Method for evaluating performance of mineral aggregate framework of asphalt mixture

Abstract

The invention discloses an asphalt mixture mineral aggregate skeleton performance evaluation method, which is based on a numerical simulation method and comprises the following steps of: establishing a simulation analysis model considering the shape and distribution characteristics of asphalt mixture mineral aggregate, loading the simulation analysis model, acquiring a transmission path and an internal force state of the internal force of an asphalt mixture under the action of a load, and evaluating the performance of the asphalt mixture mineral aggregate skeleton. And establishing characterization parameters of an internal force transmission path and an internal force state, and synthesizing the two parameters to characterize and evaluate the skeleton structure performance of the mineral aggregate. According to the technical principle that the internal force transmission path of the asphalt mixture, the internal force of the mineral aggregate and the internal force of the asphalt are closely related to the skeleton structure of the mineral aggregate, and the simulation analysis advantages of a numerical model are combined, so that the characterization and evaluation of the skeleton structure of the mineral aggregate of the asphalt mixture are realized. By changing the particle size composition of the mineral aggregate particles, the influence of different mineral aggregate particle compositions on the skeleton performance can be quantitatively compared and analyzed. The method provided by the invention has the technical advantages of rapidness, simplicity and effectiveness.

Description

Technical Field

[0001] The present invention relates to a quantitative characterization and evaluation method for the skeleton structure form and skeleton performance of asphalt mixtures. Background Art

[0002] Asphalt mixture is an important pavement material. Under the action of vehicle loads and environmental temperatures, it is required that the asphalt mixture should have sufficient high-temperature stability and low-temperature crack resistance, without rutting under high-temperature conditions and without cracking under low-temperature conditions. The high-temperature stability and low-temperature crack resistance of asphalt mixtures are closely related to their strength. When the strength is higher, the asphalt mixture has better high- and low-temperature performance. From the perspective of the material composition of asphalt mixtures, the factors affecting their strength mainly include two aspects. One is the adhesion of asphalt, and the other is the internal frictional resistance between mineral aggregates inside the asphalt mixture. Due to the high temperature sensitivity of asphalt, under high-temperature conditions, as the asphalt softens, the strength of the asphalt mixture mainly depends on the internal frictional resistance of the mineral aggregates. Under low-temperature conditions, due to the low tensile capacity of asphalt, there is also a great relationship between the internal frictional resistance of the mineral aggregates and the crack resistance of the asphalt mixture. Therefore, the internal frictional resistance of the mineral aggregates has an important influence on the strength of the asphalt mixture.

[0003] The internal frictional resistance of mineral aggregates is closely related to the skeleton structure of mineral aggregates. When the mineral aggregates have a good skeleton structure, relatively large internal frictional forces will be generated between the mineral aggregate particles. The skeleton structure type will also affect the internal force transfer of the asphalt mixture, directly affecting the ability of the asphalt mixture to resist external load actions. Based on the relationship between the internal frictional force and internal force transfer and the mineral aggregate skeleton in these two aspects, it is very important to characterize and evaluate the performance of the mineral aggregate skeleton.

[0004] The internal skeleton structure of the asphalt mixture is determined by the spatial distribution and contact state of mineral particles, and the factors affecting the mineral aggregate skeleton are relatively complex. First, it is the particle size composition of the mineral aggregates and the asphalt content. Different particle size compositions of mineral aggregates and asphalt contents will affect the distribution and contact state of mineral particles in the asphalt mixture, and further affect the skeleton structure of the mineral aggregates. Second, the construction process will also affect the skeleton structure of the mineral aggregates. For example, construction temperature and compaction technology will affect the mineral aggregate skeleton structure of the compacted asphalt mixture. Due to the complexity of the problem, there is currently no effective method for characterizing and evaluating the performance of the mineral aggregate skeleton structure, whether in terms of testing methods or theoretical analysis means.

[0005] At present, there is only a macroscopic and qualitative description of the skeleton structure state of aggregates in asphalt mixtures. According to the distribution and contact state of aggregate particles, it is simply divided into two types: suspension type and skeleton type. In the suspension type, the aggregate particles do not contact each other, and the large aggregate particles are distributed in the asphalt mortar in a suspended state, while in the skeleton type, the aggregate particles contact each other. This is a very macroscopic description of the aggregate contact state. For the skeleton type structure, there is no further detailed description. For the same skeleton type structure, different aggregate particle size compositions result in different skeleton structures, and the resistance of the skeleton structure to the action of loads is also different. Therefore, this macroscopic classification of the skeleton structure type cannot quantitatively characterize the subtle differences of the skeleton structure. Different aggregate particle size compositions can all form a skeleton structure, but the force characteristics of the skeleton and its resistance to the action of loads are very different. Therefore, it is very necessary to characterize and evaluate the performance of the aggregate skeleton.

[0006] It is very difficult to directly quantitatively describe and characterize the composition characteristics of the aggregate skeleton structure from the perspective of the distribution and contact state of aggregate particles. Under the action of an external load, the internal force transmission path of the asphalt mixture is closely related to the aggregate skeleton structure and will also affect the internal force composition of the asphalt mixture. Therefore, the performance of the aggregate skeleton structure can be quantitatively characterized and evaluated from the perspective of the internal force transmission path and internal force composition of the asphalt mixture under the action of an external load. Summary of the Invention

[0007] The present invention provides a method for evaluating the performance of the aggregate skeleton of an asphalt mixture, aiming to better analyze the strength mechanism and design materials of the asphalt mixture, effectively improve the material performance of the asphalt mixture, and realize the quantitative analysis of the aggregate skeleton.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] A method for evaluating the performance of the aggregate skeleton of an asphalt mixture includes the following steps:

[0010] Step 1: Establish digital aggregate particles:

[0011] Step 1-1: Determine the range of aggregate particle sizes of the asphalt mixture according to the type of the asphalt mixture.

[0012] Step 1-2: Through a screening test on the aggregates, take samples of particle sizes above 2.36 mm.

[0013] Step 1-3: Weigh the mass of each particle respectively, and through CT scanning and image processing of the selected aggregate particles, obtain digital aggregate particles and their corresponding volumes.

[0014] Step 1-4: Calculate the density of the aggregates according to the total mass and total volume of the aggregate particles.

[0015] Step 2. Determine the particle size composition of the mineral aggregate and the asphalt content:

[0016] Step 2-1. Determine the asphalt content according to the gradation type of the asphalt mixture.

[0017] Step 2-2. Combine the specified mineral aggregate gradation range in the specification to determine the particle size composition of the mineral aggregate and the percentage of the amount of each particle size.

[0018] Step 3. Establish a simulation analysis model for the asphalt mixture:

[0019] Step 3-1. Calculate the mass of the asphalt and the mass of the mineral aggregate based on the total mass of the cylinder simulation model, and then obtain the mass of each particle size of the mineral aggregate.

[0020] Step 3-2. Calculate the total volume of each particle size of the mineral aggregate and the volume of the asphalt according to the mass and density. Determine the number of each particle size of the digital mineral aggregate particles and the number of asphalt particles based on the total volume and the volume of each digital mineral aggregate particle.

[0021] Step 3-3. Select the corresponding digital mineral aggregate particles and asphalt particles, and generate a simulation analysis model including asphalt and mineral aggregate by means of free stacking.

[0022] Step 4. Model loading:

[0023] Step 4-1. For the simulation analysis model established in Step 3, set the loading rate and model parameters, perform radial loading, and ensure that the model is completely fractured.

[0024] Step 4-2. Obtain the load-displacement curve after the model is completely fractured according to the simulation analysis results.

[0025] Step 5. Obtain the internal force transmission path diagram:

[0026] Through the load-displacement curve obtained in Step 4, determine the loading point t1 corresponding to the maximum load and the loading point t2 corresponding to the load dropping to 90% of the maximum load value. Obtain the internal force transmission path diagrams corresponding to the loading points t1 and t2 based on the loading simulation analysis results.

[0027] Step 6. Processing of the internal force transmission path diagram:

[0028] Based on the internal force transmission path diagram, use image processing software for image processing to obtain the significant internal force transmission path contour diagrams of the loading points t1 and t2.

[0029] Step 7. Obtain the skeleton stability coefficient:

[0030] According to the contour diagrams of the significant internal force transfer paths at the loading points t1 and t2, respectively determine the angular ranges of the significant internal force transfer paths, and obtain the angular ranges α and β of the significant internal force transfer paths at the loading points t1 and t2. Define the skeleton stability coefficient μ = β / α;

[0031] Step 8: Obtain the internal force state parameters:

[0032] Step 8-1: According to the simulation analysis results corresponding to the loading points t1 and t2, respectively obtain the average values of the internal forces of the mineral aggregates and the internal forces of the asphalt;

[0033] Step 8-2: Define the internal force state ratio Where: is the average value of the internal forces of the mineral aggregates at the loading point t1, is the average value of the internal forces of the asphalt at the loading point t1, is the average value of the internal forces of the mineral aggregates at the loading point t2, is the average value of the internal forces of the asphalt at the loading point t2;

[0034] Step 9: Evaluate the skeleton performance based on the skeleton stability coefficient and the internal force state parameters:

[0035] According to the skeleton stability coefficient and the internal force state ratio, define the comprehensive evaluation parameter φ of the skeleton performance as φ = η1μ + η2λ, where η1 and η2 are the weight coefficients of the skeleton stability coefficient and the internal force state ratio respectively, and η1 + η2 = 1.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] The method for characterizing and evaluating the skeleton performance proposed by the present invention, based on the technical principle that the internal force transfer path of the asphalt mixture, the internal forces of the mineral aggregates and the asphalt are closely related to the mineral aggregate skeleton structure, combines the simulation analysis advantages of the numerical model, and realizes the characterization and evaluation of the mineral aggregate skeleton structure of the asphalt mixture. By changing the particle size composition of the mineral aggregates, the influence of different mineral aggregate particle compositions on the skeleton performance can be quantitatively compared and analyzed. The method of the present invention has the technical advantages of being fast, simple and effective, and has certain application value for the research on the strength mechanism of asphalt mixtures and the material design of asphalt mixtures. Description of the Drawings

[0038] Figure 1 is the digital mineral aggregate particle;

[0039] Figure 2 is the numerical simulation model;

[0040] Figure 3 is the loading mode;

[0041] Figure 4 is the load-displacement curve;

[0042] Figure 5 It is a diagram of the internal force transmission path. a) The internal force transmission path at the loading point t1. b) The internal force transmission path at the loading point t2;

[0043] Figure 6 It is a contour diagram of the significant internal force transmission path. a) The internal force transmission path at the loading point t1. b) The internal force transmission path at the loading point t2;

[0044] Figure 7 It is the range angle of the significant internal force transmission path. a) The range angle of the significant internal force transmission path at the loading point t1. b) The range angle of the significant internal force transmission path at the loading point t2. Specific implementation mode

[0045] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be covered by the protection scope of the present invention.

[0046] The present invention provides a method for evaluating the aggregate skeleton performance of asphalt mixtures. The method is based on a numerical simulation method to establish a simulation analysis model considering the shape and distribution characteristics of the aggregates in the asphalt mixture, load the simulation analysis model, obtain the internal force transmission path and internal force state of the asphalt mixture under the action of the load, establish the characterization parameters of the internal force transmission path and internal force state, and comprehensively characterize and evaluate the skeleton structure performance of the aggregates. The specific steps are as follows:

[0047] Step 1: Establish digital aggregate particles:

[0048] According to the type of asphalt mixture, determine the range of the aggregate particle size of the asphalt mixture. Through the sieve analysis test of the aggregates, samples are taken for particle sizes above 2.36 mm. The selected aggregate particles should have a certain quantity and should include a certain number of flat particles to ensure the representativeness of the selected aggregate particles. Weigh the mass of each particle, and through CT scanning and image processing of the selected aggregate particles, obtain the digital aggregate particles and the corresponding volume. Calculate the density of the aggregates according to the total mass and total volume of the aggregate particles.

[0049] Step 2: Determine the aggregate particle size composition and asphalt content:

[0050] According to the gradation type of the asphalt mixture, formulate the asphalt content. And in combination with the aggregate gradation range specified in the Highway Asphalt Pavement Construction Technical Specification, determine the aggregate particle size composition and the percentage of the amount of each particle size.

[0051] Step 3: Establish a simulation analysis model of the asphalt mixture:

[0052] Generate a simulation analysis model based on the selected asphalt dosage and the particle size composition of the mineral aggregate. The simulation analysis model is a cylinder. Calculate the mass of the asphalt and the mass of the mineral aggregate based on the total mass of the cylinder, and then obtain the mass of the mineral aggregate of each particle size. Calculate the total volume of the mineral aggregate of each particle size and the volume of the asphalt according to the mass and density. Determine the number of digital mineral aggregate particles of each particle size and the number of asphalt particles according to the total volume and the volume of each digital mineral aggregate particle. Select the corresponding digital mineral aggregate particles and asphalt particles, and generate a cylinder simulation analysis model including asphalt and mineral aggregate by means of free stacking.

[0053] Step 4, Model loading:

[0054] For the simulation analysis model established in Step 3, set the loading rate and model parameters, perform radial loading, and ensure that the model is completely fractured to obtain the load-displacement curve after the model is completely fractured.

[0055] Step 5, Obtain the internal force transmission path diagram:

[0056] Determine the loading point t1 corresponding to the maximum load and the loading point t2 corresponding to the load dropping to 90% of the maximum load value through the load-displacement curve obtained by the simulation analysis in Step 4. According to the loading simulation analysis results, obtain the internal force transmission path diagrams corresponding to the loading points t1 and t2.

[0057] Step 6, Processing of the internal force transmission path diagram:

[0058] According to the internal force transmission path diagram, perform image processing using image processing software to obtain a prominent internal force transmission path contour diagram.

[0059] Step 7, Obtain the skeleton stability coefficient:

[0060] According to the prominent internal force transmission path contour diagrams of the loading points t1 and t2, respectively determine the range angles of the prominent internal force transmission paths to obtain the range angles α and β of the prominent internal force transmission paths of the loading points t1 and t2, and define the skeleton stability coefficient μ = β / α.

[0061] Step 8, Obtain the internal force state parameters:

[0062] According to the simulation analysis results corresponding to the loading points t1 and t2, respectively obtain the average values of the internal forces of the mineral aggregate and the internal forces of the asphalt. The average value of the internal forces of the mineral aggregate at the loading point t1 is The average value of the internal forces of the asphalt is The average value of the internal forces of the mineral aggregate at the loading point t2 is The average value of the internal forces of the asphalt is Define the internal force state ratio

[0063] Step 9, Evaluate the skeleton performance based on the skeleton stability coefficient and the internal force state parameters:

[0064] According to the skeleton stability coefficient and the internal force state ratio, a comprehensive evaluation parameter φ of the skeleton performance is defined as φ = η1μ + η2λ, where η1 and η2 are the weight coefficients of the skeleton stability coefficient and the internal force state ratio respectively, and η1 + η2 = 1.

[0065] The basic principle of this evaluation method is as follows:

[0066] 1. Relationship between the skeleton stability coefficient and the performance of the mineral aggregate skeleton:

[0067] Based on the internal force transfer path diagram at the maximum load point t1 obtained from the load-displacement curve, at this time the load reaches the maximum, and the internal force of the mineral aggregate also reaches the maximum, which is equivalent to reaching the maximum vertical pressure state that the mineral aggregate skeleton can bear. Since the model is cylindrical, the transfer paths of the vertical pressure at both ends of the model bend in an arc shape to both sides. At the maximum load, the maximum influence range of the internal force transfer path is reached, that is, the contour range of the significant internal force transfer path corresponding to the loading point t1. The size of this range is characterized by the significant internal force transfer path range angle α.

[0068] When the load drops to the loading point t2 corresponding to 90% of the maximum value, at this time under the action of the external load, vertical cracks appear in the middle of the model. Due to the generation of cracks in the middle of the model, the ability of the model to resist horizontal deformation is reduced, resulting in the failure and disappearance of the vertical internal force transfer paths that appeared at the edges on both sides of the model at the maximum load, and the maximum influence range of the internal force transfer path will shrink, that is, the contour range of the significant internal force transfer path corresponding to the loading point t2. The size of this range is characterized by the significant internal force transfer path range angle β. When the mineral aggregate skeleton structure of the asphalt mixture is good, at the fracture point t2, the model still has a large influence range of the internal force transfer path. Therefore, the performance of the mineral aggregate skeleton can be characterized by the skeleton stability coefficient μ = β / α. The larger the μ value, the smaller the influence of the model fracture on the internal force transfer path range, and the better the skeleton performance of the mineral aggregate.

[0069] 2. Relationship between the internal force state parameter and the performance of the mineral aggregate skeleton:

[0070] The present invention uses the ratio of the average internal force of the mineral aggregate to the average internal force of the asphalt to characterize the performance of the mineral aggregate skeleton. Under the action of an external load pressure, internal forces will be generated inside the mineral aggregate and inside the asphalt. The magnitudes of these two internal forces are related to the skeleton structure. When the mineral aggregate has a good skeleton structure, under the action of the external load pressure, the internal force of the model is mainly borne by the mineral aggregate skeleton. At this time, the internal force of the mineral aggregate is large, while the internal force of the asphalt is small. On the contrary, when the skeleton structure of the mineral aggregate is poor, the internal force of the mineral aggregate is small, while the internal force of the asphalt is large. Therefore, the performance of the mineral aggregate skeleton can be characterized by the ratio of the average internal force of the mineral aggregate to the average internal force of the asphalt, that is, the internal force state ratio. The larger the internal force state ratio, the better the skeleton performance of the mineral aggregate. The present invention uses the average value of the two internal force state ratios at the loading points t1 and t2 to characterize the skeleton performance of the mineral aggregate, comprehensively reflecting the internal force states in both the intact and cracked states of the model, and can better characterize the skeleton structure performance of the mineral aggregate from the perspective of internal forces.

[0071] Example:

[0072] Taking the SMA-13 asphalt mixture as an example below, the specific application process of the method of the present invention will be described.

[0073] Step 1: Establish digital mineral aggregate particles:

[0074] The maximum aggregate size of the SMA-13 asphalt mixture is 13.2 mm. Determine the aggregate size range to be 2.36 mm to 13.2 mm, select the corresponding aggregates for sieve analysis, sample the aggregate particles of four sizes, namely 2.36 mm, 4.75 mm, 9.5 mm, and 13.2 mm, and take 10 particles for each size. Weigh the mass of each particle. When sampling, a certain number of flat particles should be included. Conduct CT scans and image processing on the selected aggregate particles to obtain digital aggregate particles, as Figure 1 shown. Calculate the volume of each particle. Based on the total mass and total volume of the selected aggregate particles, calculate the density of the aggregate to be 2.75 g / cm 3 .

[0075] Step 2: Determine the aggregate particle size composition and asphalt content:

[0076] Refer to the relevant specifications to obtain the gradation range of SMA-13 asphalt mixture, and obtain the proportion range of the aggregate dosage of four particle sizes: 2.36mm, 4.75mm, 9.5mm, and 13.2mm. The dosage range of the 2.36mm particle size is 5% - 8%, the dosage range of the 4.75mm particle size is 30% - 41%, the dosage range of the 9.5mm particle size is 25% - 40%, and the dosage range of the 13.2mm particle size is 0% - 10%. According to the dosage ranges of the four particle sizes, two different aggregate particle size compositions are selected. Particle size composition I: the dosage of the 2.36mm particle size is 6%, the dosage of the 4.75mm particle size is 35%, the dosage of the 9.5mm particle size is 37%, and the dosage of the 13.2mm particle size is 9%; Particle size composition II: the dosage of the 2.36mm particle size is 8%, the dosage of the 4.75mm particle size is 40%, the dosage of the 9.5mm particle size is 33%, and the dosage of the 13.2mm particle size is 6%. The total dosage of the aggregate above 2.36mm is 87%, and the total dosage of the aggregate below 2.36mm is 13%. The mass ratio of asphalt to aggregate is determined to be 5.5%.

[0077] Step 3: Establish a simulation analysis model for asphalt mixture:

[0078] The simulation analysis model is a cylinder with a diameter of 101.6mm and a height of approximately 63.5mm. The total mass of the aggregate in the model is 1200g. According to the aggregate particle size composition ratios of Particle size composition I and Particle size composition II determined previously, determine the mass of each particle size aggregate and asphalt. Particle size composition I: the total mass of the 2.36mm particle size is 72g, the total mass of the 4.75mm particle size is 420g, the total mass of the 9.5mm particle size is 444g, the total mass of the 13.2mm particle size is 108g, the total mass of the aggregate below 2.36mm is 156g, and the mass of asphalt is 66g; Particle size composition II: the total mass of the 2.36mm particle size is 96g, the total mass of the 4.75mm particle size is 480g, the total mass of the 9.5mm particle size is 396g, the total mass of the 13.2mm particle size is 72g, the total mass of the aggregate below 2.36mm is 156g, and the mass of asphalt is 66g. The density of the aggregate is 2.75g / cm 3 , and the density of asphalt is 1.0g / cm 3 .

[0079] According to the mass composition of Particle size composition I and Particle size composition II, the volume of each particle size aggregate and asphalt can be obtained. Particle size composition I: the total volume of the 2.36mm particle size is 26.18cm 3 、the total volume of the 4.75mm particle size is 152.73cm 3 、the total volume of the 9.5mm particle size is 161.45cm 3 、the total volume of the 13.2mm particle size is 39.27cm 3, the total volume of asphalt is 66 cm 3 , the total volume of aggregates smaller than 2.36 mm is obtained by subtracting the volume of aggregates larger than 2.36 mm and the volume of asphalt from the total volume of the model. Thus, the total volume of aggregates smaller than 2.36 mm is 68.92 cm 3 . Similarly, the volume composition of particle size composition II can be obtained. Particle size composition II: the total volume of 2.36 mm particle size is 34.91 cm 3 , the total volume of 4.75 mm particle size is 174.55 cm 3 , the total volume of 9.5 mm particle size is 144.0 cm 3 , the total volume of 13.2 mm particle size is 26.18 cm 3 , the total volume of asphalt is 66 cm 3 , the total volume of aggregates smaller than 2.36 is 68.91 cm 3 .

[0080] After determining the volume composition of each size fraction of aggregates, based on the known volume of each digital aggregate particle larger than 2.36 mm, the number of digital aggregate particles with particle sizes of 2.36 mm, 4.75 mm, 9.5 mm, and 13.2 mm can be calculated respectively. Asphalt is simulated by small balls with a diameter of 1 mm. Aggregate particles smaller than 2.36 mm are simulated by small balls with a diameter of 1.18 mm. The calculated numbers of digital aggregate particles and small balls are as follows: Particle size composition I: the number of digital aggregate particles with a particle size of 2.36 mm is 3805, the number of digital aggregate particles with a particle size of 4.75 mm is 2723, the number of digital aggregate particles with a particle size of 9.5 mm is 359, the number of digital aggregate particles with a particle size of 13.2 mm is 32, the number of small balls with a diameter of 1 mm is 126122, and the number of small balls with a diameter of 1.18 mm is 80153. The total number of digital aggregate particles and small balls is 213194. Particle size composition II: the number of digital aggregate particles with a particle size of 2.36 mm is 5075, the number of digital aggregate particles with a particle size of 4.75 mm is 3112, the number of digital aggregate particles with a particle size of 9.5 mm is 320, the number of digital aggregate particles with a particle size of 13.2 mm is 21, the number of small balls with a diameter of 1 mm is 126122, and the number of small balls with a diameter of 1.18 mm is 80141. The total number of digital aggregate particles and small balls is 214791.

[0081] Stack all the digital aggregate particles and small balls randomly to generate numerical simulation analysis models of particle size composition I and particle size composition II respectively. The schematic diagrams of the models are as Figure 2 shown.

[0082] Step 4: Model loading:

[0083] The model is radially loaded. Two simulated indenter heads are set above and below the model. The size of the indenter heads is 64 mm in length and 12.7 mm in width. The lower indenter head is fixed, and pressure is applied to the upper indenter head at a loading rate of 50 mm / min. The loading method is as shown in Figure 3 shown. The load-displacement curve is obtained through loading, as shown in Figure 4 shown.

[0084] Step 5: Obtain the internal force transmission path diagram:

[0085] According to the load-displacement curve obtained by loading, determine the loading point t1 corresponding to the maximum load, and the loading point t2 corresponding to the load dropping to 90% of the maximum value. Based on the displacements and loading rates corresponding to t1 and t2, the simulation analysis results corresponding to points t1 and t2 can be obtained. According to the simulation analysis results, the internal force transmission path diagram corresponding to the loading points t1 and t2 can be obtained. The internal force transmission path diagram of particle size composition I is as shown in Figure 5 shown.

[0086] Step 6: Processing of the internal force transmission path diagram:

[0087] Based on the internal force transmission path diagram of points t1 and t2 obtained, use image processing software for processing to obtain the prominent internal force transmission path contour diagrams of the left and right edges of the picture. The prominent internal force transmission path contour diagram of particle size composition I is as shown in Figure 6 shown.

[0088] Step 7: Obtain the skeleton stability coefficient:

[0089] For the prominent internal force transmission path contour diagram of the loading point t1 of particle size composition I, draw horizontal lines through points 20 mm away from the upper and lower tips (points A and B) of the contour, and intersect with the contour edge line to obtain four intersection points C, D, E, and F respectively. Connect AC, AD, BE, and BF to obtain angles CAD and EBF, as shown in Figure 7 shown. The two angles are α1 and α2 respectively. Define the prominent internal force transmission path range angle α = (α1 + α2) / 2. For the prominent internal force transmission path contour diagram of the loading point t2 of particle size composition I, use the same method as above to obtain the prominent internal force transmission path range angle β = (β1 + β2) / 2 of the loading point t2. According to Figure 7 it can be obtained that α1 = 82.91°, α2 = 79.29°, β1 = 77.53°, β2 = 72.34°. According to the skeleton stability coefficient μ = β / α, the skeleton stability coefficient of particle size composition I is calculated to be μ = 1.08. Similarly, the skeleton stability coefficient of particle size composition II is μ = 0.97

[0090] Step 8: Obtain the internal force state parameters:

[0091] For particle size composition I, based on the simulation analysis results corresponding to the loading points t1 and t2, the average values of the internal forces of the mineral aggregate and the internal forces of the asphalt are obtained respectively. The average value of the internal force of the mineral aggregate at the loading point t1 is The average value of the internal force of the asphalt is The average value of the internal force of the mineral aggregate at the loading point t2 is The average value of the internal force of the asphalt is According to the internal force state ratio The calculation formula of, through calculation, the internal force state ratio of particle size composition I is λ = 1.42. By using the same method, the internal force state ratio of particle size composition II can be obtained as λ = 1.35.

[0092] Step 9: Evaluate the skeleton performance based on the skeleton stability coefficient and the internal force state parameters:

[0093] Based on the skeleton stability coefficient and the internal force state ratio, use the comprehensive evaluation parameter of skeleton performance φ = η1μ + η2λ to evaluate the skeleton performance of the two models of particle size composition I and particle size composition II. Take η1 = 0.5 and η2 = 0.5, substitute the μ and λ of the two models of particle size composition I and particle size composition II into the expression of the comprehensive evaluation parameter of skeleton performance respectively, and the comprehensive evaluation parameters of skeleton performance of the two models can be obtained as 1.25 and 1.16 respectively. Since the comprehensive evaluation parameter of skeleton performance of particle size composition I is greater than that of particle size composition II, it can be known that the mineral aggregate skeleton structure of particle size composition I is better than that of particle size composition II.

[0094] In this embodiment, in order to compare and analyze the influence of asphalt performance on the performance of the mineral aggregate skeleton structure, the value of the weight coefficient η2 can be increased.

Claims

1. An evaluation method for the performance of the mineral aggregate skeleton of asphalt mixture, characterized in that The method includes the following steps: Step 1: Establish digital aggregate particles; Step 2: Determine the particle size composition of the aggregate and the asphalt dosage; Step 3: Establish a simulation analysis model of the asphalt mixture; Step 4: Model loading: Step 4-1: For the simulation analysis model established in Step 3, set the loading rate and model parameters, perform radial loading, and ensure that the model is completely fractured; Step 4-2: According to the simulation analysis results, obtain the load-displacement curve after the model is completely fractured; Step 5: Obtain the internal force transmission path diagram: Based on the load-displacement curve obtained in Step 4, determine the loading point t1 corresponding to the maximum load, and the loading point t2 when the load drops to 90% of the maximum load value. According to the loading simulation analysis results, obtain the internal force transmission path diagrams corresponding to the loading points t1 and t2; Step 6: Processing of the internal force transmission path diagram: Based on the internal force transmission path diagram, use image processing software to process the image to obtain the significant internal force transmission path contour diagrams of the loading points t1 and t2; Step 7: Obtain the skeleton stability coefficient: Based on the significant internal force transmission path contour diagrams of the loading points t1 and t2, respectively determine the significant internal force transmission path range angles, and obtain the significant internal force transmission path range angles α and β of the loading points t1 and t2. Define the skeleton stability coefficient μ = β / α; Step 8: Obtain the internal force state parameters: Step 8-1: Based on the simulation analysis results corresponding to the loading points t1 and t2, respectively obtain the average values of the internal forces of the aggregate and the internal forces of the asphalt; Step 8-2: Define the internal force state ratio Wherein: is the average value of the internal force of the mineral aggregate at the loading point t1, is the average value of the internal force of the asphalt at the loading point t1, is the average value of the internal force of the mineral aggregate at the loading point t2, is the average value of the internal force of the asphalt at the loading point t2; Step 9: Evaluate the skeleton performance based on the skeleton stability coefficient and the internal force state parameters: Based on the skeleton stability coefficient and the internal force state ratio, define the comprehensive evaluation parameter φ of the skeleton performance as φ = η1μ + η2λ, where η1 and η2 are the weight coefficients of the skeleton stability coefficient and the internal force state ratio respectively, and η1 + η2 = 1.

2. The evaluation method for the aggregate skeleton performance of asphalt mixture according to claim 1, wherein The specific steps of Step 1 are as follows: Step 1-1: According to the type of asphalt mixture, determine the range of the aggregate particle size of the asphalt mixture; Step 1-2: Through the screening test of the aggregate, take samples of the particle sizes above 2.36 mm; Step 1-3: Weigh the mass of each particle respectively. Through CT scanning and image processing of the selected aggregate particles, obtain the digital aggregate particles and the corresponding volumes; Step 1-4: Calculate the density of the aggregate according to the total mass and total volume of the aggregate particles.

3. The evaluation method for the aggregate skeleton performance of asphalt mixture according to claim 1, wherein The specific steps of Step 2 are as follows: Step 2-1: According to the gradation type of the asphalt mixture, draw up the asphalt dosage; Step 2-2: Combine the aggregate gradation range specified in the specification to determine the particle size composition of the aggregate and the percentage of the dosage of each particle size particle.

4. The evaluation method for the aggregate skeleton performance of asphalt mixture according to claim 1, wherein The specific steps of Step 3 are as follows: Step 3-1: Based on the total mass of the cylindrical simulation model, calculate the mass of the asphalt and the mass of the aggregate, and then obtain the mass of each particle size aggregate; Step 3-2: According to the mass and density, calculate the total volume of each particle size aggregate and the volume of the asphalt. According to the total volume and the volume of each digital aggregate particle, determine the number of each particle size digital aggregate particles and the number of asphalt particles; Step 3-3: Select corresponding digital mineral aggregate particles and asphalt particles, and generate a simulation analysis model including asphalt and mineral aggregate by means of free stacking.

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