A mineral thickening agent for shotcrete and a preparation method thereof

Abstract

The application discloses a mineral tackifier special for shotcrete and a preparation method thereof, and relates to the technical field of tackifiers. The mineral tackifier is obtained through graft copolymerization reaction of 1-vinyl-2-pyrrolidone, acrylic acid, xanthan gum and hyperbranched borate under the action of an initiator; the hyperbranched borate is generated through reaction of a hyperbranched product and 1,4-benzenediboronic acid under the catalysis of anhydrous magnesium sulfate; and the hyperbranched product is prepared through esterification reaction of 3-(bis(2-hydroxyethyl)amino)propionic acid methyl ester and 2-methyl-2-propenoic acid-2,3-dihydroxypropyl ester. The mineral tackifier prepared by the application has good compressive strength and short setting time.

Description

Technical Field

[0001] This invention relates to the field of thickener technology, specifically to a mineral thickener for shotcrete and its preparation method. Background Technology

[0002] Shotcrete is a type of concrete applied using a spraying method. It offers fast construction speed and low requirements for the site environment (flatness, shape, etc.), and is commonly used for lining tunnels, walls, ceilings, and other thin-walled structures, as well as for protective layers on steel structures. However, current shotcrete technologies suffer from low bond strength and high rebound rates, leading to significant material waste. During dry shotcreting, water and powdered concrete mix at the nozzle outlet and are then sprayed onto the surrounding rock surface. Due to the reaction force, a large amount of concrete rebounds into the air, resulting in high levels of cement dust in the workers' workspace, threatening the health of tunneling and construction workers. Furthermore, the substantial rebound loss of shotcrete hinders the economic efficiency of shotcrete anchoring systems.

[0003] Currently, to improve the performance of shotcrete, inorganic materials such as silica fume and fly ash, or organic natural macromolecular admixtures such as cellulose, are often added. However, these traditional thickeners have many drawbacks: inorganic materials require large dosages, are costly, and are difficult to work synergistically with accelerators; organic natural macromolecular admixtures may increase cement setting time, introduce harmful air bubbles, and impair concrete durability. Therefore, developing a high-efficiency, low-dosage mineral thickener specifically for shotcrete is of great significance. This thickener should possess good dispersibility, thickening properties, setting acceleration properties, and compatibility with other concrete components, and should be able to reduce rebound rate while improving the early strength and durability of concrete.

[0004] Chinese invention patent CN119371136A discloses a concrete composite thickener and its preparation method. In preparing the concrete composite thickener, the invention first reacts a polyacrylic acid resin obtained by polymerizing acrylic acid, methyl methacrylate, acrylamide, and vinyl diphenylphosphine with a modified porphyrin, followed by sulfonation to obtain a modified polyacrylic acid resin. Second, it reacts silica fume pretreated with vinyltrimethoxysilane with tetravinyltetramethylcyclotetrasiloxane and vinyl borate pinacol ester to obtain modified silica fume. Finally, it mixes the polyacrylic acid resin and modified silica fume to obtain the concrete composite thickener. The concrete composite thickener prepared by this invention has good workability and antibacterial properties, but its compressive strength and setting time are relatively poor. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a mineral thickener for shotcrete and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a mineral thickener specifically for shotcrete includes the following steps:

[0008] S1: Under nitrogen protection, add DMSO, methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester to the reactor, stir and mix well, then add p-toluenesulfonic acid and react for 8-10 hours to generate hyperbranched products.

[0009] S2: Hyperbranched products react with 1,4-phenylenediboronic acid to form hyperbranched borate esters;

[0010] S3: Under nitrogen protection, xanthan gum, 1-vinyl-2-pyrrolidone, acrylic acid, and hyperbranched borate esters are copolymerized under the action of an initiator to obtain a mineral thickener for shotcrete.

[0011] In step S1, the mass ratio of methyl 3-(bis(2-hydroxyethyl)amino)propionate to 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester is (25-30):5.

[0012] The reaction temperature in step S1 is 80-100℃.

[0013] In step S2, the mass ratio of the hyperbranched product to 1,4-phenylenediboric acid is 10:(3-4).

[0014] In step S3, the mass ratio of 1-vinyl-2-pyrrolidone, acrylic acid, xanthan gum, and hyperbranched borate ester is (3-5):(1-2):50:(15-18).

[0015] In step S3, the initiator is either potassium persulfate or ammonium persulfate.

[0016] The reaction temperature in step S3 is 50-60℃.

[0017] A mineral thickener for shotcrete is prepared using the method described above.

[0018] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include:

[0019] (1) First, a first-generation hyperbranched product is generated by transesterification of methyl 3-(bis(2-hydroxyethyl)amino)propionate and 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester; the hyperbranched product reacts with 1,4-phenylenediboric acid to form a three-dimensional network hyperbranched borate ester. This three-dimensional network structure can effectively fill the micropores in concrete, improve the density of concrete, and thus significantly improve its compressive strength; finally, 1-vinyl-2-pyrrolidone, acrylic acid and hyperbranched boric acid are grafted onto xanthan gum to obtain a mineral thickener for shotcrete.

[0020] (2) The borate groups of 1,4-phenylenediboric acid crosslink with the hydroxyl groups of the hyperbranched product to form a three-dimensional network structure. After being grafted onto xanthan gum, it can provide rigid skeleton support during the hardening process of concrete, enhance the internal stress transmission capacity, and thus improve the compressive strength. The hyperbranched borate ester contains borate bonds (BO bonds), which have reversible breakage-reorganization characteristics. Under the shear force or humidity changes of concrete spraying, the dynamic crosslinked network can be locally reorganized to alleviate stress concentration. At the same time, the three-dimensional network structure has a large specific surface area and strong adsorption capacity, which can better fix concrete particles together and reduce rebound loss. The carboxyl functional groups provided by the acrylic acid grafted onto xanthan gum can chelate with calcium ions in cement, accelerate the hydration reaction of cement, and thus promote the development of early strength. At the same time, the copolymer formed by the interaction of xanthan gum with 1-vinyl-2-pyrrolidone and acrylic acid not only enhances the adhesion of concrete, but also prevents excessive aggregation of cement particles through steric hindrance, further promoting uniform hydration reaction and improving early strength. Detailed Implementation

[0021] The following description, in conjunction with specific embodiments, provides further details, but the present invention is not limited to these embodiments.

[0022] Example 1: Preparation of mineral thickener for shotcrete:

[0023] S1: Under nitrogen protection, 1000g DMSO, 250g methyl 3-(bis(2-hydroxyethyl)amino)propionate (CAS No.: 118480-08-3), and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 80℃, and then 8g p-toluenesulfonic acid was added. After reacting for 10h, the mixture was cooled to room temperature, and 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30min, and 500g deionized water was added at 0-5℃ and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator and distilled under reduced pressure at 50℃ for 3h. The mixture was then dried under vacuum at 70℃ for 4h to obtain a hyperbranched product containing double bonds.

[0024] S2: Add 500g tetrahydrofuran, 100g hyperbranched product, 30g 1,4-phenyldiboronic acid, and 45g anhydrous magnesium sulfate to the reactor, stir and mix well, react at room temperature for 20h, filter under reduced pressure, distill under reduced pressure at 60℃ for 3h, then add 200ml n-hexane to precipitate, filter, and dry under vacuum at 70℃ for 4h to obtain hyperbranched borate ester.

[0025] S3: Under nitrogen protection, add 2000g deionized water, 30g 1-vinyl-2-pyrrolidone, 10g acrylic acid, 500g xanthan gum, and 150g hyperbranched borate ester to the reactor, stir and mix well, heat to 50℃, slowly add 5g potassium persulfate to the reactor, react for 3.5h, cool to room temperature, add 4kg deionized water and stir and mix well to obtain the mineral thickener for shotcrete.

[0026] Example 2: Preparation of mineral thickener for shotcrete:

[0027] S1: Under nitrogen protection, 1000g DMSO, 280g methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 90℃, and then 10g p-toluenesulfonic acid was added. After reacting for 9 hours, the mixture was cooled to room temperature. 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30 minutes. At 0-5℃, 500g deionized water was added and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator and distilled under reduced pressure at 55℃ for 2 hours. The mixture was then dried under vacuum at 70℃ for 4 hours to obtain a hyperbranched product containing double bonds.

[0028] S2: Add 500g tetrahydrofuran, 100g hyperbranched product, 35g 1,4-phenyldiboronic acid, and 50g anhydrous magnesium sulfate to the reactor, stir and mix well, react at room temperature for 22h, filter under reduced pressure, distill under reduced pressure at 60℃ for 2.5h, then add 200ml n-hexane to precipitate, filter, and dry under vacuum at 70℃ for 3h to obtain hyperbranched borate ester.

[0029] S3: Under nitrogen protection, add 2000g deionized water, 40g 1-vinyl-2-pyrrolidone, 15g acrylic acid, 500g xanthan gum, and 160g hyperbranched borate ester to the reactor, stir and mix well, heat to 55℃, slowly add 8g ammonium persulfate to the reactor, react for 3 hours, cool to room temperature, add 4kg deionized water and stir and mix well to obtain the mineral thickener for shotcrete.

[0030] Example 3: Preparation of mineral thickener for shotcrete:

[0031] S1: Under nitrogen protection, 1000g DMSO, 300g methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 100℃, and then 12g p-toluenesulfonic acid was added. After reacting for 8 hours, the mixture was cooled to room temperature, and 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30 minutes, and 500g deionized water was added at 0-5℃ and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator, and the mixture was distilled under reduced pressure at 60℃ for 1 hour and dried under vacuum at 70℃ for 4 hours to obtain a hyperbranched product containing double bonds.

[0032] S2: Add 500g tetrahydrofuran, 100g hyperbranched product, 40g 1,4-phenyldiboronic acid and 50g anhydrous magnesium sulfate to the reactor, stir and mix well, react at room temperature for 24h, filter under reduced pressure, distill under reduced pressure at 60℃ for 3h, then add 200ml n-hexane to precipitate, filter, and dry under vacuum at 70℃ for 3h to obtain hyperbranched borate ester.

[0033] S3: Under nitrogen protection, add 2000g deionized water, 50g 1-vinyl-2-pyrrolidone, 20g acrylic acid, 500g xanthan gum, and 180g hyperbranched borate ester to the reactor, stir and mix well, heat to 60℃, slowly add 10g ammonium persulfate to the reactor, react for 2.5h, cool to room temperature, add 4kg deionized water and stir and mix well to obtain the mineral thickener for shotcrete.

[0034] Comparative Example 1

[0035] The mineral thickener for shotcrete is a commercially available polyacrylate emulsion, model number: FLOWKIT74.

[0036] Comparative Example 2

[0037] The mineral thickener for shotcrete is prepared by the following method:

[0038] S1: Under nitrogen protection, 1000g DMSO, 280g methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 90℃, and then 10g p-toluenesulfonic acid was added. After reacting for 9 hours, the mixture was cooled to room temperature. 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30 minutes. At 0-5℃, 500g deionized water was added and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator and distilled under reduced pressure at 55℃ for 2 hours. The mixture was then dried under vacuum at 70℃ for 4 hours to obtain a hyperbranched product containing double bonds.

[0039] S2: Under nitrogen protection, add 2000g deionized water, 40g 1-vinyl-2-pyrrolidone, 15g acrylic acid, 500g xanthan gum, and 160g hyperbranched product to the reactor, stir and mix well, heat to 55℃, slowly add 8g ammonium persulfate to the reactor, react for 3 hours, cool to room temperature, add 4kg deionized water and stir and mix well to obtain the mineral thickener for shotcrete.

[0040] Comparative Example 3

[0041] The mineral thickener for shotcrete is prepared by the following method:

[0042] S1: Under nitrogen protection, 1000g DMSO, 280g methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 90℃, and then 10g p-toluenesulfonic acid was added. After reacting for 9 hours, the mixture was cooled to room temperature. 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30 minutes. At 0-5℃, 500g deionized water was added and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator and distilled under reduced pressure at 55℃ for 2 hours. The mixture was then dried under vacuum at 70℃ for 4 hours to obtain a hyperbranched product containing double bonds.

[0043] S2: Add 500g tetrahydrofuran, 100g hyperbranched product, 35g phenylboronic acid, and 50g anhydrous magnesium sulfate to the reactor, stir and mix well, react at room temperature for 22h, filter under reduced pressure, distill under reduced pressure at 60℃ for 2.5h, then add 200ml n-hexane to precipitate, filter, and dry under vacuum at 70℃ for 3h to obtain hyperbranched borate ester.

[0044] S3: Under nitrogen protection, add 2000g deionized water, 40g 1-vinyl-2-pyrrolidone, 15g acrylic acid, 500g xanthan gum, and 160g hyperbranched borate ester to the reactor, stir and mix well, heat to 55℃, slowly add 8g ammonium persulfate to the reactor, react for 3 hours, cool to room temperature, add 4kg deionized water and stir and mix well to obtain the mineral thickener for shotcrete.

[0045] Comparative Example 4

[0046] The mineral thickener for shotcrete is prepared by the following method:

[0047] S1: Under nitrogen protection, 1000g DMSO, 280g methyl 3-[(2-hydroxyethyl)amino]propionate, and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 90℃, and then 10g p-toluenesulfonic acid was added. After reacting for 9 hours, the mixture was cooled to room temperature. 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30 minutes. At 0-5℃, 500g deionized water was added and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator and distilled under reduced pressure at 55℃ for 2 hours. The mixture was then dried under vacuum at 70℃ for 4 hours to obtain a hyperbranched product containing double bonds.

[0048] S2: Add 500g tetrahydrofuran, 100g hyperbranched product, 35g 1,4-phenyldiboronic acid, and 50g anhydrous magnesium sulfate to the reactor, stir and mix well, react at room temperature for 22h, filter under reduced pressure, distill under reduced pressure at 60℃ for 2.5h, then add 200ml n-hexane to precipitate, filter, and dry under vacuum at 70℃ for 3h to obtain hyperbranched borate ester.

[0049] S3: Under nitrogen protection, add 2000g deionized water, 40g 1-vinyl-2-pyrrolidone, 15g acrylic acid, 500g xanthan gum, and 160g hyperbranched borate ester to the reactor, stir and mix well, heat to 55℃, slowly add 8g ammonium persulfate to the reactor, react for 3 hours, cool to room temperature, add 4kg deionized water and stir and mix well to obtain the mineral thickener for shotcrete.

[0050] Comparative Example 5

[0051] S1: Under nitrogen protection, 1000g DMSO, 280g methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50g 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester were added to the reactor and stirred until homogeneous. The mixture was heated to 90℃, and then 10g p-toluenesulfonic acid was added. After reacting for 9 hours, the mixture was cooled to room temperature. 5wt% saturated sodium bicarbonate solution was slowly added to adjust the pH to neutral. The mixture was stirred thoroughly for 30 minutes. At 0-5℃, 500g deionized water was added and shaken until homogeneous. The mixture was allowed to stand and separate into layers. The organic phase was transferred to a rotary evaporator and distilled under reduced pressure at 55℃ for 2 hours. The mixture was then dried under vacuum at 70℃ for 4 hours to obtain a hyperbranched product containing double bonds.

[0052] S2: Add 500g tetrahydrofuran, 100g hyperbranched product, 35g 1,4-phenyldiboronic acid, and 50g anhydrous magnesium sulfate to the reactor, stir and mix well, react at room temperature for 22h, filter under reduced pressure, distill under reduced pressure at 60℃ for 2.5h, then add 200ml n-hexane to precipitate, filter, and dry under vacuum at 70℃ for 3h to obtain hyperbranched borate ester.

[0053] S3: Under nitrogen protection, add 2000g of deionized water, 40g of 1-vinyl-2-pyrrolidone, 15g of acrylic acid, and 500g of xanthan gum to the reactor, stir and mix well, heat to 55℃, slowly add 8g of ammonium persulfate to the reactor, react for 3 hours, cool to room temperature, add 160g of hyperbranched borate ester and 4kg of deionized water, stir and mix well to obtain the mineral thickener for shotcrete.

[0054] Comparative Example 6

[0055] The mineral thickener for shotcrete is prepared by the following method:

[0056] S1. In a four-necked flask equipped with an electric stirrer, a dropping device, a thermometer, and nitrogen circulation, add 150 ml of DMAC solution and 57.07 g of propylene glycidyl ether. Set the oil bath temperature to 60 °C and stir until homogeneous. Then add 1.71 g of trimethylolpropane. After complete dissolution, add 2.85 g of potassium carbonate. Raise the temperature to 120 °C and then use a peristaltic pump to slowly add 57.07 g of propylene glycidyl ether dropwise to the four-necked flask. After the addition is complete, continue stirring for 3 h. Dissolve the reaction product in anhydrous methanol, then neutralize it with a cation exchange resin, and transfer the solution to 10 times its volume of acetone for precipitation. Dissolve the crude product in methanol and remove the methanol using a rotary evaporator at 45 °C to obtain hyperbranched polymer A.

[0057] S2. In a four-necked flask equipped with an electric stirrer, a dropping device, a thermometer, and a nitrogen circulation system, add 51.75 g of hyperbranched polymer A and 160 ml of deionized water, stir to dissolve, then add 10.07 g of N-hydroxysuccinimide methacrylate, 6.31 g of diethylene glycol maleate diester, and 24.75 g of methacrylamide propyl-N,N-dimethylpropanesulfonic acid to the solution, stir until homogeneous, and adjust the pH to 7-8 with 14.8 g of 32% sodium hydroxide solution; purge the inside of the four-necked flask with nitrogen, and raise the water bath temperature to 50°C while stirring; dissolve 0.56 g of azobisisobutylamidine hydrochloride in deionized water to prepare a 0.5% solution, and add it dropwise to the four-necked flask over 2 hours; after the addition is complete, raise the temperature to 50°C, continue the reaction for 4 hours, and then age at 40°C for 1 hour. Finally, 601 ml of water was added to obtain a polymer product with a solid content of 10%, which is the thickener.

[0058] Comparative Example 7

[0059] A concrete composite thickener prepared using the raw material composition and process described in Example 2 of Chinese Invention Patent Publication No. CN119371136A.

[0060] Application example: The mineral thickeners for shotcrete of Examples 1-3 and Comparative Examples 1-7 were applied to concrete, and the concrete mix proportions are shown in Table 1.

[0061] Table 1 Concrete Mix Proportion Table (kg / m³) 3 )

[0062]

[0063] The materials used in the embodiments and comparative examples of this application are as follows: The cement is P.042.5 cement, purchased from Lijiang Ancient City Southwest Cement Co., Ltd.; the main components (by weight) of the high-titanium heavy slag include: 7.67% MgO, 16.7% Al2O3, 24.88% SiO2, 27% CaO, 21.74% TiO2, and 0.34% Fe2O3, purchased from Panzhihua Huanye Metallurgical Slag Development Co., Ltd.; the main components (by weight) of the silica fume include: 94.61% SiO2, 0.06% chloride, 0.86% TFe, 0.24% Na2O, 1.60% K2O, 0.02% Mn, and 0.43% Al2O3, purchased from Sichuan Changji Composite Materials Co., Ltd.; the crushed stone particle size is 5-10mm; the water-reducing agent is... High-performance polycarboxylate superplasticizer, purchased from Jiangsu Subote New Material Co., Ltd.; accelerator: Liquid quick-setting agent (alkali-free type), Jiangsu Subote New Material Co., Ltd.; xanthan gum purchased from Shandong Fufeng Fermentation Co., Ltd.

[0064] The mineral thickeners for shotcrete in Examples 1-3 and Comparative Examples 1-7 were applied to concrete, and the performance of the concrete was tested. The results are shown in Table 2.

[0065] The compressive strength was tested according to the test method for measuring the shrinkage ratio of concrete in GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete"; the rebound rate was tested according to the method for rebound rate test of shotcrete in JGJ / T372-2016 "Technical Specification for Application of Shotcrete"; the setting time was tested according to the method in GB / T35159-2017 "Accelerating Agent for Shotcrete"; the blank group was concrete without the addition of mineral thickener.

[0066] Table 2 Concrete Performance Indicators

[0067]

[0068]

[0069] As can be seen from Table 1, the mineral thickeners prepared in Examples 1-3 of this application have excellent compressive strength, resilience and setting time.

[0070] Comparative Example 1 uses a commercially available thickener from another brand. As can be seen from the data in Table 2, the prepared concrete has poor compressive strength and a long setting time.

[0071] Comparative Example 2 is a comparative example where no boric acid was used to crosslink the hyperbranched structure; Comparative Example 3 is a comparative example where 1,4-phenylenediboric acid in step S2 was replaced with phenylboronic acid; Comparative Example 4 is a comparative example where methyl 3-(bis(2-hydroxyethyl)amino)propionate in step S1 was replaced with methyl 3-[(2-hydroxyethyl)amino]propionate; Comparative Example 5 did not graft hyperbranched borate esters onto xanthan gum. As can be seen from the data in Table 2, the compressive strength and concrete setting time are both inferior to those of this application. This is because: Firstly, boric acid reacts with the hyperbranched products to form dynamic borate ester bonds (BO bonds), constructing a stable three-dimensional crosslinked network that can form a denser network structure. This structure can effectively fill the micropores in concrete, reducing defects and thus improving the density of the concrete. The increased density makes the stress distribution more uniform when the concrete is under pressure, reducing stress concentration points and significantly improving the compressive strength. Secondly, the polar groups (-OH, -COOH) of xanthan gum react with the Ca on the surface of cement particles. 2+ Chelation improves particle dispersibility and enhances the cement-aggregate interface bonding. Furthermore, the three-dimensional network structure alters the surface charge density of cement particles, delays free water migration, regulates the hydration reaction rate, and shortens the initial setting time, thus influencing the flocculation behavior of cement particles. Simultaneously, the stable network structure formed by the three-dimensional network structure and xanthan gum works synergistically to strengthen the concrete's skeletal structure and shorten the setting time.

[0072] Comparative Example 6 is a comparative example where the preparation method of the thickener is different from that of Example 2. As can be seen from Table 2, the compressive strength is generally lower and the setting time is longer.

[0073] Comparative Example 7 is a concrete composite thickener prepared using the raw material composition and process of Example 2 of Chinese Invention Patent Publication No. CN119371136A. As can be seen from Table 2, its compressive strength after 28 days is 31.5 MPa, which is generally low, and the setting time is relatively long.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a mineral thickener specifically for shotcrete, characterized in that, Includes the following steps: S1: Under nitrogen protection, add DMSO, methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 2-methyl-2-acrylic acid-2,3-dihydroxypropyl ester to the reactor, stir and mix well, then add p-toluenesulfonic acid and react for 8-10 hours to generate hyperbranched products. S2: Hyperbranched products react with 1,4-phenylenediboronic acid to form hyperbranched borate esters; S3: Under nitrogen protection, xanthan gum, 1-vinyl-2-pyrrolidone, acrylic acid, and hyperbranched borate esters are copolymerized under the action of an initiator to obtain a mineral thickener for shotcrete. In step S1, the mass ratio of methyl 3-(bis(2-hydroxyethyl)amino)propionate to 2-methyl-2-acrylate-2,3-dihydroxypropyl ester is (25-30):

5. In step S2, the mass ratio of hyperbranched product to 1,4-phenylenediboric acid is 10:(3-4). In step S3, the mass ratio of 1-vinyl-2-pyrrolidone, acrylic acid, xanthan gum, and hyperbranched borate ester is (3-5):(1-2):50:(15-18).

2. The preparation method of a mineral thickener for shotcrete according to claim 1, characterized in that, The reaction temperature in step S1 is 80-100℃.

3. The preparation method of a mineral thickener for shotcrete according to claim 1, characterized in that, In step S3, the initiator is either potassium persulfate or ammonium persulfate.

4. The preparation method of a mineral thickener for shotcrete according to claim 1, characterized in that, The reaction temperature in step S3 is 50-60℃.

5. A mineral thickener specifically for shotcrete, characterized in that, It is prepared by the preparation method described in any one of claims 1-4.

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