Construction method of asphalt damage density-healing index master curve coupled with multiple factors

Abstract

The present application relates to a multi-factor coupled asphalt damage density-healing index master curve construction method, the steps comprising: designing a test scheme containing temperature, loading frequency, strain level and damage density; fatigue-healing cycle loading on the asphalt sample, obtaining different combination healing indexes; establishing a relationship curve with damage density as the horizontal coordinate and healing index as the vertical coordinate; selecting a reference condition, determining the shift factor using the curve shift method, and shifting to construct the reduced damage density-healing index master curve; establishing a function relationship between the shift factor and the three types of factors to obtain an arbitrary condition healing index prediction model. The present application simultaneously investigates four types of variables, overcoming the single variable defect of the prior art; through the master curve method, the damage degree interference is stripped, the independent action mechanism of each factor is revealed, and the problems of lack of multi-factor quantification and action confusion are solved. The model prediction value is highly consistent with the measured value, improving the universality and stability, and providing technical support for asphalt healing evaluation.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials technology, and in particular to a method for constructing a master curve of asphalt damage density-healing index based on multi-factor coupling. Background Technology

[0002] Asphalt pavement is widely used due to its excellent driving comfort, low noise, and ease of construction. However, under long-term vehicle loads and the effects of a thermo-oxidative environment, pavement materials inevitably suffer fatigue damage, with microcracks gradually initiating and propagating, eventually leading to pavement defects such as cracking and potholes, severely affecting the road's performance and durability. Asphalt, as a viscoelastic material, possesses self-healing properties, meaning that under static or suitable conditions, it can partially repair fatigue damage through the migration, diffusion, and rearrangement of asphalt binder molecular chains, thereby delaying crack propagation and extending pavement service life. The healing ability of asphalt binders is key to determining the overall healing performance of asphalt mixtures, and this ability is influenced by multiple factors such as temperature, degree of damage, load level (e.g., strain level), and loading frequency, exhibiting complex nonlinear characteristics. Therefore, a thorough understanding and quantitative characterization of the healing properties of asphalt binders under multi-factor coupling is crucial for accurately evaluating material durability, optimizing material design, and achieving long-life, low-carbon pavements.

[0003] Existing methods for studying and evaluating the healing performance of asphalt materials have the following four significant shortcomings:

[0004] (i) The research variables are too singular: Most existing technologies focus on the analysis of healing characteristics under the influence of a single variable (such as changing only temperature), which cannot reflect the real healing behavior under the combined effect of multiple factors.

[0005] (ii) Lack of quantitative relationship model of multi-factor coupling: At present, the description of the healing process mostly adopts empirical regression or single-factor fitting, and fails to establish a unified and quantitative relationship model between healing performance parameters and multi-dimensional variables such as temperature, strain level, loading frequency, and damage degree, making it difficult to reveal the law of multi-variable synergistic effect.

[0006] (iii) The influence of loading conditions is ignored or confused: In particular, the existing evaluation methods fail to strictly exclude the interference of changes in the degree of damage when considering the influence of key mechanical parameters such as strain level and loading frequency on healing behavior, resulting in the inability to clearly distinguish the independent action mechanism of each factor.

[0007] (iv) Poor predictive universality: Due to the lack of a unified characterization method for the nonlinear evolution characteristics of the healing process under the coupling effect of multiple factors, the existing model is difficult to extend and transfer between different service conditions, resulting in poor universality and comparability of the prediction results.

[0008] In summary, it is necessary to construct a model and analysis method that can uniformly characterize the healing performance of asphalt binders under multi-factor coupling conditions, so as to achieve systematic prediction and scientific evaluation of their healing behavior under complex service conditions. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for constructing a master curve of asphalt damage density-healing index coupled with multiple factors, so as to solve one or more problems in the prior art.

[0010] To achieve the above objectives, the technical solution of the present invention is as follows:

[0011] A method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors includes the following steps:

[0012] S1. For the asphalt material to be tested, four single-factor variable test schemes were designed for temperature, loading frequency, strain level and damage density, respectively.

[0013] S2. The asphalt samples were subjected to fatigue-healing cyclic loading tests to obtain the healing index under different combinations of temperature, loading frequency, strain level and damage density.

[0014] S3. Using damage density as the abscissa and healing index as the ordinate, establish the damage density-healing index relationship curves at various temperatures, loading frequencies, and strain levels.

[0015] S4. Select a reference temperature, a reference loading frequency, and a reference strain level. Determine the temperature shift factor, loading frequency shift factor, and strain level shift factor respectively using the curve shifting method. Then, shift the damage density-healing index relationship curves under each condition to the reference condition to construct a reduced damage density-healing index master curve.

[0016] S5. Establish the functional relationships between temperature shift factor, loading frequency shift factor and strain level shift factor and temperature, loading frequency and strain level respectively, so as to obtain a healing index prediction model under arbitrary temperature, loading frequency, strain level and damage density conditions.

[0017] Furthermore, in step S1, the temperature variable ranges from 20℃ to 30℃, with three gradients designed; the loading frequency variable ranges from 5Hz to 20Hz, with four gradients designed; the strain level variable ranges from 1% to 6%, with four gradients designed; and the damage density variable ranges from 0.2 to 0.8, with four gradients designed.

[0018] Furthermore, in step S2, the healing index is defined as the ratio of the amount of damage density restored during the interval to the initial damage density during the interval, and the calculation formula is shown below:

[0019]

[0020] In the formula: The damage density of the material at the end of the first fatigue loading. This represents the damage density of the material at the end of the intermittent healing period.

[0021] Furthermore, the formula for calculating damage density in step S2 is as follows:

[0022]

[0023] In the formula: This represents the damage density of the sample at the Nth loading cycle. This represents the crack length of the sample during the Nth loading cycle. This represents the absolute value of the complex shear modulus of the sample at the Nth loading cycle. This represents the absolute value of the complex shear modulus of the sample at the initial loading stage. The radius of the complete sample.

[0024] Furthermore, in step S4, after applying the curve shift method to each variable, a fitting process is performed to control the error. The calculation formula is shown below:

[0025]

[0026] In the formula: The sum of errors for all fitted data points. The number of data points to fit. for Measured value of the healing index at the point. for The calculated value of the healing index at the point.

[0027] Furthermore, in step S4, the reduction in damage density is defined as the product of the shift factor corresponding to the reference variable value under the current value of each variable and the actual damage density.

[0028] Furthermore, the establishment of the healing index prediction model in step S5 includes the following steps:

[0029] Calculate the composite shift factor ;

[0030] The composite reduced damage density is calculated based on the target predicted actual damage density and the composite displacement factor. ;

[0031] Composite reduction damage density Substituting these values ​​into the constructed damage density-healing index master curve, and calculating the average of the three master curves, we obtain the final predicted healing index under given target damage density, temperature, loading frequency, and strain level. .

[0032] Furthermore, composite shift factor The calculation formula is shown below:

[0033]

[0034] In the formula: Representing frequency Shift factor relative to reference frequency, Represents strain level The shift factor corresponding to the reference strain level; Represents temperature The shift factor at the corresponding reference temperature.

[0035] Furthermore, the composite reduces damage density. The calculation formula is shown below:

[0036]

[0037] In the formula: This represents the actual damage density.

[0038] Furthermore, the final prediction results of the healing index The calculation formula is shown below:

[0039]

[0040] In the formula: Represents frequency The composite reduction damage density The healing index is below; Represents the level of strain The composite reduction damage density The healing index is below; Represents temperature The composite reduction damage density The healing index below.

[0041] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0042] This invention overcomes the shortcomings of existing technologies that rely on a single variable to study the healing behavior of asphalt by simultaneously examining the effects of four variables—temperature, loading frequency, strain level, and damage density—and designing a systematic single-factor variable experimental scheme. By establishing damage density-healing index relationship curves under different temperatures, frequencies, and strain levels, and introducing a curve shifting method to construct a reduced damage density-healing index master curve, the interference of damage degree on the evaluation of each loading condition factor is effectively eliminated. This reveals the independent mechanism of each factor's effect on healing performance and forms a unified quantitative characterization model for multi-factor coupling, solving the problems of existing methods lacking multi-factor quantitative relationship models and confusing factor effects. Based on this, by establishing the functional relationship between shift factors and temperature, frequency, and strain level, and using a strategy of composite shift factors and averaging the three master curves, accurate prediction of the healing index under arbitrary temperature, loading frequency, strain level, and damage density conditions is achieved. The model's predicted values ​​are highly consistent with the measured values, significantly improving the universality and stability of the prediction model and providing strong technical support for the reliable evaluation of the healing performance of asphalt materials under complex service conditions. Attached Figure Description

[0043] Figure 1 The diagram illustrates the fatigue loading-intermittent healing-fatigue loading test process of the multi-factor coupled asphalt damage density-healing index master curve construction method according to an embodiment of the present invention.

[0044] Figure 2 The diagram illustrates the calculation of the healing index in the method for constructing the master curve of asphalt damage density-healing index using multi-factor coupling according to an embodiment of the present invention.

[0045] Figure 3 The figure shows the results of constructing the master curve of asphalt damage density-healing index under different factor variables using the multi-factor coupling method of the present invention.

[0046] Figure 4 The figure shows the results of the shift factor fitting curves under different factor variables in the method for constructing the asphalt damage density-healing index master curve with multi-factor coupling according to an embodiment of the present invention.

[0047] Figure 5 The figure shows a comparison between the predicted and measured values ​​of the healing index of the asphalt damage density-healing index master curve construction method of multi-factor coupling according to an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description of the multi-factor coupled asphalt damage density-healing index master curve construction method proposed in this invention, in conjunction with the accompanying drawings and specific embodiments, will provide a more detailed explanation. The advantages and features of this invention will become clearer from the following description. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the purpose of the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0049] A method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors includes the following steps:

[0050] S1. For the asphalt material to be tested, four single-factor variable test schemes were designed for temperature, loading frequency, strain level, and damage density. Since fatigue temperature usually occurs under medium-temperature conditions, the temperature variable range is 20℃~30℃, and three gradients were designed. The loading frequency variable range is 5Hz~20Hz, and four gradients were designed. The strain level variable range is 1%~6%, and four gradients were designed. The damage density variable range is 0.2~0.8, and four gradients were designed. The specific test variable settings are shown in Table 1.

[0051] Table 1 Experimental Variable Settings

[0052] Variable type Gradient settings temperature 20℃、25℃、30℃ Loading frequency 5Hz, 10Hz, 15Hz, 20Hz strain level 1%、2%、4%、6% Damage density 0.2、0.4、0.6、0.8

[0053] S2. Fatigue-healing cyclic loading tests were conducted on asphalt samples to obtain the healing index under different combinations of temperature, loading frequency, strain level and damage density.

[0054] The fatigue-intermittent-fatigue loading test for asphalt is a method configured to evaluate the healing ability of asphalt under given loading conditions, ambient temperature, interval time, and degree of damage. The specific loading process is as follows: Figure 1 As shown, firstly, under given loading frequency, strain level, and temperature, a time-scan test was conducted on asphalt under fatigue loading using a dynamic shear rheometer. The asphalt samples continuously undergo damage under fatigue loading, specifically manifested as a decrease in dynamic modulus and an increase in damage density.

[0055] Furthermore, based on the known principle of mechanical and energy balance during the time-scanning process of dynamic shear rheological testing, the damage density can be achieved by controlling the absolute value of the complex shear modulus of the sample during the Nth loading cycle. For example, after obtaining the initial absolute value of the complex shear modulus, the absolute value of the complex shear modulus corresponding to the target damage density can be calculated. When the absolute value of the complex shear modulus decays to the target value during sample loading, loading is stopped, and the test enters the interval period. At this time, the damage density of the sample is the set target damage density, calculated as shown in Equations 1 and 2 below:

[0056] (1)

[0057] (2)

[0058] In the formula: This represents the damage density of the sample at the Nth loading cycle. This represents the crack length of the sample during the Nth loading cycle. This represents the absolute value of the complex shear modulus of the sample at the Nth loading cycle. This represents the absolute value of the complex shear modulus of the sample at the initial loading stage. The radius of the complete sample.

[0059] Furthermore, in this embodiment, the healing index is defined as the ratio of the amount of damage density restored during the interval to the initial damage density during the interval, such as... Figure 2 As shown, a higher healing index indicates a stronger healing ability of the material, and vice versa. The calculation formula is shown in Equation 3 below:

[0060] (3)

[0061] In the formula: The damage density of the material at the end of the first fatigue loading. This represents the damage density of the material at the end of the intermittent healing period.

[0062] Based on the variable settings in Table 1, the healing index was calculated using a dynamic shear rheometer under sinusoidal oscillating shear mode, yielding results for combinations of multiple factor variables. The asphalt materials used in the experiment met all the specifications. The healing time for each test group was set to a fixed 40 minutes to ensure sufficient time for the material to heal. The entire experiment employed common fatigue test setups with 8mm parallel shear plates and a 2mm plate spacing (sample height).

[0063] S3. Using damage density as the abscissa and healing index as the ordinate, establish the damage density-healing index relationship curves at various temperatures, loading frequencies, and strain levels.

[0064] S4. Select a reference temperature, a reference loading frequency, and a reference strain level. Determine the temperature shift factor, loading frequency shift factor, and strain level shift factor respectively using the curve shifting method. Then, shift the damage density-healing index relationship curves under each condition to the reference condition to construct a reduced damage density-healing index master curve.

[0065] S5. Establish the functional relationships between temperature shift factor, loading frequency shift factor and strain level shift factor and temperature, loading frequency and strain level respectively, so as to obtain a healing index prediction model under arbitrary temperature, loading frequency, strain level and damage density conditions.

[0066] Specifically, for steps S3, S4, and S5, the construction steps are as follows:

[0067] For the loading frequency: While keeping other variables constant, only the frequency variable was changed. The damage density and healing index test results measured at different loading frequencies were plotted on the same graph, with damage density as the X-axis and healing index as the Y-axis. Then, a reference frequency of 10Hz was selected, and a frequency shift factor was used. Damage density and healing index data at different frequencies are shifted along the X-axis at a reference frequency of 10 Hz until a preliminary smooth S-shaped curve is formed. For example, the data at 15 Hz is shifted down to 10 Hz, i.e., the healing index data at 15 Hz is kept unchanged, and the damage density at 15 Hz is multiplied by a shift factor. The reduced damage density at 15Hz was then obtained. This allows for the formation of a preliminary continuous S-shaped curve between the damage density and healing index at 10Hz. Similarly, data at other frequencies are shifted using the same method. The formula for calculating frequency-reduced damage density is shown in Equation 4 below:

[0068] (4)

[0069] In the formula: Representing frequency Reduced damage density Representing frequency Shift factor relative to reference frequency, This represents the actual damage density.

[0070] Furthermore, the four sets of shifted data are fitted, and the calculation formula is shown in Equation 5 below:

[0071] (5)

[0072] In the formula: , , , These are the model fitting coefficients.

[0073] Furthermore, error control is performed, and the calculation formula is shown in Equation 6 below:

[0074] (6)

[0075] In the formula: The sum of errors for all fitted data points. The number of data points to fit. for Measured value of the healing index at the point. for The calculated value of the healing index at the point.

[0076] Furthermore, the shift factor at different frequencies is fitted, thereby allowing the frequency shift factor to be calculated at any frequency, as shown in Equation 7 below:

[0077] (7)

[0078] In the formula: , These are the fitting parameters.

[0079] Furthermore, based on Formula 4, the frequency-reduced damage density corresponding to the actual damage density predicted for a given target is calculated. Then, the calculated frequency-reduced damage density is substituted into Formula 5 to obtain the healing index result for any frequency and the actual damage density predicted for the target.

[0080] For the strain level variable: Similarly, while keeping other variables constant, only the strain level variable is changed. The damage density and healing index test results measured under different loading strain levels are plotted on the same graph, with damage density as the X-axis and healing index as the Y-axis. Then, a reference strain level of 4% is selected, and a strain level shift factor is used. Damage density and healing index data at different strain levels were shifted along the X-axis at a reference strain level of 4% until a preliminary smooth S-shaped curve was formed. For example, data at a 6% strain level were shifted to a 4% strain level, i.e., the healing index data at the 4% strain level remained unchanged, and the damage density at the 6% strain level was multiplied by a shift factor. The reduced damage density at a strain level of 4% was then obtained. This allows for the formation of a preliminary continuous S-shaped curve between the damage density and healing index at a 4% strain level. Similarly, data at other strain levels are shifted using the same method. The formula for calculating damage density reduction at strain level is shown in Equation 8 below:

[0081] (8)

[0082] In the formula: Represents strain level Reduced damage density Represents strain level The shift factor corresponding to the reference strain level, This represents the actual damage density.

[0083] Furthermore, the four sets of shifted data are fitted, and the calculation formula is shown in Equation 9 below:

[0084] (9)

[0085] In the formula: This represents reducing damage density. The healing index below , , , These are the model fitting coefficients.

[0086] Furthermore, the same error control method is used in Formula 6.

[0087] Furthermore, the shift factor under different strain levels is fitted, thereby enabling the calculation of the strain level shift factor at any strain level, as shown in Equation 10 below:

[0088] (10)

[0089] In the formula: , These are the model fitting coefficients.

[0090] Furthermore, according to Formula 8, the strain level reduced damage density corresponding to the actual damage density predicted for a given target is calculated. Then, the calculated strain level reduced damage density is substituted into Formula 9 to obtain the healing index result under any strain level and the actual damage density predicted for the target.

[0091] For temperature: Similarly, while keeping other variables constant, only the temperature variable is changed. The test results of damage density and healing index measured at different temperatures are plotted on the same graph, with damage density as the X-axis and healing index as the Y-axis. Then, a reference temperature of 25℃ is selected, and a temperature shift factor is used. Damage density and healing index data at different temperatures were shifted along the X-axis to a reference temperature of 25°C until a preliminary smooth S-shaped curve was formed. For example, the data at 30°C was shifted to 25°C, i.e., the healing index data at 25°C was kept unchanged, and the damage density at 30°C was multiplied by a shift factor. The reduced damage density at 25°C was then obtained. This allows for the formation of a preliminary continuous S-shaped curve between the damage density and healing index at a 4% strain level. Similarly, data at other temperatures are shifted using the same method. The formula for calculating temperature-reduced damage density is shown in Equation 11 below:

[0092] (11)

[0093] In the formula: Represents temperature Reduced damage density Represents temperature The shift factor at the corresponding reference temperature, This represents the actual damage density.

[0094] Furthermore, the three sets of shifted data are fitted, and the calculation formula is shown in Equation 12 below:

[0095] (12)

[0096] In the formula: This represents reducing damage density. The healing index below , , , These are the model fitting coefficients.

[0097] Furthermore, Formula 6 is also used for error control.

[0098] Furthermore, the shift factor at different temperatures is fitted, thereby enabling the calculation of the temperature shift factor at any temperature, as shown in Equation 13 below:

[0099] (13)

[0100] In the formula: , These are the model fitting coefficients.

[0101] Furthermore, the temperature-reduced damage density corresponding to the actual damage density predicted for a given target is calculated according to Formula 11. Then, the calculated temperature-reduced damage density is substituted into Formula 12 to obtain the healing index result for any temperature and the actual damage density predicted for the target.

[0102] like Figure 3 As shown, comparing the three main curves reveals that, after changing the temperature, frequency, and strain level, the three main curves obtained under the reference conditions of 25℃, 10Hz frequency, and 4% strain level are very similar. Therefore, this indicates that the effects of the three variables—temperature, frequency, and strain level—on the damage density-healing index main curve are linearly independent.

[0103] The establishment of the healing index prediction model in step S5 includes the following steps:

[0104] Calculate the composite shift factor The calculation formula is shown below:

[0105] (14)

[0106] In the formula: Representing frequency Shift factor relative to reference frequency, Represents strain level The shift factor corresponding to the reference strain level; Represents temperature The shift factor at the corresponding reference temperature.

[0107] Furthermore, the composite reduced damage density is calculated based on the target predicted actual damage density and the composite shift factor. The calculation formula is shown in Equation 15 below:

[0108] (15)

[0109] In the formula: This represents the actual damage density.

[0110] Furthermore, the composite will reduce damage density. Substituting these values ​​into the constructed damage density-healing index master curve, and calculating the average of the three master curves, we obtain the final predicted healing index under given target damage density, temperature, loading frequency, and strain level. The calculation formula is shown in Equation 16 below:

[0111] (16)

[0112] In the formula: Represents frequency The composite reduction damage density The healing index is below; Represents the level of strain The composite reduction damage density The healing index is below; Represents temperature The composite reduction damage density The healing index below.

[0113] Result verification:

[0114] Based on the above steps, three main curves for reducing damage density-healing index were obtained by individually changing the frequency, strain level, and temperature, as follows: Figure 3 As shown. The shift factor fitting results are as follows. Figure 4 As shown in Table 2, the fitting parameters for the shift factor equations 7, 10, and 13, and the principal curve equations 5, 9, and 12 are as follows:

[0115] Table 2 Fitting parameters for shift factor equation and principal curve equation

[0116] condition variables Shift factor equation fitting parameters master curve equation fitting parameters frequency =4.6479， =-0.660 =0.120， =1.055， =0.291， =3.002 strain level =0.1973， =-0.521 =0.088， =1.427， =0.227， =2.210 temperature =765.67， =-2.076 =0.086， =1.068， =0.321， =2.641

[0117] The correlation coefficients between the calculation results of the three principal curve equations and the measured values ​​corresponding to the reduced damage density after shifting by the shift factor are all greater than 0.99. Simultaneously, the goodness of fit of the shift factor equations for different variables is also greater than 0.99, indicating that the shift factor equation form and the damage density-healing index principal curve equation form used in this invention are fully applicable to describing the measured data in this invention and have good applicability.

[0118] Based on the above process, the reduced damage density-healing index master curve under different factor variables has been successfully constructed, and the healing index under different damage degrees can be predicted by the average of the three master curves.

[0119] To fully demonstrate the applicability of this method, its effectiveness was verified under arbitrary combinations of temperature, frequency, and strain level variables. Fatigue-healing experiments were conducted under six test conditions: 23℃ - 3% strain level - 13Hz loading frequency, 27℃ - 2% strain level - 18Hz loading frequency, 25℃ - 5% strain level - 15Hz loading frequency, 25℃ - 2% strain level - 5Hz loading frequency, 26℃ - 5% strain level - 7Hz loading frequency, and 21℃ - 2% strain level - 5Hz loading frequency, according to the aforementioned experimental method. The measured healing index results were obtained for damage densities of 0.2, 0.4, 0.6, and 0.8 under these six test conditions. Furthermore, based on the target damage density and the principal curve equation for the reduced damage density-healing index constructed under the aforementioned different variables, as well as the shift factor equation, the theoretical calculation results of the healing index were obtained. Then, with the measured values ​​on the X-axis and the predicted values ​​on the Y-axis, the predicted and corresponding measured healing index data were plotted on the same graph, as shown below. Figure 5 As shown, the prediction accuracy is represented by the coefficient of determination (R²). The closer R² is to 1, the higher the prediction accuracy.

[0120] according to Figure 5It can be seen that the coefficient of determination R2 between the predicted and measured values ​​obtained under different combinations of factor variables is close to 0.99, indicating that there is a good correlation and consistency between the model prediction results and the experimental measured values. It can accurately reflect the influence of multiple factors on the healing index under different damage degrees under the coupling effect, and can effectively characterize the healing behavior of asphalt materials under the coupling effect of multiple factors. It provides a reliable means for the quantitative evaluation and mechanism analysis of the material healing performance under fatigue damage state.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for constructing a master curve of asphalt damage density-healing index coupled with multiple factors, characterized in that: Includes the following steps: S1. For the asphalt material to be tested, four single-factor variable test schemes were designed for temperature, loading frequency, strain level and damage density, respectively. S2. The asphalt samples were subjected to fatigue-healing cyclic loading tests to obtain the healing index under different combinations of temperature, loading frequency, strain level and damage density. S3. Using damage density as the abscissa and healing index as the ordinate, establish the damage density-healing index relationship curves at various temperatures, loading frequencies, and strain levels. S4. Select a reference temperature, a reference loading frequency, and a reference strain level. Determine the temperature shift factor, loading frequency shift factor, and strain level shift factor respectively using the curve shifting method. Then, shift the damage density-healing index relationship curves under each condition to the reference condition to construct a reduced damage density-healing index master curve. S5. Establish the functional relationships between temperature shift factor, loading frequency shift factor and strain level shift factor and temperature, loading frequency and strain level respectively, so as to obtain a healing index prediction model under arbitrary temperature, loading frequency, strain level and damage density conditions.

2. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 1, characterized in that: In step S1, the temperature variable ranges from 20℃ to 30℃, and three gradients are designed; the loading frequency variable ranges from 5Hz to 20Hz, and four gradients are designed; the strain level variable ranges from 1% to 6%, and four gradients are designed. The damage density variable ranges from 0.2 to 0.8, and four gradients are designed.

3. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 1, characterized in that: In step S2, the healing index is defined as the ratio of the amount of damage density restored during the resting period to the initial damage density during the resting period, and the calculation formula is shown below: In the formula: The damage density of the material at the end of the first fatigue loading. This represents the damage density of the material at the end of the intermittent healing period.

4. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 1, characterized in that: The formula for calculating damage density in step S2 is as follows: In the formula: This represents the damage density of the sample at the Nth loading cycle. This represents the crack length of the sample during the Nth loading cycle. This represents the absolute value of the complex shear modulus of the sample at the Nth loading cycle. This represents the absolute value of the complex shear modulus of the sample at the initial loading stage. The radius of the complete sample.

5. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 1, characterized in that: In step S4, after the curve shifting method is applied to each variable, fitting is performed to control the error. The calculation formula is shown below: In the formula: The sum of errors for all fitted data points. The number of data points to fit. for Measured value of the healing index at the point. for The calculated value of the healing index at the point.

6. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 1, characterized in that: In step S4, the reduction in damage density is defined as the product of the shift factor corresponding to the reference variable value under the current value of each variable and the actual damage density.

7. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 1, characterized in that: The establishment of the healing index prediction model in step S5 includes the following steps: Calculate the composite shift factor ; The composite reduced damage density is calculated based on the target predicted actual damage density and the composite displacement factor. ; Composite reduction damage density Substituting these values ​​into the constructed damage density-healing index master curve, and calculating the average of the three master curves, we obtain the final predicted healing index under given target damage density, temperature, loading frequency, and strain level. .

8. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 7, characterized in that: Composite shift factor The calculation formula is shown below: In the formula: Representing frequency Shift factor relative to reference frequency, Represents strain level The shift factor corresponding to the reference strain level; Represents temperature The shift factor at the corresponding reference temperature.

9. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 7, characterized in that: Composite reduction of damage density The calculation formula is shown below: In the formula: This represents the actual damage density.

10. The method for constructing the master curve of asphalt damage density-healing index coupled with multiple factors as described in claim 7, characterized in that: Final prediction results of the healing index The calculation formula is shown below: In the formula: Represents frequency The composite reduction in damage density The healing index is below; Represents the level of strain The composite reduction in damage density The healing index is below; Represents temperature The composite reduction in damage density The healing index below.

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