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Recycling of abandoned concrete and waste asphalt in road construction

Recycling of Abandoned Concrete and Waste Asphalt in Road Construction

Yanmei YANG

School of River and Ocean Engineering ,Chongqing JiaotongUniversity,Chongqing, P.R. China

Email:cqyymei @http://www.nasyfru.cn/doc/797bdbb02af90242a995e516.html

Abstract—The present recycling situation of waste concrete and waste asphalt mixture was analyzed in the paper. It was obtained that a large number of them was not recycled in China. Recycling methods of waste concrete and waste asphalt mixture were studied and performance of recycled material was analyzed. Several pieces of advice were given to better recyle waste concrete and waste asphalt mixture.

Keywords- solid waste, recycling treatment, road construction

I.I NTRODUCTION

With the acceleration of urbanization process, the construction and transportation industries have experienced rapid development in China. Meanwhile, the output of construction waste and road maintenance waste have increased day by day. Abandoned concrete tops the wastes in construction industry. The amount of annual abandoned concrete is 20 million t merely in Shanghai and more than 100 million t in the whole nation. Asphalt pavement, the main type of road surface, varies slightly from country to country. Under normal circumstances, Asphalt road surface makes up about 70% to 80% of road pavement. Generally speaking, asphalt pavement design life is 15 years, and usually it needs repairing in large scale each ten years. Large-area maintenance and milling will produce a great deal waste asphalt mixture. Bitumen, a type of hydrocarbon polymer, is extracted from petroleum. Its degradation time is much longer than that of the white trash, and during the process it will produce benzene, phenol and other substances. In the past, measures like landfills were employed to deal with concrete and asphalt, which will occupy land and lead to threat to the surrounding environment as well as a waste of resources. Moreover, mining, accompanied by the destruction of vegetation will have a negative effect on the environment. Therefore, the necessicity of the waste concrete and asphalt recycling will be discussed in this paper.

II.S TATUS OF A BANDONED C ONCRETE AND W ASTE

A SPHALT R ECYCLING

A.Status of Abandoned Concrete Recycling

The afresh utilization rate of the abandoned concrete and other construction waste has reached 56% in Tokyo in 1988; In 1996 the Kobe earthquake led to many damages of high-ways and bridges, collapse of buildings and 1,500 t waste concrete, which was used in post-earthquake reconstruction. According to the statistics of Ministry of Construction, the abandoned concrete recycling rate reached 65% in Japan in. 1995, and 96% in 2000. "Li Fu Mu System", a decoration company in South Korea can separate cement from stone and steel in abandoned concrete and produce recycled concrete by heat treatment of cement under the high temperature about 700o C with adding special material.

An urban construction (group) in Beijing has saved 3.5 million Yuan during the process of building 9-million-m2 area with different structure types of multi-layer and high-rise building by recycling various construction waste about 840 t. The construction waste was used in bonding mortar, interior wall and ceiling plastering, fine stone concrete floors, and concrete cushion with the total area of more than 30,000 m2 and it helped save more than 35,000 Yuan. Abandoned concrete was employed to pave a "recycled road" in July 2003 in Tongji University. In July 1990 in Shanghai, in the projects named "Hua Ting" and "Holland" (total floor area of 137m2 with the wall or frame structure)in the center of Shanghai, construction waste was recycled by the Second Construction Company.

B.Status of Waste Asphalt Recycling

In 1980, 395 million dollars was saved by using old road surface material about 5000 × l04t in the United States. In the late 1980s, dosage of regenerative asphalt mixture accounted for almost half of asphalt mixture for all way-used in America. Great achievements were made in areas such as regenerating development, regeneration mixture design, construction equipment etc., and published “Asphalt Pavement Hot Mix Regenerated Technology Handbook”, “The Pavement Waste Regeneration Guide”, “The Asphalt Pavement Cold Mix Regenerated Technology Handbook Technological Data” and so on were published one after another. In September 2000, "Hot Mix Asphalt Mixture Regeneration Utilization Status" (Recycling Practices for HMA), with its main contents of recycling of waste asphalt and waste recycling in road works was published by American Asphalt Road Association (NAPA). In 2000, 80% waste asphalt mixture was regenerated and utilized, which was the first among various types of waste recycling. 92% of highways and general roads in the United States was made of asphalt pavement. Recycled asphalt mixture (RAP) is widely used in new pavement, subgrade, shoulders, and high fill embankment. According to the research by Federal Highway Administration(FHA), recycled asphalt mixture can reduce by 53.4? in materials cost, 25% in pavement cost and 50% in asphalt. Japan, a country short of

Supported by Hydro-Science and Engineering of Chongqing Jiaotong University ,the Key Laboratory Foundation Project of Ministry of Education (SLK2007B05)

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