Anti-stripping agent for acid aggregate, modified acid aggregate, and preparation method and application of modified acid aggregate

Abstract

The invention relates to the technical field of asphalt mixtures, and particularly discloses an anti-stripping agent for acid aggregate, a preparation method of the anti-stripping agent, modified acid aggregate and application of the modified acid aggregate. The anti-stripping agent for the acid aggregate comprises the following raw material components in parts by mass: 50-100 parts of coupling agent activated waste rubber powder, 10-20 parts of carbon powder, 1-2 parts of hydrofluoric acid, 2-5 parts of citric acid, 1-2 parts of a surfactant, 3-6 parts of an adhesive, 5-10 parts of an adhesive, 1-2 parts of a stabilizer and 1-2 parts of a thickening agent, and the anti-stripping agent for the acid aggregate is prepared by utilizing the synergistic effect of all the components. The anti-stripping agent for the acid aggregate is simple and convenient in preparation method and low in cost, and the adhesion performance between the acid aggregate and asphalt can be effectively improved. According to the technical scheme, the problems that in the prior art, the adhesion effect between the acid aggregate and the asphalt is poor, and the cost of the modified acid aggregate is high are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of asphalt mixtures, and particularly to an anti-stripping agent for acidic aggregates, modified acidic aggregates, a preparation method and an application thereof. Background Art

[0002] The aggregates used in asphalt mixtures are mainly alkaline aggregates such as limestone, and these aggregates have good adhesion with asphalt. However, with the rapid development of highway construction, alkaline aggregates are gradually scarce, and the purchase and modification costs of alkaline aggregates are relatively high. In contrast, acidic aggregates can be used as an alternative material to help reduce the dependence on scarce resources. Natural acidic aggregates include rocks with high SiO2 content such as granite, gabbro, and quartzite. At the same time, some solid wastes generated by industrial activities, such as iron tailings, coal gangue, and optical fiber waste, can also be regarded as acidic aggregates because they contain a high SiO2 component.

[0003] Acidic aggregates have the characteristics of high strength, good wear resistance, and excellent abrasion resistance. However, due to the high silica content in acidic aggregates, they are hydrophilic. At the same time, water has a strong polarity and can well balance the charge on the aggregate surface. Therefore, it is easier for water to adsorb on the aggregate surface than asphalt, resulting in the peeling and loosening of the asphalt film. In addition, when surface active substances in asphalt, such as asphalt acid and anhydride, contact with alkaline aggregates, chemical adsorption is more likely to occur to form a chemical bond binding force, which will produce a strong chemical adsorption effect. Moreover, the stronger the alkalinity of the aggregate, the greater the chemical bond binding force, and the stronger the adhesion between asphalt and the aggregate. Acidic aggregates are not easy to form an interfacial chemical reaction with asphalt. Therefore, the adhesion between acidic aggregates and asphalt is poor, which easily leads to the peeling of asphalt from the surface of acidic aggregates, thus affecting their road performance and restricting the wide application of acidic aggregates in highway construction, resulting in a large amount of acidic aggregates unable to be effectively utilized.

[0004] In the prior art, the methods for improving the adhesion between asphalt and acidic aggregates are mainly divided into modifying asphalt and modifying aggregates. For modifying asphalt, mainly modifiers such as rubber powder, polymer, metal soap, surfactant, polymer anti-stripping agent, and silane coupling agent are added to asphalt to improve the adhesion between asphalt and aggregates, thereby improving the anti-stripping performance of asphalt mixtures. However, such methods have the disadvantages of environmental pollution, poor modification effect, and affecting the performance of asphalt. In terms of aggregate modification, mainly spraying a liquid interfacial modifier on the surface of the aggregate or attaching a modified coating on the surface of the aggregate to improve the aggregate performance. However, the preparation cost of the liquid interfacial modifier or the modified coating is relatively high and cannot be widely applied to highway construction on a large scale.

[0005] Based on this, it is of great significance to develop a material that can effectively improve the adhesion effect between acidic aggregates and asphalt for the development of asphalt mixtures. Summary of the Invention

[0006] Aiming at the problems of poor adhesion effect between acidic aggregates and asphalt and high cost of modified acidic aggregates in the prior art, the present invention provides an anti-stripping agent for acidic aggregates, modified acidic aggregates, a preparation method and an application thereof. The anti-stripping agent for acidic aggregates comprises raw material components such as coupling agent-activated waste rubber powder, carbon powder, hydrofluoric acid, citric acid, surfactant, binder, adhesion agent, stabilizer and thickener. By utilizing the synergistic effect of each component, an anti-stripping agent for acidic aggregates that can effectively improve the adhesion performance between acidic aggregates and asphalt is prepared. Moreover, the preparation cost of the anti-stripping agent for acidic aggregates is low and the process is simple. By modifying the acidic aggregates, the problem of poor adhesion performance between the existing acidic aggregates and asphalt in the asphalt mixture is effectively solved.

[0007] To achieve the above invention object, the present invention provides the following technical solutions: The first aspect of the present invention provides an anti-stripping agent for acidic aggregates, and the anti-stripping agent for acidic aggregates comprises the following raw material components in parts by mass: 50-100 parts of coupling agent-activated waste rubber powder, 10-20 parts of carbon powder, 1-2 parts of hydrofluoric acid, 2-5 parts of citric acid, 1-2 parts of surfactant, 3-6 parts of binder, 5-10 parts of adhesion agent, 1-2 parts of stabilizer and 1-2 parts of thickener.

[0008] Compared with the prior art, the present invention designs an anti-stripping agent for acidic aggregates. The anti-stripping agent for acidic aggregates is coated on the surface of the acidic aggregates, and an anti-stripping agent coating for acidic aggregates is formed between the acidic aggregates and the asphalt components, enhancing the adhesion performance between the two. Among them, hydrofluoric acid can react with the silicon dioxide on the surface of the acidic aggregates to generate soluble hexafluorosilicic acid, thereby forming micropores and a rough structure on the surface of the acidic aggregates. As a polycarboxylic acid, citric acid undergoes a complexation reaction through its carboxyl group with the silicon atoms on the surface of the silicon dioxide, further changing the surface chemical properties and enhancing the corrosion effect of hydrofluoric acid. The synergistic effect of the two acidic substances not only increases the roughness of the surface of the acidic aggregates, but also increases the specific surface area of the acidic aggregates, providing more binding sites for the coupling agent-activated waste rubber powder and carbon powder, and improving the adhesion performance between the acidic aggregates and the asphalt.

[0009] In an acidic environment, the amino groups on the surface of the coupling agent-activated waste rubber will undergo a protonation reaction and transform into -NH3 +, it can produce strong electrostatic interaction with the silanol groups (Si-OH) on the surface of acidic aggregates, thus tightly adsorbing on the surface of acidic aggregates, and then forming a rough structure with a large area on the surface of acidic aggregates. The carbon powder can fill the microvoids to form a multi-scale composite coating. This structure not only improves the compactness of the anti-stripping agent coating for acidic aggregates, but also enhances the contact area between the acidic aggregates and asphalt. Moreover, since the light components of asphalt will diffuse into the network structure of rubber, resulting in an increase in the volume of rubber powder particles, the contact area between acidic aggregates and asphalt is further increased, enhancing the physical adsorption effect. At the same time, the aromatic compounds in the asphalt components chemically interact with the olefin groups and phenyl groups in the rubber powder, further enhancing the bonding force between acidic aggregates and asphalt. In addition, the porous properties of the carbon powder enable it to adsorb the irritating gases generated during the preparation and use processes, improving the safety of the working environment. And the micropores and active sites on the surface of the carbon powder not only improve the adhesion ability of the coating, but also provide additional mechanical support for the interface. At the same time, the carbon powder can also capture the tiny defects and impurities in the interface region, reduce the stress concentration effect, and enhance the overall performance of the anti-stripping agent coating for acidic aggregates.

[0010] In summary, the anti-stripping agent for acidic aggregates provided by the present invention can modify and coat the surface of acidic aggregates, and enhance the adhesion performance between acidic aggregates and asphalt by changing the surface structure of acidic aggregates. Moreover, the raw material components of the anti-stripping agent for acidic aggregates are low-cost and easily available, and can recycle waste rubber powder, reducing the pressure of solid waste treatment and saving the preparation cost, effectively solving the problems of poor adhesion effect between acidic aggregates and asphalt and modified acidic aggregates in the prior art.

[0011] Preferably, the preparation method of the coupling agent-activated waste rubber powder comprises the following steps: S1. Mix a silane coupling agent, an activator and an alcohol solution to obtain an activation solution; S2. Immerse the waste rubber powder in the activation solution, carry out an activation reaction at 60 - 80 °C, filter, wash and dry to obtain the coupling agent-activated waste rubber powder.

[0012] The present invention uses a silane coupling agent, an activator and an alcohol solution to perform activation pretreatment on waste rubber powder. The silane coupling agent can hydrolyze to generate silanol under the action of water, and the silanol is easily chemically bonded to the hydroxyl or carboxyl groups on the surface of the rubber powder. Combining with the activation effect of the activator on the surface of the waste rubber powder, a coupling agent-activated waste rubber powder rich in active groups on the surface is obtained, enhancing the crosslinking between the rubber powder and the carbon powder.

[0013] More preferably, in S1, the silane coupling agent is KH550 or KH560.

[0014] Further preferably, in S1, the activator is a mixture of zinc oxide and stearic acid with a mass ratio of 1:2 - 1:4.

[0015] Further preferably, in S1, the alcohol solution is an ethanol solution with a volume fraction of 50% - 70%.

[0016] Further preferably, in S2, the particle size of the waste rubber powder is 0.18 mm - 0.60 mm.

[0017] Further preferably, in S1, the mass ratio of the silane coupling agent, activator and alcohol solution is 1:1:10 - 1:1:15.

[0018] Further preferably, in S2, the mass - volume ratio of the waste rubber powder and the activation solution is 1 g:5 mL - 1 g:8 mL.

[0019] Further preferably, in S2, the activation reaction time is 3 h - 5 h.

[0020] Preferably, the purity of the carbon powder ≥99.9%, and the particle size of the carbon powder is 50 μm - 150 μm.

[0021] Preferably, the surfactant is sodium dodecylbenzenesulfonate.

[0022] Preferably, the binder is water - based epoxy resin.

[0023] Preferably, the adhesive is polyvinyl alcohol.

[0024] Preferably, the stabilizer is sodium carboxymethyl cellulose.

[0025] Preferably, the thickener is hydroxyethyl cellulose.

[0026] The second aspect of the present invention provides a preparation method of the anti - stripping agent for acidic aggregates, including the following steps: Step 1: Weigh the surfactant, stabilizer, thickener and binder according to the designed ratio, disperse them in water, and mix evenly to obtain an active solution; Step 2: Weigh the coupling agent to activate the waste rubber powder and carbon powder according to the designed ratio, add them into the active solution, and mix evenly to obtain the anti - stripping agent for acidic aggregates; Step 3: Weigh hydrofluoric acid and citric acid according to the designed ratio, add them into the anti - stripping agent for acidic aggregates, and mix evenly to obtain the anti - stripping agent for acidic aggregates.

[0027] Preferably, in Step 1, the mass - volume ratio of the total mass of the surfactant, stabilizer, thickener and binder to water is 1 g:10 mL - 1 g:20 mL.

[0028] The third aspect of the present invention provides a modified acidic aggregate, which is obtained by coating an acidic aggregate with an anti-stripping agent according to any one of claims 1-5.

[0029] The fourth aspect of the present invention provides a method for preparing a modified acidic aggregate, which comprises soaking an acidic aggregate in the anti-stripping agent for the acidic aggregate, performing solid-liquid separation, curing, cooling, and screening to obtain the modified acidic aggregate.

[0030] Preferably, the acidic aggregate is quartz sand, granite or iron tail ore.

[0031] Preferably, the soaking time is 1h-3h.

[0032] Preferably, curing is carried out by means of segmented heating, wherein the curing temperature in the first stage is 60°C-80°C and the curing time in the first stage is 25min-35min; the curing temperature in the second stage is 150°C-180°C and the curing time in the second stage is 50min-70min.

[0033] Preferably, screening is carried out using a sieve mesh with a pore size of 0.6mm-4.75mm.

[0034] The fifth aspect of the present invention provides the application of the modified acidic aggregate in the preparation of asphalt mixtures. Description of the Drawings

[0035] Figure 1 is a picture of the acidic aggregate after water washing; Figure 2 is a picture of the acidic aggregate after being corroded by hydrofluoric acid-citric acid; Figure 3 is a picture of the acidic aggregate modified with the anti-stripping agent for the acidic aggregate obtained in Example 1; Figure 4 is a surface scanning electron microscope photograph of the acidic aggregate after being corroded by hydrofluoric acid-citric acid; wherein, Figure 4 (a) is the surface morphology of the acidic aggregate after being corroded by hydrofluoric acid-citric acid; Figure 4 (b) is the surface microporous structure of the acidic aggregate after being corroded by hydrofluoric acid-citric acid; Figure 5 is a surface scanning electron microscope photograph of the acidic aggregate modified with the anti-stripping agent for the acidic aggregate obtained in Example 1; wherein, Figure 5 (a) is the surface continuous coverage area of the acidic aggregate modified with the anti-stripping agent for the acidic aggregate obtained in Example 1; Figure 5 (b) is the surface irregular coverage area of the acidic aggregate modified with the anti-stripping agent for the acidic aggregate obtained in Example 1. Detailed Embodiments

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] Example 1 This embodiment provides an anti-stripping agent for acidic aggregates, which specifically includes the following contents: The anti-stripping agent for acidic aggregates includes the following raw material components in parts by mass: 85 g of coupling agent-activated waste rubber powder, 15 g of carbon powder, 2 g of hydrofluoric acid, 3 g of citric acid, 2 g of sodium dodecylbenzenesulfonate, 4 g of waterborne epoxy resin, 8 g of polyvinyl alcohol, 2 g of sodium carboxymethylcellulose, and 2 g of hydroxyethyl cellulose.

[0038] The preparation method of the anti-stripping agent for acidic aggregates includes the following steps: Step 1: Weigh sodium dodecylbenzenesulfonate, waterborne epoxy resin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium carboxymethylcellulose according to the designed ratio, mix them evenly, and dissolve them in 300 mL of water to obtain an active solution. Step 2: Weigh the coupling agent-activated waste rubber powder and carbon powder according to the designed ratio, add them to the active solution, and mix them evenly to obtain the anti-stripping agent for acidic aggregates. Step 3: Weigh hydrofluoric acid and citric acid according to the designed ratio, add them to the anti-stripping agent for acidic aggregates, and mix them evenly to obtain the anti-stripping agent for acidic aggregates.

[0039] The preparation method of the coupling agent-activated waste rubber powder includes the following steps: S1: Mix 20 g of silane coupling agent KH550, 6 g of zinc oxide, 14 g of stearic acid, and 2200 g of an ethanol solution with a volume fraction of 60% evenly to obtain an activation solution. S2: Immerse 300 g of waste rubber powder with a particle size of 0.45 mm in the activation solution, carry out an activation reaction at 70 °C for 4 h, filter, wash, and dry to obtain the coupling agent-activated waste rubber powder.

[0040] Example 2 This embodiment provides an anti-stripping agent for acidic aggregates, which specifically includes the following contents: The anti-stripping agent for acidic aggregates includes the following raw material components in parts by mass: 65 g of coupling agent-activated waste rubber powder, 13 g of carbon powder, 2 g of hydrofluoric acid, 4 g of citric acid, 2 g of sodium dodecylbenzenesulfonate, 4 g of waterborne epoxy resin, 8 g of polyvinyl alcohol, 2 g of sodium carboxymethylcellulose, and 2 g of hydroxyethyl cellulose.

[0041] The preparation method of the anti-stripping agent for acidic aggregates includes the following steps: Step 1: Weigh sodium dodecylbenzenesulfonate, waterborne epoxy resin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium carboxymethyl cellulose according to the designed ratio, mix them evenly, and dissolve them in 300 mL of water to obtain an active solution. Step 2: Weigh the coupling agent-activated waste rubber powder and carbon powder according to the designed ratio, add them to the active solution, and mix evenly to obtain an anti-stripping agent for acidic aggregates. Step 3: Weigh hydrofluoric acid and citric acid according to the designed ratio, add them to the anti-stripping agent for acidic aggregates, and mix evenly to obtain the anti-stripping agent for acidic aggregates.

[0042] The preparation method of the coupling agent-activated waste rubber powder includes the following steps: S1: Mix 20 g of silane coupling agent KH550, 6 g of zinc oxide, 14 g of stearic acid, and 2300 g of an ethanol solution with a volume fraction of 55% evenly to obtain an activation solution. S2: Immerse 300 g of waste rubber powder with a particle size of 0.45 mm in the activation solution, carry out an activation reaction at 75 °C for 4 h, filter, wash, and dry to obtain the coupling agent-activated waste rubber powder.

[0043] Example 3 This example provides an anti-stripping agent for acidic aggregates, which specifically includes the following content: The anti-stripping agent for acidic aggregates includes the following raw material components in parts by mass: 100 g of coupling agent-activated waste rubber powder, 20 g of carbon powder, 2 g of hydrofluoric acid, 5 g of citric acid, 2 g of sodium dodecylbenzenesulfonate, 6 g of waterborne epoxy resin, 10 g of polyvinyl alcohol, 2 g of sodium carboxymethyl cellulose, and 2 g of hydroxyethyl cellulose.

[0044] The preparation method of the anti-stripping agent for acidic aggregates includes the following steps: Step 1: Weigh sodium dodecylbenzenesulfonate, waterborne epoxy resin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium carboxymethyl cellulose according to the designed ratio, mix them evenly, and dissolve them in 300 mL of water to obtain an active solution. Step 2: Weigh the coupling agent-activated waste rubber powder and carbon powder according to the designed ratio, add them to the active solution, and mix evenly to obtain an anti-stripping agent for acidic aggregates. Step 3: Weigh hydrofluoric acid and citric acid according to the designed ratio, add them to the anti-stripping agent for acidic aggregates, and mix evenly to obtain the anti-stripping agent for acidic aggregates.

[0045] The preparation method of the coupling agent-activated waste rubber powder includes the following steps: S1: Mix 20 g of silane coupling agent KH550, 6 g of zinc oxide, 14 g of stearic acid, and 2200 g of an ethanol solution with a volume fraction of 60% evenly to obtain an activation solution. S2. Immerse 300 g of waste rubber powder with a particle size of 0.45 mm in the activation solution, carry out an activation reaction at 70 °C for 4 h, filter, wash, and dry to obtain the coupling agent-activated waste rubber powder.

[0046] Comparative Example 1 This comparative example provides an anti-stripping agent for acidic aggregates, which is different from Example 1 in that the waste rubber powder is not activated, and the specific content is as follows: The anti-stripping agent for acidic aggregates comprises the following raw material components in parts by mass: 85 g of waste rubber powder, 15 g of carbon powder, 2 g of hydrofluoric acid, 3 g of citric acid, 2 g of sodium dodecylbenzenesulfonate, 4 g of waterborne epoxy resin, 8 g of polyvinyl alcohol, 2 g of sodium carboxymethylcellulose, and 2 g of hydroxyethyl cellulose.

[0047] The preparation method of the anti-stripping agent for acidic aggregates comprises the following steps: Step 1. Weigh sodium dodecylbenzenesulfonate, waterborne epoxy resin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium carboxymethylcellulose according to the designed ratio, mix them evenly, and dissolve them in 300 mL of water to obtain an active solution; Step 2. Weigh waste rubber powder and carbon powder according to the designed ratio, add them to the active solution, and mix them evenly to obtain the anti-stripping agent for acidic aggregates; Step 3. Weigh hydrofluoric acid and citric acid according to the designed ratio, add them to the anti-stripping agent for acidic aggregates, and mix them evenly to obtain the anti-stripping agent for acidic aggregates.

[0048] Comparative Example 2 This comparative example provides an anti-stripping agent for acidic aggregates, which is different from Example 1 in that hydrofluoric acid is replaced with an equal amount of hydrochloric acid, and the specific content is as follows: The anti-stripping agent for acidic aggregates comprises the following raw material components in parts by mass: 85 g of coupling agent-activated waste rubber powder, 15 g of carbon powder, 2 g of hydrochloric acid, 3 g of citric acid, 2 g of sodium dodecylbenzenesulfonate, 4 g of waterborne epoxy resin, 8 g of polyvinyl alcohol, 2 g of sodium carboxymethylcellulose, and 2 g of hydroxyethyl cellulose.

[0049] The preparation method of the anti-stripping agent for acidic aggregates comprises the following steps: Step 1. Weigh sodium dodecylbenzenesulfonate, waterborne epoxy resin, hydroxyethyl cellulose, polyvinyl alcohol, and sodium carboxymethylcellulose according to the designed ratio, mix them evenly, and dissolve them in 300 mL of water to obtain an active solution; Step 2. Weigh coupling agent-activated waste rubber powder and carbon powder according to the designed ratio, add them to the active solution, and mix them evenly to obtain the anti-stripping agent for acidic aggregates; Step 3. Weigh hydrochloric acid and citric acid according to the designed ratio, add them to the anti-stripping agent for acidic aggregates, and mix them evenly to obtain the anti-stripping agent for acidic aggregates.

[0050] The preparation method of the coupling agent-activated waste rubber powder comprises the following steps: S1. Mix 20 g of silane coupling agent KH550, 6 g of zinc oxide, 14 g of stearic acid and 2200 g of an ethanol solution with a volume fraction of 60% evenly to obtain an activation solution; S2. Immerse 300 g of waste rubber powder with a particle size of 0.45 mm in the activation solution, carry out an activation reaction at 70 °C for 4 h, filter, wash and dry to obtain the coupling agent-activated waste rubber powder.

[0051] Comparative Example 3 This comparative example provides an anti-stripping agent for acidic aggregates, which is different from Example 1 in that citric acid is replaced with an equal amount of glutaric acid. The specific contents are as follows: The anti-stripping agent for acidic aggregates comprises the following raw material components in parts by mass: 85 g of coupling agent-activated waste rubber powder, 15 g of carbon powder, 2 g of hydrofluoric acid, 3 g of glutaric acid, 2 g of sodium dodecylbenzenesulfonate, 4 g of waterborne epoxy resin, 8 g of polyvinyl alcohol, 2 g of sodium carboxymethylcellulose and 2 g of hydroxyethyl cellulose.

[0052] The preparation method of the anti-stripping agent for acidic aggregates comprises the following steps: Step 1. Weigh sodium dodecylbenzenesulfonate, waterborne epoxy resin, hydroxyethyl cellulose, polyvinyl alcohol and sodium carboxymethylcellulose according to the designed ratio, mix them evenly and dissolve them in 300 mL of water to obtain an active solution; Step 2. Weigh the coupling agent-activated waste rubber powder and carbon powder according to the designed ratio, add them into the active solution and mix them evenly to obtain the anti-stripping agent for acidic aggregates; Step 3. Weigh hydrofluoric acid and glutaric acid according to the designed ratio, add them into the anti-stripping agent for acidic aggregates and mix them evenly to obtain the anti-stripping agent for acidic aggregates.

[0053] The preparation method of the coupling agent-activated waste rubber powder comprises the following steps: S1. Mix 20 g of silane coupling agent KH550, 6 g of zinc oxide, 14 g of stearic acid and 2200 g of an ethanol solution with a volume fraction of 60% evenly to obtain an activation solution; S2. Immerse 300 g of waste rubber powder with a particle size of 0.45 mm in the activation solution, carry out an activation reaction at 70 °C for 4 h, filter, wash and dry to obtain the coupling agent-activated waste rubber powder.

[0054] To further demonstrate the technical effects of the present invention, the following tests were conducted on the anti-stripping agents for acidic aggregates obtained in Examples 1-3 and Comparative Examples 1-3, as well as on the blank control group (without using the anti-stripping agent for acidic aggregates): The anti-stripping agent for acidic aggregates was used to modify the acidic aggregates according to the following steps, and the modified acidic aggregates were mixed with asphalt to test the interfacial adhesion force between the modified acidic aggregates (iron tailings) and asphalt.

[0055] (1) Wash the iron tailings with pure water, place them in an oven at 110 °C for drying, and then put them in a desiccator for later use; (2) Immerse the iron tailings completely in the anti-stripping agent for acidic aggregates and let it stand for 2 h; (3) After standing, filter, let the iron tailings dry in the natural environment for 30 min, and then place them in an oven at 75 °C for 30 min until the surface of the aggregates is dry and the rubber powder and carbon powder adhere to the surface of the iron tailings; (4) Place the iron tailings in an oven at 180 °C for 1 h until the rubber powder softens and a composite coating is formed on the surface of the iron tailings. Then take out the iron tailings and cool them to room temperature to make the coating completely solidify on the surface of the iron tailings; Screen with a sieve having a pore size of 4.5 mm to obtain modified acidic aggregates; (5) After the modified acidic aggregates are cooled, fix them with a thin wire, immerse them in the matrix asphalt preheated to 140 °C for 45 s, then gently take them out so that the modified acidic aggregates are completely wrapped by the asphalt film. Tie the modified acidic aggregates wrapped with asphalt with a thin wire and hang them on the test rack, with a piece of waste paper placed below to let the excess asphalt flow away, and cool at room temperature for 15 min; (6) After the modified acidic aggregate particles are cooled, lift them one by one with a wire and immerse them in the center of a large beaker filled with boiling water. Adjust the heating furnace to keep the water in the beaker in a slightly boiling state, but no boiling foam is allowed; After boiling for 3 min, take out the iron tailings from the water and observe the degree of stripping of the asphalt film on the modified acidic aggregate particles to evaluate their adhesion grade.

[0056] The evaluation of the adhesion refers to the test standard of the adhesion test method (boiling water method) for asphalt and modified acidic aggregates in JTG E20-2011 (Standard Test Methods of Bitumen and Bituminous Mixtures for Highway Engineering). The test results are shown in Table 1.

[0057] Evaluation criteria:

[0058] Table 1 Adhesion test results

[0059] The present invention also conducted an electron microscopy analysis on the modification effect of the anti-stripping agent for acidic aggregates obtained in Example 1, and the results are as Figures 1-3As shown Figure 1 is the acid aggregate after water washing. According to Figure 1 it can be seen that the surface of the acid aggregate (iron tail ore) after water washing shows an obvious luster, is relatively smooth as a whole, has no obvious corrosion marks or coating coverage, and the color is mainly the original tone of the ore (such as grayish black or brown). Figure 2 is the acid aggregate after being corroded by hydrofluoric acid - citric acid after water washing. According to Figure 2 it can be seen that the surface of the acid aggregate after being corroded by hydrofluoric acid - citric acid shows significant white corrosion areas, and obvious holes and rough textures can be seen locally. The white corrosion areas may be the deposition of reaction by - products (such as fluorosilicates) or the residue of undissolved silicate minerals. The corrosion process significantly increases the surface roughness and specific surface area, providing more binding sites for subsequent coating modification. Figure 3 is the acid aggregate modified by the anti - stripping agent for the acid aggregate provided in Example 1. According to Figure 3 it can be seen that a layer of rubber powder - carbon powder composite coating adheres to the surface of the iron tail ore after modification, making its surface show a uniform black color, with a lower luster, and good overall coverage. The uniformity of the black coating indicates that the rubber powder and carbon powder form a dense covering layer on the rough surface after corrosion. The larger particles of the rubber powder fill the macroscopic pores and form a framework structure, while the fine particles of the carbon powder penetrate into the micron - level pores, eliminating interface defects through physical filling and surface wetting effects. The synergistic effect of the two not only covers the white areas formed by corrosion, but also enhances the bonding strength of the coating through the flexibility of the rubber powder and the rigid particles of the carbon powder.

[0060] The present invention further conducts a surface scanning electron microscope on the acid aggregate (iron tail ore) corroded by hydrofluoric acid - citric acid and the acid aggregate treated with the anti - stripping agent provided in Example 1. The results are as Figures 4-5 shown. From Figure 4 (a), it can be seen that the surface of the aggregate shows significant rough textures and a small amount of hole structures, and these features are highly consistent with the expected chemical corrosion effect in the experiment. The formation of the rough textures is mainly attributed to the strong corrosion effect of hydrofluoric acid on the silica (SiO2) on the surface of the aggregate, generating soluble hexafluorosilicic acid (H2SiF5), resulting in the selective dissolution of the siliceous components and thus forming uneven corrosion areas. At the same time, citric acid undergoes a complexation reaction through its carboxyl group (-COOH) with the silanol groups (Si - OH) on the surface of silica, weakening the stability of the silicon - oxygen bond and further promoting the penetration and reaction efficiency of hydrofluoric acid. The synergistic effect of the two not only accelerates the decomposition of the surface siliceous structure, but also forms complex rough textures through a dynamic corrosion - complexation process, significantly increasing the specific surface area of the aggregate. From Figure 4(b) It can be seen that the surface microporous structure of acid-aggregates of iron tailings after being treated by the synergistic corrosion of hydrofluoric acid and citric acid is shown. The appearance of local depressions and irregular edges in the pore morphology is due to the local selectivity of chemical reactions, the inhomogeneity of material composition, and the complexing and scavenging effect of citric acid on reaction by-products. This dual-acid treatment strategy not only realizes the regulation of the physical morphology of the aggregate surface, but also optimizes the surface energy through chemical modification, providing abundant physical anchoring sites and chemical bonding interfaces for subsequent coating materials (such as rubber powder and carbon powder), and ultimately enhancing the interfacial bonding strength between the aggregate and the coating. The microscopic features of the electron microscope images are completely consistent with the description of the experimental mechanism, verifying the synergistic effect of hydrofluoric acid and citric acid in the surface treatment of acid-aggregates. A small amount of void structure and local depressions can be seen in the photo, reflecting the selective effect of chemical dissolution. This dual-acid treatment strategy optimizes the physical morphology and chemical properties of the aggregate surface and enhances its interfacial bonding strength with the coating.

[0061] Figure 5 shows the continuous coverage morphology of the rubber powder and carbon powder composite coating after the acid-aggregates provided in Example 1 are used to modify the surface of iron tailings ore. From Figure 5 (a) It can be seen that on the relatively smooth acid-aggregate surface, the larger particle size of the rubber powder forms a basic support structure through the melting or solvent evaporation process, covering and filling the main pores of the substrate, while the fine particles of carbon powder further penetrate into local depressions below the micron level and sub-micron voids. Through the synergistic effect of the particle size difference, the two achieve a uniform and dense distribution. The continuity of the coating not only stems from the sufficient penetration of the high adhesiveness and wettability of the rubber powder into the corrosion pores, but is also closely related to the fine filling ability of the carbon powder - the skeleton structure of the rubber powder wraps the carbon powder particles to form a mechanical interlock, and at the same time, the micron-level size of the carbon powder compensates for the gaps between the rubber powder particles, significantly reducing interface defects. In addition, the flexibility of the rubber powder effectively alleviates the rigid characteristics of the carbon powder on the smooth surface, reducing the interface stress, and the particle size complementarity of the two further strengthens the seamless bonding between the coating and the substrate. Figure 5 (b) shows the non-uniform distribution morphology of a local area on the surface of the same composite coating after corrosion. Due to the significant rough texture and pore structure (such as local depressions and irregular edges) on the substrate surface caused by the corrosion treatment, the rubber powder-carbon powder composite coating shows a non-continuous coverage feature in such areas. Through the synergistic effect of the particle size difference between the rubber powder and the carbon powder, the rubber powder preferentially fills the macroscopic pores and covers the substrate surface, while the carbon powder particles, due to their small size, aggregate at the pore edges or sub-micron cracks to form local high-density accumulations. However, due to the complexity of the substrate morphology (such as steep edges or deep hole structures), the larger particle size of the rubber powder and the tiny particles of the carbon powder do not fully match, resulting in non-continuous coverage of the coating at the microscale.

[0062] In summary, after applying the anti-stripping agent to the surface of acid-aggregates infiltrated on the surface of iron tailings, and through operations such as standing, drying, heating, and cooling, a dense and porous structure will be formed on the surface of the aggregates. At the same time, the rubber powder and carbon powder will be cured on the surface of the acid-aggregates and form a composite coating. Then, when added to the hot matrix asphalt, due to the adsorbability of the rubber powder itself, the surface roughness can be increased through adsorption and swelling. Therefore, the adhesion with the asphalt is relatively strong, thereby enhancing the interfacial adhesion between the acid-aggregates and the asphalt. The coating can prevent moisture from penetrating between the asphalt and the aggregates, thus solving the problem of poor adhesion between the acid-aggregates and the asphalt.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An anti-stripping agent for acidic aggregates, characterized in that: The anti-stripping agent for acidic aggregates comprises the following raw material components in parts by mass: 50-100 parts of coupling agent-activated waste rubber powder, 10-20 parts of carbon powder, 1-2 parts of hydrofluoric acid, 2-5 parts of citric acid, 1-2 parts of surfactant, 3-6 parts of binder, 5-10 parts of adhesive, 1-2 parts of stabilizer and 1-2 parts of thickener.

2. The anti-stripping agent for acidic aggregates according to claim 1, characterized in that: The preparation method of the coupling agent-activated waste rubber powder comprises the following steps: S1. Mix the silane coupling agent, activator and alcohol solution evenly to obtain an activation solution; S2. Immerse the waste rubber powder in the activation solution, carry out an activation reaction at 60-80 °C, filter, wash and dry to obtain the coupling agent-activated waste rubber powder.

3. The anti-stripping agent for acidic aggregates according to claim 2, characterized in that: In S1, the silane coupling agent is KH550 or KH560; and / or In S1, the activator is a mixture of zinc oxide and stearic acid with a mass ratio of 1:2-1:4; and / or In S1, the alcohol solution is an ethanol solution with a volume fraction of 50%-70%; and / or In S1, the mass ratio of the silane coupling agent, activator and alcohol solution is 1:1:10-1:1:

15.

4. The anti-stripping agent for acidic aggregates according to claim 2, characterized in that: In S2, the particle size of the waste rubber powder is 0.18 mm-0.60 mm; and / or In S2, the mass-volume ratio of the waste rubber powder and the activation solution is 1 g:5 mL-1 g:8 mL; and / or In S2, the activation reaction time is 3 h-5 h.

5. The anti-stripping agent for acidic aggregates according to claim 1, characterized in that: The purity of the carbon powder is ≥99.9%, and the particle size is 50 μm-150 μm; and / or The surfactant is sodium dodecylbenzenesulfonate; and / or The binder is water-based epoxy resin; and / or The adhesive is polyvinyl alcohol; and / or The stabilizer is sodium carboxymethyl cellulose; and / or The thickener is hydroxyethyl cellulose.

6. A preparation method of an anti-stripping agent for acidic aggregates according to any one of claims 1-5, characterized in that: Comprises the following steps: Step 1. Weigh the surfactant, stabilizer, adhesive, thickener and binder according to the designed ratio, disperse them in water and mix evenly to obtain an active solution; Step 2. Weigh the coupling agent-activated waste rubber powder and carbon powder according to the designed ratio, add them into the active solution and mix evenly to obtain the anti-stripping agent for acidic aggregates; Step 3. Weigh hydrofluoric acid and citric acid according to the designed ratio, add them into the anti-stripping agent for acidic aggregates and mix evenly to obtain the anti-stripping agent for acidic aggregates.

7. A modified acidic aggregate, characterized in that: Comprises using the anti-stripping agent for acidic aggregates according to any one of claims 1-5 and acidic aggregates.

8. The preparation method of the modified acidic aggregate according to claim 7, characterized in that: Immerse the acidic aggregates in the anti-stripping agent for acidic aggregates, carry out solid-liquid separation, curing, cooling and screening to obtain the modified acidic aggregates.

9. The preparation method of the modified acidic aggregate according to claim 8, wherein: The acidic aggregates are quartz sand, granite or iron tailings powder; and / or The soaking time is 1 h-3 h; and / or Curing is carried out by means of segmented heating. Among them, the curing temperature in the first stage is 60 °C-80 °C, and the curing time in the first stage is 25 min-35 min; the curing temperature in the second stage is 150 °C-180 °C, and the curing time in the second stage is 50 min-70 min; and / or Screening is carried out using a sieve with a pore size of 0.6 mm-4.75 mm.

10. Use of the modified acidic aggregates according to claim 7 in the preparation of asphalt mixtures.

Images