A formwork is that impermanent structure that serves as the mould for a concrete mix in a system. The concrete mixture is poured into these formworks to take the desired shape. And when the concrete is set and dry, the formwork is removed. Formwork may be reusable or not. It all depends on several factors. However, this article will focus on the actual process of building formworks for different building projects.
Furthermore, in the construction of formworks, it is crucial to consider the actual purpose of the formwork. For instance, the foundational purpose may be to identify the kind of structure being built. Is it a private structure or a commercial structure that requires formwork? We will take a systematic approach that deals with the core properties of the formwork inside the whole system. The process may include formwork sheeting, bearers, ties, and elements.
The Formwork Sheeting (Formwork Shell)
The formwork sheeting is the mirror image of the components of the concrete that need to be produced. For instance, it comes in direct contact with the existing concrete. Also, it has a molding element in which the formwork begins to have one of the most decisive influences on the quality of concrete surface being used. However, it is crucial the formwork sheeting can resist heavy stress by taking up the surface pressure from the concrete. You can read about Formwork Full Guide: All You Need to Know About it by clicking here.
It carries it off to linear acting supports. And in a formwork pressure distribution, the involved elements include the following
- Formwork sheeting
- Main bearer
- Formwork bearer
- Columns
- Formwork pressure for the surface pressure as earlier mentioned
A typical formwork sheeting is often part of the initial formwork to wear. The reason is that it often exerts heavy stress and plain concrete with the poured concrete. This construction may also require installing a sheeting material, including sheeting boards and prefabricated wooden panels. At the same time, the formwork sheeting of individual boards may comprise dimensions such as 25 mm thickness and about 140 mm width.
- Formwork sheeting boards
Meanwhile, the heartwood side may also lie towards the concrete itself. At the same time, formwork sheeting boards have advantages such as easy workability if you have to plan, see, bore and nail them. On the flip side, they also have the following disadvantages.
- The high expenditure of the working time that the boards require are matters of concern when making the formwork
- It often has a short service lifespan
- It often leads to some loss by the wood that gets wasted
- Formwork sheeting panels
Furthermore, one can prefabricate sheeting panels from isolated boards from squared timbers as frames. However, this case is workable when you have to repeat the formwork for the same design, such as the construction of foundation strips. Meanwhile, the prefabrication is done in a workshop while it saves a lot of time on-site while installing the formwork. In other words, prefabricated sheeting panels can help to save that much time on site.
However, sheeting panels are not without some disadvantages in terms of services, similar to the weaknesses we observe in sheeting boards. Ideally, both the sheeting boards and the sheeting panels are used on the site in combination. Now, can we discuss some of the common types of formwork sheeting?
Formwork bearers
The formwork bearers directly support formwork sheeting by carrying off the exerted forces through the falsework structures of all the supporting members, formwork ties and the soil. Also, the formwork bearers consist of squared timbers, while the beam’s cross-section can depend on the loads it bears. In other words, the cross-sections of the formwork beam largely depend on the load it carries.
At the same time, if it achieves good workability, then the wooden beams have a wide field of application. In addition to the wooden beams, you can include prefabricated steel parts such as the clamps and the steel beams. Meanwhile, the clamps are used majorly for the column formwork in the entire structural buildup. A typical steel clamp for column formwork also includes a steel wedge, clamp, and holes for steel wedges.
Formwork ties
In terms of formwork ties, it depends on whether you have vertical or horizontal formwork. For the vertical formwork, the pressure of the formwork acts horizontally according to the stress that it takes up from the two adjacent faces of the formwork ties. The tying is done by slinging a steel wire of about 3.1 mm to 4.2 mm dimension around the formwork bearer’s frame.
You may also have to guide the wires through the boreholes in the formwork sheeting while tightening them through twisting. While doing that twisting, ensure that you maintain the actual width of the formwork for the structure. At the same time, ensure that there are no spaces or holes in the boards of sheets to hold the concrete mix in place before it is set to dry.
Also, you may have to remove the stull (if made of wood) while placing the concrete mix inside the structure for a practical bracing function under pressure. Alternatively, one can brace the formwork steel together by using steel screws into the boreholes.
Elements of Falsework structures
In a brief digression, a falsework structure is the formwork parts that take up the load off the formwork sheeting and bearers. Similarly, the primary functions of the formwork structures are the main bearers and columns. Besides, it has columns that take up the load away from the formwork bearer. When you employ round timber braces, you have an obtainable specially made metal tube adjustable in height. They are also employable as columns in the structure.
When using round timber columns, you may employ double wedges to the foot of the formwork—these structures help to prevent the lowering of the formwork when it is time for stripping to removal. A horizontal arrangement of the falsework elements includes the primary bearers responsible for taking away the load from the formwork away to the columns. The lattice type of metal tube structures can sometimes be employed for huge widths when lacing the columns at close intervals.
