A method for calculating the mixing degree of new and old asphalt based on composite material theory
Through the calculation method of new-old asphalt mixing degree based on composite material theory, the problem of difficult to accurately calculate the mixing degree of recycled asphalt pavement is solved, and the effective asphalt content of recycled asphalt mixture is realized is realized, and the service performance of recycled asphalt pavement is improved. and security.
Patent Information
- Application Number
- CN202410637554.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-22
- Publication Date
- 2025-02-11
- Estimated Expiration
- 2044-05-22
AI Technical Summary
During the regeneration construction of waste RAP materials, the mixing degree between new and old bitumen is difficult to accurately calculate, resulting in early diseases and service durability problems of regenerated bitumen pavement.
Using the calculation method of the mixing degree of new-old asphalt based on composite material theory, the mixing degree of new-old asphalt diffusion and fusion system is calculated through Fick's second diffusion law and composite material theory, and the effective in the regenerated asphalt mixture is accurately predicted. Asphalt content.
It reduces the inherent errors caused by routine experimental workload and indirect calculations, ensures the long-term service performance of regenerated asphalt pavement, and avoids the potential harm of the use of toxic trichloroethylene to the health of staff.
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Figure CN118538335B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of road engineering, in particular to a method for calculating the mixing degree of new and old asphalt based on composite material theory. Background Art
[0002] Public information from the Ministry of Transport shows that, with the improvement of the highway network, my country's highway construction has gradually transitioned to maintenance and reconstruction. According to statistics, about 97% of national highways, provincial highways and county and township roads will be upgraded and renovated, and the market size of highway maintenance equipment and services has reached 200 billion yuan. A large amount of waste asphalt mixture (RAP) will be generated during small-scale maintenance and repair and large-scale milling and reconstruction of old asphalt pavements. According to statistics, my country's major and medium-sized trunk road repair projects alone produce about 160 million tons of RAP materials each year, while the mileage of national and provincial trunk roads only accounts for 11.2% of the total mileage of national roads, and its pavement thickness is about twice that of other low-grade roads. Based on this calculation, the annual amount of waste pavement materials generated by my country's entire highway network will be about 790 million tons, which is basically the same as the amount of RAP materials generated by the US highway network each year. In recent years, asphalt pavement recycling technology, especially hot mix recycling and warm mix recycling technology, has been widely used in the maintenance and new construction of road projects in my country, greatly alleviating the pollution of the ecological environment, land encroachment and waste of road construction material resources caused by a large amount of RAP materials.
[0003] However, in the actual recycling construction process of waste RAP materials, the degree of mixing (DOB) between new asphalt and old asphalt controlled by diffusion and fusion is the key to determine the service performance of the recycled pavement. Overestimation or underestimation of DOB may directly lead to early diseases of the recycled asphalt pavement, and then affect its service durability. Specifically, 1) an overly high DOB estimation value will cause the total asphalt content of the recycled asphalt mixture to be lower than the actual optimal asphalt content, that is, the effective asphalt binder content is too low, which will induce cracking, peeling and other diseases of the recycled asphalt pavement, resulting in poor pavement durability and other problems; 2) an overly low DOB estimation value will lead to excessive total asphalt content in the recycled asphalt mixture, that is, the effective asphalt binder content is too high, causing high-temperature rutting, bulging, slippage and other diseases of the recycled asphalt pavement and reducing the anti-skid performance of the pavement. In order to ensure the long-term service performance of the recycled asphalt pavement and save the amount of new asphalt, it is necessary to quickly and accurately calculate the DOB value of the new-old asphalt mixture system to control the effective asphalt content. In fact, RAP old asphalt is a layer of severely aged asphalt film wrapped around RAP aggregate. During the actual high-temperature mixing process, it will immediately diffuse and fuse once it comes into contact with new asphalt, but this process is difficult to quantitatively capture through experimental means. Most existing studies use trichloroethylene solution to extract and clean the RAP aggregate and new aggregate after mixing, and use microscopic testing methods such as infrared spectroscopy (FTIR), gel chromatography (GPC), scanning electron microscopy (SEM), fluorescence microscopy (FM) and other means to detect the transfer rate of RAP old asphalt in new asphalt, thereby indirectly calculating the DOB value, or detecting the physical-rheological properties of the extracted asphalt obtained by multiple cleanings, and calculating the DOB value by comparing the physical-rheological properties between it and the new asphalt and the old asphalt. However, asphalt treated with trichloroethylene solution will have an irreversible effect on the microscopic properties of asphalt, and multiple extraction and cleaning experiments are large in volume, the cleaning timing is difficult to control, and the operation error is large, which will affect the final DOB calculation accuracy. In addition, trichloroethylene is a toxic organic compound, which will bring potential harm to the health of the test personnel during the experimental operation. Summary of the invention
[0004] To address the deficiencies of the prior art, the present invention provides a method for calculating the mixing degree of new and old asphalt based on composite material theory, which reduces the workload of conventional experiments and the inherent errors caused by indirect calculations.
[0005] To achieve the above purpose, the present invention provides the following technical solutions: a method for calculating the mixing degree of new and old asphalt based on composite material theory, after the new and old asphalt are in contact with each other at high temperature, diffusion and fusion begin to occur at the interface of the two asphalts until the new and old asphalts are fused into a uniform regenerated asphalt; the old asphalt is divided into several sublayers, and the diffusion concentration of the new asphalt in each sublayer of the old asphalt can be calculated by Fick's second diffusion law, as shown in the following formula:
[0006]
[0007] In formula (1), C is the diffusion concentration of new asphalt; x is the vertical distance from the bottom of the old asphalt to the top of any sublayer, mm; t is the diffusion time, s; D is the constant diffusion coefficient, mm 2 / s;
[0008]
[0009] In formula (2), C(x, t) is the diffusion concentration of new asphalt in a certain old asphalt sublayer; C0 is the initial concentration of new asphalt, which is 1; n is the number of old asphalt sublayers (n = 1, 2, 3, ...); l is the total thickness of old asphalt, mm;
[0010] Based on the diffusion concentration C(x, t) of the new asphalt in a certain old asphalt sublayer in equation (2), the modulus of the sublayer is calculated by the following equation:
[0011]
[0012] In formula (3), is the modulus of a certain old asphalt sublayer at a certain diffusion temperature and diffusion time, Pa; is the modulus of new asphalt, Pa; is the modulus of old asphalt, Pa;
[0013] Based on the modulus of a certain old asphalt sublayer at a certain diffusion temperature and diffusion time in formula (3), the total modulus of the new-old asphalt diffusion and fusion system at a certain diffusion temperature and diffusion time is calculated by the following formula:
[0014]
[0015] In formula (4), Total modulus of new-old asphalt diffusion and fusion system, Pa; h 总 is the total thickness of the new-old asphalt diffusion and fusion system, mm; h 新沥青 is the thickness of the new asphalt, mm; is the modulus of each sublayer of old asphalt, Pa; is the thickness of each sublayer of old asphalt, mm;
[0016] Based on the total modulus of the new-old asphalt diffusion and fusion system in formula (3), the mixing degree of the new-old asphalt diffusion and fusion system is calculated by the following formula:
[0017]
[0018] In formula (5), is the total modulus of the new and old asphalt when they are just in contact without diffusion and fusion, Pa; is the total modulus when the new and old asphalt are completely diffused and fused, Pa.
[0019] Preferably, the modulus calculation formula (3) of a certain old asphalt sublayer at a certain diffusion temperature and diffusion time is obtained by analogy with the viscosity formula of two asphalt mixing systems, as shown in the following formula:
[0020]
[0021] In formula (6), is the viscosity of the new-old asphalt mixture system, Pa·s; is the viscosity of the old asphalt, Pa·s; is the viscosity of new asphalt, Pa·s.
[0022] Preferably, the total modulus of the new-old asphalt diffusion and fusion system at a certain diffusion temperature and diffusion time is derived based on composite material theory, as shown in the following formula:
[0023]
[0024] In formula (7), E A and E B are the total elastic modulus of the composite material, the elastic modulus of phase A, and the elastic modulus of phase B; f, f A and f B are the total volume of the composite material, the volume of phase A, and the volume of phase B, respectively.
[0025] Preferably, and It is obtained through dynamic rheological shear test.
[0026] The present invention provides a method for calculating the mixing degree of new and old asphalt based on composite material theory, which has the following beneficial effects compared with the prior art:
[0027] The present invention proposes a method for calculating the mixing degree of new-old asphalt based on composite material theory. According to Fick's diffusion law and composite material theory, the mixing degree of the new-old asphalt diffusion and fusion system can be accurately predicted, thereby controlling the effective asphalt content in the recycled asphalt mixture and ensuring the long-term service performance of the recycled asphalt pavement, greatly reducing the conventional experimental workload and the inherent errors caused by its indirect calculation; at the same time, it also avoids the potential harm to the health of workers caused by the use of toxic trichloroethylene. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:
[0029] Figure 1 It is a schematic diagram of the diffusion and fusion process of the new-old asphalt mixing system of the present invention. DETAILED DESCRIPTION
[0030] The following examples are used to explain the implementation methods of the present application in detail, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.
[0031] Example 1
[0032] In this embodiment, a linear SBS polymer with a polystyrene / polybutadiene block (S / B) ratio of 3:7 is used as a matrix asphalt modifier to obtain SBS modified asphalt as new asphalt, and the asphalt is subjected to a rotary thin film oven aging (RTFO) + pressure aging vessel (PAV) to obtain an artificially aged SBS modified asphalt as old asphalt. In order to facilitate the acquisition of the modulus of the new-old asphalt diffusion and fusion system under the "zero fusion" state, a silicone mold with a diameter of 25 mm and a thickness of 1 mm and 2 mm was made. After the new and old asphalts were placed in an oven at 160°C and heated to a fluid state, they were poured into 1 mm thick silicone molds respectively, and the new and old asphalt monolayer structures were prepared after cooling at room temperature of 25°C for 1 hour. The old asphalt monolayer structure is placed at the bottom of a 2 mm thick silicone mold, and the new asphalt monolayer structure is placed at the top, so as to obtain a 2 mm thick double-layer composite structure of the new-old asphalt diffusion and fusion system under the "zero fusion" state. The double-layer composite structure in the "completely fused" state refers to an asphalt sample prepared by manually stirring the two asphalts at 150°C for 5 minutes, pouring them into a 2 mm thick silicone mold, and cooling them at room temperature of 25°C for 1 hour.
[0033] In this embodiment, the diffusion and fusion temperature of the new-old asphalt mixture system is set to 140°C, and the diffusion time is 3 minutes. When the diffusion temperature is constant, the diffusion coefficient is a constant value, which can be found in existing literature (Karlsson, R., U. Isacsson, and J. Ekblad. Rheological Characterization of Bitumen Diffusion. Journal of Materials Science, 2007, pp. 101-108.), and its value is 9.70E-8cm 2 / s. The moduli of the new asphalt, old asphalt, zero fusion and complete fusion (complete fusion refers to the asphalt sample obtained by artificially stirring the two asphalts at 150°C for 5 minutes) asphalt samples in the diffusion and fusion system were obtained through a dynamic rheological shear (DSR) frequency sweep experiment. The DSR test parameters are shown in Table 1, and the test results are shown in Table 2.
[0034] Table 1 DSR frequency sweep test parameters
[0035] parameter Frequency scanning range (0.1Hz, 1Hz, 10Hz, 100Hz) Control Mode Strain Control Strain Level 1％ Test temperature 64℃ Test indicators <![CDATA[Complex shear modulus G * > spacing 1mm or 2mm Target frequency 10Hz
[0036] Table 2 Test results of different asphalt composite shear modulus (64℃, 10Hz)
[0037] Asphalt Type Modulus / pa New asphalt 18922 Old asphalt 26185 Zero Fusion 16650 Fully integrated 34831
[0038] A new-old asphalt mixing degree calculation method based on composite material theory, the mixing degree DOB value calculation process is as follows:
[0039] S1. Solve the new asphalt diffusion concentration C(x,t) in each sublayer of the old asphalt by equation (2), refer to Figure 1 , taking the third sublayer in the old asphalt as an example (x = 0.3), the calculation method and result of the diffusion concentration of the new asphalt there are:
[0040]
[0041] Similarly, the diffusion concentration of new asphalt in each sublayer of the remaining old asphalt can be calculated in the same way. The calculation results are shown in Table 3 below.
[0042] Table 3 Diffusion concentration of new asphalt in each sublayer of old asphalt
[0043] serial number concentration <![CDATA[C1]]> 0.0172 <![CDATA[C2]]> 0.0327 <![CDATA[C3]]> 0.0452 <![CDATA[C4]]> 0.0532 <![CDATA[C5]]> 0.0562 <![CDATA[C6]]> 0.0538 <![CDATA[C7]]> 0.0462 <![CDATA[C8]]> 0.0343 <![CDATA[C9]]> 0.0190 <![CDATA[C 10 ]]> 0.0019
[0044] S2. Calculate the modulus of each sublayer of old asphalt containing new asphalt diffusion concentration by formula (3): Taking the third sublayer in the old asphalt as an example (n=3), the calculation method and result of the modulus of this sublayer are Similarly, the modulus of each sublayer containing new asphalt diffusion concentration can be calculated in the same way, and the calculation results are shown in Table 4 below.
[0045] Table 4 Modulus of each sublayer of old asphalt
[0046]
[0047]
[0048] S3. Calculate the total modulus of the new-old asphalt diffusion and fusion system after diffusion and fusion at 140°C for 3 minutes using formula (4): The calculation method and results of the total modulus of the new-old asphalt diffusion and fusion system are as follows:
[0049] So the total modulus The calculated result is 19032pa.
[0050] S4. Calculate the mixing degree DOB of the new-old asphalt mixture system after diffusion and fusion at 140°C for 3 minutes using formula (5). The calculation formula and calculation result are as follows:
[0051]
[0052] To further verify the rationality of the above theoretical calculation results, under the same conditions, the new-old asphalt double-layer composite structure in the "zero fusion" state was placed in an oven at 140°C and heated for 3 minutes together with the silicone mold to allow the new and old asphalt to diffuse and fuse. After the heating was completed, the sample was immediately placed in a -5°C freezer for 25 minutes to avoid the influence of diffusion during the cooling process on the analysis results. Subsequently, the asphalt double-layer composite structure sample was taken out, and the actual composite shear modulus was obtained by referring to the DSR frequency scanning test parameters in Table 1: The actual mixing degree DOB of the new-old asphalt mixture system after diffusion and fusion for 3 minutes at 140°C is calculated by formula (5). The calculation formula and calculation result are as follows:
[0053]
[0054] Therefore, it can be seen that the error between the theoretical value and the experimental value of the DOB calculation result is 8.01%, indicating that the DOB theoretical calculation result has a high reliability.
[0055] Example 2
[0056] It can be seen from Example 1 that when no treatment measures are taken for the old asphalt, the mixing degree of the two asphalts after diffusion and fusion for 3 minutes at 140°C is low, only 13.10%. This example discusses the addition of an appropriate amount of regeneration agent to the old asphalt, which includes an aromatic oil capable of restoring the balance of the aged matrix asphalt, and its dosage is 5% of the mass ratio of the old asphalt; triallyl isocyanurate capable of reconnecting the aged and broken SBS polymer, and its dosage is 3% of the mass ratio of the old asphalt to improve its mixing degree DOB with the new asphalt. The diffusion temperature, diffusion time and other conditions in this example are consistent with those in Example 1. By adopting the DSR frequency scanning experiment in Example 1 (the test parameters are shown in Table 2), the modulus of the new asphalt, old asphalt, zero fusion and fully fused asphalt samples in the diffusion and fusion system are tested respectively, and the test results are shown in Table 5.
[0057] Table 5 Test results of different asphalt composite shear modulus (64℃, 10Hz)
[0058] Asphalt Type Modulus / pa New asphalt 18922 Old asphalt 21219 Zero Fusion 16066 Fully integrated 22590
[0059] S1. Solve the diffusion concentration C(x,t) of the new asphalt in each sublayer of the old asphalt by using equation (2). In this example, since the diffusion temperature, diffusion time, and new asphalt type remain unchanged, the diffusion coefficient is still 9.70E-8cm 2 / s, the diffusion concentration of new asphalt in each sublayer of old asphalt is the same as that in Example 1, as shown in Table 3.
[0060] S2. Calculate the modulus of each sublayer of old asphalt containing new asphalt diffusion concentration by formula (3): Taking the third sublayer in the old asphalt as an example (n=3), the calculation method and result of the modulus of this sublayer are Similarly, the modulus of each sublayer containing new asphalt diffusion concentration can be calculated in the same way, and the calculation results are shown in Table 6 below.
[0061] Table 6 Modulus of each sublayer of old asphalt
[0062]
[0063] S3. Calculate the total modulus of the new-old asphalt diffusion and fusion system after diffusion and fusion at 140°C for 3 minutes using formula (4): The calculation method and results of the total modulus of the new-old asphalt diffusion and fusion system are as follows:
[0064] So the total modulus The calculated result is 18961pa.
[0065] S4. Calculate the mixing degree DOB of the new-old asphalt mixture system after diffusion and fusion at 140°C for 3 minutes using formula (5). The calculation formula and calculation result are as follows:
[0066]
[0067] It can be seen from this that after the old asphalt is regenerated, the DOB value of the mixing degree of the new-old asphalt diffusion and fusion system can be significantly improved.
[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for calculating the mixing degree of new and old asphalt based on composite material theory, characterized in that: When the new and old asphalt come into contact with each other at high temperature, diffusion and fusion begin to occur at the interface of the two asphalts until the new and old asphalts fuse into a uniform recycled asphalt. The old asphalt is divided into several sublayers, and the diffusion concentration of the new asphalt in each sublayer of the old asphalt can be calculated by Fick's second diffusion law, as shown in the following formula: In formula (1), C is the diffusion concentration of new asphalt; x is the vertical distance from the bottom of old asphalt to the top of any sublayer, mm; t is the diffusion time, s; D is the constant diffusion coefficient, mm 2 / s; In formula (2), C(x, t) is the diffusion concentration of new asphalt in a certain old asphalt sublayer; C0 is the initial concentration of new asphalt, which is 1; n is the number of old asphalt sublayers divided, n = 1, 2, 3, ...; l is the total thickness of old asphalt, mm; Based on the diffusion concentration C(x, t) of the new asphalt in a certain old asphalt sublayer in equation (2), the modulus of the sublayer is calculated by the following equation: In formula (3), is the modulus of a certain old asphalt sublayer at a certain diffusion temperature and diffusion time, Pa; is the modulus of new asphalt, Pa; is the modulus of old asphalt, Pa; Based on the modulus of a certain old asphalt sublayer at a certain diffusion temperature and diffusion time in formula (3), the total modulus of the new-old asphalt diffusion and fusion system at a certain diffusion temperature and diffusion time is calculated by the following formula: In formula (4), Total modulus of new-old asphalt diffusion and fusion system, Pa; h 总 is the total thickness of the new-old asphalt diffusion and fusion system, mm; h 新沥青 is the thickness of the new asphalt, mm; is the modulus of each sublayer of old asphalt, Pa; is the thickness of each sublayer of old asphalt, mm; Based on the total modulus of the new-old asphalt diffusion and fusion system in formula (4), the mixing degree of the new-old asphalt diffusion and fusion system is calculated by the following formula: In formula (5), is the total modulus of the new and old asphalt when they are just in contact without diffusion and fusion, Pa; is the total modulus when the new and old asphalt are completely diffused and fused, Pa; The modulus calculation formula (3) of a certain old asphalt sublayer at a certain diffusion temperature and diffusion time is obtained by analogy with the viscosity formula of two asphalt mixing systems, as shown in the following formula: In formula (6), is the viscosity of the new-old asphalt mixture system, Pa·s; is the viscosity of the old asphalt, Pa·s; is the viscosity of new asphalt, Pa·s.
2. The method for calculating the mixing degree of new and old asphalt based on composite material theory according to claim 1 is characterized in that: The total modulus of the new-old asphalt diffusion and fusion system at a certain diffusion temperature and diffusion time is derived based on the composite material theory, as shown in the following formula: In formula (7), E A and E B are the total elastic modulus of the composite material, the elastic modulus of phase A, and the elastic modulus of phase B; f, f A and f B are the total volume of the composite material, the volume of phase A, and the volume of phase B, respectively.
3. The method for calculating the mixing degree of new and old asphalt based on composite material theory according to claim 1 is characterized in that: and It is obtained through dynamic rheological shear test.
4. The method for calculating the mixing degree of new and old asphalt based on composite material theory according to claim 1 is characterized in that: The diffusion and fusion system of new and old asphalt is prepared as follows: after the new and old asphalt are heated to a fluid state, they are poured into molds respectively, and after cooling, the new and old asphalt single-layer structures are obtained; the old asphalt single-layer structure is placed at the bottom of the mold, and the new asphalt single-layer structure is placed on the old asphalt single-layer structure.