An alkali-free liquid quick-setting agent for shotcrete and its preparation method

Abstract

This invention proposes an alkali-free liquid accelerator for shotcrete and its preparation method, belonging to the technical field of accelerators. It is prepared from the following raw materials in parts by weight: 12-15 parts magnesium fluorosilicate, 3-5 parts hydrogen fluoride, 5-7 parts aluminum hydroxide, 20-30 parts aluminum sulfate, 3-5 parts organic alcohol amine carboxylic acid polymer, 2-3 parts organic acid, 1-2 parts polyacrylamide, and 20-30 parts water. The alkali-free liquid accelerator for shotcrete prepared by this invention has advantages such as low corrosiveness to the human body, high early strength and high later compressive strength ratio, no adverse effect on concrete durability, and the thickening components can reduce dust concentration and rebound during the spraying process. Furthermore, it has advantages such as low dosage, economical price, good stability, and significant accelerator effect.

Description

Technical Field

[0001] This invention relates to the field of accelerator technology, specifically to an alkali-free liquid accelerator for shotcrete and its preparation method. Background Technology

[0002] Shotcrete refers to the application of compressed air to the surface of freshly mixed concrete. The use of accelerators, a key component, significantly shortens the setting and hardening time of shotcrete, enabling initial support in underground engineering projects such as tunnels and hydroelectric power stations.

[0003] Traditional accelerators mainly consist of inorganic salts such as alumina clinker, carbonates, and sodium silicate. While these accelerators can generally meet the engineering requirements for setting time and early strength, they are highly alkaline. The presence of strong alkali easily causes alkali-aggregate reaction, leading to damage to the concrete structure. Later strength loss is generally 30% to 40%, failing to fully meet construction requirements. Furthermore, the high alkalinity of these accelerators poses a threat to the health of construction workers, exhibiting strong corrosive effects on human skin. Therefore, the current mainstream research and development approach for accelerator products focuses on low-alkali or alkali-free liquid accelerators.

[0004] Currently, liquid alkali-free quick-setting agents mainly use aluminum sulfate as the main component. However, as a major flocculant, aluminum sulfate cannot exist stably at high concentrations. Therefore, it is necessary to combine it with other components to solve the stability problem while taking into account the performance of the quick-setting agent.

[0005] Chinese patent application CN107857501A discloses an alkali-free quick-setting agent containing organic amines as an accelerator of early strength and its preparation method. The component raw materials and their mass percentage ratios are: aluminum sulfate 35%–50%, magnesium sulfate 3%–15%, sodium fluoride 0%–15%, organic amines 0.125%–0.5%, thickener 1%–5%, stabilizer 1%–5%, and the balance being water, with the sum of all components being 100%. This invention uses an alkali-free quick-setting agent containing organic amines as an accelerator of early strength, which can significantly improve the early strength of cement concrete while reducing later strength loss. The early strength effect of organic amines is that they promote the hydration of C3A in cement, accelerate the formation of ettringite, and thus improve the early strength of concrete. Furthermore, because organic amine molecules contain nitrogen atoms, which have a pair of unshared electrons, they easily form relatively stable complexes with metal ions, facilitating the diffusion and uniform dispersion of hydration products, thus benefiting the maintenance of later strength. However, this patent requires the addition of relatively high amounts of thickeners such as polyacrylamide and stabilizers such as hydroxycarboxylic acids to stabilize the system, resulting in a large volume viscosity, which is not conducive to mixing with materials and the coagulation-promoting function of aluminum phase materials.

[0006] Chinese patent CN108793811B discloses a method for preparing a durability-enhancing alkali-free liquid accelerator. The method involves acylation of maleic anhydride and urea to obtain an acylated product, followed by copolymerization with acrylamide and acrylic acid to obtain a suspension stabilizer, which is then used in the synthesis of the alkali-free liquid accelerator. By introducing maleic anhydride and urea acylation to obtain a suspension stabilizer with an amide structure, the coagulation of the liquid accelerator is improved, effectively inhibiting precipitation and significantly enhancing the stability of the mother liquor during storage, achieving a stability of over 15 months. Furthermore, the amide structure and urea can promote early strength development, thereby improving the early strength of concrete. However, this patented preparation process is complex and the production cost is high.

[0007] Chinese patent application CN106587704A discloses a low-dosage, environmentally friendly, high-efficiency, and durable liquid alkali-free quick-setting agent and its preparation method. The raw material formulation includes the following components by weight percentage: polyaluminum sulfate: 40-60%, magnesium sulfate: 5-15%, organic polymer: 1-5%, organic solubilizing and accelerator: 5-10%, suspending and thickening agent: 1-7%, acid regulator: 0-5%, stabilizer: 1-5%, and the remainder is water, with the total weight made up to 100%. This quick-setting agent has low early strength, which can easily affect the normal construction of shotcrete.

[0008] Chinese patent application CN106554163A relates to a chlorine-free and alkali-free liquid accelerator. The preparation process is as follows: polyaluminum sulfate is added to water, heated and stirred to promote dissolution, forming an aluminum sulfate solution; a stabilizer and an alkanolamine are added sequentially to the aluminum sulfate solution for complexation; magnesium sulfate is then added for dissolution; finally, an inorganic acid is added, and the mixture is cooled. This chlorine-free and alkali-free liquid accelerator does not contain toxic substances, requires a small dosage, has good concrete strengthening effect, and good stability. However, there is still considerable room for improvement in the dosage and setting time of this accelerator. Summary of the Invention

[0009] The purpose of this invention is to propose an alkali-free liquid quick-setting agent for shotcrete and its preparation method. It has the advantages of low corrosiveness to the human body, high early strength and high later compressive strength ratio, no adverse effect on concrete durability, and thickening components that can reduce dust concentration and rebound during the spraying process. It also has the advantages of low dosage, economical price, good stability and significant quick-setting effect.

[0010] The technical solution of this invention is implemented as follows:

[0011] This invention provides an alkali-free liquid quick-setting agent for sprayed concrete, which is prepared from the following raw materials in parts by weight: 12-15 parts magnesium fluorosilicate, 3-5 parts hydrogen fluoride, 5-7 parts aluminum hydroxide, 20-30 parts aluminum sulfate, 3-5 parts organic alcohol amine carboxylic acid polymer, 2-3 parts organic acid, 1-2 parts polyacrylamide, and 20-30 parts water.

[0012] The organic alcohol amine carboxylic acid polymer is a compound as shown in Formula I or Formula II:

[0013]

[0014]

[0015] As a further improvement of the present invention, the method for synthesizing the organic alcohol amine carboxylic acid polymer of Formula I is as follows:

[0016] S1. Diethanolamine and di-tert-butyl dicarbonate are mixed with a base and heated and stirred to obtain intermediate A, with the following structure:

[0017] S2. Intermediate A and maleic anhydride are mixed, heated, and stirred to react, yielding intermediate B, with the following structure:

[0018] S3. Intermediate B is polymerized under the action of an initiator. The product is precipitated with water, filtered, and then reacted with trifluoroacetic acid to obtain the organic alcohol amine carboxylic acid polymer of Formula I.

[0019] As a further improvement of the present invention, the molar ratio of diethanolamine and di-tert-butyl dicarbonate in step S1 is 1:1.2-1.4, the alkali is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate, and the heating temperature is 40-50°C for 1-2 hours.

[0020] As a further improvement of the present invention, the molar ratio of intermediate A and maleic anhydride in step S2 is 1:1-1.1, the heating temperature is 80-100℃, and the heating time is 2-3h.

[0021] As a further improvement of the present invention, the initiator in step S3 is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, cyclohexanone peroxide, benzoyl peroxide, and tert-butyl hydroperoxide; the mass ratio of intermediate B to initiator is 100-150:0.2-0.3; the polymerization reaction temperature is 50-60°C and the time is 2-3 hours; the mass ratio of product to trifluoroacetic acid is 20-25:10-12; and the trifluoroacetic acid reaction temperature is room temperature and the time is 1-2 hours.

[0022] As a further improvement of the present invention, the method for synthesizing the organic alcohol amine carboxylic acid polymer of formula II is as follows:

[0023] T1. Diethylene glycolamine and di-tert-butyl dicarbonate were mixed with a base and heated and stirred to obtain intermediate C, with the following structure.

[0024] T2. Intermediate C and maleic anhydride are mixed, heated, and stirred to obtain intermediate D, with the following structure:

[0025] T3. Intermediate D is polymerized under the action of an initiator. The product is precipitated with water, filtered, and then reacted with trifluoroacetic acid to obtain the organic alcohol amine carboxylic acid polymer of formula II.

[0026] As a further improvement of the present invention, in step T1, the molar ratio of diethylene glycolamine to di-tert-butyl dicarbonate is 1:1.2-1.4, the base is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate, and the heating temperature is 40-50°C for 1-2 hours; in step T2, the molar ratio of intermediate C to maleic anhydride is 1:1-1.1, the heating temperature is 80-100°C for 2-3 hours; in step T3, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, cyclohexanone peroxide, benzoyl peroxide, and tert-butyl hydroperoxide, the mass ratio of intermediate D to initiator is 100-150:0.2-0.3, the polymerization reaction temperature is 50-60°C for 2-3 hours, the mass ratio of product to trifluoroacetic acid is 20-25:10-12, and the trifluoroacetic acid reaction temperature is room temperature for 1-2 hours.

[0027] As a further improvement of the present invention, the organic alcohol amine carboxylic acid polymer includes organic alcohol amine carboxylic acid polymer of formula I and organic alcohol amine carboxylic acid polymer of formula II, in a mass ratio of 5-7:10.

[0028] As a further improvement of the present invention, the organic acid is selected from at least one of oxalic acid, malonic acid, succinic acid, acetic acid, propionic acid, glutaric acid, and maleic acid.

[0029] This invention further protects a method for preparing the above-mentioned alkali-free liquid quick-setting agent for shotcrete, comprising the following steps:

[0030] (1) At room temperature, hydrofluoric acid and organic acid are mixed and added to half of the water, aluminum hydroxide is added, and the mixture is stirred to obtain an aluminum fluoride-organic acid aluminum solution. The solution is added to aluminum sulfate, heated to 50-60℃, and stirred to dissolve, resulting in a mixture A.

[0031] (2) Mix magnesium fluorosilicate and the remaining water evenly, stir to dissolve, add organic alcohol amine carboxylic acid polymer, stir to dissolve, and obtain mixture B;

[0032] (3) Mix liquid A and liquid B evenly, heat to 40-50℃, add polyacrylamide and stir to dissolve, to obtain alkali-free liquid quick-setting agent for sprayed concrete.

[0033] The present invention has the following beneficial effects:

[0034] Aluminum sulfate is the main accelerator component in alkali-free quick-setting agents. It does not contain alkali, and Al... 3+ It has a good setting-promoting effect on cement hydration. Among them, Al 3+ The concentration of aluminum ions is a crucial factor in accelerating the setting time of accelerators. Increasing the amount of aluminum sulfate, thereby increasing the concentration of aluminum ions, can achieve a better accelerating effect. However, due to the low solubility of aluminum sulfate, when the concentration is increased to a certain limit, the stability of the liquid accelerator decreases significantly, and the precipitation of sediment greatly affects the accelerating effect.

[0035] This invention yielded two organic alcohol amine carboxylic acid polymers, and the reaction process is as follows:

[0036]

[0037]

[0038] The resulting organic alcoholamine carboxylic acid polymer possesses active complexing groups such as amino and carboxyl groups, COO 2- Able to interact with Al 3+ Complexation results in a highly soluble complex that also inhibits Al formation. 3+ Hydrolysis of the amine shortens the setting time and improves the stability of the accelerator. Simultaneously, the addition of an organic alcohol amine carboxylic acid polymer shortens the cement setting time while increasing the early strength of the mortar, resulting in a superior accelerator with both setting-promoting and early-strength-enhancing effects. The addition of this substance makes the cement paste more viscous, which is beneficial for increasing the cohesiveness of shotcrete, reducing its rebound, and increasing the thickness of the first sprayed layer. The nitrogen atom in the alcohol amine is conducive to the formation of Al. 3+ Fe 3+ The soluble complexes formed by ions such as [specific ions] during cement hydration increase the diffusion rate of hydration products, promote cement hydration, shorten setting time, and improve system stability. This effectively enhances the activity of Al in the solution. 3+ content.

[0039] Meanwhile, this invention adds an appropriate amount of magnesium fluorosilicate to hydrolyze in solution. The hydrolysis products generate multiple coating layers on the cement surface, which can effectively inhibit the hydration reaction of cement and reduce the setting time of cement.

[0040] The hydrogen fluoride, organic acid, and aluminum hydroxide added in this invention react to form an aluminum fluoride-organic acid aluminum solution, which increases the soluble aluminum content in the alkali-free liquid accelerator for shotcrete. This improves the stability and setting-promoting effect of the alkali-free liquid accelerator for shotcrete. Therefore, the amount of alkali-free liquid accelerator to be added can be greatly reduced while achieving efficient setting and improving concrete strength. The later strength not only does not decrease but is significantly improved. It has strong compatibility with cement, requires no heating during use, has low energy consumption, and better performance.

[0041] The alkali-free liquid quick-setting agent for shotcrete prepared by this invention has the advantages of low corrosiveness to the human body, high early strength and high ratio of early compressive strength, no adverse effect on concrete durability, and thickening components that can reduce dust concentration and rebound during the spraying process. It also has the advantages of low dosage, economical price, good stability and significant quick-setting effect. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Preparation Example 1: Synthesis of Organic Alcohol Amino Carboxylic Acid Polymer

[0044] Synthesis route:

[0045]

[0046] The method is as follows:

[0047] S1. 0.1 mol diethanolamine, 0.12 mol di-tert-butyl dicarbonate, and 0.4 mol sodium carbonate were added to 200 mL dichloromethane, stirred and mixed, heated to 40 °C, and stirred for 1 h. The solvent was removed under reduced pressure, and the mixture was separated by column chromatography to obtain intermediate A; ESI-MS calculated value: C9H 20 NO4(M+H)+206.13, measured value: 206.1, yield: 96.7%.

[0048] MRI results: 1 H NMR (300MHz, CDCl3) δ3.78 (t, 4H), 3.15 (t, 4H), 2.0 (br, 2H), 1.40 (s, 9H).

[0049] S2. Add 0.1 mol of intermediate A and 0.1 mol of maleic anhydride to 200 mL of N,N-dimethylformamide, heat to 80 °C, stir for 2 h, wash with water, extract with dichloromethane, and separate by column chromatography to obtain intermediate B; ESI-MS calculated value: C 13 H 22 NO7(M+H)+304.12, measured value: 304.1, yield: 72.5%.

[0050] MRI results: 1 H NMR (300MHz, CDCl3) δ11.0 (br, 1H), 6.51 (d, J = 4.2Hz, 1H), 6.35 (d, J = 4.2Hz, 1H) , 4.42(t, 2H), 3.78(t, 2H), 3.25(t, 2H), 3.17(t, 2H), 2.0(br, 1H), 1.42(s, 9H).

[0051] S3. Dissolve 10 parts by weight of intermediate B in 100 parts by weight of dichloromethane solution, add 0.02 parts by weight of azobisisobutyronitrile, heat to 50°C, and polymerize for 2 hours. Add water to precipitate the product, filter, wash with dichloromethane, then dissolve 20 parts by weight of the product in 100 parts by weight of dichloromethane, add 10 parts by weight of trifluoroacetic acid, and react at room temperature for 1 hour to obtain the organic alcohol amine carboxylic acid polymer of formula I.

[0052] The obtained organic alcohol amine carboxylic acid polymer was characterized by infrared spectroscopy, wherein the 3560 cm⁻¹... -1 The peak represents the stretching vibration of -OH, at 3296 cm⁻¹. -1 The peak value is for the stretching vibration of NH4+; 2960 cm⁻¹ -1 The absorption peak for CN is 2927 cm⁻¹. -1 The peak represents the stretching vibration of -CH- in -CH2-, at 2865 cm⁻¹. -1 The peak represents the symmetrical stretching vibration of -CH2-, at 1672 cm⁻¹. -1 The peak is the stretching vibration peak of C=O, at 1564 cm⁻¹. -1 and 1422cm -1 The peak represents the antisymmetric and symmetric stretching vibrations of -COO-, at 1320 cm⁻¹. -1 This represents the stretching vibration peak of CN.

[0053] Preparation Example 2: Synthesis of Organic Alcohol Amine Carboxylic Acid Polymer

[0054] The method is as follows:

[0055] S1. Add 0.1 mol diethanolamine, 0.14 mol di-tert-butyl dicarbonate, and 0.5 mol potassium carbonate to 200 mL dichloromethane, stir and mix, heat to 50 °C, stir and react for 2 h, remove solvent under reduced pressure, and separate by column chromatography to obtain intermediate A; yield 97.1%.

[0056] S2. Add 0.1 mol of intermediate A and 0.11 mol of maleic anhydride to 200 mL of N,N-dimethylformamide, heat to 100 °C, stir for 3 h, wash with water, extract with dichloromethane, and separate by column chromatography to obtain intermediate B; yield 73.0%.

[0057] S3. Dissolve 15 parts by weight of intermediate B in 100 parts by weight of dichloromethane solution, add 0.03 parts by weight of benzoyl peroxide, heat to 60°C, and polymerize for 3 hours. Add water to precipitate the product, filter, wash with dichloromethane, then dissolve 25 parts by weight of the product in 100 parts by weight of dichloromethane, add 12 parts by weight of trifluoroacetic acid, and react at room temperature for 2 hours to obtain the organic alcohol amine carboxylic acid polymer of formula I.

[0058] Preparation Example 3: Synthesis of Organic Alcohol Amine Carboxylic Acid Polymer

[0059] The method is as follows:

[0060] S1. Add 0.1 mol diethanolamine, 0.13 mol di-tert-butyl dicarbonate, and 0.45 mol potassium bicarbonate to 200 mL dichloromethane, stir and mix, heat to 45 °C, stir and react for 1.5 h, remove solvent under reduced pressure, and separate by column chromatography to obtain intermediate A; yield 97.4%.

[0061] S2. 0.1 mol of intermediate A and 0.105 mol of maleic anhydride were added to 200 mL of N,N-dimethylformamide, heated to 90 °C, stirred for 2.5 h, washed with water, extracted with dichloromethane, and separated by column chromatography to obtain intermediate B; the yield was 73.2%.

[0062] S3. Dissolve 12 parts by weight of intermediate B in 100 parts by weight of dichloromethane solution, add 0.025 parts by weight of tert-butyl hydrogen peroxide, heat to 55°C, and polymerize for 2.5 h. Add water to precipitate the product, filter, wash with dichloromethane, then dissolve 22 parts by weight of the product in 100 parts by weight of dichloromethane, add 11 parts by weight of trifluoroacetic acid, and react at room temperature for 1.5 h to obtain the organic alcohol amine carboxylic acid polymer of formula I.

[0063] Preparation Example 4: Synthesis of Organic Alcohol Amino Carboxylic Acid Polymers

[0064] Synthesis route:

[0065]

[0066] The method is as follows:

[0067] S1. 0.1 mol diethylene glycolamine, 0.12 mol di-tert-butyl dicarbonate, and 0.4 mol sodium carbonate were added to 200 mL dichloromethane, stirred and mixed, heated to 40 °C, and stirred for 1 h. The solvent was removed under reduced pressure, and the mixture was separated by column chromatography to obtain intermediate C; ESI-MS calculated value: C9H 20 NO4(M+H)+206.13, measured value: 206.1, yield: 97.2%.

[0068] MRI results: 1 H NMR (300MHz, CDCl3) δ 8.0 (br, 1H), 3.70 (t, 2H), 3.62 (t, 2H), 3.57 (t, 2H), 3.12 (t, 2H), 2.0 (br, 1H), 1.37 (s, 9H).

[0069] S2. Add 0.1 mol of intermediate C and 0.1 mol of maleic anhydride to 200 mL of N,N-dimethylformamide, heat to 80 °C, stir for 2 h, wash with water, extract with dichloromethane, and separate by column chromatography to obtain intermediate D; ESI-MS calculated value: C 13 H 22 NO7(M+H)+304.12, measured value: 304.1, yield: 69.8%.

[0070] MRI results: 1 H NMR (300MHz, CDCl3) 11.0 (br, 1H), 8.0 (br, 1H), 6.52 (d, J=4.5Hz, 1H), 6.37 (d, J=4.5Hz, 1H), 4.32 (t, 2H), 3.62-3.64 (m, 4H), 3.15 (t, 2H), 1.41 (s, 9H).

[0071] S3. Dissolve 10 parts by weight of intermediate D in 100 parts by weight of dichloromethane solution, add 0.02 parts by weight of azobisisoheptanenitrile, heat to 50°C, and polymerize for 2 hours. Add water to precipitate the product, filter, wash with dichloromethane, then dissolve 20 parts by weight of the product in 100 parts by weight of dichloromethane, add 10 parts by weight of trifluoroacetic acid, and react at room temperature for 1 hour to obtain the organic alcohol amine carboxylic acid polymer of formula II.

[0072] The prepared organic alcohol amine carboxylic acid polymer was characterized by infrared spectroscopy, wherein 3310 cm⁻¹ -1 The peak value is for the stretching vibration of NH4+; 2970 cm⁻¹ -1 The absorption peak for CN is 2935 cm⁻¹. -1The peak represents the stretching vibration of -CH- in -CH2-, at 2860 cm⁻¹. -1 The peak represents the symmetric stretching vibration of -CH2-, at 1668 cm⁻¹. -1 The peak for the stretching vibration of C=O is 1560 cm⁻¹. -1 and 1428cm -1 The peak represents the antisymmetric and symmetric stretching vibrations of -COO-, at 1320 cm⁻¹. -1 The peak at 1275 cm⁻¹ is the stretching vibration peak of CN, the peak at 1275 cm⁻¹ is the bending vibration peak of COC, and the peak at 1072 cm⁻¹ is the stretching vibration peak of -COC-.

[0073] Preparation Example 5: Synthesis of Organic Alcohol Amino Carboxylic Acid Polymer

[0074] The method is as follows:

[0075] S1. 0.1 mol diethylene glycolamine, 0.14 mol di-tert-butyl dicarbonate, and 0.5 mol sodium bicarbonate were added to 200 mL of dichloromethane, stirred and mixed, heated to 50 °C, and stirred for 2 h. The solvent was removed under reduced pressure, and the mixture was separated by column chromatography to obtain intermediate C; the yield was 96.9%.

[0076] S2. Add 0.1 mol of intermediate C and 0.11 mol of maleic anhydride to 200 mL of N,N-dimethylformamide, heat to 100 °C, stir for 3 h, wash with water, extract with dichloromethane, and separate by column chromatography to obtain intermediate D; yield 70.2%.

[0077] S3. Dissolve 15 parts by weight of intermediate D in 100 parts by weight of dichloromethane solution, add 0.03 parts by weight of cyclohexanone peroxide, heat to 60°C, and polymerize for 3 hours. Add water to precipitate the product, filter, wash with dichloromethane, then dissolve 25 parts by weight of the product in 100 parts by weight of dichloromethane, add 12 parts by weight of trifluoroacetic acid, and react at room temperature for 2 hours to obtain the organic alcohol amine carboxylic acid polymer of formula II.

[0078] Preparation Example 6: Synthesis of Organic Alcohol Amino Carboxylic Acid Polymer

[0079] The method is as follows:

[0080] S1. 0.1 mol diethylene glycolamine, 0.13 mol di-tert-butyl dicarbonate, and 0.45 mol potassium carbonate were added to 200 mL of dichloromethane, stirred and mixed, heated to 45 °C, and stirred for 1.5 h. The solvent was removed under reduced pressure, and the mixture was separated by column chromatography to obtain intermediate C; the yield was 97.5%.

[0081] S2. Add 0.1 mol of intermediate C and 0.105 mol of maleic anhydride to 200 mL of N,N-dimethylformamide, heat to 92 °C, stir for 2.5 h, wash with water, extract with dichloromethane, and separate by column chromatography to obtain intermediate D; yield 71.0%.

[0082] S3. Dissolve 13 parts by weight of intermediate D in 100 parts by weight of dichloromethane solution, add 0.024 parts by weight of azobisisobutyronitrile, heat to 57°C, and polymerize for 2.5 h. Add water to precipitate the product, filter, wash with dichloromethane, then dissolve 23 parts by weight of the product in 100 parts by weight of dichloromethane, add 11 parts by weight of trifluoroacetic acid, and react at room temperature for 1.5 h to obtain the organic alcohol amine carboxylic acid polymer of formula II.

[0083] Example 1

[0084] This embodiment provides an alkali-free liquid quick-setting agent for shotcrete, prepared from the following raw materials in parts by weight: 12 parts magnesium fluorosilicate, 3 parts hydrogen fluoride, 5 parts aluminum hydroxide, 20 parts aluminum sulfate, 3 parts organic alcohol amine carboxylic acid polymer, 2 parts malonic acid, 1 part polyacrylamide, and 20 parts water. The organic alcohol amine carboxylic acid polymer includes the organic alcohol amine carboxylic acid polymer of formula I obtained in Preparation Example 1 and the organic alcohol amine carboxylic acid polymer of formula II obtained in Preparation Example 4, with a mass ratio of 5:10.

[0085] The preparation method includes the following steps:

[0086] (1) At room temperature, hydrofluoric acid and malonic acid are mixed and added to half of the water, aluminum hydroxide is added, and the mixture is stirred to obtain an aluminum fluoride-aluminum malonate solution. The solution is added to aluminum sulfate, heated to 50°C, and stirred to dissolve, resulting in a mixture A.

[0087] (2) Mix magnesium fluorosilicate and the remaining water evenly, stir to dissolve, add organic alcohol amine carboxylic acid polymer, stir to dissolve, and obtain mixture B;

[0088] (3) Mix liquid A and liquid B evenly, heat to 40°C, add polyacrylamide and stir to dissolve, mix for 20 minutes to obtain alkali-free liquid quick-setting agent for sprayed concrete.

[0089] Example 2

[0090] This embodiment provides an alkali-free liquid quick-setting agent for shotcrete, prepared from the following raw materials in parts by weight: 15 parts magnesium fluorosilicate, 5 parts hydrogen fluoride, 7 parts aluminum hydroxide, 30 parts aluminum sulfate, 5 parts organic alcohol amine carboxylic acid polymer, 3 parts oxalic acid, 2 parts polyacrylamide, and 30 parts water. The organic alcohol amine carboxylic acid polymer includes the organic alcohol amine carboxylic acid polymer of formula I obtained in Preparation Example 2 and the organic alcohol amine carboxylic acid polymer of formula II obtained in Preparation Example 5, with a mass ratio of 7:10.

[0091] The preparation method includes the following steps:

[0092] (1) At room temperature, hydrofluoric acid and oxalic acid are mixed and added to half of the water, aluminum hydroxide is added, and the mixture is stirred to obtain an aluminum fluoride-aluminum oxalate solution. The solution is added to aluminum sulfate, heated to 60°C, and stirred to dissolve, resulting in a mixture A.

[0093] (2) Mix magnesium fluorosilicate and the remaining water evenly, stir to dissolve, add organic alcohol amine carboxylic acid polymer, stir to dissolve, and obtain mixture B;

[0094] (3) Mix liquid A and liquid B evenly, heat to 50°C, add polyacrylamide and stir to dissolve, mix for 20 minutes to obtain alkali-free liquid quick-setting agent for sprayed concrete.

[0095] Example 3

[0096] This embodiment provides an alkali-free liquid quick-setting agent for shotcrete, prepared from the following raw materials in parts by weight: 13 parts magnesium fluorosilicate, 4 parts hydrogen fluoride, 6 parts aluminum hydroxide, 25 parts aluminum sulfate, 4 parts organic alcohol amine carboxylic acid polymer, 2.5 parts succinic acid, 1.5 parts polyacrylamide, and 25 parts water. The organic alcohol amine carboxylic acid polymer includes the organic alcohol amine carboxylic acid polymer of formula I obtained in Preparation Example 3 and the organic alcohol amine carboxylic acid polymer of formula II obtained in Preparation Example 6, with a mass ratio of 6:10.

[0097] The preparation method includes the following steps:

[0098] (1) At room temperature, hydrofluoric acid and succinic acid are mixed and added to half of the water, aluminum hydroxide is added, and the mixture is stirred to obtain an aluminum fluoride-aluminum succinate solution. The solution is then added to aluminum sulfate, heated to 55°C, and stirred to dissolve, resulting in a mixed solution A.

[0099] (2) Mix magnesium fluorosilicate and the remaining water evenly, stir to dissolve, add organic alcohol amine carboxylic acid polymer, stir to dissolve, and obtain mixture B;

[0100] (3) Mix liquid A and liquid B evenly, heat to 45°C, add polyacrylamide and stir to dissolve, mix for 20 minutes to obtain alkali-free liquid quick-setting agent for sprayed concrete.

[0101] Example 4

[0102] The difference from Example 3 is that the organic alcoholamine carboxylic acid polymer is a single organic alcoholamine carboxylic acid polymer of Formula I obtained in Preparation Example 3.

[0103] Example 5

[0104] The difference from Example 3 is that the organic alcoholamine carboxylic acid polymer is a single organic alcoholamine carboxylic acid polymer of Formula II obtained in Preparation Example 6.

[0105] Comparative Example 1

[0106] The difference from Example 3 is that the organic alcoholamine carboxylic acid polymer is replaced by an equal amount of diethanolamine.

[0107] This comparative example provides an alkali-free liquid quick-setting agent for shotcrete, which is prepared from the following raw materials in parts by weight: 13 parts magnesium fluorosilicate, 4 parts hydrogen fluoride, 6 parts aluminum hydroxide, 25 parts aluminum sulfate, 4 parts diethanolamine, 2.5 parts succinic acid, 1.5 parts polyacrylamide, and 25 parts water.

[0108] Comparative Example 2

[0109] The difference compared to Example 3 is that no organic alcohol amine carboxylate was added.

[0110] This comparative example provides an alkali-free liquid quick-setting agent for shotcrete, which is prepared from the following raw materials in parts by weight: 13 parts magnesium fluorosilicate, 4 parts hydrogen fluoride, 6 parts aluminum hydroxide, 25 parts aluminum sulfate, 6.5 parts succinic acid, 1.5 parts polyacrylamide, and 25 parts water.

[0111] Comparative Example 3

[0112] The difference compared to Example 3 is that magnesium fluorosilicate was not added.

[0113] This comparative example provides an alkali-free liquid quick-setting agent for sprayed concrete, which is prepared from the following raw materials in parts by weight: 4 parts hydrogen fluoride, 6 parts aluminum hydroxide, 38 parts aluminum sulfate, 4 parts organic alcohol amine carboxylic acid polymer, 2.5 parts succinic acid, 1.5 parts polyacrylamide, and 25 parts water.

[0114] Comparative Example 4

[0115] The difference compared to Example 3 is that no hydrogen fluoride was added.

[0116] This comparative example provides an alkali-free liquid quick-setting agent for shotcrete, which is prepared from the following raw materials in parts by weight: 13 parts magnesium fluorosilicate, 6 parts aluminum hydroxide, 25 parts aluminum sulfate, 4 parts organic alcohol amine carboxylic acid polymer, 6.5 parts succinic acid, 1.5 parts polyacrylamide, and 25 parts water.

[0117] Comparative Example 5

[0118] The difference compared to Example 3 is that succinic acid was not added.

[0119] This comparative example provides an alkali-free liquid quick-setting agent for sprayed concrete, which is prepared from the following raw materials in parts by weight: 13 parts magnesium fluorosilicate, 6.5 parts hydrogen fluoride, 6 parts aluminum hydroxide, 25 parts aluminum sulfate, 4 parts organic alcohol amine carboxylic acid polymer, 1.5 parts polyacrylamide, and 25 parts water.

[0120] Test Example 1

[0121] The performance of the alkali-free liquid quick-setting agent for shotcrete prepared in Examples 1-5 or Comparative Examples 1-5 of the present invention was tested, and the results are shown in Table 1.

[0122] Table 1

[0123] Group pH value Stability (bottom sediment volume after 12 months) (mL) Chloride ion content (%) Example 1 3.2 0.3 Not detected Example 2 3.3 0.2 Not detected Example 3 3.3 0.2 Not detected Example 4 3.4 0.5 Not detected Example 5 3.4 0.6 Not detected Comparative Example 1 3.8 4.5 Not detected Comparative Example 2 3.0 7.5 Not detected Comparative Example 3 3.6 1.8 Not detected Comparative Example 4 4.0 3.8 Not detected Comparative Example 5 3.9 3.2 Not detected

[0124] As can be seen from the table above, the alkali-free liquid quick-setting agent for shotcrete prepared in Examples 1-3 of this invention has better stability.

[0125] Test Example 2

[0126] The cement used in the test was P·I42.5 standard cement, purchased from Shandong Lucheng Cement Co., Ltd., and the ISO standard sand was purchased from Xiamen Aisiou Standard Sand Co., Ltd. The water-reducing agent was YH-3 polycarboxylate water-reducing agent, purchased from Shanxi Yuanhang Building Materials Co., Ltd.

[0127] 90 parts by weight of reference cement, 140 parts of ISO standard sand, 4 parts of alkali-free liquid quick-setting agent for shotcrete prepared in Examples 1-5 or Comparative Examples 1-5, 1.5 parts of water-reducing agent, and 38 parts of water were mixed evenly and sprayed to obtain shotcrete. Concrete without alkali-free liquid quick-setting agent for shotcrete was used as a control group.

[0128] The setting time and cement mortar strength of the sprayed concrete with the prepared accelerator were tested according to the method in GB / T35159-2017 "Accelerators for Shotcrete". The setting time and cement mortar strength of the control group were tested according to GB / T17671-2021 "Test Method for Cement Mortar Strength".

[0129] The results are shown in Table 2.

[0130] Table 2

[0131] Group Initial setting time (min) Final setting time (min) 1-day compressive strength (MPa) 28-day compressive strength ratio (%) control group 202 275 6.5 100 Example 1 1.8 3.2 13.9 119.7 Example 2 1.9 3.3 13.7 120.2 Example 3 1.7 3.0 14.0 121.9 Example 4 2.9 5.6 13.2 114.2 Example 5 3.0 5.8 13.4 113.9 Comparative Example 1 3.9 6.7 11.2 105.7 Comparative Example 2 8.7 13.7 10.1 98.9 Comparative Example 3 6.2 10.1 12.2 113.8 Comparative Example 4 3.9 7.4 10.9 102.1 Comparative Example 5 3.5 6.2 11.9 110.2

[0132] As can be seen from the table above, the alkali-free liquid quick-setting agent for shotcrete prepared in Examples 1-3 of the present invention can significantly shorten the setting time, increase the compressive strength by 1 day, and further enhance the compressive strength after 28 days.

[0133] Compared to Example 3, Examples 4 and 5 used either the organic alcoholamine carboxylic acid polymer of Formula I obtained in Preparation Example 3 or the organic alcoholamine carboxylic acid polymer of Formula II obtained in Preparation Example 6. No organic alcoholamine carboxylic acid polymer was added in Comparative Example 2. The stability decreased, the setting time increased, and the compressive strength decreased. The organic alcoholamine carboxylic acid polymer prepared by this invention has active complexing groups such as amino and carboxyl groups, COO 2- Able to interact with Al 3+ Complexation results in a highly soluble complex that also inhibits Al formation. 3+ Hydrolysis of the amine shortens the setting time and improves the stability of the accelerator. Simultaneously, the addition of an organic alcohol amine carboxylic acid polymer shortens the cement setting time while increasing the early strength of the mortar, resulting in a superior accelerator with both setting-promoting and early-strength-enhancing effects. The addition of this substance makes the cement paste more viscous, which is beneficial for increasing the cohesiveness of shotcrete, reducing its rebound, and increasing the thickness of the first sprayed layer. The nitrogen atom in the alcohol amine is conducive to the formation of Al. 3+ Fe 3+ The soluble complexes formed by ions such as [specific ions] during cement hydration increase the diffusion rate of hydration products, promote cement hydration, shorten setting time, and improve system stability. This effectively enhances the activity of Al in the solution. 3+ Content. Simultaneously, their structures can form hydrogen bonds, creating a large network structure that effectively complexes and stabilizes aluminum ions, significantly improving storage stability. Furthermore, the combination of terminal and secondary amino groups better promotes the hydration of C3A in cement, accelerates the formation of ettringite, thereby improving the early strength of concrete, enhancing rheological properties, improving setting acceleration, and increasing the early strength of concrete, exhibiting a synergistic effect.

[0134] Compared with Example 3, the organic alcohol amine carboxylic acid polymer in Comparative Example 1 was replaced by diethanolamine, and its effect was significantly worse than that of the organic alcohol amine carboxylic acid polymer prepared in this invention.

[0135] Compared to Example 3, Comparative Example 3 did not include magnesium fluorosilicate. The setting time was prolonged and the stability decreased. This invention adds an appropriate amount of magnesium fluorosilicate, which hydrolyzes in solution. The hydrolysis products form multiple coating layers on the cement surface, effectively inhibiting the cement hydration reaction and reducing the cement setting time.

[0136] Compared with Example 3, Comparative Examples 4 and 5 did not contain added hydrogen fluoride or succinic acid. Stability decreased, setting time prolonged, and compressive strength decreased. The hydrogen fluoride and organic acid added in this invention react with aluminum hydroxide to form an aluminum fluoride-aluminum organic acid solution, increasing the soluble aluminum content in the alkali-free liquid accelerator for shotcrete. This improves the stability and setting-promoting effect of the alkali-free liquid accelerator for shotcrete. Therefore, the amount of alkali-free liquid accelerator added can be greatly reduced while achieving efficient setting and increased concrete strength. The later strength not only does not decrease but is significantly improved. It has strong compatibility with cement, requires no heating during use, has low energy consumption, and better performance.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An alkali-free liquid quick-setting agent for shotcrete, characterized in that, It is prepared from the following raw materials in parts by weight: 12-15 parts magnesium fluorosilicate, 3-5 parts hydrogen fluoride, 5-7 parts aluminum hydroxide, 20-30 parts aluminum sulfate, 3-5 parts organic alcohol amine carboxylic acid polymer, 2-3 parts organic acid, 1-2 parts polyacrylamide, and 20-30 parts water. The organic alcohol amine carboxylic acid polymer is composed of an organic alcohol amine carboxylic acid polymer of formula I and an organic alcohol amine carboxylic acid polymer of formula II in a mass ratio of 5-7:

10. The structures of Formula I and Formula II are as follows: Formula I; Formula II.

2. The alkali-free liquid quick-setting agent for shotcrete according to claim 1, characterized in that, The method for synthesizing the organic alcohol amine carboxylic acid polymer of Formula I is as follows: S1. Diethanolamine and di-tert-butyl dicarbonate are mixed with a base and heated and stirred to obtain intermediate A, with the following structure: ; S2. Intermediate A and maleic anhydride are mixed, heated, and stirred to react, yielding intermediate B, with the following structure: ; S3. Intermediate B is polymerized under the action of an initiator. The product is precipitated with water, filtered, and then reacted with trifluoroacetic acid to obtain the organic alcohol amine carboxylic acid polymer of Formula I.

3. The alkali-free liquid quick-setting agent for shotcrete according to claim 2, characterized in that, In step S1, the molar ratio of diethanolamine to di-tert-butyl dicarbonate is 1:1.2-1.4, the alkali is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate, and the heating temperature is 40-50°C for 1-2 hours.

4. The alkali-free liquid quick-setting agent for shotcrete according to claim 2, characterized in that, In step S2, the molar ratio of intermediate A to maleic anhydride is 1:1-1.1, and the heating temperature is 80-100℃ for 2-3 hours.

5. The alkali-free liquid quick-setting agent for shotcrete according to claim 2, characterized in that, In step S3, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, cyclohexanone peroxide, benzoyl peroxide, and tert-butyl hydroperoxide. The mass ratio of intermediate B to initiator is 100-150:0.2-0.

3. The polymerization reaction temperature is 50-60℃ and the time is 2-3 hours. The mass ratio of product to trifluoroacetic acid is 20-25:10-12. The trifluoroacetic acid reaction temperature is room temperature and the time is 1-2 hours.

6. The alkali-free liquid quick-setting agent for shotcrete according to claim 1, characterized in that, The method for synthesizing the organic alcohol amine carboxylic acid polymer of formula II is as follows: T1. Diethylene glycolamine and di-tert-butyl dicarbonate were mixed with a base and heated and stirred to obtain intermediate C, with the following structure. ; T2. Intermediate C and maleic anhydride are mixed, heated, and stirred to obtain intermediate D, with the following structure: ; T3. Intermediate D is polymerized under the action of an initiator. The product is precipitated with water, filtered, and then reacted with trifluoroacetic acid to obtain the organic alcohol amine carboxylic acid polymer of formula II.

7. The alkali-free liquid quick-setting agent for shotcrete according to claim 6, characterized in that, In step T1, the molar ratio of diethylene glycolamine to di-tert-butyl dicarbonate is 1:1.2-1.4, the base is selected from at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate, and the heating temperature is 40-50℃ for 1-2 hours; in step T2, the molar ratio of intermediate C to maleic anhydride is 1:1-1.1, the heating temperature is 80-100℃ for 2-3 hours; in step T3, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, cyclohexanone peroxide, benzoyl peroxide, and tert-butyl hydroperoxide, the mass ratio of intermediate D to initiator is 100-150:0.2-0.3, the polymerization reaction temperature is 50-60℃ for 2-3 hours, the mass ratio of product to trifluoroacetic acid is 20-25:10-12, and the trifluoroacetic acid reaction temperature is room temperature for 1-2 hours.

8. The alkali-free liquid quick-setting agent for shotcrete according to claim 1, characterized in that, The organic acid is selected from at least one of oxalic acid, malonic acid, succinic acid, acetic acid, propionic acid, glutaric acid, and maleic acid.

9. A method for preparing an alkali-free liquid quick-setting agent for shotcrete as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) At room temperature, hydrofluoric acid and organic acid are mixed and added to half of the water, aluminum hydroxide is added, and the mixture is stirred to obtain an aluminum fluoride-organic acid aluminum solution. The solution is added to aluminum sulfate, heated to 50-60℃, and stirred to dissolve, thus obtaining a mixture A. (2) Mix magnesium fluorosilicate and the remaining water evenly, stir to dissolve, add organic alcohol amine carboxylic acid polymer, stir to dissolve, and obtain mixture B; (3) Mix liquid A and liquid B evenly, heat to 40-50℃, add polyacrylamide and stir to dissolve, to obtain alkali-free liquid quick-setting agent for sprayed concrete.

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