High-strength lightweight solid-waste-based multi-shell concrete functional aggregate and preparation method thereof

Abstract

The invention relates to the technical field of solid waste resource utilization, in particular to a high-strength light solid waste-based multi-shell concrete functional aggregate and a preparation method thereof. The concrete functional aggregate has a three-layer spherical structure, and an internal core layer is a porous layer, provides partial strength and keeps low density; the middle layer is a strength layer and is responsible for cooperating with the core layer to provide higher strength; and the outer shell layer is a functional layer and mainly realizes slow release, temperature regulation and other properties of the aggregate. According to the invention, a traditional sintering process is abandoned, comprehensive utilization of solid wastes such as fly ash, gypsum, slag and the like is realized, and the technical problems of high density, low strength, high water absorption rate and poor interface adhesion performance with other materials of the existing sintering-free artificial aggregate can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate and a preparation method thereof. Background Art

[0002] With the rapid development of current social infrastructure construction, a large amount of resources are consumed, and a large amount of industrial solid waste, such as fly ash, red mud, slag, etc., is also generated, which seriously affects the regional ecological environment, social and economic development and residents' life safety. Using solid waste to prepare solid waste-based concrete is an important direction in the current field of solid waste resource utilization. After industrial solid waste is processed, it is made into ceramsite lightweight aggregate, which replaces coarse aggregate to prepare high-strength lightweight concrete. It has the advantages of high strength, light weight, thermal insulation, good durability, good impermeability and excellent fire resistance. It can be used to build large-span bridges and high-rise and super-high-rise buildings. It can also be used in water resource comprehensive improvement projects, permeable pavement projects and ecological slope protection projects.

[0003] Traditional ceramsite lightweight aggregates mainly include sintered fly ash ceramsite, sintered shale ceramsite, sintered red mud ceramsite, etc. These lightweight aggregates are made of powders through ultra-high temperature sintering. Not only are the preparation costs high, but the energy consumption and pollutant emissions in the preparation process are high, which is not in line with the country's macro-strategy for sustainable development. At present, the patent with patent announcement number CN110092601B discloses the use of industrial solid wastes such as steel slag powder, granulated blast furnace slag powder, low-quality fly ash, etc., supplemented by additives and water-balled, non-burning, naturally cured and slow-release artificial aggregates, with an apparent density of 2100~2200kg / m 3 , water absorption rate is 1.2~1.4%. However, the standard GB / T17431.2-2010 "Lightweight Aggregate and Its Test Methods" requires that the bulk density of lightweight aggregate should not exceed 1200kg / m 3 The water absorption rate of high-strength light coarse aggregate with a density grade of 600~1200 is no more than 10% in one hour. The existing unburned artificial aggregate materials have high density, high water absorption rate, low strength, and poor interface adhesion with other materials, and the application effect is unsatisfactory. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate and a preparation method thereof, which can effectively solve the technical problems of the existing sintering-free artificial aggregates, such as high density, low strength, high water absorption, and poor interface adhesion with other materials.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A technical solution of the present invention provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, which includes a core layer, an intermediate layer and a shell layer from the inside to the outside; In terms of weight, the raw material components of the core layer include 50 to 140 parts of fly ash, 10 to 50 parts of gypsum, 10 to 35 parts of expanded perlite, 15 to 50 parts of sodium hydroxide, 3 to 17 parts of cellulose, 5 to 25 parts of diethyl carbonate, 1 to 7 parts of aluminum hydroxide, 1 to 10 parts of white carbon black, 1 to 6 parts of rice husk ash, and 2 to 9 parts of vermiculite powder.

[0006] Preferably, the raw material components of the core layer include, by weight, 60 to 131 parts of fly ash, 20 to 45 parts of gypsum, 13 to 30 parts of expanded perlite, 20 to 44 parts of sodium hydroxide, 6 to 14 parts of cellulose, 9 to 21 parts of diethyl carbonate, 2 to 5 parts of aluminum hydroxide, 3 to 8 parts of white carbon black, 2 to 5 parts of rice husk ash, and 3 to 7 parts of vermiculite powder.

[0007] In some possible embodiments, the cellulose is selected from at least one of α-cellulose, β-cellulose, and γ-cellulose.

[0008] In some possible embodiments, the mass ratio of cellulose to diethyl carbonate is 1:(1.1-2.5).

[0009] Preferably, the mass ratio of cellulose to diethyl carbonate is 1:(1.4-1.6).

[0010] During the hydrothermal reaction of the core layer raw materials: The fly ash, gypsum and expanded perlite in the core layer are all light materials. Under the stimulation of sodium hydroxide, they generate tobermorite and ettringite through hydrothermal reaction, thus providing the core layer framework strength. The dehydration reaction of aluminum hydroxide will form capillaries inside and generate aluminum-substituted tobermorite to fill the macropores and improve the strength of the core layer. Some impurities such as hydroxyl groups on the surface of white carbon black will be gradually removed, so that its primary particles will give the core layer more capillary channels in the process of forming aggregates, optimizing the internal pore structure; in addition, some white carbon black will generate sodium silicate under alkaline conditions to enhance the interfacial adhesion between the core layer and the middle layer; Rice husk ash reacts with sodium hydroxide to form sodium silicate, which increases the interfacial bonding strength between the core layer and the middle layer of the aggregate; Vermiculite powder can increase the roughness of the surface of the ceramsite core layer, making it easier to form a stronger connection with the middle layer during the subsequent granulation process; Cellulose and diethyl carbonate react under alkaline conditions to produce ethyl cellulose derivatives, carbon dioxide (produced by hydrolysis of diethyl carbonate) and ethanol.

[0011] In the present invention, cellulose is generated in situ by cellulose and diethyl carbonate, which has the advantages that: on the one hand, cellulose can improve the fluidity of materials such as fly ash and achieve a more uniform distribution thereof in the system, and the hydroxyl groups in its structure can form hydrogen bonds, thereby giving the system a certain degree of cohesiveness, which is beneficial to the granulation and molding process of the aggregate; on the other hand, cellulose and diethyl carbonate generate ethyl cellulose in situ in the system, which can not only effectively improve the interface bonding force between the core layer and the middle layer of the aggregate, but also the carbon dioxide released during the reaction can achieve the pore optimization and internal mineralization of the ceramsite, thereby effectively improving the strength of the ceramsite, and the ethyl cellulose can achieve the slow release of water when the aggregate is subsequently used in concrete.

[0012] In some possible embodiments, the raw material components of the middle layer include, by weight, 30 to 150 parts of red mud, 140 to 500 parts of slag, 30 to 105 parts of kaolin, 30 to 105 parts of gypsum, 5 to 25 parts of shell powder, and 7 to 32 parts of waste glass fiber.

[0013] Preferably, the raw material components of the middle layer include, by weight, 50-140 parts of red mud, 165-450 parts of slag, 35-96 parts of kaolin, 35-96 parts of gypsum, 8-22 parts of shell powder, and 10-28 parts of waste glass fiber.

[0014] In some possible embodiments, the mass ratio of diethyl carbonate to the total amount of red mud and slag is 1:(20-31).

[0015] Preferably, the mass ratio of diethyl carbonate to the total amount of red mud and slag is 1:(23-28).

[0016] For the above mentioned intermediate layer materials: Red mud, slag, metakaolin and gypsum generate tobermorite, ettringite and various calcium silicate hydrates under hydrothermal conditions, which give the middle layer a certain strength; The carbon dioxide produced in the inner core layer reacts with the red mud and slag in the middle layer to produce calcium carbonate, which can further increase the strength of the aggregate; In the mineralization reaction, the loose structure of slag provides more channels for carbon dioxide to overflow from the inside to the outside, and red mud fills the gaps between slag particles, which can increase the contact area between carbon dioxide and slag particles to improve the degree of mineralization; in addition, red mud can also absorb more water, which is beneficial to the mass transfer of mineralization reaction; Shell powder provides reaction sites in the mineralization process, and calcium carbonate reactants are more likely to be generated on the carbonate surface; Waste FRP fibers, as short fibers, play a role in strengthening and toughening, thereby improving the strength of the middle layer.

[0017] In some possible implementations, the raw material components of the shell layer include, by weight, 50 to 115 parts of polyethylene glycol, 0.2 to 1.4 parts of naphthalene-based water reducer, 1 to 5 parts of vermiculite powder, 1 to 5 parts of polyacrylamide hydrogel, and 0.5 to 4 parts of acrylic emulsion.

[0018] Preferably, the raw material components of the shell layer include 55-111 parts of polyethylene glycol, 0.5-1 part of naphthalene-based water reducer, 2-4 parts of vermiculite powder, 2-4 parts of polyacrylamide hydrogel, and 1-2.5 parts of acrylic emulsion, by weight.

[0019] When the functional aggregate provided by the present invention is applied to concrete, the shell structure outside the aggregate can increase the workability of the aggregate and cement paste, avoid segregation due to density difference, and improve the interface connection strength between the aggregate and the cement matrix.

[0020] Specifically, the polyethylene glycol in the shell raw material can enhance the durability of concrete, and at the same time improve the internal structure of concrete, make hydration more complete, realize the synchronous regulation of temperature and water content, and avoid excessive local hydration of aggregates during the use of concrete; polyethylene glycol will change from a gel state to a dissolved state at about 40-50°C. As hydration proceeds, the temperature inside the concrete rises, the polyethylene glycol dissolves, and the shell layer outside the aggregate falls off, exposing the pores of the core layer and the middle layer, which facilitates the subsequent release of water in the core layer to realize the internal curing function; As the hydration reaction of naphthalene-based water reducer proceeds, due to electrostatic repulsion and repulsion of the hydration reaction, the water reducer is gradually dispersed in a larger range, cooperating with aggregates to achieve a wider dispersion of the water reducer.

[0021] The water absorption and slow release properties of vermiculite are helpful in regulating the speed of hydration; Polyacrylamide hydrogel can effectively absorb chloride ions in concrete and reduce corrosion to steel bars; Acrylic emulsion can enhance the bonding between concrete and aggregate. The polymer in the emulsion can form a polymer film between cement particles and aggregate. This film acts as a bridge, tightly bonding different components together and improving the interfacial bonding between aggregate and cement.

[0022] The present invention also provides a method for preparing a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to any of the above schemes, comprising the following steps: S1, mixing and stirring the raw material components of the core layer to obtain a core layer mixture; Mixing the raw material components of the middle layer evenly to obtain a middle layer mixture; Mixing and stirring the raw material components of the shell layer to obtain a shell layer mixed liquid; S2, placing the core layer mixture into an extrusion granulator for granulation to obtain a granular green body; S3, placing the granular green body obtained in step S2 into a disc granulator, adding the intermediate layer mixture and spraying an appropriate amount of water, and forming the green body into a spherical shape; S4, curing the spherical green body obtained in step S3 to obtain a ceramsite green body; S5, subjecting the ceramsite body obtained in step S4 to a hydrothermal curing reaction to obtain a functional granule; S6, placing the functional aggregates prepared in step S5 into the shell layer mixture in step S1, stirring, separating, and naturally drying to obtain high-strength and lightweight solid waste-based multi-shell concrete functional aggregates.

[0023] Preferably, the method for preparing the above-mentioned high-strength and lightweight solid waste-based multi-shell concrete functional aggregate comprises the following steps: S1, fly ash, gypsum, expanded perlite, sodium hydroxide, cellulose, diethyl carbonate, aluminum hydroxide, white carbon black, rice husk ash and vermiculite powder are uniformly mixed to obtain a core layer mixture; The red mud, slag, metakaolin, gypsum, shell powder and waste glass fiber reinforced plastic fiber are mixed evenly to obtain an intermediate layer mixture; The polyethylene glycol is heated and melted, and a naphthalene-based water reducer, vermiculite powder, polyacrylamide hydrogel and acrylic emulsion are added thereto, and stirred evenly to obtain a shell layer mixed liquid; S2, placing the core layer mixture into an extruder granulator for granulation, and passing through a polygonal die to obtain a polygonal granular green body; S3, placing the polygonal granular green body obtained in step S2 into a disc granulator, adding the intermediate layer mixture and spraying an appropriate amount of water, and forming the green body into a spherical green body; S4, placing the spherical green body obtained in step S3 into a curing kiln for curing to obtain a ceramsite green body; During the above curing process, the cellulose in the core layer reacts fully with diethyl carbonate to generate ethyl cellulose and carbon dioxide, wherein the carbon dioxide fully reacts with the active molecules in the red mud and slag in the middle layer, so that the functional aggregate has initial strength. At the same time, the rice husk ash, white carbon black and sodium hydroxide react in the first stage to generate a small amount of sodium silicate to further enhance the overall strength of the aggregate. S5, placing the ceramsite body obtained in step S4 into a hydrothermal reaction kettle to perform a hydrothermal curing reaction, and obtaining functional granules after the reaction is completed and the kettle temperature drops to room temperature; During the hydrothermal reaction, a large amount of hydrated calcium silicate CSH gel, tobermorite and other calcium silicate minerals are generated in the core layer and the middle layer. At the same time, sodium hydroxide, rice husk ash and white carbon black react on a large scale, which not only ensures the close connection between the core layer and the middle layer, but also greatly increases the internal and external strength. S6, placing the functional aggregates prepared in step S5 into the shell layer mixture in step S1, stirring, separating, and naturally drying to obtain high-strength and lightweight solid waste-based multi-shell concrete functional aggregates.

[0024] Furthermore, in step S2, the particle size of the polygonal granular green body is controlled to be 5-20 mm.

[0025] Further, in step S3, the disc granulator is used for forming and granulating for 1 to 3 minutes. Exemplarily, the disc granulator is used for forming and granulating for 1 minute, 2 minutes or 3 minutes.

[0026] Furthermore, in step S3, water is sprayed until the moisture content of the middle layer mixture is 10-20%.

[0027] Further, in step S4, the temperature in the curing kiln is controlled at 60-80°C, and the curing reaction time is 0.5-1h. Exemplarily, the curing temperature is 60°C, 70°C or 80°C, and the curing time is 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1h.

[0028] Further, in step S5, the temperature in the hydrothermal reactor is controlled at 160-180°C, and the hydrothermal curing reaction time is 2-8 hours. Exemplarily, the hydrothermal reaction temperature is 160°C, 170°C or 180°C, and the hydrothermal curing reaction time is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0029] Further, in step S6, the stirring time is 5 to 10 minutes. Exemplarily, the stirring time is 5 minutes, 8 minutes or 10 minutes. The present invention has the following beneficial effects: 1. The present invention generates ethyl cellulose in situ in the core layer, accompanied by the production of carbon dioxide. Ethyl cellulose can effectively improve the interlayer bonding force of the functional aggregate and increase the strength; carbon dioxide gas is beneficial to the optimization of the pores and internal mineralization of the functional aggregate, and enhances the comprehensive performance of the functional aggregate.

[0030] 2. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate provided by the present invention has a three-layer structure. The inner core layer is a porous layer, which provides partial strength and maintains a relatively low density; the middle layer is a strength layer, which is responsible for coordinating with the core layer to provide higher strength; the outer shell layer is a functional layer, which mainly realizes the sustained release and temperature regulation properties of the aggregate. The present invention realizes the efficient comprehensive utilization of solid wastes such as fly ash, gypsum, and slag.

[0031] 3. The present invention, through a unique design, gives the functional aggregate a special shell layer, which can reduce the degree of segregation in the application of concrete, thereby improving the performance of concrete. DETAILED DESCRIPTION

[0032] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, it does not mean that the features of this invention are limited to the implementation.

[0033] Example The embodiment of the present invention provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, which includes a three-layer spherical structure of a core layer, an intermediate layer and a shell layer from the inside to the outside; The raw material components of the core layer include fly ash, gypsum, expanded perlite, sodium hydroxide, cellulose, diethyl carbonate, aluminum hydroxide, white carbon black, rice husk ash, and vermiculite powder; The raw material components of the middle layer include red mud, slag, metakaolin, gypsum, shell powder, and waste glass fiber reinforced plastics; The raw material components of the shell layer include polyethylene glycol, naphthalene series water reducer, vermiculite powder, polyacrylamide hydrogel and acrylic emulsion.

[0034] Among them, the thickness ratio of the core layer, intermediate layer and shell layer is (5~5.5):(2.5~3):1.

[0035] In some embodiments, the raw material components of the core layer include, by weight, 50 to 140 parts of fly ash, 10 to 50 parts of gypsum, 10 to 35 parts of expanded perlite, 15 to 50 parts of sodium hydroxide, 3 to 17 parts of cellulose, 5 to 25 parts of diethyl carbonate, 1 to 7 parts of aluminum hydroxide, 1 to 10 parts of white carbon black, 1 to 6 parts of rice husk ash, and 2 to 9 parts of vermiculite powder.

[0036] In some embodiments, the raw material components of the core layer include, by weight, 60 to 131 parts of fly ash, 20 to 45 parts of gypsum, 13 to 30 parts of expanded perlite, 20 to 44 parts of sodium hydroxide, 6 to 14 parts of cellulose, 9 to 21 parts of diethyl carbonate, 2 to 5 parts of aluminum hydroxide, 3 to 8 parts of white carbon black, 2 to 5 parts of rice husk ash, and 3 to 7 parts of vermiculite powder.

[0037] In some embodiments, the cellulose is selected from at least one of α-cellulose, β-cellulose, and γ-cellulose.

[0038] In some embodiments, the mass ratio of cellulose to diethyl carbonate is 1:(1.1-2.5).

[0039] In some embodiments, the mass ratio of cellulose to diethyl carbonate is 1:(1.4-1.6).

[0040] In some embodiments, the raw material components of the middle layer include, by weight, 30 to 150 parts of red mud, 140 to 500 parts of slag, 30 to 105 parts of kaolin, 30 to 105 parts of gypsum, 5 to 25 parts of shell powder, and 7 to 32 parts of waste glass fiber.

[0041] In some embodiments, the raw material components of the middle layer include, by weight, 50 to 140 parts of red mud, 165 to 450 parts of slag, 35 to 96 parts of kaolin, 35 to 96 parts of gypsum, 8 to 22 parts of shell powder, and 10 to 28 parts of waste glass fiber.

[0042] In some embodiments, the mass ratio of diethyl carbonate to the total amount of red mud and slag is 1:(20-31).

[0043] In some embodiments, the mass ratio of diethyl carbonate to the total amount of red mud and slag is 1:(23-28).

[0044] In some embodiments, the raw material components of the shell layer include, by weight, 50 to 115 parts of polyethylene glycol, 0.2 to 1.4 parts of naphthalene-based water reducer, 1 to 5 parts of vermiculite powder, 1 to 5 parts of polyacrylamide hydrogel, and 0.5 to 4 parts of acrylic emulsion.

[0045] In some embodiments, the raw material components of the shell layer include, by weight, 55 to 111 parts of polyethylene glycol, 0.5 to 1 part of a naphthalene-based water reducer, 2 to 4 parts of vermiculite powder, 2 to 4 parts of polyacrylamide hydrogel, and 1 to 2.5 parts of acrylic emulsion.

[0046] The present invention also provides a method for preparing a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to any of the above embodiments, comprising the following steps: S1, mixing and stirring the raw material components of the core layer to obtain a core layer mixture; Mixing the raw material components of the middle layer evenly to obtain a middle layer mixture; Mixing and stirring the raw material components of the shell layer to obtain a shell layer mixed liquid; S2, placing the core layer mixture into an extrusion granulator for granulation to obtain a granular green body; S3, placing the granular green body obtained in step S2 into a disc granulator, adding the intermediate layer mixture and spraying an appropriate amount of water, and forming the green body into a spherical shape; S4, curing the spherical green body obtained in step S3 to obtain a ceramsite green body; S5, subjecting the ceramsite body obtained in step S4 to a hydrothermal curing reaction to obtain a functional granule; S6, placing the functional aggregates prepared in step S5 into the shell layer mixture in step S1, stirring, separating, and naturally drying to obtain high-strength and lightweight solid waste-based multi-shell concrete functional aggregates.

[0047] In some embodiments, a method for preparing a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate comprises the following steps: S1, fly ash, gypsum, expanded perlite, sodium hydroxide, cellulose, diethyl carbonate, aluminum hydroxide, white carbon black, rice husk ash and vermiculite powder are uniformly mixed to obtain a core layer mixture; The red mud, slag, metakaolin, gypsum, shell powder and waste glass fiber reinforced plastic fiber are mixed evenly to obtain an intermediate layer mixture; The polyethylene glycol is heated and melted, and a naphthalene-based water reducer, vermiculite powder, polyacrylamide hydrogel and acrylic emulsion are added thereto, and stirred evenly to obtain a shell layer mixed liquid; S2, placing the core layer mixture into an extruder granulator for granulation, and passing through a polygonal die to obtain a polygonal granular green body; S3, placing the polygonal granular green body obtained in step S2 into a disc granulator, adding the intermediate layer mixture and spraying an appropriate amount of water, and forming a complete spherical green body; S4, placing the spherical green body obtained in step S3 into a curing kiln for curing to obtain a ceramsite green body; S5, placing the ceramsite body obtained in step S4 into a hydrothermal reaction kettle to perform a hydrothermal curing reaction, and obtaining functional granules after the reaction is completed and the kettle temperature drops to room temperature; S6, placing the functional aggregates prepared in step S5 into the shell layer mixture in step S1, stirring, separating, and naturally drying to obtain high-strength and lightweight solid waste-based multi-shell concrete functional aggregates.

[0048] In some embodiments, in step S2, the particle size of the polygonal granular green body is controlled to be 5-20 mm.

[0049] In some embodiments, in step S3, the disc granulator is used for granulation for 1 to 3 minutes.

[0050] In some embodiments, in step S3, water is sprayed until the moisture content of the middle layer mixture is 10-20%.

[0051] In some embodiments, in step S4, the temperature in the curing kiln is controlled at 60-80° C., and the curing reaction time is 0.5-1 h.

[0052] In some embodiments, the temperature in the hydrothermal reactor in step S5 is controlled at 160-180° C., and the hydrothermal curing reaction time is 2-8 hours.

[0053] In some embodiments, in step S6, the stirring time is 5 to 10 minutes.

[0054] To make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention are described in further detail below. In the following examples, unless otherwise specified, the raw materials used are all common commercial products, and the reagents are analytically pure reagents.

[0055] Example 1 This embodiment provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and the preparation method thereof comprises the following steps: S1, 97.5 parts of fly ash, 32.5 parts of gypsum, 21.6 parts of expanded perlite, 32.5 parts of sodium hydroxide, 10 parts of β-cellulose, 15.3 parts of diethyl carbonate, 3.6 parts of aluminum hydroxide, 5.8 parts of white carbon black, 3.6 parts of rice husk ash, and 5 parts of vermiculite powder were uniformly mixed to obtain a core layer mixture (the mass ratio of β-cellulose to diethyl carbonate was calculated to be 1:1.53); 94 parts of sintered red mud, 305 parts of slag, 65 parts of metakaolin, 65 parts of gypsum, 15 parts of shell powder, and 19 parts of waste glass fiber reinforced plastic fibers were mixed evenly to obtain an intermediate layer mixture (the mass ratio of diethyl carbonate to the total amount of sintered red mud and slag was calculated to be 1:26.1); 83 parts of polyethylene glycol were heated to 70°C to melt, 0.75 parts of naphthalene-based water reducer, 3 parts of vermiculite powder, 3 parts of polyacrylamide hydrogel, and 1.8 parts of acrylic emulsion were added thereto, and stirred evenly to obtain a shell layer mixture; S2, placing the core layer mixture into an extruder granulator for granulation, and passing through a polygonal die to obtain a polygonal granular green body with a particle size of about 13 mm; S3, putting the polygonal granular green body obtained in step S2 into a disc granulator, adding the middle layer mixture at the same time, spraying an appropriate amount of water until the moisture content of the middle layer mixture is 15%, and molding for 2 minutes to form a complete spherical green body; S4, placing the spherical green body obtained in step S3 into a curing kiln, controlling the temperature at 70° C. for a curing time of 45 min, to obtain a ceramsite green body; S5, placing the ceramsite body obtained in step S4 into a hydrothermal reaction kettle, controlling the temperature at 170° C., and performing a hydrothermal curing reaction for 5 hours, and obtaining functional granules after the reaction is completed and the kettle temperature drops to room temperature; S6, placing the functional aggregate prepared in step S5 into the shell layer mixture in step S1, stirring for 8 minutes, separating, and drying naturally to obtain a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate.

[0056] Example 2 This embodiment provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and the preparation method thereof comprises the following steps: S1, 60 parts of fly ash, 20 parts of gypsum, 13.3 parts of expanded perlite, 20 parts of sodium hydroxide, 6.5 parts of β-cellulose, 9.2 parts of diethyl carbonate, 2.2 parts of aluminum hydroxide, 3.5 parts of white carbon black, 2.2 parts of rice husk ash, and 3.1 parts of vermiculite powder were uniformly mixed to obtain a core layer mixture (the mass ratio of β-cellulose to diethyl carbonate was calculated to be 1:1.42); 52 parts of sintered red mud, 168 parts of slag, 36 parts of metakaolin, 36 parts of gypsum, 8.4 parts of shell powder, and 10.4 parts of waste glass fiber reinforced plastics are mixed evenly to obtain an intermediate layer mixture (according to calculation, the mass ratio of diethyl carbonate to the total amount of sintered red mud and slag is 1:23.9); 55 parts of polyethylene glycol were heated to 70° C. to melt, 0.5 parts of naphthalene-based water reducer, 2 parts of vermiculite powder, 2 parts of polyacrylamide hydrogel, and 1.2 parts of acrylic emulsion were added thereto, and stirred evenly to obtain a shell layer mixture; S2, placing the core layer mixture into an extruder granulator for granulation, and passing through a polygonal die to obtain a polygonal granular green body with a particle size of about 16 mm; S3, putting the polygonal granular green body obtained in step S2 into a disc granulator, adding the middle layer mixture at the same time, spraying an appropriate amount of water until the moisture content of the middle layer mixture is 15%, and molding for 1 minute to form a complete spherical green body; S4, placing the spherical green body obtained in step S3 into a curing kiln, controlling the temperature at 60° C. for a curing time of 1 hour, to obtain a ceramsite green body; S5, placing the ceramsite body obtained in step S4 into a hydrothermal reaction kettle, controlling the temperature at 160° C., and performing a hydrothermal curing reaction for 7 hours, and obtaining functional granules after the reaction is completed and the kettle temperature drops to room temperature; S6, placing the functional aggregate prepared in step S5 into the shell layer mixture in step S1, stirring for 6 minutes, separating, and drying naturally to obtain a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate.

[0057] Example 3 This embodiment provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and the preparation method thereof comprises the following steps: S1, 130.5 parts of fly ash, 43.5 parts of gypsum, 29 parts of expanded perlite, 43.5 parts of sodium hydroxide, 13.1 parts of β-cellulose, 20.8 parts of diethyl carbonate, 4.8 parts of aluminum hydroxide, 7.6 parts of white carbon black, 4.8 parts of rice husk ash, and 6.7 parts of vermiculite powder were uniformly mixed to obtain a core layer mixture (the mass ratio of β-cellulose to diethyl carbonate was calculated to be 1:1.59); 137.5 parts of sintered red mud, 445.5 parts of slag, 95.15 parts of metakaolin, 95.15 parts of gypsum, 22 parts of shell powder, and 27.5 parts of waste glass fiber reinforced plastic fibers were uniformly mixed to obtain an intermediate layer mixture (according to calculation, the mass ratio of diethyl carbonate to the total amount of sintered red mud and slag is 1:28); 111 parts of polyethylene glycol are heated to 70° C. to melt, 1 part of naphthalene-based water reducer, 4 parts of vermiculite powder, 4 parts of polyacrylamide hydrogel, and 2.4 parts of acrylic emulsion are added thereto, and stirred evenly to obtain a shell layer mixture; S2, placing the core layer mixture into an extruder granulator for granulation, and passing through a polygonal die to obtain a polygonal granular green body with a particle size of about 10 mm; S3, putting the polygonal granular green body obtained in step S2 into a disc granulator, adding the middle layer mixture at the same time, spraying an appropriate amount of water until the moisture content of the middle layer mixture is 15%, and molding for 3 minutes to form a complete spherical green body; S4, placing the spherical green body obtained in step S3 into a curing kiln, controlling the temperature at 80° C. for a curing time of 0.5 h, to obtain a ceramsite green body; S5, placing the ceramsite body obtained in step S4 into a hydrothermal reaction kettle, controlling the temperature at 180° C., and performing a hydrothermal curing reaction for 3 hours, and obtaining functional granules after the reaction is completed and the kettle temperature drops to room temperature; S6, placing the functional aggregate prepared in step S5 into the shell layer mixture in step S1, stirring for 10 minutes, separating, and drying naturally to obtain a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate.

[0058] Example 4 This embodiment provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and its preparation method is basically the same as that of Example 1, except that: The raw material components of the core layer include 97.5 parts of fly ash, 32.5 parts of gypsum, 21.6 parts of expanded perlite, 32.5 parts of sodium hydroxide, 12 parts of β-cellulose, 13.3 parts of diethyl carbonate, 3.6 parts of aluminum hydroxide, 5.8 parts of white carbon black, 3.6 parts of rice husk ash, and 5 parts of vermiculite powder.

[0059] It was calculated that the mass ratio of β-cellulose to diethyl carbonate was 1:1.11.

[0060] Example 5 This embodiment provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and its preparation method is basically the same as that of Example 1, except that: The raw material components of the core layer include 97.5 parts of fly ash, 32.5 parts of gypsum, 21.6 parts of expanded perlite, 32.5 parts of sodium hydroxide, 7.3 parts of β-cellulose, 18 parts of diethyl carbonate, 3.6 parts of aluminum hydroxide, 5.8 parts of white carbon black, 3.6 parts of rice husk ash, and 5 parts of vermiculite powder.

[0061] After calculation, the mass ratio of β-cellulose to diethyl carbonate is 1:2.47.

[0062] Comparative Example 1 This comparative example provides a solid waste-based multi-shell concrete functional aggregate, and its preparation method is basically the same as that of Example 1, except that: The raw material components of the core layer include 97.5 parts of fly ash, 32.5 parts of gypsum, 21.6 parts of expanded perlite, 32.5 parts of sodium hydroxide, 25.3 parts of ethyl cellulose, 3.6 parts of aluminum hydroxide, 5.8 parts of white carbon black, 3.6 parts of rice husk ash, and 5 parts of vermiculite powder.

[0063] That is, 25.3 parts of ethyl cellulose are used to replace 10 parts of β-cellulose and 15.3 parts of diethyl carbonate.

[0064] Comparative Example 2 This comparative example provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and its preparation method is basically the same as that of Example 1, except that: The raw material components of the middle layer include 399 parts of slag, 65 parts of kaolin, 65 parts of gypsum, 15 parts of shell powder, and 19 parts of waste glass fiber reinforced plastic fibers.

[0065] That is, no sintered red mud is used in the middle layer.

[0066] Comparative Example 3 This comparative example provides a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, and its preparation method is basically the same as that of Example 1, except that: The raw material components of the middle layer include 399 parts of sintered red mud, 65 parts of kaolin, 65 parts of gypsum, 15 parts of shell powder, and 19 parts of waste glass fiber reinforced plastics.

[0067] That is, no slag is used in the middle layer.

[0068] Performance Testing The functional aggregates prepared in the above Examples 1 to 5 and Comparative Examples 1 to 3 were tested for cylinder compressive strength, bulk density, apparent density and water absorption with reference to the relevant requirements of GB / T 17431.2-2010 "Lightweight aggregate and its test methods Part 2: Lightweight aggregate test methods". The final results are shown in Table 1 below.

[0069] Table 1 Physical properties of functional aggregate samples

[0070] Test result analysis: The above data show that the cylinder compressive strength of the functional aggregate obtained in Examples 1-3 is ≥27.5MPa, and the bulk density is 974-1007kg / m 3 , apparent density is 1753-1782kg / m 3 , 1h water absorption rate ≤3.80%, indicating that the functional aggregate prepared in this application has relatively excellent comprehensive properties.

[0071] Comparing Example 1 and Example 4, the reason why the performance of the functional aggregate obtained in Example 4 decreases may be that: the amount of β-cellulose in the core layer of the functional aggregate in Example 4 is relatively large, and the amount of diethyl carbonate is relatively small, resulting in a decrease in the amount of ethyl cellulose generated, resulting in a decrease in the interfacial bonding force between the functional aggregate layers, and less carbon dioxide gas, which is not conducive to internal mineralization and optimization of the internal pore structure. Therefore, the cylinder compressive strength of the product is reduced and the water absorption rate is increased.

[0072] Comparing Example 1 and Example 5, the reason why the performance of the functional aggregate obtained in Example 5 is reduced may be that the amount of β-cellulose in the core layer of the functional aggregate in Example 5 is relatively low, and the amount of diethyl carbonate is relatively high, resulting in a small amount of ethyl cellulose generated and more carbon dioxide gas generated. The interfacial bonding force between the functional aggregate layers becomes weak, and the generation of more gas is not conducive to the optimization of its internal pore structure, so the overall performance of the product is reduced.

[0073] Comparing Example 1 with Comparative Example 1, the reason why the performance of the functional aggregate obtained in Comparative Example 1 decreases may be that: in Comparative Example 1, ethyl cellulose is directly added. Compared with the in-situ generation of ethyl cellulose, no carbon dioxide is produced in the system, the pore structure inside the functional aggregate is poor, and internal mineralization cannot be achieved, resulting in a decrease in its overall strength. At the same time, the water absorption rate increases.

[0074] Comparing Example 1 with Comparative Example 2, the reason why the performance of the functional aggregate obtained in Comparative Example 2 is reduced may be that: Comparative Example 2 lacks red mud, which cannot fill the gaps between the slag particles, and the mass transfer effect of the mineralization reaction is weakened, resulting in a poor degree of mineralization. At the same time, although a hard intermediate layer is formed on the surface of the core layer of the functional aggregate, the connection tightness between its hydration products is reduced, so the cylinder compressive strength and water absorption rate of the obtained functional aggregate are both deteriorated.

[0075] Comparing Example 1 with Comparative Example 3, the reason why the performance of the functional aggregate obtained in Comparative Example 3 is reduced may be that: in Comparative Example 3, only red mud is used, and its volcanic ash activity is relatively low, and excessive addition leads to a decrease in the mechanical properties of the expanded clay, and its inherent water absorption capacity also reduces the impermeability of the functional aggregate.

[0076] Although the preferred embodiments of the present invention have been disclosed as above, they are not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the contents of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A high-strength and lightweight solid waste-based multi-shell concrete functional aggregate, characterized in that: From the inside to the outside, it includes the nuclear layer, the middle layer and the shell layer; In terms of weight, the raw material components of the core layer include 50 to 140 parts of fly ash, 10 to 50 parts of gypsum, 10 to 35 parts of expanded perlite, 15 to 50 parts of sodium hydroxide, 3 to 17 parts of cellulose, 5 to 25 parts of diethyl carbonate, 1 to 7 parts of aluminum hydroxide, 1 to 10 parts of white carbon black, 1 to 6 parts of rice husk ash, and 2 to 9 parts of vermiculite powder.

2. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 1, characterized in that: In terms of weight, the raw material components of the core layer include 60 to 131 parts of fly ash, 20 to 45 parts of gypsum, 13 to 30 parts of expanded perlite, 20 to 44 parts of sodium hydroxide, 6 to 14 parts of cellulose, 9 to 21 parts of diethyl carbonate, 2 to 5 parts of aluminum hydroxide, 3 to 8 parts of white carbon black, 2 to 5 parts of rice husk ash, and 3 to 7 parts of vermiculite powder.

3. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 1, characterized in that: The mass ratio of the cellulose to diethyl carbonate is 1:(1.1-2.5).

4. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 1, characterized in that: The raw material components of the intermediate layer include 30 to 150 parts of red mud, 140 to 500 parts of slag, 30 to 105 parts of metakaolin, 30 to 105 parts of gypsum, 5 to 25 parts of shell powder, and 7 to 32 parts of waste glass fiber reinforced plastics by weight; The raw material components of the shell layer include 50-115 parts of polyethylene glycol, 0.2-1.4 parts of naphthalene-based water reducer, 1-5 parts of vermiculite powder, 1-5 parts of polyacrylamide hydrogel, and 0.5-4 parts of acrylic emulsion.

5. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 1, characterized in that: In terms of weight, the raw material components of the middle layer include 50 to 140 parts of red mud, 165 to 450 parts of slag, 35 to 96 parts of kaolin, 35 to 96 parts of gypsum, 8 to 22 parts of shell powder, and 10 to 28 parts of waste glass fiber reinforced plastics.

6. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 1, characterized in that: In terms of weight, the raw material components of the shell layer include 55-111 parts of polyethylene glycol, 0.5-1 parts of naphthalene-based water reducer, 2-4 parts of vermiculite powder, 2-4 parts of polyacrylamide hydrogel, and 1-2.5 parts of acrylic emulsion.

7. The high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 4, characterized in that: The mass ratio of the diethyl carbonate to the total amount of red mud and slag is 1:(20-31).

8. A method for preparing a high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to any one of claims 1 to 7, characterized in that: The steps include: S1, mixing and stirring the raw material components of the core layer to obtain a core layer mixture; Mixing the raw material components of the middle layer evenly to obtain a middle layer mixture; Mixing and stirring the raw material components of the shell layer uniformly to obtain a shell layer mixed liquid; S2, placing the core layer mixture into an extrusion granulator for granulation to obtain a granular green body; S3, placing the granular green body obtained in step S2 into a disc granulator, adding the intermediate layer mixture and spraying an appropriate amount of water, and forming the green body into a spherical shape; S4, curing the spherical green body obtained in step S3 to obtain a ceramsite green body; S5, subjecting the ceramsite body obtained in step S4 to a hydrothermal curing reaction to obtain a functional granule; S6, placing the functional aggregates obtained in step S5 into the shell layer mixture in step S1, stirring, separating, and naturally drying to obtain high-strength and lightweight solid waste-based multi-shell concrete functional aggregates.

9. The method for preparing the high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 8, characterized in that: The steps include: S1, fly ash, gypsum, expanded perlite, sodium hydroxide, cellulose, diethyl carbonate, aluminum hydroxide, white carbon black, rice husk ash and vermiculite powder are uniformly mixed to obtain a core layer mixture; The red mud, slag, metakaolin, gypsum, shell powder and waste glass fiber reinforced plastic fiber are mixed evenly to obtain an intermediate layer mixture; The polyethylene glycol is heated and melted, and a naphthalene-based water reducer, vermiculite powder, polyacrylamide hydrogel and acrylic emulsion are added thereto, and stirred evenly to obtain a shell layer mixed liquid; S2, placing the core layer mixture into an extruder granulator for granulation, and passing through a polygonal die to obtain a polygonal granular green body; S3, placing the polygonal granular green body obtained in step S2 into a disc granulator, adding the intermediate layer mixture and spraying an appropriate amount of water, and forming the green body into a spherical green body; S4, placing the spherical green body obtained in step S3 into a curing kiln for curing to obtain a ceramsite green body; S5, placing the ceramsite body obtained in step S4 into a hydrothermal reaction kettle to perform a hydrothermal curing reaction, and obtaining functional granules after the reaction is completed and the kettle temperature drops to room temperature; S6, placing the functional aggregates obtained in step S5 into the shell layer mixture in step S1, stirring, separating, and naturally drying to obtain high-strength and lightweight solid waste-based multi-shell concrete functional aggregates.

10. The method for preparing high-strength and lightweight solid waste-based multi-shell concrete functional aggregate according to claim 9, characterized in that: In step S4, the temperature in the curing kiln is controlled at 60-80°C, and the curing reaction time is 0.5-1h; In step S5, the temperature in the hydrothermal reactor is controlled at 160-180° C., and the hydrothermal curing reaction time is 2-8 hours.

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