At present, the recycling technology of asphalt mixture mainly includes hot recycling and cold recycling, which have not been developed significantly due to their respective defects. Thermal regeneration has the disadvantages of high energy consumption, heavy pollution and low recovery; Cold regeneration has poor road performance for a long time, and is generally only used for the middle and lower layers.
In terms of energy consumption: traditional hot mix asphalt mixture>local geothermal recycling>plant mix cold recycling>local cold recycling.
The content of recycled materials in thermal regeneration is generally 10-30%. As the mixing is carried out under the heating state, the old asphalt mixture is fully integrated with the new aggregate and new asphalt in the mixing process, so the material performance of this mixture can reach or even exceed that of conventional asphalt concrete, and can repair the deformation, cracks and other defects of most road surfaces. However, compared with cold recycling, it will cause certain pollution to the surrounding environment. Asphalt mixing equipment is required for the production of asphalt mixture. Please click the marked link to learn more about it.
Several regeneration technologies are briefly introduced as follows:
Introduction: Recycled old asphalt pavement materials (RAP) shall be mixed with new materials by selecting appropriate mixing proportion, and some regenerants shall be added when necessary, and then new hot asphalt mixture shall be produced by intermittent or continuous plant mixing equipment. The equipment here refers to the reclaimed asphalt station.
Advantages: The plant mixed hot recycling process is easy to control, the mixture after recycling has good performance, guaranteed quality and wide application range.
Disadvantages: The old materials of asphalt pavement need to be transported back and forth, and the requirements for mixing equipment are high. At present, the amount of old materials is small, generally 20-30%.
Scope of application: The recycled asphalt mixture is applicable to the construction and maintenance of asphalt pavement of all classes of highways, and can be used for asphalt pavement and flexible base course.
2、 Asphalt pavement geothermal regeneration (surface course)
Brief introduction: The asphalt pavement shall be heated and softened by using special geothermal recycling equipment, then raked (or milled) to a certain depth, and a certain amount of new asphalt, recycling agent, new asphalt mixture, etc. shall be added to form a new hot mixed recycled asphalt mixture.
Advantages: local recycling is realized, material transfer cost is saved, and the utilization rate of raw pavement materials is high.
Disadvantages: the recycling depth is only 20-50mm, and it is difficult to control the construction quality. It is easy to produce unevenness, and its service performance is inferior to that of plant mixed hot recycled mixture.
Scope of application: The pavement has sufficient bearing capacity and only has shallow minor diseases. It is generally used for the maintenance of asphalt pavement surface of expressways and Class I and II highways.
3、 Plant mixed cold recycling of asphalt pavement (surface course material, base course material)
Introduction: mix old asphalt pavement materials with new aggregates, emulsified asphalt or foam asphalt binder, hydraulic active filler and water at normal temperature, and pave at normal temperature to form pavement structure layer.
Advantages: the plant mix cold regeneration process is easy to control, the mixture after regeneration has good performance, wide application range, low energy consumption, small pollution, and obvious emission reduction effect.
Disadvantages: It takes a long time to form the strength of the mixture, and a certain thickness of overlay is required.
Scope of application: recycling of asphalt pavement old materials of all classes of highways. The recycled asphalt pavement old materials are applicable to the middle and lower layers of asphalt pavement and flexible base course; The recycled materials of base course can be used as subbase or base course.
4、 In situ cold recycling of asphalt pavement (composite recycling of surface course, base course, surface course and base course)
Introduction: special cold recycling equipment is used for cold milling, crushing and screening of asphalt pavement on site. A certain amount of new aggregate, emulsified asphalt or foam asphalt binder, hydraulic active filler and water are mixed and paved at room temperature to form the pavement structure layer. According to different regeneration layers and thicknesses, on-site cold regeneration can be divided into on-site ground layer cold regeneration, on-site base layer cold regeneration, and full depth (surface layer and base layer composite material) cold regeneration.
Advantages: realize local recycling and save material transfer cost; Low energy consumption and pollution during construction; Wide application scope.
Disadvantages: the construction quality control is difficult; Generally, it is necessary to pave a thick pavement structure layer.
Scope of application: recycling of old asphalt pavement materials of all classes of highways. The recycled surface mixture is applicable to the middle and lower layers of asphalt pavement and flexible base course; Recycled base course or full depth recycled materials can be used as subbase or base course.
The selection of the above recycling technologies shall be comprehensively considered and selected according to the highway grade, pavement conditions, nature of maintenance works, traffic volume, construction environment, production capacity and other factors. Normally:
① Asphalt surface course materials and base course materials shall be recycled and reused separately;
② Asphalt pavement materials recovered from pavement overhaul works – plant mix recycling shall be given priority;
③ Recycled asphalt mixture for middle and lower layers – plant mix cold recycling is preferred;
④ Recycled asphalt mixture for upper layer – plant mixed hot recycling technology shall be selected;
⑤ Restoration project of pavement surface function – geothermal regeneration technology can be selected;
⑥ Recycling of base course materials – mainly choose the cold recycling technology of on-site or plant mixing.