Ⅰ.The road asphalt pavement disease is the result of a variety of factors combined effect, its variety, but mainly for the cracks, rutting, subsidence, pits, oil and oil spots, pavement and so on.
① horizontal cracks. Horizontal cracks are regular cracks that are perpendicular to the direction of the route,
② longitudinal cracks. Longitudinal cracks are cracks that travel parallel or substantially parallel to the route.
③ cross cracks. Two or more cracks that cross each other are called cross cracks.
2. Rutting: it is the permanent impression of the wheel left behind when the vehicle is running on the road.
3. Subsidence: refers to the subgrade compaction is not enough or the structure of the foundation soil is bad, in the water, load and other factors under the uneven vertical deformation
4.: Pit pit road refers to the driving effect, partial loss caused by aggregate pavement potholes.
5. Oil and grease: generally refers to a result of surfactant after demulsification on the fabric surface attached to the oil, such as defoaming agent, softening agent, anionic surface active agent containing silicone more prone to breaking phenomenon. You need to remove silicon specialized agents.
6. Pavement movement: mainly refers to the mixture in the longitudinal displacement of the road, it may occur during construction, or after the road opened for a period of time, especially in hot weather.
Ⅱ, The cause of disease formation
(1) Transverse cracks: the cracks are basically perpendicular to the centerline of the road, the width of the gap is different, and the length of the seam runs through the part of the width of the road or the whole width of the road. The cracks are generally regular, producing cracks at regular intervals, depending on the local temperature and the crack resistance of the asphalt and semi-rigid base materials.
(2) Longitudinal cracks: the fracture direction is basically parallel to the driving direction, and the length and width of cracks are different. Mainly concentrated in the dense distribution of the wheel track Lane, because highway traffic channelization is clear, the wheel track position and the wheel track distribution range is small, big and slow, heavy vehicles are concentrated in the driveway, fast cars, small cars, light-duty vehicle driving on road overtaking opportunities increased significantly, the lane load is small, relatively small volume of traffic also, the longitudinal cracks is smaller, the longitudinal seam width is generally 5 ~ 10mm, located in the central lane near the line, which stretches tens of meters, even hundreds of meters. Often appear in a single crack. The reason there are two possibilities, one is surface layer of asphalt spreader shunt, two pieces of some untreated, gradually cracking in the vehicle load and atmospheric factors; another is due to uneven subgrade compaction of the subgrade edge or affected by water erosion caused by uneven subsidence.
(3) Mesh cracks: cracks criss cross, seam width of 1mm or more, the gap below 1000px, more than 1m2.
(4) Reflective cracks: mainly because the cracks caused by uneven settlement of the soft foundation are directly reflected to the asphalt pavement. In addition, the action of traffic loads accelerates the development of cracks.
2. Rutting: Rutting is generally in the higher temperature season, asphalt surface layer under repeated rolling, resulting in permanent deformation and plastic flow and gradually formed. It is usually accompanied by the asphalt layer compression subsidence and lateral uplift, the combination of the two together. The permanent deformation of the pavement occurs mainly in the asphalt surface. Therefore, in order to delay the formation of rutting, we should start from improving the high temperature stability of asphalt surface materials. In addition, the structure and the severity of the rutting of asphalt surface composition and mixing ratio have great relationship, type of Asphalt Concrete Pavement's rut resistance type is much better than. Asphalt pavement rutting of Shanghai city is common, most concentrated in the road intersection, traffic, pavement under high temperature by severe rolling more prone to rutting, repair and replacement of new asphalt concrete, but without strict maintenance is put into use in the new rolling will appear rut, often appear vicious spiral. According to the practice of highway construction and maintenance in hot and humid areas analyzes various causes of common diseases of asphalt pavement, puts forward the treatment method of various diseases, and puts forward some suggestions on China's future highway construction, design, construction and maintenance etc.. Asphalt pavement is widely used in highway because of its geological conditions, adaptability, comfortable driving and convenient maintenance. After the expressway opened to traffic, due to the traffic load, environmental impact and the shortcomings of the design and construction, the asphalt pavement will gradually appear a variety of road diseases.
3. Settlement: Asphalt viscosity is small, will affect the adhesion of asphalt and mineral. At the same time if the asphalt mixture aggregate ratio is too small, or in heating asphalt and asphalt mixture mixing process, the temperature is too high which will cause the temperature of asphalt, asphalt mixture of asphalt film is relatively thin, reduce deformation resistance increased brittleness and void ratio is too large. These will lead to asphalt membrane exposed too much, the aging of asphalt accelerated, while water permeability increased, thereby speeding up the water on asphalt spalling, and ultimately in the vehicle load caused by cracking and subsidence of the road.
4. Pit: asphalt pavement pit often has a forming process of time, beginning with local cracks, and then crack loose, in the driving load and rain and other factors, gradually form a pit.
Common reasons are mainly the following:
(1) The pavement thickness and compactness of pit enough paving surface prone to inadequate compaction process, resulting in the surface layer of asphalt mixture has high porosity and adhesion, waterproof performance; mixing plant is far from the construction site, long distance, transportation of asphalt mixture the material of heat loss is large, shipped to the site can not meet the requirements of temperature paving pavement; local grassroots level control is not strict, resulting in asphalt layer thickness is not enough in the individual places, driving under the influence of the first pit formation damage.
(2) The bonding layer is not strong pit mixing paving, lower surface containing ash mud and debris, which can not effectively lower bond, and the formation of pits, such as bridge holes, the pothole repair damaged two times higher frequency, in general should be first into the bottom of concrete surface then the asphalt filling repair.
(3) The water damage pit is the most common pit in the early damage of asphalt concrete pavement, and the damage of water often starts from the middle surface of asphalt surface. The water into the asphalt pavement, stranded in the surface layer, when the aggregate and asphalt stripping, asphalt mixture is no longer a whole, aggregate under load, the force of the grassroots, the grassroots local pine colony forming mortar from the pavement cracks to squeeze out the formation of Jack the white pulp in asphalt pavement. This cycle continues to form a water damage pit.
(4) During the operation of the vehicle, diesel pits caused by oil leaking on the road surface, the asphalt is diluted, reduction of the bond, the aggregate loss form pits; heavy rims or transport vehicles, scratch pits formed; pit jacked out of the pit and the formation of fire.
(5) Base, which pits the formation of frost damage
5. Oil and grease: the main causes of bleeding and staining of the two diseases is the mixture segregation. Mixture segregation, some positions of coarse and fine aggregate are concentrated in the layer, the uneven asphalt concrete mix gradation, inconsistent with the original design, the loss of the original mixture design to achieve adhesion on the formation of the road goes on, and will lead to uniform mixture of aggregate and separation of asphalt, asphalt to form oil and grease spots.
6. Road passes: the asphalt concrete surface layer is the main passage, mixture of longitudinal displacement occurred in the road, it is likely to occur during construction or have opened a period of time on the road, especially in hot weather when the traffic load.
Ⅲ, The treatment of various diseases
1. Cracks: according to the "asphalt pavement construction and acceptance criteria" (gb50092) requirements, according to the local climate conditions and road grades to choose the applicable asphalt type. To reduce or eliminate the asphalt surface temperature, shrinkage cracks. The use of quality asphalt is more effective.
(1) organize the construction reasonably, avoid cold joint as much as possible. For the treatment of cold joints, seams should be cut along the edge of neat, clear scrap preheating, then softening seams, daubing emulsified asphalt mixture, spreading new. When rolling, the rollers in the compacted banners, steel wheel into the new layer of 375px or so, each pressure again to new layer moving 15-500px, until the roller is all in the new layer. For longitudinal cracks, such as width spreading, the front and back should be followed, and the upper and lower longitudinal joints should be staggered over 375px. When the paving is controlled, the loose paving coefficient shall be controlled so as to make the compacted joints close and smooth.
(2) before the asphalt pavement spreading, the lower stratum should be checked carefully, and the soft clay layer can be removed in time to ensure the stability of the lower layer. On the old road, asphalt pavement structure layer, before milling the original road, and then paved, to delay the formation of reflective cracks.
(3) in the presence of tiny cracks on the pavement, it must be promptly dealt with. For fine cracks (2-5mm), the modified emulsified asphalt can be used to fill the seam. For the coarse cracks larger than 5mm, the modified asphalt (such as SBS modified asphalt) can be used to fill the gap. Before pouring, must be removed, hem seam within the particles, and the gap in dry garbage. After the seam is filled, the surface is covered with coarse sand or 3-5mm stone. For the case of large cracks, it is necessary to excavate the asphalt concrete on both sides of the cracks, first deal with the base layer and then spread the new mixture, and the semi rigid material with good water stability and small shrinkage is the first choice. If there is a weak layer or unstable structure layer, it should be removed; if the water caused by the water in the structure layer is cracked, the drainage equipment for the road seepage water shall be added to the surface after removing the surface layer.
2. Rutting: mainly to improve the high temperature stability of the mixture. In the past few years, the production and construction practice of modified asphalt mixture proves that the modified asphalt mixture is an effective way to prevent or delay the rutting of pavement. The incorporation of many properties, different modifiers can improve the asphalt in the asphalt viscosity increase, temperature stability, softening point, penetration increase, anti-aging performance is improved, and also improved the high temperature stability of asphalt and anti rutting ability. The modified asphalt is divided into three categories: the first category is the mineral fillers, such as carbon, lignin and asbestos; second kinds of polymers, rubber, SBS resin, EVA Pa; third as additives, including antioxidants and anti stripping agent etc.. From the practice of modified asphalt mixture production, it can be seen that PE has obvious effect on improving the high temperature stability of asphalt mixture, while EVA has obvious effect on improving low temperature ductility of asphalt.
3. Settlement: in order to avoid the occurrence of subsidence, we can take the following measures: first, choose the asphalt which conforms to the technical requirements of traffic road petroleum asphalt, or adopt the modified asphalt which has been proved effective. Adopt proper thickness of asphalt layer or 12 to 375px crushed rock layer between asphalt surface and semi rigid base course. In the semi rigid base, top or asphalt layer between a variety of geosynthetics, or increase the tensile strength and anti deformation ability of asphalt mixture. Strengthen the maintenance of subgrade and pavement and pay attention to work.
4. Pits: protection of early damage of Asphalt Pavement Based on the above analysis, we can see the early damage of asphalt concrete pavement and asphalt pavement construction, traffic and climate conditions of all or part of the connection, and the traffic climate condition is the objective existence, so the asphalt pavement early damage prevention should be based on the pavement construction of asphalt mixture and two considerations.
(1) strictly control the quality of asphalt mixture
Select high quality domestic or imported asphalt with good high and low temperature properties, anti-aging properties, low wax content and high viscosity. The aggregate shall be made of aggregate with rough surface, hard stone, good wear resistance, good compaction and good adhesion to asphalt.
Select reasonable mixture gradation. Gradation of mixture is the guarantee of high temperature stability and fatigue property, low temperature crack resistance, surface property and durability of asphalt mixture. In order to improve the performance of asphalt pavement, we can consider the following two ways: first, to improve the gradation of mineral aggregate, and adopt asphalt mastic macadam (SMA). Second is to improve asphalt binder, using modified asphalt.
To strictly control the mixing quality of asphalt mixture, mixing process found in the "paste" or "segregation" and other abnormal situations should be treated immediately; increase the Marshall test frequency, strictly control the asphalt aggregate ratio, stability, flow value and other indicators, when necessary for special mixture proportioning design.
(2) complete the construction according to the design
Construction quality control is not strict, early damage is inevitable. So the asphalt pavement construction must be according to the requirements of total quality management, establish a sound and effective quality assurance system, the implementation of target management, process management, a clear responsibility for the whole construction process, each process quality to strict inspection, control, evaluation, to ensure that they meet quality standards, specific to grasp the following aspects: the base top surface roughness. To improve the gradation of base material, increase of coarse aggregate, improve the large and medium size of aggregate content; control of optimum moisture content, improve the rolling method, avoiding excessive vibration is too wet, cannot make the surface form a mortar shell, with fine material compaction after leveling. For semi-rigid base of fine grained soil, the top surface roughness can be strengthened by using top surface nailing and so on when necessary. Reasonable spreading of oil and sticky oil. The top surface must be kept clean before paving each layer. According to the construction experience in recent years, for the cement stabilized semi-rigid base layer, the permeable asphalt should be emulsified with slow cracking type. With the asphalt distributor when spraying, should maintain a steady speed and spray volume, can flow and the formation of film, not a blank, and immediately spreading stone chips or coarse sand, steel tube roller pressure again, will sweep away excess floatsam. For old asphalt pavement cover, it must be sprayed with sticky layer of oil, sticky oil should have good adhesion, foot has a clear sense of adhesion, the entire surface is not easy to separate after taking the core. For the trunk highway, the I type slurry seal can be used as the bonding layer to realize the double function of interlayer bonding and waterproof, and no closed traffic is needed.
③Improve the quality of pavement spreading. In the paving mixture when the distance is too far, paving temperature should be controlled at 130 DEG -150 DEG, paving thickness, compaction equipment number should be set at about 2m/min, speed control, compaction number can not be too little, the mixture to the pore is too large; it can not be fed, especially the base layer; rain wet wet, not spreading, but not in the rain spreading; the longitudinal and transverse joints should be closely and smoothly, the amplitude of overlap between the mixture with artificial shovel.
5. Oil and grease: improve the internal stability in mixture after compaction, moderately reduce the content of asphalt and aggregate, improve the content of mixture in multi angle gravel particles, avoid mixing the phenomenon of uneven paving construction, such as when using artificial local pick.
6., road progress: when the road surface conditions, only partial eradication, the use of new mixing materials meet the requirements, and with the surrounding mixture close together.