Cold-mixed full steel slag asphalt mixture and preparation method thereof

Abstract

A cold-mixed all-steel slag asphalt mixture and its preparation method are disclosed, belonging to the field of asphalt technology. The cold-mixed all-steel slag asphalt mixture is composed of modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer. The cold-mixed all-steel slag asphalt mixture prepared by this invention has a dynamic stability of 8730~9110 cycles / mm at 60℃, a water immersion Marshall residual stability of 91.4~93.6, a freeze-thaw splitting strength ratio of 89.3~92.0%, a failure strain of 2604~2773με in the -10℃ low-temperature bending test, and an expansion rate of 0.13~0.27%.

Description

Technical Field

[0001] This invention relates to a cold-mixed all-steel slag asphalt mixture and its preparation method, belonging to the field of asphalt technology. Background Technology

[0002] Steel slag, a byproduct of steelmaking, accounts for 10-15% of crude steel production. It is characterized by its strength, wear resistance, and low content of needle-like and flaky particles, making it a viable alternative to natural aggregates in asphalt mixtures. The resource utilization of steel slag in road engineering can effectively alleviate the shortage of high-quality natural aggregates and save the large amount of land occupied by steel slag stockpiles. Although using steel slag in asphalt mixtures offers economic benefits by turning waste into treasure, its poor stability is a significant drawback in practical applications. The poor stability of steel slag is mainly due to the hydration reaction of free calcium oxide and free magnesium oxide within it. These two substances react with water in the early stages of asphalt mixture curing, causing volume expansion. This results in numerous pores within the subgrade material during the initial pavement stage. Therefore, regardless of whether steel slag is used as an admixture in cement concrete or as an aggregate in asphalt mixtures, the volume expansion in the early curing stage poses a significant risk to the road's load-bearing capacity. Furthermore, current research and applications of steel slag as an aggregate in asphalt mixtures are mostly limited to hot-mix asphalt mixtures, with very little attention paid to the preparation of steel slag asphalt mixtures using cold-mix methods. Therefore, developing cold-mix all-steel slag asphalt mixtures with low volume expansion rates is of great significance for the safe and effective utilization of steel slag, improving pavement quality, and promoting energy conservation and environmental protection.

[0003] Chinese patent CN120518341A discloses a method for preparing modified steel slag powder for cold-mixed all-steel slag asphalt mixtures, including the following preparation steps: 1) Mixing 80-90 parts by weight of steel slag, 10-20 parts by weight of waste slurry powder, and 1-2 parts by weight of triethanolamine in a mixing drum to form a mixture; 2) Grinding the mixture in a ball mill for a set time to form powder; 3) Drying the powder in a dryer to obtain modified steel slag powder. The asphalt mixture prepared from the modified steel slag powder of this patent has an expansion rate of over 0.7%, which is not particularly good. Furthermore, the freeze-thaw splitting strength is relatively low, indicating that the internal density of the asphalt mixture after curing is not particularly high, resulting in poor freeze-thaw performance.

[0004] Chinese patent CN120518348A discloses a method for preparing cold-mixed all-steel slag asphalt mixture, including the following steps: 1) Adding coarse steel slag and fine steel slag to an asphalt mixing pot according to the mass ratio and stirring to form mixed steel slag; 2) Mixing modified steel slag powder, polydimethylsiloxane, fly ash, hydrogen peroxide, and mixed steel slag according to the mass ratio to form a first batch of mixture for later use; 3) Mixing emulsified asphalt, water-based epoxy resin, water-based curing agent, and defoamer according to the mass ratio to form a second batch of mixture; 4) Mixing the first batch of mixture with the second batch of mixture, then adding modified steel slag powder and mixing to form a cold-mixed all-steel slag asphalt mixture. The cold-mixed all-steel slag asphalt mixture prepared by this patent also has prominent problems such as high expansion rate, poor low-temperature freeze-thaw resistance, and poor water immersion resistance.

[0005] As can be seen from the above, cold-mixed all-steel slag asphalt mixtures still have prominent problems such as high expansion rate, low water immersion resistance, and poor freeze-thaw resistance. Therefore, developing cold-mixed all-steel slag asphalt mixtures with low expansion rate, good freeze-thaw resistance, and excellent water immersion resistance is of great practical significance for improving the quality of road paving materials. Summary of the Invention

[0006] To address the shortcomings of the existing technology, this invention provides a cold-mixed all-steel slag asphalt mixture and its preparation method, achieving the following objectives: to prepare a cold-mixed all-steel slag asphalt mixture with low expansion rate, good freeze-thaw resistance, and excellent water immersion resistance.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A cold-mixed all-steel slag asphalt mixture and its preparation method are disclosed. The cold-mixed all-steel slag asphalt mixture is composed of modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer. In the synthetic wax emulsion, the synthetic wax is one of polyethylene wax, oxidized polyethylene wax, and polypropylene wax; The synthetic wax emulsion contains 20-35 wt% synthetic wax. The mass ratio of the modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer is 200~410:45~140:6~20:7~17:1~2. The following are further improvements to the above technical solution: Step 1: Preparation of modified steel slag Graded steel slag, silicon phosphate powder, and methyl silicate powder are added to a mixer and mixed. Then, an acid solution is added and stirred until the reaction is complete. Finally, a silicate aqueous solution is added, mixed, discharged, spread out and left to dry. Then, a methyl silicate aqueous solution is sprayed onto the surface of the graded steel slag and allowed to air dry naturally to obtain modified steel slag. The graded steel slag specifically includes No. 1 material with a particle size of 0.1~1mm, No. 2 material with a particle size of 1.1~4mm, and No. 3 material with a particle size of 4.1~10mm; The mass ratio of material #1, material #2, and material #3 is 4~15:90~200:40~100; The acid solution is one or a mixture of two of oxalic acid aqueous solution and citric acid aqueous solution in any mass ratio; The acid solution contains an acid concentration of 5-16 wt%. The particle size of the silicon phosphate powder is 1~10μm; The particle size of the methylsilicic acid powder is 1~10μm; The silicate aqueous solution is one or a mixture of two of sodium metasilicate aqueous solution and potassium silicate aqueous solution in any mass ratio; In the silicate aqueous solution, the mass fraction of silicate is 10~30wt%, and the modulus of silicate is 1.5~3; The methylsilicate aqueous solution is one or a mixture of two of potassium methylsilicate aqueous solution and sodium methylsilicate aqueous solution in any mass ratio; The methylsilicate aqueous solution has a methylsilicate concentration of 1-3.5 wt%. The mass ratio of the graded steel slag, silicon phosphate powder, methyl silicate powder, acid solution, and silicate aqueous solution is 450~850:4~18:3~13:6~20:12~30; The spraying mass of the methyl silicate aqueous solution is 0.2~0.6% of the mass of the graded steel slag; The stirring reaction was complete, the stirring rate was 100-400 rpm, and the reaction time was 20-40 minutes; After mixing, the material is discharged. The stirring speed is 100-400 rpm, and the stirring time is 15-30 minutes. The process involves spreading the fabric out to air dry for 30-50 minutes in an environment with room temperature and relative humidity less than 50%. The natural air drying process involves leaving the product to air dry for 10-30 minutes in an environment with room temperature and relative humidity less than 50%.

[0008] Step 2: Preparation of sustained-release antifreeze emulsion Antifreeze powder and ethyl acetate were added to a dispersion reactor and stirred until evenly dispersed. The mixture was then heated to the reaction temperature and stirred at low speed while maintaining reflux. An amino-containing silane coupling agent was added, and after the reaction was complete, isocyanate was added. After the reaction was complete, a crosslinking agent and a hydroxyl-containing nonionic surfactant were added. The reaction was continued until the isocyanate in the system was completely consumed. The mixture was then centrifuged, and the resulting solid was washed and dried to obtain the modified antifreeze. The modified antifreeze, alkyl glycoside, and water were then added to a high-speed emulsifier and emulsified into a homogeneous and stable emulsion to obtain the slow-release antifreeze emulsion. The particle size of the antifreeze powder is 0.5~5μm; The antifreeze is one or a mixture of two of calcium chloride and sodium chloride in any mass ratio; The amine-containing silane coupling agent is one or a mixture of any two or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-diethylaminomethyltriethoxysilane in any mass ratio. The isocyanate is one of toluene diisocyanate and diphenylmethane diisocyanate; The crosslinking agent is one or a mixture of any two or more of trihydroxyethyl isocyanurate, triethanolamine, and glycerol in any mass ratio; The hydroxyl-containing nonionic surfactant is one or a mixture of any two or more of the following in any mass ratio: Span 20, Span 40, Span 60, Span 80, Tween 20, Tween 40, Tween 60, Tween 80, tall oil diethanolamide, oleic acid diethanolamide, lauric acid diethanolamide, and lauric acid diethanolamide. The alkyl glycoside has 8-14 alkyl carbons and a degree of polymerization of 1.2-1.8; The mass ratio of the antifreeze powder, ethyl acetate, amine-containing silane coupling agent, isocyanate, crosslinking agent, and hydroxyl-containing nonionic surfactant is 90~150:450~800:5~19:15~50:5~10:15~30; The mass ratio of the modified antifreeze, alkyl glycoside, and water is 40~90:2~7:100~220; The stirring and dispersion are uniform, with a dispersion rate of 5000~9000 rpm and a dispersion time of 2~5 hours; The reaction temperature is 65~80℃; The low-speed stirring has a stirring rate of 800~1200 rpm; Once the reaction is complete, the reaction time is 4 to 7 hours. After the reaction is completed, the reaction time is 2 to 5 hours; The washing process involves washing with anhydrous ethanol 2 to 4 times, with the mass of anhydrous ethanol used in each wash being equal to the mass of the solid being washed. The drying process involves a drying temperature of 50-80℃ and a drying time of 12-15 hours.

[0009] Step 3: Preparation of cold-mixed all-steel slag asphalt mixture According to the composition of cold-mixed all-steel slag asphalt mixture and the mass ratio of each raw material in the composition, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether modified siloxane defoamer are added to the mixer and mixed evenly. Then, modified steel slag is added, and the mixture is stirred and mixed evenly before being discharged to obtain cold-mixed all-steel slag asphalt mixture.

[0010] Compared with the prior art, the present invention achieves the following beneficial effects: 1. To reduce the expansion of steel slag, this invention uses two weak acids, silicon phosphate and methyl silicate, which can chemically precipitate activated calcium oxide and activated magnesium oxide, to completely eliminate the expansion effect caused by activated calcium oxide and activated magnesium oxide in the early stage of asphalt mixture curing. To accelerate the chemical precipitation reaction of silicon phosphate and methyl silicate with calcium oxide and magnesium oxide, this invention adds two strong organic acids, oxalic acid and citric acid, to catalyze the above chemical precipitation reaction. Therefore, silicon phosphate and methyl silicate can react with magnesium oxide and calcium oxide at a relatively fast rate to generate hard calcium magnesium phosphate and calcium magnesium methyl silicate precipitates. This completely eliminates the presence of active calcium oxide and active magnesium oxide. In addition, after the active calcium oxide and active magnesium oxide are completely eliminated, the present invention adds silicate solution to further solidify the generated hard calcium magnesium phosphate precipitate and calcium magnesium methyl silicate precipitate. This will further enhance the mechanical strength of the steel slag filler itself. After the silicate solution is solidified, the surface of the steel slag is sprayed with methyl silicate aqueous solution, which will improve the alkalinity and nonpolarity of the steel slag surface, enhance the adhesion between the steel slag and asphalt, and thus enhance the overall mechanical properties of the asphalt mixture after solidification, especially the water immersion stability and the mechanical properties under freeze-thaw low temperature conditions. 2. To improve the low-temperature resistance and freeze-thaw resistance of asphalt mixtures, this invention specifically designs a coating and emulsification process for the antifreeze agent. This process disperses the antifreeze agent as fine particles into the asphalt mixture matrix and imparts slow-release properties to the antifreeze agent. This significantly improves the long-term low-temperature resistance and freeze-thaw resistance of the cured asphalt mixture, extending its service life. The specific principle of the coating and emulsification process is as follows: micron-sized sodium chloride powder or calcium chloride powder is dispersed into micron-sized single particles in an ethyl acetate organic solvent under high-speed dispersion shearing. Because sodium chloride powder and calcium chloride powder are both hygroscopic inorganic substances with many hydrated hydroxyl groups on their surface, after adding an amino-containing silane coupling agent, the silanoxy functional groups react with the hydrated hydroxyl groups, and the surface of the sodium chloride powder or calcium chloride powder is covered with amino functional groups. Then, after adding isocyanate, the isocyanate groups and amino groups react rapidly, and the surface of the sodium chloride powder or calcium chloride powder is covered with isocyanate functional groups again. Next, a crosslinking agent containing active hydroxyl groups and a nonionic surfactant are added, and the isocyanate functional groups and hydroxyl groups on the surface of the sodium chloride powder or calcium chloride powder... After the basic reaction, a polyurethane shell of a certain thickness and with a high degree of cross-linking is formed. The outer surface of this shell is covered by hydrophobic segments of nonionic surfactants. In the subsequent emulsification process, the nonionic surfactant alkyl glycosides can easily encapsulate the hydrophobic segments on the outer surface of the polyurethane shell, forming an oil-in-water micelle structure. This allows the polyurethane-encapsulated sodium chloride or calcium chloride powder to form a stable emulsion, which is particularly easy to mix evenly with raw materials such as emulsified asphalt and synthetic wax emulsions. After the asphalt mixture is cured, the polyurethane-encapsulated sodium chloride or calcium chloride powder is uniformly dispersed in the asphalt matrix. During the volume change of the polyurethane layer encapsulated by the sodium chloride or calcium chloride powder in the freeze-thaw cycle, sodium chloride or calcium chloride will slowly dissolve due to the penetration of water. Thus, the trace amount of water that has penetrated into the asphalt mixture after curing will form a salt solution of a certain concentration, thereby lowering the freezing point of the water inside the cured asphalt mixture and reducing the freeze-thaw effect caused by the freezing of water inside the asphalt mixture. Ultimately, this improves the low-temperature resistance and freeze-thaw resistance of the asphalt mixture. 3. This invention improves the hydrophobicity of the internal pore surface of asphalt mixture after curing by adding synthetic wax emulsion. The hydrophobic principle is as follows: During the curing process of asphalt mixture, as water evaporates and is lost, the demulsified wax particles will gradually migrate to the surface of the asphalt matrix due to their extremely low surface tension and surface energy. During the curing process, the areas where the asphalt matrix can form a surface are mainly concentrated on the surface of the internal pores and the surface of the paved road. Thus, the pores formed inside the asphalt matrix after curing exhibit superhydrophobicity due to the accumulation of wax particles. This will form a reverse capillary phenomenon, increasing the pressure of external water entering the internal pores of the asphalt matrix. This greatly reduces the water content inside the asphalt matrix. Furthermore, the wax particles accumulated on the surface of the pavement will also hinder the downward penetration of water from the pavement into the asphalt matrix. However, this hindering effect will not last long. Due to the road load, the wax particles accumulated on the pavement surface will be quickly worn away. However, the accumulation of wax particles on the surface of the internal pores of the asphalt matrix below the pavement surface will give the asphalt mixture lasting superhydrophobicity. 4. The cold-mixed steel slag asphalt mixture prepared by this invention has a dynamic stability of 8730~9110 cycles / mm at 60℃, a water immersion Marshall residual stability of 91.4~93.6, a freeze-thaw splitting strength ratio of 89.3~92.0%, a failure strain of 2604~2773με in the -10℃ low-temperature bending test, and an expansibility of 0.13~0.27%. Detailed Implementation

[0011] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0012] Example 1: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1: Preparation of modified steel slag Graded steel slag, silicon phosphate powder, and methyl silicate powder are added to a mixer and mixed. Then, an acid solution is added and stirred until the reaction is complete. Finally, a silicate aqueous solution is added, mixed, discharged, spread out and left to dry. Then, a methyl silicate aqueous solution is sprayed onto the surface of the graded steel slag and allowed to air dry naturally to obtain modified steel slag. The graded steel slag specifically includes No. 1 material with a particle size of 0.3mm, No. 2 material with a particle size of 2mm, and No. 3 material with a particle size of 7mm; The mass ratio of material #1, material #2, and material #3 is 11:150:60; The acid solution is an aqueous solution of oxalic acid; The acid solution has an acid concentration of 11 wt%. The particle size of the silicon phosphate powder is 5 μm; The particle size of the methylsilicic acid powder is 6 μm; The silicate aqueous solution is a sodium metasilicate aqueous solution; The silicate aqueous solution has a silicate mass fraction of 15 wt% and a silicate modulus of 2. The aqueous solution of methylsilicate is an aqueous solution of potassium methylsilicate; The methylsilicate aqueous solution has a methylsilicate mass concentration of 2 wt%. The mass ratio of the graded steel slag, silicon phosphate powder, methyl silicate powder, acid solution, and silicate aqueous solution is 550:11:8:15:20. The spraying mass of the methyl silicate aqueous solution is 0.5% of the mass of the graded steel slag; The stirring reaction was complete at a stirring rate of 300 rpm for 35 minutes. The material is discharged after mixing, with a stirring speed of 300 rpm and a mixing time of 25 minutes; The flattened and air-dried product is placed in an environment with room temperature and relative humidity of less than 50% for 40 minutes. The natural air drying process involves leaving the product to air dry for 20 minutes in an environment with room temperature and relative humidity less than 50%.

[0013] Step 2: Preparation of sustained-release antifreeze emulsion Antifreeze powder and ethyl acetate were added to a dispersion reactor and stirred until evenly dispersed. The mixture was then heated to the reaction temperature and stirred at low speed while maintaining reflux. An amino-containing silane coupling agent was added, and after the reaction was complete, isocyanate was added. After the reaction was complete, a crosslinking agent and a hydroxyl-containing nonionic surfactant were added. The reaction was continued until the isocyanate in the system was completely consumed. The mixture was then centrifuged, and the resulting solid was washed and dried to obtain the modified antifreeze. The modified antifreeze, alkyl glycoside, and water were then added to a high-speed emulsifier and emulsified into a homogeneous and stable emulsion to obtain the slow-release antifreeze emulsion. The particle size of the antifreeze powder is 1 μm; The antifreeze is calcium chloride; The amine-containing silane coupling agent is γ-aminopropyltriethoxysilane; The isocyanate is toluene diisocyanate; The crosslinking agent is trihydroxyethyl isocyanurate; The hydroxyl-containing nonionic surfactant is Span 20; The alkyl glycoside has 11 alkyl carbons and a degree of polymerization of 1.5. The mass ratio of the antifreeze powder, ethyl acetate, amine-containing silane coupling agent, isocyanate, crosslinking agent, and hydroxyl-containing nonionic surfactant is 110:600:12:40:8:25. The mass ratio of the modified antifreeze, alkyl glycoside, and water is 60:5:150; The stirring and dispersion were uniform, with a dispersion rate of 8000 rpm and a dispersion time of 4 hours; The reaction temperature is 70°C; The low-speed stirring has a stirring rate of 900 rpm; Once the reaction is complete, the reaction time is 5 hours. The reaction was completed after 4 hours. The washing process involves washing three times with anhydrous ethanol, with the mass of anhydrous ethanol used in each wash being equal to the mass of the solid being washed. The drying process is carried out at a temperature of 70°C for 14 hours.

[0014] Step 3: Preparation of cold-mixed all-steel slag asphalt mixture According to the composition of cold-mixed all-steel slag asphalt mixture and the mass ratio between each raw material in the composition, non-ionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether modified siloxane defoamer are added to the mixer and mixed evenly. Then, modified steel slag is added, and the mixture is stirred and mixed evenly before being discharged to obtain cold-mixed all-steel slag asphalt mixture. The cold-mixed steel slag asphalt mixture is composed of modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer. In the synthetic wax emulsion, the synthetic wax is polyethylene wax; The synthetic wax emulsion contains 25 wt% synthetic wax. The mass ratio of the modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer is 310:100:10:11:1.6.

[0015] Example 2: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1: Preparation of modified steel slag Graded steel slag, silicon phosphate powder, and methyl silicate powder are added to a mixer and mixed. Then, an acid solution is added and stirred until the reaction is complete. Finally, a silicate aqueous solution is added, mixed, discharged, spread out and left to dry. Then, a methyl silicate aqueous solution is sprayed onto the surface of the graded steel slag and allowed to air dry naturally to obtain modified steel slag. The graded steel slag specifically includes No. 1 material with a particle size of 0.1 mm, No. 2 material with a particle size of 1.1 mm, and No. 3 material with a particle size of 4.1 mm. The mass ratio of material #1, material #2, and material #3 is 4:90:40; The acid solution is an aqueous solution of citric acid; The acid solution has an acid concentration of 5 wt%. The particle size of the silicon phosphate powder is 1 μm; The particle size of the methylsilicic acid powder is 1 μm; The silicate aqueous solution is a potassium silicate aqueous solution; The silicate aqueous solution has a silicate mass fraction of 10 wt% and a silicate modulus of 1.5. The aqueous solution of methylsilicate is an aqueous solution of sodium methylsilicate; The methylsilicate aqueous solution has a methylsilicate mass concentration of 1 wt%. The mass ratio of the graded steel slag, silicon phosphate powder, methyl silicate powder, acid solution, and silicate aqueous solution is 450:4:3:6:12. The spraying mass of the methyl silicate aqueous solution is 0.2% of the mass of the graded steel slag; The stirring reaction was complete at a stirring rate of 100 rpm for 20 minutes. After mixing, the material is discharged. The stirring speed is 100 rpm and the mixing time is 15 minutes. The process involves spreading the fabric out to air dry for 30 minutes in an environment with room temperature and relative humidity less than 50%. The natural air drying process involves leaving the product to air dry for 10 minutes in an environment with room temperature and relative humidity less than 50%.

[0016] Step 2: Preparation of sustained-release antifreeze emulsion Antifreeze powder and ethyl acetate were added to a dispersion reactor and stirred until evenly dispersed. The mixture was then heated to the reaction temperature and stirred at low speed while maintaining reflux. An amino-containing silane coupling agent was added, and after the reaction was complete, isocyanate was added. After the reaction was complete, a crosslinking agent and a hydroxyl-containing nonionic surfactant were added. The reaction was continued until the isocyanate in the system was completely consumed. The mixture was then centrifuged, and the resulting solid was washed and dried to obtain the modified antifreeze. The modified antifreeze, alkyl glycoside, and water were then added to a high-speed emulsifier and emulsified into a homogeneous and stable emulsion to obtain the slow-release antifreeze emulsion. The particle size of the antifreeze powder is 0.5 μm; The antifreeze is sodium chloride; The amine-containing silane coupling agent is γ-aminopropyltrimethoxysilane; The isocyanate is diphenylmethane diisocyanate; The crosslinking agent is triethanolamine; The hydroxyl-containing nonionic surfactant is Span 40; The alkyl glycoside has 8 alkyl carbons and a degree of polymerization of 1.2; The mass ratio of the antifreeze powder, ethyl acetate, amine-containing silane coupling agent, isocyanate, crosslinking agent, and hydroxyl-containing nonionic surfactant is 90:450:5:15:5:15; The mass ratio of the modified antifreeze, alkyl glycoside, and water is 40:2:100; The stirring and dispersion are uniform, with a dispersion rate of 5000 rpm and a dispersion time of 2 hours; The reaction temperature is 65°C; The low-speed stirring has a stirring rate of 800 rpm; Once the reaction is complete, the reaction time is 4 hours. The reaction takes 2 hours to complete. The washing process involves washing twice with anhydrous ethanol, with the mass of anhydrous ethanol used in each wash being equal to the mass of the solid being washed. The drying process is carried out at a temperature of 50°C for 12 hours.

[0017] Step 3: Preparation of cold-mixed all-steel slag asphalt mixture According to the composition of cold-mixed all-steel slag asphalt mixture and the mass ratio between each raw material in the composition, non-ionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether modified siloxane defoamer are added to the mixer and mixed evenly. Then, modified steel slag is added, and the mixture is stirred and mixed evenly before being discharged to obtain cold-mixed all-steel slag asphalt mixture. The cold-mixed steel slag asphalt mixture is composed of modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer. In the synthetic wax emulsion, the synthetic wax is oxidized polyethylene wax; The synthetic wax emulsion contains 20 wt% synthetic wax. The mass ratio of the modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer is 200:45:6:7:1.

[0018] Example 3: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1: Preparation of modified steel slag Graded steel slag, silicon phosphate powder, and methyl silicate powder are added to a mixer and mixed. Then, an acid solution is added and stirred until the reaction is complete. Finally, a silicate aqueous solution is added, mixed, discharged, spread out and left to dry. Then, a methyl silicate aqueous solution is sprayed onto the surface of the graded steel slag and allowed to air dry naturally to obtain modified steel slag. The graded steel slag specifically includes No. 1 material with a particle size of 1mm, No. 2 material with a particle size of 4mm, and No. 3 material with a particle size of 10mm. The mass ratio of material #1, material #2, and material #3 is 15:200:100; The acid solution is an aqueous solution of citric acid; The acid solution has an acid concentration of 16 wt%. The particle size of the silicon phosphate powder is 10 μm; The particle size of the methylsilicic acid powder is 10 μm; The silicate aqueous solution is a potassium silicate aqueous solution; The silicate aqueous solution has a silicate mass fraction of 30 wt% and a silicate modulus of 3. The aqueous solution of methylsilicate is an aqueous solution of sodium methylsilicate; The methylsilicate aqueous solution has a methylsilicate mass concentration of 3.5 wt%. The mass ratio of the graded steel slag, silicon phosphate powder, methyl silicate powder, acid solution, and silicate aqueous solution is 850:18:13:20:30. The spraying mass of the methyl silicate aqueous solution is 0.6% of the mass of the graded steel slag; The stirring reaction was complete at a stirring rate of 400 rpm for 40 minutes. After mixing, the material is discharged. The stirring speed is 400 rpm and the mixing time is 30 minutes. The process involves spreading the fabric out to air dry for 50 minutes in an environment with room temperature and relative humidity less than 50%. The natural air drying process involves leaving the product to air dry for 30 minutes in an environment with room temperature and relative humidity less than 50%.

[0019] Step 2: Preparation of sustained-release antifreeze emulsion Antifreeze powder and ethyl acetate were added to a dispersion reactor and stirred until evenly dispersed. The mixture was then heated to the reaction temperature and stirred at low speed while maintaining reflux. An amino-containing silane coupling agent was added, and after the reaction was complete, isocyanate was added. After the reaction was complete, a crosslinking agent and a hydroxyl-containing nonionic surfactant were added. The reaction was continued until the isocyanate in the system was completely consumed. The mixture was then centrifuged, and the resulting solid was washed and dried to obtain the modified antifreeze. The modified antifreeze, alkyl glycoside, and water were then added to a high-speed emulsifier and emulsified into a homogeneous and stable emulsion to obtain the slow-release antifreeze emulsion. The particle size of the antifreeze powder is 5 μm; The antifreeze is sodium chloride; The amine-containing silane coupling agent is N,N-diethyl-3-aminopropyltrimethoxysilane; The isocyanate is diphenylmethane diisocyanate; The crosslinking agent is glycerol; The hydroxyl-containing nonionic surfactant is Span 60; The alkyl glycoside has 14 alkyl carbons and a degree of polymerization of 1.8. The mass ratio of the antifreeze powder, ethyl acetate, amine-containing silane coupling agent, isocyanate, crosslinking agent, and hydroxyl-containing nonionic surfactant is 150:800:19:50:10:30. The mass ratio of the modified antifreeze, alkyl glycoside, and water is 90:7:220; The stirring and dispersion were uniform, with a dispersion rate of 9000 rpm and a dispersion time of 5 hours; The reaction temperature is 80°C; The low-speed stirring has a stirring rate of 1200 rpm; Once the reaction is complete, the reaction time is 7 hours. The reaction takes 5 hours to complete. The washing process involves washing four times with anhydrous ethanol, with the mass of anhydrous ethanol used in each wash being equal to the mass of the solid being washed. The drying process involves a drying temperature of 80°C and a drying time of 15 hours.

[0020] Step 3: Preparation of cold-mixed all-steel slag asphalt mixture According to the composition of cold-mixed all-steel slag asphalt mixture and the mass ratio between each raw material in the composition, non-ionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether modified siloxane defoamer are added to the mixer and mixed evenly. Then, modified steel slag is added, and the mixture is stirred and mixed evenly before being discharged to obtain cold-mixed all-steel slag asphalt mixture. The cold-mixed steel slag asphalt mixture is composed of modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer. In the synthetic wax emulsion, the synthetic wax is polypropylene wax; The synthetic wax emulsion contains 35 wt% synthetic wax. The mass ratio of the modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer is 410:140:20:17:2.

[0021] Example 4: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The amine-containing silane coupling agent is N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane; The hydroxyl-containing nonionic surfactant is Span 80; Step 3 is the same as in Example 1.

[0022] Example 5: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The amine-containing silane coupling agent is γ-diethylaminomethyltriethoxysilane; The hydroxyl-containing nonionic surfactant is Tween 20; Step 3 is the same as in Example 1.

[0023] Example 6: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is Tween 40; Step 3 is the same as in Example 1.

[0024] Example 7: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is Tween 60; Step 3 is the same as in Example 1.

[0025] Example 8: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is Tween 80; Step 3 is the same as in Example 1.

[0026] Example 9: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is tall oil diethanolamide; Step 3 is the same as in Example 1.

[0027] Example 10: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is oleic acid diethanolamide; Step 3 is the same as in Example 1.

[0028] Example 11: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is lauryl diethanolamide; Step 3 is the same as in Example 1.

[0029] Example 12: A method for preparing cold-mixed all-steel slag asphalt mixture Step 1 is the same as in Example 1; Step 2: Preparation of sustained-release antifreeze emulsion The hydroxyl-containing nonionic surfactant is lauryl diethanolamide; Step 3 is the same as in Example 1.

[0030] Comparative Example 1: Based on Example 1, step 1, the preparation of modified steel slag, was omitted. In step 3, the preparation of cold-mixed all-steel slag asphalt mixture, 310 parts of modified steel slag were replaced with 310 parts of graded steel slag. The specific operation is as follows: Step 1, the preparation of modified steel slag, is not performed; Step 2 is the same as in Example 1; Step 3: Preparation of cold-mixed all-steel slag asphalt mixture Replace 310 parts of modified steel slag with 310 parts of graded steel slag, and perform the other operations as in Example 1; The graded steel slag specifically includes No. 1 material with a particle size of 0.3mm, No. 2 material with a particle size of 2mm, and No. 3 material with a particle size of 7mm; The mass ratio of material #1, material #2, and material #3 is 11:150:60.

[0031] Comparative Example 2: Based on Example 1, in step 1, the preparation of modified steel slag, silicon phosphate powder and methyl silicate powder were not added. Instead, 11 parts of silicon phosphate powder and 8 parts of methyl silicate powder were replaced with 19 parts of graded steel slag. The specific operation is as follows: Step 1: Preparation of modified steel slag Replace 11 parts of silicon phosphate powder and 8 parts of methyl silicate powder with 19 parts of graded steel slag, and perform the other operations as in Example 1. Steps 2 and 3 are the same as in Example 1.

[0032] Comparative Example 3: Based on Example 1, in step 1, the preparation of modified steel slag, and in step 4, the preparation of modified asphalt for heavy-duty pavement, the methyl silicate aqueous solution was not sprayed onto the surface of the graded steel slag. The specific operation is as follows: Step 1: Preparation of modified steel slag Graded steel slag, silicon phosphate powder, and methyl silicate powder are added to a mixer, mixed evenly, and then an acid solution is added. After the reaction is complete, an aqueous silicate solution is added, mixed evenly, discharged, spread out and dried to obtain modified steel slag. Other operations are the same as in Example 1. Steps 2 and 3 are the same as in Example 1.

[0033] Comparative Example 4: Based on Example 1, step 2, the preparation of the slow-release antifreeze emulsion, was omitted. In step 3, the preparation of the cold-mixed all-steel slag asphalt mixture, 11 parts of the slow-release antifreeze emulsion were replaced with 11 parts of modified steel slag in equal amounts. The specific operation is as follows: Step 1 is the same as in Example 1; Step 2, preparation of the slow-release antifreeze emulsion, is not performed; Step 3: Preparation of cold-mixed all-steel slag asphalt mixture Replace 11 parts of slow-release antifreeze emulsion with 11 parts of modified steel slag, and perform the other operations as in Example 1.

[0034] Comparative Example 5: Based on Example 1, in step 3, the preparation of cold-mixed all-steel slag asphalt mixture, synthetic wax emulsion was not added; instead, 10 parts of synthetic wax emulsion were replaced with 10 parts of modified steel slag. The specific operation is as follows: Steps 1 and 2 are the same as in Example 1; Step 3: Preparation of cold-mixed all-steel slag asphalt mixture Step 4: Preparation of modified asphalt for heavy-duty road surfaces Replace 10 parts of synthetic wax emulsion with 10 parts of modified steel slag, and perform the other operations as in Example 1.

[0035] Performance testing: Following the test methods in JTG-E20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", the dynamic stability, water-immersed Marshall residual stability, freeze-thaw splitting strength ratio, and -10℃ low-temperature bending test failure strain of the cold-mixed all-steel slag asphalt mixtures obtained in Examples 1-12 and Comparative Examples 1-5 were tested. Additionally, the expansibility was tested using the test methods described in the master's thesis "Preparation and Performance Study of Steel Slag Asphalt Mastic Mixture" from Wuhan University of Technology. The results are shown in Table 1. Table 1 As shown in Table 1, the dynamic stability of Examples 1-12 is above 8700 cycles / mm, the residual Marshall stability after immersion in water is above 91, the freeze-thaw splitting strength ratio is greater than 89%, the failure strain in the -10℃ low-temperature bending test is not less than 2600με, and the expansibility is below 0.27%. This indicates that the cold-mixed all-steel slag asphalt mixture obtained by the present invention has significant characteristics such as low expansibility, good freeze-thaw resistance, and excellent water immersion resistance. In Comparative Example 1, which does not modify the steel slag, the residual Marshall stability after immersion in water, freeze-thaw splitting strength, and failure strain in the -10℃ low-temperature bending test all decrease sharply, especially the expansibility, which is as high as 5.56%. This indicates that the unmodified steel slag has a relatively high content of free calcium oxide and free magnesium oxide, which leads to a significant increase in the expansion rate of the asphalt mixture in the early stage of curing. This results in a large internal porosity of the cured mixture, severe debonding between the steel slag and the asphalt surface, and ultimately a sharp decrease in various road performance indicators. Comparative Example 2 In the preparation of modified steel slag, without the addition of silicon phosphate powder and methyl silicate powder, the water immersion Marshall residual stability, freeze-thaw splitting strength, and -10℃ low-temperature bending test failure strain of Comparative Example 2 were significantly reduced, and the expansion ratio was as high as 4.84%. This indicates that silicon phosphate powder and methyl silicate powder can react with free calcium oxide and free magnesium oxide. Because silicon phosphate and methyl silicate are both weakly acidic, under the catalysis of oxalic acid or citric acid, silicon phosphate and methyl silicate can quickly react with magnesium oxide and calcium oxide to form hard calcium magnesium phosphate and calcium magnesium methyl silicate precipitates. In this way, the free calcium oxide and free magnesium oxide contained in the steel slag are effectively removed, thereby reducing the expansion ratio and ultimately improving the various road performance indicators of the asphalt mixture. In Comparative Example 3, without spraying the surface of the steel slag with methyl silicate aqueous solution, the dynamic stability of Comparative Example 3 was significantly reduced, the water immersion Marshall residual stability also decreased significantly, and the freeze-thaw splitting strength ratio also decreased to 77.The failure strain in the -10℃ low-temperature bending test decreased by 4%, falling below 2000, with little change in expansibility. This may be because the surface alkalinity of the steel slag increased, polarity decreased, and hydrophobicity increased after spraying with methyl silicate aqueous solution. This enhances the adhesion between the steel slag and asphalt, thereby improving the overall mechanical properties of the cured asphalt mixture, especially its water immersion stability and mechanical properties under freeze-thaw conditions. Therefore, the dynamic stability, water immersion Marshall residual stability, freeze-thaw splitting strength, and failure strain in the -10℃ low-temperature bending test of Comparative Example 3 all showed significant decreases. In addition, the expansibility of Comparative Example 3 did not change significantly, indicating that there was no chemical reaction between the methyl silicate aqueous solution and free calcium oxide and free magnesium oxide. This may also be because the free calcium oxide and free magnesium oxide in the steel slag were completely consumed by silicon phosphate and methyl silicate under the catalysis of the acid solution. Subsequent additions had no effect on the expansibility. In Comparative Example 4, without the addition of a slow-release antifreeze emulsion, the dynamic stability, water-immersed Marshall residual stability, and expansibility of Comparative Example 4 did not show a significant decrease. However, the freeze-thaw splitting strength and the failure strain in the -10℃ low-temperature bending test of Comparative Example 4 decreased significantly. This indicates that the slow-release antifreeze emulsion plays a crucial role in improving the low-temperature resistance and freeze-thaw resistance of the asphalt mixture. In Comparative Example 5, without the addition of a synthetic wax emulsion, the dynamic stability, the failure strain in the -10℃ low-temperature bending test, and the expansibility of Comparative Example 5 did not show any significant changes. However, the water-immersed Marshall residual stability and the freeze-thaw splitting strength decreased significantly. This indicates that the addition of a synthetic wax emulsion can significantly improve the overall hydrophobicity of the cured asphalt mixture, thereby greatly improving the two road performance indicators: water-immersed Marshall residual stability and freeze-thaw splitting strength.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cold-mixed all-steel slag asphalt mixture, characterized in that: The cold-mixed steel slag asphalt mixture is composed of modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer. The modified steel slag is prepared by adding graded steel slag, silicon phosphate powder, and methyl silicate powder into a mixer, mixing them, adding an acid solution, stirring until the reaction is complete, adding a silicate aqueous solution, mixing them, discharging the material, spreading it out to dry, spraying a methyl silicate aqueous solution onto the surface of the graded steel slag, and letting it air dry naturally to obtain the modified steel slag. The slow-release antifreeze emulsion is prepared as follows: antifreeze powder and ethyl acetate are added to a dispersion reactor, stirred and dispersed evenly, and then heated to the reaction temperature. Under low-speed stirring and reflux conditions, an amino-containing silane coupling agent is added. After the reaction is complete, isocyanate is added. After the reaction is complete, a crosslinking agent and a hydroxyl-containing nonionic surfactant are added. The reaction continues until the isocyanate in the system is completely consumed. The mixture is then centrifuged, and the resulting solid is washed and dried to obtain a modified antifreeze. The modified antifreeze, alkyl glycoside, and water are then added to a high-speed emulsifier and emulsified into a homogeneous and stable emulsion to obtain the slow-release antifreeze emulsion.

2. The cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: In the synthetic wax emulsion, the synthetic wax is one of polyethylene wax, oxidized polyethylene wax, and polypropylene wax; The synthetic wax emulsion contains 20-35 wt% synthetic wax. The mass ratio of the modified steel slag, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether-modified siloxane defoamer is 200~410:45~140:6~20:7~17:1~2.

3. The cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: The graded steel slag specifically includes No. 1 material with a particle size of 0.1~1mm, No. 2 material with a particle size of 1.1~4mm, and No. 3 material with a particle size of 4.1~10mm; The acid solution is one or a mixture of two of oxalic acid aqueous solution and citric acid aqueous solution in any mass ratio; The acid solution has an acid concentration of 5-16 wt%.

4. The cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: The particle size of the silicon phosphate powder is 1~10μm; The particle size of the methylsilicic acid powder is 1~10μm; The silicate aqueous solution is one or a mixture of two of sodium metasilicate aqueous solution and potassium silicate aqueous solution in any mass ratio; The silicate aqueous solution has a silicate mass fraction of 10-30 wt% and a silicate modulus of 1.5-3.

5. The cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: The methylsilicate aqueous solution is one or a mixture of two of potassium methylsilicate aqueous solution and sodium methylsilicate aqueous solution in any mass ratio; The methylsilicate aqueous solution has a methylsilicate concentration of 1-3.5 wt%. The spraying mass of the methyl silicate aqueous solution is 0.2~0.6% of the mass of the graded steel slag.

6. The cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: The particle size of the antifreeze powder is 0.5~5μm; The antifreeze is one or a mixture of two of calcium chloride and sodium chloride in any mass ratio; The amine-containing silane coupling agent is one or a mixture of any two or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and γ-diethylaminomethyltriethoxysilane in any mass ratio.

7. The cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: The isocyanate is one of toluene diisocyanate and diphenylmethane diisocyanate; The crosslinking agent is one or a mixture of any two or more of trihydroxyethyl isocyanurate, triethanolamine, and glycerol in any mass ratio; The hydroxyl-containing nonionic surfactant is one or a mixture of any two or more of the following in any mass ratio: Span 20, Span 40, Span 60, Span 80, Tween 20, Tween 40, Tween 60, Tween 80, tall oil diethanolamide, oleic acid diethanolamide, lauric acid diethanolamide, and lauric acid diethanolamide. The alkyl glycoside has 8 to 14 alkyl carbons and a degree of polymerization of 1.2 to 1.

8.

8. The method for preparing cold-mixed all-steel slag asphalt mixture according to claim 1, characterized in that: According to the composition of cold-mixed all-steel slag asphalt mixture and the mass ratio of each raw material in the composition, nonionic emulsified asphalt, synthetic wax emulsion, slow-release antifreeze emulsion, and polyether modified siloxane defoamer are added to the mixer and mixed evenly. Then, modified steel slag is added, and the mixture is stirred and mixed evenly before being discharged to obtain cold-mixed all-steel slag asphalt mixture.

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