Arrangement of a sandy foundation for the foundation. The biggest problem (headache) during the construction of the foundation is the initial geological structure of the land on the site where construction is planned. When preparing the foundation for the foundation in places where peat soil is contained, you can easily spend 50% of the total amount that was calculated for the complete construction, and this is only for creating the foundation system.
With a preliminary and competent analysis of the geology and bearing capacity of the earth, you can avoid big problems, but even with good forecasts, the builders are painstakingly engaged in the preparation of the sandy base for the foundation, and also remove the weak soil and do not save on materials.
In addition, the results of the work done must be entered into the act of accepting the foundation for the foundation.
Because of this, the preparation of the foundation requires a large investment of funds and efforts:
Please note, the most common reasons for changing the bearing capacity of the foundation is the use of those materials that do not meet the requirements of the project.
The main role is played by the acceptance protocol or act, which confirms the scope of work, the thickness of the laid sand and rubble, the presence of geotextiles. To ensure the required strength of the surface layer, they are engaged in preparing the soil, poured and compacted with crushed stone of several fractions, and then with sand. This arrangement of a sandy base under the foundation significantly increases the durability of the latter.
If you want to try to install the concrete base immediately on gravel, without sand, part of the slab or tape will be overloaded, and the second part will be unloaded. In such a situation, the concrete casting will quickly become unstable, cracks and deformations are formed.
In this case, sand plays the role of glue and elastic cushion, which makes it possible to compensate and distribute evenly all efforts, and even swelling earth or upsetting the base of the foundation.
Sandy material, which is used in preparation and filling, must necessarily meet the criteria and requirements:
Good advice! You can easily check the quality of the sand, even with the right tools. For example, if sand is poured into a hole dug in the ground and about 5 liters of water are poured, then with high-quality material the water will leave in a few minutes, and if the sand is dirty, then a puddle will remain.
In the classical version, the technology of creating a cushion for a concrete slab or tape uses crushed stone, since this is a material that provides a rigid base and drainage. Because of this, the base is covered with at least one layer of rubble. To use this material, you will have to spend a lot of money, since the cost of the material and delivery always pours into a tidy sum.
Despite the shortage and high cost, it is impossible to abandon the use of crushed stone.
In contrast to the sandy base under the foundation, for the use of crushed stone embankment, the surface is planned with excavators and bulldozers and a lot of earth is extracted to dig the slope. It is not always possible to perfectly align the gravel bed, so builders have found a way out and apply concrete preparation or intermediate concreting. This is a thin layer of concrete, which is laid on a base of sand and gravel. After that, it remains only to lay out the waterproofing and insulation.
If the ground has high bearing characteristics, the preparation technology can be simplified. In this case, the device of a sandy base under the foundation is made in a simplified manner, and a plastic wrap is placed on the tamped and leveled layer of sand, a layer of screening or fine gravel is poured, and after tamping, insulation and waterproofing are laid. After that, you can deal with the laying of reinforcement and fill everything with a concrete solution.
It is believed that the use of polyethylene film as a backing material under a layer of crushed stone or sand is done because of fears of leaving "concrete milk" through pillow into the earth layer. In life, such incidents are really possible, but due to the poor quality of concrete or delamination.
The liquid saturated with cement leaves the base, but in an amount of not more than 4% of the total volume. And the film, as well as waterproofing, is necessary so that the sand is not saturated with salts and silty deposits, which over time can reduce the effectiveness of drainage.
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