1 technical background of in-situ cold recycling
In-situ cold recycling is a new technology developed abroad in the late 1980s. Mainly used for the maintenance, transformation and upgrading of old roads. In China, the cold in-place recycling technology of asphalt pavement is also regarded as a key scientific research project, but due to the lack of necessary theoretical guidance, scientific design methods and mechanical equipment support, the cold in-place recycling technology in China was not widely used in the actual engineering construction at that time. With the increasing number of asphalt pavement maintenance and reconstruction projects in China, various construction units have gradually become interested in the in-situ cold recycling technology, and have done experimental sections in various grades of highways, with good results.
2 In-situ cold recycling technology process introduction and technical points
(1) Milling and planing the pavement. In order to ensure the reasonable gradation and uniformity of cold recycled mixture, the pavement should be cleaned before cold recycling construction, and the pavement garbage should be removed. Firstly, the bumps, waves and other parts on the original road surface are smoothed; The subsidence and low-lying areas below the original pavement should be filled with milling materials, and then the whole pavement will be broken 1 time. Leveling and rolling after crushing.
(2) paving cement. After milling, leveling and rolling, the cement dosage per square meter is calculated according to the designed cement dosage, and then artificial paving is carried out on the site to ensure uniform cement paving. Each working section adopts flow process and spreads cement vertically.
(3) Cold regeneration mixing. According to the paving situation of the test section, determine the reasonable length of the cold recycling construction section. In the process of mixing, the operator should pay attention to observe the driving track of the regenerator, ensure that the driving route is straight, and ensure that there is at least 30 cm overlap between pictures. At the same time, special personnel are needed to check the mixing depth. The amount of water added should be determined according to the water content of the test mixture, and generally should not be greater than the optimal water content.
(4) Leveling and rolling. After the mixing is completed, use a road roller for static pressure 1 time, and then use a grader for leveling. Through leveling, the transverse degree, longitudinal slope and flatness of the base can meet the design requirements. After the leveling work is completed, use a vibratory roller for static pressure 1 time, and then vibrate for 3 ~ 4 times to achieve the designed compactness.
(5) Joint treatment and maintenance. During construction, the front and rear sections shall overlap, and the adjacent sections shall not be rolled for 2 ~ 3 m.. In the latter stage of construction, cement should be added to re-mix, so as to ensure the connection and consistency of the two construction stages at the joint. After the roller compaction is completed and passed the inspection, the base shall be kept moist for not less than 7 d, and traffic shall be interrupted and vehicles shall be prohibited during the maintenance period.
Several key points that should be paid attention to in-situ cold recycling construction.
Selection of (1) stabilizer. The cement added in the construction should be retarded as far as possible to ensure the construction progress and work efficiency, and the dosage of cement should be strictly controlled during the regeneration process, which should not be too large.
(2) Control of walking speed of regenerator. The key to determine the walking speed of the recycler is whether the mixing is uniform or not. Generally speaking, the speed should not be too fast, try to ensure the progress is even, pay attention to uninterrupted water supply, and ensure that no construction joints are produced.
(3) Be careful not to produce soft bullets. For the phenomenon of soft elastic and boiling in construction, we should carefully analyze the reasons and determine the reasonable solution.
(4) Before construction, all personnel involved in cold recycling construction shall be trained, so that everyone in the working face knows what to do and how to do it, and the close cooperation of construction machinery shall be ensured to form a standard process.
3 In-situ cold recycling construction technology
(1) Reduce costs and save energy. Compared with the traditional technology, in-situ cold recycling of road is the reuse of asphalt pavement, which reduces the excavation and transportation of old materials and the mining and purchasing of new materials in road maintenance or reconstruction, reduces the construction cost and reduces the consumption of new energy.
(2) Shorten the construction period. In-situ cold regeneration is carried out under natural conditions. Except for some serious bulges and pits, other pavements do not need to be treated in advance and can be constructed at one time, which reduces the excavation time of old pavements, the transportation time of new and old materials and the construction period.
(3) Improve the performance of the old road without damaging the subgrade. In-situ cold recycling is designed according to the old pavement materials, and appropriate additives are selected and mixed accurately to ensure the construction quality and quality, and the geometric alignment and elevation of the pavement are well maintained. In-situ cold recycling, the recycled tire with high adhesion only passes through the subgrade once, which reduces the frequent high stress load of machinery on the subgrade compared with the traditional process. At the same time, cold recycling technology reduces the transportation problems of old pavement and new materials, and reduces the repeated load brought by heavy vehicle transportation to subgrade. The performance of the old road is improved, and the damage to the subgrade is less.
(4) Environmental protection. In-situ cold recycling technology can reduce the occupation and environmental pollution of waste asphalt pavement, and reduce the exploitation and environmental damage of new road materials. The transportation volume is greatly reduced, which reduces energy consumption and dust brought by transportation vehicles, so it is called "green" construction technology.
(5) Reduce construction safety interference. During construction, the whole cold recycling machinery combination is located in the same lane, which does not affect the traffic of vehicles in another lane, and is suitable for road construction with narrow pavement width and large traffic volume. Cold recycling construction is a combination of mechanization and intensive construction. The machinery has a closed automatic control and adding system, which reduces the impact of dust on the surrounding environment, is conducive to civilized construction and reduces the interference of construction on traffic.
4 Application of in-situ cold recycling technology
Now the country pays more and more attention to environmental protection and renewable resources. Especially with the development of "every village is connected", on the one hand, the state should build some rural roads, on the other hand, it should upgrade the existing rural roads and county-level roads. Due to the advantages of in-place cold recycling technology, the market of in-place cold recycling machinery is expanding year by year with the new construction and transformation of county and township highway networks. In 2008, our unit made a 5 km cold recycling test section on the township road from Lu Wu to Zhoucun, and its structure was 15 cm thick cement base, which has been in good condition so far. In order to further verify the road performance of this technology, subbase was made in the provincial highway overhaul project of Zhengzhou-Xi 'an railway in 2009, and the application effect is good so far. With the development of foamed asphalt technology, foamed asphalt is used as the base in Jizhou section of 20 10 National Road 106, and it has been used well so far. At present, cold recycling technology has been widely used in upgrading and reconstruction tests of various grades of highways by various construction units. From the engineering practice, in-situ cold recycling technology has obvious advantages in road reconstruction and upgrading. As China's high-grade highways enter the period of large and medium-sized repair, the cold in-place recycling technology of old asphalt pavement will be paid attention to and widely used.
5 conclusion
With people's attention to environmental protection and social benefits and technical progress, asphalt pavement recycling technology has been paid more and more attention. As a new construction technology, in-situ cold recycling will be more and more widely used, and its social and economic benefits will be greater and greater. Today, with the emphasis on sustainable development, it is of great significance for the construction and development of expressway to further strengthen the research on in-situ cold recycling technology of pavement.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd