A method and system for testing splitting damage of recycled asphalt mixtures

Abstract

This invention discloses a method and system for testing the splitting damage of recycled asphalt mixtures, relating to the field of mixture damage technology. The method includes: conducting a splitting test on recycled asphalt mixture specimens and recording first load-displacement data; simulating splitting damage on the specimens; using an industrial CT scanning device to scan the specimens before and after damage, acquiring scan images of the intact state and the damaged state; conducting a splitting test on the specimens after splitting damage until complete failure, recording second load-displacement data; comparing the internal characteristics and strength characteristics of the specimens in the intact and damaged states; calculating the energy ratio based on the fracture energy of the specimens in the intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the specimens. This invention can analyze the splitting damage state of recycled asphalt mixtures based on the damage stage rather than the cracking result.

Description

Technical Field

[0001] This invention relates to the field of mixture damage technology, and in particular to a method and system for testing splitting damage of recycled asphalt mixtures. Background Technology

[0002] Asphalt-aggregate interfacial debonding is one of the main causes of asphalt pavement distress, significantly impacting driving comfort and road life. Studies show that interfacial debonding is primarily caused by tensile stress, shear stress, or a combination of both (tearing). Due to material defects or external factors (temperature, load, or water), interfacial debonding damage occurs within the mixture. Microcracks first appear at weak points in the mixture, increasing and extending under stress, eventually merging with other microcracks to develop into macrocracks. Ultimately, this manifests in asphalt mixtures as low-temperature splitting failure, high-temperature shear failure, interfacial water loss failure, and fatigue failure. Especially for recycled asphalt mixtures, the introduction of old asphalt and aggregates under different mixing processes creates complex asphalt-aggregate adhesion interfaces, further complicating the debonding damage problem. Moreover, debonding damage cannot be observed with the naked eye; even after damage occurs, the mixture has not yet failed, stress continues to transfer between materials, and the damage can heal under certain conditions. However, most existing studies treat interfacial damage and mixture cracking behavior as a single concept, using cracking characteristics to characterize adhesion effects. In reality, once the mixture fails and breaks down, the point of damage cannot be found, and damage research must be conducted on the undamaged stage. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide a method and system for testing the splitting damage of recycled asphalt mixtures, which analyzes the splitting damage state of recycled asphalt mixtures based on the damage stage rather than the cracking result.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A method for testing the splitting damage of recycled asphalt mixtures, comprising:

[0006] A single scan of the recycled asphalt mixture specimen was performed using an industrial CT scanning device to obtain a scanned image of the specimen in good condition.

[0007] Splitting tests were conducted on the recycled asphalt mixture specimens under different test conditions. The first load-displacement data were recorded, and the average failure load P under each test condition was calculated.

[0008] Simulated splitting damage was performed on the recycled asphalt mixture specimens under different test conditions;

[0009] A single scan of the recycled asphalt mixture specimen after splitting damage was performed using an industrial CT scanning device to obtain a scan image of the damage state.

[0010] Splitting tests were performed on the recycled asphalt mixture specimens after splitting damage until complete failure, and the second load-displacement data were recorded.

[0011] Based on the intact scan image and the damaged scan image, compare the internal characteristics of the recycled asphalt mixture specimens under the intact and damaged states;

[0012] Based on the first load-displacement data and the second load-displacement data, the strength characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state are compared; the strength characteristics include splitting tensile strength, failure stiffness modulus and fracture energy;

[0013] The energy ratio is calculated based on the fracture energy of the recycled asphalt mixture specimens in both intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the recycled asphalt mixture specimens.

[0014] To achieve the above objectives, the present invention also provides the following solution:

[0015] A splitting damage testing system for recycled asphalt mixtures, characterized in that it comprises:

[0016] The first scanning module is used to scan the recycled asphalt mixture specimen once using industrial CT scanning equipment to obtain a scan image of the intact state.

[0017] The first splitting test module is used to conduct splitting tests on the recycled asphalt mixture specimens under different test conditions, record the first load-displacement data, and calculate the average failure load P under each group of test conditions.

[0018] The splitting damage simulation module is used to simulate splitting damage on the recycled asphalt mixture specimens under different test conditions.

[0019] The second scanning module is used to scan the recycled asphalt mixture specimen after splitting damage using industrial CT scanning equipment to obtain a scan image of the damage state.

[0020] The second splitting test module is used to perform splitting tests on recycled asphalt mixture specimens after splitting damage until complete failure, and record the second load-displacement data.

[0021] The first comparison module is used to compare the internal features of the recycled asphalt mixture specimen in the intact state and the damaged state based on the scanned image in the intact state and the scanned image in the damaged state.

[0022] The second comparison module is used to compare the strength characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state based on the first load-displacement data and the second load-displacement data; the strength characteristics include splitting tensile strength, breaking stiffness modulus and fracture energy;

[0023] The energy ratio calculation module is used to calculate the energy ratio based on the fracture energy of the recycled asphalt mixture specimens in intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the recycled asphalt mixture specimens.

[0024] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0025] This invention is simple to operate and easy to implement. It not only enables direct observation of the splitting damage process inside recycled asphalt mixture specimens using CT scans, but also allows for quantitative evaluation of the damage state, filling a gap in this field. Furthermore, this invention can evaluate the damage and cracking behavior of complex interfaces in recycled asphalt mixtures composed of multiple material components and different mixing processes under various loads and environmental conditions, providing a technical basis for improving mixing processes and enhancing mixture performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart of the splitting damage test method for recycled asphalt mixtures provided by the present invention;

[0028] Figure 2 This is a graph showing the relationship between splitting tensile strength and loading rate, test temperature, and unloading conditions in a splitting damage test.

[0029] Figure 3 CT scan images of specimens in both intact and damaged states.

[0030] Figure 4 The graph shows the relationship between the stiffness modulus and damage state of the specimens at 30℃ and two loading rates.

[0031] Figure 5 The graph shows the relationship between fracture energy and damage state of specimens at 30℃ and two loading rates.

[0032] Figure 6 The graph shows the relationship between the stiffness modulus and damage state of the specimens at 40℃ and two loading rates.

[0033] Figure 7 The graph shows the relationship between fracture energy and damage state of specimens at 40℃ and two loading rates.

[0034] Figure 8 The graph shows the relationship between the energy ratio and damage state of the specimen during splitting failure. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The purpose of this invention is to provide a method for testing the splitting damage of recycled asphalt mixtures, which uses CT scanning to directly observe the splitting damage process inside the mixture and to quantitatively evaluate the damage state.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] like Figure 1 As shown, the method for testing the splitting damage of recycled asphalt mixtures provided by this invention includes the following steps:

[0040] S1: Use industrial CT scanning equipment to scan the recycled asphalt mixture specimen once to obtain a scan image of its intact state.

[0041] The porosity of the test specimens was to differ from the average porosity by no more than ±0.5%, in order to reduce the error caused by porosity. During the CT scan, the interval between each image was 0.1 mm.

[0042] S2: Under different test conditions, splitting tests were conducted on the recycled asphalt mixture specimens, the first load-displacement data were recorded, and the average failure load P under each test condition was calculated.

[0043] Splitting tests were performed on the specimens at 30℃ (or 40℃) with loading rates of 5 mm / min and 10 mm / min until complete failure. Load-displacement data were recorded, and the average failure load P (kN) under each test condition was calculated.

[0044] Compared with the traditional splitting test, the splitting test in this embodiment uses a higher test temperature and a lower loading rate, which solves the problem that the damage process is difficult to capture when the traditional splitting test ends too quickly.

[0045] S3: Simulate splitting damage on the recycled asphalt mixture specimens under different test conditions.

[0046] For the specimen, simulate splitting damage, the test temperature and loading rate are the same as in step S2, and perform a pre-unloading loading, with the loading terminated early when the load first reaches 0.5P, 0.7P and 0.9P as unloading conditions.

[0047] S4: Use industrial CT scanning equipment to scan the recycled asphalt mixture specimen after splitting damage to obtain a scan image of the damage state.

[0048] A CT scan was performed on the specimen in the damaged state of step S3. During the CT scan, the interval between each image was 0.1 mm.

[0049] S5: Perform a splitting test on the recycled asphalt mixture specimens after splitting damage until complete failure, and record the second load-displacement data.

[0050] The specimen in the damaged state of step S3 is subjected to a splitting test until it is completely destroyed, and the load-displacement data are recorded.

[0051] S6: Based on the scan images of the intact state and the scan images of the damaged state, compare the internal characteristics of the recycled asphalt mixture specimens in the intact and damaged states. The CT scan images of the specimens in the intact and damaged states are as follows: Figure 3 As shown.

[0052] The scanned images obtained in steps S1 and S4 are processed, and the porosity, porosity distribution, asphalt layer thickness, and aggregate distribution inside the specimens in good and damaged states are compared and analyzed.

[0053] S7: Based on the first load-displacement data and the second load-displacement data, compare the strength characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state; the strength characteristics include splitting tensile strength, breaking stiffness modulus and fracture energy.

[0054] Based on the load-displacement data recorded in steps S2 and S5, the splitting tensile strength R of specimens in intact and damaged states is compared and analyzed. T (MPa), breaking stiffness modulus S (MPa), and fracture energy J (J).

[0055] S8: Calculate the energy ratio based on the fracture energy of the recycled asphalt mixture specimens in the intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the recycled asphalt mixture specimens.

[0056] The degree of damage to the mixture is evaluated by the energy ratio (ER):

[0057]

[0058] Where ER is the energy ratio (%), J d J and J0 represent the fracture energy (J) of the mixture under damaged and intact conditions, respectively.

[0059] Compared with existing technologies, this invention is simple to operate and easy to implement. It not only enables direct observation of the splitting damage process inside the mixture using CT scans, but also allows for quantitative evaluation of the damage state, filling a gap in this field. Furthermore, this invention can evaluate the damage and cracking behavior of complex interfaces in recycled asphalt mixtures composed of multiple material components and different mixing processes under various loads and environmental conditions, providing a technical basis for improving mixing processes and enhancing mixture performance.

[0060] Example 2

[0061] The method in Example 1 is applicable to various types of asphalt pavement materials. In this example, the asphalt mixture is a hot recycled asphalt mixture with a design gradation of AC-13. Specimens were formed using rotary compaction, and each specimen was a cylinder with a diameter of 100 mm and a height of 65 mm, with a porosity of 4.0%. The test temperature was 30℃.

[0062] The samples underwent CT scanning, splitting fracture test, and splitting damage test. Each test group was performed in triplicate, and the average value was taken. The specific implementation process is as follows:

[0063] (1) Prepare recycled asphalt mixture specimens to ensure that the void ratio is 4.0% ± 0.5%.

[0064] (2) Splitting tests were performed on the specimens at 30°C with loading rates of 5 mm / min and 10 mm / min until complete failure.

[0065] (3) Record the load-displacement data in step (2) and calculate the average failure load P (kN) under each group of test conditions.

[0066] (4) Perform a CT scan on the specimen in good condition in step (1) and acquire scan images at 0.1 mm intervals.

[0067] (5) Simulate splitting damage on the specimen after scanning in step (4). The test temperature and loading rate are the same as in step (2). Perform a loading with early unloading. The unloading stops when the load first reaches 0.5P, 0.7P and 0.9P, where P is the average failure load P (kN) under each test condition.

[0068] (6) Perform a CT scan on the specimen in the damaged state of step (5) and acquire scan images at 0.1 mm intervals.

[0069] (7) Process the scanned images obtained in steps (4) and (6) and compare and analyze the porosity, porosity distribution, asphalt layer thickness and aggregate distribution inside the specimens in good condition and damaged condition.

[0070] (8) Perform a splitting test on the specimen in the damage state of step (5) until it is completely destroyed. The test temperature and loading rate are the same as those used when simulating splitting damage of the corresponding specimen.

[0071] (9) Based on the load-displacement data from steps (2) and (8), compare and analyze the splitting tensile strength RT (MPa), failure stiffness modulus S (MPa), and fracture energy J (J) of specimens in the intact and damaged states, and use the energy ratio (ER) to quantify and evaluate the degree of damage:

[0072]

[0073] Where ER is the energy ratio (%), J d J and J0 represent the fracture energy (J) of the mixture under damaged and intact conditions, respectively.

[0074] The relationship between splitting tensile strength and loading rate, test temperature and unloading conditions in splitting damage test is as follows: Figure 2 As shown, at an experimental temperature of 30℃, the relationship between the stiffness modulus and damage state of the specimens under loading rates of 5 mm / min and 10 mm / min is as follows. Figure 4 As shown, the relationship between fracture energy and damage state is as follows: Figure 5 As shown.

[0075] Example 3

[0076] In this embodiment, the asphalt mixture is a hot recycled asphalt mixture with a design gradation of AC-13. Specimens were formed using rotary compaction, and each specimen was a cylinder with a diameter of 100 mm and a height of 65 mm, exhibiting a porosity of 4.0%. The test temperature was 40℃.

[0077] The samples underwent CT scanning, splitting fracture test, and splitting damage test. Each test group was performed in triplicate, and the average value was taken. The specific implementation process is as follows:

[0078] (1) Prepare recycled asphalt mixture specimens to ensure that the void ratio is 4.0% ± 0.5%.

[0079] (2) Splitting tests were conducted on the specimens at 40°C with loading rates of 5 mm / min and 10 mm / min until complete failure.

[0080] (3) Record the load-displacement data in step (2) and calculate the average failure load P (kN) under each group of test conditions.

[0081] (4) Perform a CT scan on the specimen in good condition in step (1) and acquire scan images at 0.1 mm intervals.

[0082] (5) Simulate splitting damage on the specimen after scanning in step (4). The test temperature and loading rate are the same as in step (2). Perform a loading with early unloading. The unloading stops when the load first reaches 0.5P, 0.7P and 0.9P, where P is the average failure load P (kN) under each test condition.

[0083] (6) Perform a CT scan on the specimen in the damaged state of step (5) and acquire scan images at 0.1 mm intervals.

[0084] (7) Process the scanned images obtained in steps (4) and (6) and compare and analyze the porosity, porosity distribution, asphalt layer thickness and aggregate distribution inside the specimens in good condition and damaged condition.

[0085] (8) Perform a splitting test on the specimen in the damage state of step (5) until it is completely destroyed. The test temperature and loading rate are the same as those used when simulating splitting damage of the corresponding specimen.

[0086] (9) Based on the load-displacement data from steps (2) and (8), compare and analyze the splitting tensile strength R of specimens in the intact and damaged states. T The degree of damage is quantified using the energy ratio (ER) based on the following parameters: fracture stiffness modulus S (MPa), fracture energy E (J).

[0087]

[0088] Where ER is the energy ratio (%), E d E0 and E0 are the fracture energies (J) of the mixture under damaged and intact states, respectively.

[0089] The relationship between splitting tensile strength and loading rate, test temperature and unloading conditions in splitting damage test is as follows: Figure 2 As shown, at an experimental temperature of 40℃, the relationship between the stiffness modulus and damage state of the specimens under loading rates of 5 mm / min and 10 mm / min is as follows. Figure 6 As shown, the relationship between fracture energy and damage state is as follows: Figure 7 As shown. The calculated relationship between the energy ratio of the specimen's splitting failure and the damage state is as follows. Figure 8 As shown.

[0090] from Figure 2 It can be seen that in the splitting test, the splitting tensile strength of specimens with different damage states did not show significant differences, indicating that splitting damage does not affect the performance of recycled asphalt mixtures through strength.

[0091] from Figure 3 As can be seen, CT scans can identify cracks inside damaged specimens, allowing for the observation of splitting damage inside the specimen before macroscopic cracks appear on the surface.

[0092] from Figure 4 and Figure 6 It can be seen that changing the test temperature and loading rate significantly affects the stiffness modulus of the specimen in the splitting test. The stiffness modulus increases with the severity of damage. Figure 2 The variation pattern of medium strength indicates that the specimen's resistance to deformation decreases as the degree of damage increases. This conclusion is of great significance for the study of splitting damage in recycled asphalt mixtures.

[0093] from Figure 5 and Figure 7 It can be seen that the higher the degree of damage to the specimen, the smaller the fracture energy required for the specimen to fail in the splitting test, and the easier it is to fail when subjected to splitting load again. Figure 8 Based on Figure 5 and Figure 7 The energy ratio obtained from the fracture energy calculation indicates that the smaller the energy ratio, the less energy is required for the damaged specimen to be split and destroyed, i.e., the more severe the damage.

[0094] Example 4

[0095] In order to perform the method corresponding to Embodiment 1 above and achieve the corresponding functions and technical effects, a splitting damage test system for recycled asphalt mixtures is provided below.

[0096] The system includes:

[0097] The first scanning module is used to perform a single scan on the recycled asphalt mixture specimen using industrial CT scanning equipment to obtain a scan image of its intact state.

[0098] The first splitting test module is used to conduct splitting tests on the recycled asphalt mixture specimens under different test conditions, record the first load-displacement data, and calculate the average failure load P under each group of test conditions.

[0099] The splitting damage simulation module is used to simulate splitting damage on the recycled asphalt mixture specimens under different test conditions.

[0100] The second scanning module is used to perform a single scan on the recycled asphalt mixture specimen after splitting damage using industrial CT scanning equipment, and to obtain a scan image of the damage state.

[0101] The second splitting test module is used to conduct splitting tests on recycled asphalt mixture specimens after splitting damage until complete failure, and record the second load-displacement data.

[0102] The first comparison module is used to compare the internal features of the recycled asphalt mixture specimen in the intact state and the damaged state based on the scanned image in the intact state and the scanned image in the damaged state.

[0103] The second comparison module is used to compare the strength characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state based on the first load-displacement data and the second load-displacement data; the strength characteristics include splitting tensile strength, breaking stiffness modulus and fracture energy.

[0104] The energy ratio calculation module is used to calculate the energy ratio based on the fracture energy of the recycled asphalt mixture specimens in intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the recycled asphalt mixture specimens.

[0105] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0106] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for testing the splitting damage of recycled asphalt mixtures, characterized in that, include: A single scan of the recycled asphalt mixture specimen was performed using an industrial CT scanning device to obtain a scanned image of the specimen in good condition. Splitting tests were conducted on the recycled asphalt mixture specimens under different test conditions. The first load-displacement data were recorded, and the average failure load P under each test condition was calculated. Simulated splitting damage was performed on the recycled asphalt mixture specimens under different test conditions; A single scan of the recycled asphalt mixture specimen after splitting damage was performed using an industrial CT scanning device to obtain a scan image of the damage state. Splitting tests were performed on the recycled asphalt mixture specimens after splitting damage until complete failure, and the second load-displacement data were recorded. Based on the scan images of the intact state and the scan images of the damaged state, the internal characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state are compared; Based on the first load-displacement data and the second load-displacement data, the strength characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state are compared; the strength characteristics include splitting tensile strength, failure stiffness modulus and fracture energy; The energy ratio is calculated based on the fracture energy of the recycled asphalt mixture specimens in both intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the recycled asphalt mixture specimens.

2. The method for testing splitting damage of recycled asphalt mixtures according to claim 1, characterized in that, The porosity of the recycled asphalt mixture specimens differs from the average porosity by no more than ±0.5%.

3. The method for testing splitting damage of recycled asphalt mixtures according to claim 1, characterized in that, When simulating splitting damage on the recycled asphalt mixture specimens, loading was terminated early when the load first reached 0.5P, 0.7P, and 0.9P as unloading conditions.

4. The method for testing splitting damage of recycled asphalt mixtures according to claim 1, characterized in that, The test temperature and loading rate used in the splitting test were the same as those used in the simulated splitting damage test.

5. The method for testing splitting damage of recycled asphalt mixtures according to claim 1, characterized in that, The internal characteristics of the recycled asphalt mixture specimens include: porosity, porosity distribution, asphalt layer thickness, and aggregate distribution.

6. The method for testing splitting damage of recycled asphalt mixtures according to claim 1, characterized in that, The formula for calculating the energy ratio is: Where ER is the energy ratio, J d J0 and J0 represent the fracture energies of recycled asphalt mixtures under damaged and intact states, respectively.

7. A splitting damage testing system for recycled asphalt mixtures, characterized in that, include: The first scanning module is used to scan the recycled asphalt mixture specimen once using industrial CT scanning equipment to obtain a scan image of the intact state. The first splitting test module is used to conduct splitting tests on the recycled asphalt mixture specimens under different test conditions, record the first load-displacement data, and calculate the average failure load P under each group of test conditions. The splitting damage simulation module is used to simulate splitting damage on the recycled asphalt mixture specimens under different test conditions. The second scanning module is used to scan the recycled asphalt mixture specimen after splitting damage using industrial CT scanning equipment to obtain a scan image of the damage state. The second splitting test module is used to perform splitting tests on recycled asphalt mixture specimens after splitting damage until complete failure, and record the second load-displacement data. The first comparison module is used to compare the internal features of the recycled asphalt mixture specimen in the intact state and the damaged state based on the scanned image in the intact state and the scanned image in the damaged state. The second comparison module is used to compare the strength characteristics of the recycled asphalt mixture specimens in the intact state and the damaged state based on the first load-displacement data and the second load-displacement data; the strength characteristics include splitting tensile strength, breaking stiffness modulus and fracture energy; The energy ratio calculation module is used to calculate the energy ratio based on the fracture energy of the recycled asphalt mixture specimens in intact and damaged states; the energy ratio is used to quantitatively evaluate the degree of splitting damage of the recycled asphalt mixture specimens.

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