Viscosity-reducing warm-mixing method for asphalt

Abstract

The invention discloses a technical method for realizing warm mixing by reducing asphalt viscosity through ultrasonic treatment, which comprises the following steps: firstly, performing ultrasonic treatment on asphalt in a molten state, and then mixing an asphalt mixture at a temperature lower than that of hot mixing. The ultrasonic treatment time is 3-10 min, the ultrasonic treatment mode is that an ultrasonic generating device is installed on an asphalt carrier and then ultrasonic waves are applied, the asphalt carrier is an asphalt storage tank or an asphalt pipeline, the ultrasonic generating device is an ultrasonic transducer, the temperature of the molten state is 110-150 DEG C, and the sound intensity of the ultrasonic waves is larger than or equal to 0.5 W / cm. Viscosity reduction of molten asphalt is achieved by means of the ultrasonic mechanical vibration effect and the cavitation effect, the high-temperature fluidity of the asphalt is enhanced, and therefore warm mixing of the asphalt mixture is achieved.

Description

[0001] This application is a divisional application. The original application is titled "A warm-mix asphalt method for viscosity reduction using ultrasound." The application number is 202311572515.4, and the application date is November 23, 2023. Technical Field

[0002] The present invention relates to a technical method for warm asphalt mixing, and in particular to a technical method for achieving warm mixing by utilizing ultrasonic treatment to reduce the viscosity of molten asphalt, and belongs to the technical field of road engineering. Background Art

[0003] Hot mix is ​​the primary asphalt construction method. Warm mix technology, a method that reduces the mixing temperature of asphalt mixtures compared to hot mix, significantly reduces energy consumption and emissions, making it an emerging environmentally friendly technology. Several different technical mechanisms exist for warm mix asphalt: asphalt viscosity reduction (such as by incorporating high-melting-point paraffin wax, kerosene, or diesel), interfacial lubrication (such as by incorporating oil-soluble surfactants), foaming (such as by direct foaming of asphalt or by incorporating powder containing crystalline water), and microemulsification (such as by incorporating an emulsifier during mixing to form a water-in-oil emulsion). Existing technologies require the addition of additives to the asphalt or asphalt mixture.

[0004] The mechanical vibration of ultrasound causes the molten asphalt to rapidly thixotropically change, dramatically increasing its fluidity. Simultaneously, the cavitation effect of ultrasound cracks the asphaltene in the asphalt, homogenizing and dispersing large asphaltene aggregates into smaller molecules. Some saturated hydrocarbons become unsaturated, and the chemical structure becomes more fluid, like a sol. Both the mechanical vibration and cavitation significantly reduce the viscosity of the molten asphalt and significantly enhance its fluidity, thereby achieving lower mixing temperatures relative to hot mixing. Summary of the Invention

[0005] The present invention uses the mechanical vibration and cavitation effect of ultrasound to achieve non-contact physical field asphalt viscosity reduction, thereby enhancing the high-temperature fluidity of asphalt, and further proposes an asphalt warm mixing method using ultrasound to reduce viscosity.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is: a warm-mix asphalt method using ultrasonic viscosity reduction, in which the asphalt is first ultrasonically treated in a molten state, and then the asphalt mixture is mixed at a temperature lower than that of hot mixing. The ultrasonic treatment method is to install an ultrasonic generator on an asphalt carrier and then apply ultrasonic waves.

[0007] Furthermore, the ultrasonic generating device is an ultrasonic transducer.

[0008] Furthermore, there are a plurality of ultrasonic transducers, and the plurality of ultrasonic transducers are arranged in an array on the asphalt storage tank and / or asphalt pipeline.

[0009] Furthermore, the asphalt pipeline is the last section of the asphalt pipeline before entering the mixing tower.

[0010] Furthermore, the ultrasonic treatment time is 3 to 10 minutes.

[0011] Furthermore, the temperature of the molten state is 110-150°C.

[0012] Furthermore, the temperature of the molten state of petroleum asphalt is 110-130°C, and the temperature of the molten state of polymer-modified asphalt is 130-150°C.

[0013] Furthermore, the sound intensity of the ultrasonic wave is ≧0.5W / cm2.

[0014] The beneficial effects of the present invention are:

[0015] Ultrasonic waves are used to reduce the viscosity of molten asphalt, which can be used for warm mixing of asphalt mixtures without additives, or in conjunction with other warm mixing measures using additives to reduce the amount of additives used. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure is a flow chart of the asphalt warm mix method using ultrasonic viscosity reduction according to the present invention.

[0017] Figure 2 This is a schematic diagram of an embodiment of the asphalt warm mix method using ultrasonic viscosity reduction of the present invention, in which the ultrasonic transducer is installed outside the asphalt storage tank.

[0018] Figure 3 This is a schematic diagram of an implementation method of the asphalt warm mix method using ultrasonic viscosity reduction of the present invention, in which the ultrasonic transducer is installed on the outside of the last section of the asphalt pipeline before the mixing tower.

[0019] Figure 4 It is a structural diagram of an embodiment of a laboratory ultrasonic treatment device.

[0020] Figure 5 This is a schematic diagram of the real-time viscosity change of asphalt after ultrasonic treatment in the laboratory.

[0021] Figure 6 This is a schematic diagram showing the effect of storage time on viscosity after laboratory ultrasonic treatment.

[0022] Figure 7 This is a schematic diagram of the maximum viscosity reduction rate and residual viscosity reduction rate of No. 50 asphalt.

[0023] Figure 8 This is a schematic diagram of the maximum viscosity reduction rate and residual viscosity reduction rate of No. 70 asphalt.

[0024] Figure 9This is a schematic diagram of the maximum viscosity reduction rate and residual viscosity reduction rate of No. 90 asphalt.

[0025] Figure 10 This is a 400x microscope image of different asphalts after ultrasonic treatment. DETAILED DESCRIPTION

[0026] The present invention discloses a warm asphalt mixing method using ultrasonic viscosity reduction, which can significantly improve the high-temperature fluidity of asphalt through the non-contact physical field of ultrasound, thereby achieving lower mixing temperature than hot mixing. The implementation method is to first ultrasonically treat the asphalt in the molten state, and then mix the asphalt mixture at a lower temperature than hot mixing. Figure 1 As shown, the molten state temperature is preferably 110-150°C. For road petroleum asphalt, the molten state temperature is 110-130°C, and for polymer-modified asphalt, the molten state temperature is 130-150°C. The ultrasonic treatment duration is 3-10 minutes, 3-5 minutes when the asphalt is used immediately after ultrasonic treatment, and 5-10 minutes when it is not used immediately. The acoustic power applied to the asphalt is characterized by sound intensity, with the ultrasonic sound intensity ≥ 0.5 W / cm² (the average sound intensity of the asphalt subjected to ultrasonic waves ≥ 0.5 W / cm²), thereby enhancing the viscosity reduction effect of the asphalt. The ultrasonic treatment method is to install an ultrasonic generator on the asphalt carrier, which can be an asphalt storage tank or asphalt pipeline. The ultrasonic generator can be installed on the asphalt storage tank or asphalt pipeline alone, or on both the asphalt storage tank and the asphalt pipeline, and can apply ultrasonic waves to the asphalt in the tank or flowing through the pipeline. The ultrasonic generating device is an ultrasonic transducer. Preferably, there are several ultrasonic transducers, which can increase the coverage of the ultrasonic sound field. Several of the ultrasonic transducers are arranged in an array on the asphalt storage tank or asphalt pipeline, and can evenly apply ultrasonic waves to the asphalt in the storage tank or flowing through the pipeline. Several of the ultrasonic transducers are installed internally or externally in the asphalt storage tank to form an array, which is used to generate a relatively uniform ultrasonic sound field with a specific sound wave power in the asphalt storage tank. Preferably, the asphalt pipeline is the last section of the asphalt pipeline before entering the mixing tower (mixing plant), so that the asphalt that has undergone ultrasonic treatment can immediately enter the mixing tower. Several of the ultrasonic transducers are externally installed in the last section of the asphalt pipeline before entering the mixing tower to form an array, which is used to generate a relatively uniform ultrasonic sound field with a specific sound wave power in the asphalt pipeline.

[0027] The technical solution of the present invention is further described below with reference to embodiments.

[0028] Example 1

[0029] like Figure 2As shown, several ultrasonic transducers are installed in an array on the exterior of an asphalt storage tank equipped with a heating and temperature control device. The installation position, power, and number of transducers should be calibrated through prior testing to ensure that the internal liquid (water, oil, or other room-temperature liquid media can be used for calibration) experiences an average sound field intensity ≥ 0.5 W / cm² and is relatively uniform. The temperature is pre-controlled to the target temperature, followed by ultrasonic treatment for 10 minutes. The treated asphalt is then used to mix the asphalt mixture. The specific mixing temperature can be empirically reduced by 5–15°C relative to hot mixing or determined based on the viscosity-temperature curve of the asphalt entering the mixing tower. Due to the significant differences in the properties of different asphalts, the specific ultrasonic treatment temperature, power, duration, and post-treatment life can also be determined through field testing, with the maximum viscosity reduction as the indicator.

[0030] Example 2

[0031] like Figure 3 As shown, several ultrasonic transducers are installed on the exterior of the final section of the asphalt pipeline before entering the asphalt mixing tower. The installation location, power, and number of transducers should be calibrated through prior testing to ensure that the average acoustic field intensity experienced by the liquid within (water, oil, or other ambient temperature liquid media can be used for calibration) is ≥0.5 W / cm² and relatively uniform. Ultrasonic waves are always active during the asphalt delivery phase. The ultrasonically irradiated asphalt is then immediately delivered to the mixing tower for mixing. Because the mixing tower operates intermittently, with each cycle lasting approximately 1 minute, the actual ultrasonic irradiation time of the asphalt in the pipeline before entering the mixing tower can be adjusted by adjusting the pipeline length, diameter, and flow rate. The specific mixing temperature can be empirically reduced by 5–15°C relative to hot mixing, or determined based on the viscosity-temperature curve of the asphalt entering the mixing tower. Due to the significant variability in the properties of different asphalts, the specific ultrasonic treatment temperature, power, and duration can also be determined through field testing, with the maximum viscosity reduction as the criterion.

[0032] Viscosity reduction test description:

[0033] like Figure 4As shown, a laboratory ultrasonic treatment device includes a warm mixing barrel 1, a perforated thermal insulation cover 2, an ultrasonic transducer 3, an ultrasonic generator 4, a heat jacket 5 and a temperature controller 66. The warm mixing barrel 1 is preferably made of steel to reduce the test error. The perforated thermal insulation cover 2 can be opened and installed above the warm mixing barrel 1. When the perforated thermal insulation cover 2 is opened, it is convenient to put in the ultrasonic propagation medium. The ultrasonic propagation medium can make the ultrasonic sound field cover the asphalt more evenly. The ultrasonic propagation medium can be heat transfer oil. When the perforated thermal insulation cover 2 is closed to the barrel wall of the warm mixing barrel 1, it is convenient to increase the stability of the device. The ultrasonic transducer 3 is installed on the lower surface of the bottom wall of the warm mixing barrel 1, and the ultrasonic generator 4 is installed on the outside of the warm mixing barrel 1 and connected to the ultrasonic transducer 3 through a connecting line. The ultrasonic transducer 3 and the ultrasonic generator 4 are used for the generation and application of ultrasonic waves. Preferably, there are multiple ultrasonic transducers 3, which are evenly distributed on the bottom wall of the warm mixing drum 1 along a circumference centered at the center of the bottom wall of the warm mixing drum 1, to generate a relatively uniform ultrasonic sound field. A heat jacket 5 is mounted on the side wall of the warm mixing drum 1 to heat the warm mixing drum 1. A temperature controller 6 is mounted on the outside of the warm mixing drum 1, with a probe of the temperature controller 6 extending into the interior of the warm mixing drum 1 toward the ultrasonic propagation medium to measure the temperature of the warm mixing equipment. The heat jacket 5 and the temperature controller 6 are used to adjust the temperature of the ultrasonic treatment.

[0034] Specifically, the ultrasonic waves are generated by four ultrasonic transducers 3 with a total power of 120W and an ultrasonic generator 4 connected thereto, which are arranged at the bottom of the insulated steel barrel. The ultrasonic frequency can be adjusted in three gears: 28KHz, 40KHz, and 52KHz. The container is filled with thermal oil as the ultrasonic propagation medium. The thermal oil can adjust the processing temperature (from room temperature to 160°C, with an error of no more than ±0.2°C) through the heat jacket 5 and the automatic temperature control equipment. The asphalt sample is placed in an aluminum test tube immersed in the thermal oil. The filling amount does not exceed the liquid level of the thermal oil. Each tube can hold approximately 20ml. Among them, the ultrasonic sound field in the warm mixing barrel 1 container is not uniform. The sound intensity difference between the center and the edge in the horizontal direction is about 0.21W / cm2, and the sound intensity difference between the bottom and the top in the vertical direction is about 0.23W / cm2. Considering the position of the sample in the sound field, the asphalt sample is subjected to a vertical weighted average sound intensity of about 0.6W / cm2.

[0035] Asphalt samples with three different penetrations (50, 70, and 90 gauge) were used. The Brookfield rotational viscometer's rotor was inserted through the perforated, insulated cover plate 2 of the steel drum container of the ultrasonic treatment apparatus in Example 3 and directly immersed into the asphalt sample. Viscosity was measured in real time. At the start of the test, the temperature was pre-controlled to the target temperature and allowed to stabilize for 30 minutes. The ultrasonic generator 4 was then activated for 10 minutes of ultrasonic treatment. Temperature control was continued for another 10 minutes after treatment. The rotational viscometer was maintained in the test mode, and the dynamic changes in viscosity over time were recorded during the test.

[0036] like Figure 5 The figure shows real-time viscosity measurements starting 5 minutes before ultrasonic treatment and recorded every 30 seconds until the end of temperature control. These data are based on typical treatment conditions: a temperature of 105°C and a frequency of 40 kHz. The viscosity of the molten asphalt decreases immediately upon ultrasonic irradiation. With increasing irradiation time, the viscosity of the three asphalts reaches a trough value after 5-7 minutes and remains stable without further decrease. After cessation of ultrasonic irradiation, the viscosity of the asphalt gradually increases, reaching a stable viscosity after 5-7 minutes, which remains significantly lower than the initial value. Under these typical conditions, the flat-bottomed trough viscosities of the different asphalts at maximum impact are 61% (50#), 53% (70#), and 44% (90#) of the initial values, respectively, while the irreversible stable viscosities of the residual impact are 72% (50#), 69% (70#), and 60% (90#) of the initial values, respectively. As can be seen from this, road asphalt exhibits the same significant viscosity reduction effect as other viscous petroleum products such as heavy oil and residual oil mentioned in the introduction, and this effect is quite significant. The viscosity changes almost immediately upon application and cessation of ultrasound, but each requires a certain amount of time to reach a stable state. The inflection point times for reaching stability also differ significantly for the three different asphalt types. The 50# low-penetration asphalt, with its higher asphaltene content, changes rapidly, while the 90# asphalt, with its lower asphaltene content, takes relatively longer. Asphaltene content significantly influences the colloidal structure of road asphalt. These differences in colloidal structure lead to varying speeds of response to ultrasound.

[0037] 90-110℃ is the typical storage temperature of petroleum asphalt. The asphalt treated with ultrasound under typical conditions (105℃, 40kHz) was sealed in a 105℃ environment. The viscosity of three types of asphalt, No. 50, No. 70 and No. 90, at 105℃ was measured at 0h (after treatment, the asphalt was kept warm in a homemade ultrasonic steel drum for 10min), 0.5h, 1h, 3h, 6h, 12h, 24h and 48h respectively according to the T0625 standard rotational viscosity test method. Figure 6 The data shown in Figure 2 demonstrate the effect of storage time after ultrasonic treatment on viscosity changes. After treatment, the viscosity of the treated asphalt increases slightly within 3 to 6 hours of storage at 105°C, increasing by 9-12% relative to the initial storage time. After 6 hours, there is no significant change, with the viscosities at these times reaching 78% (50#), 76% (70#), and 72% (90#) of the pre-treatment values, respectively. This phenomenon indicates that the decrease in high-temperature viscosity after treatment cannot be recovered through long-term storage, and this irreversible viscosity change is inevitably related to changes in chemical composition or structure caused by ultrasonic treatment.

[0038] The ultrasonic cavitation effect is the fundamental reason for the change in the chemical properties of the treated petroleum products, and the power ultrasonic frequency and the viscosity of the treated liquid (temperature for asphalt) are the two most significant factors affecting the cavitation threshold. A two-variable crossover test of ultrasonic frequency (28kHz, 40kHz, 52kHz) and treatment temperature (90-120℃, step size 10℃, and 105℃ in Example 3 and Example 4) was designed, and the dynamic change of viscosity was tested according to the test method of Example 3. The maximum viscosity reduction rate and the residual viscosity reduction rate were extracted respectively, as shown in Figure 3. Figure 7-9 As shown, the maximum viscosity reduction rate and the residual viscosity reduction rate are the ratios of the viscosity change value under the maximum impact state and the residual impact state in Example 3 to the initial viscosity value without treatment, respectively.

[0039] Comparing the images of maximum viscosity reduction (a, b, c) and residual viscosity reduction (d, e, f) reveals that a combination of treatment frequency and temperature causes peaks in the curves. Using software to track the peaks, the maximum viscosity reductions for the different asphalts were 50.9% (50#), 53.3% (70#), and 56.3% (90#), respectively, while the residual viscosity reductions were 36.7% (50#), 38.6% (70#), and 39.7% (90#), respectively. Further observation revealed that the ultrasonic frequency corresponding to the peaks was 40 kHz regardless of the treatment temperature; the temperatures corresponding to the peaks of the maximum viscosity reduction were 120°C (50#), 110°C (70#), and 105°C (90#), respectively; and the temperatures corresponding to the peaks of the residual viscosity reduction were the same or similar to those of the maximum viscosity reduction. The experimental phenomena show that asphalt, like other petroleum products, is dependent on ultrasonic treatment conditions. Under a certain power, there is an optimal combination of frequency and viscosity (temperature) to maximize the response. When the treatment time is sufficient to reach a stable state, the viscosity reduction rate reaches a peak.

[0040] According to the test method of Example 3, the glass slide of the asphalt sample was observed using a 400x optical transmission microscope, and the collected photos are as follows: Figure 10 As shown. Microscopic images at the same magnification show that before ultrasonic treatment, clusters of large asphaltene aggregates were prevalent in the three asphalts, but after treatment, they were clearly homogenized and dispersed into small particles. The mechanical vibration effect and cavitation effect synergistically disrupted the chemical bonds within the asphaltene micelles, causing the original macromolecular aggregates to disaggregate and disperse, converting them into relatively lightweight components. The deaggregation effect, or vibration agitation, is most pronounced when ultrasound is applied, and cracking reactions continue. When the chemical reaction reaches equilibrium, the viscosity of the molten asphalt is reduced to its maximum value without significant change. After the ultrasonic treatment is stopped, the chemical structure is restructured, and some components undergo reverse oxidation reactions, but they cannot fully recover their initial state.

[0041] Specifically, the viscosity of typical No. 90 asphalt at 135°C can be reduced by 60-70% after 10 minutes of ultrasonic treatment at an intensity of 0.6 W / cm². Viscosity recovers rapidly within the first 3-4 minutes of heat preservation and then slows, but an irreversible residual effect persists after 6 hours (at which point the viscosity is relatively reduced by 30-40%). Furthermore, due to short-term aging during mixing and chemical reorganization after cooling, the residual ultrasonic viscosity effect has minimal impact on the engineering properties of the solid asphalt at room and low temperatures after mixing. This significant reduction in high-temperature viscosity during construction, with minimal impact on service life, meets the requirements of warm-mix technology.

[0042] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for reducing viscosity of asphalt warm mix, characterized in that: The following steps are involved: First, the asphalt is ultrasonically treated in a molten state, and then the asphalt mixture is mixed at a lower temperature than hot mixing. The ultrasonic treatment method is to install an ultrasonic transducer on the asphalt carrier and then apply ultrasonic waves; the ultrasonic treatment time is 3 to 10 minutes; the sound intensity of the ultrasonic wave is ≥ 0.5W / cm 2 .

2. The method according to claim 1, characterized in that The asphalt pipeline is the last section of the asphalt pipeline before entering the mixing tower.

Images