Red-mud-based cementing material based on efficient drying, component homogenization and activity improvement, and preparation method therefor
Patent Information
- Application Number
- AU2025213723
- Authority / Receiving Office
- AU · AU
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-01-29
- Filing Date
- 2025-01-24
- Publication Date
- 2026-09-17
Abstract
Description
CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to Chinese Patent Application No. 202410120633.X, entitled “RED-MUD-BASED CEMENTITIOUS MATERIAL BASED ON EFFICIENT DRYING, COMPONENT HOMOGENIZATION AND ACTIVITY IMPROVEMENT, AND PREPARATION METHOD THEREFOR,” filed with the China National Intellectual Property Administration on January 29, 2024, the entire contents of which are incorporated herein by reference and constitute a part of the present application for all purposes. TECHNICAL FIELD The present invention belongs to the field of resource utilization of building materials and solid waste, and relates to a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement, and a preparation method therefor. BACKGROUND OF THE INVENTION The information disclosed in this Background section is merely intended to enhance an understanding of the general background of the present invention, and is not necessarily to be regarded as an admission or any form of suggestion that such information constitutes prior art already known to a person of ordinary skill in the art. At present, red mud is mainly used in the fields of preparation of building materials, soil remediation, environmental protection, and the like, and preparation of cement-type cementitious materials is the most effective route for achieving high-volume and high-value-added utilization of red mud. Studies have shown that red mud can be prepared into concrete admixtures, grouting materials, road engineering materials, and the like. However, the crux of the difficulty in large-scale popularization and application of red mud at present lies in the high water content of red mud. The water content of red mud in a storage yard is about 30%, whereas preparation of cement-type cementitious materials requires the water content of red mud to be below 4%. Therefore, the difficulty and high cost of red mud dewatering have become technical problems restricting high-volume engineering application of red mud. With respect to red mud dewatering, reported technologies mainly involve drying and filter pressing, and generally have defects such as high cost and low dewatering efficiency. In recent years, relevant researchers have conducted a large amount of research on new technologies for efficient red mud dewatering. In particular, the patent entitled “Bayer Red Mud Dewatering and Preheating Device Before Sintering Kiln Entry” discloses a method and process for red mud dewatering, but the water content of the red mud after dewatering is still 20%, which does not meet the performance requirements for preparing cement-type cementitious materials. The patent entitled “Dewatering Agent and Preparation Method and Use Thereof, and Method for Dewatering Red Mud” discloses a preparation method and dewatering process for a novel red mud dewatering agent, but after dewatering by this technology, the water content of the red mud is 6.5-18.5%, which still does not meet the performance requirements for preparing cement-type cementitious materials. The patent entitled “Bayer-Process Red Mud Dewatering Method During Sintering with Dry Feeding for Alumina Production by a Series Process” discloses a technology mainly comprising reducing, by mechanical dewatering, the water content of separated and washed Bayer-process red mud to 35-45%, pumping the red mud into a red mud drying yard or an existing red mud storage yard, and further reducing the water content of the red mud by natural sun-drying and mechanical turning. When the water content of the red mud is reduced to below 15%, the red mud is transported back to an alumina plant for batching and calcination. This technology is time-consuming and costly, and the resulting water content does not meet the performance requirements for preparing cement-type cementitious materials. In summary, existing red mud dewatering processes do not meet the water-content requirement for preparing cement-type cementitious materials. SUMMARY OF THE INVENTION To address the deficiencies of the prior art, an object of the present invention is to provide a red-mud-based cementitious material based on integrated efficient drying, component homogenization and activity improvement, and a preparation method therefor. The present invention can not only improve the dewatering efficiency of red mud, but also prepare the red-mud-based cementitious material in one step, thereby simplifying the preparation process for the red-mud-based cementitious material. In addition, the prepared red-mud-based cementitious material has the advantages of high mechanical strength, high durability, erosion resistance, and environmental friendliness, and can be used in construction fields such as bridge engineering, road engineering, tunnel engineering, and municipal engineering. To achieve the above object, the technical solutions of the present invention are as follows. In one aspect, provided is a method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement. At a mass ratio of red mud to a filter aid of 1-3:1, the filter aid is added to the red mud for sedimentation, followed by filter pressing to a water content of 14-16%. Waste heat from an alumina plant is then introduced into grinding equipment, and the filter-pressed solid material is ground and dried until the final red-mudbased cementitious material has a water content of less than 4% and a specific surface area of 350-450 m2 / kg, thereby obtaining the red-mud-based cementitious material; The filter aid comprises, on a weight-percentage basis, the following raw materials: 10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag or fly ash, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of desulfurized gypsum, phosphogypsum, or fluorgypsum. In another aspect, provided is a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement, obtained by the preparation method described above. In a third aspect, provided is use of the above red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement in bridge engineering, road engineering, tunnel engineering, or municipal engineering. The present invention has the following beneficial effects: 1) In the preparation method of the present invention, the filter aid is added. The filter aid contains polyaluminum chloride and polyaluminum sulfate, which not only have a flocculation effect during red mud dewatering and thereby improve the dewatering efficiency, but also provide aluminum that can participate in a geopolymerization reaction of the red-mud-based cementitious material, thereby improving the workability of the red-mud-based cementitious material. In addition, chloride ions and sulfate ions therein exert a salt-activation effect on solid wastes such as red mud, blast furnace slag, and steel slag, thereby promoting hydration of the red-mud-based cementitious material system. Further, the polyaluminum chloride and the polyaluminum sulfate can immobilize heavy metals such as lead, arsenic, and chromium present in the red mud, thereby ensuring the environmentally friendly characteristics of the red-mud-based cementitious material. 2) Components in the filter aid of the present invention, such as blast furnace slag, fly ash, steel slag, carbide slag, alkaline residue, and desulfurized gypsum, act as framework-building bodies in the red mud slurry to a certain extent. A hard grid framework is formed to maintain a porous structure of a red mud filter cake, thereby effectively solving the compressibility problem of the red mud and improving the dewatering efficiency of the red mud. In addition, furnace slag, fly ash, steel slag, carbide slag, alkaline residue, desulfurized gypsum, and other components in the filter aid are also main components for preparing the red-mud-based cementitious material. In cooperation with the red mud, these components can be subjected to a geopolymer reaction to prepare a red-mud-based cementitious material having a short setting time, high mechanical strength, high durability, environmental friendliness, and low cost. The red-mud-based cementitious material can completely replace Portland cement for use in construction fields such as bridge engineering, road engineering, tunnel engineering, and municipal engineering. 3) In a conventional drying process, the red mud has a relatively high water content. As drying proceeds, the red mud agglomerates, which impedes continued evaporation of water, and more energy is required to reduce the water content of the red mud to below 4%. In the present invention, addition of the filter aid, on the one hand, enables formation of a grid framework that maintains the porous structure of the red mud filter cake, which not only facilitates improvement of the dewatering efficiency during filter pressing, but also provides a porous structure more conducive to evaporation of water during drying, thereby improving the dewatering efficiency during drying and reducing energy consumption. On the other hand, the filter aid and the red mud can undergo a slight geological polymerization reaction under the alkaline action of the red mud to form hydration products having a three-dimensional framework structure, thereby further improving the dewatering efficiency of the red mud. During drying in the present invention, industrial waste heat may be used to further dry and grind the filter-pressed red mud-filter aid composite system, thereby obtaining the red-mud-based cementitious material. Industrial waste heat from an alumina enterprise can be used not only to dry the red mud-filter aid composite system, but also to improve the cementitious activity of solid wastes such as red mud and to reduce energy consumption and production cost. In addition, this can promote coordinated development of the alumina enterprise and a building-material production enterprise, reduce transportation of raw materials such as red mud during production, save costs, and reduce environmental pollution. 4) In the preparation method of the present invention, the utilization rate of red mud is high, and other solid wastes are synergistically utilized, thereby enabling high-volume utilization of solid wastes and resource utilization of solid wastes such as red mud. 5) In prior technologies, a filter aid used remains in the red mud filter cake, causing an increase in volume and weight of the red mud and increasing subsequent treatment and disposal costs. In the present invention, industrial solid wastes capable of being used in cooperation with red mud to prepare a cementitious material are selected as the filter aid, thereby providing the dual functions of red mud dewatering and cementing-material preparation with a simple process. DETAILED DESCRIPTION It should be noted that the following detailed description is exemplary and is intended to provide a further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by a person of ordinary skill in the art to which the present invention belongs. It should be noted that the terms used herein are merely for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, singular forms are also intended to include plural forms. It should further be understood that, when the terms “comprises” and / or “includes” are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and / or combinations thereof. In view of the fact that one bottleneck in preparing cement-type cementitious materials from red mud is the high water content and high dewatering cost of the red mud, the present invention provides a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement, and a preparation method therefor. In a typical embodiment of the present invention, provided is a method for preparing a red-mudbased cementitious material based on efficient drying, component homogenization and activity improvement. At a mass ratio of red mud to a filter aid of 1-3:1, the filter aid is added to the red mud for sedimentation, followed by filter pressing to a water content of 14-16%. Waste heat from an alumina plant is then introduced into grinding equipment, and the filter-pressed solid material is ground and dried until the final red-mud-based cementitious material has a water content of less than 4% and a specific surface area of 350-450 m2 / kg, thereby obtaining the red-mud-based cementitious material; The filter aid comprises, on a weight-percentage basis, the following raw materials: 10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag or fly ash, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of desulfurized gypsum, phosphogypsum, or fluorgypsum. In some embodiments, the filter aid comprises, on a weight-percentage basis, the following raw materials: 10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of desulfurized gypsum, phosphogypsum, or fluorgypsum. Studies show that, in the filter-aid system of the present invention, between blast furnace slag and fly ash, selection of blast furnace slag is more conducive to improving the setting rate and mechanical properties of the red-mudbased cementitious material. In some embodiments, the filter aid comprises, on a weight-percentage basis, the following raw materials: 10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of fluorgypsum. Studies show that, in the filter-aid system of the present invention, compared with the gypsum thereof, a red-mud-based cementitious material prepared using fluorgypsum has a shorter initial setting time and better mechanical properties. In some embodiments, the mass ratio of the red mud to the filter aid is 1-1.5:1. Studies show that, under this condition, the obtained red-mud-based cementitious material has better mechanical properties. In some embodiments, the polyaluminum chloride is in a liquid state, has a degree of neutrality n of 1-3, and has a basicity of >70%. The polyaluminum chloride not only has a flocculation effect during red mud dewatering, but also provides aluminum that can participate in a geopolymerization reaction of the red-mud-based cementitious material, thereby improving the workability of the red-mud-based cementitious material. In addition, chloride ions exert a salt-activation effect on solid wastes such as red mud, blast furnace slag, and steel slag, thereby promoting hydration of a cement-based cementitious material system. Further, the polyaluminum chloride can treat heavy metals such as lead, arsenic, and chromium present in the red mud, thereby ensuring the environmentally friendly characteristics of the red-mud-based cementitious material. In some embodiments, the polyaluminum sulfate is a liquid and has an aluminum content of 717%. The polyaluminum sulfate not only has a flocculation effect during red mud dewatering, but also provides aluminum that can participate in a geopolymerization reaction of the red-mud-based cementitious material, thereby improving the workability of the red-mud-based cementitious material. In addition, sulfate ions exert a salt-activation effect on solid wastes such as red mud, blast furnace slag, and steel slag, thereby promoting hydration of a cement-based cementitious material system. The red mud described in the present invention is a residue discharged from Bayer-process aluminum production and mainly comprises Al2O3, SiO2, Fe2O3, Na2O, and the like. The red mud has a large specific surface area, exhibits a micro-aggregate filling effect and potential cementitious activity, and, after activation treatment, has potential for preparing an admixture for mortar, concrete, or a road structure. The blast furnace slag described in the present invention mainly has a chemical composition comprising Al2O3, SiO2, and CaO, and a mineral-phase composition comprising glassy aluminosilicate components. The blast furnace slag has relatively high cementitious activity, can supplement a calcium 6 source in the red-mud-based cementitious material, and can provide framework support for the red mud filter cake, thereby improving the incompressibility of the red mud filter cake. The blast furnace slag is required to be ground to a specific surface area of 350-450 m2 / kg. The steel slag described in the present invention is a solid waste generated during steelmaking in the steel industry, and includes converter steel slag, open-hearth steel slag, and electric-furnace steel slag. The steel slag mainly comprises Al2O3, SiO2, and CaO, and its mineral-phase composition contains dicalcium silicate and tricalcium silicate. The steel slag has relatively high cementitious activity, can improve the cementitious activity of the red-mud-based cementitious material, and can provide framework support for the red mud filter cake, thereby improving the incompressibility of the red mud filter cake. The steel slag is required to be ground to a specific surface area of 350-450 m2 / kg. The fly ash described in the present invention is a solid waste generated during coal combustion in a coal-fired power plant. The fly ash mainly has a chemical composition comprising Al2O3 and SiO2, exhibits a micro-aggregate filling effect, a morphological effect, and a pozzolanic effect, and can be used in cooperation with red mud to prepare a cement-type geopolymer cementitious material. The fly ash is required to be ground to a specific surface area of 350-450 m2 / kg. The alkaline residue described in the present invention is a waste residue discharged during production of sodium carbonate and sodium bicarbonate in the chemical industry, and mainly comprises calcium- and magnesium-containing components. In the present invention, Ca(OH)2 and Mg(OH)2 in the alkaline residue are mainly used to provide an activation effect and a pozzolanic effect. The alkaline residue also has strong adsorptivity and a good adsorption and immobilization effect on heavy metals. The alkaline residue is required to be ground to a specific surface area of 350-450 m2 / kg. The desulfurized gypsum, phosphogypsum, or fluorgypsum described in the present invention mainly comprise CaSO4^2H2O. Each type of solid-waste gypsum mainly has a chemical composition comprising CaSO4^2H2O, can provide a calcium source in the red-mud-based cementitious material system, and can also provide a salt-activation effect of sulfate ions. In addition, the gypsum can provide framework support for the red mud filter cake, thereby improving the incompressibility of the red mud filter cake. The desulfurized gypsum, phosphogypsum, or fluorgypsum is required to be ground to a specific surface area of 350-450 m2 / kg. Various filter aids in the present invention can undergo a slight geological polymerization reaction under the alkaline action of the red mud slurry to generate a Na2O-CaO-SiO2-Al2O3-H2O gel having a three-dimensional network structure. On the basis of framework support by individual components, water passage channels in the red mud filter cake are further increased, thereby further improving the dewatering efficiency of the red mud. In some embodiments, according to the raw-material proportions of the filter aid, polyaluminum chloride, polyaluminum sulfate, fly ash, alkaline residue or carbide slag, and desulfurized gypsum, phosphogypsum, or fluorgypsum are first mixed and added as component 1 to the red mud, followed by uniform stirring. After 0.5-1 h, steel slag is added as component 2 to the red mud slurry, followed by further stirring for 0.2-0.5 h. After sedimentation for 0.4-0.6 h, filter pressing is immediately performed. Alternatively, according to the raw-material proportions of the filter aid, polyaluminum chloride, polyaluminum sulfate, alkaline residue or carbide slag, and desulfurized gypsum, phosphogypsum, or fluorgypsum are first mixed and added as component 1 to the red mud, followed by uniform stirring. After 0.5-1 h, blast furnace slag and steel slag are mixed and added as component 2 to the red mud slurry, followed by further stirring for 0.2-0.5 h. After sedimentation for 0.4-0.6 h, filter pressing is immediately performed. First, the polyaluminum chloride and the polyaluminum sulfate have a settling effect on the red mud slurry and thus can be added in advance. Second, filter aids such as fly ash, alkaline residue, carbide slag, desulfurized gypsum, phosphogypsum, and fluorgypsum have low cementitious activity and can be added to the red mud slurry in advance, so that they fully contact alkaline components in the red mud, thereby improving their cementitious activity. Under the action of the alkaline components, a geopolymer gel having a three-dimensional framework can also be generated, thereby improving the filtration-assisting effect. Finally, because the remaining filter aids such as blast furnace slag and steel slag have high cementitious activity and react rapidly in the alkaline environment of the red mud slurry, the reaction time is controlled within 0.2-0.5 h. This control allows hydration products to be generated to improve the dewatering-assisting efficiency, while preventing the reaction time from being excessively long and avoiding deterioration of the properties of the red-mud-based cementitious material. In addition, uniform stirring facilitates better contact between the filter aid and the red mud, thereby shortening the sedimentation time. In some embodiments, industrial waste heat is used as a heat source for drying. The industrial waste heat can dry residual water in the red mud-filter aid composite system and can heat-treat raw materials such as red mud, steel slag, and fly ash, thereby improving the cementitious activity of the raw materials. In addition, the drying cost can be reduced and the utilization efficiency of waste heat can be improved. In one or more embodiments, the temperature of the industrial waste heat is 80-300 °C. In some embodiments, grinding is performed to a specific surface area of 350-450 m2 / kg. In another embodiment of the present invention, provided is a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement, obtained by the preparation method described above. In a third embodiment of the present invention, provided is use of the above red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement in bridge engineering, road engineering, tunnel engineering, or municipal engineering. To enable a person skilled in the art to more clearly understand the technical solutions of the present invention, the technical solutions of the present invention are described in detail below with reference to specific examples. Example 1 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 5 parts of polyaluminum sulfate, 1,000 parts of blast furnace slag, 700 parts of steel slag, 400 parts of carbide slag, and 300 parts of desulfurized gypsum were first used to prepare a filter aid for red mud dewatering. The carbide slag and the desulfurized gypsum were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 3:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of 4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Example 2 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 5 parts of polyaluminum sulfate, 1,000 parts of blast furnace slag, 700 parts of steel slag, 400 parts of carbide slag, and 300 parts of desulfurized gypsum were used to prepare a filter aid for red mud dewatering. The carbide slag and the desulfurized gypsum 9 were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 1:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of <4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Example 3 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 5 parts of polyaluminum sulfate, 1,000 parts of fly ash, 900 parts of steel slag, 600 parts of alkaline residue, and 400 parts of phosphogypsum were used to prepare a filter aid for red mud dewatering. The fly ash, the alkaline residue, and the phosphogypsum were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The steel slag directly served as component 2. (2) At a ratio of the red mud to the filter aid of 3:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of <4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Example 4 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 30 parts of polyaluminum chloride, 15 parts of polyaluminum sulfate, 1,200 parts of blast furnace slag, 700 parts of steel slag, 600 parts of alkaline residue, and 300 parts of fluorgypsum were used to prepare a filter aid for red mud dewatering. The alkaline residue and the fluorgypsum were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 1:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of <4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Example 5 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 15 parts of polyaluminum sulfate, 1,200 parts of fly ash, 700 parts of steel slag, 600 parts of carbide slag, and 400 parts of phosphogypsum were used to prepare a filter aid for red mud dewatering. The fly ash, the carbide slag, and the phosphogypsum were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The steel slag directly served as component 2. (2) At a ratio of the red mud to the filter aid of 1:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of <4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Example 6 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 30 parts of polyaluminum chloride, 5 parts of polyaluminum sulfate, 1,200 parts of blast furnace slag, 700 parts of steel slag, 400 parts of alkaline residue, and 400 parts of phosphogypsum were used to prepare a filter aid for red mud dewatering. The alkaline residue and the phosphogypsum were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 1:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of <4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Example 7 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 5 parts of polyaluminum sulfate, 1,000 parts of blast furnace slag, 700 parts of steel slag, 400 parts of carbide slag, and 300 parts of desulfurized gypsum were first used to prepare a filter aid for red mud dewatering. The carbide slag and the desulfurized gypsum were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 3:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.5 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of 4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Comparative Example 1 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 1,000 parts of blast furnace slag, 700 parts of steel slag, 400 parts of carbide slag, and 300 parts of desulfurized gypsum were used to prepare a filter aid for red mud dewatering. The carbide slag and the desulfurized gypsum were directly mixed, and were then mixed with the polyaluminum chloride to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 3:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of 4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Comparative Example 2 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 5 parts of polyaluminum sulfate, 1,000 parts of blast furnace slag, 700 parts of steel slag, 400 parts of carbide slag, and 300 parts of desulfurized gypsum were used to prepare a filter aid for red mud dewatering. The carbide slag and the desulfurized gypsum were directly mixed, and were then mixed with the polyaluminum sulfate to prepare the filter aid, which served as component 1. The blast furnace slag and the steel slag were directly mixed to serve as component 2. (2) At a ratio of the red mud to the filter aid of 3:1, component 1 was first introduced into a red mud settling tank and stirred for 0.5 h. Component 2 was then added, followed by stirring for 0.2 h and standing for 0.5 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of 4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Comparative Example 3 A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement included the following steps: (1) 10 parts of polyaluminum chloride, 5 parts of polyaluminum sulfate, 1,000 parts of blast furnace slag, 700 parts of steel slag, 400 parts of carbide slag, and 300 parts of desulfurized gypsum were first used to prepare a filter aid for red mud dewatering. The carbide slag, the desulfurized gypsum, the blast furnace slag, and the steel slag were directly mixed, and were then mixed with the polyaluminum chloride and the polyaluminum sulfate to prepare the filter aid. (2) The red mud and the filter aid were introduced into a red mud settling tank at a ratio of 3:1, stirred for 1 h, and allowed to stand for 0.2 h. (3) The red mud-filter aid composite system was mechanically filter-pressed to a water content of about 15%. (4) After filter pressing, the red mud-filter aid composite system was conveyed by a belt to an industrial waste heat-grinding synergistic utilization system. The red mud-filter aid composite system was dried with industrial waste heat to a water content of 4% and ground to a specific surface area of 400 m2 / kg, thereby obtaining the red-mud-based cementitious material. Performance Testing The properties of the red-mud-based cementitious materials were tested with reference to GB 1752023 “Common Portland Cement,” and the results are shown in Table 1. Table 1 Performance of the red-mud-based cementitious materials prepared in the examples Water Content Initial Setting Time Final Setting Time 7-day Compressiv e Strength 28-day Compressiv e Strength Cr Leaching Amount Example 1 16.4% 152 min 394 min 11.3 MPa 28.6 MPa <0.01 ppm Example 2 18.1% 105 min 294 min 16.1 MPa 41.2 MPa <0.01 ppm Water Content Initial Setting Time Final Setting Time 7-day Compressiv e Strength 28-day Compressiv e Strength Cr Leaching Amount Example 3 16.2% 194 min 467 min 9.2 MPa 26.5 MPa <0.01 ppm Example 4 15.8% 96 min 281 min 18.3 MPa 44.4 MPa <0.01 ppm Example 5 16.5% 172 min 429 min 12.6 MPa 30.7 MPa <0.01 ppm Example 6 15.5% 101 min 277 min 16.1 MPa 43.8 MPa <0.01 ppm Example 7 12.1% 316 min 692 min 8.1 MPa 22.1 MPa <0.01 ppm Comparative Example 1 20.8% 156 min 406 min 11.2 MPa 29.3 MPa <0.01 ppm Comparative Example 2 20.5% 149 min 391 min 11.6 MPa 28.9 MPa <0.01 ppm Comparative Example 3 13.6% 295 min 644 min 8.9 MPa 24.0 MPa <0.01 ppm Analysis of the test data showed that a smaller mass ratio of the red mud to the filter aid resulted in better properties of the prepared red-mud-based cementitious material; the effect of blast furnace slag in the system was better than that of fly ash; the effect of desulfurized gypsum in the system was better than those of phosphogypsum and fluorgypsum; the effect of alkaline residue in the system was better than that of carbide slag; and polyaluminum chloride and polyaluminum sulfate had relatively small effects on the properties of the red-mud-based cementitious material, but provided a certain degree of improvement. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations may be made to the present invention by a person skilled in the art. Any modifications, equivalent substitutions, improvements, and the like made within the spirit and principles of the present invention shall fall within the protection scope of the present invention.
Claims
1. A method for preparing a red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement, wherein, at a mass ratio of red mud to a filter aid of 1-3:1, the filter aid is added to the red mud for sedimentation, and the resulting mixture is filter-pressed to a water content of 14-16%; the filter-pressed solid material is then dried to a water content of 4% or below; and the solid material is finally ground to obtain the red-mud-based cementitious material;wherein the filter aid comprises, on a weight-percentage basis, the following raw materials:10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag or fly ash, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of desulfurized gypsum, phosphogypsum, or fluorgypsum.
2. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein the filter aid comprises, on a weight-percentage basis, the following raw materials:10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of desulfurized gypsum, phosphogypsum, or fluorgypsum; orthe filter aid comprises, on a weight-percentage basis, the following raw materials:10-30 parts of polyaluminum chloride, 5-15 parts of polyaluminum sulfate, 1,000-1,200 parts of blast furnace slag, 700-900 parts of steel slag, 400-600 parts of carbide slag or alkaline residue, and 300-400 parts of fluorgypsum.
3. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein the mass ratio of the red mud to the filter aid is 1-3:1.
4. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein the polyaluminum chloride is in a liquid state, has a degree of neutrality n of 1-3, and has a basicity of >70%.
5. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein the polyaluminum sulfate is a liquid and has an aluminum content of 7-17%.
6. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein, according to the raw-material proportions of the filter aid, polyaluminum chloride, polyaluminum sulfate, fly ash,alkaline residue or carbide slag, and desulfurized gypsum, phosphogypsum, or fluorgypsum are first mixed to form component 1; component 1 is added to the red mud and stirred uniformly; after 0.5-1 h, steel slag is added as component 2 to the red mud slurry, followed by further stirring for 0.2-0.5 h; and filter pressing is performed immediately after sedimentation for 0.4-0.6 h; oraccording to the raw-material proportions of the filter aid, polyaluminum chloride, polyaluminum sulfate, alkaline residue or carbide slag, and desulfurized gypsum, phosphogypsum, or fluorgypsum are first mixed to form component 1; component 1 is added to the red mud and stirred uniformly; after 0.5-1 h, blast furnace slag and steel slag are mixed to form component 2 and added to the red mud slurry, followed by further stirring for 0.2-0.5 h; and filter pressing is performed immediately after sedimentation for 0.4-0.6 h.
7. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein industrial waste heat is used as a heat source for drying; orthe temperature of the industrial waste heat is 80-300 °C.
8. The method for preparing the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 1, wherein the grinding is performed to a specific surface area of 350-450 m2 / kg.
9. A red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement, obtained by the preparation method according to any one of claims 1-8.
10. Use of the red-mud-based cementitious material based on efficient drying, component homogenization and activity improvement according to claim 9 in bridge engineering, road engineering, tunnel engineering, or municipal engineering.