork.
Advantages of timber Formwork
Its Economically more advantageous, Design friendly construction works
Easy to handle and adjust to the desired shape with structure
Damaged parts can be replaced and reused for any type of construction.
Disadvantages of timber Formwork
as we know, It is not strong enough to bear large loads/ weight and external loads
Concrete materials such as concrete can leak.
Plywood formwork mostly used in roof, floor and wall sheathing. Plywood is widely used for job built forms and prefabricated form panel systems. Strength matters, Plywood is pieces of wood made of three or more layers of veneer joined with glue and usually laid with the grain of adjoining plies at right angles. Structural components, gusset plates and concrete formwork mainly used for plywood frameworks. It is possible to have a smooth finish in which case on cost in surface finishing is there.
Advantages of Plywood Formwork:
Cost, Labor and time setting can be reduce due to larger boards
Various thickness are available in the market, suitable for all type of structure shapes
Large size boards are economically advantageous.
Disadvantages of Plywood Formwork
Low durability, water and collision can separate the boards.
It is expensive compared to Timber.
Very use simple forms, Steel forms are stronger, durable and have a longer life than timber formwork and their reuses are more in a number of construction structures. Steel forms can be installed and dismantled with greater ease and speed. Formwork designed as per shape, quality of exposed concrete surface by using steel forms is good and such surfaces need no future treatment. The panels can be fabricated in large number in any desired modular shape or size. Steel shuttering is considered most suitable for circular or curved structures. The main disadvantages of steel formwork, Standard steel unit is very heavy and difficult to handle.
Related Words: Scaffolding, Staging, Centering and Shuttering.