Base for asphalt pavement. Repair of asphalt concrete pavements of roads and sidewalks. How to calculate the price of road works

An important element in the improvement of settlements are sidewalks, the correct design and construction of which should ensure the convenience and safety of pedestrian traffic.

The construction of sidewalks in different climatic zones differs little from each other and their choice is determined by the following factors: the category of the street, its significance in the city and the intensity of pedestrian traffic; the availability of local materials with soil conditions; the location of the sidewalk in relation to the roadway and the lawn; the ratio of the width of the sidewalk and the lawn; load on the sidewalk.

For the construction of sidewalks, local building materials, reinforced soils, asphalt and cement concretes, as well as cement-concrete, asphalt concrete and ceramic slabs, natural stone slabs, etc. are used. Depending on the application of materials, the sidewalk coating can be arranged in one or several layers.

To increase the service life of sidewalks, their coatings at the base are laid on the underlying sand layer with a filtration coefficient of at least 3 m / day and a thickness of at least 10 cm. The thickness of the sand layer depends on the soil group subgrade   (table. 8) and the location of the sidewalks.

The thicknesses of the underlying layer indicated in the table belong to I-II climatic zones. For zone III, the value of the thickness of the underlying layer should be reduced by 5 cm compared to the table.

In the southern regions of the IV and V zones, the underlying layer, as a rule, is not done. With the device of longitudinal drainage of shallow water and discharge of free water from the drainage layer, the thickness of the underlying layer can be reduced by 5 cm. For all climatic zones with the device of longitudinal drainage, the smallest thickness of the underlying layer should be at least 10 cm.

In especially adverse ground conditions and. in the absence of drainage, the thickness of the sand layer should be taken at least 25 cm.

The sidewalk is designed for pedestrian traffic and, if necessary, checked for possible collisions with cars or sweepers. In this case, the calculated pressure on the wheel take at least 2750 kgf / cm 2. The calculated modulus of elasticity of the clothes of the sidewalks of the main streets is taken equal to 850 kgf / cm 2, the streets of local traffic 650 kgf / cm 2.

Sidewalk structures are made monolithic (from asphalt concrete, cement concrete, bitumen-mineral mixtures) or prefabricated (from concrete slabs   and slabs made of natural stone).

Monolithic structures of sidewalks with asphalt concrete pavement are made on the basis of crushed stone with a compressive strength of 300-500 kgf / cm 2, gravel, sand and gravel, metallurgical slag, crushed stone (battle), bitumen-mineral mixture, cement-reinforced soil, and other

The asphalt concrete pavement of the sidewalks is made of sand, cast or fine-grained asphalt in one layer with a thickness of 3 cm (without a possible collision of a car) and up to 4-5 cm (with a possible collision of a car).

Monolithic cement-concrete pavement coverings are made of concrete of grade 300 and higher with a thickness of 10 cm on main roads and 8 cm on local roads.

Cement-concrete coating, depending on the width of the sidewalks, is made in the form of one monolithic slab with expansion joints according to calculation or in accordance with current regulatory documents.

The thickness of the base for asphalt concrete coatings is arranged according to the table. 9.

Table 9. The thickness of the bases for paving of various materials

Under monolithic cement-concrete pavement coverings provide foundations of sand, gravel, bitumen-mineral, cement and bituminous and other mixtures and materials.

Prefabricated pavement coverings made of concrete slabs are beginning to receive increasing use.

They have a number of advantages over monolithic, as they have a good appearance, can be made in color, easily disassembled and restored when laying or repairing underground utilities.

The thickness of the bases (cm) for prefabricated paving slabs of various materials has the following value:

When choosing designs of hard concrete coatings of city roads and sidewalks, the current standards for "Reinforced concrete slabs for paving city roads" (GOST 21924-84) "Concrete paving slabs" ( GOST 17608-81).

Calculations of hard tin coatings were carried out on the basis of current regulatory documents and instructions, in particular, the thickness of monolithic and prefabricated cement-concrete pavement coatings was determined by the maximum bending moment arising in the slabs under the estimated operational load.

After determining the maximum value of the bending moment, the thickness of the concrete slabs is established.

The determination of bending moments was made according to the method of O.Ya. Shekhter and M.I. Gorbunova-Posadova.

Operating experience asphalt concrete pavement on city streets and roads shows that their service life before overhaul is approximately 8-10 years. All kinds of cracks, shifts and ruts (especially at public transport stopping points), breaks and subsidence (near manholes, tram rails, in places of former opening of pavements, etc.) appear on asphalt pavements during operation. Under the influence of the wheels of the vehicle, the process of wear (abrasion) of the surface layer of the asphalt concrete pavement is manifested and over time, pavement loses the necessary bearing capacity.
In accordance with the classification, repair of pavement and pavement is divided into three types: current, medium and capital. Maintenance includes the urgent repair of minor damage in order to prevent further damage to the coating. The average repair is carried out in order to restore the bearing capacity of the pavement and improve the transport and operational performance of the road. At overhaul   work is underway on the full or partial replacement of structural layers of asphalt concrete pavement.
The types of deformation of asphalt concrete pavements, the causes of their occurrence and methods of elimination are given in table. 86.
The maintenance of asphalt concrete pavements includes the repair of cracks, the repair of subsidence and potholes, the restoration of pavement after tearing, the elimination of wave formation, sagging, ruts, and shifts.

Cracks in asphalt concrete pavement usually occur during periods of sharp decrease in temperature (during severe and rapidly occurring frosts). Depending on the width, the cracks are divided into small - up to 0.5 cm, medium - up to 2 cm and large - up to 3 cm. Cracks, growing, lead to the destruction of the road surface. Therefore, their termination should be considered an important preventive measure. The following materials are recommended for filling and sealing cracks: liquefied or liquid bitumen of grades SG-70/130, SG-130/200, MG-70/130, MG-130/200 with subsequent surface treatment of the weld with black seeding fractions of 3-7 mm; rubber-bitumen binder (RBB), consisting of bitumen, crumb rubber, softener; mastics, consisting of rubber-bitumen binder and solid fillers.
Rubber-bitumen binders and mastics are prepared in special stationary installations.
Small cracks (0.5 cm) should be filled with a rubber-bitumen binder or liquefied bitumen, followed by powdering with mineral material; cracks with a width of more than 0.5 cm, as a rule, are filled with a rubber-bitumen binder or mastics. Liquid and liquefied bitumen is obtained by adding kerosene to viscous bitumen heated before use to 80-100 ° C.
The material for filling cracks should have elasticity, heat resistance, good adhesion (adhesion) with asphalt concrete and stone materials, high fluidity, when pouring, it should easily pour out of the working body of the fill and completely fill the crack. Elasticity is achieved by introducing synthetic rubbers or crumb rubber into the mastic, and heat resistance is achieved by introducing solid fillers: mineral powder, asbestos crumb, or the combined use of viscous road and building bitumen. The most common synthetic material for the preparation of mastics is the flexible material polyisobutylene, which has good adhesive properties and high resistance to chemicals.
In the city road construction   for sealing cracks in asphalt concrete pavements, various compositions of mastics are used. In the table. 87 shows the compositions of mastics, selected for their use in the II, III and IV climatic zones.

The selection of the composition of the mastics is to obtain such a mixture of binder and fillers, which would have a given softening temperature and a sufficiently high fluidity at operating temperature. The softening temperature of the mastics for the II road-climatic zone should be within 60 ° C, and III and IV - from 60 to 75 ° C.
Cracks are closed in dry weather at an air temperature of at least + 5 ° C. It is best to repair cracks in the first half of the road repair season, when the cracks are most open. Before sealing, they must be thoroughly cleaned of dust and dirt and dried. Mud in medium and large cracks is first loosened with metal hooks, and then they are cleaned of dust with flat metal brushes. For final cleaning of dust and dirt, cracks are blown out of the hose with a stream of compressed air. After cleaning and drying, they are poured with waterproofing materials.
For cutting and cleaning cracks during the current repair of asphalt concrete coatings, the DE-10 machine is used. The machine is a manually operated three-wheeled trolley on which a compressor, fuel tank and thermal tool are installed, which is the working body of the machine in the form of a jet burner. Fuel from the tank is supplied under the pressure of air entering the tank and to the tool. When cutting the edges of cracks to a depth of 40 mm, the productivity of the machine is 100-110 m / h, while cleaning cracks of the same depth, the productivity reaches 600 m / h.
Cracks with a width of more than 3 cm can be closed with cold and hot asphalt mixture. When filling with a cold mixture, cracks are filled with liquefied bitumen and stone seedlings in such a way that, after compaction, 8-10 mm remain to the coating surface. A layer of cold asphalt concrete is laid on top of the seedlings, which is compacted with 1.5-3 t motor rollers. When sealed with a hot mixture, the cracks are lubricated with liquefied bitumen, and then filled with hot asphalt mix, which is compacted with 5-6 t motor rollers.
If there is a continuous fine mesh of cracks on the asphalt concrete pavement caused by the destruction of the pavement due to the mismatch of the properties of the asphalt concrete with a required or weak base, the cracks will not be repaired and the damaged coating will be completely removed and restored after the foundation is repaired.
Repair of individual subsidence and potholes in an asphalt concrete pavement must be carried out with asphalt concrete mixtures of approximately the same compositions from which the coating is built. Materials should be imported in the quantity necessary for the repair of this section of the road. Unused materials and waste must be disposed of in a timely manner.
Cutting of the repaired area should be carried out along a straight line contour. Destroyed places located at a distance of up to 0.5 m from each other are repaired with a common map. The outline of the felling is marked on the rail. If only the top layer of the coating with a thickness of not more than 1.5 cm is damaged, then repairs are carried out without cutting the bottom layer. If the coating is damaged to a greater depth, the coating is cut down to the base. Before laying the asphalt mixture, the place to be repaired is thoroughly cleaned and treated (lubricated) at the edges and base with hot or liquefied bitumen. Lubrication provides the necessary adhesion of the newly laid coating to the old base.
The temperature of the mixture to be laid should be from 140 to 160 ° C. The mixture should be homogeneous, without lumps, it should be compacted with motor rollers. After compaction of the junction of the old and newly laid asphalt to ensure a sufficiently tight interface, they are treated with hot irons or heat radiation burners.
When repairing small damages in cold asphalt pavements with potholes more than 4 cm deep, they are repaired in two layers. A hot fine-grained or medium-grained mixture is placed in the lower layer, taking into account that at least 2 cm is left when it is compacted to lay the upper layer from the cold mixture.
During the current repair of asphalt concrete pavements, along with cutting down the destroyed layer, the method of removing deformed asphalt concrete using asphalt heaters has become widespread. Asphalt heaters are advisable to use when correcting shifts, waves, flows, ruts at public transport stops. Asphalt heaters DE-2 (D-717), shown in Fig. 119, mounted on the chassis of the UAZ-451DM car, in the closed body of which the following equipment is located: gas cylinder installation, which includes liquefied gas cylinders, a low pressure reducer, pipelines and hoses; block burners infrared radiation with a lifting mechanism; hydro and electrical equipment. In addition to the described asphalt heaters manufactured by industry, certain road operating organizations produce heat radiation heaters mounted on the chassis of automobiles (RA-10, RA-20, AR-53, etc.) for their needs.

Along with asphalt heaters, repairs are also carried out using DE-5 (D-731) repairmen, who heat up asphalt concrete pavements using infrared emitters. The repairman is mounted on the chassis of a GAZ-5EA car, in the back of which there is a thermos hopper for asphalt concrete mix, containers for mineral powder and bitumen emulsion, portable units with infrared burners, a portable infrared heater, distribution trolley, electric rolling machine, S-349 electric hammer, electric tram C-690, hand tools (shovels, ironers, brushes, etc.) and enclosing shields and signs.
As a result of the use of machines equipped with infrared radiation sources, more advanced methods for repairing asphalt concrete pavements have been developed, in which the coating is heated without burning bitumen, which allows the use of asphalt concrete treated in this way to arrange the lower or leveling layer with its fresh mixture overlapping. Currently, it has been tested and recommended for the production of a machine for repairing asphalt concrete coatings using electric quartz emitters.
After repair or installation of underground utilities destroyed travel clothes   restored after a thorough compaction of ruptures and complete stabilization of the sediment of the subgrade. If it is not possible to achieve the necessary density of the base and subgrade and the occurrence of subsidence is possible, arrange a temporary coating using coarse-grained black crushed stone mixtures or cold asphalt concrete with periodic, as the precipitation, profile correction with the same materials. After precipitation attenuation, pavement in the places of tearing is made of the same materials from which the road being repaired was built.
The maintenance of sidewalks with asphalt concrete pavements is carried out by the same methods and rules that are used in the implementation current repair   carriageway of streets and roads with asphalt concrete pavement. The main difference is that when repairing sidewalks, special sidewalk machines of small dimensions and lower productivity are used: sidewalk laying machines, sidewalk rollers, crack fillers, etc.
If the asphalt concrete coating loses the necessary roughness, the appearance of a large number of cracks, as well as a significant wear of the surface layer, an average repair of the coating is planned. The roughness of the coating is restored by surface treatment. Surface treatment improves the appearance of the coating, which has undergone significant repairs, creates an independent wear layer, eliminates slippage and gives the coating a roughness that increases the safety of traffic.
For surface treatment, crushed stone is used with a strength of at least 600 kgf / cm2 (60 MPa) of fractions 5-10, 10-15, 15-20 and 20-25 mm. Crushed stone is pre-treated in stationary asphalt mixing plants or mobile concrete mixers with bitumen or bitumen emulsion. The consumption of black gravel of various fractions and a binder can be taken in accordance with the data in table. 88.

During surface treatment, it is necessary to prepare the coating for bottling, pour the binder and scatter the stone material, compact the material with rollers and care for the coating until the mat is designed. To prepare the coating for surface treatment, it is necessary to carry out the necessary repairs and repair cracks, as well as to eliminate unevenness on the coating. The last operation is especially important, as the existing irregularities cannot be eliminated by surface treatment.
The binder is poured with asphalt distributors and evenly distributed over the coating. In a single-layer treatment, after pouring a binder, blackened gravel is immediately scattered. In double processing, first stone material of larger fractions is scattered and compacted, and then bitumen is poured a second time and stone material of smaller fractions is scattered. For better contact of the stone material with the binder, the blackened crushed stone should be compacted with rollers immediately after scattering, while the spilled bitumen has the highest temperature. Sealing is carried out from the edges to the middle; the number of passes of the rink on one track 4-5. To avoid crushing of crushed stone by rollers of a skating rink, it is necessary to apply skating rinks on pneumatic tires.
The surface temperature during surface treatment should not be lower than + 15-20 ° C, and the coating surface should not be wet to ensure good adhesion of the binder to the stone material. Finally, the mat is formed under the influence of a moving vehicle, therefore, for some time after the start of movement, surface treatment should be monitored.
Along with surface treatment, the wear layer is restored by building up a new layer of asphalt concrete onto the existing coating. As with surface treatment, the wear layer is arranged only after filling cracks, subsidence, potholes and other deformations of the coating. At the same time, to increase the safety of automobile traffic, the stacked layer should have a roughness that ensures reliable adhesion of the car wheels to the road surface. The device of coatings with a high coefficient of adhesion should be started at the beginning of the season of road repair work with a stable air temperature of at least 15 ° C. In urban conditions, three methods of device of coatings with a high coefficient of adhesion are used.
According to the first method, specially selected mixtures with a high content of crushed stone are laid in the upper coating layer. To obtain a rough surface, it is necessary to have 60% crushed stone in the mixture. When installing a rough surface, the technology of work remains the same as when installing conventional asphalt pavements. The rolling of the layer in this case is carried out immediately by heavy rollers. With insufficient rolling, such a coating becomes short-lived.
According to the second method, hot black gravel is scattered on the uncompressed top layer of the asphalt concrete pavement and rolled it. Asphalt mix   the usual composition is laid with an asphalt paver and slowly rolled with light rollers, then hot black gravel of fractions of 15-20 or 20-25 mm is scattered and leveled and rolled with heavy rollers. Black gravel fractions of 15-20 mm are scattered in an amount of 15-20 kg / m2, and fractions of 20-25 mm - 20-25 kg / m2. By the beginning of the placer, the temperature of the black gravel should be 130-150 ° C, and the temperature before rolling the rollers should not be lower than 100 ° C. The mixture should be fed continuously to the place of laying; every 5-6 cars with a mixture you need to feed a car with hot black gravel.
According to the third method, a rough surface is created by the incorporation of materials (fractions less than 100 mm) treated with bitumen, during the final compaction of the asphalt mixture in the following technological sequence: the top layer of the coating is made of a fine-grained plastic mixture with a crushed stone content of 30%; pre-compact the mixture with light rollers (2-6 passes on one track); distribute the bitumen treated material over the surface of the coating in a continuous even layer using a lightweight paver or manually; compact the material with rollers on pneumatic tires or heavy rollers. The temperature of the distributed material should be 120-140 ° C, and the coating temperature -80-100 ° C. The consumption of materials treated with bitumen, fractions of 5-10 mm is 10-13 kg / m2, fractions of 3-8 mm - 8-12 kg / m2 and fractions of 2-5 mm - 8-10 kg / m2. The movement of vehicles on the coating with flooded materials treated with bitumen can be opened the next day after completion of work.
During the overhaul of asphalt concrete pavements, the foundation is prepared for laying asphalt concrete, laying the mixture, compacting asphalt concrete and surface finishing. Preparation of the base consists in building up wells with reinforced concrete segments to the design level, in cleaning the base from dust and dirt, drying and lubricating it with bitumen emulsion. The base is cleaned with mechanical brushes, street sweepers. If necessary, the base surface is washed with water-jetting machines (PM-130, PM-10) or cleaned with compressed air supplied from the compressor receiver through special nozzles.
Laying asphalt mixture on a damp surface is not allowed, as this does not provide the necessary adhesion of the coating to the base. Wet substrates are dried with asphalt heaters or hot sand heated to 200-250 ° C. Before laying asphalt concrete, the base is covered with bitumen emulsion or liquefied bitumen using mechanical sprayers mounted on a spray gun, as well as with a special brush mounted on the irrigation and washing machine.
The bitumen emulsion is applied in a thin uniform layer 2-3 hours before laying the asphalt mixture. The binder consumption per 1 m2 of coating is 200-300 g. The approximate composition of the emulsion: bitumen 55-58%, water 41-43%, sulphite-yeast mash up to 4%. The laying of the asphalt mix can only begin after the bitumen film has completely dried out and grasped well with the base.
To obtain the required coating thickness after pouring the bitumen emulsion, control beacons are installed or markings of the top of the coating are applied on the curbstone. The top of the lighthouse or the mark on the curbstone should correspond to the top of the coating after compaction. All protruding parts underground facilities   smeared with bitumen. With a two-layer coating device, the lower layer is laid on such an area that can be overlapped in the next shift by the upper layer. This achieves better adhesion of the coating layers and significantly reduces additional cleaning work.
Asphalt mixture is laid at a temperature of at least 130 ° C by various types of pavers. Pavers allow you to smoothly change the thickness of the layer (from 3 to 15 cm) and ensure the laying of the mixture in compliance with a given transverse profile. To increase the stackable strip, the stacker kit includes expanders of the screw, tamper and smoothing board. Extenders with a length of 30 cm can be installed on one or two sides.
The number of strips of the laid asphalt mixture along the width of the carriageway is taken into account the length of the tamper of the paver and the need to overlap each strip by an average of 5 cm. lengthwise adhesion of asphalt concrete strips, the length of the strip laid in one pass of the paver should be taken depending on the air temperature.
If there are curbs, the paver moves at a distance of 10 cm from them, and the resulting gap and other places inaccessible to mechanical installation (near wells, at sharp turns) are manually repaired simultaneously with the operation of the paver. The thickness of the stacked layer is taken taking into account the compaction coefficient of 1.15-1.20.
Before laying each subsequent strip, it is necessary to warm up the previously fixed spike. To do this, the edge of the sealed strip is covered with a roller hot mix   15-20 cm wide, which is removed before rolling. Adhesions can also be heated with asphalt heaters or with a gas and gas auto repair burner. The asphalt mix is \u200b\u200bfirst compacted with light rollers, and after 4-6 passes on one track, rollers on pneumatic tires or vibratory 10-13 passes on one track. Compaction should be carried out at a temperature of the mixture 100-125 ° C. It should be completed at a temperature not lower than 75 ° C. Rolling of the lower layer at an air temperature below 10 ° C is allowed immediately with heavy rollers.
The top layer is laid on the bottom only after it has cooled down to 50 ° C at an air temperature of 10 ° C or up to 20-30 ° C at an air temperature above 10 ° C. The process of arranging the upper layer is the same as the lower one. To seal the top layer of the coating during mechanical laying of the mixture, 5-7 passes of light and 20-25 passes of heavy rollers on one track are required.