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Asphalt pavement regeneration - emerging industry in highway construction

Asphalt Pavement Regeneration - emerging industry in highway construction

China Construction machinery information

Introduction: an interview with Chen Qizong, Secretary General of the pavement and compaction machinery branch of China Society of construction machinery, at an international road technology exchange conference several years ago, A British expert once expressed such feelings when talking about the development of roads in his country: the huge roads formed in Britain for more than ten years, but due to improper maintenance

-- Interview with chenqizong, Secretary General of the pavement and compaction machinery branch of the Chinese society of construction machinery

several years ago, a British expert expressed this feeling when talking about the development of his country's roads at an international road technology exchange conference: "the huge roads formed in Britain for more than a decade, but due to improper maintenance, we have to pay a greater price than when they were built to restore their functions"

at present, China's highway construction is developing rapidly, and the annual investment scale has exceeded 200billion yuan. By the end of 2003, the first-class highway has reached 29900 kilometers, the second-class highway and above has reached 271600 kilometers, and the expressway is about 29700 kilometers, of which more than 90% of the pavement is asphalt pavement. The expressways built successively after the 1990s have entered the period of large-scale and medium-sized maintenance. According to the design life of asphalt is 15-20 years, in the future, 12% of the asphalt pavement will need to be renovated every year, and the waste of old asphalt will reach 2.2 million tons per year

the above data clearly shows that China's highways have entered a period of equal emphasis on construction and maintenance, and asphalt pavement regeneration should be paid enough attention to, otherwise when we repeat the mistakes and think of the lessons of Britain, we will regret. Fortunately, there are now a group of far-sighted experts in China who have made a lot of technical explorations and attempts on asphalt pavement regeneration with their strong sense, and Chen Qizong is one of them

learn from others' strengths and use them for me

Chen Gong first introduced the development process of recycling asphalt pavement abroad

foreign research on asphalt pavement recycling began in the United States in 1915. The asphalt pavement regeneration technology is the combination of these structures, which is being paid attention to and widely studied and applied all over the world, but after the outbreak of the oil crisis in 1973. At the end of the 1980s, the amount of recycled asphalt mixture in the United States was almost half of all asphalt mixtures, and the research on the development of regenerative agent, the design of recycled mixture, construction technology and recycling equipment was also increasingly in-depth. Recycling of asphalt pavement has been a routine practice in the United States, and its recycling rate has reached 80%

Western European countries also attach great importance to this technology. The Federal Republic of Germany is one of the first countries to apply recycled materials to highways. In 1978, Germany used all recycled asphalt pavement materials. Almost all towns in Finland organize the collection and storage of old pavement materials. France is now also promoting the application of this site micro vibration measurement technical specification CECS 74:95 technology in the pavement repair works of highways and some heavy traffic roads

Chen Qizong then introduced the research situation in China in detail. China began to study the recycling technology of asphalt mixture in the 1970s; In 1982, the science and Technology Bureau of the Ministry of communications assigned the recycling of asphalt pavement as a key scientific and technological project, and Tongji University was responsible for the coordination of this research. Shanxi, Hubei, Henan, Hebei and other provinces and cities participated in the systematic experimental research on the recycling technology of Asphalt Pavement; In 1985, the Ministry of Construction organized municipal departments in Shanghai, Nanjing, Tianjin, Wuhan, Suzhou Highway Bureau, Harbin Institute of architecture and engineering and other units to conduct special research, In June, 1991, the code for construction and acceptance of hot mix recycled asphalt pavement (cjj43--91) was issued It is pointed out that the quality of mineral aggregate and asphalt used in recycled asphalt mixture and the technical requirements of mixture should meet the relevant provisions of ordinary asphalt mixture without waste. However, due to the lack of supporting projects, especially the lack of asphalt recycling equipment for actual construction, cjj43--91 specification cannot be popularized

In the 1990s, the research and promotion of asphalt pavement recycling technology were almost shelved. Newly issued technical specification for highway asphalt pavement maintenance (jtj073.) Because of the old technology and the lack of advanced recycling equipment, the provisions on recycled asphalt mixture do not jump out of the limitations of cjj43-91 specification

in the 21st century, Beijing, Tianjin, Shanghai, Guangdong, Shandong, Jiangsu, Hebei and other provinces and cities have successively introduced large-scale asphalt pavement recycling equipment

in 2001, North China expressway company took the lead in implementing asphalt recycling maintenance on Beijing Tianjin Tangshan Expressway and Beijing urban roads. In 2002, Pudong construction was put on trial in Shanghai; In 2003, the on-site thermal recycling technology of asphalt pavement was adopted in the large and medium-sized maintenance project of Shanghai section of Shanghai Nanjing Expressway, and the utilization rate of old materials in the repaired section reached 100%; From 2003 to April 2004, Guangdong guanyue road and Bridge Co., Ltd. introduced the regeneration equipment of astec from the United States and applied it to the overhaul project of the 14km section of Guangzhou Foshan expressway, and achieved very good results

nevertheless, Chen Qizong believes that the research and application of asphalt pavement recycling technology and recycling machinery in China are still lagging behind. During the interview, he used the "enlightenment stage" to describe the current situation of recycling technology, which is not too much. So what is the reason? Chen Qizong believes that the most important thing is the problem of ideology. One of the two extreme situations caused by this is conservatism. Although asphalt recycling has been widely used abroad, it is a new technology in China. Is the quality up to standard? In case of problems, who will bear it? Another attitude is not to do in-depth investigation and research, not to consider whether it is in line with the current situation of serious damage to the pavement structural layer of Expressway in China, not to consider the project cost, and to promote some foreign technologies on a large scale without analysis, only to feel good on the surface of the regenerated pavement, regardless of the regeneration quality of this technology. Chen Qizong said with emotion: when can we take the recycling of roads as a conscious behavior

the right choice is to prescribe the right medicine.

due to the project experience of Guangzhou Foshan expressway, Chen Gong has accumulated a wealth of practical experience. He said that the application of asphalt recycling technology and process should be determined in combination with the pavement damage. He divided recycling into five situations

1. Repair the potholes with a small thermal regenerator; 2. Geothermal regeneration can be used to repair shallow ruts and various cracks on the pavement, so that the surface function of the pavement can be restored. 3. The on-site cold recycling technology can be used to repair the Subgrade after the asphalt layer is "covered and mixed" and "stabilized"; 4. In the "milling Overlay" of special maintenance works, the milled old material can be recycled through plant mixing and hot recycling, and can be paved to the middle and lower layers of the original road or other projects; 5. Plant mixed cold recycling is used for the subbase or base course. In combination with the actual situation of domestic pavement, Chen Gong believes that if the pavement is guaranteed to be repaired restoratively rather than preventive maintenance, plant hot recycling is the only feasible force and method to ensure the quality in China. As for which asphalt recycling and mixing equipment is selected, Chen Gong has his own unique views: "At present, the recycling mixing equipment is divided into three key points: intermittent recycling equipment, single drum recycling equipment and double drum recycling equipment. For the asphalt recycling mixing equipment, the most important standard to measure its advantages and disadvantages, in addition to the strict requirements for the measurement of aggregate, mineral powder and asphalt to ensure the accuracy of grading and oil stone ratio, we should especially solve the pre heating and remelting method of old asphalt mixture and the measurement method of old asphalt mixture Problems. "

he introduced in detail the application process of intermittent regeneration equipment, single drum regeneration equipment and double drum regeneration equipment respectively. Chen Gong believed that among the three, the double drum regeneration mixing equipment made the regeneration of asphalt the most sufficient, even though many domestic experts were worried that the continuous mixing equipment lacked a "secondary screening" device, It has also been successfully solved in the project of asphalt pavement plant mix hot recycling technology approved by Guangdong Communications Group. Chen Qizong answered, "it's very simple. The continuous mixing equipment is equipped with a 'secondary screening' device. Using this' cold aggregate pre screening 'technology, the continuous asphalt mixing equipment has achieved a very satisfactory degree of control over the grading of finished materials and the asphalt aggregate ratio of finished materials, which has been confirmed in the successful practice of the overhaul project of Guangzhou Foshan expressway."

unlimited business opportunities favor interested people

in addition to the process, the main raw materials of asphalt pavement are asphalt and stone

the main raw materials of asphalt pavement are asphalt and stone. Most of the crude oil in China is paraffin based crude oil, which is difficult to produce high-quality road asphalt, resulting in the shortage of high-grade road asphalt in China, and the proportion of imported asphalt in the use of asphalt has reached more than 20%. The exploitation of stone materials has seriously damaged the ecological environment and caused great attention and restrictions from the government, resulting in a shortage of stone resources for paving in recent years, a sharp rise in prices, and asphalt pavement materials have become scarce resources. Therefore, the recycling technology of asphalt pavement has a wide application space

According to Chen Gong, some domestic research institutions are actively developing new materials and equipment, such as the development of regenerants

among the equipment, Chen Gong specifically mentioned the asphalt pavement comprehensive maintenance vehicle that is most frequently used in highway maintenance to repair potholes. At present, the most commonly used comprehensive maintenance vehicle in China (which can heat and mix new and old asphalt mixtures on site) can deal with old asphalt mixtures, but its configuration is too simple. He believes that the new comprehensive maintenance vehicle developed does not have to add many new functions to it, but to make it a small on-site asphalt recycling mixing equipment that can really mix recycled asphalt mixture. It shall at least include: isolated old asphalt mixture heating mixer, new aggregate (with more than two gradations) and new asphalt metering device. If it can be reasonably designed and carefully made, it will be a small on-site asphalt pavement recycling and maintenance equipment with moderate price, small size and good quality

I believe that many interested people have paid attention to asphalt recycling, an emerging industry integrating social and economic benefits, and the development of new products is quietly going on. Chen Gong predicted that the application of new materials and asphalt recycling technology and equipment will greatly reduce the cost of road maintenance. Those enterprises with rich experience and brand advantages in asphalt material research and development, paving and other aspects will stand out. We look forward to it

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