Method and system for evaluating interface failure mode of recycled asphalt mixture

Abstract

The invention discloses a method and a system for evaluating the interface failure mode of a recycled asphalt mixture, and the method comprises the following steps: cutting the recycled asphalt mixture to prepare a test piece with a preset fracture path, drawing the test piece by using drawing test equipment, and recording a force-displacement curve, the method comprises the following steps of: calculating the overall total fracture strength or total fracture energy of a test piece, identifying various different microcosmic fracture modes existing on a drawing fracture surface, quantitatively calculating the percentage of the fracture area occupied by each mode and the total fracture surface area, and establishing and solving an equation set for describing the relationship between the total fracture performance and the contribution of each mode. And calculating to obtain the unit area breaking strength or breaking energy corresponding to each specific microcosmic damage mode. The method can accurately identify, quantify and analyze the contribution of different failure modes of the regenerated asphalt mixture interface, and provides an effective means for deeply understanding material performance, optimizing design and realizing high-valued application.

Description

Technical Field

[0001] The present invention belongs to the technical field of material analysis, and in particular relates to a method and system for evaluating interface failure modes of recycled asphalt mixture. Background Art

[0002] Waste asphalt mixture has been widely used in my country's road field as a solid waste material. Its advantage is that it saves resources while protecting the environment.

[0003] In actual engineering applications, waste asphalt mixtures will inevitably encounter an unavoidable problem - the interface damage of recycled asphalt. Domestic and foreign scholars have conducted a lot of research on this issue. Some studies have conducted pull-out tests on ordinary asphalt, and specifically studied the specific failure modes between asphalt-asphalt and asphalt-aggregate under the coupling effect of aggregate roughness and asphalt film thickness. The study pointed out the specific influence of aggregate roughness and asphalt film thickness on the failure mode of ordinary asphalt mixtures. Although the asphalt film thickness in this study does not conform to the actual situation, resulting in a large variability, and the study is for ordinary asphalt rather than recycled asphalt. However, this study still has a strong reference significance, because there may be more failure modes in recycled asphalt, including old material fracture, new / old asphalt cohesive failure, aggregate and asphalt debonding failure, and new aggregate fracture. It is necessary to extend similar pull-out tests to the interface analysis research of recycled asphalt mixtures.

[0004] CN202410607805.6 discloses a method for identifying cracking characteristics of hot-regenerated asphalt mixtures based on 3D scanning technology. The method uses a Polyga3D scanning system to scan and model hot-regenerated asphalt mixture DCT specimens and calculates the modeled fracture area to more accurately calculate the fracture energy of the specimen; a shadowless lamp environment is used to enhance the image so as to clearly obtain the cracking characteristics of the mixture. Although this patent can obtain clear high-definition images and accurate fracture modeling, so as to more accurately calculate the fracture energy and observe the cracking characteristics of the mixture. However, the observation equipment is expensive, the detection cost is expensive, and only the image of the recycled asphalt surface modeling can be analyzed.

[0005] CN202210183842.X discloses a test device and method for adhesion failure and bondability between asphalt and aggregate. The test device designed by this method includes a tensile loading device and a pull head. It is worth mentioning that the asphalt forming groove provided at the bottom of the pull head can form and bond an asphalt film, and the bonding enhancement part provided at the bottom of the forming groove can enhance the bonding force between the asphalt film and the asphalt forming groove, making this bonding force greater than the bonding force between the asphalt film and the rock specimen. Finally, the adhesion force between the asphalt film and the top surface of the rock specimen is measured by pulling the pull head. Although this patent can produce an asphalt film with a uniform thickness to simulate the adhesion failure between asphalt and the aggregate surface, the test specimens of the observation equipment are difficult to restore the true and complex state of the actual asphalt mixture, and it can only test the interfacial bonding force between fresh asphalt and aggregate, and is even less able to accurately measure the complex interfacial failure modes of various interfacial failures such as recycled asphalt.

[0006] CN202323304087.5 discloses a pull-out test device for asphalt-aggregate adhesion. The pull-out test device designed by this method includes a loading rod, a pull head, an aggregate assembly, a fixing plate, and an environmental chamber. This patent mentions a method of bonding two aggregates with upper and lower plates respectively, leaving an asphalt layer between the two aggregates. One surface of the two aggregates is coated with asphalt, and the other is not coated with asphalt but the aggregate coated with asphalt is slightly squeezed by pressure, resulting in a thinner thickness of the middle asphalt layer to obtain the adhesion between the aggregate and the asphalt. Although this method can solve the problem of inaccurate measurement of the bonding force caused by the asphalt falling off, the thickness of the asphalt left by this method is small, and it is impossible to measure the fracture energy between the thick asphalt layer and the aggregate, let alone measure the fracture energy of this complex interfacial failure mode of recycled asphalt, and the calculation formula is simple and cannot more accurately reflect the fracture energy under the pull-out test.

[0007] There is an urgent need in the art for a new test and analysis method and system that can overcome the limitations of the above-mentioned existing technologies, not only be able to conduct mechanical property tests on recycled asphalt mixtures, but more importantly, be able to accurately identify various microscopic failure modes on the pull-out failure interface, quantitatively analyze the proportion of each mode, and further solve the fracture strength or fracture energy associated with each specific failure mode. Such a method will help to deeply reveal the weak links and their causes of the interfacial bonding of recycled asphalt mixtures, and provide key technical support and reliable evaluation basis for optimizing the design of recycled materials, improving the effect of recycling agents, and realizing the high-value application of recycled asphalt mixtures. Summary of the Invention

[0008] One of the objectives of the present invention is to at least solve one or more of the above problems in the prior art. In other words, one of the objectives of the present invention is to provide a method and system for evaluating the interfacial failure modes of recycled asphalt mixtures that meet one or more of the foregoing requirements.

[0009] To achieve the above invention objectives, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for evaluating the interfacial failure modes of recycled asphalt mixtures, including:

[0011] S1. Prepare Marshall specimens of recycled asphalt mixtures with reserved cutting sections to form test specimens;

[0012] S2. Use a pull-out test device to pull the test specimen until it breaks, and record the force-displacement curve;

[0013] S3. Calculate the total fracture strength or total fracture energy according to the peak force-displacement curve;

[0014] S4. Identify the percentage of the failure area of various failure modes in the total area of the pull-out section of the test specimen;

[0015] S5. Repeat steps S2 - S4 several times to obtain the average values of the total fracture strength, total fracture energy, and the percentage of the failure area of various failure modes in the total area;

[0016] S6. Calculate the fracture strength and fracture energy of various failure modes according to the average values of the total fracture strength, total fracture energy, and the percentage of the failure area of various failure modes in the total area.

[0017] As a preferred implementation, various failure modes include new aggregate fracture failure, old aggregate fracture failure, new / old asphalt cohesion failure, and aggregate-asphalt debonding failure.

[0018] As a further preferred implementation, the calculation formulas for the fracture strength and fracture energy of various failure modes are:

[0019]

[0020] where, ΔG1 total is the total fracture strength or fracture energy per unit pull-out interface for the first time, α1 is the percentage of the failure area caused by new / old asphalt cohesion failure in the total area for the first time, ΔG cohesion is the fracture strength or fracture energy per unit interface caused by new / old asphalt cohesion failure for the first time, β1 is the percentage of the failure area caused by aggregate-asphalt debonding in the total area for the first time, ΔG1 adhesion is the fracture strength or fracture energy per unit interface caused by aggregate-asphalt debonding for the first time, γ1 is the percentage of the failure area caused by new aggregate fracture in the total area for the first time, ΔG1 new aggregate is the fracture strength or fracture energy per unit interface caused by new aggregate fracture for the first time, ΔG1 aging aggregateis the unit interfacial fracture strength or fracture energy caused by the fracture of old aggregates in the first time.

[0021] As a preferred embodiment, the calculation formula for the total fracture strength is The calculation formula for the total fracture energy is

[0022]

[0023] Wherein, P is the maximum force (kN) during the loading process of the pull-out test, D is the diameter (mm) of the recycled aggregate specimen, l is the depth (mm) of the reserved cross-section groove, and f(x) is the pull-out force (kN) corresponding to the displacement x during the pull-out test.

[0024] As a preferred embodiment, the test specimen is prepared by cutting a reserved cross-section groove with a width of 5 mm and a depth of 10 mm on the recycled asphalt mixture.

[0025] As a preferred embodiment, in step S3, the image integration formula is used to calculate the total fracture strength or the total fracture energy is calculated according to the peak force.

[0026] As a preferred embodiment, in step S4, through macro observation and digital image processing technology, the percentage of the failure area of various failure modes in the total area of the pull-out section of the test specimen is identified according to the particle size difference, distribution and interface color difference between the new and old aggregates.

[0027] As a further preferred embodiment, digital image processing first grayscales the macro observation image, then divides the image into layers corresponding to various failure modes through color difference, and calculates the failure area of various failure modes through different layers.

[0028] As a preferred embodiment, before step S1, there is also step S0, using new aggregates and old materials with different particle size distributions, mixing and forming with asphalt and regenerant by the Marshall method to prepare recycled asphalt mixture Marshall specimens.

[0029] On the other hand, the present invention provides a system for evaluating the interfacial failure modes of recycled asphalt mixtures, using the method as described in any one of the above to evaluate the interfacial failure modes of recycled asphalt mixtures.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] The method and system of the present invention can inversely calculate the fracture strength or fracture energy per unit area corresponding to each specific microscopic failure mode by combining the macroscopic total fracture strength or total fracture energy data obtained from multiple pull-out tests and the area percentage data of each failure mode on the cross-section in each test, and solving the simultaneous equations. Through the quantitative analysis of various failure modes and their proportions, the present invention can clearly point out the most likely failure types and their relative severity at the interface of recycled asphalt mixture under specific conditions, thereby accurately locking the short board affecting the overall performance of the material, providing reliable data support and scientific guidance for the effect evaluation of regenerants, the optimization design of the mix ratio of recycled materials, the selection of mixing and compaction process parameters, etc., helping to solve the key technical problems in the application of recycled asphalt mixture, and promoting the higher value utilization of waste pavement materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the pull-out test in an embodiment of the present invention;

[0033] Figure 2 is a schematic diagram of the fracture surface of the test piece in an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of the percentage of the area of each failure mode in the total area in an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of the percentage of the area of each failure mode in the total area in another embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0037] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of the content of the present invention. Each example may appropriately omit, substitute, or add various processes or components. For example, the described methods may be performed in a different order from that described, and various steps may be added, omitted, or combined. In addition, the features described in some examples may be combined into other examples.

[0038] The present invention provides a method for evaluating the failure modes of the interface of recycled asphalt mixture, including:

[0039] S1. Prepare Marshall specimens of recycled asphalt mixture with reserved cutting cross-sections to form test pieces;

[0040] First, prepare the recycled asphalt mixture specimens according to the standard methods recognized in the industry. For example, the Marshall method specified in the "Technical Specification for Construction of Highway Asphalt Pavement" JTG F40 can be followed. In the specific implementation process, new aggregates and old materials with specific particle size distribution differences can be selected. For example, in a specific embodiment, AC-13 type hot recycled asphalt mixture is used, in which 40% of the old material with a particle size of 0 to 5 mm is added, and the rest is new material with a particle size of 5 to 16 mm. These aggregates, together with new asphalt, such as asphalt with a grade of 80 / 100, mineral powder, and recycling agents added as needed, are fully mixed and compacted to form Marshall specimens of recycled asphalt mixture with standard dimensions.

[0041] After the specimens are formed, they need to be left standing for a period of time to reach a stable state, for example, they can be left standing for one day. Subsequently, use cutting equipment with sufficient precision to process the specimens to preset the path where fracture occurs. Taking the G21-100 type cutting machine with an accuracy of ±0.05 mm used in the embodiment as an example, along the circumferential direction at approximately the middle position of the specimen, that is, around the periphery of the specimen, precisely cut out a groove with a predetermined size. In the preferred design of the present invention, the width of this reserved cross-section groove is set to 5 mm and the depth is set to 10 mm. After the cutting operation is completed, the groove must be thoroughly cleaned, for example, by blowing with compressed air, to completely remove the debris generated during the cutting process, so as to avoid any interference of these residues on the results of the subsequent pull-out test. After the above steps, the test specimens for the next pull-out test are prepared.

[0042] S2. Use the pull-out test equipment to pull the test specimens until they break, and record the force-displacement curve;

[0043] Firmly install the test specimens prepared in step S1 into the special fixture for the pull-out test. In the installation process, it is necessary to strictly ensure that the connection between the test specimens and the upper and lower fixtures is firm and reliable, and ensure that the central axis of the test specimens is accurately aligned with the action line of the upcoming pull-out force. This is to effectively prevent inaccurate test data caused by eccentricity during the loading process.

[0044] After the installation of the test specimens is completed, use a test equipment capable of applying a precisely controllable pull-out force to load the test specimens. Such equipment can be the WDW-100 type electronic universal testing machine used in the embodiment, or an instrument with similar functions such as the hydraulic servo device described in the claims. Apply a direct upward pull-out force to the test specimens and continuously load until the test specimens break and fail at the previously preset groove position. During the entire pull-out test process, it is necessary to set and strictly maintain a constant loading rate. For example, in the embodiment, the loading rate is set to 1 mm per minute. The schematic diagram of the pull-out test is asFigure 1 As shown, the schematic diagram of the fracture surface after the test piece breaks is as Figure 2 shown.

[0045] During the entire period from the start of the drawing load until the test piece is completely broken, it is necessary to use the professional data acquisition system equipped with the test equipment to record in real time and continuously the magnitude of the drawing force applied to the test piece, as well as the corresponding drawing displacement generated by the test piece under this drawing force. In this way, a complete force-displacement curve can be obtained, and this curve is also often called the force-displacement response curve. This curve is an important basic data for subsequent calculation of the total fracture strength and total fracture energy of the test piece. Therefore, it is especially necessary to accurately record the peak force on the curve, that is, the maximum drawing force value, and the displacement value corresponding to this peak force.

[0046] S3. Calculate the total fracture strength using the image integration formula or calculate the total fracture energy based on the peak force;

[0047] After completing the drawing test in step S2 and obtaining a complete force-displacement curve, the next step is S3, that is, processing the recorded data to calculate the key indicators characterizing the overall drawing resistance performance of the recycled asphalt mixture test piece. These key indicators mainly refer to the total fracture strength or total fracture energy per unit drawing area of the recycled material on the preset fracture surface.

[0048] When calculating the total fracture strength, it is usually based on the maximum drawing force recorded during the drawing test, that is, the peak force P on the force-displacement curve. According to a calculation method provided by the present invention, the total fracture strength per unit drawing area, denoted here by the symbol ΔG total is expressed, and its unit is usually megapascals (MPa), and can be obtained by dividing the peak force P by the nominal area of the preset fracture surface

[0049] When calculating the total fracture energy, it is necessary to utilize all the information of the force-displacement curve from the start of loading until the test piece is completely broken. The total fracture energy characterizes the ratio of the total energy consumed to cause the test piece to undergo drawing fracture to the fracture area. In the present invention, the total fracture energy per unit drawing area, also denoted by the symbol ΔG total is expressed, and its unit is usually joules per square millimeter (J / mm 2 ), and can be obtained by integrating the area under the force-displacement curve to obtain the total work done during the drawing process, and then dividing this total work value by the nominal area of the preset fracture surface.

[0050] Specifically, when implementing, an image integration method or a numerical integration method can be adopted to calculate the integral value of the drawing force f(x) over the entire drawing displacement x, and then calculate the total fracture strength according to the formula or calculate the total fracture energy according to the formula to calculate the total fracture energy.

[0051] Where: ΔG total is the total fracture strength (MPa) or total fracture energy (J / mm 2 ) of the unit drawing interface, P is the maximum force (kN) during the drawing test loading process, D is the diameter (mm) of the recycled material specimen, l is the depth (mm) of the reserved cross-section groove, and f(x) is the drawing force (kN) corresponding to the displacement x during the drawing test.

[0052] By performing this step, parameters that accurately quantify and reflect the macroscopic tensile drawing fracture properties of the recycled asphalt mixture specimen can be obtained, and these parameters are the basis for subsequent microscopic analysis and correlation of the interface failure mode.

[0053] S4. Identify the percentage of the failure area of various failure modes in the drawing cross-section of the test piece in the total area.

[0054] After obtaining the fractured test piece through step S2, perform step S4, that is, carefully observe and analyze the fracture interface of the test piece to identify and quantify the areas occupied by different microscopic failure modes.

[0055] First, it is necessary to photograph the complete failure interface formed after the test piece fractures, and use high-resolution macro-observation technology to image the drawing cross-section. For example, in the embodiment, a macro camera lens is used to photograph the cross-section under natural lighting conditions to obtain clear and detailed images.

[0056] The key to identifying different failure modes lies in using the inherent visual differences presented by the components inside the recycled asphalt mixture and different failure forms. These differences are mainly reflected in aspects such as the particle size of new / old aggregates and the color contrast at the interface between aggregates and asphalt. Specifically: Cohesive failure between new / old asphalt, that is, the adhesion failure between asphalt, is manifested as the fracture inside the asphalt body, and its cross-section color and texture are relatively uniform; The debonding failure between aggregates and asphalt clearly shows the interface trace of asphalt peeling off from the aggregate surface, and usually the exposed aggregate surface can be seen; The fracture of new aggregates or old aggregates themselves will present the unique and fresh fracture texture and color inside the aggregate minerals, and the fracture of new aggregates or old aggregates can be further distinguished by different particle sizes.

[0057] After obtaining high-quality cross-sectional images, professional digital image processing techniques and software are used to deeply analyze the images. A typical processing flow may include: First, necessary preprocessing is performed on the images. For example, grayscale conversion may be carried out to enhance image features. Next, the core step is image segmentation and recognition. Based on the visual features such as color, texture, and shape corresponding to the different failure modes mentioned above, the regions representing various failure modes (such as cohesive failure in new / old asphalt, debonding failure between aggregate and asphalt, fracture failure of new aggregate, fracture failure of old aggregate, etc.) are accurately identified and divided in the software. This can be achieved by setting different thresholds and using color differences to distinguish layers, separating the images corresponding to various failure modes into different layers respectively.

[0058] Finally, the area of each identified failure mode region is accurately calculated from the images of different layers, and this area is compared with the total area of the entire pull-out cross-section being analyzed, so as to calculate the percentage of the area occupied by each failure mode in the total cross-sectional area. This percentage data reflects the contribution degree of various micro-failure mechanisms to the overall fracture process under the conditions of this pull-out test.

[0059] S5. Repeat steps S2 - S4 several times to obtain the average values of the total fracture strength, total fracture energy, and the percentage of the failure area of each failure mode in the total area.

[0060] Given that the distribution of new and old materials, asphalt, and aggregates within the recycled asphalt mixture itself has a certain randomness, the pull-out test results of a single test piece may not be sufficient to fully represent the overall interface failure characteristics of the materials under this batch or these conditions. Therefore, in order to improve the reliability and representativeness of the test results, it is necessary to conduct repeated tests.

[0061] The specific operation is to repeat the aforementioned steps S2, step S3, and step S4 for multiple test pieces prepared from the same batch under the same preparation and test conditions.

[0062] In the embodiment, 4 groups of parallel tests are designed for each test condition. Through such repeated operations many times, a series of independent test data can be obtained. Each set of data contains a total fracture strength value and the percentage of the area of various failure modes on the cross-section corresponding to that test.

[0063] Statistical processing of the data obtained through multiple repeated tests can calculate the average values of various indicators.

[0064] S6. Calculate the fracture strength and fracture energy of each failure mode based on the average values of the total fracture strength, total fracture energy, and the percentage of the failure area of each failure mode in the total area.

[0065] The total fracture strength or total fracture energy of the recycled asphalt mixture specimens measured in the pull-out test can be regarded as the weighted average of the respective contributions of various different failure modes that make up the fracture surface. Among them, the weight is the percentage of the area occupied by this failure mode on the fracture surface measured in step S4.

[0066] Specifically, for each pull-out test in steps S2 - S4, a relational expression can be established. This expression states that the total fracture strength or fracture energy of one test is equal to the percentage of the area of cohesive failure in the new / old asphalt of this test multiplied by its fracture strength or fracture energy per unit area, plus the percentage of the area of debonding failure between the aggregate and the asphalt multiplied by its fracture strength or fracture energy per unit area, plus the percentage of the area of fracture failure of the new aggregate multiplied by its fracture strength or fracture energy per unit area, and the percentage of the area of fracture failure of the old aggregate multiplied by its fracture strength or fracture energy per unit area, etc., and the sum of these terms.

[0067] In this embodiment, step S5 was repeated multiple times, and 4 equations were obtained. In these equations, the total fracture strength or fracture energy of each test and the area percentages of each failure mode are known measured values or calculated values.

[0068] Therefore, these 4 equations together form a system of simultaneous equations.

[0069]

[0070] In the formula: ΔG x total is the total fracture strength (MPa) or fracture energy (J / mm 2 ) per unit pull-out interface under the x-th test, α x is the percentage of the failure area caused by cohesive failure of the new / old asphalt in the total area (%) under the x-th test, ΔG x cohesion is the fracture strength (MPa) or fracture energy (J / mm 2 ) per unit interface caused by cohesive failure of the new / old asphalt under the x-th test, β x is the percentage of the failure area caused by debonding between the aggregate and the asphalt in the total area (%) under the x-th test, ΔG x adhesion is the fracture strength (MPa) or fracture energy (J / mm 2 ) per unit interface caused by debonding between the aggregate and the asphalt under the x-th test, γ x is the percentage of the failure area caused by debonding between the aggregate and the asphalt in the total area (%) under the x-th test, ΔG x new aggregate is the fracture strength (MPa) or fracture energy (J / mm per unit interface caused by fracture of the new aggregate under the x-th test2 ), ΔG x aging aggregate is the unit interfacial fracture strength (MPa) or fracture energy (J / mm 2 ) caused by the fracture of old aggregates under the x-th test.

[0071] By solving this system of simultaneous equations, the numerical values of the fracture strength or fracture energy per unit area corresponding to each identified microscopic failure mode can be finally obtained.

[0072] In Example 1, taking the AC-13 type hot recycled asphalt mixture as an example, 40% of the old materials with a particle size of 0-5 mm are added, and the rest are new materials with a particle size of 5-16 mm. The old materials are obtained by milling and recycling the damaged pavement on site. When designing the hot recycled asphalt mixture, 80 / 100 asphalt is selected as the new asphalt. Among them, the first group is set as the control group, and the remaining two groups are set as the experimental groups. To deeply explore the influence of different design factors on the mixture performance and interfacial failure modes, the second group and the third group are designed as experimental groups with all other factors being the same except for the mixing time. Through the comparative analysis of the test data of these three groups, the internal relationship between different design factors and the performance of recycled asphalt mixture can be revealed more accurately.

[0073] In Example 1, three groups of tests were designed using the above-mentioned recycled asphalt mixture under the condition of -10°C. Among them, the first group is set as the control group, and the remaining two groups are set as the experimental groups. To deeply explore the influence of different design factors on the mixture performance and interfacial failure modes, the second group and the third group are designed as experimental groups with all other factors being the same except for the mixing time. Through the comparative analysis of the test data of these three groups, the internal relationship between different design factors and the performance of recycled asphalt mixture can be revealed more accurately.

[0074] Specifically, the design parameters of the recycled materials for the three groups of tests are shown in Table 1, and the volume parameters of the recycled materials are shown in Table 2.

[0075]

[0076] Table 1

[0077]

[0078] Table 2

[0079] The percentages of the areas of each failure mode calculated for the three groups of tests in the total area are as Figure 3 shown.

[0080] From Figure 3From the comparison of the failure modes, fracture energy, and fracture strength, it can be seen that the main failure modes of the recycled asphalt mixture at -10°C are cohesion failure between new and old asphalt, fracture failure of new aggregates, fracture failure of old aggregates, and debonding failure between aggregates and asphalt. In the mesoscopic failure of the -10°C specimens, the debonding failure between aggregates and asphalt is the main failure mode for all specimens. However, as the mixing time increases, the proportion of cohesion failure between new and old asphalt gradually decreases, and the fracture energy and fracture strength also gradually decrease, reaching the minimum values at a mixing time of 360 s. Therefore, the following conclusions can be drawn: at low temperatures, the fracture energy and fracture strength are still closely related and decrease with the extension of the mixing time. Moreover, the change trends of the fracture energy and fracture strength are consistent with the changes in the proportion of the debonding failure area between aggregates and asphalt, the fracture failure area of old aggregates, and the fracture failure area of new aggregates under mesoscopic conditions. This can explain and further demonstrate the correlation between the microscopic mode and the macroscopic fracture energy and fracture strength of the recycled asphalt mixture. At the same time, the results of the three groups of tests have a certain degree of discrimination, proving the feasibility and effectiveness of the analysis method using this invention.

[0081] Example 2 designed 3 groups of tests at 40°C using the above recycled asphalt mixture. The percentages of the areas of each failure mode in the total area calculated for the three groups of tests are as Figure 4 shown.

[0082] Specifically, the design parameters of the recycled materials for the 3 groups of tests are shown in Table 3, and the volume parameters of the recycled materials are shown in Table 4.

[0083]

[0084] Table 3

[0085]

[0086] Table 4

[0087] From Figure 4 From the comparison of the failure modes, fracture energy, and fracture strength, it can be seen that in the mesoscopic failure of the 40°C specimens, the cohesion failure between new and old asphalt is the main failure mode for all specimens, and as the aging duration increases, the proportion of the cohesion failure between new and old asphalt gradually increases. The main failure modes of the recycled asphalt mixture at 40°C are cohesion failure between new and old asphalt, failure of old materials, and debonding failure between aggregates and asphalt. The changes in the fracture energy and fracture strength are basically consistent, reaching the maximum values at an aging duration of 120 h, and the results of the three groups of tests have a certain degree of discrimination, once again proving the feasibility and effectiveness of the analysis method using this invention.

[0088] In Example 1 and Example 2, the fracture strengths of respective modes such as the debonding failure between aggregate and asphalt, the fracture failure of old aggregate, the fracture failure of new aggregate, and the cohesive failure of new / old asphalt were calculated under the conditions of -10°C and 40°C, respectively. These values quantitatively reveal the resistance capabilities of different failure mechanisms and are the key results for deeply evaluating the interface performance of recycled asphalt mixtures.

[0089] By combining the macroscopic total fracture strength or total fracture energy data obtained from multiple pull-out tests and the area percentage data of each failure mode on the cross-section during each test, and solving using simultaneous equations, the above method can inversely calculate the fracture strength or fracture energy per unit area corresponding to each specific microscopic failure mode. Through the quantitative analysis of various failure modes and their proportions, the above method can clearly indicate the most likely failure type and its relative severity at the interface of recycled asphalt mixtures under specific conditions, thereby accurately identifying the weak points affecting the overall performance of the material. This provides reliable data support and scientific guidance for the effect evaluation of rejuvenators, the optimization design of the mix proportion of recycled materials, the selection of mixing and compaction process parameters, etc., helps to solve the key technical problems in the application of recycled asphalt mixtures, and promotes the higher-value utilization of waste pavement materials.

[0090] The present invention also provides a system for evaluating the failure modes of the interface of recycled asphalt mixtures, using the above method.

[0091] The system includes a pull-out test and data acquisition unit, an image acquisition and analysis unit, and a data processing and calculation unit.

[0092] Among them, the pull-out test and data acquisition device is responsible for applying mechanical loading to the prepared test piece and recording the response. It usually includes a loading unit, such as an electronic universal testing machine or a hydraulic servo instrument, etc., which can accurately apply and control the pulling force. This loading unit can apply a direct pull-out force to the test piece installed in the clamping unit at a set constant rate, such as 1 millimeter per minute, until the test piece fractures at the preset groove. At the same time, the device integrates a data acquisition unit, whose function is to record the applied pull-out force and the corresponding pull-out displacement of the test piece in real time and accurately during the entire pull-out process, and record these data to form a complete force-displacement curve.

[0093] The image acquisition and analysis unit is used for microscopic inspection and quantitative analysis of the interface after the test piece breaks. It includes an image acquisition device, such as a camera equipped with a macro lens or other high-resolution imaging devices, which is specifically used to capture clear images of the cross-section exposed after the test piece is pulled and broken. More importantly, it includes an image processing module, which is usually special software or algorithms running on a computer system. This module is designed to be able to process the input cross-section images, and based on visual features such as the colors, textures, shapes or particle size differences presented by different material components and different failure forms in the images, automatically or assist manually to identify various different failure mode regions on the cross-section. After identification, this module can accurately calculate the area occupied by each identified failure mode region, and further calculate the percentage of this area in the total area of the entire analyzed cross-section.

[0094] The data processing and calculation unit is embodied as a computer system configured with specific analysis software. Its core function is to integrate and process the data from the aforementioned units and complete complex calculation tasks. Specific functions include: receiving and processing the force-displacement curve data output by the data acquisition unit, and calculating the total fracture strength or total fracture energy obtained from each pull-out test according to the calculation formula defined in the present invention; receiving and storing the area percentage data of various failure modes on the cross-section in each test output by the image analysis unit; this unit is configured to be able to integrate multiple sets of measurement data obtained through repeated tests, establish and solve the system of simultaneous equations as shown above, so as to finally calculate and output the fracture strength or fracture energy value per unit area corresponding to each specific microscopic failure mode.

[0095] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0096] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0097] The foregoing are only exemplary embodiments of the present disclosure, and thus cannot limit the scope of the present disclosure. That is, all equivalent changes and modifications made in accordance with the teachings of the present disclosure still fall within the scope covered by the present disclosure. Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the specification and practicing the disclosure herein. The present invention is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include well-known common general knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and embodiments are only regarded as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A method for evaluating the interfacial failure mode of recycled asphalt mixture, characterized in that, Including: S1. Prepare a Marshall specimen of recycled asphalt mixture with a reserved cutting section to form a test piece; S2. Use a pull-out test device to pull the test piece until it breaks, and record the peak force-displacement curve; S3. Calculate the total fracture strength or total fracture energy according to the peak force-displacement curve; S4. Identify the percentage of the failure area of each failure mode in the total area of the pull-out section of the test piece; S5. Repeat steps S2 - S4 several times to obtain the average values of the total fracture strength, total fracture energy, and the percentage of the failure area of each failure mode in the total area; S6. Calculate the fracture strength and fracture energy of each failure mode according to the average values of the total fracture strength, total fracture energy, and the percentage of the failure area of each failure mode in the total area.

2. The method for evaluating the interfacial failure mode of recycled asphalt mixture according to claim 1, characterized in that, The various failure modes include new aggregate fracture failure, old aggregate fracture failure, new / old asphalt cohesion failure, and aggregate-asphalt debonding failure.

3. A method for evaluating the interfacial failure mode of recycled asphalt mixture as claimed in claim 2, characterized in that, The calculation formulas for the fracture strength and fracture energy of the various failure modes are as follows: Among them, ΔG1 total is the total fracture strength or fracture energy of the unit drawing interface for the first time, α1 is the percentage of the failure area caused by the cohesive failure of the new / old asphalt in the total area, ΔG cohesion is the unit interface fracture strength or fracture energy caused by the cohesive failure of the new / old asphalt for the first time, β x is the percentage of the failure area caused by the debonding of the aggregate and asphalt in the total area for the first time, ΔG1 adhesion is the unit interface fracture strength or fracture energy caused by the debonding of the aggregate and asphalt for the first time, γ1 is the percentage of the failure area caused by the fracture of the new aggregate in the total area, ΔG1 newaggregate is the unit interface fracture strength or fracture energy caused by the fracture of the new aggregate for the first time, ΔG1 agingaggregate is the unit interface fracture strength or fracture energy caused by the fracture of the old aggregate for the first time.

4. The method for evaluating the interfacial failure mode of recycled asphalt mixture according to claim 1, characterized in that, The calculation formula for the total fracture strength is The calculation formula for the total fracture energy is Wherein, P is the maximum force (kN) during the pull-out test loading process, D is the diameter (mm) of the recycled material specimen, l is the depth (mm) of the reserved section groove, and f(x) is the pull-out force (kN) corresponding to the displacement x during the pull-out test.

5. The method for evaluating the interface failure mode of recycled asphalt mixture according to claim 1, characterized in that, The test piece is prepared by cutting a reserved section groove with a width of 5 mm and a depth of 10 mm on the recycled asphalt mixture.

6. The method for evaluating the interface failure mode of recycled asphalt mixture according to claim 1, wherein, In step S3, according to the force-displacement curve, the total fracture strength is calculated using the image integration formula or the total fracture energy is calculated according to the peak force.

7. The method for evaluating the interfacial failure mode of recycled asphalt mixture according to claim 1, characterized in that In step S4, through macro observation and digital image processing technology, the percentage of the failure area of each failure mode in the total area of the pull-out section of the test piece is identified according to the particle size difference, distribution, and interface color difference between the new and old aggregates.

8. The method for evaluating the interface failure mode of recycled asphalt mixture according to claim 7, characterized in that For the digital image processing, the macro observation image is first grayscale processed, and then the image is divided into layers corresponding to various failure modes through color difference, and the failure area of each failure mode is calculated through different layers.

9. A method for evaluating the interfacial failure mode of recycled asphalt mixture as described in claim 1, characterized in that, Before step S1, there is also step S0. New aggregates and old materials with different particle size distributions are used, and are mixed and formed with asphalt and a regenerant by the Marshall method to prepare a Marshall specimen of recycled asphalt mixture.

10. A system for evaluating the interface failure mode of recycled asphalt mixture, characterized in that, Use the method according to any one of claims 1 - 9 to evaluate the interface failure mode of the recycled asphalt mixture.

Images