One of the most important steps in creating a solid and long-lasting structure is pouring concrete for a strip foundation. But once the concrete is poured, the work is far from done. It’s critical to understand when to remove the formwork to guarantee that the foundation acquires the required strength and stability.
Concrete curing, also known as hardening, is a lengthy chemical process. The concrete gets stronger and more durable during this time. Early formwork removal can jeopardize the integrity of the foundation and result in future structural problems.
It is important to understand the stages of concrete hardening and the factors that affect them in order to determine the appropriate time to remove formwork. These variables include the kind of concrete mix you use, the local climate, and the particular needs of your building project.
The main points of concrete hardening time will be covered in this article, along with helpful guidance on when and how to safely remove formwork from a strip foundation. You can make sure your foundation reaches its maximum strength and continues to support your building for many years by adhering to these guidelines.
| Topic | Details |
| Concrete Hardening Time | Concrete typically reaches sufficient strength in about 7 days to remove formwork, but full curing takes 28 days. |
| Formwork Removal Work | Carefully remove the formwork after ensuring the concrete has hardened adequately. Check for cracks or defects during removal. |
For a strip foundation to be stable and long-lasting, it is important to know when to remove the formwork after pouring the foundation. It takes enough time for the concrete to solidify and become stronger; generally, this takes seven to fourteen days, depending on the type of concrete and the weather. Early formwork removal can jeopardize the integrity of the foundation and result in possible structural problems. This post will walk you through the crucial processes for figuring out when to take down formwork so your foundation is properly set and stays sturdy.
- How concrete matures?
- Standards for removing formwork
- After how much time is the formwork removed?
- Video on the topic
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- FORMWORK FOR CONCRETE 25mm / ECONOMICAL / RELIABLE / EASY TO ASSEMBLE / DO-IT-YOU FOUNDATION
- Stripping. When you can remove the formwork…
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- When to remove formwork?
How concrete matures?
A building material’s maturation is a multifaceted, intricate process. The chemical reaction between water and cement is one-way and irreversible. Concrete’s structure changes, crystal hydrates and spatial bonds between particles are created, and the liquid solidifies into cement stone during the hydration process.
A few examples of variables that affect the rate of crystallization are:
- Grinding degree.
- Composition of minerals.
- Volume of water added for mixing.
- Temperature conditions.
- Addition of fillers.
The calcium hydrosilicates are the primary carriers of concrete strength. Clinker minerals come in four varieties that influence hardening. These are the following:
- Calcium silicate 3. Is important during the first month after pouring, during the setting period it raises the reaction temperature in the working solution, forms the structure of the substance.
- Calcium silicate 2. Affects the strength characteristics during the entire period of operation of the structure.
- Calcium aluminate. Reacts to increase the hydration rate, affects setting at the initial stage – during the first day and maturity after pouring.
- Calcium aluminoferrite 4. The effect is constant, from pouring until the end of maturation.
Two stages are involved in the building material’s maturation:
- Setting, or thickening.
- Hardening, or strengthening.
Setting starts as soon as the liquid substance stops mixing, or thixotropy. Heat release is a characteristic of hydration. The temperature rises quickly at the start of the process and reaches its peak at the conclusion of the thickening process. Setting happens more slowly in colder air temperatures and more quickly in warmer air temperatures. The ideal temperature range is +20 to +25 °C.
As the thick mass disperses over the formwork, its mobility decreases. Concrete can thicken in two to three hours or up to a day. The poured material can have its shape changed because it becomes brittle during the hardening process.
Particle crystallization happens gradually. When the grade strength indicator reaches 95%, the concrete mass can fully mature in 28 days; the remaining 5% accumulates over many years.
Standards for removing formwork
After the concrete is poured, the formwork must be removed when the stripping strength is evident. "Loads and impacts" (SNiP 3.03.01-87) introduces this idea. The following table outlines when dismantling a temporary structure is required:
| Types of structures | Least strength at which the formwork can be removed |
| Surfaces located vertically | 0.2-0.3 MPa |
| Reinforced concrete from a strip foundation | 3.5 MPa, not less than 50% |
| Floors located horizontally and at an angle with a span length of 6 m | 80% |
| Horizontal surfaces with a span length of up to 6 m | 70% |
When 50% of the concrete strength is reached, experts advise dismantling the formwork system when constructing private homes and utility buildings. Pouring heavily loaded structures, like stairs, requires a 70–80% gain for formwork removal, depending on the length of the span.
After how much time is the formwork removed?
Following research, engineers created a unique table that allows them to determine the number of days that formwork can be removed for building materials M200–M300, which are based on Portland cement M400 or M500.
| Dates or quantity in days | Temperature and strength indicators | |||||
| -3°C | 0°С | +5°C | +10°C | +20°C | +30°C | |
| 1 | 0.03 | 0.05 | 0.09 | 0.12 | 0.23 | 0.35 |
| 2 | 0.06 | 0.12 | 0.19 | 0.25 | 0.4 | 55% |
| 3 | 0.08 | 0.18 | 0.27 | 0.37 | 50% | 0.65 |
| 5 | 0.12 | 0.28 | 0.38 | 50% | 0.65 | 80% |
| 7 | 0.15 | 0.35 | 48% | 0.58 | 75% | 0.9 |
| 14 | 0.2 | 50% | 0.62 | 72% | 0.9 | 1 |
| 28 | 0.25 | 0.65 | 77% | 0.85 | 1 | — |
The temperature in the table is defined as the average value between the minimum and maximum daily temperatures; for example, if the morning temperature was +8°C and the evening temperature was +20°C, then the average parameter would be +14°C. In the table, "1" is used to represent 100% maturity.
The integrity and longevity of your construction project depend on your ability to determine when to remove the formwork from a strip foundation. The concrete mix, curing techniques, and weather can all affect how long it takes for concrete to harden. Prior to removing the formwork, it is crucial to make sure the concrete has solidified enough.
The formwork can usually be removed after seven to ten days. For complete curing, though, this time frame may need to be extended to 28 days, particularly in colder regions. Make sure the concrete has sufficiently hardened by conducting a strength test and always verifying the project’s specific requirements.
Take caution not to harm the concrete when removing the formwork. Start with the side forms, then move on to the forms at the bottom. For a seamless and secure process, make use of the right equipment and methods. By following these safety measures, you can ensure that your building has a solid, long-lasting foundation.
You can guarantee a successful and long-lasting construction project by being aware of the concrete hardening process and taking the right precautions when removing formwork. Your foundation will be prepared to support the structure above it if you pay attention to the curing time and handle the formwork carefully.
