Introduction………………………………………………………2
1.General position………………………………………………………………………………………………
2. Device of the road surface………………………..4
3. Operation of the road surface……………………5
4. Classification of road surface…………………7
4.1. Coatings built using organic binders………………………………………….7
4.2. Asphalt concrete and tar concrete pavements…9
4.3 Dirt roads. Crushed stone and gravel…
………………………………………………………………….11
4.4. Cement-concrete coatings………………………….13
4.5. Bridge………………………………………………..15
4.6. Gravel coatings……………………………………………………16
4.7.Crushed stone coatings………………………………………………17
5. Structural layers of pavement……………..19
Conclusion…………………………………………………...22
List of information sources used……
…………………………………………………………………..23
Introduction.
Highways are of great economic, social and defense importance for the country. The state of the road economy is one of the most important indicators characterizing the level of development of the productive forces of society.
A dense network of highways that meets the requirements of traffic flows makes it possible to rationally transport goods and passengers, draws the resources of individual regions into economic circulation, and creates conditions for saving public time.
The growth in the carrying capacity and speeds of vehicles requires the continuous development of the road network, the improvement of pavement designs. The inconsistency of the road condition with the requirements of the traffic flow reduces the speed of movement, increases the wear and tear of cars and the cost of their repairs, increases fuel consumption and tire wear, and contributes to an increase in the number of traffic accidents.
1. General position.
The road construction consists of technological processes performed in a certain sequence and requiring large expenditures of material and labor resources. The reduction of these costs can be achieved by the widespread introduction of complex mechanization and automation of production processes.
Significant changes have taken place in the field of integrated mechanization and automation. Thus, in the construction of roads with cement concrete pavement, a new technology for pavement in sliding formwork was introduced, which almost completely replaced the technology for pavement in stationary formwork, which made it possible to increase the pace of construction by several times, reduce labor costs and significantly improve the performance of roads. The introduction of this technology became possible thanks to the creation of a new set of machines with sliding formwork. All machines of this set are equipped with automation systems. To provide a set of machines with road construction materials, new high-performance cement-concrete plants and soil-mixing plants have been created.
Significant changes have also taken place in the technology of building roads with asphalt concrete pavements. The new pavers make it possible to provide a higher degree of pre-compaction of asphalt mixtures, which not only reduces the cost of their further compaction, but also improves the quality of the pavement. Asphalt pavers are equipped with automatic systems for providing a longitudinal and transverse profile and blocking the travel drive and working bodies.
2.Paving device
Motor roads consist of a subgrade with artificial structures, a carriageway and roadsides. The stability of the subgrade is achieved by laying it out of solid soils and devices for the removal of surface and groundwater.
The width of the subgrade consists of the width of the carriageway and its two shoulders.
The carriageway is covered with pavement. Pavement is made in one or more structural layers. Multilayer pavement is usually installed on permanent roads and has the following main structural layers:
Pavement - the top layer of pavement, which in turn consists of a wear layer, periodically renewed as it wears out, and the main layer that determines the performance properties of the pavement.
Base - the bearing part of the road pavement, which, together with the coating, ensures the transfer of loads to the underlying layer or directly to the subgrade soil.
Additional base layer - the lower structural layer of the pavement, which, along with the transfer of loads to the subgrade, also functions as a frost-protective, draining, leveling and other layers.
The base materials are crushed stone, crushed stone, gravel, soil treated with binders, and for an additional layer - coarse sand, gravel soils, crushed rock and other local materials.
3. Operation of the road surface.
The strength of the pavement is achieved by restoring the wear layer, evenness - by eliminating irregularities, wheel adhesion with the coating - by removing snow and dirt, sprinkling with sand, small gravel, etc. Dust removal is carried out by treating the coatings with black binders (bitumen, road tar) and dust-binding materials. The evenness of the coating determines the speed of the vehicles.
In the spring-autumn period, it is important to maintain the transverse profile of the subgrade, which ensures the flow of water through the drainage structures. Variable loads from wheels with different traffic intensity cause waves and shifts on the surface. During the summer period, it is important to prevent dust on the roads, because. dust worsens the working conditions of drivers and increases the wear and tear of vehicles.
In order to remove dust, it is recommended to spray a dust-binding substance onto a previously leveled dry surface of the coating with watering machines. The consumption of dust-binding substances is 0.5-1.5 l per 1 m 2 of coating, and the duration of dust removal is 15-100 days, depending on the type of material.
In winter, snow removal and icing are of particular importance. Moreover, it is necessary to ensure the coefficient of adhesion of the wheels to the road is not less than 0.3. Snow removal is carried out by bulldozers, graders, snowplows, of which rotary and milling-rotary are the most effective, because. able to develop packed masses of snow. The fight against glaciation is carried out by scattering loose materials (sand, ash, boiler slag, gravel, etc.) with an approximate consumption of materials - 0.1-0.4 m 3 per 1000 m 2 of coating or treatment with chemicals that destroy the crystalline structure of ice (table salt, calcium chloride, etc. in the composition of 50 g / l) with a solution flow rate of 120-200 l / m 2 (up to 7% of anti-corrosion additives are introduced into solutions to prevent corrosion of machines and mechanisms).
Current repairs include work to prevent and eliminate minor damage to the road and road structures: patching cracks and potholes, fixing subsidence, backfilling potholes, road grading, repairing damage to the subgrade,
cleaning roads from dirt, etc.
Average repair is carried out 1-2 times a year and includes work to eliminate road wear: surface treatment of asphalt concrete, black, crushed stone and gravel coatings, replacement of individual slabs, leveling of coatings with the addition of crushed stone or gravel, surface treatment of the road.
4. Road surface classification
4.1 Coatings built using organic binders
With the use of organic binders, improved coatings of both lightweight and capital types are arranged. Improved lightweight pavements are arranged on roads with a traffic intensity of 500 to 3000 vehicles per day. The most widespread are improved lightweight coatings, arranged according to the method of surface treatment, impregnation or mixing. They have a smooth, non-slip and dust-free surface that allows the movement of vehicles at high speeds. Their design ensures the movement of heavy vehicles throughout the year.
Surface treatment. Surface treatment is arranged to create a mat on the surface of finely crushed stone material treated with bitumen. Such a mat protects the coating from wear, increases the roughness, evenness and water resistance of the pavement. Rough surface treatment is used both in the construction of new clothes and in the restoration of roughness on the worn slippery surface of existing coatings. The surface treatment device must first of all be provided for in the following sections: on slopes, on horizontal curves of a small radius, at intersections at the same level, as well as on approaches to these sections at a distance of at least 50-100 m and on other difficult sections of the road.
Depending on the purpose, surface treatment can be single or double.
4.2. Asphalt concrete and tar concrete pavements.
Asphalt concrete and tar concrete pavements are classified as advanced pavements. capital type, they are arranged on the roads of I, II, III categories with a traffic intensity of more than 3000 cars per day. These coatings are made from hot, warm and cold asphalt or tar mixes prepared in plants. Asphalt concrete, depending on the type of stone material, is divided into crushed stone, consisting of crushed stone, sand, mineral powder and bitumen; gravel, consisting of gravel, sand or gravel-sand material, mineral powder and bitumen; sandy, consisting of sand, mineral powder and bitumen.
Asphalt-concrete coatings are arranged as single-layer and two-layer on stone and concrete bases. For better adhesion with asphalt concrete, stone bases are treated with bituminous or tar materials. The number and thickness of the layers are usually set for constructive and economic reasons and are checked by strength calculations.
The disadvantages of asphalt concrete pavements include their dark color, which creates high light absorption, which can cause accidents in the evening. During the construction of asphalt concrete pavements, it is possible to use an illuminator, as a result of which an increase in the brightness of the pavement at night and an increase in its reflective ability is achieved. For this purpose, light natural or artificial crushed stone is used to prepare the asphalt concrete mixture.
Clarification of the asphalt concrete pavement is possible by surface treatment with the device of a wear layer of light materials.
The arrangement of a layer using light materials can be carried out by embedding light material into undercompacted asphalt concrete, followed by additional compaction or gluing of light material to the surface of the asphalt concrete pavement using mastics.
Changing the color of the road surface with alternating coloring reduces driver fatigue in areas with a monotonous landscape, increases the driver's attention and helps to better navigate. For the device of such coatings, colored plastic concretes are used, which are a compacted mixture of crushed stone, sand, mineral powder, pigment dye and binder, taken in certain proportions.
4.3 Dirt roads. Crushed stone and gravel coatings
Dirt roads. Unpaved roads are roads constructed from natural soil and soil reinforced with additives of other materials. The surface of the road is given a convex profile, which is created using imported soil or soil obtained during the installation of drainage ditches.
Depending on the properties of the soil, the road has greater or lesser stability, and, consequently, passability. Well maintained dirt road dry time of the year provides the passage of cars with sufficient speeds. A big disadvantage of dirt roads is their dustiness. During the period of autumn and spring thaws, due to waterlogging of the soil and loss of bearing capacity, dirt roads become impassable, as deep ruts, potholes and potholes are formed under the influence of car wheels.
To improve the passability, dirt roads are strengthened with additives. Observations show that soils with a coarse-grained skeleton containing coarse sand and gravel particles of 45–75% and clay particles of 6–12% do not get wet and do not lose their bearing capacity even with significant moisture. This composition of the soil is called optimal.
If the natural soil of the carriageway differs in composition from the optimal mixture, the missing particles are added to it and adjusted to the optimal composition. When introducing additives into natural soil, good mixing, thorough profiling and compaction must be ensured.
Improved dirt roads keep the profile well and provide passage at a traffic intensity of up to 100 vehicles per day. With more intensive traffic, the road surface is deformed and requires enhanced grading work. The improved dirt roads cannot withstand the movement of heavy vehicles. Profiling (flattening) of dirt roads must be carried out systematically, especially after rains.
It is possible to more reliably increase the water resistance of soils and their cohesion by introducing additives of mineral (cement, lime) and organic (bitumen, tar) binders. The most suitable for processing with additives of binders are sandy loamy soils and soils of optimal granulometric composition. Soils treated with additives become stable and are used for coatings at a traffic intensity of up to 500 vehicles / day.
4.4. Cement-concrete coatings.
Cement concrete pavements are installed on roads of categories I, II and III with high traffic intensity (more than 3000 cars per day). The advantages of cement-concrete pavements are high strength, evenness and at the same time sufficient roughness, which ensures good adhesion of car tires to the road surface.
Cement-concrete pavements are increasingly being used due to their cost-effectiveness and ease of use. The production of works on the installation of cement concrete pavements is almost completely mechanized.
Cement-concrete pavement is a concrete slab laid on a solid and stable base. As bases for concrete coatings, soil layers reinforced with binders, coarse-grained or medium-grained sand, crushed stone, gravel or gravel-sand mixture are used. Cement-concrete pavement on a sandy base may only be laid on category III roads and at reduced intensity on category II roads. The foundations are arranged 0.5 m wider than the carriageway on each side.
The concrete used to make the slabs is a rationally selected mixture of crushed stone, sand, cement and water. The strength of such a mixture is characterized by compressive strength after 28 days of hardening. The brand of concrete is determined precisely by this characteristic and for road surfaces it must be at least 300.
The thickness of the concrete slab is determined by calculation, taking into account the size and nature of the movement. Typically, the slab has a thickness of 18-24 cm within the entire width of the carriageway and a transverse slope for water runoff of 10-15%.
The thickness of the concrete slab can be reduced by applying prestressing reinforcement to prestress the concrete to be placed.
To protect the plate from the formation of cracks during temperature changes, expansion joints are arranged. Expansion joints (transverse), providing elongation of the slab, have a gap of 2.5–3 cm and are arranged every 20–80 m.
Compression joints (transverse) protect the slab from cracks that occur when the temperature drops, they are cut to a depth of 5 cm 1 cm wide after 4-10 m. The distance between the transverse joints depends on the type of base, slab thickness and air temperature during concreting.
Longitudinal seams are made along the axis of the roadway with a width of 7–7.5 m or parallel to the axis through 3.5–3.75 m. pin laying. The pins prevent transverse displacement of the plates at the seams and at the same time allow them to move in the longitudinal direction. To ensure water tightness, the seams are filled with elastic material or special mastic.
In some cases, pavements are made with steel reinforcement, mainly to prevent cracking. If the coating is arranged in two layers, then the metal mesh is placed between the first and second layers.
It is possible to install cement-concrete coatings from ready-made reinforced concrete slabs, which are transported to the site by trucks and laid on a pre-prepared base by truck cranes. The complexity of the installation and transportation of plates large sizes does not allow this method to be applied on a large scale.
4.5. Bridges.
A pavement is called a coating consisting of a piece of stone.
The materials used for pavements are natural and artificial.
The natural checker includes a checker of the correct form (paving stones, mosaic checker), made from durable rocks of stone, or a coarse checker, which has approximately the shape of a truncated pyramid and a height of 14-18 cm. 18 cm, which can also be used for bridging. The construction of the pavement requires skilled manual labor.
The surface of the pavement is uneven, the speed of vehicles on it is limited, so pavements are becoming less and less used.
Improved paving stones and mosaics are used only in urban areas. High strength, durability in some cases justify the high cost of their construction. Such bridges provide a traffic intensity of more than 3,000 vehicles per day with design speeds for roads of categories I-III. The complexity of mechanization, a large amount of manual labor does not allow them to be used on a large scale on country roads.
4.6. Gravel coatings.
Gravel coatings are of a transitional type, they are arranged on roads with low traffic intensity (up to 500 vehicles / day). In good condition, the gravel surface provides a speed of up to 70 km/h.
Gravel mixtures are found in nature in the form of natural deposits containing particles of rock fragments of various sizes. For the pavement, the gravel material must meet the requirements of an optimal mixture and be selected according to the principle of greatest density. Its composition should contain a sufficient amount of fine earth (clay and dusty particles), which fills the voids between large particles and, when the mixture is wetted during the period of coating compaction, seems to cement large particles together. Gravel coverings arrange a sickle-shaped or half-trough profile directly on the subgrade or on the underlying layer of sand. The thickness of the gravel coating, depending on the traffic conditions, is 8-16 cm single-layer and 25-30 cm double-layer. For the lower layer, it is possible to use mixtures with a grain size of up to 70 mm, for the upper layer - no more than 25 mm.
During the period of operation, gravel coatings require proper maintenance. Irregularities are corrected by ironing or profiling with motor graders when the coating is wet.
4.7.Crushed stone coatings.
Crushed stone pavements, as well as gravel, are arranged on roads of categories IV and V with low traffic intensity (up to 200 cars per day). For the device of crushed stone coatings, artificially crushed stone material is used, more often limestone, having a compressive strength of at least 600 kgf / cm2.
For the lower and middle layers of crushed stone bases and coatings, fractionated crushed stone with a particle size of 40-70 and 70-120 mm is used; for the upper layers of bases and coatings - 40-70 mm; for wedging - 5-10, 10-20 and 20-40 mm. Crushed stone of weak rocks is used with a size of more than 70 mm.
Crushed stone coating is arranged on a sandy underlying layer. Other local materials (slag, shell, gravel) can be used for the foundation.
The principle of the crushed stone coating device is as follows. Crushed stone with a particle size of 40 mm and above is scattered on a pre-prepared base, leveled according to a given profile and pre-compacted with rollers until the crushed stone is immobile. Then, for wedging, smaller stone material is successively scattered - crushed stone with a particle size of 10-20 mm and 5-10 mm. Rolling achieve complete jamming of gravel. When rolling, crushed stone is watered, which facilitates the mobility of crushed stones during rolling and contributes to cementation and better formation of the coating.
Crushed stone coating is arranged in a trough profile in one layer 10-18 cm thick, and with a thickness of more than 18 cm - in two layers. For the lower layer, less durable crushed stone is used. The coating surfaces are given a transverse slope of 30% o-
The crushed stone coating wears out rather quickly and is not stable during car traffic. Tangential forces from the wheels of a moving car upset the cohesion of the gravel, as a result of which the coating quickly collapses. To increase the cohesion of crushed stone, the water resistance of the coating and eliminate dustiness, crushed stone is treated with bituminous and tar materials.
5. Structural layers of pavement
Pavement is arranged on a planned and compacted subgrade surface, it must ensure the movement of vehicles of a given weight at a calculated speed and be sufficiently resistant to the influence of climatic factors.
Depending on the thickness and materials used, pavement can be placed on the subgrade along a sickle-shaped, semi-trough or trough profile.
The crescent profile is used mainly on roads of lower categories. For the installation of crescent-shaped coatings, local materials are used: gravel, soil and others, reinforced with various additives. With a sickle-shaped profile, pavement is arranged for the entire width of the earthen bed. The thickness of clothing, greatest in the middle, is gradually reduced to 3-5 cm at the brows.
Road pavement can be of different strength depending on the intensity and composition of traffic, traffic density, design speed and must meet the following requirements: its strength must ensure the absence of subsidence and high wear resistance; the evenness of the surface should provide the possibility of movement at high speeds; The surface roughness should ensure good adhesion of the coated vehicle wheels.
One of the main conditions for improving traffic safety is to reduce the slipperiness of the road surface. An analysis of traffic accidents shows that in the summer of accidents due to the slipperiness of coatings, 4-16% occur, and in autumn and spring 40-70%.
The reason for the increase in slipperiness may be dirt brought onto the roadway from roadsides, unreinforced ramps or junctions, which sharply reduces the adhesion properties of the coating. To prevent the drift of dirt onto the roadway, roadsides, ramps and junctions are strengthened.
The surface roughness of the pavement of the roadway must ensure the coefficient of adhesion of the car tire to the surface of the pavement in the wet state of at least 0.5. To create a rough surface arrange surface treatment.
The main factors on which the choice of pavement design depends are the intensity and composition of traffic. The greater the intensity of traffic on the road, the faster the pavement wears out, therefore, with a high traffic intensity, a more thorough, durable and perfect pavement should be arranged. On roads with less traffic, the pavement is subject to less wear and therefore it can be of a lighter type. In those cases where the intensity of traffic in a given period is small, but it is expected to increase in 5-10 years, transitional-type pavements are arranged, which, after strengthening, can be classified as improved. At low traffic intensity, cover of the lowest type is suitable.
Conclusion
Nowadays, the latest technologies and developments are being introduced into the road construction industry. Currently, in Belarus, the problems associated with the construction and operation of roads are the most significant. The country's economy is stabilizing, and the standard of living of Belarusians is rising accordingly. The purchasing power of people is increasing, therefore, there are more and more cars on our roads.
To date, the quality of roads for the most part does not meet the requirements of car owners. In this regard, the government of Belarus pays great attention to the problems of construction and operation of roads.
List of used information sources.
1. http://revolution.allbest.ru/transport/
2. http://www.lib.ua-ru.net/diss/
3. http://www.usecar.ru/page22
4. http://otherreferats.allbest.ru/transport/
5. Kabanov V.V., Kirillova L.M. The device of road surfaces. M ‘‘Transport’’, 1992. - 262 p.
6. Glagoleva T.N., Garmanov E.N. and other Handbook of a road engineer. 3rd edition, revised and enlarged. M ‘‘Transport’’, 1977. - 560 p.
Content. Introduction ................................................ ..............2 1.General position ............................... ..................3 2.Paving arrangement .............................. ..4 3. Maintenance of the road surface
Content. Introduction ................................................ ..............2 1.General position ............................... ..................3 2.Paving arrangement .............................. ..4 3. Maintenance of the road surface .......................... 5 4. Classification of the road surface .................. .........7 4.1. Coatings built using organic binders .................................................................. ................7 4.2. Asphalt-concrete and tar-concrete pavements...9 4.3. Dirt roads. Crushed stone and gravel coatings ....................................................... ..................................11 4.4.Cement-concrete pavement ................. ...................13 4.5. Bridges ................................................. .......15 4.6.Gravel coatings .............................................. ....16 4.7.Crushed stone coatings.......................................17 5 .Constructive layers of pavement....................19 Conclusion.................................. ..................................22 List of information sources used .......... ..... ................................................. ......................23 Introduction. Highways are of great economic, social and defense importance for the country. The state of the road economy is one of the most important indicators characterizing the level of development of the productive forces of society. A dense network of highways that meets the requirements of traffic flows makes it possible to rationally transport goods and passengers, draws the resources of individual regions into economic circulation, and creates conditions for saving public time. The growth in the carrying capacity and speeds of vehicles requires the continuous development of the road network, the improvement of pavement designs. The inconsistency of the road condition with the requirements of the traffic flow reduces the speed of movement, increases the wear and tear of cars and the cost of their repairs, increases fuel consumption and tire wear, and contributes to an increase in the number of traffic accidents. 1. General position. The construction of a highway consists of technological processes performed in a certain sequence and requiring large expenditures of material and labor resources. The reduction of these costs can be achieved by the widespread introduction of complex mechanization and automation of production processes. Significant changes have taken place in the field of integrated mechanization and automation. Thus, in the construction of roads with cement concrete pavement, a new technology for pavement in sliding formwork was introduced, which almost completely replaced the technology for pavement in stationary formwork, which made it possible to increase the pace of construction by several times, reduce labor costs and significantly improve the performance of roads. The introduction of this technology became possible thanks to the creation of a new set of machines with sliding formwork. All machines of this set are equipped with automation systems. To provide a set of machines with road construction materials, new high-performance cement-concrete plants and soil-mixing plants have been created. Significant changes have also taken place in the technology of building roads with asphalt concrete pavements. The new pavers make it possible to provide a higher degree of pre-compaction of asphalt mixtures, which not only reduces the cost of their further compaction, but also improves the quality of the pavement. Asphalt pavers are equipped with automatic systems for providing a longitudinal and transverse profile and blocking the travel drive and working bodies. 2. Construction of the road surface Highways consist of subgrade with artificial structures, carriageways and roadsides. The stability of the subgrade is achieved by laying it out of solid soils and devices for the removal of surface and groundwater. The width of the subgrade consists of the width of the carriageway and its two shoulders. The carriageway is covered with pavement. Pavement is made in one or more structural layers. Multilayer pavement is usually installed on permanent roads and has the following main structural layers: Pavement - the top layer of pavement, which in turn consists of a wear layer, periodically renewed as it wears out, and the main layer that determines the operational properties of the pavement. Base - the bearing part of the road pavement, which, together with the coating, ensures the transfer of loads to the underlying layer or directly to the subgrade soil. Additional base layer - the lower structural layer of the pavement, which, along with the transfer of loads to the subgrade, also functions as a frost-protective, draining, leveling and other layers. The base materials are crushed stone, crushed stone, gravel, soil treated with binders, and for an additional layer - coarse sand, gravel soils, crushed rock and other local materials. 3. Operation of the road surface. The strength of the pavement is achieved by restoring the wear layer, evenness - by eliminating irregularities, wheel adhesion with the coating - by removing snow and dirt, sprinkling with sand, small gravel, etc. Dust removal is carried out by treating the coatings with black binders (bitumen, road tar) and dust-binding materials. The evenness of the coating determines the speed of the vehicles. In the spring-autumn period, it is important to maintain the transverse profile of the subgrade, which ensures the flow of water through the drainage structures. Variable loads from wheels with different traffic intensity cause waves and shifts on the surface. During the summer period, it is important to prevent dust on the roads, because. dust worsens the working conditions of drivers and increases the wear and tear of vehicles. In order to remove dust, it is recommended to spray a dust-binding substance onto a previously leveled dry surface of the coating with watering machines. The consumption of dust-binding substances is 0.5-1.5 liters per 1 m2 of coating, and the duration of dust removal is 15-100 days, depending on the type of material. In winter, snow removal and icing are of particular importance. Moreover, it is necessary to ensure the coefficient of adhesion of the wheels to the road is not less than 0.3. Snow removal is carried out by bulldozers, graders, snowplows, of which rotary and milling-rotary are the most effective, because. able to develop packed masses of snow. The fight against glaciation is carried out by scattering loose materials (sand, ash, boiler slag, gravel, etc.) with an approximate consumption of materials - 0.1-0.4 m3 per 1000 m2 of coating or by treating with chemicals that destroy the crystal structure of ice (cooking salt, calcium chloride, etc. in the composition of 50 g / l) with a solution flow rate of 120-200 l / m2 (to prevent corrosion of machines and mechanisms, up to 7% of anti-corrosion additives are introduced into the solutions). Current repairs include work to prevent and eliminate minor damage to the road and road structures: sealing cracks and potholes, correcting subsidence, filling potholes, road grading, repairing damage to the subgrade, cleaning roads from dirt, etc. Average repair is carried out 1-2 times a year and includes work to eliminate road wear: surface treatment of asphalt concrete, black, crushed stone and gravel coatings, replacement of individual slabs, leveling of coatings with the addition of crushed stone or gravel, surface treatment of the road. 4. Classification of pavement 4.1. Coatings built using organic binders With the use of organic binders, improved pavements of both lightweight and capital types are arranged. Improved lightweight pavements are arranged on roads with a traffic intensity of 500 to 3000 vehicles per day. The most widespread are improved lightweight coatings, arranged according to the method of surface treatment, impregnation or mixing. They have a smooth, non-slip and dust-free surface that allows the movement of vehicles at high speeds. Their design ensures the movement of heavy vehicles throughout the year. Surface treatment. Surface treatment is arranged to create a mat on the surface of finely crushed stone material treated with bitumen. Such a mat protects the coating from wear, increases the roughness, evenness and water resistance of the pavement. Rough surface treatment is used both in the construction of new clothes and in the restoration of roughness on the worn slippery surface of existing coatings. The surface treatment device must first of all be provided for in the following sections: on slopes, on horizontal curves of a small radius, at intersections at the same level, as well as on approaches to these sections at a distance of at least 50-100 m and on other difficult sections of the road. Depending on the purpose, surface treatment can be single or double. 4.2. Asphalt concrete and tar concrete pavements. Asphalt concrete and tar concrete pavements are classified as improved capital type pavements, they are arranged on roads of categories I, II, III with a traffic intensity of more than 3,000 cars per day. These coatings are made from hot, warm and cold asphalt or tar mixes prepared in plants. Asphalt concrete, depending on the type of stone material, is divided into crushed stone, consisting of crushed stone, sand, mineral powder and bitumen; gravel, consisting of gravel, sand or gravel-sand material, mineral powder and bitumen; sandy, consisting of sand, mineral powder and bitumen. Asphalt-concrete coatings are arranged as single-layer and two-layer on stone and concrete bases. For better adhesion with asphalt concrete, stone bases are treated with bituminous or tar materials. The number and thickness of the layers are usually set for constructive and economic reasons and are checked by strength calculations. The disadvantages of asphalt concrete pavements include their dark color, which creates high light absorption, which can cause accidents in the evening. During the construction of asphalt concrete pavements, it is possible to use an illuminator, as a result of which an increase in the brightness of the pavement at night and an increase in its reflective ability is achieved. For this purpose, light natural or artificial crushed stone is used to prepare the asphalt concrete mixture. Clarification of the asphalt concrete pavement is possible by surface treatment with the device of a wear layer of light materials. The device of the layer using light materials can be carried out by embedding the light material and the undercompacted asphalt concrete, followed by additional compaction or gluing of the light material to the surface of the asphalt concrete pavement using mastics Changing the color of the road surface with alternating coloring reduces driver fatigue in areas with a monotonous landscape, increases the driver's attention and helps to better navigate.For the construction of such coatings, colored plast concretes are used, which are a compacted mixture of crushed stone, sand, mineral powder, pigment dye and binder, taken in certain proportions.4.3 Dirt roads Crushed stone and gravel pavements Dirt roads Dirt roads are roads constructed from natural soil and soil reinforced with the addition of other materials. a convex profile is created, for the creation of which imported soil or soil obtained during the installation of drainage ditches is used. Depending on the properties of the soil, the road has greater or lesser stability, and, consequently, passability. A well-maintained dirt road during the dry season allows vehicles to pass at sufficient speeds. A big disadvantage of dirt roads is their dustiness. During the period of autumn and spring thaws, due to waterlogging of the soil and loss of bearing capacity, dirt roads become impassable, as deep ruts, potholes and potholes are formed under the influence of car wheels. To improve the passability, dirt roads are strengthened with additives. Observations show that soils with a coarse-grained skeleton containing coarse sand and gravel particles of 45-75% and clay particles of 6-12% do not get wet and do not lose their bearing capacity even with significant moisture. This composition of the soil is called optimal. If the natural soil of the carriageway differs in composition from the optimal mixture, the missing particles are added to it and adjusted to the optimal composition. When introducing additives into natural soil, good mixing, thorough profiling and compaction must be ensured. Improved dirt roads keep the profile well and provide passage at a traffic intensity of up to 100 vehicles per day. With more intensive traffic, the road surface is deformed and requires enhanced grading work. The improved dirt roads cannot withstand the movement of heavy vehicles. Profiling (flattening) of dirt roads must be carried out systematically, especially after rains. It is possible to more reliably increase the water resistance of soils and their cohesion by introducing additives of mineral (cement, lime) and organic (bitumen, tar) binders. The most suitable for processing with additives of binders are sandy loamy soils and soils of optimal granulometric composition. Soils treated with additives become stable and are used for coatings at a traffic intensity of up to 500 vehicles / day. 4.4. Cement-concrete coatings. Cement concrete pavements are installed on roads of categories I, II and III with high traffic intensity (more than 3000 cars per day). The advantages of cement concrete pavements are high strength, evenness and at the same time sufficient roughness, which ensures good adhesion of car tires to the road surface. Cement concrete pavements are increasingly used due to their economy and ease of operation. The production of cement concrete pavements is almost completely mechanized. the coating is a concrete slab laid on a solid and stable base.As the bases for concrete pavements, layers of soil reinforced with binders, coarse-grained or medium-grained sand, crushed stone, gravel or gravel-sand mixture are used. only on category III roads and at reduced intensity on category II roads The bases are arranged 0.5 m wider than the carriageway on each side The concrete used to make the slabs is a rationally selected mixture of crushed stone , sand, cement and water. The strength of such a mixture is characterized by compressive strength after 28 days of hardening. The grade of concrete is determined precisely by this characteristic and for road surfaces it must be at least 300. The thickness of the concrete slab is determined by calculation, taking into account the size and nature of the movement. Typically, the slab has a thickness of 18-24 cm within the entire width of the carriageway and a transverse slope for water runoff of 10-15%. The thickness of the concrete slab can be reduced by applying prestressing reinforcement to prestress the concrete to be placed. To protect the plate from the formation of cracks during temperature changes, expansion joints are arranged. Expansion seams (transverse), which provide elongation of the slab, have a gap of 2.5-3 cm and are arranged after 20-80 m. Compression seams (transverse) protect the slab from cracks that occur when the temperature drops, they are cut to a depth of 5 cm with a width of 1 cm after 4-10 m The distance between the transverse joints depends on the type of base, the thickness of the slab and the air temperature during concreting. Longitudinal seams are made along the axis of the roadway with a width of 7-7.5 m or parallel to the axis through 3.5-3.75 m. pin laying. The pins prevent transverse displacement of the plates at the seams and at the same time allow them to move in the longitudinal direction. To ensure water tightness, the seams are filled with elastic material or special mastic. In some cases, pavements are made with steel reinforcement, mainly to prevent cracking. If the coating is arranged in two layers, then the metal mesh is placed between the first and second layers. It is possible to install cement-concrete pavements from prefabricated reinforced concrete slabs, which are transported to the site by trucks and laid on a pre-prepared base by truck cranes. The complexity of the installation and transportation of large slabs does not allow the use of this method on a large scale. 4.5. Bridges. A pavement is called a coating consisting of a piece of stone. The materials used for pavements are natural and artificial. The natural ones include a checker of the correct form (paving stones, mosaic checker), made from durable rocks of stone, or a coarse checker, which has approximately the shape of a truncated pyramid and a height of 14-18 cm. 18 cm, which can also be used for bridging. The construction of the pavement requires skilled manual labor. The surface of the pavement is uneven, the speed of vehicles on it is limited, so pavements are becoming less and less used. Improved paving stones and mosaics are used only in urban areas. High strength, durability in some cases justify the high cost of their construction. Such pavements provide a traffic intensity of more than 3000 vehicles per day with design speeds for roads of categories I-III. The complexity of mechanization, a large amount of manual labor does not allow them to be used on a large scale on country roads. 4.6. Gravel coatings. Gravel coatings are of a transitional type, they are arranged on roads with low traffic intensity (up to 500 vehicles / day). In good condition, the gravel surface provides a speed of up to 70 km/h. Gravel mixtures are found in nature in the form of natural deposits containing particles of rock fragments of various sizes. For the pavement, the gravel material must meet the requirements of an optimal mixture and be selected according to the principle of greatest density. Its composition should contain a sufficient amount of fine earth (clay and dusty particles), which fills the voids between large particles and, when the mixture is wetted during the period of coating compaction, seems to cement large particles together. Gravel coverings arrange a sickle-shaped or half-trough profile directly on the subgrade or on the underlying layer of sand. The thickness of the gravel coating, depending on the traffic conditions, is 8-16 cm single-layer and 25-30 cm double-layer. For the lower layer, it is possible to use mixtures with a grain size of up to 70 mm, for the upper layer - no more than 25 mm. During the period of operation, gravel coatings require proper maintenance. Irregularities are corrected by ironing or profiling with motor graders when the coating is wet. 4.7. Crushed stone coatings. Crushed stone pavements, as well as gravel, are arranged on roads of categories IV and V with low traffic intensity (up to 200 cars per day). For the device of crushed stone coatings, artificially crushed stone material is used, more often limestone, having a compressive strength of at least 600 kgf / cm2. For the lower and middle layers of crushed stone bases and coatings, fractionated crushed stone with a particle size of 40-70 and 70-120 mm is used; for the upper layers of bases and coatings - 40-70 mm; for wedging - 5-10, 10-20 and 20-40 mm. Crushed stone of weak rocks is used with a size of more than 70 mm. Crushed stone coating is arranged on a sandy underlying layer. Other local materials (slag, shell, gravel) can be used for the foundation. The principle of the crushed stone coating device is as follows. Crushed stone with a particle size of 40 mm and above is scattered on a pre-prepared base, leveled according to a given profile and pre-compacted with rollers until the crushed stone is immobile. Then, for wedging, smaller stone material is successively scattered - crushed stone with a particle size of 10-20 mm and 5-10 mm. Rolling achieve complete jamming of gravel. When rolling, crushed stone is watered, which facilitates the mobility of crushed stones during rolling and contributes to cementation and better formation of the coating. Crushed stone coating is arranged in a trough profile in one layer with a thickness of 10-18 cm, and with a thickness of more than 18 cm - in two layers. For the lower layer, less durable crushed stone is used. The surface of the coating is given a transverse slope of 30% o. The crushed stone coating wears out rather quickly and is not very stable during vehicular traffic. Tangential forces from the wheels of a moving car upset the cohesion of the gravel, as a result of which the coating quickly collapses. To increase the cohesion of crushed stone, the water resistance of the coating and eliminate dustiness, crushed stone is treated with bituminous and tar materials. 5. Structural layers of pavement Pavement is arranged on a planned and compacted surface of the subgrade, it must ensure the movement of vehicles of a given weight at a calculated speed and be sufficiently resistant to the influence of climatic factors. Depending on the thickness and materials used, pavement can be placed on the subgrade along a sickle-shaped, semi-trough or trough profile. The crescent profile is used mainly on roads of lower categories. For the installation of crescent-shaped coatings, local materials are used: gravel, soil and others, reinforced with various additives. With a sickle-shaped profile, pavement is arranged for the entire width of the earthen bed. The thickness of the pavement, which is greatest in the middle, is gradually reduced to 3-5 cm at the edges. Pavement pavement can be of different strength depending on the intensity and composition of traffic, traffic density, design speed and must meet the following requirements: its strength must ensure the absence of subsidence and high wear resistance ; the evenness of the surface should provide the possibility of movement at high speeds; The surface roughness should ensure good adhesion of the coated vehicle wheels. One of the main conditions for improving traffic safety is to reduce the slipperiness of the road surface. An analysis of traffic accidents shows that in the summer of accidents due to the slipperiness of coatings, 4-16% occur, and in autumn and spring 40-70%. The reason for the increase in slipperiness may be dirt brought onto the roadway from roadsides, unreinforced ramps or junctions, which sharply reduces the adhesion properties of the coating. To prevent the drift of dirt onto the roadway, roadsides, ramps and junctions are strengthened. The surface roughness of the pavement of the roadway must ensure the coefficient of adhesion of the car tire to the surface of the pavement in the wet state of at least 0.5. To create a rough surface arrange surface treatment. The main factors on which the choice of pavement design depends are the intensity and composition of traffic. The greater the intensity of traffic on the road, the faster the pavement wears out, therefore, with a high traffic intensity, a more thorough, durable and perfect pavement should be arranged. On roads with less traffic, the pavement is subject to less wear and therefore it can be of a lighter type. In cases where the traffic intensity in a given period is small, but it is expected to increase in 5-10 years, transitional-type pavements are arranged, which, after strengthening, can be classified as improved. At low traffic intensity, cover of the lowest type is suitable. Conclusion Nowadays, the latest technologies and developments are being introduced into the road construction industry. Currently, in Belarus, the problems associated with the construction and operation of roads are the most significant. The country's economy is stabilizing, and the standard of living of Belarusians is rising accordingly. The purchasing power of people is increasing, therefore, there are more and more cars on our roads. To date, the quality of roads for the most part does not meet the requirements of car owners. In this regard, the government of Belarus pays great attention to the problems of construction and operation of roads. List of used information sources. 1. http://revolution.allbest.ru/transport/ 2. http://www.lib.ua-ru.net/diss/ 3. http://www.usecar.ru/page22 4. http:/ /otherreferats.allbest.ru/transport/ 5. Kabanov V.V., Kirillova L.M. The device of road surfaces. M "Transport", 1992. - 262 p. 6. Glagoleva T.N., Garmanov E.N. and other Handbook of a road engineer. 3rd edition, revised and enlarged. M "Transport", 1977. - 560 p. one
Road pavement construction technology
Road pavements
Highway consists of subgrade and pavement. Pavement is a multi-layer structure and includes layers of coating and base. The coating is a top durable layer that resists abrasion and shock loads from car wheels, as well as the effects of natural factors. It consists of a wear layer and a main (bearing) layer.
Base - a load-bearing solid part of the pavement, consisting of several layers, arranged from stone material or soil treated with a binder.
The choice of the type of pavement, which usually costs 40-60% of the total cost of the road, is an important and responsible decision. The higher the technical category of the road, the higher the requirements for the strength and solidity of the pavement.
Motor roads, according to their importance in the general transport network of the Republic of Belarus and depending on the average daily traffic intensity of cars, are classified into five technical categories:
IA - traffic intensity more than 14,000 vehicles / day.
IB - traffic intensity 14000 - 7000 vehicles / day.
II - traffic intensity 7000 - 3000 vehicles / day.
III - traffic intensity 3000 - 1000 vehicles / day.
IV - traffic intensity 1000 - 100 vehicles / day.
V - traffic intensity less than 100 vehicles / day.
Coatings, depending on the solidity of the structure, the nature of the movement and technical and economic indicators, are:
improved capital (cement-concrete, monolithic and prefabricated; asphalt-concrete, laid in a hot and warm state, etc.)
improved lightweight (from crushed stone and gravel materials treated with organic binders, from cold asphalt concrete, etc.)
transitional (crushed stone, slag, gravel, from soils reinforced with binders, etc.)
lower (ground, improved by various local materials).
Typical pavement designs:
a- cement concrete coating;
b- asphalt concrete pavement on a crushed stone base;
in- asphalt concrete pavement on a concrete base;
G- asphalt concrete pavement on the ground, reinforced with cement;
d- crushed stone coating with a top layer treated by impregnation;
e- gravel pavement treated with bitumen by mixing on the road;
and- gravel on a low grade road,
1 - cement concrete;
2 - leveling layer of sand treated with bitumen;
3 - a layer of crushed stone, gravel or soil treated with a binder;
4 - a frost-protective layer of sand;
5 – fine-grained asphalt concrete;
6 - a layer of rubble;
7 – coarse-grained asphalt concrete;
8 - soil reinforced with cement;
9 - crushed stone treated with impregnation;
10 - gravel treated with bitumen;
11 – gravel
asphalt pavement occupy a leading position on the main roads. They have high transport and operational
performance, strong, durable, easy to repair. Their wear even with heavy and intensive traffic does not exceed 1 - 1.5 mm per year. Asphalt concrete pavements, depending on the type of foundations and traffic requirements, are arranged in one, two or three layers. The top layer must be durable, wear-resistant and waterproof. These conditions correspond to fine-grained and sand mixtures containing mineral powder.
Hot coarse-grained and medium-grained asphalt concrete mixtures with or without mineral powder are used for the device of the lower layer of coatings.
Cement concrete pavements have the following advantages over other types of coatings:
High strength, which allows all vehicles to pass at any time of the year;
Long overhaul period (30-40 years);
High coefficient of adhesion with the wheels of cars, which practically does not change when the coating is moistened:
The light color of a covering increasing safety of the movement at night;
The duration of the construction season is longer than with the use of organic binders;
Low wear of the coating, not exceeding 0.1-0.2 mm per year.
However, cement-concrete pavements have a number of disadvantages that hinder their use on roads. These include: a large number of transverse seams, which worsen the performance and evenness of the coating; difficulty of repair; impossibility to open movements immediately after covering, etc.
Cement concrete is also used for laying foundations for asphalt concrete pavements on roads with heavy and heavy traffic.
Cement-concrete pavement is arranged on the road in the form of a monolithic solid slab, divided into sections of various lengths by expansion joints, or in the form of a prefabricated pavement from slabs of various sizes prepared at the factory. In the latter case, work on the road is reduced to the installation of plates on a prepared base. Despite some advantages of this type of pavement, such as an increase in the duration of the season, construction, prefabricated concrete pavements are not used on main roads. This is due to major shortcomings that significantly worsen their transport and operational qualities.
In reinforced coatings, tensile stresses are partially or completely perceived by reinforcement. In such coatings, reinforcement is used in the form of metal meshes or steel rods with a consumption of 2 ... 5 kg / m2 of coating.
Cement-concrete coatings are arranged with the same thickness over the entire width of the carriageway in one or two layers. Two-layer coatings are used to be used in concrete for the lower layer of less durable stone materials. The thickness of the upper layer in two-layer coatings is taken at least 6 cm.
The choice and appointment of a single-layer or two-layer coating are based on technical and economic calculations. The thickness of the coating layer is determined by calculation taking into account the category of roads and must be at least: for roads of category I - 22 cm; for roads of category II - 20 cm; for roads of category III - 18 cm. In two-layer coatings, the thickness of the upper layer must be at least 6 cm.
The practicality of many vehicles often depends on the quality of the road. Such structures are obtained in several ways, which leads to a significant difference in their technical parameters.
Non-rigid coatings
All types of roads can be divided into 2 main groups, these are structures with a hard and non-rigid surface. The last elements can be divided into several varieties:
- Crushed stone coverings. This type of surface involves the use of crushed stone as the main product for their coating. This type of road is used in microdistricts, parks or places where the use of better materials is not required, since they do not lend themselves to high loads.
- Gravel surfaces in most of their parameters resemble the previous type of products, but differ only in the material for manufacturing.
- Ground. This type of path is often a decorative element of parks. Such surfaces are not intended for constant and high loads.
Rigid coatings
Roads of this type can be divided into several types:
- Prefabricated cement structures are often used in the manufacture of bridges. Differ in high resistance to loadings. Can be used in various weather conditions.
- Paved coverings. This type of expensive involves arranging them by laying natural stone. Today they are quite rare and are mainly used in the construction of paths in parks. Here the same paving stones are used, which fit tightly to each other.
- asphalt pavement. This type of road is one of the main ones. Today, the number of these coatings is huge, as they are relatively simple to arrange and can be used for quite a long time.
To increase durability, asphalt is laid on special cushions, as well as in several layers, depending on the size of the fraction. used as connecting elements. different types resins that tolerate temperature fluctuations well.
It should be understood that all these types of road surface allow only certain types of transport to be operated on them. Therefore, this is taken into account when laying them, which led to their diversity.
About protective coatings for asphalt - in this video:
