General requirements for concrete floors. Requirements for the preparation of bases for the installation of industrial polymer floors

Surface requirements

Correct surface preparation is the most important stage in the laying of bulk polymer coatings. Mostly KEMA polymers are laid on a concrete base. In approximately 90% of cases, the cause of delamination and destruction and a decrease in the service life of polymer coatings is the illiterate preparation of the concrete base. For proper preparation of the foundation, it is necessary to take into account a number of factors:

Strength Concrete slab grade at least M250. If the grade of concrete is below this value, the concrete base will not be able to adequately bear operational loads, collapsing under the polymer floor. Destruction of the base will lead to the destruction of the polymer coating. In addition, in this case, the concrete base is too porous and the primer consumption will be significantly higher than recommended. Concrete grade is measured using a Schmidt hammer, a Kashkarov hammer, KISI, Concrete-8, UK-UP, UK-16P, IUK-12P, PIK-6, Udar-1, Udar-2, MK-1, etc. type instruments. The tensile strength of concrete is at least 1.5 MPa. With concrete strength below this value, there is a high risk of delamination of the coating along with concrete. This is especially important if wheeled vehicles move indoors. This will cause high shear loads. In order for the polymer coating to be durable, it is necessary that the tensile strength of concrete is not inferior to the adhesion of the polymer coating KEMAto the base.

Humidity  The humidity of the concrete floor when laying the polymer should be no more than 4%. This is because the water vapor in the concrete creates a high partial pressure and can cause delamination of the polymer. Where separation occurs will depend on the local strength of the concrete. If the humidity of the concrete is 4-8% and it is impossible to dry the concrete, it is necessary to use a thin-layer vapor-permeable material system   KEMAPOX AQUA. Humidity is measured using a MG-4, MG-4D moisture meter, GANN Hydromette, carbide method, laboratory methods .. In addition, the presence of excess moisture can be measured by putting a 50 cm x 50 cm plastic film on a concrete, 0.15 mm thick and gluing it edges using tape. After at least 16 hours, the presence of moisture drops on its inner surface is visually checked. With its presence, the moisture content of concrete is more than 4%. Relative humidity - not more than 80% (measured by hygrometer type VIT-1, VIT-2)

Concrete age
  The concrete floor must be aged for at least 28 days. This is due to the process of hydration of concrete. At this time, there is a chemical process of gaining concrete strength. It is characterized by excessive moisture and shrinkage of concrete. Polymer coating KEMAearlier than this period is undesirable due to possible problems with coating adhesion and cracking in the future.

The presence of waterproofing
  If the concrete base is arranged on the ground, then the presence of waterproofing is a prerequisite for the installation of polymer coatings. Otherwise, as a result of the possible ingress of moisture from the soil into concrete, it will lead to excess moisture and a possible separation of the polymer coating. If there is no waterproofing of the concrete base, the use of a vapor-permeable system KEMAPOX AQUA.

Evenness of foundation
  The deviation of the evenness of the concrete base when installing a bulk polymer floor should be no more than 4 mm. when checking with a 2 meter rail. Moreover, the thinner the polymer floor layer, the more even the surface of the concrete base should be. All defects in the concrete surface will appear through a thin coating layer.

Base temperature
  The ideal temperature of the concrete base when applying a polymer coating KEMAshould be in the range + 17 ° С - + 23 ° С.
  The minimum base temperature during coating is + 12 ° C.
  The maximum temperature of the base during coating is + 30 ° C.
  Before starting work, the base temperature must be 3 ° C higher than the measured dew point. When carrying out work in open spaces, it is better to start applying in the evening, so that the sun's rays do not overheat the surface. The temperature of the base can be measured with a conventional thermometer, for this it is placed on the floor for at least 20 minutes.

Concrete base problems and methods for their elimination

The polymer base is not always ideal. In this section, we consider the problems and solutions of preparing the base for applying the polymer.

   All contaminated concrete must be removed to whiteness. It is better to do this work with a shot blasting machine. It is also possible to remove contaminated concrete using a mosaic grinder with diamond segments, and in case of deep contamination with a milling machine.   Fissures with openings up to 0.5 mm fill KEMAPOX FILL 1000.    The crack expands with a perforator 1–2 cm wide and up to 0.5 cm deep. This is done in order to remove dirt and a weak concrete layer to obtain good adhesion with putty. After this, the crack is cleaned, primed KEMAPOX GRUND 2000  and is filled with putty using a spatula to floor level.   In this case, it is necessary to dismantle the screed and apply a new one. When repairing this crack, it is impossible to guarantee the absence of delamination of the concrete screed and its monolithicity and, as a result, the formation of cracks in the polymer coating.   Crushed stone and slides are cut with a mill. (Do not grind crushed stone, for the safety of diamond milling cutters.) Low places are leveled with putty, and it is necessary to grind and dust the surface before applying putty.   To fix a low grade of concrete, the screed is primed with primer KEMAPOX GRUND 2000  or KEMAPOX FILLL 1000  to saturation (the appearance of places with a shiny surface). After that, easy grinding is carried out (full grinding of a soft screed will lead to the formation of holes) and the base is completely putty with a putty consumption of 1 kg / sq. M. After polymerization of the putty (since the soil from the putty is partially absorbed, a residue of sand is formed), it is necessary to grind and dust the surface again. The surface is prepared. Further application of systems KEMArequire less primer (0.2 kg. / sq.m. instead of 0.4 kg. in standard systems).   It must be dried with heat guns until the concrete turns white.   Raise the room temperature using heat guns or other heating equipment. If you plan to install heating in the room, it is better to plan the work of applying a polymer coating KEMAafter installing the heating. If pipes are used as guides, it is better to pull them out, and repair the resulting fractures as medium cracks. If we leave the pipes, then they must be puttied up to a thickness of 3 mm., But in this case, the customer should be warned that in these places there will be a small tubercle. Modern special guides have a plastic coating on top in the form of a cord. It must be pulled out, and the damage repaired as medium cracks.   The sealant with which the seams are filled is removed. The joints are filled with putty and repaired as medium cracks.

Problem	What affects	Solution methods
Dirty concrete    (There is paint, oil, grease, etc. on concrete)	The polymer coating will have poor adhesion to the base and will peel off during operation.
Foundation cracks	Dangerous after polymer coating KEMAduring the operation of the floor, their further increase may occur. And polymer coating KEMAmay also crack in these places. In addition, when applying the primer layer, cracks will significantly increase soil consumption.	Usually, all cracks (especially small ones) are not immediately visible and open after bead-blasting or grinding. For filling cracks with an opening of 0.5 mm or more, a special putty is used: 1 part of the primer KEMAPOX GRUND 2000, 5 parts of quartz sand EPOXY SAND ES  (0.1-0.3 mm). Dynamic cracks transversely reinforce.
Hair crack
Medium cracks
Cracks for the whole    concrete screed depth	A crack along the entire depth of the screed means its detachment from the base and the presence of strong deformations in it.
Local pits    open either    concreted	Concrete base with open local pits does not meet the requirements for flatness of the floor. And the concrete used to repair the pits (if they are concrete) has low adhesion and peels off during operation, thereby destroying the polymer coating.	Repair concrete is dismantled. The pit is sanded with a grinder to remove dirt and a weak layer of concrete. It is then dusted off with an industrial vacuum cleaner. After preparing the surface, the pit is filled with dry gravel and filled with epoxy concrete (1 part of the soil KEMAPOX GRUND 2000 : 11 parts of sand fraction 0.3-0.8 mm.). This composition should be below the floor by 0.3-0.5 cm. After polymerization, the composition will shrink. After that, the pit is leveled to the floor level with standard putty.
Roughnesses, rubble	Non-compliance with the requirement of evenness.
Low grade concrete	If the concrete base is lower than M250, then during operation it will break down under the polymer coating and as a result, the coating will break down. In addition, in this case, the tensile strength of concrete is too small and the polymer coating KEMAmay peel off with the top layer of screed.
Thin screed    (less than 5 cm)	The base will collapse and exfoliate during operation, which will lead to the destruction of the polymer coating KEMA.	Application of thick quartz-filled coating systems with fiberglass reinforcement of the first layer along the primer.
Wet concrete	It is possible to peel the polymer coating from the wet base.
Low temperature    grounds	Polymerization problems may occur.
Guides	There may be problems with the adhesion of the polymer coating. Grind carefully, it is possible to damage diamond cutters on metal pipes.
Deformation    seams	The sealant will not adhere to the polymer coating.
Fittings	A reinforcing mesh may protrude from a concrete screed.	Cut and putty.

Base requirements before applying polymer industrial floors.

Polymer floors with a small thickness (from 0.5 to 10 mm.) Can withstand high mechanical and chemical loads, very often this is the only way to repair old industrial floors. In order for the polymer floor to serve for a long time, high demands are placed on the foundation on which the industrial polymer floor will be laid. For many years, the main material for the foundations was concrete and cement-sand screed. In recent years, in connection with the growing demands on strength, modifications by polymers, fiber additions or backfilling of dry hardeners, the use of evacuation to reduce the water content in the screed, etc. are actively used. These modified substrates have limitations on the applied coatings. Wooden, asphalt, anhydrite and magnesia floors are very widespread in the industry: as they are economical, easy to apply, warm to the touch. Their poor long-term strength, high sensitivity to water, low hygienic characteristics over time force them to make repairs.

High-strength concrete. These include high strength concrete and evacuated concrete. They are difficult to mill and their surface is polished when grinding. This adversely affects the adhesion of subsequent coatings to high-strength concrete and causes delamination of these coatings. The use of low viscosity primers does not lead to a significant improvement in the results. A good result can only be obtained with high-quality shot or sandblasting.

Concrete floor with hardened topcoat. The top, hardened layer of the concrete floor contains such fillers as quartz, corundum, carborundum, etc., and the presence of various modifiers of unknown origin is also possible. These materials have very high hardness and poor adhesion to polymer coatings. Application of polymeric materials is possible only after a good surface preparation and subsequent test. In the case of a negative test result, it may be necessary to remove the entire hardened layer.

Concrete with fiber.  If concrete contains synthetic fiber, then after bead-blasting and priming, the fiber can rise and form a “bristle” on the floor surface. You can remove the stuck fiber by flame treatment. After this, light sanding, and in some cases additional primer treatment, may be required.

Requirements for all concrete substrates before applying a polymer floor:
  - tensile strength not less than 1.5 MPa;
  - humidity not more than 4%;
  - cement "milk" must be removed.

Anhydrite and gypsum floors
  Anhydrite is dehydrated gypsum and is characterized by a low rate of curing, to accelerate the reaction, special salt-based accelerators are added to it, their concentration can be from 3 to 7%. On the surface of the adhydrite floors, efflorescences may appear that prevent adhesion with subsequent coating.
  The hygroscopic effect or chemical reaction with the components of liquid epoxy resins during the period of curing can cause bubble formation, loss of strength and even delamination of large areas. Like gypsum, hardened anhydrite has a high solubility (about 2 g / l.). During temperature fluctuations, condensation may form under the surface of the polymer coating, which will cause the polymer to detach. Therefore, the humidity of the anhydrite (and gypsum) floor before applying the polymer floor should be no more than 0.3%, and this floor should be open from below for good ventilation.
Recommendation:  This screed should be removed before applying the polymer coating.

Magnesia floors
Magnesia floors are the reaction product of magnesium oxide with magnesium chlorides and sulfates to form magnesium hydroxide. Chlorides contained in such a floor cause corrosion of steel reinforcement in the concrete sublayer. When wet cleaning, moisture penetrates the floor, mixing salts (bischofite) react with magnesium hydroxide and a loss of strength of the magnesian floor occurs. Organic aggregates are often used in these floors, which, when humidity changes, cause surface cracking. A magnesia screed cannot be coated with a polymer layer until all the negative processes (shrinkage, carbonization, etc.) have ended in it. It has been experimentally established that at least 1.5 -2 years after pouring should pass. The moisture content of the magnesia screed should be no more than 0.3%, and this floor should be open from below for good ventilation. Typically, magnesia floors are coated with oil or wax to protect against moisture. These coatings penetrate deep into the screed body, which impairs adhesion. A layer of screed soaked in oil must be removed.
  Recommendation: it is better to remove this screed before applying the polymer coating.

Old polymer coatings
  Often there is a need to update old polymer floors without removing them. In this case, there is a compatibility problem between the old and the new coating.

Old base	Epoxy	Polyurethane	PMMA	Polyester
Epoxy	oK	after priming	not compatible	partially compatible
Polyurethane	pre-test	pre-test	-	-
PMMA	not compatible	-	pre-test	-
Polyester	not compatible	-	-	oK

PMMA- polymethylmethacrylate coating.
  Before applying a new polymer, the old coating must be sanded with an abrasive disc or sandpaper. The choice of the subsequent polymer coating depends on the requirements for chemical, mechanical resistance, and temperature exposure.

Existing ceramic tiles.
  It is checked for adhesion to the base by tapping. The weakened, cracked tile is removed, the defect is restored to the level with epoxy concrete. The surface of ceramic tiles, clinker bricks, acid-resistant tiles (and similar low-absorbing materials) is matted with a grinding wheel, the layer of glaze is removed as much as possible. Before applying the main coating layers, a primer absorbency test and adhesion test are carried out. If the result is positive, it is recommended to use thick-layer quartz-filled coating systems with fiberglass reinforcement of the first layer along the primer. Polyurethane coatings are preferred.

Concrete foundation preparation technology.

The polymer coating is a fundamentally different substance compared to concrete. For good adhesion to concrete, it is necessary to remove all factors that prevent adhesion: non-adhering particles of concrete, contamination of concrete, cement milk. Also, the contact area of \u200b\u200bthe polymer with concrete plays a significant role. The larger the real contact area, the higher the adhesion.

Methods for preparing the base:

• Shot blasting
     It is the most effective way to prepare a concrete base for applying a polymer coating, as it not only removes “cement milk”, weakly containing concrete particles and dirt, but also creates a high degree of surface roughness, increasing the adhesion area of \u200b\u200bthe polymer coating to the concrete surface in 2-2, 5 times. Shot blasting reveals all hidden surface defects, which significantly reduces the number of polymer floor defects. In addition, the shot blasting process is dust free, which is very important for the customer.
• Grinding
     It is produced using a mosaic grinder with diamond cutters. During the grinding process, the upper weak and contaminated concrete layer is removed. It is imperative to carry out grinding “dry”, otherwise the humidity of the concrete will increase and there will be problems with the adhesion of the polymer coating. One of the drawbacks of the use of grinding equipment is the sealing of concrete pores with dust, which impairs adhesion, as well as incomplete opening of defects on the concrete surface. However, grinding is the most common way to prepare a concrete base due to the low cost of equipment and work. The efficiency of grinding equipment depends on the quality of discs with diamond segments having different hardness and purpose.
• Milling
     It is used, first of all, for leveling out significant differences in the concrete base (up to 5 mm in one pass), for removing existing polymer coatings or thin layers of paint without destroying the concrete surface.
• Dedusting
     After that, it is necessary to collect all the dirt and dust from the floor with mops, and then thoroughly treat the surface with an industrial vacuum cleaner. Mops can not be used, but then the vacuum cleaner will often have to be cleaned.

Safety measures during the work on the device of floors.

1. General Safety Requirements (hereinafter referred to as TB): 1.1. Work must be carried out by personnel trained in working on the equipment used and trained in safety. 1.2. The equipment must be in good condition, have clear control labels, meet electrical safety standards. 1.3. Work should be carried out under the supervision of a foreman or shift supervisor, as agreed with the foreman.
      1.4 In addition to the recommendations given in these instructions, the organization and conduct of work must comply with SNiP 12-04-2002 - "Labor safety in construction. Part 2. Construction production".
2.   TB during the preparation of the concrete base:
   2.1. Concrete base preparation using a shot blasting machine.
      2.1.1. Before starting work, the worker must visually check the serviceability of the units and assemblies, check the oil level, and fill up the shot.
      2.1.2. Operation on a shot blasting machine without Personal Protective Equipment (hereinafter referred to as PPE) is prohibited. The PPE kit includes:
   
   
      - gloves;
      - Headphones or ear plugs.
   2.2. Concrete base preparation using a grinding and milling machine.
      2.2.1. Before starting work, the worker is obliged to visually check the serviceability of the units and assemblies, check the condition of the frankfurt (interchangeable cutting tool), and replace worn ones.
      2.2.2. Work on the grinding and milling machine without PPE is prohibited. The PPE kit includes:
      - Glasses or mask made of plexiglass;
      - Rob complete with a hat;
      - gloves;
      - Headphones or ear plugs;
      - Respirator.
      2.2.3. It is forbidden to work on the grinding and milling machine without the connected aspiration (vacuum cleaner).
   2.3. Concrete base preparation by a milling machine and / or a manual milling tool.
      2.3.1. Before starting work, the worker must visually check the serviceability of the units and assemblies, check the condition of the interchangeable cutting tool, and replace the worn out one.
      2.3.2. Work on the grinding and milling machine without PPE is prohibited. The PPE kit includes:
      - Glasses or mask made of plexiglass;
      - Rob complete with a hat;
      - gloves;
      - Headphones or ear plugs;
      - Respirator.
      2.3.3. It is forbidden to work on a milling machine and / or a manual milling tool without a suction connection (vacuum cleaner).
3. TB during the application of Praspan materials:
      3.1. Work on the application of materials KEMAno PPE prohibited. The PPE kit includes:
      - Glasses or mask made of plexiglass;
      - Rob complete with a hat;
      - gloves;
      - Headphones or ear plugs;
      - Headphones or ear plugs;
      - A respirator that protects the worker from volatile organic and inorganic substances.
      3.2. It is forbidden to carry out work on the application of materials KEMAin conditions of insufficient ventilation. When carrying out work, it is recommended that the ventilation work in an enhanced mode.
      3.3. Do not use material components KEMAinside. Avoid contact with skin. In case of contact with eyes, rinse with cold water and consult a doctor.
      3.4. Liquid materials KEMAcombustible, therefore it is forbidden to store and open containers, to carry out work on application near an open flame.

Storage of polymeric epoxy and polyurethane materials KEMA.

To ensure safety and optimal properties, materials should be stored in closed containers (original packaging) in a cool, dry room at temperatures below 23 ° C outside of heat and sunlight.
  In the case of storage at temperatures below + 15 ° C, it is recommended to withstand the material in the working room at temperatures above + 15 ° C for at least 24 hours.
  When stored at temperatures below 0 ° C, it is recommended to withstand the material in the working room at temperatures above + 15 ° C for at least 48 hours.
  Water-based epoxies are not allowed to be stored at low temperatures.
  All storage locations must comply with fire and building regulations. A warehouse with materials should be located outside any sources of fire or combustion. Large quantities of hardener must be stored in a cool fireproof room at a sufficient distance from other fire hazardous materials. Avoid temperature rises above 25 ° C. Overheating or mixing with other reagents, such as an accelerator, can cause an explosion. The product must be used within 12 months from the date of manufacture.

Note

For additional instructions, alternative methods of application, or information on the compatibility of the use of system materials KEMAwith other products or technologies by contacting the technical department Ettrilat NT LLC.

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Article added 04/08/2013 23:04

Concrete floor requirements:

• concrete grade not lower than M-300
• the difference in the thickness of the screeds within 3-5cm (it is recommended to level the base with a concrete)
• thickness of concrete floor on tamped base - from 12cm
• floor thickness on an existing concrete base - from 7cm
• reinforcement - road mesh (with increased loads on concrete, the recommended floor thickness is from 12 cm, reinforcement is a volume reinforcing frame)
• at high operational loads on the floor, use toppings (hardeners of the concrete surface, which will increase the grade of concrete by 100%)
• for hardening and dust removal of concrete surfaces use polymer impregnation "Ashford Formula"

Work stages

For high-quality concrete flooring, a set of the following works is required:

1. Leveling the base under the concrete floor with laser and optical levels to determine:

• topography
• floor level
• zero mark
• calculating the ramp

2. Preparation of the base under the concrete floor. The floor can be laid on unpaved, existing concrete or other types of substrates. In this case, you need to check the basis for compliance with the requirements for a concrete coating.

To prevent cracking of the floor due to subsidence of the base, it is necessary to compact the soil well before laying the concrete floor. After this, the sand cushion is laid on the ground. Its thickness can vary between 0.5-1m depending on the following factors:

• type of soil at the base
• degree of soil freezing
• groundwater elevation and so on.

The sand cushion also needs to be tamped.

Elimination of defects

If there are cracks in the existing concrete base, they must be expanded and then filled with a special repair compound. It may include either polymer or a cement-sand mixture based on tensile cement. Areas of concrete base that cannot be repaired require complete dismantling and laying of new concrete.

If there are differences in height in certain areas of the base, they should be removed with a milling machine. The dust arising from this type of work is eliminated with industrial vacuum cleaners. In case the height differences on the existing concrete base are more than 5 cm, it is leveled with a concrete.

Industrial floors  - without them in our time it is impossible to imagine a single building. Wherever we go, to the supermarket or to the stadium, to a manufacturing enterprise or food processing plant, warehouse or underground garage, exhibition hall or medical facility - everywhere we come across industrial floors. Depending on the requirements for the floor surface, on the operating conditions and aesthetic requirements, industrial floors can be made using various design solutions. Modern industrial floors are single-layer or multi-layer constructions performed using the most modern technologies and professional equipment.

The highly qualified staff of our company performs almost all options for industrial floorswhich are used today for new construction and reconstruction of old structures. These are concrete industrial floors with a hardened top layer (topping), polymer industrial floors, and industrial floors made of polished concrete, which are gaining more and more popularity.

On our site you can find comprehensive information about modern industrial floors. This will help our potential Customers and designers to choose the optimal type of industrial floor that will most fully satisfy all the stated requirements. If necessary, the engineers of our company by phone or in person will provide professional advice.

To facilitate the search for the necessary information, our site is divided into sections:

  - This is a section devoted to polymer industrial floors. Modern polymer floors  very widely used in construction. Bulk epoxy floors are used where very serious mechanical loads are applied to the floors, in the case when industrial floors need to be given increased chemical resistance, to facilitate the cleaning process. Epoxy antistatic systems are widely used in explosive industries, server rooms and assembly shops for the most complex electronics. Bulk epoxy compounds allow you to create unique highly artistic bulk floors. Bulk polyurethane floors are also a very popular type of modern polymer floors. Due to the greater elasticity compared to epoxy floors, polyurethane self-leveling floors are most often used where the base undergoes vibration, with the risk of small cracks in the base, if during operation the industrial floor is subjected to strong shear loads. Methyl methacrylate floors have a number of unique properties that epoxy or polyurethane floors do not have. The speed of their polymerization and curing is so high that within 2 hours after installation, floors from MMA compositions can be subjected to full load. Another unique property of such floors is the possibility of laying at low temperatures.

- This is a section informing about concrete industrial floors of various designs. Industrial concrete floors with a hardened layer (topping) - less often they are called armored topping floors or polished concrete floors. One of the most popular types of concrete floors. When arranging such floors, a dry hardener is used - topping, which scatters on the surface of freshly laid concrete and with the help of concrete-finishing machines (helicopters) is evenly distributed on the surface, compacted, sanded and creates a high-strength crust on the surface of the manufactured industrial concrete floor. This floor is not dusty, easy to clean, has a more attractive appearance compared to ordinary concrete. The huge advantage of these floors is the relatively high speed of work, the quick commissioning of the finished industrial floor and a relatively low cost. The technology of “polished concrete” or polished concrete floors is a fairly long-developed technology that has gained a “second life” with the advent of high-tech grinding and polishing plants, as well as modern building chemistry, which impregnates the concrete floor after multi-stage, multi-stage grinding and polishing. The main advantage of such floors is that no coating is applied to the surface of the concrete floor, which eliminates its destruction or delamination. When industrial floors are made of polished concrete, a weaker layer of cement milk and the upper concrete layer are cut from its surface until granite aggregate appears. Then the monolithic concrete is impregnated in several stages with lithium impregnations and polished with polishing machines. The concrete floor has a mirrored surface resembling a natural stone, which does not allow moisture to pass through, is resistant to chemicals, easy to clean and does not require repair for many years.

The concrete base for laying linoleum is the most durable and durable. The ability to withstand large static and dynamic loads, as well as low cost, makes them the most common type of rough floors for sports flooring.

Depending on the design features of the room, there are two ways to make a concrete floor:

• on the ground - on the ground floors without a basement or basement;
• on slabs.

The fundamental difference is the arrangement of sand and gravel pillows, waterproofing and thermal insulation. The thickness of the concrete base can be from 50 to 150 mm.

When installing concrete floors on the ground, a necessary condition is a low groundwater level and complete shrinkage of the foundation of the house. Otherwise, the base will become unusable in a short time (drawdowns will appear).

Before making a concrete floor on the ground, it is necessary to mark the level of the base. The reference point (zero) will be the thresholds of the entrance doors to the room. It is necessary to take into account the thickness of the floor covering, the concrete screed itself, the heat-insulating layers and the sand cushion.

Before starting work on the construction of a concrete base, it will be necessary to remove the topsoil to a depth of 20-30 cm. The resulting trough is filled with sand or gravel mix with layer-by-layer compaction. For effective compaction, spillage with water and the use of a vibrating plate are recommended.

The thickness of the sand layer depends on the differences in the surface of the soil and ranges from 5 to 25 cm. Thus, the primary leveling of the level of the rough floor in the room is carried out.

As an additional heat-insulating layer, expanded clay, tuff or different kinds  blast furnace slag. It is laid on a sand pad and spilled with cement milk or grout for preliminary fixation. To increase the waterproofing, it can be shed with bituminous mastic.

Heat and waterproofing of the base

One of the main stages of the construction of a concrete base is the implementation of waterproofing works. Not only the exploitation of the floor covering in the future depends on their quality, but also the safety and durability of the entire building as a whole.

For waterproofing a concrete base, roll materials are best suited - polyethylene (at least 200 microns), hydrophobic membranes, roofing material, glass insulation and others.

The waterproofing sheets are overlapped with an overlap of at least 10% of the width, the seams are glued with tape. The edges of the waterproofing must wind up on the walls above the zero mark. After concreting the base, the excess is cut off.
  As a heat-insulating layer, various types of hard insulation can be used. It can be both artificial materials, such as polystyrene foam, polyurethane foam, and mineral-based, stone basalt wool, perlite, cork.

A layer of thermal insulation is laid on top of the waterproofing material. Its thickness depends on climatic conditions and is determined by calculation, depending on the coefficient of thermal conductivity of the material. A vapor barrier is made on top of the insulation, which can be used with the same rolled materials that were used to waterproof the base.

Concrete base reinforcement

Since the floors in gyms provide significant dynamic loads, there is a need for reinforcement when installing a concrete base. As a reinforcement, either a ready-made mesh or a flat frame made of individual rods can be knitted.

For this, reinforcement of class AIII Ø 8-16 mm is used (depending on the thickness of the screed and the degree of operational load). The pitch of the reinforcement in the frame or mesh is from 50 to 150 mm and depends on the diameter of the rods.

There are various types of nylon or polyethylene fittings. It is available in the form of ready-made nets. You can use fiber, added directly to the concrete mix.

The frame or mesh is exposed on special locking beacons that ensure the distribution of reinforcement in the concrete screed. It is necessary to install the mesh in such a way that the distance from the top of the reinforcement to the top of the concrete is at least 15-25 mm, but at the same time it does not lie on the waterproofing.

Along the perimeter of the room, it will be necessary to install a damping tape that ensures the independence of the base from bearing structures  walls. This will compensate for possible shrinkage of the screed, giving this process uniformity over the entire area. The tape also serves to reduce the effect of thermal expansion of the screed during heating in the “warm floor” system.

Installation of beacons for concreting

The next step will be the placement of guide beacons, along which concrete mixture will be poured. To do this, you can use various types of pipe profiles or wooden beams.

The gym room is divided into rectangular sections of phased concreting (maps) so that each of them can be poured in one go. The direction of concreting can be both longitudinal and transverse. It all depends on its shape and location of the entrance, so the whole process should be carried out from the far wall to the doors.

Beacons are installed using a level or level (laser, water or manual) according to the zero mark of the concrete base with fixation with a hard cement mortar. The step of the guides can be arbitrary, but not exceed the width of the rule, with the help of which the concrete mix will be leveled.

Guides can be made reusable if you use a metal pipe lubricated with a composition for processing formwork. After preliminary hardening of concrete (for 2-3 days), they can be removed and used in another place, and the remaining grooves should be filled with concrete mix flush with the base.

Concrete preparation

For a quality foundation, it is necessary to fill the foundation without interrupting the process. To do this, it is advisable to use the ready-mixed concrete, ordering it at RBU. The class of concrete is determined by the design (operational loads), but must be at least B15.

But with small volumes and in order to save, it is possible to produce concrete mix independently. For preparation, a concrete mixer and components are required in the following proportions: for 10 liters of cement M400 25 kg of washed river sand and 42 kg of gravel of a fraction of 5-10 mm are needed. This will result in 0.054 m3 of concrete mix of class B15 (grade M200).

For other classes, the ratio of cement to aggregate will be different. How to choose the right proportions for various types of concrete can be found in the reference literature.

All components must be poured into a concrete mixer and thoroughly mixed “dry”. Water should be added at the rate of 5-6 liters per 10 liters of cement, controlling the mobility of the mixture. However, it should be remembered that a lack of fluid will not allow the entire cement to react, and its excess can lead to the formation of excessive capillaries in the concrete body and, consequently, further cracks. Both factors reduce the final strength of the concrete base.

Concreting is allowed only at air temperature above + 4 ° C, at lower rates additional heating of the base is required. Ideal conditions are considered at 25 ° C and 75% air humidity. But at a higher temperature, special care for concrete will be necessary (copious wetting with water during hardening).

It should be borne in mind that in the process of cement hydration a reaction occurs with the release of heat, which negatively affects the further strength of concrete. Therefore, in the manufacture of concrete mix in very hot weather (more than + 30 ° C), chilled components should be used.

Since lowering the temperature of sand, gravel or cement is quite problematic at the construction site, a source with the coldest water is needed.

Concrete Mixing and Maintenance

The “map” between the rails is filled with concrete mixture just above the lighthouses, stretching across the entire plane. To remove excess air and precipitate concrete mix, bayonet it with a shovel or metal rod, but it is best to use a depth vibrator, dipping it in a checkerboard pattern.

The radius of the vibrator depends on the size of the mace and is about 5-6 diameters. This should be repelled when immersed in a concrete mixture.
  A sign of thorough compaction is the appearance of cement milk, while the gravel is slightly precipitated without protruding on the surface.

Filling the "map" section for several meters, you can begin to level the concrete mix. To do this, use the long rule, setting it on the guides across the "card". Moving it to the left and to the right, it is gradually pulled towards itself, removing excess mixture or adding in places where there is a deficiency, leveling the surface to a zero mark.

To increase productivity when concreting large volumes, a vibrorail can be used. In this case, the concrete is compacted and leveled at the same time.
  After leveling the surface of the "card" it is covered with a plastic film to prevent accelerated evaporation of moisture. During the first 3-4 days, it is recommended to additionally periodically spray the base with water.

After 28 days, under ideal hardening conditions, concrete gains 100% strength, but its moisture content may still be excessive for laying flooring. It takes another 3-4 weeks before the evaporation of excess water and achieve a rate of 75%.

At lower temperatures and increased humidity, the hardening and drying time of concrete increases.
  To smooth the roughness, after 3-4 days, the concrete surface can be sanded with a trowel or a manual trowel.

The use of various types of topping (reinforcing mixtures) will give the surface additional rigidity, strength and elasticity, but you can do with ordinary dry cement.

Features of laying concrete mix in the "warm floor" system

Special Requirements concrete floors presented when the heating system is installed - water or electric. In this case, it is necessary to reduce heat loss due to the additional installation under the heating elements of the reflective layer. You can use various types of foil materials.

For laying in a "warm floor" system, a more plastic concrete mixture is needed so as not to damage the wiring of the pipes or the electrical circuit. For this, special plasticizers are used to make the composition elastic. The mobility of the mixture should be P4 with a draft of about 20 cm.

Instead of a reinforcing frame, it is more advisable to use plastic fiber - thin polypropylene fibers added to the concrete mixture during manufacture. This will avoid damage to the thermal circuit and facilitate its installation.
  A trial run of the system is allowed only after 100% strength gain of concrete, that is, not earlier than after 28 days.

For the final drying of the base before laying sports flooring, it is necessary to carry out a functional heating of the screed according to a special schedule with a gradual increase and subsequent decrease in temperature.

The construction of a concrete base is a rather time-consuming process, in which a violation of technology threatens to dismantle the entire screed using a perforator. But high strength, unpretentiousness in operation and low cost in comparison with other options make such floors the most suitable for sports flooring.