When to Use Concrete Formwork Systems？

Concrete needs stability to cure properly, and proper curing will give it the strength it needs to withstand the pressures it will face.

Zolo are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

Engineers have designed a variety of forms as the solution to create stable curing environments.

Each project will require proper form selection, installation, and form removal for the strongest concrete structures.

Concrete Forms

Let’s first get our bearings on concrete forms and the different types available to us.

What Is Formwork?

Concrete formwork, also known as shuttering, requires solid molds to hold liquid concrete in place until it cures.

These forms are necessary to shape and strengthen the concrete. Without a form, the concrete would just end up in one big mound of hardened liquid with no real shape or use.

Formwork can turn concrete slabs into walls, foundations, and even floors. These forms can also add surface texture to the concrete for beautification.

The 8 Types of Concrete Forms

Contractors have a choice to make when building concrete structures.

Which type of concrete form best suits the project? 

Each of these eight forms has its uses, limitations, pros, and cons.

Wood Forms

Wood forms are the most conventional type. The materials are readily available, and most contractors know the process.

To create a wooden form, wooden boards are nailed together into the desired shape. Wooden stakes are added at precise locations to help bear the weight of the concrete.

We might recommend using boards less than six inches wide for wood forms as larger boards tend to warp, depending on the project.

The limitations of wood forms stem from the fact that most wooden boards aren’t strong enough to hold large amounts of concrete and cannot be used for heavy concrete construction.

Insulated Concrete Forms

ICFs are hollow blocks of insulation with steel reinforcement cages built into the form.

The concrete mix is poured and sandwiched by the insulation. These forms are permanent and never removed.

You don’t have to worry about timing or proper formwork removal with ICFs because they stay put, and the concrete will dry and strengthen with little to no adverse effects from exterior conditions.

Steel Forms

Steel forms are the strongest type of concrete form, and you can reuse them multiple times. These forms are the most popular option for large industrial structures.

Another benefit steel forms offer is that they won’t absorb the water from the curing concrete. This hydration must evaporate from the concrete at the right speed for maximum strength.

Steel forms also present a lower risk of error after removal.

Concrete Wall Forms

Concrete wall forms are pre-manufactured forms made from wood, steel, or both, all connected with anchors. This method is often used to build large and often intricate industrial structures.

Some require the use of cranes to install, while others are designed to be fast-paced and modular for easy setup and take-down.

Decorative Concrete Forms

A decorative concrete form is used to create an artistic relief through the use of negative space as the concrete dries.

There is typically a melamine, acrylic glass, or laminated board with inserts that create the design in the mold.

Which Type of Concrete Form to Use?

The type of form you’ll need depends on several factors.

Here are some things to consider when choosing your form:

• Size of pour: The dimensions of the structure can determine which form would work best.
• Pressure and weight: The form must be strong enough to withstand the pressure it’s placed under.
• Amount of concrete: The larger the structure and amount of concrete, the stronger the form needs to be.
• Type of compaction: Certain forms handle certain types of compaction better.

Based on these factors, you can make a more informed decision. As already stated, larger projects require the use of steel forms, while wood can be used for smaller projects.

Steel is cleaner than wood, resulting in fewer bug holes in the finished product.

Wood is best for low-height structures, and steel is best for high structures where concrete can buckle under its own weight.

Of course, steel is more costly, so it’s best to reserve this form for when you need it.

How Long Should Concrete Cure Before the Form Is Removed?

The amount of time you should wait before removing your concrete forms is different for every project.

Here are some of the factors that affect curing times:

1. Weather
2. Grade and type of concrete
3. Size of concrete structure member

Let’s discuss these factors:

Weather

Frozen concrete will not dry, so if you are working in extremely cold weather, the curing process will take longer.

Rain also affects drying time, especially during the first few days when the air is still moist.

Heat aids the curing of concrete, but extreme heat can cause cracking. This can be prevented by using tarps or barriers to trap moisture.

Grade and Type of Concrete

Different types of concrete have varying drying times and reactions to outside factors.

There are five basic types of cement:

• Type I: OPC (Ordinary Portland Cement)
• Type II: Moderate Sulfate Resistant Cement
• Type III: Rapid Hardening Cement
• Type IV: Low Heat Cement
• Type V: Highly Sulfate Resistant Cement

Each of these categories has subcategories with different uses and drying times.

The grade of cement used also affects drying times. We’ll discuss this more in the next section.

Size of Concrete Structure Member

Larger sections gain strength faster due to the compaction of the weight of the concrete itself.

So, the structure’s size determines when the form is ready to be removed.

When to Remove Concrete Forms

The removal of concrete forms is known as “striking-off” or “stripping off” the forms.

According to the American Concrete Institute (ACI 308), the drying times for each type of concrete are as follows:

• ASTM C 150 Type I cement: 7 days
• ASTM C 150 Type II cement: 10 days
• ASTM C 150 Type III cement: 3 days
• ASTM C 150 Type IV or V cement: 14 days
• ASTM C 595, C 845, C cements: Varies

According to the rules for Ordinary Portland Cement, these are the average drying times of various types of structures:

• Walls and columns can be removed after about 24-48 hours
• Slabs, with their props left under them, can typically be removed after 3-4 days
• Soffits, with their props left under them, can be removed after one week
• Props supporting slabs under 15 feet can be removed after one week
• Props supporting slabs over 15 feet can be removed after two weeks
• Props to supporting beams and arches under 20 feet can be removed after two weeks
• Props to supporting beams and arches over 20 feet can be removed after three weeks

These drying times will differ for types 2, 3, 4, and 5.

Contact us to discuss your requirements of Concrete Formwork Systems. Our experienced sales team can help you identify the options that best suit your needs.

Learn More: Slab Construction

Can You Speed Up the Concrete Drying Process?

Time is a critical issue in the construction process. If you are pressed for time, there are a few ways to speed up the drying process.

Here are some ideas:

• Additives
• Weather-resistant barriers
• Dehumidification

Let’s talk about these ideas:

Additives

Admixtures can be created by adding certain chemicals or additives to the cement mixture to speed up the drying times.

Calcium chloride and silica fume are two such additives.

Weather-resistant Barriers

When weather conditions are causing an issue, you can use weather-resistant barriers to speed up the concrete drying process.

Plastic sheeting is good for trapping moisture when the temperature is high and protecting the form from rain.

Insulation blankets help to prevent freezing when the temperature drops.

Dehumidification

If the air is overly humid, dehumidification can also aid the drying process.

Desiccant dehumidifiers use a chemical reaction to draw moisture out of the air. This is best for use in an enclosed area where the chemicals won’t dissipate in the surrounding air.

Condensation dehumidifiers cool the air to drop the dew point, then soak up the humidity from that process.

Heating dehumidifiers heat the air, raising the dew point and drawing the moisture off the surface of the concrete.

How to Properly Remove Formwork

Not only is timing critical in formwork removal, but the proper techniques should be used to maintain the structure’s integrity.

Common Mistakes to Avoid

Learning formwork removal is easier when you understand some common but detrimental mistakes — and avoid those at all costs.

Here are a few common mistakes that you should avoid in your removal process:

• Don’t use a crowbar to remove forms. Use wooden wedges; they are more delicate and won’t damage the concrete.
• Follow the same sequence and pattern if more than one form is used. The concrete needs to be strong enough to support all loads.
• If you see defects, repair them before other structural members are added. You may have to start that form over, but it’s better than failing inspections or having structural defects.
• Use the correct type of concrete for the job at hand. Read our Concrete vs. Cement article for a refresher on the various types and their uses.
• Don’t pour concrete without proper site preparation. The site should be a level, compacted area.
• Place your reinforcements correctly to prevent warping, slumping, or uneven forms.
• Use the correct water-to-cement ratio. Too much or too little water can cause defects.
• Don’t overwork the concrete. This can bring too many fine materials to the surface and weaken the structure.
• Don’t rush the process. Don’t remove the forms too early!

What Happens If You Remove the Forms Too Early?

When you jump the gun and remove your forms too early, you will not be pleased with the results.

Your structure can slump to one side or bulge at the bottom. Multiple cracks can occur because it is not ready to bear the weight of the concrete on top.

Worse still, the structure can collapse due to multiple factors weakening the project’s structural integrity.

Concrete forms are a crucial part of the concrete construction process, and the information in this guide will ensure that proper formwork is used.

With the use of proper formwork, projects will go much more smoothly. There will be no need to repair or redo any structures with new concrete.

This will save money and reduce the amount of time it takes to complete a project, keeping you within budget and on schedule.

What is Formwork?

In a nutshell, formwork is the mold wherein fresh concrete is poured and formed. The mold, which can be permanent or temporary, holds the poured concrete and shapes it until it solidifies and becomes strong enough to support itself and other loads.

Formwork is also known as “shuttering.” However, in certain parts of the world, shuttering refers to using plywood or timber to create the mold.

Formwork systems can be classified according to the following parameters:

• Types of material used to create the mold (plastic, steel, timber, aluminum)
• Types of concrete structure it supports (slab, column, wall)

Construction costs usually consist of building materials (ca. 45%), labor (ca. 45%), and operating expenses (ca. 10%). Formwork material comprises 15% of the total building material and contributes roughly 44% of the total labor. Meanwhile, formwork construction accounts for up to 25% of the total cost of building the structure. For this reason, many builders and construction companies prefer reusable forms (panel forms). The process of removing formwork is called “stripping.”

2. Column

As the name suggests, column formwork is used in the construction of circular or rectangular columns. Columns have formwork sections with a “closed load transmission,” which is supported by the formwork’s design and the guaranteed tensile strength rather than by using ties.

Steel formwork is often used to form circular columns as it is economical and available in incremental dimensions. Single-use forms, which are destroyed and disposed of during stripping, can be used as an alternative. However, using single-use formwork is not advisable if you need to construct multiple circular columns.

Meanwhile, rectangular columns are formed using three systems depending on their specifications. For instance, classic timber girders with steel walers and a plywood facing are often used when builders need to construct a significant number of columns with special dimensions. The windmill system, which is composed of columns or multipurpose panels of frame formwork systems, is suitable for building single columns with a standard dimension.

Finally, a foldable column formwork is highly suitable for columns with great heights. Because all the essential components (panels, connecting devices, ladders, and access platforms) are integrated into this type of column formwork, it helps builders reduce their construction time and costs.

3. Wall

Wall formwork comes in different types and classifications, as outlined below.

Conventional
Conventional wall formwork consists of boards or sheets and squared timber. It is flexible, but it can be costly and time-consuming as each component must be assembled on-site. In addition, all of its parts should be made according to the project’s specifications, and they must be nailed together and dismantled again after concreting.

Girder

This is a better version of the conventional formwork. Its components, which usually consist of dimensionally stable girders with two chords and one web, have been standardized to facilitate the assembly of identical and ready-to-use panels. The connection of the panels has also been systematized.

Frame
This type of wall formwork helps reduce labor time since its essential components (forming face, support for forming face, and steel walers) are assembled as one panel. The profile nose of the frames protects the edges of the forming face, thereby extending its lifespan. Connecting devices are used when assembling the frame panels to large-sized units, which are then usually transported by crane.

Crane-independent (hand-set)

This type of formwork can be moved by hand. Because of weight considerations, it is usually made of aluminum or plastic. It can take less concrete pressure than crane-dependent formwork, and is often used in housing and municipal construction projects.

Crane-dependent 

Crane-dependent formwork systems feature a large frame and formwork panels, usually made of steel. As a result, they cannot be moved manually. Since they can resist more fresh concrete pressures than crane-independent forms, they are suitable for the construction of commercial buildings and other extensive infrastructure projects.

Two-sided
As the name implies, two-sided formwork is erected on both sides of the wall. Its formwork ties, which are usually sleeved by spacing plastic tubes so they can be reused, take up the fresh concrete pressure. Push-pull props or large heavy-duty braces are attached to the formwork to align and secure it against wind loads during operation.

Single-sided
Single-sided formwork is used when the concrete has to be poured against existing structures or when builders need to do concreting against a hill or soil. This is why it is most suitable for reconstruction jobs. With this type of formwork system, concrete pressure is transferred from the formwork to the base plates through a support structure. 

Prefabricated
This formwork consists of two prefabricated concrete panels which are assembled in advance, and then transported and filled with concrete on-site. Braces and push-pull props are often used to secure the walls, while working and safety scaffolds are installed with the help of special adapters to make the construction process more cost-effective. Prefabricated formwork helps minimize project duration and labor costs. However, pre-planning is required to ensure that it is transported safely to the site.

Circular
Circular formwork is designed for the construction of curved and polygonal walls. It is also quite useful in the construction of specific concrete structures, such as septic tanks and car park ramps. This formwork system comes in three different types:  

• Round girder – timber spacers are added between the timber girders and steel walers so the formwork can be adjusted to the required radius. 
• Flexible girder – ideal for the construction of curved walls with different radii. It comprises timber/steel girders and a spindle, which allows builders to adjust the formwork to the required radius without having to reassemble the panels.
• Polygonal – existing “flat” frame formwork panels can be refurbished as polygonal formwork by adding supplementary radius panels and rails, allowing builders to minimize their project costs.

Climbing
Climbing formwork is quite useful in the construction of high-rise concrete structures, such as control towers and skyscrapers, because it climbs with the wall. It comprises large wall formwork mounted to a climbing scaffold. There are three different types of climbing formwork:

• Crane-dependent – the climbing unit (scaffold and formwork) requires the use of a crane to reach the next cycle.
• Self-climbing – an automatic climbing system that does not require the use of a crane to reach the next suspension point. Hydraulic rams/pumps lift the scaffold, secondary platform, and formwork to the next pouring cycle. It is ideal for the construction of very tall concrete structures.
• Slipform – a two-sided formwork that slides upwards along the structure being built at a rate of 20–25cm per hour. A system of pipe rods, which is integrated into the already-set concrete, supports the slipform.
   

MEVA is an industry leader offering a wide variety of wall formwork systems that provide highly efficient shuttering, flexibility, and reliability. Our products are lightweight and easy to assemble, and therefore will facilitate the rapid completion of your construction projects. Click here to learn more.

For more Concrete Column Formworkinformation, please contact us. We will provide professional answers.