A method for designing gradation of recycled drainage asphalt mixture

Abstract

The application discloses a gradation design method of regenerated drainage asphalt mixture and belongs to the field of gradation design methods of asphalt mixtures. The method comprises the following steps: testing recycled RAP materials to obtain gradation parameters of the RAP materials; testing new materials to obtain gradation parameters of the new materials; establishing a calculation formula of each volume parameter of the regenerated drainage asphalt mixture; establishing an equation according to the quantity relationship of each volume parameter in the regenerated drainage asphalt mixture; and solving the equation to obtain the mass proportion of new coarse and fine aggregates under the design air voids. The mass proportion of the new coarse and fine aggregates is fitted to obtain the gradation of the regenerated drainage asphalt mixture. The air voids of the regenerated drainage asphalt mixture are tested, and the gradation design is completed when the measured air voids are within the range of the design air voids plus or minus 1%. The application simplifies the gradation design method, fully considers the characteristics of the RAP materials, makes the gradation design more reasonable, and improves the efficiency of the gradation design.

Description

Technical Field

[0001] This invention belongs to the field of asphalt mixture gradation design methods, and more specifically, relates to a gradation design method for recycled drainage asphalt mixtures. Background Technology

[0002] With the continuous increase in the mileage of drainage asphalt pavements in my country, these roads are successively entering their maintenance and overhaul periods. For general abandoned pavements, my country typically uses milling overlay or direct overlay methods. However, since the raw materials used in drainage asphalt mixtures are relatively expensive (high-viscosity asphalt, high-quality basalt), using milling overlay or direct overlay methods on drainage asphalt pavements that have exceeded their service life would be very costly. Therefore, a scientific and effective gradation design method should be adopted for the gradation design of recycled drainage asphalt mixtures to avoid wasting old drainage asphalt pavement materials, make the gradation design more reasonable, and improve the road performance of recycled drainage asphalt mixtures.

[0003] Currently, the traditional gradation design method for recycled drainage asphalt mixtures faces two main challenges: "insufficient consideration of the influencing factors of recycled materials and cumbersome calculation process." Specifically, the following problems exist:

[0004] Firstly, due to the special structure of drainage asphalt pavement, coarse aggregate accounts for more than 80% of the total. During the long-term service of drainage asphalt pavement, the coarse aggregate in the pavement will break due to factors such as traffic load. This will cause the properties of coarse and fine aggregates and mineral powder in the recycled old asphalt pavement material to change to a certain extent. The traditional gradation design method of recycled drainage asphalt mixture only focuses on the gradation changes of old drainage asphalt pavement material, which is obviously not sufficient.

[0005] Secondly, the traditional gradation design method for recycled drainage asphalt mixtures requires multiple gradation designs to determine the final design gradation, which makes the design process relatively cumbersome and results in some material waste. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a gradation design method for recycled drainage asphalt mixtures, comprising the following steps:

[0007] (1) Test the recovered RAP material to obtain the RAP material gradation parameters, including the compacted density γ of the coarse aggregate in the RAP material. j旧 The bulk relative density γ of coarse aggregate in RAP materials s旧 The loose density γ of coarse aggregate in RAP materials 松装，旧 Apparent relative density γ of fine aggregates in RAP materials f旧、The apparent relative density γ of mineral powder in RAP materials p旧 The relative density γ of bitumen in RAP materials a旧 The aggregate gradation of RAP material and the content of old bitumen in RAP material (Q) 旧 ;

[0008] (2) Test the newly added material to obtain its gradation parameters, including the compacted density γ of the coarse aggregate in the newly added material. j新、 The bulk relative density γ of coarse aggregate in the newly added material s新、 The loose density γ of coarse aggregate in the newly added material 松装，新 The apparent relative density γ of fine aggregates in the newly added materials f新、 The apparent relative density γ of mineral powder in the newly added material p新 The relative density γ of asphalt in the newly added material a新 And the gradation of the newly added materials;

[0009] (3) Determine the blending rate A of RAP material. Based on the gradation parameters in step (1), obtain the mass ratio X1 of coarse aggregate to whole aggregate in RAP material, the mass ratio X2 of fine aggregate to whole aggregate in RAP material, and the mass ratio X3 of mineral powder to whole aggregate in RAP material.

[0010] (4) Determine the asphalt-aggregate ratio Pa of the recycled drainage asphalt mixture based on engineering experience, and substitute it into the equation.

[0011]

[0012] Q B This represents the asphalt content of the recycled drainage asphalt mixture. The asphalt content Q of the recycled drainage asphalt mixture is calculated. B ;

[0013] Based on engineering experience, determine the amount of recycling agent i used in the recycled drainage asphalt mixture, and substitute it into the equation.

[0014] Q 新 =Q B -A*Q 旧 *(1+i)

[0015] Q 新 This represents the newly added asphalt content in recycled drainage asphalt mixtures. The newly added asphalt content Q in recycled drainage asphalt mixtures is calculated. 新 ;

[0016] The old asphalt content Q in the RAP material obtained in step (1) 旧 The content of fresh asphalt in recycled drainage asphalt mixtures Q 新 Substitute into the equation

[0017]

[0018] Where P represents the asphalt-aggregate ratio of the asphalt mixture, and Q represents the asphalt content of the asphalt mixture, calculate the asphalt-aggregate ratio Pa of the RAP material in the recycled drainage asphalt mixture. 旧， The newly added material has an oilstone ratio of Pa. 新 ;

[0019] Based on the gradation parameters obtained in steps (1) and (2), and the asphalt-aggregate ratio Pa of the recycled drainage asphalt mixture and the asphalt-aggregate ratio Pa of the old asphalt in the recycled drainage asphalt mixture... 旧 The asphalt-aggregate ratio (Pa) of newly added asphalt 新 The volume V of asphalt in recycled drainage asphalt mixture can be calculated. 沥青 The calculation formula is as follows:

[0020]

[0021] (5) Based on engineering experience, determine the mass ratio z of mineral powder in the recycled drainage asphalt mixture and the gradation parameters obtained in steps (1) and (2). Preset the mass ratio x of newly added coarse aggregate and the mass ratio y of newly added fine aggregate in the recycled drainage asphalt mixture. Calculate the V in each volume parameter of the recycled drainage asphalt mixture. 粗 V 细 V 矿 VCA 再生 The calculation formula is as follows:

[0022]

[0023]

[0024]

[0025]

[0026] Among them, V 粗 VCA represents the compacted volume of coarse aggregate in recycled drainage asphalt mixtures. 再生 V represents the coarse aggregate void ratio of recycled drainage asphalt mixtures. 细 V represents the apparent volume of fine aggregates in recycled drainage asphalt mixtures. 矿 This represents the apparent volume of mineral powder in recycled drainage asphalt mixtures.

[0027] (6) Based on the quantitative relationships of various volumetric parameters in the recycled drainage asphalt mixture, the following equation is established:

[0028]

[0029] Determine the design void ratio VV of the recycled drainage asphalt mixture according to the engineering requirements. Substitute the volume parameters obtained in steps (3)(4)(5) into the equation established by the quantitative relationship of the volume parameters in the recycled drainage asphalt mixture, and solve for the mass ratio x of the newly added coarse aggregate and the mass ratio y of the newly added fine aggregate in the recycled drainage asphalt mixture.

[0030] (7) Based on the calculation results of step (6), the gradation of the recycled drainage asphalt mixture is obtained. Under this gradation, the recycled drainage asphalt mixture is prepared, and the void ratio of the recycled drainage asphalt mixture is tested. When the measured void ratio is within the range of ±1% of the design void ratio, the gradation design is completed. When the measured void ratio is not within the range of ±1% of the design void ratio, the mass ratio z of mineral powder in the recycled drainage asphalt mixture is adjusted, and the gradation design is carried out again.

[0031] Beneficial effects

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] (1) The gradation design method of recycled drainage asphalt mixture of the present invention introduces the density parameter of RAP material into the gradation calculation process of recycled drainage asphalt mixture, which more comprehensively considers the complexity of the internal components of recycled drainage asphalt mixture and reflects the characteristics of recycled drainage asphalt mixture. At the same time, it improves the gradation design efficiency of recycled drainage asphalt mixture compared with traditional methods.

[0034] (2) The gradation design method of recycled drainage asphalt mixture of the present invention establishes the quantitative relationship of volume parameters between the components of recycled drainage asphalt mixture based on the structural characteristics of recycled drainage asphalt mixture itself, and finally obtains the gradation of recycled drainage asphalt mixture by determining the mass ratio of mineral powder in recycled drainage asphalt mixture, the asphalt-aggregate ratio of recycled drainage asphalt mixture and the design void ratio. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1 This is a flowchart of the gradation design method according to one or more embodiments of the present invention.

[0037] Figure 2 This is a schematic diagram of the gradation curve design of recycled drainage asphalt mixture according to one or more embodiments of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention.

[0039] Example 1

[0040] Step 1: Test the recycled RAP material to obtain the RAP material gradation parameters, including the compacted density γ of the coarse aggregate in the RAP material. j旧、 The bulk relative density γ of coarse aggregate in RAP materials s旧、 The loose density γ of coarse aggregate in RAP materials 松装，旧 Apparent relative density γ of fine aggregates in RAP materials f旧、 The apparent relative density γ of mineral powder in RAP materials p旧、 The relative density γ of bitumen in RAP materials a旧、 The aggregate gradation of RAP material and the old bitumen content Q in RAP material 旧 .

[0041] Step 2: Test the newly added material to obtain its gradation parameters, including the compacted density γ of the coarse aggregate in the newly added material. j新 The bulk relative density γ of coarse aggregate in the newly added material s新、 The loose density γ of coarse aggregate in the newly added material 松装，新 The apparent relative density γ of fine aggregates in the newly added materials f新 The apparent relative density γ of mineral powder in the newly added material p新 The relative density γ of asphalt in the newly added material a新 And the gradation of the newly added materials.

[0042] Step 3: Determine the blending rate A of the RAP material. Based on the gradation parameters in step (1), obtain the mass ratio X1 of coarse aggregate to monolithic aggregate in the RAP material, the mass ratio X2 of fine aggregate to monolithic aggregate in the RAP material, and the mass ratio X3 of mineral powder to monolithic aggregate in the RAP material.

[0043] Step 4: Calculate the mass percentage (x) of newly added coarse aggregate and the mass percentage (y) of newly added fine aggregate in the recycled drainage asphalt mixture.

[0044] Based on engineering experience, determine the mass ratio z of mineral powder in recycled drainage asphalt mixture, the asphalt-aggregate ratio Pa of recycled drainage asphalt mixture, and the design void ratio VV.

[0045] Based on the quantitative relationships of various volumetric parameters in recycled drainage asphalt mixtures, the following equations are established:

[0046]

[0047] Among them, V 粗 VCA represents the compacted volume of coarse aggregate in recycled drainage asphalt mixtures. 再生 V represents the coarse aggregate void ratio of recycled drainage asphalt mixtures. 细 V represents the apparent volume of fine aggregates in recycled drainage asphalt mixtures. 矿 V represents the apparent volume of mineral powder in recycled drainage asphalt mixtures. 沥青 This indicates the volume of asphalt in the recycled drainage asphalt mixture.

[0048] Let the total mass number of the recycled drainage asphalt mixture aggregate be 1, V 粗 V 细 V 矿、 VCA 再生 V 沥青 The calculation formula is:

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] Substitute the parameters obtained from steps one to three into the calculation formula to calculate the volume parameters of the recycled drainage asphalt mixture. Substitute these parameters into the equation establishing the quantitative relationship of the volume parameters in the recycled drainage asphalt mixture to solve for the mass percentage of newly added coarse aggregate x and the mass percentage of newly added fine aggregate y in the recycled drainage asphalt mixture.

[0055] Step 5: Based on the calculation results in Step 4, obtain the gradation of the recycled drainage asphalt mixture. Prepare the recycled drainage asphalt mixture under this gradation and test its porosity. When the measured porosity is within ±1% of the design porosity, the gradation design is complete. When the measured porosity is not within ±1% of the design porosity, adjust the mass ratio z of mineral powder in the recycled drainage asphalt mixture and redesign the gradation.

[0056] Example 2

[0057] This embodiment uses recycled PAC-13 as an example to specifically describe the implementation process of a gradation design method for recycled drainage asphalt mixtures:

[0058] Step 1: Test the recycled RAP material to obtain the RAP material gradation parameters.

[0059] Grading parameters g / cm3 <![CDATA[Compacted density γ of coarse aggregate j旧 > 1.773 <![CDATA[Bulk specific gravity γ of coarse aggregate s旧 > 2.825 <![CDATA[Loose bulk density γ of coarse aggregate 松装，旧 > 1.562 <![CDATA[Apparent relative density γ of fine aggregate f旧 > 2.732 <![CDATA[Apparent relative density γ of mineral powder p旧 > 2.746 <![CDATA[Relative density γ of asphalt a旧 > 1.03

[0060] RAP particle size 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Asphalt content 12-22mm 91.6 33.6 14.2 11.6 9.2 7.3 5.9 5.2 4.9 3.24 5-12mm 100 93.2 32.1 17.4 13.6 10.7 8.9 7.7 6.9 3.93 Synthetic Gradients 95.4 60.4 22.3 14.2 11.2 8.8 7.2 6.3 5.8 3.55

[0061] Step 2: Test the newly added material and obtain its gradation parameters.

[0062] Grading parameters <![CDATA[g / cm 3 ]]> <![CDATA[Compacted density γ of coarse aggregate j新 > 1.813 <![CDATA[Bulk specific gravity γ of coarse aggregate s新 > 2.875 <![CDATA[Loose bulk density of coarse aggregate γ 松装，新 > 1.600 <![CDATA[Apparent relative density γ of fine aggregate f新 > 2.750 <![CDATA[Apparent relative density γ of mineral powder p新 > 2.769 <![CDATA[Relative density γ of asphalt a新 > 1.08

[0063]

[0064] Step 3: Determine the RAP material blending rate A. Based on the RAP material gradation parameters obtained in Step 1, calculate the mass ratio of coarse aggregate to monolithic aggregate in the RAP material X1, the mass ratio of fine aggregate to monolithic aggregate in the RAP material X2, and the mass ratio of mineral powder to monolithic aggregate in the RAP material X3.

[0065]

[0066] Step 4: Based on engineering experience, determine the following parameters for the recycled drainage asphalt mixture: mineral powder mass percentage z = 5%, asphalt-aggregate ratio Pa = 5%, recycling agent dosage i = 8%, and design porosity VV = 20%. Substituting these parameters into the calculation formula, the calculated mass percentage of newly added coarse aggregate in the recycled drainage asphalt mixture is x = 58.90%, and the mass percentage of fine aggregate is y = 7.84%. The fitted gradation and gradation curve of the recycled drainage asphalt mixture are shown in the table below. Figure 2 As shown:

[0067] Particle size / mm 16.0 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 Design gradation 100.0 92.4 59.8 19.5 15.4 12.1 10.9 8.2 6.3 5.1 Lower limit of gradation 100.0 90.0 40.0 10.0 9.0 7.0 6.0 5.0 4.0 3.0 Upper limit of grade 100.0 100.0 71.0 30.0 20.0 17.0 14.0 12.0 9.0 6.0 Median of gradation 100.0 95.0 55.5 20.0 14.5 12.0 10.0 8.5 6.5 4.5

[0068] Step 5: Prepare Marshall specimens according to the calculated gradation of the recycled drainage asphalt mixture, and test the porosity of the recycled drainage asphalt mixture. The test results are shown in the table below:

[0069] Specimen Number porosity Specimen 1 20.45％ Specimen 2 20.21％ Specimen 3 20.13％ Specimen 4 20.64％

[0070] As shown in the table above, the average void ratio of the recycled drainage asphalt mixture prepared according to the design gradation is 20.36%, and the error between the design void ratio and the gradation design is within ±1%. The gradation design is completed, and the error between the void ratio of each specimen and the design void ratio is also within ±1%. This embodiment illustrates the effectiveness and stability of a gradation design method for recycled drainage asphalt mixture.

[0071] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A method for gradation design of recycled drainage asphalt mixture, characterized in that, Includes the following steps: (1) Test the recovered RAP material to obtain the RAP material gradation parameters, including the compacted density γ of the coarse aggregate in the RAP material. j旧 The bulk relative density γ of coarse aggregate in RAP materials s旧 The loose density γ of coarse aggregate in RAP materials 松装，旧 Apparent relative density γ of fine aggregates in RAP materials f旧 Apparent relative density γ of mineral powder in RAP material p旧 The relative density γ of bitumen in RAP materials a旧 The aggregate gradation of RAP material and the content of old bitumen in RAP material (Q) 旧 ; (2) Test the newly added material to obtain its gradation parameters, including the compacted density γ of the coarse aggregate in the newly added material. j新 The bulk relative density γ of coarse aggregate in the newly added material s新 The loose density γ of coarse aggregate in the newly added material 松装，新 The apparent relative density γ of fine aggregates in the newly added materials f新 The apparent relative density γ of mineral powder in the newly added material p新 The relative density γ of asphalt in the newly added material a新 And the gradation of the newly added materials; (3) Determine the blending rate A of RAP material. Based on the gradation parameters in step (1), obtain the mass ratio X1 of coarse aggregate to whole aggregate in RAP material, the mass ratio X2 of fine aggregate to whole aggregate in RAP material, and the mass ratio X3 of mineral powder to whole aggregate in RAP material. (4) Determine the asphalt-aggregate ratio Pa of the recycled drainage asphalt mixture based on engineering experience, and substitute it into the equation. Q B This represents the asphalt content of the recycled drainage asphalt mixture. The asphalt content Q of the recycled drainage asphalt mixture is calculated. B ; Based on engineering experience, determine the amount of recycling agent i used in the recycled drainage asphalt mixture, and substitute it into the equation. Q 新 =Q B -A*Q 旧 *(1+i) Q 新 This represents the content of newly added asphalt in recycled drainage asphalt mixtures. The content of newly added asphalt in recycled drainage asphalt mixtures, Q, is calculated. 新 ; The amount of old asphalt in RAP material Q 旧 The content of fresh asphalt in recycled drainage asphalt mixtures Q 新 Substitute into the equation Where P represents the asphalt-aggregate ratio of the asphalt mixture, and Q represents the asphalt content of the asphalt mixture, calculate the asphalt-aggregate ratio Pa of the RAP material in the recycled drainage asphalt mixture. 旧 The newly added material has a Pa ratio of oilstone. 新 ; Based on the gradation parameters obtained in steps (1) and (2), and the asphalt-aggregate ratio Pa of the recycled drainage asphalt mixture and the asphalt-aggregate ratio Pa of the RAP material in the recycled drainage asphalt mixture... 旧 The ratio of the newly added material to the oilstone (Pa) 新 The volume V of asphalt in recycled drainage asphalt mixture can be calculated. 沥青 The calculation formula is as follows: (5) Based on engineering experience, determine the mass ratio z of mineral powder in the recycled drainage asphalt mixture and the gradation parameters obtained in steps (1) and (2). Preset the mass ratio x of newly added coarse aggregate and the mass ratio y of newly added fine aggregate in the recycled drainage asphalt mixture. Calculate the V in each volume parameter of the recycled drainage asphalt mixture. 粗 V 细 V 矿 VCA 再生 The calculation formula is as follows: Among them, V 粗 VCA represents the compacted volume of coarse aggregate in recycled drainage asphalt mixtures. 再生 V represents the coarse aggregate void ratio of recycled drainage asphalt mixtures. 细 V represents the apparent volume of fine aggregates in recycled drainage asphalt mixtures. 矿 This represents the apparent volume of mineral powder in recycled drainage asphalt mixtures. (6) Based on the quantitative relationships of various volumetric parameters in the recycled drainage asphalt mixture, the following equation is established: V 粗 *VCA 再生 =V 粗 *VV+V 细 +V 矿 +V 沥青 Determine the design void ratio VV of the recycled drainage asphalt mixture according to the engineering requirements. Substitute the volume parameters obtained in steps (3)(4)(5) into the equation established by the quantitative relationship of the volume parameters in the recycled drainage asphalt mixture, and solve for the mass ratio x of the newly added coarse aggregate and the mass ratio y of the newly added fine aggregate in the recycled drainage asphalt mixture. (7) The gradation of the recycled drainage asphalt mixture is obtained by fitting the calculation results of step (6). The recycled drainage asphalt mixture is prepared under this gradation. The void ratio of the recycled drainage asphalt mixture is tested. When the measured void ratio is within the range of ±1% of the design void ratio, the gradation design is completed. When the measured void ratio is not within the range of ±1% of the design void ratio, the mass ratio z of mineral powder in the recycled drainage asphalt mixture is adjusted and the gradation design is carried out again.

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