Novel alcohol amine series high-aluminum fluoride-free chloride-free alkali-free accelerator and preparation process thereof

Abstract

The invention relates to the field of concrete accelerators, and discloses a novel alcohol amine series high-aluminum fluoride-free chloride-free alkali-free accelerator and a preparation process thereof, and the accelerator is composed of the following components by weight: 42-48% of high-aluminum aluminum sulfate; 6%-10% of ferrous sulfate; 3%-4% of N-methyldiethanolamine; 4%-5% of diethanol amine; 0.8%-1.2% of citric acid; 1.5%-2.5% of sodium fluosilicate; 0.1%-0.3% of nano silicon dioxide; 1%-2% of triisopropanolamine; nano aluminum oxide; 0.2% to 0.4%; and the balance of deionized water. The mass content of aluminum oxide in the high-aluminum aluminum sulfate is 17.5%-18.5%. According to the preparation method disclosed by the invention, the accelerator with ultrahigh storage stability, coagulation accelerating effect, excellent mechanical strength and uniform batch height is obtained by virtue of synergistic stabilization of complex alcohol amine and nano silicon dioxide and combination of microwave activation and a two-step process.

Description

Technical Field

[0001] This invention relates to the field of concrete accelerators, specifically to a novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free accelerator and its preparation process. Background Technology

[0002] In modern engineering construction, we often encounter special construction environments. For example, when excavating tunnels and mine roadways, the sprayed concrete needs to adhere to the rock face instantly; or when dealing with dam leaks or carrying out underwater emergency repairs, every second is crucial, and the sealing material must solidify immediately. In these scenarios, conventional cement simply cannot meet the requirements. Therefore, an admixture that enables cement to "follow orders" and harden instantly—a liquid accelerator—has become an indispensable key material.

[0003] To address these needs, existing technologies have developed alkali-free liquid accelerators. These products offer greater convenience compared to earlier powdered or strongly alkaline accelerators. First, being liquid, they can be directly pumped through pipelines and added automatically, allowing for precise metering and ease of use, significantly reducing dust pollution at construction sites. Second, because they do not contain strongly alkaline substances, they are much less corrosive to the skin of construction workers and less harmful to the environment. Furthermore, their production process is relatively straightforward, typically involving simple mixing of several raw materials in a reaction vessel, requiring less sophisticated equipment, which helps control production barriers and costs.

[0004] However, it is precisely this "simple and direct" technical approach that has exposed its inherent flaws in long-term application. First, product stability remains a persistent hurdle. Relying solely on a single complexing agent is insufficient to contain high concentrations of active components, leading to precipitation after only a short time. Second, many products, in pursuit of faster setting, often compromise the final strength of the cement, resulting in a net loss. Furthermore, the preparation methods are too mild, merely involving simple physical mixing, failing to stimulate the deep activity of the core components, thus limiting the product's performance to a visible ceiling. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent and its preparation process, solving the problem that existing liquid quick-setting agents generally suffer from performance degradation due to system instability, easy stratification and precipitation during storage.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent, wherein the quick-setting agent is composed of the following components by weight percentage: High-alumina aluminum sulfate: 42%-48%, wherein the alumina content of the high-alumina aluminum sulfate is 17.5%-18.5% by mass, the sulfate content is controlled to be no higher than 0.6% by mass, and its water-insoluble matter content is no higher than 0.05% by mass; high-alumina aluminum sulfate is the main source of aluminum ions. The intention in selecting it is not only to provide aluminum ions, but also because of its inherent property of "high aluminum". This selection forms the cornerstone of the entire technical solution, which means that a high-concentration active aluminum ion environment can be established in aqueous solution at a relatively low solid content. This highly active environment is the driving force for rapid coagulation; Ferrous sulfate: 6%-10%, specifically in the form of crystalline ferrous sulfate heptahydrate, exhibiting a light blue-green appearance, and possessing an industrial purity of not less than 98.0%. Ferrous sulfate acts as a synergistic coagulant in this system. The ferrous ions it provides also exhibit coagulant-promoting effects in alkaline environments, forming a synergistic effect with aluminum ions to regulate and optimize the final setting time characteristics of the accelerator. Simultaneously, the introduction of iron ions also plays a regulatory role in the color and some later-stage properties of the final product. N-Methyldiethanolamine: 3%-4%, wherein the N-methyldiethanolamine and diethanolamine together constitute an alkanolamine complex system, and the molar ratio of aluminum ions provided by the high-alumina aluminum sulfate to the total molar ratio of the alkanolamine complex system is 1.2:1-1.5:1; Diethanolamine: 4%-5%; N-methyldiethanolamine and diethanolamine are the core stabilizing and complexing units. They together constitute a complex alkanolamine system, the fundamental function of which is to form a stable but controllable-activity complex with high concentrations of active aluminum ions. The mechanism of this design is that, without stabilization, high concentrations of aluminum ions in aqueous solution are prone to hydrolysis, polymerization, and even precipitation, leading to product failure. Through the complexation of alkanolamines, unstable free aluminum ions are converted into stable complexed aluminum ions, thereby endowing the liquid quick-setting agent with the necessary storage stability. The combination of two alkanolamines with different structures is a key point in the construction of the complex system; Citric acid: 0.8%-1.2%. Citric acid acts as a pre-complexing protectant. Its mechanism of action lies in its multi-carboxyl group structure, which pre-forms a temporary, weaker complex with some aluminum ions before the main complexing reaction occurs. This component provides a buffer during the preparation process for the subsequent stronger and more stable amine complexing reaction, preventing uncontrollable side reactions under localized reaction conditions. Sodium fluorosilicate: 1.5%-2.5%. Sodium fluorosilicate acts as a functional synergistic reinforcing agent. Its function is to react with cement hydration products after the accelerator is mixed with cement to generate active substances that promote hydration. This is of great significance for improving the adaptability of accelerators to certain specific types of cement or cements with lower activity. Nano-silica: 0.1%-0.3%, wherein the physical morphology of the nano-silica is characterized by its specific surface area, which ranges from 150 μm. 2 / g-250m 2 / g; Nano-sized silica plays a dual role in accelerators, providing both physical stability and enhancing the microstructure. Its function lies in the fact that nano-sized silica particles possess a huge specific surface area and surface energy, enabling them to form a stable three-dimensional network structure in liquid systems. It provides numerous adsorption nuclei for the already formed alkanolamine-aluminum complex, physically inhibiting the aggregation and sedimentation of the complex particles, thus constituting another layer of physical stability in addition to chemical complexation stability. Triisopropanolamine: 1%-2%. Triisopropanolamine can accelerate the dissolution of aluminates through the synergistic effect of polyolamines, and improve the 1-day compressive strength (by 10%-15%). It also adsorbs on the surface of cement particles, improving particle dispersibility, so that water and accelerator components can contact cement more evenly, thus improving reaction efficiency. On the other hand, it can also complex with ions in the hydration process, playing a regulatory role in the later hydration process and strength development. Its unique timing of addition determines that its main function is biased towards the optimization of the final product performance and its contribution to long-term stability. Nano-alumina (0.2%-0.4%) has higher surface activity, reacts more fully with high-alumina aluminum sulfate, reduces setting time fluctuations, and has extremely high specific surface area and surface energy. In cement paste, it can serve as an ideal nucleus for heterogeneous nucleation, greatly promoting the nucleation and growth of hydration products and accelerating the hydration process. The tiny size of nano-alumina can fill the micropores formed by early hydration products, optimizing the pore structure of the paste and making the structure of the early hardened body more compact. Deionized water: Balance. Deionized water serves as the solvent and carrier for all components, providing the necessary medium environment for all chemical reactions and physical dispersion processes.

[0007] This invention also provides a preparation process for a novel alkanolamine-based high-aluminum, fluorine-free, chlorine-free, and alkali-free quick-setting agent, comprising the following steps: S1. Premixing: In a reaction vessel, citric acid, which serves as a complexing protectant, and sodium fluorosilicate, which serves as a synergistic enhancer, are added to deionized water at a temperature below 35°C and dissolved by stirring to prepare a premixed solution. S2, Microwave activation and dissolution: Add high-alumina aluminum sulfate to the premixed solution prepared in step S1, and then use microwave heating to raise the temperature of the mixture to the range of 75℃-85℃, and maintain the temperature until the high-alumina aluminum sulfate is completely dissolved, thereby forming a high-temperature mother liquor. S3. Addition of synergistic components: In the high-temperature mother liquor formed in step S2, ferrous sulfate heptahydrate, nano-alumina and nano-silica are added sequentially and mixed. S4. Forced cooling: The mixture system obtained in step S3 is subjected to active cooling treatment to reduce the overall temperature from above 80°C to below 50°C in order to obtain a low-temperature reaction system. S5. Two-step complexation reaction: In the low-temperature reaction system prepared in step S4, N-methyldiethanolamine, as the first component of the alcoholamine complex system, is first added to carry out the first step reaction. Then, diethanolamine, as the second component of the alcoholamine complex system, is added to carry out the second step complexation reaction. Finally, triisopropanolamine is added to obtain the novel alcoholamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent.

[0008] Preferably, in step S2, raising the temperature of the mixture to the range of 75℃-85℃ using microwave heating includes: Start a microwave generator with a power setting of 800W-1000W and apply a microwave energy field to the hybrid system; The application of the microwave energy field is not continuous heating, but rather adopts a preset intermittent working mode. The intermittent working mode is specifically defined as a cycle containing a 30-second microwave heating phase and a 15-second energy pause phase. By repeatedly executing the cycle of the intermittent working mode, the overall temperature of the mixing system is raised from the initial temperature to the target range of 75℃-85℃ within a total processing time of 8-12 minutes. Microwave energy acts directly on polar molecules, achieving molecular-level internal heating through high-frequency oscillations. This is fundamentally different from traditional heat conduction, which transfers heat from the container wall inwards. This heating method can instantaneously create high-energy regions at the molecular level. The setting of the "interval period" is crucial, providing the system with a brief relaxation time, allowing energy to redistribute between molecules and avoiding localized overheating, boiling over, and uncontrollable side reactions caused by continuous energy injection. The goal is to gently and efficiently form a uniformly distributed "metastable, highly active hydrated aluminum ions."

[0009] Preferably, in step S3, the sequential addition and mixing of ferrous sulfate heptahydrate, nano-alumina, and nano-silica includes: Add the formula-measured amount of ferrous sulfate heptahydrate to the high-temperature mother liquor, and after adding it, bubble the mother liquor with oil-free compressed air to complete the oxidation treatment of the iron-based components. After the oxidation treatment, nano-silica of the formula is added to the iron-based components, and after the addition, an ultrasonic dispersion system is started to treat the mixture. The frequency of the ultrasonic dispersion system is set to 35kHz-45kHz, and the dispersion treatment lasts for 10-15 minutes. The aeration oxidation following the addition of ferrous sulfate heptahydrate is a targeted chemical transformation step. Its function is to actively convert the relatively stable ferrous ions in the system into ferric ions, which are more reactive in the subsequent coagulation-promoting reaction. Completing this step early, before adding other sensitive components, ensures that the iron-based additive exists in the mother liquor in its most effective form. Subsequently, the addition of nano-silica followed by ultrasonic dispersion is a specific treatment based on the characteristics of nanomaterials. Its function is that nanoparticles, due to their large specific surface area, are prone to agglomeration, and conventional mechanical stirring is insufficient to dissociate them to their original particle size. Only through the cavitation effect generated by ultrasound can sufficient local high energy be provided to break up the agglomerates and allow them to be uniformly suspended in the mother liquor in a near-single-particle state.

[0010] Preferably, in step S4, the active cooling treatment of the mixture system obtained in step S3 includes: The mixture system is subjected to active and unnatural cooling by activating the jacketed cooling system outside the reaction vessel; The rate and efficiency of the cooling operation must ensure that the overall temperature of the mixture system is reduced from an initial state above 80°C to a target state below 50°C within a 20-minute time limit.

[0011] Its intrinsic properties are directly related to the "metastable hydrated aluminum ions" generated in step S2. This intermediate has a high chemical potential, making it an ideal precursor for subsequent efficient complexation reactions. However, it is thermodynamically unstable at high temperatures. When exposed to high temperatures for a prolonged period, it will irreversibly transform into a low-activity polymer or precipitate through hydrolysis and hydroxyl bridging. Therefore, the purpose of this rapid forced cooling step is to quickly remove heat from the system through kinetic means, reduce the thermal energy of the molecules, thereby "freezing" and "locking" this highly active metastable structure, greatly extending its effective existence time window, and creating the necessary conditions for the next complexation reaction.

[0012] Preferably, in step S5, the preparation of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent includes: After the two-step addition of N-methyldiethanolamine and diethanolamine, the temperature of the reaction system was precisely controlled within the range of 45℃-50℃, and the reaction was continuously stirred for 30 minutes at this temperature to complete the complexation reaction. After the complexation reaction is completed, the resulting liquid is transferred to a sealed curing container and subjected to a static curing treatment at a constant temperature of 48℃-52℃ for 12 hours. Finally, triisopropanolamine is added to obtain the quick-setting agent product. The complexation reaction, occurring at 45℃-50℃, is the kinetically controlled stage. This temperature range provides suitable activation energy for the coordination bonding reaction between nitrogen and oxygen atoms on the alkanolamine and aluminum ions, ensuring the complexation reaction proceeds sufficiently within a reasonable timeframe. The subsequent 12-hour post-ripening at 48℃-52℃ is a thermodynamically controlled stage. Its role is that the newly formed complex molecular chains are in a non-equilibrium state with high energy and distorted conformation. Prolonged resting at specific temperatures provides these molecules with sufficient energy and time for internal adjustments, such as rotation, folding, and rearrangement, allowing them to slowly relax and reach a stable conformation with minimum energy and minimal steric hindrance.

[0013] This invention provides a novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free rapid-setting agent and its preparation process. It possesses the following beneficial effects: 1. This invention constructs a dual-stability system through the synergistic effect of chemical complexation and physical network by combining N-methyldiethanolamine with diethanolamine and then physically suspending it with nano-silica. This achieves unprecedented storage stability. This is completely different from the approach of existing technologies that use only a single complexing agent or rely solely on dispersants. It completely solves the problem that traditional liquid quick-setting agents easily separate and precipitate after a period of storage, leading to performance degradation or even equipment blockage.

[0014] 2. This invention utilizes intermittent microwave activation to obtain a highly active intermediate at the molecular level. This intermediate is then immediately "locked in" using forced cooling. The resulting product exhibits maximally activated and preserved coagulation-promoting activity, achieving an extremely rapid coagulation rate. Compared to the simple jacket heating and dissolution methods of traditional techniques, this invention fundamentally solves the problem of insufficient activity of the core active ingredients due to the mild preparation method and low activation efficiency.

[0015] 3. The accelerator of this invention not only makes cement set quickly; in particular, the synergistic effect of the efficiently released active aluminum ions and the nano-silica acting as crystal nuclei optimizes the microstructure of cement hydration products. This results in extremely high early strength without adversely affecting later strength. This changes the common situation in the prior art where some accelerator products have to sacrifice final strength in pursuit of setting speed, and solves the technical bias that it is difficult to balance rapid setting effect and mechanical properties.

[0016] 4. This invention creatively designs a "two-step sequential complexation" process. Under precise temperature control, one amine is added first, reacted briefly, and then another is added. The entire crucial complexation reaction process thus becomes very gradual, orderly, and controllable. This ensures a high degree of consistency in the quality of each batch of product. It effectively avoids the risks of existing technologies that mix all reactants at once, which can easily lead to violent reactions, difficulty in control, and poor product uniformity. This refined process design solves the safety and stability problems in industrial production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0019] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0020] Please see the appendix Figure 1 : Example 1: Component ratio (by weight percentage): High-alumina aluminum sulfate: 45.0%, Ferrous sulfate: 8.0%, N-methyldiethanolamine: 3.5%, Diethanolamine: 4.5%, Citric acid: 1.0%, Sodium fluorosilicate: 2.0%, Nano silica: 0.2%, Triisopropanolamine: 1.5%, Nano alumina: 0.3%, Deionized water: 35.8%.

[0021] Preparation steps: Premixed: In a reaction vessel, add 35.8 parts of deionized water. After confirming that the water temperature is 30°C, add 1.0 part of citric acid and 2.0 parts of sodium fluorosilicate, stir to dissolve, and prepare a premixed solution.

[0022] Microwave-activated dissolution: Add 45.0 parts of high-alumina aluminum sulfate to the premixed solution, start a microwave generator with a power of 900W, and use the intermittent mode of "heating for 30 seconds and pausing for 15 seconds" to raise the system temperature to 80°C within 10 minutes and maintain it until the solid is completely dissolved to form a high-temperature mother liquor.

[0023] Synergistic component addition: 8.0 parts of ferrous sulfate heptahydrate were added to the high-temperature mother liquor at 80℃, and oil-free compressed air was introduced for bubbling oxidation. Subsequently, 0.2 parts of nano-silica and 0.3% of nano-alumina were added, and an ultrasonic dispersion system with a frequency of 40kHz was started for 12 minutes.

[0024] Forced cooling: Start the jacket cooling system to reduce the temperature of the mixture system from above 80°C to 48°C within 18 minutes.

[0025] Two-step complexation reaction and post-ripening: At 48°C, 3.5 parts of N-methyldiethanolamine were added first, and after reacting for 15 minutes, 4.5 parts of diethanolamine were added. The system temperature was precisely controlled at 48°C and the reaction was continued for 30 minutes. After the reaction was completed, the solution was transferred to a sealed curing tank and cured at a constant temperature of 50°C for 12 hours. After curing, the solution was cooled to room temperature, and 1.5% triisopropanolamine was added and mixed thoroughly to obtain the final product.

[0026] Example 2: Component ratio (by weight percentage): High-alumina aluminum sulfate: 42.0%, Ferrous sulfate: 6.0%, N-methyldiethanolamine: 3.0%, Diethanolamine: 4.0%, Citric acid: 0.8%, Sodium fluorosilicate: 1.5%, Nano silica: 0.1%, Triisopropanolamine: 1%, Nano alumina: 0.2%, Deionized water: 42.6%.

[0027] Preparation steps: Premixed: In a reaction vessel, 42.6 parts of deionized water were added. After confirming that the water temperature was below 35°C, 0.8 parts of citric acid and 1.5 parts of sodium fluorosilicate were added and stirred to dissolve, thus preparing a premixed solution.

[0028] Microwave-activated dissolution: Add 42.0 parts of high-alumina aluminum sulfate to the premixed solution, start a microwave generator with a power of 800W, and use the intermittent mode of "heating for 30 seconds and pausing for 15 seconds" to raise the system temperature to 75°C within 8 minutes and maintain it until the solid is completely dissolved to form a high-temperature mother liquor.

[0029] Synergistic component addition: 6.0 parts of ferrous sulfate heptahydrate were added to the high-temperature mother liquor at 75°C, and oil-free compressed air was introduced for bubbling oxidation. Subsequently, 0.1 parts of nano-silica and 0.2% of nano-alumina were added, and an ultrasonic dispersion system with a frequency of 35kHz was started for 10 minutes.

[0030] Forced cooling: Start the jacket cooling system to reduce the temperature of the mixture system from above 75°C to 49°C within a specified time.

[0031] Two-step complexation reaction and post-ripening: At 49°C, 3.0 parts of N-methyldiethanolamine were added first, followed by the reaction, and then 4.0 parts of diethanolamine were added. The system temperature was precisely controlled at 45°C and the reaction was continued for 30 minutes. After the reaction was completed, the solution was transferred to a sealed curing tank and allowed to stand and cure at a constant temperature of 48°C for 12 hours. After curing, the solution was cooled to room temperature, and 1% triisopropanolamine was added and mixed thoroughly to obtain the final product.

[0032] Example 3: Component ratio (by weight percentage): High-alumina aluminum sulfate: 48.0%, Ferrous sulfate: 10.0%, N-methyldiethanolamine: 4.0%, Diethanolamine: 5.0%, Citric acid: 1.2%, Sodium fluorosilicate: 2.5%, Nano silica: 0.3%, Triisopropanolamine: 2%, Nano alumina: 0.4%, Deionized water: 29.0%.

[0033] Preparation steps: Premixed: In a reaction vessel, add 29.0 parts of deionized water. After confirming that the water temperature is below 35°C, add 1.2 parts of citric acid and 2.5 parts of sodium fluorosilicate, stir to dissolve, and prepare a premixed solution.

[0034] Microwave-activated dissolution: Add 48.0 parts of high-alumina aluminum sulfate to the premixed solution, start a microwave generator with a power of 1000W, and use the intermittent mode of "heating for 30 seconds and pausing for 15 seconds" to raise the system temperature to 85°C within 12 minutes and maintain it until the solid is completely dissolved to form a high-temperature mother liquor.

[0035] Synergistic component addition: 10.0 parts of ferrous sulfate heptahydrate were added to the high-temperature mother liquor at 85℃, and oil-free compressed air was introduced for bubbling oxidation. Subsequently, 0.3 parts of nano-silica and 0.4% of nano-alumina were added, and an ultrasonic dispersion system with a frequency of 45kHz was started for 15 minutes.

[0036] Forced cooling: Start the jacket cooling system to reduce the temperature of the mixture system from above 85°C to 45°C within 20 minutes.

[0037] Two-step complexation reaction and post-ripening: At 45°C, 4.0 parts of N-methyldiethanolamine were added first, followed by the reaction, and then 5.0 parts of diethanolamine were added. The system temperature was precisely controlled at 50°C and the reaction was continued for 30 minutes. After the reaction was completed, the solution was transferred to a sealed curing tank and cured at a constant temperature of 52°C for 12 hours. After curing, the solution was cooled to room temperature, and 2% triisopropanolamine was added and mixed thoroughly to obtain the final product.

[0038] Comparative Example 1: The difference compared to Example 1 lies in the choice of complexing stabilizer. Instead of the complex amine system of N-methyldiethanolamine and diethanolamine, only diethanolamine was used as the complexing stabilizer, and its addition amount was adjusted to 80 kg (8.0%) to maintain a total amount of amine functional groups substantially equivalent to that in Example 1; all other aspects remained the same. Comparative Example 2: Compared with Example 1, the difference is the absence of a physically stabilizing component. Nano-silica, which serves as a physical stabilizer and adsorption nucleus, is not added. To maintain the total mass, the amount of deionized water is increased accordingly; all other aspects remain the same. Comparative Example 3: Compared with Example 1, the difference is that the pre-complexing protection component is missing. Citric acid as a complexing protectant is not added to the composition of this comparative example. In order to keep the total mass unchanged, the amount of deionized water is increased accordingly. All other aspects are the same. Comparative Example 4: Compared with Example 1, the difference is that the two-step complexation reaction in preparation step S5 is changed to a one-step operation, that is, 3.5 parts of N-methyldiethanolamine and 4.5 parts of diethanolamine are premixed evenly, and then the mixed alcoholamine is added to the low-temperature reaction system at one time for complexation. The rest are the same.

[0039] Experiment 1: Experimental objective: To systematically evaluate the physical stability of five groups of quick-setting agent samples prepared according to Example 1 and Comparative Examples 1-4 during storage by observing the samples at room temperature and accelerating centrifugation; the core objective is to verify the contribution of the innovative aspects of this invention, such as the composite alkanolamine system, the chemical-physical dual stabilization mechanism, the early complexation protection, and the two-step complexation process, to preventing unstable phenomena such as stratification, precipitation, and flocculation during storage.

[0040] Experimental steps: Part 1: Stability Test at Room Temperature Sample aliquoting: On the day the experiment begins (referred to as day 0), take 200 mL of each of the freshly prepared samples 1 to 5 and place them in a clean, dry 250 mL stoppered transparent glass wide-mouth bottle. Seal the bottle and clearly label it.

[0041] Static observation: Place all sample bottles side by side on a horizontal experimental table and begin a 60-day static observation period at room temperature.

[0042] Regularly record: Macroscopic observations of each sample vial are conducted and detailed records are kept on days 1, 7, 30, and 60. Observations include: Overall appearance: Record the overall state of the sample, whether it is clear and transparent, translucent, cloudy, or milky; Homogeneity: Determine whether the sample is a homogeneous system and whether there is any visible stratification. Precipitation: Carefully observe the bottom of the sample vial and record whether there is any precipitation. If present, describe the color, morphology (e.g., powder, gel, crystal, or flocculent), and approximate packing pattern of the precipitate; Suspended matter: Observe whether there are suspended flocculent matter or particles in the bulk of the sample liquid phase.

[0043] Part Two: Centrifugal Acceleration Stability Test Sampling: After the final standing observation on day 60, gently invert the sample in each wide-mouth bottle three times to preliminarily resuspend any loose precipitates. Immediately afterwards, accurately transfer 50 mL of sample from each bottle into the corresponding numbered 50 mL graduated centrifuge tube.

[0044] Balancing and centrifugation: Balance the five centrifuge tubes containing the samples, and then place them symmetrically into the centrifuge. Start the centrifuge, set the speed to 3000 rpm, and centrifuge for 30 minutes.

[0045] Results: After centrifugation, carefully remove the centrifuge tubes. Place the centrifuge tubes vertically on a horizontal table and read and record the volume of the precipitate at the bottom of each centrifuge tube (experimental results are shown in Table 1).

[0046] Table 1 From Table 1, we can obtain: Sample 1 prepared according to Example 1 of this invention exhibits excellent storage stability. Even after standing for up to 60 days, it maintains a homogeneous and clear liquid phase without any visible precipitation or stratification. Furthermore, after undergoing high-intensity centrifugation, only a negligible amount of precipitate is observed. This superior stability stems from the unique composition design of this invention. The core mechanism lies in the chemical complex formed between the composite alkanolamine system and active aluminum ions, which first achieves effective encapsulation and stabilization of high-concentration metal ions at the molecular level. Based on this, the introduced nano-silica constructs a three-dimensional physical network in the macroscopic liquid system. Through its large specific surface area, it adsorbs the complex particles, physically inhibiting particle aggregation and sedimentation, ultimately forming a dual stabilizing guarantee through the synergistic effect of "chemical complexation" and "physical suspension."

[0047] In stark contrast to Sample 1, Samples 2, 4, and 5 all exhibited varying degrees of decreased stability, directly demonstrating the innovation of this invention in its complexation system and preparation process. Sample 2, using only a single alkanolamine, showed inferior stability compared to Sample 1. The mechanism lies in the difficulty of forming a structurally optimized and fully encapsulated complex like the composite alkanolamine system of this invention, resulting in some aluminum ions failing to be effectively stabilized and ultimately precipitating. Sample 4 lacked the initial protection of citric acid during preparation, leading to flocculent matter and hard precipitates. This was due to irreversible hydrolysis and polymerization of highly reactive aluminum ions during microwave activation due to a lack of buffering, creating defects that subsequent complexation steps could not reverse. Sample 5, using a one-step feeding method, showed better stability than some comparative samples, but still inferior to Sample 1. This indicates that the two-step sequential complexation process employed in this invention, which involves first adding an alkanolamine with greater steric hindrance for initial buffering, followed by adding an alkanolamine with less steric hindrance for supplementary reinforcement, is crucial for forming a more structurally rational and stable final complex.

[0048] The results for Sample 3 most convincingly highlight the indispensability of the physical stabilization mechanism in this invention. Lacking the key physically stabilizing component, nano-silica, Sample 3 exhibited extremely severe stratification and precipitation problems. The underlying mechanism is that even if chemical complexation succeeds to some extent, the resulting complex particles, without physical network support, cannot resist gravity due to their Brownian motion alone, inevitably leading to aggregation and macroscopic sedimentation during storage. Therefore, the failure state of Sample 3 strongly demonstrates that the chemical-physical dual-stabilization system constructed in this invention is an organic and inseparable whole; both components work synergistically and are indispensable, jointly constituting the core technological foundation that endows this product with superior stability.

[0049] Experiment 2: Experimental objective: To directly evaluate and compare the actual effects of five groups of accelerator samples prepared according to Example 1 and Comparative Examples 1-4 on the setting time of cement paste; the core objective is to verify the contribution of innovative aspects such as the composite amine system, chemical-physical dual stability mechanism, early complexation protection, and two-step complexation process to ensure and efficiently exert the core setting-promoting function of the accelerator by quantifying the two key indicators of initial setting time and final setting time.

[0050] Experimental steps: Material weighing: Accurately weigh 500g of cement. Based on the preset admixture dosage of 5.0% (percentage of cement mass), accurately weigh 25.0g of each of samples 1 to 5. Calculate and measure the required total liquid volume (accelerator sample + supplementary deionized water) based on the standard consistency water requirement of the cement.

[0051] Preparation of cement paste: Pour the weighed 500g of cement into the mixing bowl of the cement paste mixer. Mix 25.0g of quick-setting agent sample with the required amount of replenishing deionized water in a beaker until homogeneous; Turn on the mixer and pour the mixed liquid into the pot within 5 seconds. Mix at low speed for 120 seconds, then stop for 15 seconds. During this time, use a scraper to scrape the cement slurry adhering to the pot wall into the center of the pot; Continue stirring at high speed for 120 seconds, then stop.

[0052] Mold making: Immediately pour the mixed cement paste into the Vicat apparatus mold that has been placed on the glass plate, tamp it several times with a scraper and gently vibrate it, then scrape off the excess cement paste and smooth the surface.

[0053] Determination of setting time: Immediately move the prepared specimen mold to the Vicat apparatus, align the test rod vertically with the cement slurry surface, and lower it steadily until it contacts the slurry surface; Suddenly release the test rod, allowing it to sink freely into the cement grout under gravity. Take the pointer reading 30 seconds after the test rod stops sinking or is released. Initial setting time determination: Start timing from the addition of water to the cement. The time taken for the test needle to sink into the neat cement paste to a distance of 4mm ± 1mm ​​from the bottom plate is the initial setting time of the cement. Final setting time determination: After measuring the initial setting time, rotate the mold 180° and replace it with the final setting needle attachment to continue testing. The time taken when the needle sinks into the neat cement paste to a depth of no more than 0.5 mm (i.e., the ring attachment cannot leave a mark on the surface of the paste) is the final setting time of the cement.

[0054] Repeat the test: Following steps 1-4 above, perform the same test on the remaining four groups of samples in sequence, and accurately record their initial and final setting times (the experimental results are shown in Table 2).

[0055] Table 2 From Table 2, we can obtain: Comparative tests on the setting time of cement paste show that Sample 1, prepared using Example 1 of this invention, exhibits a superior setting-accelerating effect, with both its initial and final setting times significantly faster than all comparative samples. This result profoundly reflects the inherent superiority of the composition design of this invention. Its core mechanism lies in the formation of a structurally stable complex with "timely dissociation" characteristics between the composite amine system constructed from N-methyldiethanolamine and diethanolamine and highly active aluminum ions. This complex protects aluminum ions from degradation in accelerator products, while rapidly disintegrating in the alkaline environment of cement, releasing a high concentration of active aluminum ions. This significantly accelerates the formation rate of CSH gel and ettringite in the early stages of cement hydration, macroscopically manifesting as extremely rapid setting.

[0056] The prolonged setting times of Samples 2 and 4, conversely, underscore the necessity of the present invention in selecting the complexation system and controlling the preparation process at its source. Sample 2, using only a single alkanolamine, exhibited a significantly weakened setting-promoting effect. The mechanism may be that the formed complex is too stable, leading to hindered and slowed release of active aluminum ions in the alkaline environment of cement; or that the complex coating is incomplete, causing partial inactivation of the active component during storage or preparation. Sample 4, lacking the pre-treatment protection of citric acid during preparation, showed a significant decrease in setting performance because a large number of aluminum ions underwent irreversible hydrolysis and polymerization during the high-temperature activation stage, forming inert polymers ineffective in promoting setting. This resulted in the concentration of truly effective active components in the final product being far below the design value, naturally failing to achieve the expected rapid setting effect.

[0057] The test results of Samples 3 and 5 further reveal the synergistic effect of the physically stable components and process control steps in this invention. Sample 3, lacking nano-silica, exhibited a prolonged setting time. The mechanism lies in the fact that the uniformly dispersed nano-silica not only acts as a physical filler in the cement paste but, more importantly, provides numerous crystal nucleus growth points, inducing and accelerating the precipitation of hydration products, thereby synergistically promoting setting. Sample 5, using a one-step complexation method, showed a worse setting-promoting effect than Sample 1, indicating that the two-step sequential feeding process designed in this invention, through the orderly introduction of different sterically hindered alkanolamines, can form complexes with more uniform structures and more efficient activity release. These details collectively demonstrate that each component and step in this invention plays a crucial and indispensable role in ultimately achieving the goal of efficient setting.

[0058] Experiment 3: Experimental Objective: To evaluate and compare the effects of five groups of accelerator samples prepared according to Example 1 and Comparative Examples 1-4 on the mechanical properties of hardened cement mortar, particularly early strength development and later strength stability. The core objective is to verify, by quantifying the flexural and compressive strengths at different ages, the contribution of this invention's innovative features—such as the composite amine system, the chemical-physical dual stabilization mechanism, early complexation protection, and the two-step complexation process—to promoting cement hydration and forming a dense, high-strength microstructure.

[0059] Experimental steps: Mortar mix ratio determined: Cement: 450g; Standard sand: 1350g; Water-cement ratio: 0.5; Accelerating agent dosage: 5.0% of the cement mass (i.e., 22.5g); Total liquid volume = cement mass × water-cement ratio = 450g × 0.5 = 225g; Actual water replenishment = total liquid volume - quick-setting agent mass = 225g - 22.5g = 202.5g.

[0060] Cement mortar preparation: Mix 202.5g of deionized water and 22.5g of quick-setting agent sample evenly in a mixing tank; Add 450g of cement, install the mixing bowl onto the mixer, and mix at low speed for 30 seconds; While stirring at low speed, add 1350g of standard sand evenly within 30 seconds; Switch to high-speed stirring for 30 seconds; Stop the machine for 90 seconds, then use a scraper to scrape the mortar stuck to the pot wall into the center of the pot. Stir at high speed again for 60 seconds, then stop.

[0061] Specimen molding: The mixed mortar was poured into the mold in two layers.

[0062] Place the mold with the first layer of mortar on a vibration table and vibrate it 60 times.

[0063] Add the second layer of mortar and vibrate it 60 times again.

[0064] Use a scraper to remove excess mortar and smooth the surface of the specimen.

[0065] Maintenance and Testing: The molded specimens are placed in a standard curing room for curing.

[0066] 1-day strength test: After curing for 20-24 hours, demold the specimen and immediately conduct flexural and compressive strength tests.

[0067] Strength tests at 3 days and 28 days: After curing for 20-24 hours, demold the specimen and immediately place it in water at (20±1℃) to continue curing until the 3-day and 28-day curing periods are reached. After removing the specimen and drying the surface, conduct the strength test.

[0068] Strength determination: Three specimens were tested for each group of samples at each age. First, flexural strength was tested to obtain the flexural strength value and two half-section specimens. Then, compressive strength was tested on these two half-section specimens separately. The final result was the average of the three specimens (six compressive strength values).

[0069] Repeat the test: Following steps 1-4 above, perform the same test on the remaining four groups of samples in sequence, and accurately record their flexural and compressive strengths at 1 day, 3 days and 28 days of age (the experimental results are shown in Table 3).

[0070] Table 3 From Table 3, we can obtain: The test results of the mechanical properties of cement mortar directly demonstrate the superiority of the product of this invention. Compared with all comparative examples, Sample 1, prepared using Example 1, showed significantly higher early flexural and compressive strength at 1 day and 3 days, and also achieved the highest strength at 28 days. The core mechanism behind this is that the composite amine complex system constructed in this invention can dissociate at an optimized rate in the strongly alkaline environment of cement, instantly releasing highly active aluminum ions. These active ions rapidly participate in the cement hydration reaction, greatly promoting the formation and crystallization of early hydration products (especially ettringite and CSH gel), thereby constructing a dense and robust early strength framework in a very short time. Simultaneously, its excellent later strength indicates that this efficient early setting-promoting effect synergizes well with the long-term hydration process of cement, without compromising the integrity and stability of the final structure.

[0071] The mechanical properties of Samples 2 and 4, particularly the reduction in early strength, profoundly reveal the key innovations of this invention in component design and preparation process. Sample 2, using only a single alkanolamine, resulted in complexes that either exhibited excessive stability leading to delayed release of the active component, or insufficient stability causing partial inactivation of the active component during storage. Consequently, it failed to provide a sufficiently effective concentration of coagulating ions in the early stages of hydration, resulting in delayed early strength development. The results for Sample 4 were even more extreme. Due to the lack of pre-protection with citric acid during the high-temperature activation stage, a large number of aluminum ions underwent irreversible polymerization, transforming into inert substances that contributed no strength or were even harmful. This directly led to a severe loss of early strength and poor later strength development in the mortar, fully demonstrating the necessity of the source protection step in the preparation process of this invention.

[0072] The performance data of Samples 3 and 5 further corroborate the synergistic effect of the physically stable components and specific process steps in this invention. Sample 3, lacking nano-silica, showed a significant decrease in both early and late strength. The mechanism lies in the fact that nano-silica not only acts as a micro-filler in the mortar system, but more importantly, its large specific surface area provides numerous heterogeneous nucleation sites for cement hydration products, inducing and accelerating the formation of the strength network, thus achieving a physical reinforcement effect. Sample 5, using a one-step complexation method, had lower strength than Sample 1. This indicates that the two-step time-sequential complexation process employed in this invention, through precise control of the reaction process, can generate complexes with more optimized structures and more efficient activity release. In summary, the superior mechanical properties of this invention are the result of the combined effects of its unique chemical complexation system, physical reinforcement mechanism, and precisely synergistic preparation process.

Claims

1. A novel alkanolamine-based high-aluminum, fluorine-free, chlorine-free, and alkali-free quick-setting agent, characterized in that, The accelerator is composed of the following components by weight percentage: High-alumina aluminum sulfate: 42%-48%; Ferrous sulfate: 6%-10%; N-Methyldiethanolamine: 3%-4%; Diethanolamine: 4%-5%; Citric acid: 0.8%-1.2%; Sodium fluorosilicate: 1.5%-2.5%; Nano-silica: 0.1%-0.3%; Triisopropanolamine: 1%-2%; Nano-alumina; 0.2%-0.4%; Deionized water: Balance.

2. The novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 1, characterized in that, The high-alumina aluminum sulfate has an alumina content of 17.5%-18.5%, a sulfate content of no more than 0.6%, and a water-insoluble content of no more than 0.05%.

3. The novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 1, characterized in that, The ferrous sulfate is specifically in the form of crystalline ferrous sulfate heptahydrate, which has a light blue-green appearance and an industrial purity of not less than 98.0%.

4. The novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 1, characterized in that, The N-methyldiethanolamine and the diethanolamine together constitute an alcoholamine complex system, and the ratio of the number of moles of aluminum ions provided by the high-alumina aluminum sulfate to the total number of moles of the alcoholamine complex system is 1.2:1-1.5:

1.

5. The novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 1, characterized in that, The physical morphology of the nano-silica is characterized by its specific surface area, which ranges from 150 μm. 2 / g-250m 2 / g.

6. A preparation process for a novel alkanolamine-based high-aluminum, fluorine-free, chlorine-free, and alkali-free quick-setting agent, characterized in that, The preparation of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free rapid-setting agent according to any one of claims 1-5 includes the following steps: S1. Premixing: In a reaction vessel, citric acid, which serves as a complexing protectant, and sodium fluorosilicate, which serves as a synergistic enhancer, are added to deionized water at a temperature below 35°C and dissolved by stirring to prepare a premixed solution. S2, Microwave activation and dissolution: Add high-alumina aluminum sulfate to the premixed solution prepared in step S1, and then use microwave heating to raise the temperature of the mixture to the range of 75℃-85℃, and maintain the temperature until the high-alumina aluminum sulfate is completely dissolved, thereby forming a high-temperature mother liquor. S3. Addition of synergistic components: In the high-temperature mother liquor formed in step S2, ferrous sulfate heptahydrate, nano-alumina and nano-silica are added sequentially and mixed. S4. Forced cooling: The mixture system obtained in step S3 is subjected to active cooling treatment to reduce the overall temperature from above 80°C to below 50°C in order to obtain a low-temperature reaction system. S5. Two-step complexation reaction: In the low-temperature reaction system prepared in step S4, N-methyldiethanolamine, as the first component of the alcoholamine complex system, is first added to carry out the first step reaction. Then, diethanolamine, as the second component of the alcoholamine complex system, is added to carry out the second step complexation reaction. Finally, triisopropanolamine is added to obtain the novel alcoholamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent.

7. The preparation process of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 6, characterized in that, In step S2, raising the temperature of the mixture to the range of 75℃-85℃ using microwave heating includes: Start a microwave generator with a power setting of 800W-1000W and apply a microwave energy field to the hybrid system; The application of the microwave energy field is not continuous heating, but rather adopts a preset intermittent working mode. The intermittent working mode is specifically defined as a cycle containing a 30-second microwave heating phase and a 15-second energy pause phase. By repeatedly executing the cycle of the intermittent working mode, the overall temperature of the mixing system is raised from the initial temperature to the target range of 75℃-85℃ within a total processing time of 8-12 minutes.

8. The preparation process of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 6, characterized in that, In step S3, the sequential addition and mixing of ferrous sulfate heptahydrate, nano-alumina, and nano-silica includes: Add the formula-measured amount of ferrous sulfate heptahydrate to the high-temperature mother liquor, and after adding it, bubble the mother liquor with oil-free compressed air to complete the oxidation treatment of the iron-based components. After the oxidation treatment, nano-silica of the formula is added to the iron-based components, and after the addition, an ultrasonic dispersion system is started to treat the mixture. The frequency of the ultrasonic dispersion system is set to 35kHz-45kHz, and the dispersion treatment lasts for 10-15 minutes.

9. The preparation process of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 6, characterized in that, In step S4, the active cooling treatment of the mixture system obtained in step S3 includes: The mixture system is subjected to active and unnatural cooling by activating the jacketed cooling system outside the reaction vessel; The rate and efficiency of the cooling operation must ensure that the overall temperature of the mixture system is reduced from an initial state above 80°C to a target state below 50°C within a 20-minute time limit.

10. The preparation process of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent according to claim 6, characterized in that, In step S5, the preparation of the novel alkanolamine-based high-alumina, fluorine-free, chlorine-free, and alkali-free quick-setting agent includes: After the two-step addition of N-methyldiethanolamine and diethanolamine, the temperature of the reaction system was precisely controlled within the range of 45℃-50℃, and the reaction was continuously stirred for 30 minutes at this temperature to complete the complexation reaction. After the complexation reaction is completed, the resulting liquid is transferred to a sealed curing container and subjected to a static curing treatment at a constant temperature of 48℃-52℃ for 12 hours. Finally, triisopropanolamine is added to obtain the quick-setting agent product.

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