Environment-friendly low-dosage alkali-free accelerator and preparation method thereof

Abstract

The invention discloses an environment-friendly low-dosage alkali-free accelerator and a preparation method thereof, and belongs to the technical field of accelerators. The method comprises the following steps: performing closed hydrolysis and acid dissolution treatment on aluminum ash to obtain an aluminum-containing active component; drying and grinding the desulfurized gypsum into active gypsum powder; and carrying out composite reaction on the two substances and the pretreated waste acid under specific conditions, and adding organic alcohol amine and a polymer stabilizer to modulate and age to finally prepare a target product. The accelerator is low in alkali content, low in ammonia release amount, small in mixing amount, capable of enabling concrete to be rapidly coagulated, high in later strength retention rate, excellent in anti-freezing and anti-seepage durability and good in storage stability. According to the invention, industrial wastes such as aluminum ash, desulfurized gypsum, waste acid and the like are successfully converted into high-performance green building materials, the purpose of treating wastes with wastes is realized, and outstanding environmental protection benefits and economic benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of accelerator technology, and in particular to an environmentally friendly, low-dosage, alkali-free accelerator and its preparation method. Background Technology

[0002] Accelerators are key materials in shotcrete construction, enabling concrete to set and harden within minutes. Traditional powdered alkali metal accelerators and some liquid accelerators have drawbacks such as high alkali content, significant later-stage strength loss, susceptibility to alkali-aggregate reaction, strong corrosiveness, and poor environmental performance. To overcome these shortcomings, alkali-free liquid accelerators have become a development trend, but their core raw materials (such as aluminum hydroxide, pure sulfuric acid, and industrial-grade aluminum sulfate) are expensive.

[0003] Meanwhile, my country generates large quantities of aluminum ash (hazardous waste HW48), desulfurization gypsum (byproduct of coal-fired power plants), and waste acid (such as steel pickling waste liquid) annually, placing enormous pressure on the environment due to their storage and disposal. While existing technologies have attempted to utilize single waste materials to prepare building materials, a systematic and mature solution for the co-processing of multiple large-scale industrial wastes and their conversion into high-performance alkali-free quick-setting agents has yet to be found. The technical challenge lies in the complex and fluctuating composition of the wastes, and the presence of harmful impurities (such as Cl). - ,F - The high content of alkali metals makes them difficult to utilize directly. How to transform impurities into harmless components or effectively remove them through precise pretreatment and synthesis process design, and stably produce high-performance accelerators that meet engineering requirements, is an urgent problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing an environmentally friendly, low-dosage, alkali-free quick-setting agent and its preparation method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention first proposes a method for preparing an environmentally friendly, low-dosage, alkali-free quick-setting agent, comprising the following steps:

[0007] S1. Raw material pretreatment:

[0008] S1.1. Aluminum ash pretreatment: The aluminum ash is hydrolyzed, and after solid-liquid separation, an aluminum-containing filter cake is obtained; the aluminum-containing filter cake is reacted with waste acid to obtain an Al-containing... 3+ Acidic aluminum salt solution;

[0009] Under sealed conditions, metallic aluminum in aluminum ash undergoes a hydrolysis reaction with water, producing aluminum hydroxide and ammonia gas.

[0010] ;

[0011] In actual hydrolysis, the reaction between metallic aluminum and water is slow. Closed conditions can improve the reaction efficiency. Ammonia mainly comes from the hydrolysis side reaction of trace nitrogen compounds in aluminum ash.

[0012] The aluminum-containing filter cake (Al(OH)3) reacts with waste acid (sulfuric acid) to produce an acidic aluminum sulfate solution.

[0013] ;

[0014] The inert aluminum compounds in aluminum ash are converted into water-soluble, highly active Al. 3+ The source (aluminum sulfate) is removed, while some insoluble impurities, such as silicon oxide, are also removed to ensure the purity of the core components that accelerate condensation.

[0015] S1.2. Pretreatment of desulfurized gypsum: The desulfurized gypsum is dried and ground to obtain active gypsum powder;

[0016] Desulfurized gypsum is mainly calcium sulfate dihydrate (CaSO4·2H2O), which has low natural activity and large particles. It needs to be activated by a dual process of "drying + grinding". During drying, the dihydrate gypsum loses some of its water of crystallization and is converted into hemihydrate gypsum (CaSO4·0.5H2O). The reaction formula is as follows:

[0017] ;

[0018] Specific surface area after grinding ≥400m² 2 / kg, the particle size is reduced, the surface energy is significantly increased, and the number of active sites increases.

[0019] The removal of water of crystallization transforms gypsum from an inert state into a hemihydrate gypsum with gelling activity. Fine grinding further enhances its reactivity, providing highly active SO4 for subsequent rapid setting in conjunction with aluminum sulfate. 2- source.

[0020] S1.3. Waste acid pretreatment: The waste acid is subjected to sedimentation and filtration to obtain clarified waste acid;

[0021] Waste sulfuric acid from steel pickling and chemical byproducts contains suspended solids (such as Fe(OH)3 and silt) and soluble impurities (such as Fe). 2+ Fe 3+ After sedimentation and filtration:

[0022] Physical change: Solid-liquid separation removes insoluble impurities and avoids the formation of iron-containing precipitates in subsequent reactions, which would affect the uniformity of the quick-setting agent;

[0023] Chemical changes: Some soluble impurities (such as Fe) 3+ The aluminum sulfate solution is removed by hydrolysis and sedimentation to ensure the purity of the subsequent aluminum sulfate solution and avoid impurities interfering with cement hydration.

[0024] S2. Synthesis reaction: Add 100 parts of acidic aluminum salt solution to the reaction vessel, and under stirring conditions, add 50-80 parts of active gypsum powder. React at 80-100℃ for 2-4 hours to form a mixed slurry.

[0025] Under stirring conditions at 80-100℃, acidic aluminum salt solution (aluminum sulfate) reacts with activated gypsum powder for 2-4 hours. The core process is the formation of a highly active mixed slurry of "aluminum sulfate calcium double salt + activated hemihydrate gypsum". The physicochemical changes are as follows:

[0026] Aluminum sulfate (Al2(SO4)3) provides Al 3+ Activated gypsum (CaSO4・0.5H2O) provides Ca 2+ and SO4 2- At medium to high temperatures, a double salting reaction occurs, producing alunite-type double salt (3CaO・Al2O3・3CaSO4・32H2O). The reaction equation is as follows:

[0027] ;

[0028] Complex salts (alumite type) are "rapid-setting precursors" for cement hydration. They have higher reactivity than single aluminum sulfate or gypsum and can quickly trigger the hydration reaction when mixed with cement.

[0029] A reaction temperature of 80-100℃ accelerates ion diffusion and crystal growth, ensuring the integrity and stability of the double salt formation, while inhibiting secondary crystallization and agglomeration of gypsum, thus ensuring the uniformity of the slurry.

[0030] S3. Stabilization and Modulation: Cool the mixed slurry to below 40°C, add organic alcohol amine compounds and polymer stabilizers in sequence, stir evenly, add water to adjust to the target density, and age to obtain an environmentally friendly alkali-free liquid quick-setting agent;

[0031] After the mixed slurry is cooled to below 40°C, organic alcohol amines and polymeric stabilizers are added and the mixture is aged. The core principle is to regulate the rapid setting rate and improve storage stability through the synergistic effect of organic and inorganic materials.

[0032] The organic alcohol amine compound is at least one of triethanolamine and triisopropanolamine, and the amount added is 15-25 parts;

[0033] The polymeric stabilizer is at least one of polyacrylamide and polyvinylpyrrolidone, and the amount added is 0.5-2 parts.

[0034] Preferably, in step S1.1, the hydrolysis treatment is carried out under closed conditions, and the generated ammonia gas is treated by an absorption system; the waste acid is waste sulfuric acid from steel pickling or by-product sulfuric acid from chemical production.

[0035] Preferably, in step S1.2, the drying temperature is 120-180℃; the specific surface area of ​​the gypsum powder after grinding is ≥400m². 2 / kg.

[0036] Preferably, the aging process is carried out at 10-40℃ for 24-72 hours under stirring conditions.

[0037] Aging at 10-40℃ for 24-72 hours allows the complex salt crystals to grow slowly and perfect the lattice. The organic additives and inorganic phases interact fully, and the system tends to be thermodynamically stable, avoiding fluctuations in the rapid solidification effect due to incomplete reaction during use.

[0038] This invention also proposes an environmentally friendly, low-dosage, alkali-free quick-setting agent prepared by the aforementioned method, wherein the quick-setting agent has a pH value of 1.5-4.0 and a density of 1.30-1.45 g / cm³ at 20°C. 3 Its alkali content is less than 1.0% based on Na2O equivalent.

[0039] This invention also proposes the application of environmentally friendly alkali-free liquid quick-setting agent in shotcrete, slope protection, tunnel engineering, or building repair and reinforcement projects.

[0040] Compared with the prior art, the beneficial effects of the present invention are:

[0041] 1. The alkali-free design eliminates the durability risks of traditional alkaline accelerators at the mechanistic level, solving the pain point of "high alkali leading to deterioration" in existing technologies:

[0042] Most mainstream quick-setting agents in existing technologies are sodium-based or potassium-based alkaline systems (alkaline content usually >3%). Their core mechanism is to accelerate the hydration of cement C3A to form ettringite through high concentrations of OH-, thereby achieving quick setting. However, high concentrations of alkaline ions (Na+) can lead to this problem. + K + Alkaline aggregates react with active silica in concrete aggregates to undergo alkali-aggregate reaction (AAR), generating expansive products that lead to structural cracking and reduced durability. Furthermore, the alkaline system poses a corrosive hazard to the construction environment and personnel. This invention, through mechanistic innovation, uses solid waste / wastewater such as aluminum ash, desulfurized gypsum, and waste acid as raw materials. Through acid dissolution and double salt synthesis, it constructs an alkali-free system of "acidic aluminum salt-active gypsum-organic alcohol amine," with an alkali content (Na2O equivalent) of less than 1.0%, eliminating the introduction of high-alkali ions at the source. Simultaneously, its rapid setting mechanism relies on the highly active Ca provided by the dissociation of the double salt. 2+ Al 3+ SO4 2- It reacts with cement C3A to form stable ettringite, rather than relying on OH. -Catalysis ensures rapid setting while completely avoiding the risk of alkali-aggregate reaction, significantly improving the long-term service stability of shotcrete. It is suitable for engineering scenarios with high durability requirements, such as tunnels and slope protection, and solves the technical bottleneck of the "contradiction between rapid setting and durability" of existing alkaline quick-setting agents.

[0043] 2. The multi-component synergistic mechanism achieves a synergistic improvement in "rapid setting and strength," solving the problem of "strength reduction" in existing technologies:

[0044] In existing technologies, single aluminum sulfate-based quick-setting agents rely on high concentrations of Al. 3+ Rapid formation of ettringite achieves rapid setting, but Al 3 + Rapid release can easily lead to "flash setting," and the uneven distribution of hydration products and high porosity in the later stages result in sufficient early strength but a decline in strength after 28 days (the loss rate is usually >15%). Meanwhile, single gypsum-based quick-setting agents have insufficient activity and poor quick-setting effect. This invention addresses these pain points through a synergistic mechanism of "double salt formation - organic regulation": On the one hand, the alumite-type double salt (3CaO・Al2O3・3CaSO4・32H2O) generated in the synthesis reaction acts as a highly active quick-setting precursor, with 3-5 times higher reactivity than single aluminum sulfate or gypsum, and can rapidly trigger the formation of ettringite at low dosages, ensuring early quick setting and strength; on the other hand, organic alcohol amines (triethanolamine, triisopropanolamine) and Al... 3+ Formation of complexes, precise regulation of Al 3+ The release rate is improved to avoid flash setting, while promoting the hydration of cement C3S to generate CSH gel (the core source of concrete's later strength). The active gypsum inhibits the excessive hydration of C3A to generate the low-strength AFm phase. The three work synergistically to form a uniform and dense three-dimensional network structure between ettringite and CSH gel, significantly reducing the internal porosity of concrete and achieving early rapid setting (initial setting ≤ 5 min) and stable later strength (28-day strength loss ≤ 10%), completely solving the core contradiction of "rapid setting and strength reduction" in existing technologies.

[0045] 3. The synergistic mechanism of solid waste resource utilization and high activity achieves a balance between environmental protection and low dosage, overcoming the shortcomings of existing technologies such as "high consumption and high dosage":

[0046] Existing quick-setting agents mostly use virgin chemical raw materials (such as pure aluminum sulfate and virgin gypsum). The preparation process consumes a lot of resources and has high carbon emissions. Moreover, due to the insufficient activity of single components, the actual dosage is usually 6%-8% of the cement mass, which not only increases construction costs but may also affect the workability of concrete. Some solid waste-based quick-setting agents have problems such as large dosage and unstable quick-setting effect due to insufficient pretreatment of raw materials and low activity. This invention achieves a dual breakthrough in "environmental protection" and "low dosage" through innovative solid waste pretreatment and complex salt synthesis mechanisms: Firstly, at the raw material level, the pretreatment mechanism of aluminum ash hydrolysis-acid dissolution, desulfurized gypsum drying-grinding, and waste acid sedimentation filtration transforms industrial solid waste / waste liquids such as aluminum ash, desulfurized gypsum, and waste acid into high-purity, high-activity reaction raw materials (acidic aluminum salt solution and active hemihydrate gypsum), realizing the resource utilization of solid waste, reducing solid waste stockpiling pollution and consumption of raw materials, and the preparation process has no toxic gas emissions, making it significantly more environmentally friendly than existing technologies. Secondly, at the functional level, through the synergistic effect mechanism of complex salts, gypsum, and organic alcohol amines, the complex salts provide a highly active ion source, gypsum assists in cementation, and organic alcohol amines act as a coagulation catalyst to reduce the critical dosage of accelerators, so that the dosage of accelerators in this invention is only 3%-5% of the cement mass, far lower than existing technologies, which reduces construction costs and minimizes the interference of accelerators on the performance of concrete matrices, achieving a balance between environmental and engineering benefits. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0048] Example 1: A method for preparing an environmentally friendly, low-dosage, alkali-free quick-setting agent, comprising the following steps:

[0049] S1. Raw material pretreatment:

[0050] S1.1. Aluminum ash pretreatment: The aluminum ash is hydrolyzed, and after solid-liquid separation, an aluminum-containing filter cake is obtained; the aluminum-containing filter cake is reacted with waste acid to obtain an Al-containing... 3+ Acidic aluminum salt solution;

[0051] S1.2. Pretreatment of desulfurized gypsum: The desulfurized gypsum is dried and ground to obtain active gypsum powder;

[0052] S1.3. Waste acid pretreatment: The waste acid is subjected to sedimentation and filtration to obtain clarified waste acid;

[0053] S2. Synthesis reaction: Add 100 kg of acidic aluminum salt solution to the reactor, add 50 kg of active gypsum powder under stirring, react at 90 °C for 3 h to form a mixed slurry;

[0054] S3. Stabilization and Modulation: Cool the mixed slurry to below 40°C, add organic alcohol amine compounds and polymer stabilizers in sequence, stir evenly, add water to adjust to the target density, and age to obtain an environmentally friendly alkali-free liquid quick-setting agent;

[0055] The organic alcohol amine compound is at least one of triethanolamine and triisopropanolamine, and the amount added is 25 kg.

[0056] The polymeric stabilizer is at least one of polyacrylamide and polyvinylpyrrolidone, and the addition amount is 0.5 kg.

[0057] In S1.1, the hydrolysis treatment is carried out under closed conditions, and the generated ammonia gas is treated by an absorption system; the waste acid is sulfuric acid from steel pickling or sulfuric acid from chemical byproducts.

[0058] In step S1.2, the drying temperature is 150℃; the specific surface area of ​​the gypsum powder after grinding is ≥400m². 2 / kg.

[0059] In step S3, the aging process is performed by aging at 30°C for 48 hours under stirring conditions.

[0060] Example 2: A method for preparing an environmentally friendly, low-dosage, alkali-free quick-setting agent, comprising the following steps:

[0061] S1. Raw material pretreatment:

[0062] S1.1. Aluminum ash pretreatment: The aluminum ash is hydrolyzed, and after solid-liquid separation, an aluminum-containing filter cake is obtained; the aluminum-containing filter cake is reacted with waste acid to obtain an Al-containing... 3+ Acidic aluminum salt solution;

[0063] S1.2. Pretreatment of desulfurized gypsum: The desulfurized gypsum is dried and ground to obtain active gypsum powder;

[0064] S1.3. Waste acid pretreatment: The waste acid is subjected to sedimentation and filtration to obtain clarified waste acid;

[0065] S2. Synthesis reaction: Add 100 kg of acidic aluminum salt solution to the reactor, add 65 kg of active gypsum powder under stirring, react at 90°C for 3 h to form a mixed slurry;

[0066] S3. Stabilization and Modulation: Cool the mixed slurry to below 40°C, add organic alcohol amine compounds and polymer stabilizers in sequence, stir evenly, add water to adjust to the target density, and age to obtain an environmentally friendly alkali-free liquid quick-setting agent;

[0067] The organic alcohol amine compound is at least one of triethanolamine and triisopropanolamine, and the amount added is 20 kg;

[0068] The polymeric stabilizer is at least one of polyacrylamide and polyvinylpyrrolidone, and the addition amount is 1 kg.

[0069] In S1.1, the hydrolysis treatment is carried out under closed conditions, and the generated ammonia gas is treated by an absorption system; the waste acid is sulfuric acid from steel pickling or sulfuric acid from chemical byproducts.

[0070] In step S1.2, the drying temperature is 150℃; the specific surface area of ​​the gypsum powder after grinding is ≥400m². 2 / kg.

[0071] In step S3, the aging process is performed by aging at 30°C for 48 hours under stirring conditions.

[0072] Example 3: A method for preparing an environmentally friendly, low-dosage, alkali-free quick-setting agent, comprising the following steps:

[0073] S1. Raw material pretreatment:

[0074] S1.1. Aluminum ash pretreatment: The aluminum ash is hydrolyzed, and after solid-liquid separation, an aluminum-containing filter cake is obtained; the aluminum-containing filter cake is reacted with waste acid to obtain an Al-containing... 3+ Acidic aluminum salt solution;

[0075] S1.2. Pretreatment of desulfurized gypsum: The desulfurized gypsum is dried and ground to obtain active gypsum powder;

[0076] S1.3. Waste acid pretreatment: The waste acid is subjected to sedimentation and filtration to obtain clarified waste acid;

[0077] S2. Synthesis reaction: 100 kg of acidic aluminum salt solution is added to the reaction vessel, and 80 kg of active gypsum powder is added under stirring conditions. The reaction is carried out at 90°C for 3 hours to form a mixed slurry.

[0078] S3. Stabilization and Modulation: Cool the mixed slurry to below 40°C, add organic alcohol amine compounds and polymer stabilizers in sequence, stir evenly, add water to adjust to the target density, and age to obtain an environmentally friendly alkali-free liquid quick-setting agent;

[0079] The organic alcohol amine compound is at least one of triethanolamine and triisopropanolamine, and the amount added is 15 kg.

[0080] The polymeric stabilizer is at least one of polyacrylamide and polyvinylpyrrolidone, and the addition amount is 2 kg.

[0081] In S1.1, the hydrolysis treatment is carried out under closed conditions, and the generated ammonia gas is treated by an absorption system; the waste acid is sulfuric acid from steel pickling or sulfuric acid from chemical byproducts.

[0082] In step S1.2, the drying temperature is 150℃; the specific surface area of ​​the gypsum powder after grinding is ≥400m². 2 / kg.

[0083] In step S3, the aging process is performed by aging at 30°C for 48 hours under stirring conditions.

[0084] The following comparison model was also set:

[0085] Comparative Example 1: Based on Example 2, the difference is that aluminum ash, desulfurized gypsum and waste acid are not used, and reagent-grade aluminum hydroxide is used to react with pure sulfuric acid to prepare aluminum sulfate solution. The rest is the same as Example 2.

[0086] Comparative Example 2: Based on Example 2, the difference is that desulfurized gypsum is not used, and pure sulfuric acid is used to directly adjust the sulfate concentration of the system to be the same as in Example 2. The rest is the same as in Example 2.

[0087] Comparative Example 3: Based on Example 2, the difference is that aluminum ash is directly reacted with waste acid to undergo acid dissolution, skipping the hydrolysis and solid-liquid separation steps, while the rest is the same as Example 2.

[0088] Comparative Example 4: Based on Example 2, the difference is that in S3, after adding water and preparing the mixture, it is not aged but directly filtered and packaged. The rest is the same as in Example 2.

[0089] Performance testing: Setting time, 1-day and 28-day compressive strength of mortar, and 14-day bond strength ratio of mortar were tested according to GB / T 35159-2017 "Accelerating agents for shotcrete"; ammonia release was tested according to GB 18588-2001 "Limits for ammonia release from concrete admixtures"; and the durability of hardened concrete was tested according to GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The results are shown in Table 1.

[0090] Table 1. Test results of various properties of the accelerator

[0091]

[0092] Data Analysis:

[0093] The core mechanism of aluminum ash hydrolysis pretreatment lies in completely eliminating the negative effects of aluminum nitride (AlN) and soluble salts. Comparative Example 3 (without deep hydrolysis) showed an ammonia release rate as high as 0.21%, far exceeding other groups (≤0.03%), directly confirming that residual AlN reacts with water in the later stages to release ammonia. A high-ammonia environment not only endangers construction safety but also interferes with the normal hydration process of cement paste, leading to a significant extension of its setting time (initial setting 7.2 min, final setting 16.8 min) and severely impaired strength (28-day strength ratio only 69.4%). Simultaneously, soluble salts (such as Cl-)... - ,K + Na + The residue of alkali metals resulted in a high alkali content and compromised the compactness of the slurry structure, which together led to the lowest durability indicators such as freeze resistance (F50) and impermeability (P4) among all groups. In stark contrast, Examples 1-3 effectively controlled the ammonia and alkali metal content through thorough hydrolysis and solid-liquid separation, providing a pure and highly active aluminum-containing precursor for subsequent synthesis reactions.

[0094] The introduction of desulfurized gypsum constructed an "aluminum-calcium-sulfur" composite coagulation system, the core mechanism of which is the regulation of the nucleation and growth kinetics of ettringite (AFt). Data from Comparative Example 2 (without desulfurized gypsum) fully demonstrates this: although its ammonia release and alkali content control are acceptable, the lack of a stable and continuous calcium and sulfate source results in insufficient ettringite formation rate and quantity, leading to inadequate setting and hardening kinetics. Its final setting time (13.4 min) exceeds the standard, and its 1-day and 28-day strengths are only 76% and 84% of those of Example 1, respectively. This is because ettringite is not only the main contributor to early strength, but its interlocked crystal structure also forms the framework for later microstructural densification. The absence of this framework directly leads to a significant decline in durability (freeze-thaw resistance F100, impermeability P6). In the embodiment, the pretreated active gypsum powder gradually dissolves in an acidic aluminum salt solution, forming a large number of uniform and fine ettringite crystals with aluminate ions, thereby achieving rapid solidification and high early strength, and laying the structural foundation for excellent long-term performance (freezing resistance F200 and impermeability P8 and above).

[0095] The core mechanism of organic alcohol amines (such as triethanolamine) lies in their dual role of complexation stabilization and catalytic regulation. The performance of Comparative Example 4 (without organic alcohol amines) indirectly confirms this function: although its ammonia release and alkali content were well controlled, the product exhibited "partial precipitation" in storage stability, and all strength and durability indicators were significantly lower than those of the examples. This is because organic alcohol amines can form stable complexes with metal ions such as aluminum ions, preventing hydrolysis precipitation or adverse pre-reactions during storage, thus ensuring product homogeneity and shelf life (as shown by the acceptable storage stability in the examples). During cement hydration, this complex can gradually release aluminum ions, reacting in an orderly manner with calcium and sulfate ions provided by gypsum to form a more uniform ettringite network, resulting in a higher later-stage strength ratio (>98% in the examples, 86.2% in Comparative Example 4) and better durability (freezing resistance F80 vs F200). Furthermore, it can catalyze the early hydration of tricalcium silicate (C3S), further improving 1-day strength.

[0096] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly, low-dosage, alkali-free quick-setting agent, characterized in that, Includes the following steps: S1. Raw material pretreatment: S1.

1. Aluminum ash pretreatment: The aluminum ash is hydrolyzed, and after solid-liquid separation, an aluminum-containing filter cake is obtained; the aluminum-containing filter cake is reacted with waste acid to obtain an Al-containing... 3+ Acidic aluminum salt solution; S1.

2. Pretreatment of desulfurized gypsum: The desulfurized gypsum is dried and ground to obtain active gypsum powder; S1.

3. Waste acid pretreatment: The waste acid is subjected to sedimentation and filtration to obtain clarified waste acid; S2. Synthesis reaction: Add 100 parts of acidic aluminum salt solution to the reaction vessel, and under stirring conditions, add 50-80 parts of active gypsum powder. React at 80-100℃ for 2-4 hours to form a mixed slurry. S3. Stabilization and Modulation: Cool the mixed slurry to below 40°C, add organic alcohol amine compounds and polymer stabilizers in sequence, stir evenly, add water to adjust to the target density, and age to obtain an environmentally friendly alkali-free liquid quick-setting agent; The organic alcohol amine compound is at least one of triethanolamine and triisopropanolamine, and the amount added is 15-25 parts; The polymeric stabilizer is at least one of polyacrylamide and polyvinylpyrrolidone, and the amount added is 0.5-2 parts.

2. The preparation method of an environmentally friendly, low-dosage, alkali-free quick-setting agent according to claim 1, characterized in that, In S1.1, the hydrolysis treatment is carried out under closed conditions, and the generated ammonia gas is treated by an absorption system; the waste acid is sulfuric acid from steel pickling or sulfuric acid from chemical byproducts.

3. The preparation method of an environmentally friendly, low-dosage, alkali-free quick-setting agent according to claim 1, characterized in that, In step S1.2, the drying temperature is 120-180℃; the specific surface area of ​​the gypsum powder after grinding is ≥400m². 2 / kg.

4. The preparation method of an environmentally friendly, low-dosage, alkali-free quick-setting agent according to claim 1, characterized in that, In step S3, the aging process involves aging at 10-40°C for 24-72 hours under stirring conditions.

5. An environmentally friendly, low-dosage, alkali-free quick-setting agent prepared by any one of the preparation methods described in claims 1-6, characterized in that, The quick-setting agent has a pH value of 1.5-4.0 and a density of 1.30-1.45 g / cm³ at 20°C. 3 Its alkali content is less than 1.0% based on Na2O equivalent.

6. The application of the environmentally friendly alkali-free liquid quick-setting agent as described in claim 5 in shotcrete, slope protection, tunnel engineering or building repair and reinforcement engineering.

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