Reflections on the recycling of construction waste?

What is the specific content of thinking about the recycling of construction waste? Here, Zhong Da Consulting will answer your questions.

The process of urbanization in China is striding forward, and at the same time, it is faced with four major problems of mutual restriction of land, resources, population and environment. Construction waste intensifies the shortage of land resources and seriously affects the coordinated development of social economy and ecological environment. It is urgent to strengthen the comprehensive utilization of construction waste. Therefore, the comprehensive utilization of construction waste must be considered as a major strategy. Construction waste management is an important part of urban management. Construction waste is produced in the process of building construction, maintenance and demolition, mainly solid waste, including abandoned concrete blocks, asphalt concrete blocks, mortar and concrete scattered during construction, brick residue, metal, bamboo and wood, waste generated from decoration, various packaging materials and other wastes. Recycling it as a building material is an effective means of recycling construction waste. 1 The types and distribution of construction waste mainly include: construction waste generated by demolition of old buildings in the process of old city reconstruction; Construction waste generated in the process of building construction. Table 1 lists the proportion of construction waste in construction sites with different structural forms and the amount of waste generated per unit construction area. From the table 1, we can see the components of construction waste and their respective proportions. For different construction sites, the proportion of garbage composition is slightly different. However, due to different construction management conditions, the amount of garbage varies greatly from place to place. The construction waste produced during the transformation of the old city of Hong Kong is mainly reinforced concrete, concrete and muck, accounting for 65% in total. The garbage generated in the construction is mainly muck, gravel and wood, accounting for 55% in total. During the period of 1998, the output of construction waste in Hong Kong SAR was about 32710t/d. In order to treat such a large amount of construction waste, Hong Kong adopted the following strategies: recycling inert parts (such as sand, bricks and concrete); Non-inert parts (such as bamboo, plastic, wood, paper, vegetables and other organic matter) are buried in landfills as waste. 2 Utilization of construction waste Construction waste is not garbage, but a renewable resource. The main components of construction waste are: soil, muck, waste steel bars, scrap iron wires and various waste fittings, waste metal pipes, waste bamboo and wood, sawdust, shavings, packing boxes of various decorative materials, scattered mortar and concrete, broken bricks and concrete blocks, yellow sand, stones and stones scattered during handling, etc. These materials account for about 80% of the total construction waste. The proportion of garbage in different construction sites is slightly different; The amount of garbage varies greatly with different levels of construction management. Many wastes in construction waste can be reused as renewable resources after sorting, elimination or crushing. For example, metals such as waste steel bars, waste wires, waste wires and various waste fittings can be re-processed into various specifications of steel after sorting, concentration and re-melting. Waste bamboo can be used to make artificial wood; Brick, stone, concrete and other wastes can be used instead of sand for masonry mortar, plastering mortar, concrete cushion and so on. , can also be used to make building blocks, paving bricks, decorative bricks and other building materials. Bricks and tiles can be reused after cleaning; After crushing, screening and cleaning, waste bricks, waste tiles and waste concrete can be used as recycled aggregate to prepare low-grade recycled aggregate concrete for foundation reinforcement, road engineering cushion, indoor floor cushion, non-load-bearing concrete hollow block, concrete hollow partition board or autoclaved fly ash brick. The earthquake disaster that occurred in Wenchuan, Sichuan on May 28th, 2008, affected an area of more than 65,438+10,000 square kilometers, and construction wastes piled up like mountains, which is the primary problem faced by the reconstruction work. If it is customary, it can only be transported to a certain place for stacking, occupying land and wasting resources. Whether these construction wastes can be recycled or not involves many aspects and needs the great attention of the government and relevant departments. The government should attach great importance to the comprehensive utilization of construction waste in disaster areas as an important task of developing circular economy. The construction waste in the disaster area is different from that in ordinary cities, which is characterized by large quantity and concentration. First, organize experts to investigate and formulate garbage classification treatment methods. It is necessary to learn from the advanced experience of foreign developed countries and combine with the actual situation in disaster areas, promote the comprehensive utilization of construction waste with high starting point, high standard and high efficiency, vigorously develop circular economy, and completely solve the problem of nowhere to pile up construction waste. 3 Comprehensive utilization of foreign construction waste After sorting, cleaning or crushing, most of the construction waste can be reused as renewable resources. Japan, the United States, Germany and other developed countries started early in these areas, and there are many experiences and treatment methods worth learning. (1) Japan In Japan, construction waste is regarded as a by-product of construction, and its re-development and utilization as a renewable resource is attached great importance. Its recycled materials are used as raw materials for building materials, road subgrade, fillers for expanding land reclamation, etc. 1977, the Japanese government formulated the Code for the Use of Recycled Aggregate and Recycled Concrete, and successively established recycling processing plants in various places to produce recycled cement and recycled aggregate. The largest factory can process and produce100 t/h ..1991year. The Japanese government has enacted the Law on the Promotion of Resource Reuse, which stipulates that construction wastes such as muck, concrete blocks, asphalt concrete blocks, wood and metals generated during construction must be sent to recycling facilities for treatment. Japan's leading policy for construction waste is: try not to discharge construction waste from the construction site; Construction waste should be reused as much as possible; If it is difficult to reuse, it should be properly handled. (2) The United States ① Comprehensive Utilization As early as 19 15, the United States studied and utilized the waste asphalt produced in road construction. According to relevant data, the United States produces 800 million tons of municipal waste every year, including 325 million tons of construction waste, accounting for 40% of the total municipal waste. After sorting, processing and transformation, about 70% of it is recycled, and the remaining 30% of the construction waste is buried (utilized) where it is needed. ② Classified treatment The comprehensive utilization of construction waste in the United States can be roughly divided into three levels: ① Low-level utilization, that is, on-site classified utilization and general backfilling. , accounting for 50% ~ 60% of the total construction waste; (2) Secondary utilization, that is, as the basic material of buildings or roads, it is processed into aggregates by treatment plants and then made into various building bricks, accounting for about 40% of the total construction waste. Large and medium-sized cities in the United States have established construction waste treatment plants to deal with construction waste in their own cities; (3) Advanced utilization, such as recycling construction waste into cement and asphalt (this proportion is not high). ③ Four modernizations management Four modernizations management is the reduction, recycling and harmlessness of construction waste, and it is the industrialization of comprehensive utilization of construction waste. The United States pays special attention to reduction. From standard and normative policies and regulations, from government control measures to enterprise self-discipline, from architectural design to on-site construction, from survival of the fittest to on-site use regulations, the generation of construction waste is restricted, and zero emission of construction waste is encouraged and rewarded. This source control method can reduce resource exploitation, reduce manufacturing and transportation costs, and reduce environmental damage, which is more effective than various end treatments. The United States also takes the treatment of construction waste as a new industry to cultivate, and deeply discusses how to make the treatment of construction waste form a new industry. According to statistics, the scale of renewable resources industry in developed countries was $250 billion at the end of 20th century, and it has increased to $600 billion at the beginning of this century, and it is estimated that it will reach $ 654.38+0.8 trillion in 2065.438+00. (4) Legal norms In the practice of nearly a century, the United States has formed a series of complete, comprehensive and effective management measures, policies and regulations on construction waste disposal. In terms of construction waste management policy, it has been developed for three generations. The first generation is the government-led command and control mode, which realizes pollution control through administrative means; The second generation is market-based economic stimulus, emphasizing the role of enterprises in reducing the source of construction waste; On the basis of further improving policies, the third generation realizes the combination of government advocacy and enterprise self-discipline, and improves the public's awareness and ability to participate. The U.S. government has enacted the Superfund Law, which stipulates that any enterprise that produces industrial waste must dispose of it properly by itself and shall not dump it at will without authorization. Therefore, the quantity of construction waste is limited from the source, and enterprises are urged to consciously seek ways to recycle construction waste. The American Association of Building Builders is promoting a resource-saving house. Its walls are made of recycled tires and aluminum alloy waste. Most of the steel used for roof truss is recovered from the construction site. The board used is made of sawdust and broken wood plus 20% polyethylene. The main raw materials of the roof are old newspapers and cartons. This kind of residence not only makes active use of scrap metal, wood and cardboard, but also solves the contradiction between housing shortage and environmental protection. In addition, CYCLEAN Company of the United States adopts microwave technology, which can recycle the old asphalt pavement fabric 1 0,000%, with the same quality as the new asphalt pavement fabric, while the cost can be reduced by13, and at the same time, the cost of garbage removal and treatment is saved, greatly reducing the environmental pollution of the city. The pretreated construction waste will be transported to the resource treatment center for centralized incineration. (3) France CSTB is a leading garbage and construction group in Europe, which specializes in coordinating the garbage and construction business in Europe. The overall plan of waste management put forward by the company has two major goals: first, to control the generation of site waste from the source by studying the environmental protection characteristics of newly designed building products; Second, in the construction, improvement and demolition projects, predict and evaluate the generation and collection of on-site waste to determine the relevant recycling application procedures, so as to improve the level of waste management. Based on a powerful database, the company uses software tools to analyze and control the whole process of construction waste from generation to treatment, thus helping decision-making at different stages of building service life. For example, it can evaluate the overall environmental protection of building products; According to the relevant implementation process, maintenance category and different types of building demolition, it can be evaluated to reduce the amount of waste generated by a product; Be able to provide consultants, general contractors and contractors (customers) with relevant overview information about the impact of a product or product series on environmental protection and health; Be able to predict the procedures and materials needed for waste management; Transportation scheme can be made according to the final use or quality of waste; Evaluate the technical, economic and environmental feasibility of any new process using recycled raw materials, and evaluate the performance of products.

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