Insufficient cracks or broken asphalt concrete pavement surface layer or base layer strength is insufficient, temperature stress and load stress exceed the tensile strength of concrete, asphalt concrete pavement will produce cracks and develop into plate fractures, some of which are due to concrete Treatment of transverse cracks in highway cracks caused by shrinkage stress caused by early shrinkage
1 1.1 Traditional process of crack repair on asphalt pavement According to the construction experience, both emulsified asphalt and hot asphalt are difficult to be poured into the joint, and the asphalt and crack are not firmly adhered. The asphalt is easily extruded after being heated, which not only affects the appearance, but also does not seal the water. The role. In recent years, the cracks have been expanded by a special slot machine, and the joints with good compatibility with the old asphalt mixture, high bonding strength, and low temperature are not brittle. The advantage is that the crack treatment is more thorough, but special expansion joint machinery is needed, and the cost is high. According to long-term experience, expansion and extrusion at high temperatures are still the main obstacles to their promotion. At present, the application of highways is mainly based on the method of filling the grooves along the cracks to fill the compaction with new mixed materials. In addition, the repair of the pit is to remove the accumulated water in the pit and the surrounding loose material and then fill the mixture to compact and level; the repair of the rut is to remove the surface layer of the rut and then re-paved the asphalt concrete surface layer. In fact, these treatment methods have obvious interface between new and old asphalt mixture, which will cause the road surface damage along the road surface joints. Moreover, due to the small working surface, the repaired road surface strength, compaction degree and flatness are all It is difficult to obtain effective guarantee. The key point is that this part becomes the weakest place in the pavement structure, and it is prone to secondary damage.
1. 2 Asphalt pavement crack repair new technology construction method Highway traffic volume is large, there are many overweight vehicles, traffic can not be interrupted during construction, only half-width construction scheme can be adopted, vertical joint treatment is extremely difficult, and design and construction are carried out according to construction specifications. Corresponding treatment, although carefully constructed, cracks in the joints will be reflected to the surface sooner or later. The earliest situation was the crack that appeared shortly after the completion of the construction, mostly after 2 years. At present, many new materials and new technologies for the maintenance and repair of asphalt concrete pavement have been developed at home and abroad. For example, the cracks are sealed by the Kui road surface sealing material. After field test, the effect is more obvious. The construction is simple. In addition to the safety facilities, only one worker is needed. The heating equipment can be connected to a gas tank. The main points of construction are as follows: 1) Clean dust, dirt and loose sand on the gravel surface. 2) Determine the width of the seal tape according to the slit width and prepare the seal tape. 3) Heat the seal tape with a blowtorch or spray gun, and seal the seal tape to the seam along the crack position. The heating temperature will make the surface become oily. 4) In order to overcome the effect of the chromatic aberration of the sealing tape and the original road surface, some fine sand, fine mud or fly ash may be sprinkled on the surface of the sealing tape when it is not completely cooled. 5å€ã€‚ The width of the slit is about 1.5 times the width of the slit. Dissolve the large seam sealant and pour it into the seam, and add a proper amount of clean gravel. Repeat this step until the seam is full. This process is manually tamped and the seam tape is applied to it. When the crack is less than 10 mm, the seam tape can be directly sealed. When the crack is between 10 mm and 20 mm, the fine sand is used for filling and then the seam is sealed.
1. 3 Traffic control should be done at the construction site to ensure the safety of construction. The causes of various types of cracks are very complicated. Because the different cracks of the cause have a large difference in the vertical depth of the pavement structure, many monographs have been discussed in detail. A lot of research has been done on prevention measures. At the same time, due to the existence of cracks, the underlying layer of the pavement structure is discontinuous in rigidity or load transfer. Therefore, only the treatment of the pavement structure is incomplete and the repairing effect is poor. However, it is often unavoidable that the asphalt pavement does not crack during use. The key is our attitude towards the occurrence of cracks. As soon as a crack is found, it is the most important thing to seal it. It prevents the rainwater from infiltrating the base layer and the strength of the soil foundation, causing a vicious circle. The new material and new technology are used to ensure that the rainwater does not infiltrate, and the effect is more obvious. The service life of the pavement has good social and economic benefits, which has become a consensus in the industry.
3 Daily Maintenance Principles for Cracks in Expressway 1) Adhere to the principle of preventive maintenance. Preventive maintenance of highway roads and bridges is essential. Especially in the high-incidence period of roads and bridges, that is, before the spring melt and rainy season, if preventive maintenance is not implemented in time, it is often difficult to achieve timely maintenance in the high-risk period of the disease, and it will be more difficult to obtain more manpower and material resources. Good maintenance results. Therefore, daily inspections and inspections must be strengthened, and maintenance and repairs should be carried out during the initial period of road and bridge diseases to avoid further expansion of diseases, thereby achieving economical savings and ensuring the timeliness of maintenance. 2) Conduct road surface inspection regularly. Regular road surveys are carried out: a. The system collects road surface technical data in the road sections and establishes a highway pavement database to provide a scientific basis for road maintenance and management. Check and determine the degree of road damage and the actual bearing capacity, and make a safety assessment of the damaged condition of the road surface to ensure the safe and smooth highway. b. Understand the performance of highway pavement performance and implement dynamic tracking management of pavement. The three major indicators of pavement: deflection, flatness, rutting and structural depth (coefficient of friction) are tested across the entire line. These basic work have important guiding significance for highway maintenance management. 3) Focus on road maintenance. The perfect condition of the road is the primary condition for ensuring the safe and smooth highway. With the service life of highways and the increase of traffic flow, especially the severe damage of over-limit and overloaded vehicles, various types of diseases on highway pavements have appeared in large numbers, technical indicators have dropped sharply, and even safety hazards have occurred. Therefore, it is necessary to focus on road maintenance. 4) Ensure the timeliness of project maintenance. Due to the high speed and large capacity of the expressway, daily maintenance projects, road surface disease maintenance and crash barrier maintenance, greening and other projects must be timely and efficient. At the same time, in response to various emergencies, the engineering maintenance department should establish an all-weather rapid response mechanism, formulate corresponding emergency measures, and rush to repair at any time to ensure the smooth flow of the expressway.
2 Causes of cracks in highway pavement
2.1. 1 Insufficient cracks or broken asphalt concrete pavement surface layer or base layer strength is insufficient, temperature stress and load stress exceed the tensile strength of concrete, asphalt concrete pavement will produce cracks and develop into plate fractures. Some of these fractures are Lateral cracks caused by shrinkage stress caused by early shrinkage of concrete, or cracks formed by different degrees of foundation subsidence caused by increased stress caused by uneven settlement of foundation or erosion of foundation, Some are due to repeated use of vehicle loads, resulting in repeated load stresses that exceed the longitudinal or transverse cracks caused by the fatigue strength of the concrete.
2.1. 2 Creep and shrinkage of cement concrete Under the long-term constant load, no instantaneous elastic deformation and plastic deformation will occur, and in the inelastic condition with increasing load time, the concrete shrinks. Cracks are generated, but shrinkage cracks are produced when the perimeter of the concrete panel has a confinement that prevents it from shrinking freely.
2.1. 3 Insufficient or uneven strength of the base layer causes the broken plate 1) The strength of the base layer is lower than the design requirements, and it will be difficult to withstand the load transmitted from the concrete slab. Under the repeated load, deformation and damage will occur, resulting in the base layer and the plate. The body is emptied, causing cracks or broken plates. 2) The stability of the base layer is poor and the integrity is not uniform. The excessive friction of the base layer causes the shrinkage and creep of the concrete when the concrete slab changes in temperature, and the stress concentration of the slab causes the broken plate. 3) Soft soil foundation, underground pipeline (line), etc., if improperly handled, the unevenness of the local section is uneven, which may easily cause uneven strength of the base layer, thereby causing road surface breakage. 4) Failure to comply with the specifications during construction, resulting in the failure of the basic structure to meet the requirements of the compactness requirements of the standard, resulting in insufficient road strength to cause road signs, the reverse side can be added with the corporate company's advertising (to negotiate with the media company), by the company Maintenance costs are provided and local villagers implement practical maintenance. 3 Conclusion This paper combines field research, provides a more detailed analysis of rural road traffic safety environment and safety marking lines and other facilities, and puts forward corresponding improvement suggestions on the practical problems of rural roads. In addition, in addition to improvements in facilities such as the environment and marking lines, the accident rate can be reduced. Remedial measures after road traffic accidents should also be improved. For example, a security system can be constructed for different road sections, which can be the first after a traffic accident. Time to get the most reasonable rescue; Another example is to arrange the nearest health protection department on the corresponding road section, so that the injured person can go to the nearest hospital for treatment. In addition, it is possible to conduct security analysis and analysis on special road sections (schools, kindergartens, corners, etc.) and to form improved standards for promotion and use. Due to the limited level of the author, this article is only used as a joke, and readers are also requested to criticize and correct. The broken plate of the panel. The inspection indexes such as the compaction degree of the base structure should meet the specification requirements of JTJ 071-98 highway engineering quality inspection and evaluation standards.
2.1. 4 Influence of concrete mix ratio Under the action of various factors, the volume of concrete should be reduced, that is, what we usually call shrinkage. When the outside world has no constraint on the concrete, it can shrink freely. Concrete mix ratio has a great influence on concrete shrinkage. The shrinkage of concrete increases with the increase of water consumption, and the shrinkage of concrete increases with the increase of water-cement ratio. The shrinkage of concrete increases with the increase of cement dosage and sanding rate, but the increase is small.
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