Regenerant for microwave heating in-place thermal regeneration and preparation and use methods thereof

Abstract

The invention provides a regenerant for microwave heating in-place hot regeneration of an asphalt pavement, and belongs to the technical field of road engineering. The regenerant comprises 50-60 wt% of a blender, 35-45 wt% of a stabilizer and 4-6 wt% of a diffusion accelerator. The regenerant not only contains a component blending component and a diffusion promoting component in a traditional regenerant, but also contains a stabilizing component for improving the chemical structure of microwave heating aged asphalt, so that the asphalt can be moderately vulcanized under a construction condition, dispersed asphaltene forms cross-linked molecules with stable chemical properties, and meanwhile, the mechanical property of the asphalt is improved. Free radicals generated by microwave degradation are consumed in the sulfuration process, so that the oxidative condensation process in subsequent use is prevented and delayed. The invention also provides a preparation method and a use method of the regenerant. The problem that the aged asphalt is not resistant to secondary aging due to the microwave chemical effect can be solved, and the aged asphalt mixture of the old road can be fully recycled.

Description

Technical Field

[0001] The invention relates to a regeneration agent for on-site thermal regeneration of an asphalt pavement, in particular to a regeneration agent for on-site thermal regeneration by microwave heating and a preparation and use method thereof, belonging to the technical field of road engineering. Background Art

[0002] In-situ hot regeneration of asphalt pavement is a technology that uses special in-situ hot regeneration equipment to heat, loosen, and mill the asphalt pavement, add a certain amount of new asphalt, new aggregate, regeneration agent, etc. on-site, and then regenerate the old asphalt pavement within a certain depth range of the surface at one time through hot mixing, paving, rolling and other processes. Traditionally, the heating methods for in-situ hot regeneration include open flame, hot air, infrared, etc., all of which heat the asphalt pavement within a certain depth range to a state that is convenient for loosening and subsequent operations through top-to-bottom heat conduction.

[0003] Microwave heating has a large depth of action, uniform heating, high efficiency and low energy consumption. It is a commonly used industrial and civilian heating technology. In recent years, microwave heating asphalt pavement in-situ heat regeneration equipment has been developed and applied experimentally in my country. Microwave heating has technical advantages that traditional heating methods do not have, and is generally considered to be a technological innovation with broad application prospects.

[0004] However, when microwaves are used to heat aged asphalt, significant chemical effects will occur. Tests have shown that after microwave heating at room temperature to 160°C, the aged asphalt becomes thinner and softer on a macroscopic level, and dispersed asphaltene aggregates (asphalt micelles) on a microscopic level. Chemical analysis shows that the asphaltene content is significantly reduced, and some saturated compounds are converted into unsaturated compounds. This significant chemical effect is due to the fact that the dielectric constants of asphaltene and sulfur components in asphalt are much greater than other substances such as aromatic components and saturated components. Therefore, when exposed to microwave radiation, "hot spots" or "local overheating" phenomena will occur, and local thermal cracking and degradation will occur when the overall temperature of the asphalt is low. This degradation and chemical activation caused by microwave heating of aged asphalt or aged pavement has not yet been widely recognized, but its consequences make the aged asphalt thinner, softer and less resistant to secondary aging, and the demand for regeneration agents is also completely different from traditional heating methods.

[0005] Therefore, a regeneration agent suitable for on-site thermal regeneration by microwave heating and a method for its preparation and use should be specially developed to meet actual engineering needs. Summary of the invention

[0006] In order to adapt to the significant changes in the proportion of aged asphalt components caused by microwave chemical effects and to solve the problem that aged asphalt becomes less resistant to secondary aging after microwave heating, a regeneration agent for in-situ thermal regeneration by microwave heating and a method for preparing and using the regeneration agent were invented.

[0007] The technical solution adopted by the present invention to solve the above problems is:

[0008] A regeneration agent for microwave heating in-situ thermal regeneration, the weight percentages of the components are as follows:

[0009] 50-60wt% of conditioning agent;

[0010] Stabilizer 35-45wt%;

[0011] Diffusion accelerator 4-6wt%.

[0012] Furthermore, the blending agent is waste internal combustion engine oil.

[0013] Furthermore, the waste internal combustion engine oil should comply with level 2 or above in the Technical Guidelines for Recovery and Recycling of Waste Lubricating Oil GB / T17145.

[0014] Furthermore, the stabilizer is sulfur and a vulcanization accelerator, and the mass ratio of the sulfur to the vulcanization accelerator is 9:1.

[0015] Furthermore, the sulfur is a commercial sulfur additive for asphalt modification, which contains more than 95% elemental sulfur and odor-free and smoke-suppressing components.

[0016] Furthermore, the vulcanization accelerator is sodium dimethyldithiocarbamate.

[0017] Furthermore, the diffusion enhancer is an oil-soluble nonionic surfactant.

[0018] Furthermore, the oil-soluble nonionic surfactant is erucamide or oleamide.

[0019] A method for preparing a regeneration agent for microwave heating in-situ thermal regeneration, the preparation method is achieved by the following steps:

[0020] S1: Mixing a conditioning agent, a stabilizer and a diffusion accelerator in proportion to obtain a mixture;

[0021] S2: within 10 minutes, the mixture obtained in S1 is heated from room temperature to 50-60°C, and stirring is continued during the heating process. After reaching the target temperature, stirring is continued for 10 minutes, and then cooled to room temperature to obtain a regeneration agent for microwave heating in-situ thermal regeneration;

[0022] S3: The regeneration agent obtained in S2 for microwave heating in situ thermal regeneration is sealed and stored away from light.

[0023] A method for using a regeneration agent for microwave heating on-site thermal regeneration, the method comprising adding the regeneration agent into the heated and loosened old asphalt mixture. The regeneration agent should be heated to 50-60°C before use and continuously stirred during use to prevent the precipitation of a stabilizer in the mixture.

[0024] The beneficial effects of the present invention are:

[0025] The regeneration agent proposed by the present invention is a composite regeneration agent, wherein the stabilizer component can make the aged asphalt that has been cracked and degraded by microwave action moderately vulcanized under construction conditions, and consume the free radicals generated by cracking, so that the dispersed asphaltene forms cross-linked molecules with stable chemical properties, thereby preventing and delaying the oxidation condensation process in subsequent use, and avoiding the aggravation of secondary aging. The conditioning agent component in the regeneration agent can supplement the components of the aged asphalt, and the diffusion promoter component can promote the fusion of the aged asphalt with the recycled asphalt and the new asphalt in the gaps of the old material. The stabilizer component and the conditioning agent component of the present invention improve the asphalt performance on the surface of the old material, and the road performance balance of the recycled mixture is transformed in a favorable direction. DETAILED DESCRIPTION

[0026] Specific implementation method 1: The weight percentage of each component of the regeneration agent for microwave heating in-situ thermal regeneration described in this implementation method is as follows: 50-60wt% of the regulator; 35-45wt% of the stabilizer; 4-6wt% of the diffusion promoter.

[0027] The blending agent is waste internal combustion engine oil, which is derived from petroleum products and has good compatibility with asphalt; its main components are aromatics and saturated components, which are suitable for supplementing the relatively lacking chemical components in aged asphalt; it generally contains antioxidant components, which is beneficial to improving the ability of recycled asphalt to resist secondary aging. The waste internal combustion engine oil should comply with the second level and above in the Technical Guidelines for the Recovery and Regeneration of Waste Lubricating Oil GB / T 17145. The blending agent converts the chemical component ratio of aged asphalt to that of new asphalt by supplementing aromatics and saturated components, thereby achieving blending and regeneration.

[0028] The stabilizer is sulfur and a vulcanization accelerator, and the mass ratio of the sulfur to the vulcanization accelerator is 9:1. The sulfur adopts a commercial sulfur additive for asphalt modification, which contains more than 95% elemental sulfur and odor-free and smoke-suppressing ingredients. The preferred one is Thiopave sulfur. Thiopave sulfur is a commercial additive specially used for sulfur-modified asphalt. Its elemental sulfur content accounts for more than 95%, and it also contains smoke-suppressing and odor-free ingredients, which can reduce the environmental pollution caused by toxic substances such as hydrogen sulfide released during asphalt vulcanization. The vulcanization accelerator is sodium dimethyl dithiocarbamate, i.e. sodium thiocarbamate. Sodium thiocarbamate is an ultra-fast vulcanization accelerator that can accelerate the asphalt vulcanization process and is suitable for short-term heating states of on-site thermal regeneration. Compared with other vulcanization accelerators, it has low toxicity and is relatively cheap. Sulfur and vulcanization accelerators are used to moderately vulcanize the aged asphalt that has been degraded by microwaves under construction conditions, and consume the free radicals generated by microwave degradation, so that the dispersed asphaltene forms chemically stable cross-linked molecules, thereby preventing and delaying the oxidation condensation process in subsequent use and avoiding the aggravation of secondary aging. Stabilizers achieve the effect of reaction regeneration by improving the asphalt structure and resisting secondary aging.

[0029] The diffusion promoter is an oil-soluble nonionic surfactant, which is an aliphatic amide, preferably erucic acid amide or oleic acid amide. These two nonionic surfactants have better compatibility with asphalt and are relatively inexpensive. They are used to promote the dissolution of aged asphalt with recycled asphalt and new asphalt in the gaps of old materials, which is beneficial to the interface fusion of old materials.

[0030] A method for preparing a regeneration agent for microwave heating in-situ thermal regeneration, the preparation method is achieved by the following steps:

[0031] S1: Mixing a conditioning agent, a stabilizer and a diffusion accelerator in proportion to obtain a mixture;

[0032] S2: within 10 minutes, the mixture obtained in S1 is heated from room temperature to 50-60°C, and stirring is continued during the heating process. After reaching the target temperature, stirring is continued for 10 minutes, and then cooled to room temperature to obtain a regeneration agent for microwave heating in-situ thermal regeneration;

[0033] S3: The regeneration agent obtained in S2 for microwave heating in situ thermal regeneration is sealed and stored away from light.

[0034] A method for using a regeneration agent for microwave heating on-site thermal regeneration, the method comprising adding the regeneration agent into the heated and loosened old asphalt mixture. The regeneration agent should be heated to 50-60°C before use and continuously stirred during use to prevent the precipitation of a stabilizer in the mixture.

[0035] The regeneration agent for in-situ thermal regeneration by microwave heating described in the present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0036] 1. Regeneration Agent Preparation

[0037] Prepare according to the weight ratio in Table 1, the mixing temperature is 60°C, and keep stirring to ensure the uniformity of insoluble matter.

[0038] Table 1 Regeneration agent ratio

[0039]

[0040] 2. Preparation of recycled asphalt from old roads

[0041] The service life of the old asphalt pavement is 10 years, the original asphalt grade is No. 90, the designed regeneration depth is 4cm, and the original pavement AC-16 is regenerated to AC-16. According to the sampling method of in-situ hot regeneration recycled materials specified in the "Technical Specifications for Highway Asphalt Pavement Regeneration" (JTG / T 5521), a single piece of old pavement recycled materials weighing about 1000g within the designed depth is taken and placed in a household microwave oven. After heating from room temperature to a surface temperature of 185℃, it is manually crushed into small pieces as dispersed as possible, and it is ensured that the aggregate particles are not broken during the artificial dispersion process. After that, according to the T0722 centrifugal separation method and T0727 rotary evaporator method in the "Technical Specifications for Testing Asphalt and Asphalt Mixtures for Highway Engineering" (JTG E20), the old asphalt is extracted and distilled to recover for further analysis and testing. Repeat the above steps several times to obtain enough recycled asphalt for testing.

[0042] 3. Comparative analysis of the performance of recycled aged asphalt

[0043] The regeneration agents configured in the three embodiments (Example 1, Example 2, Example 3) and a commercially available traditional asphalt regeneration agent for in-situ hot regeneration (Comparative Example 1) were added to the old road recycled asphalt at the same empirical dosage (the asphalt temperature was 160°C when added), and the performance indicators of the regenerated asphalt were measured as shown in Table 2. The commonly used road asphalt grade under the same conditions in the local area is No. 90. According to the provisions of the "Technical Specifications for Highway Asphalt Pavement Regeneration" (JTG / T 5521), the target grade of regenerated asphalt is reduced by one level to No. 70, and its technical requirements are listed in Table 2.

[0044] Table 2 Performance indexes of recycled asphalt

[0045]

[0046]

[0047] The data in the table show that the needle penetration of the aged asphalt (without regeneration agent) recycled after microwave heating reaches the standard of No. 70 asphalt, the dynamic viscosity at 60℃ is low, and all indicators after the RTFOT test obviously exceed the technical requirements. This state is completely different from ordinary aged asphalt, showing a trend of being thinner and softer, but at the same time it does not have the low-temperature crack resistance of thin and soft asphalt (lower ductility). This specificity means that its component ratio and chemical structure are different from those of ordinary aged asphalt, and special considerations are required during regeneration.

[0048] After adding the commercially available traditional asphalt regeneration agent for in-situ hot regeneration (Comparative Example 1) to the microwave-heated aged asphalt, it can be found that its penetration is significantly improved. Although the ductility and secondary aging resistance of the RTFOT test, which characterize the low-temperature performance, are improved, its 60°C dynamic viscosity and softening point are further away from the target technical requirements. This phenomenon is attributed to the fact that the composition ratio of the traditional asphalt regeneration agent is designed according to the blending principle, mainly aromatic and saturated. After microwave heating, the degradation of asphalt micelles in the aged asphalt is most obvious, and the relative proportions of other components do not change much. The blending components of the traditional asphalt regeneration agent do not match it.

[0049] The addition of the regeneration agents of the three embodiments makes the property indicators of the aged asphalt meet the target technical requirements, which shows that moderate vulcanization makes the various properties of the microwave-heated aged asphalt tend to be balanced. Regardless of which embodiment, the higher the proportion of the stabilizing component (Thiopave sulfur + sodium thiopave), the more significant the improvement of the high temperature resistance (the lower the needle penetration, the higher the viscosity at 60°C), and the higher the proportion of the blending component (waste internal combustion engine oil), the more significant the improvement of the low temperature cracking resistance (the greater the 15°C elongation and residual elongation), which shows that the stabilizing component that plays a vulcanizing role and the blending component that supplements aromatic hydrocarbons and saturated hydrocarbons of the present invention can well adjust the chemical composition and chemical structure of the aged asphalt, so that its properties develop in the direction of excellent asphalt.

[0050] 4. Comparative analysis of recycled asphalt mixture performance

[0051] Take a piece of AC-16 recycled material from the old road surface weighing about 1000g within the designed depth, place it in a household microwave oven, heat it from room temperature to a surface temperature of 185℃, and then manually break it into small pieces that are as dispersed as possible. Repeat the operation multiple times in parallel to obtain enough old asphalt mixture for further testing.

[0052] According to the design method of recycled asphalt mixture specified in the Technical Specification for Highway Asphalt Pavement Regeneration (JTG / T 5521), the asphalt content of the old material, the particle gradation of the old material, the gradation design of the recycled material (design of the amount of new aggregate added), and the design of the amount of new asphalt added were carried out. When mixing the recycled mixture, the construction process of hot-in-situ regeneration was simulated. The regeneration agent of Example 2 and the comparative example was first added to the old material at an empirical ratio of 5wt% of the old asphalt, and then mixed with the new aggregate and the new asphalt. The mix ratio design result is old material: new aggregate: new asphalt = 88:12:0.9. The test results of the Marshall test, rutting test, beam bending test, etc. at the optimal new asphalt dosage are shown in Table 3.

[0053] Table 3 Test results of recycled asphalt mixture

[0054]

[0055] From the data in Table 3, when 5% of the regeneration agent of Example 2 is added, the Marshall stability, dynamic stability and bending failure strain of the former are 2.0 times, 3.4 times and 1.3 times of the latter, respectively, and the high temperature stability and low temperature crack resistance are comprehensively improved. The data show that the regeneration agent proposed by the present invention is more suitable for in-situ thermal regeneration of aged asphalt mixture heated by microwave.

[0056] The present invention proposes a regeneration agent for in-situ thermal regeneration of asphalt pavement by microwave heating. The regeneration agent not only contains the component blending component and diffusion promoting component in the traditional regeneration agent, but also contains a stabilizing component that improves the chemical structure of asphalt, which can make the asphalt moderately vulcanized under construction conditions, so that the dispersed asphaltene forms cross-linked molecules with stable chemical properties. At the same time, the vulcanization process consumes the free radicals generated by microwave degradation, thereby preventing and delaying the oxidation condensation process in subsequent use. The present invention also proposes a preparation method and a use method of the regeneration agent. The problem that aged asphalt is not resistant to secondary aging due to microwave chemical effects can be solved, so that the aged asphalt mixture of old roads can be fully recycled.

[0057] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A regeneration agent for in-situ thermal regeneration by microwave heating, characterized in that: The weight percentage of each component is as follows: 50-60wt% of conditioning agent; Stabilizer 35-45wt%; Diffusion accelerator 4-6wt%.

2. A regeneration agent for microwave heating in-situ thermal regeneration according to claim 1, characterized in that: The blending agent is waste internal combustion engine oil.

3. The regeneration agent for in-situ thermal regeneration by microwave heating according to claim 1, characterized in that: The stabilizer is sulfur and a vulcanization accelerator, and the mass ratio of the sulfur to the vulcanization accelerator is 9:

1.

4. A regeneration agent for microwave heating in-situ thermal regeneration according to claim 3, characterized in that: The sulfur is a commercial sulfur additive for asphalt modification, in which elemental sulfur accounts for more than 95% and contains odor-free and smoke-suppressing components.

5. The regeneration agent for in-situ thermal regeneration by microwave heating according to claim 3, characterized in that: The vulcanization accelerator is sodium dimethyldithiocarbamate.

6. The regeneration agent for in-situ thermal regeneration by microwave heating according to claim 1, characterized in that: The diffusion accelerator is an aliphatic amide oil-soluble nonionic surfactant.

7. A regeneration agent for microwave heating in-situ thermal regeneration according to claim 6, characterized in that: The surfactant is erucamide or oleamide.

8. A method for preparing a regeneration agent for microwave heating in-situ thermal regeneration according to any one of claims 1 to 7, characterized in that: The preparation method is achieved by the following steps: S1: Mixing a conditioning agent, a stabilizer and a diffusion accelerator in proportion to obtain a mixture; S2: heating and stirring the mixture obtained in S1, and then cooling to room temperature to obtain a regeneration agent for in-situ thermal regeneration by microwave heating; S3: The regeneration agent obtained in S2 for microwave heating in situ thermal regeneration is sealed and stored away from light.

9. The method for preparing a regeneration agent for microwave heating in-situ thermal regeneration according to claim 8, characterized in that: The heating temperature in S2 is 50-60° C., and the heating time is less than or equal to 10 min.

10. A method for using a regeneration agent for microwave heating in-situ thermal regeneration according to claim 8, characterized in that: The method of use is: add the regeneration agent for microwave heating on-site thermal regeneration into the heated and loosened old asphalt mixture, the regeneration agent for microwave heating on-site thermal regeneration should be heated to 50-60°C before use, and continuously stirred during use to prevent the precipitation of the stabilizer in the mixture.

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