A direct-injection solid waste foaming warm mix agent and its preparation method and application

Abstract

The present invention discloses a direct-injection solid waste foaming warm mix agent, its preparation method, and application, belonging to the technical field of materials for road engineering. The invention provides a direct-injection solid waste foaming warm mix agent comprising: 80-100 parts red mud, 80-120 parts modified solution, 0.5-2 parts sodium dodecylbenzene sulfonate, and 15-35 parts water. The solid waste foaming warm mix agent is used in the preparation of warm-mix asphalt mixtures. The warm-mix asphalt mixtures comprise: 85-95 parts aggregate, 4-6 parts asphalt, 2-5 parts filler, and 0.5-2 parts solid waste foaming warm mix agent. The present invention utilizes the porous and highly water-absorbent properties of industrial solid waste red mud to modify it and prepare the solid waste foaming warm mix agent. The warm-mix asphalt mixture is prepared by direct injection, consuming more red mud while ensuring the road performance of the mixture, thereby realizing resource utilization of solid waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of road engineering materials, and in particular relates to a direct-injection solid waste foaming warm mix agent, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, hot-mix asphalt (HMA), the mainstream mixture used for asphalt pavement construction, suffers from high mixing temperatures, high energy consumption, and significant emissions. Excessively high construction temperatures can also cause asphalt aging, which in turn affects pavement performance. Warm-mix asphalt (WMA) technology, however, can reduce HMA construction temperatures by 30 to 60°C, making it an effective way to reduce carbon emissions and extend construction time. The three existing WMA technologies all rely on warm-mix agents. Foaming viscosity reduction technology has been widely adopted due to its low cost. However, the foaming effect of water-based and some hydrous mineral-based warm-mix agents is limited in duration and easily forms residual water, resulting in poor low-temperature performance and water stability in the mixture. This can lead to premature defects in warm-mix asphalt pavements, adversely affecting transportation and driving safety.

[0003] Red mud is a solid waste material discharged from the aluminum industry, with annual emissions reaching millions of tons. Currently, it is mainly used in three areas: first, the recovery of valuable metals; second, its addition to building materials such as cement, microcrystalline glass, concrete, and bricks; and third, its application in environmental remediation, such as utilizing its porous structure to absorb harmful gases and serving as a desulfurizer. However, these areas consume relatively little red mud and are subject to technical limitations, resulting in low red mud utilization rates. Red mud has been used in HMA technology, but few studies have been reported on its application in WMA technology.

[0004] In existing invention patents, red mud is used to prepare warm mix agents, and foamed asphalt is prepared by foaming hydrated minerals. However, due to the limitations of the structure and composition of red mud itself, it needs to be compounded with other materials. For example, CN109626872B discloses a foamed asphalt warm mix agent compounded with red mud and boron mud. In another example, CN116254005B compounded natural zeolite with red mud to prepare a warm mix agent, and the alkalinity of red mud is used to modify the natural zeolite and enhance the foaming properties. Since the inventions of these two warm mix agents rely on compounding and the foaming matrix is not entirely red mud, the red mud foaming WMA technology has not been fully realized. In addition, existing research is limited to the foaming properties of foamed asphalt, and it has not yet been put into asphalt mixture for WMA technology testing. Therefore, the performance of warm mix asphalt mixture, especially in terms of low temperature and water stability, is still unknown. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a direct-injection solid waste foaming warm mix agent and its preparation method and application. By utilizing the porous and highly water-absorbent properties of industrial solid waste red mud, it is modified to prepare a solid waste foaming warm mix agent, and a direct-injection method is adopted to prepare warm-mix asphalt mixture. While ensuring the road performance of the mixture, more red mud is consumed, thereby realizing the resource utilization of solid waste.

[0006] To achieve the above-mentioned object, the present invention provides a direct-injection solid waste foaming warm mix agent, which is prepared by including the following raw materials in parts by weight: 80-100 parts of red mud, 80-120 parts of modified solution, 0.5-2 parts of sodium dodecylbenzene sulfonate, and 15-35 parts of water.

[0007] Preferably, the method is prepared from the following raw materials in parts by weight: 80-100 parts of red mud, 100-110 parts of modified solution, 1-1.5 parts of sodium dodecylbenzenesulfonate, and 20-30 parts of water.

[0008] Preferably, the red mud is sintered red mud.

[0009] Preferably, the modified solution is an alkaline solution, the concentration of the alkaline solution is 0.08-0.12 mol / L, and the alkaline solution is potassium hydroxide solution and / or sodium hydroxide solution.

[0010] The present invention also provides a method for preparing the solid waste foaming warm mix agent, comprising the following steps:

[0011] (1) Red mud is initially dried, ground, and then dried again to obtain red mud powder;

[0012] (2) mixing the red mud powder obtained in step (1) with the modified solution, reacting, filtering, and performing a first drying treatment to obtain modified red mud powder;

[0013] (3) mixing the modified red mud powder obtained in step (2) with sodium dodecylbenzenesulfonate and water to obtain a solid mixture; and shearing the mixture to obtain a solid waste foaming warm mix agent.

[0014] Preferably, the temperature of the preliminary drying in step (1) is 90-120°C, and the time of the preliminary drying is 2-4 hours; the grinding in step (1) is ball milling, and the grinding time is 30-60 minutes; the temperature of the re-drying in step (1) is 90-120°C, and the time of the re-drying is 2-4 hours; the particle size of the red mud powder in step (1) is ≤0.075mm; the reaction time in step (2) is 5-10 minutes; the temperature of the first drying in step (2) is 90-120°C, and the time of the first drying is 2-4 hours.

[0015] Preferably, the shearing speed in step (3) is 800-1500 rpm, and the shearing time is 5-10 min.

[0016] The present invention also provides the use of the solid waste foaming warm mix agent in preparing warm mix asphalt mixture.

[0017] Preferably, the warm mix asphalt mixture is prepared from the following raw materials in parts by weight: 85-95 parts of aggregate, 4-6 parts of asphalt, 2-5 parts of filler, and 0.5-2 parts of solid waste foaming warm mix agent.

[0018] Preferably, the method for preparing the warm mix asphalt mixture comprises the following steps:

[0019] A. Heat the asphalt at 130-160℃ for 1-2 hours to obtain melted asphalt, and preheat the aggregate and filler at 160-180℃ for 2-4 hours to obtain preheated aggregate and preheated filler respectively;

[0020] B. Add melted asphalt to the preheated aggregate obtained in A, and immediately add solid waste foaming warm mix agent on the surface for mixing, mixing for the first time to obtain a mixture; add the preheated filler obtained in A to the mixture, mixing for the second time to obtain a warm mix asphalt mixture.

[0021] Preferably, the temperature of the first mixing in step B is 120-150°C; the temperature of the second mixing in step B is 120-150°C.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] This invention utilizes the porous structure and superior water absorption and retention capabilities of sintered red mud, further optimizing its structure with modifiers to produce a direct-injection modified red mud solid waste foaming warm mix agent. Surfactants further enhance foaming performance. Furthermore, its primary component, aluminosilicate, further reduces asphalt viscosity, enabling warm mix. Furthermore, the red mud ultimately remains in the mixture as a filler, where the strong physical adsorption of Al2O3 on light asphalt components improves the mixture's resistance to water damage.

[0024] The innovation of this invention lies in leveraging the porous structure and strong water absorption properties of sintered red mud, further optimizing its pore structure and properties through chemical modification. This allows the preparation of a direct-injection solid waste foaming warm-mix agent, which uses red mud as a foaming matrix, providing a new consumption pathway for red mud solid waste. During the mixing process, the water in the warm-mix agent evaporates due to heat and combines with the asphalt, causing the asphalt to foam and reduce viscosity. After mixing, the red mud, the main component of the warm-mix agent, restores its porous structure, adsorbs the asphalt, and enhances the bonding ability between the asphalt and the aggregate, thus avoiding adverse effects on the performance of the asphalt mixture.

[0025] Because the warm-mix agent described herein can be directly added, the warm-mix asphalt mixture preparation process is simple. Furthermore, red mud, the primary component of the warm-mix agent, ultimately serves as a filler, replacing some mineral powder in the mixture. The pore structure and properties of red mud enhance the adsorption between the filler and the asphalt, improving asphalt-aggregate adhesion and enhancing the water stability and low-temperature performance of the warm-mix asphalt mixture.

[0026] Another advantage of this invention is that the direct-injection solid waste foaming warm mix agent can replace expensive warm mix agents such as organic viscosity reducers and chemical additives, reducing the capital investment in warm mix agents for warm mix asphalt mixtures. Using solid waste red mud as the foaming matrix not only reduces costs, but also allows red mud to partially replace mineral powder, reducing the use of mineral resources. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] Unless otherwise specified, the "parts" described in the present invention are based on mass parts.

[0033] Sources of materials used in the present invention: sintered red mud comes from Shandong Aluminum Co., Ltd.; No. 70 matrix asphalt is provided by Shandong Chambroad Holding Group Co., Ltd.; and all reagents used are commercially available analytical grade reagents.

[0034] Example 1

[0035] Solid waste foaming warm mix agent: 85 parts of sintered red mud, 100 parts of 0.1 mol / L sodium hydroxide solution, 1 part of sodium dodecylbenzenesulfonate, and 25 parts of water (municipal tap water).

[0036] (1) The sintered red mud was initially dried at 110°C for 3 h, ball-milled for 45 min, and then dried at 110°C for 2 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0037] (2) Red mud powder was mixed with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred manually for 6 min to allow the chemical reaction to proceed fully. The mixture was then filtered and dried at 110°C for 3 h to obtain modified red mud powder.

[0038] (3) The modified red mud powder was mixed with sodium dodecylbenzene sulfonate and water, and stirred manually for 6 minutes to allow the chemical reaction to proceed fully, thereby obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 1200 rpm for 8 minutes to obtain a solid waste foaming warm mix agent.

[0039] Warm mix asphalt mixture (type AC20): 90 parts of aggregate, 5.1 parts of asphalt, 3 parts of filler, and 1.2 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0040] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0041] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 130°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C for the second time to obtain a warm mix asphalt mixture.

[0042] Example 2

[0043] Solid waste foaming warm mix agent: 90 parts of sintered red mud, 110 parts of 0.1 mol / L sodium hydroxide solution, 1.5 parts of sodium dodecylbenzene sulfonate, and 30 parts of water (municipal tap water).

[0044] (1) The sintered red mud was initially dried at 120°C for 2 h, ball-milled for 60 min, and then dried at 120°C for 1 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0045] (2) Red mud powder was mixed with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred manually for 8 min to allow the chemical reaction to proceed fully. The mixture was then filtered and dried at 120°C for 2 h to obtain modified red mud powder.

[0046] (3) The modified red mud powder was mixed with sodium dodecylbenzene sulfonate and water, and stirred manually for 8 minutes to allow the chemical reaction to proceed fully, thereby obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 1500 rpm for 5 minutes to obtain a solid waste foaming warm mix agent.

[0047] Warm mix asphalt mixture (type AC20): 88 parts of aggregate, 4.8 parts of asphalt, 2.4 parts of filler, and 1.8 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0048] (1) Asphalt is heated at 140°C for 2 hours to obtain melted asphalt, and aggregate and filler are preheated at 180°C for 3.5 hours to obtain preheated aggregate and preheated filler respectively;

[0049] (2) Preheat the aggregate to 120°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 120°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 120°C for the second time to obtain a warm mix asphalt mixture.

[0050] Example 3

[0051] Solid waste foaming warm mix agent: 100 parts of sintered red mud, 80 parts of 0.1 mol / L sodium hydroxide solution, 0.6 parts of sodium dodecylbenzenesulfonate, and 18 parts of water (municipal tap water).

[0052] (1) The sintered red mud was initially dried at 90°C for 2.5 h, ball-milled for 30 min, and then dried at 90°C for another 2 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0053] (2) Red mud powder was mixed with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred manually for 5 min to allow the chemical reaction to proceed fully. The mixture was then filtered and dried at 90°C for 2.5 h to obtain modified red mud powder.

[0054] (3) The modified red mud powder was mixed with sodium dodecylbenzene sulfonate and water, and stirred manually for 5 minutes to allow the chemical reaction to proceed fully, thereby obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 800 rpm for 5 minutes to obtain a solid waste foaming warm mix agent.

[0055] Warm mix asphalt mixture (type AC20): 88 parts of aggregate, 4.8 parts of asphalt, 3.6 parts of filler, and 0.6 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0056] (1) Asphalt is heated at 160°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 180°C for 2 hours to obtain preheated aggregate and preheated filler respectively;

[0057] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 130°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C for the second time to obtain a warm mix asphalt mixture.

[0058] Example 4

[0059] Solid waste foaming warm mix agent: 85 parts of sintered red mud, 100 parts of 0.1 mol / L sodium hydroxide solution, 1 part of sodium dodecylbenzenesulfonate, and 25 parts of water (municipal tap water).

[0060] (1) The sintered red mud was initially dried at 110°C for 3 h, ball-milled for 45 min, and then dried at 110°C for 2 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0061] (2) Red mud powder was mixed with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred manually for 6 min to allow the chemical reaction to proceed fully. The mixture was then filtered and dried at 110°C for 3 h to obtain modified red mud powder.

[0062] (3) The modified red mud powder was mixed with sodium dodecylbenzene sulfonate and water, and stirred manually for 6 minutes to allow the chemical reaction to proceed fully, thereby obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 1200 rpm for 8 minutes to obtain a solid waste foaming warm mix agent.

[0063] Warm mix asphalt mixture (type AC25): 90 parts of aggregate, 5.1 parts of asphalt, 3 parts of filler, and 1.2 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0064] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0065] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 130°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C for the second time to obtain a warm mix asphalt mixture.

[0066] Example 5

[0067] Solid waste foaming warm mix agent: 85 parts of sintered red mud, 100 parts of 0.1 mol / L sodium hydroxide solution, 1 part of sodium dodecylbenzenesulfonate, and 25 parts of water (municipal tap water).

[0068] (1) The sintered red mud was initially dried at 110°C for 3 h, ball-milled for 45 min, and then dried at 110°C for 2 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0069] (2) Red mud powder was mixed with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred manually for 6 min to allow the chemical reaction to proceed fully. The mixture was then filtered and dried at 110°C for 3 h to obtain modified red mud powder.

[0070] (3) The modified red mud powder was mixed with sodium dodecylbenzene sulfonate and water, and stirred manually for 6 minutes to allow the chemical reaction to proceed fully, thereby obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 1200 rpm for 8 minutes to obtain a solid waste foaming warm mix agent.

[0071] Warm mix asphalt mixture (type AC25): 90 parts of aggregate, 5.1 parts of asphalt, 3 parts of filler, and 1.2 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0072] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0073] (2) Preheat the aggregate to 120°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 120°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 120°C for the second time to obtain a warm mix asphalt mixture.

[0074] Comparative Example 1

[0075] Solid waste foaming warm mix agent: 85 parts of sintered red mud, 100 parts of 0.1 mol / L sodium hydroxide solution, 1 part of sodium dodecylbenzenesulfonate, and 25 parts of water (municipal tap water).

[0076] (1) The sintered red mud was initially dried at 110°C for 3 h, ball-milled for 45 min, and then dried at 110°C for 2 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0077] (2) Red mud powder was mixed with sodium dodecylbenzene sulfonate and water, and stirred manually for 6 minutes to allow the chemical reaction to proceed fully, thereby obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 1200 rpm for 8 minutes to obtain a solid waste foaming warm mix agent.

[0078] Warm mix asphalt mixture (type AC20): 90 parts of aggregate, 5.1 parts of asphalt, 3 parts of filler, and 1.2 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0079] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0080] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 130°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C for the second time to obtain a warm mix asphalt mixture.

[0081] Comparative Example 2

[0082] Solid waste foaming warm mix agent: 85 parts of sintered red mud, 100 parts of 0.1 mol / L sodium hydroxide solution, and 25 parts of water (municipal tap water).

[0083] (1) The sintered red mud was initially dried at 110°C for 3 h, ball-milled for 45 min, and then dried at 110°C for 2 h to obtain red mud powder with a particle size of ≤0.075 mm. The initial drying and re-drying treatments were performed to remove excess moisture. The particle size after ball milling met the technical requirements for fillers in the Technical Specifications for Highway Asphalt Pavement Construction (JTG F40-2004).

[0084] (2) Red mud powder was mixed with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred manually for 6 min to allow the chemical reaction to proceed fully. The mixture was then filtered and dried at 110°C for 3 h to obtain modified red mud powder.

[0085] (3) The modified red mud powder was mixed with water and stirred manually for 6 minutes to allow the chemical reaction to proceed fully, obtaining a blocky and slightly moist solid mixture; a high-speed shearing machine was used to shear at a speed of 1200 rpm for 8 minutes to obtain a solid waste foaming warm mix agent.

[0086] Warm mix asphalt mixture (type AC20): 90 parts of aggregate, 5.1 parts of asphalt, 3 parts of filler, and 1.2 parts of solid waste foaming warm mix agent. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTGF40-2004).

[0087] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0088] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and immediately add solid waste foaming warm mix agent to the surface to mix it. This will facilitate the solid waste foaming warm mix agent to adhere evenly to the hot asphalt and improve the foaming effect. Mix it evenly at 130°C for the first time to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C for the second time to obtain a warm mix asphalt mixture.

[0089] Comparative Example 3

[0090] Warm mix asphalt mixture (type AC20): 90 parts of aggregate, 5.1 parts of asphalt, and 3 parts of filler. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004).

[0091] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0092] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and mix it evenly at 130°C to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C to obtain a warm mix asphalt mixture.

[0093] Comparative Example 4

[0094] Warm mix asphalt mixture (type AC20): 90 parts of aggregate, 5.1 parts of asphalt, and 3 parts of filler. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004).

[0095] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0096] (2) Preheat the aggregate to 140°C and mix it evenly. Add melted asphalt to the preheated aggregate and mix it evenly at 140°C to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 140°C to obtain a warm mix asphalt mixture.

[0097] Comparative Example 5

[0098] Warm mix asphalt mixture (type AC25): 90 parts of aggregate, 5.1 parts of asphalt, and 3 parts of filler. The aggregate is limestone, which meets the technical requirements for aggregate in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004). The asphalt is No. 70 base asphalt, and the filler is limestone mineral powder, which meets the technical requirements for filler in the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004).

[0099] (1) Asphalt is heated at 150°C for 1.5 hours to obtain melted asphalt, and aggregate and filler are preheated at 170°C for 3 hours to obtain preheated aggregate and preheated filler respectively;

[0100] (2) Preheat the aggregate to 130°C and mix it evenly. Add melted asphalt to the preheated aggregate and mix it evenly at 130°C to obtain a mixture. Add preheated filler to the mixture and mix it evenly at 130°C to obtain a warm mix asphalt mixture.

[0101] The performance tests were performed on the warm mix asphalt mixtures prepared in Examples 1 to 5 and Comparative Examples 1 to 5.

[0102] A. To evaluate the high-temperature rutting resistance of warm-mix asphalt mixtures, an indoor wheel rolling test was conducted in accordance with JTG E20-2011. Rutting slabs of asphalt mixtures prepared in Examples 1-5 and Comparative Examples 1-5, measuring 300 mm × 300 mm × 50 mm, were compacted using a roller and then placed in a constant-temperature chamber at 60±1°C for 12 hours, along with the mold, to ensure uniform heating. During the test, the contact pressure between the asphalt mixture surface and the test wheel surface was 0.7 MPa. The tire was subjected to a continuous reciprocating motion over the asphalt mixture surface at a rolling speed of 21 reciprocating strokes / min for 1 hour, covering a distance of 230±10 mm. Rutting depth was automatically measured using an LVDT displacement sensor. Rutting deformations d1 and d2 were recorded at 45 minutes (t1) and 60 minutes (t2), respectively. The dynamic stability of the mixture was calculated. Three parallel specimens were prepared for each warm-mix asphalt mixture, and the average value was taken. The higher the dynamic stability, the better the high-temperature rutting resistance of the warm-mix asphalt mixture.

[0103] B. Prepare rutting plate specimens according to the method in A. After demolding, use a high-precision cutting machine to cut the rutting plates into rectangular specimens (250 mm × 30 mm × 35 mm). Then, perform a low-temperature bending creep test on a universal testing machine. The test temperature is controlled at -10℃±0.5℃, and the specimens are kept at the preset temperature for 1 hour before the test officially begins. The loading rate of the testing machine is 50 mm / min. Based on the performance indicators of the specimens at failure, calculate the bottom bending tensile strain of the small beam specimens made of different warm-mix asphalt mixtures. Similarly, use three parallel specimens to take the average value as the final result.

[0104] C: The water stability of warm-mix asphalt mixtures is evaluated using the Marshall immersion test. According to T0702 of JTG E20-2011, samples compacted 75 times on both sides are immersed in water at 60±1°C for 60 minutes and 48 hours, respectively. Based on the difference between Marshall stability and Marshall stability after immersion, the residual stability after immersion is used as the key evaluation indicator, calculated using Formula T0709-2 of JTG E20-2011.

[0105] The results are shown in Table 1.

[0106] Table 1 Performance test results of warm mix asphalt mixtures prepared in Examples 1 to 5 and Comparative Examples 1 to 5

[0107]

[0108] From the performance test results in Table 1, we can see that:

[0109] (1) The warm-mix asphalt mixture prepared using the direct-injection solid waste foaming warm-mix agent of the present invention can reduce the mixing temperature by 20 to 30°C while meeting the requirements of the "Technical Specifications for Highway Asphalt Pavement Construction". Therefore, it is feasible to use modified sintered red mud as a matrix to prepare a hydrous mineral foaming warm-mix agent. If no warm-mix agent is added or unmodified sintered red mud is used to prepare the warm-mix asphalt mixture, its low-temperature cracking resistance and water stability are difficult to meet the requirements of the specification.

[0110] (2) The direct-injection solid waste foaming warm mix agent described herein not only reduces mixing temperature but also ultimately remains in the asphalt mixture as a filler, thereby improving the performance of the asphalt mixture, particularly its low-temperature performance and water stability. The use of red mud to prepare the warm mix agent not only consumes solid waste but also maintains the performance of the warm mix asphalt mixture and reduces the use of limestone powder, resulting in favorable economic and environmental benefits.

[0111] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A direct-injection solid waste foaming warm mix agent, characterized in that: The invention is prepared by comprising the following raw materials in parts by weight: 80-100 parts of red mud, 80-120 parts of modified solution, 0.5-2 parts of sodium dodecylbenzenesulfonate, and 15-35 parts of water; The red mud is sintered red mud; the modified solution is an alkaline solution, the concentration of the alkaline solution is 0.08-0.12 mol / L, and the alkaline solution is a potassium hydroxide solution and / or a sodium hydroxide solution; The preparation method of the solid waste foaming warm mix agent comprises the following steps: (1) Red mud is initially dried, ground, and then dried again to obtain red mud powder; (2) mixing the red mud powder obtained in step (1) with the modified solution, reacting, filtering, and performing a first drying treatment to obtain modified red mud powder; (3) mixing the modified red mud powder obtained in step (2) with sodium dodecylbenzene sulfonate and water to obtain a solid mixture; shearing the mixture to obtain a solid waste foaming warm mix agent; The temperature of the preliminary drying in step (1) is 90-120°C, and the time of the preliminary drying is 2-4 hours; the temperature of the secondary drying in step (1) is 90-120°C, and the time of the secondary drying is 2-4 hours; the temperature of the first drying in step (2) is 90-120°C, and the time of the first drying is 2-4 hours.

2. The solid waste foaming warm mix agent according to claim 1, characterized in that: The invention is prepared by comprising the following raw materials in parts by weight: 80-100 parts of red mud, 100-110 parts of modified solution, 1-1.5 parts of sodium dodecylbenzenesulfonate and 20-30 parts of water.

3. The method for preparing the solid waste foaming warm mix agent according to claim 1 or 2, wherein: The following steps are involved: (1) Red mud is initially dried, ground, and then dried again to obtain red mud powder; (2) mixing the red mud powder obtained in step (1) with the modified solution, reacting, filtering, and performing a first drying treatment to obtain modified red mud powder; (3) mixing the modified red mud powder obtained in step (2) with sodium dodecylbenzenesulfonate and water to obtain a solid mixture; and shearing the mixture to obtain a solid waste foaming warm mix agent.

4. The method for preparing the solid waste foaming warm mix agent according to claim 3, wherein: The temperature of the preliminary drying in step (1) is 90-120° C., and the time of the preliminary drying is 2-4 hours; the grinding in step (1) is ball milling, and the grinding time is 30-60 minutes; the temperature of the secondary drying in step (1) is 90-120° C., and the time of the secondary drying is 2-4 hours; the particle size of the red mud powder in step (1) is ≤0.075 mm; the reaction time in step (2) is 5-10 minutes; the temperature of the first drying in step (2) is 90-120° C., and the time of the first drying is 2-4 hours.

5. The method for preparing the solid waste foaming warm mix agent according to claim 3, wherein: The shearing speed in step (3) is 800-1500 rpm, and the shearing time is 5-10 min.

6. Use of the solid waste foaming warm mix agent according to claim 1 or 2 in the preparation of warm mix asphalt mixture.

7. The application according to claim 6, characterized in that The warm-mix asphalt mixture is prepared from the following raw materials in parts by weight: 85-95 parts of aggregate, 4-6 parts of asphalt, 2-5 parts of filler, and 0.5-2 parts of solid waste foaming warm-mix agent.

8. The application according to claim 6, characterized in that: The method for preparing the warm mix asphalt mixture comprises the following steps: A. Heat the asphalt at 130-160℃ for 1-2 hours to obtain melted asphalt, and preheat the aggregate and filler at 160-180℃ for 2-4 hours to obtain preheated aggregate and preheated filler respectively; B. Add melted asphalt to the preheated aggregate obtained in A, and immediately add solid waste foaming warm mix agent on the surface for mixing, mixing for the first time to obtain a mixture; add the preheated filler obtained in A to the mixture, mixing for the second time to obtain a warm mix asphalt mixture.

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