Fluorine-free, alkali-free and chlorine-free liquid accelerator and preparation method thereof

Abstract

The application discloses a kind of fluorine-free, alkali-free and chlorine-free liquid accelerator and a preparation method thereof, and belongs to the technical field of concrete admixture.A kind of fluorine-free, alkali-free and chlorine-free liquid accelerator, by weight parts, comprising the following raw materials: aluminum sulfate 44-52 parts, composite modified hydroxy aluminum wet gel 6-12 parts, aluminum nitrate 2-5 parts, calcium nitrate 0.6-1.8 parts, diethanol mono-isopropanol amine 0.7-1.8 parts, lactic acid 1.0-2.2 parts, hydroxypropyl starch ether 0.10-0.38 parts, sorbitol 0.5-1.6 parts, water is supplemented to 100 parts.The present application realizes rapid setting and early strength development under the condition of not adding fluorine-containing coagulation component and strong alkali coagulation component.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent and its preparation method. Background Technology

[0002] Shotcrete is widely used in tunnels, mines, slopes, underground engineering, and emergency repair and support applications. Liquid accelerators can shorten the setting time of cement-based materials and improve early support capabilities, making them one of the key admixtures in wet shotcrete construction. Compared to powder accelerators, liquid accelerators have certain advantages in metering, mixing uniformity, and wet shotcrete application. Compared to strongly alkaline accelerators, alkali-free or low-alkali liquid accelerators help reduce construction irritation, high alkali content, and the risk of later strength loss.

[0003] Existing fluorine-free and alkali-free liquid quick-setting agents mainly adopt aluminum salt quick-setting systems, which provide quick-setting effects through aluminum sulfate, polyaluminum sulfate or other aluminum sources, and are combined with organic stabilizers, inorganic suspension components, early strength components and pH adjusters to achieve product stability and performance balance.

[0004] Existing patent document CN113603384A discloses an ultra-early-strength, fluorine-free, and alkali-free liquid quick-setting agent. It mainly achieves rapid setting, early strength, and storage stability of the fluorine-free and alkali-free system through a high content of aluminum sulfate, a ternary organic solubilizer, an inorganic stabilizer, an early-strength agent, and a pH adjuster. However, the stability and solubility of this technical solution mainly rely on a specific ternary organic solubilizer system and inorganic stabilizing systems such as sepiolite and boehmite. Regarding the long-term storage stability of the high-aluminum salt system, its performance varies under different temperature conditions.

[0005] Existing patent document CN114014582A discloses a chlorine-free, fluorine-free, and alkali-free liquid accelerator, which mainly achieves fluorine-free and alkali-free aperture and shotcrete performance through an early-strength system of aluminum sulfate, diethanolamine / N-methyldiethanolamine, and stabilizing components such as magnesium aluminum silicate and bio-adhesive. However, the stability of this technical solution mainly depends on magnesium aluminum silicate and adhesive stabilizing components, and its adaptability varies under different cement mineral composition conditions.

[0006] Existing patent document CN115636615A discloses an alkali-free, chlorine-free, and fluorine-free early-strength liquid quick-setting agent, which mainly consists of polyaluminum sulfate, diethanolamine, pH adjuster, amino acid complexing agent, and Tween 20, achieving both early strength and stability within a relatively narrow formulation window. This approach relies on amino acid complexing agents and Tween-type surfactants, and single-batch addition can easily lead to paste formation, limiting the flexibility of formulation adjustments.

[0007] Existing patent document CN117209197A discloses a high-performance fluorine-free and alkali-free liquid accelerator, which mainly improves aluminum content, dispersibility, and sprayable application performance through polycarboxylate aluminum dispersion, aluminum sulfate, a small amount of alkaline liquid accelerator, alkaline amino acids, and colloidal suspension stabilizers. Patent document CN117585930A discloses a highly adaptable alkali-free liquid accelerator, which mainly improves adaptability and shotcrete performance through sodium fluorosilicate, aluminum sulfate, sodium aluminate, and alkanolamine stabilizing components. However, the above technical solutions present certain complexities in strictly controlling the fluorine-free and alkali-free nature of the process.

[0008] Existing patent document CN119638254A discloses a low-temperature resistant, fluorine-free, and alkali-free liquid quick-setting agent, which mainly achieves low-temperature storage stability through high aluminum sulfate, magnesium olivine suspension components, urea / ethylene glycol antifreeze components, diethanolamine complexing agents, and alkylphenol polyoxyethylene ether solubilizing components. However, this technical solution relies on magnesium olivine, antifreeze components, and alkylphenol polyoxyethylene ether solubilizing components, resulting in differences in environmental friendliness and foam control.

[0009] In summary, this application proposes a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent and its preparation method to solve the above-mentioned technical problems. Summary of the Invention

[0010] To address the deficiencies in the aforementioned technical solutions, the present invention aims to provide a fluorine-free, alkali-free, and chlorine-free liquid accelerator and its preparation method, thereby improving the problems of difficulty in simultaneously achieving storage stability, 6h / 1d early strength, later strength retention, and adaptability to different gelation systems in high-aluminum salt liquid accelerators under fluorine-free, alkali-free, and chlorine-free conditions.

[0011] To achieve the above objectives, the present invention provides a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, comprising the following raw materials by weight: 44-52 parts aluminum sulfate, 6-12 parts composite modified aluminum hydroxyl wet gel, 2-5 parts aluminum nitrate, 0.6-1.8 parts calcium nitrate, 0.7-1.8 parts diethanolamine, 1.0-2.2 parts lactic acid, 0.10-0.38 parts hydroxypropyl starch ether, 0.5-1.6 parts sorbitol, and water to a total of 100 parts.

[0012] The aluminum sulfate is aluminum sulfate octadecahydrate, which is a white or light-colored solid in appearance. The effective aluminum content, calculated as Al2O3, is 15%-17%, and the water-insoluble matter content is not higher than 0.2%.

[0013] The composite modified aluminum hydroxyl wet gel comprises, by total mass, 18%-25% aluminum hydroxyl solid component, 0.15%-0.65% phytic acid, 0.12%-0.55% tannic acid, 0.3%-1.2% lactic acid and water.

[0014] The composite modified aluminum hydroxyl wet gel has a pH of 2.4-3.2 and an effective aluminum content (calculated as Al2O3) of 10%-14%. 50 The particle size is 0.5-2.5μm, and no hard precipitate is formed after standing for 24 hours.

[0015] The aluminum nitrate in question is aluminum nitrate nonahydrate.

[0016] The calcium nitrate mentioned is calcium nitrate tetrahydrate.

[0017] The diethanol monoisopropanolamine has an active component content of not less than 85%.

[0018] The hydroxypropyl starch ether is a cold water-dispersible hydroxypropyl starch ether with a drying loss of no more than 12% and a 2% aqueous solution that is weakly acidic to neutral.

[0019] The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Add aluminum hydroxyl wet gel to water to adjust the solid content of the system to 18%-25%, and stir at 400-800 r / min for 20-40 min to obtain aluminum hydroxyl pre-dispersion; S2. Add lactic acid to the aluminum hydroxyl pre-dispersion solution to adjust the pH of the system, and stir at 35-45℃ for 20-30 min to form an acidified dispersion state on the surface of the aluminum hydroxyl particles. S3. Dilute phytic acid with 5-10 times its mass of water to prepare a phytic acid dilution solution. Under the stirring conditions of 35-45℃ and 500-900r / min, add it dropwise to the acidified aluminum hydroxide pre-dispersion solution within 20-40min. After the dropwise addition is completed, continue stirring for 30-60min to allow phytic acid to coordinate and adsorb with the aluminum hydroxyl groups on the surface of aluminum hydroxide. S4. Dissolve tannic acid in 8-15 times its mass of water to obtain an aqueous solution of tannic acid. Add the solution to the system obtained in step S3 at 30-40℃ and stir for 20-40 minutes to allow the tannic acid to form an adsorption and dispersion layer on the surface of the aluminum hydroxide particles. S5. The system obtained in step S4 is sheared and dispersed at 1500-2500 r / min for 15-30 min, and then aged at 25-35℃ for 4-12 h. S6. Detect the pH, solid content, and particle size of the matured system. When the pH is 2.4-3.2, the solid content is 18%-25%, and the D... 50 When the particle size is 0.5-2.5μm and no hard precipitate is formed after standing for 24 hours, a composite modified aluminum hydroxide wet gel is obtained.

[0020] Further, in step S2, the pH is adjusted to 2.6-3.1.

[0021] A method for preparing a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent includes the following steps: Step 1: Heat some water to 60-70℃, add aluminum sulfate, and stir at 300-600r / min for 40-70min to form a clear or basically clear aluminum salt solution. Step 2: Lower the system temperature to 45-55℃, add lactic acid, sorbitol and diethanol monoisopropanolamine, stir for 20-40 minutes to obtain acidic complex aluminum salt mother liquor; Step 3: Add the composite modified aluminum hydroxyl wet gel at 45-55℃, stir at 500-800 r / min for 20-30 min, and then shear and disperse at 1200-1800 r / min for 10-20 min to ensure that the composite modified aluminum hydroxyl is uniformly dispersed in the aluminum salt mother liquor. Step 4: Add aluminum nitrate and calcium nitrate, and stir at 40-50℃ for 20-35 minutes; Step 5: Add hydroxypropyl starch ether and shear and disperse at 1500-2500 r / min for 15-30 min; Step six: Add the remaining water, filter, and a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent is obtained.

[0022] Furthermore, in step five, the system temperature needs to be lowered to 30-40℃ before adding hydroxypropyl starch ether; Furthermore, the fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent has a pH of 2.6-3.3, a viscosity of 45-110 mPa·s, and a solid content of 45%-56%.

[0023] The beneficial effects of this invention are: 1. This invention provides aluminum source, calcium source and early hydration regulating components in synergy with aluminum sulfate, composite modified aluminum hydroxyl wet gel, aluminum nitrate, calcium nitrate and diethanol monoisopropanolamine, which promotes the early reaction of C3A and C3S in the cement system and the formation of aluminum phase hydration products such as ettringite, thereby achieving rapid setting and early strength development without the addition of fluorine-containing accelerators and strong alkaline accelerators. 2. This invention performs composite modification of aluminum hydroxyl wet gel by lactic acid acidification dispersion, phytic acid coordination regulation and tannic acid adsorption dispersion, so that aluminum hydroxyl wet gel can maintain a good dispersion state in acidic aluminum salt system, reduce the risk of hydrolysis aggregation, crystallization, hard precipitation and long-term stratification, thereby improving the storage stability and redispersibility of liquid quick-setting agent before use. 3. This invention achieves a good balance between setting time, 6h / 1d strength, 28d / 90d strength retention rate, low-temperature storage, and adaptability to different gelling systems through the synergistic regulation of nitrate early strength component, diethanol monoisopropanolamine, water-soluble organic acid, polyol and appropriate amount of hydroxypropyl starch ether. This avoids the problems of stability, workability or later strength loss caused by simply increasing the aluminum salt concentration or simply adding thickener. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for explanation only and are not intended to limit the invention. Furthermore, regarding numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] Example 1 A fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, by weight, comprises the following raw materials: 48 parts aluminum sulfate, 8 parts composite modified aluminum hydroxyl wet gel, 3 parts aluminum nitrate, 1.20 parts calcium nitrate, 1.10 parts diethanolamine monoisopropanolamine, 1.40 parts lactic acid, 0.22 parts hydroxypropyl starch ether, 1 part sorbitol, and 36.08 parts water.

[0029] The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Take 100 parts of aluminum hydroxyl wet gel with a solid content of 22%, add 18 parts of water, and stir at 600 r / min for 30 min to obtain aluminum hydroxyl pre-dispersion. S2. Heat the system to 40°C, add 0.80 parts of lactic acid, adjust the pH to 2.8, and continue stirring for 25 minutes. S3. Take 0.42 parts of phytic acid and dilute it with 3 parts of water to obtain a diluted phytic acid solution. Under the stirring conditions of 40℃ and 700r / min, add the diluted phytic acid solution dropwise to the acidified aluminum hydroxide pre-dispersion solution within 30min. After the addition is completed, continue stirring for 45min. S4. Take 0.32 parts of tannic acid, dissolve it in 4 parts of water to obtain an aqueous solution of tannic acid, add it to the system obtained in step S3 at 35°C, and stir for 30 min. S5. Shear dispersion at 2000 r / min for 20 min, and then mature at 30℃ for 8 h; S6. After curing, the solid content of the composite modified aluminum hydroxyl wet gel was measured to be 20.6%, the pH was 2.8, and the effective aluminum content (calculated as Al2O3) was 11.8%. 50 The particle size was 1.3 μm, and no hard precipitate was observed after standing for 24 hours.

[0030] A method for preparing a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent includes the following steps: Step 1: Heat 27 parts of water to 65°C, add aluminum sulfate, and stir at 500 r / min for 50 min to obtain a clear or basically clear aluminum salt solution. Step 2: Cool to 50°C, add lactic acid, sorbitol and diethanol monoisopropanolamine, stir for 30 minutes to obtain acidic complex aluminum salt mother liquor; Step 3: Add the above-mentioned composite modified aluminum hydroxyl wet gel, stir at 700 r / min for 25 min, and then shear at 1500 r / min for 15 min; Step 4: Add aluminum nitrate and calcium nitrate, and stir at 40-50℃ for 20-35 minutes; Step 5: Cool down to 30-40℃, add hydroxypropyl starch ether, and shear at 2000r / min for 20min; Step 6: Add the remaining water, filter to obtain liquid quick-setting agent, and measure the pH to be 2.9.

[0031] Example 2 A fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, comprising the following raw materials by weight: 45 parts aluminum sulfate, 6.50 parts composite modified aluminum hydroxyl wet gel, 2.20 parts aluminum nitrate, 0.80 parts calcium nitrate, 0.80 parts diethanolamine, 1.20 parts lactic acid, 0.15 parts hydroxypropyl starch ether, 0.80 parts sorbitol, and 42.55 parts water.

[0032] The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Take 100 parts of aluminum hydroxyl wet gel with a solid content of 20%, add 14 parts of water, and stir at 500 r / min for 30 min to obtain aluminum hydroxyl pre-dispersion. S2. Heat the system to 38°C, add 0.60 parts of lactic acid, adjust the pH to 3.1, and continue stirring for 25 minutes. S3. Take 0.26 parts of phytic acid and dilute it with 2 parts of water to obtain a diluted phytic acid solution. Under the stirring conditions of 38℃ and 650r / min, add the diluted phytic acid solution dropwise to the acidified aluminum hydroxide pre-dispersion solution within 25min. After the addition is completed, continue stirring for 40min. S4. Take 0.22 parts of tannic acid, dissolve it in 3 parts of water to obtain an aqueous solution of tannic acid, add it to the system obtained in step S3 at 35°C, and stir for 25 minutes. S5. Shear dispersion at 1800 r / min for 18 min, and then mature at 30℃ for 6 h; S6. After curing, the solid content of the composite modified aluminum hydroxyl wet gel was measured to be 19.4%, the pH was 3.0, and the effective aluminum content (calculated as Al2O3) was 10.8%. 50 The particle size was 1.8 μm, and no hard precipitate was observed after standing for 24 hours.

[0033] In this embodiment, the liquid quick-setting agent was prepared as follows: Step 1: 31.50 parts of water were heated to 64°C, aluminum sulfate was added, and the mixture was stirred at 450 r / min for 55 min to obtain a clear or basically clear aluminum salt solution; Step 2: The temperature was lowered to 50°C, lactic acid, sorbitol, and diethanol monoisopropanolamine were added, and the mixture was stirred for 28 min to obtain an acidic complexed aluminum salt mother liquor; Step 3: The above-mentioned composite modified hydroxyaluminum wet gel was added, and the mixture was stirred at 650 r / min for 25 min, and then sheared at 1400 r / min for 15 min; Step 4: Aluminum nitrate and calcium nitrate were added, and the mixture was stirred for 28 min; Step 5: The temperature was lowered to 35°C, hydroxypropyl starch ether was added, and the mixture was sheared at 1800 r / min for 20 min; Step 6: The remaining water was added, and the mixture was filtered to obtain the liquid quick-setting agent, with a measured pH of 3.1.

[0034] Example 3 A fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, comprising the following raw materials by weight: 49 parts aluminum sulfate, 9.50 parts composite modified aluminum hydroxyl wet gel, 3.60 parts aluminum nitrate, 1.40 parts calcium nitrate, 1.30 parts diethanolamine, 1.60 parts lactic acid, 0.24 parts hydroxypropyl starch ether, 1.20 parts sorbitol, and 32.16 parts water.

[0035] The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Take 100 parts of aluminum hydroxyl wet gel with a solid content of 23%, add 16 parts of water, and stir at 650 r / min for 30 min to obtain aluminum hydroxyl pre-dispersion. S2. Heat the system to 40°C, add 0.85 parts of lactic acid, adjust the pH to 2.8, and continue stirring for 25 minutes. S3. Take 0.48 parts of phytic acid and dilute it with 3.50 parts of water to obtain a diluted phytic acid solution. Under the stirring conditions of 40℃ and 750r / min, add the diluted phytic acid solution dropwise to the acidified aluminum hydroxide predispersant solution within 30min. After the addition is completed, continue stirring for 50min. S4. Take 0.36 parts of tannic acid and dissolve it in 4.50 parts of water to obtain an aqueous solution of tannic acid. Add the solution to the system obtained in step S3 at 35°C and stir for 30 minutes. S5. Shear dispersion at 2100 r / min for 22 min, and then mature at 30℃ for 8 h; S6. After curing, the solid content of the composite modified aluminum hydroxyl wet gel was measured to be 21.5%, the pH was 2.8, and the effective aluminum content (calculated as Al2O3) was 12.3%. 50 The particle size was 1.1 μm, and no hard precipitate was observed after standing for 24 hours.

[0036] In this embodiment, the liquid quick-setting agent was prepared as follows: Step 1: 23.50 parts of water were heated to 65°C, aluminum sulfate was added, and the mixture was stirred at 500 r / min for 55 min to obtain a clear or basically clear aluminum salt solution; Step 2: The temperature was lowered to 50°C, lactic acid, sorbitol, and diethanol monoisopropanolamine were added, and the mixture was stirred for 30 min to obtain an acidic complexed aluminum salt mother liquor; Step 3: The above-mentioned composite modified hydroxyaluminum wet gel was added, and the mixture was stirred at 720 r / min for 25 min, and then sheared at 1600 r / min for 15 min; Step 4: Aluminum nitrate and calcium nitrate were added, and the mixture was stirred for 30 min; Step 5: The temperature was lowered to 35°C, hydroxypropyl starch ether was added, and the mixture was sheared at 2000 r / min for 20 min; Step 6: The remaining water was added, and the mixture was filtered to obtain the liquid quick-setting agent, with a measured pH of 2.8.

[0037] Example 4 A fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, comprising the following raw materials by weight: 47 parts aluminum sulfate, 11.50 parts composite modified aluminum hydroxyl wet gel, 2.80 parts aluminum nitrate, 1 part calcium nitrate, 1.20 parts diethanolamine monoisopropanolamine, 1.55 parts lactic acid, 0.26 parts hydroxypropyl starch ether, 1.10 parts sorbitol, and 33.59 parts water.

[0038] The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Take 100 parts of aluminum hydroxyl wet gel with a solid content of 24%, add 18 parts of water, and stir at 700 r / min for 35 min to obtain aluminum hydroxyl pre-dispersion. S2. Heat the system to 40°C, add 0.95 parts of lactic acid, adjust the pH to 2.6, and continue stirring for 30 minutes. S3. Take 0.56 parts of phytic acid and dilute it with 4 parts of water to obtain a diluted phytic acid solution. Under the stirring conditions of 40℃ and 800r / min, add the diluted phytic acid solution dropwise to the acidified aluminum hydroxide pre-dispersion solution within 35min. After the addition is completed, continue stirring for 55min. S4. Take 0.46 parts of tannic acid, dissolve it in 5 parts of water to obtain an aqueous solution of tannic acid, add it to the system obtained in step S3 at 35°C, and stir for 35 minutes. S5. Shear dispersion at 2300 r / min for 25 min, and then mature at 30℃ for 10 h; S6. After curing, the solid content of the composite modified aluminum hydroxyl wet gel was measured to be 22.8%, the pH was 2.7, and the effective aluminum content (calculated as Al2O3) was 12.9%. 50 The particle size was 0.9 μm, and no hard precipitate was observed after standing for 24 hours.

[0039] In this embodiment, the liquid quick-setting agent was prepared as follows: Step 1: 24 parts of water were heated to 65°C, aluminum sulfate was added, and the mixture was stirred at 500 r / min for 55 min to obtain a clear or basically clear aluminum salt solution; Step 2: The temperature was lowered to 50°C, lactic acid, sorbitol, and diethanol monoisopropanolamine were added, and the mixture was stirred for 30 min to obtain an acidic complex aluminum salt mother liquor; Step 3: The above-mentioned composite modified hydroxyaluminum wet gel was added, and the mixture was stirred at 750 r / min for 25 min, and then sheared at 1700 r / min for 15 min; Step 4: Aluminum nitrate and calcium nitrate were added, and the mixture was stirred for 30 min; Step 5: The temperature was lowered to 35°C, hydroxypropyl starch ether was added, and the mixture was sheared at 2100 r / min for 20 min; Step 6: The remaining water was added, and the mixture was filtered to obtain the liquid quick-setting agent, with a measured pH of 2.7.

[0040] Example 5 A fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, comprising the following raw materials by weight: 50 parts aluminum sulfate, 9 parts composite modified aluminum hydroxyl wet gel, 4.80 parts aluminum nitrate, 1.70 parts calcium nitrate, 1.40 parts diethanolamine, 1.65 parts lactic acid, 0.28 parts hydroxypropyl starch ether, 1.30 parts sorbitol, and 29.87 parts water.

[0041] The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Take 100 parts of aluminum hydroxyl wet gel with a solid content of 23%, add 16 parts of water, and stir at 650 r / min for 30 min to obtain aluminum hydroxyl pre-dispersion. S2. Heat the system to 40°C, add 0.90 parts of lactic acid, adjust the pH to 2.7, and continue stirring for 25 minutes. S3. Take 0.50 parts of phytic acid and dilute it with 3.50 parts of water to obtain a diluted phytic acid solution. Under the stirring conditions of 40℃ and 750r / min, add the diluted phytic acid solution dropwise to the acidified aluminum hydroxide predispersant solution within 30min. After the addition is completed, continue stirring for 50min. S4. Take 0.38 parts of tannic acid and dissolve it in 4.50 parts of water to obtain an aqueous solution of tannic acid. Add the solution to the system obtained in step S3 at 35°C and stir for 30 minutes. S5. Shear dispersion at 2200 r / min for 22 min, and mature at 30℃ for 8 h; S6. After curing, the solid content of the composite modified aluminum hydroxyl wet gel was measured to be 21.7%, the pH was 2.7, and the effective aluminum content (calculated as Al2O3) was 12.2%. 50 The particle size was 1.0 μm, and no hard precipitate was observed after standing for 24 hours.

[0042] In this embodiment, the liquid quick-setting agent was prepared as follows: Step 1: 21 parts of water were heated to 66°C, aluminum sulfate was added, and the mixture was stirred at 520 r / min for 55 min to obtain a clear or basically clear aluminum salt solution; Step 2: The temperature was lowered to 50°C, lactic acid, sorbitol, and diethanol monoisopropanolamine were added, and the mixture was stirred for 30 min to obtain an acidic complex aluminum salt mother liquor; Step 3: The above-mentioned composite modified hydroxyaluminum wet gel was added, and the mixture was stirred at 720 r / min for 25 min, and then sheared at 1600 r / min for 15 min; Step 4: Aluminum nitrate and calcium nitrate were added, and the mixture was stirred for 30 min; Step 5: The temperature was lowered to 35°C, hydroxypropyl starch ether was added, and the mixture was sheared at 2100 r / min for 20 min; Step 6: The remaining water was added, and the mixture was filtered to obtain the liquid quick-setting agent, with a measured pH of 2.7.

[0043] Comparative Example 1 The difference between this comparative example and Example 3 is that the composite modified aluminum hydroxyl wet gel is not added, and the volume is made up with an equal amount of water. Apart from this, all other components, their amounts, preparation methods, usage methods, and testing conditions in this comparative example are the same as in Example 3.

[0044] Comparative Example 2 The difference between this comparative example and Example 3 is that the composite modified aluminum hydroxyl wet gel is replaced with an equal amount of unmodified aluminum hydroxyl wet gel. Otherwise, all other components, their amounts, preparation methods, usage methods, and testing conditions in this comparative example are the same as in Example 3.

[0045] Comparative Example 3 The difference between this comparative example and Example 3 is that phytic acid was not added during the preparation of the composite modified aluminum hydroxyl wet gel, and the volume was made up with an equal amount of water. Apart from this, all other components, their amounts, preparation methods, usage methods, and testing conditions in this comparative example are the same as in Example 3.

[0046] Comparative Example 4 The difference between this comparative example and Example 3 is that tannic acid is not added during the preparation of the composite modified aluminum hydroxyl wet gel, and the volume is made up with an equal amount of water. Apart from this, all other components, their amounts, preparation methods, usage methods, and testing conditions in this comparative example are the same as in Example 3.

[0047] Comparative Example 5 The difference between this comparative example and Example 3 is that aluminum nitrate and calcium nitrate are not added, and the volume is made up with an equal amount of water. Apart from this, all other components, their amounts, preparation methods, usage methods, and testing conditions are the same as in Example 3.

[0048] Comparative Example 6 The difference between this comparative example and Example 3 is that the degree of acidification was reduced during the preparation of the composite modified aluminum hydroxide wet gel, and the pH of the final liquid quick-setting agent was adjusted to 3.8. Apart from this, all other components, their amounts, preparation methods, usage methods, and testing conditions in this comparative example are the same as in Example 3.

[0049] Comparative Example 7 The difference between this comparative example and Example 3 is that the amount of hydroxypropyl starch ether is increased to 1.2 parts, and the amount of water is reduced accordingly. Otherwise, all other components, their amounts, preparation methods, usage methods, and testing conditions in this comparative example are the same as in Example 3. Experimental Example 1 Storage stability test: Referring to the stability test method of liquid accelerators in Appendix C of GB / T 35159-2017, 100 mL of the liquid accelerators prepared in Examples 1-5 and Comparative Examples 1-7 were placed in stoppered graduated cylinders and allowed to stand at (20±2)℃ for 28 days. The precipitation volume (mL / 100mL) was recorded. Simultaneously, crystallization was observed after storage at 5±2℃ for 14 days, and layering was observed after storage at 40±2℃ for 7 days. After storage, the mixture was hand-shaken for 30 seconds and stirred at a low speed of 300 r / min for 2 minutes to evaluate redispersibility. The viscosity change rate before and after storage was also recorded. The test results are shown in Table 1. Table 1 Experimental Example 2 Setting time and mortar strength tests: The same batch of P.O42.5 ordinary Portland cement was used. The accelerator dosage was 7 wt% of the cementitious material mass, and the water-cement ratio was 0.40. Water introduced by the liquid accelerator during the test was included in the total water consumption. All groups maintained the same water-cement ratio and the same accelerator dosage. Setting time was conducted according to the testing methods for evaluating the setting performance of accelerators in GB / T35159-2017 "Accelerators for Shotcrete" and GB / T1346 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". Mortar compressive strength was tested according to the specimen preparation and compressive strength testing methods in GB / T17671 "Test Methods for Cement Mortar Strength". The mortar specimen size was 40mm × 40mm × 160mm. The test results are shown in Table 2. Table 2 Experimental Example 3 Adaptability testing of multiple cementitious systems: Adaptability tests were conducted on ordinary Portland cement, slag cement, and high-admixture cementitious systems. Ordinary Portland cement was P.O42.5 cement; the slag cement system used slag cement or cementitious materials containing 15% slag powder; the high-admixture cementitious system used low-aluminate cement or cementitious materials containing 25% fly ash / slag composite admixture. The accelerator dosage in each system was 7 wt% of the cementitious material mass, the water-cement ratio was 0.40, and the water introduced by the liquid accelerator was included in the total water consumption. Initial setting, final setting, 1-day compressive strength, and 28-day strength retention were tested. The test results are shown in Table 3. Table 3 Test Example 4 Fluorine-free, alkali-free, and chloride-free content test: The liquid accelerators prepared in Examples 1-5 and Comparative Examples 1-7 were used to evaluate the content of fluoride ions, chloride ions, and alkali in GB / T17671 "Chemical Analysis Methods for Cement". The fluoride ion, chloride ion, and Na2O equivalent were determined. The test results are shown in Table 4. Table 4 As can be seen from Tables 1 to 4, Examples 1-5 all achieved rapid setting, high early strength, excellent 28-day storage stability according to GB / T 35159-2017, a 90-day strength ratio significantly higher than the 28-day strength ratio, and extremely low fluorine / chlorine / alkali content without the addition of fluorine-containing or strongly alkaline coagulant components. Among them, Example 3 exhibited a superior overall balance in terms of setting time, 6h / 1d strength, 28d / 90d strength ratio, 28d sedimentation volume at (20±2)℃, low-temperature crystallization, redispersibility, and adaptability to multi-gelling systems. Example 4 showed the lowest sedimentation volume and viscosity change rate, indicating that a higher proportion of composite modified aluminum hydroxyl wet gel is beneficial for long-term storage stability. Example 5 showed slightly better setting and early strength, with a 90-day strength ratio reaching 105%, indicating that the synergistic effect of nitrates, alkanolamines, and composite modified aluminum hydroxyl can achieve a good balance between early coagulation and sustained strength development in the later stages.

[0050] In Comparative Example 1, without the addition of the composite modified aluminum hydroxyl wet gel, the initial setting time increased from 2.5 min to 4.8 min, the 6-hour compressive strength decreased from 2.35 MPa to 0.98 MPa, the 28-day / 90-day strength ratio decreased from 103% / 107% to 96% / 98%, and the precipitation volume at (20±2)℃ for 28 days increased from 0.2 mL / 100 mL to 2.1 mL / 100 mL. The possible reason is that the composite modified aluminum hydroxyl wet gel not only provides dispersible aluminum hydroxyl active components, but also participates in the suspension stability of the acidic aluminum salt system and the regulation of effective aluminum release. Without this component, there is insufficient aluminum component in the system that can stably participate in early hydration and later strength development, resulting in a decrease in coagulation, early strength, later strength retention, and storage stability.

[0051] Comparative Example 2, after using unmodified aluminum hydroxyl wet gel, showed a 28d / 90d strength ratio inferior to Example 3. The initial and final setting times were significantly prolonged, the sediment volume increased to 4.8 mL / 100 mL, and hard sedimentation occurred, making redispersibility difficult. The possible reason is that unmodified aluminum hydroxyl is more prone to agglomeration or hard sedimentation in acidic high-aluminum salt systems, making it difficult to maintain a stable dispersion state and to continuously provide usable active aluminum components. Therefore, its storage stability, early coagulation promotion, and later strength development effects are all significantly weaker than those of Example 3.

[0052] In Comparative Example 3, without phytic acid, needle-like crystals appeared after 14 days of storage at 5°C, and the precipitation volume increased to 3.5 mL / 100 mL after 28 days. The strength ratio at 28 days / 90 days was slightly lower than that in Example 3. The possible reason is that phytic acid mainly regulates the local state of aluminum / calcium ions through multidentate coordination, reducing the risk of disordered hydrolysis and crystal growth in the acidic aluminum salt system. When phytic acid is absent, the main body of coagulation is still present, but the low-temperature crystallization, ionic stability and the ability to continuously develop strength in the later stage are significantly worse.

[0053] In Comparative Example 4, the precipitation volume increased to 4.2 mL / 100 mL after 28 days due to the lack of tannic acid. The stratification was obvious, and the redispersion was slow. The strength ratio at 28 days / 90 days was 101% / 103%. The possible reasons are that tannic acid mainly has an adsorption and dispersion effect on aluminum hydroxide particles through polyphenolic hydroxyl groups, reducing the aggregation and sedimentation of gel particles. When tannic acid is lacking, the active aluminum source can still participate in early hydration, but its contribution to suspension stability and later strength maintenance is insufficient.

[0054] In Comparative Example 5, without the addition of aluminum nitrate and calcium nitrate, the compressive strength at 6 hours decreased from 2.35 MPa to 0.88 MPa, the compressive strength at 1 day decreased from 14.6 MPa to 8.2 MPa, and the strength ratio at 28 days / 90 days decreased to 99% / 101%, while the storage stability showed relatively little change. The possible reason is that aluminum nitrate and calcium nitrate mainly serve as auxiliary aluminum sources, early calcium sources, and ionic strength regulators, which can promote the formation of early calcium-aluminum hydration products and support the development of later strength. Without this early strength synergistic component, the development of both early and later strength is insufficient.

[0055] In Comparative Example 6, under conditions of high pH and insufficient acidification, the precipitate volume increased to 6.3 mL / 100 mL after 28 days, with obvious stratification at 40℃, significantly prolonged initial and final coagulation, decreased strength at 6 h / 1 day, and a strength ratio of only 95% / 97% at 28 days / 90 days. The possible reasons are: the acidic stability window helps to inhibit excessively rapid hydrolysis, flocculation, and crystal growth in the high-aluminum salt system; when the pH is high, aluminum species are more likely to undergo hydrolysis and aggregation, resulting in a poorer dispersion of effective aluminum, which in turn affects coagulation, early strength, storage stability, and later strength retention.

[0056] In the comparative example, when hydroxypropyl starch ether was added in excess, the initial viscosity increased to 136 mPa·s, the viscosity change rate increased to +19.8% after 28 days, the redispersion was slow, and the strength at 6 h and 1 day decreased significantly. The strength ratio at 28 days / 90 days was 99% / 100%. The possible reason is that an appropriate amount of hydroxypropyl starch ether helps with suspension stability and anti-stratification, but an excess will form an excessively strong viscous network, affecting the dispersion, pumping, and effective contact efficiency of the liquid accelerator with cement particles, thereby reducing both early hydration efficiency and later strength development.

[0057] Furthermore, considering the adaptability to various cementitious systems, Example 3 maintained a shorter setting time, higher 1-day strength, and a 90-day strength better than that of 28-day cement in ordinary Portland cement, slag cement, and high-admixture cementitious systems. This demonstrates that the technical solution of this application, through the rational combination of aluminum source, nitrate early-strength component, alkanolamine hydration regulator component, and lactic acid / sorbitol / hydroxypropyl starch ether, forms a balanced system for accelerating setting, stabilizing, and developing later-stage strength, exhibiting good adaptability to different cement mineral compositions and admixture conditions. Moreover, the product of this invention simultaneously meets the requirements of being fluorine-free (<0.01%), chlorine-free (<0.01%), and alkali-free (Na2O equivalent 0.05-0.07%).

[0058] Specifically, the "fluorine-free" claim in this application means that no fluorine-containing coagulating components are added to the formula, and the fluoride ion content in the product meets the relevant standards or detection limits.

[0059] Specifically, the "alkali-free" claimed in this application means that the formulation does not contain any external strong alkali, alkali metal silicate or alkali metal carbonate coagulant components, and the alkali content of the product, calculated in terms of Na2O equivalent, meets the relevant limit requirements for alkali-free liquid quick-setting agents.

[0060] Specifically, the "chlorine-free" claim in this application means that no chloride salt coagulant components are added to the formula, and the chloride ion content in the product meets the relevant standards or detection limits.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent, characterized in that, By weight, the following raw materials are included: 44-52 parts aluminum sulfate, 6-12 parts composite modified aluminum hydroxyl wet gel, 2-5 parts aluminum nitrate, 0.6-1.8 parts calcium nitrate, 0.7-1.8 parts diethanol monoisopropanolamine, 1.0-2.2 parts lactic acid, 0.10-0.38 parts hydroxypropyl starch ether, 0.5-1.6 parts sorbitol, and water to make up to 100 parts.

2. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The composite modified aluminum hydroxyl wet gel comprises, by total mass, 18%-25% aluminum hydroxyl solid component, 0.15%-0.65% phytic acid, 0.12%-0.55% tannic acid, 0.3%-1.2% lactic acid and water.

3. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The composite modified aluminum hydroxyl wet gel has a pH of 2.4-3.2 and an effective aluminum content of 10%-14% based on Al2O3.

4. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The aluminum sulfate is aluminum sulfate octadecahydrate, which is a white or light-colored solid in appearance. The effective aluminum content, calculated as Al2O3, is 15%-17%, and the water-insoluble matter content is not higher than 0.2%.

5. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The aluminum nitrate in question is aluminum nitrate nonahydrate.

6. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The calcium nitrate mentioned is calcium nitrate tetrahydrate.

7. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The preparation method of the composite modified aluminum hydroxyl wet gel includes the following steps: S1. Add aluminum hydroxyl wet gel to water to adjust the solid content of the system to 18%-25%, and stir at 400-800 r / min for 20-40 min to obtain aluminum hydroxyl pre-dispersion; S2. Add lactic acid to the aluminum hydroxyl pre-dispersion solution to adjust the pH of the system, and stir at 35-45℃ for 20-30 min; S3. Dilute phytic acid with 5-10 times its mass of water to prepare a phytic acid dilution solution. Under the conditions of stirring at 35-45℃ and 500-900r / min, add it dropwise to the acidified aluminum hydroxyl pre-dispersion solution within 20-40min. After the addition is completed, continue stirring for 30-60min. S4. Dissolve tannic acid in 8-15 times its mass of water to obtain an aqueous solution of tannic acid, add it to the system obtained in step S3 at 30-40℃, and stir for 20-40 minutes. S5. The system obtained in step S4 is sheared and dispersed at 1500-2500 r / min for 15-30 min, and then aged at 25-35℃ for 4-12 h. S6. The pH, solid content and particle size of the system after maturation are detected, and when no hard precipitate is found after standing for 24 hours, the composite modified aluminum hydroxyl wet gel is obtained.

8. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 7, characterized in that, The D50 particle size of the composite modified aluminum hydroxyl wet gel is 0.5-2.5 μm.

9. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 7, characterized in that, In step S2, the pH is adjusted to 2.6-3.

1.

10. The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 1, characterized in that, The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent comprises, by weight, the following raw materials: 49 parts aluminum sulfate, 9.50 parts composite modified aluminum hydroxyl wet gel, 3.60 parts aluminum nitrate, 1.40 parts calcium nitrate, 1.30 parts diethanolamine, 1.60 parts lactic acid, 0.24 parts hydroxypropyl starch ether, 1.20 parts sorbitol, and 32.16 parts water.

11. A method for preparing a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to any one of claims 1-10, characterized in that, The preparation method includes the following steps: Step 1: Heat some water to 60-70℃, add aluminum sulfate, and stir at 300-600r / min for 40-70min to form an aluminum salt solution; Step 2: Lower the system temperature to 45-55℃, add lactic acid, sorbitol and diethanol monoisopropanolamine, stir for 20-40 minutes to obtain acidic complex aluminum salt mother liquor; Step 3: Add the composite modified aluminum hydroxyl wet gel at 45-55℃, stir at 500-800 r / min for 20-30 min, and then shear and disperse at 1200-1800 r / min for 10-20 min to ensure that the composite modified aluminum hydroxyl is uniformly dispersed in the aluminum salt mother liquor. Step 4: Add aluminum nitrate and calcium nitrate, and stir at 40-50℃ for 20-35 minutes; Step 5: Lower the system temperature to 30-40℃, add hydroxypropyl starch ether, and shear and disperse at 1500-2500 r / min for 15-30 min; Step six: Add the remaining water, filter, and a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent is obtained.

12. The method for preparing a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 11, characterized in that, In step five, the system temperature needs to be lowered to 30-40℃ before adding hydroxypropyl starch ether.

13. The method for preparing a fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent according to claim 11, characterized in that, The fluorine-free, alkali-free, and chlorine-free liquid quick-setting agent has a pH of 2.6-3.3, a viscosity of 45-110 mPa·s, and a solid content of 45%-56%.

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