Low-alkali chlorine-free powder type masterbatch soluble accelerator and preparation process thereof

Abstract

The application discloses a low-alkali chlorine-free powdery master batch soluble rapid setting agent and a preparation process thereof, and relates to the technical field of building materials.The raw materials of the low-alkali chlorine-free powdery master batch soluble rapid setting agent include, in percentage by mass, 2-5% of sodium aluminate, 23-35% of aluminum sulfate, 5-10% of aluminum hydroxide, 5-10% of silica sol, 0.5-1.5% of triethanolamine, 3-8% of borax, 0.5-2% of a thickening agent, 1-3% of a dispersing agent, 1.6-1.8% of a pH regulator, 1.5-2.0% of a complexing agent, and the rest of water; and the preparation process comprises dissolving and mixing, mixing reaction, adding an additive, and post-treatment.The low-alkali chlorine-free powdery master batch soluble rapid setting agent prepared by the application has the characteristics of strong adaptability, good stability, convenient storage and transportation, and the like; and when applied to concrete, the low-alkali chlorine-free powdery master batch soluble rapid setting agent can significantly improve the mechanical properties of the concrete and meet higher application requirements.

Description

[Technical Field]

[0001] This invention relates to the field of building materials technology, and in particular to a low-alkali, chlorine-free powdered soluble quick-setting agent and its preparation process. [Background Technology]

[0002] In a series of complex and critical underground and open-pit engineering projects, such as tunnel excavation, mine shaft excavation, and slope protection, shotcrete plays a vital role, and quick-setting agents, as the core additives in this process, are indispensable. They enable concrete to quickly set and harden in a short time, effectively meeting the urgent needs of projects for early strength and the strict requirements for construction timeliness, ensuring that both project progress and quality standards are met.

[0003] However, the use of traditional accelerators is not without its drawbacks. Currently, accelerators are mainly classified into three categories based on their alkali content: alkali-containing, low-alkali, and alkali-free. Alkali-containing accelerators suffer from severe later-stage strength loss and poor stability; alkali-free accelerators require high dosages and are sensitive to temperature. While low-alkali accelerators offer superior performance, combining high later-stage strength retention and economic advantages, they still suffer from problems such as significant differences in compatibility with different cements and mineral admixtures, poor compatibility with other admixtures, limited manufacturers leading to poor product quality stability, prolonged setting time, insufficient later-stage strength guarantee, and higher dosage requirements. Furthermore, traditional accelerators contain chloride ions, which pose a significant threat to the reinforcing steel inside the concrete. This chloride ion accelerates the corrosion process of the steel, thereby reducing the load-bearing capacity of the entire structure and shortening its service life.

[0004] Furthermore, traditional accelerators also present numerous inconveniences in terms of their physical form. While liquid accelerators are convenient to use, they suffer from problems such as easy sedimentation and stratification, and poor stability during storage and transportation, causing considerable difficulties in construction. Powdered accelerators, although easy to transport and store, are difficult to disperse evenly in concrete, thus affecting the accelerator's performance and making it difficult for the concrete's setting time and strength development to meet expectations.

[0005] Therefore, developing a low-alkali, chloride-free, and highly soluble powdered accelerator masterbatch is particularly important to address the aforementioned issues. This accelerator can not only effectively avoid the hazards of high-alkali aggregate reaction and chloride ion corrosion, improving the durability and structural safety of concrete, but also ensure the uniform dispersion of the accelerator in concrete, achieving optimal acceleration performance and providing more reliable technical support for shotcrete operations in underground and open-pit engineering.

[0006] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. [Summary of the Invention]

[0007] The purpose of this invention is to provide a low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent and its preparation process, so as to solve the technical problems existing in the prior art.

[0008] Therefore, the present invention adopts the following technical solution:

[0009] A low-alkali, chlorine-free powdered soluble quick-setting agent is made from the following raw materials in the indicated weight percentages:

[0010] Sodium aluminate 2%-5%, aluminum sulfate 23%-35%, aluminum hydroxide 5%-10%, silica sol 5%-10%, triethanolamine 0.5%-1.5%, borax 3%-8%, thickener 0.5%-2%, dispersant 1%-3%, pH adjuster 1.6%-1.8%, complexing agent 1.5%-2.0%, balance water.

[0011] Furthermore, the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent is made from the following raw materials in weight percentages:

[0012] Sodium aluminate 3%, aluminum sulfate 27%, aluminum hydroxide 7.2%, silica sol 7.5%, triethanolamine 1.2%, borax 5.5%, thickener 1.2%, dispersant 1.8%, pH adjuster 1.7%, complexing agent 1.8%, balance water.

[0013] Furthermore, the thickener is hydroxypropyl methylcellulose.

[0014] Furthermore, the dispersant is one or more of amine-modified lignin and ammonium polyacrylate.

[0015] Furthermore, the pH adjuster is one or more of citric acid and tartaric acid.

[0016] Furthermore, the complexing agent is prepared by reacting N-methyl-2-acrylamide, cyclohexylmethyldimethoxysilane, β-aminoethanesulfonic acid, cyclohexanone peroxide, carotene, and water.

[0017] The design principle of the quick-setting agent raw material composition described in this invention is as follows:

[0018] Sodium aluminate: Sodium aluminate can ionize into aluminum ions (Al) in aqueous solution. 3+Aluminum ions can participate in the hydration reaction of cement, accelerating the hydration process of mineral components and promoting the rapid formation and crystallization of hydration products, thereby shortening the setting time of concrete. Simultaneously, sodium aluminate, aluminum sulfate, and other raw materials work synergistically to promote the setting and hardening of concrete and improve its early strength.

[0019] Aluminum hydroxide: Aluminum hydroxide plays a unique role in accelerator systems. At room temperature, it possesses a certain degree of chemical stability, but under the alkaline environment generated during cement hydration and through interactions with other raw materials, aluminum hydroxide gradually reacts. It can decompose and release aluminum ions (Al). 3+ These aluminum ions can participate in the hydration reaction of cement. Unlike sodium aluminate and aluminum sulfate, which directly provide aluminum ions, aluminum hydroxide releases aluminum ions at a relatively slower but more continuous rate. In the early stages of concrete setting, it can replenish the aluminum ions consumed by other rapid reactions, maintaining the activity of the cement hydration reaction for a longer period. This helps optimize the setting process, making the setting more uniform and reducing the structural inhomogeneity problems that may result from sudden changes in aluminum ion concentration. Aluminum hydroxide also reacts synergistically with other components during the reaction, jointly influencing the formation and structure of cement hydration products. It can combine with sulfate ions, altering the formation rate and crystal morphology of products such as ettringite to some extent, thus affecting the early strength development and microstructure of concrete. In this way, aluminum hydroxide helps improve the early strength of concrete and also has a positive effect on the sustained growth of later strength, allowing concrete to maintain good mechanical properties for a longer period.

[0020] Silica sol: Silica sol plays a role in promoting early strength development. Its main component is silicon dioxide, which reacts with alkaline substances in the system to form cementitious substances such as calcium silicate, enhancing the setting effect of the accelerator. Silica dioxide reacts chemically with alkaline substances in the system to form cementitious substances such as calcium silicate (CaSiO3). It can also react with calcium ions in cement to form hydrated calcium silicate (CSH) gel. This gel not only fills the pores inside the concrete, increasing its density, but also strengthens the bond between cement paste and aggregates, thus significantly improving the early strength of the concrete and enabling it to reach a certain load-bearing capacity in a short time, meeting the requirements of rapid construction and early support of shotcrete.

[0021] Triethanolamine: Triethanolamine molecules contain active groups such as amino and hydroxyl groups, which play a crucial role in the cement hydration process. These groups can adsorb onto the surface of cement particles, reducing their surface energy and thus promoting the dissolution of cement mineral components and driving the hydration reaction. Among the many mineral components of cement, triethanolamine has a significant impact on the hydration reaction of tricalcium aluminate. It can accelerate the hydration reaction of tricalcium aluminate, promoting the formation of more hydrated calcium aluminate crystals and contributing to the rapid development of the cement hydration system. Simultaneously, the complex formed between aluminum ions and triethanolamine can alter the hydration reaction pathway of tricalcium aluminate, lowering the activation energy and significantly accelerating the hydration rate. Furthermore, there is a synergistic effect between silicate ions and triethanolamine, which can promote the formation of hydrated calcium silicate (CSH) gel. Moreover, even at low dosages, triethanolamine can effectively shorten the setting time of concrete and significantly improve its early strength.

[0022] Borax: Borax hydrolyzes in aqueous solution to produce borate ions. These ions can react with calcium ions and other substances in cement hydration products, altering the structure and morphology of the cement hydration products to form a denser and more stable structure, thus promoting early setting of concrete. Simultaneously, borax itself is a low-alkali substance, meeting the design requirements of low-alkali and chloride-free accelerators, and will not introduce excessive alkali metal ions, avoiding alkali-aggregate reactions.

[0023] Thickeners: Thickeners prevent sedimentation and stratification. Hydroxypropyl methylcellulose (HPMC) is a good thickener with excellent water solubility and thickening properties. After the masterbatch is compounded into a quick-setting agent solution, thickeners increase the viscosity of the solution, forming a stable colloidal structure that ensures uniform dispersion of the quick-setting agent components. This not only improves the storage stability of the quick-setting agent but also ensures that it is uniformly dispersed in the concrete during use, resulting in consistent quick-setting effects and improving the uniformity of concrete quality. The addition amount of thickener is between 0.5% and 2%, which achieves a good thickening effect without negatively impacting other properties of the quick-setting agent.

[0024] Dispersants: The role of dispersants is to improve the dispersibility of raw materials. Amino-modified lignin and ammonium polyacrylate, as dispersants, can adsorb onto the surface of raw material particles, reducing particle surface energy and preventing particle aggregation through electrostatic repulsion and steric hindrance. In the preparation of accelerators, ensuring uniform dispersion of raw materials improves their reactivity and solubility, making the accelerator's performance more stable and reliable. The amount of dispersant added is 1%-3%, adjusted according to the characteristics of the raw materials and process requirements to achieve the best dispersion effect.

[0025] pH adjusters: Citric acid and tartaric acid are both organic acids containing multiple acidic functional groups. In accelerator systems, when a pH adjuster is added, these acidic functional groups ionize to release hydrogen ions. These hydrogen ions combine with hydroxide ions in the system, thus lowering the pH value of the solution. By controlling the amount of pH adjuster added, the pH value of the accelerator system can be precisely adjusted within a suitable range. In cement hydration reactions, a suitable pH value helps activate the active components in cement, promoting their dissolution and hydration reactions. They can effectively reduce the alkalinity of accelerators. While ensuring that other properties of the accelerator are not significantly affected, by reacting with alkaline substances, alkali metal ions are converted into relatively stable salts, thereby reducing the content of alkali metal oxides (in sodium oxide equivalents) and ensuring that the alkali content of the accelerator meets the low-alkali requirements. This is of great significance for preventing alkali-aggregate reactions in concrete and improving the durability of concrete. In addition, precise control of pH value can avoid adverse effects on concrete performance caused by excessively high or low pH. For example, excessively high pH may lead to alkali-aggregate reaction, while excessively low pH may inhibit cement hydration reaction.

[0026] Complexing Agent: The complexing agent is prepared by reacting N-methyl-2-acrylamide, cyclohexylmethyldimethoxysilane, β-aminoethanesulfonic acid, cyclohexanone peroxide, carotene, and water. Among these, organic components such as N-methyl-2-acrylamide form complexes with metal ions (such as aluminum ions), altering the state and reactivity of the metal ions and optimizing the accelerator's setting effect and performance stability. Components such as cyclohexylmethyldimethoxysilane play a certain role in surface modification in concrete, enhancing the interfacial bonding force within the concrete. Components such as β-aminoethanesulfonic acid participate in regulating the chemical balance of the system, further improving the compatibility of the accelerator with materials such as cement. Components such as cyclohexanone peroxide and carotene have certain antioxidant and stabilizing effects, preventing raw material deterioration or performance degradation, thereby ensuring the stability and effectiveness of the accelerator during storage and use. The addition amount of the complexing agent in the accelerator is 1.5%-2.0%, and through synergistic effects with other raw materials, it comprehensively improves the overall performance of the accelerator.

[0027] A preparation process for a low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent includes the following steps:

[0028] (1) Dissolving and mixing: Add sodium aluminate, aluminum sulfate and water to a reaction vessel equipped with a stirring device and a heating device, turn on the stirring and heat at the same time; after the mixture is uniform, add aluminum hydroxide and react for 30-60 min at the same temperature and stirring rate.

[0029] (2) Mixed reaction: Add silica sol and borax in sequence. Stir for 15-30 min at the same temperature and stirring rate as in step (1) for each addition; add triethanolamine solution and react for 20-40 min at the same stirring rate at 60-70℃.

[0030] (3) Adding additives: After the reaction in step (2) is completed, add pH adjuster, thickener, dispersant and complexing agent. After each raw material is added, heat and stir for 5-10 minutes to finally generate a water-containing solid.

[0031] (4) Post-processing: The generated water-containing solids are dried using a drying device. After drying, the grinding device is turned on to grind the solids to obtain the quick-setting agent masterbatch powder, which is then packaged and stored to obtain the low-alkali, chlorine-free powdered soluble quick-setting agent masterbatch finished product.

[0032] Furthermore, in step (1), the stirring rate is 500-600 r / min, and the reaction vessel is heated to 40-60°C.

[0033] Furthermore, the heating in step (3) is to raise the temperature to 75-80℃.

[0034] Furthermore, the stirring rate in step (3) is 200-300 r / min.

[0035] Furthermore, in step (4), the grinding precision of the grinding device is set to a particle size of 80-200 mesh.

[0036] The preparation process principle of the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent is as follows:

[0037] Dissolution and Mixing: After sodium aluminate, aluminum sulfate, and water are heated and stirred until homogeneous, aluminum hydroxide is added, and the mixture is reacted for 30-60 minutes at the same temperature and stirring rate. Stirring ensures thorough mixing of the sodium aluminate, aluminum sulfate, and water to form a homogeneous system, guaranteeing that the sodium aluminate and aluminum sulfate dissolve uniformly in the water. Heating accelerates the dissolution rate of the sodium aluminate and aluminum sulfate, while also increasing molecular activity and promoting subsequent reactions. Higher temperatures intensify molecular motion, increasing the probability of collisions between reactants and thus accelerating the chemical reaction rate. Simultaneously, the slow dissolution and reaction process of aluminum hydroxide helps control the reaction's progress and rate, providing a stable source of aluminum ions for subsequent reactions.

[0038] Mixing Reaction: Silica sol, primarily composed of silicon dioxide, reacts with alkaline substances in the system to generate cementitious substances such as calcium silicate, enhancing the setting effect of the accelerator. Borax in the system alters the structure and morphology of cement hydration products, promoting early setting of cement. Slow addition and thorough stirring ensure sufficient reaction with other components in the system, forming a homogeneous mixture. Silica sol provides the basic silicon-oxygen tetrahedral structural units for forming the setting skeleton, while borax hydrolysis products optimize the structure of the setting skeleton through complexation with calcium ions, making the concrete setting process faster and more stable. Triethanolamine solution is added at 60-70℃ and reacted for 20-40 minutes. Triethanolamine promotes the dissolution and hydration of cement minerals; its activity is high within this temperature range, exhibiting synergistic effects with aluminum ions and silicate ions in the system. The complex formed by aluminum ions and triethanolamine alters the hydration reaction pathway of tricalcium aluminate, lowering the activation energy and thus accelerating the hydration rate of tricalcium aluminate. The synergistic effect between silicate ions and triethanolamine promotes the formation of hydrated calcium silicate (CSH) gel.

[0039] Additives: Add a pH adjuster at 75-80℃ to create a suitable acid-base environment for subsequent chemical reactions by adjusting the pH value of the system. Different chemical reactions have optimal reaction rates and effects within specific pH ranges. Add thickener, dispersant, and complexing agent at a stirring rate of 500-600 r / min and stir for 5-10 min respectively. The thickener increases the viscosity of the system and forms a three-dimensional network structure through intermolecular interactions, effectively preventing precipitation and stratification, ensuring the accelerator remains uniform and stable during storage and use. The dispersant adsorbs onto the surface of raw material particles through electrostatic repulsion and steric hindrance, working synergistically with the thickener to ensure uniform dispersion of various raw material particles in the system, avoiding agglomeration and thus improving the uniformity and efficiency of the reaction. The complexing agent undergoes a complexation reaction with metal ions (such as aluminum ions) in the system, adjusting their activity and form by changing the electron cloud distribution and coordination environment of the metal ions, enhancing the compatibility of the accelerator with materials such as cement, and synergistically optimizing the performance of the accelerator with other additives.

[0040] Post-processing: Use drying equipment to dry the water-containing solids, and grind the dried material to 80-200 mesh to further refine the particles, making them more soluble and dispersible, so that they can be quickly and uniformly dissolved when the quick-setting agent solution is prepared in the future.

[0041] The beneficial effects of this invention include:

[0042] 1. Excellent rapid setting performance: Multiple accelerating components work synergistically, with sodium aluminate and aluminum sulfate providing aluminum ions, aluminum hydroxide continuously releasing aluminum ions, sodium aluminate and aluminum sulfate generating ettringite, and triethanolamine promoting early strength. This effectively meets the construction requirements for rapid setting of shotcrete. This not only improves construction efficiency and reduces construction time, but also provides timely early support strength for the project, enhancing its safety and stability.

[0043] 2. High retention rate of later-stage strength: The rational use of components such as aluminum hydroxide and silica sol not only helps the rapid development of early-stage strength in concrete, but also ensures the continuous growth of later-stage strength. The 28-day compressive strength ratio of concrete can reach over 100%, and the 90-day compressive strength retention rate is greater than 95%, ensuring the load-bearing capacity and stability of concrete structures during long-term use.

[0044] 3. Excellent adaptability and stability: The low-alkali, chloride-free powdered soluble quick-setting agent prepared in this invention is adaptable to various types of cement and mineral admixtures, and exhibits good compatibility with other admixtures (such as water-reducing agents and air-entraining agents). It can stably exert its quick-setting effect under different engineering environments and material conditions, ensuring the uniformity of concrete quality and performance stability. This avoids engineering quality risks caused by material compatibility issues. Furthermore, the powdered form of the masterbatch facilitates storage and transportation, exhibits good stability under different environmental conditions, is not easily deteriorated or ineffective, and has good water solubility and high solution stability. It does not show sedimentation or stratification even after long-term storage, ensuring the long-term usability of the product.

[0045] 4. Environmentally friendly and chlorine-free: Free of chloride ions, eliminating the risk of chloride ion corrosion to steel bars, ensuring the long-term stability of steel bars in reinforced concrete structures, extending the service life of concrete structures, reducing construction waste caused by structural damage, and meeting the requirements of environmental protection and sustainable development.

[0046] 5. Enhanced Overall Performance: The presence of the complexing agent optimizes the synergistic effect among the components of the accelerator, enhances its compatibility with materials such as cement, and improves the product's stability and effectiveness. Thickeners and dispersants ensure the uniformity and stability of the accelerator during preparation, storage, and use, resulting in consistent accelerating effects and improved concrete quality uniformity. These factors work together to give the accelerator of this invention significant advantages in overall performance, meeting the requirements of various complex engineering environments and high-standard engineering quality, providing the construction industry with a high-performance, reliable accelerator product.

Detailed Implementation Methods

[0047] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0048] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to 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.

[0049] In this embodiment of the invention, the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent is made from the following raw materials in the indicated mass percentages:

[0050] Sodium aluminate 2%-5%, aluminum sulfate 23%-35%, aluminum hydroxide 5%-10%, silica sol 5%-10%, triethanolamine 0.5%-1.5%, borax 3%-8%, thickener 0.5%-2%, dispersant 1%-3%, pH adjuster 1.6%-1.8%, complexing agent 1.5%-2.0%, balance water.

[0051] The thickener is hydroxypropyl methylcellulose.

[0052] The dispersant is one or more of amine-modified lignin and ammonium polyacrylate.

[0053] The pH adjuster is one or more of citric acid and tartaric acid.

[0054] The complexing agent is prepared by reacting N-methyl-2-acrylamide, cyclohexylmethyldimethoxysilane, β-aminoethanesulfonic acid, cyclohexanone peroxide, carotene and water.

[0055] The preparation process of the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent includes the following steps:

[0056] (1) Dissolving and mixing: Add sodium aluminate, aluminum sulfate and water to a reaction vessel equipped with a stirring device and a heating device, turn on the stirring and heat at the same time. The stirring rate is 500-600 r / min, and the reaction vessel is heated to 40-60℃. After the mixture is uniform, add aluminum hydroxide and react for 30-60 min at the same temperature and stirring rate.

[0057] (2) Mixed reaction: Add silica sol and borax in sequence. Stir for 15-30 min at the same temperature and stirring rate as in step (1) for each addition; add triethanolamine solution and react for 20-40 min at the same stirring rate at 60-70℃.

[0058] (3) Adding additives: After the reaction in step (2) is completed, add pH adjuster, thickener, dispersant and complexing agent. After each raw material is added, stir at 75-80℃ for 5-10 minutes at a stirring rate of 200-300 r / min. Finally, a water-containing solid is generated.

[0059] (4) Post-processing: The generated water-containing solids are dried using a drying device. After drying, the grinding device is turned on to grind the solids to obtain the quick-setting agent masterbatch powder. The grinding device is set to a particle size of 80-200 mesh. The powder is packaged and stored to obtain the low-alkali, chlorine-free powdered soluble quick-setting agent masterbatch finished product.

[0060] To make the present invention more fully disclosed, more specific embodiments are described below.

[0061] Example 1

[0062] A low-alkali, chlorine-free powdered soluble quick-setting agent is made from the following raw materials in the indicated weight percentages:

[0063] Sodium aluminate 3%, aluminum sulfate 27%, aluminum hydroxide 7.2%, silica sol 7.5%, triethanolamine 1.2%, borax 5.5%, thickener 1.2%, dispersant 1.8%, pH adjuster 1.7%, complexing agent 1.8%, balance water.

[0064] The thickener is hydroxypropyl methylcellulose.

[0065] The dispersant is amine-modified lignin.

[0066] The pH adjuster is tartaric acid.

[0067] The complexing agent is prepared by reacting N-methyl-2-acrylamide, cyclohexylmethyldimethoxysilane, β-aminoethanesulfonic acid, cyclohexanone peroxide, carotene, and water; the preparation steps of the complexing agent are as follows:

[0068] (1) Mix 42 parts of N-methyl-2-acrylamide, 10 parts of cyclohexylmethyldimethoxysilane, 70 parts of β-aminoethanesulfonic acid, 1.5 parts of cyclohexanone peroxide and 360 parts of water, and then react for 50 min under the conditions of 200 r / min rotation speed, 300 W microwave power and 38 °C temperature to obtain the reaction mixture.

[0069] (2) Add 0.5 parts of carotene and 90 parts of water to the reaction mixture obtained in step (1), and then react for 60 minutes under the conditions of 300 r / min, 200 W microwave power and 42 °C. Then cool to room temperature to obtain the complexing agent.

[0070] The preparation process of the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent includes the following steps:

[0071] (1) Dissolving and mixing: Sodium aluminate, aluminum sulfate and water are added to a reaction vessel equipped with a stirring device and a heating device. Stirring is started and heating is carried out at a stirring rate of 550 r / min. The reaction vessel is heated to 50°C. After the mixture is uniform, aluminum hydroxide is added and the reaction is carried out at the same temperature and stirring rate for 45 min.

[0072] (2) Mixed reaction: Add silica sol and borax in sequence, and stir for 20 min at the same temperature and stirring rate as in step (1) for each addition; add triethanolamine solution and react for 35 min at the same stirring rate at 65℃.

[0073] (3) Adding additives: After the reaction in step (2) is completed, add pH adjuster, thickener, dispersant and complexing agent. After each raw material is added, stir at 78°C for 10 min at a stirring rate of 300 r / min. Finally, a water-containing solid is generated.

[0074] (4) Post-processing: The generated water-containing solids are dried using a drying device. After drying, the grinding device is turned on to grind the solids to obtain the quick-setting agent masterbatch powder. The grinding device is set to a particle size of 120 mesh. The powder is packaged and stored to obtain the low-alkali, chlorine-free powdered soluble quick-setting agent masterbatch finished product.

[0075] Example 2

[0076] A low-alkali, chlorine-free powdered soluble quick-setting agent is made from the following raw materials in the indicated weight percentages:

[0077] Sodium aluminate 2.5%, aluminum sulfate 24%, aluminum hydroxide 8%, silica sol 8.5%, triethanolamine 1.1%, borax 6.3%, thickener 1.5%, dispersant 2.2%, pH adjuster 1.6%, complexing agent 1.9%, balance water.

[0078] The thickener is hydroxypropyl methylcellulose.

[0079] The dispersant is ammonium polyacrylate.

[0080] The pH adjuster is citric acid.

[0081] The preparation method of the complexing agent is the same as that in Example 1.

[0082] The preparation process of the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent includes the following steps:

[0083] (1) Dissolving and mixing: Sodium aluminate, aluminum sulfate and water are added to a reaction vessel equipped with a stirring device and a heating device. Stirring is started and heating is carried out at a stirring rate of 520 r / min. The reaction vessel is heated to 45°C. After the mixture is uniform, aluminum hydroxide is added and the reaction is carried out at the same temperature and stirring rate for 50 min.

[0084] (2) Mixed reaction: Add silica sol and borax in sequence, and stir for 25 min at the same temperature and stirring rate as in step (1) for each addition; add triethanolamine solution and react for 30 min at the same stirring rate at 62℃.

[0085] (3) Adding additives: After the reaction in step (2) is completed, add pH adjuster, thickener, dispersant and complexing agent. After each raw material is added, stir at 76°C for 8 minutes at a stirring rate of 280 r / min. Finally, a water-containing solid is generated.

[0086] (4) Post-processing: The generated water-containing solids are dried using a drying device. After drying, the grinding device is turned on to grind the solids to obtain the quick-setting agent masterbatch powder. The grinding device is set to a particle size of 100 mesh. The powder is packaged and stored to obtain the low-alkali, chlorine-free powdered soluble quick-setting agent masterbatch finished product.

[0087] Example 3

[0088] A low-alkali, chlorine-free powdered soluble quick-setting agent is made from the following raw materials in the indicated weight percentages:

[0089] Sodium aluminate 3%, aluminum sulfate 30%, aluminum hydroxide 6%, silica sol 6%, triethanolamine 1.5%, borax 4.2%, thickener 0.8%, dispersant 1.5%, pH adjuster 1.8%, complexing agent 1.6%, balance water.

[0090] The thickener is hydroxypropyl methylcellulose.

[0091] The dispersant is ammonium polyacrylate.

[0092] The pH adjuster is citric acid.

[0093] The preparation method of the complexing agent is the same as that in Example 1.

[0094] The preparation process of the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent includes the following steps:

[0095] (1) Dissolving and mixing: Sodium aluminate, aluminum sulfate and water are added to a reaction vessel equipped with a stirring device and a heating device. Stirring is started and heating is carried out at a stirring rate of 580 r / min. The reaction vessel is heated to 55°C. After the mixture is uniform, aluminum hydroxide is added and the reaction is carried out at the same temperature and stirring rate for 35 min.

[0096] (2) Mixed reaction: Add silica sol and borax in sequence, and stir for 20 min at the same temperature and stirring rate as in step (1) for each addition; add triethanolamine solution and react for 25 min at the same stirring rate at 68℃.

[0097] (3) Adding additives: After the reaction in step (2) is completed, add pH adjuster, thickener, dispersant and complexing agent. After each raw material is added, stir at 80°C for 6 minutes at a stirring rate of 220 r / min. Finally, a water-containing solid is generated.

[0098] (4) Post-processing: The generated water-containing solids are dried using a drying device. After drying, the grinding device is turned on to grind the solids to obtain the quick-setting agent masterbatch powder. The grinding device is set to a particle size of 150 mesh. The powder is packaged and stored to obtain the low-alkali, chlorine-free powdered soluble quick-setting agent masterbatch finished product.

[0099] Comparative Example 1

[0100] The process is basically the same as in Example 1, except that no thickener, dispersant, or complexing agent is added to the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent, and the remainder is made up with water.

[0101] Comparative Example 2

[0102] The process is basically the same as in Example 1, except that no thickener is added to the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent, and the remainder is made up with water.

[0103] Comparative Example 3

[0104] The process is basically the same as in Example 1, except that no dispersant is added to the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent, and the remainder is made up with water.

[0105] Comparative Example 4

[0106] The process is basically the same as in Example 1, except that no complexing agent is added to the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent, and the remainder is made up with water.

[0107] The low-alkali, chlorine-free powdered soluble accelerators prepared in Examples 1-3 and Comparative Examples 1-4 were mixed with water to form a low-alkali, chlorine-free liquid accelerator. The liquid accelerator was then tested for setting time, compressive strength, and stability of concrete with the added accelerator according to GB / T35159-2017 "Accelerators for Shotcrete". The test results are shown in the table below. The dosage of the liquid accelerator was 6% of the binder weight.

[0108]

[0109] In this case, “√” indicates that there is no stratification phenomenon.

[0110] The experimental data show that the initial setting time of Comparative Example 1 was 3:56 and the final setting time was 7:10; the initial setting time of Comparative Example 2 was 3:23 and the final setting time was 6:36; the initial setting time of Comparative Example 3 was 3:29 and the final setting time was 6:42; and the initial setting time of Comparative Example 4 was 3:37 and the final setting time was 6:50. Compared with the examples, the setting time of the comparative examples was significantly prolonged. Thickeners can form a stable colloidal structure in the solution, ensuring uniform distribution of raw materials and promoting rapid reaction to shorten the setting time. Comparative Example 2 lacked thickeners, resulting in raw material precipitation and delayed reaction. Dispersants can uniformly disperse raw material particles, increase contact area and improve reaction activity. Comparative Example 3 did not add dispersants, resulting in particle agglomeration and affecting setting. Complexing agents can optimize component performance and regulate metal ion activity. Comparative Example 4 lacked complexing agents, which affected metal ion activity and reaction efficiency, thus prolonging the setting time.

[0111] Regarding mortar strength, the 1-day compressive strength of Comparative Example 1 was 9.5 MPa, the 28-day compressive strength ratio was 90.5%, and the 90-day compressive strength retention rate was 88.1%; the 1-day compressive strength of Comparative Example 2 was 10.1 MPa, the 28-day compressive strength ratio was 92.6%, and the 90-day compressive strength retention rate was 89.3%; the 1-day compressive strength of Comparative Example 3 was 10.2 MPa, the 28-day compressive strength ratio was 95.1%, and the 90-day compressive strength retention rate was 93.2%; and the 1-day compressive strength of Comparative Example 4 was 9.9 MPa, the 28-day compressive strength ratio was 91.5%, and the 90-day compressive strength retention rate was 88.7%, all of which were far lower than those of the Examples. Thickeners help cement hydration reaction to be uniform and complete, which is beneficial to strength development. In Comparative Example 2, the lack of thickeners resulted in insufficient hydration and limited strength. Dispersants enable the components to react better with cement minerals and enhance the structure. In Comparative Example 3, the absence of dispersants resulted in a less dense internal structure and affected strength. Complexing agents regulate the activity of metal ions and optimize the product structure. In Comparative Example 4, the lack of complexing agents resulted in poor reaction process and product structure, leading to reduced strength.

[0112] Regarding stability, Comparative Example 1 showed 15 mL of separation after 90 days, Comparative Example 2 showed 10 mL, Comparative Example 3 showed 7 mL, and Comparative Example 4 showed 4 mL, while the examples showed no separation. Thickeners increase solution viscosity and stability, preventing precipitation; Comparative Example 2, lacking a thickener, exhibited poor stability and severe precipitation and separation. Dispersants prevent particle agglomeration and precipitation, maintaining homogeneity; Comparative Example 3, lacking a dispersant, experienced separation. Complexing agents also have a certain impact on system stability; Comparative Example 4, lacking a complexing agent, showed decreased stability.

[0113] In summary, thickeners, dispersants, and complexing agents are indispensable in low-alkali, chlorine-free powdered soluble accelerators. They work synergistically to ensure the high efficiency and good stability of the accelerator from multiple aspects. The absence of any one or more of them will result in poor performance of the accelerator in terms of setting time, mortar strength, and stability, failing to achieve the excellent performance of the examples. Therefore, the addition of these additives is essential when preparing this accelerator to meet the requirements of engineering applications.

[0114] Those skilled in the art will recognize that numerous variations are possible with respect to the above description, and therefore the embodiments are merely illustrative of one or more specific implementations.

[0115] Although exemplary embodiments of the invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the invention without departing from the central concepts of the invention described herein. Therefore, the invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the invention.

Claims

1. A preparation process for a low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent, characterized in that, The low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent is made from the following raw materials in the indicated mass percentages: Sodium aluminate 3%, aluminum sulfate 27%, aluminum hydroxide 7.2%, silica sol 7.5%, triethanolamine 1.2%, borax 5.5%, thickener 1.2%, dispersant 1.8%, pH adjuster 1.7%, complexing agent 1.8%, balance water; The preparation process of the low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent includes the following steps: (1) Dissolving and mixing: Add sodium aluminate, aluminum sulfate and water to a reaction vessel equipped with a stirring device and a heating device, turn on the stirring and heat at the same time; after mixing evenly, add aluminum hydroxide and react for 30-60 min at the same temperature and stirring rate; (2) Mixed reaction: Add silica sol and borax in sequence, and stir for 15-30 min at the same temperature and stirring rate as in step (1) for each addition; add triethanolamine solution and react for 20-40 min at the same stirring rate at 60-70℃. (3) Adding additives: After the reaction in step (2) is completed, add pH adjuster, thickener, dispersant and complexing agent. After each raw material is added, heat and stir for 5-10 minutes to finally generate a water-containing solid. (4) Post-processing: The generated water-containing solids are dried using a drying device. After drying, the grinding device is turned on to grind the solids to obtain the quick-setting agent masterbatch powder, which is then packaged and stored to obtain the low-alkali, chlorine-free powdered soluble quick-setting agent masterbatch finished product. In step (1), the stirring rate is 500-600 r / min, and the reaction vessel is heated to 40-60℃ at the same time; The heating in step (3) is to raise the temperature to 75-80℃; Step (3) The stirring rate is 200-300 r / min; In step (4), the grinding precision of the grinding device is set to a particle size of 80-200 mesh.

2. The preparation process of a low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent according to claim 1, characterized in that, The thickener is hydroxypropyl methylcellulose.

3. The preparation process of a low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent according to claim 1, characterized in that, The dispersant is one or more of amine-modified lignin and ammonium polyacrylate.

4. The preparation process of a low-alkali, chlorine-free powdered masterbatch soluble quick-setting agent according to claim 1, characterized in that, The pH adjuster is one or more of citric acid and tartaric acid.

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