Technology of construction of monolithic cement-concrete pavements. Concrete coverings Construction of cement-concrete coverings

Main material used for road construction - asphalt. After a few years, such a coating needs repair, then it operational properties are restored annually. Concrete pavement is much better than asphalt, but its use is limited. There are reasons for this, related to insufficient funding, low productivity levels, climatic conditions, insufficient quantities of cement of the required grades, and relief areas. This technology is not yet particularly popular in Russia, since asphalt roads are much cheaper. However, we note that gradually the cost of these types of canvas is slowly equalizing. The construction of concrete roads, bridges, and runways at airfields begins.

Advantages of concrete roads

Such coatings have certain advantages:

• The concrete road is of good strength and does not require repair work. The coating can be used for at least four decades, and for asphalt this period is limited to a decade with annual repairs;
• Automotive vehicles consume less fuel. This is due to the fact that when a heavy vehicle is moving, road concrete is not subject to deformation, which causes vehicle it takes a fifth less fuel to move;
• The coating is resistant to sudden changes in climatic conditions. It is not affected by heavy rains or sudden changes in temperature;
• air purity is maintained, because cars require less fuel, the exhaust gases of which pollute the environment;
• natural resources are used sparingly. Limestone is needed to make concrete, and petroleum is used to make asphalt.

Construction technology

The construction of concrete roads includes certain stages:

1. The soil base is being prepared. It is rolled to achieve the desired density, and if necessary, moistened or dried.
2. Water drainage is organized to extend the service life of the canvas and make driving safer.
3. The underlying layer is installed. It is a sandy layer, the thickness of which is up to two to four tens of centimeters.
4. The formwork structure is being assembled. Its elements are made of lumber, and the height of the fill is taken into account.

If water seeps into the ground, the road surface gradually deteriorates.

The construction technology is complex, and each stage will be considered in detail.

Concrete road structure

The canvas includes certain layers:

• underlying - for its construction, crushed stone is used, which drains groundwater, and sand, with the help of which the resulting loads are compensated;
• strengthening – represented by low-grade concrete that binds the backfill layer;
• road surface - concrete surface.

The structure of a concrete road for heavy vehicles is made of stressed and non-stressed reinforced concrete, reinforcement frame base in which it does not allow the stone to crack from the weight of trucks.

In private types of construction work or when arranging concrete road surfaces on soils supersaturated with moisture, it is laid out on a sand cushion. waterproofing material, preventing severe wetting of the road surface and subsequent corrosion of stones and reinforcement. Ordinary roofing felt is used as a waterproofing material.

Execution of work

Let’s look in more detail at what this or that construction stage of road concreting is.

Preparation

Excavation work is difficult, and it is quite expensive. They are preceded by the preparation of a detailed design solution, the conclusions of which are based on geological studies of the area. If there is such a possibility, then concreting roads is done horizontally, removing small hills or placing compacted rock in the depressions.

If a large highway is being built, then the layer of fertile soil is completely removed, and to install a concrete road in the yard, it will be enough to remove fifteen to twenty centimeters of soil.

The prepared base is compacted with rollers and vibration mechanisms, which are heavy.

This stage is considered a crucial moment, since the rigidity indicator and integrity of the road surface depend on the strength of the base, even when the dynamic loads are quite intense.

During excavation work, the installation of a drainage system is considered so that it is possible to remove ground and rain moisture. For this purpose, the base is placed in a plane, the inclined angle of which is from two to four degrees. Concrete gutters are installed on the sides of the road or natural slopes are arranged, along the slopes of which water will flow into receiving wells or go into the ground.

Litter layer

Getting settled sand cushion, the thickness of which is twenty to forty centimeters. This element can be omitted, but it perfectly protects against moisture coming from the ground and improves the drainage process. The bedding layer is necessary to prevent erosion and swelling during frosts, which leads to the formation of depressions and cracks in monolithic concrete.

The most problems appear in clay, peat and other areas of the terrain that can hold water. In most cases, such layers are partially removed, and the bottom is covered with large stones and gravel. The rolled layer reaches a height of thirty centimeters. Such preparation will determine the costs and time required for construction.

The minimum base thickness depends on the type of soil and climatic conditions. It is determined using a special table. If the layer is laid out from various materials, then geotextiles are spread between them.

Level the layers in accordance with the designed slopes. Stone backfills are strengthened with binding materials - cement, granulated slag from metallurgical production, to which quicklime is added, ash from thermal power plants, ground slag.

Formwork

To make this structure, boards are used, the height of which corresponds to the level of pouring concrete for the road. As a rule, it is equal to ten to fifteen centimeters. When determining its dimensions, it is necessary to take into account that ribs are installed along the edges of the concrete to improve strength. The thickness of the boards should not be less than 5 cm. Each structural element must be coated with a special compound that will facilitate detachment from the hardened concrete.

Wooden formwork panels are subject to requirements regarding the level of strength against expansion by fresh concrete mass and the forces that will arise as a result of compaction.

If heavy machinery is used to construct roads made of concrete, which is used to compact the concrete, then formwork made of steel material should be installed. It will last much longer. Each element is based on a sole that improves stability.

The formwork sections are aligned in one line and firmly fixed. This is especially important if the vibration of the concrete mass is carried out by heavy machinery. In places where the level of the base decreases, thin concrete is poured under the formwork to improve stability.

Reinforcement

If the technological process of constructing a concrete road involves this type of work, then the reinforcement should be a metal mesh, the cell area of ​​which reaches 150 mm. sq. This choice of material will make it possible to avoid expansion and the appearance of cracks in the concrete thickness.

The laying of the reinforcing mesh is carried out during the process of pouring the concrete mixture at a height of three to four centimeters from the lower level. Before this, the poured concrete is leveled, a frame mesh is laid, and, if necessary, fixed. Now you can continue working.

Fill

The bedding layer is covered with material that is resistant to getting wet, waterproofing, or simply moistened. Road concrete that complies with GOST is laid out in one thickness at a time. When reinforcement is applied, the process is carried out in stages.

Concrete for the road, the grade of which meets all the requirements, is applied quickly, since it does not have long-term viability. It is not recommended to add water to the mass, because the mechanical properties of the coating will deteriorate. Since the construction volumes are large, factory-prepared road cement is supplied to the work site. The mixture is unloaded one cubic meter at a time and leveled to give the entire layer the same density.

The best option for laying concrete is two or three layers.

The concrete mixture is compacted using special mechanisms, represented by wooden or metal beams, which are impacted by pneumatic hammers attached to them. Such a device is lowered into the mixture and begins to move in it. Having processed one area, the timber is moved further.

If reinforcement is used, the vibration device should be located five to seven centimeters above the top edge of the frame.

In addition to the vibration device, the special machine also has a leveling device located in front.

The concrete composition must be plastic and sufficiently mobile, but not very liquid so that it cannot float, flowing through the formwork panels. All this will negatively affect the strength of the coating.

Seam cutting

A prerequisite is the installation of expansion joints. This type of work is possible when the concrete reaches a certain strength level of 50 - 60 percent. In this form, the canvas is able to withstand the weight of not only the worker, but also a special tool for cutting seams.

In this way, thermal expansion, to which concrete is subject to varying degrees, is compensated. Road segments do not form cracks during seasonal changes.

Sawing is done by jointing - special tool. The distances between the seams are determined by design calculations. As a rule, to do this, the thickness of the monolithic coating is multiplied by thirty.

To prevent moisture from getting into such seams, they are filled with mastic.

Materials for constructing concrete sheets

M400 – universal concrete composition. Its strength allows it to withstand loads from various wheeled vehicles. The basis is Portland cement, which is resistant to moisture. Plasticizers are also added to the solution to improve hydrophobicity and strength.

The concrete mixture consists of:

• cement – ​​1 part;
• crushed stones - 5 parts;
• sand - 2 parts.

Concrete compositions and its characteristics are specified in the construction project.

Slab covering installation

Concrete slabs for the road are made as follows:

1. Forms are being prepared the right size, or formwork panels are placed.
2. If necessary, a reinforcement cage is prepared to improve the strength of the slabs.
3. Pouring is done with a ready-made concrete mixture; it is advisable to tamp it immediately to remove air bubbles.
4. After some time, when the concrete has hardened, you can remove the formwork and give the slabs time to gain the required strength.

Using this material you can make a concrete road with your own hands. If all conditions are met, it will serve you well for a long time.

Conclusion

The concrete road surface is durable, but requires some maintenance. The resulting cracks must be repaired immediately so that they do not increase in size. To do this, use special putty compounds or concrete mortar. If a crack has formed, the entire section of the concrete sheet should be removed.

8.2.2 In livestock buildings, concrete floor coverings are recommended for use in pens, boxes, etc. when keeping animals on bedding or using mats or grids, as well as in driveways and passages.

8.2.3 Concrete pavements can be designed in the form of an exploitable underlying layer, over a concrete base and over reinforced concrete floor(Fig. 3 and 4).

8.2.4 The thickness of the coating should be determined depending on the intensity of mechanical impacts (Section I, Table 2). When making a coating that simultaneously functions as an underlying layer, the thickness should be increased by at least 100 mm.

8.2.5 Coverings with a thickness of 50 to 120 mm are recommended to be reinforced with one layer of metal mesh made of wire with a diameter of 5 mm with cells of 100´100 or 150´150 mm, with a thickness of 120-180 mm - two layers of metal mesh, and with a thickness of more than 180 mm, a frame determined by calculation. The bottom layer of metal mesh is laid on spacers with a thickness of at least 20 mm, the top layer - with 6´6 m cards, and in special cases cards 3´3 m on supports welded to the bottom layer of the mesh.

Rice. 3 Structural schemes of floors with concrete covering over the underlying layer ( A) and by overlap ( b)

1 - concrete covering; 2 3 - waterproofing; 4 - foundation soil; 5 - heat and sound insulation; 6 - overlap; 7 - pipeline.

Rice. 4 Structural schemes of floors with steel fiber concrete covering over the underlying layer ( A) and by overlap ( b)

1 - steel fiber concrete coating; 2 - concrete underlying layer; 3 - waterproofing;

4 - foundation soil; 5 - heat and sound insulation; 6 - pipeline; 7 - overlap; 8 - concrete screed.

8.2.6 For the reinforcement of concrete pavements, steel fiber with a length of 50-80 mm and a diameter of 0.3-1 mm can also be used. In this case, it is recommended to use fine-grained concrete of class B25 and B35 with maximum size coarse aggregate 20 mm (Table 8.2.1). It is recommended to make coatings made of steel fiber reinforced concrete with a thickness of 40-100 mm.

Table 8.2.1

8.2.7 In floor coverings with a thickness of more than 50 mm, it is recommended to provide expansion joints in the longitudinal and transverse directions in increments of 3 to 6 m. The seams must coincide with the axes of the columns, with the seams of the floor slabs, expansion joints of the underlying layer, and in case of two-layer reinforcement with mesh boundaries of the upper layer of reinforcement. The depth of the expansion joint must be at least 40 mm and at least 1/3 of the coating thickness, width - 3-5 mm.

8.2.8 When performing floor coverings on the base soil, in order to prevent floor deformation in case of possible settlement of the building, it is necessary to ensure that the floor covering is cut off from columns and walls through gaskets made of rolled waterproofing materials.

8.2.9 To prepare concrete, Portland cement (GOST 10178-85) of grade no lower than 400 should be used. At the same time, sulfate-resistant expanding cement is recommended for waterproof and frost-resistant concrete.

8.2.10 For coatings light colors white cement (GOST 965-78) should be used, and for colored coatings - colored cement (GOST 15825-80) of grade no lower than 400.

8.2.11 Crushed stone from natural stone (GOST 8267-82), gravel (GOST 8268-82) and crushed stone from gravel (GOST 10260-82) for concrete classes B30, B22.5 and B15 must have a strength of 100, 80 and 60, respectively MPa. The size of crushed stone or gravel should not exceed 15 mm and 0.6 of the total thickness of the coating.

8.2.12 Quartz or crushed sand (GOST 8736-85) from natural stone of crystalline rocks (granite, syenite, basalt and the like), coarse- or medium-grained, used for concrete pavements, must contain no more than 3% clay or silt particles .

8.2.13 Consumption of coarse aggregate for concrete pavements (crushed stone, gravel, marble chips) should be at least 0.8 m 3 per 1 m 3 of concrete, and sand 10-30% of the volume of voids in the coarse aggregate.

8.2.14 For non-sparking concrete pavements, crushed stone and sand from limestone, marble and other clean stone materials that do not produce sparks when struck by steel or stone objects should be used.

8.2.15 For alkali-resistant concrete pavements, it is recommended to use crushed stone, gravel and sand from dense sedimentary (serpentinites, porphyrites, limestones, dolomites) or igneous (diabase, granites) rocks or basic blast furnace slag. The use of pure quartz sand is allowed. Materials for such coatings must withstand at least 15 cycles of alternate saturation with sodium sulfate solution and drying without signs of destruction.

8.2.17 For concrete pavements produced by vibration processing, it is recommended to use the concrete compositions given in Table 8.2.2

Table 8.2.2

8.2.18 Concrete mixtures, which do not include plasticizers, for coatings made by vibration processing, should be characterized by a cone settlement of 2-4 cm. The mobility of mixtures should be increased only by introducing plasticizers of grades S-3, SNV, etc. in an amount up to 0. 8% by weight of cement.

8.2.19 Work on laying concrete and steel-fiber concrete mixtures should be carried out at an air temperature at floor level not lower than +5 °C. This temperature must be maintained until the concrete reaches 50% of its design strength. When laying concrete in winter conditions at sub-zero temperatures concrete mixture sodium nitrate, potash, etc. should be added. In this case, white spots may appear on the surface of the concrete coating.

8.2.20 Before laying concrete mixtures, the underlying layer must be cleaned of dirt and dust, and grease stains must be removed by washing with a 5% solution of soda ash, followed by rinsing with water.

8.2.21 The gaps between prefabricated floor slabs, the places where they adjoin the walls, as well as installation holes should be sealed with cement-sand mortar with a strength of at least 15 MPa flush with the surface of the slabs.

8.2.22 It is recommended to cover the lower parts of walls and columns to a height equal to the thickness of the coating with waterproofing roll material or in the case of construction of expansion joints in these places - sheet foamed polyethylene.

8.2.23 When installing coatings up to 50 mm thick, to improve interlayer adhesion, it is recommended to prime the surface of the underlying concrete layer with a composition based on PVA emulsion or latex.

8.2.24 When installing floor coverings on old oily concrete bases, it is recommended to provide a separating layer of polyethylene film, kraft paper, etc., and make the floor covering at least 100 mm thick from concrete of class B30 or higher.

8.2.25 The concrete mixture should be laid on the base in strips limited by lighthouse slats (rolled metal, permanent aluminum or concrete rail forms) of a height corresponding to the thickness of the coating. In this case, the width of the stripes is selected taking into account technical characteristics the equipment used, the distance between columns in the building, as well as the planned location of expansion joints. The installation seams must coincide with the expansion joints.

8.2.26 It is recommended to install beacon slats parallel to the long side of the wall on marks made of cement-sand mortar, oriented to the mark placed on the wall. In this case, the first row of slats should be placed at a distance of 0.5-0.6 m from the wall opposite the entrance to the room, and the next rows should be placed parallel to the first at a distance of up to 3 m.

8.2.27 In places where the floor should have a slope towards ladders or channels, lighthouse slats should be installed in such a way that the top of the slats has a given slope.

8.2.28 Immediately before laying the concrete mixture, the underlying layer should be moistened abundantly with water so that by the time of laying it is moist, but there is no accumulation of water on it.

8.2.29 The concrete mixture should be laid between the lighthouse slats in strips one at a time. In this case, the thickness of the leveled concrete layer, taking into account its subsequent settlement during the vibration treatment process, should be taken 3-5 mm higher than the lighthouse slats.

8.2.30 When the thickness of the concrete floor covering is up to 100 mm, it is recommended to compact the concrete mixture using a vibrating screed, and for larger thicknesses, the laid concrete mixture should be pre-treated with an in-depth vibrator before compacting with a vibrating screed. The speed of movement of the vibrating screed should be 0.5-1 m/min with a number of passes of 1-2.

8.2.31 Concreting is recommended to be carried out without technological interruptions. Otherwise, before resuming concreting, the hardened vertical edge of the previously laid concrete must be cleaned of dirt and dust and washed with water. In areas of working seams, compaction and smoothing of concrete should be carried out until the seam becomes invisible.

8.2.32 The missing strips are concreted after removing the lighthouse slats, using the concreted strips as formwork and guides.

8.2.33 Vacuuming of concrete is carried out using a set of equipment, including: a vacuum unit, suction mats, vibrating screed, smoothing machines, guides for vibrating screeds, hoses and connecting devices, containers for washing suction mats.

8.2.34 When using the vacuum method, the recommended concrete mixtures should have an increased sand content of 150-200 kg per 1 m 3 of concrete mixture compared to the compositions according to table 8.2.2.

8.2.35 Concrete mixtures used when using the vacuum method should be characterized by a cone slump of 8-12 cm. An increased water-cement ratio makes it easier to lay and compact the mixture, and also makes it possible to obtain a more even floor covering.

8.2.36 The technological regulations for the manufacture of floor coverings using the vacuum method provide for laying mats with vacuum cavities on the vibration-compacted surface of the floor covering, connecting them with hoses to a vacuum pump and suctioning out excess water, thereby increasing the strength and uniformity of concrete.

8.2.37 Suction mats are laid on a freshly laid concrete mixture with an overlap of 10-15 cm on each side, when laying on hardened concrete - by at least 20 cm. In this case, the lower filter cloth is laid directly on the concrete (if work is carried out simultaneously with two and lower panels, they must be overlapped by at least 3 cm), and the upper one is rolled out starting from the middle. This rolling order improves sealing. The panels must be laid flat, without wrinkles or folds. In addition, after installation, it is recommended to iron the top panel with a roller, brush, etc.

8.2.38 The vacuum unit at idle should create a vacuum of the order of 0.09-0.095 MPa. The normal operating vacuum of a vacuum pump is considered to be 0.07-0.08 MPa.

The duration of evacuation increases in inverse proportion to the decrease in vacuum. If the vacuum is less than 0.06 MPa, evacuation should not be performed. The evacuation time is calculated based on 1-1.5 minutes per 1 cm of concrete coating thickness. The end of the process is judged by the cessation of flow of the water-air mixture into the pipeline.

8.2.39 After completing the vacuuming process, it is necessary to roll up the top panel so that the filter panel is open 1-2 cm on both sides with the vacuum pump turned on for 10-15 s. Then the top panel is completely rolled up.

8.2.40 In order to increase the evenness and smoothness of the surface of concrete floor coverings, after compacting the concrete mixture and setting it to a state where light traces remain on the surface when walked, the coating should be subjected to initial treatment - grouting using concrete finishing machines with leveling discs. Secondary processing of the coating using concrete finishing machines with blades is carried out no later than after 6 hours.

8.2.41 When using the vacuum method, the primary smoothing of the concrete surface is carried out immediately after the end of the vacuum, and secondary processing - after 3-5 hours.

8.2.42 To increase the resistance of concrete floor coverings to mechanical stress To reduce dust separation and reduce water permeability, it is recommended to harden the surface of coatings with dry mixtures or impregnate coatings with polymeric materials. A combination of these technological methods is also possible. The use of colored strengthening mixtures makes it possible to obtain colored concrete floor surfaces.

8.2.43 Concrete pavement with a reinforced top layer is recommended to be at least 70 mm thick.

8.2.44 The installation of a reinforced top layer can be provided over a coating made as traditional way, and with the use of vacuum.

8.2.45 For hardened concrete floor coverings, concrete of the following compositions, wt., is recommended. h.:

8.2.46 Dry mixtures used to strengthen concrete pavements must contain Portland cement of a grade not lower than M400 and wear-resistant filler, which can be metal powders, corundum, quartz, etc., as well as modifying additives. As such a mixture, it is recommended to use a strengthening mixture of the Mastertop brand according to TU 5745-003-40129229-01.

8.2.47 The application of strengthening mixtures is carried out on the wet concrete surface of the concrete pavement, that is, before the stages of grouting and smoothing. When strengthening concrete coatings made using vacuum, the strengthening mixture is applied immediately after vacuuming.

8.2.48 Before applying the strengthening mixture, the concrete must be smoothed to soften the crust formed on the surface. After moisture appears on the smoothed concrete surface, the dry mixture should be applied to the concrete manually or using a mechanical spreader. The consumption of the strengthening mixture is 5 kg per 1 m2 of coating surface.

8.2.49 It is recommended to apply the strengthening mixture in 2-3 steps. At the beginning, 2/3 of the total amount of the mixture is applied. The mixture must be completely and evenly saturated with moisture sucked from the concrete, as judged by the uniform darkening of the mixture. Adding water to the strengthening mixture is not allowed.

8.2.50 Smoothing of the surface is carried out using a concrete finishing machine with a disk, eliminating the formation of bubbles and cavities. Areas that cannot be smoothed by machine must be smoothed by hand. After applying the remaining mixture, smoothing is repeated.

8.2.51 Final processing of the hardened surface should be carried out using a machine with blades.

8.2.52 No later than 2 days after application of the coating, expansion joints should be cut using seam cutters with a diamond blade. When using non-removable rail forms, the grooves in the upper part of the rail forms are used as expansion joints and the cutting of the seams is carried out only in the transverse direction.

8.2.53 After installation, the concrete pavement must be kept in wet conditions (coating plastic film etc.) for at least 7 days, then natural drying occurs. It is also possible to use compositions applied to a wet concrete surface and forming a film to prevent premature removal of moisture from concrete. As a rule, one-component compositions based on acrylic dispersions are used as such compositions, in particular sealant-hardening brand Master-Cur 113 (MVT concern, Belgium). It is also recommended to use water-dispersed epoxy paint brand Rizopox 5601W (TU 2257-011-43548961-2002) and water-dispersive epoxy primers-impregnations brand Rizopox 1301W (TU 2257-027-43548961-2003) and brand Koropox (company Korodur, Germany).

8.2.54 Application of such compositions is carried out with a roller immediately after the smoothing stage is completed, and at least two layers of the composition are applied.

8.2.55 The use of the compositions specified in clause 8.2.54 to prevent premature drying of concrete on coatings on which polymer impregnations are planned to be applied is not recommended.

8.2.56 After the concrete reaches an air-dry state (humidity not exceeding 5%), expansion joints should be sealed by placing an elastic polyurethane cord in the formed groove and filling it flush with a hardening elastic urethane composition, for which the Gertex sealant is recommended (TU 5770- 006-04002274-00). When making expansion joints near columns and along walls, the polyethylene foam gaskets should be removed and the resulting groove filled with a polyurethane composition.

8.2.57 When the concrete reaches an air-dry state, in order to reduce dust separation from floor coverings and their water and oil permeability, it is also possible to apply impregnating compositions, the compositions of which and application technologies are given in Chapter 9.

8.2.58 The use of floors is allowed after the concrete has acquired the design compressive strength; pedestrian traffic on these floors can be allowed if the concrete compressive strength is at least 5 MPa.

The road surface in Russia and abroad is different: in our country, highways for various purposes made from asphalt, and in Europe and the USA mainly from concrete. This is the obvious difference in their quality. In Russia, concrete roads have not become widespread due to their significant cost - after all, the country’s vast expanses and updating the road surface will cost the population another increase in taxes. However, no one forbids homeowners to build car parks and driveways from durable concrete.

Why are concrete roads needed?

The construction of concrete roads is advisable in places where there is no possibility frequent repairs and there is a need for a durable road surface. In Russia it is:

• Autodromes;
• Runways and landing pads at airports;
• Parking of cars and other equipment;
• Pedestrian paths and sidewalks in cities;
• Coastal roads and embankments where high humidity and exposure to water prevail.

The service life of a concrete slab exceeds the service life of asphalt by up to 2-3 times. For this reason, it is advisable to replace asphalt concrete road pavements that cannot withstand climatic conditions, to cement concrete everywhere, which is gradually happening in the USA.

The difference between asphalt and concrete

Why is asphalt road surface not as durable as concrete road surface? It's all about the quality of the basic materials:

• Asphalt is a composite of sand, crushed stone, mineral fillers, and their binder is bitumen polymers.
• Concrete is Sand and gravel, mixed with cement and additives.

The main difference between concrete and asphalt is the binder in their compositions. Bitumen, unlike cement, does not form a strong stone, sags under weak soils when loaded, softens in the sun and does not winter well. Concrete, if the technology of preparation and installation is followed, is free from these disadvantages.

The road surface consists of several layers:

1. The underlying is crushed stone, draining water from the ground, and sand, compensating for loads coming from above and below from the ground.
2. Strengthening – this is a layer of low-grade concrete that binds the bedding.
3. The main road surface is a layer of concrete.

When laying highways with large traffic of heavy vehicles, the road must be made of unstressed and stressed reinforced concrete, the reinforcement cage in which does not allow the stone to crack under the weight of heavy trucks.

In private construction, as well as when organizing road surfaces on or with water-saturated soils high level waterproofing for the road surface is laid on the sand and gravel embankment (roofing felt materials can be used). The layer prevents constant wetting of the concrete and, as a result, corrosion of the stone and reinforcement frame.

Types of canvas

The concrete road is good for both high-traffic highways and village driveways. For these cases choose different types canvases differing in quality and cost:

• Single layer coating High Quality for roads of any purpose, suitable for laying top and bottom layers;
• Concrete for the bottom layer of the canvas is cheap - it has low strength, and minimal requirements are imposed on its components. A coating made of such material can be used when arranging local areas with a small flow of passenger cars;
• Base concrete with average characteristics for heavy and advanced coatings. Can be laid on village roads;
• The organization of roads with ready-made concrete slabs can be included in a separate group.

Materials for filling the canvas

The universal material for laying roads is M400 concrete. Its strength is sufficient to withstand the pressure of the wheels of cars and trucks on city and village driveways.

The basis of the concrete is Portland cement, resistant to water (1 part). Plasticizers are also introduced into the solution, increasing the hydrophobicity of the coating and its strength. The working solution also includes:

• Crushed stone – 5 parts;
• Sand – 2 parts.

For concreting a road, it is rational to order ready-made concrete from a factory - even for a small site you will need a lot of mortar, which must be poured quickly, without allowing individual batches to set.

Road surfacing materials may differ in properties depending on the expected load and installation conditions.

Requirements for the quality of concrete roads

When choosing components for preparing road concrete, they are guided by SNiP 3.06.03-85 “Highways”. The document regulates the quality requirements for the finished fabric:

• Resistance to mechanical loads is the main requirement for a road surface. For roads for different purposes, the indicator is determined individually.
• No cracks in the coating after installation and during operation. Compliance with the technology for constructing concrete roads and the correctly selected composition of the working solution helps solve the problem.
• Water resistance and resistance to chemical reagents. Highways are located in different conditions of relief and soil quality, and in the absence of organized drainage (if construction technology is violated), water accumulates on the road surface, worsening its quality.

Concrete requirements

The quality of the fabric is determined by the constituent components, which must also undergo careful selection in accordance with relevant GOST standards. For example, the strength of crushed stone, capable of ensuring reliable and long-term operation of the road, is at least 1200 kg/cm 2. For a pillow, less durable crushed stone 800-1000 kg/cm 2 will do.

The mobility of the concrete solution is 2 cm when testing with a cone. A large number of mineral inclusions of different fractions helps to avoid deviations from this parameter.

Another requirement for concrete is high bending strength; for this purpose, plasticizers are introduced into the solution and the canvas is additionally reinforced with reinforcement.

Pros and cons of concrete roads

Compared to asphalt roads, concrete roads have a number of advantages:

• High strength and rigidity of the coating;
• Resistance to heat and temperature changes;
• Long service life without the need for repairs;
• Good adhesion of the road surface and car wheels increases traffic safety.

The roads have fewer disadvantages, but they are significant:

• High construction cost;
• The need for strict adherence to technology when preparing solutions and selecting components;
• The need for the concrete to fully gain strength before starting the road.

Construction of a concrete road

Let us consider in detail the stages of constructing concrete roads, since the service life of the coating depends on compliance with the laying technology.

Excavation work is one of the most expensive and complex. Before they begin, it is compiled detailed project, based on a geological study of the relief. If possible, the laying plane of the road is made horizontal - the mounds are removed, and a board is made into the recesses with rock compaction.

The fertile layer of soil is removed: for large-scale construction of a highway, completely; for private laying of adjacent areas, 15-20 cm is enough. The lower ones are compacted with rollers and vibrating plates with a large weight. This is one of the most critical stages - the rigidity and integrity of the coating under intense dynamic loads depends on the strength level of the base.

At the stage of preparatory work with the soil, a drainage system is thought out to drain groundwater and rainwater. To do this, the base is made not in an ideal plane, but at a slight angle of 2-4%. Concrete gutters or natural slopes can be installed along the road, along which water flows into a receiver or into the ground.

Laying the bedding layer

Crushed stone and sand are poured onto the compacted soil. They perform the function of load compensator and water drainage.

The thickness of the bedding layers depends on the type of relief and the properties of the foundations and fluctuates around 20-40 cm. When laying intercity roads, geotest is often laid between sand and crushed stone - it does not allow the factions to mix and the embankments perform their functions better.

On high level bases groundwater It is rational to make the mound of crushed stone thicker - it does not wash out and drains water well. Sand must be placed under layers of concrete - it forms a dense cushion.

Both sand and crushed stone layers must be compacted with a roller or vibratory pits to achieve high cushion strength.

For convenience, the bedding layer is sometimes covered with a thin concrete screed up to 5 cm thick, and a waterproofing sheet is laid on top.

Concrete is weak to bending loads, so the use of reinforcement is never superfluous - the choice of its type again depends on the characteristics of the base. In some cases, reinforcement may not be used at all.

The diameter of the reinforcement for the concrete sheet is taken only structurally according to calculations. Usually these are rods from 10 mm, welded into a mesh with a cell from 150 mm. The reinforcement products are laid in a concrete layer at a height of at least 4 cm from the bottom plane. It is important that the mesh is in the lower part of the slab, since it is there that the destructive load is concentrated and cracks form.

The easiest way to make formwork is to use thick boards with a section of 50×150 mm (the choice of height depends on the design layer concrete base and coatings). Thick plywood will also work. Boards and plywood are fixed with reinforcing pegs stuck into the ground with outside canvases. When laying paths for pedestrians and parking lots for cars, the formwork can be replaced by curb stone installed at the stage of preparation for pouring.

Laying concrete pavement

Pouring the road with concrete must be carried out continuously, so the materials for the roadbed are prepared immediately in the required quantity. It is advisable to order concrete from the factory; during the construction of large roads, temporary mobile workshops for the production of mortar are installed near the sites, which reduces delivery costs.

If necessary, low-grade concrete (for example, M200) is laid on the base with bedding, then with finishing mortar M400 with additives.

Laying the top covering occurs in 2 stages: first, pour a 30-40 mm substrate, lay it on it reinforcing mesh and fill in the remaining thickness.

The total layer thickness is about 12 cm, sometimes more or less.

Concrete is poured for preparation without interruption and the surface is immediately leveled. Material is constantly being delivered, work goes on around the clock.

After laying, the concrete must be compacted using vibrocompression. The procedure expels air bubbles and compacts the structure of the finished coating.

Cutting and sealing expansion joints

The construction of a concrete road includes cutting the road surface into segments. This is possible, then the concrete will gain sufficient strength of 50-60% and will withstand the weight of a person and cutting equipment.

Seams are needed to compensate for thermal expansion, which the concrete stone is subjected to to varying degrees. When the volume of slabs changes seasonally, cracks do not form in the road surface.

Sawing is carried out with a special tool - a jointer.

Expansion joints are made at a distance determined by calculations. One of the determination formulas is coating thickness × 30.

To prevent water from penetrating into the slab through the seams, they are filled with bitumen-polymer sealants.

Care and prevention of concrete pavement

To ensure that the work does not go in vain, according to technology, a concrete road can be opened for traffic only after the concrete has fully gained strength, that is, after 28 days.

To prevent destruction of the canvas, it is protected with polymer impregnations, which form a waterproof film on the surface. True, these reduce the roughness of the road and its grip on the wheels. This negative quality for expressways, so in most cases the roadbed is left as is. If the soil preparation and laying technology have been followed, the seams are cut correctly, nothing threatens the integrity of the slabs for a long time.

Another way to prevent and repair concrete roads is to lay a wear layer. Asphalt is applied to the concrete, which provides traction between the wheels and the surface, and extends the service life of the highway itself several times. In addition, repairing asphalt concrete pavement is much cheaper.

If cracks appear, it is necessary to take measures to eliminate them. To repair small damage, special putties are used, and to repair deeper damage, concrete mortar is used. In all cases, the crack is cleaned and moistened before introducing the filler.

If a fault occurs, the entire section of the canvas will have to be removed. The cause of such deformations is insufficient compaction of the soil base or embankment.

→ Building quality control

Polyvinyl acetate-cement-concrete coatings

Polyvinyl acetate-cement-concrete coatings are made from a mixture of crushed stone, sand, cement, polyvinyl acetate emulsion and water, and, if appropriately indicated in the project, pigments and dyes. This type of flooring consists of several films of polyvinyl acetate mastic, each 1-1.5 mm thick, applied to a well-prepared base. Polyvinyl acetate coatings are highly durable, wear-resistant, fire-resistant, have good adhesion to any type of substrate and are a type of warm and elastic floors. The installation of polyvinyl acetate floors is not allowed in rooms with abundant or. long-term moisture, as they are weakly water-resistant. To increase water resistance, floors can be coated one or two times with high-strength varnishes No. 170, 52 or 4-c. The bases for polyvinyl acetate coatings must be rigid, so they are made of concrete, cement mortar or xylolite. Humidity. concrete base or cement screed before application, mastic should not exceed 6%, xylolite - 15%; the strength of concrete and xylolite should be at least 50 kg/cm2, lightweight concrete panels - 150, gypsum concrete - 75 kg/cm2. Before applying polyvinyl acetate mastic, it is necessary to accept the bases prepared for the self-leveling coating. Polyvinyl acetate mastics are prepared from a mixture of polyvinyl acetate emulsion, dust filler, pigments and water. The use of a mushy emulsion with resinous grains exfoliated from water for the production of coatings is prohibited. The emulsion can be stored in a hermetically sealed container at temperatures from O to +40 ° C for no more than one year. This must be taken into account when accepting it during construction. Emulsions stored at sub-zero temperatures, regardless of shelf life, are rejected. As dust-like fillers, marshalite or finely ground stone materials of light colors with a compressive strength of at least 400 kg/cm2 (quartz sand, light granite, marble, etc.) and a grain size of no more than 0.15 mm are used. The dust filler must be uniform in color for a given amount of work, air-dry, with a moisture content of no more than 3%. without lumps, clay, organic and other impurities. Dust-like materials must be stored in a dry place. Pigments used for mastic must be finely ground, acid-resistant and light-resistant (ochre, red lead, mummy). Before use, they must be ground with the addition of a small amount of water, which ensures their uniform distribution in the mastic and completely prevents the formation of dry lumps. The color of the coating is selected visually according to standards, assessed in daylight using hardened dry samples (cement-sand standard tiles measuring 20X30 cm). The color must be agreed upon with the customer and the designer's supervision. All sinking irregularities, cracks and potholes in the base are filled with polyvinyl acetate mastic with a composition of 1:3 (polyvinyl acetate emulsion, dust filler) without adding dye and water, and the tubercles are ground off with carborundum or an electric grinder. When preparing mastic, control its weight composition, the amount of added water, viscosity (90-100 s, measured with a 133-4 viscometer) and the duration of movement (at least 5 minutes). The prepared mastic is filtered through a sieve with a cell size of 0.5 mm. Then, after settling for 15-20 minutes, the floating foam is removed from the surface of the mastic, and the mastic is loaded into the tank of the spray apparatus. The tank has a conical bottom, and the mastic sampling tube must reach the cone so that no foam gets into the nozzle. Spraying is carried out using a nozzle nozzle or a gun. Spraying units have spare nozzles to replace clogged ones. The prepared mastic should be used within 5-6 hours at an air temperature of 10-15 °C and within 2-3 hours at 20-25 °C. Dilution of thickened mastic with water or polyvinyl acetate emulsion is prohibited. It is necessary to ensure that the tanks of the spraying units are washed with water before loading new, freshly prepared mastic. The hardening time of coatings made of polyvinyl acetate mastic is 4-5 hours for putty mixtures and 3-4 hours for the covering layer. It is recommended to apply the second layer 24 hours after applying the first and to thoroughly remove dust from its surface before doing so. Layers should be applied in strips 1-1.25 m wide in the direction of the exit door. Walking on unhardened mastic or laying walking boards and other devices on it is not allowed. When there is a break in work, the floor area is fenced off with slats or strips of plywood. When resuming work, the edge of the previously laid layer is covered with slats to protect it from fresh spray and the mastic continues to be applied to the adjacent section of the floor. It is necessary to control that hardening of the applied layer occurs without moisture and dust getting on the floor; the room should be ventilated without creating drafts. IN living rooms Mastic floors are usually rubbed with colorless wax parquet mastics. Washing polyvinyl acetate floors with water is not allowed. When accepting polyvinyl acetate floors into operation, they are subject to the same requirements as parquet floors.

The installation of monolithic concrete floors is often required in facilities that require severe operational loads. These can be hypermarkets, shopping and exhibition complexes, industrial buildings. Monolithic floors are often installed in residential buildings. When choosing materials for the manufacture of this structure, it is necessary to be guided by calculations of the resistance of the prepared floor to the influence of various destructive factors. Often the only thing the right decision in this case, monolithic floors remain.

The distinctive properties of concrete floors are a long service life, extremely high wear resistance, and ease of maintenance. Through the use of strengthening additives in the mixture, upper layer the base becomes resistant to moisture and chemicals.

Technological process for installing concrete pavement

At the base of this type of industrial floor, a cement-sand mixture containing crushed stone or a ready-made reinforced concrete slab is used. The presented concrete laying technology is suitable for both large industrial or public premises, as well as private homes.

All work is carried out in strict compliance with SNiP and all requirements technological process. Concrete slab must be laid on a reinforced and cleaned base. The reason for such requirements is that if a low-quality solution is used in an old screed, the adhesion of the coating deteriorates, and the concrete surface will begin to crumble under heavy impacts. Also, the cause of weak adhesion is unresolved stains of grease or technical oils.

For effective preparation the base for pouring monolithic floors, it is necessary to perform a number of the following measures:

1. Mechanically remove all dirt, grease stains, any peeling and crumbling. To remove traces of technical oil, a painting solution is used; acid washing is effective against concrete glue.
2. Irregularities in the horizontal surface level are eliminated using a milling mechanism. If the height difference is up to 10%, there is no need to eliminate it.
3. If there are cracks or potholes on the surface, they should be expanded and filled with a mixture that contains polymers.
4. Areas that cannot be reconstructed must be dismantled and filled with new concrete.
5. The top layer of the old screed should also be cleaned of dust. Otherwise, the quality of the adhesion will decrease, and some of the contaminants will float to the top, disrupting the smoothness of the surface.

After preparatory work completed in full, the base is being leveled. As a result of this event, the highest elevation of the coating will be determined, and therefore the thickness of the concrete screed.

Main types of monolithic floors

Today there are three key types of concrete floors:

1. Single-layer cement-sand floor. Used for rooms with small square footage. This type of coating is not very resistant to loads due to the absence of an additional layer of concrete coating. The option is relevant for small apartments, residential buildings or utility premises.
2. Multilayer floor. The manufacture of this structure is complex, since the concrete mixture is laid in two or more layers. Recommended use similar method coatings for reconstruction work.
3. Reinforced monolithic floors. It is distinguished by the extreme strength of all variants of similar bases. By using reinforcing bars, it becomes possible to reduce the thickness of the coating and the weight of concrete floors. Steel rods or mesh are used as reinforcing material, and if necessary, synthetic elements. This design typical for premises with a heavy load on the coating: production workshops, car parks, agricultural hangars, etc.

The technological process for installing a concrete floor differs depending on the functional purpose of the premises. In this case, the goal of this measure is of considerable importance - to level the surface of the floor inside the room, insulate the concrete covering, increase the height of the base, etc. Using various methods for producing cement-sand screed, it is possible to improve the quality of the structure and the duration of the service life.

It is important to note that the preparation of a monolithic floor must comply with established building regulations and rules, i.e. SNiP. Their requirements may vary depending on the operational factors of the product and the location of pouring.

Waterproofing the base

The leveled and cleaned surface is treated with mastic ( waterproofing mixture on an adhesive basis). This step functionally provides:

• high-quality adhesion of the old concrete screed with the new cement-sand layer;
• additional waterproofing level.

A worthy alternative to such a solution is hydroglass insulation. The product is applied in two layers, each height at least 5 mm. Possessing high plasticity and resistance to atmospheric loads, this coating creates a durable waterproofing barrier for 10-15 years.

Monolithic concrete pavement is laid according to “maps” - rectangular areas prepared for laying the mortar. The size of such areas is determined on the basis of production potential. Guides are installed along the perimeter of the cards, i.e. beacons.

Reinforcement and thermal insulation of concrete floors

The laying of reinforcing elements is carried out to eliminate the likelihood of the formation of floor splits throughout the entire operational period, especially if the screed thickness is large. This type of work is carried out in full accordance with design calculations of future loads.

For these purposes, steel mesh is often used, the diameter of the rod is 5 mm, and the size of an individual cell is 100 × 100 mm / 150 × 150 mm. The material for the manufacture of the mesh is BP1 class reinforcement.

When serious loads are expected on the concrete floor covering, it is recommended to use a reinforced frame for strengthening. The reinforcement is tied directly at the construction site; the diameter of the rod varies from 8 to 18 mm.

The reinforcement should be tied together with wire. It is impossible to weld under any circumstances, this is due to varying degrees of shrinkage and expansion of metal and concrete during temperature changes.

DIY beacon installation

This is the most critical stage in the production of monolithic floors, since the level of the exposed beacon slats determines the evenness of the coating.

1. As a rule, the room is divided into sections not exceeding two meters in width. Special T-shaped lighthouse slats are used as guides, but a regular profile or round pipe. In some situations, a simple wooden block, previously calibrated on a flat surface, is also used.
2. Beacons are placed on small-thick mounds of fresh mortar. After this, by pressing the slats into the solution or, conversely, raising it, the exact horizontal level is set. Pouring the first layer of concrete is allowed only after the exposed beacons have completely hardened.
3. When the room has a large area, and one-time filling of the floor is not possible, the base is divided into rectangular or square cards. The boundaries of such areas are fenced with wood formwork. When all sections have been poured and the concrete coating has hardened, the partitions are removed, and the space formed under them is filled with ready-made mortar.

Laying concrete floors, pouring concrete

For successful work It is strongly recommended to use a concrete mixer when pouring floors. For large volumes, special automobile mixers are used. This approach provides the ideal possibility of continuous supply of solution, which has a positive effect on the quality of monolithic floors.

1. The finished mixture is laid on the prepared base in cells, then leveled with an ordinary shovel to prevent the formation of voids and increase the density of the layer. If possible, a vibration compactor is used. It is immersed in the solution itself and held until milk appears on top of the coating.
2. When the thickness of the concrete has slightly exceeded the beacons, it is leveled using a rule. The movements should be directed towards yourself and simultaneously to the left and to the right. Sometimes, instead of a rule, a special vibrating screed is used, installed along guides. The principle of its operation is the same as that of the manual rule, only mechanized.
3. After the screed is ready, the coating is regularly moistened with water to prevent intense drying and cracking. The period until the floor is completely ready for use is at least one month.

To prepare concrete floors yourself, you need to use a technological map for installing a cement-sand coating. Routing includes the following stages of floor installation:

• preparing the base;
• then the base is waterproofed;
• then laying reinforcing materials;
• installation of guides and formwork frame;
• production of cement-sand mixture and its installation;
• leveling the top layer;
• After the floor has completely dried, final sanding of the finished coating.

Installing concrete floors is a challenging task various options technological process. As a result of high-quality implementation of all stages of the production process, a durable monolithic flooring structure is formed that can withstand high pressure and not deform even after a long period of use.