With the rapid development of high-grade highways in China, asphalt pavement has become a common pavement material for high-grade highways.
However, with the improvement and renovation of a large number of asphalt pavement, asphalt mixture leads to a large degree of pollution.
So asphalt pavement maintenance and maintenance has become the most important task.
Due to the limited bituminous materials, resources and pollution problems, bituminous regeneration technology has become an economic and effective maintenance technology studied at home and abroad, and has been rapidly developed at home and abroad.

Asphalt pavement regeneration

Asphalt pavement regeneration technology and for the old asphalt pavement after the crushing and screening of the new asphalt materials and regeneration agent mixed in accordance with a certain proportion of remixing into a mixture;
It can be repaved.
The recycling of asphalt pavement materials can effectively save construction costs, reduce the use of aggregates and cementitious materials, and can be very effective in protecting the environment and saving energy.
And because asphalt pavement regeneration technology can save a lot of asphalt and sand materials and save energy and protect the environment, greatly reduce the construction cost, is conducive to the disposal of waste.
Therefore, it has very significant economic benefits as well as social and environmental benefits.

1. Current situation of asphalt regeneration technology at home and abroad

In the last century the world's major countries attach great importance to asphalt regeneration technology, asphalt regeneration technology from materials to process technology and equipment has also been a vigorous development.
In the United States, due to the outbreak of the oil crisis in the early 1970s and the development and use of large-scale cold-gouging equipment in 1975, people paid attention to asphalt again.
Since then, asphalt regeneration technology has developed rapidly.
From 1980, more than 2 million tons of hot mix recycled asphalt mixture was laid in 25 states, and in 1985, it soared to 200 million tons, accounting for 50 percent of the total asphalt mixture.
And now it has become a very conventional technology.
However, in Europe, Germany and other countries, in the mid-1970s, all the wastes of the road surface were reused.
And the French highway sector is also vigorously promoting and using asphalt regeneration technology.
However, China began to build a large number of asphalt pavements in the 1990s, especially in the national highways and highways and some senior highways widely used asphalt pavements.
After nearly 20 years of use, these roads have generally entered the stage of major repair and maintenance, and minor repairs cannot meet the needs.
As the main raw material of asphalt pavement, the resource characteristics and material characteristics of asphalt are very prominent.
However, due to the worldwide shortage of petroleum, asphalt material has become a scarce resource, which is especially obvious in China, a country with a shortage of petroleum resources.
China's annual asphalt consumption reached a staggering 67 million tons, of which nearly 2 million tons were imported.
On the other hand, asphalt material in the construction and use of the process, the environment has a great impact on pollution.
In China, after 30 years of rapid development, the pressure to improve resources and environment is very urgent, and environment-friendly and resource-saving society is the next strategic direction of China's development.
Therefore, how to use asphalt reasonably becomes an important issue in the future development of asphalt pavement construction and maintenance.
In the 1980s, asphalt pavement regeneration technology was set up as a key scientific research project by the transportation department.
In 1982, tongji university organized and coordinated transportation departments of jiangxi, hubei, hebei, henan, shanxi, shandong and other provinces to carry out "research on asphalt (residual oil) pavement recycling", and built 600 km of recycled asphalt pavement accumulatively.
After entering 90 generations, asphalt pavement regeneration technology was aborted due to the rapid construction of high-grade highways.

Basic principles of asphalt pavement aging and regeneration technology

2.1 aging mechanism of asphalt pavement
Asphalt pavement under the action of water temperature and traffic load for a long time, asphalt binder embrittlement and aging lead to loose and cracked pavement, pitted surface and pits.
Due to the aging of old asphalt, oil content decreases, asphaltene and gum increase, aging is more obvious.
Its physical characteristics are as follows: the annual increase of reaction rheological properties, the enhancement of non-newtonian properties and the most obvious decrease in penetration and ductility, which lead to the increase in softening point.

2.2 on-site heating and regeneration technology
Field heating and regeneration technology can also be called skin regeneration technology. This technology USES heating equipment to heat the old pavement layer to the depth required by the construction and then breaks the old pavement. According to the aging degree of asphalt, regenerating agent is added to mix it, and then paving is completed.
According to the different construction, it can be divided into heating and loosening, remixing and relaying.
But the field heating regeneration has very obvious advantages, which can ensure the smooth construction of the road by lane, directly use the cost of materials generated, save the construction cost and protect the environment. Using the mixture layer of the old road asphalt and the new asphalt to connect can restore the flexibility of the road to prevent the diseases caused by the floating asphalt and avoid joint leakage.
Scarifying heating method is the use of heating equipment to the old asphalt pavement after heated to 120 ℃ to 150 ℃, using complex mixer and broken pavement and join the regenerant, make the new hybrid materials after stir to mix well in blender to the original road paving and rolling forming complete repair methods.
It is suitable for the road with light pavement damage, small area and no damage or cracks in the deep layer of the road surface.
After regeneration, pavement damage can be removed, friction degree can be improved and smoothness can be restored.
The mixed reproduction method is to heat the old road surface to the construction temperature, use the mixed machine to crush the old asphalt mixture material and the new asphalt mixture in the agitator to stir, and then spread the stirred mixture on the road surface to roll forming, complete the road surface repair.
Suitable for road surface damage tends to moderate road surface.
The re-paving and regeneration method is based on the construction of the heating and loosening regeneration method. The asphalt mixture after mixing is leveled as the lower layer, and the new asphalt mixture is used to lay the upper layer. Finally, a brand new road surface is formed by rolling.
It is suitable for repairing the seriously damaged road surface and upgrading and reconstruction engineering.

2.3 plant mixing heat regeneration technology
The technology of hot mix regeneration in the factory is to mill and planer the old asphalt pavement and then transport it back to the factory to produce the asphalt mixture in line with the requirements of the specification under the state of heating and stirring. Then the pavement is paved by the same method as the common asphalt pavement construction.
Before mixing in the factory, it is necessary to obtain the screening results after crushing, the content of asphalt in the old asphalt mixture, the degree of asphalt aging and other indicators.
According to the index, new aggregate and asphalt regeneration agent were added proportionally.
After the material is determined, it is mixed and stirred in the heating state to form a regenerative mixture.
The advantage of thermal regenerating technology of mixed plant is that it is easy to form a set of more perfect practical technology of regenerated asphalt mixture in each construction process.
It can effectively use the advantages of the original mixing and mixing building and experimental transportation equipment.
The application results show that as long as reasonable mix proportion design and strict quality control are carried out for the old materials, the thermal regenerated asphalt pavement can achieve the same pavement performance and durability as the ordinary asphalt pavement.

2.4 full-thickness regeneration technology
Full-thickness regeneration technology is a kind of technology that takes asphalt pavement surface layer and pre-determined thickness integrated material even including subgrade material milling and planing, mixing and stabilizing after crushing and then reserving as the base layer.
The cutting head of the full-thickness regeneration equipment usually runs through the asphalt pavement surface layer and goes deep into the subgrade of the underlying layer, with a depth of more than 30 cm. The crushed old materials are added with admixtures and become the new base material.
This technique was used in the early days for low-grade roads, such as gravel roads, dirt roads, and surface treated roads.
However, since these roads do not take into account the increase of traffic volume in the future, when the full-thickness regeneration treatment is adopted, the work of widening roads can also be carried out at the same time.
And because the technology is more flexible and can extend the life of the road surface, more and more road renovation will use full-thickness regeneration technology.
As long as the construction management is appropriate, but also can not affect the normal traffic, and because of the improvement of the basic material structure performance, stone debris sealing layer or surface treatment can be used directly, in order to save a lot of material and transport costs.

3. Economic advantages of asphalt pavement regeneration technology, environmental protection and traffic dredging

3.1 advantages of renewable technology for environmental protection

In today's more stringent requirements on the environment, asphalt pavement regeneration technology reflects its advantages.
On the one hand, there is no need to exploit a large number of resources such as sand, gravel, asphalt and other raw materials;
This can effectively protect the forest, natural landscape and so on.
On the other hand, a large amount of waste asphalt mixture can not be discharged outwards.
However, according to the investigation, the waste mixture is difficult to be degraded naturally due to its chemical inertia, which has a great impact on the surrounding environment and even threatens the health of nearby residents.

3.2 regeneration technology will not cause traffic jams
Asphalt pavement regeneration technology is only for the renovation of a single lane, and the renovation only needs to close the maintenance of the lane, the rest of the lane will not be affected, thus greatly reducing the impact of the renovation of the road to traffic,

especially for highways and other senior highways.

3.3 economy and economy of regeneration technology for construction
So - called economy saves reduce cost nothing more than "surplus value".
Regeneration technology promotes the recycling of old pavement materials and reduces the waste of resources.
In the past, traditional construction waste has to be transported away, and it takes too much construction economy to extract new resources and then mix them.
And the advent of regenerative technology almost perfectly solves the waste described above.
The total utilization of waste recycling and the reduction of shipping link have greatly saved the construction cost, and the surveyed recycling technology is nearly three times cheaper than the traditional maintenance of roads.

Application prospect of asphalt pavement regeneration technology

In the context of the whole society advocating "resource-saving and environment-friendly society", the traffic department, as an energy-consuming and resource-occupying one, has a more prominent sense of mission.
The problem of reuse of waste materials is becoming more and more serious in the maintenance of higher highways in China.
How to further develop the "surplus value".
The research and application of asphalt regeneration technology has become an important task for highway departments.
For the production enterprises, the research and use of asphalt regeneration technology has become a key link to ensure future economic benefits and the quality of engineering construction.

5 conclusion

According to the different conditions of road surface, the maintenance scheme can be selected according to the application conditions of various regeneration modes.
The regeneration technology of asphalt pavement can protect the environment to the greatest extent and the economic and social benefits can be immeasurable.
From the current situation of road technology development at home and abroad, asphalt pavement regeneration technology is bound to become an important and the most important maintenance and maintenance technology in the future.
Asphalt pavement regeneration