A task patching consists in restoring the continuity, evenness, strength, adhesion and water resistance of the coating and ensuring the standard service life of the repaired areas. 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 duration repair work etc.
The traditional method involves trimming the edges of the pothole to give it 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. 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 of 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 work in cold weather with a wet and wet coating, but 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 based on the use of hot mix asphalt as a repair material: fine-grained, coarse-grained and sand mixtures, cast asphalt concrete, etc. The composition and properties of the asphalt concrete mixture used for repair should be similar to the one from 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 work on patching is carried out in early spring as soon as weather and surface conditions permit. In summer and autumn, potholes and pits are sealed immediately after they appear. Technology and organization of work different 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);
punching, breaking or milling damaged areas 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 repair material:
a - cutting of weakened places; 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 machine to cut a pothole, rounded front and back walls of the pothole are formed, which must be cut with a circular saw or a 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 preparatory work. 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 flexible hose large diameter directly into the pothole and 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 static smooth-roller rollers light type 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 pothole patches protruding 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 optimal 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 pavement, arbitrary map shapes in plan, insufficient compaction and poor connection of the repair material with the material of the old pavement, the presence of protrusions and sags on the edges of the map, etc. Under the influence of transport and climatic factors, the areas of such repair are quickly destroyed.
Pothole repair of black crushed stone or gravel coatings. When repairing such coatings, more than simple materials and repair methods that reduce the cost of maintaining roads with black gravel and black gravel coatings. 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 of these materials 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), mixed;
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 bitumen-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, the old coatings are scraped off and the 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 covered manually with rubble large size- 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 interacting with mineral material having natural humidity, foaming occurs with hot bitumen 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 thermally 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 of 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 the appearance of the patch repeats the outlines of the pothole.
patching asphalt concrete pavement 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. No work allowed gas burners at a wind speed of more than 6-8 m / s, when a gust of wind can extinguish the flame on some 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 of asphalt concrete pavements with the use of 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 repair using 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. 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 an emulsion from a spray ring, and from it the treated material is ejected at high speed into a pothole, 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, the payments are irregular shapes which degrades 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 the 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 easily 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 lies in the fact that the operations of 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 of fractions 3-10 in the amount of 85% by weight of the mineral material, screenings of 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 in the presence of 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.
The presence of a large number of patching methods 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.
ODM 218.3.060-2015
INDUSTRY ROAD GUIDELINE
Foreword
1 DEVELOPED by the Federal State Budgetary Educational Institution of Higher Professional Education "Moscow Automobile and Highway State Technical University (MADI)"
2 INTRODUCED by the Department of Scientific and Technical Research and Information Support of the Federal Highway Agency
5 INTRODUCED FOR THE FIRST TIME
1 area of use
1 area of use
2 Normative references
Thermal cracks occur as a result of cooling and resistance of the coating to thermal shrinkage. Vertically, these cracks develop from top to bottom, from the surface of the coating to the base.
Fatigue cracks that occur when a monolithic layer is bent from multiple transport loads develop from bottom to top from the base to the surface of the coating.
Reflected cracks replicate seams or cracks in cement concrete pavements and are most characteristic of asphalt concrete layers laid on a cement concrete pavement. With a decrease in temperature, the deformation of the cement concrete coating occurs in the form of a shortening of the slabs. As a result, joints or cracks in the cement concrete pavement expand, which leads to stretching and rupture of the overlying layers of asphalt concrete with the formation of reflected cracks. To these tensile stresses are added their own tensile stresses from a decrease in the temperature of the asphalt concrete. This is a time cyclic process leading to the destruction of the asphalt concrete pavement.
By width, cracks are classified into narrow (up to 5 mm), medium (5-10 mm) and wide (10-30 mm). This classification is typical for thermal and fatigue cracks. For reflected cracks, this approach is incorrect, due to the presence of thermal deformations of the underlying cement concrete pavement causing the crack edges to move depending on temperature, the length of the cement concrete slab, the thickness of the asphalt concrete pavement and other factors.
Depending on the width and type of cracks, the technology of their repair and the composition of the equipment used are selected. The main task in the repair of cracks is to prevent the penetration of water through them into the underlying layers of the pavement. Waterproofing of cracks is achieved by sealing them with special mastics and repair mixtures.
6.1.3 When choosing mastics, it is necessary to focus on their main physical and mechanical properties. One of the most important indicators for choosing mastics is adhesive strength, the requirements for which must comply with GOST 32870-2014.
6.1.4 Sealing narrow temperature or fatigue cracks on the surface of asphalt concrete layers laid on a cement concrete pavement does not require complex technological operations. Cracks are cleaned by blowing with compressed air, dried, heated and filled with bituminous emulsion or mastic with high penetrating power.
6.1.5 On thin temperature or fatigue cracks (2-5 mm), heated polymer-bitumen mastic can be applied in the form of a tape that prevents the coating from chipping at the edges of the crack. It is smoothed out with a special heating iron (shoe) and sprinkled with fractionated sand. The coating in the crack zone is preliminarily dried with a heated jet of compressed air.
6.1.6 If the crack has destroyed edges, the repair technology should begin with the operation of cutting it, that is, artificial expansion of the upper part of the crack with the formation of a chamber in which the sealing material performs optimally in tension during the crack opening.
6.1.7 The width of the chamber must not be less than the destruction zone of the crack edges. To create the best working conditions for the sealant in the chamber, the ratio of the width and depth of the chamber is usually taken as 1:1. In addition, when determining the geometric dimensions of the chamber, it is necessary to take into account the maximum possible crack opening and the relative elongation of the sealing material used. Typically, the width of the chamber is in the range of 12-20 mm.
6.1.8 If the temperature or fatigue crack is not cut to the full depth (the thickness of the cracked coating exceeds 10 cm), then before sealing, a special sealing cord made of an elastic material that is thermally and chemically resistant to the sealant and the environment is placed in the crack at the bottom of the chamber. When using a sealing cord for pressing in, it must be taken into account that its diameter should be 1.2-1.3 times the width of the chamber of the split crack.
The depth of the groove after pressing the sealing cord (upper free part of the chamber) is taken depending on the properties of the sealant.
Instead of a sealing cord, a layer of bituminized sand or a layer of rubber crumb laid on the bottom of the chamber, with a thickness equal to an average of 1/3 of its depth, can also be used, after which the chamber is filled with sealant.
When bituminized sand is used, coarse and medium sand is used that meets the requirements of GOST 8736-2014 and GOST 11508-74 *.
Rubber crumb must have particle sizes in the range of 0.3-0.5 mm and meet the requirements *.
________________
* See section . - Database manufacturer's note.
Depending on the stickiness temperature and the resistance of the sealant to wear under the influence of car wheels, it should be filled with underfilling, flush or with the formation of a patch on the surface of the coating.
6.1.9 In the case when the edges of a temperature or fatigue crack have not been destroyed and it is possible to seal the crack without cutting it, this operation can be excluded from the technological process.
6.1.10 The most important condition for ensuring the quality of crack sealing is the presence of good adhesion of the sealant to the walls of an uncut crack or a milled chamber. In this connection, much attention is paid to the preparatory work for cleaning and drying the crack. To improve adhesion, the walls of the milled chamber are primed with a primer - a low-viscosity film-forming (gluing) liquid.
6.1.11 The main technological operation in the repair of temperature or fatigue cracks is their filling with hot mastic. The mastic is preheated to a temperature of 150-180°C, after which it is fed into an arranged chamber or directly into the crack cavity. In this case, depending on the equipment used, it is possible to seal either the crack itself, or, simultaneously with filling with mastic, arrange a plaster on the surface of the coating in the crack zone. Such a patch 6-10 cm wide and 1 mm thick makes it possible to strengthen the edges of the crack and prevent their destruction.
Sealing with a plaster is advisable to use for cracks with significant destruction of the edges (10-50% of the crack length), because. in this case, the defects on the coating surface in the crack zone are healed.
The method of rehabilitation of medium and wide temperature or fatigue cracks in asphalt concrete layers laid on cement concrete is divided into five stages:
1. Cutting cracks. In this case, special crack separators are used. To avoid damage to the edges when cutting a crack in an asphalt concrete pavement, it is necessary when choosing cutting tool take into account the composition of asphalt concrete. With a grain size of crushed stone of 20 mm or more, it is recommended to use a diamond tool, and with a grain size of up to 20 mm, cutters with hard facing can be used.
2. Removal of destroyed asphalt concrete. For this, a high performance compressor is used. For thorough cleaning both from the dust that appeared as a result of cutting, and to remove deposits remaining in the depth of the crack.
3. Drying and warming up. The split cavity of the crack is dried and heated by the so-called thermal spear.
The parameter for stopping the heating is the appearance of melted bitumen cracks on the walls. In no case should the crack be overheated, bitumen burning will lead to a sharp decrease in adhesion and further destruction of the coating around the crack.
In this regard, crack heating with open flame burners is unacceptable.
4. Filling the crack cavity with sealant. In the cleaned, dried and heated cavity of the butchered crack, bituminous mastic from a melting machine.
Modern pourers in general form are a heated tank mounted on a frame equipped with a wheel drive. Heating can be carried out by means of an oil coolant, gas or a burner with diesel fuel. The sealing material is loaded into the tank, where it is heated to the operating temperature, and then, using a pump, it is fed into the prepared crack through heat-resistant hoses.
Direct sealing of cracks is carried out through various nozzles, the size of which depends on the width of the crack being filled. If necessary, the filling nozzle can be equipped with shoes for installation on the surface of the coating in the area of the crack in the mastic patch.
To reduce the dynamic load on the seam, and reduce the adhesion of the sealant to the wheel of a passing car, it is necessary to fill only the inner cavity of the crack without spilling on the edges.
5. Powder. Immediately after filling the crack with sealant, the repair site is covered with sand or a mixture of fine gravel with mineral powder from above.
6.1.12 For powdering, special equipment is used - a distributor. The equipment is a bunker mounted on three wheels. Moreover, the front, piano wheel allows you to move exactly in the direction of the crack, and a dosing roller is mounted on the axis of the rear wheels inside the hopper. The distributor is moved manually along the sealed crack, immediately behind the filler, while the wheels rotate the roller, dosing crushed sand or fine gravel onto the surface of the mastic poured into the crack.
The powder serves to restore the overall texture and roughness of the coating, prevents the mastic from sticking to the wheels of the car, and reduces the fluidity of the sealant immediately after the crack is filled.
6.1.13 When carrying out work on the rehabilitation of cracks, it is necessary to ensure the continuity of the technological process. Permissible time gaps between individual technological operations should not exceed the following values: 1 - crack cutting - up to 3 hours; 2 - crack cleaning - up to 1 hour; 3 - heating of the side walls of the crack - up to 0.5 min; 4 - crack sealing - up to 10 min; 5 - powdering the surface of the sealant with sand or fine gravel with mineral powder.
6.1.14 Crack repair technology is implemented by a set of equipment consisting of:
Crack splitter with a diamond tool with a pavement aggregate size of more than 20 mm, with a filler size of up to 20 mm, cutters with hard-alloy surfacing are used;
A mechanical brush or a wheeled tractor with a mounted brush (in the case when it is necessary to rehabilitate sufficiently wide and heavily contaminated cracks, they can be cleaned with disc brushes with metal bristles, brushes with a disc with a diameter of 300 mm and a thickness of 6, 8, 10 or 12 mm, the thickness should be 2-4 mm less than the width of the crack to be cleaned);
compressor;
Gas generator installation or thermal lance. The principle of operation of the thermal lance is based on the fact that compressed air from a compressor with a capacity of 2.5-5.0 m/min at a pressure of 3.5-12 kg/cm is mixed with natural gas and in the form of a gas-air mixture enters the combustion chamber, where it is ignited. Air heated to a temperature of 200-1300°C is fed through a nozzle at a speed of 400-600 m/s into the treated crack zone. The gas consumption in this case is 3-6 kg/h. A high-speed compressed air flow, in addition to heating, effectively cleans the cavity of the crack itself and, in addition, pulls out individual destroyed particles of the coating from the area adjacent to the crack;
Melting and pouring machine mounted on a car chassis;
Equipment for filling a sealed crack.
6.1.15 When repairing reflected cracks, first of all, it is necessary to establish whether the repaired crack belongs to the reflected type. Visually reflected cracks are easy to distinguish from temperature and fatigue cracks, as they pass over the joints of the underlying cement concrete pavement, as if "copying" them.
If there are cracks in the cement concrete itself, then on the surface of the asphalt concrete layer such reflected cracks can be established using GPR survey.
6.1.16 One way to repair reflected cracks is to artificially expand its upper part to form a chamber with a width that takes into account the maximum possible crack opening (as a rule, at least 1 cm) and the relative elongation of the sealing material used.
The technology for the production of repairs of this type is considered in paragraphs 6.1.6-6.1.8.
6.1.17 Another method is to repair reflected cracks using reinforcing geogrids in combination with solid non-woven geotextiles. In this case, the geogrid is included in the tensile work during bending, preventing the crack from opening, and the geotextile acts as a damping layer that perceives stresses that arise in the crack zone during temperature movements of cement concrete slabs.
The following requirements are imposed on the geogrid: it must have high thermal stability, low creep at sufficiently high temperatures for laying the asphalt concrete mixture (120-160°C) and good adhesion to bitumen. Cell sizes are taken depending on the composition of the asphalt mix and ensuring good adhesion between the layers of the coating (about 30-40 mm when using hot asphalt mixes on viscous bitumens).
The following requirements are imposed on the non-woven interlayer of geotextiles: the density of the interlayer should be no more than 150–200 g/m, the tensile strength is 8–9 kN/m, and the relative elongation at break is 50–60%.
6.1.18 Repair of reflected cracks using reinforcing geogrids in combination with non-woven geotextiles is carried out according to the following technology:
Organization of traffic at the work site, installation of fences;
Cleaning the coating from dust and dirt;
Milling of the existing asphalt concrete pavement in the crack zone to a width of 30-50 cm and to the depth of the repaired layer (but not less than 5 cm);
Priming of the milled surface of asphalt concrete with a cationic bitumen emulsion in an amount of at least 1 l / m in terms of bitumen;
Laying a layer of geotextile to a width of 30 cm strictly symmetrical to the axis of the crack being repaired (when laying a strip of geotextile, its pre-tension should be at least 3%. The sheet is stretched by 30 cm with a strip length of 10 m);
Laying a layer of coarse-grained asphalt concrete mixture on the geotextile layer to the width of the milled crack, followed by layer-by-layer compaction with a layer thickness of 5-6 cm. existing coverage;
Priming the surface of the laid layer of asphalt concrete with a bitumen emulsion in an amount of at least 0.6 l/m2 in terms of bitumen for a geogrid laying width of 150-170 cm;
Laying the geogrid sheet strictly symmetrically to the axis of the crack being repaired;
Repeated pouring of the binder over the entire width of the coating surface;
Laying and compaction of the top layer of the pavement of a dense fine-grained asphalt concrete mixture with a layer of at least 5-6 cm over the entire width of the pavement being repaired.
6.1.19 One of the ways to repair reflected cracks is their sanitation with crack filling with hot fine-grained asphalt concrete mixture with bitumen-rubber binder. This makes it possible to largely extinguish the stresses arising above the joints of the cement concrete pavement and absorb internal plastic deformations. Rubber crumb in the composition of the binder acts as particles of the polymer component, which carry out the dispersion-elastic reinforcement of asphalt concrete.
Asphalt concrete mixtures based on bitumen-rubber binder should be designed, depending on the type and purpose of asphalt concrete, in accordance with GOST 9128.
Technical requirements for composite bitumen-rubber binders must comply with the established requirements.
For a composite bitumen-rubber binder, viscous oil road bitumen grades BN, BND according to GOST 22245 and liquid bitumen grades MG and MGO according to GOST 11955 are used as initial ones.
Finely dispersed rubber crumb is used, which is a crumb of general-purpose rubber, including rubber obtained by crushing worn-out car tires or other rubber-technical products. The crumb must have a particle size in the range of 0.3-0.5 mm and meet the requirements.
6.1.20 The technology of repairing reflected cracks using hot fine-grained asphalt concrete mixture with a bitumen-rubber binder includes the following technological operations:
Crack cutting;
Mechanical cleaning of the crack;
Blowing out the crack with compressed air;
Heating of the side walls of the crack, priming of the bottom and walls of the crack;
Crack filling with hot fine-grained asphalt concrete mixture with bitumen-rubber binder;
Compaction of asphalt mix.
For compaction, a small-sized roller or vibrating plate is used.
The temperature of the asphalt concrete mixture on bitumen BND 40/60, BND 60/90, BND 90/130, BND 130/200, BND 200/300 with bitumen-rubber binder at the beginning of compaction should not be lower than 130-160 ° C for dense asphalt concrete types A and B and high-density asphalt concrete.
6.1.21 Technological sequence of work, when repairing potholes, consists of the following operations: cleaning the asphalt concrete pavement from moisture, dirt and dust at the work site; marking the boundaries of repair work in straight lines along and across the axis of the road with a grip of the undestroyed pavement by 3-5 cm (if several closely spaced potholes are being repaired, they are combined with one contour or map); cutting═ cutting or cold milling of repaired asphalt concrete along the outlined contour to the entire depth of the pothole═ but not less than the thickness of the asphalt concrete layer. In this case, the side walls must be vertical; cleaning the bottom and walls of the repair site from small pieces═ crumbs═ dust═ dirt and moisture; treatment of the bottom and walls with a thin layer of liquid (hot) or liquefied bitumen or bitumen emulsion, laying the asphalt concrete mixture; leveling and compaction of the coating layer.
6.1.22 In the event of the formation of chips in the cement concrete pavement slabs, the pothole formed as a result of this in the overlapping asphalt concrete layer can be significant in depth (more than 20-25 cm). Repair of such areas must be carried out with the removal of the destroyed layer of asphalt concrete for the entire thickness, for the width of the surface of the chipped cement concrete slab. Repair of a chipped surface of a cement concrete slab must be carried out in accordance with. After that, the asphalt concrete mixture is laid and compacted.
6.1.23 For patching of an asphalt concrete layer laid on a cement concrete pavement, it is recommended to use mainly hot mix asphalt or cast asphalt concrete of types I and II in accordance with the requirements of GOST 9128-2013 and GOST R 54401-2011, respectively.
It is recommended to use asphalt concrete mixtures corresponding in terms of strength, deformability and roughness to the asphalt concrete of the existing pavement. Hot fine-grained mixtures of types B and C should be used, since they are more technologically advanced for work with shovels, rakes and trowels in auxiliary operations than multi-gravel mixtures of type A.
For the preparation of hot fine-grained asphalt concrete mixtures, viscous road bitumen BND 40/60, BND 60/90, BND 90/130, BND 130/200, BND 200/300 according to GOST 22245, as well as modified, polymer-bitumen binders according to OST 218.010- 98 .
6.1.24 To perform edge trimming, small milling machines, circular saws, and perforators are used.
Depending on the area of the repaired area, trimming of the coating is performed in various ways. Small areas (up to 2-3 m) are contoured using a seam cutter equipped with special thin (2-3 mm) diamond discs with a diameter of 300-400 mm. Then, with jackhammers, the coating inside the circuit is disassembled. The asphalt crumb is removed and the site is prepared for laying the asphalt concrete mixture.
6.1.25 When preparing for the repair of long narrow potholes or sections of more than 2-3 m, it is advisable to use permanently installed, trailed or mounted cutters that cut off defective coating material 200-500 mm wide to a depth of 50-150 mm.
If the area is large, then special high-performance road milling machines with a large width of cut material (500-1000 mm) and a maximum depth of up to 200-250 mm are used.
6.1.26 Priming of the bottom and walls of a contoured pothole═ cleaned of small pieces and dust═ with a thin layer of liquid (hot) or liquefied bitumen or bitumen emulsion (bitumen consumption 0═3-0═5 l/m) can be performed using: ═ asphalt distributor═ road repairer, etc.
Effective for lubricating a repaired pothole are small-sized installations (5 hp) ═ pumping bitumen emulsion into the spray nozzle of a hand-held fishing rod with a hose 3-4 m long, installations supplying emulsion from a barrel with a manual pump.
For small volumes of work and small potholes, priming with emulsion can be carried out from portable containers (10-20 l) with spraying with compressed air according to the principle of a spray gun.
6.1.27 The asphalt mix is laid manually or using small-sized asphalt pavers. When laying the mixture manually, the leveling of the asphalt concrete mixture is carried out with improvised means (rakes and trowels).
The pothole is filled with asphalt concrete mixture in layers of 5-6 cm, taking into account the safety factor for compaction. Of the means of mechanization for compaction, a small-sized skating rink or a vibrating plate is used. The surface of the repaired area after compaction should be at the level of the existing pavement.
6.1.28 To increase the efficiency of repairing potholes 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 dedusting repair cards, a jackhammer drive for cutting the edges of repair cards, a vibrating plate for compacting the asphalt concrete mixture.
6.1.29 When carrying out work in conditions of increased moisture, the potholes are dried with compressed air (hot or cold) before priming.
6.1.30 Repair of potholes by the jet-injection method using a cationic bitumen emulsion is carried out using trailed special equipment. Cleaning the pothole for repair is carried out with a jet of compressed air or by suction, priming - with an emulsion heated to 60-75 ° C, filling - with crushed stone blackened during injection. With this repair method, edge trimming can be omitted (Fig. 6.1).
Figure 6.1 - The sequence of operations for the jet-injection method of filling the pothole: 1 - cleaning the pothole with a high-speed air jet; 2 - coating the surface of the pothole; 3 - filling and sealing; 4 - dry dressing
Figure 6.1 - The sequence of operations for the jet-injection method of filling the pothole: 1 - cleaning the pothole with a high-speed air jet; 2 - coating the surface of the pothole; 3 - filling and sealing; 4 - dry dressing
6.1.31 As a repair material, crushed stone of a fraction of 5-10 mm and an emulsion of the EBK-2 type are used. A concentrated emulsion (60-70%) based on bitumen BND 90/130 or BND 60/90 is used with an approximate consumption of 10% by weight of crushed stone. The surface of the "seal" is sprinkled with white crushed stone with a layer of one crushed stone. The traffic opens in 10-15 minutes. Works are carried out at an air temperature not lower than + 5 ° C, both on dry and wet surfaces.
6.1.32 On roads III-IV categories and in cases of "emergency" repairs for higher categories of roads, the repair of potholes in the asphalt concrete layer on the cement concrete pavement can be carried out using wet organic-mineral mixtures (WOMS). The repair method using FOMS provides for cleaning a pothole, filling it with a mixture of moistened mineral material of a selected composition and a liquid organic binder (tar or liquefied bitumen) and compacting the mixture. The thickness of the laid layer of material must be at least 3 cm.
The composition of VOMS consists of limestone or dolomite crushed stone of a fraction of 5 ... 20 mm (up to 40%) ═ sand with a particle size modulus of at least 1═0═ mineral powder (6 ... 12%)═ binder (tar ═ liquid or liquefied viscous bitumen) in the amount 6…7% and water. Instead of crushed stone, it is allowed to use screenings of crushing═ PGS═ crushed slag. The mixture can be harvested for the future with preparation in conventional asphalt concrete plants, retrofitted with a water supply and dosage system.
VOMS can be used at air temperatures down to -10°C and laid on a damp surface of a pothole.
6.1.33 Another method of "emergency repair" of potholes is the repair using cold asphalt concrete (repair) mixes.
This type of repair is used when the area of the pothole is up to 1 m.
The repair cold mix consists of a mineral filler, an organic binder with the introduction of special additives into it. The mixing of the mixture is carried out in forced action installations.
As an organic binder, bitumen grades BND 60/90 and BND 90/130 are used, which meet the requirements of GOST 33133-2014. The properties of bitumens have been improved by introducing various additives with an organic solvent (thinner).
Thinners used to give the initial bitumen grade MG 130/200 a given viscosity (GOST 11955-82) must meet the requirements of GOST R 52368-2005 and GOST 10585-99. The amount of thinner is 20-40% by weight of the bituminous binder and is specified by the laboratory.
In the process of preparing repair mixtures, surfactants are used to increase the adhesion strength of the binder to the surface of mineral materials and ensure the desired properties.
The temperature of the mixture should not be below -10°C. It is allowed to lay the repair mixture on a frozen and wet base, but in the absence of puddles, ice and snow in the repaired map.
When repairing potholes in the coating, depending on the depth of destruction, the repair mixture is laid in one or two layers with a thickness of not more than 5-6 cm with careful compaction of each layer.
When removing potholes on the coating, the technological sequence is followed, which includes cleaning the damaged area, leveling and compacting the repair mixture.
It is not necessary to prime the repaired surface with bitumen or bitumen emulsion.
The repair mixture is laid taking into account the reduction in the layer thickness during compaction, for which the thickness of the applied layer should be 25-30% more than the depth of the pothole.
When repairing potholes, depending on the area of the repaired area, the mixture is compacted with a vibrating plate, manual vibrating roller, mechanical, and for small amounts of work - with a manual rammer. With a pothole size exceeding 0.5 m, the mixture is compacted with a vibrating plate. The movement of the sealing means is directed from the edges of the section to the middle. The seal is considered complete if there is no trace of the sealing agent.
The mixture, as a rule, is packed in plastic bags weighing 20, 25, 30 kg or in other quantities as agreed with the consumer. Unpackaged mixture is allowed to be stored under a canopy in open stacks on concrete floor within 1 year. Packed in sealed bags, the mixture retains its properties for two years.
6.1.34 One of the pothole repair methods is to fill them with a poured asphalt concrete mixture. This mixture differs from the usual asphalt concrete mixture by the increased content of mineral powder (20-24%) and bitumen (9-10%) grade BND 40/60. The content of crushed stone is 40-45%. At a laying temperature of 200-220°C, the mixture has a cast consistency, which eliminates the need for compaction. The mixture is delivered to the place of work special machines with a heated container and fill in the prepared pothole repair card.
After the mixture cools down to 50-60°C, traffic is opened along the repaired area.
When laying new layers of asphalt concrete pavement, the use of cast asphalt concrete mixtures for repairing potholes is not allowed. When laying new asphalt concrete layers, the poured asphalt repair cards on the underlying layers should be removed.
6.1.35 Separate defects on the surface of the asphalt concrete pavement in the form of chipping and peeling are eliminated by the jet-injection method, similar to the repair of potholes.
6.2 Surface treatment device on pavement
6.2.1 The surface treatment device on the road surface improves its grip properties, as well as protection against wear and weather conditions. With the surface treatment device, the tightness of the coating increases and its service life increases. In addition, minor irregularities and defects are eliminated.
6.2.2 A single surface treatment is carried out on the surface of the asphalt concrete pavement if it has defects in the form of: peeling, chipping, cracks and small potholes.
Double surface treatment is performed if there is a significant amount of destruction on the asphalt concrete pavement (more than 15% of the total pavement area). In this case, a decision can be made to mill the top layer of the asphalt concrete pavement.
6.2.3 A single surface treatment device is produced in accordance with the Guidelines for the device of a single rough surface treatment using a technique with synchronous distribution of bitumen and crushed stone.
6.2.4 Single surface treatment is carried out, as a rule, in the summer warm periods of the year, on a dry and sufficiently warm surface at an air temperature of at least +15°C.
The sequence of the single surface treatment device:
Preparatory work;
Single surface treatment device;
Care of the surface treatment layer.
6.2.5 Preparatory work includes:
Elimination of coating defects;
Selection and preparation of crushed stone and bitumen;
Selection of the initial consumption rate of crushed stone and bitumen;
Selection and adjustment of equipment and machines that are part of a specialized detachment;
Education and training of service personnel of machines and mechanisms.
6.2.6 In the areas selected for the single surface treatment device, the elimination of defects on the roadway is carried out in accordance with the requirements. Patching of potholes and cracks must be completed at least 7 days before the start of the surface treatment device.
6.2.7 The choice of the approximate consumption rate of crushed stone and bitumen for a single surface treatment device is carried out according to Table 6.1.
Table 6.1 - Selection of the approximate consumption rate of crushed stone and bitumen for a single surface treatment device
|
Fraction of crushed stone, mm |
Consumption |
|
|
crushed stone, m/100 m |
bitumen, kg/m |
|
6.2.8 For surface treatment, it is recommended to use machines with synchronous distribution of binder and crushed stone (synchronous distribution of binder and crushed stone, Fig. 6.2).
6.2.9 The surface treatment device is carried out in the following sequence:
Cleaning the surface from dust and dirt;
Clarification of material consumption rates;
Synchronous distribution of bitumen and crushed stone on the surface of the carriageway;
Compaction of the freshly laid rough layer;
Surface care.
6.2.10 Cleaning the surface of the coating from dust and dirt is carried out by specialized machines with nylon, and in case of severe contamination of the surface - with a metal brush and watering equipment. The coating is cleaned in two to five passes along the trail.
Figure 6.2 - Synchronous distribution of binder and crushed stone with a surface treatment device
Figure 6.2 - Synchronous distribution of binder and crushed stone with a surface treatment device
6.2.11 Compaction of the freshly laid layer is carried out immediately after the passage of the machine with synchronous distribution of binder and crushed stone. 5-6 passes of a self-propelled ice rink on pneumatic wheels are carried out along the surface with a wheel load of at least 1.5 tons and a tire pressure of 0.7-0.8 MPa, or a skating rink with rubberized metal rollers. The final formation of the layer occurs under the influence of passing road transport with a speed limit of up to 40 km/h. The period of formation of a freshly laid layer should be at least 10 days.
6.2.12 Maintenance of freshly laid surface treatment includes the following operations:
Speed limit up to 40 km/h;
Regulation of traffic across the entire width of the carriageway with the help of guide fences;
Cleaning of unattached crushed stone with a brush of a watering machine no later than one day after the completion of compaction;
Reconsolidation with a roller.
6.2.13 With a single surface treatment device in a synchronous way, the time interval between bitumen pouring and crushed stone distribution is less than 1 s. This provides a significant improvement in the adhesive quality of the binder, by penetrating it into the micropores of crushed stone. In this case, the crushed stone adheres well to the surface of the coating. With the synchronous distribution of binder and crushed stone, the quality of surface treatment is significantly increased, both when using hot bitumen as a binder and bitumen emulsion.
6.2.14 Work on the double surface treatment device is carried out on a clean, dust-free surface of the coating, dry when using bitumen and moistened when using bitumen emulsions. The air temperature when used as a binder bitumen should not be lower than +15°C, and when using a bitumen emulsion - not lower than +5°C. In some cases, if it is impossible to ensure the required purity of the milled coating, it is recommended to prime it by pouring liquid bitumen at a rate of 0.3-0.5 l/m.
6.2.15 The technological process of the double surface treatment device includes:
Milling of asphalt concrete pavement;
Cleaning the milled coating from dust and asphalt crumb residues;
Priming of the surface of the coating (if necessary);
The first pouring of bituminous binder - 1.0 ... 1.2 l / m and the distribution of processed crushed stone of a fraction of 20 ... 25 mm in the amount of 20 ... 25 kg / m, followed by rolling the layer with two or three passes of a light roller (5 ... 8 tons);
The second bottling of the binder at a rate of 0.8 ... 0.9 l / m;
Distribution of treated crushed stone with a fraction of 10…15 mm (13…17 kg/m) followed by compaction with four or five passes of a light roller.
6.2.16 Estimated costs of binder and crushed stone during their distribution on the coating are given in Table 6.2.
Table 6.2 - Consumption of binder and crushed stone (excluding pre-treatment)
|
Crushed stone size, mm |
Consumption rate |
|||
|
crushed stone, m/100 m |
bitumen, l/m |
emulsion, l/m, at bitumen concentration, % |
||
|
Single surface treatment |
||||
|
Double surface treatment |
||||
|
First placer |
First bottling |
|||
|
Second placer |
Second bottling |
|||
|
Note - When using black crushed stone, the binder consumption rates are reduced by 20-25%. |
||||
6.2.17 The decision on pre-treatment of crushed stone with a binder in the installation (blackening of crushed stone) is made based on the results of laboratory studies of the adhesion of crushed stone with a binder in accordance with GOST 12801-98 *. For blackening, it is recommended to use bitumen grades BND 60/90, BND 90/130, BND 130/200, MG 130/200, MG 70/130.
6.2.18 The main filling of the binder is carried out on half of the roadway in one step without gaps and gaps. If it is possible to provide a detour, the binder is poured over the entire width of the carriageway.
6.2.19 The temperature of the bitumen during its distribution should be within the following limits: for viscous bitumen grades BND 60/90, BND 90/130 - 150160°C; for grades BND 130/200 - 100130°C; for polymer-bitumen binders - 140160°C.
6.2.20 For surface treatment using bitumen emulsions, cationic emulsions EBK-1, EBK-2 and anionic emulsions EBA-1, EBA-2 are used. When using a surface treatment device using cationic bitumen emulsions, crushed stone is used that has not been pre-treated with organic binders. When using anionic emulsions - mainly black gravel.
6.2.21 The temperature and concentration of the emulsion are set depending on weather conditions:
At air temperatures below 20°C, the emulsion should have a temperature of 4050°C (with a bitumen concentration in the emulsion of 55-60%). The emulsion is heated to this temperature directly in the asphalt distributor;
At air temperatures above 20°C, the emulsion can not be heated (at a bitumen concentration in the emulsion of 50%).
6.2.22 Immediately after the scattering of crushed stone, it is compacted with smooth-roller rollers weighing 6-8 tons (4-5 passes along one track). Then with heavy smooth-roller rollers weighing 10-12 tons (2-4 passes along one track). For a better manifestation of the rough structure, it is advisable to carry out the final stage of compaction with smooth-roller rollers with rubber-coated rollers.
6.2.23 When using bitumen emulsions, work is carried out in the following sequence:
Wetting the treated coating with water (0.5 l/m);
Pouring the emulsion over the coating in the amount of 30% of the consumption;
Distribution of 70% of crushed stone from the total consumption (gap no more than 20 m with a time interval of no more than 5 minutes from the moment of pouring the emulsion);
Pouring the remaining emulsion;
Distribution of the remaining rubble;
Compaction with rollers weighing 6-8 tons, 3-4 passes along one track (the beginning of compaction should coincide with the beginning of the breakdown of the emulsion);
Surface care.
6.2.24 When using cationic bitumen emulsions, traffic is opened immediately after compaction. Care for double surface treatment is carried out within 10 ... 15 days, by regulating traffic along the width of the carriageway and limiting the speed to 40 km / h.
In the case of using an anionic emulsion, the movement should be opened no earlier than one day after the surface treatment device.
6.3 Installation of thin friction wear-resistant protective layers on the pavement surface
6.3.1 The device of thin protective layers of cast emulsion-mineral mixtures
6.3.1.1 Thin frictional wear-resistant protective layers of cast emulsion-mineral mixtures (LEMS) are used as frictional and waterproofing wear layers to increase the service life of road surfaces and improve traffic conditions. Wear layers are primarily needed to restore the performance of coatings.
6.3.1.2 When repairing asphalt concrete layers laid on a cement concrete pavement, the following options for using cast emulsion-mineral mixtures are possible:
1) laying LEMS on the top layer of asphalt concrete pavement;
2) laying LEMS on the milled asphalt concrete pavement.
6.3.1.3 Before laying a layer of LEMS, the coating is primed with emulsion or bitumen grades BND 200/300 at the rate of 0.3-0.4 l/m (in terms of bitumen).
6.3.1.4 Preparation and laying of LEMS is carried out with special single-pass machines that mix materials and distribute the mixture over the surface of the coating.
It is recommended to use crushed stone of various fractions up to 15 mm from stone of igneous and metamorphic rocks with a strength of at least 1200. Sand fraction 0.1 (0.071) -5 mm consists of crushed sand or a mixture of natural and crushed sand in equal proportions. For a mineral powder (preferably activated) from carbonate rocks, it is assumed that the total amount of particles smaller than 0.071 mm contained in the mixture is 5-15%. The binder is used in the form of cationic bitumen emulsions of the EBK-2 and EBK-3 class, containing 50-55% bitumen. The compositions of LEMS are given in Table 6.3.
Table 6.3 - Compositions of cast emulsion-mineral mixtures
|
Mix type |
Number of components, % by weight |
|||||||
|
granite crushed stone, mm |
mine- |
portland- |
water for pre- |
bitumen emulsion (in terms of bitumen) |
||||
|
crushed- |
nature- |
|||||||
|
rubble |
||||||||
|
Sandy |
||||||||
|
[email protected], we'll figure it out. | ||||||||
If the asphalt is laid according to all the rules, then it should serve for more than one year. But that's in theory. In our life, everything is different. As a rule, the first pits on the roads appear within a few months after the renewal of the road surface.
Why it happens? The main reasons, of course, are negligence and violation of asphalt laying technology. For the sake of economy (I want to get more money and spend less), road builders add less bituminous emulsion to the mixture, save on sand and gravel. Because of this, the asphalt becomes brittle and as a result, breaks, cracks and pits appear.Current regulations do not allow road services to wait for good and comfortable weather to carry out repairs. Judge for yourself, existing GOSTР 50597–93 “Automobile roads and streets. Requirements for the operational state permissible under the conditions for ensuring road safety "sets the maximum allowable dimensions for pits on the roads: along the width of the road - no more than 60 cm, along the length - 15, in depth - 5.
And in case of identifying problem areas, immediately notify the road builders. Those, in turn, are obliged to promptly repair the roadway. After all, if a car gets into such a hole, it is the organization serving this section of the road that will have to answer.
That is why, despite the rain and snow, the asphalt rolls into holes. After all, according to the standards, the elimination period is a maximum of 10 days. Is it correct?Road work on laying asphalt (including patching) is carried out in accordance with SNIPs and GOSTs. When repairing patching, as a rule, a cold laying method is used. In this case, the asphalt mix seizes very quickly and almost immediately you can drive along the repaired area.
There is another hot way. It is used mainly in the construction of new roads and the reconstruction of old ones. Here they use a hot bituminous mixture and roll it until it cools completely. Occasionally, hot laying is also resorted to during patching. More often in warm weather, when the temperature outside is not lower than 10ºС. However, there are so-called cast mixtures that allow hot styling even at sub-zero temperatures. Such a mixture is brought to the place of repair in a special thermos trailer. The composition is in a liquid state, like a thick glue. The temperature of the mixture is under 200ºС. Observing the technology, it can be laid even in harsh winter conditions. From the high temperature, the moisture from the pit simply evaporates. After the mixture hardens, the road section can be exploited. Pleasure is quite expensive. Therefore, this type of repair is used for serious damage to the canvas, when it is necessary to quickly restore traffic in an emergency section.
So, if hot styling is used in the warm season (+10ºС and above), cold styling is limited to slight frosts (not lower than -5ºС), and cast mixtures are more suitable for cold weather, already at -10ºС, for example. It is clear that, if necessary, road builders will patch up the road even with more low temperatures. If a pit (fault, etc.) suddenly forms on the highway, traffic is blocked, and it’s minus 30 on the street, you won’t wait for spring warming. In general, any winter asphalt laying repairs, in fact, are emergency. Their task is to make sure that the repaired area lasts until it gets warm, when restoration can be done in earnest.As you can see, roads can be repaired in winter as well. The main thing is to follow the technology. But in our reality, few people think about high-quality road repairs. Indeed, for most road services it is more important to have a good and constant income from the repair and maintenance of roads. If you do everything qualitatively, you won't get money from the budget. The problem is that we have not yet established guarantees for the service life of the road surface. If such a period existed, then the road builders would eliminate all the pits at their own expense. And so they built the road, got the money. Potholes appeared - they patched them up, they got money again. As a result, we are simply doomed to drive through pits and potholes.
Well, for example, some numbers. Last year, the repair of the road and street network was spent: in Kazan - 2.87 billion rubles, in Vladivostok - 2 billion, in the Moscow region - 12 billion, in the capital - 22.4 billion. This is for comparison. Now imagine how much you could save if the roads after laying (reconstruction and overhaul) did not require repairs for at least four years.
With small sizes of potholes, the distribution and leveling of the mixture is carried out, as a rule, manually with shovels and trowels or using boxes without a bottom (Fig. 9), and on large repaired maps (area of more than 20–25 m 2) it is advisable to use a small sidewalk paver.
After filling the pothole (card) with a hot mixture, it is compacted with special vibrating plates or small-sized vibrating rollers in compliance with all technological rules and requirements (see Section 3). The surface of the repaired area after sealing should be at the level of the main coating, i.e., it should not have any depressions, or protrusions, or the appearance of a “clumsy blotch”.
Traffic on the repaired area of the coating is opened immediately after the completion of all work and the cooling of the laid mixture to a temperature not exceeding 30 ° C. In hot weather, the cooling time of the mixture can be shortened by pouring water at a rate of approximately 2 l/m 2 .
Quite often the question arises about the repair of pavements with the help of poured asphalt, which has been known since 1914. Molded asphalt is a hot mixture of pasty consistency, in which the most important component is mastic, consisting of high-viscosity solid bitumen, a large amount of mineral powder and sand (sometimes fine gravel). Molded asphalt can contain up to 13% bitumen and up to 30–35% mineral powder, which makes it much more expensive than traditional asphalt mixes. In addition, the temperature of its preparation and placement must be sufficiently high (220–250°C).
The need for special vehicles (coherers with agitators and heating) and special pavers (for pavement construction) that cannot work on paving other mixtures also lead to a noticeable increase in the costs of using poured asphalt. All this hinders the use in Russia of quite attractive cast asphalt for patching and pavement construction.
Jet-injection cold technology for filling potholes on road surfaces using bitumen emulsion is now one of the most advanced and progressive, despite the fact that in some European countries and in America it has been successfully used for a long time.
Its essence lies in the fact that all the necessary operations (Fig. 10) are performed by the working body of one machine (installation) of a self-propelled or trailed type (Fig. 11).
The preparation of a pothole for repair actually comes down to its thorough cleaning of dust, debris and moisture by blowing with a high-speed air jet and to treating the surface of the pothole with a bitumen emulsion. The operation of cutting, breaking or milling asphalt around a pothole may not be performed in this technology.
The very filling of the pothole is carried out by filling it with fine gravel, pre-treated with bituminous emulsion in the mixing chamber of the machine. Due to the involvement and supply of crushed stone with an air jet, its laying in a pothole occurs at a high speed, which ensures its good packing (compaction), practically eliminating the need for additional use of vibrating plates and vibrating rollers.
For patching according to the jet-injection cold technology, it is recommended to use pure fine crushed stone of a fraction of 5–10 (15) mm and a rapidly decaying cationic (for acidic rocks‚ eg granite) or anionic (for base rocks ‚ eg limestone) 60% bituminous emulsion.
Beforehand, the laboratory should check the adhesion of bitumen to crushed stone and the time of disintegration of the emulsion, which should not exceed 25-30 minutes. If necessary, make adjustments to the composition of the emulsion and adhesive additives.
The consumption of the emulsion of the specified concentration for priming potholes and processing crushed stone in the mixing chamber of the machine can approximately be 3-5% by weight of crushed stone (according to bitumen consumption - no more than 2-3%).
The main elements of the machine or installation for the jet-injection method of filling potholes are shown in fig. 12.
All these elements and assemblies can be permanently mounted on a light trailer or base truck. In some cases, it is possible to combine them on a separate frame in the form of a hinged or rearranged module for a suitable transport.
Such units and machines provide for the exit of the repairman-driver from the cab of the vehicle to perform patching at the rear of the car or trailer. In the future, some improvements were made to this technology and the scheme of work, which reduced the cost of the repair itself.
In particular, a flexible hose that feeds materials into a pothole was installed in front of the car and mounted on a light hydraulic manipulator boom, which is able to lengthen, fold and turn horizontally, serving a certain sector of coverage. The control panel for all operations is located in the cab of the truck, and the driver of the repairman no longer needs to leave his workplace. He fills the pothole directly from the cab within 20-30 seconds (Fig. 13).
The jet-injection method for patching potholes can be used for almost all year round. Little experience in Russia (Roshchinskoye DRSU Leningrad region‚ Moscow region, Saratov region and elsewhere) and more extensive practice of its application, for example, in the USA, England and Sweden, show that in fact strong and durable sealing of a pothole can be provided even at air temperatures up to -10 ... -15 ° С .
As a rule, potholes in initial stage pitting destruction of coatings‚ i.e. mainly small size(diameter no more than 40–60 cm)‚ although there are no fundamental and serious objections and obstacles to the repair of potholes and larger maps.
Research and experimental work for several recent years(mainly in the USA) have shown that the cleanliness and dryness of the pothole play a more important role than even the temperature of the material and the outside air for the quality of patching. Therefore, the jet-injection technology has recently undergone further qualitative improvement, the essence of which was to replace the cleaning and drying of the pothole by blowing with a high-speed air jet for vacuum cleaning (Fig. 14).
high performance Vacuum pump sucks debris, dust and moisture out of potholes. The surface is drier and cleaner than with conventional sweeping or blowing with compressed air.
Priming with bitumen emulsion and filling the pothole with crushed stone treated with emulsion in vacuum-jet-injection technology are similar to the same operations in jet-injection technology.
The developers of the method and equipment, based on experience in its use in 25 US states, guarantee a 3-year service life of the repaired sites.
Russian road builders have already begun a broader practical use jet-injection repair method using the BCM-24 equipment kit, manufactured by JSC "Betsema" (Moscow region), trailed to a dump truck (Fig. 15).
It is appropriate to note that in some Russian places the method of patching with mixtures has not lost its relevance and attractiveness so far.
Cold asphalt mixes include all types or compositions according to GOST 9128-97 (except for type A), prepared on liquid or liquefied bitumen grades SG 70/130 (medium thickening) or MG 70/130 (slow thickening). As a rule, preference is given to medium-thickening bitumen, since with it a layer of material in the coating is formed faster than on slow-thickening bitumen.
Such mixtures are prepared in the same mixing units as hot ones. However, the temperature for preparing cold mixes is 40–50% lower. After the agitator, the mixture goes through the obligatory stage of cooling to the outside temperature, then it is stored and only after that it can be laid in the coating layer in a cold state. It is allowed to store it in a warehouse in a stack and use it as needed within 3-5 months. It lends itself well to loading machines and transportation by conventional vehicles over any distance.
The most important and special technological problem for a cold mix is to ensure its non-caking, i.e., maintaining looseness without sticking mineral grains into lumps. Without this, it is impossible to prepare the mixture for future use and further effective use.
Usually, the caking of the mixture before storage is reduced by cooling it in air with repeated shoveling with the blade of a bulldozer, loader or motor grader, and sometimes with watering. Cooled and hardened on mineral grains, thin layers and films of bitumen lose their stickiness, and the mixture in stock piles does not cake. In order to restore stickiness to bitumen and form the structure of the mixture after laying in the coating, it must be warmed up for some time by the heat of air and the sun to evaporate light bitumen fractions with simultaneous good compaction by rollers and transport within 2–3 weeks. Therefore, such patching of asphalt concrete pavements is preferable in spring or summer and only on roads of categories III–IV (traffic intensity is not more than 3000–1000 vehicles/day).
The technology and all repair operations in this case are similar to patching coatings with hot mixes. In cold technology, there is only a strict restriction on the laying and compaction time, which is imposed in hot technology due to the possibility of rapid cooling of the mixture and a decrease in its compactibility.
In some foreign countries (Sweden, Finland, Norway, etc.), asphalt concrete mixtures based on low-viscosity and liquid bitumens, as well as on a special oil binder (the mixture in this case is called oil gravel) are used for the construction of coatings from the so-called "soft asphalt concrete", the use of which is limited roads with a traffic intensity of up to 1000–1500 vehicles / day. Moreover, when using low-viscosity or liquid bitumen, a mixture for soft asphalt concrete is prepared and laid in a coating using conventional hot technology.
If an oil binder or a bitumen emulsion based on low-viscosity and liquid bitumens is used as a binder, the material for such mixtures can be cold or warm (heated with steam up to 40 ° C). Thus, in particular, in Finland, cold storage mixes are produced for the specified type of asphalt concrete. Their high-quality preparation is carried out in special mobile (mobile) installations MX-30S of the Finnish company Kalottikon, in which there is no drying drum, but there is a special container for the emulsion and a turbine unit for steam production.
Equally effective for patching are cold asphalt mixes prepared on very popular and widely used emulsions based on viscous bitumen. Such mixtures are called emulsion-mineral, and they can be both porous and dense.
Depending on the category of the road and the strength of the material in the coating, the required type or grade of emulsion is selected according to the viscosity of the bitumen used, the necessary mineral materials and cold mixtures are prepared that can be stored and stored.
In "cold" mixing plants, an emulsion of a given type, concentration and temperature is mixed with an unheated aggregate. Mixing plants themselves can be of almost any design and purpose, including very simple ones with low capital investments. When using high grade emulsions and mineral aggregates in combination with more efficient and sophisticated mixing and dosing equipment, emulsion-mineral mixes can provide pavement properties and quality close to those of hot mix asphalt pavements.
Terms (up to 2–3 months) and conditions of storage in a warehouse (open area‚ closed premises‚ sealed containers or sealed plastic bags) of such cold mixes depend on the type of emulsion, the viscosity of the bitumen, the time of disintegration of the emulsion and are set individually in each specific case.
If it is necessary to urgently repair potholes that are dangerous for traffic, you can use any simple and accessible methods, materials and means that can ensure temporary (at least 2-3 months) accident-free operation of the road.
Emergency repairs are carried out at any time of the year - in late autumn (wet and cold)‚ winter (cold) and early spring (cold and wet), which, of course, cannot but affect the quality of repair work.
Such poorly repaired places with the onset of warm and dry weather are subject to re-repair, but in compliance with all the requirements and rules for the implementation of high-quality pothole repair. This is economically quite feasible and acceptable, given the not quite massive nature and insignificant volumes of accident-defective places on the coating.
During emergency repairs, as a rule, such methods of temporary sealing are used that do not require special preparation of potholes, with the exception of their possible cleaning from dirt, moisture, snow and ice.
The main thing in such a repair is to fix the material used in the pothole so that it has an acceptable connection with the bottom and walls of the pothole and that the particles of such material have sufficiently strong contacts between themselves due to mechanical expansion and bitumen, cement, polymer or other adhesive layers.
For emergency repairs, it is recommended to use limestone, dolomite or other not very strong crushed stone materials (fractions of 5–20 mm) pre-treated (“cold” black crushed stone) or processed directly in the pothole with liquid bitumen with surfactant or bitumen emulsion.
As a rule, liquid bitumen should have a viscosity index of at least 130–200 s, and the bitumen emulsion should be rapidly disintegrating, 50–60% concentration when heated. Crushed stone for these purposes is sometimes treated with lime or cement (1.5–2% by weight).
Some of the repair materials with appropriate technologies of use can be used even at negative air temperatures (up to -10...-15°C), although other materials and technologies are effective only at +5°C and above.
Recently, in foreign countries, emergency repair of potholes and other defective places has been widely practiced with special repair mixtures with a shelf life of 1–2 years in finished form in sealed plastic containers (buckets, barrels, boxes)‚ in sealed plastic bags (25–50 kg) and even stacked outdoors. Such mixtures include Repasfalt, Bormix and Stralasfalt from Germany, Vespro and Silvax from the USA, Kolmak from England, Excel from Canada and a number of others.
For the most part, the binder for these cold materials is liquid bitumen modified with polymers with special additives or an emulsion based on it, which makes such repair mixtures quite expensive - about 200 USD / t, while the binder price is about 1000 USD / t. However, their attractive technological advantages (cold technology, long shelf life, performance of work on a wet surface and even in frost), together with a high strength of sealing defective places, make it possible and even expedient to use them in small and single emergency patching.
Sometimes, given the temporary nature and not too high quality of emergency repairs, they deliberately go to simplify and reduce the cost of both the repair material itself and the technology of its preparation and application.
For example, the road service of Helsinki has taken this path, which for more than 20 years has been annually producing about 3,000 tons of stored cold mix "Korsal" for urgent (urgent) repair of coatings and temporary sealing of trench openings on city streets.
It consists of crushed stone (3–8 mm)‚ sand and bitumen emulsion (7–8%). The repair mixture is prepared in a cold way in a conventional concrete mixer (capacity 3 m 3) of periodic action and stored in an open area. Before use in winter, the mixture is heated in a warm room.
In the presence of a bitumen emulsion and an appropriate machine or installation, it is advisable to use the already considered jet-injection cold method for emergency patching. However, due to the inability to do a thorough cleaning and preparation of the pothole, the service life of such an insert will be significantly lower than under normal normal conditions.
In the absence of the required jet-injection technique, filling a pothole is possible by manually stuffing (ramming) it with cold gravel (preferably blackened) and then treating it from the surface with a bitumen emulsion by simple spraying from improvised means. As a result, the pothole will be filled with rubble impregnated with bitumen emulsion.
The method of impregnation of crushed stone in a pothole, but with bitumen, somewhat liquefied and hot, is also practiced by road builders from different countries, including Russia, to eliminate emergency pitting. Its difference from the emulsion impregnation method is that the impregnation itself is carried out before crushed stone is compacted. In this case, the bitumen is heated to a temperature not lower than 170–180°C. Satisfactory results can be obtained even at low air temperatures (down to -5...-10°C).
The peculiar technological methods include the Russian method of reverse impregnation, in which the bitumen heated to a minimum of 170-180 ° C, getting on the moisture remaining on the bottom and walls of the potholes and on the wet rubble, foams with a multiplicity of up to 4-6 and covers the surface of the pothole with a thin layer and rubble particles. The penetration of bitumen between the particles and grains of crushed stone goes from the bottom up, so this repair technique is called the “reverse impregnation method”. Its efficiency is limited by air temperature +5...+10°C. At lower temperatures, bitumen is poorly and difficult to foam.
In the impregnation method, polymeric materials are sometimes used instead of bitumen. In particular, when repairing with polymer concrete, the pothole is filled with crushed stone, which is then impregnated with a fluid composition based on polyurethane, acrylic or other resin, while in the process of tamping, the residual water is squeezed out of the hole up.
Such repairs are possible at air temperatures from -30 to + 50°C. Traffic opens in 30 minutes. In unfavorable weather conditions(dampness‚ cold) emergency patching can also be performed with a wet organo-mineral mixture (VOMS), the composition and technology of preparation and use of which was developed at RosdorNII.
VOMS consists of limestone or dolomite crushed stone with a fraction of 5–20 mm (up to 40%), sand with a particle size modulus of at least 1.0, mineral powder (6–12%), binder (tar, liquid or liquefied viscous bitumen) in the amount of 6 -7% and water. Instead of crushed stone, it is possible to use screenings of crushing, ASG, crushed slag. Such a mixture is prepared in cold form in ABZ mixing plants, equipped with a system for supplying and dosing water to the mixer. After unloading from the mixer ready mix at a temperature of 25–40°C, it is delivered to a warehouse, where it is stored in a pile for several months.
Potholes with a depth of at least 3-4 cm are repaired with such a mixture. The main advantage of VOMS is that it is used already in finished form using cold technology, on dry or wet surfaces and at air temperatures up to -10 ° C. However, it should be borne in mind that in winter and early spring, the formation of a strong FOMS structure in the coating is slow and difficult due to frequent transitions of air temperature through 0°C.
This material acquires the greatest strength after complete drying, but this strength is not so great (1.5–2 times lower than the strength of cold and 2.5–3 times lower than the strength of hot asphalt concrete) to use FOMS even for ordinary patching of road surfaces high categories. Only emergency (temporary) repair of such roads is permissible with this mixture.
An equally interesting and useful development for patching pavements, including emergency ones, was once made at SoyuzdorNII: stored asphalt concrete mixtures (SAC) on viscous bitumens that can be stored, laid and compacted in cold form.
They are prepared on viscous bitumen with enhanced thixotropic properties, which is achieved by introducing special plasticizers into them (LTD summer automotive and tractor diesel fuel and SB oil feedstock for the production of viscous road bitumen). But the situation with the practical use and implementation of the SAS remains the same as with the VOMS, that is, not very satisfactory.
Is it possible to lay asphalt in puddles, mud or just on snow? infographics
Editorial responseMany have observed the process of laying asphalt in winter or late autumn more than once. But hardly anyone tried to penetrate into technical features this process. It turns out that it is possible to repair roads at this time of the year, but under certain circumstances.
According to the current Soviet SNIPs, asphalt cannot be laid at temperatures below +15, but now new materials and technologies have appeared that make it possible to perform work even at sub-zero temperatures. But not below -10 ºС.
What needs to be done to lay asphalt in winter?
To repair the road in winter, it is necessary to prepare the area: remove snow, ice and treat the place with special reagents.
Rain and snow reduce the temperature of the mix, so thick asphalt layers are not recommended in wet weather. Lay pavement in case of light precipitation, it is possible only along the entire width of the road, and not in parts on different days. In a downpour and a snowstorm, laying the canvas is impossible.
How is asphalt laid?
Asphalt laying consists of the following steps: the cleared area for the new route is covered with rubble. Then pour the emulsion, which should ensure the fixation of the asphalt. Another layer of bitumen and dry gravel is applied on top, the surface is leveled with a roller.
Why do holes and cracks appear on the road?
When laying asphalt, road services often save money. First of all, on an emulsion, the task of which is to hold the rubble. As a result, the asphalt is laid on a dry surface, so it quickly begins to disperse, forming cracks.
The second thing they are trying to save on is crushed stone. Instead, they can put a chipped brick under the asphalt, which is incomparable in strength with gravel. As a result, the asphalt fails, forming holes. According to the regulations, for an “easy” road, one layer of medium fraction (20-40 mm) is enough. If this is a highway, then it is recommended to lay crushed stone in several layers: the first layer is from a large fraction (40-70 mm), followed by a medium one, the last one is from a fine one (5-20 mm). The main thing is to roll each layer with a roller.
Road builders also save on the surface itself - asphalt. It, like bitumen emulsion, is made from oil. But not every grade of this raw material is suitable for high-quality road laying. As a rule, builders do not check the quality of oil, hence the fragility of the coating. The thickness of the asphalt depends on the intended use of the road. Minimum Thickness is 4-5 cm (for yard areas, etc.). At high traffic intensity, asphalt is again laid in layers using different grain sizes. Coarse-grained asphalt concrete is placed in the first layer, fine-grained concrete is placed on top. For greater reliability, a third surface layer is placed. Before applying each next layer, the previous one is poured with bitumen.
Well, the main reason for bad roads is negligence. Cracks often appear due to water that penetrates under the coating and freezes during cold weather, thereby expanding holes in roadway. Builders can ignore the technical requirements and put asphalt on the snow. In these actions lies not only negligence, but also the possibility of obtaining another order. You put it in a puddle - in a couple of months everything will be redone, so a new order is ready, and everything can be attributed to the harsh climate.
When should cold and hot asphalt be used?
There is a cold and hot way of laying asphalt.
Cold laying is most often used in road repairs. The main thing in this process is to compact the coating well. The advantage of using cold asphalt is its all-weather application.
Work on the repair of the road can not be stopped even in winter.
There are several types of cold asphalt:
Summer cold asphalt. Temperature environment when laying from +15 to +30 °С.
Interseasonal cold asphalt. Ambient temperature during laying from -5 to +15 °C.
But this method is not suitable for the construction of a new road or overhaul old. In this case, resort to hot styling. Asphalt must be installed hot. However, in autumn and early spring, it is difficult to achieve high-quality road repair using hot laying.
Instead, poured asphalt technology is used. Molded asphalt is a mixture of sand, gravel and crushed limestone with bitumen. Cast asphalt does not have to be rolled with rollers, its consistency is such that it lays down in a dense cast layer without the need for additional compaction. Molded asphalt is water resistant, so it can be laid even when it rains. The temperature of the poured asphalt during laying can vary between 200-250 degrees. The technology allows laying asphalt at -10 °C. Max Thickness cast asphalt should not exceed 25-30 mm. Cast asphalt, like other types of asphalt, can be used not only in road construction, but also in such types of work as roofing, bridge covering, and interior decoration.
Roads are measured to serve three years
Since 2011, new rules have come into force, according to which road repairs should be carried out not once every seven years, as it was before, but once every three years. According to officials, due to climatic conditions, the road in Russia serves no more than three years.
In the same year, the capital's communal services began to keep the history of roads. The documents indicate when a particular kilometer of the highway was repaired. If a marriage is found, the contractors who carried out the work must correct the errors at their own expense.
Comparative cost of roads in Russia and abroad
Some road works in Russia cost many times more than the cost of roads abroad. The first in this list is the land that needs to be redeemed from the owners. In Russia, it is usually included in the cost of the project, but not in Europe. At the same time, the cost of land acquisition in Russia is 6-7% of the project cost, in the Moscow region - 30%, and in Moscow - up to 70%. Many people buy up the land adjacent to the future highway in advance and then sell it to the state at exorbitant prices.
The next most expensive is the cost of design. In Russia, there are virtually no standard road designs, so each new road has to be designed anew. Then the project is sent for state expertise, which is almost impossible to pass the first time. The re-examination costs up to 70% of the initial one - and this is without taking into account the cost of finalizing the project.
And the third is the delivery of materials. High-quality sand and gravel often have to be transported for tens or even hundreds of kilometers. A simple example: during the construction of some tunnels in the Olympic Sochi, finishes made in Krasnoyarsk were used. With delivery for five thousand kilometers.
As a result, it is not surprising that the construction of the Adler - Krasnaya Polyana road cost 285 billion rubles - 1.9 times more expensive than foreign analogues. In Europe, the cost of laying one kilometer of a tunnel in a mountain range is about $70 million.
The only reason why a road in Russia can be cheaper than a European one is thinner pavement, designed for a shorter service life. In Germany, the thickness of the top layer of asphalt should be 22 cm. In Russia - 8 cm. All this affects the service life. In addition, if the quality of the asphalt used can be checked, then the amount of sand and gravel cannot. Therefore, road builders use this: if you want, put less material If you want, indicate in the documents the delivery range of the required sand is 200 km, and bring the usual one from the nearest quarry.
Russians can only dream of good roads or build them under contracts life cycle so that the contractor himself maintains the constructed road and pays fines in case of poor laying.