Fresh concrete is an important and indispensable material in all construction projects, from family homes to large projects such as apartments or factories. When combined in the right proportions, concrete has the ability to withstand compression and tensile forces with high durability. The article below from Uretek Vietnam will provide information about the setting time of concrete.
What is the setting time of concrete?
Fresh concrete after being mixed has a liquid form and needs time to change from this state into a solid mass, which is called the setting time of concrete. This time usually varies depending on environmental conditions and the ratio of the building material mix, also known as the concrete mac.
Accurately determining concrete dead time is extremely important to ensure quality and avoid the appearance of cracks. Proper drying will ensure that the concrete surface meets quality standards and bearing capacity. Conversely, not waiting enough time for concrete to set or leaving it longer than necessary can weaken its structure, causing serious problems and reducing its durability.
What factors affect the setting time of concrete?
The setting time of concrete depends on many external factors and the ratio of ingredients in the mixture. There are several methods to determine this time:
1. Weather conditions: High humidity in the air can increase concrete setting time, while hot and dry weather can cause concrete to dry too quickly and easily cause cracks.
2. Air temperature: Ambient air temperature above 40 degrees Celsius is usually ideal for proper concrete setting. On cold days, low temperatures may require the use of hot water to speed up the setting process.
3. Material ratio in concrete: Using high-fineness cement can promote rapid setting. The combination of different ingredients in the mix can also affect the setting time of the concrete.
How long does it take for fresh concrete to set?
Fresh concrete, after being mixed well, is usually poured into molds and fixed with formwork until it reaches hardness. The setting time of this concrete will depend on the factors mentioned above. Below are the freezing time levels corresponding to different conditions:
- With an ambient temperature of 30 to 40 degrees Celsius, this is the most ideal weather condition. After about 3 to 4 weeks, the formwork can be removed from concrete. If you want the concrete to age completely, you can leave it for another 1 to 2 days.
- If the air humidity is high, longer concrete setting time is needed to ensure its hardness. Or you can use hot water above 80 degrees Celsius to stimulate the freezing process.
However, this time is still not enough for the concrete to be able to withstand the full load of the floor and ceiling surfaces. After removing the formwork, support from other structures such as beams and steel is needed.
Should concrete be taken care of while it is setting?
The quality of concrete can be reduced if daily inspections are not performed properly. While waiting for it to set, concrete maintenance is extremely important. Here are some ways to ensure the quality of concrete blocks:
- Avoid walking on concrete surfaces and avoid dropping any objects for the first 1 to 3 days, as this can cause holes and cracks.
- In the rain, it is necessary to use a shield to protect the concrete surface from unsightly pits.
- In hot weather, it is necessary to water the concrete surface regularly, especially over the entire area, to avoid drying and cracking.
- Watering frequency will increase when the concrete’s setting time has been about 1 week. Watering can be done 4 times a day, morning, noon, afternoon and evening.
- Concrete parts such as ceilings, floors and foundations often need longer setting times to increase their ability to withstand compression and tensile forces.
The necessity of fresh concrete in construction projects
Certainly, concrete is one of the important and indispensable elements in the rough construction phase of a project. Its inert properties resist the influence of external factors such as harsh weather, helping to preserve the durability of the structure.Thanks to these advantages and its ability to adapt to the environment and surface, concrete is increasingly proving its necessity and importance.
Những lưu ý khi đổ bê tông tươi
Pouring fresh concrete not only creates solid structures for construction projects but also requires special care and attention from investors. Here are the basic things to keep in mind when using this service:
- Choose the appropriate time to pour the floor, with a temperature of about 34 degrees Celsius to ensure the most accurate setting time of the concrete. You need to know how to care for concrete surfaces to ensure the best quality.
- Make sure to pour concrete evenly on all positions of the floor, avoid pouring the mixture in one place and then raking it around. The formula for pouring concrete in layers over layers, in the horizontal direction and in each beam cell section, should be followed.
- Before pouring the floor, it is necessary to mix the concrete well according to the standard ratio of sand, stone, cement and water.
- Ensure safety of surface locations before pouring concrete. The foundation must be complete and capable of bearing the load before performing this work.
