- Factors affecting concrete drying
- Precautions with concrete
Once the concrete slab is poured, it is necessary to be patient: the concrete needs a lot of time to harden: up to 3 months! This step is the most important in the process because it will allow the concrete to obtain good compressive strength and ensure its longevity.
Factors affecting concrete drying
Several factors come into play for determine the drying time of the concrete. This time is governed by NF EN 206-1 standards, regardless of the type of concrete used. DTUs (Unified Technical Documents) include all the standards to be considered for each use of concrete.
Outside temperature is paramount in the drying process. In cold weather, concrete does not take not below 0° C; the cold delays the setting and hardening of the concrete. In hot weather, on the contrary, the concrete hardens quickly; the slab must harden and not dehydrate at the risk of cracking and losing strength.
Quality and class of concrete
The composition of the concrete as well as its strength class will also influence the drying time. In hot weather, it is sometimes necessary to cool the aggregates of the concrete; in contrast, when temperatures are low, they can be heat with hot water or steam.
Concrete aggregates also have a role to play in the drying time: they are minerals so they are more or less porous. They absorb some of the water when they are dry and reject it if they are wet.
To know: the minimum drying time is 28 days. This minimum period allows the concrete to be quite resistant in view of his class. However, there are quick setting concrete.
Precautions with concrete
Unfortunately, there is no system to ensure the proper drying of a concrete slab; however, failing to go faster, it is possible to promote the process by taking certain precautions.
In cold weather:
- Choose a concrete from superior resistance.
- Protect the slab frost overnight.
- Use a setting and hardening accelerator to limit the impact of cold and increase the strength of the concrete.
- Never concreting below -5° C.
In hot weather:
- humidify the support of the future concrete slab and concrete aggregates: the water contained in the concrete mix will not be absorbed by the structure.
- To bewitch cool hours of the day and protect the site from the wind, to the maximum.
- Use a setting and hardening retarder to overcome the strong heat
To go further: How to use a concrete mixer?