Constructions of pavements with asphalt concrete gost. TTK. Asphalt pavement

The invention relates to the field of road construction and can be used in the construction of structures of the upper layers highways high categories and runways of airfields, as well as for asphalt concrete pavements on bridges and overpasses in all climatic zones. Technical result: obtaining high strength and durable asphalt concrete pavement with a minimum content of expensive high-strength granite crushed stone, reducing material consumption and facilitating the design. A method of arranging asphalt concrete pavement involves preparing the base, laying and compacting the lower layer of the coating with further laying and compacting the upper layer onto the still-cooled lower layer, and surface treatment by crushing crushed stone. The top layer of the coating with a thickness of 1.5-3 cm is formed from granular asphalt-binding material obtained by rolling, with a bitumen content of not more than 15%, and for surface treatment use pre-prepared crushed stone with a particle size of 3-5 mm, the surface of which is coated with an asphalt binder obtained by the method of pelletizing, while the amount of asphalt binder in the shell is 5-10% of the mass of crushed stone, the consumption of crushed stone is not more than 5 kg / m 2, and the crushed stone is heated after the laid layer cools down to temperature 80 ° C. 1 tab.

The invention relates to the field of road construction and can be used in the construction of structures of the upper layers of high roads of high categories and runways of airfields, as well as for asphalt concrete pavements on bridges and overpasses in all climatic zones.

The installation of asphalt concrete pavements is carried out in accordance with applicable regulations and is determined by the project depending on the category of roads. A typical road structure is formed by sequential laying on a sealed and prepared subgrade sand drainage layer, on which the layers of the road base and pavement are laid. Asphalt concrete pavement is the top of the road structure, consisting of one or more layers laid on the prepared road base. The coating is obtained by laying asphalt mix on prepared foundation with further compaction in accordance with TP 103-07 technical recommendations.

The thickness of the asphalt concrete coating laid in one layer is 3-6 cm. Coatings of larger thickness are usually laid in 2-3 layers with an asphalt concrete mixture with separate compaction of each of the layers. The thickness of the upper layer is taken within 3-5 cm, and the thickness of each of the lower layers of the asphalt concrete pavement is 4-8 cm. Thin-layer coatings with a thickness of 1.5-2.5 cm are usually made of asphalt mixtures of a special composition to ensure surface roughness.

For the lower layers of the coating mainly used porous asphalt concreteand for the top layer of the coating, the brand of hot, warm and cold asphalt concrete, the grade of bitumen and the type of particle size distribution are selected depending on the category of road and climatic conditions of the construction area. The top layer of asphalt concrete is the most critical element. pavementdirectly perceiving loads from moving vehicles. It is this layer that should provide reliable grip of the wheels of the car with the road surface. The top layer of asphalt concrete pavement is more susceptible to climatic conditions than other layers. The coating should be strong, even, rough, withstand plastic deformations at high positive temperatures, be crack resistant and resist wear well - it should provide the necessary operational qualities of the roadway. In accordance with this, the most stringent requirements are imposed on him.

The present invention relates to methods for arranging asphalt concrete pavement of special composition asphalt mixtures. Such coatings are used in the following cases:

When installing coatings on roads with heavy traffic and in difficult climatic conditions to ensure high strength and durability of asphalt concrete pavement, reduce the cost of repairs;

When installing asphalt concrete pavements on bridges and overpasses, when the requirements are imposed on the coatings for increased deformability and water resistance with a minimum weight of the coating.

An analogue of the proposed method for the construction of an asphalt concrete coating can be a method for the device of an upper coating layer based on crushed stone-mastic asphalt concrete (ЩМА). In accordance with GOST 31015-2002 crushed stone and mastic asphalt concrete mix (ЩМАС) - a rationally selected mixture of mineral materials (crushed stone, sand from crushing screenings and mineral powder), road bitumen (with or without polymeric or other additives) and stabilizing additives, taken in certain proportions and mixed in a heated state. Crushed stone mastic asphalt concrete (ЩМА) - compacted crushed stone and mastic asphalt concrete mixture. Stabilizing additive - a substance that has a stabilizing effect on the alkaline earth matter and ensures its resistance to delamination.

Crushed stone and mastic asphalt mixes (ЩМА), prepared in accordance with GOST 31015-2002, differ from traditional asphalt mixes (GOST 9128-2009) with a high content of crushed stone (up to 70-80% by weight). Crushed stone and mastic asphalt mixtures are hot dense mixtures prepared with the obligatory introduction of stabilizing additives such as fibers or polymers to prevent binder from draining during storage of the mixture in storage bins or during transportation.

ShchMA is recommended to be used for the device of upper layers of coatings with a thickness of 3-6 cm on highways of I-III categories and on city streets in all climatic zones. The minimum temperature of the mixture during installation should be at least 150 ° C. The use of crushed stone and mastic asphalt as the top layer of the coating with proper use and selection of the composition of the mixture provides high resistance of the coating to the formation of plastic deformations in the most difficult operating conditions. Residual porosity and water saturation of alkali metal oxide provide increased water resistance of such coatings. The high content of crushed grains (crushed stone and sand) creates a higher roughness of the coatings in comparison with traditional asphalt concrete.

The disadvantages of coatings from crushed stone-mastic mixtures include the stringency of the requirements for both the quantitative composition of the mixture and the properties of its individual components. When preparing such mixtures, it is necessary to accurately maintain the design composition of the mixture. The dosage error of the components of the mixture should not exceed ± 2% for crushed stone, ± 1.5% for mineral powder and bitumen, and ± 5% of the weight of each component for fiber additives. SCHMAS are dense asphalt mixtures. Low residual porosity of the material is achieved by careful selection of the granulation composition of the mixture. This takes into account not only the grain size of the mineral part, but also their shape. The structure of alkaline alkaline grains is formed mainly due to grains of crushed stone of a cuboid shape. The content of grains of another form is strictly limited.

No less stringent requirements are imposed on the strength characteristics of stone materials in the composition of the alkali metal alloy. In this case, there is a mismatch between the requirements for the strength of crushed stone used in the mixture and the strength of the asphalt concrete itself. The strength of crushed granite in the coating is 1000-1200 kg / cm 2, while the requirements of GOST for the coating itself are in the range of 20-25 kg / cm 2. This is due to the mechanism of perception of external loads in coatings of this type.

The stone material in such coatings forms a framework in which each particle of the mineral part of the mixture is in direct contact with neighboring ones. The stability of the coatings is ensured mainly due to the wedging of large grains of crushed stone into smaller fractions. The frame of the material perceives an external load and redistributes it between the particles. Given that most of the stone frame consists of particles of irregular geometric shape, many point contacts arise in the structure of the material, in which, when the external load is perceived, high specific pressures are formed, leading to cracking of the frame particles.

Due to the high content of binder in the gravel-mastic asphalt and the complete enveloping of grains of crushed stone with a binder film, as a rule, at the time of opening traffic sufficient roughness is not achieved. To obtain a rough surface, it is recommended to evenly sprinkle with washed high-strength crushed stone with a particle size of 2-5 mm or a mixture of crushed stone with crushed sand (1-4 kg / m 2). The bulk material is applied to a hot surface. With later application, the material cannot penetrate the surface layer and collapses upon rolling.

These problems are a serious obstacle to the widespread use of this method of device asphalt concrete pavement.

Closest to the proposed method for the construction of an asphalt concrete pavement is a method for the device of an upper coating layer of cast asphalt [TU 5718-002-04000633-2006. Mixtures of cast asphalt and cast asphalt] taken as a prototype. For the manufacture of cast asphalt mixes, polymer bitumen binders, rubber bitumen binders and other types of modified bitumen with a wide range of ductility, providing increased crack resistance and shear resistance of the coating, are used.

Coatings from cast asphalt concrete are arranged on road sections that require increased performance in terms of wear resistance, water resistance, deformation and friction properties under operating conditions. Cast asphalt mixes are used in the device and repair of coatings and layers of monolithic road constructionsdesigned from the operating conditions of asphalt concrete pavement as an elastic plate lying on an elastic foundation. These types of coatings include coatings on bridges, overpasses, overpasses, etc. In the practice of building coatings on bridges, cast asphalt mixes are used, prepared both on standard bitumen and polymer bitumen binders. Cast asphalt mixes are placed in the top layer of the coating 4-5 cm thick along the previously compacted lower layer of compacted hot asphalt mix [VSN 60-97].

For the preparation of mixtures, mineral materials are used: crushed stone from natural stone obtained by crushing rocks, crushed stone from gravel and gravel. The requirements for the strength of stone materials are less stringent than in the ShchMA (strength is at least 1000 kg / cm 2). According to the shape of the grains, the crushed stone should be cuboid in shape, contain no more than 1% of dusty and clay particles, without impurities. The content of grains of weak breeds should not exceed 5% by weight. The number of large fractions with a particle size of more than 55 mm, depending on the brand of the mixture, ranges from 35 to 65%. The content of asphalt binder in such mixtures reaches 30% with a mass ratio of bitumen / mineral powder from 0.35 to 0.75. The laying temperature of cast asphalt mixes, depending on the brand, is 200-240 ° C. The finished mixture of aircraft is transported to the place of work by self-propelled units with a thermos boiler or a bunker with heating and a stirrer.

The advantage of cast asphalt concrete pavement is the fact that after paving, their compaction is not required due to the increased content of asphalt binder. Cast asphalt mixes (LA) are hot mixes and have good fluidity, which eliminates, in most cases, the need for compaction. Another important advantage of cast asphalt is almost zero porosity and water saturation, which ensures high water resistance of the coatings, as well as their high fatigue life. The rigidity of requirements for stone materials has been reduced since cast asphalt does not form a frame structure.

The disadvantages of asphalt concrete pavements of this type include a higher susceptibility to random fluctuations in the content of mineral powder and bitumen, which negatively affects the physical and mechanical properties of asphalt concrete. The experience of using such mixtures has shown that in coatings, especially on roads with heavy and heavy traffic, waves, shears and other plastic deformations are formed. Such manifestations are especially strong at high external temperatures. Cast asphalt mixes are prone to segregation, as a result of which the material is stratified in the pavement layer. Particles of large fractions of the mixture settle to the bottom, and asphalt binder is released in the upper part of the layer, the strength characteristics of which are determined mainly by the properties of the bitumen used. The content of mineral powder and bitumen in the asphalt binder is such that a significant part of the bitumen is in a bulk state, reducing the strength characteristics of the material. The strength of the cast asphalt is normalized only at a temperature of 50 ° C and is 7-10 kg / cm 2. The use of high temperatures in the production of asphalt concrete mix and its laying creates serious problems in transporting the material to the place of use and requires special equipment. The production of works on the device of pavements using cast asphalt requires a lot of experience and the necessary production skill.

The surface roughness of the cast asphalt pavement is insufficient to provide high adhesion to the wheels of cars, based on traffic safety conditions. Surface finish is used to provide the necessary grip. In this case, the surface of the coating is treated with black gravel fractions (10-15 mm) with its rolling in 10-15 minutes after laying with a light roller weighing 3 tons. This surface treatment is called the method of embedding crushed stone [VSN 38-90. Technical guidelines for the construction of pavements with a rough surface]. The crushed stone used must be pre-treated with an organic binder (black crushed stone). The consumption rate of crushed stone for incorporation into a cast asphalt concrete coating is determined by the size of its particles and is 7-10 kg / m 2. The use of finer gravel for surface treatment could reduce its consumption and increase its frictional qualities. However, the low strength of the material and its floating structure do not allow this. Small particles of crushed stone are buried under the influence of loads in the layer of asphalt concrete, reducing its adhesion to the wheels of the car.

In addition, problems arise when processing crushed stone with an organic binder. Each particle of crushed stone during surface treatment should be moistened with bitumen over the entire surface to ensure reliable adhesion of the binder to the stone material. An obstacle to this is the presence of dust particles on the surface of the gravel. In this regard, gravel is washed and dried before treatment with bitumen.

The objective of the invention is to develop a method for the device of the top layer of asphalt concrete pavement, having improved performance indices necessary for the device of coatings on roads with heavy traffic and in difficult climatic conditions, as well as the device of asphalt concrete coatings on bridges and overpasses, when the demands are made on the coatings of increased deformability and waterproofness with a minimum coating weight. At the same time, a reduction in the cost of production and operation of the road surface is achieved.

The problem is solved in that the top layer of the coating with a thickness of 1.5-3 cm is formed from granular asphalt-binding material obtained by the pelletizing method, with a bitumen content of not more than 15%, and for surface treatment using pre-prepared crushed stone with a particle size of 3-5 mm, on the surface of which a layer of asphalt binder obtained by the pelletizing method is applied, while the amount of asphalt binder in the shell is 5-10% by weight of crushed stone, crushed stone consumption is not more than 5 kg / m 2, and crushed stone is heated after Bani-laid layer to a temperature of 80 ° C.

The basis of the asphalt concrete coating made in accordance with the proposed method is the material obtained by the method for producing the asphalt concrete mixture [RF Patent No. 2182136, 05/10/2002]. This material is a granular asphalt binder obtained from a mixture of mineral powder and bitumen by pelletizing by pelletizing. The application of the pelletizing method for producing granules allows to obtain a homogeneous asphalt binder structure with a uniform distribution of bitumen in the mass of mineral powder with a minimum bitumen content. In addition, an ordered arrangement of the grains of the mineral powder in the structure of the asphalt binder is ensured with the creation of bitumen films of nanoscale, providing a significant increase in the strength characteristics of the mixture. The high plasticity of the granules in the preheated state makes it possible to obtain practically monolithic samples of asphalt concrete with minimal water absorption and a water resistance coefficient exceeding unity.

Granular asphalt binder according to the method of [RF Patent No. 2182136, 05/10/2002] is used for its intended purpose, i.e. is introduced into the heated asphalt mixture, carrying out adhesion between the particles of the mineral part. With such an application, the listed advantages of asphalt-binding material cannot be fully realized. Literary sources indicate that a composite material whose structure is ordered and the amount of binder is minimal is close to an ideal composite. This is indicated in the works of the creator of a new scientific field of physico-chemical mechanics, Academician P.A. Rebinder [Rebinder P.A .. Selected Works. Surface phenomena in disperse systems. C. Physico-chemical mechanics. - M .: Nauka, 1979. - 469 s]. In the works of L.B. Gesentzwei [Gesenzvey LB Asphalt concrete from activated mineral materials. - M .: Publishing House for Construction, 1971. - 255 pp.] It is noted that there is an optimal ratio of the contents of mineral powder and bitumen in the binary system, in which there is a sharp increase in the strength characteristics of the system. According to L.B. Gesenzwei this ratio is 87% and 13% of mineral powder and bitumen in weight fractions.

Example I of the method.

Samples of asphalt concrete were formed from granular asphalt binder based on dolomite flour with a BND bitumen content of 60-90 13.6%. The test results of samples of asphalt concrete are given in table I.

Table I.
The name of indicators	Granular asphalt binder	GOST 31015-2002 requirements for ЩМА	Requirements of TU 5718-002-04000633-2006 to cast asphalt concrete
Water saturation%	0,3	1,0-4,0	1,0
The compressive strength at a temperature of 50 ° C MPa

3,10	not less than 0.65	not less than 1.0
Tensile strength at compression at a temperature of 20 ° C MPa

9,00	not less than 2.2	not standardized
Shear resistance: coefficient of internal friction; shear adhesion at a temperature of 50 ° C MPa.

0,86	not less than 0.93	not standardized

	not less than 0.18
0,58		not standardized
Water resistance coefficient
1,03	not less than 0.85	not standardized

The data presented in the table show a significant excess of almost all indicators of the properties of asphalt concrete from granular asphalt binding requirements of GOST and TU. The only indicator by which the material is inferior to alkali-ferrous alloys is the coefficient of internal friction. This result is quite obvious given the structure of the structure of the compared materials. The ALA has a skeleton structure formed of large gravel particles, which leads to a high value of the coefficient of internal friction. Granular asphalt binder does not contain crushed stone, but the shear resistance of the material is ensured by the high shear adhesion.

The data given are explained by the structural features of the granular asphalt binder obtained by the pelletizing method. With a uniform distribution of bitumen in the mass of material, bitumen films with nanoscale thicknesses are formed in the structure. This contributes to the manifestation of the nano-effect of system structuring, leading to a sharp increase in the bonds between the powder particles and the strength of the material. In cast asphalt concrete this effect is not manifested, despite the rather high content of asphalt binder in the material. The ratio of bitumen / mineral powder in this material is far from optimal, and therefore, the asphalt binder has the properties of bitumen, which softens with increasing temperature, and the coating layer forms inflows and waves from moving vehicles.

In addition, the strength of the structure is ensured by the mechanism of perception of external loads, which is fundamentally different from the load distribution of the coating core in multi-grained materials. Granular asphalt binder is a practically homogeneous material, and therefore, the external load is distributed evenly over the contact area of \u200b\u200bthe road surface and the wheels of the car, reducing specific pressures and particle strength requirements of the mineral part of the material.

A sharp increase in the strength characteristics of granular asphalt binder allows to reduce the thickness of the upper layer of asphalt concrete coating to values \u200b\u200bof 1.5-3 cm with guaranteed ensuring the strength of the coating and at the same time reducing the material consumption of the layer. A decrease in the layer thickness leads to a decrease in tensile stresses arising from bending deformation. It is known that asphalt concrete, like many building materials, works well in compression and is much worse in tension. Thus, the integrated use of the procedures described in the characterizing part of the claims provides strength characteristics of asphalt concrete pavement.

The durability of the coating is guaranteed by the minimum water saturation of the material by analogy with cast asphalt concrete. It is known that asphalt concrete pavement is most susceptible to destruction during thaws with alternating frosts. During the thaw, the material is saturated with moisture, the volume of which increases with freezing, leading to cracking of the material and its destruction. The asphalt concrete pavement made of granular asphalt binder, having minimal water saturation, prevents the implementation of such a destruction mechanism.

Laying a granular asphalt binder with a small thickness on the surface of a freshly laid lower layer with further compaction leads to a partial indentation of the granules into the body of the lower layer, guaranteeing reliable adhesion of the upper and lower layers of the coating. It also helps to increase the strength characteristics of the coating as a whole.

The use of surface treatment to ensure the necessary adhesion of the road surface with the wheels of the car is traditionally used in the construction of coatings of fine-grained or sand mixtures. At the same time, a serious problem when wetting crushed stone for surface treatment with bitumen is the insufficient adhesion of stone material and bitumen. This often leads to the tearing of gravel particles from the road surface, which leads to the creation of emergency situations. The reason is dusty particles on the surface of the stone material. In this regard, many asphalt plants crushed stone before treatment with bitumen is pre-washed with water and then dried and treated with bitumen.

When creating an asphalt binder layer deposited on the surface of crushed stone particles, adhesion of the asphalt binder particles to the crushed stone surface is ensured by the fact that during the pelletizing process, each crushed stone particle repeatedly interacts with microvolumes of bitumen and is guaranteed to be wetted by it. The asphalt binder shell on the surface of the gravel provides reliable adhesion of the particle to the top layer of the coating, preventing it from flying out under the influence of the wheels of the car. This reduces the consumption of crushed stone for surface treatment of the coating. The optimum roughness of the surface of the coating in accordance with the experiments is achieved when the treated gravel with a temperature of 80-100 ° C is embedded in the roadway at a temperature of 80 ° C.

The measures considered make it possible to obtain high-strength and durable asphalt concrete pavement with a minimum content of expensive high-strength granite crushed stone. The increased content of bitumen in comparison with other types of coatings is compensated by the strength characteristics of the material, which allows to reduce the coating layer, reducing material consumption and facilitating the design. This allows the use of the proposed asphalt concrete pavement on bridges and overpasses.

A method of arranging an asphalt concrete pavement, including preparing the base, laying and compacting the lower coating layer with further laying and compacting the upper layer onto the still-cooled lower layer and surface treatment by crushing crushed stone, characterized in that the upper coating layer is 1.5-3 cm thick from granular asphalt-binding material obtained by the pelletizing method, with a bitumen content of not more than 15%, and for surface treatment use pre-prepared crushed stone with a particle size of 3 -5 mm, on the surface of which a layer of asphalt binder obtained by the pelletizing method is applied, while the amount of asphalt binder in the shell is 5-10% by weight of crushed stone, crushed stone consumption is not more than 5 kg / m 2, and crushed stone is heated after the laid layer cools down to a temperature 80 ° C.

Related patents:

The invention relates to a method for producing a waterproofing composition, which can be used in construction as a waterproofing material for sealing potholes and road cracks.

Historians claim that the first mention of something similar to asphalt appeared in the 6th century BC in Babylon. But the technologies of those times were not reliable, plus unnecessarily expensive, as a result, such roads were forgotten until the twentieth century. The construction of asphalt concrete pavements in Russia began in 1928 and to this day it is predominant.

What it is

This composition is used everywhere, starting with the laying of federal highways and ending with the arrangement of urban squares and garden paths in private construction.

According to GOST and SNiP, the device of asphalt concrete coating can be different.

But the overall composition of the mixture, for more than 100 years, remains unchanged:

First of all, as an astringent, bitumen enters there..
Surely, to one degree or another, sand and large mineral fillers are present.
Various mineral or synthetic additives complete the list..

In those days when the composition was developed, natural bitumen was used, but since it is scarce in nature, an artificial analogue was synthesized based on oil products, which is still successfully used by road workers around the world.

The sand is taken quarry, as for the large filler, then along with various, crushed rock and some crystallized slag are widely used.

Natural mineral or synthetic additives are used to increase certain beneficial properties of the coating. In particular, it increases frost resistance, road adhesion, viscosity coefficient and much more.

What formulations are produced

The assortment of the presented types is quite wide, depending on the percentage ratio of the components, as well as on what additives were used, experts divide asphalt into the following varieties.

For the arrangement of sidewalks, garden paths or the inner space of urban courtyards, sand compositions are used.
Fine-grained structures cover the city streets with medium and high traffic.
Coarse-grained asphalt is used as a base layer in multi-layer paving technology.
Bitumen-polymer coatings are used in the installation of bridges, three-dimensional parking or road junctions. They have increased strength and durability.
Crushed stone mastic types of asphalt are considered the strongest; they are laid by federal highways and high-speed autobahns with increased traffic load.
For stadiums, treadmills or bicycle paths, as well as other sports facilities, there is a rubber-bitumen coating.

Making asphalt at home

The manufacture of pavement is considered to be difficult and inaccessible. But, nevertheless, there are enthusiasts who are ready for experiments. Of course, such compositions are not designed for the federal highway, but in the country it is quite realistic to prepare such asphalt with your own hands.

Tip: from experience it can be said that a mixture prepared by a makeshift method, of course, is suitable for arrangement, but more often it is used to repair potholes on an already finished coating.

Classic recipe

For preparation, we need ordinary river or quarry sand, bituminous resin or bitumen, and fine gravel. From the equipment you will need a metal barrel and a bucket.

It is better to cook asphalt at the stake, since it is unsafe and expensive to use gas.

Initially, we pour crushed stone with sand in a ratio of 2: 1 and mix well. All this should be filled with water and suspended over a fire.
At the same time we are preparing a bitumen base. To do this, take a metal bucket and heat the bitumen in it to a boil, synthetic polymers can be added as a plasticizer, but it is cheaper to use shampoo or any detergent.
When the resin has warmed up, and the water in the barrel with crushed stone has also boiled, they need to be combined. Water is needed so that crushed stone with sand does not heat up above 100ºС. Next, this broth should be stirred, maintaining a boil until all the water has boiled away. While the solution is hot it can be poured.

Important: be careful, at 80 ºС the bitumen melts, and at 100 - 120 ºС it boils.
But even at 170 ºС, bitumen can ignite.
Actually, in order to prevent such a fire, we use water.

Use of old pavement

Dismantling of asphalt concrete pavements and substrates can be a good material for the preparation of new asphalt.

The technology is partly reminiscent of the previous version, but with some amendments.

The dismantling of asphalt concrete pavement itself is carried out by the old-fashioned method, using a sledgehammer and other percussion instruments. Only the top layer of asphalt connected with bitumen is used, you can not touch the travel pillow.
The old road surface is broken into pieces with a fraction of not more than 40 mm. For 100 kg of old asphalt, 10 kg of bitumen is taken.
After that, the crushed substance must be poured with water and boiled in a barrel until melted. Further, the technology repeats the above option. Heated bitumen combines with molten asphalt and water evaporates.

Cold asphalt

The two methods described above are well suited for economical repair of damaged asphalt in the yard or near the yard. If you need to cover an area with a large quadrature, then we recommend using cold asphalt.

In the market of our country, this coating appeared about 5 years ago. The principle of operation here is similar to the well-known cold welding. For ligament used modified bitumenthanks to which it can be laid even at subzero temperatures. Instructions are on the packaging.

The only disadvantage of this material is the significant price. But, as you know, the asphalt from the factory is released hot and must also be laid hot. Therefore, for remote locations, cold polymer asphalt is the only alternative.

Important: when repairing pavement, the problem is the quality of the joint seam in asphalt concrete pavement.
Cold asphalt based on polymers completely solves this problem, since it reliably fits with any composition based on bitumen.

Rules for laying coatings

The construction of asphalt concrete pavement is a responsible matter and it will not be so important whether you lay it yourself or hire professionals. Laying and acceptance of asphalt concrete pavement is carried out according to SNiP 2.07.01-89, as well as a number of GOSTs.

Only a specialist can understand these documents, therefore we have outlined the main provisions of these norms and rules in a more understandable language.

Preparatory stage

Any work begins with markup. You need to clearly decide where the asphalt will be laid. Where the border will be mounted, and what it will be. It is also very important to make sure that the drainage, drainage system and drainage systems are fully installed.

All work on the installation of underground utilities by this time should be completely completed. If you are arranging a parking lot or access roads to an office, it is best to find out in advance where city communications are located, as if necessary, municipal services will tear your coverage and may still be fined.

It was mentioned above about the varieties and purpose of existing types of asphalt. So, at the preparation stage, you need to choose which material you are going to stack.

Important: the estimate for the asphalt paving device should not only contain data on the cost of the material and the amount of work.
It will be useful to include transportation costs in it, as well as leave the column for unforeseen expenses, such as permission to work from the relevant official or service.

If a pedestrian walkway or a platform with occasional passage of cars is laid, then a gravel-gravel pillow can be made up to 15 cm thick. The thickness of the asphalt concrete coating will be in the range of 4 - 5 cm.

If you equip a gas station or any access roads along which, with a high degree of probability, heavy-duty equipment will periodically pass, then in this case the thickness of the gravel pillow will be about 25 - 35 cm. Plus, asphalt itself is laid at least in 2 layers.

After marking, the arrangement of the so-called trough or pit under the road begins. In the urban area or in private construction, as a rule, roads and sites are made at approximately the same level, so the soil must be chosen completely for the entire thickness of the “road cake”. Federal highways are equipped with a slightly different technology, but we will not dwell on it.

When the soil is selected, the entire site should be well compacted, this is done with a roller or vibrating plate. Pay attention to the presence of trees nearby, the roots may tear the asphalt over time, so it is best to remove them immediately if possible. Although the price of work will be slightly increased, we advise you to cover the soil with geotextiles, so that the vegetation does not break through the coating.

Important: at this stage, borders are installed, they play the role of a kind of formwork for the "road cake".
If laying paving slabs the curb is made below the level of the road, then here, on the contrary.
In this regard, it is necessary to immediately plan the drains for water drainage.

Now you can begin to dump the pillows from crushed stone. For footpaths with a pillow thickness of 10 - 15 cm, 1 layer of crushed stone of a fraction of 30 - 40 mm is sufficient. More powerful bases fit into several layers.

The lower layer is used for drainage in the event of a rise in groundwater; it is sprinkled with large gravel with a fraction of 40 - 70 mm. The next layer with a fraction of 20 - 40 mm will be responsible for the even distribution of the load on the base of the road.

The final layer of filling is made of fine gravel with a fraction of 5 - 20 mm. He will also be responsible for the distribution of the load, but in addition he will turn the pillow into a dense, monolithic structure.

All layers laid must be tightly packed. For serious coatings, road rollers weighing from 2 to 10 tons are used. Each ball of filling is compacted separately, the skating rink must be walked on it at least 5 times, plus in modern road skating rinks there is a vibropress function, which increases the efficiency several times. During tamping, the surface should be watered regularly.

Tip: in the process of tamping, you must immediately take into account the angle of inclination of the road, on average it is on the order of 1º per 1 linear meter.
To do this, periodically check with the markup or level data.

Asphalt paving

After tamping the pillows, you can proceed directly to the laying of asphalt. As mentioned earlier, for sidewalks and adjoining territories, it is enough to lay a fine-grained composition with a layer of up to 50 mm. Heavy road rollers are also not required, you can get by with a light roller or vibrating plate.

Note!
This type of coating according to SNiP is not recommended for laying in places for rest.

More serious objects are paved in 2 layers. In this case, the lower layer is laid coarse asphalt at the level of 40 - 50 mm. A fine-grained composition is imposed on it almost immediately, which in most cases is the finish.

Currently, technologies have been developed according to which a reinforcing mesh made of polymer materials should be laid between the layers of hot asphalt. As a result, the durability and strength of such a road increases significantly. This technology is used when laying federal highways and roads with increased load.

Although according to GOST, thermal profiling of asphalt concrete coatings should be carried out.
This procedure involves preheating roadbed to a depth of 2 - 5 cm.

The mixture must be delivered hot to the object, as a rule, it is brought by dump trucks with a loading capacity of 7 - 20 tons. After that, asphalt is manually or mechanically distributed evenly along the road plane, observing the slope. On average, 1 ton of asphalt with a thickness of 40 mm is consumed per 10 m² of roadbed.

The construction of asphalt concrete pavements is a weather-dependent process. In the cold season, that is, at temperatures below +5 ºС, work is generally not recommended. Plus, during rain or in wet weather, the styling quality is significantly reduced, since the composition is moistened and cools faster.

Conclusion

We outlined the general basic principles of high-quality asphalt paving, but science does not stand still and technologies are supplemented and improved. In the video in this article, you can consider the process of laying asphalt in more detail.

The Russian standards of the road industry are allowed to arrange asphalt concrete pavements only at positive air temperatures (not lower than +10 ° С in the fall and +5 ° С in the spring). Although many still working specialists remember that in the 60-70s of the last century, the USSR was practiced and even encouraged road construction in the winter time. For example, a departmental temporary instruction (VVI 112-58) or BCH 120-65 (Technical instructions for the construction of roads in winter conditions, Ministry of Transport of the USSR M., 1966) gave a whole list of conditions, rules and types of work allowed for production in winter (up to -5 ... -10 ° C), including the device of asphalt concrete coatings.

True, the practical experience accumulated in those years has shown that nothing good happens in winter in terms of quality and durability of coatings. Therefore, the following regulatory and instructional documents (SNiP 2.05.02-85, SNiP 3.06.03-85, etc.) rightly and strictly prescribed to lay such coatings only at positive air temperatures. And most road customers and contractors follow these restrictions and requirements, although at times it is still possible to observe asphalting of roads at + 2 ... + 3 ° С or even at 0 ° С.

This sometimes happens “without malicious intent” of the contractor in those places and regions (Murmansk, Arkhangelsk, Vologda and Leningrad regions, the Republic of Karelia and Komi), where autumn or spring weather is sometimes subject to sudden and sharp changes for the worse within 2-3 hours .

The started asphalt concrete work at + 5 ... + 6 ° С can continue until its completion when the temperature decreases by 3–4 ° С, and even with increased wind and rainfall in the form of rain or wet snow, that is, beyond the permissible temperature and weather restrictions. What, then, should a master, foreman or other leader do? Stop work ?!

The solution, it would seem, is simple, logical, and meets the requirements of SNiPa, but does not fit well into reality. After all, dozens, and sometimes hundreds of tons of asphalt concrete mix have already been released at the ABZ, dump trucks are transporting it or brought to the place of masonry. Yes, and work schedules can sometimes not be disrupted.

In addition, in Russia there are also special and even somewhat typical cases when a road worker is involuntarily forced to arrange asphalt concrete pavements when low temperatures air up to -5 ... -10 ° С. This applies, first of all, to some industrial and residential areas of the Far North, Siberia and the Far East (Tyumen oil and gas production areas, the region of the Norilsk mining and metallurgical plant, in the Krasnoyarsk Territory, Magadan Region, the Republic of Sakha-Yakutia and other places), where the duration of the period with positive air temperature is extremely short (2-3 months a year) and it is not enough to fulfill all volumes road works, including final asphalt concrete.

In the European part of Russia sometimes isolated emergency or emergency situations arise when it is required, for example, in November-December to urgently lay an asphalt concrete pavement on a bridge or on a destroyed section of an existing road.

To help road workers seeking to reduce or even eliminate serious defects associated with a possible deterioration in the quality of the asphalt pavement device in the above adverse conditions and in places, SoyuzdorNII and its Leningrad and Omsk branches in 1990 developed “Guidelines for the construction of asphalt concrete pavements at low positive and negative (up to -10 ° С) air temperatures” (authors Nikolsky Yu. E., Kostelov M. P. , Babak O.G., Fursov S.G., Permyakov V.B. et al.). But the data and advice presented here are based not only on these “ Guidelines... ”, they also take into account the practical experience of many Russian and foreign contractors, including seven road construction and repair companies of the Dorstroyproekt association.

Of course, if asphalt concrete work at low or even negative air temperatures is foreseen or planned in advance, then it is simpler and easier to carry out mandatory preparation for such working conditions of the ABZ, vehicles, laying and compacting equipment, people and the object itself. If such work arises spontaneously and it is impossible to carry out the required training, the payment for it may be inadequate or even too high.

And not only because of possible loss of quality of the work itself. For example, the company “Roads of the North” during start-up and adjustment of the operating mode of the mixing plant DS-158 (Yaniga village near the town of Lodeynoye Pole, Leningrad Region) for two days in December 2000 with a sudden drop in air temperature to -13 and - 18 ° C burned 7 or 8 electric motors. True, high-quality hot mix on the device of the lower coating layer of the new bridge across the river. Yandeba (instead of the old emergency one) was nevertheless fully released, laid and motor traffic was opened across the bridge.

The main thing in the preparation of ABZ and vehicles is to take care of the insulation of all bitumen pipelines, conveyors, screws, bins, bodies and the materials themselves, which are part of the asphalt mix. Particular attention should be paid to reducing potential heat loss. hot mix during transportation to the installation site. How all this is done, Russian road workers are well aware.

The most difficult and responsible in such conditions are two operations - laying the mixture in the coating and its compaction. The technology for performing these operations cannot be the same as, for example, at + 25 or + 10 ° С. It should be changed in relation to the real temperature of the air and other conditions at the facility, carefully thought out and reflected in the technological scheme of the work or in the PPR, i.e., preliminary engineering and organizational preparation should be carried out with a concrete decision on the technology for performing these operations.

This is due to the rather rapid cooling of the mixture layer after laying in the coating and the inability for this reason to seal it qualitatively. It is known that the thinner the mixture layer, the faster it cools to a temperature of + 60 ° C (sand mixtures G and D) or 70 ° C (crushed stone mixtures of types A and B), at which it is advisable and necessary to complete the laying of the coating.

Studies specially conducted in Russia and abroad, including on road construction and in laboratory conditions (freezers), showed that the nature and speed of cooling (Fig. 1), and accordingly, for the time from the moment the mixture appeared in the coating (usually at 130–140 ° С after the stacker) and until the seal is completed (at temperatures of 60–70 ° С) two factors mainly affect the layer thickness and weather (air temperature, wind).

On thin layers (2-3 cm) and at negative temperatures (-5 ...- 10 ° С), the time allotted for packing can be no more than 10 minutes, which will be clearly insufficient for a complete and high-quality compaction. Under the same conditions, a thicker layer (9–10 cm) can maintain the temperature necessary for rolling in almost 4 times longer (Table 1). Therefore, the need for technological methods and means of fast and effective compaction is more important for thin layers than for thick ones.