A method for surface modification of RAP material using coal gangue micro powder

Abstract

The present invention discloses a method for surface modification of RAP material using coal gangue powder. The coal gangue is calcined and activated at a high temperature of 600-800 °C, and SiO 2 nano-particles are added during the preparation of emulsified asphalt. 1-5 parts by weight of activated coal gangue powder, 75-90 parts by weight of RAP material and 5-15 parts by weight of stone materials are premixed; then 2-5 parts by weight of water are added for mixing, and then 1-4 parts by weight of cement and 3-8 parts by weight of emulsified asphalt are added, and mixing is carried out to obtain the product. The activation of coal gangue endows it with higher reactivity and adsorption capacity. Adding SiO 2 nano-particles in the emulsified asphalt can form more chemical bonds in the emulsified asphalt, improving the strength and durability of the material. This method utilizes the adsorption performance and pozzolanic active components of coal gangue to change the reaction inertness between the RAP material and the emulsified asphalt, increase the adsorption strength between the two, and further improve the adhesion performance, high-temperature rheological performance and durability of the mixture.

Description

Technical Field

[0001] The present invention belongs to the technical field of the recycling of normal temperature recycled asphalt mixture and cold recycled asphalt mixture, and particularly relates to a method for surface modification of RAP material by using coal gangue powder. Background Art

[0002] With the development of society and the continuous advancement of infrastructure construction, the demand for road construction materials is increasing day by day. As a commonly used road construction material, emulsified asphalt is widely used due to its good adhesion, high temperature stability and durability. However, in practical applications, the problem of reaction inertia between emulsified asphalt and reclaimed asphalt pavement (RAP) materials has always existed, which limits the further application of RAP materials in road construction. Therefore, how to improve the adsorption strength between RAP materials and emulsified asphalt, and improve the adhesion performance, high temperature rheological properties and durability of the mixture, is an urgent problem to be solved in the current road construction field.

[0003] In recent years, some studies have tried to use industrial waste, such as coal gangue, to improve the reaction performance between RAP materials and emulsified asphalt. As a common industrial waste, coal gangue has good adsorption performance and pozzolanic activity, which can provide the required physical and chemical modification for the mixture. During the preparation of the mixture, the microporous structure and surface active components of coal gangue can effectively adsorb the oil components and active components in emulsified asphalt, thereby promoting the full mixing between RAP materials and emulsified asphalt. The pozzolanic active components in coal gangue will react with the nanoparticles in emulsified asphalt. The pozzolanic active components are mainly composed of oxides such as silicon, aluminum, and iron. These components can chemically react with the nanoparticles in emulsified asphalt under certain conditions to form compounds such as silicates and aluminates. These compounds can effectively improve the adhesion performance, high temperature rheological properties and durability of the mixture. This practice of using industrial waste for road construction not only facilitates the recycling of resources, but also helps to reduce environmental pollution and project costs. However, how to effectively utilize these characteristics of coal gangue to achieve enhanced adsorption between RAP materials and emulsified asphalt still faces many technical challenges.

[0004] The difficulties of the prior art mainly include: 1) How to effectively utilize the adsorption properties of coal gangue to improve the reaction inertness between RAP material and emulsified asphalt, which involves the regulation of the surface properties of coal gangue and the understanding of the interaction mechanism with RAP material and emulsified asphalt. 2) How to activate the pozzolanic active components in coal gangue to promote their reaction with the nanoparticles in emulsified asphalt to further improve the performance of the mixture. This requires an in-depth understanding of the mechanism of pozzolanic reaction and the ability to precisely control the reaction conditions. 3) How to optimize the formula and preparation process of the mixture to obtain the best performance. This requires an in-depth understanding of the interaction between various components, and at the same time requires a large number of experiments and tests to find the best formula and process conditions. Based on this, the present application is developed. Summary of the Invention

[0005] The object of the present invention is to overcome the defects of the prior art and provide a method for surface modification of RAP material using coal gangue fine powder, aiming to use coal gangue to improve the reaction performance between RAP material and emulsified asphalt to solve the deficiencies existing in the prior art. This method utilizes the adsorption properties and pozzolanic active components of coal gangue, can change the reaction inertness between RAP material and emulsified asphalt, increase the adsorption strength between the two, and further improve the adhesion performance, high-temperature rheological performance and durability of the mixture, thereby promoting the technological progress and sustainable development in the field of road construction.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A mixture for surface modification of RAP material using coal gangue fine powder is mainly made of raw materials with the following weight ratio: 1-5 parts of activated coal gangue powder, 75-90 parts of RAP material, 5-15 parts of stone, 2-5 parts of water, 1-4 parts of cement, and 3-8 parts of emulsified asphalt.

[0008] The above mixture for surface modification of RAP material using coal gangue fine powder is mainly made of raw materials with the following weight ratio: 1-3 parts of activated coal gangue powder, 80-85 parts of RAP material, 7-10 parts of stone, 2-4 parts of water, 1-3 parts of cement, and 3-6 parts of emulsified asphalt.

[0009] Further, the stone is limestone gravel with a particle size of 10-30mm.

[0010] A method for surface modification of RAP material using coal gangue fine powder includes the following steps:

[0011] Step S1: Prepare emulsified asphalt: Heat the base asphalt in an oven to 130 - 150 °C and maintain it for 20 - 40 min. First, pour the soap solution into a colloid mill preheated to 70 - 80 °C, and then slowly pour in the heated asphalt while stirring to relieve the phenomenon of emulsion boiling caused by the addition of asphalt. After the addition of asphalt is completed, add SiO 2 nanoparticles, grind evenly to obtain emulsified asphalt, seal and store for later use;

[0012] Step S2: Premix 1 - 5 parts by weight of activated coal gangue powder, 75 - 90 parts by weight of RAP material, and 5 - 15 parts by weight of stone materials to obtain a premixed RAP material;

[0013] Step S3: Mix 2 - 5 parts by weight of water with the premixed RAP material, and then add 1 - 4 parts by weight of cement and 3 - 8 parts by weight of emulsified asphalt, and mix to obtain the product.

[0014] Specifically, in Step S1, the soap solution is prepared through the following steps: Stir and mix the emulsifier and hot water at 50 - 70 °C evenly in a beaker, and then add an appropriate amount of hydrochloric acid to adjust the pH to 2.0 - 2.5 to meet the acidic conditions required by the emulsifier, and that's it. Further, the emulsifier is an emulsifier for cold recycling. The emulsified asphalt is prepared using a German RINKMD - 1 type asphalt colloid mill.

[0015] Further limitation, adding SiO 2 nanoparticles during the preparation of emulsified asphalt can form more chemical bonds in the emulsified asphalt, improving the strength and durability of the material. Nano - SiO 2 has a very high specific surface area and a rich pore structure, which enables it to provide a large number of active sites and reaction interfaces. When nano - silica is mixed with coal gangue, these active sites and reaction interfaces can promote the chemical reactions on the surface of coal gangue, increasing its activity. In addition, the pore structure of nano - SiO 2 can also adsorb impurities and harmful substances in coal gangue, improving its quality. The surface of nano - silica contains rich hydroxyl (-OH) groups, which makes it have strong hydrophilicity and chemical activity. When nano - silica contacts with coal gangue, the hydroxyl groups can undergo chemical reactions with the polar groups on the surface of coal gangue to form chemical bonds. This chemical bonding can increase the activity of the surface of coal gangue and promote the progress of the reaction. The unsaturated bonds and hydroxyl groups on the surface of nano - SiO 2 particles can also undergo chemical reactions with the components in asphalt to form chemical bonds, thereby enhancing the adhesion and durability of asphalt. Nano - SiO 2It also has a high adsorption capacity and can effectively absorb the oil in asphalt, thereby increasing the viscosity and stability of asphalt. At the same time, the nanoparticles can form chemical bonds with the modifier to form a dense network structure. This network structure can effectively improve the mechanical properties and durability of asphalt.

[0016] In the above method for surface modification of RAP material using coal gangue powder, by weight percentage, the asphalt addition amount is 60 - 65% of the weight of emulsified asphalt, the emulsifier addition amount is 2 - 5% of the weight of emulsified asphalt, SiO 2 The nanoparticle addition amount is 0.15 - 0.35% of the weight of emulsified asphalt, and the balance is hot water.

[0017] Activating coal gangue endows it with higher reactivity and adsorption capacity. Specifically, in step S2, the activated coal gangue powder is obtained through the following steps: placing coal gangue in an oven at 50 - 70 °C and drying it to constant weight, mechanically grinding it and then sieving it to make coal gangue powder, and then calcining it at 600 - 800 °C for 0.5 - 1 h to obtain the activated coal gangue powder. The obtained activated coal gangue powder after calcination should be premixed with RAP material and stone while it is still hot. The coal gangue powder is black and the loss on ignition is 30%. Before preparing the premixed RAP material, the coal gangue powder needs to be calcined at 700 ± 100 °C for 0.5 - 1 h for activation to endow it with higher reactivity and adsorption capacity. The thermal activation of coal gangue is mainly for the activation of kaolinite in coal gangue. Kaolinite will undergo dehydroxylation in a high-temperature environment. The dehydroxylation causes the deformation of the tetrahedral sheet and octahedral sheet, making the regularly arranged structure distorted and generating a large number of broken bonds, which makes the structure of kaolinite tend to be disordered, thereby increasing the activity of coal gangue. Moreover, during this process, there are also changes in the coordination number of Al and the polymerization degree of silicon-oxygen tetrahedra. During the calcination process, aluminum transforms from a high coordination number to a low coordination number, and silicon dioxide transforms from a crystalline state to an amorphous state, that is, using high temperature to change the chemical state of the stable silicon-aluminum crystal under normal temperature and pressure to make it a stable state under high-temperature conditions, so as to have activity when returning to normal temperature.

[0018] It is further specified that the activated coal gangue powder obtained by high-temperature calcination should be premixed with RAP material and stone while it is still hot. The coal gangue powder in a high-temperature state is rapidly mixed with RAP material and stone under normal temperature conditions. While the heat energy activates the chemical properties of coal gangue, it also improves the binding effect with the asphalt on the surface of RAP material, making the surface properties of RAP material closer to polarity and having a better wrapping property with emulsified asphalt.

[0019] Furthermore, although the addition of coal gangue powder can improve certain properties of asphalt mixtures, excessive or improper addition may lead to uneven mixing, thus affecting its durability. Some components in coal gangue powder may chemically react with asphalt, accelerating asphalt aging and reducing the durability of the mixture. In addition, the addition of coal gangue powder increases the viscosity of asphalt mixtures and reduces their fluidity, thus affecting their workability in construction and paving. This may make it difficult to achieve the desired uniformity and compactness during paving. Therefore, according to the control requirements of cold recycling and workability, it is necessary to monitor the properties of emulsified asphalt mixtures, adjust the premixing ratio of coal gangue powder and RAP material, and optimize the mixing and forming time. For this reason, the design examples of this patent are comprehensively compared and analyzed with the intention of finding the best premixing ratio and mixing time.

[0020] Further, in step S2, premixing is carried out by mixing for 2 - 5 minutes; in step S3, the mixing time is 0.5 - 2 minutes.

[0021] In order to increase the adsorption strength between RAP material and emulsified asphalt and improve the adhesion performance, high-temperature rheological properties and durability of the mixture, the present invention provides a preparation method of a mixture using coal gangue fine powder to modify the surface of RAP material. This method utilizes the adsorption property of coal gangue to change the reaction "inertness" between RAP material and emulsified asphalt and increase the adsorption strength between RAP material and emulsified asphalt; and utilizes the pozzolanic active components of coal gangue to react with SiO 2 nanoparticles in emulsified asphalt, thereby further improving the adhesion performance, high-temperature rheological properties and durability of the mixture.

[0022] The innovation points of this application are mainly reflected in: 1. Calcination activation of coal gangue powder: Utilizing the pozzolanic activity and adsorption properties of coal gangue, it is used as an additive for emulsified asphalt cold recycled mixture. First, heat-activate the coal gangue powder to make it have higher reactivity and adsorption capacity. 2. Thorough mixing of high-temperature coal gangue powder and RAP material: The high-temperature coal gangue powder is rapidly mixed with the RAP material at normal temperature (or a certain temperature). While the heat energy activates the chemical properties of the coal gangue, it also improves the binding effect with the surface asphalt of the RAP material. This makes the surface properties of the RAP material closer to polarity, with better wrapping property with emulsified asphalt. The distribution of coal gangue powder is more uniform. 3. Adding reactive nanoparticles to emulsified asphalt: (Search for reactive nanoparticles paired with coal gangue) Add reactive nanoparticles to emulsified asphalt. The coal gangue powder adsorbed on the surface of the RAP material has pozzolanic activity and can form more chemical bonds in the emulsified asphalt, improving the strength and durability of the material. 4. Control of workability: According to the control requirements of the workability of cold recycling, monitor the properties of the emulsified asphalt mixture, adjust the premixing ratio of coal gangue powder and RAP material, and optimize the mixing and forming time (too much surface coating, too high activity, too fast reaction, and the workability cannot meet the requirements).

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1) The present invention utilizes the pozzolanic activity and adsorption properties of coal gangue, taking it as an additive for emulsified asphalt cold recycled mixture. Through heating activation technology, the kaolinite in coal gangue undergoes dehydroxylation in a high-temperature environment, causing deformation of the tetrahedral sheet and octahedral sheet, distorting the regularly arranged structure, and generating a large number of broken bonds to make the structure of kaolinite tend to be disordered, thereby improving the activity of coal gangue. Since the RAP material has old asphalt compared with the new material (i.e., stone material), its surface shows an oily property, which leads to the fact that the RAP material is not easy to react with emulsified asphalt, and the demulsification time of the RAP material is longer than that of the new material. A longer demulsification time will result in an extended construction period and affect the traffic opening time. In addition, if the demulsification is too late, that is, the emulsified asphalt has not been completely demulsified after the mixture has been compacted, then the strength of the mixture will be affected because the asphalt fails to fully fill the voids between the aggregates, resulting in a decrease in the compactness and durability of the mixture. Too late demulsification may also cause an uneven asphalt film to form on the surface of the aggregates, leading to stress concentration when the mixture is stressed, thereby reducing its strength. Therefore, the present invention pre-mixes the calcined coal gangue powder with the RAP material while it is hot. The heat energy activates the chemical properties of the coal gangue and also improves the binding effect with the asphalt on the surface of the RAP material. The surface of coal gangue usually has a certain roughness and porous structure, which provides a large surface area, endowing it with good adsorption properties, changing the surface activity of the RAP material and making it closer to polarity. In the mixture, coal gangue can adsorb the water and asphalt components in the emulsified asphalt, thus affecting the dispersion state and stability of the emulsified asphalt. This adsorption effect will reduce the water content in the emulsified asphalt and accelerate the demulsification speed. At the same time, the porous structure on the surface of coal gangue may also provide a better dispersion site for the emulsified asphalt, making it more evenly distributed in the RAP material. Chemical reaction and interfacial activity: Coal gangue contains various active components, such as aluminum oxide (Al 2 0 3 ), silicon dioxide (SiO 2 ), and other oxides. These components will undergo chemical reactions such as acid-base reactions and ion exchanges with the components in the emulsified asphalt under certain conditions. These chemical reactions can change the components and structure of the emulsified asphalt, and thus affect its demulsification behavior. In addition, the active components in coal gangue may also improve the surface activity of the RAP material and enhance the interaction with the emulsified asphalt, thereby facilitating the demulsification process.

[0025] 2) In order to promote the reaction between coal gangue powder and emulsified asphalt and increase the stability and durability of the asphalt mixture, the present invention adds SiO 2 nano-particles to the emulsified asphalt. Nano-SiO 2It has a very high specific surface area and a rich pore structure, which enables it to provide a large number of active sites and reaction interfaces. When nano-silica is mixed with coal gangue, these active sites and reaction interfaces can promote the chemical reactions on the surface of coal gangue and increase its activity. In addition, the pore structure of nano-SiO 2 can also adsorb impurities and harmful substances in coal gangue and improve its quality. Due to its high specific surface area and pore structure, the tiny particles of nano-silica are easily adsorbed onto the surface of coal gangue. During the adsorption process, the active hydroxyl (-OH) groups on the surface of nano-silica have a preliminary interaction with the polar groups (such as carboxyl, hydroxyl, etc.) on the surface of coal gangue. After adsorption, the hydroxyl groups on the surface of nano-silica will be activated under the influence of the surface environment of coal gangue. The polar groups on the surface of coal gangue, such as carboxyl (-COOH), hydroxyl (-OH) or phenolic hydroxyl (-ArOH), etc., have partial positive or negative charges. When these groups approach the hydroxyl groups on the surface of nano-silica, electron transfer or polarization occurs between them, making the hydroxyl groups on the surface of nano-silica more active. The activated hydroxyl groups have higher reaction activity. Chemical reactions occur between the activated hydroxyl groups and the polar groups on the surface of coal gangue, forming chemical bonds such as hydrogen bonds and ether bonds. By forming chemical bonds, the interaction between nano-silica and coal gangue is enhanced, increasing the surface energy of coal gangue. The increase in surface energy means that the surface of coal gangue is more active and easier to react with other substances or adsorb other substances. The formation of chemical bonds generates new reaction sites on the surface of coal gangue. These sites can serve as the starting points for chemical reactions and promote chemical reactions with other substances. Therefore, the activity of coal gangue is improved, making it easier to participate in various chemical reaction processes. These new structures or functional groups can change the adsorption property of the surface of coal gangue. In addition to enhancing the bonding between coal gangue and asphalt, nano-SiO 2 particles also improve the performance of emulsified asphalt. Nano-SiO 2 particles have a small size effect and a high specific surface area, which means they can interact more effectively with asphalt molecules. When nano-SiO 2 particles are mixed with asphalt, they can penetrate into the gaps between asphalt molecules and fill the molecular chains, thereby enhancing the bonding force between the particles and the asphalt matrix. This enhanced bonding force not only improves the rutting resistance and stripping resistance of asphalt but also helps to improve the strength of asphalt mixtures. Secondly, the high elastic modulus and degradation temperature of nano-SiO 2 enable asphalt to maintain good performance even in high-temperature environments. Under high-temperature conditions, asphalt tends to soften and flow, resulting in rutting and deformation of the road surface. However, due to the high elastic modulus of nano-SiO 2 , it can resist this deformation and maintain the stability and durability of asphalt.

[0026] 3) When there is too much coating on the surface of the RAP material and the reaction is too fast, the workability of the asphalt mixture will not meet the requirements. According to the control requirements of the cold recycling workability, the present invention monitors the properties of the emulsified asphalt mixture, adjusts the premixing ratio of the coal gangue powder and the RAP material, and optimizes the mixing and forming time. Description of the Drawings

[0027] Figure 1 It is the process flow chart of the method of the present invention. Detailed Embodiments

[0028] The technical solutions of the present invention will be further introduced in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0029] In the following embodiments, the used stone material is limestone gravel with a particle size of 10 - 30 mm, which is a common commercially available product that can be purchased.

[0030] SiO 2 The nano - particles are purchased from Suzhou Kaifa New Material Technology Co., Ltd., in the form of solid powder, with a particle size of about 200 nm.

[0031] The soap solution is prepared through the following steps: The emulsifier and 60 °C hot water are stirred and mixed evenly in a beaker, and then an appropriate amount of hydrochloric acid is added to adjust the pH to 2.0 - 2.5 to obtain it. The emulsifier used is the cold recycling emulsifier KZW - 801 produced by Tianjin Kangzewei Technology Co., Ltd., and the emulsified asphalt is prepared by a German RINKMD - 1 type asphalt colloid mill.

[0032] Unless otherwise specified, the room temperature or normal temperature mentioned in the text refers to 25 ± 5 °C.

[0033] Examples 1 to 5

[0034] A mixture for surface modification of RAP material using coal gangue fine powder is mainly made of activated coal gangue powder, RAP material, stone material, water, cement and emulsified asphalt. The weight - part ratio of each raw material is shown in Table 1.

[0035] Table 1 Material Mixing Proportions (weight parts) of Different Examples

[0036]

[0037] A preparation method of the above - mentioned mixture for surface modification of RAP material using coal gangue fine powder (the process flow chart is as Figure 1 shown), which includes the following steps:

[0038] Step S1: Prepare emulsified asphalt: Heat the base asphalt in an oven to 140 °C and keep it for 30 min. First, pour the soap solution into a colloid mill preheated to 75 °C, and then slowly pour in the heated asphalt while stirring to relieve the phenomenon of emulsion boiling caused by the addition of asphalt. After the addition of asphalt is completed, add SiO 2 nano-particles, accelerate grinding for 1 minute to grind evenly, and then pour out to obtain emulsified asphalt, which is stored sealed for standby. Measured by weight percentage, the asphalt addition amount is 62% of the weight of the emulsified asphalt, the emulsifier addition amount is 3% of the weight of the emulsified asphalt, and the SiO 2 nano-particle addition amount is 0.25% of the weight of the emulsified asphalt, and the balance is hot water;

[0039] Step S2: Premix the activated coal gangue powder with the RAP material and the stone material. The premixing times of Examples 1, 2, and 3 are 120 s, 150 s, and 180 s respectively to obtain the premixed RAP material; the activated coal gangue powder is prepared through the following steps: Place the coal gangue in an oven at 60 °C and dry it to a constant weight, grind it mechanically and then pass it through a sieve to make coal gangue powder, and then calcine it at 700 °C for 45 min to obtain the activated coal gangue powder. The obtained activated coal gangue powder is premixed with the RAP material and the stone material while it is hot;

[0040] Step S3: Mix water with the premixed RAP material for about 1 min, then add cement and emulsified asphalt and mix for about 1 min to obtain the mixture.

[0041] Load the evenly mixed mixture into a standard test mold (standard compaction test mold: a cylinder with a diameter of 101.6 mm x 87 mm, an inner diameter of 101.6 mm + 0.2 mm, and a height of 87 mm + 0.1 mm. One base (with a diameter of about 120.6 mm) and one sleeve (with an inner diameter of 101.6 mm and a height of 70 mm + 0.4 mm) each), place it on a Marshall compactor, and compact the specimen 50 times on each side. Place the specimen together with the test mold on its side in a forced-draft oven at 60 °C and cure it to a constant weight and then take it out (the curing time is generally not less than 40 h), then immediately place it on the Marshall compactor and compact it 25 times on each side, then place it on its side on the ground, cool it at room temperature for at least 12 h, and then demold it.

[0042] Comparative Examples 1 and 2

[0043] The raw material ratios of the mixtures in Comparative Examples 1 and 2 are shown in Table 1, and their preparation methods refer to Example 1. The main difference in Comparative Example 1 is that no SiO 2 nano-particles are added during the preparation of emulsified asphalt. The main difference in Comparative Example 2 is that no activated coal gangue powder is added during the preparation of the mixture.

[0044] Comparative Example 3

[0045] The raw material ratios of the mixture described in Comparative Example 3 are shown in Table 1, and its preparation method refers to Example 1. The difference is that in step S2, after the activated coal gangue powder obtained by calcination is placed at room temperature, it is premixed with the RAP material and the stone material.

[0046] Comparative Example 4

[0047] The raw material ratios of the mixture described in Comparative Example 4 are the same as those in Comparative Example 3. The difference is that coal gangue is used to replace the activated coal gangue, that is, the coal gangue is placed in an oven at 60°C and dried to a constant weight, mechanically ground, and then sieved to make coal gangue powder, which is used directly without calcination activation treatment.

[0048] Cold recycled mixture specimens are prepared in accordance with the "Test Regulations for Bitumen and Bituminous Mixtures for Highway Engineering" (JTG E20 - 2011). By adjusting the premixing ratio of the coal gangue powder and the RAP material and optimizing the mixing and forming time to control its workability during construction, the splitting strength index is used to evaluate the anti-cracking ability of the mixture, and the freeze-thaw splitting strength ratio TSR is used to evaluate the anti-water damage ability of the mixture. The test results are shown in Table 2.

[0049] Table 2 Performance test results of different specimens

[0050]

[0051] It can be seen from the results in Table 2 that the freeze-thaw splitting strength of the mixture is affected by the premixing time. When the premixing time is 150 s, the final freeze-thaw splitting strength of the asphalt mixture is not significantly different from that at 180 s, but the early strength is significantly higher than the splitting strength at the mixing times of 120 s and 180 s. In addition, by comparing Example 2 with Comparative Example 1, it can be seen that the addition of SiO 2 nano-particles significantly improves the splitting strength of the mixture, which is mainly because of SiO 2The active groups on the surface of nanoparticles can react with the polar groups on the surface of coal gangue, greatly improving the reaction activity of coal gangue fine powder and the stability of emulsified asphalt mixture. By comparing Example 2 with Comparative Example 2, it can be seen that the addition of activated coal gangue significantly improves the later strength of the mixture, and increasing the content of coal gangue powder also increases the splitting strength of the mixture. This is because the surface of activated coal gangue powder has a porous structure, which can effectively adsorb the polar components in asphalt to form a stable structure, thereby improving the strength of asphalt mixture. After the coal gangue is activated, its activity is increased, further improving the reaction efficiency between coal gangue and asphalt and the strength of the mixture. When the proportion of coal gangue increases to 3 parts, the improvement of performance is no longer significant. Therefore, within a suitable range, the proportion of coal gangue powder should be increased as much as possible, and the pre-mixing proportion of 3 parts by weight is the best. By comparing Example 2 with Comparative Example 3, the performance of the mixture prepared by mixing coal gangue powder at high temperature is higher than that of the mixture mixed at normal temperature, indicating that the mixing effect of coal gangue powder and RAP material at high temperature is better than that at normal temperature. By comparing Example 2 with Comparative Example 4, the performance of the mixture mixed with activated coal gangue powder is significantly higher than that of the mixture mixed with unactivated coal gangue powder, indicating that the activation of coal gangue powder can effectively improve the performance of asphalt mixture.

[0052] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the principles of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A mixture for surface modification of RAP material using coal gangue powder, characterized in that: It is mainly made of the following raw materials in the following weight proportions: 1-5 parts of activated coal gangue powder, 75-90 parts of RAP material, 5-15 parts of stone material, 2-5 parts of water, 1-4 parts of cement and 3-8 parts of emulsified asphalt; The activated gangue powder is prepared by the following steps: placing the gangue in an oven at 50-70° C. to dry to constant weight, grinding and sieving to obtain gangue powder, and then calcining at 600-800° C. for 0.5-1 h to obtain activated gangue powder, and premixing the activated gangue powder with RAP material and stone while hot; The emulsified asphalt is prepared by the following steps: heating the asphalt to 130-150°C and maintaining the temperature for 20-40 minutes, pouring the soap solution into a colloid mill preheated to 70-80°C, and then pouring the heated asphalt while stirring. After the asphalt is added, adding SiO2 nanoparticles, grinding evenly, and obtaining emulsified asphalt.

2. The mixture of RAP material surface modified by using coal gangue powder as claimed in claim 1, characterized in that: The invention is mainly made of the following raw materials in proportion by weight: 1-3 parts of activated coal gangue powder, 80-85 parts of RAP material, 7-10 parts of stone material, 2-4 parts of water, 1-3 parts of cement and 3-6 parts of emulsified asphalt.

3. The mixture of RAP material surface modified by coal gangue powder as claimed in claim 1, characterized in that: The stone material is limestone crushed stone with a particle size of 10-30 mm.

4. A method for preparing a mixed material using coal gangue powder to modify the surface of RAP material as claimed in any one of claims 1 to 3, characterized in that: The steps include: Step S1: preparing emulsified asphalt: heating the asphalt to 130-150°C and maintaining the temperature for 20-40 minutes, pouring the soap solution into a colloid mill preheated to 70-80°C, and then pouring the heated asphalt into the mill while stirring. After the asphalt is added, adding SiO2 nanoparticles, grinding evenly, obtaining emulsified asphalt, and sealing and storing for later use; Step S2: premixing 1-5 parts by weight of activated gangue powder with 75-90 parts by weight of RAP material and 5-15 parts by weight of stone material to obtain a premixed RAP material; Step S3: Mix 2-5 parts by weight of water with the premixed RAP material, and then add 1-4 parts by weight of cement and 3-8 parts by weight of emulsified asphalt, and mix to obtain.

5. The method for preparing a mixture of RAP material surface modified by coal gangue powder as claimed in claim 4, characterized in that: In step S1, the soap solution is prepared by the following steps: the emulsifier is mixed evenly with 50-70° C. hot water, and then the pH is adjusted to 2.0-2.

5.

6. The method for preparing a mixture of RAP material surface modified by using coal gangue powder as claimed in claim 5, characterized in that: The emulsifier is an emulsifier for cold regeneration.

7. The method for preparing a mixed material using coal gangue powder to modify the surface of RAP material as claimed in claim 5, characterized in that: Measured in weight percentage, the amount of asphalt added is 60-65% of the weight of the emulsified asphalt, the amount of emulsifier added is 2-5% of the weight of the emulsified asphalt, the amount of SiO2 nanoparticles added is 0.15-0.35% of the weight of the emulsified asphalt, and the balance is hot water.

8. The method for preparing a mixed material using coal gangue powder to modify the surface of RAP material as claimed in claim 4, characterized in that: In step S2, the premixing is performed for 2-5 minutes; in step S3, the mixing time is 0.5-2 minutes.

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