At present, asphalt pavement has become the main form of road in our country because of its good driving safety and comfort. However, after a certain number of years of use, asphalt pavement is easily affected by traffic stress, temperature stress, etc., resulting in asphalt aging and structural layer damage, thereby reducing its road performance. Therefore, the asphalt pavement must be regularly maintained and transformed, and a large amount of waste asphalt mixture produced during the transformation process is usually disposed of, which will not only occupy a large amount of land, but also cause pollution to the environment. Moreover, the cost of re-paving with new asphalt mixture is too high. At the same time, waste mixture is discarded as a renewable material resource, which also causes a huge waste of resources. Therefore, the recycling technology of waste asphalt mixture has become a major issue in the world today. Asphalt mixture regeneration technology is to use the old asphalt pavement that needs to be repaired or discarded, after excavation, recycling, crushing, screening, and then mix it with some new aggregates and new asphalt to obtain the regeneration that meets the road performance requirements.

1. Asphalt recycling method

There are four main categories of classification methods for asphalt mixture recycling technology, namely plant-mixed hot recycling, in-situ hot recycling, in-situ cold recycling, and factory-mixed cold recycling.

1.1 Plant-mixed heat regeneration technology

Plant mixing hot recycling technology is to transport the waste asphalt mixture to the asphalt mixing plant, crush and screen, and mix a certain proportion of new Asphalt materials, regenerant (if necessary), and new aggregates are mixed and stirred in a hot state to form an asphalt mixture that meets the requirements, and then paved in exactly the same way as ordinary asphalt pavement. Factory-mixed hot-recycled asphalt mixture is suitable for urban expressways, main roads, expressways and first-class highways, middle and lower layers of newly built and reconstructed asphalt pavements, that is, hot-mix medium-grain and coarse-grain asphalt mixtures; Hot-mixed fine-grained, medium-grained and coarse-grained asphalt mixtures for urban sub-trunk roads and their lower grades, first-class highways and their lower grades, hot-mixed fine-grained, medium-grained and coarse-grained asphalt mixtures for the upper layer, middle layer and lower layer of new and reconstructed asphalt pavements . According to foreign experience and laboratory test research results, as long as the appropriate mix design and strict quality control measures are adopted, the factory-mixed hot recycled asphalt pavement has the same road performance and durability as ordinary asphalt pavement.

1.2 Hot-in-place regeneration technology

The hot-in-place regeneration technology is a construction method that uses equipment to heat the old pavement surface to the required depth on site, loosen the old pavement, add reducing or regenerating agents, and re-pave the shape. Due to the addition of a large amount of reducing or regenerating agents, its road performance and durability are affected to a certain extent, and its scope of application is not as wide as that of plant-mixed hot regeneration. The in-situ regeneration unit mainly includes a heating system, a road raking system, a regeneration mixing system, a paving system, and a compaction system. In the early 1990s, the technology was considered a revolution in the road industry. However, later practice proved that on-site thermal regeneration also has many limitations, and it is not suitable for expressway pavement regeneration. Treatment of the surface layer paved with modified asphalt, large initial investment in equipment, etc.

1.3 Plant-mixed cold recycling technology

Factory-mixed cold recycling technology is a construction method in which emulsified asphalt or hot low-viscosity asphalt is mixed with waste asphalt mixture materials at room temperature and new aggregates to form a recycled mixture, which is transported to the construction site and paved and compacted to form a pavement. The factory-mixed cold recycled mixture is mainly used as the base or sub-base. This process first mills the asphalt pavement material, transports it back to the mixing plant, and crushes it as a stabilized aggregate, adding cement or lime, fly ash, emulsified asphalt and other stabilizers Mix with new material (if necessary), then spread on the base or sub-base. The technology makes little use of old bitumen from waste materials, but its production requires little special equipment. For old materials that cannot be regenerated by heat (such as modified asphalt mixtures, mixtures that are seriously aged and difficult to regenerate), it can effectively solve the problems of waste of old materials and environmental pollution. It is widely used in foreign countries, and practice has proved to have a very important application value.

1.4 In-situ cold recycling technology

In-situ cold recycling technology is a construction method of cold crushing and loosening of the road surface, adding emulsified asphalt and other admixtures, mixing, paving, and compacting to form the road surface. There are two main ways of in-situ cold regeneration: one way is to use a special recycling machine to mill, crush, add new materials (including emulsified asphalt or other regeneration agents, stabilizers and aggregates, if necessary) to mix and pave and preloading, and then further compacted by a road roller. This kind of regenerated pavement is mainly used for low-grade pavement and high-grade pavement base. Another way is to spread the regenerant seal layer on the old pavement, and the regenerant can penetrate 5~6mm , Activate the activity of oxidized asphalt on the surface, and form a seal layer, prolonging the service life of the pavement for 2 to 3 years. This regeneration method actually belongs to the category of preventive maintenance, and its scope of application is narrow.

2. Application range of recycled asphalt mixture

Cold-mixed recycled asphalt mixture can be used for asphalt pavement maintenance and pothole repair of roads below low-grade and fourth-grade roads, and cold-mixed recycled asphalt mixture can also be used for the base layer of road asphalt pavement at all levels. Although the cost of cold recycled asphalt mixture is low, it is limited by many factors; the service life of the asphalt pavement repaired by hot recycled asphalt mixture is longer, the road surface is smoother, and has the same road performance as ordinary asphalt pavement and durability. Therefore, the application of factory-mixed hot recycled asphalt mixture is more extensive.

The application of asphalt mixture regeneration technology can effectively utilize the resource of waste asphalt mixture, which not only protects the environment, reduces waste of resources, but also reduces the cost of pavement repair. This should also be in line with the concept of "energy saving, emission reduction, low carbon and environmental protection" type of building, which has good social and economic benefits.