Method for evaluating crack resistance of asphalt mixture

Abstract

The invention discloses a method for evaluating the crack resistance of an asphalt mixture, which belongs to the field of road engineering, and comprises the following steps of: performing semicircular bending test on a semi-cylindrical test piece in low-temperature and medium-temperature environments, and recording data when cracks are generated after the test; drawing a vertical load-vertical displacement curve graph, and calculating flexural tensile strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy; according to the working state needing to be evaluated, the analytic hierarchy process is used for giving different weights to the five single indexes, and the anti-cracking index for evaluating the anti-cracking performance of the asphalt mixture in the ultimate failure state and the anti-cracking index for evaluating the anti-cracking performance of the asphalt mixture in the working state with cracks are obtained respectively; the semi-cylindrical test piece does not need to be subjected to pre-joint cutting, machining is convenient, and the cutting error caused by pre-joint cutting and the aggregate influence of the tip end of a notch are reduced; the method is more scientific through the crack resistance before the crack appears and the crack development resistance after the crack appears in the actual working state of the asphalt pavement.

Description

Technical Field

[0001] The invention relates to the field of road engineering, in particular to an evaluation method for the anti-cracking performance of asphalt mixture. Background Art

[0002] As one of the main diseases of asphalt pavement, cracks have a great impact on the driving comfort and structural stability of the pavement. The development of cracks in asphalt mixtures includes the ultimate failure state before the cracks occur and the working state with cracks after the cracks occur. The causes of cracks are relatively complex, including excessive external vehicle loads and temperature differences, and the slow expansion of internal microcracks. The above factors are related to the crack resistance of asphalt mixtures. The ultimate failure state before the cracks occur and the working state with cracks after the cracks occur are two aspects of evaluating the crack resistance of asphalt mixtures.

[0003] Asphalt mixture is a nonlinear viscoelastic-plastic material that is sensitive to temperature. Its stress and strain responses are greatly affected by time and temperature. In the semicircular bending fracture test, the two key parameters are loading rate and test temperature. Therefore, it is of great significance to determine the appropriate test temperature and loading rate and evaluate the anti-cracking performance of asphalt mixture in medium and low temperature working environments.

[0004] The semicircular bending test is an effective method for evaluating the anti-cracking performance of asphalt mixtures. The existing semicircular bending test uses a specimen with a pre-cut slit, which requires the specimen to be pre-cut in advance. The cutting of the pre-cut slit is prone to errors and the aggregate at the tip of the slit will have an impact. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a method for evaluating the anti-cracking performance of asphalt mixture without pre-cutting the test piece.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A method for evaluating the anti-cracking performance of asphalt mixture comprises the following steps:

[0008] The material formed by the asphalt mixture or the road surface is cut to form a semi-cylindrical specimen;

[0009] Conduct semicircular bending tests on semi-cylindrical specimens in low and medium temperature environments, and record the vertical load and vertical displacement data when cracks occur after the test;

[0010] Draw a vertical load-vertical displacement curve according to the vertical load and vertical displacement data, and calculate the bending strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy based on the curve;

[0011] According to the working state to be evaluated, the analytic hierarchy process is used to assign different weights to the five individual indicators of flexural strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy. The anti-cracking index for evaluating the anti-cracking performance of asphalt mixture under the ultimate damage state and the anti-cracking index for evaluating the anti-cracking performance of asphalt mixture under the working state with cracks are obtained respectively.

[0012] Furthermore, the bending tensile strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy are calculated based on the curve graph as follows:

[0013]

[0014] In the formula, σ m is the bending tensile strength, F is the vertical load, D is the specimen diameter, and B is the specimen thickness;

[0015] The peak displacement is the abscissa value corresponding to the highest point of the curve;

[0016] The pre-peak slope is determined by the vertical load value and its corresponding vertical displacement value when the vertical load first reaches 1 / 2 of the peak load.

[0017]

[0018] Where IRT is the pre-peak slope, F max is the peak force, d t is the displacement corresponding to 1 / 2 peak force;

[0019] The pre-peak fracture energy is the area enclosed by the curve and the horizontal axis before reaching the peak load;

[0020]

[0021] In the formula, G bf is the pre-peak fracture energy, W bf is the pre-peak fracture work, A is the fracture surface area;

[0022] The post-peak fracture energy is the area enclosed by the curve and the horizontal axis from the time when the peak load is reached to the time when the load drops to 1 / 2 of the peak load.

[0023]

[0024] In the formula, G af is the post-peak fracture energy, W af is the post-peak fracture work.

[0025] Furthermore, the calculation formula of the anti-cracking index is:

[0026]

[0027] In the formula, Gm-bf is the maximum value of the main curve of post-peak fracture energy, σ m-max is the maximum value of the main curve of flexural strength, IRT m It is the maximum value of the slope before the peak.

[0028] Furthermore, the calculation formula of the crack resistance index is:

[0029] Furthermore, the analytic hierarchy process is used to assign different weights to the five individual indicators of flexural strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy. Specifically, on the basis of pairwise comparison between various indicators, matrix operation is performed to obtain the weight of each indicator for the overall target.

[0030] Furthermore, 1, 3, 5, 7, and 9 are used to represent the importance of row elements to column elements as equally important, slightly important, relatively important, strongly important, and extremely important. 2, 4, 6, and 8 are the intermediate values ​​of the above judgments. Next, each row and column of the judgment matrix is ​​normalized and summed, and the weights are obtained after consistency verification.

[0031] Furthermore, in the semi-cylindrical specimens under the low-temperature and medium-temperature environments, the low temperature is -12°C to -8°C, and the medium temperature is 22°C to 27°C.

[0032] Furthermore, when the semi-circular bending test is performed on the semi-cylindrical specimen in the low temperature environment, the loading rate is 4-6 mm / min, and when the semi-circular bending test is performed on the semi-cylindrical specimen in the medium temperature environment, the loading rate is 45-55 mm / min.

[0033] Furthermore, in the step of recording the vertical load and vertical displacement data when cracks occur after the test, when the crack occurs at ±25 mm from the bottom center of the specimen, the test data is recorded; when the crack occurs at not ±25 mm from the bottom center of the specimen, the test data is discarded.

[0034] Compared with the prior art, in the method for evaluating the anti-cracking performance of asphalt mixtures of the present invention, the semi-cylindrical specimens do not need to be pre-cut, and the processing is convenient, reducing the cutting error caused by the pre-cutting and the influence of the aggregate at the tip of the cut; through the anti-crack performance before the appearance of cracks and the anti-crack development performance after the appearance of cracks in the actual working state of the asphalt pavement, comprehensive evaluation indicators are proposed respectively, and the hierarchical analysis method is used to assign different weights to the basic indicators so that the evaluation results are consistent with the evaluation content. Compared with the existing single indicator evaluation method, the evaluation method proposed by the present invention has the advantages of more scientific method, more comprehensive angle, clearer working conditions, high discrimination and small variability. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1A flow chart of the method for evaluating the anti-cracking performance of asphalt mixture of the present invention;

[0036] Figure 2 It is a schematic diagram of a test piece in the method for evaluating the anti-cracking performance of asphalt mixture of the present invention;

[0037] Figure 3 It is a schematic diagram of the force when the specimen is subjected to a semicircular bending test in the method for evaluating the anti-cracking performance of asphalt mixture of the present invention;

[0038] Figure 4 A crack diagram generated by a test piece in the method for evaluating the anti-cracking performance of asphalt mixture of the present invention;

[0039] Figure 5 A crack diagram is generated for another test piece in the method for evaluating the anti-cracking performance of asphalt mixture of the present invention;

[0040] Figure 6 It is the vertical load-vertical displacement curve. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0044] See also Figure 1 The present application provides a method for evaluating the anti-cracking performance of asphalt mixture, comprising the following steps:

[0045] The material formed by the asphalt mixture or the road surface is cut to form a semi-cylindrical specimen;

[0046] Conduct semicircular bending tests on semi-cylindrical specimens in low and medium temperature environments, and record the vertical load and vertical displacement data when cracks occur after the test;

[0047] Draw a vertical load-vertical displacement curve according to the vertical load and vertical displacement data, and calculate the bending strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy based on the curve;

[0048] According to the working state to be evaluated, the analytic hierarchy process is used to assign different weights to the five individual indicators of flexural strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy. The anti-cracking index for evaluating the anti-cracking performance of asphalt mixture under the ultimate damage state and the anti-cracking index for evaluating the anti-cracking performance of asphalt mixture under the working state with cracks are obtained respectively.

[0049] Specifically, in the step of cutting the material or road surface formed by the asphalt mixture to form a semi-cylindrical specimen, as Figure 2 As shown in the figure, the specimen is a semi-cylinder with a diameter of 150 mm and a thickness of 50 mm, and has no pre-cut seams. Compared with the commonly used specimens with pre-cut seams, the use of semi-cylindrical specimens without pre-cut seams can improve processing efficiency and reduce cutting errors caused by pre-cut seams and the influence of aggregates at the tip of the cut.

[0050] Perform semicircular bending tests on semi-cylindrical specimens in low and medium temperature environments, and record the vertical load and vertical displacement data when cracks occur after the test. Figure 3 As shown in the figure, the distance between the two stress points at the bottom of the semicircular bending test is 120mm, and the top stress point is the midpoint of the arc. The low temperature is -12℃ to -8℃, and the medium temperature is 22℃ to 27℃. The test was conducted under typical medium and low temperature damage conditions of asphalt mixture, and the results are representative.

[0051] Asphalt mixture is a temperature-sensitive nonlinear viscoelastic-plastic material. The stress and strain response are affected by time and temperature, which are reflected in the two key parameters of the semicircular bending fracture test: loading rate and test temperature. Therefore, different test loading rates are set for different test temperatures. When the semicircular bending test is performed on the semi-cylindrical specimen in a low temperature environment, the loading rate is 4-6mm / min, and when the semi-cylindrical specimen is performed on the semicircular bending test in a medium temperature environment, the loading rate is 45-55mm / min. The test results obtained at these two loading rates have the highest discrimination and low variability.

[0052] Specifically, the temperature of the universal testing machine's environmental chamber is set to 25°C. Figure 2Place the specimen in the environmental chamber and keep it warm for 4 hours. Place a polyethylene film under the test mold to eliminate friction between the mold and the test machine. Figure 3 Put it into the test mold as shown, set the loading rate of the pressure head to 50mm / min, set appropriate contact stress and test termination conditions. Start the test and stop the test when the test reaches the termination condition. Figure 4 as well as Figure 5 As shown, check whether the cracked part of the specimen is within ±25mm of the center of the bottom of the specimen. If so, save the load and displacement data recorded by the data acquisition system. Otherwise, discard the test data.

[0053] Finally, the test data under medium temperature test conditions are obtained. Repeat the steps described in this paragraph, but set the environmental chamber temperature to -10℃ and the indenter loading rate to 5mm / min to obtain the test data under low temperature test conditions. Reduce the test error and ensure that the cracking mode belongs to type I cracking.

[0054] like Figure 6 As shown in the figure, a vertical load-vertical displacement curve is drawn according to the vertical load and vertical displacement data, and the bending tensile strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy are calculated based on the curve:

[0055] Draw the vertical load-vertical displacement curve of the test results under two test conditions. Obtain the maximum vertical load value Fmax of the curve and the peak displacement D corresponding to the maximum vertical load value Fmax. m , calculate the bending tensile strength σ m , and the area of ​​the curve enclosed by the coordinate origin to the maximum vertical load value Fmax and the horizontal coordinate, the pre-peak fracture energy G bf . Calculate half of the maximum vertical load value Fmax, and get two points before and after the peak corresponding to 1 / 2Fmax on the graph. The pre-peak slope IRT is calculated from the coordinates of the pre-peak point; the area of ​​the curve enclosed by the curve between the two points and the horizontal coordinate is calculated from the coordinates of the post-peak point and the coordinates corresponding to the point with the maximum vertical load value Fmax, and the post-peak fracture energy G is obtained. af .

[0056] Bending tensile strength m : The maximum tensile stress at the bottom of the specimen, the stress and modulus formula when the distance between the bottom support of the semicircular specimen and the specimen diameter is 0.8 times:

[0057]

[0058] Where:

[0059] σ m ——Tensile stress value at the bottom of the specimen (MPa);

[0060] F——vertical load (N);

[0061] D——test piece diameter (mm);

[0062] B——test piece thickness (mm);

[0063] Peak displacement D m : The horizontal coordinate value corresponding to the highest point of the curve.

[0064] Pre-peak slope IRT: The slope of the rising stage of the curve, determined by the vertical load value and its corresponding vertical displacement value when the vertical load first reaches 1 / 2 of the peak load, also known as the tensile stiffness index. The calculation formula is:

[0065]

[0066] Where:

[0067] IRT——Bending Tensile Stiffness Index (kN / mm)

[0068] F max ——Peak force (N)

[0069] d t ——Displacement corresponding to 1 / 2 peak force (mm)

[0070] Pre-peak fracture energy G bf : The area enclosed by the curve and the horizontal axis before reaching the peak load. The calculation formula is:

[0071]

[0072] Where:

[0073] G bf ——Pre-peak fracture energy (J / m 2 )

[0074] W bf ——Pre-peak fracture work (J)

[0075] A——fracture surface area (m 2 )

[0076] Post-peak fracture energy G af : The area enclosed by the curve and the horizontal axis from the time when the peak load is reached to the time when the load drops to 1 / 2 of the peak load. The calculation formula is:

[0077]

[0078] Where:

[0079] G af ——Post-peak fracture energy (J / m2 )

[0080] W af ——Post-peak fracture work (J)

[0081] A——fracture surface area, product of thickness and radius (m 2 )

[0082] The evaluation indexes of strength, displacement, modulus and energy were obtained respectively. The strength index represents the maximum stress of asphalt mixture at fracture; the displacement index represents the maximum ductility of asphalt mixture at fracture; the modulus index represents the stiffness of asphalt mixture at the initial stage of mechanical response; when the work done by external force is equal to the fracture energy of the material, the material is destroyed, that is: W = U, and the energy index is a comprehensive index including force and displacement response.

[0083] The above five single indicators are assigned different weights according to the working conditions to be evaluated. The analytic hierarchy process is used to obtain the Fracture Resistance Index (FRI) for evaluating the crack resistance of asphalt mixtures under the ultimate damage state and the Crack Resistance Index (CRI) for evaluating the crack resistance of asphalt mixtures under the working condition with cracks. The specific results are as follows:

[0084] Analytic hierarchy process: Based on the comparison between each indicator, through matrix operation, the weight of each indicator for the overall goal is obtained. First, the judgment matrix needs to be determined, that is, the matrix generated by the comparison between each indicator. 1, 3, 5, 7, 9 represent the importance of row elements to column elements as equally important, slightly important, relatively important, strongly important, and extremely important, and 2, 4, 6, and 8 are the intermediate values ​​of the above judgments. Secondly, the rows and columns of the judgment matrix are normalized and summed, and the weights are obtained after consistency verification. The beneficial effect is that the analytic hierarchy process is used to organically combine qualitative methods with quantitative methods to decompose complex multi-factor systems, and the results are scientific and reliable.

[0085] Cracking resistance index FRI: Pre-peak fracture energy is a comprehensive reflection of stress and displacement, and is the most important indicator. Flexural strength and peak displacement are supplementary and are less important, and peak displacement is slightly less important than flexural strength. The judgment matrix and weights are shown in Table 1:

[0086] Table 1 FRI three indicators judgment matrix

[0087]

[0088] The maximum eigenvalue of the judgment matrix λ max =3.0183, consistency index: Concordance ratio:

[0089] The units of various indicators are inconsistent, and the data needs to be normalized. The proportional function method is used for normalization, that is, the target value is equal to the ratio of the current value to the difference between the two extreme values, and the indicator value range is 0 to 100. It should be noted that in the definition of the anti-cracking index, the IRT index is used to make up for the insufficient pre-peak fracture energy. When the pre-peak fracture energy is equal, the larger the IRT, the smaller the displacement to reach the failure point and the shorter the time, which is not conducive to maintaining good anti-cracking performance. The FRI value should be smaller. Therefore, in the fractional conversion process of IRT, the numerator is the maximum value minus the current value. The final calculation formula for the anti-cracking index is shown in formula (5):

[0090]

[0091] in,

[0092] G m-bf ——Maximum of the main curve of post-peak fracture energy

[0093] σ m-max ——Maximum of the main curve of flexural strength

[0094] IRT m ——Maximum of the main curve of flexural strength

[0095] Crack resistance index CRI: post-peak fracture energy, pre-peak fracture energy, peak displacement, flexural tensile strength have a good correlation with fatigue life and cumulative dissipated energy. Under fatigue cracking conditions, since the tensile stress on the pavement surface is very small, the weight of flexural tensile strength is smaller than that of energy indicators; among energy indicators, post-peak fracture energy is more important than pre-peak fracture energy; peak displacement involves strain level. Since asphalt pavement is a flexible pavement, the deformation under load is more obvious, and its importance is greater than the strength indicator. The criticality of each indicator is ranked as follows: G af >G bf >IRT≈D m >σ m ,The judgment matrix is ​​shown in Table 2. After normalization and summation, the weight is obtained through consistency verification.

[0096] Table 2 CRI four indicators judgment matrix

[0097]

[0098] The maximum eigenvalue of the judgment matrix λ max =4.051, consistency index: Concordance ratio:

[0099] After normalizing each indicator, the calculation formula of CRI is shown in formula (6):

[0100]

[0101] Table 3 Weights of each indicator of FRI and CRI

[0102]

[0103] According to the different evaluation contents, namely the ultimate damage state and the working state with cracks, different weights are assigned to individual indicators, corresponding to the resistance to ultimate cracking and the resistance to crack development, respectively, so that the evaluation results are more scientific and accurate.

[0104] The analytic hierarchy process is used to calculate the crack resistance index FRI and the crack resistance index CRI of the test data according to the weights shown in Table 3 and the formulas shown in formula (5) and formula (6). The two comprehensive evaluation indicators proposed in the present invention can be used to analyze the medium-temperature and low-temperature crack resistance of the test specimens.

[0105] This application uses a semicircular specimen without pre-cut slits as a test specimen. Compared with the commonly used specimen with pre-cut slits, it is easy to process and reduces the cutting error caused by the pre-cut slits and the influence of the aggregate at the tip of the cut. Comprehensive evaluation indicators are proposed for the anti-crack performance before the cracks appear and the anti-crack development performance after the cracks appear in the actual working state of the asphalt pavement. The analytic hierarchy process is used to assign different weights to the basic indicators so that the evaluation results are consistent with the evaluation content. Compared with the existing single indicator evaluation method, the evaluation method proposed in the present invention has the advantages of more scientific methods, more comprehensive angles, clearer working conditions, high discrimination and small variability. Since cracks are the focus of current pavement maintenance planning, on the basis of the present invention, it can be: ① After coring the pavement of the cracked section, the evaluation method proposed in the present invention is used to evaluate the core sample performance, which can help maintenance decision makers determine the cause of the pavement cracks and assist in formulating maintenance decision methods; ② Establishing the relationship between multiple factors and the anti-cracking performance of asphalt mixtures, it lays a foundation for comprehensive research and improvement of the anti-cracking performance of asphalt mixtures, and has important theoretical significance and application value.

[0106] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which are equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of them belong to the protection scope of the present invention.

Claims

1. A method for evaluating the anti-cracking performance of asphalt mixture, characterized in that: The following steps are involved: The material formed by the asphalt mixture or the road surface is cut to form a semi-cylindrical specimen; Conduct semicircular bending tests on semi-cylindrical specimens in low and medium temperature environments, and record the vertical load and vertical displacement data when cracks occur after the test; Draw a vertical load-vertical displacement curve according to the vertical load and vertical displacement data, and calculate the bending strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy based on the curve; According to the working state to be evaluated, the analytic hierarchy process is used to assign different weights to the five individual indicators of flexural strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy. The anti-cracking index for evaluating the anti-cracking performance of asphalt mixture under the ultimate damage state and the anti-cracking index for evaluating the anti-cracking performance of asphalt mixture under the working state with cracks are obtained respectively.

2. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 1, characterized in that: The calculation of the bending tensile strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy based on the curve graph is specifically as follows: In the formula, σ m is the bending tensile strength, F is the vertical load, D is the specimen diameter, and B is the specimen thickness; The peak displacement is the abscissa value corresponding to the highest point of the curve; The pre-peak slope is determined by the vertical load value and its corresponding vertical displacement value when the vertical load first reaches 1 / 2 of the peak load. Where IRT is the pre-peak slope, F max is the peak force, d t is the displacement corresponding to 1 / 2 peak force; The pre-peak fracture energy is the area enclosed by the curve and the horizontal axis before reaching the peak load; In the formula, G bf is the pre-peak fracture energy, W bf is the pre-peak fracture work, A is the fracture surface area; The post-peak fracture energy is the area enclosed by the curve and the horizontal axis from the time when the peak load is reached to the time when the load drops to 1 / 2 of the peak load. In the formula, G af is the post-peak fracture energy, W af is the post-peak fracture work.

3. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 2, characterized in that: The calculation formula of the anti-cracking index is: In the formula, G m-bf is the maximum value of the main curve of post-peak fracture energy, σ m-max is the maximum value of the main curve of flexural strength, IRT m It is the maximum value of the slope before the peak.

4. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 2, characterized in that: The calculation formula of the crack resistance index is:

5. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 1, characterized in that: The analytic hierarchy process is used to assign different weights to the five individual indicators of flexural strength, peak displacement, pre-peak slope, pre-peak fracture energy and post-peak fracture energy. Specifically, based on the pairwise comparison between the indicators, matrix operations are performed to obtain the weight of each indicator for the overall goal.

6. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 5, characterized in that: 1, 3, 5, 7, and 9 represent the importance of row elements to column elements as equally important, slightly important, relatively important, strongly important, and extremely important. 2, 4, 6, and 8 are the intermediate values ​​of the above judgments. Next, each row and column of the judgment matrix is ​​normalized and summed up, and the weights are obtained after consistency verification.

7. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 1, characterized in that: In the semi-cylindrical specimens under the low-temperature and medium-temperature environments, the low temperature is -12°C to -8°C, and the medium temperature is 22°C to 27°C.

8. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 7, characterized in that: When the semi-circular bending test is performed on the semi-cylindrical specimen in the low temperature environment, the loading rate is 4-6 mm / min, and when the semi-circular bending test is performed on the semi-cylindrical specimen in the medium temperature environment, the loading rate is 45-55 mm / min.

9. The method for evaluating the anti-cracking performance of asphalt mixture according to claim 1, characterized in that: In the step of recording the vertical load and vertical displacement data when cracks occur after the test, when the crack occurs at ±25 mm from the bottom center of the specimen, the test data is recorded; when the crack occurs not at ±25 mm from the bottom center of the specimen, the test data is discarded.

Images