An evaluation method for the miscibility of new and old asphalt in hot recycled mixtures based on layer-by-layer elution

Abstract

The present invention discloses a method for evaluating the miscibility of old and new asphalt in a thermally regenerated mixture based on layer-by-layer elution, including: collecting pavement recycled materials to obtain the old asphalt and the RAP old material gradation; determining the ratio of new asphalt to old asphalt to prepare a thermally regenerated asphalt mixture; taking the thermally regenerated asphalt mixture, performing layer-by-layer elution and layer-by-layer extraction to obtain the regenerated asphalt eluted layer by layer; mixing and stirring the old asphalt with the new asphalt to obtain the completely miscible regenerated asphalt; respectively testing the old asphalt, the new asphalt, the regenerated asphalt eluted layer by layer, and the completely miscible regenerated asphalt to obtain the complex shear modulus curve in logarithmic coordinates; calculating the average equivalent spacing coefficient of the complex shear modulus curve to evaluate the miscibility degree of old and new asphalt; the present invention provides an indoor test process applicable to the evaluation of the mixing degree of old and new asphalt; and proposes an average equivalent spacing coefficient index to quantitatively evaluate the partial miscibility degree of old and new asphalt.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt miscibility, and particularly to an evaluation method for the miscibility of new and old asphalt in hot recycled mixtures based on layer-by-layer elution. Background Art

[0002] Most of the high-grade highways built in China are asphalt pavements. Asphalt, as the main paving raw material, is expensive and relies on imports. The large-scale exploitation of aggregates and stone mines has caused serious ecological environment damage. In China, asphalt pavements have gradually shifted from mainly construction to both construction and maintenance. The traditional milling and resurfacing process will generate a large amount of RAP old materials, and the old materials cannot be recycled, which will cause a great burden on the economy and the environment. The efficient recycling of waste asphalt mixtures is a major challenge and urgent need in the development of solid waste resource utilization and pavement recycling and maintenance technologies in China.

[0003] The hot recycling technology for asphalt pavements, as a green, environmentally friendly and high-quality road maintenance technology, has been widely applied, and this technology can achieve the efficient recycling of old pavement materials. At present, in-situ hot recycling and plant-mixed hot recycling are two commonly used hot recycling technologies in China. However, there are problems of insufficient miscibility between new and old asphalt in both in-situ and plant-mixed hot recycling technologies, which weakens the crack resistance and durability of hot recycled asphalt mixtures and reduces the long-term service effect of hot recycled asphalt pavements. During the maintenance construction of hot recycled asphalt pavements, due to the short mixing time, the outer part of the RAP old materials is wrapped by new asphalt, and there is an interface transition zone between new and old asphalt. It is difficult to judge the interface miscibility degree, and the mesoscopic miscibility mechanism is not clear, which hinders the further improvement of the efficiency of hot recycled asphalt maintenance technology.

[0004] The existing research on hot recycled asphalt mixtures focuses on exploring the miscibility mechanism of new and old asphalt from four levels: macroscopic, mesoscopic, microscopic and molecular, and fails to propose a quantitative evaluation method with high accuracy for the miscibility degree of new and old asphalt. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the specification of this application, to avoid obscuring the purpose of this part, the abstract and the title. Such simplifications or omissions shall not be used to limit the scope of the present invention.

[0006] In view of the above existing problems, the present invention is proposed.

[0007] To solve the above technical problems, the present invention provides the following technical solutions, including: collecting pavement recycled materials to obtain old asphalt and the gradation of RAP old materials; determining the ratio of new asphalt to old asphalt to prepare hot recycled asphalt mixture; taking the hot recycled asphalt mixture, performing layer-by-layer elution and layered extraction to obtain regenerated asphalt by layer-by-layer elution; mixing and stirring the old asphalt and the new asphalt to obtain completely miscible regenerated asphalt; respectively testing the old asphalt, the new asphalt, the regenerated asphalt by layer-by-layer elution, and the completely miscible regenerated asphalt to obtain the complex shear modulus curve in logarithmic coordinates; calculating the average equivalent spacing coefficient of the complex shear modulus curve to evaluate the miscibility degree of new and old asphalt.

[0008] As a preferred embodiment of the method for evaluating the miscibility of new and old asphalt in hot recycled mixture based on layer-by-layer elution according to the present invention, wherein, obtaining the old asphalt and the gradation of RAP old materials includes: milling the old asphalt pavement to obtain pavement recycled materials, and using extraction and screening to obtain the old asphalt and the gradation of RAP old materials; for the old aggregates after extraction, the water washing and screening method is used, and the old asphalt after extraction needs to be reheated to remove the residual trichloroethylene.

[0009] As a preferred embodiment of the method for evaluating the miscibility of new and old asphalt in hot recycled mixture based on layer-by-layer elution according to the present invention, wherein, preparing the hot recycled asphalt mixture includes: determining the ratio of new and old materials added to the recycled asphalt mixture according to the regeneration ratio design process in the hot recycling construction technology.

[0010] As a preferred embodiment of the method for evaluating the miscibility of new and old asphalt in hot recycled mixture based on layer-by-layer elution according to the present invention, wherein, obtaining the regenerated asphalt by layer-by-layer elution includes: taking the hot recycled asphalt mixture with a stainless steel filter screen, placing it in an elution device filled with trichloroethylene solution, performing layer-by-layer elution, and using a high-speed centrifuge and a rotary evaporator for layered extraction; the elution device for hot recycled asphalt mixture includes a glass beaker, a stainless steel filter screen, a glass stirring rod, and trichloroethylene solution; the mesh size of the stainless steel filter screen is 0.1 mm; the volume of the taken hot recycled asphalt mixture ≤ 2 / 3 of the volume of the stainless steel filter screen; when performing layer-by-layer elution, the number of elution layers n ≥ 3, and the soaking time for each elution is 10 s.

[0011] As a preferred embodiment of the method for evaluating the miscibility of new and old asphalt in hot recycled mixture based on layer-by-layer elution according to the present invention, wherein, obtaining the complex shear modulus curve in logarithmic coordinates includes: using a DSR dynamic shear rheometer to respectively test the complex shear modulus of the old asphalt, the new asphalt, the regenerated asphalt by layer-by-layer elution, and the completely miscible regenerated asphalt at various temperatures to obtain the complex shear modulus curve in logarithmic coordinates.

[0012] As a preferred embodiment of the method for evaluating the mixing of fresh and aged asphalt in a hot recycling mixture based on layer-by-layer elution according to the present invention, wherein the mixing and stirring include: stirring temperature > 130 °C, stirring time > 10 min.

[0013] As a preferred embodiment of the method for evaluating the mixing of fresh and aged asphalt in a hot recycling mixture based on layer-by-layer elution according to the present invention, wherein the average equivalent spacing coefficient includes:

[0014] Calculate the average equivalent spacing of the complex shear modulus curve in logarithmic coordinates:

[0015]

[0016] Wherein, is the average equivalent spacing of the complex shear modulus curves of the recycled asphalt eluted layer by layer in n layers and the completely miscible recycled asphalt in logarithmic coordinates, d i is the equivalent spacing of the complex shear modulus curves of the recycled asphalt eluted in the i-th layer and the completely miscible recycled asphalt in logarithmic coordinates;

[0017] Determine the value range of the average equivalent spacing of the complex shear modulus curve in logarithmic coordinates:

[0018]

[0019] Wherein, d 新 is the average equivalent spacing of the complex shear modulus curves of the fresh asphalt and the completely miscible recycled asphalt in logarithmic coordinates, d 旧 is the average equivalent spacing of the complex shear modulus curves of the aged asphalt and the completely miscible recycled asphalt in logarithmic coordinates.

[0020] As a preferred embodiment of the method for evaluating the mixing of fresh and aged asphalt in a hot recycling mixture based on layer-by-layer elution according to the present invention, wherein it further includes:

[0021] Calculate the average equivalent spacing coefficient Λ i of the complex shear modulus curve in logarithmic coordinates:

[0022]

[0023] Obtain the Λ i value range from the value range of the average equivalent spacing of the complex shear modulus curve in logarithmic coordinates, and the

[0024]

[0025] As a preferred embodiment of the method for evaluating the mixing of new and old asphalt in a thermally regenerated mixture based on layer-by-layer elution according to the present invention, the evaluation of the mixing degree of new and old asphalt includes: according to the value range of the average equivalent spacing coefficient, the mixing degree of new and old asphalt in the thermally regenerated asphalt mixture is equally divided into five levels at an interval of 0.2, including the first level, the second level, the third level, the fourth level, and the fifth level.

[0026] As a preferred embodiment of the method for evaluating the mixing of new and old asphalt in a thermally regenerated mixture based on layer-by-layer elution according to the present invention, it further includes: when the average equivalent spacing coefficient Λ i ∈[0, 0.2], the corresponding mixing degree is the first level, representing that the new and old asphalt are nearly completely mixed; when the average equivalent spacing coefficient Λ i ∈[0.8, 1.0], the corresponding mixing degree is the fifth level, representing that the new and old asphalt are nearly completely unmixed; the higher the level of the average equivalent spacing coefficient, the worse the mixing degree of the new and old asphalt.

[0027] Advantages of the present invention: The present invention selects the asphalt DSR rheological property test with greater controllability to conduct research on the evaluation of the mixing degree, further eliminating the influence of the properties and dosages of mineral powder on the test accuracy; exploring the mixing situation of new and old asphalt in thermally regenerated mixtures from the asphalt level, and giving the indoor test process of layer-by-layer elution applicable to the evaluation of the mixing degree of new and old asphalt; through the complex shear modulus rheological test on the dynamic shear rheometer, taking the measured complex shear dynamic modulus curve of the completely mixed regenerated asphalt as the benchmark, calculating the average equivalent spacing coefficient index of the complex shear modulus curve in logarithmic coordinates to quantify the mixing degree of new and old asphalt in thermally regenerated asphalt mixtures; the present invention can solve the problem that the mixing degree of new and old asphalt in the existing asphalt mixture thermal regeneration maintenance technology cannot be accurately quantified and expressed, providing technical support for further improving the service performance of thermally regenerated asphalt mixtures. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0029] Figure 1 It is a flowchart of the method for evaluating the mixing of new and old asphalt in a thermally regenerated mixture based on layer-by-layer elution according to the first embodiment of the present invention;

[0030] Figure 2 It is a diagram of the elution device of the method for evaluating the mixing of new and old asphalt in a thermally regenerated mixture based on layer-by-layer elution according to the first embodiment of the present invention;

[0031] Figure 3 Stainless steel filter screen diagram of an evaluation method for the mixing of new and old asphalt in hot recycled mixtures based on layer-by-layer elution according to the first embodiment of the present invention;

[0032] Figure 4 Schematic diagram of the mixing and diffusion degree of new and old asphalt in an evaluation method for the mixing of new and old asphalt in hot recycled mixtures based on layer-by-layer elution according to the first embodiment of the present invention;

[0033] Figure 5 Schematic diagram of the average equivalent spacing in an evaluation method for the mixing of new and old asphalt in hot recycled mixtures based on layer-by-layer elution according to the first embodiment of the present invention. Detailed implementation manners

[0034] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following will describe the detailed implementation manners of the present invention with reference to the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0036] Secondly, the so-called "one embodiment" or "embodiment" herein refers to specific features, structures, or characteristics that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0037] The present invention is described in detail in conjunction with schematic diagrams. When detailing the embodiments of the present invention, for the convenience of explanation, the cross-sectional views showing the device structure will be enlarged locally not in accordance with the general scale, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0038] Meanwhile, in the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper, lower, inner, and outer" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first, second, or third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0039] Unless otherwise clearly specified and defined in the present invention, the terms "installation, connection, and coupling" shall be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can also be a mechanical connection, an electrical connection, or a direct connection, and can also be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] Example 1

[0041] Refer to Figures 1 to 5 , which is the first embodiment of the present invention. This embodiment provides a method for evaluating the mixing of new and old asphalt in a hot recycled mixture based on layer-by-layer elution, including:

[0042] S1: Collect pavement recycled materials to obtain the old asphalt and the RAP old material gradation.

[0043] Milling the old asphalt pavement to obtain pavement recycled materials, and using extraction and screening to obtain the old asphalt and the RAP old material gradation; for the extracted old aggregates, use the water washing and screening method, and the extracted old asphalt needs to be reheated to remove the residual trichloroethylene.

[0044] Specifically, for the RAP old materials recycled by milling the old asphalt pavement, use extraction and screening tests to obtain the old asphalt and the old material gradation; first, put the RAP old materials into an oven at 120 ± 5 °C and heat them to a molten state, disperse them into granular form and place them in an automatic asphalt mixture extractor, and soak them in trichloroethylene solution for 20 min and then conduct an extraction test. Add 400 ml of trichloroethylene solution and extract again until the discharged filtrate is light yellow; place the extracted filtrate in a high-speed centrifuge and rotate it for 15 min at a speed of 3000 revolutions per minute to remove the mineral powder in the filtrate, and then conduct a rotary evaporation asphalt recovery test. The obtained old asphalt is heated with an electric furnace and stirred for 10 min to remove the residual trichloroethylene solvent; conduct a water washing and screening test on the extracted RAP old materials to obtain the corresponding sieve hole passing rate, and calculate the old material asphalt-aggregate ratio through the old asphalt, RAP old aggregates, and mineral powder.

[0045] S2: Determine the ratio of new asphalt and old asphalt to prepare the hot recycled asphalt mixture.

[0046] According to the regeneration ratio design process in the hot regeneration construction technology, determine the proportion of new and old materials added to the recycled asphalt mixture, and prepare the hot recycled asphalt mixture.

[0047] Specifically, select the type of hot recycled asphalt mixture according to the RAP material gradation and asphalt-aggregate ratio, and determine the asphalt type according to the corresponding asphalt mixture type; determine the mixing ratio of the old material, and by adjusting the mixing ratio of each grade of new aggregate, make the gradation of the recycled asphalt mixture close to the target gradation. Convert the ratio of new and old mixtures into the ratio of new asphalt and old asphalt, and determine the amount of new asphalt to be added through the target asphalt-aggregate ratio, RAP material content and old material asphalt-aggregate ratio, and design the hot recycled asphalt mixture.

[0048] Put the new asphalt into an oven at 163 °C and heat it to the molten state. Put the RAP material and new aggregates into the oven respectively and heat them to 120 ± 5 °C and keep them warm for 4 h for standby. Heat mixer A to 175 °C, put the preheated RAP material into mixer A and mix for 90 s, and keep it warm for standby; heat mixer B to 175 °C, put the preheated coarse and fine aggregates into mixer B and mix for 90 s, add the molten new asphalt and mix for 90 s, and then add the preheated mineral powder and mix for 90 s to obtain the newly mixed asphalt mixture. Put the RAP material kept warm in mixer A into mixer B and mix for 180 s to prepare the hot recycled asphalt mixture.

[0049] S3: Take the hot recycled asphalt mixture, carry out layer-by-layer elution and layered extraction to obtain the recycled asphalt by layer-by-layer elution.

[0050] Use a stainless steel filter screen to take the hot recycled mixture, place it in an elution device containing trichloroethylene solution, carry out layer-by-layer elution, and use a high-speed centrifuge and a rotary evaporator for layered extraction to obtain the recycled asphalt by layer-by-layer elution.

[0051] The elution device for the hot recycled asphalt mixture includes a glass beaker, a stainless steel filter screen, a glass stirring rod and trichloroethylene solution. See Figure 2 , in the figure, ① is the stainless steel filter screen, ② is the trichloroethylene solution, ③ is the glass beaker, ④ is the glass stirring rod, and ⑤ is the hot recycled asphalt mixture; see Figure 3 , the mesh size of the stainless steel filter screen is 0.1 mm; the volume of the hot recycled asphalt mixture taken ≤ 2 / 3 of the volume of the stainless steel filter screen; when carrying out layer-by-layer elution, the number of elution layers n ≥ 3, and the soaking time for each elution is 10 s.

[0052] Specifically, take the hot recycled asphalt mixture and place it on a filter screen with a 0.1 mm sieve pore size, soak it in trichloroethylene solution, stir with a glass rod during soaking to ensure complete contact between the mixture and trichloroethylene, elute layer by layer at 10 s intervals, the number of elution layers n ≥ 3, and the total soaking time is 10n s; use a high-speed rotary centrifuge to remove the mineral powder in the solution from the filtrate of the layered dissolution, and then obtain the recycled asphalt eluted layer by layer through a rotary evaporation device. Adjust the temperature of the electric furnace to 163 °C, heat and stir until constant weight to remove the residual trichloroethylene in the recycled asphalt.

[0053] This method first uses the experimental method of eluting layer by layer to separate the asphalt on the surface of the old material; if the new and old asphalt in the recycled mixture is not evenly miscible, the elution layer by layer method can obviously separate the new asphalt layer, the transition layer between new and old asphalt, and the old asphalt layer wrapped on the surface of the old aggregate. The schematic diagram of the diffusion degree of the new and old asphalt miscibility is shown in Figure 4 .

[0054] S4: Mix and stir the old asphalt and the new asphalt to obtain a completely miscible recycled asphalt.

[0055] The stirring temperature > 130 °C, and the stirring time > 10 min.

[0056] Specifically, place the old asphalt and the new asphalt in an oven at 163 °C respectively and heat them to the molten state, mix them in proportion, and the ratio of the new and old asphalt refers to the mixing ratio of the new and old materials. Use a stirrer to stir for 15 min until the new and old asphalt is completely miscible to obtain a completely miscible recycled asphalt.

[0057] S5: Test the old asphalt, the new asphalt, the recycled asphalt eluted layer by layer, and the completely miscible recycled asphalt respectively to obtain the complex shear modulus curve under the logarithmic coordinate.

[0058] Use a DSR dynamic shear rheometer to test the complex shear modulus of the old asphalt, the new asphalt, the recycled asphalt eluted layer by layer, and the completely miscible recycled asphalt at various temperatures respectively to obtain the complex shear modulus curve under the logarithmic coordinate, as shown in Figure 5 .

[0059] S6: Calculate the average equivalent spacing coefficient of the complex shear modulus curve to evaluate the miscibility degree of the new and old asphalt.

[0060] Calculate the average equivalent spacing of the complex shear modulus curve under the logarithmic coordinate:

[0061]

[0062] Among them, is the average equivalent spacing of the complex shear modulus curves of the recycled asphalt eluted layer by layer with n layers and the completely miscible recycled asphalt under the logarithmic coordinate, d iIt is the equal - value spacing of the complex shear modulus curves of the regenerated asphalt eluted layer by layer in the i - th layer under logarithmic coordinates and the completely miscible regenerated asphalt;

[0063] Determine the value range of the average equal - value spacing of the complex shear modulus curve under logarithmic coordinates:

[0064]

[0065] where, d 新 is the average equal - value spacing of the complex shear modulus curves of the new asphalt and the completely miscible asphalt under logarithmic coordinates, and d 旧 is the average equal - value spacing of the complex shear modulus curves of the old asphalt and the completely miscible asphalt under logarithmic coordinates.

[0066] Calculate the average equal - value spacing coefficient Λ of the complex shear modulus curve under logarithmic coordinates i :

[0067]

[0068] From the value range of the average equal - value spacing of the complex shear modulus curve under logarithmic coordinates, obtain the value range of Λ i The value range is 0 - 1:

[0069]

[0070] According to the value range of the average equal - value spacing coefficient, divide the miscibility degree of the new and old asphalts in the hot - regenerated asphalt mixture into five levels at an interval of 0.2, including the first level, the second level, the third level, the fourth level, and the fifth level.

[0071] When the average equal - value spacing coefficient Λ i ∈[0, 0.2], the corresponding miscibility degree is the first level, representing that the new and old asphalts are close to complete miscibility; when the average equal - value spacing coefficient Λ i ∈[0.8, 1.0], the corresponding miscibility degree is the fifth level, representing that the new and old asphalts are close to complete immiscibility;

[0072] The higher the grade of the average equal - value spacing coefficient, the worse the miscibility degree of the new and old asphalts.

[0073] Example 2

[0074] In order to verify and illustrate the technical effects adopted in this method, this example conducts experiments on this method to verify the real effects possessed by this method.

[0075] (1) Determination of the gradation and asphalt - aggregate ratio of the RAP old material

[0076] In this test, the RAP material was taken from the in-situ hot-milled and planed asphalt mixture on the 233 section of the national and provincial trunk roads in Baoying, Yangzhou. The extraction and screening tests were used to obtain the old asphalt and the gradation of the RAP old material. First, the hot-milled and planed material was placed in an oven at 120 ± 5 °C and heated to a molten state. It was dispersed into granular form and placed in an automatic asphalt mixture extractor, and soaked in trichloroethylene solution for 20 minutes before the extraction test. After the filtrate was drained, 400 ml of trichloroethylene solution was added for extraction again, and the extraction test was repeated until the filtrate discharged from the automatic asphalt mixture extractor was light yellow. The extracted filtrate was placed in a high-speed centrifuge and rotated for 15 minutes at a speed of 3000 revolutions per minute to remove the mineral powder in the filtrate. Then, the rotary evaporation asphalt recovery test was carried out. The obtained asphalt was heated to 163 °C with an electric furnace and stirred with a glass rod for 10 minutes until the quality of the asphalt remained unchanged, and the residual trichloroethylene was removed. The extracted RAP material and mineral powder were subjected to a water washing and screening test to obtain the corresponding passing rates of the sieve holes. The results obtained are shown in Table 1. The asphalt-aggregate ratio was calculated through the RAP old aggregate, mineral powder, and extracted old asphalt.

[0077] Table 1: Results of the old material extraction test.

[0078]

[0079] The raw material screening test was carried out on the mineral materials in the stockpile to obtain the passing rates of the sieve holes of Material No. 1, 2, 3, 4, and mineral powder, as shown in Table 2:

[0080] Table 2: Results of the mineral material screening.

[0081]

[0082] (2) Design and preparation of hot recycled asphalt mixture

[0083] The RAP material is of the Sup-13 gradation. Therefore, the gradation of the in-situ hot recycled asphalt mixture is selected as Sup-13. The new asphalt selected is 70# base asphalt. The blending ratio of the RAP material is 70%. According to the Marshall design method, the mix proportion design of the recycled asphalt mixture is carried out, and the asphalt-aggregate ratio of the recycled asphalt mixture is obtained as 4.67%. The synthetic gradation is shown in Table 3. Take 3500 g of RAP material, 540 g of No. 1 material, 555 g of No. 2 material, 75 g of No. 3 material, 300 g of No. 4 material, and 540 g of mineral powder. Put them into the oven and heat to 120 ± 5 °C and keep warm for 4 h for standby. Put the new asphalt into the oven at 163 °C and heat it to the molten state. Heat mixer A to 175 °C, put the preheated RAP material into mixer A and mix for 90 s, and keep it warm for standby. Heat mixer B to 175 °C, put the preheated coarse and fine aggregates into mixer B and mix for 90 s, add 76.7 g of asphalt and mix for 90 s, then add the preheated mineral powder and mix for 90 s to obtain the newly mixed asphalt mixture. Put the RAP material kept warm in mixer A into mixer B and mix for 180 s to obtain the hot recycled asphalt mixture.

[0084] Table 3: Gradation composition of the hot recycled asphalt mixture.

[0085]

[0086] (3) Layer-by-layer elution of the hot recycled asphalt mixture

[0087] Take the recycled asphalt mixture and place it on a filter screen with a 0.1 mm sieve hole, soak it in trichloroethylene solution, stir with a glass rod during soaking to make the mixture fully contact with trichloroethylene, soak it 3 times at 10 s intervals, and the total soaking time is 30 s. Use a high-speed rotating centrifugal sedimentation machine to remove the mineral powder from the layered dissolved filtrate, and then obtain the layer-by-layer eluted asphalt through a rotary evaporation device. Adjust the temperature of the electric furnace to 163 °C, heat and stir the layer-by-layer eluted asphalt until it reaches a constant weight, and remove the residual trichloroethylene to obtain the layer-by-layer eluted recycled asphalt.

[0088] (4) Preparation of the completely miscible recycled asphalt

[0089] Place the old asphalt and the new asphalt separately in an oven at 163 °C and heat them to the molten state. Take 70 g of old asphalt and 30 g of new asphalt, and stir with a stirrer for 15 min until the old and new asphalts are completely miscible. Place the asphalt on the electric furnace during stirring to ensure that the asphalt temperature is 163 °C to obtain the completely miscible recycled asphalt.

[0090] (5) Determination of the rheological parameters of the old and new asphalts and the recycled asphalt

[0091] Heat the old asphalt, new asphalt, the thermally regenerated asphalt eluted layer by layer, and the completely miscible regenerated asphalt to the molten state, pour specimens, conduct DSR tests on them, and obtain the complex shear modulus at 52 - 82 °C as shown in Table 4, and obtain the complex shear modulus curve in logarithmic coordinates.

[0092] Table 4: Complex shear modulus of different asphalts.

[0093]

[0094] (6) Quantitative evaluation of the miscibility degree of old and new asphalts

[0095] Calculate the average equal-spacing coefficient of the complex shear modulus curve in logarithmic coordinates according to the following formula:

[0096]

[0097] The calculation results of the average equal-spacing coefficient of the complex shear modulus curve in logarithmic coordinates are shown in Table 5. The average equal-spacing coefficient of the asphalt eluted for the first time in the thermally regenerated asphalt mixture is 0.25, the average equal-spacing coefficient of the asphalt eluted for the second time is 0.14, the average equal-spacing coefficient of the asphalt eluted for the third time is 0.46, and the total average equal-spacing coefficient for the three elutions is 0.28. The results show that: in this embodiment, the miscibility grade of the in-situ thermally regenerated asphalt mixture on the 233 section of the national and provincial trunk lines in Baoying, Yangzhou is grade 2, and the miscibility degree is good. This method can also evaluate the miscibility degree of the asphalt eluted once. The results show that the miscibility grade of the asphalt eluted for the first time is grade 2, the miscibility grade of the asphalt eluted for the second time is grade 1, and the miscibility grade of the asphalt eluted for the third time is grade 3.

[0098] Table 5: Average equal-spacing coefficient Λ i 。

[0099] Recycled asphalt mixture First elution Second elution Third elution Average value of three elutions Average equivalent spacing factor 0.25 0.14 0.46 0.28

[0100] Another infrared spectroscopy experiment is used as a comparison to verify the effectiveness of this method. Heat the old asphalt, new asphalt, the regenerated asphalt eluted layer by layer, and the completely miscible regenerated asphalt to the molten state, pour specimens, and conduct infrared spectroscopy experiments to obtain SI, that is, the sulfoxide group index of the asphalt, as an index to evaluate the miscibility of the asphalt. Calculate the flow rate of the old asphalt and the fusion degree of the old and new asphalts through the SI value, and the results are shown in Table 6:

[0101] Table 6: Flow rate β of the old asphalt and miscibility degree η of the asphalt eluted layer by layer.

[0102]

[0103] It can be seen from Table 6 that the miscibility of the asphalt eluted for the second time is the best, followed by the asphalt eluted for the first time, while the miscibility of the asphalt eluted for the third time is the worst; the conclusions drawn from the infrared spectroscopy experiment and this method are basically the same. Therefore, the evaluation method of the new and old asphalt miscibility of the hot recycled asphalt mixture in this invention patent has high accuracy.

[0104] It should be appreciated that embodiments of the present invention can be implemented or carried out by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable memory. The methods may be implemented in a computer program using standard programming techniques - including a non-transitory computer-readable storage medium configured with the computer program, wherein the storage medium so configured causes the computer to operate in a specific and predefined manner - in accordance with the methods and the drawings described in the specific embodiments. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, if desired, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. In addition, for this purpose the program is capable of running on a programmed application-specific integrated circuit.

[0105] In addition, the operations of the processes described herein can be performed in any suitable order, unless otherwise indicated herein or otherwise clearly contradicted by the context. The processes described herein (or variations and / or combinations thereof) can be performed under the control of one or more computer systems configured with executable instructions, and can be implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) collectively executed on one or more processors, by hardware, or by a combination thereof. The computer program includes a plurality of instructions executable by one or more processors.

[0106] Further, the method can be implemented in any type of computing platform operatively connected to a suitable one, including but not limited to personal computers, minicomputers, mainframes, workstations, network or distributed computing environments, separate or integrated computer platforms, or communicating with charged particle tools or other imaging devices, etc. Aspects of the present invention can be implemented in machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into the computing platform, such as a hard disk, optical read and / or write storage medium, RAM, ROM, etc., such that it can be read by a programmable computer and, when the storage medium or device is read by the computer, can be used to configure and operate the computer to perform the processes described herein. In addition, the machine-readable code, or portions thereof, can be transmitted via a wired or wireless network. When such media includes instructions or programs that implement the above-described steps in conjunction with a microprocessor or other data processor, the invention described herein includes these and other different types of non-transitory computer-readable storage media. When programmed according to the methods and techniques of the present invention, the present invention also includes the computer itself. The computer program is capable of applying to input data to perform the functions described herein, thereby transforming the input data to generate output data stored to non-volatile memory. The output information can also be applied to one or more output devices such as a display. In a preferred embodiment of the present invention, the transformed data represents physical and tangible objects, including a specific visual depiction of the physical and tangible objects generated on the display.

[0107] As used in this application, the terms "component", "module", "system", etc. are intended to refer to a computer-related entity, which can be hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component can be, but is not limited to: a process running on a processor, a processor, an object, an executable file, a thread in execution, a program, and / or a computer. As an example, an application running on a computing device and the computing device can both be components. One or more components can exist in a process and / or thread in execution, and the components can be located in one computer and / or distributed between two or more computers. In addition, these components can execute from various computer-readable media having various data structures thereon. These components can communicate in a local and / or remote process manner via signals such as according to one or more data packets (e.g., data from one component that interacts with another component in a local system, a distributed system, and / or communicates with other systems via a network such as the Internet in a signal manner).

[0108] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. A method for evaluating the mixing of new and old asphalt in a hot recycled mixture based on layer-by-layer elution, characterized in that Including: Collecting pavement recycled materials to obtain old asphalt and RAP old material gradation; Determining the ratio of new asphalt to old asphalt to prepare hot recycled asphalt mixture; Taking the hot recycled asphalt mixture, conducting layer-by-layer elution and layered extraction to obtain regenerated asphalt by layer-by-layer elution; Mixing and stirring the old asphalt and the new asphalt to obtain completely miscible regenerated asphalt; Testing the old asphalt, the new asphalt, the regenerated asphalt by layer-by-layer elution and the completely miscible regenerated asphalt respectively to obtain the complex shear modulus curve in logarithmic coordinates; Calculating the average equivalent spacing coefficient of the complex shear modulus curve to evaluate the miscibility degree of new and old asphalt; Wherein, the average equivalent spacing coefficient includes: Calculating the average equivalent spacing of the complex shear modulus curve in logarithmic coordinates: Among them, is the average equivalent spacing of the complex shear modulus curves of the regenerated asphalt eluted layer by layer for n layers and the completely miscible regenerated asphalt in logarithmic coordinates, d i is the equivalent spacing of the complex shear modulus curves of the regenerated asphalt eluted layer by layer for the i-th layer and the completely miscible regenerated asphalt in logarithmic coordinates; Determining the value range of the average equivalent spacing of the complex shear modulus curve in logarithmic coordinates: Among them, d 新 is the average equal-value spacing of the complex shear modulus curves of the new asphalt and the completely miscible recycled asphalt in the logarithmic coordinate, and d 旧 is the average equal-value spacing of the complex shear modulus curves of the old asphalt and the completely miscible recycled asphalt in the logarithmic coordinate.

2. The method for evaluating the miscibility of fresh and aged asphalt in a hot recycled mixture based on layer-by-layer elution according to claim 1, wherein, The obtaining of the old asphalt and RAP old material gradation includes: Milling and planing the old asphalt pavement to obtain pavement recycled materials, and using extraction and screening to obtain the old asphalt and RAP old material gradation; The old aggregate after extraction adopts the water washing and screening method, and the old asphalt after extraction needs to be reheated to remove the residual trichloroethylene.

3. The method for evaluating the mixing of new and old asphalt in a hot recycled mixture based on layer-by-layer elution according to claim 2, characterized in that, The preparation of the hot recycled asphalt mixture includes: According to the regeneration ratio design process in the hot recycling construction technology, determining the ratio of new and old materials added to the recycled asphalt mixture.

4. The method for evaluating the miscibility of fresh and aged asphalt in a thermally regenerated mixture based on layer-by-layer elution according to claim 3, characterized in that The obtaining of the regenerated asphalt by layer-by-layer elution includes: Taking the hot recycled mixture with a stainless steel filter screen, placing it in an elution device filled with trichloroethylene solution, conducting layer-by-layer elution, and using a high-speed rotary centrifuge and a rotary evaporator for layered extraction; The elution device for the hot recycled asphalt mixture includes a glass beaker, a stainless steel filter screen, a glass stirring rod and trichloroethylene solution; the screen hole size of the stainless steel filter screen is 0.1 mm; the volume of the hot recycled asphalt mixture taken ≤ 2 / 3 of the volume of the stainless steel filter screen; when conducting layer-by-layer elution, the number of elution layers n ≥ 3, and the soaking time for each elution is 10 s.

5. The method for evaluating the miscibility of fresh and aged asphalt in a hot recycled mixture based on layer-by-layer elution according to claim 4, wherein The obtaining of the complex shear modulus curve in logarithmic coordinates includes: Using a DSR dynamic shear rheometer to test the complex shear modulus of the old asphalt, the new asphalt, the regenerated asphalt by layer-by-layer elution and the completely miscible regenerated asphalt at various temperatures respectively to obtain the complex shear modulus curve in logarithmic coordinates.

6. The method for evaluating the miscibility of new and old asphalt in a thermally regenerated mixture based on layer-by-layer elution according to claim 5, characterized in that, Mixing and stirring includes: The stirring temperature > 130 °C and the stirring time > 10 min.

7. The method for evaluating the mixing of new and old asphalt in a hot recycled mixture based on layer-by-layer elution according to claim 6, wherein Also including: Calculate the average equivalent spacing coefficient Λ of the complex shear modulus curve in logarithmic coordinates i : The Λ is obtained from the value range of the average equal-value spacing of the complex shear modulus curve in the logarithmic coordinates i The value range is 0 to 1:

8. The method for evaluating the mixing of new and old asphalt in a thermally regenerated mixture based on layer-by-layer elution according to claim 1 or 7, characterized in that, The evaluation of the miscibility degree of new and old asphalt includes: According to the value range of the average equivalent spacing coefficient, dividing the miscibility degree of new and old asphalt in the hot recycled asphalt mixture into five levels at an interval of 0.2, including level one, level two, level three, level four, and level five.

9. The method for evaluating the mixing of new and old asphalt in a heat regenerated mixture based on layer-by-layer elution according to claim 8, wherein Also including: When the average equivalent spacing coefficient Λ i ∈ [0, 0.2], the corresponding miscibility level is first level, representing that the new and old asphalt are nearly completely miscible; When the average equivalent spacing coefficient Λ i ∈ [0.8, 1.0], the corresponding miscibility level is five, indicating that the new and old asphalt are nearly completely immiscible; The higher the grade of the average equivalent spacing coefficient, the worse the miscibility degree of new and old asphalt.

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