A method for healing cracks in asphalt ultra-thin overlays using ultrasonic energy

Abstract

The present invention discloses a method for healing cracks in an asphalt ultra-thin overlay by using ultrasonic energy, which includes: S1. Cleaning the asphalt ultra-thin overlay to be treated, determining the length and width of the cracks in the asphalt ultra-thin overlay, and marking the positions of the cracks; S2. Processing the marked cracks in the asphalt ultra-thin overlay by using the ultrasonic vibration generated by an ultrasonic energy emission device, and stopping the vibration after the cracks are healed. The present invention uses ultrasonic waves as the energy input to achieve rapid and efficient healing of cracks without adding any conductive phase materials to the asphalt ultra-thin overlay.

Description

Technical Field

[0001] The present invention belongs to the technical field of asphalt pavement repair, and particularly relates to a method for healing cracks in an asphalt ultra-thin overlay by using ultrasonic energy. Background Art

[0002] When asphalt pavements are affected by sunlight ultraviolet radiation, water erosion, and impurity intrusion, early damage will occur. To prevent the damage from intensifying, an asphalt ultra-thin overlay is now mostly used to pave on the original road surface. The asphalt ultra-thin overlay is a wearing course with a thickness of about 2-3 mm formed by hot mixing or warm mixing a mixture of asphalt, aggregates, and other additives, followed by paving and rolling. It can quickly restore the service performance of the road surface and ensure transportation. Therefore, the asphalt ultra-thin overlay is welcomed by road maintenance units, and there are more and more application cases in China.

[0003] The ultra-thin overlay also has some disadvantages. For example, the thickness of the wearing course is only 2-3 mm, and its compressive and shear strengths are relatively low. It is also prone to damage when the temperature fluctuates violently. A typical disease is cracking. Under the existing asphalt pavement structure, the water-stable base will generate shrinkage cracks due to shrinkage, which will conduct upward to the asphalt surface layer and then to the ultra-thin wearing course. In addition, repeated rolling of the traffic load is also likely to cause fatigue cracks in the ultra-thin wearing course. Therefore, cracks are the main diseases causing the failure of the ultra-thin overlay.

[0004] At present, there are studies attempting to endow asphalt pavements with a healing function:

[0005] CN202011162394.2 discloses a multifunctional pothole repair method for asphalt pavements using induction heating and microwave heating. The lower surface and the periphery of the asphalt brick are coated with asphalt. Induction heating or microwave heating can be selected according to the different materials of the repaired road surface, and induction or wave-absorbing media are scattered around and at the bottom of the asphalt brick; the area is heated by induction / microwave to complete the repair of the pothole. The scope of application of this patent is only the repair method for asphalt pavement pothole diseases and cannot achieve the healing of cracks in the asphalt ultra-thin overlay.

[0006] CN201611189826.2 discloses an asphalt concrete repair method based on microcapsules and induction heating. When preparing asphalt concrete, steel sand and microcapsules containing asphalt rejuvenator are incorporated to obtain conductive asphalt concrete; the asphalt concrete pavement is heated to 80-110 °C by using an asphalt pavement induction heater, and thus the cracks in the asphalt concrete are thermally induced for self-repair by using induction heating technology. This patent requires pre-preparing a kind of microcapsule containing asphalt rejuvenator and preparing a certain amount of steel sand, and adding the above two materials during the mixing of the asphalt pavement, that is, a special healing-type asphalt mixture needs to be prepared to achieve thermal-induced repair in the later stage.

[0007] CN202110044984.3 discloses a flame-retardant warm-mix induction heating self-healing asphalt concrete and its preparation method. By adding organosilicon-modified layered double metal hydroxides, graphene, organic viscosity reducers, and steel wool fibers to the system, the self-healing function is achieved by utilizing the induction heating performance of the steel wool fibers. This patent requires adding graphene and steel wool fibers during the mixing of asphalt mixtures in advance. Similar to the second method, it is necessary to prepare special self-healing asphalt mixtures to achieve thermal-induced repair in the later stage.

[0008] None of the above three methods can achieve the healing of cracks in conventional asphalt ultra-thin overlays.

[0009] In addition, in this field, the repair of asphalt pavement cracks often adopts the method of injecting polymers into the cracks, which is time-consuming and laborious. There are problems such as incompatibility between the polymer and the materials on both sides of the asphalt crack and easy failure of adhesion. Summary of the Invention

[0010] In order to overcome the deficiencies of the above-mentioned existing background technologies, the present invention provides a method for healing cracks in asphalt ultra-thin overlays using ultrasonic energy. The present invention uses ultrasonic waves as the energy input to achieve rapid and efficient healing of cracks without adding any conductive phase materials to the asphalt ultra-thin overlay.

[0011] To achieve the above object, the present invention is realized through the following technical solutions:

[0012] A method for healing cracks in asphalt ultra-thin overlays using ultrasonic energy, comprising:

[0013] S1. Clean the asphalt ultra-thin overlay to be treated, determine the length and width of the cracks in the asphalt ultra-thin overlay, and mark the positions of the cracks;

[0014] S2. Use the ultrasonic vibration generated by the ultrasonic energy emission device to treat the marked cracks in the asphalt ultra-thin overlay, and stop the vibration after the cracks are healed;

[0015] S3. Remove the ultrasonic energy emission device and place it at the next crack for repeated use.

[0016] Preferably, in step S2, the ultrasonic vibration frequency generated by the ultrasonic energy emission device is 10 - 20 KHz, and the amplitude is 30 - 50 μm.

[0017] Preferably, in step S2, the ultrasonic energy emission device generates ultrasonic vibration through a pressure head provided at its lower part. The pressure head is in contact with the cracks in the asphalt ultra-thin overlay, and the pressure head can cover the cracks.

[0018] Preferably, the shape of the indenter is circular or rectangular. The circular indenter corresponds to the treatment of diseases such as "net cracks" in the ultra-thin wearing surface, while the rectangular one corresponds to single long and narrow cracks.

[0019] Preferably, in step S2, the healing time is 3 - 5 s.

[0020] Preferably, in step S2, when the temperature at the crack exceeds 180 degrees, the vibration is stopped.

[0021] The principle of the present invention is as follows: Through the high-frequency mechanical vibration of 10 - 20 KHz generated by the indenter in contact with the ultra-thin asphalt wearing surface, the asphalt mortar at both ends of the crack undergoes molecular friction during vibration, causing the temperature at the crack to rise rapidly. During vibration, the asphalt molecules oscillate violently, realizing the rapid diffusion of asphalt crack interface molecules. Macroscopically, it is manifested as the mutual flow and fusion of asphalt, thereby achieving the healing of the crack. At the same time, the amplitude of the high-frequency mechanical vibration is set at 30 - 50 μm to ensure that no permanent deformation diseases occur to the ultra-thin asphalt wearing surface during the healing process.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] The technology of the present invention can be applied to all ultra-thin asphalt wearing surfaces without adding any conductive phase materials to the original wearing surface layer. Therefore, there is no need to specially produce healing-type asphalt mixtures, and it has the advantages of wide application range and simple operation.

[0024] The technology of the present invention has the advantages of fast speed and high efficiency. Through ultrasonic vibration, the temperature at the asphalt crack can reach 180 degrees in the fastest 2 s, realizing the rapid healing of the crack. The ultrasonic energy generated by the high-speed vibrating indenter can heal multiple cracks at the disease location simultaneously, with high efficiency. Description of the Drawings

[0025] Figure 1 It is a working schematic diagram of the ultrasonic energy emission device of the present invention for treating cracks.

[0026] Reference numerals: 1 - ultrasonic energy emission device; 11 - indenter; 2 - ultra-thin asphalt wearing surface; 21 - crack. Detailed Embodiments

[0027] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the preferred implementation solutions of the present invention will be described below in conjunction with specific embodiments. However, it should not be understood as a limitation to the present invention, and it is only for example.

[0028] In the following embodiments, the test methods or testing methods, unless otherwise specified, are all conventional methods; the reagents and materials, unless otherwise specified, are all obtained from conventional commercial channels or prepared by conventional methods.

[0029] Example 1

[0030] (1) Preparation stage: Use manual or automated detection equipment to determine the length and width of the cracks 21 on the ultra-thin asphalt overlay 2, and mark the positions of the cracks. It is found that the cracks at the damaged parts are reticulated, so a circular indenter is selected and installed at the lowest end of the ultrasonic energy emission device to ensure that the indenter can cover the reticulated cracks, as shown in Figure 1 shown.

[0031] (2) Parameter setting: Select the ultrasonic vibration frequency to be 15KHz and the amplitude to be 50μm.

[0032] (3) Crack healing: Turn on the ultrasonic energy emission device 1 to make the indenter 11 generate ultrasonic vibrations as in the "Parameter setting" above, and use an infrared thermometer to monitor the temperature at the crack.

[0033] (3) During implementation, it is found that when the ultrasonic vibration time is 4s, the temperature at the crack has reached 181 degrees. Immediately remove the ultrasonic energy emission device and observe that the crack has completely healed.

[0034] Example 2

[0035] (1) Repeat the preparation stage as in Example 1.

[0036] (2) Parameter setting: Select the ultrasonic vibration frequency to be 20KHz and the amplitude to be 30μm.

[0037] (3) Crack healing: Turn on the ultrasonic energy emission device to make the indenter generate ultrasonic vibrations as in the "Parameter setting" above. Use an infrared thermometer to monitor the temperature at the crack and stop the vibration when the temperature exceeds 180 degrees.

[0038] (3) During implementation, it is found that when the ultrasonic vibration time is 2s, the temperature at the crack has reached 182 degrees. Immediately remove the ultrasonic energy emission device and observe that the crack has completely healed.

[0039] Example 3

[0040] (1) Repeat the preparation stage as in Example 1. It is found that the damage is a single long and narrow crack, so a rectangular indenter is selected and installed at the lowest end of the ultrasonic energy emission device to ensure that the indenter can cover the crack.

[0041] (2) Parameter setting: Select the ultrasonic vibration frequency to be 15KHz and the amplitude to be 35μm.

[0042] (3) Crack healing: Turn on the ultrasonic energy emission device to make the indenter generate ultrasonic vibrations as in the "Parameter setting" above. Use an infrared thermometer to monitor the temperature at the crack and stop the vibration when the temperature exceeds 180 degrees

[0043] (3) During implementation, it was found that when the ultrasonic vibration time was 3 s, the temperature at the crack had reached 184 degrees. Immediately remove the ultrasonic energy emission device, and it was observed that the crack had completely healed.

[0044] Example 4

[0045] (1) Repeat the preparation stage as in Example 3.

[0046] (2) Parameter settings: Select the ultrasonic vibration frequency to be 18 KHz and the amplitude to be 40 μm.

[0047] (3) Crack healing: Turn on the ultrasonic energy emission device to make the indenter generate ultrasonic vibrations as in the "parameter settings" above. Use an infrared thermometer to monitor the temperature at the crack, and stop the vibration when the temperature exceeds 180 degrees.

[0048] (3) During implementation, it was found that when the ultrasonic vibration time was 5 s, the temperature at the crack had reached 184 degrees. Immediately remove the ultrasonic energy emission device, and it was observed that the crack had completely healed.

[0049] Comparative Example 1

[0050] (1) Repeat the preparation stage as in Example 3.

[0051] (2) Parameter settings: Select the ultrasonic vibration frequency to be 20 KHz and the amplitude to be 80 μm.

[0052] (3) Crack healing: Turn on the ultrasonic energy emission device to make the indenter generate ultrasonic vibrations as in the "parameter settings" above.

[0053] (3) When the temperature at the crack had reached 180 degrees, immediately remove the ultrasonic energy emission device.

[0054] Comparative Example 2

[0055] (1) Repeat the preparation stage as in Example 1.

[0056] (2) Parameter settings: Select the ultrasonic vibration frequency to be 20 KHz and the amplitude to be 30 μm.

[0057] (3) Crack healing: Turn on the ultrasonic energy emission device to make the indenter generate ultrasonic vibrations as in the "parameter settings" above, and vibrate continuously for 10 s.

[0058] As described in the above examples, the main technical parameters of the repaired asphalt ultra-thin wearing course are shown in Table 1 below. Three main technical indicators are used to evaluate the repair effect, namely the crack damage area ratio (%), permanent deformation (mm), and asphalt aging index (%).

[0059] The crack damage area ratio is the proportion of the crack area to the monitored area, which can be calculated using an automatic laser scanner and is a conventional practice in the art.

[0060] Permanent deformation, also known as rutting disease, refers to the irreversible longitudinal deformation that occurs in the ultra-thin asphalt overlay.

[0061] The calculation formula for the asphalt aging index (α) is:

[0062]

[0063] Among them, S1 is the dynamic shear modulus of the asphalt after repair, which can be measured using a DSR dynamic shear rheometer; S2 is the dynamic shear modulus of the asphalt before repair.

[0064] Table 1 Technical indicators of the ultra-thin asphalt overlay before and after crack repair in each embodiment

[0065]

[0066] As can be seen from Table 1, after the asphalt pavement was repaired in Examples 1 to 4, the cracks were all completely healed and would not have an impact on permanent deformation of the asphalt pavement. On the contrary, in Comparative Examples 1 and 2, the healing was not carried out according to the technical indicators shown in the claims. In Comparative Example 1, the ultrasonic amplitude was too large, resulting in obvious permanent deformation of the road surface, reaching 0.81 mm; in Comparative Example 2, the healing time was too long, and the temperature at the crack was as high as 278 degrees. Although the crack was completely healed, the asphalt underwent severe aging, and the dynamic shear modulus after implementation increased sharply. The rapid aging of asphalt in some areas would cause the asphalt pavement to crack rapidly under the influence of vehicle load and the environment and could no longer accept secondary repair.

[0067] It should be noted that the above-described embodiments are only the preferred embodiments of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in any other specific form. Therefore, this embodiment is merely a demonstrative case and is non-limiting. The scope of the present invention is defined by the appended claims rather than the above description, and is intended to encompass all changes falling within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A method for healing cracks in an asphalt ultra-thin overlay using ultrasonic energy, characterized in that, Including: S1. Clean the asphalt ultra-thin overlay to be processed, determine the length and width of the cracks in the asphalt ultra-thin overlay, and mark the positions of the cracks; S2. Use the ultrasonic vibration generated by the ultrasonic energy emission device to treat the marked cracks in the asphalt ultra-thin overlay, and stop the vibration after the cracks are healed; S3. Remove the ultrasonic energy emission device and place it at the next crack for repeated use; In step S2, the ultrasonic vibration frequency generated by the ultrasonic energy emission device is 10 - 20 KHz, the amplitude is 30 - 50 μm, the healing time is 3 - 5 s, and when the temperature at the crack exceeds 180 degrees, stop the vibration; the ultrasonic energy emission device generates ultrasonic vibration through the indenter provided at its lower part, the indenter is in contact with the cracks in the asphalt ultra-thin overlay, and the indenter can cover the cracks.

2. The method for healing cracks in an asphalt ultra-thin overlay using ultrasonic energy according to claim 1, wherein: The shape of the indenter is circular or rectangular.

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