A method for modifying asphalt by using a microwave chemical effect to activate asphalt

Abstract

The present application discloses a method for preparing asphalt modification by activating asphalt with microwave chemical effect. The method is to activate asphalt with microwave heating equipment before mixing modifier with asphalt for modification. The activation of microwave heating is to make the asphaltene in asphalt homogenized and dispersed and the chemical property more active and the viscosity reduced by the chemical effect accompanying microwave heating. When the modifier is mixed with the microwave activated asphalt to prepare modified asphalt, better molecular cross-linking or more stable colloidal system and other favorable effects will be produced to obtain products with better performance. The initial temperature for heating asphalt is the temperature for liquid storage or pump allowing, and the temperature of asphalt is raised by 50-60 DEG C after microwave heating.

Description

TECHNICAL FIELD

[0001] The present application relates to a bitumen modification preparation method, in particular to a bitumen modification preparation method for activating bitumen by using microwave chemical effect, and belongs to the technical field of road engineering. BACKGROUND

[0002] Modern roads have high performance requirements for asphalt pavement, and the application of modified asphalt is very common. Bitumen modification is a process and means of adding appropriate and appropriate modifiers to ordinary bitumen, or chemical and physical processing, to improve or improve some properties of bitumen, so as to meet the requirements of road use. For common modifiers such as synthetic rubber (the most widely used), resin, waste tire rubber powder, etc., the mixing process of bitumen modification needs only simple physical blending, and some need shear blending and swelling development to form a stable system. The improvement of chemical activity and compatibility of bitumen itself helps to produce better molecular crosslinking and more stable colloidal system, thereby obtaining better performance.

[0003] When microwave acts on substances with large dielectric constant or magnetic permeability, it has significant thermal effect, and in addition to thermal effect, it may also produce special effects such as electric effect, magnetic effect and chemical effect. When bitumen is heated by microwave, because the dielectric constant of bitumen (near carbon substance) is much larger than that of other components, the system will produce obvious non-uniform stress heating, which can make the local critical temperature (300℃-500℃) of thermal cracking reach the cracking reaction under the condition of lower overall heating temperature (lower than 150℃-160℃). The bitumen after microwave heating is homogenized and dispersed, and the chemical properties become more active, the compatibility is enhanced, and the high temperature viscosity is significantly reduced. This bitumen after microwave heating is called microwave activated bitumen, and its property change is beneficial to further bitumen modification.

[0004] With the development of traffic and road construction demand, material technology needs to be further improved, and as a method to improve the performance of modified asphalt, the present technology is necessary.

[0005] Based on the above, the invention patent with publication number CN112608760A and publication date of April 6, 2021 discloses a method for preparing mesophase pitch by microwave heating, which comprises the following steps: 1) using heavy oil as raw material; 2) microwave heating; 3) preparing mesophase pitch product. Heavy oil is used as raw material, and microwave method is used to heat heavy oil, which converts microwave electromagnetic energy into heat energy, produces thermal effect, and makes heavy oil uniformly heated to a high temperature in a short time to occur cracking and condensation reaction. However, the processing method of microwave activated bitumen for road engineering modified bitumen is not disclosed in this document, and it cannot be applied in the present technology. SUMMARY

[0006] The application provides a technical method for improving modification effect and performance of road petroleum asphalt, and relates to an asphalt modification preparation method using microwave chemical effect to activate asphalt.

[0007] The technical solution of the application is an asphalt modification preparation method using microwave chemical effect to activate asphalt, wherein before modification processing of a modifier and asphalt, the asphalt is heated and activated by a microwave heating device to prepare microwave activated asphalt, and then the microwave activated asphalt is processed.

[0008] Further, the asphalt refers to heavy traffic road petroleum asphalt defined in "Heavy Traffic Road Petroleum Asphalt" (GB / T 15180) or road petroleum asphalt defined in "Technical Specification for Highway Asphalt Pavement Construction" (JTG F40).

[0009] Further, the microwave refers to electromagnetic waves with a frequency of 300 MHz-300 GHz.

[0010] Further, the microwave heating device is a microwave oven, and the microwave oven includes an industrial microwave oven and a household microwave oven.

[0011] Further, the starting temperature of the microwave heating of the asphalt refers to a liquid storage temperature suitable for the asphalt model or a temperature allowing pumping suitable for the asphalt model, and is generally 90-110 DEG C.

[0012] Further, the temperature rise of the asphalt after the microwave heating is 50-60 DEG C.

[0013] Further, the temperature rising time of the microwave heating to reach the temperature rise is 8-10 min.

[0014] Further, the temperature rising rate of the microwave heating is 5-7 DEG C / min.

[0015] The application has the following beneficial effects.

[0016] The microwave heating causes low-temperature cracking reaction of the asphalt, so that the microwave activated asphalt with homogenized and dispersed asphaltene aggregates, enhanced chemical activity and significantly reduced high-temperature viscosity is prepared. When the microwave activated asphalt is mixed with the modifier for further modification processing, better molecular crosslinking or more stable colloidal system and other favorable effects are generated, so that the modified asphalt has better performance. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a flowchart of the asphalt modification preparation method using microwave chemical effect to activate asphalt.

[0018] Figure 2 is a component comparison diagram of untreated asphalt and microwave activated asphalt.

[0019] Figure 3 This is a comparison chart of the colloidal stability index (CI) values ​​of untreated asphalt and microwave-activated asphalt.

[0020] Figure 4 This is a 400x magnification comparison image of untreated asphalt diluent and microwave-activated asphalt diluent.

[0021] Figure 5 This is a comparison of Fourier transform infrared (FTIR) spectra of untreated asphalt and microwave-activated asphalt.

[0022] Figure 6 This is a comparison chart of the double logarithmic viscosity-temperature curves of untreated asphalt and microwave-activated asphalt. Detailed Implementation

[0023] This invention discloses a method for preparing modified asphalt by activating asphalt using microwave chemical effects, combined with... Figure 1 This implementation method is described below. For example... Figure 1 As shown, before the modifier is mixed with asphalt for modification, the asphalt is first activated by microwave heating using a microwave heating device to prepare microwave-activated asphalt, which is then modified. Asphalt refers to heavy-traffic road petroleum asphalt as defined in "Heavy Traffic Road Petroleum Asphalt" (GB / T 15180) or road petroleum asphalt as defined in "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40). Microwave refers to electromagnetic waves with frequencies between 300MHz and 300GHz. The microwave heating device is an industrial microwave oven or a civilian microwave oven. When it is a civilian microwave oven, it is used for microwave heating in a laboratory; when it is an industrial microwave oven, it is used for microwave heating during industrial processing. The initial temperature of the microwave heating is the temperature at which the liquid is stored or pumped, which varies slightly depending on the type of asphalt, but is typically 90℃ to 110℃. After microwave heating, the temperature rise of the asphalt is 50℃ to 60℃. The specific microwave irradiation time required to reach the temperature rise is controlled between 8 and 10 minutes, and the heating rate is 5℃ to 7℃ / min. This method is used to prevent uneven cracking due to short heating times and low temperatures, and excessive cracking due to long heating times and high temperatures. The heating time to a specific temperature is adjusted by microwave oven power and asphalt flow rate in industrial processing, and by the amount of asphalt heated in laboratory preparation. Asphalt treated or processed using the above microwave heating method is called microwave-activated asphalt. Subsequently, the microwave-activated asphalt is used for modification processing. The modification processing involves mixing a modifier into the microwave-activated asphalt. The modifier can be any one of commonly used modifying additives such as synthetic rubber, resin, waste tire rubber powder, natural asphalt, sulfur, polyphosphoric acid, and nanomaterials. The mixing method between the modifier and asphalt is a conventional method in road engineering, and direct application, mechanical stirring, colloid milling, and high-speed shearing are all applicable.

[0024] Example 1

[0025] Industrial production: A tunnel-type industrial microwave oven (30 kW power adjustable, frequency 915 MHz, with a 40 m long and 5 cm inner diameter PTFE coil) is used to heat the 90# road petroleum asphalt. The preferred input temperature is 100°C; the preferred output temperature is 150°C; the time for the asphalt to reach the output temperature in the oven is adjusted by the flow pump and heating power, and the preferred time is 8-10 min. The industrial production of microwave-activated asphalt is completed by the above method, and the subsequent incorporation of modifiers for modification is the same as the conventional method of road engineering.

[0026] Example 2

[0027] Laboratory preparation: A domestic microwave oven (800 W, frequency 2450 MHz) is used to heat 150 g of 90# road petroleum asphalt. The preferred asphalt sample container is a heat-resistant glass conical flask with a cap; the preferred initial asphalt heating temperature is 100°C; the preferred initial heating temperature is preheated to 100°C in an oven; the preferred heating time is about 8-10 min, with the final temperature reaching 150°C. The laboratory preparation of microwave-activated asphalt is completed by the above method, and the subsequent incorporation of modifiers for modification is the same as the conventional method in the laboratory.

[0028] Working principle:

[0029] Asphalt is an organic hetero-compound, and its chemical composition can be divided into four components: asphaltene, colloid, aromatic fraction, and saturated fraction. Because the dielectric constant of asphaltene is much higher than that of other components, when subjected to microwave irradiation, the asphalt system will undergo selective and non-uniform stress heating. When the overall temperature is relatively low (e.g., from 100°C to 150°C), the asphaltene aggregates will reach the thermal cracking critical temperature (300°C-500°C) and undergo cracking reactions. Due to the cracking reaction, the large molecular asphaltene aggregates in the asphalt are broken down into smaller molecules (the proportion of heavy components decreases and the proportion of light components increases), and the decomposed molecules have free radicals, making the chemical properties more active and the high-temperature viscosity greatly reduced. The asphalt in this state has improved compatibility with other materials and can be referred to as microwave-activated asphalt.

[0030] Asphalt modification is a common processing technique in road engineering. It is a process and means to improve or modify some properties of asphalt by adding appropriate and suitable modifier or by chemical and physical processing to meet the requirements of road use. The common asphalt modifiers used in road engineering include artificial synthetic rubber (mainly SBS, most widely used), resin (mainly PE) and waste tire rubber powder. For different modifiers, the blending process of asphalt modification is simple physical blending for some, shear mixing for some, and swelling development for some after blending for several hours. When preparing modified asphalt based on microwave-activated asphalt, the dispersion of asphaltene aggregates and the enhancement of chemical activity help to produce better molecular crosslinking to form a more stable colloidal system, and the increase in the proportion of light components helps to swell and develop, so that the modified asphalt achieves better performance. In addition, the reduction of high-temperature viscosity of asphalt also helps to reduce the difficulty of modification processing and energy saving and environmental protection.

[0031] The following examples illustrate the effects of microwave heating and activation of asphalt and modification. Figures 2 to 6 The comparative data of laboratory tests of Table 1 show the effects of microwave heating and activation of asphalt and modification. The comparative data are obtained by the same tests on the microwave heating and activation of asphalt prepared by the method of Example 2 and the same asphalt without treatment (blank group).

[0032] Figure 2 The four-component test results of microwave heating and activation of asphalt and asphalt without treatment. It can be seen that after microwave heating, the content of heavy components (asphaltene and colloid) decreases significantly, and the content of light components (saturates and aromatics) increases significantly. Microwave heating does not make the asphalt "age", but shows obvious "hydrogenation" phenomenon, which is the performance of thermal cracking reaction.

[0033] Figure 3 The colloidal stability index (CI) test results of microwave heating and activation of asphalt and asphalt without treatment. CI is the ratio of the mass fraction of the dispersion medium (aromatics and colloid) to the mass fraction of the dispersed phase (saturates and asphaltene) in the colloid. When CI is low, the colloid tends to be a gel-type structure with poor structural stability, and vice versa, it tends to form a more stable sol-type structure. The calculation results in the figure show that the CI of microwave heating and activation of asphalt is significantly improved, i.e. the content of dispersion medium is increased, the structure develops towards sol type, and the colloidal stability and compatibility are improved.

[0034] Figure 4The test results of the comparative 400 times microscopic observation of the microwave heating activated asphalt and the untreated asphalt. The same concentration of n-heptane diluent in the component test was made into a slide, and then microscopic observation was carried out by using a 400 times optical transmission microscope. At this time, the insoluble matter is only asphaltene, and the microscopic picture can show the state of the asphaltene at this time. The same magnification microscopic picture shows that there are cluster-like large particle asphaltene aggregates in the untreated asphalt, and the asphaltene of the microwave heating activated asphalt is obviously homogenized and dispersed into smaller particles.

[0035] Figure 5 The test results of the comparative Fourier infrared spectrum scanning of the microwave heating activated asphalt and the untreated asphalt. In the figure, the microwave heating activated asphalt has relatively obvious changes in two marked areas (black dotted frame), which are that some characteristic peak intensities and peak areas become larger, and some are weakened or even disappear. Among them, the first marked area near 3000 cm -1 corresponds to the stretching vibration of X-H, such as 2924 cm -1 and 2853 cm -1 correspond to the asymmetric vibration of C-H bond in the methylene group, the microwave activated asphalt is weakened here, which represents that the concentration of n-alkane in the asphalt is reduced; the second marked area mainly has two characteristic peaks of 1600 cm -1 and 1455 cm -1 , 1600 cm -1 corresponds to the anti-symmetric breathing vibration of the substituted benzene ring, and 1455 cm -1 is the superposition of the methylene bending vibration (shoulder peak right) and the asymmetric bending vibration of the methyl group (shoulder peak left), the peak intensity and area of 1600 cm -1 of the microwave activated asphalt are weakened and reduced, which represents that some specific aromatics disappear; at 1455 cm -1 , not only the peak intensity is weakened, but also the right side methyl bending vibration of the shoulder peak disappears, the sawtooth peak type becomes a simple single peak type, which represents that the concentration of saturated hydrocarbons in the aliphatic group is reduced or disappears. From the analysis, after the microwave heating treatment, some saturated compounds in the asphalt are converted into unsaturated compounds, and the chemical activity of the asphalt is enhanced.

[0036] Figure 6 The comparative double logarithmic viscosity-temperature curve of the microwave heating activated asphalt and the untreated asphalt, in which the temperature is in Kelvin. The test data and viscosity-temperature curve shown in the figure show that the viscosity of the microwave activated asphalt is reduced at the high temperature section.

[0037] Table 1 is a comparative test result after preparing modified asphalt based on microwave heating activation and non-treatment of two kinds of asphalt, under the same subsequent modifier dosage and modification process (4% SBS, high-speed shearing) conditions. The results show that the SBS modified asphalt prepared by using microwave activated asphalt has little difference in penetration (little difference in softness and hardness), but the softening point, 5℃ ductility and elastic recovery are significantly improved, which shows that the high temperature stability, low temperature ductility and medium temperature elastic properties of the asphalt are improved, which is beneficial to improve the performance of asphalt mixture. After short-term aging (after RTFOT), the quality change of microwave heating activated asphalt changes from positive to negative, and the absolute value of quality change increases, showing that the aging resistance is slightly reduced. The penetration ratio of microwave activated asphalt after aging decreases, showing that the stiffness (softness and hardness) decreases after aging, which is also a slight decrease in aging resistance; the 5℃ ductility increases, which shows that the low temperature ductility of aging is slightly enhanced, which is beneficial to service. Overall, the SBS modified asphalt prepared based on microwave activated asphalt has improved performance at high and low temperature stages, and the aging resistance is slightly reduced.

[0038] Table 1 Performance parameters of SBS modified asphalt prepared based on different asphalt

[0039]

[0040] Among them, the technical requirements are SBS I-C standard in China "Highway Asphalt Pavement Construction Technical Specification" (JTG F40).

[0041] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and make equivalent embodiments with equivalent changes. Any simple modification, equivalent replacement and improvement of the above embodiments, which does not depart from the technical solution of the present application, is within the protection scope of the present application.

Claims

1. A method for modifying asphalt by using a microwave effect to activate asphalt, characterized by: Before mixing the modifier with the asphalt for modification processing, the asphalt is heated and activated by a microwave heating device to prepare microwave-activated asphalt, and then the microwave-activated asphalt is modified, wherein the asphalt is road petroleum asphalt, the starting temperature of the microwave heating of the asphalt is the liquid storage temperature suitable for the asphalt type or the temperature allowed for pumping suitable for the asphalt type, and the starting temperature is 90-110 DEG C; the temperature of the asphalt rises by 50-60 DEG C after the microwave heating. The microwave heating device is a microwave oven. The temperature rising time of the microwave heating is 8-10 min.

2. The asphalt modification preparation method using a microwave effect to activate asphalt according to claim 1, characterized by: The temperature rising rate of the microwave heating is 5-7 DEG C / min.

Images