Types of Formwork Used in Construction
Reinforced concrete is widely used in construction to give structures the strength needed to bear loads and resist forces. It is also used to create building elements, and to do this, concrete is poured into a formwork designed for that purpose.
The formwork is used to hold the poured concrete in shape until it is hard enough and achieves enough strength to support itself. Though most formworks are temporary, it can be permanent. There are different types of formwork used to hold concrete in shape but they are categorized according to the type of material used; the concrete element supported, and either they are removable or permanent.
Material Classification of Formwork
- Timber Formwork
- Plywood Formwork
- Metallic Formwork
- Plastic Formwork
- Fabric Formwork
- Stay-in Place Formwork
- Permanent Insulated Formwork
The timber formwork is fabricated using timber and is widely used in the construction industry. Though it is time-consuming for larger structures, it is quite easy to produce. It is also easy to fix and remove because it is lightweight. The timber formwork is the most flexible type and is suitable for any type of shape and size. Timber is easy to fix and remove. Apart from being lightweight, the timber formwork should be well-seasoned, free from termite attacks and easily workable.
The Plywood formwork is constructed by attaching resin-bonded plywood sheets to timber frames to design the panels of the required sizes. It is more cost-effective than the timber formwork. To make it cheaper, it should have a smooth finishing. Money can also be saved in the labour cost of fixing and dismantling by using large-size panels. The plywood formwork can be reused multiple times compared with the timber formwork.
Metallic formwork comprises of steel and aluminum formworks. Steel formwork has long service life and can be reused multiple times but it is costly. It is useful for multiple projects because it is strong and durable and has long lifespan; it creates a smooth finish on concrete surfaces, reduces honeycombing effect in concrete, is waterproof and easily installed and dismantled.
The plastic formwork can be reused up to 100 times. It requires less handling cost as it is lightly weighted. It can be used for normal concrete construction. It is mostly being used now for similar shapes and large housing schemes. The plastic formwork can be utilized in large concrete section and it is highly economical.
The fabric formwork is used for construction of irregular shape and complex members. It is produced through the use of lightweight and high-strength fabric sheets. It can be used to produce concrete at any shape because of its flexibility.
This type is made from prefabricated fibre-reinforced plastic forms, and assembled onsite. It is used to construct columns and piers. It stays in place once the concrete has set and acts as axial and shear reinforcement which prevents environmental damage such as corrosion and freeze-thaw cycles.
It is one of the most advanced formwork and is permanently insulated to provide additional thermal, acoustic, fire-resistant, and rodent-resistant properties. One of the most common types is Insulating Concrete Forms (ICF) where concrete structures are insulated with polystyrene foam which stays in place after the concrete has cured. Permanent insulated formwork is energy efficient, sustainable, and environmentally friendly.
Structural Classification of Formwork
- Wall Formwork
- Beam Formwork
- Foundation Formwork
- Column Formwork
This has vertically arranged upright timbers to which sheeting boards are nailed at the concrete side. The upright timbers are diagonally braced by means of boards at both sides. There are horizontally arranged walers on cleats situated at every third upright timber. The opposite walers are tied at specified distances. Prefabricated sheeting panels may also be used instead of sheeting boards.
Beam formwork takes the form of a three-sided box which is supported and propped in the correct position and to the desired level. The removal time for this formwork depends on the air temperature, humidity, and curing rate. It takes about 9-12 days to remove the sides; 8-14 days for the soffits, and 15-21 days to remove the props.
The foundation form can be projected in several styles or ways. Usually, the size or the height of the foundation form defines which type of designed it is. Individual foundation form (socket foundation) and strip foundation form, both designs have such difference between them.
The formwork for individual foundations is similar to column form and the form of strip foundations is similar to the form.
Column formwork is utilized for structures that are used to bolster forms or shape for pouring concrete columns. It can be as simple as a strengthened cardboard tube for small cylindrical columns or extremely complex forms built from numerous bits of wood and metal. The structures may be bound with braces on account of columns with flat sides or complex shapes. Now and again, the form is proposed to be left in place after the concrete is poured, and in others, it is evacuated after the concrete has set.