Special mineral tackifier for sprayed concrete and preparation method thereof

Abstract

The invention discloses a special mineral tackifier for sprayed concrete and a preparation method of the special mineral tackifier, and relates to the technical field of tackifiers. The mineral tackifier is obtained by carrying out graft copolymerization reaction on 1-vinyl-2-pyrrolidone, acrylic acid, xanthan gum and hyperbranched borate under the action of an initiator; the hyperbranched boric acid ester is generated by reacting a hyperbranched product with 1, 4-benzene diboronic acid under the catalysis of anhydrous magnesium sulfate; the hyperbranched product is prepared by carrying out esterification reaction on 3-(bis (2-hydroxyethyl) amino) methyl propionate and 2-methyl-2-acrylic acid-2, 3-dihydroxy propyl ester, and the hyperbranched product is obtained by carrying out esterification reaction on the 3-(bis (2-hydroxyethyl) amino) methyl propionate and the 2-methyl-2-acrylic acid-2, 3-dihydroxy propyl ester. The mineral tackifier prepared by the invention has good compressive strength and short setting time.

Description

Technical Field

[0001] The present invention relates to the technical field of tackifiers, and particularly relates to a special mineral tackifier for shotcrete and a preparation method thereof. Background Art

[0002] Shotcrete is concrete constructed by spraying method. It has a fast construction speed and low requirements for the construction site environment (flatness, shape, etc.). It is often used for pouring thin-walled structures such as tunnel linings, walls, and ceilings, or linings of other structures and protective layers of steel structures. However, the shotcrete in the prior art has problems of low bonding strength and high rebound rate, resulting in serious waste of shotcrete materials. When spraying dry concrete, water and powdered concrete mixture are mixed at the nozzle outlet and then sprayed onto the surrounding rock surface. Due to the reaction force, a large amount of concrete rebounds into the air, resulting in a large amount of cement dust in the air where the workers are located, threatening the physical health of roadway tunneling workers and construction workers. At the same time, the large amount of rebound loss of shotcrete also makes it difficult to improve the economic benefits of shotcrete support.

[0003] Currently, in order to improve the performance of shotcrete, methods such as adding inorganic materials such as silica fume and fly ash or organic natural macromolecule admixtures such as cellulose are often used. However, these traditional tackifiers have many defects: large dosages of inorganic materials, high costs, and difficulty in synergistic action with accelerators; organic natural macromolecule admixtures may increase the setting time of cement, introduce harmful air bubbles, and damage the durability of concrete. Therefore, it is of great significance to develop a special mineral tackifier for shotcrete with high efficiency and low dosage. This tackifier should have good dispersibility, tackifying property, coagulation-promoting property, and compatibility with other components of concrete, and be able to improve the early strength and durability of concrete while reducing the rebound rate.

[0004] Chinese invention patent with publication number CN119371136A discloses a concrete composite tackifier and a preparation method thereof. When preparing the concrete composite tackifier, first, a polyacrylic acid resin obtained by polymerizing acrylic acid, methyl methacrylate, acrylamide, and vinyl diphenylphosphine reacts with a modified porphyrin, and then is sulfonated to obtain a modified polyacrylic acid resin; second, silica fume pretreated with vinyltrimethoxysilane reacts with tetravinyltetramethylcyclotetrasiloxane and vinylboronic acid pinacol ester to obtain modified silica fume. Finally, the polyacrylic acid resin and the modified silica fume are mixed to obtain the concrete composite tackifier. The concrete composite tackifier prepared by this invention has good workability and antibacterial property, but has poor compressive strength and setting time performance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a special mineral tackifier for shotcrete and a preparation method thereof.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] A preparation method of a special mineral thickening agent for shotcrete, comprising the following steps:

[0008] S1: Under nitrogen protection, add DMSO, methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 2,3-dihydroxypropyl 2-methyl-2-propenoate into a reactor, stir and mix evenly, and then add p-toluenesulfonic acid and react for 8-10 h to generate a hyperbranched product;

[0009] S2: React the hyperbranched product with 1,4-benzenediboronic acid to generate a hyperbranched borate ester;

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

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

[0012] The reaction temperature of the step S1 is 80-100 °C.

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

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

[0015] The initiator in the step S3 is one of potassium persulfate and ammonium persulfate.

[0016] The reaction temperature of the step S3 is 50-60 °C.

[0017] A special mineral thickening agent for shotcrete is prepared by using the above preparation method.

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

[0019] (1) First, a first-generation hyperbranched product formed by the transesterification reaction of methyl 3-(bis(2-hydroxyethyl)amino)propionate and 2,3-dihydroxypropyl 2-methylacrylate; a three-dimensional network hyperbranched borate formed by the reaction of the hyperbranched product with 1,4-benzenediboronic acid. This three-dimensional network structure can effectively fill the micro-pores in concrete, improve the compactness of concrete, and thus significantly enhance its compressive strength; finally, a special mineral thickening agent for shotcrete is obtained by grafting 1-vinyl-2-pyrrolidone, acrylic acid, and hyperbranched borate onto xanthan gum.

[0020] (2) The borate groups of 1,4-benzenediboronic acid crosslink with the hydroxyl groups of the hyperbranched product to form a three-dimensional network structure. After grafting it onto xanthan gum, it can provide a rigid skeleton support during the hardening process of concrete, enhance the internal stress transfer ability, and thus improve the compressive strength; the hyperbranched borate contains borate bonds (B-O bonds), and this bond has the characteristics of reversible fracture-recombination. Under the shear force or humidity change during concrete spraying, the dynamic crosslinking network can be locally reorganized to relieve stress concentration. At the same time, the three-dimensional network structure has a large specific surface area and strong adsorption ability, which can better fix the concrete particles together and reduce the 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, xanthan gum, 1-vinyl-2-pyrrolidone, and acrylic acid act together to form a copolymer that not only enhances the adhesion of concrete but also prevents the excessive aggregation of cement particles through steric hindrance effects, further promoting uniform hydration reactions and enhancing early strength. Specific embodiments

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

[0022] Example 1 Preparation of a special mineral thickening agent for shotcrete:

[0023] S1: Under nitrogen protection, add 1000 g of DMSO, 250 g of methyl 3-(bis(2-hydroxyethyl)amino)propionate (CAS No.: 118480-08-3), and 50 g of 2,3-dihydroxypropyl 2-methylacrylate to the reactor, stir and mix evenly, heat up to 80 °C, then add 8 g of p-toluenesulfonic acid, react for 10 h, then cool to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, add 500 g of deionized water and shake evenly at 0-5 °C, let it stand for stratification, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 50 °C for 3 h, and dry under vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

[0024] S2: Add 500 g of tetrahydrofuran, 100 g of hyperbranched product, 30 g of 1,4-benzenediboronic acid, and 45 g of anhydrous magnesium sulfate to the reactor, stir to mix evenly, react at room temperature for 20 h, then perform vacuum filtration, carry out vacuum distillation at 60 °C for 3 h, then add 200 ml of n-hexane for precipitation, filter, and dry in vacuum at 70 °C for 4 h to obtain hyperbranched borate ester;

[0025] S3: Under nitrogen protection, add 2000 g of deionized water, 30 g of 1-vinyl-2-pyrrolidone, 10 g of acrylic acid, 500 g of xanthan gum, and 150 g of hyperbranched borate ester to the reactor, stir to mix evenly, heat up to 50 °C, slowly add 5 g of potassium persulfate to the reactor, after reacting for 3.5 h, cool to room temperature, add 4 kg of deionized water and stir to mix evenly to obtain the special mineral viscosity-increasing agent for shotcrete.

[0026] Preparation of the special mineral viscosity-increasing agent for shotcrete in Example 2:

[0027] S1: Under nitrogen protection, add 1000 g of DMSO, 280 g of methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50 g of 2,3-dihydroxypropyl 2-methyl-2-propenoate to the reactor, stir to mix evenly, heat up to 90 °C, then add 10 g of p-toluenesulfonic acid, after reacting for 9 h, cool to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir thoroughly for 30 min, at 0 - 5 °C, add 500 g of deionized water and shake evenly, let it stand for liquid separation, transfer the organic phase to a rotary evaporator, carry out vacuum distillation at 55 °C for 2 h, and dry in vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

[0028] S2: Add 500 g of tetrahydrofuran, 100 g of hyperbranched product, 35 g of 1,4-benzenediboronic acid, and 50 g of anhydrous magnesium sulfate to the reactor, stir to mix evenly, react at room temperature for 22 h, then perform vacuum filtration, carry out vacuum distillation at 60 °C for 2.5 h, then add 200 ml of n-hexane for precipitation, filter, and dry in vacuum at 70 °C for 3 h to obtain hyperbranched borate ester;

[0029] S3: Under nitrogen protection, add 2000 g of deionized water, 40 g of 1-vinyl-2-pyrrolidone, 15 g of acrylic acid, 500 g of xanthan gum, and 160 g of hyperbranched borate ester to the reactor, stir to mix evenly, heat up to 55 °C, slowly add 8 g of ammonium persulfate to the reactor, after reacting for 3 h, cool to room temperature, add 4 kg of deionized water and stir to mix evenly to obtain the special mineral viscosity-increasing agent for shotcrete.

[0030] Preparation of the special mineral viscosity-increasing agent for shotcrete in Example 3:

[0031] S1: Under nitrogen protection, add 1000 g of DMSO, 300 g of methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50 g of 2,3-dihydroxypropyl 2-methylacrylate into the reactor, stir to mix evenly, heat up to 100 °C, then add 12 g of p-toluenesulfonic acid, react for 8 h, cool down to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, add 500 g of deionized water and shake evenly at 0 - 5 °C, let it stand for liquid separation, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 60 °C for 1 h, and dry in vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

[0032] S2: Add 500 g of tetrahydrofuran, 100 g of hyperbranched product, 40 g of 1,4-benzenediboronic acid, and 50 g of anhydrous magnesium sulfate into the reactor, stir to mix evenly, react at room temperature for 24 h, then filter under reduced pressure, distill under reduced pressure at 60 °C for 3 h, then add 200 ml of n-hexane for precipitation, filter, and dry in vacuum at 70 °C for 3 h to obtain hyperbranched borate ester;

[0033] S3: Under nitrogen protection, add 2000 g of deionized water, 50 g of 1-vinyl-2-pyrrolidone, 20 g of acrylic acid, 500 g of xanthan gum, and 180 g of hyperbranched borate ester into the reactor, stir to mix evenly, heat up to 60 °C, slowly add 10 g of ammonium persulfate into the reactor, react for 2.5 h, cool down to room temperature, add 4 kg of deionized water and stir to mix evenly to obtain the special mineral viscosity-increasing agent for shotcrete.

[0034] Comparative Example 1

[0035] The special mineral viscosity-increasing agent for shotcrete is a commercially available polyacrylate emulsion with the model FLOWKIT74.

[0036] Comparative Example 2

[0037] The special mineral viscosity-increasing agent for shotcrete is prepared by the following method:

[0038] S1: Under nitrogen protection, add 1000 g of DMSO, 280 g of methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50 g of 2,3-dihydroxypropyl 2-methylacrylate into the reactor, stir to mix evenly, heat up to 90 °C, then add 10 g of p-toluenesulfonic acid, react for 9 h, cool down to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, add 500 g of deionized water and shake evenly at 0 - 5 °C, let it stand for liquid separation, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 55 °C for 2 h, and dry in vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

[0039] S2: Under nitrogen protection, add 2000 g of deionized water, 40 g of 1-vinyl-2-pyrrolidone, 15 g of acrylic acid, 500 g of xanthan gum, and 160 g of hyperbranched product into the reactor. Stir to mix evenly, heat up to 55 °C, slowly add 8 g of ammonium persulfate into the reactor, after reacting for 3 h, cool down to room temperature, add 4 kg of deionized water and stir to mix evenly, then the special mineral viscosity-increasing agent for shotcrete is obtained.

[0040] Comparative Example 3

[0041] The special mineral viscosity-increasing agent for shotcrete is prepared by the following method:

[0042] S1: Under nitrogen protection, add 1000 g of DMSO, 280 g of methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50 g of 2,3-dihydroxypropyl 2-methyl-2-propenoate into the reactor. Stir to mix evenly, heat up to 90 °C, then add 10 g of p-toluenesulfonic acid, after reacting for 9 h, cool down to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, at 0 - 5 °C, add 500 g of deionized water and shake evenly, let it stand for layering, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 55 °C for 2 h, and dry in vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

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

[0044] S3: Under nitrogen protection, add 2000 g of deionized water, 40 g of 1-vinyl-2-pyrrolidone, 15 g of acrylic acid, 500 g of xanthan gum, and 160 g of hyperbranched borate ester into the reactor. Stir to mix evenly, heat up to 55 °C, slowly add 8 g of ammonium persulfate into the reactor, after reacting for 3 h, cool down to room temperature, add 4 kg of deionized water and stir to mix evenly, then the special mineral viscosity-increasing agent for shotcrete is obtained.

[0045] Comparative Example 4

[0046] The special mineral viscosity-increasing agent for shotcrete is prepared by the following method:

[0047] S1: Under nitrogen protection, add 1000 g of DMSO, 280 g of methyl 3-[(2-hydroxyethyl)amino]propionate, and 50 g of 2,3-dihydroxypropyl 2-methylacrylate into the reactor, stir to mix evenly, heat up to 90 °C, then add 10 g of p-toluenesulfonic acid, after reacting for 9 h, cool down to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, at 0 - 5 °C, add 500 g of deionized water and shake evenly, let it stand for phase separation, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 55 °C for 2 h, and dry under vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

[0048] S2: Add 500 g of tetrahydrofuran, 100 g of hyperbranched product, 35 g of 1,4-benzenediboronic acid, and 50 g of anhydrous magnesium sulfate into the reactor, stir to mix evenly, after reacting at room temperature for 22 h, filter under reduced pressure, distill under reduced pressure at 60 °C for 2.5 h, then add 200 ml of n-hexane for precipitation, filter, and dry under vacuum at 70 °C for 3 h to obtain hyperbranched borate ester;

[0049] S3: Under nitrogen protection, add 2000 g of deionized water, 40 g of 1-vinyl-2-pyrrolidone, 15 g of acrylic acid, 500 g of xanthan gum, and 160 g of hyperbranched borate ester into the reactor, stir to mix evenly, heat up to 55 °C, slowly add 8 g of ammonium persulfate into the reactor, after reacting for 3 h, cool down to room temperature, add 4 kg of deionized water and stir to mix evenly to obtain a special mineral viscosity-increasing agent for shotcrete.

[0050] Comparative Example 5

[0051] S1: Under nitrogen protection, add 1000 g of DMSO, 280 g of methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 50 g of 2,3-dihydroxypropyl 2-methylacrylate into the reactor, stir to mix evenly, heat up to 90 °C, then add 10 g of p-toluenesulfonic acid, after reacting for 9 h, cool down to room temperature, slowly add 5 wt% saturated sodium bicarbonate solution to adjust the pH to neutral, stir well for 30 min, at 0 - 5 °C, add 500 g of deionized water and shake evenly, let it stand for phase separation, transfer the organic phase to a rotary evaporator, distill under reduced pressure at 55 °C for 2 h, and dry under vacuum at 70 °C for 4 h to obtain a hyperbranched product containing double bonds;

[0052] S2: Add 500 g of tetrahydrofuran, 100 g of hyperbranched product, 35 g of 1,4-benzenediboronic acid, and 50 g of anhydrous magnesium sulfate into the reactor, stir to mix evenly, after reacting at room temperature for 22 h, filter under reduced pressure, distill under reduced pressure at 60 °C for 2.5 h, then add 200 ml of n-hexane for precipitation, filter, and dry under vacuum at 70 °C for 3 h to obtain hyperbranched borate ester;

[0053] S3: Under nitrogen protection, add 2000 g of deionized water, 40 g of 1-vinyl-2-pyrrolidone, 15 g of acrylic acid, and 500 g of xanthan gum into the reactor, stir to mix evenly, heat up to 55 °C, slowly add 8 g of ammonium persulfate into the reactor, after reacting for 3 h, cool down to room temperature, add 160 g of hyperbranched borate ester and 4 kg of deionized water, stir to mix evenly, then the special mineral viscosity-increasing agent for shotcrete is obtained.

[0054] Comparative Example 6

[0055] The special mineral viscosity-increasing agent for shotcrete is prepared by the following method:

[0056] S1. Add 150 ml of DMAC solution and 57.07 g of allyl glycidyl ether into a four-necked flask equipped with an electric stirrer, a dropping device, a thermometer and a nitrogen circulation system, set the oil bath temperature to 60 °C, and stir evenly; then add 1.71 g of trimethylolpropane, and after complete dissolution, add 2.85 g of potassium carbonate; raise the temperature to 120 °C, and then use a peristaltic pump to slowly drop 57.07 g of allyl glycidyl ether into the four-necked flask; after the dropping is completed, continue to stir for 3 h; dissolve the reaction product with anhydrous methanol, then neutralize it with a cation exchange resin, and transfer the solution to 10 times the volume of acetone for precipitation, then dissolve the crude product with methanol, and remove methanol at 45 °C using a rotary evaporator to obtain hyperbranched polymer A.

[0057] S2. Add 51.75 g of hyperbranched polymer A and 160 ml of deionized water into a four-necked flask equipped with an electric stirrer, a dropping device, a thermometer and a nitrogen circulation system, stir to dissolve, then add 10.07 g of N-hydroxysuccinimide methacrylate, 6.31 g of diethylene glycol maleate bisester and 24.75 g of methacrylamidopropyl-N,N-dimethylpropylsulfonic acid into the solution, stir evenly, and adjust the pH value to 7-8 with 14.8 g of sodium hydroxide solution with a mass concentration of 32%; purge the inside of the four-necked flask with nitrogen, and while stirring, raise the water bath temperature to 50 °C; dissolve 0.56 g of azodiisobutyramidine hydrochloride in deionized water to prepare a solution with a mass percentage concentration of 0.5%, and drop it into the four-necked flask within 2 h; after the dropping is completed, raise the temperature to 50 °C, continue to react for 4 h, and age at 40 °C for 1 h. Finally, add 601 ml of water to obtain a polymerization product with a solid content of 10%, that is, the viscosity-increasing agent.

[0058] Comparative Example 7

[0059] A concrete composite viscosity-increasing agent prepared with the raw material composition and process of Example 2 of the Chinese invention patent with the publication number of CN119371136A.

[0060] Application Example: The special mineral viscosity-increasing agent for shotcrete in Examples 1-3 and Comparative Examples 1-7 was applied to concrete, and the mix ratio of the concrete is shown in Table 1.

[0061] Table 1 Mix Ratio of Concrete (kg / m 3 )

[0062]

[0063] The materials used in the examples 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% Al 2 O 3 , 24.88% SiO 2 , 27% CaO, 21.74% TiO 2 , 0.34% Fe 2 O 3 , purchased from Panzhihua Huanye Metallurgical Slag Development Co., Ltd.; The main components (by weight) of the silica fume include: 94.61% SiO 2 , 0.06% chloride, 0.86% TFe, 0.24% Na 2 O, 1.60% K 2 O, 0.02% Mn, 0.43% Al 2 O 3 , purchased from Sichuan Changji Composite Materials Co., Ltd.; The crushed stone has a particle size of 5-10 mm; The water reducer is type polycarboxylate superplasticizer, purchased from Jiangsu Sobute New Materials Co., Ltd.; The accelerating agent is liquid accelerating agent (non-alkali type), Jiangsu Sobute New Materials Co., Ltd.; Xanthan gum is purchased from Shandong Fufeng Fermentation Co., Ltd.

[0064] The special mineral viscosity-increasing agent for shotcrete in Examples 1-3 and Comparative Examples 1-7 was applied to concrete, and the performance test of the concrete was carried out, and the results are shown in Table 2.

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

[0066] Table 2 Concrete Performance Index

[0067]

[0068]

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

[0070] Comparative Example 1 is a comparative example using a commercially available tackifier of another brand. From the data in Table 2, it can be seen that the prepared concrete has poor compressive strength and a long setting time.

[0071] Comparative Example 2 is a comparative example in which the hyperbranched structure is not crosslinked with boric acid substances; Comparative Example 3 is a comparative example in which 1,4-benzenediboronic acid in Step S2 is replaced with benzeneboronic acid; Comparative Example 4 is a comparative example in which methyl 3-(bis(2-hydroxyethyl)amino)propionate in Step S1 is replaced with methyl 3-[(2-hydroxyethyl)amino]propionate; Comparative Example 5 does not graft hyperbranched borate on xanthan gum; from the data in Table 2, it can be seen that both the compressive strength and the setting time of the concrete are inferior to those of this application. This is because: firstly, boric acid reacts with the hyperbranched product to form dynamic borate bonds (B-O bonds), constructing a stable three-dimensional crosslinked network, which can form a denser network structure; this structure can effectively fill the micropores in the concrete, reduce defects, and thus improve the density of the concrete; the increase in density makes the stress distribution more uniform when the concrete bears pressure, reduces the stress concentration points, and thus significantly improves the compressive strength. Secondly, the polar groups (-OH, -COOH) of xanthan gum chelate with the surface of cement particles 2+ to improve particle dispersibility and enhance the cement-aggregate interface bonding. In addition, the three-dimensional network structure can change the surface charge density of cement particles, delay the migration of free water, adjust the hydration reaction rate, shorten the initial setting time, and thus affect the flocculation behavior of cement particles. At the same time, the stable network structure formed by the three-dimensional network structure and xanthan gum can act synergistically to enhance the skeleton structure of the concrete and shorten the setting time.

[0072] Comparative Example 6 is a comparative example in which the preparation method of the tackifier is different from that of Example 2. From Table 2, it can be seen that the compressive strength is average and the setting time is long.

[0073] Comparative Example 7 is a concrete composite tackifier prepared with the raw material composition and process of Example 2 of the Chinese invention patent with the publication number CN119371136A. From Table 2, it can be seen that its compressive strength after 28 days is 31.5 MPa, the compressive strength is average, and the setting time is long.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. However, for those of ordinary skill in the art, within the scope of the technical solution of the present invention, any minor changes, modifications and equivalent variations made by using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any changes, modifications and equivalent variations made to the above embodiments based on the essential technology of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a special mineral viscosity enhancer for shotcrete, characterized in that: The following steps are involved: S1: Under nitrogen protection, DMSO, methyl 3-(bis(2-hydroxyethyl)amino)propionate, and 2-methyl-2-acrylate-2,3-dihydroxypropyl ester were added to the reactor, stirred and mixed, and then p-toluenesulfonic acid was added to react for 8-10 hours to generate hyperbranched products; S2: The hyperbranched product reacts with 1,4-phenylenediboronic acid to form a hyperbranched borate ester; S3: Under nitrogen protection, xanthan gum, 1-vinyl-2-pyrrolidone, acrylic acid and hyperbranched boric acid ester are copolymerized under the action of an initiator to obtain a mineral thickener for shotcrete.

2. The method for preparing a special mineral viscosity enhancer for shotcrete according to claim 1, characterized in that: In the step S1, the feed mass ratio of methyl 3-(bis(2-hydroxyethyl)amino)propionate to 2-methyl-2-acrylate-2,3-dihydroxypropyl ester is (25-30):

5.

3. The method for preparing a special mineral viscosity enhancer for shotcrete according to claim 1, characterized in that: The reaction temperature of step S1 is 80-100°C.

4. The method for preparing a special mineral viscosity enhancer for shotcrete according to claim 1, characterized in that: In the step S2, the mass ratio of the hyperbranched product to 1,4-phenylenediboronic acid is 10:(3-4).

5. The method for preparing a special mineral viscosity enhancer for shotcrete according to claim 1, characterized in that: In step S3, the mass ratio of 1-vinyl-2-pyrrolidone, acrylic acid, xanthan gum and hyperbranched borate is (3-5):(1-2):50:(15-18).

6. The method for preparing a special mineral viscosity enhancer for shotcrete according to claim 1, characterized in that: In step S3, the initiator is one of potassium persulfate and ammonium persulfate.

7. The method for preparing a special mineral viscosity enhancer for shotcrete according to claim 1, characterized in that: The reaction temperature of step S3 is 50-60°C.

8. A mineral viscosity enhancer for shotcrete, characterized in that: The preparation method is described in any one of claims 1 to 7.

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