Artificial coarse aggregate and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and discloses artificial coarse aggregate and a preparation method thereof. The artificial coarse aggregate is prepared from the following raw materials in parts by weight: 100 parts of sea sand; 12 to 20 parts of a binder; 0.06 to 0.18 part of a coalescing agent; 12 to 20 parts of water; wherein the binder is an acrylate copolymer emulsion with the solid content of 50%, and the coalescing agent is propylene glycol monobutyl ether. The preparation method comprises the steps of raw material pretreatment and mixing, adhesive solution preparation, rolling agglomeration granulation, curing maintenance, screening and the like. By controlling the particle size grading of the sea sand, the use amount of the binder and process parameters, the prepared artificial coarse aggregate is in an irregular polygonal form, has a rough and porous surface, has proper bulk density, cylinder compressive strength and water absorption, and can meet the use requirements of C25-C35 grade lightweight concrete. According to the method, efficient utilization of sea sand resources is achieved, the process is simple, energy consumption is low, and the method has good engineering application prospects.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to an artificial coarse aggregate and its preparation method. Background Technology

[0002] With the rapid development of the construction industry, the demand for concrete aggregates is increasing. Natural sand and gravel resources are becoming increasingly depleted due to long-term mining, while environmental protection requirements are constantly rising. Therefore, finding alternative aggregate materials to replace natural sand and gravel has become an important research direction in the field of building materials.

[0003] Sea sand, as an abundant marine resource, has the advantages of wide availability and relatively low extraction costs. However, sea sand contains harmful components such as chloride salts, and direct use can lead to corrosion of steel reinforcement in concrete, affecting structural durability. Although salt can be removed by washing with fresh water, how to achieve high-value utilization of sea sand resources remains an urgent problem to be solved.

[0004] Currently, the main methods for preparing artificial aggregates include sintering and cement curing. Sintering requires high-temperature treatment, consumes a lot of energy, and is a complex process; cement curing produces a strongly alkaline environment, which may affect the aggregate-paste interface properties. In addition, existing artificial aggregates mostly pursue spherical or near-spherical shapes, which, although beneficial for construction fluidity, result in lower bond strength with cement paste, making it difficult to meet the requirements of high-performance concrete.

[0005] Studies have shown that aggregates with irregular, multi-faceted shapes can significantly improve the interfacial strength of concrete through mechanical interlocking. Therefore, developing an artificial aggregate with irregular shape, rough surface, and porous interior is of great significance for improving concrete performance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an artificial coarse aggregate and its preparation method. The artificial coarse aggregate has an irregular multi-faceted shape and a rough and porous surface, which can effectively improve the bonding strength with cement paste. At the same time, the preparation process is simple and energy consumption is low, realizing the efficient utilization of sea sand resources.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an artificial coarse aggregate, made from the following raw materials in parts by weight: Sea sand: 100 parts; Adhesive: 12-20 parts; Film-forming aid: 0.06-0.18 parts; Water: 12-20 parts; The adhesive is an acrylate copolymer emulsion with a solid content of 50%; the film-forming aid is propylene glycol monobutyl ether.

[0008] Preferably, the sea sand is a mixture of fine sand, medium sand, and coarse sand with different particle size ranges; wherein: The fine sand particle size D1 is: 0.15 ≤ D1 < 0.6 mm. The particle size D2 of medium sand is: 0.6 ≤ D2 < 1.18 mm. The coarse sand particle size D3 is: 1.18≤D3≤2.36mm. The mass ratio of fine sand, medium sand, and coarse sand is 35:50:15.

[0009] Preferably, the particle size of the copolymer in the acrylate copolymer emulsion is 80-300 nm.

[0010] Secondly, the present invention provides a method for preparing artificial coarse aggregate, which includes the following steps: S1. Raw material pretreatment and mixing: After the sea sand raw material is washed and desalinated with fresh water and dried, the sea sand of different particle size ranges is mixed evenly according to the preset ratio to form aggregate raw material with set gradation. S2. Preparation of adhesive solution: After adding film-forming aid to the adhesive, dilute with water to obtain an adhesive solution suitable for spraying; S3, Rolling Agglomeration Granulation: The mixed sea sand raw material is added into the granulator, and the adhesive solution is evenly sprayed in under rolling conditions, so that the sea sand particles adhere to each other under the action of liquid bridge, forming irregular multi-faceted agglomerate aggregate. S4. Curing and solidification: The agglomerated aggregate is cured in the first stage and the second stage in sequence. The first stage is cured under normal temperature and high humidity conditions, and the second stage is dried and solidified under heating conditions. S5. Screening: After the cured agglomerated aggregates are cooled to room temperature, they are screened, and the aggregates within the target particle size range are taken as finished products.

[0011] Preferably, the granulator is a disc or drum granulator; during granulation, the rotation speed is 20-30 rpm; and the agglomeration granulation time is 20-30 minutes.

[0012] Preferably, the disc tilt angle of the disc granulator is 45°-60°, and the rotation speed during granulation is 28 rpm.

[0013] Preferably, in step S4, the first stage of curing is carried out at 20-30℃ and relative humidity ≥90% for 12-24 hours; the second stage of curing is carried out at 65-80℃ for 24-48 hours for drying and curing.

[0014] Preferably, the target particle size range in step S5 is 4.75-26.5 mm, and the obtained artificial coarse aggregate meets the continuous gradation requirements by controlling the sieve residue rate of each particle size.

[0015] Preferably, the continuous gradation requirements are: 0% residue on 4.75mm sieve, 15%-35% residue on 9.5mm sieve, 60%-85% residue on 16.0mm sieve, ≥90% residue on 19.0mm sieve, and ≥98% residue on 26.5mm sieve.

[0016] Preferably, in step S2, when preparing the adhesive solution, the mass ratio of adhesive to water is 1:1.

[0017] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: (1) Compared with traditional dense spherical aggregate, the artificial coarse aggregate prepared by the present invention has an irregular multi-faceted shape, a rough and multi-faceted surface, and a porous interior, which can form a good mechanical bond with cement paste and significantly improve the interfacial bond strength of concrete.

[0018] (2) By controlling the particle size distribution and process parameters of sea sand, the physical properties of aggregates can be precisely controlled to meet the requirements of different grades of concrete.

[0019] (3) The preparation process is simple, energy consumption is low, and there is no need for high-temperature sintering or large amount of cement curing, which meets the requirements of green environmental protection.

[0020] (4) It realizes the efficient utilization of sea sand resources and solves the problem of the effect of sea sand salt content on concrete durability; the process is simple, the raw materials are widely available, and industrial preparation can be realized, which has significant economic and social benefits.

[0021] (5) The prepared artificial coarse aggregate has low bulk density, moderate water absorption, good compressive strength and crushing index, and can meet the requirements of C30 and above grade lightweight concrete. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a flow chart of the artificial coarse aggregate preparation process provided by the present invention; Figure 2 This is a schematic diagram of granulation using a disc granulator; Figure 3 This is a schematic diagram of the structure of the artificial coarse aggregate prepared according to the present invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] Example 1: This embodiment provides an artificial coarse aggregate and its preparation method.

[0026] The artificial coarse aggregate is made from the following raw materials by weight: 100 kg of sea sand, 16 kg of acrylate copolymer emulsion (50% solid content), 0.08 kg of propylene glycol monobutyl ether (PPD) film-forming aid, and 16 kg of water. The particle size of the copolymer in the acrylate copolymer emulsion is 80–300 nm.

[0027] The preparation method includes the following steps: S1. Raw Material Pretreatment and Mixing: The sea sand is thoroughly washed with clean water to remove salt and impurities, then dried at 105℃ until the moisture content is less than 1%. The dried sea sand is then sieved to obtain fine sand, medium sand, and coarse sand. The particle size D1 of the fine sand is 0.15 ≤ D1 < 0.6 mm, the particle size D2 of the medium sand is 0.6 ≤ D2 < 1.18 mm, and the particle size D3 of the coarse sand is 1.18 ≤ D3 ≤ 2.36 mm. 35 kg of fine sand, 50 kg of medium sand, and 15 kg of coarse sand are weighed and mixed to obtain 100 kg of rationally graded sea sand raw material.

[0028] S2. Preparation of adhesive solution: Mix 16 kg of acrylate copolymer emulsion (solid content 50%) with 0.08 kg of film-forming aid propylene glycol monobutyl ether, and then add 16 kg of water to prepare a spray adhesive solution.

[0029] S3. Rolling Agglomeration Granulation: A disc granulator is used. The disc diameter is 1 meter, the disc inclination angle is set to 50 degrees, and the rotation speed is set to 28 rpm. The mixed sea sand raw material from step S1 is added to the disc granulator while the spray adhesive prepared in step S3 is sprayed in. After granulation for 25 minutes, irregular agglomerated aggregates with a diameter of 5-30 mm are obtained. (Details follow...) Figure 2 As shown, the inclined disc is rotated by the drive device, and the sea sand raw material is added while the spray adhesive prepared in step S3 is sprayed in to carry out the granulation operation.

[0030] S4. Curing and solidification: Place the agglomerated aggregate at 25°C and relative humidity greater than 95% for 18 hours; then transfer it to 75°C for 30 hours to complete the curing.

[0031] S5. Screening: Cool the solidified aggregate to room temperature, screen to remove particles with a diameter less than 4.75 mm and greater than 26.5 mm, and obtain the finished aggregate.

[0032] Test results show that the bulk density is 1220 kg / m³, the compressive strength of the cylinder is 19.5 MPa, and the water absorption rate is 7.5%.

[0033] Example 2: This embodiment provides an artificial coarse aggregate and its preparation method.

[0034] Artificial coarse aggregate is made from the following raw materials by weight: 100 kg of sea sand, 20 kg of acrylic copolymer emulsion (50% solid content), 0.15 kg of film-forming aid propylene glycol monobutyl ether, and 20 kg of water.

[0035] The preparation method includes the following steps: S1. Raw Material Pretreatment and Mixing: The sea sand is washed with clean water to remove salt, then dried. The dried sea sand is sieved to obtain fine sand, medium sand, and coarse sand, wherein: the particle size D1 of fine sand is 0.15≤D1<0.6mm, the particle size D2 of medium sand is 0.6≤D2<1.18mm, and the particle size D3 of coarse sand is 1.18≤D3≤2.36mm. 35kg of fine sand, 50kg of medium sand, and 15kg of coarse sand are weighed and mixed to obtain 100kg of sea sand raw material with reasonable gradation.

[0036] S2. Preparation of adhesive solution: Mix 20 kg of acrylate copolymer emulsion (solid content 50%) with 0.15 kg of film-forming aid propylene glycol monobutyl ether, and then add 20 kg of water to prepare a spray adhesive solution.

[0037] S3. Rolling Agglomeration Granulation: A disc granulator is used. The diameter of the disc is 1 meter, the disc inclination angle is set at 55 degrees, and the rotation speed is set at 30 revolutions per minute. The sea sand raw material mixed in step S1 is added into the disc granulator while the spray adhesive prepared in step S3 is sprayed in. Granulation is carried out for 20 minutes, so that the sea sand particles adhere to each other under the action of liquid bridge, forming irregular multi-faceted agglomerate aggregate.

[0038] S4. Curing: Place the aggregated aggregate at 25℃ and relative humidity greater than 95% for 16 hours; then carry out intensive curing at 70℃ for 36 hours.

[0039] S5. Screening: Screen particles with a diameter of 4.75-26.5 mm as the finished product.

[0040] Test results show that the bulk density is 1180 kg / m³, the cylinder compressive strength is 20.7 MPa, and the water absorption rate is 8.9%.

[0041] Example 3: This embodiment provides an artificial coarse aggregate and its preparation method.

[0042] Artificial coarse aggregate is made from the following raw materials by weight: 100 kg of sea sand, 12 kg of acrylate copolymer emulsion (solid content 50%), 0.06 kg of film-forming aid propylene glycol monobutyl ether, and 12 kg of water.

[0043] The preparation method includes the following steps: S1. Raw Material Pretreatment and Mixing: The sea sand is thoroughly washed with clean water to remove salt and impurities, and then dried. The dried sea sand is sieved to obtain fine sand, medium sand, and coarse sand, where: fine sand particle size D1 is 0.15 ≤ D1 < 0.6 mm, medium sand particle size D2 is 0.6 ≤ D2 < 1.18 mm, and coarse sand particle size D3 is 1.18 ≤ D3 ≤ 2.36 mm. 35 kg of fine sand, 50 kg of medium sand, and 15 kg of coarse sand are weighed and mixed to obtain 100 kg of rationally graded sea sand raw material.

[0044] S2. Preparation of adhesive solution: Mix 12 kg of acrylate copolymer emulsion (solid content 50%) with 0.06 kg of film-forming aid propylene glycol monobutyl ether, then add 12 kg of water to dilute and prepare a spray adhesive solution.

[0045] S3. Rolling Agglomeration Granulation: A disc granulator is used. The disc diameter of the granulator is 1 meter, the disc inclination angle is set to 45 degrees, and the rotation speed is set to 25 revolutions per minute. While adding the sea sand raw material mixed in step S1 into the disc granulator, the spray adhesive prepared in step S3 is sprayed in. The granulation time is 30 minutes, so that the sea sand particles adhere to each other under the action of liquid bridge to form irregular multi-faceted agglomerate aggregate.

[0046] S4. Solidification and Curing: The agglomerated aggregates are subjected to a first-stage curing and a second-stage curing. The first-stage curing conditions are 30℃, relative humidity ≥90%, and curing time 20 hours. The second-stage intensive curing conditions are 65℃ and curing time 48 hours.

[0047] S5. Screening: Screen particles with a diameter of 4.75-26.5 mm as the finished product.

[0048] Test results show that the bulk density is 1260 kg / m³, the cylinder compressive strength is 18.2 MPa, and the water absorption rate is 6.5%.

[0049] Example 4: This embodiment provides an artificial coarse aggregate and its preparation method.

[0050] Artificial coarse aggregate is made from the following raw materials by weight: 100 kg of sea sand, 18 kg of acrylic copolymer emulsion (50% solid content), 0.18 kg of film-forming aid propylene glycol monobutyl ether, and 18 kg of water.

[0051] The preparation method includes the following steps: S1. Raw Material Pretreatment and Mixing: After being washed and desalinated with fresh water, the sea sand is dried. The dried sea sand is then sieved to obtain fine sand, medium sand, and coarse sand. The particle size D1 of the fine sand is 0.15 ≤ D1 < 0.6 mm, the particle size D2 of the medium sand is 0.6 ≤ D2 < 1.18 mm, and the particle size D3 of the coarse sand is 1.18 ≤ D3 ≤ 2.36 mm. 35 kg of fine sand, 50 kg of medium sand, and 15 kg of coarse sand are weighed and mixed to obtain 100 kg of sea sand raw material with reasonable gradation.

[0052] S2. Preparation of adhesive solution: Mix 18 kg of acrylate copolymer emulsion (solid content 50%) with 0.18 kg of film-forming aid propylene glycol monobutyl ether, then add 18 kg of water to dilute and prepare a spray adhesive solution.

[0053] S3. Rolling Agglomeration Granulation: Granulation is performed using a granulator drum with a diameter of 1.2 meters. The mixed sea sand raw material from step S1 is added to the drum granulator while the spray adhesive prepared in step S3 is sprayed in. The rotation speed is set to 20 rpm, and the granulation time is 25 minutes. This causes the sea sand particles to adhere to each other under the action of liquid bridging, forming irregular, multi-faceted agglomerated aggregates.

[0054] S4. Solidification and curing: The agglomerated aggregates are subjected to the first stage of curing and the second stage of curing in sequence. The initial curing conditions for the first stage are 20℃, relative humidity greater than or equal to 95%, and curing time of 24 hours. The conditions for the second stage of intensive curing are 80℃ and curing time of 24 hours.

[0055] S5. Screening: Screening to obtain aggregates of 4.75-26.5 mm as finished products.

[0056] Test results show that the bulk density is 1150 kg / m³, the compressive strength of the cylinder is 21.3 MPa, and the water absorption rate is 10.2%.

[0057] Example 5: This embodiment provides an artificial coarse aggregate and its preparation method.

[0058] Artificial coarse aggregate is made from the following total amounts of raw materials: 100 kg of sea sand, 14 kg of acrylate copolymer emulsion (50% solid content), 0.07 kg of film-forming aid propylene glycol monobutyl ether, and 14 kg of water.

[0059] The preparation method includes the following steps: S1. Raw Material Pretreatment and Mixing: After being washed and desalinated with fresh water, the sea sand is dried. The dried sea sand is then sieved to obtain fine sand, medium sand, and coarse sand. The particle size D1 of the fine sand is 0.15 ≤ D1 < 0.6 mm, the particle size D2 of the medium sand is 0.6 ≤ D2 < 1.18 mm, and the particle size D3 of the coarse sand is 1.18 ≤ D3 ≤ 2.36 mm. 35 kg of fine sand, 50 kg of medium sand, and 15 kg of coarse sand are weighed and mixed to obtain 100 kg of sea sand raw material with reasonable gradation.

[0060] S2. Preparation of adhesive solution: Mix 14 kg of acrylate copolymer emulsion (solid content 50%) with 0.07 kg of film-forming aid propylene glycol monobutyl ether, then add 14 kg of water to dilute and prepare a spray adhesive solution.

[0061] S3. Rolling Agglomeration Granulation: A disc granulator is used. The disc diameter is 1 meter, the disc inclination angle is set to 60 degrees, and the rotation speed is set to 28 rpm. The sea sand raw material mixed in step S1 is added to the disc granulator while the spray adhesive prepared in step S3 is sprayed in. The granulation time is 22 minutes. This causes the sea sand particles to adhere to each other under the action of liquid bridging, forming irregular, multi-faceted agglomerated aggregate.

[0062] S4. Solidification and curing: The agglomerated aggregates are cured in the first stage and the second stage in sequence. The initial curing conditions for the first stage are 25℃, relative humidity greater than 95%, and curing time of 18 hours; the conditions for the second stage of intensive curing are 75℃ and curing time of 30 hours.

[0063] S5. Screening: Screen particles with a diameter of 4.75-26.5 mm as the finished product.

[0064] Test results show that the bulk density is 1200 kg / m³, the compressive strength of the cylinder is 19.8 MPa, and the water absorption rate is 7.8%.

[0065] To more clearly illustrate the raw material ratios of Examples 1 to 5, a summary is shown in the table below: Table 1. Raw material ratios for Examples 1 to 5

[0066] In the above embodiments, the cement content of the prepared artificial coarse aggregate is between 6% and 10% (Note: the measurement basis is the dry weight of the finished product); and the above embodiments 1 to 5 cover different granulation conditions (tilt angle / speed / time) and different curing conditions.

[0067] The properties of the artificial coarse aggregates prepared in Examples 1 to 5 are shown in the table below: Table 2. Properties of the artificial coarse aggregates prepared in Examples 1 to 5

[0068] The data in the table show that the artificial coarse aggregate prepared by this invention exhibits good performance under different raw material ratios and process conditions. The bulk density of the aggregate is between 1150-1260 kg / m³, the compressive strength is stable in the range of 18.2-21.3 MPa, and the 24-hour water absorption rate is controlled at 6.5%-10.2%, which can meet the requirements for use in lightweight concrete of grades C25 to C35.

[0069] By adjusting the amount of acrylate copolymer emulsion and curing conditions, the mechanical properties and water absorption of aggregates can be flexibly controlled within a certain range. Higher cementitious content (9%-10%) helps to improve the strength of aggregates, while lower admixture (6%-7%) can increase bulk density and reduce water absorption, demonstrating good controllability.

[0070] This invention achieves balanced optimization of the morphology, pore structure, and performance of artificial coarse aggregate through a controllable agglomeration process and staged curing. The resulting aggregate exhibits a typical three-dimensional irregular "flower-shaped" morphology, with a rough and porous surface and interconnected pores inside. This allows for good interfacial bonding with cement paste, resulting in higher interfacial friction and mechanical interlocking force. The interconnected pore structure also facilitates the penetration of cement paste into the pores on the aggregate surface, forming an "interlocking" effect. This significantly improves the bond strength between the aggregate and cement paste and the overall mechanical properties of the concrete. Figure 3 The irregular, multi-faceted shape of the aggregate's exterior and its interconnected pore structure are displayed from a three-dimensional perspective, intuitively demonstrating the characteristics that distinguish the aggregate of this invention from spherical artificial aggregates.

[0071] The method for preparing artificial coarse aggregate provided by this invention has a simple process flow, a wide range of raw material sources, and can be industrialized, with good engineering application prospects and economic benefits.

[0072] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. An artificial coarse aggregate, characterized in that, Made from the following parts by weight of raw materials: Sea sand: 100 parts; Adhesive: 12-20 parts; Film-forming aid: 0.06-0.18 parts; Water: 12-20 parts; The adhesive is an acrylate copolymer emulsion with a solid content of 50%; the film-forming aid is propylene glycol monobutyl ether.

2. The artificial coarse aggregate according to claim 1, characterized in that, The sea sand is a mixture of fine, medium, and coarse sand with different particle sizes; wherein: The fine sand particle size D1 is: 0.15 ≤ D1 < 0.6 mm. The particle size D2 of medium sand is: 0.6 ≤ D2 < 1.18 mm. The coarse sand particle size D3 is: 1.18≤D3≤2.36mm. The mass ratio of fine sand, medium sand, and coarse sand is 35:50:

15.

3. The artificial coarse aggregate according to claim 1, characterized in that, The copolymer in the acrylate copolymer emulsion has a particle size of 80–300 nm.

4. A method for preparing artificial coarse aggregate, used to prepare the artificial coarse aggregate according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Raw material pretreatment and mixing: After the sea sand raw material is washed and desalinated with fresh water and dried, the sea sand of different particle size ranges is mixed evenly according to the preset ratio to form aggregate raw material with set gradation. S2. Preparation of adhesive solution: After adding film-forming aid to the adhesive, dilute with water to obtain an adhesive solution suitable for spraying; S3, Rolling Agglomeration Granulation: The mixed sea sand raw material is added into the granulator, and the adhesive solution is evenly sprayed in under rolling conditions, so that the sea sand particles adhere to each other under the action of liquid bridge, forming irregular multi-faceted agglomerate aggregate. S4. Curing and solidification: The agglomerated aggregate is cured in the first stage and the second stage in sequence. The first stage is cured under normal temperature and high humidity conditions, and the second stage is dried and cured under heating conditions. S5. Screening: After the cured agglomerated aggregates are cooled to room temperature, they are screened, and the aggregates within the target particle size range are taken as finished products.

5. The preparation method according to claim 4, characterized in that, The granulator is a disc or drum granulator; during granulation, the rotation speed is 20-30 rpm; the agglomeration granulation time is 20-30 minutes.

6. The preparation method according to claim 5, characterized in that, The disc of the disc granulator has an inclination angle of 45°-60° and a rotation speed of 28 rpm during granulation.

7. The preparation method according to claim 4, characterized in that, In step S4, the first stage of curing is carried out at 20-30℃ and relative humidity ≥90% for 12-24 hours; the second stage of curing is carried out at 65-80℃ for 24-48 hours for drying and curing.

8. The preparation method according to claim 4, characterized in that, The target particle size range mentioned in step S5 is 4.75-26.5 mm, and the artificial coarse aggregate obtained meets the continuous gradation requirements by controlling the sieve residue rate of each particle size.

9. The preparation method according to claim 8, characterized in that, The continuous gradation requirements are as follows: 0% residue on 4.75mm sieve, 15%-35% residue on 9.5mm sieve, 60%-85% residue on 16.0mm sieve, ≥90% residue on 19.0mm sieve, and ≥98% residue on 26.5mm sieve.

10. The preparation method according to claim 4, characterized in that, In step S2, when preparing the adhesive solution, the mass ratio of adhesive to water is 1:1.

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