Method for determining the amount of recycled powder in an asphalt mixture

Abstract

The application discloses a method for determining the mixing amount of recycled powder in asphalt mixture, and comprises the following steps: S1, preparing test mineral powder and recycled powder; S2, obtaining particle size distribution; S3, determining reference particle size; S4, preparing asphalt mixture; S5, preparing extracted powder; S6, determining standard working curve; and S7, testing sample preparation and determining the mixing amount of recycled powder. The method solves the problems of neglecting the detection of recycled powder and lacking detection methods in the current quality control of asphalt mixture production, and can effectively control the production quality of asphalt mixture.

Description

TECHNICAL FIELD

[0001] The application relates to a method for measuring the mixing amount of recycled powder in asphalt mixture and belongs to the field of asphalt mixture testing. BACKGROUND

[0002] Asphalt pavement is widely used in the construction of highways and urban roads in China due to its high flatness, good comfort, and easy maintenance. Asphalt pavement is paved by asphalt mixture, which is mainly composed of asphalt, aggregate and filler (usually mineral powder). The production of asphalt mixture is carried out in an asphalt mixing plant. A large amount of micron-sized dust is generated during the mixing process. In order to reduce the pollution of dust to the environment, dust removal devices are installed in the mixing plant to recycle these dusts. According to statistics, the yield of recycled powder during mixing is about 5% of the asphalt mixture. A large amount of recycled powder will occupy space resources, pollute the environment and increase transportation costs.

[0003] In recent years, some scholars have conducted research on the application of recycled powder in asphalt mixture and have achieved certain results, mainly in the use of recycled powder instead of mineral powder in asphalt mixture production. Domestic research mainly focuses on the influence of recycled powder content on the performance of asphalt mixture, but the research results are difficult to reach a consensus. In foreign countries, different countries and regions have different opinions. France allows all recycled powder to be added to the mixture; the United Kingdom has more stringent control over the addition of recycled powder. The American Asphalt Association study shows that if the quality of the aggregate used is good and stable, the recycled powder obtained from this aggregate can also be used in asphalt mixture to obtain satisfactory results, but some states do not allow the addition of recycled powder in asphalt mixture, mainly because recycled powder can make asphalt mixture difficult to compact, brittle, and increase water sensitivity, etc. In addition, many foreign studies have also pointed out the same problem. It can be seen that the application of recycled powder in asphalt mixture is not mature enough.

[0004] The current “Technical Specification for Highway Asphalt Pavement Construction” (JTG F40-2004) in China stipulates that dust can be recycled and used as part of the mineral powder, but the amount of each disc should not exceed 25% of the total amount of filler, and the plasticity index after mixing with mineral powder should be less than 4%. In the paper “Influence of Recycled Powder on Performance Indexes of Mineral Powder for Asphalt Pavement”, Jiang Yi pointed out that the basic performance of asphalt mixture mixed with 25% recycled powder can meet the specification requirements, but the performance is lower than that of mixture without recycled powder. It is suggested that the use of recycled powder should be prohibited in asphalt pavement construction. In order to ensure engineering quality, many road projects also rigidly prohibit the use of recycled powder.

[0005] In the production process of asphalt mixture, quality control is needed, and the main detection indexes include Marshall volume index, asphalt content and mixture gradation. It can be seen that the test of mineral powder is ignored. However, in the mixing process of some construction units, in order to reduce the cost, the recycled powder is partially or completely replaced by mineral powder, which will undoubtedly affect the quality of the mixture. In addition, the detection method of whether the recycled powder is added in the asphalt mixture is still blank at present.

[0006] Therefore, it is necessary to develop a method for determining the mixing amount of recycled powder in asphalt mixture, so as to effectively control the production quality of asphalt mixture. SUMMARY

[0007] The purpose of the present application is to provide a method for determining the mixing amount of recycled powder in asphalt mixture, so as to solve the problems of ignoring the detection of recycled powder and lacking detection method in the production quality control of asphalt mixture, thereby effectively controlling the production quality of asphalt mixture.

[0008] The present application provides a method for determining the mixing amount of recycled powder in asphalt mixture, characterized in that it comprises the following steps:

[0009] S1, preparing test mineral powder and recycled powder

[0010] The mineral powder and recycled powder used for producing asphalt mixture are respectively passed through a sieve with a pore size of 0.075 mm to obtain mineral powder A and recycled powder A;

[0011] S2, obtaining particle size distribution

[0012] The particle size distribution of mineral powder A and recycled powder A is obtained by using a laser particle size analyzer;

[0013] S3, determining the reference particle size

[0014] The reference particle size corresponding to the maximum difference in the percentage of particles passing under a certain particle size is determined according to the particle size distribution of mineral powder A and recycled powder A, i.e. the reference particle size;

[0015] S4, preparing asphalt mixture

[0016] Asphalt mixtures with different mixing amounts of recycled powder are prepared according to the designed mixing ratio, wherein: mixture A: recycled powder accounts for 0% of the total filler amount; mixture B: recycled powder accounts for 5% of the total filler amount; mixture C: recycled powder accounts for 25% of the total filler amount; mixture D: recycled powder accounts for 50% of the total filler amount; mixture E: recycled powder accounts for 75% of the total filler amount; and mixture F: recycled powder accounts for 100% of the total filler amount;

[0017] S5, preparing extracted powder

[0018] The filler is separated from the mixed asphalt mixture by using a full-automatic asphalt extraction instrument and high-speed centrifugal extraction, and extraction powders A, B, C, D, E and F are obtained after the extraction separation;

[0019] S6, determining a standard working curve

[0020] The particle passing percentage of the extraction powders A, B, C, D, E and F under the reference particle size is obtained by using a laser particle size analyzer; and a standard working curve equation is fitted according to the particle passing percentage under the reference particle size;

[0021] S7, sample preparation and determination of the content of the recycled powder

[0022] The asphalt mixtures with different contents of the recycled powder are mixed according to the designed mixing ratio: the recycled powder accounts for 10% of the total filler in the mixture A1, the recycled powder accounts for 30% of the total filler in the mixture B1, and the recycled powder accounts for 60% of the total filler in the mixture C1; the particle passing percentage of the mixtures A1, B1 and C1 under the reference particle size is obtained by using the full-automatic extraction instrument and the laser particle size analyzer, and the content of the recycled powder in the asphalt mixture is obtained by substituting the particle passing percentage into the standard working curve equation.

[0023] Preferably, the dispersion concentration of the laser particle size analyzer in step 2 is controlled to be between 0.25 and 0.45 g / L, the continuous mixing rate is 2200-2500 r / min, the dispersion medium is distilled water, and the dispersion time is 15 minutes.

[0024] Preferably, the particle size distribution of the mineral powder A and the recycled powder A is measured for three times in step 2, and the average value is taken.

[0025] Preferably, the minimum aperture screen of the full-automatic asphalt extraction instrument in step 5 is 0.075 mm.

[0026] Preferably, the asphalt mixture with different contents of the recycled powder is soaked in a trichloroethylene solution for 0.5 h and fully stirred by using a glass rod before the extraction in step 5.

[0027] The technical scheme provided by the application has at least the following technical effects or advantages:

[0028] The method for determining the content of the recycled powder in the asphalt mixture provided by the application solves the problem of the blank of the detection method for the content of the recycled powder in the asphalt mixture. The quality control of the production process of the asphalt mixture by using the application can effectively prevent the phenomenon of the illegal addition of the recycled powder by the construction unit. The application perfects the test content of the quality control in the production process of the asphalt mixture, and has important significance for controlling the production quality of the asphalt mixture and ensuring the engineering quality. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Standard working curve for the embodiments of the present application. Embodiment

[0030] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0031] The present embodiment provides a method for determining the mixing amount of recycled powder in asphalt mixture, and the specific implementation steps are as follows:

[0032] S1, preparing test mineral powder and recycled powder

[0033] Take an appropriate amount of mineral powder used for producing asphalt mixture and recycled powder from the mixing station, pass the mineral powder and the recycled powder through a sieve with a pore size of 0.075 mm to obtain mineral powder A and recycled powder A.

[0034] S2, obtaining particle size distribution

[0035] Use a laser particle size analyzer to obtain the particle size distribution of the mineral powder A and the recycled powder A; control the dispersion concentration between 0.25-0.45 g / L, the continuous mixing rate is 2200-2500 r / min, and the dispersion medium is distilled water. Perform three parallel measurements on the particle size distribution of the mineral powder A and the recycled powder A, and take the average value. The test results of the mineral powder A and the recycled powder A are shown in Table 1.

[0036] Table 1 Test results of particle size analysis of mineral powder A and recycled powder A

[0037]

[0038]

[0039]

[0040] S3, determining the reference particle size

[0041] From the particle size distribution, it can be determined that the percentage of particles passing through the mineral powder A and the recycled powder A is the largest when the particle size is 9 μm, therefore, the reference particle size of the present embodiment is 9 μm.

[0042] S4, preparing asphalt mixture

[0043] According to the Highway Engineering Asphalt and Asphalt Mixture Test Regulation (JTG E20-2011), according to the design mixing ratio (see Table 2), the asphalt mixture with different recycled powder contents is prepared in the laboratory using a small mixing pot: Mixture A (recycled powder accounts for 0% of the total filler), Mixture B (recycled powder accounts for 5% of the total filler), Mixture C (recycled powder accounts for 25% of the total filler), Mixture D (recycled powder accounts for 50% of the total filler), Mixture E (recycled powder accounts for 75% of the total filler), Mixture F (recycled powder accounts for 100% of the total filler).

[0044] Table 2 Design mixing ratio of each material

[0045] Type of raw material 1# 2# 3# 4# Filler Oil stone ratio (%) Proportion (%) 36 35 5 14 10 6.1

[0046] S5, Preparation of extraction powder

[0047] Take asphalt mixture A, soak it in trichloroethylene solution for 0.5h, and stir it thoroughly with a glass rod. Then pour it all into the screen of the full-automatic extraction instrument, filter and separate the filler by high-speed centrifugal extraction, i.e. extraction powder A. Similarly, asphalt mixtures B, C, D, E and F can be obtained after being filtered and separated by high-speed centrifugal extraction. The minimum aperture screen of the full-automatic asphalt extraction instrument is a 0.075mm aperture screen.

[0048] S6, Determine the standard working curve

[0049] Use the laser particle size analyzer to obtain the particle passing percentage of extraction powders A, B, C, D, E and F at the reference particle size. The dispersion concentration is controlled between 0.25-0.45g / L, the continuous mixing rate is 2200-2500r / min, and the dispersion medium is distilled water. For each extraction powder, 3 parallel measurements are performed, and the average value is taken.

[0050] According to the passing percentage of extraction powders A, B, C, D, E and F at the reference particle size (9μm), a linear equation, i.e. the standard working curve, is fitted, as Figure 1 .

[0051] The standard working curve equation is y=0.2077x+53.82, and the correlation coefficient R 2 =0.9951.

[0052] S7, Preparation of three test samples and determination of recycled powder content

[0053] According to the design mixing ratio, the asphalt mixtures with different recycled powder contents are prepared by using a small indoor mixing pot: mixture A1: recycled powder accounts for 10% of the total filler, mixture B1: recycled powder accounts for 30% of the total filler, and mixture C1: recycled powder accounts for 60% of the total filler. The percentage of passing under the reference particle size of mixtures A1, B1 and C1 is obtained by using a full-automatic extraction instrument and a laser particle size analyzer, and the working curve is drawn. The content of recycled powder in the asphalt mixture is as follows.

[0054] Sample Average measured value of reclaimed powder content Actual value of reclaimed powder content Mix A1 9.7％ 10％ Mix B1 30.4％ 30％ Mix C1 60.5％ 60％

[0055] As shown in the above table, the contents of recycled powder in the three samples to be tested are 9.7%, 30.4% and 60.5%.

[0056] The particle size distribution of the mixture A1, mixture B1 and mixture C1 to be tested in the above embodiment is tested for three times, and the average value is taken.

[0057] The results obtained by using the present application show that the correlation coefficient between the content of recycled powder and the percentage of passing of the corresponding reference particle size is 0.9951, which indicates that they have an excellent linear relationship. The test results of the three asphalt mixtures to be tested are verified by using the working curve equation, and the average relative error between the test results and the actual content of recycled powder is 1.39%, and the detection accuracy is as high as 98.61%.

[0058] The method of the embodiment perfects the test content of quality control in the production process of the asphalt mixture, and has important significance for controlling the production quality of the asphalt mixture and ensuring the engineering quality.

[0059] The above description is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements can be made, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A method for determining the amount of recycled powder in asphalt mixtures, characterized in that, Includes the following steps: S1. Preparation of experimental mineral powder and recycled powder The mineral powder and recycled powder used in the production of asphalt mixtures are passed through a sieve with a 0.075mm aperture to obtain mineral powder A and recycled powder A. S2. Obtain granularity distribution The particle size distribution of mineral powder A and recovered powder A was obtained using a laser particle size analyzer. S3. Determine the reference particle size The reference particle size is determined based on the particle size distribution, when the difference in the percentage of particles passing through mineral powder A and recycled powder A is the largest at a certain particle size. S4. Preparation of asphalt mixture Asphalt mixtures with different recycled powder contents were prepared according to the design mix proportions, where: Mixture A: recycled powder accounts for 0% of the total filler content; Mixture B: recycled powder accounts for 5% of the total filler content; Mixture C: recycled powder accounts for 25% of the total filler content; Mixture D: recycled powder accounts for 50% of the total filler content; Mixture E: recycled powder accounts for 75% of the total filler content; and Mixture F: recycled powder accounts for 100% of the total filler content. S5. Preparation of extraction powder The prepared asphalt mixture was filtered and the filler was separated by high-speed centrifugation using a fully automatic asphalt extractor. After extraction and separation, extract powder A, extract powder B, extract powder C, extract powder D, extract powder E, and extract powder F were obtained. S6. Determine the standard working curve The percentage of particles passing through extract powders A, B, C, D, E, and F at a reference particle size was obtained using a laser particle size analyzer; a standard working curve equation was fitted based on the percentage of particles passing through at the reference particle size. S7. Sample preparation and determination of recovered powder content Asphalt mixtures with different recycled powder contents were prepared according to the design mix proportions: Mixture A1: recycled powder accounts for 10% of the total filler volume; Mixture B1: recycled powder accounts for 30% of the total filler volume; Mixture C1: recycled powder accounts for 60% of the total filler volume. The percentage of passing particles at the reference particle size of mixtures A1, B1, and C1 was obtained using a fully automatic extractor and a laser particle size analyzer. The percentage of recycled powder in the asphalt mixture was then substituted into the standard working curve equation from the previous step to obtain the amount of recycled powder in the asphalt mixture.

2. The method for determining the amount of recycled powder in asphalt mixtures as described in claim 1, characterized in that, In step S2, the dispersion concentration of the laser particle size analyzer is controlled between 0.25 and 0.45 g / L, the continuous mixing rate is 2200–2500 r / min, and the duration is 15 minutes. Distilled water is used as the dispersion medium.

3. The method for determining the amount of recycled powder in asphalt mixtures as described in claim 2, characterized in that, In step S2, the particle size distribution of mineral powder A and recycled powder A is measured three times in parallel, and the average value of the results is taken.

4. The method for determining the amount of recycled powder in asphalt mixtures as described in claim 1, characterized in that, The minimum aperture screen of the fully automatic asphalt extractor described in step S5 is 0.075 mm.

5. The method for determining the amount of recycled powder in asphalt mixtures as described in claim 1, characterized in that, In step S5, the asphalt mixtures with different amounts of recycled powder are soaked in trichloroethylene solution for 0.5 hours before extraction and thoroughly stirred with a glass rod.

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