Formwork for concrete – installation and removal time

Formwork is an essential part of building with concrete because it serves as a makeshift mold that forms and supports the concrete until it solidifies. Whether concrete is being used for walls, columns, slabs, or other structural elements, it guarantees that the material sets in the proper shape. The effectiveness of the design, installation, and removal of the formwork has a significant impact on the final concrete structure’s quality.

Formwork installation calls for meticulous preparation and accuracy. In order to create a sturdy frame that holds the concrete in place, a variety of materials, including wood, metal, and plastic, must be arranged and secured. The complexity of the structure and the type of formwork being used will determine how long it takes to set up. To prevent any accidents during the pouring process, it is imperative to make sure that the formwork is correctly aligned and braced.

The formwork needs to be taken down at the appropriate time after the concrete has been poured and given time to cure. If it is removed too soon, the structure may collapse, and if it is left in place too long, needless delays and additional expenses may occur. The type of concrete, the surrounding circumstances, and the particular project requirements all affect when formwork should be removed.

A successful concrete project requires knowing the proper protocols for both formwork installation and removal. Through adherence to best practices and consideration of the unique requirements of each project, builders can guarantee that the concrete sets safely and correctly, resulting in a long-lasting and sturdy structure.

Classification and types of formwork

The following criteria are used to classify formwork for concrete in compliance with GOST R 52085-2003 requirements:

• Type of structure being erected: vertical (columns, walls, foundations) or horizontal (floors, platforms, bridge spans).
• Design: flexible formwork for concrete, block, panel, sliding, pneumatic, permanent concrete formwork, climbing.
• Material of construction: metal (steel or aluminum), plastic, wood, combined.
• Possibility of use at different air temperatures: insulated, regular, warming and combined.
• Turnover: one-time and reusable.

One crucial aspect that is not covered by GOST R 52085-2003’s specifications is the formwork’s origin, which can be either self-made or produced industrially.

Today’s construction companies use prefabricated, reusable industrial "products." With very few exceptions, private developers construct their own disposable formwork for concrete using leftover scraps like sheet iron, wooden blocks, and boards.

Rules for pouring formwork

Let’s look at some typical concrete projects in private construction that you can do yourself with formwork:

• Pouring a blind area, garden path, car platform and other similar "horizontal" concrete work can be performed in formwork made of new or used red brick. Brick formwork for pouring concrete is laid out along the contour of the future structure in a shallow trench (50-60 mm) according to the building level. The space between the brick "contours" is filled with concrete. In this case, the brick remains in the trench and performs the function of protecting the contours of the concrete structure from destruction.
• Pouring the foundation of a building. As a rule, this is a strip foundation poured into a trench of the appropriate depth and width. In this case, the walls of the trench perform the function of the main formwork. If for one reason or another it is necessary to raise the upper edge of the foundation above the zero point (ground surface), concrete is poured into the formwork made of boards at least 25 mm thick and 40×40 or 50×50 mm bars. Boards are knocked together from boards and bars. Boards are installed along the outer and inner perimeter of the foundation, connected to each other with steel pins. Work is carried out on pouring concrete. The air temperature will “tell” when to remove the formwork after pouring concrete. At an air temperature of 20-25 degrees Celsius, the structure is dismantled after 3-4 days. At a temperature of 5-10 degrees, the formwork is removed after 7-10 days.
• Pouring concrete walls. In this case, homemade movable formwork made of wooden panels about 70 cm high is used, first supported by the base of the building. After pouring and setting of the first "belt", the shields are moved higher and rest on the already poured "belt", and so on until all the walls are "driven out". The outer shield belt is connected to the inner belt using two rows of steel threaded adjustable studs. In this case, the lower row of studs serves as a support for the base and the next "belts" of the wall.
• Filling the floor. Homemade formwork for pouring the floor slab consists of two structures. These are wooden shields, fixed in one way or another along the outer perimeter of the walls and an additional horizontally located wooden shield, placed inside the room at the height of the ceiling using powerful logs. This is a rather complex, but viable design. The main problem is to correctly and reliably set the horizontal shield. Otherwise, it will either fall under the weight of the concrete or collapse.

When you can remove the formwork after pouring concrete?

The answer to this question is found in the fact that concrete’s setting and hardening times are influenced by outside temperature, as was previously mentioned. It is well known that the setting and hardening process of the material slows down considerably and almost stops at 0 degrees Celsius and below. This process also occurs at temperatures below 5 degrees Celsius.

The answer to the question of when to remove formwork from concrete is given in the current regulatory document, SNiP 3.03.01-87: "When 50-70% of the structural strength is reached" (except for floor slabs).

Since a private developer will find it difficult to ascertain the point at which the concrete reaches 50–70% strength, we will address the question of when to remove the formwork from concrete using two tables for horizontal (floor slabs) and vertical (foundation, columns, and walls).

Table for vertical structures

Table for horizontal structures

Table analysis, including responses to a frequently asked question by developers: when should formwork be removed in the summer after concrete is poured? These are the minimal terms, falling between 72 and 96 hours following the conclusion of the concrete work.

In conclusion, readers’ attention must be drawn to the following query: how can concrete be poured into formwork? An essential and crucial point. When pouring concrete into the formwork, each subsequent section must be bayoneted, and even better, the formwork walls should vibrate.

The timely installation and removal of formwork is essential for the accomplishment of any concrete project. While prompt removal of the formwork helps prevent damage to the structure and expedites the construction process, proper formwork installation guarantees that the concrete maintains the desired shape.

Careful planning and close attention to detail are necessary during the installation phase. Before pouring concrete, make sure the formwork is firmly in place to avoid expensive errors and delays. To guarantee safety and efficacy, it’s critical to adhere to manufacturer guidelines and best practices during this step.

Patience is essential when removing the formwork. Before the forms are removed, the concrete must have enough time to solidify. If this process is rushed, it may result in surface flaws, structural failures, or cracks. Always follow the advised curing times, which can change based on the particular concrete mix used and the surrounding conditions.

By carefully monitoring when to install and remove formwork, you can protect the quality of your concrete work and increase the overall efficiency of your construction project. You can create a long-lasting, sturdy structure that withstands damage with the appropriate method.

Knowing when to install and remove formwork when working with concrete is essential to creating a sturdy, long-lasting structure. To keep projects on schedule, formwork—the temporary mold into which concrete is poured—needs to be set up fast and effectively. On the other hand, waiting too long can result in needless delays, while removing it too soon can jeopardize the integrity of the concrete. When it comes to installation and removal, builders can attain optimal outcomes without compromising on safety or quality by determining the appropriate timing.

Video on topic

Example of assembling formwork for walls

Dismantling formwork for concrete floors

Lesson No. 1 installing formwork for concrete From X to Y