The term “dry time” is not in itself applicable to concrete because, strictly speaking, it is what is known as setting. A chemical process of crystallization. This can last for several years.
If you want, you can now plaster the inner surfaces of the reveals. In the case of a door breakthrough, this is usually not necessary, as you will put a new frame there.
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The term drying applies to concrete only to a limited extent. Because the material does not harden because moisture escapes. In fact, concrete always contains a certain amount of residual moisture. The water evaporates, but hardening takes place through crystallization or so-called setting. The thicker the concrete layer, the longer this chemical process takes.
The escape of water depends on various factors. These include:
- the temperature
- the surrounding soil moisture
If the weather and the environment are dry and warm, the setting is faster. At less than 12 ° C, the process is significantly slowed down. If the temperature is below -10 ° C, it is completely stopped. Therefore, it makes sense to have the foundation poured as early as possible in the year, as soon as the temperatures are above 12 ° C. The ideal temperature range is between 15 and 20 ° C. In addition, late frosts should no longer be expected. This allows it to set well over the summer and will last longer.
On the other hand, it should not be warmer than 30 ° C immediately after application, as excessive temperatures can cause stress cracks in the surface of the foundation. It is also ideal if light rain falls in the days after watering. Because this keeps the surface moist and the effort for post-treatment is reduced.
Minimum load capacity
After pouring the concrete, you have to wait at least 28 days before the foundation can be reworked and loaded for the first time. Even then, however, it is not to be expected that it will be completely dry.
At least, several months are required for this. In the case of very moist soil, or in cold areas with high levels of precipitation, drying and hardening can even take several years.
Speed up drying
It is possible to accelerate the hardening of the concrete by adding additives or using alternatives. These are, for example, mineral compounds that accelerate drying or setting.
Possible additives are, for example calcium chloride or calcium nitrate. These are catalysts that are used for the crystallization processes. They are cheap and easy to use, but not suitable for every use. Because if they come into contact with steel, they cause corrosion. They must therefore not be used in conjunction with steel girders or reinforcement bars. However, there are also non-corrosive calcium compounds, but they are usually more expensive. The admixtures are added to the water before the concrete is mixed.
This means that concrete that is poured in difficult areas, which are cool and damp, can harden significantly faster. In addition, this can prevent moisture from staying too long and mold from developing.
So-called CSH germs can also accelerate the hardening of the concrete foundation and can be added directly to the mixture. Just like the calcium compounds, they act as catalysts. The CSH germs are also known as seed crystals and ensure faster setting. It is extremely easy to use. The agent is only added according to the manufacturer’s instructions. However, products with seed crystals are usually comparatively expensive. It is therefore often not worthwhile to use them, especially in dry areas.
Rapid concrete can also be used as a further alternative to the long drying times or the sometimes-tedious setting of normal concrete. This contains binders and catalysts. This enables setting times of half an hour to be achieved. A complete hardening is also only given after several weeks to months with the rapid accentuation. However, it can be charged within a shorter period of time. A potential disadvantage, however, is that the quick-setting concrete is only suitable for smaller areas, blocks, and lighter foundations. So such as for the foundations of:
- small workshops
It can also be used for other areas, including:
- concreting of driveways
- embedding playground equipment or arches in concrete
- Manufacture of bases
- Create root barriers and lawn edges
- Create little-used sidewalks
- the repair and renovation of stairs
Pouring an entire house foundation with quick-setting concrete, on the other hand, is not recommended, as it is often less resilient than concrete.
Follow-up treatment: tools & information
Anyone who pours a concrete foundation usually wants a short drying time and a quick minimum load capacity. However, post-treatment is necessary so that the quality of the concrete is as high as possible, no cracks form or the material shrinks. There are two main factors that need to be taken into account: temperature and humidity.
15 to 20 ° C and a humidity of 85 percent or more are ideal. If freezing temperatures occur, a heating cannon can be used to ensure that the fresh concrete is not damaged by the frost. If they rise above 30 ° C and the humidity is very low, the foundation should either be constantly moistened or covered with a vapor-impermeable film to keep it moist. This prevents the surface from drying out too quickly and cracks from forming due to the tension that occurs.
It is important, however, that the film does not lie directly on the fresh concrete. Otherwise, unsightly and uneven discoloration could form. The cover is therefore stretched over the concrete and the formwork in such a way that it reduces evaporation but has no contact with the foundation.