Cracks are one of the most common diseases of the road, and the harm to the road is very great. Especially in the winter and spring, when the rain and snow are infiltrated, the pavement disease, which is already in the crack state, In the event of serious damage. Therefore, for the early cracks in the road prevention and repair work is the most important. Here we come to understand the types of highway cracks and causes, hazards, treatment measures and technology.
Types and Causes of Cracks
1.1 transverse cracks
The transverse cracks are cracks that are basically perpendicular to the direction of the traffic, including the cracks in the temperature and the semi-rigid base asphalt pavement. However, the fractures can be divided into two types: load-type cracks and non-load-type fractures. The main causes of transverse cracks are as follows: (A) the shrinkage of the asphalt surface itself or the shrinkage of the semi-rigid base layer; (B) the compaction of the roadbed is not enough, or the longitudinal slope is large, (C) the construction of tenders at the junction of the compaction of the compaction uneven.
(1) Load type cracks
Load-type cracks are caused by the decline in the carrying capacity of the road, the strength is not enough to bear the vehicle load or repeated cyclic load caused by fatigue caused. The load cracks are first generated on the surface of the road, and under the repeated action of the vehicle load, the cracks gradually extend up to the surface. It may also cause cracking due to the concentration of the top stress caused by the cracking of the lower layer, or cracking at the same time. The cracks caused by the wheel load are reflected on the surface layer, often not separate, sparse or more regular cracks, but dense, from time to time interrelated mesh cracks.
Load-type cracks mainly include: fatigue cracks or cracks, edge cracks, slip cracks. (A) Fatigue cracks or cracks are caused by repetitive heavy traffic loads that cause the road to lose a range of cracks in service capacity. Fatigue cracks usually begin at the bottom of the asphalt surface at the bottom of the wheel load under the maximum tensile stress. In the loop connected to form a polygonal, acute angle of the block-shaped area, and finally developed into turtle-like. (B) edge cracks. The edge cracks are expanded due to traffic loads and are particularly severe for pavements that are not or are only partially paved. The edge cracks were initially caused by insufficient lateral force on the shoulder or weakening of the base due to poor water, poor drainage or freezing and thawing. (C) Slip cracks Slip or deformation due to frequent braking or turning of vehicles. Usually occurs in the HMA overlay, because the undercoat layer and the new layer between the adhesive layer is insufficient or poor adhesion.
(2) non-load type cracks
The causes of non-load fractures are complex, and they can be cracks, cracks, irregular cracks, freezing cracks, cracks (cracks or fractures), structural streets (expansion joints, etc.) cracks, aging cracks Etc., of which the most important is the temperature cracking and semi-rigid base cracking caused by the emission of cracks.
Non-load type cracks mainly include: temperature shrinkage cracks, reflection cracks, block crack. (A) temperature shrinkage cracks, asphalt surface shrinkage occurred in the winter temperature is low or prone to sudden changes in temperature areas. The asphalt surface layer is cracked when the average temperature in the asphalt surface layer is lower than its fracture temperature, or when the temperature stress generated by the asphalt surface layer accumulates beyond its tensile strength at that temperature. (B) Reflective cracks, the base reflection cracks are semi-rigid base layer is better than the asphalt surface cracking, under the combined action of load stress and temperature stress, at the bottom of the surface layer of the bottom of the surface stress concentration caused by the bottom of the bottom The corresponding position of the crack, and then gradually upward or downward expansion of the cracks through. (C) The block is a staggered crack that divides the road surface into an approximately rectangular crack and has an acute angle. The lumps range from 30 cm x 30 cm to 300 cm x 300 cm. Blocking usually occurs in the large traffic area of the asphalt pavement, but occasionally only in non-traffic areas.
1.2 longitudinal cracks
Longitudinal cracks are divided into top-down surface cracks and bottom-up fatigue cracks, basically parallel to the center line of the road, generally occurring in the road from the edge of the road 3 ~ 5m. There are two types of cracks, one is linear, the other is the vertical arc and both ends of the embankment to extend the edge. There are several reasons for this: (A) the role of the load is too large, the bearing capacity caused by the lack of longitudinal cracking. (B) due to the asphalt pavement paving shop construction longitudinal seam did not do the cracks. (C) non-uniform roadbed compaction or cracks due to uneven erosion caused by erosion of the roadbed edge. (D) The wheel is fractured by the wheel running on the road after the tire is damaged.
1.3 mesh cracks
Mesh cracks are caused by the development of a single crack. The reason for this is: (A) the overall strength of the road surface cracks. (B) the road began to appear after the cracks did not timely filling, resulting in water into the lower layer, especially in the snow melt during the freeze-thaw, will exacerbate the destruction of the road to promote the formation of cracks. (C) Asphalt during construction and in the long-term use of aging is also caused by asphalt road pavement formation of one of the reasons
2 the hazards of cracks
2.1 damage type
(1) Loose off
When the asphalt pavement cracks, the water will enter the pavement structure. Due to the role of water or frozen so that the asphalt binder and aggregate adhesion gradually worse, in the repeated hydrodynamic effect, there will be loose aggregate.
(2) pumping pulp
Refining slurry refers to the water into the grassroots or subgrade, under the action of the traffic load to produce a large hydrodynamic pressure, so that the base or subgrade materials continue to be washed, erosion, and the material in the small particles with the liquid was squeezed to the road surface The The pulp is usually caused by penetrating cracks.
The disease is mainly water damage. When the semi-rigid base layer and the asphalt surface are cracks, the road surface water through the pavement structure gap, into the roadbed, under the action of driving creep sinking
2.2 The root cause of road damage
Cracks will have a similar pumping effect on the road surface, resulting in damage to the road surface. The following figures show the damage to the road after the cracks are generated
As mentioned earlier, asphalt pavement in the cracks, will lead to a series of other road damage, which will seriously affect the asphalt pavement life and use of function. In order to prevent destructive damage to the pavement, it is necessary to first prevent or control the generation and development of cracks in semi-rigid asphalt pavement and prolong the service life of the pavement structure.
3 treatment measures and technology
Pavement irrigation technology is an effective preventive maintenance methods, better to prevent rain, snow road damage, extend the service life, improve road quality, enhance the user's satisfaction with the road. Domestic and foreign statistics show that the correct use of road sealing technology can generally extend the road life of 1-5 years.