Asphalt concrete pavement: general information
The first asphalt concrete pavements were built in Babylon 600 BC. The construction of pavements using bitumen resumed only in the 19th century in Western Europe and then in the USA. The first section of asphalt concrete pavement in Russia was built on Volokolamsk Highway in 1928.
Asphalt concrete pavement has a number of positive properties and high transport and operational indicators: slow wear under the influence of heavy vehicles; relatively high strength and resistance to climatic factors and water; hygiene (does not create dust and is easy to clean from dust and dirt); ease of repair and strengthening of the coating.
Asphalt concrete pavement is laid on roads with a longitudinal slope of up to 60 ppm. The transverse slope is prescribed within 15-20 ppm.
Asphalt pavement designs are constantly changing due to the fact that traffic loads and traffic intensity are constantly increasing. Even 20-30 years ago, two-layer asphalt concrete pavements with a thickness of 10-12 cm on a crushed stone base of 18-25 cm were used on roads of high categories. Now such structures are suitable only for roads of lower (IV and V) categories, and on roads of categories II and I, the structures have become more powerful; at the base, thin (rolled) concrete with a thickness of 20-35 cm is increasingly used, and the total thickness of the laid asphalt is equal to 18-25 cm.
The service life of asphalt concrete pavements depends not only on the quality of the asphalt concrete, but also on the design of the road pavement. Asphalt concrete pavements of the same quality work differently on different substrates. Thus, in asphalt concrete pavements laid on bases made of monolithic cement concrete, cracks appear due to the thermophysical incompatibility of the coating and base materials, i.e., seams and cracks in cement concrete bases are repeated in asphalt concrete pavements.
Crushed stone foundations do not have this drawback; however, they are subject to uneven shrinkage occurring due to the mutual movement of crushed stone grains under the influence of repeated exposure to transport loads.
In relation to the selected road pavement design, it is necessary to select the type asphalt concrete mixture. Pavements made from asphalt concrete mixtures should be installed in dry weather. Laying asphalt (paving) should be done at an ambient temperature of at least +5oC. Laying asphalt (asphalting) can be done as follows: mechanized way, using an asphalt paver, and manually.
Filling and restoration of roads to holiday villages and garage cooperatives, roads with light traffic, asphalt road crumbs is a progressive method of road restoration. Due to its low cost and higher resistance to destruction than crushed stone and sand. Asphalt road crumbs have a higher density and are saturated with bitumen, which serves as an additional link and a sealing element, which allows the road to last much longer.
The best material for filling roads inside holiday villages and garage communities is asphalt chips. The advantage of asphalt chips is that they are laid much denser than sand and crushed stone. Asphalt crumbs, after being dumped, are rolled away by car wheels to such an extent that they become like asphalt. A road covered with asphalt chips is more resistant to erosion and other damage caused by water. The bitumen present in the crumbs serves as an additional binding and compacting element, which allows the road to last much longer than a road made of sand and crushed stone.
Technology of filling and restoration of unpaved roads:
Before laying asphalt chips, leveling is carried out, using a motor grader to knock down road unevenness, profiling the base, achieving the required evenness. After an even base layer has been achieved, the road crumbs are leveled along the entire road and the slopes are profiled. Achieving evenness of the coating with the same layer thickness. At the final stage, compaction is carried out using a road roller, thereby achieving high density and resistance to erosion and other damage caused by water.
After the road roller has compacted the surface, the new road is ready for use.
Before installing the base, it is necessary to install side stones and curbs. The bases for asphalt concrete pavements are made from crushed stone, slag, broken bricks, and other waste obtained from the dismantling of buildings and structures. Crushed old asphalt concrete (asphalt chips) is also used as a base material. The thickness of the base is usually 10-15 cm, depending on the properties of the underlying soil. The base material is leveled with a layer of the required thickness and then compacted with rollers with a scattering of stone or slag fines for crushing and decluttering.
The thickness of the asphalt concrete pavement is usually taken to be 3-4 cm. At the entrances to neighborhoods and courtyards, the thickness of the asphalt concrete layer is raised to 5 cm or more. Sandy or fine-grained asphalt concrete mixtures are used to construct sidewalk surfaces. Vibratory plates or small-class rollers are used to compact asphalt concrete.
Asphalting a sports ground
font-size:12.0pt;font-family:" times new roman>The asphalt base is built for a special sports surface on tennis courts, volleyball, basketball and other sports grounds. The construction of such a base includes a set of works:
- Excavation work (preparing the “trough”). Excavation and removal of soil to the required height, usually to the height of the crushed stone base. Layout, leveling the soil inside the trough; Installation of side stones, curbs and drainage system around the perimeter of the site; Construction of a sandy base 10-20 cm thick if the soil contains clay; Construction of a crushed stone base 15-18 cm thick. From crushed stone fractions 40x70 and 20x40. Can be used instead of crushed stone fr. 40x70, black crushed stone, and on upper layer- fine asphalt chips. It is advisable, to increase the reliability of the crushed stone base, to perform additional declinging by screening. Installation of embedded parts for racks; The top layer is made of fine-grained asphalt concrete mixture of type “G”, with a total thickness of 8 cm. The asphalt is laid in two layers of 4 cm each. To drain water from the surface of the court, the base must be set to a slope of 0.5 - 1 ‰ on the short side; Due to the specifics of asphalt laying technology, it is impossible to achieve ideal evenness of the base. Therefore, before laying the sports surface, it is necessary to level the base with special mixtures.
Laying in an embankment and soil compaction is carried out during planning work, construction of various embankments, backfill trenches, foundation cavities, etc. Compaction is carried out in order to increase the bearing capacity of the soil, reduce its compressibility and reduce water permeability. The compaction can be superficial or deep. In both cases it is carried out by mechanisms.
There is soil compaction by rolling, tamping and vibration. The most preferable method of compaction is the simultaneous transfer of various influences to the ground (for example, vibration and rolling), or combining compaction with another work process (for example, rolling and vehicle movement, etc.).
To ensure uniform compaction, the dumped soil is leveled with bulldozers or other machines. Greatest soil compaction with at the lowest cost labor is achieved at a certain optimal humidity for a given soil. Therefore, dry soils must be moistened, and waterlogged soils must be drained.
The soil is compacted in sections (grips), the dimensions of which should provide a sufficient scope of work. Increasing the scope of work can lead to drying out of the soil prepared for compaction in hot weather or, conversely, to waterlogging in rainy weather.
The most difficult thing is to compact the soil when backfilling the sinuses of foundations or trenches, since the work is carried out in cramped conditions. To avoid damage to foundations or pipelines, the adjacent soil to a width of 0.8 m is compacted using vibrating plates, pneumatic and electric tampers in layers 0.15...0.25 m thick. More productive methods, for example, self-moving vibrating plates and others, are used when compacting the backfill under the floors.
The penetrations of soil compaction machines are made with a slight overlap to avoid missing uncompacted soil. The number of penetrations in one place and the thickness of the layer are set depending on the type of soil and the type of soil-compacting machine or are established experimentally (usually 6...8 penetrations).
Embankments that do not have high requirements for soil density can be compacted by vehicles during the soil filling process. The work scheme is drawn up so that the loaded vehicle moves along the dumped layer of soil.
Unlike ordinary concrete, cement-crushed stone mixtures contain significantly less cement and can be compacted by the static action of self-propelled rollers with smooth rollers. A base of lean concrete is laid over a technological layer of compacted crushed stone, cement soil or sand and gravel mixture 10-15 cm thick. On the base of lean concrete on highways with heavy traffic, a two-layer asphalt concrete covering with a total thickness of 8-12 cm is laid; on other driveways and roads, a single-layer asphalt concrete covering with a thickness of at least 10 cm is laid over a layer of lean concrete. Lean concrete is laid. into the base with a concrete paver, crushed stone paver or using small-scale mechanization. The mixture is distributed in a layer of up to 20 cm and immediately compacted, first with light and then with heavy rollers until the traces of rolling completely disappear.
The construction of an asphalt concrete pavement over lean concrete can be done after it has been compacted or after 2-3 days. In the latter case, the base surface should be treated with bitumen emulsion in two layers. The total emulsion consumption is 0.7 kg per 1 m2 of base. The construction of foundations made of lean concrete significantly reduces labor costs, as well as the start time for laying asphalt concrete. Temperature transverse joints are installed in lean concrete foundations. The distance between them is taken from 20 to 40 m, depending on the air temperature when laying the concrete mixture, the grade of lean concrete and the type of asphalt concrete pavement. The seams are cut with special cutters or arranged by laying spruce or pine boards into the base.
Asphalt reinforcement as a way to increase its durability
The issue of road surface reinforcement is by no means idle, since the bulk of roads and streets are covered with asphalt concrete, and its often deplorable condition and rapid destruction within several years are familiar to everyone who moves on their own or municipal wheels.
The quality of asphalt paving and the service life of asphalt concrete depend both on the quality of the base on which it is laid, and on the properties inherent in the very nature of the asphalt concrete pavement.
Asphalt concrete pavements, which have good resistance to short-term loads, have low tensile strength during bending and insufficient distributing capacity when a load is repeatedly applied. Therefore, fatigue and reflected cracks that arise during the operation of an asphalt concrete pavement, developing intensively, lead to its premature destruction.
For a long time, all over the world, the service life of asphalt concrete pavement has been increased by reinforcing it with geogrids. Today on the market there are geogrids made of fiberglass, polyester, basalt fibers and a number of others.
Based on the results of numerous laboratory studies and operating experience, the following requirements are imposed on reinforcing geogrids:
- the modulus of elasticity of the reinforcing material must be greater than the modulus of elasticity of asphalt concrete in order to absorb tensile forces in the same way as happens in reinforced concrete; The adhesion between the asphalt and the reinforcing material must be very good in order to distribute the tensile stresses in the reinforcement material into adjacent areas of the asphalt concrete pavement. In this case, two important factors affecting the strength of this adhesion must be taken into account: the difference between the coefficients of thermal expansion of asphalt concrete and the reinforcing material should be as small as possible, since temperature changes cause secondary local stresses at the point of their connection, which can exceed the limit values, and the system will stop working as a single whole. An example is the excellent behavior of reinforced concrete, where steel and concrete have the same coefficients of thermal expansion; The elastic modulus of the reinforcement material should not exceed the elastic modulus of asphalt concrete by several orders of magnitude. This is explained by the fact that, being an elastic-plastic material, asphalt concrete under transport (dynamic) load behaves like an elastic material, perceives stress and redistributes the load over a large area of the underlying layers together with the reinforcing material. If you use too rigid reinforcement, the main part of the tensile stresses will be absorbed by it. These stresses must be transmitted into the asphalt layers through adhesive forces, and a very large area of reinforcement embedding in the asphalt would be required so that the stresses do not exceed the adhesive forces of the reinforcement with the asphalt.
Characteristics of some materials and finished products |
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Name | Modulus of elasticity, N/mm2 |
Asphalt | 1000 – 7000 |
Concrete | 20000 – 40000 |
Steel | 200000 – 210000 |
Fiberglass | 69000 |
Polyester fiber | 12000 – 18000 |
Hatelit polyester geogrid strands | 7300 |
Strands of basalt geogrid | 35000 |
Analyzing the data presented above from the positions stated above, one can understand why materials such as glass, steel or basalt work worse when paired with asphalt concrete than polyester.
The difference between the modulus of elasticity of fiberglass, steel, basalt, on the one hand, and asphalt concrete, on the other, causes problems with the adhesion strength between them. Reinforcement with the mentioned materials would be possible if the reinforcing material extended over the entire width of the roadway and sufficient fastening was ensured along its edges. Otherwise, the reinforcement will simply be pulled out of the asphalt concrete.
There are examples of the use of fiberglass meshes for reinforcing asphalt concrete when the length of the mesh embedding in asphalt concrete is insufficient. The permissible adhesion forces between the mesh and asphalt concrete are exceeded, delamination occurs between the mesh and asphalt concrete, and under the influence of dynamic transport loads, relative movements between the mesh and asphalt appear, which lead to complete destruction glass fibers. This was found out when taking core samples, when only white powder remained from the fiberglass mesh after several years of use.
The reinforcement material should not be affected dynamic loads from moving vehicles, otherwise the reinforcement will not work well in the long term. Studies have shown that fiberglass meshes do not tolerate dynamic loads well. The breaking strength of the tested glass meshes dropped to 20–30% of the original value after 1000 loading cycles, and none of them withstood 5000 loading cycles, while Hatelit successfully withstood 6000 cycles.
Studies of glass fiber mesh reinforcement have shown disappointing results when different conditions. On two different road sections, the behavior of asphalt concrete reinforced with fiberglass mesh and unreinforced was studied over a period of four years.
In the first section, the glass mesh reinforced pavement had significantly more cracks on the roadway than the non-reinforced pavement.
In the second section, the final inspection showed the absence of cracks in the transition zone of both the reinforced and unreinforced pavement. At the same time, the fiberglass mesh did not prevent the appearance of cracks in the area of intersection with the old railway tracks.
Thus, based on research results, it is not recommended to use fiberglass mesh as crack-breaking reinforcement.
The most serious approach to the choice of reinforcement for asphalt concrete pavements should be taken when constructing airfield runways with asphalt concrete pavement. After all, potholes in the asphalt on the roadway force drivers to slow down and only sometimes lead to damage to the car’s suspension. Violation of the integrity of asphalt concrete on the runway is a direct path to a disaster with loss of life.
Most optimal choice for reinforcing asphalt concrete in comparison with fiberglass mesh is a reinforcing mesh of the Hatelit type. This type of mesh has fairly high technical and economic indicators:
- significant reduction in the thickness of asphalt concrete; increasing its crack resistance by 3 times or more; increasing the service life of the coating and reducing operating costs for its maintenance.
The use of fiberglass reinforcing mesh did not produce a positive effect due to their low physical and mechanical characteristics and inability to effectively prevent the development of cracks in asphalt concrete.
Despite the fact that new types of fiberglass reinforcing mesh are constantly being developed, their efficiency and durability remain significantly lower than that of Hatelit-type polyester mesh.
The most effective geogrids are Hatelit S grids according to the following indicators:
- The reinforcing threads of the mesh are made of polyester and, in comparison with threads made of fiberglass, they are good at absorbing not only stresses in horizontal plane, but also stresses from repeated vertical loads. Polyester threads are resistant to vertical stress and deformation. Glass threads do not perceive vertical deformations and stress; already at the factory, the mesh is treated with bitumen, which ensures good adhesion to asphalt concrete; is a composite material. In addition to reinforcing threads, the mesh has a geotextile base, which ensures the design position of the mesh during installation without additional operations; The cell dimensions of the reinforcing mesh must be equal to twice the size of the largest fraction of crushed stone. For fine-grained asphalt concrete, the optimal mesh size is 40x40 mm.
It should also be noted that during dynamic bending tests of samples at maximum tensile stresses equal to 10 MPa, the number of cycles before failure for a sample with Khatelite C is 13 times higher than for a sample with a basalt mesh. With three passes of the compaction roller, the basalt mesh lost almost 50% of its strength (Hatelit S - 10%), and with 5 passes - 60% (Hatelit S - 13%). Thus, there is an obvious tendency for the basalt mesh to lose its strength, reduce its ability to deform and collapse with an increase in the number of compaction cycles or simply the passage of heavy vehicles during road works. For comparison, with Hatelit S the coefficient of mechanical damage, even with 5-fold compaction, remained within the acceptable range - did not exceed 1.15.
Shear resistance studies have shown that for core with Hatelit S it is equal to 34 kN/m (due to good bitumen impregnation, reflow and seal nonwoven fabric, applied to the mesh), and for the core with a basalt mesh, the shear resistance was 6 kN/m with a minimum permissible value of 15 kN/m.
In addition, the consumption of 70% bitumen emulsion when laying Hatelit S mesh is 0.3–0.5 l/m. sq., and when laying basalt mesh - 1.0–1.2 l/m. sq.
In the end, it should be noted that the Hatelit S geogrid is certified in Russia and Ukraine. In addition, in Ukraine there is a “Technological regulation for the use of Hatelit 40/17 C mesh for reinforcing asphalt concrete.”
Road reinforcement: | Geogrid Hatelit S in rolls: |
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Geogrid Hatelit 40/17 C: | Laying asphalt over geogrid Hatelit 40/17 C: |
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If you get to the dacha in your own car, then sooner or later you will get tired of parking it just next to the porch of the house. You will think that it is time to build a permanent parking lot for your “iron horse”, protecting it during your country holiday from hot sun rays and precipitation. The easiest and fastest to implement is parking for a car at the dacha in the form of a platform with a canopy. Let's talk about how to build such a parking lot and select materials for it.
Choosing a parking location
The resting place for your car should be located on a level area. A slope is absolutely not suitable for parking, since you will subsequently have to constantly put the car on the handbrake, place stones or bricks under the wheels, and simply be nervous that the car, despite your efforts, will leave without your permission. However, despite this, it is necessary to provide a slight slope for the site. This will make it easier for the car to enter the parking lot. Also ensure that the site is not in a low place, but slightly above ground level. Then rainwater and snow will not stagnate here.
Site structure
The construction of the site begins with the removal of a 10-20 cm thick layer of soil in a selected location. Sand or sand is poured into this small pit and compacted crushed stone cushion.
Concrete screed
If the soil on the site is sufficiently stable and not subject to seasonal movements, then you can choose a concrete screed reinforced with reinforcement. To do this, it is installed along the perimeter of the site wooden formwork from edged boards required height. A layer of concrete about 5 cm thick is poured on top of the sand, on which a reinforcing mesh is immediately placed, without waiting for it to harden. From above it is again filled with concrete.
The thickness of the concrete platform should be at least 10 cm, but if the car is large and heavy, then it is better to increase this figure. Despite the fact that the concrete will set in 2-3 days (at this time it will be possible to remove the formwork), it cannot yet be used. Wait another month until the concrete reaches its final strength - then it will be able to support the weight of the car.
Paving slabs
If the soil is susceptible to swelling, then within a year concrete surface sites can be hacked, so you need to choose another option. Good choice can become paving slabs, which, due to the gaps between each other, will allow moisture to evaporate better from the surface of the earth and the base of the parking lot will warp less.
Such tiles come in completely different textures and colors - stylized to resemble a certain type of wood or stone. For a car park, it is better to use granite-like tiles.
Paving slabs are laid very easily - on a compacted crushed stone cushion or on a layer of sand and cement. No other binders, such as glue, are required. The tile is nailed to the surface with a special rubber hammer and adheres tightly to the base. After the tiles have been laid, it is advisable to install a curb stone along its borders. Instead of tiles, paving stones can be used as cladding for the site, a natural stone, clinker brick.
Crushed stone filling
In the case of swelling soils, ordinary crushed stone can also be used for the surface of the site. It is enough to fill the dug hole with a layer of crushed stone and the parking area is ready.
Lawn grate
And this is an option for lovers of environmentally friendly coatings that fit perfectly into the natural landscape. Eco-parking is a special rigid plastic lattice that creates the basis for the soil into which lawn grass is sown.
The polymer grid will evenly distribute the weight of the machine throughout the entire area, so wheel ruts will not form on the grass and the lawn will always look well-groomed. The advantages of eco-parking are durability (up to 25 years), water disposal, frost resistance. The grille will not require any maintenance during the entire period of use, but is relatively expensive.
Canopy over the site
Regardless of what kind of covering you choose for your parking lot, it is not advisable to leave it exposed to rain and sunlight. Modern construction market offers a huge selection of carports for parking lots. The canopy, which is a lightweight design from steel frame and roofs - coverings made of polycarbonate, slate, metal tiles, corrugated sheets.
Such designs are sold ready-made or can be ordered in parts. If you wish, you can make such a canopy yourself. This will require support and transverse metal pipes, from which a frame is constructed using welding or bolts. The top of the roof is covered with wooden boards, slate or roofing felt - depending on what you have available.
Thus, parking for a car at the dacha can have the most varied look– from frankly urban (with a concrete platform and a polycarbonate canopy) to the most natural (eco-parking with a wooden canopy). The main thing is that it can protect the car from external negative factors and fit into the overall style of your site.
Preparation of the base includes the following operations: checking the quality of the base and correcting any defects in it, cleaning the base surface from dust and dirt, treating the base surface with bitumen or bituminous materials to ensure the necessary adhesion of the coating being installed to the base.
The most important condition for obtaining a high-quality and durable asphalt concrete pavement is a strong, level and well-compacted base with high-quality rainwater drainage. Therefore, before starting work on the installation of the coating, it is necessary to carefully prepare the foundations. The density of the base can be checked by test passing a heavy roller over it. If, when passing the rear rollers of the roller, subsidence is detected or the base “springs”, it is necessary to strengthen it or additionally compact it. If necessary, the underlying layer is also corrected. Small irregularities 3-5 cm deep can be corrected by adding an asphalt concrete mixture with the necessary compaction with a roller or tampers.
Correcting deep potholes in the base with an asphalt concrete mixture, as a rule, leads to the formation of unevenness on the asphalt concrete surface. This happens because a thick layer of asphalt concrete mixture is usually poorly compacted by rollers, and additional compaction that occurs over time under the influence of passing traffic inevitably leads to deformations. The resulting deformations will be greater, the thicker the layer of asphalt concrete mixture. Thus, a crushed stone base with significant potholes repaired by adding an asphalt concrete mixture behaves like an unequally strong base made of materials that differ sharply in their properties.
Potholes and large unevenness in the crushed stone base are corrected as follows. The area to be repaired is cleared of dust and dirt, then loosened with a pick. The resulting crushed stone is passed through a screen, separated from the dirt, and again poured into the pothole. Then fresh crushed stone is added, which is poured slightly above the edges and compacted with a roller or tamper. Compaction is carried out from the edges to the middle of the repaired area.
To improve compaction conditions for crushed stone, it is recommended to sprinkle a small amount of cold or hot asphalt concrete mixture on top of the crushed stone layer during compaction. Good results are obtained by pouring a small amount of hot bitumen (approximately 1 l/m2). Crushed stone bases and old crushed stone coverings used as bases can also be repaired using cold or hot black crushed stone (crushed stone treated with liquid or viscous bitumen). The use of black crushed stone allows you to speed up the process of compacting the base in the repaired area.
If there are individual low spots on the base, they are also pre-leveled with the material from which the base is made. In some cases, the base is leveled by laying a so-called leveling layer. Large potholes should be corrected before the leveling layer is installed. Cross profile of old stone coverings, used as bases, are also corrected by laying a leveling layer. However, this leveling method leads to excessive consumption of asphalt concrete mixture and is not always economically beneficial. The base prepared for laying asphalt must have the required geometric characteristics: width, thickness, longitudinal and transverse slope. Particular attention should be paid to the evenness of the base surface, since it ultimately determines the evenness of the coating surface. Largest size When checking with a three-meter rod, the unevenness of the base should not exceed 4-5 mm.
Strong adhesion of the asphalt concrete pavement to the base is one of the conditions for the pavement’s stability against shear forces that appear during the passage of vehicles. An indispensable condition To obtain the necessary adhesion of the asphalt concrete pavement to the base is to thoroughly clean the latter from dirt and dust. Treatment with bitumen or bituminous materials does not achieve the goal if it is carried out on a dusty or contaminated surface. In such cases, defects may appear during work. The surface of the base is cleaned with road brushes or watering machines. The washed base must be allowed to dry before it is treated with bitumen or bituminous materials.
Good results are obtained by cleaning the surface of the base from dust and dirt with compressed air. It is most convenient to use automobile compressor stations for this purpose. Workers involved in this operation must be provided with protective equipment to protect their eyes, mouth and nose from dust. The best results are obtained when treating bases with bitumen pastes or bitumen emulsions. These materials provide good adhesion of the top layer of coating to the bottom during the construction of two-layer coatings.
Asphalt concrete mixture can be used; lay; only after the surface of the base (or the lower layer of coating) has completely dried. The emulsion consumption is 0.2--0.4 l/m2. Emulsion or liquid bitumen is poured 3-5 hours before installation.
Historians claim that the first mention of something similar to asphalt concrete appeared in the 6th century BC in Babylon. But the technologies of those times were unreliable, 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.
Photo of laying a country road.
What it is
This composition is used everywhere, from laying federal highways to arranging city squares and garden paths in private construction.
According to GOST and SNiP, the design of asphalt concrete pavement can be different.
But the general composition of the mixture has remained unchanged for more than 100 years:
- First of all, bitumen is included as a binder..
- Sand and large mineral fillers must be present to one degree or another..
- The list is completed by various mineral or synthetic additives.
At the time when the composition was developed, natural bitumen was used, but since there is little of it in nature, an artificial analogue was synthesized based on petroleum products, which is still successfully used by road workers around the world.
Quarry sand is taken, as for coarse filler, along with various types crushed stone for concrete, crushed rocks and some crystallized slags are widely used.
Natural mineral or synthetic additives are used to increase certain beneficial properties coverings. In particular, frost resistance, road adhesion level, viscosity coefficient and much more increase.
Bitumen resin.
What formulations are produced
The range of presented types is quite wide, depending on the percentage of components, as well as what additives were used, experts divide asphalt into the following varieties.
Fine-grained asphalt.
Cover cut.
Making asphalt at home
The production of road surfaces is considered to be difficult and inaccessible. But, nevertheless, there are enthusiasts who are ready to experiment. Of course, such compounds are not designed for federal highways, but at the dacha it is quite possible to prepare such asphalt with your own hands.
Advice: from experience, we can say that a mixture prepared in a homemade way is, of course, suitable for arranging a garden concrete path, but more often it is used to repair potholes on an already finished surface.
Laying temperature of the composition.
Classic recipe
For preparation, we will need ordinary river or quarry sand, bitumen resin or bitumen and fine crushed stone. Equipment you will need is a metal barrel and a bucket.
It is better to cook asphalt over a fire, since using gas is unsafe and expensive.
- Initially, add crushed stone and sand in a 2:1 ratio and mix well. All this should be filled with water and hung over the fire.
- At the same time we prepare the bitumen base. To do this, take a metal bucket and heat the bitumen in it until it boils. You can add synthetic polymers as a plasticizer, but it’s 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 to ensure that the crushed stone and sand do not heat up above 100ºС. Next, this broth must be stirred, maintaining a boil until all the water has boiled away. While the solution is hot, it can be poured.
Hand laying.
Important: be careful, bitumen melts at 80 ºС, and boils at 100 - 120 ºС.
But already at 170 ºС bitumen can ignite.
Actually, to prevent such a fire, we use water.
Using old road surfaces
Dismantling asphalt concrete pavements and bases can become good material to prepare new asphalt.
The technology is partly similar to the previous version, but with some amendments.
- The dismantling of the asphalt concrete pavement itself is carried out using the old-fashioned method, using a sledgehammer and other percussion instruments. Only the top layer of asphalt bound with bitumen is used, travel pillow you don't have to touch it.
- Old road surface is broken into pieces with a fraction of no more than 40 mm. For 100 kg of old asphalt, take 10 kg of bitumen.
- After this, the crushed substance must be poured with water and boiled in a barrel until melted. The technology then repeats the option described above. The heated bitumen combines with the molten asphalt and the water evaporates.
Cold asphalt.
The two methods described above are well suited for economical repairs damaged asphalt in the yard or near the yard. If you need to cover a large area, we recommend using cold asphalt.
This coating appeared on the market in our country about 5 years ago. The principle of operation here is similar to the well-known cold welding. Modified bitumen is used for the binder, so it can be laid even when sub-zero temperatures. Instructions are included on the packaging.
Manual vibrating rammer.
The only disadvantage of this material is its significant price. But, as you know, asphalt is shipped hot from the factory and must also be laid hot. Therefore, for remote locations, cold polymer asphalt is the only alternative.
Important: when repairing road surfaces, the problem is the quality of the joint in the asphalt concrete pavement.
Cold polymer-based asphalt completely solves this problem, since it reliably adheres to any bitumen-based composition.
Cutting cold asphalt.
Rules for laying coatings
The construction of asphalt concrete pavements is a responsible matter and it is not so important whether you lay it yourself or hire professionals. Laying and acceptance of asphalt concrete pavement is carried out in accordance with SNiP 2.07.01-89, as well as a number of GOST standards.
Only a specialist can understand these documents, so we have outlined the main provisions of these norms and rules in a more understandable language.
Scheme for laying roads with medium load.
Preparatory stage
Any work begins with markings. You need to clearly decide where the asphalt will be laid. Where will the curb be installed and what will it be like? It is also very important to ensure that the drainage and drainage system is fully installed and drainage systems are installed in advance.
All work on the installation of underground communications must be completely completed by this time. If you are developing a parking lot or driveway to an office, it is better to find out in advance where city communications are located, since, if necessary, municipal services will tear down your coverage and may also impose a fine.
The types and purposes of existing types of asphalt were mentioned above. So, at the preparation stage, you need to choose what kind of material you are going to lay.
Working with a vibrating plate.
Important: the estimate for installing an asphalt concrete pavement should contain not only 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 a column for unforeseen expenses, such as permission to carry out work from the relevant official or service.
If a pedestrian path or platform with occasional passage of passenger cars is being laid, then the crushed stone-gravel cushion can be made up to 15 cm thick. The thickness of the asphalt concrete pavement will be within 4 - 5 cm.
If you are equipping 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 gravel bed it will be about 25 – 35 cm. Plus the asphalt itself is laid in at least 2 layers.
Heavy roller.
After marking, the construction of the so-called trough or foundation pit for the road begins. In urban areas or in private construction, as a rule, roads and sites are built at approximately the same level, so the soil must be selected to cover the entire thickness of the “road pie”. Federal highways are being developed using a slightly different technology, but we will not dwell on it.
When the soil has been selected, the entire site must be well compacted, this is done with a roller or vibrating plate. Pay attention to the presence of trees nearby; the roots can tear up the asphalt over time, so, if possible, it is better to remove them immediately. Although the price of the work will be slightly increased, we recommend covering the soil with geotextiles so that vegetation does not break through the covering.
Mobile installation for thermal profiling of asphalt.
Important: at this stage, curbs are installed; they act as a kind of formwork for the “road cake”.
If when laying paving slabs the curb is made below the road level, here it’s the other way around.
In this regard, it is necessary to immediately plan drains for water drainage.
Now you can start filling the crushed stone cushion. For pedestrian paths with a cushion thickness of 10–15 cm, 1 layer of crushed stone of a fraction of 30–40 mm is sufficient. More powerful bases are laid in several layers.
The bottom layer serves for drainage in case of lifting groundwater, it is filled with large crushed stone with a fraction of 40 - 70 mm. The next layer with a fraction of 20 - 40 mm will be responsible for uniform distribution of the load on the base of the road.
Road reinforcement with polymer mesh.
The final layer of filling is made of fine gravel with a fraction of 5 - 20 mm. It will also be responsible for distributing the load, but in addition it will turn the pillow into a dense, monolithic structure.
All laid layers must be compacted tightly. For serious surfaces, road rollers weighing from 2 to 10 tons are used. Each ball of filling is compacted separately, the roller must go over it at least 5 times, plus modern road rollers have a vibrating press function, which increases efficiency several times. During the compaction process, the surface should be regularly watered.
Advice: during the compaction process, you must immediately take into account the angle of inclination of the road; on average, it is about 1º per 1 linear meter.
To do this, you should periodically check the markings or data of the level.
Laying the federal highway.
Laying asphalt
After completing the compaction of the cushion, you can proceed directly to laying the asphalt. As mentioned earlier for sidewalks and adjacent areas enough to lay fine-grained composition layer up to 50 mm. Heavy road rollers are also not required; you can get by with a light roller or vibrating plate.
Note!
According to SNiP, this type of coating is not recommended for laying in recreation areas.
More serious objects are paved in 2 layers. In this case, the bottom layer is laid with coarse-grained asphalt at a level of 40 - 50 mm. A fine-grained composition is almost immediately applied to it, which in most cases is the finishing compound.
Currently, technologies have been developed according to which a reinforcing mesh made of polymer materials must be laid between layers of hot asphalt. As a result, the durability and strength of such a road increases significantly. This technology used when laying federal highways and roads with increased load.
Complex road laying.
Important: restoration of asphalt concrete pavement is most often done only with hot bitumen.
Although according to GOST, thermal profiling of asphalt concrete pavements must be carried out.
This procedure involves preheating the road surface to a depth of 2–5 cm.
The mixture must be delivered to the site hot; as a rule, it is delivered by dump trucks with a carrying capacity of 7 - 20 tons. After which the asphalt is manually or by machine distributed evenly along the road plane, observing the slope. On average, 1 ton of asphalt is consumed per 10 m² of road surface with a thickness of 40 mm.
The construction of asphalt concrete pavements is a weather-dependent process. In the cold season, that is, at temperatures below +5 ºС, it is generally not recommended to carry out work. Plus, during rain or wet weather, the quality of installation is significantly reduced, as the composition becomes moisturized and cools faster.
Unit for removing old coating.
We have outlined the general basic principles high-quality styling asphalt, but science does not stand still and technologies are supplemented and improved. In the video in this article you can look at the process of laying asphalt in more detail.
The road is considered one of the most advantageous coatings. It is practical, inexpensive and, in general, provides the necessary characteristics for operation. Of course, there are some shortcomings, but they usually appear in cases of non-compliance with the installation technology. On the other hand, a high-quality asphalt concrete pavement provides a fairly high load-bearing capacity and elasticity. At the same time, there are different approaches to creating such roads and sites, the differences in which are determined by the composition of the mixture and laying technologies.
Composition of asphalt concrete mixture
Traditional asphalt construction technology involves the presence of mineral fillers and a binder component in the main composition. The first group of materials includes sand and crushed stone. In this case, crushed stone can be replaced with gravel, and sand can be used in whole or crushed form.
Also, depending on the requirements for the coating and its operating conditions, a finely dispersed organic component can be used to bind the base composition, usually bitumen. The characteristics that the resulting asphalt concrete pavement receives are determined by the approach to the formation of the base mixture. Differences in the methods of making the solution are due to the parameters of the components used. For example, gravel or crushed stone can be selected with a fraction from 10 to 40 mm. Likewise, bitumen can have different viscosity and density. These and other factors ultimately determine the characteristics of the coating.
Instructions for delivering mixtures to the site
First of all, the type, number and carrying capacity of vehicles that will carry out delivery are determined. This choice depends on the scale of the work, the volume of the mixture and the pace of future installation. The transportation process includes several stages, including weighing, loading of material, actual transportation and unloading at the receiving point. To service crushed stone, cold and hot mixtures, use a dump truck with a clean body, which is covered with a protective awning or waterproof canopies. The cast mixtures from which the asphalt concrete pavement is formed are transported in so-called kochers. These are cars with thermos-mixers, which ensure mixing and heating of the composition during transportation. As for the transportation time, in the case of hot and mastic mixtures it depends on the characteristics of the mixture, but for cold solutions there are no restrictions on the duration of transportation.
Preparatory work
The main activity in the process of preparing for final laying of the mixture is the installation of a test coating. The length of such a strip is at least 200 m, and the width is taken in accordance with the parameters of the asphalt paver passage. Based on the results of the trial installation, technologists determine the most suitable mixture recipe, and, if necessary, make adjustments to the installation method and compaction technology.
The trial asphalt concrete pavement is checked for characteristics such as temperature, compaction quality, base condition, etc. For this purpose, special control technologies are used. In particular, non-destructive express methods and taking core samples, which are further studied in laboratory conditions. Based on the conclusion obtained, technologists make recommendations for the manufacturer. If necessary, the composition of the mixture is adjusted to suit the specific operating conditions of the coating.
Mixture distribution technique
Before distributing the finished mass, the asphalt paver slab is installed on the edge of the previously laid beam, the height of which will correspond to the thickness of the layer being installed. To prevent the mixture from spreading, sliding formwork is used - it must move behind the asphalt paver. If there is no such device, then before starting distribution in the longitudinal direction it is necessary to secure metal strips about 20 m long. In this case, the thickness of this barrier should be no less than the height of the coating being formed. By the way, the thickness of asphalt concrete pavements varies on average from 5 to 10 cm. As the mass is laid and compacted, the metal bars are removed. As for the width, most often the mixture is distributed to cover the entire roadway.
If, after spreading the base, defects are detected on the surface, they must be processed manually. It is practiced to use tampers, which allow spot correction of loose seams, bumps and other defects. Typically, defects form in the areas where the strips adjoin the thrust elements - the same metal bars. Crushed stone and gravel are also poured separately. These layers of asphalt concrete pavement are formed evenly in bulk immediately after the mixture is distributed. Next, the granular material is sunk into the base of the coating with a light roller.
Compaction technology
The compaction process must run parallel to the operation of the asphalt distributor, which distributes the mixture. Compaction is carried out continuously by a link of rollers. Smooth roller, pneumatic wheel and combined special equipment can also be used in the work. The force and load of compaction of cold and hot asphalt in structural layers are calculated using several indicators. In particular, technologists take into account the density characteristics and temperature of the mass.
The asphalt concrete pavement is constructed from a dense hot mixture with a compaction coefficient of 0.99. Cold mixtures assume a load with a coefficient of 0.96. The transverse junctions of the laid lines are arranged perpendicular to the road axis in one lane without leaving any ledges. To fulfill this condition, the end of the previously arranged strip is cut off with a special tool with
Instructions for repairing asphalt concrete pavements
Before carrying out actual repair operations, the coating is inspected. To do this, the surface is cleaned using road brushes, after which surveying tools are used to check the evenness of the surface. Depending on the nature of the detected defects, appropriate repair measures are taken. To further ensure the evenness of the layers, the cutting area is marked using a strip. A block with a level is overlapped over the coating. The place under the plank, where a decrease in thickness is noted, is considered as a line for future transverse trimming. Also, repair of asphalt concrete pavement may involve operations to build up layers. Typically, such measures are used to install coatings framing wells. For this purpose, special liners and reinforced concrete segments can be used.
Safety instructions
Even before the start of work, the target area must be fenced off using appropriate road signs. People working on the site must wear protective clothing established by regulations. At night, the area should also be provided with lighting and signal lights. Separate safety measures are provided for solutions handling processes. Thus, when unloading a carrier with a mixture, it is prohibited for people to be between the vehicle and the bunker with the material. During laying and compaction, asphalt concrete road surfaces must be free of foreign objects and workers. After completion of the events, all equipment, equipment and Consumables must be removed from the covering and delivered to appropriate storage areas.
Coating quality control
The quality of the installed coating is assessed using special tools. In particular, calibrated automated measurement instruments are used, as well as special equipment that allows a complex conclusion to be drawn based on the data obtained. Among the most common characteristics on the basis of which the “performance” of asphalt concrete pavements is assessed are compliance with design parameters in terms of thickness and width, evenness of layers, slopes, temperature and quality of seams between strips.
Conclusion
Asphalt installation work is a complex of technical activities. At the same time, initial design calculations are of considerable importance from the point of view of forming a high-quality road surface. Even with careful installation and compaction, the coating will not be able to perform its functions if the wrong mixture has been selected. Although the basic technology of asphalt concrete pavements involves the use of a standard set of components to obtain a solution for laying, their parameters may differ. Therefore, it is practiced to lay test mixtures, which later give an idea of the most advantageous characteristics of the coating for a particular area. And in the future, responsibility for the quality of the road passes directly to the work team, which distributes and compacts the asphalt concrete mass.
Asphalt belongs to the group building materials, intended for covering the road surface. Its main purpose is to create reliable safe conditions for organizing pedestrian or vehicular traffic.
Asphalt pavement at correct installation can withstand heavy loads, this is facilitated by the grade of asphalt, which is legislated by GOST 11-10-75: M1200 - for roads, M1000 - for sidewalks and paths.
Asphalt is environmentally friendly, has a high level of practicality and is attractive appearance, somewhat labor-intensive to manufacture and use, and not the most expensive of road surfaces.
Types and composition of asphalt
There are two types of asphalt used to cover roads: cold and hot. The composition of any type will be the same, the difference lies in the percentage of components.
The components of asphalt are:
- sand;
- crushed stone;
- bitumen;
- mineral powder.
The percentage of components depends on the road for which purpose the coating will be laid.
Hot paving of asphalt is a method by which a new road surface is formed by compacting the mixture before it hardens.
Percentage composition of components
The percentage of all components of the asphalt mixture and the compaction coefficient are given by SNiP 3.06.03-85.
If asphalt is laid on a highway surface, then the percentage of crushed stone that can withstand short-term loads of up to several tens of tons will be large. When laying paths and driveways for passenger cars, crushed stone is either not used at all or is replaced with fine gravel. 
Mineral powder is obtained by crushing limestone and fossilized remains. The structure of the powder is viscous and contains a lot of carbon, which helps relieve internal stress. It is most often used when laying asphalt pavements on bridges and highways; it is practically not used on secondary roads.
The last component of the asphalt mixture is sand. It is carefully cleaned of impurities to increase the strength of the final mass.
Asphalt impregnations
Asphalt laying technology involves the use of impregnations that improve the quality of the road surface.
Acrylic polymer based mass. It is very expensive, fits on small areas(tennis courts, special grounds, etc.) have high quality protection, produced in several colors.
Coal tar. It is not subject to destruction from the ingress of petroleum products, lasts a long time, has a high-quality structure and color.
Asphalt emulsion. A common and affordable coating, short-lived, requiring constant repair.
To extend the service life when laying, SNiP 3.06.03-85 recommends using mesh under asphalt. They increase the density of the fabric and ensure its adhesion. The same characteristics are achieved by high-quality compaction of the asphalt concrete mixture, for which an asphalt roller is used.
Protective impregnations and coatings for asphalt - materials and equipment
Hot styling method
Hot paving of asphalt is common, less expensive and produces good results. SNiP recommends heating the finished mixture to 130ºС; at the time of filling the roadway, the temperature should be at least 100 ºС.
Hot asphalt can be laid manually. The step-by-step process is as follows:
- Preparing the concrete mixer. For this purpose, a metal barrel in which electric drill(16 mm drill) holes are drilled at the bottom and top center. A strong axle is inserted into them and scalded in a circle. Sturdy handles for scrolling are attached to the sides. The entire structure is installed on a support.
- Bookmark ingredients. Crushed stone and mineral powder are placed in a barrel and mixed. For bitumen, take another vessel, the mass is heated until homogeneous. Heated bitumen is added to a barrel containing a mineral-crushed stone composition. The barrel must be turned all the time. After adding sufficient quantity resin (10%) is poured into sand, the resulting composition is mixed well.
- Rolling up. Place hot asphalt on the prepared area about 5 cm thick and compact it tightly with a hand roller. When in contact with the mass, the tool must be moistened with water to ensure a smooth surface.
If the asphalt is laid efficiently, it can withstand a weight of up to 5 tons without deteriorating from water and sun.
Cold styling method
These works are carried out using a ready-made mixture, which can be bought in the store. It will eliminate the laboriousness of preparing a hot mixture. But such a mass is expensive, and coatings made from it do not withstand high summer temperatures.
GOST 11-10-75 prohibits this method of paving on main roads and provides for the use of cold asphalt only for road repairs or in summer cottages.
This method is performed in stages:
- Preparatory stage. Purchasing a ready-made mixture in a store. On future paths, a layer of earth (10 cm) is removed, half of the depression is filled with crushed stone and compacted.
- Layer-by-layer laying of asphalt mixture. Two layers are laid at intervals of 20 minutes, each carefully compacted with a hand roller. The thickness of the laid layer is 2-3 cm.
- Final works. On last stage The canvas is compacted again and sprinkled with water. You can use it within a day.
Laying asphalt this way will take a little time because the mixture is already ready. It will take several hours to lay the path, but the hole can be closed in 5 minutes.
Possible defects in asphalt pavement
Asphalt laying work on main roads may be accompanied by some defects appearing on the surface if the asphalt paving rules are violated.
When using a paver, short waves may appear on the pavement. In this case, you need to ensure a uniform supply of the hot mixture. Long waves will indicate that the temperature of the mass is not maintained or the roller is moving unevenly.
Tears may form on the canvas, which will be a consequence of improper operation of the screed plate. It will violate the compaction coefficient due to inappropriate temperature of the mass and the presence of foreign inclusions in it. In this case, it is necessary to strictly control the operation of the laying equipment; isolated small breaks can be eliminated immediately.
Temperatures above the norm approved by SNiP can lead to cracking or uneven surface texture due to the sharp contrast between the base and the hot mass.
Bitumen stains appearing on the surface are a consequence of a violation of the percentage composition of the mixture. They will make the surface slippery. Precise adherence to proportions will prevent this defect.
Poor quality seams are the rules of installation. To avoid them, the cold edge warms up gas burners, and only then the hot mixture is laid.
Incorrect operation of the asphalt paving machine can result in different layer thicknesses or longitudinal cracks, so the equipment must be well adjusted.
Repair work
Even well-laid asphalt will someday begin to deteriorate. This process will call physical exercise and sun rays. This coating can be repaired.
The following restoration technologies can be used for repairs:
- Sealing cracks with tar. The crack is cleaned, covered with sand and filled with tar, after 15 minutes the asphalt is leveled with a spatula.
- Laying rolls of finished asphalt on the old one. Freed from protective film the layer is located above the damaged area and pressed tightly.
- Using cold asphalt. In the area of damage, the prepared mixture must be laid out on the old asphalt, leveled and compacted.
Such work must be carried out regularly, then the coating will last a long time. If we are talking about main highways, then SNiP recommends that the canvas be changed completely.
Video: Asphalt laying technology
