Good afternoon, dear guests and subscribers of my channel!
Today, private housing construction is gaining momentum and in this regard, the network is written very a lot of unreasonable and contradictory information about the construction of foundations and everyone writes about it to whom laziness. Conjectures are transmitted from one to another by word of mouth and without understanding the details - people bury tens of thousands in the ground, among other things, builders also make good money on this.
In this article, I would like to bring to the surface some stereotypes that are very often discussed on construction forums ...
Sand bedding
One of them is sand bedding. Now, it is done wherever possible and where not. Arranging a sand bed of 10 cm. under the foundation, the builder justifies this by the fact that the sand increases the bearing capacity, does not shrink, levels the base and saves from frost heaving.
Friends, the sand pillow is a layer far from 10 cm. and such a pillow is a necessary measure if the soils, according to the geology made, do not provide the necessary bearing capacity, which is not assessed by eye, but by calculation!
10 cm. sand does not affect this fact in any way. If the soil is weak, then the strengthening of the base is made with SCHPS (crushed stone-sand mixture) and not 10 cm thick, but at least 50 cm, or even 1 meter, depending on how much it was necessary to go deeper and reach more or less dense soil (clay, sandy loam, loam or rocky rocks).
Does 10 cm save? sand from frost heaving? A firm "NO"! Any soil is heaving, including sand and it all depends on how saturated it is with water. So, if the soil around the foundation consists of loam, sandy loam or clay, then the sand under the foundation is a potentially dangerous place for the accumulation of moisture. In other words, we ourselves make drainage under the foundation of the house and exacerbate the situation! What for? In the spring, when the groundwater level rises, the groundwater, moving along the aquifers, will look for weak points, and sand and will be such a place, especially if there is clay / loam at the bottom of a trench or foundation pit.
Leveling the base - yes, it is easy to level the base with sand, but why? Leveling the base is required only in order to make a high-quality foundation using factory elements - reinforced concrete products (figure above). But, if we pour the monolith in place, leveling the base is completely unnecessary. The foundation will not be worse if the bottom is a wave and has drops of 10-15 cm. or more. Undoubtedly, you will overpay for half a cube of concrete, but you will avoid sand filling, and this, believe me, is better!
In addition, the foundation on its native continental soil works 100%, transfers the load from the house and distributes it evenly over the entire area of support on Homogeneous soil.
Cement glue (milk)
As for the leakage of cement glue from concrete, this is a pure myth. The chemical reaction of cement and liquid occurs in such a way that the cement does not release water from itself. Each particle of cement forms a rigid bond with its neighbors within 2 minutes. Enveloping grains of aggregate (sand, crushed stone, screenings), the cement glue will never be separated from them, even 5 minutes after mixing, thus - it cannot seep into the ground anywhere, leaving the rubble or sand.
Each particle of cement takes on the required percentage of water, the rest is free water during concreting is displaced by the mixture and rises to the surface, but this is not "cement milk" - it is unreacted (free) water. And through the cracks in the formwork the same free water flows out.
When a person speaks to me about cement milk, I always ask him whether he has ever tried to drill a foundation that has been poured into the ground or just break a cake of concrete that has fallen on the grass. Believe me, this is very difficult! But why do the builders stretch the film over the formwork?
The film on the walls of the foundation formwork is arranged for one single purpose, not to allow water to evaporate in hot weather, since the hardening process of the mixture must take place in humid conditions. And this is achieved by creating a greenhouse (greenhouse) effect around the structure.
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