In the reconstruction of old asphalt pavement, there are two traditional construction methods: one is to directly cover the surface, and the other is to strip the damaged surface layer. Although the direct covering method is low in cost, simple in construction, and non-polluting, the pavement will inevitably be raised with the increase of the number of covering layers, affecting the surrounding environment. At present, the method of stripping the worn surface layer is generally adopted, but the waste generated by this method is not only difficult to dispose of, pollutes the environment, but also is a great waste of asphalt and stone resources. The Road cold recycler technology of old asphalt pavement developed in the 1970s is exactly to solve this problem. It has attracted much attention because of the advantages of saving materials, reducing cost and reducing environmental pollution.
According to the research results of the National Western Project (200431800002) undertaken by us, the reuse of asphalt pavement can significantly reduce the cost of the project, compared with the laying of brand-new asphalt pavements. Among them, hot-mixed recycled asphalt pavement can reduce the cost by 20-30%, and cold-recycled asphalt mixed with plant The pavement can reduce the cost by about 40%, and the in-situ thermally recycled asphalt pavement can reduce the cost by nearly half. Therefore, the recycling of asphalt pavement should become a strategic means for sustainable development of China's highway construction and protection of the ecological environment.
The development of asphalt recycling technology in China is relatively slow
Judging from the research and development status of asphalt pavement recycling technology in developed countries such as Europe and the United States (China Recycled Asphalt Network), these countries pay special attention to the research on the practicality of recycling technology. They have made great achievements in the development of regenerants and the development of various excavation, milling, crushing and other mechanical equipment in practical engineering applications. They have gradually formed a relatively complete set of practical regeneration technologies, which have achieved standardized and standardized degree. Foreign researchers have accumulated a wealth of data on the regeneration effect of regenerants and the pavement performance of recycled asphalt mixtures, laying a foundation for the promotion of asphalt pavement regeneration technology.
China's research on the recycling of asphalt pavement materials is relatively late. In the early days, waste asphalt was used to repair roads, and it is generally only used for light traffic roads, sidewalks or road cushions. In 1983, the Ministry of Construction issued a research project on "Recycling of Asphalt Mixtures", led by the Shanghai Municipal Engineering Research Institute and organizing relevant units to conduct special research. The main attack at that time was to soften the residue pavement with appropriate light oil instead of the conventional asphalt mixture. The "CJJ43-91 Code for Construction and Acceptance of Hot-Mixed Recycled Asphalt Pavement" issued in June 1991, puts forward the technical requirements for the minerals, asphalt quality and mixtures used in recycled asphalt mixtures. These requirements are mainly for medium and light traffic the way. The description of the original pavement performance evaluation, the choice of regenerant, and the construction technology are less, and it can not guide the construction well.
Energy saving and environmental protection of renewable technology is of great significance
China began large-scale highway construction in the mid-to-late 1980s. Due to the lack of manpower and material resources, and the insufficient attention to asphalt recycling technology at that time, this research in China was basically at a standstill. In recent years, China's highway construction has developed rapidly. Expressways built after the 1990s have entered major and intermediate repairs. A large number of digging and milling asphalt mixtures have been abandoned, causing environmental pollution on the one hand, and China, a country with extremely poor quality asphalt, is a waste of resources. A large amount of stone mining will cause serious ecological environment damage such as forest vegetation destruction and soil erosion. According to the design life of the asphalt pavement (15 to 20 years), from now on, about 12% of the asphalt pavement will need to be renovated every year, and the amount of old asphalt waste will reach 2.2 million tons per year. If it can be used, it can save each year Material cost is about 400 million yuan. After 10 years, the old asphalt mixture produced by large and medium repair of asphalt pavement will reach 10 million tons. By then, the annual material cost can be saved by 1.6 billion yuan through recycling. Therefore, the research on asphalt pavement regeneration technology is of great significance for protecting the ecological environment and for China's highway construction.
The problems and suggestions urgently to be solved in the promotion and application of asphalt pavement regeneration technology are as follows:
(1) Design and construction specifications and acceptance assessment standards
In view of the significant economic and social and environmental benefits of asphalt pavement regeneration, it should be widely used. At the same time, with the increase of high-grade asphalt pavements in China, more old pavement regeneration problems will be faced in the future. Therefore, on the basis of existing research results, the technology can be organized and processed in a comprehensive and systematic manner, and the necessary tests and verifications must be performed to make the technology standardized and standardized to guide the nation's road maintenance. Engineering construction projects are an important task before us.
(2) Standardization and serialization of regenerant
Foreign regenerants are provided by the chemical industry research, and China's petroleum sector has not yet taken care of it. Because most asphalt pavement structures in China's highways have been thin in the past, they are generally not reused, so the total demand for regenerants is small. However, with the development of China's highway construction, the future use of asphalt pavement as a daily application technology for highways will greatly increase the demand for regenerants. To this end, the source and variety of regenerants will be expanded to meet specifications Chemical and serialization will be the joint research topics of the petrochemical sector and the highway sector.
(3) Detection of regeneration effect of old asphalt
Under the hot state, the old asphalt is in a molten state and can be blended with the liquid new asphalt. However, this is only a theoretical guess. It is impossible to know how the actual cross-mixing situation is. Although the physical and mechanical performance test of the recycled mixture can indirectly analyze the advantages and disadvantages of the regeneration effect, it is still not an intuitive detection method. For this reason, it is necessary to study convenient and fast detection methods.
(4) Regeneration machinery
Paving recycled asphalt pavements has many procedures and complicated processes, which not only requires increased labor but is also quite troublesome, which makes some people discourage them. Therefore, how to improve the level of construction mechanization and reduce manual labor is the key to the large-scale promotion of asphalt pavement regeneration technology. Large-scale paving of recycled asphalt pavement urgently requires pavement turning machinery, old material crushing, screening machinery, and mixing machinery. There should be both large machinery suitable for centralized plant mixing and various small machines suitable for use by road maintenance departments. It is imperative to actively organize forces, formulate plans, and effectively grasp the development and production of various regeneration machinery.
Adopting bitumen recycling technology can make full use of the old materials. By selecting the appropriate mix ratio and the blending ratio of the new and old materials, you can get a very good quality recycled mixture. Preliminary research and practice have shown that this recycled mixture can be used in the asphalt surface layer of high-grade highways. At the same time, considerable economic and social benefits can be achieved by using asphalt regeneration technology.
(5) Study on asphalt additive characteristics and road performance of its mixture
In view of the many diseases that occur during the use of asphalt pavements, road mixer experts have conducted a lot of research and pointed out that the addition of asphalt additives can significantly improve the performance of asphalt pavements; in addition to commonly used resin, rubber and copolymer asphalt In addition to modifiers, new types of additives have appeared internationally in recent years.