Method for controlling mechanical property of asphalt in situ

Abstract

The invention discloses a method for in-situ control of mechanical properties of asphalt. The method comprises the following steps: (1) preparing an asphalt mixture sample; and (2) putting the asphalt mixture into an ultra-thin metal disc, fixing the ultra-thin metal disc on a heating and cooling platform, and controlling the temperature of the heating and cooling platform to be between room temperature and 65 DEG C so as to obtain asphalt mixture samples with different mechanical properties. The method has the beneficial effects that asphalt with different mechanical properties is obtained by controlling the temperature, and the requirements of different application scenes are met.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt and asphalt mixture test devices in the field of road engineering, and particularly to a method for in-situ controlling the mechanical properties of asphalt. Background Art

[0002] In China's expressways, asphalt pavements have become the mainstream pavement materials. However, during the service life of asphalt concrete, the main problem is that the service life is much shorter than the designed life. In order to deeply study the changes of asphalt pavement materials during the service process, it is very necessary to study the interaction forces between asphalt pavement materials and their micro-mechanical properties. Asphalt pavement materials are mainly asphalt mixtures, which are composed of asphalt, aggregates and pores, and their properties are affected by factors such as the proportion of each component, the microscopic structure and the interaction between components. Different environments may require asphalt with different mechanical properties, and there is currently no report on controlling the mechanical properties of asphalt to meet different requirements.

[0003] For example, Chinese Patent Publication No. CN115436197A discloses a method for evaluating the low-temperature performance of asphalt based on rheological mechanics theory. The temperature is selected according to the actual low-temperature application scenario of asphalt, and a constant horizontal shear strain is applied to the asphalt at an appropriate loading frequency. The stress generated by the asphalt due to resisting deformation and the shear compliance calculated based on the rheological mechanics theory are measured, which are used to accurately evaluate the low-temperature performance of asphalt. This patent focuses on the analysis and evaluation of the low-temperature performance of asphalt and does not involve the control of the mechanical properties of asphalt.

[0004] Chinese Patent Publication No. CN118913958A discloses a method for optimizing the mechanical properties of asphalt based on the regulation of asphaltene content. First, the back-mixed asphalt is prepared by the asphalt component extraction-reblending technology, and then the high-temperature, medium-temperature and low-temperature performances of the back-mixed asphalt are determined through dynamic shear rheological tests. The measured relevant data are substituted into the sensitive factor formula to calculate the most sensitive or least sensitive content at different asphalt contents, and the asphaltene content with the optimal comprehensive performance of asphalt is determined through peak fitting. Although this patent involves tests at different temperatures, its purpose is to calculate the average values of the creep stiffness modulus S and the creep rate m of the back-mixed asphalt at three temperatures, and to select the average values of the rutting factor, G-R parameter, and the average values of the creep stiffness modulus S and the creep rate m at -6°C, -12°C and -18°C and substitute them into the sensitive factor formula to calculate the sensitivity of different properties of the back-mixed asphalt to the asphaltene content. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that there is a lack of simple and effective control methods for the existing asphalt properties, and for this reason, a method for in-situ controlling the mechanical properties of asphalt is provided.

[0006] The technical solution of the present invention is: a method for in-situ controlling the mechanical properties of asphalt, comprising the following steps: (1) preparing an asphalt mixture specimen; (2) placing the asphalt mixture into an ultra-thin metal disc, which is fixed on a temperature control platform, and controlling the temperature of the temperature control platform between room temperature and 65 °C to obtain asphalt mixture specimens with different mechanical properties.

[0007] In the above solution, when the temperature of the temperature control platform is between room temperature and 55 °C, an asphalt mixture specimen with a higher modulus and lower adhesion is obtained.

[0008] In the above solution, when the temperature of the temperature control platform is between 55 °C and 65 °C, an asphalt mixture specimen with a lower modulus and higher adhesion is obtained.

[0009] In the above solution, the step (1) of preparing the asphalt mixture specimen includes: (101) heating the specimen: heating the asphalt mixture specimen to be studied with a heating table to a certain temperature and stirring evenly, then taking an appropriate amount of asphalt with a clean tool into the ultra-thin metal disc heated to a certain temperature, and then taking out the ultra-thin metal disc containing asphalt and naturally cooling it at room temperature; (102) specimen storage: storing the ultra-thin metal disc specimen containing asphalt in a clean and airtight plastic box or metal box.

[0010] In the above solution, the temperature range of the heating table in the step (101) is 25 °C to 150 °C.

[0011] In the above solution, the heating time in the step (101) is greater than 10 minutes and less than 4 hours.

[0012] In the above solution, the volume of the asphalt mixture taken in the step (101) is 2 ml to 10 ml.

[0013] In the above solution, when the asphalt is transferred to the ultra-thin metal disc heated to a certain temperature, its surface is flat and the overall height of the asphalt does not exceed the edge of the ultra-thin metal disc.

[0014] The beneficial effect of the present invention is to obtain asphalt with different mechanical properties by controlling the temperature, meeting the needs of different application scenarios. Description of the Drawings

[0015] Figure 1 is a flow chart of the method for studying the variable-temperature in-situ micro-mechanical properties of the asphalt mixture of the present invention; Figure 2a - Figure 2j is a three-dimensional morphology image of the asphalt mixture specimen under different temperature conditions; Figure 3a - Figure 3j is a modulus characteristic image of the asphalt mixture specimen at different temperatures; Figure 4a - Figure 4jIt is the adhesion force distribution diagram of asphalt mixture specimens at different temperatures; Figure 5 It is the diagram of the change of modulus and adhesion force at different temperatures. Specific implementation mode

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] As Figure 1 shown, a method for in-situ controlling the mechanical properties of asphalt includes the following steps: (1) preparing an asphalt mixture specimen; (2) putting the asphalt mixture into an ultra-thin metal disc, the ultra-thin metal disc is fixed on a temperature control platform, and controlling the temperature of the temperature control platform between room temperature and 65 °C to obtain asphalt mixture specimens with different mechanical properties.

[0018] When observing the asphalt mixture specimens from room temperature to 65 °C using the PFQNM nano-scale mechanical property quantification module of the atomic force microscope, first select a small observation area in the asphalt mixture specimen, and then gradually expand the size of the observation area. Start observing the force curve shape of each pixel point in the observation area within the size range including the characteristic area, and then obtain the mechanical property image of the entire observation area. The mechanical property images include modulus characteristic images, adhesion force characteristic images, dissipation energy characteristic images, and deformation amount characteristic images.

[0019] Use Nanoscope Analysis software to quantitatively analyze each mechanical property image respectively to obtain the modulus value, adhesion force value, dissipation energy value, and deformation amount value of the component to be studied.

[0020] When studying the variable-temperature in-situ micro-mechanical properties of asphalt mixture specimens, a method of taking multiple samples, multiple observation areas, and taking the average of multiple measurements is used, which avoids randomness and improves the accuracy of the final result.

[0021] Generally, asphalt is a typical temperature-sensitive material, and its modulus (stiffness modulus) decreases significantly with the increase of temperature. At high temperatures, asphalt softens, the viscosity decreases, and more obvious viscoelastic behavior appears, resulting in a weakened ability to resist deformation. However, the applicant's research found that this is not the case.

[0022] As Figure 2a 、 Figure 2b 、 Figure 2c 、 Figure 2d 、 Figure 2e 、 Figure 2f 、 Figure 2g 、 Figure 2h 、 Figure 2i and Figure 2j It can be seen that with the increase of temperature, the colloidal pupa structure decreases, as Figure 2hAs shown, when the temperature reaches 60°C, the disappearance of the colloidal structure cannot be observed, and a uniform surface morphology is presented. From a more microscopic morphological structure, it can be seen that there is a circle of protrusions with significantly different properties from the bottom around the silkworm pupa structure. With the increase of temperature, the protrusions gradually disappear, and the disappearing areas show no obvious tendency, presenting a random disappearance phenomenon. As Figure 2f shown, when the temperature rises to 50°C, fewer protrusions are observed. When the temperature reaches 60°C, the protrusions completely disappear. During the in-situ heating process, the protrusions may be colloids related to the silkworm pupa.

[0023] As Figure 3a - Figure 3j shown, from the results at 35°C and 40°C, it can be seen that the modulus distribution has a strong correlation with the presence or absence of protrusions. The modulus in the area with protrusions is smaller. However, the modulus differences at different temperatures are not significant, indicating that within a certain temperature range, asphalt as a pavement material can provide support for road vehicles, and the support strength changes little. Until the temperature rises to 60°C, the modulus suddenly drops to 400 - 500 MPa. When the temperature reaches 70°C, the modulus decreases to 300 MPa. This shows that after the temperature reaches 60°C, the No. 70 asphalt begins to soften, and after the temperature reaches 70°C, it softens further. Too high a temperature may cause the support force of the asphalt material for road vehicles to decrease.

[0024] As Figure 4a - 4j shown, the adhesion force between the colloid and the silkworm pupa structure decreases significantly with the increase of temperature. The surface temperature has a greater impact on the adhesion force of the asphalt surface. An increase in the adhesion force indicates an increase in the interaction force between the asphalt and the aggregate, and the aggregate provides the friction force between the vehicle and the road surface. At room temperature, from the adhesion force distribution curve, it can be seen that there are significant differences in the adhesion force between the silkworm pupa structure and the protrusions and other positions, and there is a sudden change in the adhesion force. With the gradual increase of temperature, the differences in the adhesion force between the silkworm pupa structure and the protrusions and other positions decrease. When the temperature reaches 60°C, the silkworm pupa structure and the protrusions disappear, and the adhesion force distribution of the whole asphalt is consistent, and the overall adhesion force decreases.

[0025] As Figure 5 shown, further analysis of the adhesion force cross-section results reveals that the adhesion force gradually increases with the increase of temperature, and there is a sudden change at 55°C - 60°C, and the adhesion force at 65°C is greater than that at 70°C.

[0026] Further analysis of the modulus cross-section results shows that the modulus changes little at 55°C and below, fluctuating within a certain range, and does not continuously decrease with the increase of temperature. However, when the temperature rises to 55°C - 60°C, the overall modulus becomes smaller, and the modulus distribution range becomes narrower. The modulus differences between 60°C and 65°C are smaller, but the modulus further decreases when the temperature rises to 70°C.

[0027] It was observed that there were two mutation points in the micro modulus with the increase of temperature, which were 55°C - 60°C and 65°C - 70°C respectively. This is contrary to the technical inspiration given by the existing technology that the modulus decreases with the increase of temperature. The adhesion force results showed a different trend, with an obvious mutation at 55°C - 60°C and gradually increasing at 60°C and 65°C. However, at 70°C, the adhesion force decreased to some extent. Therefore, the mechanical properties of asphalt can be controlled within the available range by controlling the temperature range. For example, when the temperature of the temperature rise and fall platform is between room temperature and 55°C, asphalt mixture specimens with a higher modulus and a lower adhesion force can be obtained. When the temperature of the temperature rise and fall platform is between 55°C - 65°C, asphalt mixture specimens with a lower modulus and a higher adhesion force can be obtained. When the temperature of the asphalt exceeds 65°C, both the modulus and the adhesion force decrease, and it is not recommended to use asphalt samples in this temperature range.

Claims

1. A method for in-situ control of asphalt mechanical properties, characterized by: The following steps are involved: (1) preparing asphalt mixture samples; (2) placing the asphalt mixture into an ultra-thin metal disc, wherein the ultra-thin metal disc is fixed on a temperature-elevating platform, and the temperature of the temperature-elevating platform is controlled between room temperature and 65° C., so as to obtain asphalt mixture samples with different mechanical properties.

2. A method for in-situ controlling the mechanical properties of asphalt as claimed in claim 1, characterized in that: When the temperature of the heating and cooling platform is between room temperature and 55°C, an asphalt mixture sample with higher modulus and lower adhesion is obtained.

3. The method for in-situ controlling the mechanical properties of asphalt according to claim 1, characterized in that: When the temperature of the heating and cooling platform is between 55°C and 65°C, an asphalt mixture sample with lower modulus and higher adhesion is obtained.

4. The method for in-situ controlling the mechanical properties of asphalt according to claim 1, characterized in that: The step (1) of preparing the asphalt mixture sample comprises: (101) sample heating: heating the asphalt mixture sample to be studied to a certain temperature using a heating table and stirring it evenly, then using a clean tool to take an appropriate amount of asphalt into an ultra-thin metal disc heated to a certain temperature, then taking out the ultra-thin metal disc containing asphalt and cooling it naturally at room temperature; (102) sample storage: the ultra-thin metal disc sample containing asphalt is stored in a clean and sealed plastic box or metal box.

5. A method for in-situ controlling the mechanical properties of asphalt as claimed in claim 4, characterized in that: The temperature range of the heating platform in the step (101) is 25°C to 150°C.

6. The method for in-situ controlling the mechanical properties of asphalt according to claim 4, characterized in that: The heating time in step (101) is greater than 10 minutes and less than 4 hours.

7. The method for in-situ controlling the mechanical properties of asphalt according to claim 4, characterized in that: The volume of the asphalt mixture used in step (101) is 2ml-10ml.

8. The method for in-situ controlling the mechanical properties of asphalt according to claim 4, characterized in that: When the asphalt is transferred to the ultra-thin metal disc heated to a certain temperature, the surface thereof is flat and the overall height of the asphalt does not exceed the edge of the ultra-thin metal disc.

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