Formwork

FORMWORK

Formwork is the temporary mold in which concrete is poured to cast the required shape of concrete. For concrete formwork mostly timber and steel are the materials most commonly used for formwork, a range of other materials are used, mainly for specialist applications. The formwork and its associated false work must have sufficient strength to support the weight of the wet concrete without significant distortion. In general, once the concrete has gained sufficient strength, the formwork is removed although in some circumstances it may be left in place (permanent formwork).

TYPES OF FORMWORK

Various types of formwork used in construction are Timber Formwork, Steel Formwork, Aluminum Formwork, Plywood Formwork, Fabric Formwork and Plastic Formwork.

❖Timber Formwork: Timber formwork is the most common type of formwork among all others. Timber forms are extensively used in construction from the ancient period. It is the oldest type of form used in construction. Timber offers onsite fabrication of the required shape and size. It is easily used in any construction but it may prove time consuming for large projects. It is low-cost and easily workable formwork. It can be cut and joined in any shape and size.

Advantages

❖ Timber Shuttering is easy to form any shape, size, and height.

❖ It is proven economical for small projects.

❖ It can make using locally available timber.

❖ Timber is light weighted compared to steel or aluminum forms.

❖ Steel formwork: This type of formwork is more popular due to its strength, durability, and repetitive reuse for a long period. Steel formwork is costly for small work but can be used for a large number of projects. Steel shuttering offers a smooth surface finish to concrete compared to timber formwork. It can be used for circular or curved structures such as tanks, columns, chimneys, sewers, tunnels, and retaining walls.

Advantages

❖ Steel is strong, durable & has a longer life.

❖ It offers a smooth finish to the surface of the member.

❖ It is completely waterproof or moisture-proof and minimizes the honeycombing effect.

❖ It can be reused for more than 100 times.

❖ Steel formwork can be fixed and removed with greater ease.

❖ Aluminum Formwork: Aluminum formwork is almost the same as the formwork made from steel. Formwork done with aluminum is proven economical if large numbers of repetitions are made in construction. Its major drawback is that no alteration is possible once the formwork is constructed. As we know the density of aluminum is less than compare to steel and that makes it light weighted than steel. This is the main advantage when compared to steel.

❖ Plywood Formwork: In this type of formwork, re-molded timber resin- bonded plywood sheets are attached to timber frames to make up panels of the required sizes. It is strong, flexible, and easy to handle. Its lifespan is too short compared to other materials.

❖ Fabric Formwork: With the advancement and new technology trends in building planning and designing, the construction of complex shaped structural members is increased. To satisfy this need the fabric formwork is introduced. The flexibility of fabric formwork makes it possible to produce concrete members of any shape.

❖ Plastic Formwork: Plastic formworks are light weighted, have interlocking systems and can be re-used many times. It can be used for normal concrete construction. This type of formwork is now becoming popular for typical shapes and large housing schemes.

Advantages

❖ Plastic forms are light in weight hence requires less handling cost.

 ❖ It can be utilized in the large concrete section.

❖ With careful installation and use, multiple reuses are possible making it highly economical.

SAFETY CONSIDERATIONS IN FORMWORK

Formwork is made from different materials, and requires great skill and experience in its execution. To produce concrete forms that meet all job requirements, engineer must understand the characteristics, properties, and behaviors of the materials used. The following are the safety considerations in formwork:

❖ Strong: To ensure the safety of the structure and the protection of the workers, it is essential that formwork be designed to carry the full load and side pressures from freshly placed concrete, together with construction traffic and any necessary equipment.

❖ Sound: The materials used to construct the forms must be of the correct size and quantity, of good quality, and sufficiently durable for the job.

❖ Avoid Deflection: Deflection is the most important consideration for design of formwork, the limit for deflection varies according to class of the work. For simply supported spans, this limit is not more than span/360.