A design method for reducing real gradation of asphalt mortar in asphalt mixture

Abstract

This invention discloses a design method for reproducing the true gradation of asphalt mortar in asphalt mixtures, comprising the following steps: screening, washing, and density determination of coarse aggregates; performing three-dimensional blue light scanning on the washed coarse aggregates according to different grades; importing the scanned data into three-dimensional software to obtain the median and minor axes and aggregate surface area of ​​the minimum bounding box; fitting the obtained major, median, and minor axes and specific surface area to obtain a normal distribution function; weighing the mass of aggregates at each grade and obtaining an average mass stability curve; obtaining the gradation of the target asphalt mixture using the Marshall design method; and calculating the mix proportion of asphalt mortar according to the model and formula proposed in this invention. The gradation design method of this invention can reproduce the distribution ratio of fine aggregates, asphalt, and mineral powder in asphalt mortar of asphalt mixtures, solving the current problem of unclear asphalt and mineral powder dosages in asphalt mortar preparation.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, and in particular relates to a design method for the true gradation of asphalt mortar in reduced asphalt mixtures. Background Technology

[0002] Asphalt pavement, due to its driving comfort and relatively short construction period, is widely used in the construction of high-grade highways in my country. However, with the continuous increase in traffic volume and the diversity of regional climates, the actual service life of asphalt pavement in my country is generally lower than the design expectation. Drawing on the Materials Genome Initiative, asphalt mortar, as the main component of asphalt mixtures that bears the load-bearing deformation, plays a crucial role in the fatigue performance of the mixture and has become the main focus of current micro-scale research on asphalt mixtures. In-depth research on asphalt mortar can more stably predict the fatigue performance of asphalt mixtures. Currently, it is generally accepted that the gradation of asphalt mortar should be related to the gradation of the target asphalt mixture, and the gradation design of asphalt mortar directly affects the accuracy of its prediction of the service life of the asphalt mixture. However, a unified standard has not yet been established for how to extract the gradation of asphalt mortar from the target asphalt mixture. Therefore, it is necessary to develop a design method that restores the true gradation of asphalt mortar in asphalt mixtures to ensure better stability and accuracy in predicting pavement service life using asphalt mortar. Summary of the Invention

[0003] The main objective of this invention is to provide a design method for the true gradation of asphalt mortar in asphalt mixtures, aiming to accurately reproduce the distribution ratio of fine aggregates, asphalt and mineral powder in asphalt mortar in asphalt mixtures, and to solve the problem of unclear asphalt and mineral powder dosage in the current preparation of asphalt mortar.

[0004] Therefore, the present invention provides a method for designing the true gradation of asphalt mortar in exothermic reducing asphalt mixtures, comprising the following steps:

[0005] S1. Screen the coarse aggregate and divide it into multiple grades according to different particle sizes. After washing and drying the screened coarse aggregate, measure its apparent density and bulk density.

[0006] S2. Perform three-dimensional blue light scanning on the cleaned coarse aggregate according to different grades;

[0007] S3. Import the scanned data into the 3D visualization software to obtain the major, middle, and minor axes of the minimum bounding box of the aggregate, as well as the surface area and volume information of the aggregate.

[0008] S4. Normal distribution fitting is performed on the long, medium and short axes of aggregates of different grades to obtain the axis length normal distribution function, and the best fitting effect is selected as the particle size characterization index of that grade.

[0009] S5. Based on the obtained volume information and apparent density, calculate the mass of each aggregate in each grade, and calculate the specific surface area of ​​each aggregate in combination with the surface area.

[0010] S6. Fit the particle size characterization index of each grade of aggregate with the specific surface area of ​​all aggregates to obtain the axis length-specific surface area function of different characterization indexes.

[0011] S7. Weigh coarse aggregates of different grades, record the data and form an average mass fluctuation chart. Select the average mass after the critical value with small variation and average it to determine the average mass of the aggregate of that grade.

[0012] S8. Determine the gradation of the target asphalt mixture and the mass distribution table of a specimen using the Marshall design method;

[0013] S9. Divide the mass of the coarse aggregate corresponding to the mass distribution table of a specimen by the average mass to obtain the average number of aggregates in that grade.

[0014] S10. Calculate the surface area of ​​the aggregate at each grade using the following formula;

[0015]

[0016] S - The sum of the surface areas of this gear position;

[0017] f(x) - the normal distribution function of the axis length of this gear;

[0018] G(x) is a function of the axis length and specific surface area of ​​this gear position.

[0019] m i - Average quality for this gear;

[0020] y i - Average number of aggregates in this grade;

[0021] S11. Calculate the mass of asphalt absorbed by the aggregate at each grade.

[0022] S12. Calculate the asphalt mass of the pure asphalt layer;

[0023] S13. Calculate the quality of asphalt and mineral powder in the mortar layer;

[0024] S14. Remove the corresponding asphalt and mineral powder from the asphalt mixture specimens. Remove the coarse aggregate according to the target maximum particle size of the asphalt mortar. The remaining fine aggregate is used to form a gradation curve according to the principle of proportional scaling.

[0025] Specifically, based on the apparent density and bulk density of the aggregate, the absorption coefficient C of the aggregate is calculated, and the mass of asphalt absorbed by the aggregate at each grade is calculated using the following formula:

[0026] γse =C×γ sa +(1-C)×γ sb

[0027]

[0028] In the formula: γ se —The effective relative density of the synthetic mineral, dimensionless;

[0029] C—asphalt absorption coefficient;

[0030] w x —Water absorption rate of synthetic mineral materials;

[0031] γ sa —Relative apparent density of mineral aggregates;

[0032] γ sb —Relative bulk density of mineral aggregates;

[0033]

[0034] Y 吸 -Asphalt absorption capacity at this gear level;

[0035] M i - The mass of this grade in a test piece;

[0036] ρ 毛 - The bulk density of the aggregate in this grade;

[0037] ρ 表 - The apparent density of the aggregate in this grade;

[0038] ρ 沥 - Density of asphalt, at 25℃.

[0039] Specifically, assuming the aggregate surface area is a plane, calculate the total coarse aggregate surface area S that needs to be reduced. 总 The mass of asphalt in a pure asphalt layer is calculated using the following formula:

[0040] m 纯-沥 =S 总 ×h 纯 ×ρ 沥

[0041] m 纯-沥 - The quality of the pure asphalt layer outside the coarse aggregate that needs to be removed;

[0042] h 纯 - The thickness of the pure asphalt layer.

[0043] Specifically, the quality of asphalt and mineral powder in the adhesive layer is calculated according to the following formula;

[0044] m沥 =M 沥 -Y 吸 -m 纯-沥

[0045]

[0046] m 沥 - The bitumen content in areas of the specimen that do not contain mineral powder;

[0047] FB - Pure Powder Glue Ratio;

[0048] h 胶 - Thickness of the adhesive layer;

[0049] m 胶-矿 - The mass of mineral powder in the mortar layer;

[0050] m 胶-沥 - The quality of asphalt in the mortar layer.

[0051] Specifically, the corresponding asphalt mass of the asphalt mixture specimen is Y. 吸 +m 纯-沥 +m 胶-沥 The mineral powder is m 胶-矿 .

[0052] Specifically, the 3D visualization software used is Avizo.

[0053] Specifically, the apparent density and bulk density of coarse aggregates at different grades were determined using the basket method.

[0054] Specifically, the screened coarse aggregate is divided into four grades: 2.36-4.75mm, 4.75-9.5mm, 9.5-13.2mm, and 13.2-16mm.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] 1. In the calculation of the surface area of ​​coarse aggregate, the large differences in particle size and surface area of ​​coarse aggregate in the same grade of sieve commonly used in China were taken into consideration, and a more detailed division of coarse aggregate in the same grade was made.

[0057] 2. In the gradation calculation of asphalt mortar, the effects of coarse aggregate surface morphology, asphalt layer on asphalt reduction, and density difference between the mortar layer and the asphalt layer were considered.

[0058] 3. By using three-dimensional blue light scanning and the auxiliary flipping device provided by this invention, precise scanning of irregular objects is achieved. Combined with a high-precision balance, the fluctuation curves of coarse aggregate quality at each grade are obtained. The resulting asphalt mortar gradation can better match the actual material distribution of asphalt mortar in the target asphalt mixture.

[0059] In summary, the gradation design method of the present invention can restore the distribution ratio of fine aggregates, asphalt and mineral powder in asphalt mortar in asphalt mixtures, and solve the problem of unclear asphalt and mineral powder dosage in the current preparation of asphalt mortar. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0061] Figure 1 This is the coarse aggregate interface reduction model of the present invention;

[0062] Figure 2 This is a three-axis schematic diagram of the minimum enclosure box for coarse aggregates provided in an embodiment of the present invention;

[0063] Figure 3 This is a diagram showing the axis length distribution provided in an embodiment of the present invention;

[0064] Figure 4 This is the axis length-specific surface area fitting function provided in the embodiments of the present invention;

[0065] Figure 5 This is a graph showing the average mass fluctuation of aggregates provided in an embodiment of the present invention. Detailed Implementation

[0066] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0067] The method for designing the true gradation of asphalt mortar in reduced asphalt mixtures provided in this embodiment specifically includes the following steps:

[0068] S1, 1500g of coarse aggregate in four grades (2.36-4.75mm, 4.75-9.5mm, 9.5-13.2mm, and 13.2-16mm) were screened out. After washing and drying, the apparent density and bulk density of the coarse aggregate in different grades were determined by the basket method. The density of each grade calculated in this case is shown in the table below.

[0069] Table 1. Coarse Aggregate Density Table

[0070]

[0071] S2. After the density of the four grades of coarse aggregate is measured, it is dried. Then, 120 pieces of coarse aggregate from each of the four grades are selected using the quartering method and three-dimensional blue light scanning is performed according to the above steps to form STL files for the four grades. The surface area and volume information of coarse aggregate obtained by combining three-dimensional blue light with Avizo software is more accurate.

[0072] S3. Import the STL files for the four grades into Avizo software, and execute the commands convert geometry to label, label analysis, spreadsheet to point cloud, and line set to spatial graph in sequence to obtain the major, minor, and intermediate axis lengths of the minimum bounding box for each aggregate in the four grades (e.g., ...). Figure 2 ) and surface area and volume information;

[0073] S4. Normal distribution fitting is performed on the long, medium, and short axes of aggregates at different grades to obtain the axis length normal distribution function f(x). The function with the best fitting effect is selected as the particle size characterization index for that grade. In this case, the medium axis of the smallest bounding box is determined as the particle size characterization index for the 13.2-16mm and 2.36-4.75mm grades, and the short axis is determined as the characterization index for the 9.5-13.2mm and 4.75-9.5mm grades. An example is shown below. Figure 3 ;

[0074] S5, the mass of each aggregate in the four grades is calculated by combining the volume obtained by Avizo with the apparent density measured by S1, and the specific surface area of ​​each aggregate is calculated by combining the surface area.

[0075] S6, fit the particle size characterization index of each aggregate grade to the specific surface area of ​​all aggregates to obtain the axis length-specific surface area function g(x) for different characterization indices, as shown in the example. Figure 4 ;

[0076] S7. Using a high-precision scale, weigh the coarse aggregate at four different speeds, record the mass data, and generate an average mass fluctuation chart. (Example shown). Figure 5 The average mass m of the aggregate at that grade is determined by averaging the average mass after selecting a critical value with a small number of variations. i The average mass of each gear calculated in this case is shown in the table below;

[0077] Table 2 Average Quality of Each Grade

[0078]

[0079] S8. The gradation of OGFC-13 and the mass distribution of a rotary compacted specimen were determined by the Marshall design method, as shown in the table below. The asphalt-aggregate ratio is 5.1% and the asphalt content is 85.43g.

[0080] Table 3 OGFC-13 Gradation and Specimen Usage Table

[0081]

[0082] S9. Divide the mass of the coarse aggregate corresponding to the mass distribution table of a specimen by the average mass m to obtain the average number y of aggregates in that grade. i The average number of aggregates calculated in this case is shown in the table below:

[0083] Table 4 Average Quantity of Coarse Aggregate in OGFC-13

[0084]

[0085] S10, calculate the sum of the surface areas of the aggregates in the four gear positions according to the formula proposed in this invention;

[0086]

[0087] S - The sum of the surface areas of this gear position;

[0088] f(x) - the normal distribution function of the axis length of this gear;

[0089] G(x) is a function of the axis length and specific surface area of ​​this gear position.

[0090] m i -The average quality of the i-th gear;

[0091] y i -Average number of aggregates in the i-th grade;

[0092] x represents the axis length;

[0093] The calculated surface areas for each gear position in this case are shown in the table below:

[0094] Table 5 Total Surface Area of ​​Coarse Aggregate in OGFC-13 at Various Grades

[0095]

[0096] S11. Based on the apparent density and bulk density of the aggregate in S1, and referring to the formula in the standard JTG E20-2011, the absorption coefficient C of the aggregate is calculated to be 0.5471. The mass of asphalt absorbed by the aggregate in each grade is calculated with reference to the following formula.

[0097] γ se =C×γ sa +(1-C)×γ sb

[0098]

[0099] In the formula: γ se —The effective relative density of the synthetic mineral, dimensionless;

[0100] C—asphalt absorption coefficient;

[0101] w x —Water absorption rate of synthetic mineral materials;

[0102] γ sa —Relative apparent density of mineral aggregates;

[0103] γ sb —Relative bulk density of mineral aggregates;

[0104]

[0105] Y 吸 -Asphalt absorption capacity at this gear level;

[0106] M i - The mass of a specimen in that grade (the i-th grade);

[0107] ρ 毛 - The bulk density of the aggregate in this grade;

[0108] ρ 表 - The apparent density of the aggregate in this grade;

[0109] ρ 沥 - Density of asphalt, at 25℃;

[0110] The calculated asphalt absorption capacity of coarse aggregate in this case is shown in the table below:

[0111] Table 6 Asphalt Absorption Mass of OGFC-13 Coarse Aggregate at Different Grades

[0112]

[0113] S12, such as Figure 1 As shown, based on the aggregate interface reduction model assumed in this invention, the aggregate surface area is assumed to be planar, and the total coarse aggregate surface area S that needs to be reduced is calculated. 总 The asphalt quality of a pure asphalt layer is calculated using the following formula.

[0114] m 纯-沥 =S 总 ×h 纯 ×ρ 沥

[0115] m 纯-沥 - The quality of the pure asphalt layer outside the coarse aggregate that needs to be removed;

[0116] h 纯 -Thickness of the pure asphalt layer;

[0117] The calculated quality of the pure asphalt layer in this case is shown in the table below:

[0118] Table 7. Quality of Pure Asphalt Layer for Each Grade of OGFC-13 Coarse Aggregate

[0119]

[0120] S13. Calculate the mass of asphalt and mineral powder in the mortar layer according to the following formula;

[0121] m 沥 =M 沥 -Y 吸 -m 纯-沥

[0122]

[0123] m 沥 - The bitumen content in areas of the specimen that do not contain mineral powder;

[0124] FB - Pure Powder Glue Ratio;

[0125] h 胶 - Thickness of the adhesive layer;

[0126] m 胶-矿 - The mass of mineral powder in the mortar layer;

[0127] m 胶-沥 - The quality of asphalt in the mortar layer;

[0128] In this case, the calculated powder-to-rubber ratio (FB) is 1.415. At this powder-to-rubber ratio, the density of the asphalt mastic is constant, and the calculated density is 1.622 g / cm³. 3 After obtaining the powder-to-binder ratio and the asphalt mastic, the mass of asphalt and mineral powder in the mastic layer can be calculated using the above formula, as shown in the table below:

[0129] Table 8. Quality of Asphalt and Mineral Powder in the Latex Layer for Each Grade of OGFC-13 Coarse Aggregate

[0130]

[0131] S14. In this case, the gradation calculations were performed for asphalt mortars with maximum particle sizes of 1.18, 2.36, and 4.75 mm, respectively. Following the steps described above, the corresponding asphalt and mineral powder in the asphalt mixture specimens were removed. The asphalt mass is Y. 吸 +m 纯-沥 +m 胶-沥 The mineral powder is m 胶-矿Based on the target maximum particle size of the asphalt mortar, coarse aggregates are removed accordingly, and the remaining fine aggregates are scaled up proportionally to form a gradation curve. The final asphalt mortar gradation is shown in the table below:

[0132] Table 9 shows the asphalt mortar gradation for different maximum particle sizes in OGFC-13.

[0133] Compared with the prior art, the present invention has the following beneficial effects:

[0134] 1. In the calculation of the surface area of ​​coarse aggregate, the large differences in particle size and surface area of ​​coarse aggregate in the same grade of sieve commonly used in China were taken into consideration, and a more detailed division of coarse aggregate in the same grade was made.

[0135] 2. In the gradation calculation of asphalt mortar, the effects of coarse aggregate surface morphology, asphalt layer on asphalt reduction, and density difference between the mortar layer and the asphalt layer were considered.

[0136] 3. By using three-dimensional blue light scanning and the auxiliary flipping device provided by this invention, precise scanning of irregular objects is achieved. Combined with a high-precision balance, the fluctuation curves of coarse aggregate quality at each grade are obtained. The resulting asphalt mortar gradation can better match the actual material distribution of asphalt mortar in the target asphalt mixture.

[0137] The multi-layer enclosed model of coarse aggregate-asphalt-asphalt binder-asphalt mortar provided by this invention can reflect the true proportion of fine aggregate, asphalt binder and mineral powder in asphalt mortar by reducing the asphalt and mineral powder in the outer layer of coarse aggregate.

[0138] For those skilled in the art, various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for designing the true gradation of asphalt mortar in a reduced asphalt mixture, characterized in that, Includes the following steps: S1. Screen the coarse aggregate and divide it into multiple grades according to different particle sizes. After washing and drying the screened coarse aggregate, measure its apparent density and bulk density. S2. Perform three-dimensional blue light scanning on the cleaned coarse aggregate according to different grades; S3. Import the scanned data into the 3D visualization software to obtain the major, middle, and minor axes of the minimum bounding box of the aggregate, as well as the surface area and volume information of the aggregate. S4. Normal distribution fitting is performed on the long, medium and short axes of aggregates of different grades to obtain the axis length normal distribution function, and the best fitting effect is selected as the particle size characterization index of that grade. S5. Based on the obtained volume information and apparent density, calculate the mass of each aggregate in each grade, and calculate the specific surface area of ​​each aggregate in combination with the surface area. S6. Fit the particle size characterization index of each grade of aggregate with the specific surface area of ​​all aggregates to obtain the axis length-specific surface area function of different characterization indexes. S7. Weigh coarse aggregates of different grades, record the data and form an average mass fluctuation chart. Select the average mass after the critical value with small variation and average it to determine the average mass of the aggregate of that grade. S8. Determine the gradation of the target asphalt mixture and the mass distribution table of a specimen using the Marshall design method; S9. Divide the mass of the coarse aggregate corresponding to the mass distribution table of a specimen by the average mass to obtain the average number of aggregates in that grade. S10. Calculate the surface area of ​​the aggregate at each grade using the following formula; S - The sum of the surface areas of this gear position; f(x) - the normal distribution function of the axis length of this gear; G(x) is a function of the axis length and specific surface area of ​​this gear position. m i - Average quality for this gear; y i - Average number of aggregates in this grade; S11. Calculate the mass of asphalt absorbed by the aggregate at each grade. S12. Calculate the asphalt mass of the pure asphalt layer; S13. Calculate the quality of asphalt and mineral powder in the mortar layer; S14. Remove the corresponding asphalt and mineral powder from the asphalt mixture specimens. Remove the coarse aggregate according to the target maximum particle size of the asphalt mortar. The remaining fine aggregate is used to form a gradation curve according to the principle of proportional scaling.

2. The design method according to claim 1, characterized in that: Based on the apparent density and bulk density of the aggregate, the absorption coefficient C of the aggregate is calculated, and the mass of asphalt absorbed by the aggregate at each grade is calculated using the following formula: c se =C×γ sa +(1-C)×γ sb In the formula: γ se —The effective relative density of the synthetic mineral, dimensionless; C—asphalt absorption coefficient; w x —Water absorption rate of synthetic mineral materials; γ sa —Relative apparent density of mineral aggregates; γ sb —Relative bulk density of mineral aggregates; Y 吸 -Asphalt absorption capacity at this gear level; M i - The mass of aggregate of that grade in a specimen; ρ 毛 - The bulk density of the aggregate in this grade; ρ 表 - The apparent density of the aggregate in this grade; ρ 沥 - Density of asphalt, at 25℃.

3. The design method according to claim 2, characterized in that: Assuming the aggregate surface area is planar, calculate the total coarse aggregate surface area S that needs to be reduced. 总 The mass of asphalt in a pure asphalt layer is calculated using the following formula: m 纯-沥 =S 总 ×h 纯 ×ρ 沥 m 纯-沥 - The quality of the pure asphalt layer outside the coarse aggregate that needs to be removed; h 纯 - The thickness of the pure asphalt layer.

4. The design method according to claim 3, characterized in that: Calculate the quality of asphalt and mineral powder in the mortar layer using the following formula; m 沥 - The bitumen content in areas of the specimen that do not contain mineral powder; FB - Pure Powder Glue Ratio; h 胶 - Thickness of the adhesive layer; m 胶-矿 - The mass of mineral powder in the mortar layer; m 胶-沥 - The quality of asphalt in the mortar layer.

5. The design method according to claim 4, characterized in that: asphalt The corresponding asphalt mass of the mixture specimen is Y. 吸 +m 纯-沥 +m 胶-沥 .

6. The design method according to any one of claims 1-5, characterized in that: The 3D visualization software used is Avizo.

7. The design method according to any one of claims 1-5, characterized in that: The apparent density and bulk density of coarse aggregates of different grades were determined by basket method.

8. The design method according to any one of claims 1-5, characterized in that: The screened coarse aggregate is divided into four grades: 2.36-4.75mm, 4.75-9.5mm, 9.5-13.2mm, and 13.2-16mm.

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