Design method for real gradation of asphalt mortar in reduced asphalt mixture

Abstract

The invention discloses a design method for real gradation of asphalt mortar in a reduced asphalt mixture. The design method comprises the following steps: screening and cleaning coarse aggregate and measuring the density of the coarse aggregate; performing three-dimensional blue light scanning on the cleaned coarse aggregate according to different gears; data obtained through scanning are imported into three-dimensional software, and the medium axis, the short axis and the aggregate surface area of the minimum bounding box are obtained; fitting the obtained long, medium and short axes with the specific surface area to obtain a normal distribution function; weighing the mass of the aggregate of each gear and obtaining an average mass stability curve; gradation of the target asphalt mixture is obtained through a Marshall design method; the mix proportion of the asphalt mortar is obtained through calculation according to the model and the formula provided by the invention. According to the gradation design method, the distribution proportion of the fine aggregate, asphalt and mineral powder of the asphalt mortar in the asphalt mixture can be reduced, and the problem that the use amount of the asphalt and the mineral powder is not clear in the preparation of the asphalt mortar at present is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering, and in particular relates to a design method for the real gradation of asphalt mortar in a reduced asphalt mixture. Background Art

[0002] Asphalt pavement is widely used in the construction of high-grade highways in my country due to its driving comfort and short construction period. However, with the continuous increase in traffic volume and the diversity of regional climate, the actual service life of asphalt pavement in my country is generally lower than the design expectation. Drawing on the Material Genome Project, asphalt mortar, which is the main load-bearing deformation in asphalt mixture, plays a vital role in the fatigue performance of the mixture and has become the main object of the current mesoscale research on asphalt mixture. Through in-depth research on asphalt mortar, the fatigue performance of asphalt mixture can be predicted more stably. At present, it is generally recognized 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 its accuracy in predicting the service life of asphalt mixture, but how to extract the gradation of asphalt mortar according to the target asphalt mixture has not yet formed a unified standard. Therefore, it is necessary to develop a design method to restore the real gradation of asphalt mortar in asphalt mixture to ensure better stability and accuracy in predicting the service life of pavement using asphalt mortar. Summary of the invention

[0003] The main purpose of the present invention is to provide a design method for restoring the true gradation of asphalt mortar in asphalt mixture, aiming to accurately restore the distribution ratio of fine aggregate, asphalt and mineral powder in asphalt mortar in asphalt mixture, and solve the current problem of unclear dosage of asphalt and mineral powder in the preparation of asphalt mortar.

[0004] To this end, the present invention provides a method for designing the real gradation of asphalt mortar in an exothermic reduction asphalt mixture, comprising the following steps:

[0005] S1. Screening the coarse aggregate and dividing it into multiple gears according to different particle sizes, washing and drying the screened coarse aggregate, and then measuring the apparent density and bulk density;

[0006] S2, performing three-dimensional blue light scanning on the cleaned coarse aggregate according to different gears;

[0007] S3, import the scanned data into the 3D visualization software to obtain the long, medium and short axes of the minimum bounding box of the aggregate and the surface area and volume information of the aggregate;

[0008] S4. Perform normal distribution fitting on the long, medium and short axes of aggregates at different gears and obtain the normal distribution function of axis length, and select the one with the best fitting effect as the particle size characterization index of the gear;

[0009] S5. Calculate the mass of each aggregate in each gear according to the obtained volume information and apparent density, and calculate the specific surface area of ​​each aggregate in combination with the surface area;

[0010] S6. Fitting the particle size characterization index of each gear aggregate and the specific surface area of ​​all aggregates to obtain the axis length-specific surface area function of different characterization indexes;

[0011] S7, weigh the coarse aggregates at different levels, record the data to form an average mass fluctuation diagram, and average the average mass after the critical value with a small variance to determine the average mass of the aggregate at that level;

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

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

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

[0015]

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

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

[0018] G(x) - axis length of the gear - specific surface area function;

[0019] m i -The average quality of the gear;

[0020] y i -The average number of aggregates in this gear;

[0021] S11. Calculate the mass of asphalt absorbed by each level of aggregate;

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

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

[0024] S14. The corresponding asphalt and mineral powder of the asphalt mixture specimen are removed, and the coarse aggregate is removed accordingly according to the asphalt mortar with the target maximum particle size. The remaining fine aggregate is formed into a grading curve according to the principle of equal proportion amplification.

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

[0026] γse =C×γ sa +(1-C)×γ sb

[0027]

[0028] Where: γ se —effective relative density of synthetic ore, dimensionless;

[0029] C—asphalt absorption coefficient;

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

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

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

[0033]

[0034] Y 吸 -The asphalt absorption quality at this gear;

[0035] M i -The mass of the gear in a test piece;

[0036] ρ 毛 - The bulk density of the aggregate at this level;

[0037] ρ 表 - the apparent density of the aggregate at this level;

[0038] ρ 沥 - Density of bitumen, 25°C.

[0039] Specifically, the aggregate surface area is assumed to be a plane, and the total surface area of ​​the coarse aggregate that needs to be reduced is calculated as S 总 , the asphalt mass of the pure asphalt layer is calculated by the following formula:

[0040] m 纯-沥 =S 总 ×h 纯 ×ρ 沥

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

[0042] h 纯 -Thickness of the pure bitumen layer.

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

[0044] m沥 =M 沥 -Y 吸 -M 纯

[0045]

[0046] m 沥 - The asphalt content in the area of ​​the specimen that does not contain mineral powder;

[0047] FB-pure powder-rubber ratio;

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

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

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

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

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

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

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

[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 coarse aggregate in the same sieve hole currently used in China still has large differences in particle size and surface area, and the coarse aggregate in the same sieve hole is divided more finely;

[0057] 2. In the calculation of asphalt mortar gradation, the surface morphology of coarse aggregate, the influence of asphalt layer on asphalt reduction, and the difference in density between the mortar layer and the asphalt layer are taken into account;

[0058] 3. Accurate scanning of irregular objects is achieved through three-dimensional blue light scanning and the auxiliary flipping device provided by the present invention. The fluctuation curve of the mass of coarse aggregate at each gear is obtained in combination with a high-precision balance. The obtained asphalt mortar grading can better meet the actual material distribution of asphalt mortar in the target asphalt mixture.

[0059] In summary, the grading design method of the present invention can restore the distribution ratio of fine aggregate, asphalt and mineral powder in asphalt mortar in asphalt mixture, and solve the current problem of unclear dosage of asphalt and mineral powder in the preparation of asphalt mortar. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

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

[0062] Figure 2 is a three-axis schematic diagram of the minimum bounding box of coarse aggregate provided by an embodiment of the present invention;

[0063] Figure 3 is an axial length distribution diagram provided by an embodiment of the present invention;

[0064] Figure 4 is the axial length-specific surface area fitting function provided by an embodiment of the present invention;

[0065] Figure 5 It is a graph of average aggregate mass fluctuation provided by an embodiment of the present invention. DETAILED DESCRIPTION

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

[0067] The design method of the real gradation of asphalt mortar in the reduced asphalt mixture provided in this embodiment specifically includes the following steps:

[0068] S1, 1500g of coarse aggregate of four grades of 2.36-4.75mm, 4.75-9.5mm, 9.5-13.2mm and 13.2-16mm were screened out, washed and dried, and the apparent density and bulk density of coarse aggregate of different grades were measured 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

[0070]

[0071] S2. Dry the four levels of coarse aggregate after the density is measured, and use the quartering method to select 120 coarse aggregates from each of the four levels for three-dimensional blue-light scanning according to the above steps to form STL files of the four levels. The surface area and volume information of the coarse aggregate calculated by three-dimensional blue-light combined with Avizo software is more accurate.

[0072] S3, import the STL files of the above four gears 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 long, medium, and short axis lengths of the minimum bounding box of each aggregate in the four gears (such as Figure 2 ) and surface area and volume information;

[0073] S4, normal distribution fitting is performed on the long, middle and short axes of aggregates at different levels respectively to obtain the normal distribution function f(x) of the axis length, and the one with the best fitting effect is selected as the particle size characterization index of the level. In this case, the middle axis of the minimum bounding box is determined as the particle size characterization index of the two levels of 13.2-16mm and 2.36-4.75mm, and the short axis is determined as the characterization index of the two levels of 9.5-13.2mm and 4.75-9.5mm. For example, Figure 3 ;

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

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

[0076] S7, use a high-precision scale to weigh the coarse aggregate at four levels respectively, record the quality data and form an average quality fluctuation graph, as shown in the following example: Figure 5 , the average mass after selecting the critical value with the smallest variance is averaged to determine the average mass m of the aggregate at this gear i , the average mass of each gear calculated in this case is shown in the following table;

[0077] Table 2 Average quality of each gear

[0078]

[0079] S8, the gradation of OGFC-13 and the mass distribution table of a rotary compaction specimen were determined by the Marshall design method, as shown in the following table, the oil-stone ratio is 5.1%, and the asphalt dosage is 85.43g;

[0080] Table 3 OGFC-13 gradation and test piece dosage

[0081]

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

[0083] Table 4 Average quantity of coarse aggregate in OGFC-13

[0084]

[0085] S10, calculating the sum of the surface areas of the aggregates in the four gears according to the formula proposed by the present invention;

[0086]

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

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

[0089] G(x) - axis length of the gear - specific surface area function;

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

[0091] y i -The average number of aggregates in the i-th gear;

[0092] x represents the axis length;

[0093] The surface areas of each gear calculated in this case are shown in the following table:

[0094] Table 5 Total surface area of ​​each level of OGFC-13 coarse aggregate

[0095]

[0096] S11. According to the apparent density and bulk density of the aggregate in S1, the absorption coefficient C of the aggregate is calculated as 0.5471 with reference to the formula in the specification JTG E20-2011. The mass of asphalt absorbed by each level of aggregate is calculated with reference to the following formula;

[0097] γ se =C×γ sa +(1-C)×γ sb

[0098]

[0099] Where: γ se —effective relative density of synthetic ore, dimensionless;

[0100] C—asphalt absorption coefficient;

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

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

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

[0104]

[0105] Y 吸 -The asphalt absorption quality at this gear;

[0106] M i -The mass of the gear (i-th gear) in a test piece;

[0107] ρ 毛 - The bulk density of the aggregate at this level;

[0108] ρ 表 - the apparent density of the aggregate at this level;

[0109] ρ 沥 - Density of asphalt, 25°C;

[0110] The asphalt absorption quality of coarse aggregate calculated in this case is as follows:

[0111] Table 6 Asphalt absorption quality of each level of OGFC-13 coarse aggregate

[0112]

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

[0114] m 纯-沥 =S 总 ×h 纯 ×ρ 沥

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

[0116] h 纯 -thickness of the pure bitumen layer;

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

[0118] Table 7 Quality of pure asphalt layer at each level 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

[0122]

[0123] m 沥 - The asphalt content in the area of ​​the specimen that does not contain mineral powder;

[0124] FB-pure powder-rubber ratio;

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

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

[0127] m 胶-沥 - Quality of asphalt in the mastic layer;

[0128] The powder-rubber FB calculated in this case is 1.415. The density of asphalt mortar under this powder-rubber ratio is fixed. The density of asphalt mortar can be calculated to be 1.622 g / cm 3 After obtaining the powder-rubber analog asphalt mortar, the mass of asphalt and mineral powder in the mortar layer can be calculated by the above formula, see the table below:

[0129] Table 8 Asphalt and mineral powder quality of mortar layer at each level of OGFC-13 coarse aggregate

[0130]

[0131] S14. In this case, the gradation of asphalt mortar with maximum particle sizes of 1.18, 2.36 and 4.75 mm is calculated respectively. According to the above steps, the corresponding asphalt and mineral powder are removed from the asphalt mixture specimens. The asphalt quality is Y 吸 +m 纯-沥 +m 胶-沥 , mineral powder is m 胶-矿According to the target maximum particle size of asphalt mortar, the coarse aggregate is removed accordingly, and the remaining fine aggregate is enlarged in proportion to form a gradation curve. The final asphalt mortar gradation is shown in the following table:

[0132] Table 9 Asphalt mortar gradation with different maximum particle sizes in OGFC-13

[0133]

[0134] Compared with the prior art, the present invention has the following beneficial effects:

[0135] 1. In the calculation of the surface area of ​​coarse aggregate, the coarse aggregate in the same sieve hole currently used in China still has large differences in particle size and surface area, and the coarse aggregate in the same sieve hole is divided more finely;

[0136] 2. In the calculation of asphalt mortar gradation, the surface morphology of coarse aggregate, the influence of asphalt layer on asphalt reduction, and the difference in density between the mortar layer and the asphalt layer are taken into account;

[0137] 3. Accurate scanning of irregular objects is achieved through three-dimensional blue light scanning and the auxiliary flipping device provided by the present invention. The fluctuation curve of the mass of coarse aggregate at each gear is obtained in combination with a high-precision balance. The obtained asphalt mortar grading can better meet the actual material distribution of asphalt mortar in the target asphalt mixture.

[0138] The coarse aggregate-asphalt-asphalt mortar-asphalt mortar multi-layer enclosure model provided by the present invention can reflect the real proportion of fine aggregate, asphalt binder and mineral powder in the asphalt mortar in the asphalt mixture by reducing the asphalt and mineral powder in the outer layer of the coarse aggregate to obtain the asphalt mortar gradation.

[0139] For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. However, obvious changes or modifications derived from this are still within the protection scope of the present invention.

Claims

1. A method for designing the real gradation of asphalt mortar in reduced asphalt mixture, characterized in that: The steps include: S1. Screening the coarse aggregate and dividing it into multiple gears according to different particle sizes, washing and drying the screened coarse aggregate, and then measuring the apparent density and bulk density; S2, performing three-dimensional blue light scanning on the cleaned coarse aggregate according to different gears; S3, import the scanned data into the 3D visualization software to obtain the long, medium and short axes of the minimum bounding box of the aggregate and the surface area and volume information of the aggregate; S4. Perform normal distribution fitting on the long, medium and short axes of aggregates at different gears and obtain the normal distribution function of axis length, and select the one with the best fitting effect as the particle size characterization index of the gear; S5. Calculate the mass of each aggregate in each gear according to the obtained volume information and apparent density, and calculate the specific surface area of ​​each aggregate in combination with the surface area; S6. Fitting the particle size characterization index of each gear aggregate and the specific surface area of ​​all aggregates to obtain the axis length-specific surface area function of different characterization indexes; S7, weigh the coarse aggregates at different levels, record the data to form an average mass fluctuation diagram, and average the average mass after the critical value with a small variance to determine the average mass of the aggregate at that level; S8. Determine the gradation of the target asphalt mixture and the mass distribution table of a specimen by the Marshall design method; S9. Divide the mass of the coarse aggregate corresponding to a specimen in the mass distribution table by the average mass to obtain the average number of aggregates at that level; S10. Calculate the surface area of ​​each gear aggregate using the following formula; S-the sum of the surface areas of the gear; f(x)-normal distribution function of the axis length of the gear; G(x) - axis length of the gear - specific surface area function; m i -The average quality of the gear; y i -The average number of aggregates in this gear; S11. Calculate the mass of asphalt absorbed by each level of aggregate; S12. Calculate the asphalt mass of the pure asphalt layer; S13. Calculate the mass of asphalt and mineral powder in the mortar layer; S14. The corresponding asphalt and mineral powder of the asphalt mixture specimen are removed, and the coarse aggregate is removed accordingly according to the asphalt mortar with the target maximum particle size. The remaining fine aggregate is formed into a grading curve according to the principle of equal proportion amplification.

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

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

4. The design method according to claim 3, characterized in that: Calculate the mass of asphalt and mineral powder in the mortar layer according to the following formula; m 沥 =M 沥 -Y 吸 -M 纯 m 沥 - The asphalt content in the area of ​​the specimen that does not contain mineral powder; FB-pure powder-rubber ratio; h 胶 -Thickness of the glue layer; m 胶-矿 -Quality of mineral powder in the mortar layer; m 胶-沥 -Quality of asphalt in the mortar layer.

5. The design method according to claim 3, characterized in that: asphalt The corresponding asphalt mass of the mixture specimen is Y 吸 +m 纯-沥 +m 胶-沥 , mineral powder is m 胶-矿 .

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

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

8. The design method according to any one of claims 1 to 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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