Asphalt self-healing performance evaluation method based on equal modulus process

Abstract

The invention discloses an asphalt self-healing performance evaluation method based on an equal modulus process, and belongs to the technical field of asphalt material performance detection and evaluation.The asphalt self-healing performance evaluation method comprises the steps that the linear viscoelastic stress threshold value tau L of asphalt is determined through a linear amplitude scanning test, and control stress tau T is selected for a fatigue test; sequentially implementing a fatigue test I, an intermittent healing period and a fatigue test II, determining a modulus initial value delta0 and a modulus termination value deltaL in an equal modulus process through dynamic shear modulus change data, and calculating a loading frequency difference deltaN corresponding to the equal modulus process; and establishing a self-healing degree index HI in combination with the normalization processing and the intermittent time, and quantifying the recovery of the fatigue resistance of the asphalt. According to the method, the influence of viscous flow is effectively separated through the equal modulus process, fatigue performance recovery related to molecular diffusion is accurately represented, index reliability is verified through the molecular diffusion model, the problem that in the prior art, asphalt anti-fatigue performance recovery cannot be accurately represented is solved, and a scientific basis is provided for research and development of high-performance asphalt materials.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt material performance detection and evaluation, and in particular to an asphalt self-healing performance evaluation method based on an isomoduli process. Background Art

[0002] As a core component of asphalt pavements, asphalt plays an irreplaceable role in bonding aggregates, buffering vehicle loads, and inhibiting pavement cracking. Currently, the construction of long-life asphalt pavements has become a key goal for achieving sustainable road infrastructure development, placing higher demands on asphalt material performance. As a typical temperature-sensitive viscoelastic material, asphalt exhibits remarkable self-healing properties under suitable temperature conditions and static loads. However, current asphalt material performance evaluation systems have not fully considered the potential for fatigue life improvement due to self-healing effects. As a result, the role of asphalt self-healing in extending service life is generally ignored in pavement structural safety design. This not only limits the scientific validity of design methods but also may lead to excessive maintenance and resource waste. Furthermore, to further enhance the self-healing performance of asphalt, a series of active self-healing technologies, represented by thermally induced repair, microencapsulation technology, and shape memory polymer materials, have been proposed and gradually applied in engineering practice. However, existing testing methods make it difficult to scientifically evaluate the effectiveness of different technologies. Therefore, the development of a scientific and quantifiable asphalt self-healing performance evaluation method will not only guide the development of high-performance asphalt materials but also provide an important theoretical basis for the reliable design of long-life pavements. This is of great significance for improving the durability of asphalt pavements and reducing their lifecycle costs.

[0003] The self-healing theory based on the molecular diffusion mechanism shows that the healing of asphalt cracks can be divided into three main processes: (1) rearrangement of surface molecules; (2) wetting and closure of crack surfaces related to viscous flow; and (3) free diffusion and random distribution of molecules. The self-healing characteristics of asphalt are macroscopically manifested as the recovery of dynamic shear modulus and the recovery of fatigue resistance. That is, in processes (1) and (2), the modulus value lost due to cracking is restored, but due to the weak connection between molecules on the crack surface, the fatigue resistance of the newly healed asphalt is weak; after experiencing free diffusion and random distribution of molecules, the intermolecular interaction is enhanced, and the fatigue resistance is restored to a large extent. Compared with the recovery of modulus, the recovery of fatigue resistance has a more significant impact on the long-term service performance of asphalt pavement. The dynamic shear modulus can be directly measured through experiments, and the evaluation method of asphalt self-healing performance based on dynamic shear modulus has been relatively complete. However, the experimental characterization of the free diffusion and random arrangement process of molecules is relatively difficult, and the increase in asphalt fatigue life after the interval is usually attributed entirely to process (3). However, the increased fatigue life of asphalt after the intermittent treatment is not only related to process (3), but also to the recovery of the effective cross-sectional area due to crack closure. Therefore, in order to effectively characterize the asphalt fatigue performance recovery related to process (3), it is necessary to eliminate the influence of other factors. Summary of the Invention

[0004] In view of the above background, the present invention aims to solve the difficulties in evaluating the recovery of asphalt fatigue resistance in the prior art. Specifically, when the fatigue life of asphalt increases due to the mechanism of molecular free diffusion and random distribution, it is difficult for the prior art to accurately characterize this process, resulting in an inaccurate and incomplete evaluation of the recovery of asphalt fatigue resistance. The present invention proposes an asphalt self-healing performance evaluation method based on an isomodular process. By selecting an isomodular process, it separates the effect of modulus recovery on fatigue performance recovery, and can more accurately quantify the asphalt fatigue performance recovery process driven by the mechanism of molecular free diffusion and random distribution. It provides reliable technical support for accurately evaluating the dynamic performance of asphalt materials, and provides an important scientific basis for the development and optimization of high-performance asphalt materials.

[0005] The present invention provides a method for evaluating the self-healing performance of asphalt based on an isomodular process, which is characterized by comprising the following steps:

[0006] S1. Linear amplitude sweep test:

[0007] After the asphalt sample is kept at the test temperature until the temperature stabilizes, a stress scanning test is performed using a dynamic shear rheometer to determine the stress threshold τ of the asphalt sample. L , and select ≥τ L The control stress τ T Conduct subsequent fatigue tests;

[0008] S2. Self-healing test:

[0009] S21. Fatigue test I: Applying controlled stress τ to asphalt specimen T The time sweep test is performed until the dynamic shear modulus decreases to the preset termination condition |G*| D , record the dynamic shear modulus value at different loading times and the total number of loading times ΔN I ;

[0010] S22, intermittent healing period: unload the load and set different intermittent times t to restore the asphalt performance;

[0011] S23, Fatigue Test II: After the rest period, repeat the test conditions of Fatigue Test I and record the dynamic shear modulus data at different times during the loading process;

[0012] S3. Determine the isomoduli process:

[0013] Based on the dynamic shear modulus change data of fatigue test I and fatigue test II, the initial modulus value Δ0 and the final modulus value ΔL of the isomoduli process are selected, and the loading number difference ΔN corresponding to the isomoduli process is calculated;

[0014] S4. Evaluation of asphalt self-healing performance:

[0015] The difference in loading times ΔN was normalized and combined with the interval time to calculate the self-healing index HI, which was used to quantify the recovery process of asphalt anti-fatigue performance.

[0016] Preferably, the stress threshold τ in S1 L It is defined as the stress value corresponding to the dynamic shear modulus value decreasing to 90% of the initial value. L Round up to the nearest tenth to get τ T As the control stress in fatigue tests.

[0017] Preferably, the termination condition |G*| is preset in S21. D The dynamic shear modulus is reduced to 20% to 80% of the initial value.

[0018] Preferably, the intermittent time t in S22 is set to i different time periods, wherein t1<t2<···<t i , where i is an integer ≥3.

[0019] Preferably, S3 includes S31 and selection of an equal modulus process, wherein in S31, the change process of the asphalt modulus after the interval time is t1 is selected as the research object, and the durability of the modulus process at different interval times is analyzed.

[0020] Preferably, S3 further includes S32, determination of the isomodular process, wherein the normalized modulus initial value Δ0 and the normalized modulus termination value Δ L Determined by the normalization formula:

[0021]

[0022] Where |G*|0 is the initial dynamic shear modulus of fatigue test I, and are the initial modulus and final modulus of the isomoduli process, respectively.

[0023] Preferably, S3 further includes S33, determining the number of loading times of the isomodulus process, and the number of loading times corresponding to the isomodulus process under different intermittent times in S33 is ΔN:

[0024] ΔN=N1-N0 (3)

[0025] Where N0 and N1 are the loading times corresponding to the initial modulus value Δ0 and the final modulus value ΔL of the isomoduli process, respectively.

[0026] Preferably, S3 further includes S34, normalization of the loading times of the isomodular process, wherein the loading times of the fatigue process I are used to normalize the loading times of the isomodular process, as shown below:

[0027]

[0028] Where: ΔN * is the normalized loading times of the isomodular process; ΔN I is the number of loading times in fatigue process I.

[0029] Preferably, the self-healing degree index HI in S4 is calculated by the following formula:

[0030]

[0031] Where: t is the interval time, min; is the normalized value of the number of loading times in the isomodular process before the intermittent period; ΔN * (t) is the normalized value of the loading times in the isomodular process after the interval.

[0032] Preferably, the stress range of the stress sweep test is 0 to 0.8 MPa, the loading frequency is 1 to 30 Hz, the dynamic shear rheometer uses an 8 mm parallel plate fixture, and the test temperature is 10 to 30°C.

[0033] The beneficial effects are as follows:

[0034] (1) The asphalt self-healing performance evaluation method based on the isomodular process proposed in this paper effectively separates the effect of modulus increase on fatigue performance recovery, accurately quantifies the asphalt fatigue performance recovery driven by molecular free diffusion and random distribution mechanisms, and realizes the refined characterization of asphalt self-healing behavior;

[0035] (2) Compared with modulus recovery, asphalt fatigue performance recovery behavior related to molecular free diffusion and random distribution mechanisms has a more significant beneficial effect on the long-term service performance of asphalt. This invention can accurately evaluate the effects of different self-healing technologies on the promotion of molecular free diffusion and random distribution processes, promote the research and development of self-healing technologies, and thus promote the performance improvement of asphalt materials in fields such as road engineering and enhance the service performance of pavements. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 shows an overall logic schematic diagram of an embodiment of the present invention;

[0037] Figure 2 It shows a diagram of the loading process of a stress sweep test in an embodiment of the present invention;

[0038] Figure 3 shows the attenuation curve of dynamic shear modulus with stress in an embodiment of the present invention;

[0039] Figure 4 The self-healing test process in an embodiment of the present invention is shown;

[0040] Figure 5 The figure shows the dynamic shear modulus change curve before and after the intermission period of 60 minutes in the embodiment of the present invention;

[0041] Figure 6 The modulus change curves after different pause times in the embodiment of the present invention are shown;

[0042] Figure 7 A schematic diagram of the analysis process of the intermediate modulus process according to an embodiment of the present invention is shown;

[0043] Figure 8 The calculation results of asphalt self-healing degree with different pause times in the embodiment of the present invention are shown;

[0044] Figure 9 The fitting results of the effect of the pause time on the self-healing degree of asphalt in the embodiment of the present invention are shown. DETAILED DESCRIPTION

[0045] In order to make the purpose, solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of specific embodiments of the present invention.

[0046] Please refer to the instruction manual Figures 1 to 9 :

[0047] The present invention provides an asphalt self-healing performance evaluation method based on the isomodular process. The overall logic is as follows: Figure 1 As shown, please follow the steps below:

[0048] S1. Conduct a linear amplitude sweep test and determine the control stress τ of the asphalt sample through a stress sweep test. T ;

[0049] In the stress scanning test of asphalt specimens, the specimens need to be temperature-balanced and kept at the test temperature until the temperature stabilizes, i.e., during the temperature curing process, so that the temperature of the asphalt specimens is consistent with the test setting temperature, which can be set at 10-30°C. A dynamic shear rheometer is used for scanning, and the loading frequency can be set to 1-30Hz according to actual needs. Based on the stress scanning test results, a stress-dynamic shear modulus normalized value relationship curve is drawn with stress as the horizontal axis and the dynamic shear modulus normalized value as the vertical axis. The corresponding value when the dynamic shear modulus drops to 90% of the initial value is defined as the stress threshold τ L In order to take into account the test time and the representativeness of the asphalt fatigue process, a suitable stress level τ is selected outside the linear viscoelastic range. T (τ T ≥τ L ) is used as the control stress for fatigue test. L Round up to the nearest tenth to get τ T As the control stress of fatigue test, generally τ T >τ L , if the tenth digit is exactly zero, then this operation is not performed, and τ L =τ T .

[0050] In a preferred embodiment, the test temperature is selected to be 20°C, and the asphalt sample is kept at the test temperature for at least 30 minutes. There are many types of rheometers. For example, the CVO100 dynamic shear rheometer of Malvern Company in the UK is selected to perform a stress sweep test on the asphalt. The test uses an 8mm plate, the stress variation range of the sweep test is 0-0.8MPa, the loading frequency is 10Hz, and the loading process is as follows: Figure 2 shown.

[0051] According to the stress sweep test results, the stress-dynamic shear modulus normalized value relationship curve is drawn with stress as the horizontal axis and the dynamic shear modulus normalized value as the vertical axis. Figure 3 As shown, where |G*| L is the dynamic shear modulus of the asphalt specimen during loading, is the dynamic shear modulus of the asphalt specimen at the initial loading. According to the relationship curve, find the data point where the dynamic shear modulus value drops to 90% of the initial dynamic shear modulus value. The stress value corresponding to this data point is the stress threshold τ in the linear viscoelastic range of the asphalt material. L In this example, the asphalt is Karamay 70# matrix asphalt after long-term aging. L is 0.31MPa, τ T Take 0.4MPa.

[0052] S2. Conduct self-healing tests with different interval times;

[0053] Self-healing process Figure 4 As shown, the specific steps are as follows:

[0054] S21. Conduct fatigue test I

[0055] Select a new asphalt sample and conduct a time sweep test under stress control mode on the asphalt sample, controlling the stress level to τ T , with the dynamic shear modulus reduced to the preset termination condition |G*| D As the end condition of fatigue test I, record the dynamic shear modulus value and the total number of loading times ΔN at different loading times during the whole process of fatigue test I. I ; where |G*| D It can be taken as 20% to 80% |G*|0, preferably 50% |G*|0, where |G*|0 is the dynamic shear modulus value of the asphalt specimen at the initial loading;

[0056] At the beginning of the test, the asphalt sample was first temperature-balanced. Based on the above specific embodiment, the test temperature was kept at 20°C for at least 30 minutes to make the asphalt sample temperature consistent with the test setting temperature; where |G*| D Take 50%|G*|0;

[0057] S22, intermittent healing period self-healing

[0058] After the fatigue test I is completed, the load is removed to allow the asphalt performance to recover during the intermittent healing period. In order to analyze the recovery process of the asphalt anti-fatigue performance, the intermittent time t is set to i different time periods, where t1<t2<···<t i , where i is an integer ≥3.

[0059] Based on the above specific embodiment, the interval duration is set to 2min, 5min, 10min, 30min and 60min;

[0060] S23, Fatigue Test II

[0061] After the intermittent healing period, the specimen scanning test (i.e., fatigue test II) was continued on the asphalt specimen. The test conditions of fatigue test I were repeated. The test temperature, stress amplitude, loading frequency, and end conditions of fatigue test II were set to be the same as those of fatigue test I. The dynamic shear modulus data at different times during the loading process were recorded.

[0062] S24, according to the self-healing test results, with the number of loading as the horizontal axis and the normalized dynamic shear modulus value |G*| / |G* |0 The vertical axis is used to draw the dynamic shear modulus change curve during the self-healing test, where |G*| is the measured value of the dynamic shear modulus at different loading moments;

[0063] Based on the above specific embodiments, Figure 5 The cumulative loading times with an interval of 60 minutes (including fatigue test I and fatigue test II) are shown. Figure 6 The modulus change curves after different rest times (i.e., fatigue test II) are shown.

[0064] S3, determining the isomoduli process;

[0065] Specifically:

[0066] S31. Selection of isomoduli process

[0067] Considering that the asphalt modulus reduction process after the intermittent time is t1 (the shortest intermittent time) will also occur at other intermittent times, the change process of the asphalt modulus after the intermittent time is t1 is taken as the research object to analyze the durability of the modulus process at different intermittent times;

[0068] Based on the above specific embodiment, the change process of asphalt modulus after an interval of 2 minutes was selected as the research object, and the durability of the modulus process at different interval times was analyzed;

[0069] S32. Determination of isomoduli process

[0070] Determine the initial modulus value of the isomodular process based on the test results of fatigue test II and modulus termination value Taking into account the sample error between different asphalt specimens, the dynamic shear modulus |G*|0 measured at the initial loading moment of fatigue test I is used to normalize the initial modulus value and the final modulus value of the isomodulus process. Then, the normalized initial modulus value Δ0 and the normalized final modulus value Δ L Expressed as:

[0071]

[0072] Based on the above specific embodiment, the normalized modulus initial value Δ0 with an interval length of 2 minutes is calculated to be 0.587, and the normalized modulus final value ΔL is 0.500.

[0073] S33. Determination of the number of loading times in the equal modulus process

[0074] According to the test results of fatigue test I and fatigue test II, the loading times N0 and N1 corresponding to the normalized modulus initial value Δ0 and the normalized modulus terminal value ΔL of the isomoduli process were determined, and the loading times ΔN corresponding to the isomoduli process under different interval lengths were calculated.

[0075] ΔN=N1-N0 (3)

[0076] Based on the above specific embodiment, the analysis diagram of the isomoduli process is as follows Figure 7 As shown, Figure 7 The isomodular processes with an intermittent time of 2 min and 60 min are shown. Other processes can be calculated similarly and are not shown in the figure.

[0077] S4. Evaluation of self-healing performance of asphalt;

[0078] The details are as follows:

[0079] S41. Normalization of loading times in equal modulus process

[0080] Because different asphalt specimens are used under different working conditions with different intermittent time, the fatigue life of different asphalt specimens varies to a certain extent. In order to eliminate the influence of sample differences on the evaluation of asphalt self-healing performance, the present invention uses the loading number of fatigue process I to normalize the loading number of the isomoduli process, as shown below:

[0081]

[0082] Where: ΔN * is the normalized loading times of the isomodular process; ΔN I is the number of loading times in fatigue process I.

[0083] Based on the above specific embodiment, the normalized isomodular process loading times before the pause and at different pause durations are calculated as shown in Table 1.

[0084] Table 1 Normalized calculation results of the number of loading times of the isomodular process in the embodiment

[0085] Interval duration / min Before the interval 2 5 10 30 60 <![CDATA[ΔN * ]]> 0.041 0.014 0.022 0.026 0.032 0.035

[0086] Among them, calculate the ΔN before the interval *Based on the initial modulus value and the final modulus value of the isomoduli process, the dynamic modulus change process before the pause is analyzed to determine the number of loading times corresponding to the initial modulus value and the final modulus value. and Will and Substituting into formula (3) can determine the corresponding number of loading times of the equal modulus process ΔN0, and substituting ΔN0 into formula (4) can calculate the result.

[0087] S42. Asphalt self-healing evaluation index

[0088] According to the number of loading times of the isomodular process obtained under different working conditions, the self-healing degree HI of asphalt is determined using the following formula:

[0089]

[0090] Where, t is the interval time, min; is the normalized value of the number of loading times in the isomodular process before the intermittent period; ΔN * (t) is the normalized value of the loading times in the isomodular process after the interval.

[0091] Based on the above specific embodiments, That is 0.041 in the above table. The calculated asphalt self-healing evaluation index results are as follows: Figure 8 shown.

[0092] In order to verify the reliability of the self-healing evaluation index proposed in the present invention, the simplified static healing behavior equation in the molecular diffusion theory model (as shown in formula (6)) is used to fit the indicators of the above specific embodiments, thereby realizing the rationality analysis of the asphalt self-healing evaluation index.

[0093] HI(t)=R0+Kt 0.25 (6)

[0094] Where R0 is the instantaneous healing degree of asphalt, dimensionless; K is the healing rate, (1 / min) －0.25 .

[0095] The fitting results are as follows Figure 9 As shown, where HI(t) = 0.3031×t 0.25 +0.0524, goodness of fit R 2 It is 0.936, which is greater than 0.9, indicating that the healing behavior equation has a high degree of fit, indicating that the self-healing index of the present invention can better characterize the self-healing behavior of asphalt.

Claims

1. A method for evaluating the self-healing performance of asphalt based on an isomodular process, characterized in that The steps include: S1. Linear amplitude sweep test: After the asphalt sample is kept at the test temperature until the temperature stabilizes, a stress scanning test is performed using a dynamic shear rheometer to determine the stress threshold τ of the asphalt sample. L , and select ≥τ L The control stress τ T Conduct subsequent fatigue tests; S2. Self-healing test: S21. Fatigue test I: Applying controlled stress τ to asphalt specimen T The time sweep test is performed until the dynamic shear modulus decreases to the preset termination condition |G*| D , record the dynamic shear modulus value at different loading times and the total number of loading times ΔN I ; S22, intermittent healing period: unload the load and set different intermittent times t to restore the asphalt performance; S23, Fatigue Test II: After the rest period, repeat the test conditions of Fatigue Test I and record the dynamic shear modulus data at different times during the loading process; S3. Determine the isomoduli process: Based on the dynamic shear modulus change data of fatigue test I and fatigue test II, the initial modulus value Δ0 and the final modulus value ΔL of the isomoduli process are selected, and the loading number difference ΔN corresponding to the isomoduli process is calculated; S4. Evaluation of asphalt self-healing performance: The difference in loading times ΔN was normalized and combined with the interval time to calculate the self-healing index HI, which was used to quantify the recovery process of asphalt anti-fatigue performance.

2. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 1, characterized in that: Stress threshold τ in S1 L It is defined as the stress value corresponding to the dynamic shear modulus value decreasing to 90% of the initial value. L Round up to the nearest tenth to get τ T As the control stress in fatigue tests.

3. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 1, characterized in that: The preset termination condition |G*| in S21 D The dynamic shear modulus is reduced to 20% to 80% of the initial value.

4. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 3, characterized in that: In S22, the intermittent time t is set to i different time periods, where t1<t2<···<t i , where i is an integer ≥3.

5. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 4, characterized in that: S3 includes S31 and the selection of equal modulus processes. In S31, the change process of the asphalt modulus after the interval time is t1 is selected as the research object, and the durability of the modulus process at different interval times is analyzed.

6. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 5, characterized in that: S3 also includes S32 and the determination of the isomodular process. The normalized modulus initial value Δ0 and the normalized modulus terminal value ΔL of the isomodular process in S32 are determined by the normalization formula: Where |G*|0 is the initial dynamic shear modulus of fatigue test I, and are the initial modulus and final modulus of the isomoduli process, respectively.

7. The method for evaluating asphalt self-healing performance based on an isomodular process according to claim 6, characterized in that: S3 also includes S33, determination of the number of loading times of the isomodulus process. The number of loading times corresponding to the isomodulus process under different intermittent times in S33 is ΔN: ΔN=N1-N0 (3) Where N0 and N1 are the loading times corresponding to the initial modulus value Δ0 and the final modulus value ΔL of the isomoduli process, respectively.

8. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 7, characterized in that: S3 also includes S34, normalization of the number of loading times of the equal modulus process. In S34, the number of loading times of the fatigue process I is used to normalize the number of loading times of the equal modulus process, as shown below: Where: ΔN * is the normalized loading times of the isomodular process; ΔN I is the number of loading times in fatigue process I.

9. The asphalt self-healing performance evaluation method based on the isomodular process according to claim 8, characterized in that: The self-healing index HI in S4 is calculated by the following formula: Where: t is the interval time, min; is the normalized value of the number of loading times in the isomodular process before the intermittent period; ΔN * (t) is the normalized value of the loading times in the isomodular process after the interval.

10. The asphalt self-healing performance evaluation method based on the isomodular process according to any one of claims 1 to 9, characterized in that: The stress range of the stress sweep test was 0 to 0.8 MPa, the loading frequency was 1 to 30 Hz, the dynamic shear rheometer used an 8 mm parallel plate fixture, and the test temperature was 10 to 30 °C.

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