A method for evaluating the blending efficiency of new and old asphalt

Abstract

The invention discloses an evaluation method for the blending efficiency of new and old asphalt. Based on materials studio, an amorphous crystal cell model of new asphalt and an amorphous crystal cell of old asphalt containing a regeneration agent are constructed. According to the in-situ hot regeneration technology of asphalt pavement, a double-layer model of new asphalt and old asphalt containing a regeneration agent is established through a build layer function. The new and old asphalt are fused with each other through dynamic simulation. The relative concentration curves of the new and old asphalt after fusion are analyzed, the fusion area is divided, the fusion amount is calculated, and the fusion degree of the new and old asphalt is quantitatively evaluated. The invention has high accuracy and simple operation, and selects microscopic quantifiable indicators to evaluate the fusion degree of the new and old asphalt under different working conditions of in-situ hot regeneration from a molecular scale.

Description

Technical Field

[0001] The invention relates to an evaluation method for the blending efficiency of new and old asphalt, in particular to a testing technology for quantitatively evaluating the regeneration effect of old asphalt pavement based on a molecular dynamics method, and belongs to the technical field of highway pavement engineering and computer experiments. Background Art

[0002] At present, the main road surface type in my country is asphalt concrete pavement, accounting for about 80% of the total mileage of my country's road pavement. Among them, about 12% of asphalt pavements require large-scale repairs and maintenance every year, and the waste asphalt mixture generated can reach 20 million tons.

[0003] As one of the important means of asphalt pavement maintenance, the old asphalt pavement recycling technology can make full use of waste materials and save asphalt and stone. By recycling waste materials, it can save resource costs and protect the ecological environment. It is a "green" engineering technology that has been widely studied and applied around the world.

[0004] In asphalt pavement regeneration technology, the degree of fusion of new and old asphalt is currently a hot topic of international research. Based on the molecular dynamics method, the asphalt-aggregate interface model can be established at the microscopic level. It is considered to be the third scientific method in addition to theoretical analysis and experimental observation since this century. It is called "computer experiment" method. It is guided by classical molecular dynamics theory and uses molecular dynamics simulation software as a platform to dynamically monitor the fusion process of new and old asphalt at the microscopic level, which can provide a scientific basis for the selection and development of asphalt pavements.

[0005] Through the method of molecular dynamics, we can carry out microscopic modeling of new and old asphalt and regeneration agent from a molecular perspective. By using classical Newtonian mechanics, we can give the model an appropriate force field and select microscopic indicators that can characterize the degree of fusion of new and old asphalt, thus providing guidance for the further development of recycled asphalt pavement. Summary of the invention

[0006] In view of the problems and shortcomings in the prior art, the present invention provides a method for evaluating the blending efficiency of new and old asphalt to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution, comprising the following steps:

[0008] Step 1, conducting infrared spectroscopy tests on the simulated new asphalt and old asphalt, calculating the peak area ratio of the carbonyl and sulfoxide functional groups in the infrared spectral image to obtain the carbonyl and sulfoxide functional group indexes, and the ratio of the functional group index in the old asphalt to that in the new asphalt is the relative content of the aging functional groups in the old asphalt;

[0009] Step 2, conducting a gas phase mass spectrometry test on the regeneration agent, and analyzing the mass spectrum to determine the main components and mass ratios thereof;

[0010] Step 3, performing a stick thin layer chromatography test on the simulated new asphalt and old asphalt, and analyzing the asphalt chromatogram according to the heavy oil type to determine the mass ratio of the four components in the new and old asphalt;

[0011] Step 4: Establish the molecular models of new asphalt and regeneration agent in materials studio software. According to the relative content of aging functional groups in old asphalt, add aging functional groups to the molecular model of new asphalt to obtain the molecular model of old asphalt.

[0012] Step 5: According to the results of the stick thin layer chromatography test, the molecular model contained in the new asphalt is assembled into a new asphalt amorphous crystal cell. When assembling the old asphalt amorphous crystal cell, the regeneration agent molecules are added according to the regeneration agent dosage to form the old asphalt amorphous crystal cell containing the regeneration agent;

[0013] Step 6: Based on the buildlayer function, a double-layer model of new asphalt and old asphalt containing regeneration agent is established. After dynamic simulation, the new and old asphalt are integrated with each other. The concentration curves of the new and old asphalt are derived by the software. The entire double-layer model is evenly divided into 1000 plates, and the length, width and height of each plate are the length, width and height of the entire double-layer model. The relative concentration of asphalt is calculated as follows:

[0014]

[0015] Where: c n is the concentration of plate n; c bulk is the average concentration of the entire two-layer model; N n is the number of molecules in the plate; V is the plate volume; RC n is the relative concentration at the location of plate n;

[0016] Step 7: Draw the relative concentration of each plate into a continuous relative concentration curve along the OZ direction of the double-layer model, perform noise reduction on the relative concentration curve, divide the area where the relative concentrations of new and old asphalt coexist as the fusion area, calculate the average relative concentration of asphalt in the fusion area by integration, multiply it by the length D of the fusion area and the cross-sectional area S of the fusion area, and get the fusion amount I F , the specific calculation process and formula are as follows:

[0017] D=D1+D2 (3)

[0018]

[0019] I F =C·D·S (5)

[0020] Where: D is the length of the fusion area; D1 and D2 are the diffusion depths of the new asphalt and the old asphalt, respectively, which are directly read from the relative concentration curve after diffusion; C is the average relative concentration of asphalt in the fusion area; x1 and x2 are the coordinates of the positions where the relative concentrations of the new and old asphalt are 0 after diffusion, respectively. The middle area between the two is where the new and old asphalt coexist, which is the fusion area; c1 and c2 are the relative concentrations of the new and old asphalt at a certain coordinate, respectively; S is the cross-sectional area of ​​each fusion area.

[0021] Preferably, in step 1, the infrared spectroscopy test adopts attenuated total reflection mode to perform functional group index analysis on the carbonyl and sulfoxide groups appearing after asphalt aging.

[0022] Preferably, in step 3, the rod-shaped thin layer chromatography test results are analyzed and processed according to the type of heavy oil in the asphalt sample scanning results, and when calculating the peak area, a correction normalization method is used to eliminate the influence of peak distortion and tailing.

[0023] Preferably, the new and old asphalt models in step 4 contain four components and twelve molecular structures. When constructing the molecular model of the old asphalt, carbonyl and sulfoxide functional groups are added to the middle structure of the asphaltene, colloid, and aromatic molecules of the new asphalt in turn to replace the methylene group in the middle of the molecular chain, while the methyl groups on the side chains and chain ends remain unchanged.

[0024] Preferably, in step 5, the structure of each new and old asphalt molecule monomer is optimized, and the construction function in the amorphous cell is used to optimize the structure of each new and old asphalt molecule monomer according to different molecular ratios at an initial density of 0.1 g / cm 3 The new and old asphalt amorphous unit cell models are assembled in a 3D periodic cubic box.

[0025] Preferably, the kinetic simulation process in step 6 is as follows: the interface model adopts periodic boundary conditions, and then the dynamic kinetic simulation in the forcite module is performed, the temperature is raised to the thermal regeneration temperature under the NVT ensemble, the running step length is 200ps, and after the heating is completed, it is run for 1000ps under the NPT ensemble, the initial speed is set to random, the thermostat is set to Anderson, and the barostat is set to Berendsen.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses molecular dynamics simulation based on materials studio software to quantitatively evaluate the degree of fusion of new and old asphalt during regeneration. It has high accuracy and simple operation steps, effectively avoiding the subjectivity of traditional experimental methods, thereby guiding engineering practice;

[0028] 2. The evaluation method proposed in the present invention can evaluate the degree of fusion of new and old asphalt under different regeneration agents, temperatures, and asphalt conditions by adjusting the model and parameters;

[0029] 3. In the selection of asphalt molecular models, the present invention fully considers the diversity of asphalt molecules. It is currently the most accurate asphalt molecular model, which is reliable and has accurate calculation results, and fully considers the anisotropy of the material. In terms of the operation sequence and parameter setting of dynamic simulation, it overcomes the shortcomings of previous models such as large system energy, instability, and insufficient relaxation, and has better simulation capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 AAA-1 model diagram of new and old asphalt of the present invention;

[0031] Figure 2 Schematic diagram of the new and old asphalt amorphous unit cells of the present invention;

[0032] Figure 3 The molecular model diagram of the regeneration agent in Example 1 of the present invention;

[0033] Figure 4 It is a new asphalt-old asphalt double-layer diffusion model in the embodiment of the present invention;

[0034] Figure 5 It is a relative concentration curve diagram in Example 1 of the present invention;

[0035] Figure 6 Schematic diagram of the method for delineating the fusion area of ​​the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be noted that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The technical parameters in the specific implementation case are only reasonable settings under the case, and any modification of the technical parameters only falls within the scope of protection of the present invention.

[0037] Example 1

[0038] Step 1, conducting infrared spectroscopy tests on the simulated new asphalt and old asphalt, calculating the peak area ratio of the carbonyl and sulfoxide functional groups in the infrared spectral image to obtain the carbonyl and sulfoxide functional group indexes, and the ratio of the functional group index in the old asphalt to that in the new asphalt is the relative content of the aging functional groups in the old asphalt;

[0039] Step 2, conducting a gas phase mass spectrometry test on the regeneration agent, and analyzing the mass spectrum to determine the main components and mass ratios thereof;

[0040] Step 3, performing a stick thin layer chromatography test on the simulated new asphalt and old asphalt, and analyzing the asphalt chromatogram according to the heavy oil type to determine the mass ratio of the four components in the new and old asphalt;

[0041] Step 4: Establish the molecular models of new asphalt and regeneration agent in materials studio software. According to the relative content of aging functional groups in old asphalt, add aging functional groups to the molecular model of new asphalt to obtain the molecular model of old asphalt.

[0042] Step 5: According to the results of the stick thin layer chromatography test, the molecular model contained in the new asphalt is assembled into a new asphalt amorphous crystal cell. When assembling the old asphalt amorphous crystal cell, the regeneration agent molecules are added according to the regeneration agent dosage to form the old asphalt amorphous crystal cell containing the regeneration agent;

[0043] Step 6: Based on the build layer function, a double-layer model of new asphalt and old asphalt containing regeneration agent is established. After dynamic simulation, the new and old asphalt are integrated with each other. The concentration curves of the new and old asphalt are derived from the software. The entire double-layer model is evenly divided into 1000 plates, and the length, width and height of each plate are the length, width and height of the entire double-layer model. Calculate the relative concentration of bitumen;

[0044] Step 7: Draw the relative concentration of each plate into a continuous relative concentration curve along the OZ direction of the double-layer model, perform noise reduction on the relative concentration curve, divide the area where the relative concentrations of new and old asphalt coexist as the fusion area, calculate the average relative concentration of asphalt in the fusion area by integration, multiply it by the length D of the fusion area and the cross-sectional area S of the fusion area, and get the fusion amount I F .

[0045] The formula involved in the embodiment is as follows:

[0046] Formula 1:

[0047] Formula 2:

[0048] Formula 3: D = D1 + D2;

[0049] Formula 4:

[0050] Formula 5: I F =C·D·S.

[0051] The specific implementation steps are:

[0052] Step 1: Conduct infrared spectroscopy tests on the 70# new asphalt used and the old asphalt recycled after three years of service, calculate the peak area ratio of the carbonyl and sulfoxide functional groups in the infrared spectral image to obtain the carbonyl and sulfoxide functional group indexes, and the ratio of the functional group index in the old asphalt to the new asphalt is the relative content of the aging functional groups in the old asphalt.

[0053] Step 2: Conduct a gas chromatography-mass spectrometry test on the regeneration agent used, and analyze the mass spectrum to determine the main components and mass ratios. Table 1 shows the composition of a regeneration agent commonly used in China.

[0054] Table 1 Main components of regeneration agent

[0055]

[0056] Step 3: Conduct stick thin layer chromatography test on the simulated new asphalt and old asphalt, and analyze the asphalt chromatogram according to the heavy oil type to determine the mass ratio of the four components in the new and old asphalt.

[0057] After the asphalt is fully dissolved in the toluene solution, it is spotted onto the activated silica gel chromatographic stick. After drying and shaping, the chromatographic stick is placed in the TLC analyzer for testing. Three groups of chromatographic columns are prepared for the new and old asphalt to measure and take the average value. According to the chromatogram processing method provided by Mitsubishi Chemical Pharmaceuticals in the Iatroscan Applications Booklet, the scanning results of the asphalt sample are analyzed and processed according to the type of heavy oil. The peak area calculation is completed in MATLAB software. When identifying the peak area, peak tailing and peak distortion are considered. The correction normalization method is used to automatically calculate the content through the correction factor. The results are shown in Table 2.

[0058] Table 2 Mass percentage of four components of new and old asphalt

[0059]

[0060] Step 4: Establish the molecular models of new asphalt and regeneration agent in materials studio software. According to the relative content of aging functional groups in old asphalt, add aging functional groups to the molecular model of new asphalt to obtain the molecular model of old asphalt.

[0061] The new asphalt model is the AAA-1 model proposed by SHRP (US Highway Strategic Research Program), which contains four components and twelve molecular structures. The C=O and S=O functional group indices in the old asphalt are 0.05 and 0.13, respectively. The functional group index represents the relative mass content of the aged functional groups in the old asphalt. In the new asphalt molecular model, carbonyl and sulfoxide groups are configured on the aging molecules in the order of asphaltene, colloid, and aromatic components. The specific molecular numbers and molecular formulas are shown in Table 3 and Appendix. Figure 1 shown.

[0062] Table 3 Molecular number distribution of new and old asphalt

[0063]

[0064] Step 5: According to the content of the four components in the new and old asphalt, each molecular structure was optimized separately, and then the amorphous cell construction function in the materials studio software was used to optimize the structure of each molecule according to different molecular proportions at an initial density of 0.1g / cm 3 The amorphous unit cell models of new and old asphalt (including regeneration agent) are assembled in a 3D periodic cubic box. When constructing the amorphous unit cell of old asphalt, the regeneration agent dosage is adjusted and the regeneration agent molecules are added at the same time to form the amorphous unit cell of old asphalt containing the regeneration agent. The amorphous unit cells of new and old asphalt are shown in the attached figure. Figure 2 As shown, the regenerant molecule is Figure 3 shown.

[0065] Step 6: Based on the build layer function, a double-layer model of new asphalt and old asphalt containing regeneration agent is established. The model diagram is as follows: Figure 4 As shown in the figure, after dynamic simulation, the new and old asphalt are integrated with each other, and the concentration curve of the new and old asphalt is derived by the software. The whole double-layer model is evenly divided into 1000 plates, and the length, width and height of each plate are the length, width and height of the whole double-layer model. Calculate the relative concentration of asphalt according to formula 1 and 2.

[0066] Step 7: Draw the relative concentration of each plate along the OZ direction of the double-layer model into a continuous relative concentration curve, as shown in the attached figure. Figure 5 As shown in the figure, the relative concentration curve is denoised, and the area where the relative concentrations of new and old asphalt coexist is divided into the fusion area. The method for demarcating the fusion area is shown in the attached figure. Figure 6 As shown, the average relative concentration of asphalt in the fusion area C is calculated by integration, multiplied by the length of the fusion area D and the cross-sectional area S of the fusion area, and the fusion amount I is obtained. F The specific calculation process is as follows: Formula 3-5. The calculated diffusion depth D is The cross-sectional area S of the fusion region is The average relative concentration of asphalt C is 1.9, and the fusion volume I F 720132,I F The larger it is, the more new and old asphalt molecules participate in the fusion per unit time, the higher the degree of fusion of new and old asphalt, and the higher the fusion efficiency.

Claims

1. A method for evaluating the blending efficiency of new and old asphalt, characterized in that: The following steps are involved: Step 1, performing infrared spectroscopy test on the simulated new asphalt and old asphalt, calculating the peak area ratio of carbonyl and sulfoxide functional group benchmarks in the infrared spectral image, and obtaining the functional group index of carbonyl and sulfoxide. The ratio of the aging functional group index in the old asphalt to that in the new asphalt is the relative content of the aging functional group in the old asphalt; Step 2, performing a gas chromatography-mass spectrometry test on the regeneration agent, and analyzing the mass spectrum to determine the main components and mass ratios thereof; Step 3, performing a stick thin layer chromatography test on the simulated new asphalt and old asphalt, and analyzing the asphalt chromatogram according to the heavy oil type to determine the mass ratio of the four components in the new and old asphalt; Step 4: Establish the molecular models of new asphalt and regeneration agent in materials studio software. According to the relative content of aging functional groups in old asphalt, add aging functional groups to the molecular model of new asphalt to obtain the molecular model of old asphalt. Step 5: According to the ratio of the four components in the asphalt, the molecular model contained in the new asphalt is assembled into a new asphalt amorphous unit cell model. When assembling the old asphalt amorphous unit cell model, the regeneration agent molecules are added according to the regeneration agent dosage to form an old asphalt amorphous unit cell model containing the regeneration agent; Step 6: Based on the build layer function, a double-layer model of new asphalt and old asphalt containing regeneration agent is established. After dynamic simulation, the new and old asphalts are integrated with each other. The concentration curves of the new and old asphalts are respectively derived by the materials studio software. The entire double-layer model is evenly divided into 1000 plates, and the length, width and height of each plate are the length, width and height of the entire double-layer model. The relative concentration of asphalt at a certain plate location is calculated according to the following formula: Where c n is the concentration of plate n; c bulk is the average asphalt concentration of the entire double-layer model; N n is the number of molecules in the plate; V is the plate volume; RC n is the relative concentration of asphalt at the location of plate n; Step 7: Draw the relative concentration of each plate into a continuous relative concentration curve along the OZ direction of the double-layer model, perform noise reduction on the relative concentration curve, divide the area where the relative concentrations of new and old asphalt coexist as the fusion area, calculate the average relative concentration of asphalt in the fusion area by integration, multiply it by the length D of the fusion area and the cross-sectional area S of the fusion area, and get the fusion amount I F , the specific calculation process and formula are as follows: D=D1+D2 (3) I F =C·D·S (5) Where D is the length of the fusion area; D1 and D2 are the diffusion depths of the new asphalt and the old asphalt, respectively, which are directly read from the relative concentration curve after diffusion; C is the average relative concentration of asphalt in the fusion area; x1 and x2 are the coordinates of the position where the relative concentration of the new and old asphalt is 0 after diffusion, respectively. The middle area between the two is where the new and old asphalt coexist, which is the fusion area; C1 and C2 are the relative concentrations of the new and old asphalt at a certain coordinate. S is the cross-sectional area of ​​each fusion region.

2. The method for evaluating the blending efficiency of new and old asphalt according to claim 1, characterized in that: In step 4, the molecular models of the new and old asphalts include four components and a total of twelve molecular structures. After optimizing the structure of each molecular monomer, the construction function in the amorphous cell is used to assemble the amorphous cell models of the new and old asphalts according to the proportions of the four components of asphalt.

3. The method for evaluating the blending efficiency of new and old asphalt according to claim 1, characterized in that The kinetic simulation process in step 6 is as follows: the interface model adopts periodic boundary conditions, and then the dynamic kinetic simulation is carried out in the forcite module. The temperature is raised to the thermal regeneration temperature under the NVT ensemble, and the running step length is 200ps. After the heating is completed, it is run for 1000ps under the NPT ensemble, the initial speed is set to random, the thermostat is set to Anderson, and the barostat is set to Berendsen.

4. The method for evaluating the blending efficiency of new and old asphalt according to claim 1, characterized in that The noise reduction process described in step 7 of claim 1 is to perform median filtering on the relative concentration of each sampling point in the numerical processing software after the relative concentration curve is derived, and replace the individual positions where the relative concentration is distorted with the median of the values ​​of each point in the neighborhood, thereby eliminating the concentration mutation caused by the sampling size when the molecular dynamics software is sampling the concentration, and reducing the error in calculating the fusion amount.

5. The method for evaluating the blending efficiency of new and old asphalt according to claim 1, characterized in that The fusion area is defined as the area where the relative concentrations of new and old asphalt coexist by comparing the relative concentration curves of the new and old asphalt before and after blending, and the absolute value of the difference in coordinates at the position where the relative concentration is 0 before and after blending is defined as the diffusion depth.

Images