Types of formwork – Usage, pros and cons, impact on the economy
The use of the formwork method dates back to the time when concrete earned a position as a suitable building material. Formwork, ordinarily known as shuttering or moulding, refers to the type of casing or moulds used for creating the required shape of a structure in construction. It serves as casting cases or dyes for the ready-mix concrete until it attains sufficient strength to bear the desirable weight (both dead and alive). The concrete structural components poured into the moulds in its viscous state shapes itself as per the model formwork. Being one of the initial steps of construction, assembling of formwork takes time and involves a cost of at least 20-25% or above of the whole budget.
There are various types of formwork available in the market. Steel, plastic, and timber formworks are few of the top listed options in the category, while Aluminium Formwork trumps the rest in terms of demand and popularity in the market. Re-usable plastic, permanent insulated fibre, and fibreglass are few other variants of formworks consumed by the construction industry. Due to the availability of different types of formwork in the construction industry, the choice is made based on the primary parameters like convenience in designing, fabricating, erection, and dismantling. And since aluminium formwork techniques can be conveniently mastered in all these domains, its demand has been on the rise lately.
The selection of formwork depends on the following factors:
Here is a list of the different types of formwork materials that are readily prevalent in the industry:
1. Aluminium Formwork: Aluminium formwork has taken an edge over other formworks in the modern construction industry due to the extensive benefits it has to offer. Better completion timeline, quality management, and reliable performance are some of the perks of using aluminium formwork. It is used widely in India for residential units and mass construction projects. This type of formwork is suitable for requirements of tailor-made formwork for cast-in-situ concrete structures. Let us have a look at the pros and cons related to uses of Aluminium formwork.
- Advantages of using Aluminium Formwork:
Economy: The overall costing per square feet of Aluminium formwork is much less as compared to other conventional types of formwork materials due to high reusability factor. The erection process can be executed even by the unskilled labour force, without incurring high costs of hoisting cranes or lifting equipment.
Time: Features like easy mobility, adaptability, no plastering, and simultaneous casting of slab/walls reduce the construction time to 2/3rd of total time.
Eco Friendly: Zero usage of timber, manifold reusability make its environment friendly. The resulting structures are earthquake resistant.
Finishing: Superior wall finish saves finishing time and cost of plastering material.
Others: Custom designing, reusability in case of repetition of floor layouts, monolithic crack free structures, low maintenance.
- Disadvantages of using Aluminium Formwork:
Architectural modifications of the structure are not possible after fabrication.
The initial cost can be over budget in case of a small project.
The precision in alignment and safety standards requires a short training for labours to get equipped with the whole process. It is not a big challenge with Aluform technology though.
2. Steel Formwork: Steel formwork consists of thin steel plates panel stiffened at edges with the help of small steel angles. Steel formwork is a semi-traditional form used in case of large projects, with pre-planning of reusing the formwork material. Steel structures provide strength and durability in the form of finishing and no shrinkage in formwork. Steel formwork is used extensively for the construction of circular or curved structures. Massive projects like dams, bridges, tanks, chimneys, sewer tunnels require super strong structures, attainable from the steel formwork. Here are some of the pros and cons faced while opting for steel formwork over other types of formwork in construction.
- Advantages of using Steel Formwork:
Strength: The weight-bearing capacity and metal strength support gigantic structures.
Durability: Steel formwork is durable and has a longer life with excellent reusability. It does not warp or shrink and can be recycled.
Fabrication: Steel structures are easy to install and dismantle.
Finishing: The finish on the concrete is smooth and without any honeycombing.
Others: No moisture absorption from concrete, better exposed concrete surface, need lesser volume.
- Disadvantages of using Steel formwork:
Economy: The steel formwork is better suited for large budget projects due to high material costs.
Weight: This formwork is heavy and requires the assistance of machinery and lifting equipment.
Corrosion: The maintenance of steel from corrosion due to excess water contact is necessary for durability.
Limited moulding: The steel formwork has restricted shapes and sizes.
3. Plastic Formwork: There has been a visible rise in the popularity of plastic formwork in recent times. Plastic formwork has superiority over other types of formwork in terms of finish, customized designs, and negligible maintenance. The formwork gives the flexibility to create unusual designs and textures. Glass reinforced plastic, fibre-reinforced plastic, and thermoplastics are some of the trending types of formwork materials. Manufactured from a specific class of plastic, it prevents reaction due to chemicals in poured material, resulting in a clean finish on the reinforced concrete element.
- Advantages of using Plastic formwork:
Cost Efficiency: Plastic formwork is highly cost-effective in terms of reusability, low maintenance, and minimal efforts for installation.
Designing: It gives independence in the form of complex shape structures, intrinsic designs.
Weight: It is remarkably lightweight and easy to handle.
Break free: Plastic formwork is resealable with a hot air gun in - situ in case of breakage.
Others: Water-resistant, easy to erect and dismantle, recyclable, and excellent finishing.
- Disadvantages of using Plastic Formwork:
Requires pre-planning and designing as field fabrication is not possible.
Depending upon the class and durability of the chosen plastic material, it can be a little expensive.
Requires special attention to heat damage from accelerated curing of concrete poured into the formwork.
Lesser load endurance than other types of formworks in construction.
4. Timber formwork: It is the most traditional formwork that has been in use since ancient times. As timber has been in use since the beginning, the construction of the framework is well known to the labourers. Timber formwork is adaptable to changes on the site, hence provides flexibility in design changes after planning also. It is the most economical formwork among different types of formworks in construction. Usually, timber forms of plywood, planks, or joist are prevalent in the formwork market. Here is an overview of the pros and cons of traditional timber formwork.
- Advantages of using Timber Formwork:
Economy: Timber formwork is economical for low budget and small construction projects. The requirement of skilled labour is low. Among various types of formwork material, timber is one of the least costly.
Weight: Timber is light in weight and does not require heavy lifting equipment.
Thermal Insulation: For its heat resistant quality, timber is very suitable for cold regions, to protect concrete from any damage due to low temperature.
Designing: It is easy to craft designs and shapes with timber.
Others: Easy erection and dismantling, no splitting due to nails, and easy replacement of damaged parts.
- Disadvantages of using Timber Formwork:
Improperly cured timber may absorb water from concrete and reduce structure strength.
High moisture timber can cause cracks in concrete member and lead to leakage in joints.
The life of timber is not long, low reusability, and not environment friendly.
Economic Impact of Different types of formwork in construction
The construction industry comes only second to the agriculture industry in its size and employability.
There has been a drastic surge in the use of Aluminium in the construction industry. Make In India initiative and Smart City schemes, have pushed the demand for the Aluminium to a next level high. The support of the government has accelerated the use of Aluminium in the formwork and infrastructure sector. Increased number of the high rise, clustered, and symmetrical projects at lower costs have given an open market for the use of Aluminium as the prime formwork material. The steel industry is a significant part of the Indian economy, also termed as the backbone of the economy. The contribution of the Steel industry is directly proportional to GDP. Therefore with the growth of Megaprojects and skyscrapers, steel formworks will be in fluent demand. The plastic industry has seen double-digit growth in the past year in the country. The technological advancement with Plastic formwork in construction has given an extended new market for plastic industry other than traditional needs for pipes, wires, waterproofing membranes, etc. A strong stand for eco-friendly, environment-supporting, and sustainability practices have reduced the market for timber. Being a traditional formwork method, demand for timber formwork has taken a small back foot, limiting it to projects that have a specific need for the same.
Technological inventions and growth have flooded the construction industry with diverse types of formwork material. The need for modern construction practices, flexible and convenient structure shape and size, and other parameters (as discussed above) have become the deciding factors for the formwork in the current competitive market. Currently, government incentives, global market pricing, technological support and quality, and timely rapid completion are the major influencing factors for the selection of formworks in the construction sector.