Surface treatment of the road surface. Surface treatment. Structures of rough surface treatment layers Surface treatment methods

Surface treatment is technological process the construction of wear layers of the closing layer of the coating or the creation of a rough surface by pouring viscous bitumen and scattering strong stone materials on it with dimensions of 5 ... 25 mm.

A single surface treatment is arranged on coatings made of asphalto concrete mix types V and D of all brands, types B and G of brands II and III , as well as on coatings arranged by the impregnation method or from soils treated with organic (inorganic) binders.

Surface treatment is carried out on a clean, dry and dust-free coating at an air temperature of at least + 15 ° C.

Viscous bitumen grades BND (BN) 60/90, BND (BN) 90/130, BND (BN) 130/200, and mineral material- crushed stone, mainly cubic-shaped, fractions 5...10, 10...15, 15...25 mm from hard-to-grind rock with a strength of at least 120 MPa. Crushed stone must be clean, free of dust and dirt.

The pouring temperature of bitumen grades BND (BN) 60/90, BND (BN) 90/130 - 130 ... 160 ° C, grades BND (BN) 130/200 - 100 ... 130 ° C.

Better surface treatment is carried out using black crushed stone with fractions of 10...15, 15...20 mm. Black crushed stone is laid with a bituminous crushed stone distributor of the RD-701 type with a strip of 3.5 m with a technical capacity of up to 4000 m 2 / h.

However, both of these methods of surface treatment have significant drawbacks.

1. Crushed stone, difficult to grind, cuboid, strength 120 MPa, is a scarce material.

2. Insufficient service life, high traffic noise, intensive tire wear.

3. Torn-out grains of crushed stone reduce the safety of traffic, especially when they hit the windshield.

Surface treatment from sand-rubber-bitumen mixture eliminates the above disadvantages, eliminates shear deformations and improves road operation in winter.

The mixture can be prepared on conventional asphalt plants with the addition of a feed unit crumb rubber into the mixer.

The composition of the mixture:

river fraction sand 0.5 mm - 78%;

mineral powder (fly ash) - 15%;

crushed rubber with a size of 0 ... 1.5 mm - 7%;

viscous bitumen grades BND 60/90, BND 90/130 - 11.5% of the total mass.

Sand heated to 220 ° C, mineral powder, rubber crumb are mixed for 30 s.

Next, bitumen is fed into the bunker with a temperature of 150 ... 160 ° C and the mixture is mixed for 1 min. Ready mix with a temperature of 160 ... 170 ° C, it is laid with an asphalt paver (bitumen-chip distributor) with a layer thickness of 1.0 ... 1.5 cm on a primed coating with liquid bitumen SG (MG) 70/130 at the rate of 0.5 ... 0.8 l / m 2.

Compaction of crushed stone (mixture) is carried out by heavy rollers weighing 10 ... 18 tons in 4 ... 6 passes along one track.

An increase in roughness and compaction of the coating can be achieved by embedding black crushed stone into freshly laid upper layer coatings made of low gravel or sand mixture- website. The top layer of the coating is pre-rolled by a self-propelled roller weighing 6...8 tons in 2...4 passes. Crushed stone is distributed by a crushed stone distributor based on:

fractions 5...10 mm - 12...14 kg/m2,

fractions 10...15 mm - 15...17 kg/m2 and fractions 15...20 mm - 18...21 kg/m2.

Embedding black crushed stone into the top layer of the coating is carried out by a self-propelled roller weighing 6 ... 8 tons in 2 ... 4 passes. Further compaction of the top layer of the coating is carried out by heavy rollers weighing 10...18 tons in 12...18 passes.

When using a surface treatment device using foamed bitumen, the same grades of bitumen and crushed stone are used. Foamed bitumen is a conglomerate consisting of bubbles of an air-steam mixture, the walls of which are composed of bitumen films. Foaming occurs when water is supplied to the bitumen in an amount of 1 .... The optimal amount of water is determined empirically for each specific case. Surface treatment with the use of foamed bitumen is carried out at an air temperature of at least +10 °C.

Bottling of foamed bitumen is carried out by an asphalt distributor or a chipped bitumen distributor of the RD-701 type, equipped with a foaming system.

Benefits of using foamed bitumen:

improving the quality of bottling (the layer is thinner, continuous, uniform in thickness);

reduction in binder consumption;

the ability to spill the binder in wet weather;

better adhesion with stone material and coating.

The bitumen temperature when pouring into a container is 170...190 ° C, and when pouring 150...170 ° C.

The RD-701 machine can operate in bitumen pouring mode with simultaneous scattering of crushed stone, or these operations are performed independently, separately. During breaks in work with the supply of crushed stone, 2 ... 3 m before stopping, the bitumen is blocked, the remnants of the system drain and fall asleep with crushed stone.

Following RD-701, a team of 4 ... 5 road workers corrects emerging defects in surface treatment. Rolling is carried out by rollers weighing 10...13 tons in 3...5 passes at a speed of 2...4 km/h.

On roads with intensive heavy traffic, rough layers 1.5, 2.0, 2.5 cm thick are arranged as wear from hot crushed stone (50 ... ...0.5 l/m2. The mixture is distributed by an asphalt paver and compacted at a temperature of 120...140 ° C by rollers weighing up to 9 tons on a pneumatic track in 8...12 passes and by heavy smooth-rollers weighing 10...18 tons in 6...10 passes. The consumption of the mixture depends on the size of the crushed stone and ranges from 30 to 60 kg/m.

Double surface treatment is used for significant damage to asphalt concrete and cement concrete pavements.

Crushed stone, not treated with binders, is allowed to be used on roads with a traffic intensity of not more than 1000 vehicles / day.

The surface treatment device on old coatings is started after all damages and deformations (potholes, subsidence, etc.) have been eliminated. thorough cleaning covers from dust and dirt. The construction technology of various types of surface treatment of the coating is set out in Table. 61, 62, and fig. 17, possible disadvantages and ways to eliminate them in table. 63.

Table 61

The technology of the device for single surface treatment of the coating using various materials and machines

Note. Bitumen is poured according to the rate of 1 ... 1.3 l / m 2 according to the fractions of white crushed stone, and according to the norm of 0.8 ... 0.9 l / m 2 - according to the fractions of black crushed stone.

Table 62

The technology of the double surface coating device using various materials and machines

Note. Bitumen consumption (1.0 ... 1.6), (0.8 ... 0.9) l / m 2 is provided for white crushed stone, and (0.8 ... 0.9), (0, 6 ... 0.7) l / m 2 for black gravel.

Table 62

Disadvantages and ways to eliminate them in the device for surface treatment of the coating

Quality control of works

1. The bitumen temperature in each asphalt distributor is checked.

2. Constantly check the uniformity and purity of crushed stone, the uniform distribution of bitumen and crushed stone on the surface.

3. At least once per shift, the adhesion of the binder to the surface of crushed stone grains is checked in accordance with GOST 12801-84.

Surface treatment consists in the fact that a thin layer of hot bitumen is poured onto a rolled and prepared, dust-free road surface, over which stone fines (or coarse sand) are distributed.

The thickness of single surface treatment is 1-1.5 and double 2.5-4 cm. An even waterproof layer is created on the road surface with sufficient wear resistance and a rough surface that provides a good braking effect. For surface treatment, viscous bitumen BND 130/200 and BND 200/300 are used, having an operating temperature of 90-150 ° C, and liquid bitumen MG 130/200 and SG 130/200, heated to a temperature of 80-100 ° C.

The production technology of a single surface treatment includes the following operations: preparation of the surface of the coating for surface treatment (repair, correction of the transverse profile and cleaning the surface from dirt and dust); preliminary bottling of liquid binder (0.5 -0.8 l / m 2) on the coating, arranged without the use of black binders; the main filling of the binder on the surface of the coating with the consumption of bitumen (tar) 0.7-2.4 l/m 2 ; scattering of mineral materials 3-15 mm in size into a spilled layer of hot bitumen (fine crushed stone, gravel, coarse sand); rolling of the surface treatment layer.

Surfaces on which surface treatment is intended should not have transverse slopes exceeding 30‰. With a larger slope, they must be softened using, for example, a mixture of sand and bitumen. Coatings before surface treatment should be cleaned with mechanical brushes, sweepers or watering machines (2-3 passes). Coatings of hardened soils are cleaned of lumps and layers of dried mud by passages of light graders, while metal brushes should be used very carefully so as not to damage the top layer of the hardened soil.

Particularly thorough cleaning requires the surface and seams of pavements. Coatings made without black binder (particularly gravel) will almost always leave some dusty particles on the surface, which can cause the surface treatment to peel off the coating. To avoid this, it is necessary to create a contact layer in the form of a preliminary filling, which, if possible, is best done 1-2 days before the main work. At the same time, liquid bitumen in warm weather can be used without heating.

Binders are usually poured with an asphalt distributor. Before bottling, they are heated to the operating temperature indicated above. 20-30 minutes after pouring, a layer of liquid bitumen or tar should be covered with mineral material, which is best used as crushed stone from hard rock stone; worse - gravel and coarse sand.

In the conditions of forestry (timber industry) it is necessary to use any durable material, including crushed blast-furnace slag. largest size particles should not exceed the thickness of the binder layer by more than 5 mm. If it rains or becomes cold immediately after the wear layer has been rolled, the area should be closed to traffic until completely dry and then rolled. For better adhesion of bitumen to mineral filler, 1-3% slaked lime should be added. It is convenient to spread the mineral material using mounted distributors for dump trucks or mineral fertilizer distributors available in state farms, collective farms and departments of Selkhoztekhnika.

The vehicle with the mineral material must be driven in reverse with the wheels resting on the loose layer of fine stone. Immediately after the distribution of the mineral material (before the binder hardens), rolling begins. Usually quite heavy rollers (5-8 tons) are used, but they should not crush pieces of mineral material; when using weak materials, compaction should be carried out with lighter rollers. Good results are obtained when rollers are operated on pneumatics (of any weight). The final rolling and formation of the surface treatment layer is carried out under the influence of moving machines for about a month. With double surface treatment after rolling the 1st layer, all other operations are repeated.

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The method of surface treatment is most widely used in the construction of protective and wear layers. To do this, a binder is poured over the prepared base, then mineral fine-grained material is scattered in a thin layer and it is sunk into the layer of spilled binder with rollers. Gradually, under the influence of solar radiation, the binder envelops the entire mineral material. Thus, the formation of a layer is completed, which can also serve as a thin layer coating.

Surface treatment can be double and triple, if these operations are repeated. The thickness of the layer of a single surface treatment is 1.5-2.5 cm, double reaches 3-4, triple - 5 cm. The number of treatments depends on the type and quality of the layer on which the surface treatment is carried out, its purpose.

For a better connection of surface treatment with the base or coating, they are thoroughly cleaned of dust and dirt. It is not always possible to completely remove dust and loose coating wear products, especially on crushed stone and gravel bases and coatings. So that these dusty particles do not reduce the adhesion of the surface treatment to the layer on which it is laid, a binder is preliminarily poured, i.e., they make a primer. The purpose of this pouring is to bind dusty particles and lightly impregnate the layer on which the surface treatment will be laid. For priming, liquid bitumen is used, thickening at an average speed (SG15/25, SG 25/40), slowly thickening (MG 25/40), coal tar (D-1, D-2) and fast-setting emulsions.

For surface treatment, taking into account the road-climatic zone, petroleum viscous road bitumen BND 200/300 and BN 200/300, BN 130/200 and BND 130/200 and BND 90/130 (GOST 22245-76) are used; petroleum liquid bitumen (GOST 11955-74), SG 40/70, SG 70/130 and SG 130/200; coal tar (GOST 4661-76) and D-5 and D-6. More viscous materials are used in southern road climatic zones, less viscous - in the northern. Direct road emulsions made on viscous bitumen are also suitable, while in the northern climatic zones, II and even III, it is desirable to use only cationic emulsions, and anionic ones can also be used in southern ones. Coal tar is desirable in the lower layers and completely unacceptable in the upper layers in settlements.

The mineral material is fine crushed stone (up to 25 mm) of high-strength rocks (according to wear I-1 and less often I-2), crushed stone equivalent to it from acidic blast-furnace and steel-smelting slags and crushed gravel. The material is selected by size, taking into account the purpose and type of surface treatment.

If the surface treatment is intended to serve as lightweight advanced coatings and the bottom layer of double or triple treatment, crushed stone is used in sizes 0-15, 0-20 and 0-25 mm. On roads of II and III categories for the top layer and single surface treatment, crushed stone and crushed gravel with dimensions of 5 (3) -10, 5 (3) -15, 15-25 mm without screenings are used. From such material, dense, but smooth elephants are obtained. For the construction of special surface wear layers by the method of single surface treatment on improved coatings, I use! crushed stone of uniform size 10 - 15, 15-20 or 20-25 mm. Large grains should differ from the smallest ones by no more than 5 mm, abroad - no more than 2 mm -12 mm), i.e. more one-dimensional with narrow limits of extreme dimensions.

Requirements for material uniformity across dimensional limits are based on the experience of the surface treatment service. After completion of work on the device for surface treatment, even rolling does not give a solid combined layer; it is necessary that all the gravel firmly stick with its edges to the spilled binder. With homogeneous crushed stone, scattered in one layer (Fig. 86), this can be

reach. In a heterogeneous material, there will always be small grains that will be on top and will not get proper adhesion to the bitumen (Fig. 87). Under the influence of the tangential forces of the wheels of cars, these gravel break out and fly out to the sides, the pavement turns out to be uneven and additional manual work is needed to sweep them from the roadside onto the pavement. Gravelled stones flying out from under the wheels are dangerous, injure passers-by and pedestrians, and break the windows of cars. Therefore, in areas with completed surface treatment, traffic is restricted by putting up posters "Do not exceed the speed of 10 (20) km - you will break the glass." The formation of surface treatment until the crushed stone stops flying out, even in dry, warm weather, lasts up to 2 weeks. This causes a speed limit on a significant stretch of the road, and therefore a decrease in productivity. road transport. Therefore, they seek to accelerate the formation of surface treatment, increasing the effectiveness of binders, adding mineral powder, activators (lime and cement), surfactants (coal, wood, peat, brown coal and shale tars and resins, as well as various anionic and cationic additives) to them.

The addition of activators to crushed stone to improve its adhesion to the binder is 2-3% of the mass fraction. Surfactants are added to bitumen when it is heated before bottling; mass fraction their 5-15%. Bitumen consumption is reduced accordingly. Improvements in adhesion are achieved by using crushed stone, previously treated with a binder in the installation. For this, liquid bitumen SG 70/130 and SG 130/200, tar D-6 and road emulsions are used. To facilitate the adhesion of the binder to the mineral material in the northern regions, it is mandatory to use crushed stone, pre-treated with bitumen or tar in a mass fraction of 1.5-2%.

Work on the surface treatment device is carried out in dry, warm weather. The air temperature when using viscous bitumen should not be lower than 15 ° C, liquid bitumen and tar - not lower than 10 ° C, emulsions - not lower than 5 ° C. If a reverse cationic emulsion is used, in extreme cases, surface treatment can be carried out at a temperature of 0 up to 5 ° C. At the lower temperature limit, work is carried out in the spring, taking into account the fact that in the future the air temperature will rise. In autumn, work is completed 15-20 days before the onset of a rainy and cold period, when the air temperature falls below the specified limits, so that the formation of surface treatment ends in the year of its establishment. In order to reduce transportation distances, all materials are harvested and transported in advance to bases that have storage facilities for binders, boilers for heating and preparing them, warehouses for additional materials for them, and platforms for crushed stone. Taking into account the time and sources of obtaining materials, primarily binders, the bases are located at the stations to which they arrive, along the road after a certain distance. The location of the bases is established by technical and economic calculations so that the transportation distances, especially by asphalt distributors, do not exceed 20 - 25 km.

The organization of work on the surface treatment device requires preparatory work which include the organization of bitumen bases and warehouses, road preparation (fencing of the working area, installation of road signs and preparation of the base). The base is given a transverse profile corresponding to the desired profile of the finished coating or wear layer. In this case, repair work may be required to seal the destroyed places and lay local leveling layers. Before starting these works, the base is thoroughly cleaned of dirt and dust with brush and watering machines. But after that, the base must be dried with road dryers and infrared heaters or wait until the water evaporates under the influence of solar radiation.

Dust removal is carried out by installations that blow it to the side, where possible, or, conversely, suck dust. When there is no confidence in the dustlessness of the base, an under-primer is produced with a binder consumption in the range of 0.5 - 0.6 l / m 2. If the asphalt distributor cannot provide such a filling rate, emulsions are used. The emulsion containing 50% binder is poured in the amount of 1 - 1.2 l/m 2 , which after evaporation of water will be 0.5 - 0.6 l/m 2 of binder.

After the primer thickens (preferably the next day), proceed to the main work. The binder delivered by the asphalt distributor for the base layer is poured in strips. When working with an asphalt distributor, the productivity is calculated by the formula (in tons / shift):

where T - shift duration, h; K in - time utilization factor (0.85 - 0.9); A - asphalt distributor capacity, t; L - binder delivery distance, km; V 1 and V 2 - the speed of movement of the loaded and empty asphalt distributor, respectively, km/h; t n - the time of stay of the asphalt distributor on the base, h; t p - time for bottling the binder, h (approximately 0.1 - 0.2 h per 1 ton of binder).

In order to evenly distribute the binder and avoid its excess in certain places, automatic machines are used that ensure a constant consumption of material per unit surface of the coating or base. The binder consumption per 1 m 2 of the treated surface is determined (in l / m 2):

where Q - consumption of binder flowing through the main pipeline, l; B- filling strip width, m; V - speed of the asphalt distributor, m/min.

Considering that B remains constant during the emptying of one distributor, we can assume that the amount of binder per 1 m 2 is proportional to . The HADI flow meter system is based on the use of a ratio meter that measures the ratio of two currents, one of which is proportional to the binder flow rate, the other - to the asphalt distributor speed. Logometer shows specific consumption binder, and its scale can be graduated in l / m 2. When the asphalt distributor moves at a certain speed V , required for a given ratio, the pipeline delivers binder per unit time Q. When the speed changes, the feed rate changes immediately.

The binder consumption during single processing, depending on the size of the mineral material and the purpose, is from 1 to 2 l/m 2 . For rough wear layers on improved coatings, the consumption should not exceed 0.5-0.7 l/m 2 so that after the formation of the layer, the bitumen does not come to the surface. The D-61A asphalt distributor carries out bottling in the amount of 0.3-0.7 l/m 2 . If the asphalt distributor cannot provide such a rate, then in order to obtain a thin layer of binder, a rubber trowel is strengthened behind the asphalt distributor, which evenly distributes the binder, and shifts the excess to the adjacent lane. If it is impossible to ensure the minimum filling rate of the binder, road emulsions are used.

The binder consumption for the main filling depends on the purpose and thickness of the surface treatment, the size of the mineral material. The binder consumption increases at the same layer thickness with a decrease in grain size, as well as when using low-strength, capable of crushing during rolling. For a surface treatment device on worn improved or transitional (crushed stone) coatings, the binder consumption is increased by 10%.

During pouring, the binder must be fluid in order to be evenly distributed over the surface of the layer and to better envelop the grains of the mineral material. In order to increase the workability and temporarily reduce the viscosity, mineral materials are heated.

When leaving the asphalt distributor, the binder, depending on its type and brand, must have an operating temperature of:

Working temperature, °С

BND 200/300, BN 200/300 .............................. ................... 80-130

BND 130/200, BN 130/200 ...........………………………………140-160

BND 90/130, BN 90/130 ...........………………………………150-170

MG 40/70, SG 40/70 .............………………………………………..60-70

MG 70/130, SG 70/130 .............................. ...............................80-90

MG 130/200, SG 130/200 .............................. .........................90-100

D-5. . . ................................................. .........................80-90

D-6. . . ................................................. .........................90-120

Rice. .88. Scheme of the breakdown of the replaceable gripper into bitumen bottling areas and the organization of work with the asphalt distributor:

1 - places of stops of a tank truck for filling the asphalt distributor with bitumen (positions I, І and ІІІ); 2 - breakdown of the axis of the coating (in 25 m); 3 - signal flags at the end of the bottling section; 4 - places of the protective layer; 5 - asphalt distributor in incomplete position before pouring bitumen. The numbers in the circles are the serial number of the bottling section.

With the introduction of surfactants, the highest heating temperature of viscous bitumen should not exceed 140°C.

The binder is poured with an asphalt distributor immediately over the entire width of the roadway. If it is necessary to skip traffic, work is carried out along the halves of the carriageway. The length of the main filling section is assigned on the basis that the volume of the binder poured in one pass of the asphalt distributor is equal to the capacity of its tank. On average, with a width of 7–7.5 m, the length of the section (grip) on which surface treatment is carried out should be 500–800 m. binder at a given rate. The amount of binder poured by the asphalt distributor per 1 m 2 depends on the operation of the pump and the speed of movement. Therefore, the speed of the asphalt distributor during filling should be strictly uniform - no more than 7-8 km/h.

At the beginning and end of the section, when the asphalt distributor picks up speed and brakes, uneven distribution of the binder may occur. Therefore, at the beginning and end of the section for 2-3 m, the coating is covered with roofing paper, thick paper or sand with a layer of 1-2 cm. After filling, the protective materials are removed. In areas with a longitudinal slope, in order to avoid the spreading of the binder, the filling is carried out when the asphalt distributor moves up.

On fig. 88 shows a diagram of the breakdown of the replaceable gripper into bitumen pouring areas and the organization of the work of the asphalt distributor. Sprinkle the mineral material immediately after pouring; when using emulsin - not earlier than after 3-5 hours. It is advisable to use box-type distributors mounted on dump trucks, which are hung at the back of the body. The dump truck approaches the strip of spilled binder in reverse, the body overturns and gradually the material is poured into the distributor hopper, from which the material flows evenly onto the spilled binder. The dump truck moves in reverse at a speed of up to 10 km / h on already scattered rubble.

The movement of cars on the spilled binder is unacceptable, since it will stick to the wheels, which will break the continuity of the film and the treatment layer will not form.

To facilitate work, all dump trucks delivering crushed stone must have overhead distributors. If there are not enough of them, after spreading the material, the hopper distributor is left on the goats at the end of the treated area. A new loaded car drives up to the goats and attaches the distributor.

The industry produces self-propelled mineral material distributors DS-49 on a wheeled chassis, with which the productivity reaches 75 m 3 / h.

The consumption of mineral material depends on its size and the desired layer thickness. For single processing consumption will be:

Consumption, m 2 / 10P m 2

Crushed stone up to 5 mm ……………………………………………………………… ........... 0.55-0.6

» » » 10-25 mm .............................................. .............................1.2-3.0

With double processing, the consumption ranges from 1.8 to 4.5 m 3 per 100 m 2 of surface, with triple processing from 4.5 to 6.5, depending on the size of the crushed stone selected for each layer.

The rolling of the mineral material is carried out in 2-3 passes of a roller with smooth rollers weighing 5-8 tons, and for one-sized crushed stone, 1-2 passes along one track are sufficient. The task of rolling is to press the crushed stone to the binder and distribute it over the surface of the base.

Care of surface treatment consists in basting discarded grains, correcting dry places and depressions, adding binder, and in places with excess binder - adding fine gravel.

With double and triple treatments, there is no need to prepare the previously laid layer. In dry, hot weather, when there is confidence in the rapid formation of the layer, subsequent layers can be laid one after the other. Sometimes they prefer to start moving on the first layer in order to reveal weak spots, fix them and then lay subsequent layers. With double and triple processing, crushed stone should be of different sizes. For example, for the first layer 15-20 mm, for the second 10-15 and for the third, the topmost 5-10. Accordingly, the consumption of bitumen varies. If for the first filling 1-1.4 l / m 2, for the second 1 -1.2, for the third 0.8-1. With the device of a single surface treatment on an improved coating, in order to achieve a rough surface, a minimum binder spill is required - 0.5-0.8 l/m 2 . Bitumen must not protrude onto the surface of the coating. It should only be enough to envelop the rubble for 2/3 of its height.

The construction of surface treatment to obtain particularly rough and wear-resistant wear layers is possible using special sharp-edged materials, preferably reflective, for example, crushed glass, porcelain, etc.

Surface treatment is a technological process of building thin layers on road surfaces in order to ensure roughness, water resistance, wear resistance and density of coatings. The layer arranged in this way is also called surface treatment.

Surface treatments are used:
or as a preventive layer that closes and protects the main structural layers of road surfaces from premature destruction in bad weather;
or as a wear layer subject to abrasion during movement, protecting the best way road structure. Such a layer only needs periodic renewal to restore the road structure to its original qualities;
or as a top layer pavement with roughness characteristics that provide grip and good drainage of surface water, leading to a significant reduction in the hydroplaning threshold and creating, due to the increased specific pressure, good resistance to the formation of ice.

In addition to the technical advantages, surface treatments have a fairly competitive cost compared to the complex pavement used in these cases.

There are many different ways to arrange surface treatments, of which only one is considered in this article - the use of fractional crushed stone and various organic binders, including emulsified ones, for this purpose.

In order to create a surface treatment that meets the requirements presented, it is necessary to observe several fundamental provisions when constructing it:

use a binder that is firmly and permanently connected to the surface of the coating or base. This connection is called a binder-base pair;
the stone material must be attached to the pavement or base, and each rubble must be firmly connected to its neighbors. This interaction is called a pair of "binder - crushed stone";
the amount of binder should be sufficient to cover each crushed stone with a film to the required height and fill all the microcracks in the coating, but not be excessive so as not to protrude onto the surface of the crushed stone layer. This is the basic principle of the dosage and distribution of the binder;
stone material must be clean, have high physical and mechanical properties (strength, frost resistance, abrasion resistance, etc.), have certain shapes and sizes. These are the basic requirements for stone materials;
amount stone material should be sufficient to create the desired surface structure, but not be redundant to avoid having to remove it. This is the principle of dosage and distribution of stone material;
each gravel should take the most stable position, and all together should create a continuous monolithic layer with a rough surface. This is the basic principle of compaction.

These are the basic principles for ensuring high quality surface finishes. In addition, there are a number of additional conditions:

all work on the surface treatment device must be carried out in the most favorable weather conditions. This is the principle of assigning deadlines for the performance of work;
Before the start of work, all organizational issues related to the supply of materials, preparation of machinery and equipment must be resolved. This is the principle of organizing work;
in the process of work, the requirements for the technology of work production and the quality of the materials used must be strictly observed. This is the principle of quality control organization.

Surface treatments using fractionated crushed stone are arranged mainly on road sections with dangerous and difficult traffic conditions on roads of categories I - III.

Depending on the type and condition of the coating, surface treatments can be single or double; on cement concrete pavements - only double.

Material requirements
rubble

Crushed stone of surface treatment perceives and transfers the load from cars to the underlying layers, serves as a wear layer and provides adhesion between the road and the wheels of cars.

The stone material used for the surface treatment device must have high physical and mechanical properties, such as strength, frost resistance, resistance to impact and wear (abrasion), good bonding strength with a binder, etc. The conformity of the rock to the binder is determined by testing in laboratory conditions for adhesion strength.
Influence of the shape of gravel on the stability of their position
Rice. 1. Influence of the shape of gravel on the stability of their position

The shape of the gravel should be as close to cubic as possible in order to ensure a stable position on the surface of the coating. The ovoid shape of gravel, the so-called "Columbian egg" shape, does not have a stable position. Flat tiles and gravel in the form of an elongated needle are fragile and poorly fit into the coating (Fig. 1).

Crushed stone of surface treatment must be very clean, which causes it to be thoroughly washed during production. The presence of clay, even in very low proportions, is highly undesirable: clay is extremely hydrophilic, and the strong swelling that occurs in the presence of water tends to break the binder-crushed stone bond.

Properly chosen shape and size of gravel form the roughness of surface treatment, provide noise reduction in the car when driving.
Trailed chipped bitumen distributor BShchR-375 jointly produced by Strommashina OJSC and Breining (Fayat Group), Germany
Trailed chipped bitumen distributor BShchR-375 jointly produced by Strommashina OJSC and Breining (Fayat Group), Germany

The choice of gravel size is important. It has been established that crushed stone sizes of the order of 10–15 and 15–20 mm cause a rather high noise level in the car interior and interfere with listening to music at a speed of more than 130 km/h. Based on this, preference is given to surface treatment of crushed stone with fractions of 5–10 mm.

Another factor that must be taken into account when setting requirements for the size of crushed stone is to exclude the possibility of breaking the windshields of cars with crushed stones flying out from under the wheels of cars when driving with high speed. The use of fine-grained gravel almost completely solves this problem.

For surface treatment, crushed stone of grade not lower than 1200 according to GOST 8267-82 from hard-to-grind igneous and metamorphic rocks is used for highways of categories I and II, grade 1000 - for roads of category III and grade not lower than 800 - for roads of category IV, fractions 5 –10, 10–15, 15–20 mm (it is allowed to use crushed stone with fractions of 5–15 and 10–20 mm, provided that the coefficient of adhesion is ensured) predominantly cube-shaped grains (grains of lamellar shape do not exceed 15%); the content of dusty, clay and silty particles in crushed stone should not exceed 1% of the mass. The choice of crushed stone fraction is made depending on the hardness of the road surface.
astringent

In the surface treatment device, viscous bitumen, bitumen with tar additives, bitumen and tar with polymer additives, bitumen emulsions are used as binders.

The binder provides waterproofing of the coating, gluing the stone material to the coating or base and connecting the gravel into a single layer.

The grade of bitumen is chosen according to GOST 22245-90, taking into account the road-climatic zone: for I - BND 90/130 and BND 130/200, for II and III - BND 60/90, BND 90/130, BND 130/200, BN 60 /90, BN 90/130 and BN 130/200, for IV and V - BND 60/90, BND 90/130, BN 60/90 and BN 90/130.

The bitumen must pass the adhesion test with the crushed stone used for the surface treatment device. In case of unsatisfactory adhesion of bitumen to crushed stone, additives of appropriate surfactants should be used or pre-processing crushed stone with tar or a mixture of bitumen with tar.

Used coal tar must be grade D-5, D-6 or D-7 according to GOST 4641-80 and be used on highways not higher than III category. On sections of roads passing through settlements, the use of coal tar is not allowed.

When surface treatment using emulsions, mainly cationic bitumen emulsions of the EBK-1, EBK-2 class are used that meet the requirements of GOST 52128. 1, EBA-2. Emulsions must pass the binder film adhesion test with crushed stone.

When using a surface treatment device on cationic bitumen emulsions, crushed stone untreated with an organic binder is used, on anionic emulsions - mainly black crushed stone.

When arranging surface treatment on roads with a traffic intensity of more than 3000 vehicles / day, with the movement of mainly trucks, also in areas with a sharply continental climate, bitumen and tar with polymer additives are used. The polymer tar binder is used on roads not higher than category II.

Types of surface treatments

There are several types of surface treatments, each of which has its own scope of the most effective application(Fig. 2).

Types of surface treatments
Rice. 2. Types of surface treatments

Single-layer surface treatment with a single distribution of binder and crushed stone. It is used to create a rough surface and wear layer of pavement with sufficient strength. This is the most common type of rough surface treatment and is most suitable for all types of movement. Most often, it is arranged from crushed stone of fractions of 5-10 mm.
Single-layer surface treatment with double distribution of crushed stone. A large fraction of crushed stone (for example, 10–15 or 15–20 mm) is first scattered on the layer of applied binder, rolled with a roller, and then a finer fraction of crushed stone (for example, 5–10 mm) is scattered and compacted. It is used on roads with heavy traffic and high speed. Such surface treatment improves the tightness of the coating, eliminates minor irregularities and deformations, and better distributes the forces from the wheels of cars. Such processing works especially effectively on a good hard base.
Double layer surface treatment. A large fraction of crushed stone is scattered on the first layer of the spilled binder and compacted. Then the second layer of the binder is poured, the finer fraction of crushed stone is scattered and finally compacted. It is used on coatings with insufficient strength, in the presence of a network of cracks, pitting, ruts, at high traffic intensity, i.e. in cases where it is necessary not only to create a rough wear layer and a protective layer, but also to improve evenness, to slightly increase strength and shear resistance. It is also used on cement concrete pavements.
Sandwich surface finish. Crushed stone of a larger fraction is scattered on the coating, then the binder is distributed, crushed stone of a fine fraction is scattered and compacted. The structure of the obtained layer of surface treatment is comparable to a single-layer surface treatment, arranged by pouring binder and double scattering of crushed stone. Such surface treatment is recommended for non-uniform evenness of the coating for its leveling and some strengthening. It is used on roads of secondary, local importance.

When choosing a method for surface treatment of coatings, it is necessary to take into account its purpose, traffic conditions on the road, climatic conditions of the construction area, the hardness index of the road surface, the availability of materials and means of mechanization.

Work production technology

There are two ways to arrange surface treatments:

traditional - with separate distribution materials;
method with synchronous distribution of binder and crushed stone.

The traditional way

Works on the device of a single surface treatment traditional way using bitumen, tar bitumen, bitumen and tar polymer binders are produced in the following order:

pouring binder;
crushed stone distribution;
rolling;
care during the formation period.

Work on the device for double surface treatment is carried out in the following sequence:

surface preparation (cleaning from dust and dirt) and repair work;
the first bottling of the binder;
the first scattering of rubble;
rolling;
the second bottling of the binder;
the second scattering of crushed stone (between the first and second scattering of crushed stone, a break of no more than 3-5 days is allowed);
rolling;
care during the formation period.

Chipsealer-19 bitumen distributor by Secmair, France

Cleaning the coating from dust and dirt is carried out with mechanical brushes, the most contaminated areas are washed with a watering machine.

Brush strings, whatever their nature (nylon, steel), must be in good condition and stiff enough to provide effective scraping.

In cases where the old coating cannot be completely cleaned of dust and dirt remaining in small cracks and depressions, it must be primed by pouring liquid bitumen at a rate of 0.3–0.5 l / m2 or bitumen emulsion at a rate of 0.5– 0.8 l/m2.

The binder is poured by an asphalt distributor. For uniform filling of the binder, it is necessary to ensure the uninterrupted operation of the nozzles, the uniformity of the pump and the required speed of the distributor.

The nozzles must be thermally insulated and equipped with a heating device to maintain or provide certain temperature binder.

Depending on the selected binder and the width of the treated surface, the driver determines, using the adjustment elements of the asphalt distributor (nomogram, calculating disk, programming), the necessary ratio between the speed of movement and the number of revolutions of the pump, which determines the dosing of the binder on the pavement. During distribution, the ratio between vehicle speed and pump revolutions is kept constant, either by automatic tracking or by direct reading of the tachometer and rev counter by the driver.

During filling, the temperature of bitumen grades BND 60/90, BND 90/130, BN 60/90 and BN 90/130 should be 150–160°C; grades BND 130/200 and BN 130/200 – 100–130°C; the temperature of the polymer-bitumen binder is 140–160°C; tar-polymer binder - 100–110°C.

The distribution of crushed stone is carried out by a self-propelled crushed stone distributor, a dump truck with an attachment or other mechanism that ensures quick and even distribution of crushed stone. The body of all these mechanisms must be flat and without local deformations. The height of the crushed stone drop should be low to ensure a more uniform distribution of the aggregate on the pavement. Chip spreaders can be equipped with a hydraulic expansion system that allows changing the working width from 2.50 to 4 m without stopping.

Bitumen distributor NR-27 from Savalco

Crushed stone is distributed immediately after pouring the binder in a layer into one crushed stone and rolled with a roller of 6–8 tons in 4–5 passes along one track.

The compaction of the surface treatment of coatings ensures the laying of crushed stone and its fixation on the coating. Pneumatic tire seals provide these features superbly. They adapt to the unevenness of the road and do not crush gravel.

During the first days of operation, it is necessary to take care of the emerging layers. Loose gravel must be removed from the coating no later than 1 day after the opening of the movement. The speed of vehicles is limited to 40 km/h and regulated by the width of the roadway.

The thrown out excess crushed stone is picked up by cleaning machines-collectors, cleaning machines and retracting machines. Equipped with various brushes and suction nozzles, they are equipped with collection containers for the fine material they lift. These suction mechanisms represent a great advance in surface coating technology, as they can significantly reduce the biggest harm from pollution: the shattering of car windshields after resuming traffic.

Surface treatment using bitumen emulsions is performed in the following order:

surface preparation (cleaning from dust and dirt) and performing repairs if necessary;
wetting the surface with water (in hot dry weather);
pouring the emulsion over the coating in the amount of 30% of the norm;
distribution of crushed stone in the amount of 70% of the norm;
pouring the remaining emulsion (70%);
distribution of the remaining crushed stone (30%);
rolling;
care during the formation period.

The temperature and concentration of the emulsion is set depending on the weather conditions. At air temperatures below 20°C, it is recommended to use an emulsion with a temperature of 40–50°C and a bitumen concentration of 55–60%. The heating of the emulsion to the specified temperature should be carried out directly in the asphalt distributor during transportation to the place of work. At air temperatures above 20°C, the emulsion is applied cold, and the concentration of bitumen can be reduced to 50%.

The distribution of crushed stone is carried out in such a way that the crushed stone is distributed no further than 20 m from the asphalt distributor pouring the emulsion.

Surface treatment with bitumen emulsions is carried out in the same way as with bitumen. When using anionic emulsions, the movement of vehicles opens no earlier than 1 day after the completion of work.
Surface treatment technology with synchronous distribution of binder and crushed stone

The main difference new technology surface treatment device is synchronous, almost simultaneous distribution of binder and scattering of crushed stone (Fig. 3).
Surface Finishing with Synchronized Material Distribution
Rice. 3. Surface finishing with synchronous distribution of materials

With surface treatment device traditional methods the gap in time between the distribution of the binder and the scattering of crushed stone is limited by the cooling time of hot bitumen and can reach 1 hour.

With synchronous distribution of binder and crushed stone, the gap between these operations does not exceed 1 second, which significantly affects the quality of surface treatment, both when using hot bitumen as a binder and bitumen emulsion.

The quality improvement when using hot bitumen as a binder is explained by the fact that in such a short period of time the bitumen does not have time to cool down and retains a liquid consistency and high adhesive ability. As a result, bitumen penetrates well into the micropores of crushed stone and coating, envelops each gravel and firmly sticks them to the coating and one to the other.

Twinsealer bitumen distributor from Rincheval (Fayat Group), France

The compaction of the laid layer also occurs when the bitumen is hot, which ensures maximum effect seals.

When used as a binder bitumen emulsion high quality surface treatment with synchronous distribution of binder and crushed stone is explained by the fact that in such a short period of time, the disintegration of the emulsion will only begin, and the emulsion in the liquid state will fill all the micropores of crushed stone and coating, cover each crushed stone with a thin layer of binder and ensure good compaction of the surface treatment layer.

Synchronous distribution solves all the problems of organizing and coordinating work arising from asynchronous distribution, since at each stop in the distribution of crushed stone, the distribution of the binder is automatically stopped. Significantly reduced downtime due to climatic conditions and increase work productivity. This is important when using high viscosity binders, but is especially important when working in adverse weather conditions.

The synchronous distribution of the binder and crushed stone favorably affects the formation of the interface between the binder and crushed stone, which guarantees high performance characteristics surface treatment, reduces the risk of work failure due to the temperature difference between the base and the binder, as well as due to the presence of dry fine fractions during surface treatment using emulsions.
Twinsealer bitumen distributor from Rincheval (Fayat Group), France
Twinsealer bitumen distributor from Rincheval (Fayat Group), France

Experience shows that a high level of quality surface treatment with synchronous distribution of binder and crushed stone can achieve amazing results when thin layer crushed stone and binder can withstand the intense impact of car wheels for 10-15 years.

Thus, the synchronous distribution of binder and crushed stone with a delay time of 1 second is the most important innovation in the practice of surface treatment in the last 20 years.

To implement the idea of ​​surface treatment with synchronous distribution of binder and crushed stone, SECMAIR has developed and produces a wide range of bitumen spreaders of various capacities, as well as other machines for maintaining and repairing road surfaces using crushed stone treated with bitumen or bitumen emulsion.

Produced machines can work when moving forward or when moving in reverse (Fig. 4).
Working Principles of Surface Finishing Machines
Rice. 4. Operating principles of surface treatment machines

Given the significant interest of Russian road workers in the introduction of surface treatment technology with synchronous distribution of binder and bitumen, the French company SECMAIR and the State Unitary Enterprise Saratov Research and Production Center Rosdortekh created a joint production of Chipsealer machines in Saratov.

In 1999, the production of the following machines began:

Chipsealer-40. This is a high-performance equipment designed for rough surface treatment in large volumes. The Chipsealer-40 equipment is mounted on the base of the Caizer semi-trailer and has a fully autonomous system energy supply. In one cycle of loading the body with crushed stone, it allows performing surface treatment on a strip 3.75 m wide and up to 800 m long in 10 minutes.
Chipsealer-26 is made on the basis of the Russian SZAP-9905 semi-trailer. MAZ and KamAZ truck tractors can be used as a tractor vehicle. It has the same characteristics as the Chipsealer-40, but smaller dimensions of the gravel body and the binder tank.
Chipsealer-19 is designed for small scale pavement repairs and rough surface treatments.

Stopper machines

They are used to curb erosion of the coating at an early stage by arranging local surface treatment in areas of peeling and chipping of the coating, the appearance of small cracks, a network of cracks, small potholes and ruts. The machine has on one chassis a container for a binder, a body for crushed stone, a clamshell bucket for loading crushed stone into the body and distributing devices for applying bitumen and crushed stone (Fig. 5).
Machine equipment type "Stopper"
Rice. 5. Equipment of the machine type "Stopper"
1 - heat-insulated tank for binder;
2 - clamshell bucket for loading crushed stone;
3 - a body for crushed stone;
4 – operator platform;
5 - binder distributor;
6 - crushed stone distributor;
7 - pneumatic roller;
8 - direction of movement

Another difference is that the “Stopper” has a sealing block of 8 pneumatic smooth wheels, which, with the help of 4 hydraulic jacks descend to the surface in working position and lift up to the transport position. This is especially important for the accelerated formation of the repair layer in cold and humid climates. In dry and hot climates, this formation occurs under the action of moving traffic, and the need for a sealing block is eliminated. In addition, "Stoppers" are adapted for local repairs using surface treatment.
Machines for surface treatment device

For a surface treatment device in a traditional way, i.e. with separate distribution of binder and crushed stone, asphalt distributors and crushed stone distributors are used.

Asphalt distributors are distinguished and selected by:

tank capacity (carrying capacity);
binder distribution width; in this case, as a rule, the distribution width is chosen equal to the width of the road lane or 5-10 cm less.

Crushed stone distributors are distinguished by:

capacity (capacity) of the bunker for crushed stone;
crushed stone distribution width; in this case, as a rule, the width of the distribution of crushed stone is taken equal to the width of the distribution of the binder;
type of travel (movement): trailed and mounted base machines. As a rule, dump trucks are used as base machines for trailed and mounted crushed stone spreaders.

For a surface treatment device by the method of synchronous (simultaneous sequential) distribution of binder and crushed stone, bitumen-(emulsion) crushed stone distributors are used.

Bitumen distributors are distinguished by:

processing width, i.e. according to the correspondence (multiplicity) of this parameter to the width of the carriageway of the highway;
capacity (capacity) of the tank for the binder and the bunker for crushed stone;
gravel loading method, i.e. the use of special loading machines for loading crushed stone into the bunker or special self-loading equipment.

Rice. 6. Development of machines for loading emulsion and crushed stone

On fig. Figure 6 shows the production schedules (in thousand m2) of all three types of machines: asphalt distributors, crushed stone distributors and bitumen-(emulsion)-crushed stone distributors at a bitumen emulsion filling rate of 1.4 and 2.1 l/m2 and a crushed stone distribution rate of 10, 0 and 15.0 kg/m2. Depending on the width of the filling of the binder and the distribution of crushed stone in fig. 6 also shows the development in the lin. m processing lane.

The presented graphs, taking into account the capacity of the binder tank and the crushed stone bin and bitumen distributors, show that the capacity of the binder tank provides a significantly higher output than the capacity of the crushed stone bunker. Thus, the crushed stone hopper must be filled several times to ensure the release of the binder. The ratio of workings for binder and crushed stone for various bituminous chip spreaders ranges from 2.0 to 9.5. Therefore, the method of loading crushed stone has a significant impact on shift production (productivity).
Joint operation of the asphalt distributor and the trailed crushed stone distributor of ZAO "Betsema", loaded from a dump truck
Joint operation of the asphalt distributor and the trailed crushed stone distributor of ZAO "Betsema", loaded from a dump truck

When loading crushed stone into the hopper of a crushed stone distributor (without self-loading) on ​​the base using a single-bucket front loader or a crane with a grab (jaw bucket), i.e. with a double run from the place of work to the base and back, the time spent on one load is from 40 minutes to 1 hour 20 minutes.

When loading crushed stone into the hopper of a bituminous chip distributor at the work site using self-loading or using a dump truck with a crane equipped with a grab, the time spent on one load is from 10 to 15 minutes.

When loading crushed stone into the bunker of the bitumen spreader with self-loading from the receiving hopper located behind the machine and loaded from the dump truck, even when the bitumen spreader is stopped, the time spent on one load is from 2 to 6 minutes.

When calculating, the binder load is combined with the crushed stone load, i.e. is carried out after two to nine loads of crushed stone, the speed of the bitumen-split spreader is taken to be 4 km/h = 1.1 m/sec = 66 m/min., the distribution width is taken to be 3 m, the time utilization factor is taken to be 0.8 on the base) and 0.6 (when loaded on the road), which is associated with the need and great complexity of the rhythmic supply of materials, the use of additional machines (dump trucks, bitumen trucks).

TECHNOLOGIES FOR THE PRODUCTION OF HIGH-QUALITY CRUSHED STONE
Technologies for the production of high-quality crushed stone

Crushed stone is the most widely used product of mining and processing of non-metallic building materials.

The volume of crushed stone production in the world exceeds 3 billion m3 per year. An interesting feature crushed stone as a product made from natural mineral raw materials is that its prices around the world have increased by 2.5–3 times over the past 50 years. At the same time, prices for most products based on mineral raw materials (for example, ferrous and non-ferrous metals) fell 3-5 times over the same period.

The apparent simplicity of the production of crushed stone - crushing of rocks - is deceptive, since modern technologies for the production of building materials and products based on them are increasingly demanding high requirements to the quality of crushed stone, used mainly as an aggregate in the production of concrete, asphalt concrete and road surfaces.

Crushed stone for road construction

Crushed stone is one of the main materials used for the construction, repair and maintenance of roads. Their quality largely depends on their consumer properties(flatness, friction coefficient, etc.) and durability. This is especially true for crushed stone used for the construction of the upper layers of road pavement, which directly perceive high mechanical loads from moving vehicles, which are under the influence of natural factors and anti-icing chemicals.

Crushed stone used in the road sector can be conditionally divided into three groups:

crushed stone for the construction of pavement bases (any, but mainly sedimentary rocky and loose rocks with a particle size of 5–20, 20–40, 40–70, 0–40, 0–70 mm);
crushed stone for the lower layers of coatings (metamorphic and igneous rocks with a particle size of 5–20 and 20–40 mm);
crushed stone for the upper layers of coatings from asphalt concrete mixtures of type A and surface treatment (igneous and partially metamorphic rocks with a crushed stone size of 5 to 20 mm) with a content of lamellar (flaky) and needle-like grains of not more than 15% (group 1 according to GOST 8267-93 ), which is commonly called "cubic".

The total volume of production of stone materials (crushed stone, gravel, sand) in Russia is currently about 140 million m3 per year, and about half of this amount is used in road construction.

Behind last years there has been a steady demand for cube-shaped crushed stone from road construction organizations, but this need in the Russian Federation is now satisfied only by 30-40%.

In accordance with the presidential program “Roads of Russia of the 21st Century”, SoyuzdorNII calculated the need for road construction materials, including various types of crushed stone. Table 1 shows the need for crushed stone of narrow cube-shaped fractions from igneous rocks for different regions Russia.
Name of the region Demand value by years and periods
2001 2002 2003 2004 2005 2001–05 2006–10 2011–20 2001–20
Center 2.3 2.4 2.5 2.6 2.7 12.5 25.8 96.6 134.9
Northwest 1.1 1.1 1.2 1.2 1.3 5.9 10.6 38.88 55.3
Volga region 1.7 1.8 1.9 1.9 2 9.3 16.2 70.3 95.8
Northern Caucasus 0.6 0.6 0.6 0.7 0.7 3.2 7.7 23.7 34.6
Ural 1.5 1.6 1.6 1.6 1.7 8 14.4 52.9 75.3
Siberia 1.4 1.4 1.4 1.6 1.7 7.5 15.5 57.7 80.7
Far East 0.7 0.7 0.8 0.8 0.8 3.8 6.7 30 40.5
Total crushed stone: 9.3 9.6 10 10.4 10.9 50.2 96.9 370 517.1
Average per year by periods: 10 19.4 37 25.8

Table 1
The need for crushed stone of narrow fractions of a cubic shape (million m3) for the development of a network of roads in the regions of Russia (2001 - 2020)

At present, the length of the road network common use with a hard surface in Russia is about 600 thousand km, and the main part of the cube-shaped crushed stone will be used for their repair and maintenance. The largest amount of all types of crushed stone will be consumed in the Central region, where road construction is carried out most intensively.

Modern practice shows that crushed stone from igneous rocks for road construction in our country is produced mainly at stationary crushing and screening plants located near deposits, mainly in northwestern Russia and the Urals.
Mobile stone crushing plant for producing cube-shaped crushed stone at the site of NCC Industry LLC (St. Petersburg)
Mobile stone crushing plant for producing cube-shaped crushed stone at the site of NCC Industry LLC (St. Petersburg)

An analysis of products manufactured by non-metallic industry enterprises that develop deposits of igneous rocks shows that they mainly produce crushed stone in the form of fractions of 5–20 mm and 20–40 mm, in some cases - fractions of 5–10, 10–20 and 5– 15 mm. There are serious complaints from road construction organizations about crushed stone of a fraction of 5–20 mm used for the preparation of asphalt concrete mixtures for the upper layers of pavements.

Produced crushed stone fraction 5–20 mm is usually very coarse. This does not allow choosing the optimal grain composition of the mineral part of asphalt concrete mixtures, which significantly worsens physical and mechanical characteristics asphalt concrete. Research by SoyuzdorNII, as well as domestic and foreign experience in the construction and operation of roads, made it possible to establish that crushed stone for the preparation of asphalt concrete mixtures for the upper layers of coatings should be produced in the form of narrow fractions (5–10, 10–15, 15–20 mm). From narrow fractions, it is relatively easy to select the required mixtures of the optimal grain composition.

The delivered crushed stone of fraction 5–20 mm in most cases contains an excessive amount of flaky grains - 25–40% or more. Their increased content adversely affects the workability and density of asphalt mixtures. They have a lower mechanical strength compared to cube-shaped ones and, therefore, are destroyed during the construction and operation of roads, which can lead to the formation of surfaces not covered with bitumen. These places are the primary centers of destruction of asphalt concrete during the penetration of water and then the action of alternate freezing-thawing.

Asphalt-concrete mixtures on cube-shaped crushed stone (group I) have better compactability compared to crushed stone of groups II and V due to mutual movement and interlocking of grains.

In this regard, the current regulatory and technical documentation limits the content of flaky grains in mixtures: 15% for mixtures of type A, 25% for type B, 35% for mixtures of type C.

The effect of flaky grains is especially negative during the surface treatment of asphalt concrete pavements using graded crushed stone, when most of such grains are destroyed during the laying of the material. In this case, their content in crushed stone should not exceed 10%.

A negative impact on the properties of asphalt concrete is also exerted by an increased amount of dusty-clay impurities, which prevent the contact of bitumen with the surface of crushed stone. Therefore, their content should not exceed: 1% - for the preparation of an asphalt concrete mixture; 0.5% - for surface treatment.

Crushing and screening plant with a KID-900 crusher at the Abzakovsky quarry

When forming the structure of asphalt concrete, crushed stone is the main component that determines the stability of the mineral core. Laboratory studies have established that the coefficient of internal friction tg c depends on the grain composition of asphalt concrete. It is practically unaffected by the viscosity of the applied bitumen and asphalt binder. In asphalt concrete with a residual porosity of 3.0–3.5%, the coefficient of internal friction increases with an increase in the content of cuboid crushed stone grains.

High rates of internal friction are provided by dense asphalt concretes of type A based on crushed stone materials and special multi-crushed stone compositions, for example crushed-stone-mastic asphalt concrete(ShMA) according to TU 5718.030.01393697-99.

Crushed-stone-mastic asphalt-concrete mixtures contain a high content of strong fractionated crushed stone (70–80%) with an improved (cubic) grain shape, which creates a stable framework. The increased content of mineral activated powder (8–15%) and bituminous binder (not less than 5.5%) significantly reduces the number of voids in the compacted coating layer. To structure and stabilize the bituminous binder, it is recommended to introduce special stabilizing additives, such as fibers.

The structure of SMA optimally combines the maximum rigidity of the mineral core and the high plasticity of the asphalt binder. The increased content of strong cube-shaped crushed stone is designed to provide high adhesion to the car wheel, roughness, shear resistance and wear resistance of the coating, and an increased amount of asphalt binder (mastic) - to increase water and frost resistance, water resistance, resistance to deformation and fatigue resistance of the protective layer. On device rough coatings it is important to provide increased requirements for the properties of stone materials. Crushed stone must be made of rocks with high wear resistance, have a cubic shape, be uniform in strength, difficult to grind and not have contaminants. The content of flaky grains in it should be limited. Crushed stone should have a well-defined roughness of natural cleavage, therefore, preference is given to rocks with a granular crystalline structure, as well as rocks that can remain rough due to components of different hardness according to VSN 73-67.
Complete production line based on the crusher KID-1200M at JSC "Pavlovskgranit", Voronezh region
Complete production line
based on crusher KID-1200M at Pavlovskgranit JSC, Voronezh region

For the reconstruction of the Moscow Ring Road (MKAD), Tsentrodorstroy JSC used three Svedala crushing and screening plants and launched the production of improved crushed stone from gabbro-diabase. The resulting crushed stone with a fraction of 5–10 and 10–15 mm with a flakiness of less than 15% was used in an asphalt concrete mix of type A on a polymer-bitumen binder for the construction of the top layer of the coating instead of the previously used granite crushed stone with a fraction of 5–20 mm. According to the results of quality control of the top layer of the MKAD pavement, one can judge the impact of the quality of crushed stone on the properties of asphalt concrete.

The asphalt concrete pavement has become more shear resistant, although the maximum size of crushed stone used in the mixture has been reduced from 20 to 15 mm. The average value of the angle of internal friction increased by about 1.5°, and the spread of this indicator decreased by almost 2 times. The average shear resistance under the design conditions for the Moscow Ring Road increased from 0.789 to 0.840 MPa. At the same time, the standard compressive strength at 50°C increased by an average of 0.3 MPa, and its variation did not exceed 12%.

The use of higher-quality crushed stone in asphalt concrete made it possible to reduce the likelihood of rutting in the top layer of the pavement, even in force majeure cases of convoy traffic and traffic jams.

Crushed stone for concrete production

Crushed stone as a large aggregate of concrete, forming a rigid skeleton, increases its strength and modulus of deformation, reduces creep, shrinkage, increases its durability, reduces cement consumption.

Fine aggregate - sand - affects the rheological properties of the concrete mixture - viscosity, ultimate shear stress of concrete, as well as its density.

The shape of coarse aggregate grains directly affects the workability of the concrete mix. In addition, crushed stone with flat (flaky) or needle-shaped grains has a significantly larger void space than crushed stone with cube-shaped grains. According to VNIIZhelezobeton, the bulk bulk density of crushed stone with the content of flat and needle-shaped grains is up to 15% lower than that of crushed stone with cube-shaped grains.

The volumetric bulk density of crushed stone, consisting entirely of flat or needle-shaped grains, is 9–10% lower than crushed stone with cube-shaped grains. These factors cause an increase in cement consumption. Therefore, although the shape of coarse aggregate grains, according to a number of studies, does not have a significant effect on the strength of concrete, serious attention should be paid to it.

in rubble for road concrete the content of flat and needle-shaped grains is permissible up to 25%, for asphalt concrete - up to 15%, for road foundations (untreated) - up to 25%.

It should be noted that the accepted limitation of the content of flat and acicular grains in crushed stone with a ratio of larger and smaller sizes above 3 does not fully characterize the shape of the grains. In this regard, of interest is the assessment of the grain shape adopted in some foreign standards according to the so-called "shape index", that is, the average ratio of the largest and smallest grain sizes of the sample. Such an assessment makes it possible to judge the shape of the entire number of crushed stone grains.

According to the Belgian standard NB No. 329, 1962, crushed stone is divided into three categories: ordinary, not crushed, and crushed cubic (Table 2).
Size of fractions in mm Category of crushed stone
conventional uncrushed re-crushed cubic
8–16; 8–12; 12–16 0,275 0,39 0,45
16–22 0,275 0,425 0,485
22–40 0,35 0,425 –
40–63 0,35 – –

table 2
The lowest values ​​of the "form index" for various categories of crushed stone (according to the Belgian standard NB No. 329, 1962)

As can be seen from the data in the table, there are practically no requirements for the shape of grains for ordinary crushed stone (it can be classified as crushed stone of a flat and acicular shape according to our standards), but for crushed stone of higher categories, the requirements for the shape of grains are quite stringent.

In a number of works, the negative role of flat and elongated aggregates is noted, the use of which reduces the strength and increases the consumption of cement, and also worsens the frost resistance of concrete. With this in mind, during the construction of a concrete roadbed, it should be ensured that there are no pieces of flaky and needle-shaped pieces in the rubble, based on the fact that the concrete mixture with such aggregates becomes difficult to place, poorly compacted, and shells remain in the concrete, the fight against which requires an increase in cement consumption.

To check the effect on the concrete parameters of the presence of pieces of flaky form in the crushed stone, research was carried out at the Institute of VNIIZhelezobeton. In the experiments, crushed stone from natural rocks was used. The results showed that the strength of concrete, as the content of flaky-shaped pieces in crushed stone increases (up to 50 and 100%), as a rule, decreases with a simultaneous decrease in the volumetric weight of concrete, that is, when the concrete mixture is undercompacted. Availability in in large numbers(more than 50%) crushed stone of a flaky form made it difficult to compact concrete, and this led to a decrease in strength.

The negative impact of the presence in the crushed stone of more than 50% of the pieces of the flaky form is explained by the laying of the crushed stone mainly flat, in a tile-like manner, which makes it difficult for the mutual sliding of adjacent pieces and requires an increase in the power of the vibration equipment.

Comparative physical and mechanical properties of crushed stone of various flakiness are given in table. 3.
Properties Crushed stone flaky Crushed stone cuboid
Content of flaky and needle-shaped grains, % 89 0
Ultimate compressive strength in a water-saturated state (in a cylinder), MPa 40–60 120
Crushability during compression in the cylinder,% 15–22 2–5
Index of resistance of crushed stone to impact on a pile driver PM 41–152 120–370
Wear in the shelf drum, % 18–29 15–20
Frost resistance, brand 25 300

Table 3 Physical and mechanical properties crushed stone of various flakiness

Surface treatment is a technological process of building thin layers on road surfaces in order to ensure roughness, water resistance, wear resistance and density of coatings. The layer arranged in this way is also called surface treatment.

Surface treatments are used:

• or as a preventive layer that closes and protects the main structural layers of road surfaces from premature destruction in bad weather;
• or as a wear layer subject to abrasion during driving, protecting the road structure in the best possible way. Such a layer only needs periodic renewal to restore the road structure to its original qualities;
• or as a pavement top layer with roughness characteristics that provide grip and good drainage of surface water, leading to a significant reduction in the hydroplaning threshold and creating, due to the increased specific pressure, good resistance to the formation of ice.

In addition to the technical advantages, surface treatments have a fairly competitive cost compared to the complex pavement used in these cases.

There are many different ways to arrange surface treatments, of which only one is considered in this article - the use of fractional crushed stone and various organic binders, including emulsified ones, for this purpose.

In order to create a surface treatment that meets the requirements presented, it is necessary to observe several fundamental provisions when constructing it:

• use a binder that is firmly and permanently connected to the surface of the coating or base. This connection is called a binder-base pair;
• the stone material must be attached to the pavement or base, and each rubble must be firmly connected to its neighbors. This interaction is called a pair of "binder - crushed stone";
• the amount of binder should be sufficient to cover each crushed stone with a film to the required height and fill all the microcracks in the coating, but not be excessive so as not to protrude onto the surface of the crushed stone layer. This is the basic principle of the dosage and distribution of the binder;
• stone material must be clean, have high physical and mechanical properties (strength, frost resistance, abrasion resistance, etc.), have certain shapes and sizes. These are the basic requirements for stone materials;
• the amount of stone material should be sufficient to create the desired surface structure, but not be excessive in order to avoid the need to remove it. This is the principle of dosage and distribution of stone material;
• each gravel should take the most stable position, and all together should create a continuous monolithic layer with a rough surface. This is the basic principle of compaction.

These are the basic principles for ensuring high quality surface finishes. In addition, there are a number of additional conditions:

• all work on the surface treatment device must be carried out in the most favorable weather conditions. This is the principle of assigning deadlines for the performance of work;
• Before the start of work, all organizational issues related to the supply of materials, preparation of machinery and equipment must be resolved. This is the principle of organizing work;
• in the process of work, the requirements for the technology of work production and the quality of the materials used must be strictly observed. This is the principle of quality control organization.

Surface treatments using fractionated crushed stone are arranged mainly on road sections with dangerous and difficult traffic conditions on roads of categories I - III.

Depending on the type and condition of the coating, surface treatments can be single or double; on cement concrete pavements - only double.

Material requirements

rubble

Crushed stone of surface treatment perceives and transfers the load from cars to the underlying layers, serves as a wear layer and provides adhesion between the road and the wheels of cars.

The stone material used for the surface treatment device must have high physical and mechanical properties, such as strength, frost resistance, resistance to impact and wear (abrasion), good bonding strength with a binder, etc. The conformity of the rock to the binder is determined by testing in laboratory conditions for bond strength.

Rice. 1. Influence of the shape of gravel on the stability of their position

The shape of the gravel should be as close to cubic as possible in order to ensure a stable position on the surface of the coating. The ovoid shape of gravel, the so-called "Columbian egg" shape, does not have a stable position. Flat tiles and gravel in the form of an elongated needle are fragile and poorly fit into the coating (Fig. 1).

Crushed stone of surface treatment must be very clean, which causes it to be thoroughly washed during production. The presence of clay, even in very low proportions, is highly undesirable: clay is extremely hydrophilic, and the strong swelling that occurs in the presence of water tends to break the binder-crushed stone bond.

Properly chosen shape and size of gravel form the roughness of surface treatment, provide noise reduction in the car when driving.

Trailed chipped bitumen distributor BShchR-375 jointly produced by Strommashina OJSC and Breining (Fayat Group), Germany

The choice of gravel size is important. It has been established that crushed stone sizes of the order of 10–15 and 15–20 mm cause a rather high noise level in the car interior and interfere with listening to music at a speed of more than 130 km/h. Based on this, preference is given to surface treatment of crushed stone with fractions of 5–10 mm.

Another factor that must be taken into account when setting requirements for the size of crushed stone is to exclude the possibility of breaking the windshields of cars with crushed stones flying out from under the wheels of cars when driving at high speed. The use of fine-grained gravel almost completely solves this problem.

For surface treatment, crushed stone of grade not lower than 1200 according to GOST 8267-82 from hard-to-grind igneous and metamorphic rocks is used for highways of categories I and II, grade 1000 - for roads of category III and grade not lower than 800 - for roads of category IV, fractions 5 –10, 10–15, 15–20 mm (it is allowed to use crushed stone with fractions of 5–15 and 10–20 mm, provided that the coefficient of adhesion is ensured) predominantly cube-shaped grains (grains of lamellar shape do not exceed 15%); the content of dusty, clay and silty particles in crushed stone should not exceed 1% of the mass. The choice of crushed stone fraction is made depending on the hardness of the road surface.

astringent

In the surface treatment device, viscous bitumen, bitumen with tar additives, bitumen and tar with polymer additives, bitumen emulsions are used as binders.

The binder provides waterproofing of the coating, gluing the stone material to the coating or base and connecting the gravel into a single layer.

The grade of bitumen is chosen according to GOST 22245-90, taking into account the road-climatic zone: for I - BND 90/130 and BND 130/200, for II and III - BND 60/90, BND 90/130, BND 130/200, BN 60 /90, BN 90/130 and BN 130/200, for IV and V - BND 60/90, BND 90/130, BN 60/90 and BN 90/130.

The bitumen must pass the adhesion test with the crushed stone used for the surface treatment device. In case of unsatisfactory adhesion of bitumen to crushed stone, additives of appropriate surfactants should be used or crushed stone should be pre-treated with tar or a mixture of bitumen with tar.

Used coal tar must be grade D-5, D-6 or D-7 according to GOST 4641-80 and used on roads not higher than category III. On sections of roads passing through settlements, the use of coal tar is not allowed.

When surface treatment using emulsions, mainly cationic bitumen emulsions of the EBK-1, EBK-2 class are used that meet the requirements of GOST 52128. 1, EBA-2. Emulsions must pass the binder film adhesion test with crushed stone.

When using a surface treatment device on cationic bitumen emulsions, crushed stone untreated with an organic binder is used, on anionic emulsions - mainly black crushed stone.

When arranging surface treatment on roads with a traffic intensity of more than 3000 vehicles / day, with the movement of mainly trucks, also in areas with a sharply continental climate, bitumen and tar with polymer additives are used. The polymer tar binder is used on roads not higher than category II.

There are several types of surface treatments, each of which has its own area of ​​the most effective application (Fig. 2).

Rice. 2. Types of surface treatments

1. Single-layer surface treatment with a single distribution of binder and crushed stone. It is used to create a rough surface and wear layer of pavement with sufficient strength. This is the most common type of rough surface treatment and is most suitable for all types of movement. Most often, it is arranged from crushed stone of fractions of 5-10 mm.
2. Single-layer surface treatment with double distribution of crushed stone. A large fraction of crushed stone (for example, 10–15 or 15–20 mm) is first scattered on the layer of applied binder, rolled with a roller, and then a finer fraction of crushed stone (for example, 5–10 mm) is scattered and compacted. It is used on roads with heavy traffic and high speed. Such surface treatment improves the tightness of the coating, eliminates minor irregularities and deformations, and better distributes the forces from the wheels of cars. Such processing works especially effectively on a good hard base.
3. Double layer surface treatment. A large fraction of crushed stone is scattered on the first layer of the spilled binder and compacted. Then the second layer of the binder is poured, the finer fraction of crushed stone is scattered and finally compacted. It is used on coatings with insufficient strength, in the presence of a network of cracks, pitting, ruts, at high traffic intensity, i.e. in cases where it is necessary not only to create a rough wear layer and a protective layer, but also to improve evenness, to slightly increase strength and shear resistance. It is also used on cement concrete pavements.
4. Sandwich surface treatment. Crushed stone of a larger fraction is scattered on the coating, then the binder is distributed, crushed stone of a fine fraction is scattered and compacted. The structure of the obtained layer of surface treatment is comparable to a single-layer surface treatment, arranged by pouring binder and double scattering of crushed stone. Such surface treatment is recommended for non-uniform evenness of the coating for its leveling and some strengthening. It is used on roads of secondary, local importance.

When choosing a method for surface treatment of coatings, it is necessary to take into account its purpose, traffic conditions on the road, climatic conditions of the construction area, the hardness index of the road surface, the availability of materials and means of mechanization.

Work production technology

There are two ways to arrange surface treatments:

• traditional - with separate distribution of materials;
• method with synchronous distribution of binder and crushed stone.

The traditional way

Work on the device of a single surface treatment in the traditional way using bitumen, tar bitumen, bitumen and tar polymer binders is carried out in the following order:

• pouring binder;
• crushed stone distribution;
• rolling;
• care during the formation period.

Work on the device for double surface treatment is carried out in the following sequence:

• surface preparation (cleaning from dust and dirt) and repair work;
• the first bottling of the binder;
• the first scattering of rubble;
• rolling;
• the second bottling of the binder;
• the second scattering of crushed stone (between the first and second scattering of crushed stone, a break of no more than 3-5 days is allowed);
• rolling;
• care during the formation period.

Cleaning the coating from dust and dirt is carried out with mechanical brushes, the most contaminated areas are washed with a watering machine.

Brush strings, whatever their nature (nylon, steel), must be in good condition and stiff enough to provide effective scraping.

In cases where the old coating cannot be completely cleaned of dust and dirt remaining in small cracks and depressions, it must be primed by pouring liquid bitumen at a rate of 0.3–0.5 l / m 2 or bitumen emulsion at a rate of 0.5 -0.8 l / m 2.

The binder is poured by an asphalt distributor. For uniform filling of the binder, it is necessary to ensure the uninterrupted operation of the nozzles, the uniformity of the pump and the required speed of the distributor.

The nozzles must be thermally insulated and equipped with a heating device that allows maintaining or providing a certain temperature of the binder.

Depending on the selected binder and the width of the treated surface, the driver determines, using the adjustment elements of the asphalt distributor (nomogram, calculating disk, programming), the necessary ratio between the speed of movement and the number of revolutions of the pump, which determines the dosing of the binder on the pavement. During distribution, the ratio between vehicle speed and pump revolutions is kept constant, either by automatic tracking or by direct reading of the tachometer and rev counter by the driver.

During filling, the temperature of bitumen grades BND 60/90, BND 90/130, BN 60/90 and BN 90/130 should be 150–160°C; grades BND 130/200 and BN 130/200 – 100–130°C; the temperature of the polymer-bitumen binder is 140–160°C; tar-polymer binder - 100–110 ° C.

The distribution of crushed stone is carried out by a self-propelled crushed stone distributor, a dump truck with an attachment or other mechanism that ensures quick and even distribution of crushed stone. The body of all these mechanisms must be flat and without local deformations. The height of the crushed stone drop should be low to ensure a more uniform distribution of the aggregate on the pavement. Chip spreaders can be equipped with a hydraulic expansion system that allows changing the working width from 2.50 to 4 m without stopping.

Crushed stone is distributed immediately after pouring the binder in a layer into one crushed stone and rolled with a roller of 6–8 tons in 4–5 passes along one track.

The compaction of the surface treatment of coatings ensures the laying of crushed stone and its fixation on the coating. Pneumatic tire seals provide these features superbly. They adapt to the unevenness of the road and do not crush gravel.

During the first days of operation, it is necessary to take care of the emerging layers. Loose gravel must be removed from the coating no later than 1 day after the opening of the movement. The speed of vehicles is limited to 40 km/h and regulated by the width of the roadway.

The thrown out excess crushed stone is picked up by cleaning machines-collectors, cleaning machines and retracting machines. Equipped with various brushes and suction nozzles, they are equipped with collection containers for the fine material they lift. These suction mechanisms represent a great advance in surface coating technology, as they can significantly reduce the biggest harm from pollution: the shattering of car windshields after resuming traffic.

Surface treatment using bitumen emulsions is performed in the following order:

• surface preparation (cleaning from dust and dirt) and performing repairs if necessary;
• wetting the surface with water (in hot dry weather);
• pouring the emulsion over the coating in the amount of 30% of the norm;
• distribution of crushed stone in the amount of 70% of the norm;
• pouring the remaining emulsion (70%);
• distribution of the remaining crushed stone (30%);
• rolling;
• care during the formation period.

The temperature and concentration of the emulsion is set depending on the weather conditions. At air temperatures below 20°C, it is recommended to use an emulsion with a temperature of 40–50°C and a bitumen concentration of 55–60%. The heating of the emulsion to the specified temperature should be carried out directly in the asphalt distributor during transportation to the place of work. At air temperatures above 20 ° C, the emulsion is applied cold, and the concentration of bitumen can be reduced to 50%.

The distribution of crushed stone is carried out in such a way that the crushed stone is distributed no further than 20 m from the asphalt distributor pouring the emulsion.

Surface treatment with bitumen emulsions is carried out in the same way as with bitumen. When using anionic emulsions, the movement of vehicles opens no earlier than 1 day after the completion of work.

Surface treatment technology with synchronous distribution of binder and crushed stone

The main difference of the new surface treatment device technology is the synchronous, almost simultaneous distribution of the binder and the scattering of crushed stone (Fig. 3).

Rice. 3. Surface finishing with synchronous distribution of materials

In case of surface treatment using traditional methods, the gap in time between the distribution of the binder and the scattering of crushed stone is limited by the cooling time of hot bitumen and can reach 1 hour.

With synchronous distribution of binder and crushed stone, the gap between these operations does not exceed 1 second, which significantly affects the quality of surface treatment, both when using hot bitumen as a binder and bitumen emulsion.

The quality improvement when using hot bitumen as a binder is explained by the fact that in such a short period of time the bitumen does not have time to cool down and retains a liquid consistency and high adhesive ability. As a result, bitumen penetrates well into the micropores of crushed stone and coating, envelops each gravel and firmly sticks them to the coating and one to the other.

The compaction of the laid layer also takes place when the bitumen is hot, which ensures the maximum compaction effect.

When bitumen emulsion is used as a binder, the high quality of surface treatment with synchronous distribution of binder and crushed stone is explained by the fact that in such a short period of time, the breakdown of the emulsion will only begin, and the emulsion in the liquid state will fill all the micropores of crushed stone and coating, cover each crushed stone with a thin layer of binder and will allow good compaction of the surface treatment layer.

Synchronous distribution solves all the problems of organizing and coordinating work arising from asynchronous distribution, since at each stop in the distribution of crushed stone, the distribution of the binder is automatically stopped. Downtime due to climatic conditions is significantly reduced and work productivity is increased. This is important when using high viscosity binders, but is especially important when working in adverse weather conditions.

The synchronous distribution of the binder and crushed stone has a positive effect on the formation of a mating between the binder and crushed stone, which guarantees high performance characteristics of surface treatment, reduces the risk of work failure due to the temperature difference between the base and the binder, as well as due to the presence of dry fine fractions when arranging surface treatments with using emulsions.

Experience shows that a high level of quality surface treatment with synchronous distribution of binder and crushed stone can achieve amazing results when a thin layer of crushed stone and binder can withstand the intense impact of car wheels for 10-15 years.

Thus, the synchronous distribution of binder and crushed stone with a delay time of 1 second is the most important innovation in the practice of surface treatment in the last 20 years.

To implement the idea of ​​surface treatment with synchronous distribution of binder and crushed stone, SECMAIR has developed and produces a wide range of bitumen spreaders of various capacities, as well as other machines for maintaining and repairing road surfaces using crushed stone treated with bitumen or bitumen emulsion.

Produced machines can work when moving forward or when moving in reverse (Fig. 4).

Rice. 4. Operating principles of surface treatment machines

Given the significant interest of Russian road workers in the introduction of surface treatment technology with synchronous distribution of binder and bitumen, the French company SECMAIR and the State Unitary Enterprise Saratov Research and Production Center Rosdortekh created a joint production of Chipsealer machines in Saratov.

In 1999, the production of the following machines began:

• Chipsealer-40. This is a high-performance equipment designed for rough surface treatment in large volumes. The Chipsealer-40 equipment is mounted on the basis of the Caizer semi-trailer and has a completely autonomous power supply system. In one cycle of loading the body with crushed stone, it allows performing surface treatment on a strip 3.75 m wide and up to 800 m long in 10 minutes.
• Chipsealer-26 made on the basis of the Russian semi-trailer SZAP - 9905. MAZ and KamAZ truck tractors can be used as a tractor vehicle. It has the same characteristics as the Chipsealer-40, but smaller dimensions of the gravel body and the binder tank.
• Chipsealer-19– designed for repairing road surfaces and rough surface treatments in small volumes.

Stopper machines

They are used to curb erosion of the coating at an early stage by arranging local surface treatment in areas of peeling and chipping of the coating, the appearance of small cracks, a network of cracks, small potholes and ruts. The machine has on one chassis a container for a binder, a body for crushed stone, a clamshell bucket for loading crushed stone into the body and distributing devices for applying bitumen and crushed stone (Fig. 5).

Another difference is that the “Stopper” has a compacting block of 8 pneumatic smooth wheels, which, with the help of 4 hydraulic jacks, are lowered to the surface into the working position and rise up to the transport position. This is especially important for the accelerated formation of the repair layer in cold and humid climates. In dry and hot climates, this formation occurs under the action of moving traffic, and the need for a sealing block is eliminated. In addition, "Stoppers" are adapted for local repairs using surface treatment.

Machines for surface treatment device

For a surface treatment device in a traditional way, i.e. with separate distribution of binder and crushed stone, asphalt distributors and crushed stone distributors are used.

Asphalt distributors are distinguished and selected by:

• tank capacity (carrying capacity);
• binder distribution width; in this case, as a rule, the distribution width is chosen equal to the width of the road lane or 5-10 cm less.

Crushed stone distributors are distinguished by:

• capacity (capacity) of the bunker for crushed stone;
• crushed stone distribution width; in this case, as a rule, the width of the distribution of crushed stone is taken equal to the width of the distribution of the binder;
• type of travel (movement): trailed and mounted base machines. As a rule, dump trucks are used as base machines for trailed and mounted crushed stone spreaders.

For a surface treatment device by the method of synchronous (simultaneous sequential) distribution of binder and crushed stone, bitumen-(emulsion) crushed stone distributors are used.

Bitumen distributors are distinguished by:

• processing width, i.e. according to the correspondence (multiplicity) of this parameter to the width of the carriageway of the highway;
• capacity (capacity) of the tank for the binder and the bunker for crushed stone;
• gravel loading method, i.e. the use of special loading machines for loading crushed stone into the bunker or special self-loading equipment.

On fig. 6 shows the production schedules (in thousand m 2) of all three types of machines: asphalt distributors, crushed stone distributors and bitumen (emulsion) - crushed stone distributors at a bitumen emulsion filling rate of 1.4 and 2.1 l / m 2 and a crushed stone distribution rate of 10.0 and 15.0 kg/m2. Depending on the width of the filling of the binder and the distribution of crushed stone in fig. 6 also shows the development in the lin. m processing lane.

The presented graphs, taking into account the capacity of the binder tank and the crushed stone bin and bitumen distributors, show that the capacity of the binder tank provides a significantly higher output than the capacity of the crushed stone bunker. Thus, the crushed stone hopper must be filled several times to ensure the release of the binder. The ratio of workings for binder and crushed stone for various bitumen-split distributors ranges from 2.0 to 9.5. Therefore, the method of loading crushed stone has a significant impact on shift production (productivity).

Joint operation of the asphalt distributor and the trailed crushed stone distributor of ZAO "Betsema", loaded from a dump truck

When loading crushed stone into the hopper of a crushed stone distributor (without self-loading) on ​​the base using a single-bucket front loader or a crane with a grab (jaw bucket), i.e. with a double run from the place of work to the base and back, the time spent on one load is from 40 minutes to 1 hour 20 minutes.

When loading crushed stone into the hopper of a bituminous chip distributor at the work site using self-loading or using a dump truck with a crane equipped with a grab, the time spent on one load is from 10 to 15 minutes.

When loading crushed stone into the bunker of the bitumen spreader with self-loading from the receiving hopper located behind the machine and loaded from the dump truck, even when the bitumen spreader is stopped, the time spent on one load is from 2 to 6 minutes.

When calculating, the binder load is combined with the crushed stone load, i.e. is carried out after two to nine loads of crushed stone, the speed of the bitumen-split spreader is taken to be 4 km/h = 1.1 m/sec = 66 m/min., the distribution width is taken to be 3 m, the time utilization factor is taken to be 0.8 on the base) and 0.6 (when loaded on the road), which is associated with the need and great complexity of the rhythmic supply of materials, the use of additional machines (dump trucks, bitumen trucks).