Concrete pool

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A concrete pool is a very important and expensive construction. And it doesn’t matter what size the pool is – small or large. This does not reduce the complexity of the task..

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Design work

A pool is a complex hydraulic structure, in the design of which various specialists are involved. Determining the purpose of the pool (sports or entertainment), its hydraulic device (skimmer or overflow), the shape and size of the bowl, the bottom profile, specialists are guided by the wishes of the customer and his household, the client’s financial capabilities, the area of ​​the allocated land, the convenience and safety of operation. At the same time, the location of technical equipment, pipelines, cleaning equipment, microclimate systems (for indoor pools), a bypass path and a recreation area are taken into account. To better use the area of ​​the site, they try to place the bowl of the outdoor pool as close as possible to the building where the auxiliary rooms are located. However, it should be borne in mind that the minimum distance from the pool to buildings longer than 12 m should be equal to the average building height; to a building less than 12 m long with windows – half, and to the same buildings without windows – one third of the average building height, but not less than 3 m. In the immediate vicinity of the outdoor pool, there should be no trees that annually shed their foliage (poplar, linden, larch), as they contribute to water pollution. The thickness of the bottom slab and the walls of the pool, the class and grade of concrete, the class and diameter of the main reinforcement are determined on the basis of a hydrostatic calculation. At the same time, various load options are considered and the most unfavorable one is selected. The density of the earth and the level of groundwater are also taken into account. These are decisive factors in determining the scope and method of construction work. If all of the above actions are not performed, then damage to the product, or even the entire complex of buildings, may occur..

Preparing the base

Construction work is preceded by the preparation of the base. When constructing an outdoor pool, it includes a foundation pit, if necessary – a sand cushion (15-30 cm thick), laying a concrete preparation (about 10 cm thick). If the bottom slab is below the groundwater level, drainage is placed along its perimeter and under it. To solve possible problems with underground and flowing atmospheric water that can get under the product, we recommend equipping the perimeter of the main slab and the drainage channel with drains. This means digging a trench (width and depth 25-50 cm) around the perimeter and in the space of the drainage channel and backfilling it with coarse gravel. The depth of the trench depends on the method of construction of the stone floor of the pool and the depth of its immersion into the ground if the pool is partially settled above the surface.

The complex of works on preparing the foundation for an indoor pool depends on whether the structure is being erected according to the project and in the process of building a house or is being introduced into an existing cottage (if possible). In the first case, the project takes into account the specifics of the hydraulic structure, as well as the mutual arrangement of the building foundation and the bottom of the pool, provides space for pipelines, a technical room, and the base is prepared together with the foundation of the house. If the pool is built into an existing cottage, the approach will be different. Suppose that the bath is planned to be placed in the basement or basement, which means that the probability that the depth of the bottom slab will be below the level of the foundation of the house is quite high. In other words, during earthworks, the supporting part of the building may be undermined, and the underlying soil layer may be disturbed, which will lead to serious deformation of the supporting structures. To prevent this from happening, an individual technological scheme is developed for each case..

Installation of embedded elements

Before concreting, it is necessary to install and fix embedded elements: bottom drain, nozzles, embedded for nozzles, skimmers, headlights, embedded counterflow, etc., tie all this equipment with PVC pipes, cables. Then all the listed elements are poured with concrete. When installing embedded elements, it should be borne in mind that when casting bowls, concretes are usually used, which shrink after laying. Therefore, a technology should be used that does not allow the appearance of shells, voids. In addition, when pouring concrete bowls, shrinkage deformations occur, which can lead to displacements and reversals of the embedded elements. This is unwanted­serious consequences, since the accuracy of the shape of the molded bowl and the location of the embedded elements will no longer be corrected. To prevent movement of the embedded elements when placing concrete, it is necessary to ensure the rigidity of their fastening. Usually fastening is carried out directly to the formwork elements and reinforcement using bolted joints and tying wire. Some construction organizations do the opposite – first they cast a concrete bowl, then use a jackhammer to hollow out windows and grooves for the subsequent installation of embedded elements of technological equipment in them. This violates the integrity of the bowl. Attention!!! The bowl of the cast pool should not be exposed to any mechanical stress, otherwise water will necessarily go into the formed cracks, voids. Sealing any crack is much more expensive and more difficult than doing everything right at once..

Formwork installation

Formwork installation is a very important operation. The required bowl geometry, the specified dimensional accuracy and the strength of the formwork elements must be ensured in order to avoid buckling under the influence of the hydrostatic pressure of the concrete masses. Reusable (unified metal, plywood) and disposable (wooden) formwork are used for the manufacture of reinforced concrete pool bowls. In the manufacture of rounds, steps and other complex elements, one-time is used. This is due to the fact that the configuration of the bowls of concrete pools is most often non-standard (meaning the private sector). In addition, the bottom of such bowls is most often “broken”, with steps, etc..

It is not always possible to provide such forms using a unified formwork. At the same time, when using disposable wooden formwork, the consumption of leveling compounds increases sharply. This is due to the lower accuracy of formwork manufacturing in the conditions of the construction site compared to the factory conditions. Therefore, in straight sections, it is better to use a unified reusable formwork. The choice of the type of formwork is very important, since the amount of materials for the subsequent leveling of the surfaces of the bowl depends on its accuracy. These materials are quite expensive. Most of them are imported from abroad. The higher the accuracy when casting the bowl, the less will be the consumption of leveling compounds. It is extremely difficult to cast a perfect bowl that does not require further refinement. This is especially true for bowls that have rounded sections, bottom of variable depth, protrusions, etc..

Pit reinforcement

After the installation along the bottom of the pit of the underlying layer with a thickness of 100-200 mm of sand, crushed stone or gravel and a cement-sand screed with a thickness of 30 mm, they begin reinforcement work. If the pit is dug in solid ground, and not on an embankment, there is no need to reinforce the concrete slab with a steel mesh. Otherwise, it is necessary to use a steel network with cells of 150 x 150 mm and with a minimum reinforcement diameter of 6.3 mm. In the first case, if a bottom outlet is used in the pool, which serves to drain water from the pool, or as a suction element for filtration, it is necessary to create technological channels in the main plate in accordance with the drawing documentation. Of course, it is necessary to observe the maximum horizontal plane or the slope of the slab in accordance with the drawing documentation, since each deviation will appear after the pool is filled with water, when the edge of the pool is not parallel to the water level.

The most common approach is to erect tongue-and-groove walls, which are made up of metal or timber vertical elements. By the way, tongue piles are also used when building outdoor pools, for example, if it is impossible to arrange slopes. The grooved walls fix the soil, prevent it from crumbling, so that the bath can be buried below the base of the foundation.

For reinforcement, reinforcement of a periodic profile is used. Reinforcement section, cell spacing are determined at the design stage. Most often, rods with a diameter of 8-10 mm are used for vertical and horizontal reinforcement. The pitch of the horizontal rods is 3-60 cm, of the vertical rods 15-30 cm. The use of electric welding is unacceptable, since the microstructure of the metal is disturbed, carbon burns out, and during operation, intensive corrosion is observed in the welding places. The volumetric reinforcement cage of an outdoor pool is mounted on a concrete preparation, closed structures located on the ground floor, as a rule, are installed on special supporting structures. This makes it easier to lay pipelines, place equipment, organize monitoring of their condition and repair and maintenance work. Reinforcing rods are tied with steel wire, leaving “windows” for the installation of embedded parts, welded frames are not used – large internal stresses can occur in the thickness of reinforced concrete. Outlets of reinforcement are made along the contour of the bottom slab at the locations of the walls – they fix the frame of the walls. The bottom formwork is usually made of edged boards or laminated water-resistant plywood of increased strength.

The armature must necessarily be treated with special anti-corrosion compounds to ensure corrosion resistance and durability of the entire structure. Usually these are polymer paints. On the surface of standard hot-rolled rebar there is a layer of Fe3O4 (iron scale), the physical and mechanical properties of which differ from the rebar material. The scale is hard enough, but fragile. The strength of its connection with the base metal is low, therefore, under the influence of oxidative reactions, the scale layer exfoliates from the base metal. The polymer with which the reinforcement is coated should create an additional film that protects the metal from corrosion. If the paint is applied in one layer, then the likelihood of corrosion is high, since when the solvent evaporates on the metal surface, microscopic­Peak areas not covered with paint. For greater reliability, double staining is performed.

In cases where the highest level of corrosion resistance is required, multi-layer painting with paints or special polymer mastics are used. In addition, it is necessary to pay attention to the technology of installation of materials in accordance with the instructions of manufacturers and designers. If the reinforcement has a reliable multi-layer anti-corrosion or waterproofing coating with special mastics, then its durability can far exceed the durability of the reinforcement with traditional painting. This is due to the chemical and bacterial resistance of the coatings used (depending on the chemical composition), as well as the effects to which these waterproofing materials are exposed.

To provide a protective layer of concrete, special clamps are used. Clamps ensure accurate positioning of frames and compliance with the design thickness of the concrete cover, which prevents corrosion of reinforcing steel.

The walls are erected in the same sequence. For concreting rectangular pools, inventory metal formwork is used, curved sections are arranged with the help of circles from boards and plywood. The stability of the formwork is provided by wooden or metal retaining elements.

Concreting

The traditional technology for the construction of a reinforced concrete pool involves the stage-by-stage concreting of the bottom and walls of the bowl, and the quality of construction must be very high. This applies not only to indicators of strength, water resistance and hydrostatic stability, but also to the geometry of the pool. The sides should be almost perfectly level, the slopes of the bottom slab should ensure complete drainage of water.

The bowl is cast from heavy concrete of a class not lower than B15 (strength) and a grade not lower than W4 (water resistance). The frost resistance grade for the mixture used in the construction of an outdoor pool should be F100-F150, then the structure will withstand at least 100-150 cycles of alternating freezing and thawing. The concrete must be strong, waterproof and ductile. Since the water in swimming pools contains dissolved oxygen, chlorine, microorganisms, limiting their access to polymer and metal parts helps to stop oxidative processes. To increase the waterproofing properties of the bowl, additives such as SATURFIX or 1DROBETON and FLUXAN will be added to the concrete, increasing the water resistance, mechanical strength, mortar use time and the adhesion of concrete to reinforcement). The durability of the structure is the greater, the smaller the impacts on the anti-corrosion and waterproofing coatings of the reinforcement. Therefore, the denser the concrete, the more resistance it exerts on water seeping through its capillaries. The high density of concrete is provided, among other things, by a strictly dosed amount of water, which is used to mix cement, and its high-quality compaction. However, the lack of liquid makes monolithic work difficult, therefore plasticizers are added to the mixture, which, among other things, have waterproofing properties. The laid concrete mix is ​​compacted in order to get rid of internal voids and to streamline its structure. If the density of the concrete from which the bowl is cast is high {what up­observed during vibration and evacuation), i.e. there are no shells, the size of the capillaries is minimal, then the viability of a reinforced concrete basin bowl can be compared with other types of structures operating in a less aggressive environment (50-100 years). The minimum thickness of the main slab is 100 mm, the dimensions and quality of concrete must correspond to the drawing documentation

There are two main technologies for concreting a pool bowl: continuous pouring and casting in two steps. In the first case, the bowl turns out to be monolithic and is made in one go. The next layer of concrete sets with the previous one without the formation of “cold joints”. This is the most reliable concreting technology, but it involves the use of the most advanced construction equipment – concrete mixer trucks and concrete pumps. With this method, the continuity of the supply of concrete, the coordination of the work of all construction services are especially important. Concreting is carried out using platform and submersible vibrators. Unfortunately, this technology is used less often than others for technical and financial reasons. It is used only by firms with a high organization of production and supply of concrete of the required grades..

Sometimes, during the casting of pool bowls, for some reason, it is not possible to ensure continuous supply and reception of concrete. In this case, the “two steps” technology is used. It is carried out using a self-expanding cord, the so-called “dowel”, which will ensure the tightness of the bowl at the junction of new and already hardened concrete (“cold joint”). In this case, the bottom is first concreted, then the sides. A self-expanding cord with a cross section of 2.5×3.5 cm (for example EXPAN BENTONITICO) is pre-laid at the joints of frozen and uncured concrete. Then concreting is done. The tightness of the joints is ensured by the physical properties of the cord. When immersed in water, its volume increases at least 6 times. The cord covers all possible gaps and does not allow water to pass through.

This technology has been applied in domestic construction relatively recently. It helps to simplify the process and makes it cyclical. During construction with this method, it is necessary to strictly ensure the cleanliness of the joints. The fact is that during construction work, unwanted foreign bodies (sand, clay, dust, debris) may get into the place of the proposed joint. Places of prospective joints must be thoroughly cleaned and rinsed with water before pouring concrete..

Adjusting the bowl to the exact geometric dimensions is carried out with water-resistant repair mortars RESISTO UNIFIX, RESISTO TIXO, RESISTO BIFINISHING AB or plaster mortar (cement M-500 + sand) with latex additives COLLASEAL or LATIFLEX, which increase adhesion, water resistance and elasticity of the plaster) monolithic Regardless of technology, monolithic work is carried out at a certain temperature (not lower than + 5 ° C). In addition, freshly poured concrete is protected from direct sunlight and moisturized at low humidity..

Waterproofing

After removing the formwork, work is carried out to ensure the tightness of the bowl. A pool is a structure of complex dynamics, where the formation of cracks in concrete is possible. Therefore, the main task is to apply an elastic waterproofing coating to the surface of the bowl that can withstand the opening of cracks..

For this, its inner surface is sometimes impregnated with special solutions. The shells revealed after concreting are sealed with special putties, impregnations that ensure the tightness of the bowl, having previously treated the surface with solutions to open pores in the concrete surface. For better penetration into the depth of impregnating liquids, solutions of mineral acids are used.

Today on the market there is a huge variety of hydro­insulating materials: impregnating compounds operating on the principle of water-repellent liquids; polymerizing impregnations, water emulsions of polymer resins, which penetrate into the concrete and after a while polymerize, turning into plastic. The main task of this group of impregnations is to strengthen the surface layers of the concrete bowl and create an adhesive base for gluing the plaster layer. The most common polymers used for these purposes are epoxy, acrylic resins.

But in general, measures for internal waterproofing are largely determined by the selected finishing materials. So, if PVC film is used as a finishing material, labor-intensive waterproofing work is not required, but the base for ceramics or mosaics is prepared, on the contrary, very carefully. First, defects and minor errors are corrected using plasters or special repair compounds. The latter are preferable – they harden faster and, in addition, can have a water-stopping ability. In order for the plaster layer to adhere better to smooth concrete, contact adhesives are first applied to it. Plastering is carried out on a metal mesh fixed on a concrete surface with dowels. Thus, the resistance of the leveling, waterproofing and finishing layers to dynamic loads is ensured. Deviations from the vertical and horizontal are controlled by rack and pinion metal beacons.

Small indoor pools are coated with waterproofing compounds that form a hard coating. Open and closed structures that are installed on supports or have large dimensions are sealed with cement-polymer materials. These two-component formulations, consisting of a cement base and an elasticizer, such as Mapelastic (Mapei), Aquafin-2k (Schomburg), Osmoflex (Index), Vandex BB75E (Vandex International), Ceresit CR 66 and Ceresit CR 166 (Henkel Bautechnik), form coating capable of bridging a crack up to 1 mm wide. Sometimes penetrating waterproofing is used to seal pools, for example, Osmoseal (Index), Penetron (ICS / Penetron International LTD), Kalmatron (New Technologies), Khurekh (Khurekh Chemical), Vandex S (Vandex International). Such materials are dry cement mixtures with active ingredients. The latter penetrate into the concrete and react with calcium hydroxide, forming insoluble crystals and filling the pores. And you shouldn’t save on sealing layers either. It is recommended to apply two layers of two-component elastic waterproofing layer with a thickness of 2.5 to 4 mm. Too thin a layer is not waterproof and can peel off the surface under water loads. Too thick layers increase the bonding time of the material, which can subsequently lead to cracking, especially in the inner corners of the bowl.

Don’t forget expansion joints. Ignoring this moment, you cannot avoid troubles.

The finishing of critical areas with alternative waterproofing is of great importance. The joints of the walls and the bottom must additionally be glued with sealing tapes. A prerequisite for the construction of a concrete pool, tiled with mosaics or ceramic tiles, is to check the bowl for water leaks. The watertightness test must be carried out after the manufacture and leveling of the concrete bowl surfaces. In this case, the pool is filled with water and kept for 10 days. It will not be superfluous to make sure that the bowl is waterproof even after applying waterproofing. It should be borne in mind that after draining the water, the surface of the bowl may remain contaminated, which will lead to a decrease in the adhesion of the adhesive solution when laying the lining.

After plastering the bath, the embedded elements are installed; Expanded concrete or special cords are used to seal the frames, for example, Expan Bentonitico (Index), Bentorub (De Neef conchem), SDM Duroseal Quellband type U, Quellpaste type E, Asoflex, ASO Dichtband-2000-S (Schomburg).

After the completion of the waterproofing measures, the bowl is subjected to hydrotechnical tests. Water is poured into it and the state of the structure is monitored for three days. If the tightness is confirmed and there are no leaks, the pool is drained, backfilled and the structure is finished..

Decoration and decor

To decorate the bowls of pools, special mixtures are used for tiles of different colors, as a rule, blue, blue and white tones. Tiles and mosaics in elite-class pools are laid in the form of art panels. Moreover, not only on the inner surfaces of the pool bowls, but also on the walls of the room.

Glue for ceramics is a pasty mass that is applied to the surface with special comb spatulas. Latex is part of adhesives and grouts as a mixing liquid. The adhesives used for the installation of tiles and mosaics are durable and elastic. They are held firmly enough on a prepared surface. In addition, such adhesives have waterproofing properties. The glue is applied in a thin layer using a special comb-type trowel. The width of the grooves and protrusions on the working part of the trowel is selected depending on the thickness of the tiles and the size of the tile joints. Before laying tiles and especially mosaics, it is necessary to ensure­high quality base surface, otherwise everything will not­the evenness of the surface of the bowl will appear on the surface of the panel.

A special film (Alkorplan 2000, Flagpool, Efolie) makes finishing work easier and cheaper. In accordance with the size and configuration of the bowl, a “bag” is made from it, which is then fixed on the walls and bottom of the pool using fasteners. An underlay carpet is laid under the film to prevent the formation of condensation and the appearance of microorganisms. The service life of such a coating is 7-12 years..

And, finally, the finishing stage – grouting of inter-tile joints. In places subject to particularly high mechanical stress and rinsing (for example, in the area of ​​rough water surface), it is recommended to use epoxy grout.

That, in fact, is all. As for the curtain, I would like to remind you that the correct and competently constructed works on the construction of the pool guarantee the trouble-free operation of the structure.

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