Emulsified asphalt and steel slag ultrathin overlay mixture as well as preparation method and application thereof

Abstract

The invention discloses an emulsified asphalt and steel slag ultrathin overlay mixture as well as a preparation method and application thereof, and relates to the technical field of road building materials. The emulsified asphalt and steel slag ultrathin overlay mixture comprises mineral aggregate, emulsified asphalt and cement, the mineral aggregate comprises 30%-35% of modified steel slag aggregate with the particle size of 5-10 mm, 60%-70% of limestone aggregate with the particle size of 0-5 mm and 1%-3% of limestone mineral powder; the preparation method of the modified steel slag comprises the following steps: primarily treating the steel slag with CO2 gas, soaking with cement slurry, soaking with a sulfydryl silane coupling agent, spraying the surface with methyl phenyl silicone resin to enable the steel slag to obtain hydrophobic coating, and finally spraying epoxidized soybean oil. By modifying the steel slag and optimizing mineral aggregate gradation, the ultrathin overlay prepared from the mixture is durable, anti-slip, anti-crack and waterproof, stable in structure and high in overall cohesive force.

Description

Technical Field

[0001] The present invention relates to the technical field of road construction materials, in particular to an emulsified asphalt steel slag ultra-thin overlay mixture and a preparation method and application thereof. Background Art

[0002] Under repeated loads, the road surface will develop cracks, lack of fine aggregate, coarse aggregate wear and other defects of varying degrees. In order to further inhibit the development of defects and prevent the occurrence of structural defects, preventive maintenance technologies such as ultra-thin coverings and micro-surfacing are generally used for pre-maintenance to extend the service life of the road and save maintenance costs.

[0003] Steel slag is a byproduct of the primary steelmaking process and a steelmaking waste product. my country produces over 100 million tons annually, but its comprehensive utilization rate is only around 20%. The large amount of accumulated steel slag not only wastes resources but also pollutes the environment. Steel slag is generally alkaline, has a rough, porous structure, is rich in angular shapes, and offers high strength and wear resistance, making it a valuable road construction material. To improve its comprehensive utilization, steel slag is currently being used in asphalt concrete as a substitute for natural, high-quality aggregate. This not only eliminates the use of steel slag waste but also reduces the use of natural stone resources, making it an ideal natural aggregate substitute. However, the efficiency of steel slag in road construction remains insufficient, primarily because it contains a certain amount of free calcium oxide and magnesium oxide, which easily expand in volume when exposed to water, potentially causing cracking in asphalt pavements. This limits its efficient use.

[0004] Numerous existing methods address the problem of steel slag swelling when exposed to water. For example, patent CN 114835439 B discloses soaking steel slag in a silicone waterproofing agent to coat the slag surface with a hydrophobic film. Patent CN 113563010 B discloses treating the slag with epoxy resin, long-chain diluent, polyetheramine, polyurethane prepolymer, and curing agent to coat the slag surface with a hydrophobic film to address this swelling issue. However, if the hydrophobic coating is used for extended periods, exposed to large amounts of water, or soaked in water for extended periods, the calcium oxide and magnesium oxide within the slag will absorb water and dissolve, causing the coating to rupture, thereby compromising its performance. Furthermore, some hydrophobic coatings can reduce the bonding between the slag and asphalt. This is particularly true in the construction of cold-mix, cold-laid, ultra-thin overlays, where insufficient asphalt-aggregate adhesion and difficulty compacting the mixture can easily lead to engineering issues such as loosening and rutting in the early stages of asphalt pavement opening to traffic. Therefore, it is necessary to modify and optimize the emulsified asphalt steel slag ultra-thin overlay mixture to enhance the road performance and durability of the cold-mixed and cold-laid ultra-thin overlay. Summary of the Invention

[0005] To address the above shortcomings, the present invention provides an emulsified asphalt steel slag ultra-thin overlay mixture, its preparation method, and its application. The ultra-thin overlay prepared from the mixture is durable and anti-slip, crack-resistant and waterproof, with a stable structure and strong overall cohesion. The specific technical solution is as follows: An emulsified asphalt steel slag ultra-thin overlay mixture comprises the following components by mass fraction: 100 parts of mineral material, 7-11 parts of emulsified asphalt and 1-3 parts of cement; When the mineral material passes through the standard square hole sieves with apertures of 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm, the corresponding passing ratios are 100%, 70%-90%, 45%-70%, 28%-50%, 19%-34%, 12%-25%, 7%-18%, 7%-18% and 6%-12% respectively; The mineral materials are divided into three groups according to particle size: the first group: 5-10 mm modified steel slag aggregate; the second group: 0-5 mm limestone aggregate; the third group: limestone slag powder; the first group of aggregates accounts for 30-35% of the mass of the mineral materials, the second group of aggregates accounts for 60-70% of the mass of the mineral materials, and the third group of slag powder accounts for 1-3% of the mass of the mineral materials.

[0006] Furthermore, the preparation method of the modified steel slag aggregate is: Step 1: First, soak the steel slag aggregate in water. After it is completely soaked, heat it to 60-70°C, then introduce carbon dioxide into the water while stirring for reaction. After the reaction time is 3-5 hours, filter the filtered steel slag aggregate, soak it in a cement slurry with a mass concentration of 30-40% for 1-2 hours, and filter it to obtain the pretreated steel slag aggregate; Step 2: first, soak the pretreated steel slag aggregate in an ethanol solution of a mercaptosilane coupling agent for 20-30 minutes, then dry it at 60-70° C. to a moisture content of 5-8%, then spray it with a methylphenyl silicone resin with a solid content of 10-20%, and cure it at 150-180° C. for 10-15 minutes to obtain a steel slag aggregate coated with a hydrophobic layer; Step 3: Spraying epoxy soybean oil onto the steel slag aggregate coated with the hydrophobic layer to obtain the modified steel slag aggregate.

[0007] Furthermore, in step 1, the carbon dioxide concentration is 20-30% and the flow rate is 2-5 L / min.

[0008] Furthermore, in step 2, the mass concentration of the mercaptosilane coupling agent ethanol solution is 5-9wt%.

[0009] Furthermore, in step 3, the amount of the epoxidized soybean oil is 0.1-0.5% of the weight of the steel slag aggregate coated with the hydrophobic layer.

[0010] Furthermore, the emulsified asphalt includes the following components in weight percentage: base asphalt 80-90%, SBS modifier 1-3%, emulsifier 1-3%, SBR latex 6-8%, NaCl stabilizer 0.2-0.5% and warm mix agent 2-3%.

[0011] Furthermore, the preparation method of the emulsified asphalt is: (1) Weigh each component by weight percentage, add the emulsifier into 60-70°C water and stir, add hydrochloric acid while stirring to adjust the pH to 2-3, after the emulsifier is completely dissolved, add SBR latex and mix well, and continue to adjust the pH to 2-3 to obtain soap solution; (2) heating the base asphalt to 180-200°C, adding SBS modifier, high-speed shearing at 3000-5000 rpm for 30-40 minutes, and then developing at 180-200°C for 3-5 hours to obtain modified asphalt; (3) Add the soap solution, modified asphalt, NaCl stabilizer and warm mix agent into a colloid mill for shear grinding and cooling to obtain emulsified asphalt.

[0012] The present invention also provides a method for preparing the emulsified asphalt steel slag ultra-thin overlay mixture, comprising the following steps: weighing mineral material, emulsified asphalt and cement in parts by weight, mixing them evenly, adding 5-8% water by weight of the mineral material and mixing for 80-90 seconds to obtain the mixture.

[0013] The present invention also provides an application of the emulsified asphalt steel slag ultra-thin overlay mixture in road maintenance.

[0014] Furthermore, when the mixture is used for road maintenance, the construction temperature is room temperature, the compaction thickness is 0.7-1.0 cm, and after the mixture is spread for 2 hours, the pavement is rolled 1-3 times with a rubber-wheel roller before being opened to traffic.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention is based on the relevant standards and technical requirements of preventive maintenance seals. By modifying steel slag and optimizing the emulsified asphalt preparation method, the ultra-thin cover prepared from the mixture is durable, anti-slip, crack-resistant and waterproof, with a stable structure and strong overall cohesion. Among them, the compatibility of various materials in the emulsified asphalt is improved by combining high-speed shearing and colloid grinding, so that the prepared emulsified asphalt has good stability and high viscosity, and improves the bonding performance with the mineral aggregate; at the same time, when modifying the steel slag aggregate, carbon dioxide is introduced into the mixture of steel slag and water, which can convert part of the free calcium oxide in the steel slag into non-hydrophobic calcium carbonate, reducing the volume expansion rate of the steel slag and preventing the capsule from rupturing due to water absorption and expansion. The pores in the steel slag are then filled and sealed by soaking in cement slurry, reducing the water absorption of the steel slag aggregate. After pretreatment, the steel slag is hydrophobically coated with a mercaptosilane coupling agent and a methylphenyl silicone resin, further reducing the water absorption of the steel slag aggregate. After hydrophobic coating, epoxy soybean oil is sprayed on the surface of the steel slag. One end of the epoxy soybean oil is connected to the hydrophobic membrane, and the other end is anchored to the asphalt through van der Waals force, thereby improving the adhesion between the asphalt and the steel slag aggregate, and solving the problem of insufficient adhesion of the asphalt-hydrophobically modified steel slag aggregate and difficulty in compacting the mixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0017] Figure 1 This is the gradation curve of the emulsified asphalt steel slag ultra-thin overlay mixture of the present invention. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0019] 1. Preparation of emulsified asphalt 1. Material preparation: The raw materials for preparing emulsified asphalt are: base asphalt (70# road petroleum asphalt), SBS modifier, LX811G emulsifier, LX65 cationic SBR latex, NaCl stabilizer and warm mix agent (sasobit warm mix agent).

[0020] (1) The technical indicators of matrix asphalt are shown in Table 1: Table 1 Matrix asphalt test results

[0021] (2) The technical indicators of SBS modifier are shown in Table 2: Table 2 Technical indicators of SBS modifier

[0022] (3) The technical indicators of SBR latex are shown in Table 3: Table 3 Technical indicators of SBR latex

[0023] 2. Preparation method of emulsified asphalt: (1) Weigh each component by weight percentage, add the emulsifier into 60-70°C water and stir, add hydrochloric acid while stirring to adjust the pH to 2-3, after the emulsifier is completely dissolved, add SBR latex and mix well, and continue to adjust the pH to 2-3 to obtain soap solution; (2) heating the base asphalt to 180-200°C, adding SBS modifier, high-speed shearing at 3000-5000 rpm for 30-40 minutes, and then developing at 180-200°C for 3-5 hours to obtain modified asphalt; (3) Add the soap solution, modified asphalt, NaCl stabilizer and warm mix agent into a colloid mill for shear grinding and cooling to obtain emulsified asphalt.

[0024] 2. Preparation of emulsified asphalt steel slag ultra-thin overlay mixture 1. Material Preparation: The emulsified asphalt steel slag ultra-thin overlay mixture includes the following components by weight: 100 parts mineral aggregate, 7-11 parts emulsified asphalt, and 1-3 parts cement. The mineral aggregate is divided into three groups based on particle size: Group 1: 5-10 mm modified steel slag aggregate; Group 2: 0-5 mm limestone aggregate; and Group 3: limestone slag powder. The first group of aggregates accounts for 30-35% of the total mineral aggregate mass, the second group of aggregates accounts for 60-70% of the total mineral aggregate mass, and the third group of slag powder accounts for 1-3% of the total mineral aggregate mass.

[0025] (1) The density of 0-5 mm limestone aggregate is shown in Table 4: Table 4 Water absorption and density test results

[0026] (2) The gradation of 5-10 mm modified steel slag aggregate and 0-5 mm limestone aggregate is shown in Table 5: Table 5 Aggregate gradation screening results

[0027] (3) Limestone powder, the screening test results are shown in Table 6: Table 6 Results of ore screening test

[0028] (4) The cement used is Pumiao brand PO42.5 ordinary Portland cement.

[0029] (5) The mixture gradation is shown in Table 7 and Figure 1 As shown: Table 7 Mixture gradation

[0030] 2. The preparation method of the emulsified asphalt steel slag ultra-thin overlay mixture is as follows: weigh the mineral material, emulsified asphalt and cement according to the weight parts, mix them evenly, add 5-8% of the weight of the mineral material water and mix for 80-90 seconds to obtain the mixture.

[0031] Example 1 Emulsified asphalt preparation method: (1) Weigh 87.5% of base asphalt (70# road petroleum asphalt), 2% of SBS modifier, 2% of LX811G emulsifier, 6.8% of LX65 cationic SBR latex, 0.3% of NaCl stabilizer and 2.5% of sasobit warm mix agent by weight percentage, add the emulsifier into 70°C water and stir, add hydrochloric acid while stirring to adjust the pH to 3, after the emulsifier is completely dissolved, add SBR latex and mix well, and continue to adjust the pH to 3 to obtain soap solution; (2) heating the base asphalt to 190°C, adding SBS modifier, high-speed shearing at 4000 rpm for 35 minutes, and then developing at 190°C for 4 hours to obtain modified asphalt; (3) Add the soap solution, modified asphalt, NaCl stabilizer and warm mix agent into a colloid mill for shear grinding and cooling to obtain emulsified asphalt.

[0032] The properties of the prepared emulsified asphalt, including the residue on sieve, Ngualla viscosity, and evaporation residue, were tested. The test results are shown in Table 8: Table 8 Technical indicators of emulsified asphalt

[0033] As can be seen from the above table, the emulsified asphalt prepared by the present invention has strong high-temperature stability and low-temperature ductility. The SBR and SBS modifiers form a continuous structure in the emulsified asphalt. Its softening point can reach 65.3°C, and its ductility at 5°C can reach 36.0 cm. The performance indicators can meet the requirements of the specifications.

[0034] Example 2 Preparation method of emulsified asphalt steel slag ultra-thin overlay mixture: (1) Preparation of modified steel slag aggregate: Step 1: First, soak the steel slag aggregate in water. After it is completely soaked, heat it to 65°C, then introduce 25% carbon dioxide into the water while stirring, at a carbon dioxide flow rate of 4 L / min. After reacting for 4 hours, filter, and soak the filtered steel slag aggregate in a cement slurry with a mass concentration of 35% for 1.5 hours, filter, and obtain pretreated steel slag aggregate; Step 2: first, immerse the pretreated steel slag aggregate in an ethanol solution of a mercaptosilane coupling agent having a mass concentration of 7 wt% for 25 minutes, then dry at 65° C. to a water content of 6%, and then spray-coat with a methylphenyl silicone resin having a solid content of 16%, and cure at 160° C. for 12 minutes to obtain a steel slag aggregate coated with a hydrophobic layer; Step 3: Spraying epoxy soybean oil onto the steel slag aggregate coated with the hydrophobic layer, wherein the amount of epoxy soybean oil is 0.3% of the weight of the steel slag aggregate coated with the hydrophobic layer, thereby obtaining the modified steel slag aggregate.

[0035] (2) Material preparation: Emulsified asphalt steel slag ultra-thin overlay mixture includes the following components in mass fractions: 100 parts of mineral material, 9.6 parts of emulsified asphalt prepared in Example 1, and 2.2 parts of cement. The mineral material is divided into three groups according to particle size: the first group: 5-10 mm modified steel slag aggregate; the second group: 0-5 mm limestone aggregate; the third group: limestone slag powder; the first group of aggregates accounts for 33% of the mass of the mineral material, the second group of aggregates accounts for 65% of the mass of the mineral material, and the third group of slag powder accounts for 2% of the mass of the mineral material; the synthetic gradation is shown in Table 9: Table 9 Mixture synthesis gradation

[0036] (3) Preparation of emulsified asphalt steel slag ultra-thin overlay mixture: weigh the mineral material, emulsified asphalt and cement according to the weight ratio and mix them evenly. Add 7% water of the mineral material weight and mix for 85 seconds.

[0037] Example 3 Preparation method of emulsified asphalt steel slag ultra-thin overlay mixture: (1) Preparation of modified steel slag aggregate: Step 1: First, soak the steel slag aggregate in water. After it is completely soaked, heat it to 70°C, then introduce 30% carbon dioxide into the water while stirring, at a carbon dioxide flow rate of 5 L / min. After reacting for 5 hours, filter it, soak the filtered steel slag aggregate in a cement slurry with a mass concentration of 40% for 2 hours, and filter it to obtain pretreated steel slag aggregate; Step 2: first, immerse the pretreated steel slag aggregate in an ethanol solution of a mercaptosilane coupling agent having a mass concentration of 9 wt% for 30 min, then dry the solution at 70° C. to a water content of 8%, and then spray-coat the solution with a methylphenyl silicone resin having a solid content of 20%, and cure the solution at 180° C. for 15 min to obtain a steel slag aggregate coated with a hydrophobic layer; Step 3: Spray epoxy soybean oil onto the steel slag aggregate coated with the hydrophobic layer, wherein the amount of epoxy soybean oil used is 0.5% of the weight of the steel slag aggregate coated with the hydrophobic layer, thereby obtaining the modified steel slag aggregate.

[0038] (2) Material preparation: Emulsified asphalt steel slag ultra-thin overlay mixture includes the following components in mass fractions: 100 parts of mineral material, 11 parts of emulsified asphalt prepared in Example 1, and 3 parts of cement. The mineral material is divided into three groups according to particle size: the first group: 5-10 mm modified steel slag aggregate; the second group: 0-5 mm limestone aggregate; the third group: limestone slag powder; the first group of aggregates accounts for 35% of the mass of the mineral material, the second group of aggregates accounts for 70% of the mass of the mineral material, and the third group of slag powder accounts for 3% of the mass of the mineral material; the synthetic gradation is shown in Table 10: Table 10 Mixture synthesis gradation

[0039] (3) Preparation of emulsified asphalt steel slag ultra-thin overlay mixture: weigh the mineral material, emulsified asphalt and cement according to the weight ratio and mix them evenly. Add 8% of the weight of the mineral material into water and mix for 90 seconds.

[0040] Example 4 Preparation method of emulsified asphalt steel slag ultra-thin overlay mixture: (1) Preparation of modified steel slag aggregate: Step 1: First, soak the steel slag aggregate in water. After it is completely soaked, heat it to 60°C, then introduce 20% carbon dioxide into the water while stirring, at a carbon dioxide flow rate of 2L / min. After reacting for 3 hours, filter, and soak the filtered steel slag aggregate in a cement slurry with a mass concentration of 30% for 1 hour, filter, and obtain pretreated steel slag aggregate; Step 2: first, immerse the pretreated steel slag aggregate in an ethanol solution of a mercaptosilane coupling agent having a mass concentration of 5 wt% for 20 minutes, then dry at 60° C. to a moisture content of 5%, and then spray-coat with a methylphenyl silicone resin having a solid content of 10%, and cure at 150° C. for 10 minutes to obtain a steel slag aggregate coated with a hydrophobic layer; Step 3: Spraying epoxy soybean oil onto the steel slag aggregate coated with the hydrophobic layer, wherein the amount of epoxy soybean oil used is 0.1% of the weight of the steel slag aggregate coated with the hydrophobic layer, thereby obtaining the modified steel slag aggregate.

[0041] (2) Material preparation: Emulsified asphalt steel slag ultra-thin overlay mixture includes the following components in mass fractions: 100 parts of mineral material, 7 parts of emulsified asphalt prepared in Example 1, and 1 part of cement. The mineral material is divided into three groups according to particle size: the first group: 5-10 mm modified steel slag aggregate; the second group: 0-5 mm limestone aggregate; the third group: limestone slag powder; the first group of aggregates accounts for 30% of the mass of the mineral material, the second group of aggregates accounts for 60% of the mass of the mineral material, and the third group of slag powder accounts for 1% of the mass of the mineral material; the synthetic gradation is shown in Table 11: Table 11 Mixture synthesis gradation

[0042] (3) Preparation of emulsified asphalt steel slag ultra-thin overlay mixture: weigh the mineral material, emulsified asphalt and cement according to the weight ratio and mix them evenly. Add 5% of the weight of the mineral material into water and mix for 80 seconds.

[0043] Comparative Example 1: In this comparative example, the steel slag material is not modified, and other raw materials and preparation methods are the same as those in Example 4.

[0044] Comparative Example 2: In this comparative example, when preparing modified steel slag aggregate, step 1 is omitted, and other raw materials and preparation methods are the same as those in Example 4.

[0045] Comparative Example 3: In this comparative example, when preparing modified steel slag aggregate, step 3 is omitted, and other raw materials and preparation methods are the same as those in Example 4.

[0046] The mixtures prepared in Examples 2 to 4 and Comparative Examples 1 to 3 were subjected to wet wheel abrasion test, load wheel sand adhesion (LWT) and rutting deformation test, and expansion test, respectively. The wet wheel abrasion test is to study the abrasion resistance of the mixture under the conditions of immersion in water for 1 hour and 6 days; the expansion test is carried out in accordance with the "Test Procedure for Aggregates in Highway Engineering (JTG E42-2005)".

[0047] The wet wheel wear of the mixtures prepared in each embodiment and comparative example is shown in Table 12: Table 12 Wet wheel wear of each mixture

[0048] The amount of sand adhered to the load wheel of the mixtures prepared in each embodiment and comparative example is shown in Table 13: Table 13 Load wheel sand adhesion (LWT) of each mixture

[0049] The deformation rate per unit width of the PLD of the mixtures prepared in each embodiment and comparative example is shown in Table 14: Table 14 Deformation rate per unit width of PLD of each mixture

[0050] The PVD-rutting depth rate per unit thickness of the mixtures prepared in each embodiment and comparative example is shown in Table 15: Table 15 PVD-rutting depth rate per unit thickness of each mixture

[0051] The expansion results of the mixtures obtained in the embodiments and comparative examples are shown in Table 16: Table 16 Water expansion ratio of each mixture

[0052] From the results of wet wheel wear, load wheel adhesion sand (LWT), rutting deformation test and expansion test, it can be seen that the present invention modifies steel slag and optimizes the emulsified asphalt preparation method, so that the ultra-thin cover prepared by the mixture is durable and anti-skid, crack-resistant and waterproof, with stable structure and strong overall cohesion.

[0053] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An emulsified asphalt steel slag ultra-thin overlay mixture, characterized in that: The composition comprises the following components by mass fraction: 100 parts of mineral material, 7-11 parts of emulsified asphalt and 1-3 parts of cement; When the mineral material passes through the standard square hole sieves with apertures of 9.5mm, 4.75mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm, 0.15mm and 0.075mm, the corresponding passing ratios are 100%, 70%-90%, 45%-70%, 28%-50%, 19%-34%, 12%-25%, 7%-18%, 7%-18% and 6%-12% respectively; The ore materials are divided into three groups according to particle size: the first group of aggregates: 5-10 mm modified steel slag aggregates; the second group of aggregates: 0-5 mm limestone aggregates; the third group of slag powder: limestone slag powder; the first group of aggregates accounts for 30-35% of the ore material mass, the second group of aggregates accounts for 60-70% of the ore material mass, and the third group of slag powder accounts for 1-3% of the ore material mass; The preparation method of the modified steel slag aggregate is: Step 1: First, soak the steel slag aggregate in water. After it is completely soaked, heat it to 60-70°C, then introduce carbon dioxide into the water while stirring for reaction. After the reaction time is 3-5 hours, filter the filtered steel slag aggregate, soak it in a cement slurry with a mass concentration of 30-40% for 1-2 hours, and filter it to obtain the pretreated steel slag aggregate; Step 2: first, soak the pretreated steel slag aggregate in an ethanol solution of a mercaptosilane coupling agent for 20-30 minutes, then dry it at 60-70° C. to a moisture content of 5-8%, then spray it with a methylphenyl silicone resin with a solid content of 10-20%, and cure it at 150-180° C. for 10-15 minutes to obtain a steel slag aggregate coated with a hydrophobic layer; Step 3: Spraying epoxy soybean oil onto the steel slag aggregate coated with the hydrophobic layer to obtain the modified steel slag aggregate.

2. The emulsified asphalt steel slag ultra-thin overlay mixture according to claim 1, characterized in that: In step 1, the carbon dioxide concentration is 20-30%, and the flow rate is 2-5 L / min.

3. The emulsified asphalt steel slag ultra-thin overlay mixture according to claim 1, characterized in that: In the step 2, the mass concentration of the mercaptosilane coupling agent ethanol solution is 5-9wt%.

4. The emulsified asphalt steel slag ultra-thin overlay mixture according to claim 1, characterized in that: In step 3, the amount of the epoxidized soybean oil used is 0.1-0.5% of the weight of the steel slag aggregate coated with the hydrophobic layer.

5. The emulsified asphalt steel slag ultra-thin overlay mixture according to claim 1, characterized in that: The emulsified asphalt comprises the following components in weight percentage: 80-90% of base asphalt, 1-3% of SBS modifier, 1-3% of emulsifier, 6-8% of SBR latex, 0.2-0.5% of NaCl stabilizer and 2-3% of warm mix agent.

6. The emulsified asphalt steel slag ultra-thin overlay mixture according to claim 5, characterized in that: The preparation method of the emulsified asphalt is: (1) Weigh each component by weight percentage, add the emulsifier into 60-70°C water and stir, add hydrochloric acid while stirring to adjust the pH to 2-3, after the emulsifier is completely dissolved, add SBR latex and mix well, and continue to adjust the pH to 2-3 to obtain soap solution; (2) heating the base asphalt to 180-200°C, adding SBS modifier, high-speed shearing at 3000-5000 rpm for 30-40 minutes, and then developing at 180-200°C for 3-5 hours to obtain modified asphalt; (3) Add the soap solution, modified asphalt, NaCl stabilizer and warm mix agent into a colloid mill for shear grinding and cooling to obtain emulsified asphalt.

7. A method for preparing an emulsified asphalt steel slag ultra-thin overlay mixture according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: weighing mineral materials, emulsified asphalt and cement according to weight, mixing them evenly, adding 5-8% water of the weight of the mineral materials and stirring for 80-90 seconds to obtain the product.

8. Use of the emulsified asphalt steel slag ultra-thin overlay mixture according to any one of claims 1 to 6 in pavement maintenance.

9. The use according to claim 8, characterized in that When the emulsified asphalt steel slag ultra-thin overlay mixture is used for road maintenance, the construction temperature is room temperature, the compaction thickness is 0.7-1.0 cm, and after the mixture is spread for 2 hours, the pavement is rolled 1-3 times with a rubber-wheel roller before being opened to traffic.

Images