Construction materials concrete, for its exceptional properties is widely used to create building element. It must be poured into a specially designed mold, which is called formwork or shuttering.
Formwork hold the poured concrete in shape until it hardens and achieves enough strength to support itself and structure material weight. Formwork can be classified in many ways:
- By materials
- By place used
Formwork has a fundamental role in concrete construction. It must have enough strength to bear all the loads present during casting operations, and must then hold its shape while concrete hardens.
Which Are the Requirements for Good Formwork?
Although there are many formwork materials, the following are general performance features to meet the needs of concrete construction:
- Capable of bear weight loads.
- keep its shape with adequate supports.
- Concrete leak-proof.
- Concrete not damaged when removing the formwork.
- Material can be reused and recycled after life span.
- The formwork material should not warp or distort.
Types of formwork by material:
Timber formwork was one of the first types formwork ever used. It is assembled on site and is the most flexible type, easily customized. Its Advantages:
- Easy to produce and remove
- Lightweight, especially when compared with metallic formwork
- Workable, allowing any shape, size and height of concrete structure
- Economical in small projects
- Allows the use of local timber
However, is also have shortcomings: it has a short life span and is time consuming in large projects. In general, timber formwork is recommended when labor costs are low, or when complex concrete sections require flexible formwork, construction structure is not repeated much.
Plywood is often used with timber. It is a manufactured wooden material, which is available in different sizes and thicknesses. In formwork applications, it is mainly used for sheathing, decking and form linings.
Plywood formwork has similar properties as timber formwork, including strength, durability and being lightweight.
Metallic Formwork: Steel and Aluminum
Steel formwork is becoming more popular due to its long service life and multiple reuses. Although it is costly, steel formwork is useful for multiple projects, and it is a viable option when many opportunities for reuse are expected.
The following are some of the main features of steel formwork:
- Strong and durable, with a long lifespan
- Creates a smooth finish on concrete surfaces
- Reduces honeycombing effect in concrete
- Easily installed and dismantled
- Suitable for curved structures
Aluminum formwork is very similar to steel formwork. The main difference is that aluminum has a lower density than steel, which makes formwork lighter. Aluminum also has a lower strength than steel, and this must be considered before using it.
This type of formwork is assembled from interlocking panels or modular systems, made of lightweight and robust plastic. Plastic formwork works best in small projects consisting on repetitive tasks, such as low-cost housing estates.
Plastic formwork is light and can be cleaned with water, while being suitable for large sections and multiple reuses. Its main drawback is having less flexibility than timber, since many components are prefabricated.
Classifying Formwork Based on Structural Components
In addition to being classified by material, formwork can also be classified according to the building elements supported:
- Wall formwork
- Column formwork
- Slab formwork
- Beam formwork
- Foundation formwork
All formwork types are designed according to the structure they support, and the corresponding construction plans specify the materials and required thickness. It is important to note that formwork construction takes time, and it can represent between 20 and 25% of structural costs. To mitigate the cost of formwork, consider the following recommendations:
- Building plans should reuse building elements and geometries as much as possible to allow formwork reusing.
- When working with timber formwork, it should be cut into pieces that are large enough to be reused.
Concrete structures vary in design and purpose. Like in most project decisions, no option is better than the rest for all applications; the most suitable formwork for your project varies depending on building design.
Post time: Sep-09-2020