Geotextile is a relatively new multifunctional roll material used to protect buried building structures from adverse effects. It is made of polyester, polyester and polypropylene in the form of woven fabrics (geotextile) or heat-treated non-woven perforated film.
Geological fabric is obtained by traditional textile weaving of polymer threads at right angles to each other. Such a canvas is characterized by high strength, elasticity and is capable of transmitting moisture only in one direction. Increased elasticity allows the use of geological textiles in places with complex spatial configuration of building structures with breaking deformation of insulating layers.
For the manufacture of nonwoven webs, polymer fibers are used from viscose, polyamides, polyesters and polypropylene, which are randomly bonded to each other by thermal or punching methods. The structure of the material may consist of one type of raw material or a combination of different polymers.
Application
What is geotextile in the foundation for? It is used to solve various problems, since it takes into account:
- high strength and durability of the material;
- ability to strengthen the soil;
- resistance to moisture and low temperatures;
- unique waterproofing properties;
- more uniform distribution of weight loads;
- cessation of growth of weeds;
- moisture transfer in one direction;
- resistance to the effects of fungus, insects and rodents.
In addition, it should be noted the ability of geotextiles for the foundation to increase density and strength after additional heat treatment. As a result, geotextile webs are used for:
- strengthening soft soils and load distribution from structures;
- separation of various layers of bulk building materials;
- drainage moisture away from the bearing base.
At the same time, the affordable cost of the web makes such protection effective and economically justified.
Material Selection Criteria
The operational characteristics of the polymer threads used for the manufacture of geotextiles are very close. At the same time, it should be remembered that non-woven fabrics have better waterproofing properties and are cheaper, and geo-fabric is more plastic, stronger, but more expensive.
By density
When choosing a roll material, first of all, you should focus on its density:
- 150-200 g / m2 used for drainage and effective removal of moisture;
- 250-300 g / m2 for the separation of soil and bulk layers with an increase in their stability and strength;
- more than 350 g / m2 for more efficient distribution of weight load on the soil and protection against heaving soils.
As practice shows, in the absence of moving or unstable soil, a canvas with a density of 250-300 g / m will correctly be used to protect the foundation for buildings up to 2 floors high2.
By thickness and other parameters
Material manufacturers supply geological textiles from 0.8 to 3.8 mm thick to the market. The greater the thickness, the stronger the canvas, but also costs more. The best option for laying geotextiles under the foundation is a material with a thickness of 1.6-2.4 mm.
Other important parameters include the filtration coefficient, which determines the amount of moisture passed per unit time, and the tensile strength index.
Laying geotextiles for the construction of foundations
The level of effectiveness of the use of protective geological paintings for the foundations of buildings largely depends on the exact observance of the technology of laying the material. For each type of foundation, it has certain features. But before laying geotextiles under the foundation, you should study the basic principles:
- the surface of the soil or bulk material should be well compacted and horizontally aligned as much as possible;
- the overlap of adjacent canvases during laying is a strip of at least 200 mm, with a slope - twice as much;
- if possible, it is recommended to use the thermal method of joining the paintings, otherwise plastic or metal staples should be used.
For welding canvases, a gas torch or blowtorch is used. After sufficient heating, adjacent edges are superimposed on each other and pressed tightly. Concrete on geotextiles is not poured. Before concreting, the canvas is covered with a layer of compacted sand with a thickness of 50-100 mm.
Monolithic foundation of tape type
Geological canvas with a density of 300 or more g / m2 they are laid on the bottom of the trench before filling the underlying pillow. If a layer of gravel and sand is poured separately, and not in the form of a mixture, then they should also be separated by geotextiles for a strip foundation with a density of 200-300 g / m2. This will eliminate the gradual leaching of sand into the gravel layer.
The lower layer of textile should be connected to a vertical canvas on the outside of the tape and only after that proceed with the assembly of the formwork structure. With non-removable polystyrene formwork, a vertical strip of roll insulation is not needed, since the foam itself will become sufficient protection.
Upon completion of pouring the concrete mixture and its setting, the upper plane of the monolithic tape should also be covered with a cloth with a density of 150-250 g / m2. Higher density in this case is not required.
Precast concrete strip foundation
The difference between protection and a monolithic structure is that the side wall of the tape is protected with geotextiles, gluing it to a concrete surface using bitumen mastic. In this case, the edges of the side web should extend beyond the edges of the wall and connect with other layers.
Tile base
Stripes of paintings spread over the entire bottom of the pit so that they go beyond the perimeter of the foundation by 150-200 mm. Then the formwork is installed, the reinforcing cage is assembled and concrete is poured.
After removing the formwork panels, the film is wrapped on the side ends and glued using bitumen mastic. The upper plane of the monolithic slab is not insulated, since it will be closed from external influences.
What geotextile to use for the foundation of a monolithic slab? As a material, it is recommended to choose a non-woven material with a density of 150-200 g / m2. Or woven with a density of 200-250 g / m2. It will fully provide good protection of the structure and improve its stability.
Column and pile foundations
The pillars and piles themselves do not need waterproofing the foundation with geotextiles. But, if there is a basement, before installing the grillage, it is recommended to cover the leveled soil with a cloth and pour sand, gravel on top or fill the surface with concrete. After that, you can proceed to the installation of the grillage and basement walls.
As a protective material, you can choose a non-woven film material with a density of 150-200 g / m2.
The use of polymer canvases when installing the blind area
A blind area is a wall adjacent to the wall in the form of a solid continuous strip around the entire perimeter of the house. It protects the walls and foundation of the building from the adverse effects of precipitation, reduces the depth and freezing zone, reduces heat loss in the lower part of the house.
However, the blind area itself can be destroyed over time under the pressure of expanded soil or when snow melts. To protect it, canvases can be used if the insulation is laid and fixed correctly.
Before placing a bulk cushion, two layers of canvas should be laid on the ground so that the geotextile layer extends 300-400 mm beyond the edge of the blind area. In addition, the insulation should be placed on the wall and raised 50-100 mm above the planned level of the concrete surface.
From above, pour a layer of crushed stone (we wrote here about which crushed stone is better to choose), tamp and cover it with another layer of canvas. In this case, the sand will not be washed with water into the crushed stone layer. Voids do not form, and the blind area will stand on a solid foundation for a long time. Then sand is poured, spilled with water and a concrete strip is poured along the perimeter of the house.
For this design, it is recommended to use a non-woven needle-punched fabric with a density of at least 350 g / m2. This geotextile has maximum strength and most effectively removes moisture. Less dense material may be used on stable non-porous soils.