13.4. Pothole repair of asphalt concrete and bituminous materials. The main methods of patching and technological operations
The task of patching is to restore the continuity, evenness, strength, grip and water resistance of the coating and ensure normative term refurbished site services. When patching, various methods, materials, machines and equipment are used. The choice of one or another method depends on the size, depth and number of potholes and other defects in the coating, the type of coating and the materials of its layers, available resources, weather conditions, requirements for the duration of repair work, etc.
The traditional method involves cutting the edges of the pothole into a rectangular shape, cleaning it from asphalt concrete scrap and dirt, priming the bottom and edges of the pothole, filling it with repair material and compacting it. To give the pothole a rectangular shape, small cold milling machines, circular saws, and punchers are used.
As a repair material, asphalt concrete mixtures that require compaction are mainly used, and from mechanization means - small-sized rollers and vibrorammers.
When working in conditions of increased moisture, potholes are dried before priming with compressed air (hot or cold), as well as using infrared burners. If the coating is repaired with small cards (up to 25 m 2), the entire area is heated; when repairing large maps - along the perimeter of the site.
After preparation, the pothole is filled with repair material, taking into account the margin for compaction. With a pothole depth of up to 5 cm, the mixture is laid in one layer, more than 5 cm - in two layers. Compaction is carried out from the edges to the middle of the repaired areas. When filling potholes deeper than 5 cm, a coarse-grained mixture is placed in the bottom layer and compacted. This method allows you to get a high quality repair, but requires a significant number of operations. It is used in the repair of all types of coatings made of asphalt concrete and bitumen-mineral materials.
Small potholes up to 1.5-2 cm deep on an area of 1-2 m 2 or more are repaired by the method of surface treatment using crushed stone of fine fractions.
The repair method with heating the damaged pavement and reusing its material is based on the use of special equipment for heating the pavement - an asphalt heater. The method makes it possible to obtain a high quality repair, saves material, simplifies the technology of work, but has significant limitations due to weather conditions (wind and air temperature). It is applied at repair of all types of coverings from asphalt concrete and bituminous mixes.
The method of repair by filling potholes, pits and subsidence without cutting or heating the old pavement consists in filling these deformations and destructions with cold polymer-asphalt concrete mix, cold asphalt concrete, wet organo-mineral mix, etc. The method is simple to perform, allows you to perform work in cold weather with wet and wet coating, however, does not provide high quality and durability of the repaired coating. It is used when repairing pavements on roads with low traffic volumes or as a temporary, emergency measure on roads with high traffic volumes.
According to the type of repair material used, there are two groups of patching methods: cold and hot.
cold ways are based on the use of cold bituminous mineral mixtures, wet organic mineral mixtures (VOMS) or cold asphalt concrete as a repair material. They are mainly used for the repair of black gravel and cold asphalt concrete pavements on low-grade roads, as well as for urgent or temporary filling of potholes in more early dates on high grade roads.
Work on patching by this method begins in the spring, as a rule, at an air temperature of at least + 10 ° C. If necessary, cold mixtures can be used for patching and at lower temperatures (from +5°C to -5°C). In this case, before laying, cold black crushed stone or cold asphalt concrete mixture is heated to a temperature of 50-70 ° C, with the help of burners, the bottom and walls of potholes are heated until bitumen appears on their surface. In the absence of burners, the surface of the bottom and walls is coated with bitumen with a viscosity of 130/200 or 200/300, heated to a temperature of 140-150°C. After that, the repair material is laid and compacted.
The formation of the coating at the place of repair in a cold way occurs under the traffic for 20-40 days and depends on the properties of liquid bitumen or bitumen emulsion, type of mineral powder, weather conditions, traffic intensity and composition.
Cold asphalt concrete layers for patching are prepared using liquid medium thickening or slow thickening bitumen with a viscosity of 70/130, using the same technology as hot asphalt concrete mixtures, at a bitumen heating temperature of 80-90 ° C and a mixture temperature at the outlet of the mixer 90-120 °C. Mixtures can be stored in stacks up to 2 m high. In summer, they can be kept in open areas, in autumn and winter - in closed warehouses or under a canopy.
Repair work can be carried out at a lower air temperature, and repair material must be prepared in advance. The cost of work on this technology is lower than with the hot method. The main drawback is the relatively short service life of the repaired pavement on roads with the movement of heavy trucks and buses.
hot ways are based on the use of hot asphalt concrete mixtures as a repair material: fine-grained, coarse-grained and sandy mixtures, poured asphalt concrete, etc. The composition and properties of the asphalt concrete mixture used for repair should be similar to that of which the coating is made. The mixture is prepared according to the usual technology for the preparation of hot asphalt concrete. Hot methods are used in the repair of roads with asphalt concrete pavement. Works can be carried out at an air temperature of at least +10°C with a thawed base and a dry coating. When using a heater of the repaired coating, it is allowed to carry out repairs at an air temperature of at least +5°С. Hot patching methods provide higher quality and longer service life of the repaired pavement.
As a rule, all patching work is carried out in early spring, as soon as weather conditions and pavement conditions allow. In summer and autumn, potholes and pits are sealed immediately after they appear. Technology and organization of work in various ways have their own characteristics. However, for all methods of patching there are common technological operations that are performed in a certain sequence. All these operations can be divided into preparatory, main and final.
Preparatory work includes:
installation of fencing of work sites, road signs and lighting, if work is performed at night;
marking of places of repair (maps);
cutting, breaking or milling of damaged areas of the coating and cleaning of the removed material;
cleaning potholes from material residues, dust and dirt;
drying the bottom and walls of the pothole, if the repair is carried out in a hot way with a wet coating;
processing (priming) of the bottom and walls of the pothole with bitumen emulsion or bitumen.
The marking of repair sites (repair maps) is carried out using a stretched cord or chalk using a rail. The repair site is outlined with straight lines parallel and perpendicular to the axis of the road, giving the contour the correct shape and capturing the intact coating to a width of 3-5 cm. Several potholes located at a distance of up to 0.5 m from one another are combined into a common map.
Cutting, breaking or milling of the coating within the marked map is carried out for the thickness of the destroyed layer of the coating, but not less than 4 cm throughout the repair area. In this case, if the depth of the pothole has affected the lower layer of the coating, the thickness of the lower layer with the destroyed structure is loosened and removed.
It is very important to remove and remove the entire destroyed and weakened layer of asphalt concrete, capturing a strip of at least 3-5 cm wide from a strong, undestroyed asphalt concrete along the entire marked contour. These edge bands of the pothole cannot be left unremoved, since the solidity of the asphalt concrete is weakened here due to the formation of microcracks, loosening and chipping of individual gravel from the walls of the pothole (Fig. 13.10, a). Water collects in the pothole, which, under the dynamic influence of the wheels of cars, penetrates into the interlayer space and weakens the adhesion of the upper layer of asphalt concrete to the lower one. Therefore, if the weakened edges of the pothole are left, then after laying the repair material, after some time, the weakened edges may collapse, the newly laid material will lose its connection with the strong old material and the development of the pothole will begin.
Rice. 13.10. Cutting a pothole before laying the repair material: a - cutting weak spots; b- cutting the edges of the pothole after milling; 1 - weakened wall of the pothole; 2 - exfoliated part of the coating; 3 - destroyed part of the bottom of the pothole; 4 - chopped off or beveled wall of the pothole
The walls of the edges of the pothole after cutting should be vertical along the entire contour. The cutting and breaking of the coating can be carried out using a pneumatic jackhammer or scrap, a concrete breaker, a seam cutter and a ripper, or using a road milling machine.
When using a road milling cutter for cutting a pothole, rounded front and rear wall potholes that must be trimmed with a circular saw or jackhammer. Otherwise, the upper part of the laid layer of repair material at the interface with the old material will be very thin and will quickly collapse (Fig. 13.10, b).
The loosened material of the old pavement is manually removed from the pothole, and when using a road milling machine, the removed material (granulate) is fed into a dump truck by a loading conveyor and taken out. The cleaning of the map is carried out with the help of shovels, compressed air, and with a large area of the map - with the help of sweepers. Drying of the bottom and walls of the card is carried out as necessary by blowing with hot or cold air.
Treatment with a binder (priming) of the bottom and walls of potholes is carried out in the case of laying hot asphalt mixes as a repair material. This is necessary in order to ensure better adaptation of the old asphalt concrete material to the new one.
The bottom and walls of the cleaned card are treated with liquid medium-thickening bitumen with a viscosity of 40/70, heated to a temperature of 60-70°C with a flow rate of 0.5 l/m 2 or a bituminous emulsion with a flow rate of 0.8 l/m 2 . In the absence of means of mechanization, bitumen is heated in mobile bitumen boilers and distributed over the base using a watering can.
Filling the pothole with repair material can only be done after all the preparatory work has been completed. The laying technology and the sequence of operations depend on the method and volume of work performed, as well as on the type of repair material. With small volumes of work and the absence of mechanization, the laying of repair material can be done manually.
The temperature of the hot mix asphalt delivered to the place of laying should be close to the temperature of preparation, but not lower than 110-120°C. It is most expedient to lay the mixture at such a temperature when it is easily processed, and during the laying process, waves and deformations are not formed during the passage of the rink. Depending on the type of mixture and its composition, such a temperature is considered: for a multi-gravel mixture - 140-160 ° C; for medium crushed stone mixture - 120-140 ° C; for low gravel mixture - 100-130°C.
Laying the mixture in the card is carried out in one layer at a cutting depth of up to 50 mm and in two layers at a depth of more than 50 mm. At the same time, a coarse-grained mixture with a crushed stone size of up to 40 mm can be laid in the lower layer, and in upper layer- only a fine-grained mixture with a fraction size of up to 20 mm.
The thickness of the laying layer in a loose body should be greater than the thickness of the layer in a dense body, taking into account the safety factor for compaction, which is taken: for hot asphalt mixes 1.25-1.30; for cold asphalt mixes 1.5-1.6; for wet organo-mineral mixtures 1.7-1.8, for crushed stone and gravel materials treated with a binder, 1.3-1.4.
When laying the repair material in a mechanized way, the mixture is fed from the thermos hopper through a rotary tray or a large-diameter flexible hose directly into the pothole and is evenly leveled over the entire area. The laying of asphalt concrete mixtures when embedding maps with an area of 10-20 m 2 can be carried out by an asphalt paver. In this case, the mixture is laid over the entire width of the map in one pass in order to avoid an additional longitudinal seam for conjugating the laying strips. The compaction of the asphalt concrete mixture laid in the bottom layer of the coating is carried out by pneumatic rammers, electric rammers or manual vibratory rollers in the direction from the edges to the middle.
The asphalt concrete mixture laid in the top layer, as well as the mixture laid in one layer with a pothole depth of up to 50 mm, is compacted with a self-propelled vibratory roller (first two passes along the track without vibration, and then two passes along the track with vibration) or light-type static smooth-roller rollers weighing 6-8 tons up to 6 passes along one track, and then heavy rollers with smooth rollers weighing 10-18 tons up to 15-18 passes along one track.
The compaction coefficient should be at least 0.98 for sandy and low-gravel asphalt concrete mixtures and 0.99 for medium- and high-gravel mixtures.
Compaction of hot asphalt mixes is started at the highest possible temperature at which deformations are not formed during the rolling process. Compaction should provide not only the required density, but also the evenness of the repair layer, as well as the location on the same level of the repaired coating with the old one. For better mating of the new coating with the old one and the formation of a single monolithic layer when laying hot mixes, the joint along the entire contour of the cutting is heated using a line of burners or an electric heater. The joints of potholes that protrude above the surface of the coating are eliminated by milling or grinding machines. The final work is the cleaning of the remaining repair waste with their loading into dump trucks and the removal of fences and road signs, the restoration of marking lines in the patching area.
The quality of the repair and the service life of the repaired coating depend primarily on compliance with the quality requirements for the performance of all technological operations (Fig. 13.11).
Rice. 13.11. The sequence of basic patching operations: a - correct; b- wrong; 1 - pothole before repair; 2 - cutting or cutting, cleaning and processing with a binder (priming); 3 - filling with repair material; 4 - seal; 5 - view of the repaired pothole
The most important requirements are:
repairs must be carried out at an air temperature not lower than that allowed for this repair material on a dry and clean surface;
when cutting down the old coating, weakened material should be removed from all areas of the pothole where there are cracks, breaks and spalling; the repair card must be cleaned and dried;
the shape of the repair map must be correct, the walls are sheer, and the bottom is even; the entire surface of the pothole must be treated with a binder;
repair material must be laid at the optimum temperature for this type of mixture; the layer thickness should be greater than the depth of the pothole, taking into account the margin for the compaction factor;
the repair material must be carefully leveled and compacted flush with the surface of the coating;
the formation of a layer of new material on the old coating at the edge of the map is not allowed to avoid shocks when a car runs over and the rapid destruction of the repaired area.
The result of a properly executed repair is the height of the laid layer after compaction, exactly equal to the depth of the pothole without unevenness; correct geometric shapes and invisible seams, optimal compaction of the laid material and its good connection with the material of the old pavement, long service life of the repaired pavement. The result of an incorrectly performed repair may be unevenness of the compacted material, when its surface is higher or lower than the surface of the coating, arbitrary map shapes in plan, insufficient compaction and poor connection of the repair material with the material of the old coating, the presence of protrusions and sags on the edges of the map, etc. Under the influence of transport and climatic factors areas of such repair are quickly destroyed.
Pothole repair of black crushed stone or gravel coatings. When repairing such pavements, simpler materials and repair methods can be used to reduce the cost of maintaining roads with black gravel and black gravel pavements. Most often, these methods are based on the use of cold bituminous mineral mixtures or materials treated with bitumen emulsion as a repair material. One such material is a mixture of organic binder (liquid bitumen or emulsion) with wet mineral material (crushed stone, sand or gravel-sand mixture), laid in a cold state. Cement or lime is used as an activator when using liquid bitumen or tar.
So, for example, to repair potholes up to 5 cm deep, a repair mixture is used in the composition: crushed stone 5-20 mm - 25%; sand - 68%; mineral powder - 5%; cement (lime) - 2%; liquid bitumen - in excess of 5% mass; water - about 4%.
The mixture is prepared in forced action mixers in the following sequence:
mineral materials are loaded into the mixer at natural humidity(crushed stone, sand, mineral powder, activator), mix;
add the calculated amount of water and mix;
enter the organic binder, heated to a temperature of 60°C, and finally mix.
The amount of water introduced is adjusted depending on the intrinsic moisture content of the mineral materials.
During the preparation of the mixture, mineral materials are not heated or dried, which greatly simplifies the preparation technology and reduces the cost of the material. The mixture can be prepared ahead of time.
Before laying the mixture, the bottom and walls of the pothole are not primed with bitumen or emulsion, but moistened or washed with water. The laid mixture is compacted and movement is opened. The final formation of the layer occurs under the traffic.
Patching with the use of wet bituminous mineral mixtures can be carried out at a positive temperature not higher than +30°C and at a negative temperature not lower than -10°C in dry and damp weather.
Pothole repair of black gravel coatings by impregnation. As a repair material, crushed stone is used, pre-treated in a mixer with hot viscous bitumen in an amount of 1.5-2% by weight of crushed stone.
After marking the contour of the pothole, its edges are cut off, old coatings are scraped off and loosened material is removed, the bottom and walls of the pothole are treated with hot bitumen at a flow rate of 0.6 l / m 2. Then, black crushed stone with a fraction of 15-30 mm is laid and compacted with a manual rammer or vibratory roller; bitumen is poured with a flow rate of 4 l / m 2; lay the second layer of black crushed stone with fractions of 10-20 mm and compact it; crushed stone is treated with bitumen at a rate of 2 l/m 2 ; scatter stone screenings of fractions of 0-10 mm and compact with a pneumatic vibrating roller. Using the same technology, it is possible to carry out repairs by impregnation and using crushed stone not treated with bitumen. This increases the bitumen consumption: at the first spill - 5 l/m 2 , at the second - 3 l/m 2 . The distributed bitumen impregnates the layers of crushed stone to the full depth, as a result of which a single monolithic layer is formed. This is the essence of the impregnation method. For impregnation apply viscous bitumen 130/200 and 200/300 at a temperature of 140-160°C.
A simplified method of patching with impregnation of crushed stone with bitumen emulsion or liquid bitumen is widely used in France for patching small potholes on roads with low and medium traffic. Such potholes are called "chicken nest".
The repair technology consists of the following operations:
first, potholes or pits are manually covered with large-sized crushed stone - 10-14 or 14-25 mm;
then, as it is filled, small crushed stone of fractions of 4-6 or 6-10 mm is scattered until the road profile is completely restored;
binder is poured: bitumen emulsion or bitumen in a ratio of 1:10, i.e. one part binder per ten parts crushed stone by weight;
compaction is carried out manually using a vibrating plate.
The binder penetrates the crushed stone layer to the base, as a result of which a monolithic layer is formed. The final formation occurs under the action of moving cars.
In addition to direct impregnation for patching, the reverse impregnation method is used. In this case, bitumen with a viscosity of 90/130 or 130/200, heated to a temperature of 180-200°C, is poured onto the bottom of the prepared card. The thickness of the bitumen layer should be equal to 1/5 of the depth of the pothole. Immediately after the spill of hot bitumen, mineral material is poured: crushed stone of fractions 5-15; 10-15; 15-20 mm, ordinary crushed stone or gravel-sand mixture with a particle size of up to 20 mm. The mineral material is leveled and compacted with a rammer.
When the mineral material, which has natural moisture, interacts with hot bitumen, foaming occurs and the material is impregnated with bitumen from the bottom up. If the foam has not risen to the surface of the material, the binder is poured again at the rate of 0.5 l / m 2, covered with a thin layer of crushed stone and compacted.
With a pothole depth of up to 6 cm, all its fillings are performed in one layer. At a greater depth, filling is carried out in layers 5-6 cm thick. Patching works can be performed in this way even at negative air temperatures. However, the service life of the repaired sections in this case is reduced to 1-2 years.
Pothole repair using crushed stone treated with bituminous emulsion has a number of advantages: there is no need to heat the binder to prepare the mixture; can be laid at a positive ambient temperature, i.e. from the beginning of spring to the end of autumn; rapid disintegration of the cationic emulsion, which contributes to the formation of a repair layer; no edge trimming, material removal or priming.
To perform work, a repair vehicle is used, which includes: a base vehicle with a heat-insulated emulsion tank with a capacity of 1000 to 1500 liters; distribution device for emulsion (compressor, hose, nozzle); bunkers of crushed stone of fractions from 2-4 to 14-20. The cationic emulsion used must be fast disintegrating, contain 65% bitumen and be kept warm at temperatures between 30°C and 60°C. The surface to be treated must be clean and dry.
The technology for repairing deep pits over 50 mm of the "chicken's nest" type (French terminology) consists of the following operations: laying a layer of crushed stone of fraction 14-20; distribution of binder on a layer of crushed stone 14-20; laying the 2nd layer of crushed stone 10-14; spraying binder on a layer of crushed stone 10-14; laying the 3rd layer of crushed stone 6-10; spraying binder on a layer of crushed stone 6-10; laying the 4th layer of crushed stone 4-6; spraying binder on a layer of crushed stone 4-6; laying the 5th layer of crushed stone 2-4 and compaction.
It is important to ensure the correct dosing of the binder when spraying the emulsion over crushed stone. Crushed stone should only be covered with a binder film, but not drowned in it. The total consumption of the binder should not exceed the ratio binder: crushed stone = 1:10 by weight. The number of layers and the size of crushed stone fractions depends on the depth of the pothole. When repairing small potholes up to 10-15 mm deep, the repair is carried out in the following order: laying a layer of crushed stone 4-6; spraying binder on crushed stone 4-6; crushed stone distribution 2-4 and compaction.
These methods are applicable in the repair of black gravel and black gravel pavements on roads with low traffic volumes. The disadvantages of using such methods are that the presence of a layer of variable thickness can cause destruction of the edges of the patch, and appearance patch repeats the outlines of the pothole.
Pothole repair of asphalt concrete pavements using an asphalt heater. The technology of work is greatly simplified in the case of patching with preliminary heating of the asphalt concrete pavement over the entire area of the map. For these purposes, a special self-propelled machine can be used - an asphalt heater, which allows you to heat the asphalt concrete pavement up to 100-200 ° C. The same machine is used for drying repaired areas in wet weather.
The heating mode consists of two periods: heating the coating surface to a temperature of 180°C and further more gradual heating of the coating over the entire width to a temperature of about 80°C in the lower part of the heated layer at a constant temperature on the coating surface. The heating mode is regulated by changing the gas flow rate and the height of the burners above the coating from 10 to 20 cm.
After heating, the asphalt concrete pavement is loosened with a rake to the entire depth of the pothole, a new hot asphalt concrete mixture is added to it from the thermos hopper, mixed with the old mixture, distributed over the entire width of the map with a layer 1.2-1.3 times greater than the depth, taking into account the compaction coefficient and compact from the edges to the middle of the repaired area with a manual vibratory roller or a self-propelled roller. The junctions of the old and new coatings are heated using a line of burners that are part of the asphalt heater. The line of burners is a mobile metal frame with infrared burners mounted on it, which are supplied with gas from cylinders through a flexible hose. During the repair work, the temperature of the coating should be in the range of 130-150°C, and by the end of the compaction work - not lower than 100-140°C.
The use of an asphalt heater greatly simplifies the technology of patching and improves the quality of work.
The use of gas-fired asphalt heaters requires special attention and compliance with safety regulations. It is not allowed to operate gas burners at a wind speed of more than 6-8 m / s, when a gust of wind can extinguish the flame on part of the burners, and the gas from them will flow, concentrate in large quantities and may explode.
Asphalt heaters operating on liquid fuel or with electrical sources of infrared radiation are much safer.
Repair asphalt concrete pavement using special machines for patching or road repairers. The most effective and high-quality type of patching is the repair performed using special machines, which are called road repairers. Road repairers are used as a means of complex mechanization of road repair work, since they are used not only for patching road surfaces, but also for sealing cracks and filling joints.
The technological scheme of patching with the use of a road repairer includes the usual operations. If the repairer is equipped with a heater, the repair technology is greatly facilitated.
Simplified methods of patching (injection methods). In recent years, simplified methods of patching using special machines such as Savalco (Sweden), Rasko, Dyura Petcher, Blow Petcher, etc. have become more widespread. In Russia, similar machines are produced in the form of special trailed equipment. - sealer brand BCM-24 and UDN-1. Repair of potholes by injection is performed using a cationic emulsion. Cleaning the pothole for repair is carried out with a jet of compressed air or by suction; primer - heated to 60-75 ° C emulsion; filling - with blackened crushed stone in the process of injection. With this repair method, edge trimming can be omitted.
As a repair material, crushed stone of a fraction of 5-8 (10) mm and an emulsion of the EBK-2 type are used. A concentrated emulsion (60-70%) is used on bitumen BND 90/130 or 60/90 with an approximate consumption of 10-11% by weight of crushed stone. The surface of the repaired area is sprinkled with white gravel with a layer of one gravel. The traffic opens in 10-15 minutes. Works are carried out at an air temperature of at least +5 ° C, both on dry and wet surfaces.
Patch repair by injection is performed in the following order (Fig. 13.12):
Rice. 13.12. Pothole repairs according to a simplified technology: 1 - cleaning potholes by blowing with compressed air; 2 - priming with bituminous emulsion; 3 - filling with crushed stone treated with emulsion; 4 - applying a thin layer of raw gravel
the first stage - the place of the pit or patch is cleaned with a jet of air under pressure to remove pieces of asphalt concrete, water and debris;
the second stage - priming with a bitumen emulsion of the bottom, walls of the pothole and the surface of the asphalt concrete pavement adjacent to it. The emulsion flow is controlled by a control valve on the main nozzle. The emulsion enters the air stream from the spray ring. The temperature of the emulsion should be about 50°C;
the third stage is filling the pothole with repair material. The crushed stone is introduced into the air stream by means of a screw conveyor, then it enters the main mouthpiece, where it is covered with emulsion from the spray ring, and from it the processed material is thrown into the pothole at high speed, distributed in thin layers. Compaction occurs due to the forces resulting from the high speeds of the ejected material. The suspended flexible hose is controlled remotely by the operator;
the fourth stage is the application of a protective layer of dry, untreated crushed stone to the patch area. In this case, the valve on the main nozzle that controls the flow of the emulsion is turned off.
It should be noted that the exclusion of pre-cutting the edges of the pothole leads to the fact that in the marginal zone of the pothole there remains old asphalt concrete with a disturbed structure, which, as a rule, has reduced adhesion to the underlying layer. The service life of such a patch will be less than with traditional technology. In addition, patches have irregular shapes, which impairs the appearance of the coating.
Pothole repairs using cast asphalt mixes. A distinctive feature of cast asphalt mixes is that they are laid in a fluid state, as a result of which they easily fill potholes and do not require compaction. Fine-grained or sandy cast asphalt can be used for repairs at low air temperatures (down to -10°C). Most often, a sandy cast asphalt concrete mixture is used for repair work, consisting of natural or artificial quartz sand in an amount of 85% by weight, mineral powder - 15% and bitumen - 10-12%. For the preparation of cast asphalt, viscous refractory bitumen with a penetration of 40/60 is used. The mixture is prepared in mixing plants with forced action mixers at a mixing temperature of 220-240°C. Transportation of the mixture to the place of laying is carried out in special mobile boilers of the Kocher type or in thermos bunkers.
The delivered mixture at a temperature of 200-220°C is poured into the prepared pothole and easily leveled with wooden trowels. The easy-moving mixture fills all the irregularities, due to the high temperature it heats up the bottom and walls of the pothole, as a result of which a strong connection of the repair material from the side of the coating is achieved.
Since a fine-grained or sandy cast mixture creates a surface with increased slipperiness, measures must be taken to improve its grip. For this purpose, immediately after the mixture is distributed, black crushed stone 3-5 or 5-8 is scattered over it with a consumption of 5-8 kg / m 2 so that the crushed stone is evenly distributed in a layer of one crushed stone. After the mixture has cooled down to 80-100°C, crushed stone is rolled with a manual roller weighing 30-50 kg. When the mixture has cooled to ambient temperature, the excess gravel that has not sunk into the mixture is swept away and movement is opened.
Laying of cast asphalt mixes during patching can be done manually or with a special asphalt paver with a heating system. The advantage of this technology is that operations for priming the repair card and compacting the mixture are excluded, as well as the high strength of the repair layer and the reliability of the joints of the interface of new and old materials. The disadvantages are the need to use special mixers, heated mobile rollers and mixers or thermos bunkers, viscous refractory bitumen, as well as increased safety and labor protection requirements when working with a mixture that has a very high temperature.
In addition, poured asphalt during operation has a significantly greater strength and lower deformability compared to conventional asphalt concrete. Therefore, in the case when poured asphalt is repairing a coating of conventional asphalt concrete, after a few years this coating begins to collapse around the patch of poured asphalt, which is explained by the difference in the physical and mechanical properties of the old and new material. Molded asphalt is most often used for patching city roads and streets.
One of the ways to simplify the work technology and increase the construction season is the use of cold asphalt concrete mixtures based on polymer bitumen binder (PBV) as a repair material. These mixtures are prepared using a complex binder, which consists of bitumen with a viscosity of 60/90 in an amount of about 80% by weight of the binder, a polymer modifying additive in an amount of 5-6% and a solvent, for example diesel fuel, in an amount of 15% by weight of the binder. The binder is prepared by mixing the components at a temperature of 100-110°C.
Asphalt-concrete mix on PMB is prepared in mixers with forced mixing at a temperature of 50-60°C. The mixture consists of fine crushed stone fractions 3-10 in the amount of 85% by weight of the mineral material, screenings 0-3 in the amount of 15% and a binder in the amount of 3-4% of the total mass of the mineral material. The mixture is then stored in an open stack, where it can be stored for up to 2 years, or loaded into bags or barrels, in which it can be stored for several years, retaining its technological properties, including mobility, plasticity, lack of caking and high adhesive characteristics.
The repair technology using this mixture is extremely simple: the mixture from the body of a car or from the bunker of a road repairer is manually or using a hose fed into a pothole and leveled, after which traffic is opened, under the influence of which the road layer is formed. The whole process of repairing a pothole takes 2-4 minutes, since operations for marking the map, cutting and cleaning the pothole, as well as compacting with rollers or vibratory rollers are excluded. The adhesive properties of the mixture are also preserved when it is laid in potholes filled with water. Repair work can be carried out at negative air temperatures, the limit of which needs to be clarified. All this makes this method of patching very attractive for practical purposes.
However, it also has a number of significant drawbacks. First of all, there is a possibility of rapid destruction of the repaired pothole due to the fact that its weakened edges are not removed. When performing work in wet weather or if there is water in a pothole, part of the moisture can get into microcracks and pores of the old coating and freeze when the coating temperature drops below 0. In this case, the process of destruction of the zone of conjugation of new and old materials can be initiated. The second disadvantage of this method of repair is the preservation of the irregular external shape of the pothole after repair, which worsens the aesthetic perception of the road.
Availability a large number methods of patching makes it possible to choose the optimal one based on specific conditions, taking into account the condition of the road, the number and size of coating defects, the availability of materials and equipment, the timing of repairs and other circumstances.
In any case, it is necessary to strive to eliminate pitting at an early stage of its development. After patching, in many cases it is advisable to arrange a surface treatment or lay a protective layer, which will give a uniform appearance to the coating and prevent its destruction.
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26.03.2019
Cover condition requirements highways are clearly spelled out in the relevant regulatory documents (GOST R 50597-93, SNiP 2.07.01 and others). However, they do not take into account the rapid increase in the number of vehicles and the corresponding increase in the load on the road surface. Along with the progress of technology, the number of materials and technologies for road repair is also growing.
In particular, patching of asphalt pavement is justified if the degree of damage allows it. Otherwise, major road repairs should be carried out. Only strict observance of technological conditions and requirements for such repairs provides strong "patches". Let's take a closer look at the technology.
Types of patching
The type of repair required in a particular case depends on the nature and extent of damage to the pavement, the operational load on the pavement (measured in the number of vehicles per day). The procedure is also divided into different kinds depending on the materials and technologies used:
- Laying hot mix asphalt.
- hot way asphalting.
- Casting with a fluid mixture.
- Jet-injection (injector) method.
- Repair with infrared heating units.
Each of the methods has its own advantages and disadvantages and is used depending on a number of factors related to the characteristics of the damaged pavement, the climatic conditions of the region, and even the budget allocated for the work. Efficiency of work is not the last indicator that affects the choice of technology. For example, patching with poured asphalt in winter is unacceptable due to high humidity.
The preferred technology and material must meet a number of criteria:
- Correspondence of the surface properties of the finished patch and the base coat.
- Correspondence of the strength of the asphalt concrete mix to the operational loads on the repaired site.
- Availability and accessibility of materials and technical means for repairs.
- Material requirements for weather conditions during repairs.
- Efficiency of resumption of traffic upon completion of work and overall speed of execution.
- Economic features of a particular method of performing work.
New Asphalt Technologies – NovTecAs is a company engaged in road and road patching, asphalt laying and related activities in Moscow.
Technology features
The technologies of the methods mentioned above differ in some details, but there are a number of general requirements which govern the performance of any type of repair. First of all, it must be carried out under appropriate weather conditions: the air temperature is at least 5ºС and in the absence of precipitation.
The exception is hot asphalt mixes, which can be worked with at 0ºС, but only in the presence of special additives and with a layer thickness of more than 4 centimeters.
Preparatory work
Before pouring or laying the mixture, it is necessary to prepare the damaged area of \u200b\u200bthe coating. Preparatory work includes:
- Marking of repaired areas;
- Cutting out potholes to the full depth of the pavement, capturing at least 3 cm of whole asphalt around the pit (some technologies involve reusing the cut material);
- mechanical cleaning a cut-out recess from moving particles (using pneumatic, hydraulic and mechanical devices for removing debris);
- Impregnation of the walls and bottom of the recess with a special preparatory compound or bitumen (depending on the requirements of a particular technology).
Of course, the required amount and types of preparation depend entirely on the chosen method. For example, infrared repair is performed by heating the coating, does not require cutting a pothole.
Laying a section of a new coating
The appropriately prepared pavement is filled with asphalt concrete mixture according to the selected technology. The mixture is poured, poured or sprayed into the recess, and then leveled and compacted.
Road patching technology, which includes recycling, involves the introduction of crushed old pavement into a fresh mixture to reduce material costs. In the case of using the jet-injection method, all preparatory and basic processes are performed using one installation, but the method has its limitations.
After the repair is completed, the patch must become operational within a time period consistent with the characteristics of the material used.
Asphalting with hot mixes
Hot mix asphalt can be free-flowing or flowable. Laying the heated material ensures its increased adhesion to the base.
Asphalt for casting has a pasty consistency and fills the unevenness of the base under the influence of gravity. In addition, poured asphalt does not require mechanical compaction, since it acquires the necessary density during the cooling process. On the other hand, such asphalt softens during the hot season, which leads to the formation of ruts.
Loose hot sweep of bitumen with aggregate of a certain fraction and type (sand, crushed stone) have their own advantages. First of all, not expensive transportation. At the same time, the technology of laying loose hot mixes involves the use of vibrotamping hand-held units or massive rollers, which complicates the process and increases the time spent on work.
Stored cold mix asphalts differ in paving temperature and, to a large extent, composition. Modified bitumen and special additives expand the range of climatic conditions, allowing asphalting at temperatures down to -10ºС. Moreover, the packaged organo-mineral mixture:
- Does not require special equipment (except for a gas burner for heating the surface);
- Can fit into potholes without pre-cutting;
- No special requirements for transportation;
- Does not require special qualifications of the workforce.
On the other hand, the laid and compacted organo-mineral mixture is characterized by low shear resistance, which does not allow it to be laid in places where vehicles decelerate. The combination of price and quality of the material characterizes it as a means to quickly eliminate potholes when winter comes, that is, outside the traditional roadworks season and a means of preventing damage from increasing in winter.
Injection or jet-injection method - special case work with cold asphalt mixes. Appropriate installations (for example, UYAR-1 or foreign analogues) allow you to quickly repair small and medium damage to the road surface even without cutting. A single unit performs all the preparatory and main stages of the repair, and additional compaction is not required due to the application of the mixture under pressure.
There are several types of cold mix asphalt:
- With emulsion for immediate use. Mixtures of this type, as a rule, are used for repairs by the injection method. A portion of the prepared mixture is placed in the tank of the unit before the start of the shift.
- Emulsion mixtures with mineral additives.
- Packaged stored organic mixture. In packaged form, such a mixture can be stored for up to 8 months and retain its properties after breaking the packaging for up to two months.
There are other, highly specialized types of mixtures, but they are used much less frequently than those listed above.
Quality control
After the patching of the road surface is completed, visual and instrumental quality control (GOST 310515, SNiP 3.06.03 and others) of the patch is carried out according to the following parameters:
- strength;
- Coating thicknesses;
- The presence of defects (drawdowns, etc.)
- planes;
- Coating roughness.
The results of the control are compared with the regulatory documentation, and based on the comparison, the quality of the work is determined.
| Product type | Name of product | Unit | Price, rub | |
|---|---|---|---|---|
| cold asphalt | Cold asphalt 30 kg for orders over 1000 kg | mesh. | 350 rub. | |
| cold asphalt | Cold asphalt 30 kg for orders over 1000 kg | mesh. | 320 rub. | |
The current repair of the asphalt concrete road surface is designed to restore the damaged sections of the roadway. Work begins with a survey of the condition of the road and the identification of damaged sections. This is followed by spot or complete dismantling of the old pavement.
Dismantling is carried out using manual pneumatic and power tools (jackhammers, cutters), or specialized machines (excavators and seam cutters). The destroyed part of the coating is removed and the base is prepared for laying a layer of a new coating, cleaning it as much as possible from crumbs and dust.
patching
Distinguish between overhaul and patching of asphalt concrete pavements. The purpose of patching is to eliminate damage to the road surface that is small in area and thickness.
Repair work must be carried out in compliance with the requirements of laying technology, taking into account temperature and humidity. So, patching with cold and hot asphalt and asphalt concrete can be carried out under various weather conditions. Basically, asphalt is restored using the technology of patching asphalt roads by the method of reverse impregnation, in which, first, bitumen heated to 170 degrees is fed into the pit, then the pit is covered with crushed stone and tamping is carried out. In case of severe damage, equipment for patching by the jet-injection method will eliminate defects with high quality.
TO damage pavement includes:
- potholes;
- cracks;
- chipped.
Crack repair
Sealing of cracks refers to the current repair of the road and is an important part of it. The elimination of cracks can significantly extend the life of the pavement and prevent its further destruction. The technology of work involves three stages:
- crack cutting - a special cutting tool cuts out the collapsed edges of the crack (without water supply), the crack is slightly expanded and deepened;
- blowing and drying - the resulting cut in the roadway is blown and dried to remove dust and moisture;
- sealing - the cut is filled with hot mastic using special melting pots and a supply system.
As it hardens, the mixture adheres to the walls of the incision and forms a durable surface.
Asphalt paving
Forming the surface of the road from asphalt chips is a practical and inexpensive way. The crumb itself is obtained in the process of recycling old asphalt pavements, so it has good characteristics and at the same time is affordable. Asphalt crumb is used on unloaded roads (for example, in garage or country cooperatives) as a better alternative to a dirt road.
Laying is carried out by analogy with backfilling with gravel: the base is leveled, asphalt crumb is brought in and crumbles in an even layer. Then it is rammed with a roller, or rolled already in the process of operation by the wheels of machines.
Capital repairs of roads
The overhaul of a highway is a rather difficult and costly business. In the case of asphalt concrete pavements, this may include:
- complete dismantling of the old coating;
- replacement of worn out and destroyed elements of the drainage system;
- strengthening works and restoration of the base of the roadway;
- installation of a new continuous road surface.
Unlike routine repairs, major repairs to a well-done road are rarely needed. Of all the options for current road repair to cost overhaul only the price of patching the road surface with poured asphalt is close.
Installation of boards and curbs
Laying roads and sidewalks often requires the installation of curbs - boards and curbs. They serve as roadway dividers, separate platforms and lawns. Installation is carried out in several stages:
- marking and breakdown of the site;
- land management works - the device of troughs;
- dumping the base from crushed stone according to the level;
Of the technological processes of current repair, the most common are patching technologies. In turn, the most popular methods include laying the following repair materials:
1) fine-grained asphalt concrete mixtures;
2) cast asphalt concrete;
3) emulsion-mineral mixtures.
patching consists of the following main operations:
- formation of a patching map, i.е. rectangular cutout of the AB coating using a milling cutter or a jackhammer;
- cleaning the map with compressed air using a compressor or pneumatic vacuum sweeper (if necessary, washing with water followed by drying with compressed air);
- priming of card surfaces with bitumen or bitumen emulsion;
- laying the AB mixture and filling the repaired card with a margin for compaction;
- compaction of the laid mixture with a vibrating plate or a vibrating roller.
To ensure the comprehensive mechanization of patching work using the specified repair materials, specialized machines or sets of machines and additional equipment are used that ensure the performance of all or some of the patching operations.
These machines are classified according to the type of repair work, the type of working equipment and its drive, as well as the method of movement. Table 8.1 presents options for sets of domestic machines and equipment for patching and repairing cracks.
For patching, hinged cutters based on a pneumatic wheeled tractor are used. They are divided according to the following main features:
1) by appointment- for cutting cracks and making a map;
2) by milling drum drive- with mechanical and hydraulic drive;
3) by drum type- with fixed and movable in the transverse direction;
4) by type of support device- with support rollers and sliding traverses.
Figure 8.1 shows the structural diagram of the cutter type "Amkodor 8047A". The cutter with a fixed drum 2 is attached using frame 3 to rear axle tractor MTZ-82. The drive of the working equipment is carried out from the power take-off shaft of the tractor through the bevel and cylindrical gearboxes. In the working position, the milling equipment rests on two support rollers 1, which increases the accuracy of technological operations. The position of the cutter (raise-lower) is controlled by two hydraulic cylinders 4. The machine is equipped with a water cooling system with forced water supply. Its productivity is up to 2000 m3 per shift with a milling width of 0.4 m.
Figures 8.2 and 8.3 show the structural and kinematic diagrams of a similar milling equipment(type MA-03 manufactured by Mosgormash), which is also installed on the chassis of the MTZ tractor. The milling drum 9 with the cutters 10 is attached with the support bracket 1 to the rear axle of the tractor (see figure 8.2).
The transfer of equipment from the transport (shown in the figure) to the working position is carried out using hydraulic cylinders 2 and a swivel bracket 3. Its drive includes a flange 12 mounted on the power take-off shaft of the tractor and a cardan shaft 11. Two support wheels 6 are installed on the traverses 5, which have the ability to move by means of a screw transmission 4 in a vertical plane relative to the drum.
The torque (see figure 8.3) from the power take-off shaft 1 of the tractor through the cardan shaft 3, bevel gear 4, 5 and final drive 8 is transmitted to the spindle 7 and the milling drum with cutters 6.
Table 8.2 shows specifications hinged milling cutters of small size manufactured by Amkodor on the chassis of MTZ tractors. They are mainly used for patching AB coatings or for other small road works.
As can be seen from the table, some models have cutters with a transverse movement of the drum.
Figure 8.4 shows a structural diagram of the cutter of the Amkodor 8048 A model with a transverse movement of the working body. The milling drum 9 with the help of hydraulic cylinders 7 can be installed within the dimensions of the guides 10 without changing the position of the tractor, which significantly expands the technological capabilities of the cutter when developing a map for patching. In the working position, the machine rests on traverses 5, which ensures the accuracy of the map. The drive of rotation and movement of the drum is carried out from the hydraulic system of the tractor. At the same time, the drum rotation frequency can be adjusted in the range from 0 to 1800 rpm with a maximum torque of up to 2.4 kN * m.
When evaluating the main parameters of the cutter make traction and energy calculations, calculate the hydraulic system of the tractor, taking into account the presence of a cutter, and select hydraulic equipment to control the working bodies.
Traction calculation carried out on the basis of the analysis of the traction balance equation. The total resistance force includes the following resistances:
- milling of cold asphalt concrete
- movement of the tractor Wper.
Milling resistance (N) of cold asphalt concrete determined by the formula
Movement resistance tractor (H)
To overcome the resistance forces that arise during the operation of the machine, the condition must be satisfied
Knowing the power of the power plant, it is possible to determine the thrust force from the expression
Tractor power plant power general case is spent on the drive of the movement mechanism and the drive of the milling drum.
Power (kW) of the drive of the moving mechanism
Power (kW) cutter drive evaluated according to the formula
Machines for laying fine-grained AB mixtures work according to the method of "hot" restoration of coatings. They have different sets of additional equipment, as well as various working bodies that distribute the mixture (spreading disc, distribution trolley with a tray or unloading auger).
The simplest design is the combined road machine (KDM), shown in Figure 8.5, which allows you to implement only one repair operation - the distribution of the mixture using a spreading disc 6. It is a body 1 mounted on frame 3, which is attached to the vehicle chassis when help of stepladders. The material is transported from the body by a chain conveyor to the tailgate, which is equipped with a gate valve that regulates the flow of material. Then it falls on the spreading disc and is distributed over the treated surface. The drive of the conveyor and the spreading disc is carried out by hydraulic motors from the hydraulic system of the base chassis.
The body for the material does not have the possibility of heating, which leads to a rapid cooling of the AB mixture. In addition, the uneven supply of material using the disc requires additional use hand tool to fill the card with the mixture. Therefore, machines of this type are mainly used for winter maintenance of roads (for spreading anti-icing materials), completing them with a snow plow.
More wide opportunities have DE-5 and DE-5A vehicles, as well as MTRD and MTRDT mounted on a truck chassis. They differ from each other in the type of drive (electric or pneumatic) of the additional working equipment, which allows most patching operations to be carried out.
Figure 8.6 shows the structural diagram of the DE-5A machine. It contains a hopper-thermos 1 for hot AB mix, equipped with a distribution cart 9 for material, containers for mineral powder 14 and bitumen emulsion 16, as well as gas equipment (gas cylinders 11 with a pressure regulator) with a block of infrared radiation burners 12. The transfer of the thermos hopper from the transport to the working position is carried out by a hydraulic drive. Machine DE-5A has pneumatic drive working equipment (from the compressor). The drive 6 of the compressor 3 is carried out from the engine of the base chassis through the power take-off, gearbox, cardan and belt drives. A hydraulic pump is installed on the compressor drive gearbox, which ensures the operation of the hydraulic equipment of the machine.
The DE-5 model differs from the DE-5A model by the presence of an autonomous power generator set to drive the working equipment (compressor, electric vibratory roller, electric jackhammer). The drive of the working equipment is carried out from asynchronous three-phase electric motors with squirrel-cage rotors.
The design of these machines allows you to repair the coating in two ways:
- firstly, by the "hot" method - heating the repaired area to a temperature of 120-160 ° C with IR emitters, followed by mixing the heated mixture of the old coating with a portion of the new mixture from the hopper-thermos, leveling and rolling with a manual vibratory roller;
- secondly, by the "cold" method - by mechanically cutting out the old coating, cleaning the resulting map with compressed air and filling the pit with a new mixture from a thermos hopper, followed by compaction of the mixture with a hand roller.
The MTRDT and MTRD machines have approximately the same technological capabilities. Figure 8.7 shows a structural diagram of one of them. It is also equipped with a hopper-thermos 2 for hot AB mixture with a distribution trolley for the material, as well as a heated tank 8 for bitumen with a device for mixing it. In addition, the MTRDT machine is equipped with an electric generator 4 driven by the base chassis engine, which provides power to the working equipment (compressor, electric jackhammers, electric vibration rammer, electric vibration roller). The drive of the electric generator is carried out from the engine of the base chassis through the power take-off, cardan and V-belt transmissions.
The working equipment allows repairing the AB coating in a “hot” way using an electric heater and an electric iron. Pothole repairs are carried out by cutting and heating the old pavement, cleaning the map from cut-out fragments of asphalt concrete with a manual scraper and compressed air, treating the pit with sprayed hot bitumen, laying a new AB mixture and compacting it, followed by soldering the new and old pavement along the contour of the map.
The MTRD machine has a compressor that supplies the working equipment with compressed air. In addition to these machines, in the CIS, ED-105.1 and ED-105.1A models for patching are produced, which differ in the type of base chassis and a set of working equipment. The design of both models includes a thermos hopper for hot AB mixture and a bitumen boiler, a compressor, a pneumatic tool (jackhammer) and a bitumen sprayer, as well as an additional cabin for transporting service personnel. To compact the laid mixture, the ED-105.1 model has a vibrating plate with an autonomous drive, and the ED-105.1 A model has a manual roller. The model ED-105.1 also includes an edge cutter.
Along with these machines, the country's road enterprises operate imported equipment, the technical characteristics of which are given in Table 8.3. The machines of leading manufacturers usually contain the previously mentioned set of main units and additional working equipment. For example, a TR-4 machine is mounted on a truck chassis with a carrying capacity of at least 10 tons. The main mechanisms and units are driven from hydraulic systems, and compressed air is supplied from the pneumatic system of the base chassis. Among the main units of the machine:
- hopper-thermos for AB mixture, having two heating systems (gas and electric) and equipped with a stirrer for mixing and auger for unloading the mixture:
- heated tank for bitumen emulsion with spray system;
- a device with a container for collecting crushed old asphalt concrete;
- hand burner to remove moisture and heat the edges of the card;
- hydraulically controlled lifting platform with a jackhammer for cutting out the edges of the card and a vibrating plate for compacting the laid mixture;
- manual sprayer with a nozzle for spraying bituminous emulsion for priming the surfaces of the pit.
An important problem is the processing of old asphalt concrete granulate, which is formed when cutting out maps of a repaired pit and milling a damaged pavement. For this, special equipment is produced, including small-sized recyclers, which are produced in our country and abroad. For example, the PM-107 asphalt concrete regeneration plant (manufactured by Beldortechnika) is mounted on a trolley trailed to a tractor or truck. It is equipped with a rotating heat-insulated container, in which the granulate is heated with the addition of bitumen and mineral material (crushed stone, screenings), as well as mixing the resulting mixture. The container has a loading hopper on one side, and an unloading window with a valve on the other, through which the prepared mixture is unloaded into a distribution trolley or directly into the repaired pit. The container is rotated by a hydraulic motor from a hydraulic pump driven by an autonomous engine. To heat the mixture, a burner operating on diesel fuel is installed in the front of the tank. APA-1 asphalt concrete processing units (Volkovysk Plant of Roofing and Construction and Finishing Machines) have a similar design scheme.
The main technical characteristics of domestic recyclers for the processing of asphalt granulate are shown in Table 8.4.
Machines for patching by laying poured asphalt concrete also work on the method of "hot" restoration of coatings.
For patching by laying poured asphalt concrete, thermos-mixers are used - heat-insulated heated bins equipped with mechanisms for mixing and unloading poured asphalt concrete mix. It is advisable to classify them according to the following criteria:
1) by size(m3) - small (≤ 4.5), medium (up to 9) and large (≥ 9) capacity;
2) according to the location of the mixer shaft- horizontal and vertical;
3) according to the type of mixer drive- with mechanical from an autonomous engine or hydromechanical from the hydraulic system of the base chassis;
4) according to the cyclical work- with continuous, batch and combined issuance of the mixture;
5) according to the shape of the container- trough-shaped and barrel-shaped.
They are mounted on a car chassis of the appropriate load capacity.
Road organizations of the country operate thermos mixers from various manufacturers. Their main technical characteristics are given in table 8.5.
A typical design of a thermos mixer (model ORD) is shown in Figure 8.8. The machine has a tank 4 insulated by a casing 3 with a mixer 5. The tank is heated through flame tubes 6, 7 by two automatic heaters 15 that run on liquid fuel. Hydromechanical drive 10 from an autonomous engine 13 provides reverse rotation of the mixer shaft 5. Changing the position of the container is carried out using two hydraulic cylinders of the lift 14. Due to the possibility of reversing the mixer during transportation, the mixing of the mixture is accompanied by its injection to the front wall, and during unloading - to the back, where the hole is located for unloading, equipped with a gate valve.
The technological capabilities of thermos-mixers are significantly expanded in the presence of a combined system for dispensing the mixture both by batch and in-line methods. Such a system allows them to be used both for patching and for the overhaul of road surfaces. In a number of models of thermos mixers, a duplicated drive is provided, which significantly increases the reliability of the machine and allows you to choose the optimal mode of operation of the mixer, depending on the technological task. Some models, shown in Table 8.5, have a system of stepless regulation of the speed of the mixer shaft, which allows you to effectively mix organic and mineral binders with various materials, including those with mineral fillers, reclaimed asphalt granulate, rubber and polymer modifiers.
Machines for patching by laying emulsion-mineral mixtures implement the method of "cold" restoration of coatings. In the production of patching of roads by laying emulsion-mineral mixtures (EMS), the following are used:
- laying pre-prepared EMS;
- mechanized laying of EMS when mixing components in the working body of the machine.
For laying pre-cooked EMS(packaged or prepared directly at the work site) the following machines and equipment are used:
1) stationary or mobile installation for the preparation of the mixture;
2) a compressor with a set of jackhammers or a road mill for cutting the edges of the pit;
3) equipment for laying EMC in the pit;
4) a vibrating plate or a manual vibratory roller for compacting the EMC laid in the pit;
5) a vehicle for transporting EMS from the base to the work sites.
For mechanized installation of EMC(according to the second method) use the following technique:
1) compressor or road milling machine;
2) a machine for preparing, stacking and sealing EMC;
3) vibrating plate or vibrating roller.
Mechanized laying is carried out by pneumatic transportation, combination and distribution of EMC components (this type of laying is called the pneumatic spray method). Its essence lies in the fact that the combination of components is carried out in a machine during the transportation of bitumen emulsion with compressed air from a compressor at a pressure of up to 1 MPa. As a result, an emulsion cloud is formed in the spray nozzle of the working body of the machine, passing through which the crushed stone particles are enveloped in the emulsion. The treated particles at the outlet of the nozzle have a speed of up to 30 m/s, which ensures good seal repair material in the pit.
Machines for mechanized laying of EMS combine several technological operations of patching. All main operations (preparation of the mixture, its laying in the repaired pit and compaction) are carried out by air flow. The working equipment of machines for mechanized laying of EMS includes bins for mineral materials (crushed stone of various fractions) and bitumen emulsion, a system for pneumatic supply of initial components (mineral materials and bitumen emulsion) to the laying area, their distribution and compaction.
The equipment of these machines can be classified according to the following main features:
1) according to the way the working equipment is located- mounted, trailed and semi-trailed;
2) blower drive- from an autonomous power plant or from the power take-off shaft of the base chassis;
3) according to the complete set of auxiliary equipment- with a device for cleaning crushed stone, with a system for modifying crushed stone, with a compaction device (vibration or pneumatic rammer, manual roller).
The main technical characteristics of machines and installations for patching by mechanized EMC laying are presented in Table 8.6. The designs of these machines differ in the sets of components and the location (mounted, trailed and semi-trailed) of the working equipment units. An example is the installation of the German company "Schafer", which includes a two-section bin for crushed stone mounted on a trailer chassis, separate tanks for water and bitumen emulsion, a diesel engine that drives the hydraulic system of augers for supplying crushed stone from the bunker to the crushed stone pipeline, a pneumatic system compressor and a blower. It creates an air flow, with the help of which the crushed stone is fed through the crushed stone pipeline to the working body (nozzle) and mixed with the bitumen emulsion supplied by the tank with a diaphragm pump. The resulting EMS is continuously placed in a repaired pit, previously cleaned with water from dirt and weeds.
The durability of asphalt concrete during patching increases significantly if the initial components are pre-activated before mixing. In particular, the treatment of crushed stone with anionic surface-active substances (surfactants) significantly improves the physical, mechanical and operational properties of EMS by enhancing the adhesive interaction between the mineral material and the binder.
The implementation of activation processes when mixing EMC components was carried out in the design of the device, which is aggregated with machines for patching. It is a paddle or screw feeder, in the body of which surfactant supply nozzles are mounted. The activation of mineral components in this device is carried out by mixing them with surfactants, followed by treatment with a binder.
Figure 8.9 shows a structural diagram of a universal patching machine equipped with an activation device. The machine consists of a metal structure that forms a bin for crushed stone 1, tanks for water 2 and bitumen emulsion 3. It can be installed on the chassis or in the back of a vehicle 4. An auger 5 is installed at the bottom of the bunker driven by a power plant 6. Crushed stone is fed by an auger from hopper into the receiving tray 7 and then by the air flow through the crushed stone pipeline 8 into the nozzle 9. The air flow is created by a blower driven from the power plant 6. At the same time, a bitumen emulsion is supplied under pressure from the tank 3 through the pipeline 10 into the nozzle. In nozzle 9, crushed stone is mixed with bitumen emulsion. As a result, the mixture is continuously placed in the repaired pit and compacted in it. The machine provides for the possibility of cleaning the pit with water that enters it: from tank 2 through pipeline 11. The machine has an activation device 14, in which surfactant crushed stone is processed. The liquid activating agent is located in tank 12, connected by pipeline 15 to nozzles 13, through which it is sprayed, mixing with crushed stone in activator 14.
The drive of units and assemblies of the machine is carried out from an autonomous power plant or from the base chassis, which can be used as domestic MAZ-53373 or MAE-5337. In addition, a trailed chassis option is available, which is aggregated with a tractor of traction class 1.4. Mineral materials are loaded using auxiliary equipment, for example, an elevator or a hydraulic manipulator equipped with a grab.
The machine has advanced technological capabilities. It can also be used for the distribution of anti-icing materials (both liquid reagents and sand-salt mixtures) in winter. To do this, instead of a nozzle, a spreading disc is installed, onto which a sand-salt mixture is fed from the bunker by a screw conveyor, and in the case of using liquid reagents, they are filled into the tanks of the machine and fed to the treated strip using pumps.
operational performance(m/h) machines for maintenance are determined by the formula
Total time to repair (s)
Auxiliary time
The time spent filling the bunker,
The number of fillings of the bunker with the mixture, necessary to carry out the work,
Means of small mechanization. The specificity of patching (small volumes and a large number of objects) determines the technological and economic necessity of using small-scale mechanization. Among them are cutters and joint fillers, vibrating plates and vibrorammers, as well as other small-sized equipment.
Seam cutters. In patching, joint cutters are used to cut out the edges of the repaired pits and cut cracks. It is advisable to classify them according to the following main features;
1) by motor power (kW)- light (up to 15), medium (up to 30) and heavy (up to 50);
2) by way of movement- manual and self-propelled;
3) according to the type of drive of the working body- with mechanical, hydraulic and electric drive;
4) by type of working body- with a cutting disc and with a thin cutter.
The main element of the seam saw is the working body - the cutting disc (or milling cutter), which drives the power plant - the internal combustion engine, Electrical engine powered from the mains (or from a stationary source) or a combined power plant (ICE - electric drive or ICE - hydraulic drive).
For patching, mainly hand-operated cutters with a mechanical drive are used. Self-propelled machines are used for large-scale road works, including for cutting grooves of expansion joints in the CB coating.
The simplest design is mechanically driven seam saws. Such a cutter (Figure 8.10) is a trolley, on the frame 1 of which an internal combustion engine 6 is installed, which drives through the transmission (clutch and V-belt drive 5) the cutting disc 3, the position of which is adjusted manually lifting mechanism 8. The movement of the cutter when cutting the coating is carried out by the operator manually. The cutting disc is set to the required cutting depth manually by mechanism 8. The disc is closed by a protective casing 4 with a tube through which water is supplied from tank 7 to cool the disc. Removal of dust and cutting products from working area can be done with a vacuum cleaner, additionally mounted on the frame.
Two types are used as a working body in cutters cutting tool: firstly, diamond-segment cutting discs (i.e., diamond-coated discs), which are combined in a package to provide the required width of the groove; secondly, cutters with the required width of the cutting edge of the teeth made of carbide materials or with a diamond coating.
In Belarus, seam cutters are manufactured by Beldortekhnika. They are also produced as plug-in adapters for universal power modules, for example, for the Polesie-30 power facility (manufactured by the GSKB of the Gomselmash association). Leading manufacturers of road equipment produce several sizes of floor saws, differing in the type and power of the engine, the diameter of the cutting disc and the depth of cut. Among them are Cedima, Stow and Breining (Germany), Dynapac and Partner (Sweden) and others.
When cutting material with cutters equipped with hard-alloy teeth, crushing and even pulling out of large grains of crushed stone from the edge of the crack being cut occurs, which is accompanied by a decrease in the strength characteristics of the coating in this zone. Therefore, it is advisable to use equipment with carbide tools when cutting cracks in asphalt concrete with a maximum aggregate size of no more than 10 mm. When cutting with a diamond tool, this problem does not arise, since in this case the crushed stone in the asphalt concrete is carefully cut.
Figure 8.11 shows a manual floor saw.
The speed of the working process of seam saws depends on the depth and width of cut, on the material being developed and is 30-200 m/h. If it is necessary to clean heavily contaminated cracks, disc brushes are used, which are installed instead of cutting discs.
Self-propelled floor saws have a hydraulic drive of the movement mechanism, which allows them to move in working mode at a speed of up to 480 m/h. The large mass provides them low level vibrations when working with carbide tools.
Calculation of seams includes the definition of basic parameters, power balance, etc.
The power (kW) expended on cutting the seam is determined by an empirical dependence that relates it to the dimensions of the groove being cut, as well as to the cutting speed:
You can check the correctness of the calculations of cutting power using the expression
The amount of coolant (l) is also estimated from the empirical dependence
Crack repair equipment. After milling and cleaning with a disc brush with a metal bristle, which is installed instead of a cutting disc on a seam saw, the crack should be prepared for subsequent filling with sealant, which includes drying and heating the seam.
For these preparatory operations, both specialized equipment and gas-flame welding, adapted for repair work, are used. Specialized equipment includes gas generators, which are equipped with a compressor, burner and cylinders with natural or other combustible gas. Through a controlled nozzle, they supply hot (200-300 °C) air into the crack cavity at a speed of 400-600 m/s. The result is not only cleaning and drying of the cavity of the crack itself, but also the removal of destroyed coating particles from the crack zone.
When using gas-flame installations, drying and heating of cracks is carried out by burners with an open flame, which leads to burnout of the binder and accelerated destruction of asphalt concrete in the crack zone.
The final operation to repair cracks is their sealing, which is carried out by special machines - joint fillers. It is advisable to classify them according to the following main features:
1) by drive type- self-propelled, trailed and manual;
2) according to the type of heating of the tank with sealant- heat transfer oil, combustible gas and diesel burner;
3) by the presence of a mixer- with horizontal and vertical shaft.
The pourer is a heated tank mounted on a frame equipped with wheels. The tank can be equipped with a mixer, as well as equipment (pump, communications, nozzle) for transporting the sealant to the crack. The sealant is loaded into the tank, heated to operating temperature, and pumped through a controlled nozzle into the prepared crack using a pump. The hydraulic drive of the mixer and the sealant supply pump from an autonomous power plant (internal combustion engine) through the hydraulic pump and the hydraulic motor ensures effective regulation of the sealant supply.
Figure 8.12 shows a structural diagram of a self-propelled joint filler, which is placed on a truck chassis. It is equipped with a pneumatic system with compressor 1; tank 2 for heating the sealant with nozzle 4 of the gas burner and communications; a sealant supply system, including a rotary rack 5 with a tubular beam, equipped with a pipeline 3; a drive for supplying air and sealant into the cavity of the seam. Cranes, pump and pipelines are also heated with hot gas. The compressor provides blowing and cleaning of the seam with compressed air, as well as its supply to the fuel injector. The compressor is driven from the vehicle engine through a power take-off gearbox. The heated sealant with the help of a pump through the pipeline and the nozzle enters the cavity of the seam. With the help of a turntable and a beam, the pipeline nozzle is moved along the seam to fill it.
After pouring, the crack is covered with a layer of sand or crushed stone of small fractions (5-10 mm) to create a protective rough wear layer, as well as to prevent bitumen from sweating. To perform surface treatment of cracks, there are manual crushed stone spreaders on pneumatic wheels, the main unit of which is a conical hopper with a damper to control the thickness of the spread material layer. The damper is controlled and the bunker is moved manually.
Table 8.8 shows the characteristics of some joint fillers.
Figure 8.13 shows a trailed joint filler manufactured by Beldortechnika. It is designed for heating and supplying bitumen-elastomer sealing mastics under pressure when performing work on sealing cracks, seams and waterproofing during repair and construction work on roads, airfield pavements, bridges, overpasses. It is equipped with two easily removable nozzles - for filling joints and for filling cracks.
Vibrating plates for compaction of road materials are self-propelled equipment. They are equipped with centrifugal vibrators - unbalance shafts as vibration exciter. When such a shaft rotates, a centrifugal force of inertia develops. Its projection on the vertical axis is the driving (disturbing) force, under the influence of which the vibrations of the vibrator and the plate itself occur. Vibrating plates are classified according to the following main features:
1) by size- light (weighing 50-70), medium (70-110) and heavy (more than 110 kg);
2) according to the type of vibrator drive- mechanical, hydraulic, electrical and pneumatic;
3) according to the nature of vibrations of the vibrator- with non-directional (circular) and directional vibrations;
4) by the number of vibrator shafts- one- and two-shaft;
5) according to the method of working movement single-stroke (with a stroke only forward) and reversible (with a stroke forward - backward);
6) according to the degree of autonomy- independent equipment or additional equipment for recyclers.
The principle of operation of centrifugal debalais vibrators - single-shaft and two-shaft - is shown in Figure 8.14. The most significant difference between these vibrators is the nature of the action of the centrifugal force of inertia. For single-shaft vibrators, the centrifugal force has a constant value and a variable direction, and for two-shaft vibrators, the centrifugal force has a constant direction and a variable value. In this case, the driving force of the unbalance shaft changes in time from zero to the maximum (amplitude) value equal to the centrifugal force.
For a single-shaft vibrator (Figure 8.14, a), the centrifugal force Q1 remains constant during shaft rotation, but continuously changes direction, creating circular non-directional vibrations. Its driving force at each moment of time is equal to the projection onto the vertical axis of the centrifugal force. Accordingly, the single-shaft vibrator transmits non-directional vibrations to the vibrating plate, which, in turn, transmits the vibrations to the material to be compacted.
For a two-shaft vibrator (Figure 8.14, b), both shafts are interconnected (for example, by gears) and rotate in opposite directions with the same angular speed. Due to this, the vertical components of the centrifugal forces are always directed in one direction, which provides vertical directional vibrations that are transmitted to the plate and provide a more efficient compaction of the material. In this case, the horizontal components of these forces (Q1 sin φ) are mutually balanced.
When the unbalance shaft rotates, the centrifugal force is determined by the formula
The driving force of the unbalance shaft corresponds to the vertical projection of the centrifugal force. For one- and two-shaft vibrators, it has different values.
For a single-shaft vibrator of non-directional action, the projections of the centrifugal force on the coordinate axes
Thus, the driving force (i.e., Qy) of the single-shaft vibrator changes in magnitude as the shaft rotates, which reduces the sealing efficiency.
For a two-shaft directional vibrator, the projections of centrifugal forces on the x and y axes
Comparing formulas (8.16) and (8.17), it is easy to verify that the total driving force of a two-shaft vibrator is much greater than this parameter of a single-shaft vibrator.
The two-shaft vibrator is mounted on reversible vibrating plates. If the axis of the centers of the shafts is horizontal, the plate will work in place, making vertical vibrations under the action of the force Oy. If the axis of centers is set at an angle to the vertical, the plate will move in the direction of deviation of the axis of centers.
Table 8.9 shows the influence of the standard size of single-stroke and reversible vibratory plates on the thickness of the layers of AB mixtures they compact.
Table 8.10 compares the operational characteristics of vibrating plates and vibratory rollers depending on their main parameter - mass. As can be seen from the table, in terms of performance, the plates are significantly inferior to the rollers. Therefore, they are used for small volumes of road works, i.e. where high productivity is not required: firstly, during patching; secondly, when sealing trenches crossing the coating; thirdly, when compacting crushed stone and granulate, which are used to strengthen roadsides; fourthly, when compacting the lower and upper layers of pavement when widening the carriageway in places of short length (at interchanges, bus stops, etc.).
The vibrating plate (figure 8.15) is a working plate-pallet 1 with a vibrator 2, which is equipped with a sub-frame 4, an engine 5, a transmission 3, a suspension system 7 and a control mechanism 6. This figure shows circuit diagrams a single-pass plate with a non-directional vibrator (a) and a reversible plate with a directional vibrator (b).
The working movement (self-movement) of the single-stroke and reversible vibrating plates occurs as follows. A vibrating plate with a single-shaft vibrator can only move forward by installing a vibrator with an offset relative to the center of inertia of the plate (Figure 8.15, a). A vibrating plate with a two-shaft vibrator can work in place, as well as move forward or backward depending on the position of the axis of the centers of the unbalanced shafts (in the position shown in Figure 8.15, b, the plate moves to the left). The position of the axis of the centers is changed with the help of an adjusting rod (not shown in the figure). The turn and control of the movement of the plate is carried out using the handle 6.
mechanical drive The vibrator consists of an air-cooled internal combustion engine and a transmission (clutch and V-belt drive).
Hydraulic drive, which have heavy vibrating plates, includes an internal combustion engine, a hydraulic pump, a hydraulic motor, a hydraulic distributor, a tank for working fluid and communications.
Pneumatic drive contains a pneumatic motor, a pneumatic distributor and communications through which compressed air is supplied from the compressor unit.
Figure 8.16 shows the structural and kinematic diagrams of a self-advancing vibrating plate with a mechanical drive of a single-shaft vibrator. It contains the following assembly units: plate 1, vibrator 3, sub-frame 5, capstan 2 with pulley 15, motor 6 and clutch 32. The trough-shaped steel plate 1 is a sealing working body. In its front part there is a platform for fastening the capstan drive 2.
A vibrator 3 is installed on the plate, the body 19 of which is bolted to it. The main shaft of the vibrator 33 has four unbalances - 20, 21, 26 and 27.
The internal combustion engine 6 through the bevel gear 18, cardan gears 17 and 31, as well as through V-belts 16 and 29 drives the vibrator shaft 33. The average unbalances 21 and 26 rotate in the direction opposite to the direction of rotation of the extreme unbalances 20 and 27, thanks to the gear mechanism in the vibrator housing. With the initial location of the mass of unbalances exactly in the vertical plane (relative to the shaft 33), the plate oscillates only in the vertical direction. When the unbalances are displaced relative to the shaft 33 in terms of forward, backward and in different directions, the plate will move forward, backward or around the axis, respectively.
The operation of the vibrating plate is controlled manually through two gears using handwheels 23 and 24.
To dampen vibrations and eliminate their impact on the engine, the frame 5 is equipped with an elastic suspension of a hinged design, which has horizontal 7 and vertical shock absorbers 4 and 11.
Table 8.11 shows the main technical characteristics of the most common vibrating plates of various sizes.
Domestic enterprises have also launched the production of vibrating plates. For example, the Beldortekhnika machine-building enterprise produces two models of vibrating plates PV-1 and PV-2 (weight 70 and 120 kg); The Mogilev plant "Strommashina" produces vibratory plates of the UV-04 model (weighing 233 kg) driven by a 4.4 kW engine; Gomel SKTB "Technopribor" - light vibrating plates driven by a pneumatic motor.
Calculation of vibrating plates. The main characteristics of vibrating plates include gravity and working area dimensions, oscillation frequency and driving force, engine power and travel speed. Usually, most indicators are chosen on the basis of experimental data.
The gravity of the vibrating plate is chosen according to the static pressure
The dimensions of the plate are associated with the thickness of the compacted layer. In particular, the relation
Based on experience, it is recommended to take
In addition, to estimate the mass (kg) of the vibrating plate, the expression is used
To check or determine some characteristics, you can use the well-known rule about the equality of the static moment of an unbalanced vibrator and the static moment of a vibrating plate when compacting a material of a given thickness.
Static moment (N*m) of unbalance shaft
Static moment (N*m) of vibrating plate
From the equality of these moments, it is possible to determine the geometric characteristics of the unbalance.
The greatest compaction effect is achieved in those cases when the frequency of the forcing vibrations of the plate corresponds to the frequency of natural vibrations of the compacted material.
In some cases, it is necessary to determine the speed of movement (m/min) of the vibrating plate. To do this, you can use the formula
For each material, the optimal frequency of unbalance and the speed of movement of the plate are selected experimentally. The maximum speed of self-movement of the plate corresponds to the angle φ = 45...50°.
The unbalance rotation frequency (rpm) can be determined using an empirical dependence through the thickness of the compacted layer (m):
Engine power plate is spent on its movement Ntrans, on the drive of the unbalance shaft Npr and on overcoming the friction forces Npc in its supports (bearings):
Power (W) spent on movement,
The total force of resistance to movement ΣW of the plate consists of the following components:
1) movement resistance(H) vibrating plates on the surface of the mixture
2) drag prism drawing(H) mixtures in front of the stove
3) inertial force resistance (N)
Power (N) spent on the drive of the unbalance shaft,
The calculated oscillation amplitude (hell) of the unbalanced shaft can be determined through the amplitude of plate oscillations necessary for compaction:
Power (N) expended to overcome friction forces vibrated in bearings, determined by the formula
The consumer properties of a highway are, first of all, speed, continuity, safety and convenience of movement, throughput and load levels. Prompt, timely and high-quality elimination of constantly arising defects on roads is the main goal of services involved in the maintenance of country roads and the road network of cities. The coating should not have subsidence, potholes, cracks and other damage that impede the movement of vehicles and affect road safety. The limiting area of damage to coatings and the period for their elimination are given in GOST R 50597–93.
The impact of dynamic loads from the movement of modern cars on road surfaces, and, consequently, the internal stresses arising in them are many times higher than those for which road pavements are calculated, which is why asphalt concrete layers wear out and age faster.
Depreciation occurs for various reasons, for example, due to the initially low quality of materials, violations of technology in the production of road construction works. Common mistake when installing non-rigid pavements, it is a failure to comply with the required temperature regime asphalt concrete mixture and, as a result, poor compaction, which is why during the operation of the road, irregularities, deformations, peeling, chipping, cracks, chips, potholes, pits are formed. But as experience shows, even if all the requirements of the standards are met and high-quality asphalt concrete is obtained on the pavement, it is impossible to prevent the development of deformations and damages that reduce the service life of pavements and the efficiency of road transport operation.
Maintenance
Annual maintenance of the pavement is required for 2–3% of the total pavement area. When serious damage and defects reach 12–15%, it is customary to repair 100% of the area.
The current repair of asphalt concrete pavements is carried out using various technologies and materials, which together determine the quality, reliability and cost, that is, the effectiveness of repair work. This type of repair includes the elimination of cracks, potholes, subsidence, restoration of the roughness and evenness of the coating, the installation of wear layers. At the same time, the main goal is to ensure safe and comfortable movement of vehicles on the road at the speed allowed by the rules of the road.
Repair of road surfaces is most often carried out in the warm season at a temperature not lower than +5 ° C and in dry weather. But if the resulting damage can lead to serious consequences, urgent unscheduled or emergency repairs do not depend on the time of year and weather conditions.
The choice of a technological method of repair must meet certain regulatory requirements and efficiency criteria for the timely elimination of defects on the road surface within the prescribed time frame and is the right and obligation of the customer and the manufacturer of the work. The elimination of the defect must be of high quality and correspond to the required indicators of density, strength, evenness and roughness of the main part of the coating. The repaired site as a result of properly carried out work and subject to all requirements will last long enough and will not create problems for the entire period between repairs.
patching
Asphalt concrete (up to 95–96%) is laid on the streets of Russian cities and on most roads with an improved type of pavement, so the main amount and the greatest variety of repair materials, machines and technologies relate to this type of pavement. The most affordable and common method of their repair is patching with hot mix asphalt due to the availability of materials and proven work technology.
An example of equipment for such repairs is the TEKFALT crackFALT joint filler, a reliable equipment for all installations for filling cracks in road and airport pavements. All types of installations are equipped with tanks with a capacity of 300 and 500 l and various optional equipment: double bitumen lance, flame tube with direct or indirect thermal heating, etc. This brand is represented on the market by the ISP GROUP, which is the exclusive distributor of TEKFALT MAKINA A.S. (Turkey).
The slow development of patching methods using emulsion-mineral, wet organo-mineral mixtures and cold polymer asphalt predetermines the wide availability of both raw materials for own hot mix preparation and products of asphalt concrete plants.
The quality and, accordingly, the service life of the repaired defective areas are related to the quality of the preparation of the card for repair, the delivery of the mixture at the proper temperature, the quality of the mixture compaction and, in general, compliance with the rules, requirements and technologies for conducting repair work. Properly performed preparatory work contribute to improving the quality of patching and guarantee the full operation of the road surface for 3–4 years or more. Pothole repairs performed without proper preparation will ensure the service life of the coating is 2-4 times less.
- Preparation of the repaired coating area includes the following operations:
- cleaning from dust, dirt and moisture;
- marking the boundaries of the repair with straight lines along and across the axis of the road with the capture of the undestroyed pavement layer by 3–5 cm, while several closely spaced potholes are combined with one contour or map;
- contouring the map with manual seam cutters, breaking and removing the cut material of the coating using a jackhammer with a flat tip (pothole area up to 2-3 m 2) or cold vertical milling of the repaired coating along the contour to the entire depth of the pothole, but not less than the thickness of the coating layer at areas of destruction;
- cleaning the bottom and walls of the repair site from crumbs, dust, dirt and moisture;
- treatment with a thin layer of bitumen or bitumen emulsion.
For example, high-quality preparation and subsequent repair of defective areas is provided by the TEKFALT combiFALT machine, which is a combination of a bitumen emulsion and bitumen distributor, a sweeper and watering machines. The capacity of emulsion and water tanks is 4000-8000 liters each. Productivity at distribution of an emulsion from 150 g/m 2 to 4 kg/m 2. Available water system dust suppression.
Transportation of the asphalt concrete mix during the execution minor repairs using a conventional dump truck is irrational. The mixture loses its plastic properties, it cools down, cakes and, as a result, fits and compacts worse, which leads to poor-quality repairs. In addition, often in the process of patching, a large amount of asphalt concrete mixture is not required.
Thus, it is advisable to deliver the mixture from the asphalt concrete plant to the place of work by a vehicle equipped with a special thermos hopper that keeps the mixture hot for several hours.
Repair machines
For patching with hot asphalt mix, special repair machines are used. A thermal container for hot asphalt mix with thermal insulation and heating is placed on the base machine; tank, pump and sprayer for bitumen emulsion; a compressor for cleaning and dust removal of repair cards and a jackhammer drive for cutting the edges of repair cards, as well as a vibrating plate for compacting the asphalt concrete mixture. Repairers have become widespread mainly due to the greater economic feasibility of their use.
Today, the use of road repairers with thermal containers for asphalt mix has proven to be beneficial and is widely used by road maintenance organizations that take their duties responsibly and try to carry out work with high level quality.
- The advantages of asphalt thermal container are as follows:
- maintaining the temperature of the asphalt mix, providing the possibility of its longer use without loss of chemical and physical properties;
- rational, economical use of asphalt concrete mix;
- absence of claims of the organizations performing the work against the producers of the mixture, since when performing repairs, a standard asphalt concrete mixture with operating temperature laying, which cannot be observed when the mixture is transported in the back of a dump truck;
- due to auger unloading, loosening the material, there is no compaction, which occurs when the mixture is transported in the back of a dump truck;
- no waste associated with the cooling of the material;
- the possibility of using the container for cold mixed material;
- the possibility of using a container for distributing fine gravel (fraction size up to 8 mm), sand or other dry road building materials;
- no need to distribute the material manually: thanks to the screw conveyor and the discharge chute, the material is dosed distributed over the map;
- reduction in the number of road workers involved in repairs;
- saving time when distributing material on the map;
- extension of the road construction season.
An example of domestic road repairers with an efficient thermos bunker with a capacity of 4 to 6 m 3 (approximately for sealing 80–100 potholes and pits about 100x100x5 cm in size) can serve as a model range of ED-105 universal machines.
The TEKFALT patchFALT asphalt pothole patching truck has a thermally insulated triangular bin with a capacity of 8–12 m 3 , which can be optionally supplemented with an oil heater, a feeding auger (which increases productivity) and a manual emulsion distribution system.
Cast asphalt concrete
The use of poured asphalt concrete provides greater durability compared to other types of asphalt concrete. It has a high density, is the most waterproof, more resistant to corrosion, and also less prone to wear.
Molded asphalt concrete differs from traditional asphalt concrete in its bitumen content increased to 7.5–10% (by mass) and the proportion of mineral powder increased to 20–30%. The content of crushed stone (grains larger than 5 mm) is from 0 to 50% by weight, which at a given concentration causes the formation of a semi-framework or frameless structure of asphalt concrete. The cast mixture is also characterized by more heat during preparation, transportation and laying in the road surface. The increased content of asphalt binder causes the poured mixtures to flow, thus eliminating the need for compaction of the laid layer. Molded asphalt concrete itself acquires the required density after cooling.
Despite the higher cost of the cast mixture (by 10–25%) due to the higher content of bitumen and mineral powder, its use in the repair and construction of road surfaces provides savings due to long terms services.
The production of cast asphalt mixtures is carried out on batch asphalt mixing plants. Their transportation to the place of laying is carried out in special vehicles. The finished mass of cast asphalt concrete in its consistency approaches a suspension in which mineral particles settle unevenly. The mixture that separates due to this quickly loses its homogeneity and becomes unsuitable for use. If you move such a mixture in conventional dump trucks, the delamination process is enhanced. Therefore, the transportation of the cast mixture to the place of laying is carried out in special heat-insulated mixers (thermos-mixers, thermos-bunkers), also called kochers (from German kocher - boiler, cooking apparatus), equipped with forced mixing systems and maintaining the set temperature. After delivery to the work site, the mixture in a heated state is unloaded onto the prepared base in a liquid or viscous consistency, followed by manual or mechanical leveling. Cast asphalt mix is laid at a temperature of 200 to 250 °C in a layer 2.0 to 5.0 cm thick. Thus, working with it requires more qualification of repair teams. This, along with the higher cost of the mixture, hinders the use of poured asphalt concrete.
An integral part of the technology for top layers of poured asphalt concrete pavements is the process of creating a rough surface to ensure the proper coefficient of adhesion by surface treatment. Under road operating conditions, surface treatment with crushed stone is also additional protection cast asphalt concrete from abrasive wear under the influence of studded car tires. On road surfaces, processing is carried out by embedding fractionated crushed stone with a particle size of 5-10 mm or 5-20 mm into the surface of a still hot asphalt concrete mixture, for which light smooth-roller rollers or hand-held vibrating plates are used.
Inkjet-injection repair
Jet-injection cold technology for sealing potholes on road surfaces using bitumen emulsion and stone material is now considered advanced and progressive, despite the fact that it has been used successfully in Europe and America for a long time. The main feature of this technology is that all the necessary operations are performed by the working body of one machine (installation) of a self-propelled or trailed type.
Inkjet pothole repair machines must be capable of repairing pavement damage in all weather conditions and without pre-training repaired area, which actually comes down to its thorough cleaning of dust, debris and moisture by blowing with a high-speed air jet, washing and treating the surface of the pothole with a bitumen emulsion.
Cutting, breaking or milling of asphalt concrete around a pothole can be omitted in this technology. When filling a pothole, it is filled with fine gravel mixed with a bituminous emulsion. Due to the entrainment and supply of crushed stone with an air jet, its laying in the pothole occurs at a high speed, which ensures good compaction.
The work can be divided into the following five stages.
– Dust removal. The place of repair is cleared, freed from pieces of asphalt, rubble, dust, dirt. In winter, heating is necessary.
– Priming of the repair site with bituminous emulsion.
– Filling the repair site with fine gravel, pre-treated with bituminous emulsion in the mixing chamber of the machine.
- Powdering with raw gravel.
– Sealing. This operation is not provided for by either the manufacturers of equipment or regulatory documents, but it has a positive effect. It is necessary to rationally compact the crushed stone in the pothole, and not only create a layer that is additionally compacted under the wheels of cars, as a result of which cracks may appear, which, during rain, are filled with water and broken by hydraulic shock.
For patching by jet-injection cold technology it is recommended to use clean fine crushed stone with a fraction of 5–15 mm and a rapidly decomposing cationic (for acidic rocks, such as granite) or anionic (for basic rocks, such as limestone) bituminous emulsion of 60% concentration.
The TEKFALT emulFALT machine is designed for the production of bitumen emulsion. The 30 kW high efficiency colloid mill, designed and manufactured by TEKFALT, guarantees excellent emulsion quality even with Pen 50/70 impregnating bitumen. The loading funnel with a capacity of 316 l is made of stainless steel. Models with a productivity from 2 to 30 t/hour are offered.
The consumption of emulsion for priming potholes and processing crushed stone in the mixing chamber of the machine can be approximately 3-5% by weight of crushed stone. Beforehand, the laboratory should check the adhesion of bitumen to crushed stone and the time of emulsion disintegration, which should not exceed 15-20 minutes. If necessary, make adjustments to the composition of the emulsion and adhesive additives.
- The unit can be permanently mounted on a trailer or on the chassis of MAZ, KamAZ vehicles. For patching by the jet-injection method, CJSC Kominvest-AKMT offers a model range of ED-205M machines. The machine includes:
- base chassis, KAMAZ-55111, MAZ-533603-240, trailer;
- two-section bunker for two fractions of crushed stone: 5–10 mm - 2.4 m 3, 10–15 mm - 2.4 m 3;
- heated and insulated 1300 l emulsion tank with emulsion level control in the tank;
- water tank for 1000 l;
- blower for pneumatic supply of crushed stone high performance(from 13 to 24 m 3 / min);
- two augers for supplying crushed stone from the compartments of the bunker to the pipeline with adjustable speed of rotation of hydraulic motors;
- two diaphragm pumps for supplying emulsion and water with adjustable pressure;
- economical air-cooled diesel engine with a power of 38 kW;
- a set of equipment with a gas burner for heating the emulsion;
- compressor with flow rate of 510 l/min and pressure up to 12 atm;
- two pressure regulators with manometers for water and emulsion;
- lightweight boom with pneumatic lift for work within a radius of up to 8 m;
- control panel to control technological process pavement repair for one operator;
- a circular circulation system that prevents the emulsion from solidifying in pipelines at low temperatures;
- a system that allows flushing and blowing pipelines of emulsion residues, pumping the emulsion into the tank using its own diaphragm pump, washing the bottom of the pit with water from clay and dirt under pressure up to 8 atm, moistening and washing crushed stone before feeding it into the pipeline to improve adhesion;
- crushed stone supply pipeline with a diameter of 75 mm and a length of 4.5 m, wear-resistant, seven-layer, with two strands of steel cord;
- removable nozzle with separate supply of water and bitumen emulsion.
"Slurry Seal"
All the previously described technologies and machines are designed for repair work when damage has already appeared on the asphalt concrete pavement. To prevent them, it is rational to arrange thin protective layers of cast emulsion-mineral mixtures.
An example of this is Slurry Seal, a technology originally from the USA. It can be equally successfully used in areas with both high and low traffic intensity. The essence of the technology is to apply an emulsion-mineral mixture of a cast consistency 5–15 mm thick to the surface of an existing coating. It does not require special compaction, hardens independently and is finally formed under the influence of traffic. The curing time of emulsion-mineral mixtures should be no more than 30 minutes. The time until the opening of traffic, depending on weather conditions, is no more than 4 hours. After the mixture has hardened, a dense layer with high adhesion is created on the surface of the coating.
The composition of the mixture in proportions selected in advance in the laboratory when designing the mixture includes stone material (crushed stone mixture 0–10 mm), cationic bitumen emulsion, cement and various additives. The emulsion acts as a "glue" and holds the hard aggregate together and also glues the "Slurry Seal" layer and old layer coating on which it was applied. Portland cement is used as a stabilizer or modifier. With the addition of water, the mixture is ready for application.
The Slurry Seal mixture comes in three types. The size of the stone material gives the pavement a different texture.
Type I - the smallest in terms of granulometric composition, is used for parking lots, roads with low traffic intensity.
Type II - has a larger solid aggregate and is used for all types of road works, including expressways, regional, republican, local roads.
Type III - stone material has the largest size and is used on national highways, highways, industrial areas. Usage various types stone material gives a darker or more light color coatings.
Preparation and laying of the mixture are made special machine or a set of machines, the device of the protective layer is carried out by a distribution box. When laying the mixture, the emulsion fills the cracks and minor defects in the coating. Slurry Seal pavement is arranged to prevent the influence of negative natural, climatic and technical factors on the pavement, which makes it possible to slow down the aging process of bitumen and significantly extend the life of the pavement, as well as a wear layer, providing the necessary grip properties of the pavement.
Protective maintenance is much more economical than repairing serious defects, but this layer must be reapplied, either in its entirety or by cards in areas with the highest traffic, after 2-5 years, depending on the volume of traffic. On roads with low intensity, the service life of the Slurry can be even longer, and during this period you can almost forget about patching. But the whole essence of the technology is to apply the emulsion-mineral mixture on a still strong and not destroyed coating without visible defects in order to “preserve” the top layer of the asphalt concrete pavement.
