Types of damage on asphalt concrete pavements. Defects in asphalt concrete pavement of highways and methods for its assessment Types of destruction of asphalt concrete pavement

Under the influence of light, heat, air oxygen, bituminous materials used for road surfaces age. In the process of aging, some of their constituents volatilize or oxidize, while others aggregate and condense. Plasticity of bitumens decreases, fragility increases, cracks appear. This is especially dangerous in aggressive chemical environments.

Due to the complexity and high degree polymerization compounds that are part of the bituminous materials have a relatively high acidity. However, prolonged exposure to concentrated solutions mineral acids bituminous materials are destroyed. Bitumens and compositions based on them, made using acid-resistant fillers (natural and artificial), resistant to long-term exposure to sulfuric acid at a concentration of not more than 50%, hydrochloric acid - 30%, nitric acid - 25%, acetic acid - 70%, phosphoric acid - 80 %.

Prolonged exposure to concentrated aqueous solutions (up to 40...50%), caustic alkalis and carbonates alkali metals at normal and elevated temperatures causes a gradual destruction of bituminous compositions. Even saturated solutions of lime, for example, in concrete, saponify bitumen. They are not affected by aqueous solutions of mineral and organic salts. Bituminous materials resist non-oxidized organic acids well, but dissolve in organic solvents.

Corrosion of bitumen leads to a decrease physical and mechanical properties asphalt concrete, occurrence in road surfaces various kinds defects.

Road surface defects ty (pavement) - these are deviations geometric parameters, textures and structures of pavement from regulatory requirements. Depending on the nature, location and size, defects are divided into the following types:

cracks- discontinuity defects pavement arising as a result of alternating load, fatigue phenomena, thermal expansion and other factors (Fig. 9.1). An increase in the number and length of cracks indicates the beginning of the process of pavement destruction. Asphalt concrete pavements are characterized by individual and frequent cracks.

Separate cracks- transverse and oblique cracks, not interconnected, the average distance between which is 4 meters or more. When determining road defects, the total length of cracks is recorded in running meters

Frequent cracks- transverse and oblique cracks with branches, sometimes interconnected, but, as a rule, not forming closed figures; the average distance between adjacent cracks is 1-4 m. square meters

crack grid- mutually intersecting transverse, longitudinal and curvilinear cracks dividing the surface of a previously monolithic coating into cells. Defects are measured in square meters.

potholes- local destruction of the pavement, having the form of depressions with sharply defined edges, formed due to the destruction of the pavement material; when diagnosing roads, they are measured in square meters. The reasons for the formation of potholes may be undercompaction of the material in this place, the use of heterogeneous or contaminated material, the formation of cracks or places of increased dynamic impact of vehicle wheels due to uneven pavement, etc. To prevent the development of potholes in area and depth, it is necessary to take emergency measures to eliminate them immediately after detection

Patches– sections where the original pavement has been removed and replaced with similar or different material; measured in square meters. They are the result of the use of patching, in case of poor performance of which evenness worsens due to the difference in the levels of the surface of the coating and patches. The patches also have an effect on the uniformity of the brightness of the coating.

Rutting- a defect in the road surface due to the presence of ruts on the carriageway - longitudinal recesses correct form in places of rolling, systematic application of loads from the wheels of the rolling stock (Fig. 9.12). Rutting is formed under significant (limiting) axial loads due to the rheological properties of materials and insufficient strength of the pavement structure. When diagnosing highways secretion is distinguished by depth: up to 15 mm (Fig. 9.13), from 15 to 30 mm (Fig. 9.14), over 30 mm (Fig. 9.15); it is measured in running meters.

chipping– destruction of the road surface as a result of the loss of individual grains mineral material- gravel, crushed stone (on transitional type coatings); due to the loss of communication between the grains of the material on improved coatings of a lightweight type, as well as on capital coatings of a non-rigid type with poor adhesion (adhesion) of crushed stone grains with bitumen; with poor mixing of the mixture, the use of low-quality materials in the coating; when laying the material in rainy or cold weather or when the coating is under-compacted. When diagnosing roads, it is measured in square meters (Fig. 9.16).

Peeling- destruction of the coating surface due to the separation of the outer thin films material caused by exposure to water and negative temperatures. It occurs especially intensively with frequent freezing and thawing of the coating and with the use of salt mixtures to combat ice. The intensity of peeling depends on the quality of the materials.

Edge destruction- destruction of the edges of the coating in the form of a network of cracks or chipping of its material (Fig. 9.17). Edge breaking occurs when the wheels of heavy vehicles move over the edge, when the wheels hit at the joints of cement concrete slabs, and also when the strength of the road pavement in the edge zone is insufficient. When diagnosing roads, it is measured in running meters. To protect the edges of the coating from damage, curbs are installed at the points of their junction with the curbs, arrange edge bands, reinforce the shoulders, the seams between the plates are sealed with mastic.

Among the above defects, cracks can be considered the most characteristic. According to the causes of occurrence, they are divided into temperature and temperature-fatigue.

31. The concept of rutting, its types and methods of determination

Rutting- pavement defect caused by the presence of ruts on the roadway - longitudinal recesses of the correct form in places of rolling, systematic application of loads from the wheels of the rolling stock (Fig. 9.12). Rutting is formed at significant (limiting) axial loads due to the rheological properties of materials and insufficient strength of the pavement structure. Under the influence of heavy vehicles, with heavy traffic, the adhesion can progress and lead to the formation of cracks, breaks. The presence of secrecy makes it difficult to maneuver cars, impairs drainage from the coating and increases the danger traffic. When diagnosing roads, secrecy is distinguished by depth: up to 15 mm (Fig. 9.13), from 15 to 30 mm (Fig. 9.14), over 30 mm (Fig. 9.15); it is measured in running meters.

Repair measures to eliminate the gauge are divided into two groups:

1. Ways to eliminate ruts without eliminating or with partial elimination of the causes of rutting:

1) partial cold or hot milling, in which the ridges are cut along the ruts, and the depth of the ruts is reduced to acceptable limits;

2) partial hot milling along the rolling strips using the Remix method and laying the removed layer to the entire depth of the track with the addition of new material with its mixing and compaction;

3) double surface treatment or laying a layer of cold cast asphalt mixes;

4) laying a thin layer of coating over the entire width of the carriageway using a hot or cold method without milling the old coating.

2. Ways to eliminate the rut with the elimination of the causes of rutting:

1) repair and reinforcement of pavement with correction of the cross profile of the entire roadway and laying of new, additional layers of pavement, strengthening them with geogrids, etc.;

2) rebuilding all the old pavement, and sometimes strengthening or replacing the soil of the upper part subgrade, as well as the replacement of non-rigid type pavement with pavement with cement concrete pavement.

It is always convenient to drive a car on a flat and smooth freeway, developing great speed. Not infrequently, the quality of the track does not allow this, as the surface has a deviation from the norm and is unsuitable for a quality ride. Over time, under the pressure of the wheels of cars, especially large trucks, the influence of adverse natural conditions in the form of rain, hail, a sharp change in temperature, asphalt concrete flooring loses its original appearance. It is covered with small cracks, pits, potholes, which shortens the time of high-quality work of the highway. Driving on such worn-out roads leads to damage to cars and can even lead to an accident.

Causes of destruction

As a result of the use of asphalt concrete pavements, they are subjected to various deformations. Road wear is formed due to external and internal influences on. Defects on the coating from the influence external factors include:

• power loads from automobile wheels;
• atmospheric precipitation (rain, temperature changes, thawing, snow, freezing).

Internal factors associated with the destruction of asphalt concrete pavement arise as a result of incorrect design for roads, their construction and repair:

1. Incorrect design of an asphalt concrete highway leads to the destruction of the road surface. Inaccurate studies, calculations and errors made in determining the intensity of the flow of vehicles can contribute to the formation of defects on the road from asphalt concrete and lead to the destruction of the road structure, namely: the integrity of the asphalt layer on the road surfaces will be violated; the soil of the base will sag; the strength of the soil cushion will decrease; deterioration of the asphalt concrete floor will follow.
2. Old techniques are applied and poor quality materials are chosen when working with asphalt concrete pavement. More recently, for installation, laying asphalt mortar and repairing tracks, hot ones were used, which included low-quality bitumen. It caused damage to the road deck and worsened the strength characteristics. ready mix for asphalt pavement. However, construction does not stand still, and even today the latest technologies are being developed and implemented. polymer- bituminous materials, which can significantly improve the properties of the material and the future route. Various additives to the mixture have gained great popularity for: improving adhesion, increasing resistance to water and cracking. Thanks to these additives, the resistance of the roadway to sub-zero temperatures is ensured. In order to avoid defects and wear of the roadway, it is necessary not only to use new mixes for asphalt paving, but also to choose new technologies that will stabilize and strengthen the weakened mobile base soils. To prevent the destruction of coatings, a reinforcing mesh is used, which will strengthen the road structure and increase the life of the asphalt road.
3. Defects and wear on the asphalt concrete pavement occur due to improper technological process during the construction of the road structure. Destruction is formed due to mistakes made when laying asphalt and repairing the track. Violations of the rules for the transportation of asphalt concrete mortar contribute to the occurrence of defects, as a result of which the mixture is supplied at the wrong temperature. When compacting the laid mixture, air bubbles were not removed or, conversely, the solution was too compacted, then the asphalt canvas will begin to crack and delaminate. Destruction of the route may occur as a result of poor-quality preparation of the subgrade and work on laying the road structure.
4. Defects on the road surface are most often formed as a result of weather conditions when, during rains, moisture penetrates the pavement, and the hot rays of the sun spoil upper layer routes - the strength of asphalt concrete is deteriorating, which leads to the formation of potholes. During the period sub-zero temperatures the collected moisture in the layers of asphalt concrete is able to increase in volume and thereby destroy the structure and compaction of the asphalt.
5. As a result of heavy loads from vehicles, the roadway is destroyed. High loads on the surface of the route are due to the intensive flow of vehicles, as a result of which, the norm bandwidth exceeded in 24 hours, and as a result, the life of the track is reduced. An increase in the axial load due to the operation of the road surface by heavy-duty vehicles leads to the destruction of the asphalt concrete pavement, the formation of ruts and cracks.

Damage to asphalt concrete pavement can occur due to the complex influence of external and internal factors.

Main types of defects

Asphalt damage are of the following types:

• Break. It is a slot on the paved area where the flow of vehicles passes. If cracks are not patched in time, they can grow in size and turn into a large-diameter breach.
• Service life expiration. The destruction associated with the long-term operation of the roadbed, which was not repaired, affects the thickness of the asphalt concrete layer.
• Reducing the strength of asphalt concrete. As a result of heavy loads from heavy trucks a subsidence of the canvas is formed and the destruction of the upper layer of the coating in the form of bumps, potholes and ruts.
• potholes. Pothole failures are depressions with a sharp edge break that occur due to improper asphalt concrete laying using poor quality materials.
• Peeling. The formation of peeling on the road surface due to the separation of particles from the top layer of the coating. It is formed due to constant variable effects on the road surface of frost and thaw.
• Climatic influences. During the melting period of snow masses, a large number of liquid, which is capable of destroying the roadbed, which entails a decrease in the strength characteristics of asphalt concrete.
• Chipping. This type of damage occurs due to a violation of the laying or repair of the roadway, namely, work in precipitation or sub-zero temperatures.
• Cracks. Cracks form on the road surface as a result of a sharp change in temperature.
• Drawdown. Settling occurs due to poor quality paving materials selected, as well as insufficient compaction of the asphalt mix or soil.

Under the influence of light, heat and oxygen, bituminous materials age. In the process of aging, some constituents evaporate or oxidize, while others become denser. Plasticity of bitumen decreases, brittleness increases, cracks appear. This is especially dangerous in aggressive chemical environments.

Rutting- a defect in the road surface due to the presence of ruts on the carriageway, longitudinal recesses of the correct form in the places of rolling of the systematic application of loads from the wheels of the rolling stock. It is formed with significant axial loads, due to insufficient strength of the pavement, under the influence of heavy cars with intensive formation of cracks and breaks. The presence of rutting makes it difficult to maneuver a car, impair drainage and increase the danger of road traffic. When diagnosing blood pressure, rutting is distinguished in depth up to 15 mm, 15-30 mm and over 30 mm. Gauges are measured manually and instrumentally. At manual way a rail with a recommended length of 2 m is laid on the crest of the ruts in the runway. The track is measured for each lane separately in a straight line and reverse direction. The main instrumental measurement method is a laser profiler.

chipping- destruction of roads. coatings, as a result of the loss of individual grains of gravel and crushed stone, or due to the loss of communication between the grains of the material on improved coatings, as well as on a capital coating of a non-rigid type, with poor adhesion of crushed stone grains to bitumen, or poor mixing of the mixture, when using low-quality materials in the coating or when laying materials in rainy or cold weather. When diagnosing, it is measured in m 2

Peeling– destruction of the coating surface due to the separation of the outer thin films of the material caused by the action of water and low temperature. It occurs especially intensively with frequent freezing and thawing of the coating and with the use of salt mixtures to combat ice. The intensity of peeling depends on the quality of the material. Porous and weak materials are more sensitive to temperature fluctuations and are more likely to peel. Peeling of the AB coating most intensively occurs in the spring. When diagnosing, it is measured in m 2

Defects in asphalt concrete pavement layers can be divided into two groups: - associated with the technical condition, adjustment and use of equipment; - caused by properties asphalt mix.

If the cause of the defect is the technological properties of the mixture, then it is usually eliminated by making changes to the composition of the mixture or to the operations of its preparation, storage and transportation. Some defects may be related to equipment and mixture properties at the same time. It is difficult to prioritize them.

1 - wavy surface - short waves;

2 - wavy surface - long waves;

3 - rupture of the coating over the entire width;

4 - rupture of the coating in the middle;

5 - rupture of the coating along the edges;

6 - uneven structure of the coating;

7 - traces from the screed;

8 - roughness of the coating;

9 - surface shadows;

10 - insufficient pre-compaction;

11 - poor quality longitudinal joint;

12 - poor-quality transverse joint;

13 - transverse cracks;

14 - shift of the coating during compaction with a roller;

15 - "fat" spots on the surface of the coating;

16 - traces of the rink;

17 - insufficient compaction of the coating.

Reasons for defects

1 - low temperature mixtures;

2 - temperature heterogeneity of the mixture;

3 - the mixture contains moisture;

4 - mixture segregation (separation);

5 - irrational composition of the mixture for bitumen;

6 - incorrect composition of the mixture according to the filler;

7 - standing of the rink on a hot surface;

8 - a quick change in the direction of the roller;

9 - incorrect rolling process;

10 - poor-quality preparation of the base;

22. Quality control of construction of asphalt concrete pavements

When constructing pavements, the quality of work is controlled during the entire construction cycle. The control begins with checking the quality of the original laid materials and evaluating the suitability of the subgrade, base or pavement on which the new layer of material is laid.

The technical control service of a construction organization checks the quality of the asphalt concrete pavement in the process of its installation. After completion of construction, quality control finished coating.

Checking the source materials and subgrade can be carried out for all indicators or selectively. The required amount of material is taken from the mass delivered to the construction site and sent to the laboratory.

Checking the quality of the roadbed consists in determining the soil compaction coefficient, surface evenness, determining the width of the roadbed and slopes, and the grain composition of the soil.

When laying an asphalt concrete mixture on a cement-soil, bitumen-soil and a long-standing asphalt concrete base or. the coating is checked to see how evenly the binder is distributed over the surface of the layer. The temperature of the asphalt concrete mixture delivered to the construction site is checked directly in the car body.

Quality control of the asphalt concrete pavement during its installation, i.e. in the process of laying and compacting the mixture, includes quality control, installation of side support bars; evenness and uniformity of distribution of the asphalt concrete mixture; thickness of the laid layer;, width of the laid coating; coating slopes; the quality of the seams in the joints of the laid strips; adhesion of the coating layers to each other; technological sequence of operation of light, medium and heavy rollers, their performance of the required number of passes and a given speed; temperature of the compacted mixture; surface roughness.

Quality control of the finished coating includes checking for evenness; compaction factor; layer thicknesses; adhesion strength of layers; compliance of asphalt concrete properties with technical documentation; surface roughness.

The quality of the seams is determined by visual inspection for the presence of shells and cracks. A three-meter rail and roughness testers can also be used.

When determining the transport and operational state of the road, the state of such an element as the road surface is of paramount importance. Coating wear and appearance various defects during its operation is an inevitable process that cannot be completely stopped, but can be significantly slowed down by timely preventive and road repair work, which include: the device of a wear layer, thin-layer surface treatment of the asphalt pavement, regular sealing of small cracks and a grid of cracks, creation waterproofing membrane and etc.

The main defects of the pavement arising during its operation include:

• cracks (single and network of interconnected large and small cracks);
• pits and potholes;
• track.

Cracks in the road surface and the causes of cracking

cracks- a pavement defect resulting from the brittle fracture of an asphalt concrete or cement concrete layer, manifested as a discontinuity of the pavement. In the case of asphalt concrete pavement, cracks are the most common defect.

Depending on the location of the cracks relative to the axis of the road, they can be transverse, longitudinal or curvilinear (oblique). Also, cracks are classified based on the nature of their relative position:

• single cracks located at a considerable distance from each other;
• separate, located approximately at the same distance from each other, but not less than 10 ... 20 meters;
• rare, unrelated cracks;
• frequent, interconnected and located at a distance of 1 to 4 meters from each other.

crack grid- intersecting transverse, longitudinal and/or curvilinear cracks.

The impact of vehicles and adverse weather and climatic conditions are the main factors contributing to the appearance of cracks on the pavement surface. Under the influence of the load from cars and temperature fluctuations (especially with the combined action of these factors), tensile and bending stresses inevitably arise in various layers of the pavement, and when such stresses begin to exceed the tensile strength of the material of the corresponding layer, cracks form (first small, imperceptible to the naked eye, and eventually larger).

Depending on the nature of the formation (causes), cracks are:

• temperature arising on the surface of the coating due to temperature fluctuations;
• fatigue, arising in the lower layer of the pavement along the roll strips, as a result of fatigue failure of the pavement layer from repeated load action;
• reflected resulting from copying by a new layer of already existing cracks in the old pavement (on which a new layer of asphalt concrete is laid).

The main reasons for the formation of cracks are:

• insufficient strength of subgrade and pavement;
• uneven compaction of subgrade and pavement layers;
• big swings temperatures from positive to negative;
• insufficient crack resistance of asphalt concrete pavement;
• difference in thermophysical properties of materials of layers of adjacent coatings;
• heaving, which is expressed in the redistribution of moisture in the subgrade, causing an increase in the moisture content of the subgrade soil in winter period, the formation of ice layers in it and, thus, an increase in the volume of the subgrade soil. As a result of such a process, the pavement first swells (raises the mound), and then, when thawed, it softens (weakening the pavement).

The presence of cracks in the road surface has a great impact on the strength and service life of the road for the following reasons:

• cracks violate the integrity and solidity of the road surface, dividing it into separate blocks that are not interconnected, as a result of which the load from the wheel vehicle transferred to a weakened structure, distributed over a smaller area, creating increased stresses and deformations in them;
• water penetrating through cracks into the base of the pavement and subgrade, weakens their strength and bearing capacity road construction generally;
• when the wheels of the vehicle hit the edge of the crack, individual parts of the coating begin to crumble and break off, the walls of the crack move relative to each other in a vertical plane, due to which a pothole forms over time.

Thus, each crack that is not repaired in a timely manner inevitably turns into a pothole over time.

Potholes on the road surface and the reasons for their formation

Pothole- local destruction of the coating, which has the form of a recess with sharply defined edges. Potholes can also include subsidence, breaks, places with strong chipping of the material, as well as large cracks.

As noted above, one of the reasons for the formation of potholes is the development of single cracks or a network of cracks. Another possible cause the occurrence of potholes, there is unevenness of the road surface in the form of shifts, sagging and other defects that occur not only during the operation of the highway, but also at the stage of its construction, for example, if technological requirements in the process of asphalting the road. Immediately after the car wheel passes through the protrusion of such an unevenness, a dynamic impact occurs on the coating, while repeated repetition of such impacts leads to a weakening of the material structure, the appearance and / or development of cracks and small potholes, which then turn into one large pothole.

An additional source of the formation of pits and potholes can be sections of the road surface on which peeling and chipping occur. stone material from a layer of asphalt concrete.

Regardless of the reasons for the formation, potholes must be repaired at an early stage of their appearance. Practice shows that each unsealed pothole quickly increases in size and contributes to the appearance of new potholes. And although on initial stage this process is relatively slow, if no measures are taken, then over time it becomes an avalanche. So, if the damaged sections of the road are made in a timely manner (usually in early spring) is taken as a unit, then with a delay of such work for 2-3 months, this cost increases by 2 times or more.

Rutting on the road surface and the causes of rutting

Track- deformation of the transverse profile of the carriageway with the formation of recesses along the rolling lanes, with or without ridges of uplift.

The appearance of a rut on the road surface can be due to several reasons:

• insufficient compaction of one or more layers of pavement;
• abrasion (wear) of the coating under the action of the wheels of cars (especially when using tires with spikes);
• accumulation of residual plastic deformations;
• structural destruction of the pavement layer material;
• uneven residual deformation in the subgrade soil.

If during the construction of the road base or the asphalting of the road, some layers of the pavement were not sufficiently compacted, a rut may occur due to the additional compaction of these layers under the influence of passing vehicles. From total number causes of rutting, the share of insufficient compaction of layers of pavement accounts for 5 ... 10%.

Another important reason rutting may be wear (abrasion) of the asphalt pavement by the wheels of cars. Use in winter time studded tires significantly accelerates the process of rutting. Under high traffic intensity, abrasion of the coating may be main reason rutting.

In 15–20% of cases, the formation of ruts on asphalt pavements occurs due to their plastic deformation. The essence of plastic deformation is that due to a decrease in the viscosity of bitumen (a decrease in the viscous shear resistance of bitumen), the structural viscosity of asphalt concrete decreases, that is, its plasticity increases. During the passage of one car, the deformation that occurs in such a coating is insignificant, but with repeated passage, vertical residual deformations accumulate, which causes the appearance of a rut. Simultaneously with vertical residual deformations, horizontal deformations also accumulate, when, under the action of shear stresses, asphalt concrete particles are extruded into different sides, resulting in ridges appearing on the sides of the track. A decrease in the viscosity of the bituminous binder and, accordingly, an increase in the plasticity of the asphalt concrete pavement occurs in summer at an air temperature above +30 ° C, when the temperature of the road surface rises to +40 ° C and above.

Another cause of rutting may be structural failure of the material in the pavement layer. Under the action of repeatedly applied loads in the pavement layers, conditions may arise when vertical or horizontal stresses exceed the maximum permissible values ​​and the destruction of the continuity or structure of the layer material begins with a loss of strength and shear resistance. Of the total number of cases of rut formation, structural damage occurs in 25...35%.

In 20…30% of cases, the cause of rutting is uneven residual deformation in the subgrade soil. The accumulation of residual deformations in the subgrade soil most actively occurs in the spring. Biggest Influence on local extrusion and buckling of the soil has high humidity soil in places with unsecured drainage of surface or groundwater.

Pothole repair of asphalt and asphalting of roads in Kyiv

Elimination of small and large defects in the road surface, filling cracks, repairing pits and potholes in the asphalt concrete pavement, fixing rutting on the asphalt pavement, as well as the installation of wear layers from a cast asphalt concrete mixture or crushed-stone-mastic asphalt.