Self-healing asphalt concrete under microwave action and preparation method thereof

Abstract

The present invention provides a method for preparing asphalt concrete that can rapidly heat up and self-heal under the action of microwaves. The microwave self-healing asphalt concrete is prepared from steel slag aggregate, steel slag powder, and microwave-absorbing modified asphalt, with the proportions ranging from 83.8% to 89.6% by weight, steel slag powder from 2.3% to 7.9% by weight, and microwave-absorbing modified asphalt from 2.8% to 12.8% by weight. The coarse and fine steel slag aggregates, steel slag powder, and microwave-absorbing asphalt are mixed to form the asphalt concrete. The asphalt concrete's loss factor is improved under microwaves. When microwaves act on a damaged pavement surface of the microwave self-healing asphalt concrete, the steel slag aggregate, steel slag powder, and microwave-absorbing modified asphalt experience dielectric and magnetic losses. The asphalt concrete converts the microwave electromagnetic energy into thermal energy, and by heating for a certain period of time, the asphalt concrete is rapidly and evenly heated to 45°C to 85°C. The thermal repair effect of the asphalt is utilized to achieve rapid self-healing of the asphalt concrete.

Description

Technical Field

[0001] The present invention belongs to the field of material technology, and in particular relates to self-healing asphalt concrete under the action of microwaves and a preparation method thereof. Background Art

[0002] With my country's growing traffic volume and the prevalence of heavy and overloaded vehicles, asphalt pavements often develop early signs of wear and tear, such as rutting, potholes, and cracks, just a few years after opening. Asphalt possesses a certain degree of self-healing ability, but this process is slow under natural conditions and cannot effectively repair cracks and other defects. Heating asphalt behaves like a near-Newtonian fluid, significantly enhancing its flow properties. This allows it to close microcracks and reattach previously detached aggregates, achieving self-healing of the asphalt mixture and extending the pavement's service life.

[0003] Currently, most asphalt self-repair methods, both domestically and internationally, are based on direct heating, electromagnetic heating, infrared radiation heating, and microwave heating. Microwave heating, with its advantages over other heating methods, such as fast heating, no hysteresis, and uniform temperature field, has become a research hotspot in self-repair technology.

[0004] Patent CN 202210788958 proposes an absorbing asphalt mixture that can quickly repair cracks in asphalt pavement and its preparation method. The absorbing materials are carbonyl iron powder and nickel-zinc ferrite powder. Although magnetic metal powder or ferrite has good wave absorption performance, magnetic metal powder is easy to corrode, has poor wettability with asphalt, and is expensive, so it is not suitable for large-scale use in asphalt mixtures; Patent CN 202110535953 proposes a method based on carbon nanotube / graphene / rubber composite modification to achieve electromagnetic induction self-healing, which can effectively improve the self-healing ability of asphalt, but this method is expensive and has problems such as large limitations of electromagnetic induction heating technology. Therefore, there is an urgent need for a self-healing asphalt with a simple preparation process, stable products and low cost. Summary of the Invention

[0005] The present invention aims to overcome the existing problems of the prior art by improving the dielectric and magnetic loss of asphalt concrete to microwaves, converting microwave electromagnetic energy into thermal energy, and enabling rapid heating and self-healing of asphalt concrete under the action of microwaves. This improves the self-healing properties of the prepared asphalt material while also ensuring that the asphalt concrete exhibits both good high- and low-temperature performance.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a self-healing asphalt concrete under the action of microwaves, which is prepared from the following raw materials: 83.8% to 89.6% by weight of coarse and fine aggregates of steel slag, 2.3% to 7.9% by weight of steel slag powder, and 2.8% to 12.8% by weight of microwave-absorbing modified asphalt, the total mass of which satisfies 100%;

[0008] A second aspect of the present invention provides a method for preparing the self-healing asphalt concrete under the action of microwaves, comprising the following steps: mixing the microwave-absorbing modified asphalt with coarse and fine steel slag aggregate and steel slag powder according to the above-mentioned proportions, then heating to 185-195°C and mixing for 120-200s to obtain an asphalt mixture, then casting and molding the asphalt mixture at 170-175°C using microwave heating, and curing the mixture to obtain the asphalt mixture;

[0009] Furthermore, the method for preparing the self-healing asphalt concrete under the action of microwaves comprises the following steps:

[0010] S1: heating the wave-absorbing modified asphalt to 155° C. to 180° C. according to the above mass ratio;

[0011] S2: heating the steel slag coarse and fine aggregates to 180-190° C. according to the above mass ratio; preferably, heating to 185° C.;

[0012] S3: Turn on the stirring pot, add the steel slag coarse and fine aggregates and steel slag powder in sequence, stir at 180-190°C for 80-120s, then add the wave-absorbing modified asphalt, continue stirring at 180-190°C for 90-150s to obtain an asphalt mixture, then cast and shape it at 170-175°C, and let it stand for at least 24 hours to obtain the asphalt mixture; preferably, add the steel slag coarse and fine aggregates and steel slag powder in sequence, stir at 185°C for 90s; preferably, add the wave-absorbing modified asphalt and stir for 180s; preferably, the casting temperature is 170-175°C;

[0013] Furthermore, the preparation method of the microwave-absorbing modified asphalt comprises the following steps: reacting styrene-butadiene-styrene (i.e., SBS), de-crosslinked rubber, and a microwave-absorbing modifier in an internal mixer to obtain an asphalt modifier having microwave-absorbing properties; then blending the asphalt modifier with a base asphalt in a high-speed shear disperser, adding a stabilizer and a compatibilizer, and performing shear stirring to obtain the microwave-absorbing modified asphalt;

[0014] Furthermore, the mass ratio of the SBS: decrosslinked rubber: absorbing modifier is (0-50): (20-60): (5-20);

[0015] Furthermore, the Mooney viscosity of the de-crosslinked rubber is 10 to 40, and the sol content is 40% to 60wt%;

[0016] Furthermore, the absorbing modifier is selected from one or more of pyrolyzed carbon black, polyaniline, polypyrrole, silicon nitride, graphite, and recycled carbon fiber;

[0017] Furthermore, the base asphalt grade is 70# or 90#;

[0018] Furthermore, the stabilizer is sulfur;

[0019] Furthermore, the compatibilizer is rubber oil or aromatic oil;

[0020] Furthermore, the mass ratio of the matrix asphalt, the wave absorbing modifier, the stabilizer, and the compatibilizer is: 100: (10-25): (0.5-3): (1-4);

[0021] Furthermore, the reaction temperature in the internal mixer is 60-140° C., and the reaction time is 5-15 min;

[0022] Furthermore, the stirring speed of the high-speed shearing machine is 3000-5000 r / min, the shear stirring temperature is 150-200°C, and the stirring time is 30-60 min; further preferably, the stirring speed of the high-speed shearing machine is 4000 r / min, the shear stirring temperature is 180°C, and the stirring time is 40 min;

[0023] Beneficial effects

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The present invention prepares modified asphalt with good microwave absorption capacity by compounding polyaniline, polypyrrole, silicon nitride and other microwave absorbing modifiers with SBS and de-crosslinked rubber, and shear-blending them with matrix asphalt. At the same time, it has good high and low temperature performance and solves the problems of poor wettability and high cost of absorbing asphalt prepared from magnetic metal powder or ferrite. The constructed microwave absorbing asphalt helps to improve the service life of asphalt mixture performance;

[0026] (2) The raw materials of the present invention use steel slag coarse and fine aggregates and steel slag powder to replace ordinary aggregates and mineral powder, which improves the loss factor of asphalt concrete under microwaves. When microwaves act on the damaged pavement of the micro self-healing asphalt concrete, both the aggregates and the asphalt have dielectric loss and magnetic loss to the microwaves. The asphalt concrete converts the electromagnetic energy of the microwaves into thermal energy. After heating for a certain period of time, the asphalt concrete is quickly and evenly heated to 45-85°C. The thermal repair effect of asphalt is utilized to achieve rapid self-healing of the asphalt concrete. At the same time, the asphalt concrete utilizes the steel slag solid waste from the metallurgical industry, solving the problem of handling large-scale industrial solid waste.

[0027] (3) The present invention does not require a complex preparation process and does not use electromagnetic heating equipment for heating and self-healing, thus solving the problems of the existing self-healing asphalt, such as the complicated preparation process, the large limitations of electromagnetic heating technology, and the high cost. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention.

[0029] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0030] Example 1

[0031] (1) Preparation of wave-absorbing modified asphalt

[0032] S11: SBS, de-crosslinked rubber (Mooney viscosity of 20, sol content of 50wt%), and wave-absorbing modifier polypyrrole are mixed in a mass ratio of 25:40:11, and reacted in an internal mixer at 120°C for 8 minutes until the torque is balanced, thereby obtaining an asphalt modifier with wave-absorbing properties; S12: 1000g of 70# matrix asphalt is weighed into a round iron can, and heated to 160°C using an electric heating jacket to completely melt it; S13: The stirring speed of the high-speed shear disperser is set to 4000r / min, 150g of the asphalt modifier with wave-absorbing properties prepared in S11 is added to 1000g of 70# matrix asphalt and blended, and 10g of stabilizer sulfur and 12g of rubber oil are added at the same time, and shear stirring is performed. The shear stirring temperature is 180°C and the stirring time is 40min, thereby obtaining the wave-absorbing modified asphalt;

[0033] (2) Preparation of self-healing asphalt concrete

[0034] AC-13 grading is adopted, and the raw materials are selected according to the proportion. The coarse and fine aggregates of steel slag account for 84.6wt% (among the coarse and fine aggregates of steel slag, the 9.5-16mm grade steel slag aggregate accounts for 38.9% of the total raw materials, the 4.75-9.5mm grade steel slag aggregate accounts for 30.9% of the total raw materials, the 2.36-4.75mm grade steel slag aggregate accounts for 5.1% of the total raw materials, and the 0-2.36mm grade steel slag aggregate accounts for 9.7% of the total raw materials), steel slag powder accounts for 7.9%, and the wave-absorbing modified asphalt accounts for 7 .5%, heat the coarse and fine aggregates of steel slag to 185°C, heat the wave-absorbing modified asphalt to 165-170°C, start the stirring pot, add the coarse and fine aggregates and steel slag powder in the above proportions, stir at 185°C for 90s, add the wave-absorbing modified asphalt in proportion, stir for 120s to obtain an asphalt mixture, and then cast and form a large rutting plate at 170-175°C. After standing for 24 hours, cut the rutting plate to obtain a four-point bending beam for fatigue test.

[0035] The healing effect of beams after microwave heating was tested through four-point bending fatigue tests at 15°C and 850με. It was found that after fatigue loading to a 50% decrease in stiffness modulus, rapid microwave heating to 65-70°C, and stabilization for three hours, the average fatigue life extension (i.e., the ratio of the fatigue life of the healed beam to the fatigue life before healing) was 153.3%, and the bending stiffness modulus recovery (i.e., the ratio of the bending stiffness modulus recovered after healing to the bending stiffness modulus at fatigue failure) was 119.3%, demonstrating that rapid thermal repair of asphalt concrete can be achieved.

[0036] Example 2

[0037] (1) Preparation of wave-absorbing modified asphalt

[0038] S11: SBS, de-crosslinked rubber (Mooney viscosity of 30, sol content of 45wt%), silicon nitride, and polypyrrole are mixed in a mass ratio of 50:40:10:10, and the mixture is reacted in an internal mixer at 140°C for 7 minutes until the torque is balanced, thereby obtaining an asphalt modifier with wave-absorbing properties; S12: 1000g of 70# matrix asphalt is weighed and placed in a round iron can, and heated to 160°C using an electric heating jacket to completely melt it; S13: The stirring speed of the high-speed shear disperser is set to 5000r / min, 200g of the asphalt modifier with wave-absorbing properties prepared in S11 is added to 1000g of 70# matrix asphalt and blended, and 20g of sulfur and 15g of rubber oil as stabilizers are added at the same time, and shear stirring is performed. The shear stirring temperature is 180°C and the stirring time is 50min, thereby obtaining a modified asphalt with wave-absorbing function;

[0039] (2) Preparation of self-healing asphalt concrete

[0040] AC-13 grading is adopted, and the raw materials are selected according to the proportion. The coarse and fine aggregates of steel slag account for 86.0wt% (among the coarse and fine aggregates of steel slag, the 9.5-16mm grade steel slag aggregate accounts for 38.8% of the total raw materials, the 4.75-9.5mm grade steel slag aggregate accounts for 32.5% of the total raw materials, the 2.36-4.75mm grade steel slag aggregate accounts for 5.6% of the total raw materials, and the 0-2.36mm steel slag aggregate accounts for 9.1% of the total raw materials), steel slag powder accounts for 7.9%, and the wave absorbing material accounts for 1. The mixture was stirred at 170-175°C for 24 hours and the rutting plate was cast and formed into a large rutting plate. After standing for 24 hours, the rutting plate was cut into four-point bending beams for fatigue test.

[0041] The healing effect of beams after microwave heating was tested in a four-point bending fatigue test at 15°C and 850με. The results showed that after fatigue loading to a 50% decrease in the stiffness modulus, rapid microwave heating to 65-70°C, and stabilization for three hours, the average fatigue life extension (i.e., the ratio of the fatigue life of the healed beam to the fatigue life before healing) was 168.4%, and the flexural modulus recovery (i.e., the ratio of the flexural modulus recovery value after healing to the flexural modulus at fatigue failure) was 125.6%, demonstrating that rapid thermal repair of asphalt concrete can be achieved.

[0042] Example 3

[0043] (1) Preparation of wave-absorbing modified asphalt

[0044] S11: SBS, de-crosslinked rubber (Mooney viscosity of 40, sol content of 40wt%), silicon nitride, and polyaniline are mixed in a mass ratio of 50:40:5:10, and the mixture is reacted in an internal mixer at 120°C for 10 minutes until the torque is balanced, thereby obtaining an asphalt modifier with wave-absorbing properties; S12: 1000g of 70# matrix asphalt is weighed and placed in a round iron can, and heated to 160°C using an electric heating jacket to completely melt it; S13: The stirring speed of the high-speed shear disperser is set to 5000r / min, 210g of the asphalt modifier with wave-absorbing properties prepared in S11 is added to 1000g of 70# matrix asphalt and blended, and 20g of stabilizer sulfur and 15g of rubber oil are added at the same time, and shear stirring is performed. The shear stirring temperature is 180°C and the stirring time is 50min, thereby obtaining a modified asphalt with wave-absorbing function;

[0045] (2) Preparation of self-healing asphalt concrete

[0046] AC-13 grading is used, and the raw materials are selected according to the proportion. The coarse and fine aggregates of steel slag account for 87.6wt% (among the coarse and fine aggregates of steel slag, the 9.5-16mm grade steel slag aggregate accounts for 38.8% of the total raw materials, the 4.75-9.5mm grade steel slag aggregate accounts for 31.5% of the total raw materials, the 2.36-4.75mm grade steel slag aggregate accounts for 5.2% of the total raw materials, and the 0-2.36mm grade steel slag aggregate accounts for 9.1% of the total raw materials), steel slag powder accounts for 7.0%, and the wave absorbing material is used as the raw material. The mixture was stirred at 170-175°C for 24 hours and the rutting plate was cast and formed. After standing for 24 hours, the rutting plate was cut into four-point bending beams for fatigue test.

[0047] The healing effect of beams after microwave heating was tested through four-point bending fatigue tests at 15°C and 850με. It was found that after fatigue loading to a 50% decrease in stiffness modulus, rapid microwave heating to 65-70°C, and stabilization for three hours, the average fatigue life extension (i.e., the ratio of the fatigue life of the healed beam to the fatigue life before healing) was 153.1%, and the bending stiffness modulus recovery (i.e., the ratio of the bending stiffness modulus recovered after healing to the bending stiffness modulus at fatigue failure) was 119.3%, demonstrating that rapid thermal repair of asphalt concrete can be achieved.

[0048] Comparative Example 1

[0049] (1) Weigh 1000 g of 70# base asphalt in a round iron can and heat it to 160°C using an electric heating mantle to completely melt it. Set the high-speed shear disperser speed to 4000 r / min, add 150 g of SBS modifier material and blend it with 1000 g of 70# base asphalt. Simultaneously add 10 g of stabilizer sulfur and 12 g of rubber oil, and shear stirring is carried out at 160°C for 50 min to obtain SBS modified asphalt.

[0050] (2) Using AC-13 grading, the mass percentage of each raw material is as follows: coarse and fine aggregates account for 83.1% (of which 9.5-16 mm grade aggregates account for 33.7%, basalt; 4.75-9.5 mm grade aggregates account for 34.2%, basalt; 2.36-4.75 mm grade aggregates account for 5.3%, limestone; 0-2.36 mm grade aggregates account for 9.9%, limestone), limestone powder 2.3%, SBS modified asphalt 4.6%, soft ferrite powder 8.1%, fiber 0.3%; the coarse and fine aggregates are heated To 185℃, the composite modified asphalt is heated to 180-185℃, the stirring pot is turned on, and coarse and fine aggregates, fibers, and SBS modified asphalt are added in sequence. After stirring at 185℃ for 90s, limestone powder and soft ferrite powder are added and stirred for 180s. Large rutting plates are formed at 170-175℃. After standing for 24 hours, the rutting plates are cut to obtain four-point bending beams for fatigue testing. Through the four-point bending fatigue test, the healing effect of the beams after microwave heating is tested at 15℃ and 850με.

[0051] It was found that after the beam was fatigue loaded until the stiffness modulus dropped by 50%, it was rapidly heated to 65-70°C in a microwave and left to stand for 3 hours. The average fatigue life extension rate of the beam after healing (that is, the ratio of the fatigue life of the specimen when it was again subjected to the same fatigue damage after healing to the fatigue life before healing) was 116.8%, and the bending stiffness modulus recovery rate (that is, the ratio of the bending stiffness modulus recovery value after the specimen was healed to the bending stiffness modulus of the specimen at fatigue damage) was 103.7%, indicating that rapid thermal repair of asphalt concrete can be achieved.

[0052] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A self-healing asphalt concrete under microwave action, characterized in that: It is prepared from the following raw materials: 83.8%~89.6wt% of steel slag coarse and fine aggregates, 2.3%~7.9wt% of steel slag powder, and 2.8%~12.8wt% of wave-absorbing modified asphalt, with the total mass meeting 100%; in, The preparation method of the wave-absorbing modified asphalt comprises the following steps: reacting styrene-butadiene-styrene, de-crosslinked rubber and a wave-absorbing modifier in an internal mixer to obtain an asphalt modifier with wave-absorbing performance; then blending the asphalt modifier with a base asphalt in a high-speed shear disperser, adding a stabilizer and a compatibilizer, and performing shear stirring to obtain the wave-absorbing modified asphalt; wherein the base asphalt is 70# or 90#; the Mooney viscosity of the de-crosslinked rubber is 10-40, and the sol content is 40%-7 0wt%, the absorbing modifier is selected from one or more of pyrolysis carbon black, polyaniline, polypyrrole, silicon nitride, graphite, and recycled carbon fiber; the stabilizer is sulfur; the compatibilizer is rubber oil or aromatic oil; the mass ratio of styrene-butadiene-styrene: decrosslinked rubber: absorbing modifier is 0~50:20~60:5~20; the mass ratio of the matrix asphalt, absorbing modifier, stabilizer, and compatibilizer is: 100: (10~25): (0.5~3): (1~4).

2. The self-healing asphalt concrete under microwave action according to claim 1, characterized in that: The reaction temperature in the internal mixer is 60-140° C., and the reaction time is 5-15 min.

3. The self-healing asphalt concrete under microwave action according to claim 1, characterized in that: The stirring speed of the high-speed shearing disperser is 3000-5000 r / min, the shear stirring temperature is 150-200° C., and the stirring time is 30-60 min.

4. The self-healing asphalt concrete under microwave action according to claim 1, characterized in that: The stirring speed of the high-speed shearing disperser is 4000 r / min, the shear stirring temperature is 180° C., and the stirring time is 40 min.

5. A method for preparing self-healing asphalt concrete under microwave action according to any one of claims 1 to 4, characterized in that: The following steps are involved: The absorbing modified asphalt is mixed with steel slag coarse and fine aggregate and steel slag powder according to the above ratio, and then heated to 185-195° C. and mixed for 120-200 seconds to obtain an asphalt mixture, which is then poured and formed at 170-175° C. using microwave heating and allowed to stand for at least 24 hours.

6. The method for preparing self-healing asphalt concrete under microwave action according to claim 5, characterized in that: The method for preparing self-healing asphalt concrete under microwave action comprises the following steps: S1: heating the wave-absorbing modified asphalt to 155° C. to 180° C. according to the mass ratio; S2: heating the coarse and fine aggregates of the steel slag to 180-190° C. according to the mass ratio; S3: Turn on the mixing pot, add the steel slag coarse and fine aggregates and steel slag powder in sequence, stir at 180-190°C for 80-120s, then add the wave-absorbing modified asphalt, continue stirring at 180-190°C for 160-200s to obtain the asphalt mixture, and then pour and form it at 170-175°C, and let it stand for at least 24 hours.

7. The method for preparing self-healing asphalt concrete under microwave action according to claim 6, characterized in that: In S2, the heating temperature is increased to 185°C.

8. The method for preparing self-healing asphalt concrete under microwave action according to claim 6, characterized in that: In S3, the steel slag coarse and fine aggregates and steel slag powder are added in sequence and stirred at 185° C. for 90 seconds.

9. The method for preparing self-healing asphalt concrete under microwave action according to claim 6, characterized in that: In S3, add the wave-absorbing modified asphalt and continue stirring for 180 seconds.

10. The method for preparing self-healing asphalt concrete under microwave action according to claim 6, characterized in that: In S3, the pouring temperature is 170-175°C.