Waste asphalt mixture sampling method for preparing cold recycling test piece

Abstract

The invention provides a waste asphalt mixture sampling method for preparing a cold recycling test piece, and belongs to the technical field of asphalt pavement cold recycling. The problems of large sampling error, low representativeness, poor grading uniformity, nonstandard operation, many man-made interference factors, insufficient consideration of reclaimed material characteristics, low sampling efficiency and the like existing in the existing waste asphalt mixture sampling method for preparing the cold recycled test piece are solved. The method comprises the following steps: sampling by amplifying the actual required quality of the waste asphalt mixture by five times, selecting four standard sieves of 16mm, 9.5 mm, 4.75 mm and 0.075 mm to divide the waste asphalt mixture into five grades, and feeding the five-grade aggregate into a distributor to be uniformly divided into three parts again through the design of a three-bin distributor with a feeding bin, a distributing bin, a partition plate, a bin dividing cone and a stock bin. The method overcomes the limitation of the traditional sampling method of the waste asphalt mixture, has the advantages of simplicity and convenience in operation, high sampling efficiency, good repeatability and the like, improves the sampling accuracy, and ensures the authenticity and reliability of test results.

Description

Technical Field

[0001] The present application discloses a method for sampling waste asphalt mixture for preparing cold regeneration specimens, and belongs to the technical field of cold regeneration of asphalt pavement. Background Art

[0002] Asphalt pavement cold recycling technology, as an environmentally friendly and efficient method for the reuse of waste asphalt mixtures, has received widespread attention at home and abroad. With the continuous expansion of highway construction and maintenance, the generation of a large amount of waste asphalt mixtures has made its resource utilization an important issue that needs to be solved urgently. Cold recycling technology can effectively reduce construction costs, save energy, and reduce environmental pollution by adding appropriate amounts of regeneration agents, cement, emulsified asphalt and other materials, combined with remixing of waste asphalt mixtures.

[0003] In recent years, with the promotion of green highways and sustainable development concepts, domestic scholars and engineering and technical personnel have made remarkable progress in cold recycled mixture mix design, performance evaluation, construction technology, etc.

[0004] The distribution of aggregates, pores and asphalt in asphalt mixture affects the strength and deformation of asphalt mixture. Coarse aggregates contact each other to form a skeleton and are the main body that bears the load. The macroscopic performance of asphalt mixture is determined by the force chain network within the asphalt mixture, which is composed of coarse aggregates in contact with each other. Force chains are considered to be the paths for transmitting external loads in asphalt mixtures. Therefore, for cold recycled specimens of waste asphalt mixtures, the actual particle gradation of aggregates directly affects the road performance of the specimens. In the application of cold recycling technology, people pay special attention to the dosage of waste asphalt mixtures and their particle size distribution, so as to form a suitable gradation curve.

[0005] "Technical Specification for Regeneration of Highway Asphalt Pavement" (JTG / T 5521-2019) is the current industry standard for the application of highway pavement recycling technology in my country. For sampling of mixing plant stockpiles, the specification specifies that the divider method or the quartering method should be used. The divider method uses a divider to divide the sample into two approximately equal parts and continuously reduce the number of parts, while the quartering method is to naturally flatten the aggregate and roughly divide the sample into four parts. It can be seen that the original sampling method of waste asphalt mixtures is more accidental and is more affected by random factors. The aggregate gradation used in the actual preparation of the test specimens is quite different from the original screening results. At the same time, due to the obvious difference in aggregate particle size, artificial reduction can easily lead to the problem of separate accumulation of coarse aggregate and fine aggregate.

[0006] In terms of sampling methods for waste asphalt mixtures, the American Association of Highway and Transportation Officials and the American Society for Testing and Materials have formulated relevant standards and specifications, emphasizing the representativeness and uniformity of sampling to ensure the accuracy of the test results of recycled mixture performance. European countries such as Germany and France have also conducted in-depth research on recycling technology and sampling methods, and gradually improved the laboratory and on-site sampling processes to improve the applicability of recycled materials in actual projects.

[0007] However, there are still some urgent problems to be solved in the sampling method of waste asphalt mixture. At present, most domestic laboratories and on-site sampling still use the traditional aggregate quartering method. This method relies on manual operation and is easily affected by factors such as the technical level and operating habits of the sampling personnel, resulting in poor sampling uniformity and insufficient representativeness, which in turn affects the quality of the formed cold recycled mixture specimens and the reliability of the mechanical properties test results. Specifically, the traditional quartering method has the following main problems: First, it is difficult to ensure the uniform distribution of aggregates during the manual material division process, especially when dealing with waste asphalt mixtures with a wide particle size distribution range. Coarse and fine aggregates are prone to segregation, affecting the density and strength test results of the specimens. Secondly, the sampling operation is complicated and time-consuming, which increases the workload of the test and reduces work efficiency.

[0008] In addition, poor repeatability is also a shortcoming of traditional sampling methods. Sampling differences between different operators may lead to large fluctuations in test data, making it difficult to accurately evaluate the actual performance of cold recycled mixtures. Therefore, domestic and foreign scholars have proposed some improvement methods, such as improved mechanical material distribution equipment, vibration screening technology, etc., to improve the uniformity and work efficiency of sampling. However, these methods still have shortcomings such as complex equipment, high cost, and limited scope of application during application, making it difficult to fully meet the needs of laboratory and field sampling. Therefore, it is particularly important to develop a new sampling method that is simple in structure, easy to operate, and can effectively reduce sampling errors.

[0009] In view of this, this application proposes a method for sampling waste asphalt mixture for preparing cold recycled specimens. By innovatively designing a three-bin distributor and optimizing the sampling process, the uniformity and representativeness of sampling are significantly improved, overcoming the limitations of traditional sampling methods. This method has the advantages of simple operation, high sampling efficiency, and good repeatability. It can effectively ensure the representativeness of the sampling of cold recycled specimens and the accuracy of performance testing, and has broad engineering application prospects and promotion value. Summary of the invention

[0010] (1) Technical issues

[0011] The purpose of this application is to propose a method for sampling waste asphalt mixture for preparing cold recycled specimens. The method increases the sampling volume of waste asphalt mixture, selects four standard sieves to divide the waste asphalt mixture into five grades, and then divides the five grades of aggregates into three parts evenly through the design of a three-bin divider. Figure 1 and Figure 2 , thereby solving the problems of large sampling error, low representativeness, poor gradation uniformity, irregular operation, many human interference factors, insufficient consideration of recycled material characteristics, low sampling efficiency, etc. in the existing sampling method for waste asphalt mixture when preparing cold recycled specimens, which leads to the accuracy, repeatability and comparability of the test results of the prepared specimens being affected, and it is difficult to objectively reflect the gradation of the waste asphalt mixture. This provides a more scientific, standardized and highly operational sampling method for waste asphalt mixture to improve sampling accuracy, ensure the authenticity and reliability of the test results, and provide strong guarantees for the preparation of cold recycled specimens.

[0012] (2) Technical solution

[0013] In view of the many problems mentioned above in the current method for sampling waste asphalt mixtures for preparing cold recycled specimens, the present application provides a method for sampling waste asphalt mixtures for preparing cold recycled specimens, starting from refining the sampling steps of waste asphalt mixtures, to provide a more scientific, standardized, and highly operational method for sampling waste asphalt mixtures, thereby improving sampling accuracy and ensuring the authenticity and reliability of test results. The technical solution of the present application is as follows: First, according to the coarseness of the waste asphalt mixture, the particle size distribution and the mass of the specimen to be prepared, the waste asphalt mixture is weighed at five times the required mass; then, four standard sieves with mesh sizes of 16mm, 9.5mm, 4.75mm and 0.075mm are used to divide the waste asphalt mixture into five grades; finally, the five grades of aggregates are respectively passed through a three-bin divider, and each grade of waste asphalt mixture is divided into three parts by the three-bin divider, such as Figure 1 and Figure 2 , randomly select one portion of each grade of waste asphalt mixture and weigh it to prepare the mass required for cold recycling specimens, then re-mix each grade of waste asphalt mixture evenly into a waste asphalt mixture for preparing cold recycling specimens.

[0014] (3) Beneficial effects

[0015] Compared with the existing sampling methods, the significant effect of this application is that the uniformity and representativeness of the aggregate sampling process are significantly improved through the innovative design of the divider. Compared with the traditional four-division method, the three-bin divider can effectively avoid sampling errors caused by improper human operation or uneven distribution of aggregates, ensuring that the results of the specimens in various performance tests are more accurate and reliable. In addition, this method simplifies the operating process, reduces the technical requirements of test personnel, improves sampling efficiency, and has good promotion and application value. The three-bin divider of this application has a reasonable structural design and can achieve efficient and uniform distribution of waste asphalt mixtures of different particle sizes. By optimizing the sampling link, the problems of segregation of large-size aggregates and uneven distribution of fine aggregates in traditional sampling methods are solved, which helps to improve the accuracy of performance evaluation of recycled mixture specimens, reduce the influence of human or accidental factors on aggregate sampling, and improve the accuracy of grading design results of cold recycled mixture specimens. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Three-bin distributor physical model

[0017] Figure 2 Schematic diagram of the three-bin distributor structure

[0018] 1-Feeding bin 2-Sub-bin 3-Partition 4-Sub-bin cone 5-Binyard DETAILED DESCRIPTION

[0019] The present application provides a method for sampling waste asphalt mixture for preparing cold recycled specimens, and the specific implementation steps are as follows:

[0020] (1) According to the Technical Specification for Highway Asphalt Pavement Regeneration (JTG / T 5521-2019), the mass of waste asphalt mixture aggregate required for each test specimen preparation is recorded as m a , weigh the waste asphalt mixture according to five times the required mass, and record the total mass of the weighed waste asphalt mixture as m;

[0021] (2) Using four standard sieves with mesh sizes of 16 mm, 9.5 mm, 4.75 mm and 0.075 mm, the waste asphalt mixture weighed in step (1) is sieved according to the standard sieve mesh sizes from large to small, and the mass of the residue on each sieve is accurately recorded and stored separately; the waste asphalt mixture is then divided into five grades according to the mesh sizes of greater than 16 mm, 9.5-16 mm, 4.75-9.5 mm, 0.075-4.75 mm and less than 0.075 mm, and the mass of the waste asphalt mixture in the five grades is weighed as m 1 、m 2 、m 3 、m 4 and m 5;

[0022] (3) The five grades of aggregates in step (2) are respectively passed through Figure 1 and Figure 2 The distributor shown includes a feeding bin 1, a dividing bin 2, a partition 3, a dividing bin cone 4, and a bin 5. The working principle is as follows: the dividing bin cone divides the distributor bin into three parts evenly. Before use, the aggregates of each batch are mixed evenly. When in use, the waste asphalt mixture is scooped up by a shovel and quickly poured into the feeding bin. The waste asphalt mixture is randomly distributed to any bin through the transition zone of the dividing bin. After the waste asphalt mixture of that batch is put into the bin, the distributor is lifted and a portion of the waste asphalt mixture is selected for testing.

[0023] (4) Each batch of waste asphalt mixture aggregate is divided into three parts by a three-bin divider. One part of each batch of waste asphalt mixture is randomly selected and weighed to obtain the required mass m. 1 / 5m,m 2 / 5m,m 3 / 5m,m 4 / 5m and m 5 / 5m, and then re-mix the weighed waste asphalt mixture of each grade evenly into waste asphalt mixture for preparing cold recycled specimens.

Claims

1. A method for sampling waste asphalt mixture for preparing cold recycled specimens, characterized in that The specific steps of this method are as follows: (1) According to the Technical Specification for Highway Asphalt Pavement Regeneration (JTG / T 5521-2019), based on the coarseness of the waste asphalt mixture and the mass of the test specimen to be prepared, record the mass of the waste asphalt mixture required for each test specimen preparation, and weigh the waste asphalt mixture at five times the required mass; (2) using four standard sieves with mesh sizes of 16 mm, 9.5 mm, 4.75 mm and 0.075 mm, the waste asphalt mixture weighed in step (1) is sieved according to the standard sieve mesh sizes from large to small, and the mass of the residue on each sieve is accurately recorded and the mass of the residue on each sieve is separately saved; then the waste asphalt mixture is divided into five grades according to the sizes of greater than 16 mm, 9.5 to 16 mm, 4.75 to 9.5 mm, 0.075 to 4.75 mm and less than 0.075 mm, and the masses of the waste asphalt mixture in the five grades are weighed respectively; (3) The five grades of aggregates in step (2) are respectively passed through a three-bin divider, and each grade of waste asphalt mixture is divided into three portions by the three-bin divider. A portion of each grade of waste asphalt mixture is randomly selected and weighed to obtain the required mass. Then, each grade of waste asphalt mixture is re-uniformly mixed into a waste asphalt mixture for preparing cold recycled specimens.

2. A three-bin distributor for preparing cold recycled specimens of waste asphalt mixture, characterized in that: It includes a feeding bin, a distribution bin, a partition, a distribution bin cone and a silo.

3. A three-bin distributor for preparing cold recycled specimens of waste asphalt mixture according to claim 2, characterized in that: A transitional sub-bin is designed between the feeding bin and the material bin.

4. A three-bin distributor for preparing cold recycled specimens of waste asphalt mixture according to claim 2, characterized in that: The silo is used to evenly divide the waste asphalt mixture into three parts through the dividing cone.

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