In daily study and work, when it comes to papers, everyone is certainly familiar with them. Thesis is a means to discuss problems and conduct academic research. What papers have you seen? The following are the papers I collected for you about the performance characteristics and application engineering of recycled concrete, hoping to help you.

On the performance characteristics and application of recycled concrete;

Both the construction of new building projects and the demolition of old building projects will produce a large amount of construction waste, which not only causes environmental pollution, but also wastes a lot of resources. How to deal with the increasing construction waste and reduce environmental pollution has become an important problem that all countries must face. By analyzing the physical, mechanical, durability, shear resistance and seismic performance of recycled concrete, the application prospect of recycled concrete is discussed.

Keywords: recycled concrete; Performance indicators; Construction waste; Application prospect

introduce

At present, China is in a period of large-scale construction. The rapid development of civil buildings has driven the national economy, and it has also become the industry that consumes the most resources and produces the most garbage. In order to effectively reduce the pollution and damage to the environment, reduce the amount of waste concrete and achieve sustainable and coordinated development, the only way to solve this problem is recycling, so some technologies and research related to recycled concrete have also developed rapidly.

Recycled aggregate or recycled concrete aggregate [1-2] refers to the aggregate formed by crushing, grading and mixing waste concrete blocks according to a certain gradation. The concrete prepared with recycled aggregate as part or all of the aggregate is called recycled aggregate concrete, which is an important part of the recycling of building materials, coordinated with the development of ecological environment and in line with the national sustainable development strategy. This paper mainly discusses the basic properties of recycled concrete.

1, Research Status of Recycled Concrete

1. 1 Research status abroad The research on recycled concrete in foreign countries is relatively early, which can be traced back to World War II. Years of war have destroyed a lot of buildings and produced a lot of garbage, so many countries in Europe are faced with the problem of how to deal with garbage to varying degrees [2]. In 1950s, in order to deal with a large number of waste concrete and provide new raw materials for urban reconstruction, the Soviet Union and Germany successively carried out research work on recycled concrete technology. 1977, the Japanese government formulated JIS TR A 0006 "Specification for Use of Recycled Aggregate and Recycled Concrete"; 199 1 year, the Japanese government enacted the Law on the Promotion of Resource Reuse, which stipulated that construction wastes such as muck, concrete blocks, asphalt concrete blocks, wood and metals generated during construction must be sent to "renewable resource facilities" for treatment.

For the reuse of waste, the U.S. government has also enacted the Super Fund Law, which stipulates that "any enterprise that produces industrial waste must dispose of it properly by itself and shall not dump it at will." This provision provides an operational basis and legal guarantee for the development of recycled concrete.

1.2 domestic research status

The research on recycled concrete in China started late and is still in the laboratory research stage. However, the government attaches great importance to the research of recycled concrete, and has invested a lot of money and achieved some results. Tongji University has carried out a lot of research work on recycled concrete technology [2-3]. Including the strength and working performance of recycled concrete, the research of broken recycling technology of waste concrete, the durability of recycled concrete, the experimental research of recycled concrete beams and columns, the experimental research of recycled concrete frame joints and the seismic performance of recycled concrete frame structures. In 2007, Tongji University compiled the local standard Technical Specification for the Application of Recycled Concrete (DG/TJ 08-20 18-2007), which provided technical guidance for the application of recycled concrete.

In addition, China Academy of Sciences, Southeast University, Zhejiang University and Beijing University of Technology and other related scientific research units have also carried out a lot of research work on recycled concrete and developed related recycled concrete technologies.

2. Performance characteristics of recycled concrete

2. 1 physical and mechanical properties Chen Liang of Southeast University, etc. The latest progress in the development and research of recycled aggregate concrete technology is summarized and compared [3]. The analysis results show that the failure process and failure mode of recycled aggregate concrete are basically the same as that of ordinary concrete. Judging from the failure form, the failure of recycled concrete basically begins with the bond failure between coarse aggregate and cement gel surface. The development law of long-term compressive strength of recycled concrete is different from that of ordinary concrete. The analysis also points out that the compressive strength, tensile strength, compressive elastic modulus and tensile elastic modulus of recycled concrete are reduced by 9%, 7%, 28% and 34% respectively, which indicates that the brittleness of recycled concrete is reduced. Toughness increases. However, the ultimate tensile strain of recycled concrete with waste concrete as aggregate increased by 28%, the tensile modulus decreased by 34%, and the compressive strength ratio increased, indicating that the crack resistance of recycled concrete is better.

Through a series of tests, Luo of Wuhan Institute of Geotechnical Mechanics of Chinese Academy of Sciences analyzed the influence of different replacement rates of recycled concrete on static mechanical properties, and studied the variation law of acoustic wave propagation characteristic parameters of recycled concrete with axial compression deformation of recycled concrete [4]. It is pointed out that with the increase of replacement rate of recycled concrete, the peak stress of recycled concrete decreases. The elastic modulus and deformation modulus of recycled concrete are also decreasing. The analysis also shows that with the deformation of recycled concrete under axial compression, the sound wave propagation speed of recycled concrete first increases and then decreases, and the amplitude of ultrasonic wave in recycled concrete first increases and then decreases during axial compression.

Xiao Jianzhuang of Tongji University analyzed the influence of recycled coarse aggregate replacement rate on the stress-strain curve shape, compressive strength, elastic modulus, peak value and ultimate strain of recycled concrete through the uniaxial compression stress-strain curve test of recycled concrete with different replacement rates of recycled coarse aggregate [5]. The research shows that the overall shape of the stress-strain curve of recycled concrete is similar to that of ordinary concrete, but the stress and strain values of each characteristic point on the curve are different. The ratio of prism compressive strength to cube compressive strength of recycled concrete is higher than that of ordinary cement soil. The peak strain of recycled concrete is greater than that of ordinary concrete; The elastic modulus of recycled concrete is obviously lower than that of ordinary concrete, and it is pointed out that the rising and falling sections of the stress-strain curve of recycled concrete can be fitted by cubic polynomial and rational fraction respectively.

Xu Yidong of Zhejiang University successfully prepared C40—C60 high-performance recycled concrete with high-quality mineral admixture and superplasticizer, and made uniaxial compression test on high-performance recycled concrete with electro-hydraulic servo pressure testing machine, measured its stress-strain curve and made theoretical analysis, and summarized the mathematical expression of the full stress-strain curve of recycled concrete under uniaxial compression, which was in good agreement with the test results [6-7].

Etxeberria of Catalonia University of Technology, Spain designed four different replacement rates of coarse aggregate of recycled concrete, obtained the same compressive strength through the ratio of four kinds of concrete, and analyzed the mechanical properties of recycled concrete [8]. In the test, recycled aggregate is in the state of water absorption, but it is not saturated. In order to control the performance, effective water-cement ratio and low strength deviation of fresh concrete, the research results show that the necessity of producing recycled concrete with medium and low compressive strength aggregates has been proved to be attributed to the cement dosage, and the relatively low elastic modulus of recycled concrete has been measured, which verifies the effectiveness of the mathematical model put forward by many scholars.

Noun (abbreviation of Noun) Fonseca of Lisbon University of Technology in Portugal analyzed the physical and mechanical properties of recycled concrete under different curing conditions, and analyzed the compressive strength, splitting strength, elastic modulus and wear value of recycled concrete. The analysis results show that the curing conditions affecting the physical and mechanical properties of recycled concrete are basically the same as those of ordinary concrete [9].

Valeria Corinaldesi of Ma Erkai University of Technology used recycled aggregate with a replacement rate of 30% to prepare recycled concrete, and analyzed the feasibility of using recycled concrete in beam-column joints of structures under periodic loads [10]. When the replacement rate is 30%, recycled concrete has almost the same compressive strength as ordinary concrete. However, the tensile strength, splitting strength and elastic modulus of recycled concrete are lower than those of ordinary concrete. Based on the results of periodic load test, the performance of beam-column joints is evaluated by the parameters of crack type, distributed energy, ductility and design value. The results show that the joints poured with recycled concrete have sufficient structural performance.

2.2 Durability

Liu Shuhua and Rao Meijuan of Wuhan University mainly discuss the deformation performance of recycled concrete, including elastic behavior, dry shrinkage and creep, and temperature deformation performance. The durability of recycled concrete includes permeability, frost resistance and chemical erosion resistance [1 1]. The deformation and durability of recycled concrete are deeply analyzed. The results show that recycled aggregate has different effects on the deformation and durability of recycled concrete, but it can also meet the engineering application.

Gong Xianbing of Hunan Provincial Expressway Administration Bureau, Liu Chaohui and Li Jiusu of Changsha University of Science and Technology conducted a systematic experimental study on the durability of road recycled aggregate concrete, including sulfate corrosion resistance test, frost resistance test and drying shrinkage test. The results show that the durability of recycled aggregate concrete can meet the needs of road engineering [12].

According to the characteristics of recycled aggregate and the technology of "high performance concrete", Xu Yidong and Shen Jiansheng of Zhejiang University make recycled concrete develop towards high performance [13]. The research shows that although recycled aggregate belongs to low quality aggregate, recycled concrete can have good workability and interface enhancement effect by using mineral admixtures such as fly ash, slag and silica fume in recycled concrete and making full use of the optimal combination of powders and interface enhancement effect.

Wei of Anhui University of Water Resources and Hydropower analyzed the impermeability, freeze-thaw resistance, carbonation resistance, chloride ion permeability, sulfate corrosiveness and wear resistance of recycled concrete, and put forward some measures to improve the durability of recycled concrete, such as reducing water cement ratio, adding fly ash, adopting secondary mixing technology, reducing the maximum particle size of recycled aggregate and adopting semi-saturated surface [14]. The research results show that recycled concrete has impermeability, freeze-thaw resistance and other properties.

A. Gokce of the University of Wisconsin-Madison in the United States conducted freeze-thaw durability tests on air-entraining recycled concrete and non-air-entraining recycled concrete in the free state under the medium-dry test environment [15]. The results show that the direct freeze-thaw fastness test provides a more practical test condition for judging the firmness of recycled concrete aggregates, and the sulfate fastness test can not predict the freeze-thaw difficulty of recycled concrete aggregates.

Allen Richardson of Northumbria University, UK, etc. The freeze-thaw durability test of recycled concrete based on mass loss and ultimate compressive strength [16] was studied. The results show that the durability of recycled concrete is almost similar to that of ordinary concrete, which is due to the careful selection and treatment of recycled aggregate before batching. Durability is an important index of materials, and recycled aggregate needs a lot of industrial production tests. This paper shows the possibility of future application.

2.3 Shear performance

Huang Ying and TANG Chi Hang Johnny of Guangxi University conducted the shear test of the beam with four-point stress and constant width, and discussed the influence of the replacement rate of recycled aggregate on the shear performance of recycled concrete under the same water-cement ratio [17]. The research shows that the shear failure form of recycled concrete is similar to that of ordinary concrete, but its shear strength and deformation capacity are lower than that of ordinary concrete. Through the analysis of shear strength, shear deformation and shear modulus of recycled concrete, the shear stress and strain of recycled concrete are obtained.

Xiao Jianzhuang, Department of Architectural Engineering, Tongji University, Huang Jianhe, and Lei Bin, Guangdong Institute of Building Research, made a qualitative analysis of various factors affecting the shear capacity of recycled concrete beams, and obtained the shear mechanism of recycled concrete beams. The influence trend of many factors, including shear span ratio, concrete strength and stirrup ratio, on the shear bearing capacity of recycled concrete beams is basically the same as that of ordinary concrete beams [18]. At the same time, it is pointed out that increasing the load subentry coefficient can obviously improve the shear reliability index of recycled concrete beams, but when the stirrup ratio is small and the load subentry coefficient is increased to 1.5, the shear reliability of recycled concrete beams cannot meet the reliability requirements. It is the best way to improve the average compressive strength of recycled concrete to make its standard value reach the same level as that of ordinary concrete, and the shear reliability of recycled concrete beams can meet the requirements of the code.

Liu Feng, Guoliang Bai of Xi University of Architecture and Technology, etc. In their experiments, beams of the same height and different widths were used. Considering the strength grade of concrete and the replacement rate of recycled aggregate, the shear strength, deformation and its development law of recycled concrete beams are studied [19], and it is concluded that the shear ultimate bearing capacity of recycled concrete beams is not directly related to the replacement rate. At the same time, it is concluded that the shear stress principal strain curve of recycled concrete beams is close to a straight line, and the shear strength obtained from the test is lower than that of ordinary concrete.

Zhang Leishun of Zhengzhou University conducted a comparative test between 13 recycled concrete beam and ordinary concrete beam, and Xiao Jianzhuang and Zhu Xiaohui of Tongji University Department of Architectural Engineering completed the experimental study on the seismic performance of three kinds of recycled concrete frame side joints with different replacement rates of recycled coarse aggregate under vertical axial compression load and horizontal low cyclic loading [23]. It is pointed out that the failure process of recycled concrete joints is similar to that of ordinary concrete. Although the seismic performance of recycled concrete joints is slightly lower than that of ordinary concrete, the ductility and other seismic performance of recycled concrete joints still meet the corresponding seismic fortification requirements, which shows that recycled concrete can be used for frame joints with seismic fortification requirements.

Sun Yuedong, Institute of Structural Engineering, Tongji University, compared the seismic performance of three frame models with the ratio of 1∶2 under different vertical axial compression loads and horizontal low cyclic loading, and studied the influence of recycled concrete frames and different axial forces on the seismic performance under low cyclic loading [24]. The results show that the mechanical properties and failure of recycled concrete frames under different axial forces and low cyclic loading. Recycled concrete frame has good seismic performance. After the structure enters the elastic-plastic stage, the hysteretic curve of the frame is full, which shows that the frame has good energy dissipation capacity. The displacement ductility coefficient of the frame is 3.76 ~ 4.34, which indicates that the ductility of the frame is good. The displacement ductility of recycled concrete frame is less than that of ordinary concrete frame, and the ductility of frame decreases with the increase of axial load.

School of Architecture and Engineering, Beijing University of Technology, Cao et al. Seven low-cycle cyclic loading tests were carried out on medium-high shear walls with shear span ratio of 65,438+0.5 [25]. Based on the test, the bearing capacity, ductility, stiffness, hysteretic characteristics, energy dissipation capacity and failure characteristics of each shear wall are analyzed. The research shows that the seismic performance of recycled concrete medium-high shear wall decreases with the increase of reinforcement ratio. Its bearing capacity, ductility and energy dissipation capacity are all improved, and it is pointed out that with the increase of axial compression ratio, the bearing capacity of recycled concrete shear wall is improved and the elastic-plastic deformation capacity is reduced.

Yin Haipeng of Beijing University of Technology and others carried out model tests of 1 ordinary concrete columns and three recycled concrete columns with different replacement rates under low cyclic loading [26], and the model scale was 1/2. The test results show that with the increase of the replacement rate of recycled aggregate, the elastic modulus of concrete, the initial stiffness of the specimen, the bearing capacity, energy consumption and seismic capacity are obviously reduced.

3. Existing problems and application prospects

3. 1 The research on recycled concrete has made some achievements in recent years. However, in view of the limitations of recycled aggregate itself and the actual situation of recycled concrete in China, there are still some obstacles and deficiencies, mainly in the following aspects.

(1) At present, there are few equipment and related technologies suitable for treating waste concrete, and the understanding of recycling waste concrete is not in place.

(2) Waste concrete has a wide range of sources and is very complicated, so how to treat it in a reasonable grade is the key problem to be solved.

(3) There are too few corresponding standards and specifications, which are difficult to operate in practice and difficult to popularize in a large area at present.

3.2 Application prospect

Compared with ordinary concrete, the physical and mechanical properties of recycled aggregate concrete are slightly inferior, but there is no doubt that recycled aggregate concrete has broad application prospects. In specific applications, [27-28] can be selectively replaced according to the position of the structure. For the main load-bearing structure, the replacement rate of recycled coarse aggregate can be appropriately reduced, and the limit value or allowable range can be set. For general structural engineering, such as sidewalk boards, bridge guardrails, protective blocks and other ancillary structures,

On the performance characteristics and application of recycled concrete;

In order to effectively reduce the environmental pressure caused by the increasing amount of waste concrete and reduce the waste of resources, it is suggested that waste concrete be recycled into recycled aggregate, and partially or completely replace natural aggregate to prepare recycled concrete, so that waste concrete will become a green resource in the field of civil engineering. This paper introduces the research progress of recycled concrete technology at home and abroad from the production technology and performance of recycled aggregate, physical properties, mechanical properties and durability of recycled concrete, analyzes the basic characteristics and research problems of recycled concrete from the aspects of material, structure, mechanical properties and durability, and points out the direction that needs further research, with a view to providing reference opinions for the application of recycled concrete technology in scientific research and engineering.

Key words:

Recycled concrete; Recycled aggregate; Mechanical properties; keep patience

1, introduction of recycled concrete and the necessity of research.

Recycled concrete refers to a new type of concrete made of waste concrete blocks after crushing, crushing, cleaning and screening, which partially or completely replaces natural aggregate. It is the abbreviation of recycled aggregate concrete (RAC).

In recent years, China's construction waste has increased year by year, and the amount of construction waste has accounted for 30% ~ 40% of the total urban waste, mainly waste concrete, which has seriously affected the urban living environment and caused great environmental pollution. At present, there are two ways to deal with these waste concrete in China: one is to transport them to the suburbs for storage. This will become a new source of garbage, which is obviously not desirable; Second, it is simply used as backfill material. This will waste resources and does not meet the requirements of building a resource-saving society in China. It is estimated that the Wenchuan earthquake in 2008 produced about 300 million tons of construction waste. The amount of construction waste caused by the earthquake far exceeds the sum of construction waste produced in China every year. The amount of construction waste caused by the earthquake is huge. How to use it as a resource is a new topic and challenge before us. Recycled concrete technology is a good solution. By reprocessing waste concrete, its original properties can be restored, new building materials products can be formed, limited resources can be reused, and some environmental protection problems can be solved. This is not only an important way to develop green concrete and realize the sustainable development of building resources and environment, but also a concrete embodiment of building a resource-saving and environment-friendly society.

2. Production technology and performance of recycled aggregate

2. 1 recycled aggregate production technology

The premise of fully reusing waste concrete is to ensure that the production process of recycled aggregate is economical and feasible. The production of recycled aggregate needs to solve a series of problems, including the recovery, crushing and screening of waste concrete blocks or reinforced concrete blocks. The simple concrete crushing and screening process is shown in figure 1.

2.2 Performance of recycled aggregate

The recycled aggregate produced by crushing waste concrete contains about 30% hardened cement mortar. Most of these cement mortars are independent blocks, and only a small amount is attached to the surface of natural aggregate, which leads to the characteristics of low density, high water absorption and weak bonding ability of recycled aggregate. Generally speaking, recycled aggregate has many edges and corners and rough surface. In the process of regeneration and destruction of waste concrete blocks, a large number of micro-cracks will be produced in recycled aggregate due to the accumulation of damage. The research shows that recycled aggregate has higher porosity, lower density, higher water absorption and lower aggregate strength than natural aggregate.

3. Physical and mechanical properties of recycled concrete

3. 1 Physical properties of recycled concrete

Because the apparent density of recycled aggregate is less than that of natural aggregate, the density of recycled concrete is lower than that of ordinary concrete. With the increase of recycled aggregate content, the density of recycled concrete decreases regularly. If recycled aggregate is used in recycled concrete, its density is 7.5% lower than that of ordinary concrete. Recycled concrete has the characteristics of light weight, which can reduce the weight of the structure and improve the seismic performance of the components. At the same time, due to the high porosity of recycled aggregate, recycled concrete has good thermal insulation performance.

3.2 Strength of recycled concrete

The strength of recycled concrete is closely related to the strength of matrix concrete (compared with recycled concrete, the original concrete used to produce recycled aggregate is called matrix concrete), the crushing technology of recycled aggregate, the replacement rate of recycled aggregate, and the mixture ratio of recycled concrete. Due to the different strength grades of matrix concrete, different application environments, different cracking and crushing processes and quality control measures, the strength variation law of recycled concrete is not obvious, and different researchers draw different conclusions. Hansen's test results show that the strength of recycled concrete decreases with the decrease of the strength of matrix concrete. In general, the compressive strength of recycled aggregate concrete matrix concrete or ordinary concrete with the same proportion is relatively low, with a reduction range of 0%-30%, with an average reduction of 15%. Xing et al. all use waste concrete recycled aggregate to produce recycled concrete, pointing out that the flexural strength of recycled concrete is about 75%-90% of the strength of benchmark concrete. Compared with the benchmark concrete with the same mixture ratio, the compressive strength and tensile strength are reduced by 9% and 7% respectively.

It should be noted that the surface of recycled aggregate is wrapped with cement mortar, which makes the elastic modulus between recycled aggregate and new cement mortar basically the same, and the interface bonding may be strengthened to some extent. At the same time, a large number of micro-cracks on the surface of recycled aggregate will suck in new cement particles, which will make the hydration of the contact area more complete and eventually form a dense interface structure. Because the interfacial bonding is strengthened, the performance deterioration of recycled concrete caused by the low strength of recycled aggregate is compensated to some extent.

3.3 Elastic modulus of recycled concrete

Because there are a lot of old mortar attached to the original aggregate particles in recycled aggregate, the elastic modulus of recycled concrete is usually low, generally about 70%-80% of the matrix concrete. Recycled concrete has low elastic modulus, large deformation, strong seismic performance and dynamic load resistance. The water-cement ratio has a great influence on the elastic modulus of recycled concrete. When the water-cement ratio decreased from 0.8 to 0.4, the compressive elastic modulus of recycled concrete increased by 33.7%.

3.4 Drying shrinkage and creep of recycled concrete

The shrinkage and creep of recycled concrete are increased by 40%-80% compared with ordinary concrete. The quality of recycled aggregate, the performance of matrix concrete and the mixture ratio of recycled concrete determine the increase of drying shrinkage. Yamato et al.' s research shows that the drying shrinkage of recycled concrete will increase when natural aggregate and recycled aggregate are used together; When the water-cement ratio increases, the drying shrinkage of recycled concrete will also increase.

4. Durability of recycled concrete

4. 1 impermeability of recycled concrete

The factors related to the permeability of concrete are mainly divided into two categories.

(1) Composition, mixture ratio and technological parameters of concrete mixture, namely preparation, molding and maintenance of mixture;

(2) Concrete changes with time, that is, the physical and chemical changes of concrete under the influence of external environment, structural stress, fluid properties and seepage conditions.

Due to the high porosity of recycled aggregate, the impermeability of recycled concrete is lower than that of ordinary concrete. However, after adding fly ash into recycled concrete, the impermeability of recycled concrete is greatly improved because fly ash can refine the capillary channels of recycled aggregate.

4.2 Sulfate resistance of recycled concrete

Recycled concrete has high porosity and permeability, and its sulfate resistance is worse than that of ordinary concrete. Similarly, adding fly ash into it can reduce the permeability of sulfate and greatly improve its resistance to sulfate attack.

4.3 Crack resistance of recycled concrete

Compared with ordinary concrete, the ultimate elongation of recycled concrete is increased by 27.7%. Recycled concrete has lower elastic modulus and higher tension-compression ratio, so the crack resistance of recycled concrete is better than that of matrix concrete.

4.4 Frost-thaw resistance of recycled concrete

The freeze-thaw resistance of recycled concrete is worse than that of ordinary concrete. The research of Yamato et al. shows that the frost resistance of recycled concrete can be improved when recycled aggregate is mixed with natural aggregate or the water-cement ratio is reduced.

5. Conclusion

Through the research on recycled concrete, we draw the following conclusions and suggestions, hoping to attract the attention of the industry or relevant departments.

First, recycled concrete technology can fundamentally solve the problem of waste concrete, which can not only reduce the pollution of waste concrete to the environment, but also save natural aggregate resources. It has remarkable social, economic and environmental benefits, and is one of the main ways to develop green concrete, which meets the requirements of China's sustainable development strategy.

Secondly, in engineering application research, we should not only study how to improve the strength of recycled concrete, but also strengthen the research on its durability such as impermeability and crack resistance, and gradually improve the performance of recycled concrete.

Thirdly, compared with ordinary concrete, the mix design and construction technology of recycled concrete have many differences, which should be treated differently.

Fourthly, reasonable design of recycled concrete can basically meet the performance requirements of ordinary concrete. In order to better popularize the application of recycled concrete technology, we need to strengthen the research on its structural properties (bending, shearing, punching and seismic, etc.). ) and design method.

Fifth, there are great differences between recycled concrete and ordinary concrete in raw materials, mixture ratio and construction technology. According to the current standards and regulations of ordinary concrete, there are obviously many shortcomings. On the other hand, there are great differences in composition and performance between domestic cement and aggregate and those used abroad, and it is even more impossible to directly use relevant foreign standards. Therefore, it is suggested that the relevant standards and regulations of recycled concrete suitable for China's national conditions should be formulated as soon as possible in combination with the classification of recycled aggregate.

Sixthly, through the comprehensive study on the economy of recycled concrete, the wide application of recycled concrete in China needs the support of xx active industrial policies and the protection of national laws and regulations.

refer to

[1] Southern Wang Bolin. Discussion on the quality of recycled coarse aggregate from waste concrete and the engineering performance of recycled concrete [J]. China Journal of Civil and Hydraulic Engineering, 2009, 12 (03): 435-444.

Wu Zhongwei. Green high-performance concrete and technological innovation [J]. Journal of Building Materials, 2011(01):1~ 5.

Feng Xing, Feng Naiqian, Ding Jiantong. Recycled aggregate concrete [J]. Concrete and cement products,1999 (02):10 ~13.

Sun Yuedong, Xiao Jianzhuang. Recycled concrete aggregate [J]. Concrete, 20 14 (06): 33-36.

Xing, farming on Sunday. Research and development of recycled concrete [J]. Development of building technology, 2005,25 (05): 28-31.

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