Coating surface treatment device. Surface treatment Single surface treatment
1.9.2 Surface Finishing
During construction, rough layers arranged by surface treatment are divided into the following types:
Single surface treatment;
Serrated surface treatment (single with double scattering of crushed stone);
Double surface treatment;
Surface treatment of the "sandwich" type (Figure 1.12).
Single surface treatment (Figure 1.12, a) includes a layer of organic binder and a layer of fractionated crushed stone (V / Sh).
jagged surface treatment (Figure 1.12, b) includes a layer of organic binder and two layers of fractionated crushed stone (V / Shch / Shch).
double surface processing (Figure 1.12, c) consists of two layers of organic binder and two layers of fractionated crushed stone (V / Shch / V / Shch).
superficial processing of the "sandwich" type (Figure 1.12, d) consists of two layers of fractionated crushed stone, fastened with a binder layer (Shch / V / Sch).
Figure 1.12 - Structures rough layers surface treatment:
1 - asphalt concrete pavement; 2 - binder layer; 3 - distributed crushed stone; 4 - compacted crushed stone
The design of the rough surface treatment layer is assigned:
On road surfaces made of asphalt concrete and materials treated with organic binders, depending on the degree of hardness of the surface, taking into account the intensity of vehicle traffic;
Coatings of cement concrete, depending on the intensity of traffic.
Crushed stone for surface treatment is obtained by crushing igneous and metamorphic rocks. For roads of I, II categories, the abrasion grade is I-1, the crushability grade is not lower than 1200. For the roads of III-V categories, the abrasion grade is I-2, the crushability grade is not lower than 1000. Frost resistance is not lower than R-50. Crushed stone should be clean cube-shaped.
When choosing a crushed stone fraction, the type of coating is taken into account. For coatings made of asphalt concrete and materials treated with organic binders, it is necessary to use crushed stone with fractions of 5-10, 10-15, 15-20 or 20-25 mm. RD 0219.1.09-99 also recommends the use of fractions 2-4, 4-6, 6-9, 9-12 and 12-16 mm. The specific size of the fraction is taken depending on the actual conditions (vehicle traffic intensity, coating hardness category) at the work site.
For cement concrete coatings, crushed stone of a fraction of 5-10 or 10-15 mm is used. The choice of the size of the fraction when creating a single rough layer depends on the degree of destruction of the coating surface. In areas without signs of peeling and with a peeling depth of up to 5 mm, a fraction of 5-10 mm is used, with a peeling depth of more than 5 mm, a fraction of 10-15 mm. When constructing a double rough layer, a fraction of 10-15 mm is used for the first placer, and a fraction of 5-10 mm is used for the second placer.
As the main binder material for the device of rough coatings by surface treatment, the following are used:
Bitumen grades BND 40/60, BND 60/90, BND 90/130, and also BM 100/130;
Bituminous emulsions of grades EBK-B-65, EBK-B-70, EBKM-B-65, EBKM-B-70.
The device of rough layers by surface treatment is performed in summer in dry weather:
For bitumen at an average daily air temperature of at least 15 °C, or at an average daily coating temperature of at least 22 °C;
Bituminous emulsions at an average daily air temperature of at least 10 ° C.
Technological process the device of rough layers by surface treatment includes three main stages:
Preparatory work;
Rough wear layer device;
Rough wear layer care.
Preparatory work. During the preparatory period, perform:
Fencing the working area and installing road signs to transfer traffic to a detour or block one lane;
Cleaning the coating from dust and dirt;
Coating primer.
Cleaning of the surface of the coating is carried out with mechanical brushes with moistening of heavily polluted places. When bitumen is used as a binder, wet spots must be completely dry before installation.
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 embedded 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; oil 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. Gravels 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 road, and therefore a decrease in the productivity of 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 coating or wear layer in ready-made. 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 radiation 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 asphalt 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. The logometer shows the specific consumption of the 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 flow rate 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 a single treatment, the 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. 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 different size. 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 filling of the binder 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 Finishing
Asphalt concrete pavement undergoes significant changes under the influence of transport and atmospheric factors, which come down to pavement wear and increased brittleness of asphalt concrete, cracks appear, increased wear and peeling is observed. This is also true for the areas of the coating on which the asphalt mix with insufficient bitumen content. One of the measures to ensure the stability of the properties of asphalt concrete is surface treatment to protect it from the direct impact of vehicles and atmospheric factors.
For surface treatment, slag crushed stone up to 25 mm in size, obtained by crushing metallurgical slags, is used. Crushed stone is selected by size, taking into account the purpose and type of surface treatment. Crushed stone is used both processed and unprocessed. Best results are achieved with crushed stone treated with organic binders. Black crushed stone can be prepared in asphalt mixers in stationary conditions and directly at the work site.
Depending on the accepted method of work, the viscosity of the bitumen is chosen. So, black crushed stone treated with bitumen BND 130/200, BND 90/130 or D-6 tar is used only in a hot state at temperatures above 120 ° C; when treated with BND 200/300 bitumen, it is laid at 60-100 °C; when processing with bitumen MG 70/130 or (T 130/200 and tar D-5, black crushed stone is laid in a cold state. The use of hot and warm black crushed stone provides the best quality of the coating, but this is associated with organizational difficulties. Approximate amount of bitumen for the preparation of black crushed stone is 1.5-2% by weight of crushed stone.
The surface treatment device consists in pouring an organic binder over a pre-cleaned base, spreading a thin layer of mineral fine-grained material and then compacting the layer with self-propelled two-roller rollers with smooth rollers weighing up to 6 tons. The final formation of the surface treatment layer occurs under the influence of solar radiation and the impact of vehicles . The binder and its viscosity are prescribed depending on climatic and weather conditions, chemical and mineralogical composition and structural and textural features of the mineral material.
The process of forming the surface treatment of cand. tech. Sciences V. T. Kuzmichev 1 conventionally divides into three stages.
The first stage is characterized by relatively weak adhesion of the binder to mineral grains due to the insignificant contact area between them, as well as by the low viscosity of the binder.
During this period, there is a separation of gravel under the influence of the tangential forces of the wheels of cars.
The second stage is characterized by the stable position of crushed stone, the redistribution of the binder in upper part layer due to the forces of intermolecular attraction, an increase in the viscosity of the binder and compaction by car. The second stage, even in dry, warm weather, lasts about two weeks.
The third stage - the surface treatment layer is fully formed. During this period, the layer works for abrasion. The roughness of the wear layer gradually decreases due to the indentation of large grains into the coating and their polishability, changes in the granulometric composition of crushed stone, which is partially abraded and crushed first when rolling with rigid-drum rollers, and then by car wheels.
Therefore, to ensure High Quality surface treatment, it is necessary that the binder wets the mineral material well and forms strong stable bonds at the bitumen-crushed stone interface. This is achieved by choosing mineral materials, capable of actively interacting with the binder, the introduction of surface-active substances (surfactants) into the binder or activators on the surface of crushed stone grains.
Petroleum bitumens adhere relatively poorly to the surface of gravel from acidic rocks and better from basic rocks. Basic metallurgical slags actively interact with bitumen. There may be chemical bonds between them. The anionic components of bitumen are able to form new chemical compounds with positive ions that are part of the slag. The large development of the surface of slag gravel contributes to the manifestation of mechanical adhesion.
The addition of activators (lime or cement) to crushed stone from acidic slags to improve its adhesion to the binder is 2-3% by weight. Surfactants are added to bitumen when it is heated before bottling; their mass fraction is 1 -10%. Significantly improve adhesion by using crushed slag pre-treated with a binder in an asphalt mixer.
When using crushed stone from metallurgical slags for a surface treatment device, the following method of work is most widely used. Before starting work, the coating or base is thoroughly cleaned of dirt and dust, and the movement is transferred to a detour, which is systematically watered to prevent dust from entering the work site.
Bitumen BND 130/200 in the amount of 1.1-1.2 l/m2 is poured with asphalt distributors, after which crushed stone is immediately scattered in the amount of 1.3-1.5 m3 per 100 m2 of surface and rolling is started by self-propelled road rollers with smooth rollers weighing up to 6 tons, three or four passes along one track. The viscosity of the binder at an air temperature above 25 ° C should be within 120-150 ° of the needle penetration depth. In cooler weather, the penetration depth should be in the range of 150-200 degrees. The distribution of crushed stone over spilled bitumen must be completed within 30 minutes.
Transportation opens on finished site not earlier, with cement 6-10 hours after the bitumen has cooled down.
In case of rain during the completion of work or at night, as well as on the second day, traffic should be immediately closed on the finished site until dry and warm weather. After establishing the appropriate weather, it is necessary to repeat the compaction of the wear layer with two or three passes of the roller and only then open the movement.
When using crushed slag for a surface treatment device, it is necessary to take into account its specific properties. All grains of crushed slag have different porosity. According to the data presented earlier, the porosity of dense and densely porous varieties reaches 10%, porous-porosity 15–25%, and pumice-like varieties up to 50%. The water absorption of these slags varies within 1.5-20%. The nature of the pores of slag rubble is very different. Pores can be closed (closed) and open. Closed pores are isolated from open ones and do not communicate with each other and environment. Open pores communicate with the environment, which must be taken into account.
The presence of pores of various diameters in crushed stone causes capillary phenomena, leading to suction into the depths of grains of low molecular bitumen components. If the capillary diameter is less than 200 A°, bitumen fractionation occurs. Oils penetrate to the greatest depth inside the grains, while asphaltenes are concentrated at a smaller depth of resins and at the surface. The viscosity of film bitumen on grains is much higher than on dense gears from dense rocks. Therefore, when using crushed slag stone for processing surfaces, the viscosity of bitumen should be less than for crushed stone from dense rocks.
The porosity of crushed slag significantly affects the processes of formation of the surface treatment layer. In the case of dense crushed stone, the wetting of grains with bitumen occurs according to outer surface crushed stone, while with a porous texture, capillary phenomena first occur, and then, after filling the pores, wetting of the grain perimeter with bitumen occurs. Consequently, the formation of surface treatment on crushed slag proceeds more slowly. In addition, the grains of crushed slag are always covered with a film of dusty particles, which also slows down the wetting process.
In this regard, it is most expedient to use crushed stone pre-treated with organic binders for surface treatment with crushed slag. In this case, there are all conditions for the rapid formation of the layer. For the processing of crushed slag, coal tar D-2, D-3 or bitumen MG 25/40 and MG 40/70 are used in an amount of 1.1-=-1.3% by weight of crushed stone. The filling rate of the binder is 1.0 l / m2 of coating, approximately 10-15% more than for crushed stone from igneous rocks.
Experimental areas of surface treatment, performed during the repair of roads with asphalt concrete pavement in the Donbass, showed that surface treatment with crushed stone from blast-furnace slags is much better than processing with crushed stone from local limestones and sandstones.
The need to use crushed slag was caused by the absence of crushed stone from igneous rocks.
Based on the data obtained during the operation of the experimental sites, later crushed slag was used on a wider scale, hundreds of kilometers.
The use of crushed slag for a surface treatment device is more economical than similar surface treatment areas using granite crushed stone, as well as limestone crushed stone. If the cost of 1 m2 of surface treatment with crushed granite is 0.421 rubles, then with limestone crushed stone it will be 0.87, and for slag crushed stone 0.72 of the cost of the standard.
The use of crushed stone from limestones and sandstones for a surface treatment device leads to the formation of protective layers that do not have sufficient roughness due to crushing of different-strength grains of crushed stone during rolling, while with slag crushed stone it is possible to obtain a coating with a rough surface. In the process of processing blast-furnace slag into crushed stone, less durable grains are destroyed and screened, i.e., crushed stone is enriched in strength.
Based on site exploitation data asphalt concrete pavement with surface treatment with crushed slag, the roughness of the coating is preserved in some areas for 2-3 years.
It should be noted that in almost all surveyed areas of surface treatment, an excess amount of bitumen is observed, which fills the intergranular space and reduces the roughness of the coating, and in some cases completely evens out the surface of the coating and softens it. upper layer. Slag crushed stone is well glued to the bitumen film and only excess crushed stone is dumped by vehicles on the side of the road. However, the formation of the surface treatment due to the porosity of the grains is somewhat inhibited and, if the air temperature drops, this can lead to the destruction of the surface treatment. Similar phenomena are observed only at the binder filling rate necessary for the formation of a rough surface treatment, i.e. 1.1-1.3 l/m2. With a higher consumption of bitumen, crushed slag is well retained on the surface of the coating, but this leads to the elimination of roughness. If the surface treatment is carried out with crushed stone pre-treated with a binder, the formation of the layer ends much faster, no damage is observed, and the roughness is well preserved for 2-3 years.
Surface Finishing- this is a method of creating a rough surface of the coating and arranging wear and protective layers by pouring a thin layer of organic binder onto the base, distributing high-grade crushed stone and compacting it (Fig. 3). In many countries, surface treatment is called Chip Seals - crushed stone protective (insulating) layers.
Rice. 3. The main technological operations of the surface treatment device:
1 - preparatory work; 2 - pouring bitumen; 3 - distribution of crushed stone; 4 - crushed stone compaction; 5 - sweeping away excess gravel
Before the surface treatment device, the road surface must be prepared in advance. The composition of the preparatory work for the installation of surface treatment on a new coating includes:
cleaning the coating from dust and dirt;
installation of signs for the organization of traffic, fencing of the place of work.
In cases where the coating cannot be completely cleaned of dust and dirt remaining in small cracks and depressions, it is recommended to prime it 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/m2.
The main works include pouring bitumen, distribution and compaction of crushed stone. After that, individual unstrengthened gravel is swept away and traffic is opened. Process final formation surface treatment lasts about 10 days, during which the speed of vehicles is limited and daily sweeping of unhardened gravel is carried out.
Appointment and types of surface treatments. Surface treatment performs the following functions:
restores and improves the grip of the road surface;
forms a wear layer and a protective layer against the penetration of water into the pavement;
stops the destruction and prolongs the service life of old coatings, which showed signs of wear in the form of cracks, peeling, chipping, and others;
when installing on crushed stone and gravel provides dedusting and much more comfortable conditions car movements.
There are several types of surface treatment, which are used in various conditions:
single or simple processing with a single filling of the binder and the distribution of crushed stone. It is used to create a wear layer and a rough layer on coatings with sufficient strength and low traffic intensity. The layer thickness is 1.5-2.5 cm;
single or simple processing with double distribution of crushed stone. A larger fraction of crushed stone (for example, 8/11 or 15-20 mm) is first distributed on a layer of spilled binder, rolled with a roller, and then a finer fraction of crushed stone (for example, 2/5 or 5-10 mm) is distributed and compacted. Used on roads high speed car movements. The thickness of the layer can be 3-4 cm;
simple sandwich processing. A large fraction of crushed stone is distributed on the surface of the coating, then a binder is poured, a fine fraction of crushed stone is distributed and compacted. It is used with a non-uniform base for leveling and some reinforcement;
double surface treatment or double "sandwich" type surface treatment. A large fraction of crushed stone is distributed 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 distributed and finally compacted. The layer thickness is 3–4 cm. evenness, slightly increase strength and shear resistance. It is also used on cement concrete pavements;
double surface treatment with a layer of crushed stone. On a cleaned and leveled gravel or crushed stone coating, a layer of coarse crushed stone is scattered and compacted. Then the first layer of the binder is poured, the finer fraction of crushed stone is distributed and compacted. After that, the second layer of the binder is poured, the crushed stone of the fine fraction is distributed and finally compacted. The layer thickness can reach 5 cm. It is used on “white” gravel and crushed stone coatings to transfer them to a “black” highway.
Requirements for stone materials for surface treatment. For surface treatment, crushed stone from high-strength igneous or metamorphic rocks with a strength of more than 100-120 MPa and wear during abrasion in the Deval drum of no more than 35% is used.
For roads with low traffic intensity, it is allowed to use crushed stone from sedimentary rocks (limestone) with a strength of at least 80 MPa with abrasion of not more than 40%. Crushed stone must be washed: clean and dust-free. The proportion of grains smaller than 0.63 mm should not exceed 0.5%. Crushed stone grains should be one-dimensional narrow fractions of a cuboid shape.
In order to save expensive high-strength crushed stone on roads with medium traffic intensity, it is possible to arrange surface treatment from a mixture of stone materials of different strength, in which 50% or more is crushed stone with a strength of 100 MPa and higher and up to 50% crushed stone with a strength of 60-80 MPa. Experience shows that during operation, weaker gravel wears out faster and decreases in height, while stronger gravel protrudes from the pavement and provides good grip properties of the wet pavement.
By European standards apply the size of crushed stone fractions, mm - 2/5; 5/8; 8/11; 11/16. In Russia, a wider range of fraction sizes is allowed, mm - 5-10; 10-15; 15-20 and 20-25. However, in recent years there has been a trend towards a transition to smaller sizes and narrower fractions of crushed stone, close to European standards.
Material homogeneity requirements according to limit sizes based on surface treatment lifetime experience. It is necessary that all gravel firmly adhere with its edges to the spilled binder. With homogeneous crushed stone, scattered in one layer (Fig. 4, a), this can be achieved. In a heterogeneous material, there will always be small grains that will lie on top and will not receive proper adhesion to bitumen (Fig. 4, b). 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, often manual work is needed to sweep the gravel from the curb onto the pavement.
Rice. 4. Surface treatment: 1 - binder; 2 - crushed stone, not held by a binder; 3 - crushed stone held by a binder
Gravels flying out from under the wheels are dangerous, injure passers-by and pedestrians, and break car windows.
The choice of the size of the fractions depends on many factors, including what transport and operational characteristics of the pavement need to be obtained, at what intensity, in what traffic composition the pavement operates and in what climatic conditions, as well as the condition of the old coating and its hardness. So, to obtain a waterproof protective layer of small thickness on local driveways and squares in settlements, crushed stone of fractions 2/5 is used, which creates a fine roughness of the type sandpaper. Fractions 5/8 provide good roughness on strong and even coatings with a minimum level of sound emission. The 8/11 and 11/16 crushed stone surface treatment creates deeper roughness, more tire wear and sound emission levels, but it is more durable in heavy traffic and more effective on soft surfaces. On very soft surfaces in regions with a hot climate in Russia, crushed stone of fractions of 15-20 and even 20-25 mm is used.
To determine the stiffness or hardness of the old coating, hardness testers are used. To bring the results of measurements performed at different temperatures to a comparable form, they are brought to the calculated temperature (Fig. 5).
For a surface treatment device, crushed stone is used, previously treated with a small amount of organic binder or pure crushed stone. For processing, crushed stone is heated to a temperature of 170-180 ° C, loaded into a mixer, where hot bitumen is injected in an amount of 1-1.5% by weight of crushed stone and mixed. Get the so-called black gravel. This treatment is often used in the construction of rough layers on roads in the northern regions.
It is believed that in processed crushed stone, bitumen penetrates into micropores and closes them for water penetration, as a result of which the water resistance and frost resistance of crushed stone, which is used on roads with high traffic intensity and in areas with a cold humid climate, increases. Untreated crushed stone is used on roads with a traffic intensity of up to 1000 vehicles / day, as well as for the second placer in a surface treatment device with a double distribution of crushed stone.
Rice. 5. Evaluation of coating hardness:
Hardness zones: 1 - very soft; 2 - soft; 3 - normal; 4 - solid; 5 - very hard.
However, it can be assumed that the presence of a bitumen film in the pores of the treated crushed stone can prevent the bitumen emulsion or bitumen spilled on the coating from penetrating into them and, conversely, the bitumen emulsion interacts well with the fresh clean surface of the crushed stone, penetrates deep into the micropores and thereby provides stronger bonds mineral materials. Therefore, untreated crushed stone is increasingly used for surface treatment.
Requirements for binders for surface treatment. Bitumen emulsions and, to a lesser extent, bitumen are mainly used as binders for surface treatment. In Russia, viscous bitumen BND 60/90, BND 90/130, BND 130/200, MG 130/200, MG 70/130 are more often used.
Due to the watery nature of the bitumen emulsion, it has a high wetting ability of the crushed stone surface. When the emulsion breaks up, adhesion (adhesion) of bitumen with stone material occurs and the water is simultaneously displaced from the surface. stone material.
Usually, cationic bitumen emulsions are used, in which bitumen droplets have a positive electric charge, and the surface of the stone material receives a negative charge. There is an exchange of charges, which means the beginning of the disintegration of the bitumen emulsion, after which the bitumen enters into rigid adhesion to the surface of the crushed stone.
In modern technology, highly concentrated bitumen emulsions of the EBK-2 type are used, in which the bitumen content is 65-70%. Since such emulsions have a relatively high viscosity, they are heated to 50-70°C before use for ease of processing.
To improve the rheological and other physical properties of bitumen emulsions, polymer additives are now widely used.
Polymer modified bitumen emulsions should have a warm impact temperature of at least 60-65°C and a cold impact temperature of at least minus 5°C. In addition to emulsions for surface treatment, polymer-modified hot bitumen is often used (Table 20.2). In Russia, this is viscous bitumen BND 130/200 and BND 90/130.
When using bitumen emulsion as a binder, the consumption of emulsion and crushed stone must comply with the standards given in Table. 20.3.
In France, the consumption rate of bitumen for surface treatment on old coatings is taken equal to 10% of the consumption of crushed stone, of which 8% goes to ensure the connection of crushed stones with each other and with the base and 2% for sealing small cracks in the old coating (Table 20.4).
The principal approach to setting the crushed stone consumption rate is to ensure that it is sufficient to create a dense stone skeleton, and the amount of binder is assigned from the condition that the binder should ensure that all crushed stones are enveloped to a height of 2/3 of the crushed stone size and the old coating is sealed.
Organization of work on the surface treatment device. Surface treatment is usually arranged in summer in dry weather at an air temperature of at least 15 ° C. It is allowed to perform work at an air temperature of 5°C in spring and 10°C in autumn.
When using a bituminous emulsion as a binder, surface treatment can be carried out on a wet surface and with light rain.
When using hot viscous bitumen as a binder, all work must be completed before the bitumen temperature drops below the allowable bitumen thickening. When pouring bitumen, the temperature must be maintained:
for viscous bitumen grades BND 60/90, BND 90/130, BN 60/90 and BN 90/130 within 150-160°C;
for grades BND 130/200 and BN 130/200 within 100-130°C;
for polymer bitumen binders within 140-160°C;
for tar-polymer binder in the range of 100-110°C.
table 2
Norms of pouring binders and distribution of crushed stone during surface treatment
| Type of surface treatment | Fraction of crushed stone, mm | crushed stone consumption | Binder consumption, l / m 2 | |
| kg/m2 | m 3 /100 m 2 | |||
| Single on viscous bitumen | 5-10 | 11-15 | 0,9-1,1 | 0,7-1,0 |
| 10-15 | 15-20 | 1,1-1,4 | 0,9-1,0 | |
| 20-25 | 25-30 | 1,4-1,6 | 1,1-1,4 | |
| Single on viscous bitumen with a double scattering of crushed stone | First scattering 15-25 | 16-18 | 1,2-1,4 | 1,4-1,5 |
| Second scattering 5-10 | 6-8 | 0,6-0,8 | - | |
| Single for 50% bituminous emulsion | 5-10 | 12-15 | 0,9-1,1 | 1,6-1,8 |
| 10-15 | 15-20 | 1,2-1,4 | 1,8-2,0 | |
| 15-20 | 20-25 | 1,3-1,5 | 2,0-2,4 | |
| 20-25 | 25-30 | 1,4-1,6 | 2,4-2,6 | |
| Double on viscous bitumen | First placer | first bottling | ||
| 15-25 or | 20-25 | 1,2-1,5 | 1,1-1,4 | |
| 20-25 | 25-303 | 1,4-1,6 | ||
| Second placer | second bottling | |||
| 5-10 or | 15-20 | 1,2-1,3 | 0,6-0,8 | |
| 10-15 | 15-20 | 11,2-1,4 | ||
Note. When using raw crushed stone, the bitumen filling rates are increased by 20%. The fraction of crushed stone for a single surface treatment is selected according to the calculation and depending on the hardness of the coating
Table 20.3
| Processing method | Crushed stone size, mm | Crushed stone consumption, m 3 / 100 m 2 | Emulsion consumption, l/m2, at bitumen concentration, % | |
| 60 | 50 | |||
| Single | 5-10 | 0,9-1,1 | 1,3-1,5 | 1,5-1,8 |
| Double | 15-20 | 1,1-1,3 | 1,5-1,8 | 1,8-2,2 |
| First placer | First bottling | |||
| 5-10 | 0,7-1,0 | 1,3-1,5 | 1,5-1,8 | |
| Second placer | Second bottling | |||
Table 20.4
The temperature and concentration of the emulsion are set depending on weather conditions as follows:
at air temperatures below +20°C, the emulsion should have a temperature of 40 to 50°C (with a bitumen concentration in the emulsion of 55-60%). The heating of the emulsion to this temperature is carried out directly by the asphalt distributor;
at an air temperature above +20°C, the emulsion (with a bitumen concentration in the emulsion of 50%) can have the same temperature, but not less.
For strong adhesion of the bitumen emulsion to the treated coating, it is necessary to ensure its purity. Cleaning of the coating is carried out immediately before the start of surface treatment. In dry hot weather, the coating is moistened (0.5 l / m 2) immediately before the main bottling of the emulsion. The temperature and concentration of the emulsion are set depending on weather conditions: at air temperatures below 20°C, an emulsion with a bitumen concentration of 55-60% and a temperature of 40-50°C is used; at air temperatures above 20°C, it is not necessary to heat the emulsion and the bitumen concentration can be reduced to 50%. The viscosity of the emulsion should be in the range of 15-30 s.
The distribution of emulsion and crushed stone can be carried out separately and simultaneously. With separate distribution, the emulsion is initially poured in an amount of 30% of the norm and 70% of the crushed stone norm is scattered. Immediately after this, the rest of the emulsion (70%) is poured and the remaining crushed stone is distributed. The crushed stone spreader should move as close as possible to the asphalt distributor and spread the crushed stone in front of it. Compaction (self-propelled rollers on pneumatic or rubber-coated rollers make 4-5 passes at a speed of up to 5 km / h) starts from the moment the emulsion breaks up and ends at the moment it ends. With synchronous distribution, the emulsion and crushed stone fall on the coating with a time interval of no more than 1 s. Under such conditions, the emulsion has time to fill the pores of the coating and crushed stone before the start of decomposition and thereby create favorable conditions for subsequent compaction of surface treatment.
The main filling of the binder is carried out, as a rule, on one half of the carriageway or on the width of one lane in one step without gaps and gaps. If it is possible to organize the movement of the traffic flow along the detour, it is advisable to pour the binder and distribute the crushed stone over the entire width of the carriageway at the same time or with a small ledge. This will avoid the formation of longitudinal seams in the surface treatment.
When determining the length of the interchangeable gripper and selecting the composition of the machines, it is necessary to proceed from the fact that all work on the distribution of bitumen emulsion and crushed stone and compaction must be completed within the time of emulsion breakdown, which is easy to determine visually by appearance, when Brown color emulsion will change to dark.
The distribution of crushed stone must be carried out as soon as possible after pouring the binder. Therefore, the crushed stone distributor should go immediately after the asphalt distributor. Crushed stone spreaders are self-propelled or mounted on dump trucks. In any case, the crushed stone distributor works according to the “push” scheme, that is, so that its wheels move along the already distributed crushed stone, and not along the binder layer. To do this, the vehicle with the mounted distributor is driven in reverse.
The general composition of the main link of machines for surface treatment consists of a machine for cleaning the coating from dust and dirt, an asphalt distributor, a crushed stone distributor (one or two), a link of rollers and a machine for sweeping excess gravel. Compaction begins immediately after the distribution of crushed stone, first with a medium roller for two or three passes in one place at a speed of 10-15 km / h, and then with a heavy roller for at least two or three passes in one place. The best results are obtained when self-propelled rollers on pneumatic tires are used for compaction.
In the process of compaction, it is necessary to take into account the features of the device of various types of surface treatments. Simple surface treatments with double distribution of crushed stone compact only after the second distribution of crushed stone. Both layers must be laid very quickly one after the other, and the subsequent compaction must be carried out very intensively with five passes of the roller on one track. With sandwich-type surface treatments, the first layer of crushed stone is also not compacted and compaction begins after the distribution of the second (upper) layer of crushed stone. With double treatments, compaction begins after the first distribution of crushed stone. The second layer is then immediately laid and compacted.
Surface care. After compaction with rollers and the completion of the breaking of the emulsion, the surface treatment movement is opened. During the first period, which is 3-10 days, it is necessary to ensure the movement of cars at a speed of no more than 40 km / h so that excess gravel does not fly out from under the wheels and cannot break the car windows. Excess gravel in the early days is regularly removed by sweeping or suction machines. Within a few days, the bitumen, under the influence of heat and moving traffic, will rise and cover all the gravel with a thin layer, giving the surface a uniform color.
Surface treatment with synchronous distribution of binder and crushed stone. The quality of surface treatment largely depends on the reliability of the "binder-crushed stone" and "crushed stone-binder-base" systems.
Experience in the operation of surface treatments has shown that this interaction is most effective when the binder fills the contact zone between adjacent crushed stones to a height h, which should be equal to 2/3 of the height of the crushed stone, that is
h = 2/3 D, where
h- the height of the binder layer in the contact zone of adjacent gravel, mm;
D- crushed stone size in height, mm.
It has been established that up to 80% of defects in surface treatment are separation and chipping of gravel due to insufficient bonding in the zone of their contact.
Reliable pairing of crushed stones with each other occurs due to the extrusion of the binder into the gaps between the crushed stones and further upward movement according to the laws of capillary rise. The height of this rise depends on the size of the gaps between the gravel and the viscosity of the binder (Fig. 6). A binder with a low viscosity in the capillaries forms a deep meniscus and rises to a great height, enveloping the gravel in a thin layer (Fig. 6, a). A binder with a high viscosity does not allow the formation of a meniscus, rises to a small height, leaving a significant part of the gravel without a binder film (Fig. 6, b). During operation, the bonds between such gravel are weakened and they are separated from the coating, chipping occurs.
Rice. 6. Options for pairing crushed stone with a coating:
a - with normal rise of bitumen with the formation of a high meniscus;
b - with insufficient rise of bitumen without the formation of a meniscus
In order to reduce the viscosity of the bitumen during the surface treatment device, it is heated and distributed at a temperature of 140-160°C. However, hot bitumen spilled over the surface of the coating with a film thickness of 0.5-2.0 mm cools very quickly. At the same time, its viscosity also increases rapidly and by the time the crushed stone is distributed, it can reach a significant value.
Highly concentrated bitumen emulsions also have a relatively high viscosity and therefore it is recommended to heat them up to 50-70°C before distribution. In addition, in the bitumen emulsion, after distribution, the process of rapid decomposition begins, before the end of which the crushed stone should already be distributed. Thus, the quality of surface treatment big influence renders the time period from pouring the binder to the distribution of crushed stone t (Fig. 7).
Rice. 7. Time interval between the distribution of binder and crushed stone
With the usual, asynchronous distribution of binder and crushed stone, when the binder is distributed by an asphalt distributor, and crushed stone by a crushed stone distributor following it at a distance of 10-100 m or more, the time interval t ranges from 5 s with very accurate operation of the machines to 10 minutes or more with small delays with rubble distribution. Therefore, the task of reducing the period between the distribution of binder and crushed stone is the task of improving the quality and durability of surface treatment.
This problem has been successfully solved in the technology of a surface treatment device with synchronous distribution of binder and crushed stone. For this, combined machines and equipment for the distribution of binder and crushed stone were created with a time interval of only 1 s. For surface treatment with synchronous distribution of binder and crushed stone in Russia, BSCHR-375 machines and chipper bitumen distributors of the Saratov Federal State Unitary Enterprise Rosdortekh type Chipsiler-40 and Ripsiler-26 are used (Fig. 8). The performance of these machines is 3-6 km/h.
The machine consists of a container for a heated binder, a body for crushed stone, a binder distribution system, a crushed stone distributor and a special console (platform) for the operator with a remote control for automated control of the working parts of the machine and the distribution process. The body of the car is divided by transverse partitions, which allow the crushed stone to be consumed in parts. The binder distribution system consists of flat jet nozzles located on one cross beam at a distance of 10 cm from one another with a total distribution width of up to 4 m. The binder from the nozzles is distributed under pressure in the form of tiny particles and covers the coating with a thin uniform layer. Each nozzle has independent switching on and off, which provides the possibility of flexible adjustment of the distribution width of the binder (bitumen or bitumen emulsion).
The crushed stone distributor of the original design allows distributing fractions with a size of 2-20 mm in a layer into one crushed stone. For better formation, the loose gravel must be immediately compacted with rollers on pneumatic tires or rollers with rubber-coated rollers.
Rice. 8. Combined machine "Chipsiler" company "SEKMER" for synchronous distribution of binder and crushed stone:
1 - container for binder; 2 - a body for crushed stone; 3 - binder distributor; 4 - crushed stone distributor; 5 - operator's working platform with control panel
To ensure reliable year-round performance highways in conditions of increasing intensity of traffic flows, it is necessary to monitor their condition and timely eliminate road defects caused by natural factors and non-compliance with the rules for the transportation of goods. Scientifically substantiated introduction of innovative technologies based on the use of new materials makes it possible to achieve high results in this area.
Rough surface treatment with the distribution of binder and crushed stone "Chip Seal" (Chip Seal) is used to restore protective properties more expensive than other similar methods. The principle of this type of coating device is quite simple. After applying the binder, spreading on it inert material and its sealing results in a relatively strong wear layer with a smooth, rough surface, good grip and anti-reflective effect. "Chip Seal" fills and seals microcracks, and also limits the access of water to the top layer of asphalt concrete. This type of protective treatment avoids the laying of a new asphalt concrete layer in cases where existing coverage not very worn out yet. The cost savings can be up to 50%.
The ratio of materials should be such that a monolithic structure of gravel covered with bitumen at 2/3 of the height is obtained. The binder consumption is approximately 10% relative to the crushed stone consumption, of which 8% goes to fixing individual crushed stones, and 2% to sealing the defects of the old coating. Depending on the given conditions, several types of surface treatment are used: with a single distribution of binder and crushed stone, with a double distribution of crushed stone per one layer of binder, with a double distribution of binder and crushed stone. The two-fold distribution of materials helps to improve the evenness, strength and shear resistance of the coating.
Various types of binder can be used with the Chip Seal device, for example, modified and unmodified, fast-setting and medium-setting bitumen emulsions, asphalt concrete modified with polymer or rubber crumb, as well as unmodified asphalt concrete. The appropriate type of binder is selected based on an assessment of the pavement condition, climate, aggregate properties, required service life and cost. The condition of the rubble is also of great importance. It must be of uniform size, crushed and hard, in order to ensure a long service life of the coating. Bituminous emulsion will not stick to gravel that is too dusty or too wet.
"Chip Seal" is used to prevent deformation and destruction of roads, therefore it is not suitable for problematic surfaces. The future base must be strong and not have structural damage. Only minor imperfections on the surface are allowed. Weather during work have a direct impact on their efficiency. The weather must be dry and warm to promote the best possible placement and curing of the binder.
The structure of the technology link for surface treatment includes machines for pre-cleaning coatings against dust and dirt, distribution of bitumen and gravel, compaction of the applied layer and sweeping. In traditional split spreading, a dump truck with crushed stone distribution equipment moves behind the asphalt distributor in reverse and scatters crushed stone in front of it. With synchronous distribution, the binder and crushed stone fall on the surface behind the bitumen spreader almost simultaneously, with an interval of less than 1 second. In this case, the binder that has not had time to cool down fills the micropores of the crushed stone, which ensures high performance characteristics of the coating. The uniformity of the filling of the binder is achieved by overlapping the jets at a given height. To do this, it is necessary to adjust the height of the comb and the nozzle jet. The compaction of the crushed stone layer should be carried out immediately after its laying.
To avoid crushing of stone material, pneumatic tire rollers with tire pressure from 0.7 to 0.8 MPa with a wheel load of at least 1.5 tons are used for compaction. To prevent crushed stones from moving, the speed of the rollers should not exceed 10 km / h. The number of passes in this case can vary from one to six. Finish passes can be made with light tandem or combination rollers. After completion of the work, the road will be opened to traffic, but subject to a speed limit of up to 40 km/h for a period of up to five days, in order to prevent damage to vehicles associated with the release of rubble from under the wheels. As soon as the layer is formed, the exfoliated gravel must be removed with a brush, for example, a watering machine or KDM. The pressure of the brush on the surface should not be too strong.
Market Participants
French company specialists SECMAIR(since 2008 part of the group of companies FAYAT), a major European developer and manufacturer of road maintenance equipment, in 1985 was the first to introduce a bitumen-split distributor (chipsealer) into production with the technology of synchronous distribution of binder and crushed stone. A modern version of the chassis-based chip-sealer truck is a high-tech complex for the repair and maintenance of roads with computer dosing of materials. To reduce the time required for restocking, the chip-sealers are equipped with large tanks that can hold up to 9000 liters of binder and up to 9 m 3 of inert material, which allows you to apply a layer up to 4.5 m wide in one pass, which corresponds to one traffic lane. To load crushed stone, a manipulator with a clamshell bucket mounted on a car is used. To save binder and crushed stone, if necessary, it is possible to apply the coating locally to areas of the web where cracks have appeared using the GPS system. A camera located at the front of the vehicle recognizes the areas to be treated and feeds the data to the New Pilot control system, which in turn displays it on a display in the operator's cab.
For the Russian market, SECMAIR offers a chip-sealer model 320-2 on a KAMAZ chassis with a 3500 l binder tank covered with a 10 cm layer of Rockwool thermal insulation. The heating system includes an automatic diesel burner with electric ignition and a tank for diesel fuel 50 l. Heated manifold with 200 mm side shift includes 28 flat jet nozzles. The uniformity of the filling of the binder is achieved due to the triple overlap of the jets when the comb is positioned at a certain height. After the binder has been dispensed, the residues from the binder circuit and the comb are sucked back into the container.
The 3.2 m wide crushed stone distribution system is equipped with 14 dampers with automatically adjustable feed. A hydraulically driven distribution drum with a diameter of 220 mm creates a flow of crushed stone. The distribution system is controlled by a microprocessor, which calculates and adjusts the bitumen pump flow depending on the speed of the machine, measured by the radar, the number of nozzles involved and the width of the material distribution. The operator has the ability to switch to a semi-automatic mode of operation and independently control individual dampers and nozzles or their groups, activate separately the binder supply mode, the crushed stone distribution mode, or both modes at the same time.
Together with SECMAIR Russian company "Special equipment" produces bitumen-chip non-distributor SDT-126 with a tank for a binder with a volume of 3500 l and with a body with a capacity of 5.5 m 3, which is enough for an average of 3.3 minutes of work. Comb SDT-126 expands from 2.5 m to 3.1 m with a step of 0.22 m, the binder consumption is from 0.3 to 3 m 2 with a step of 0.05 m 2. The temperature of the binder is maintained automatically by a diesel burner. As an option, the machine, which has a working speed of 3 to 5 km/h, can be equipped with metal rollers for pre-rolling the crushed stone.
Stacking machines OB-VARIO companies Schafer-Technic, as indicated by the manufacturer, are responsible modern requirements required for the maintenance and repair of roads and are suitable for surface treatment on federal, regional, district roads, as well as on roads inside settlements. Schäfer-Technic equipment allows the use of any type of binder and high-grade crushed stone, is distinguished by high productivity and quality. The loading device allows you to load crushed stone from a dump truck and feed it into the bunker right on the job site. This results in a significant increase in productivity per shift. Thanks to dosing automatics with touch control, binder and crushed stone are fed into the right amount without restrictions on the entire working width. The operator sets the desired dosage on the monitor. The top model 45/12 STH with a working width of 4.5 m is mounted on a semi-trailer, equipped with a 12,000 l binder tank and a 17.5 t gravel hopper.
Model of chip spreader KD 3D, which is produced by the Polish engineering company MADROG, mounted on the base of a trailer and designed to work as part of a link consisting of a tractor and a bitumen truck. In addition, MADROG, founded in 1985, manufactures asphalt distributors, curb pavers, equipment for surface treatment and road repair. All components and parts of this brand, according to MADROG, undergo multiple tests. The KD 3D road harvester is equipped with a crushed stone bin and a bitumen pump for taking binder from an external tank, the performance of which is automatically synchronized with the crushed stone supply.
Besides, electronic system maintains the supply of binder and crushed stone set by the operator, regardless of the speed of movement, takes into account the distance traveled and the cultivated area. The distribution width of the KD 3D is 2.5 m (3 m is available as an option). Each of the supply nozzles with a pneumatic drive can be switched on separately. This function is necessary for patching or to eliminate rutting. The operator has the ability to change the width, length and density of the distribution of materials directly during movement. For pre-compaction, integrated pneumatically driven pressure rollers are used. For a better view of the work site, the operator's station, equipped with an electronic display control panel, is located at the front of the machine.
Surface treatment technologies are traditionally very popular with contractors from France, which is why Acmar from the French city of Craon has focused its efforts on the development of equipment for the distribution of crushed stone and bitumen. Acmar offers two models with synchronous distribution, RGA and RGS. The RGA model with binder tank from 5000 to 8000 l is mounted on a 3- or 4-axle chassis. Used to heat the binder automatic burner which is controlled by a computer. System cleaning is also computerized. The capacity of the bitumen pump is 45 m 3 /h. The body for crushed stone with a built-in pusher has a volume of 6 to 8 m3. The maximum width of the telescopic combs for crushed stone and bitumen spreading is 4.4 m. A material supply bar with a reel and a flexible hose, as well as a pallet with a shovel are provided for filling potholes. The equipment is controlled by a joystick from the driver's cab. All operating parameters are stored in the memory of the control system. RGS is a similar machine, but with smaller containers for materials: tank and body - up to 6 m3.
One of the latest developments of the company - the first in the world frontal crushed stone distributor, which is attached to the front of the dump truck, in front of the driver's cab. The use of this equipment makes it possible for a dump truck with crushed stone to move forward, following immediately behind the asphalt distributor. Benefits of the new concept include increased safety, precise feeding with automatic control and telescopic extension up to 4.4 m, as well as the ability to remove the front linkage, which allows the use of a dump truck. all year round, including for its intended purpose.
Italian company MASSENZA with over 70 years of experience is considered one of the world leaders in the field bitumen technologies. MASSENZA is currently focusing its efforts on the development of new equipment for road maintenance. Combined machine COMBIMAS 10, designed for Chip Seal coating applications, reduces turnaround time with an innovative material loading system with two hydraulically driven conveyors. Crushed stone can be loaded into a hopper with a volume of 10 m 3 directly from a dump truck, without a front loader. A cubic container for a binder made of S355JR structural steel, thermally insulated with mineral wool, also has a volume of 10 m 3 and a wall thickness of 4 mm. It is allowed to use bitumen, bitumen emulsion, polymer-bitumen materials as a binder, while ensuring productivity up to 20,000 m 2 per shift. An oil heating station with an automatic diesel burner is used to heat the bitumen, which allows saving up to 30% of diesel fuel compared to flare heating systems, preserves the properties of the bitumen material and uses it completely, without the need to maintain the technological volume of the binder. The comb is heated with hot oil over the entire width. The dosing system regulates the supply of material depending on temperature, pressure, vehicle speed, nozzle size, which allows automatic distribution of bituminous raw materials. Dosing is carried out with an accuracy of up to 10 g of binder per square meter coatings. An additional manual dispensing gun with three nozzles and a 4 m flexible hose is used for local applications. As a power plant, a Deutz BF4M2012 diesel engine with a power of 74.9 kW at 2500 rpm is used.
Bitumen-spreader DS-180 production JSC "Kurgandormash"; also allows for rough surface treatment with synchronous distribution of binder and crushed stone. The DS-180 bitumen distributor consists of a KAMAZ-65116 truck tractor and a semi-trailer, on the frame of which the equipment is installed. The kit includes a bituminous tank with a volume of 6 m 3 s heat-insulating layer glass fiber 50 mm thick, circulation type bitumen distributor, bitumen pump, 10 m 3 crushed stone storage bin, rotary type crushed stone distributor, crushed stone compactor, loading mechanism and operator's work platform. Heating of bitumen in the tank is provided by a stationary diesel burner through a flame tube. The maximum distribution width of DS-180 is 3.5 m with a change step of 0.19 m. According to the manufacturer, the machine improves the quality of surface treatment, increases its uniformity and significantly reduces the cost of work performed.
Russian roads are mainly made of asphalt concrete, which is quite difficult to keep in its original form for a long time in our climate. After the first years of operation, on some sections of the road, due to a weak foundation, rutting may form, potholes, longitudinal and transverse cracks appear in the spring. Already at an early stage of wear, road builders must carry out a set of works to prevent further destruction roadbed. To extend the durability, all new materials are used and Hi-tech to achieve good results.
In order to increase the turnaround time of highways, the Chip Seal method was developed, with the help of which a thin layer of wear is applied quickly and at the lowest cost. Experts argue that if such work is done in a timely manner and in compliance with all technological requirements, you can forget about a new repair for years. "Chip Seal" traditionally provides fast, reliable and economical surface treatment, protecting it from water and increasing wear resistance.
Recent technological and design advances in materials and equipment have made it possible to significantly reduce the dependence of the result on the experience, intuition and skills of the repair team, which were decisive in the recent past. So, from the moisture content associated with adhesion, you can accurately calculate when to start cleaning excess gravel and open the movement. Special tests allow you to evaluate physical properties emulsions. It is practiced to use one-dimensional crushed stone of narrow fractions, polymer emulsions, mineral additives, fibers, rubber crumb, etc. The use of computer control simplifies the uniform application of materials and allows you to quickly make the necessary adjustments.
Thus, today Chip Seal processing, along with Slurry Seal and Novachip technologies, reliably preserves various road surfaces under a wide variety of working conditions.