Unburned hollow artificial aggregate and its preparation method

Abstract

The application discloses a kind of baking-free hollow artificial aggregate and preparation method thereof, adopt agar, carrageenan and gelatin solution mixing, prepare inner core material hydrogel;Sodium hydroxide, water glass and water are mixed to prepare intermediate binder A;Regenerated micro powder is mixed with biochar to prepare intermediate binder B;Binder A and B are mixed to obtain intermediate binder;Regenerated micro powder and granulated blast furnace slag powder are mixed to obtain outer core material;Hydrogel is placed in binder A and B, after hydrogel surface is wrapped with mixed binder solution, it is placed in binder B, to obtain material C dry maintenance, obtain hollow inner core;Hollow inner core is granulated, it is poured into shell powder while spraying binder A, form spherical aggregate, obtain baking-free hollow artificial aggregate under the condition of rotating speed rolls.The application uses regenerated micro powder, slag solid waste material as shell, hydrogel as inner core, and prepares baking-free hollow artificial aggregate with lower bulk density and higher single-particle compressive strength by alkali activation.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization and building materials, and relates to a fire-free hollow artificial aggregate and a preparation method thereof. Background Art

[0002] Replacing natural aggregate with artificial aggregate is an important approach to addressing the shortage of natural sand and gravel. There are two curing processes for artificial aggregate: sintering, which consumes significant energy and carries the risk of secondary pollution; and cold curing, which utilizes solid waste such as construction waste (recycled micropowder) and slag. This process can be prepared at room temperature and curing, resulting in energy savings and emissions reductions.

[0003] Recycled micropowder is a fine powder with a particle size of less than 0.15mm produced during the recycling process of recycled concrete aggregate. The particle surface is rough and porous, with high water absorption and low activity, resulting in low utilization rate of recycled micropowder.

[0004] CN118145905A (application publication date June 7, 2024) patents apply for a coal-based solid waste lightweight high-strength aggregate and its preparation method and application. It is mainly made of coal gangue and coal gasification ash of a certain particle size mixed evenly, granulated and sintered to form a bulk density of 900kg / m 3 ~1100kg / m 3 The granular product has a single particle compressive strength of 8-20MPa. This product is calcined at a high temperature of 1000-1200℃ and consumes a lot of energy.

[0005] Patent CN117510225A (publication date: February 6, 2024) discloses a method for preparing gypsum-based lightweight hollow aggregates. The method involves adding molten paraffin wax to a mixed reactant, granulating the aggregate before the wax fully hardens, and then irradiating the aggregate in a microwave oven. The gypsum-based cementitious material is prepared using a sintering process, which consumes a lot of energy and results in a low cylinder compressive strength (1.8-3.1 MPa).

[0006] Patent CN115259815A (application publication date November 1, 2021) applied for a method for preparing artificial aggregates from metal tailings, which mainly includes: mixing metal tailings, gypsum and auxiliary agents, and granulating them through a high-speed granulator, with a bulk density of 1282-1320 kg / m 3 The cylinder compressive strength of copper tailings ceramsite is 7-15 MPa. The aggregate of this invention has high cylinder compressive strength and high bulk density.

[0007] The above-mentioned solid artificial aggregates in the prior art are limited to use in load-bearing structural components of building structures, and have the following problems: high sintering temperature of the aggregate, high energy consumption; high bulk density; and low cylinder compressive strength due to the use of a non-sintering process. There is an urgent need to provide a method for preparing a fire-free hollow artificial aggregate. Summary of the Invention

[0008] In order to solve the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a fire-free hollow artificial aggregate and a preparation method thereof. The present invention uses the prepared hydrogel as a bonding layer template. When the bonding layer is dried, the moisture in the hydrogel is discharged to form a hollow structure; by introducing an alkali-activated material into the intermediate adhesive layer as a template for the fire-free hollow artificial aggregate, recycled micropowder and granulated blast furnace slag powder are mixed and granulated, and the prepared fire-free hollow artificial aggregate has a lower bulk density and higher single-particle compressive strength.

[0009] The present invention is achieved through the following technical solutions.

[0010] One aspect of the present invention provides a method for preparing a fire-free hollow artificial aggregate, comprising the following steps:

[0011] A. Preparation of core materials:

[0012] a1) Prepare a gelatin solution by mixing gelatin and water in a mass ratio of (1-2):(4-7);

[0013] a2) adding agar and carrageenan to hot water in a mass ratio of (1-2):(0.1-0.5):(5-10) of agar, carrageenan, and water, mixing thoroughly, then mixing the mixture with a gelatin solution in a mass ratio of 1:1, and dropping the mixture into a spherical mold to prepare a spherical hydrogel;

[0014] B. Preparation of intermediate binder:

[0015] b1) Mixing sodium hydroxide, water glass, and water in a mass ratio of (1-2):(5-10):(1-5) to obtain an intermediate binder A;

[0016] b2) Mixing the recycled micropowder and the biochar in a mass ratio of (1-2): (0.01-0.02) to prepare an intermediate binder B;

[0017] b3) Mixing and stirring binder A and binder B in a mass ratio of binder A:B = 1:1.2 to prepare an intermediate binder;

[0018] C. Shell material preparation:

[0019] Recycled micro powder and granulated blast furnace slag powder are mixed in a mass ratio of (5-10):(1-5) to obtain shell powder;

[0020] D. Preparation of unburned hollow artificial aggregate:

[0021] d1) placing the core material hydrogel into a mixed solution of binders A and B. After the surface of the hydrogel is coated with the binder, the hydrogel is placed into binder B to obtain material C. Material C is dried and cured to obtain a hollow core.

[0022] d2) Pour a small amount of shell powder into the granulator, place the solidified hollow core in the granulator, and pour the shell powder into the granulator while spraying the binder A to form a uniform spherical aggregate. The spherical aggregate is rolled at a certain speed to obtain a certain particle size of unburned hollow artificial aggregate;

[0023] The granulated artificial aggregate is cured in an environment of high temperature and relative humidity.

[0024] Preferably, in step a1), gelatin is mixed with water and the gelatin powder absorbs water and swells for 1 to 2 hours.

[0025] Preferably, in step a2), agar and carrageenan are poured into hot water at 70-90° C. and stirred thoroughly; and the mixture is refrigerated for 2-3 hours to prepare a hydrogel.

[0026] Preferably, in step C, the regenerated micro powder and granulated blast furnace slag powder are placed in a granulator, stirred for 2 to 5 minutes, and rolled at a rotation speed of 10 to 20 r / min.

[0027] Preferably, in step d1), material C is placed in a drying oven at a temperature of 25-35° C. and cured for 18-36 hours.

[0028] Preferably, in step d2), the pelletizing is completed by rolling at a rotation speed of 10-20 r / min for 20-30 min, and when the aggregates agglomerate to 10-15 mm.

[0029] Preferably, in step d2), the granulated artificial aggregate is cured for 28 days in an environment with a temperature of 20±2° C. and a relative humidity of 95% or higher.

[0030] Preferably, the oxide content of the regenerated micropowder material is SiO2≥48.85%; CaO≥22.11%; Al2O3≥13.28%; Fe2O3≥6.44%; MgO≥2.7%; and SO3≥0.67%.

[0031] Preferably, the oxide content of the granulated blast furnace slag material is SiO2≥34.2%; CaO≥34%; Al2O3≥17.6%; Fe2O3≥1.01%; MgO≥6.21%; and SO3≥5.36%.

[0032] Another aspect of the present invention provides a fire-free hollow artificial aggregate prepared by the method for preparing the fire-free hollow artificial aggregate.

[0033] The present invention adopts the above technical solution, which has the following beneficial effects:

[0034] 1. The hydrogel prepared by mixing agar, carrageenan and gelatin solution in the present invention can discharge water through the pore structure of the biochar in the binder layer after the middle binder layer dries, forming a hollow structure.

[0035] 2. The intermediate binder of the present invention uses regenerated micropowder and biochar as precursors and a mixture of sodium hydroxide, water glass and water as an activator to form an alkali activation system, which can form a gel with a certain strength in a relatively short time.

[0036] 3. The present invention adopts recycled micro powder and granulated blast furnace slag powder to mix and granulate to obtain unburned hollow artificial aggregate; it has a lower bulk density and higher single particle compressive strength.

[0037] 4. The present invention utilizes solid waste such as construction waste (recycled micropowder) and slag, thereby solving the problem of accumulation and land occupation and achieving energy conservation and emission reduction.

[0038] 5. The present invention adopts cold hardening process, uses solid waste materials such as recycled micro powder and slag as the shell, and hydrogel as the core, and is prepared by alkali excitation to obtain a bulk density of 923kg / m 3 The unburned hollow artificial aggregate has a single particle compressive strength of about 4.5 MPa and has good application prospects in thermal insulation walls. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0040] Figure 1 Schematic diagram of the shape of aggregate of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0042] The hollow artificial aggregate provided by the embodiment of the present invention includes: an inner core material, an intermediate binder material and an outer core material, which are prepared by a cold hardening process.

[0043] The inner core materials include gelatin, carrageenan and agar; the middle binder materials include sodium hydroxide, water glass, recycled micropowder and biochar; and the outer core materials include granulated blast furnace slag and recycled micropowder.

[0044] The method for preparing hollow artificial aggregate of the present invention specifically comprises the following steps:

[0045] A. Preparation of core materials:

[0046] a1) Prepare gelatin solution: Mix gelatin and water in a gelatin to water ratio of (1-2):(4-7). Allow the gelatin powder to absorb water and swell for 1-2 hours. Stir the gelatin solution thoroughly and set aside.

[0047] a2) Hydrogel Preparation: Pour agar and carrageenan into hot water at 70-90°C in a mass ratio of (1-2):(0.1-0.5):(5-10) of agar, carrageenan, and water. Stir thoroughly, then mix with gelatin solution in a 1:1 mass ratio. Use a rubber-tipped dropper to drip the mixture into a silicone mold. Refrigerate for 2-3 hours to prepare a spherical hydrogel.

[0048] B. Preparation of intermediate binder:

[0049] b1) Preparation of Binder A:

[0050] Sodium hydroxide, water glass and water are mixed in a mass ratio of (1-2): (5-10): (1-5) to obtain an intermediate binder A;

[0051] b2) Preparation of Binder B:

[0052] The recycled micro powder and biochar are mixed in a mass ratio of (1-2): (0.01-0.02) to obtain the intermediate binder B;

[0053] b3) Preparation of intermediate binder:

[0054] Mix adhesive A and adhesive B in a mass ratio of adhesive A:B=1:1.2 and stir evenly for use.

[0055] C. Shell material preparation:

[0056] Place the recycled micro powder and granulated blast furnace slag powder in a granulator according to the mass ratio of (5~10): (1~5), stir for 2~5 minutes to fully mix the powders, and set aside.

[0057] D. Preparation of unburned hollow artificial aggregate:

[0058] d1) Preparation of hollow core:

[0059] The core material hydrogel is placed in a mixed solution of binders A and B. After the surface of the hydrogel is coated with the mixed binder solution, it is placed in binder B so that the surface of the hydrogel is coated with the powder to obtain material C. Material C is placed in a drying oven at a temperature of 25-35°C for 18-36 hours to obtain a hollow core;

[0060] d2) Mixing and granulation:

[0061] The prepared hollow core is used as the raw material for granulation, and the prepared binder A is placed in a spray bottle; first, a small amount of shell powder is poured into the granulator, and the solidified hollow core is placed in the disc granulator. While spraying binder A, the shell powder is poured in to make it into a uniform spherical aggregate. It is rolled at a speed of 10~20r / min (to ensure that the aggregate is not thrown out of the disc granulator). The hollow core adheres to the surrounding outer core powder, making its own particle size larger. The granulation process lasts for 20~30 minutes. When the aggregate agglomerates to a particle size of 10~15mm, the granulation is completed, and the unburned hollow artificial aggregate is obtained. The schematic diagram of the unburned hollow artificial aggregate structure is shown in Figure 1 shown.

[0062] The granulated artificial aggregate is cured in an environment with a temperature of 20±2°C and a relative humidity of 95% or more for 28 days.

[0063] Disc granulator parameters: disc diameter 50cm, disc circle 12cm, inclination angle 30-60°.

[0064] The present invention introduces alkali-activated materials into the preparation of artificial aggregate to improve the performance of the aggregate. While adding a high amount of recycled micropowder, in order to reduce the weight of the aggregate, a fire-free hollow artificial lightweight aggregate is prepared using hydrogel as the core, recycled micropowder and granulated blast furnace slag as the shell powder, and water glass and sodium hydroxide as activators.

[0065] The hydrogel, prepared by mixing agar, carrageenan, and gelatin solutions, gels at 0-5°C and liquids at 25-35°C. The gelled hydrogel serves as a spherical mold. An intermediate binder is attached to the hydrogel surface, forming a self-contained adhesive layer. The adhesive layer utilizes an alkali-activated system for rapid coagulation. The coagulated structure is dried, allowing the core hydrogel to decompose and expel water through the pore structure of the intermediate binder, biochar, to form a bonding layer. This bonding layer serves as a mold for preparing unfired hollow artificial aggregate. Recycled micropowder and granulated blast furnace slag powder are then mixed and granulated to produce the unfired hollow artificial aggregate, which exhibits a certain level of single-particle compressive strength.

[0066] By introducing alkali-activated materials, we have produced high-quality, fire-free hollow artificial aggregates that not only have high compressive strength but also good density. Due to the hollow nature of the aggregate, it can be used in thermal insulation walls.

[0067] The hollow artificial aggregate material requirements of the present invention are as follows:

[0068] (1) Recycled micropowder: The recycled micropowder used in this experiment comes from the waste concrete aggregate of Shaanxi Hongwei Ecological Environmental Protection Co., Ltd. The company produces a large amount of building solid particles with a particle size of less than 4.75 mm in the process of crushing construction waste. The solid particles are dried at 80 0 C, 24 hours, then ball milled for 40 minutes using a planetary ball mill (model XU-XQM-4A) at 300 rpm. Sieve through a 0.15 mm standard square mesh sieve to obtain the test raw material, construction waste powder, with a particle size less than 150 μm. The oxide content of the material is detailed in Table 1.

[0069] (2) Granulated blast furnace slag: S95 slag produced by Henan Wuhu Environmental Protection Technology Co., Ltd., with a specific surface area of ​​430m 2 / kg, about 500 mesh, the oxide content of the material is shown in Table 1.

[0070] (3) Sodium hydroxide: Shanghai test, white uniform flaky solid, purity is 98±1%.

[0071] (4) Water glass: It is composed of 65.8% water and 30.6% industrial grade sodium silicate powder with a purity of 98%. Accordingly, it contains 8.2% Na2O, 26% SiO2 and 65.8% H2O (by weight), and the modulus of water glass powder (molar ratio of SiO2 to Na2O) is 3.2.

[0072] (6) Other materials: Gelatin powder; the main component is animal collagen, with a gel strength of 250, about 80 mesh. Carrageenan: extracted from agar-agar, 100 mesh. Agar: extracted from seaweed, 100 mesh.

[0073] Table 1 Oxide content of materials

[0074]

[0075] S95 slag contains a large amount of active SiO2 and Al2O3. Under the action of strong alkali, the slag undergoes crystal reorganization to form a cementitious material with oxygen-silicon tetrahedrons and aluminum-oxygen tetrahedrons as the main components, presenting a three-dimensional network structure. Recycled micropowder contains a large amount of SiO2 and Al2O3. After ball milling, the recycled micropowder not only has a certain degree of pozzolanic activity but also provides nucleation sites for hydration products, playing a filling role.

[0076] The present invention is further illustrated below by way of examples:

[0077] Example 1

[0078] A. Preparation of core materials:

[0079] a1) Prepare gelatin solution: Mix gelatin and water in a mass ratio of 1:5.8. Allow the gelatin powder to absorb and swell for 1 hour. Stir the gelatin solution thoroughly and set aside.

[0080] a2) Hydrogel Preparation: Pour agar and carrageenan into 80°C hot water at a mass ratio of 1:0.25:7.7. After thorough stirring, mix with gelatin solution at a mass ratio of 1:1. Pour the mixture into a silicone mold using a rubber-tipped dropper and refrigerate for 2 hours to produce a spherical hydrogel.

[0081] B. Preparation of intermediate binder:

[0082] b1) Preparation of Binder A:

[0083] Sodium hydroxide, water glass and water are mixed in a mass ratio of 1:8:2.4 to obtain an intermediate binder A;

[0084] b2) Preparation of Binder B:

[0085] The recycled micro powder and biochar were mixed in a mass ratio of 1:0.01 to obtain the intermediate binder B;

[0086] b3) Preparation of intermediate binder:

[0087] Mix adhesive A and adhesive B in a mass ratio of adhesive A:B=1:1.2 and stir evenly for use.

[0088] C. Shell material preparation:

[0089] Place the recycled micro powder and granulated blast furnace slag powder in a granulator at a mass ratio of 7:3, stir for 2 to 5 minutes to fully mix the powders, and set aside.

[0090] D. Preparation of unburned hollow artificial aggregate:

[0091] d1) Preparation of hollow core:

[0092] The core material hydrogel is placed in a mixed solution of binders A and B. After the surface of the hydrogel is coated with the mixed binder solution, it is placed in binder B so that the surface of the hydrogel is coated with the powder to obtain material C. Material C is placed in a drying oven at a temperature of 30°C and cured for 24 hours to obtain a hollow core;

[0093] d2) Mixing and granulation:

[0094] The prepared hollow core is used as a raw material for granulation, and the prepared binder A is placed in a spray bottle; first, a small amount of shell powder is poured into the granulator, and the solidified hollow core is placed in a disc granulator. While spraying binder A, the shell powder is poured into it to make it into a uniform spherical aggregate. The aggregate is rolled at a speed of 15 r / min (to ensure that the aggregate is not thrown out of the disc granulator). The granulation process lasts for 25 minutes. When the aggregate agglomerates to a particle size of 10 mm, the granulation is completed to obtain a fire-free hollow artificial aggregate.

[0095] The granulated artificial aggregate is cured in an environment with a temperature of 20±2°C and a relative humidity of 95% or more for 28 days.

[0096] Example 2

[0097] A. Preparation of core materials:

[0098] a1) Prepare gelatin solution: Mix gelatin and water in a ratio of 1.5:4. Allow the gelatin powder to absorb water and swell for 2 hours. Stir the gelatin solution thoroughly and set aside.

[0099] a2) Hydrogel Preparation: Pour agar and carrageenan into 70°C hot water at a mass ratio of 2:0.5:5. After thorough stirring, mix with gelatin solution at a mass ratio of 1:1. Use a rubber-tipped dropper to drip the mixture into a silicone mold and refrigerate for 3 hours to produce a spherical hydrogel.

[0100] B. Preparation of intermediate binder:

[0101] b1) Preparation of Binder A:

[0102] Sodium hydroxide, water glass and water are mixed in a mass ratio of 2:5:1 to obtain an intermediate binder A;

[0103] b2) Preparation of Binder B:

[0104] The recycled micro powder and biochar were mixed in a mass ratio of 2:0.015 to obtain the intermediate binder B;

[0105] b3) Preparation of intermediate binder:

[0106] Mix adhesive A and adhesive B in a mass ratio of adhesive A:B=1:1.2 and stir evenly for use.

[0107] C. Shell material preparation:

[0108] Place the recycled micro powder and granulated blast furnace slag powder in a granulator at a mass ratio of 5:1, stir for 2 minutes to fully mix the powders, and set aside.

[0109] D. Preparation of unburned hollow artificial aggregate:

[0110] d1) Preparation of hollow core:

[0111] Put the inner core material hydrogel into the mixed solution of binder A and B, and then put it into the binder B after the surface of the hydrogel is wrapped with the mixed binder solution. The surface of the hydrogel is wrapped with the powder, and material C is obtained. The material C is placed in a drying box at a temperature of 35℃ for 18h to obtain a hollow core;

[0112] d2) Mixing and granulation:

[0113] The prepared hollow core is used as raw material for granulation, and the prepared binder A is placed in a spray pot. First, a small amount of shell powder is poured into the granulator, and the solidified hollow core is placed in the granulator. Spray binder A while pouring shell powder to make it into a uniform spherical aggregate. The prepared hollow core is used as raw material for granulation, and the prepared binder A is placed in a spray pot. First, a small amount of shell powder is poured into the granulator, and the solidified hollow core is placed in the disc granulator. Spray binder A while pouring shell powder to make it into a uniform spherical aggregate. Under the condition of rotating speed 10r / min (to ensure that the aggregate is not thrown out of the disc granulator), the granulation process continues for 20 minutes. When the aggregate is aggregated to a particle size of 15mm, the granulation is completed, and the unfired hollow artificial aggregate is obtained.

[0114] The artificial aggregate after granulation is cured in an environment with a temperature of 20±2℃ and a relative humidity of 95%RH or more for 28 days.

[0115] Example 3

[0116] A, preparation of inner core material:

[0117] a1) Preparation of gelatin solution: mix gelatin and water according to the mass ratio of 2:7. Swell the gelatin powder for 1.5 hours. Stir the gelatin solution uniformly and wait for use.

[0118] a2) Preparation of hydrogel: mix agar and carrageenan into hot water at 90℃ according to the mass ratio of 1.5:0.1:10. Stir well, then mix with the gelatin solution according to the mass ratio of 1:1. Drop the mixed liquid into the silica gel mold with a rubber head dropper. Put it in the refrigerator for 2.5 hours to prepare spherical hydrogel.

[0119] B, preparation of intermediate binder:

[0120] b1) Preparation of binder A:

[0121] Mix sodium hydroxide, water glass and water according to the mass ratio of 1.5:10:5 to obtain intermediate binder A;

[0122] b2) Preparation of binder B:

[0123] The recycled micro powder and biochar were mixed in a mass ratio of 1.5:0.02 to obtain the intermediate binder B;

[0124] b3) Preparation of intermediate binder:

[0125] Mix adhesive A and adhesive B in a mass ratio of adhesive A:B=1:1.2 and stir evenly for use.

[0126] C. Shell material preparation:

[0127] Place the recycled micro powder and granulated blast furnace slag powder in a granulator at a mass ratio of 10:5, stir for 5 minutes to fully mix the powders, and set aside.

[0128] D. Preparation of unburned hollow artificial aggregate:

[0129] d1) Preparation of hollow core:

[0130] The core material hydrogel is placed in a mixed solution of binders A and B. After the surface of the hydrogel is coated with the mixed binder solution, it is placed in binder B so that the surface of the hydrogel is coated with the powder to obtain material C. Material C is placed in a drying oven at a temperature of 25°C and cured for 36 hours to obtain a hollow core;

[0131] d2) Mixing and granulation:

[0132] The prepared hollow core is used as a raw material for granulation, and the prepared binder A is placed in a spray bottle; first, a small amount of shell powder is poured into the granulator, and the solidified hollow core is placed in the granulator. While spraying the binder A, the shell powder is poured into the granulator to make it into a uniform spherical aggregate. The aggregate is rolled at a speed of 20 r / min (to ensure that the aggregate is not thrown out of the disc granulator). The granulation process lasts for 30 minutes. When the aggregate agglomerates to a particle size of 15 mm, the granulation is completed, and the unburned hollow artificial aggregate is obtained.

[0133] The granulated artificial aggregate is cured in an environment with a temperature of 20±2°C and a relative humidity of 95% or more for 28 days.

[0134] Strength Test: This experiment uses single-particle strength (crushing strength) to characterize the crushing strength of artificial aggregates. Normal granulated aggregates are set as a control group. The testing instrument is a CMT-20 microcomputer-controlled electronic universal testing machine. Specific testing method: 10 aggregates are tested in each group of specimens. To eliminate the influence of aggregate size on strength results, the aggregate diameter is controlled at approximately 10mm. The aggregate diameter is the average of the three-dimensional measurements of a single aggregate. The aggregate is placed between the loading plate and the support plate, and pressure is applied at a loading rate of 1mm / min until the aggregate breaks. The peak pressure at the time of aggregate failure is recorded. The strength of the aggregate is calculated using the following formula:

[0135]

[0136] Where, σ c : compressive strength, unit MPa; F c : Load at aggregate failure, unit N; d m : Average diameter of aggregate, unit: mm.

[0137] In the present invention, the hydrogel can be used as a mold for the intermediate bonding layer when in a gel state. After the water in the hydrogel evaporates, only a thin colloid shell is left, so that the artificial aggregate forms a hollow state, which can reduce the weight of the artificial aggregate.

[0138] The comparative examples are given below for comparison with the embodiments of the present invention to further illustrate the effects of the present invention.

[0139] Comparative Example 1

[0140] Gypsum-based lightweight hollow aggregate is prepared using the following mass ratio: gypsum-based cementitious material: retarder: water reducer: thickener: chopped fiber = 1: 0.1-0.3%: 0.1-0.5%: 0.05-0.3%: 1-2%. The raw materials are granulated before the paraffin wax is completely dried and hardened to produce mixed pellets. The pellets are then coated with a gypsum mixture and irradiated to produce the gypsum-based lightweight hollow aggregate.

[0141] The performance test results of the embodiment and the comparative example are compared in Table 2.

[0142] Table 2 Properties of unburned hollow artificial aggregate (28 days)

[0143]

[0144] As can be seen from Table 2, the single particle strength of the unburned hollow artificial aggregate prepared by the cold hardening process of the present invention is not less than 4.38 MPa, the cylinder pressure strength is not less than 4.54 MPa, and the bulk density is not less than 946 kg / m 3 The unfired hollow artificial aggregate material prepared by the present invention not only has high mechanical properties, but also has light weight, high strength, good stability, and is green and environmentally friendly. It is an unfired hollow artificial aggregate material with good processing performance.

[0145] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some of the technical features therein according to the disclosed technical content without creative labor, and these substitutions and modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing a fire-free hollow artificial aggregate, characterized in that: The following steps are involved: A. Preparation of core materials: a1) Prepare a gelatin solution by mixing gelatin and water in a mass ratio of (1-2):(4-7); a2) adding agar and carrageenan to hot water in a mass ratio of (1-2):(0.1-0.5):(5-10) of agar, carrageenan, and water, mixing thoroughly, then mixing the mixture with a gelatin solution in a mass ratio of 1:1, and dropping the mixture into a spherical mold to prepare a spherical hydrogel; B. Preparation of intermediate binder: b1) Mixing sodium hydroxide, water glass, and water in a mass ratio of (1-2):(5-10):(1-5) to obtain an intermediate binder A; b2) Mixing the recycled micropowder and the biochar in a mass ratio of (1-2): (0.01-0.02) to prepare an intermediate binder B; b3) Mixing and stirring binder A and binder B in a mass ratio of binder A:B = 1:1.2 to prepare an intermediate binder; C. Shell material preparation: Recycled micro powder and granulated blast furnace slag powder are mixed in a mass ratio of (5-10):(1-5) to obtain shell powder; D. Preparation of unburned hollow artificial aggregate: d1) placing a core material hydrogel into a mixed solution of binders A and B. After coating the surface of the hydrogel with the mixed binder solution, the hydrogel is placed into binder B to obtain material C. Material C is dried and cured to obtain a hollow core. d2) Pour a small amount of shell powder into the granulator, place the solidified hollow core in the granulator, and pour the shell powder into the granulator while spraying the binder A to form a uniform spherical aggregate. The spherical aggregate is rolled at a certain speed to obtain a certain particle size of unburned hollow artificial aggregate; The granulated artificial aggregate is cured in an environment of high temperature and relative humidity.

2. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: In step a1), gelatin is mixed with water and the gelatin powder absorbs water and swells for 1 to 2 hours.

3. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: In step a2), agar and carrageenan are poured into hot water at 70-90° C. and stirred thoroughly; the mixture is refrigerated for 2-3 hours to prepare a hydrogel.

4. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: In step C, the regenerated micro powder and granulated blast furnace slag powder are placed in a granulator and stirred for 2 to 5 minutes.

5. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: In step d1), material C is placed in a drying oven at a temperature of 25-35° C. and cured for 18-36 hours.

6. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: In step d2), the pelletizing is completed by rolling at a rotation speed of 10-20 r / min for 20-30 min, when the aggregate agglomerates to a particle size of 10-15 mm.

7. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: In step d2), the granulated artificial aggregate is cured for 28 days in an environment with a temperature of 20±2° C. and a relative humidity of 95% or higher.

8. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: The oxide content of the recycled micropowder material is SiO2≥48.85%; CaO≥22.11%; Al2O3≥13.28%; Fe2O3≥6.44%; MgO≥2.7%; SO3≥0.67%. The sum of the oxide contents in the recycled micropowder material is 100%.

9. The method for preparing the unburned hollow artificial aggregate according to claim 1, characterized in that: The oxide content of the granulated blast furnace slag material is SiO2≥34.2%; CaO≥34%; Al2O3≥17.6%; Fe2O3≥1.01%; MgO≥6.21%; SO3≥5.36%, and the sum of the oxide contents in the granulated blast furnace slag material is 100%.

10. A fire-free hollow artificial aggregate prepared by the method for preparing fire-free hollow artificial aggregate according to any one of claims 1 to 9.

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