An active activator for finely ground fly ash, its preparation method and application

Abstract

This application relates to the field of new materials, specifically disclosing an active activator for finely ground fly ash, its preparation method, and its application. The active activator comprises the following raw materials in parts by weight: 3-7 parts of polycarboxylate additive, 2-4 parts of anhydrous sodium sulfate, 15-18 parts of alkanolamine, and 2-6 parts of glucose monohydrate; wherein the polycarboxylate additive is obtained by polymerization of diethylene glycol monovinyl ether and acrylic acid as monomers. This application also discloses its preparation method, which includes the following steps: mixing the raw materials evenly according to the specified ratio to obtain the active activator for finely ground fly ash. This application also discloses the application of the above-mentioned active activator, wherein the active activator is mixed with fly ash at a mass ratio of 1:(900-1000) and then ground for application. This application has the characteristics of improving the activity and mechanical properties of fly ash.

Description

Technical Field

[0001] This application relates to the field of new materials technology, and more specifically, it relates to an activation method for ultrafine fly ash, its preparation method, and its application. Background Technology

[0002] Currently, among various cementitious materials, silicate cement is the most commonly used. However, the raw materials for this type of cement contain a large amount of calcium carbonate and silicon dioxide. These two substances react during the calcination of the cement raw materials, releasing a large amount of carbon dioxide, which is detrimental to the ecological environment. Therefore, a new type of cementitious material—fly ash—was later discovered. Its raw material comes from the smoke and dust emissions from power plants, etc. Through equipment recycling, registration, screening, and processing, it is transformed into a cementitious material with certain activity. This material is used in cement products, thereby reducing the amount of cement used, thus reducing carbon dioxide emissions, effectively improving the environment, and achieving sustainable development.

[0003] Fly ash is the powdery ash particles emitted from the flue of finely ground coal in coal-fired power plants after combustion in boilers and absorbed by dust collectors. Fly ash emissions from thermal power generation have become the largest single source of industrial solid waste pollution and a major component of industrial solid waste. Because it contains a large amount of pozzolanic active substances such as silica, alumina, and calcium oxide, it is a potentially active pozzolanic powder that can be used as an admixture in building materials such as cement and concrete. The utilization of fly ash in the field of cementitious materials not only disposes of a large amount of industrial waste but also saves a significant amount of artificial cementitious materials. Using fly ash as an admixture in silicate cement is an effective technical approach for treating and utilizing fly ash.

[0004] Fly ash consists of active ingredients and a smooth, hard glassy substance. The presence of this glassy substance hinders the hydration of the active ingredients, resulting in low activity of the fly ash in the early stages of use and affecting its dosage in cement and concrete. Although fly ash emissions are currently large, utilization rates are low. By activating the fly ash, its dosage in cementitious materials such as concrete and cement can be increased, thereby reducing dependence on natural resources and lowering production costs.

[0005] Currently, the activation of fly ash mainly employs physical-mechanical methods, namely, mechanical grinding to disrupt the glassy structure of the fly ash surface and further increase the specific surface area, thereby activating the pozzolanic activity of silica and alumina in the fly ash. While the activity does gradually increase with increasing fly ash fineness, it is not infinitely increasing. Once a certain fineness is reached, the activity stops increasing. Furthermore, continued grinding of fly ash can lead to agglomeration, which negatively impacts its activity. Moreover, the reduction in fly ash fineness is limited, and grinding fly ash requires pulverization, which is costly and consumes a large amount of energy. Therefore, a new fly ash activation activator is needed to give fly ash better activity intensity. Summary of the Invention

[0006] To improve the activity and mechanical properties of fly ash, this application provides an activity activator for finely ground fly ash, its preparation method, and its application.

[0007] In a first aspect, this application provides an active activator for finely ground fly ash, employing the following technical solution:

[0008] An active activator for finely ground fly ash comprises the following raw materials in parts by weight:

[0009] 3-7 parts polycarboxylate additive, 2-4 parts anhydrous sodium sulfate, 15-18 parts alkanolamine, and 2-6 parts glucose monohydrate;

[0010] The polycarboxylic acid additive is obtained by polymerization of diethylene glycol monovinyl ether and acrylic acid as monomers.

[0011] By adopting the above technical solution, this application uses anhydrous sodium sulfate and alkanolamine as activation agents, and also adds polycarboxylic acid. Anhydrous sodium sulfate, as an activation agent, allows sulfate ions ionized in the aqueous solution to react with the active components in fly ash, destroying the dense oxide shell layer on the surface of the fly ash spherical glass, exposing the internal aluminosilicates, thereby increasing the activity of fly ash. Moreover, sodium sulfate can also promote the reaction between fly ash and cement hydration products, generating more hydrated calcium silicate and hydrated calcium aluminate and other cementitious products, which helps to improve the strength and durability of fly ash concrete. The addition of alkanolamine is alkaline in aqueous solution, which can provide an alkaline environment conducive to the activation of fly ash activity, and facilitate the dissolution and hydration reaction of active silica and alumina in fly ash.

[0012] In this application, the polycarboxylic acid (PCA) synthesized by polymerization of diethylene glycol monovinyl ether and acrylic acid as monomers exhibits a chain-like, comb-like morphology. It possesses a significant steric hindrance effect and high surface activity, making it readily adsorbed onto the surface of fly ash gel materials. Through its long-chain structure and steric hindrance effect, the PCA molecules adsorbed on the fly ash surface can prevent the agglomeration of fly ash particles, improving the dispersibility of the fly ash. This not only helps expose more fly ash surface area, facilitating the mechanical action during subsequent fly ash grinding to break down the oxide shell on the fly ash surface and expose active substances, but also allows the carboxylic acid in the PCA molecule to form chemical bonds with the fly ash surface oxides, reducing their surface energy and increasing reactivity. Furthermore, the carboxyl groups can complex with metal ions such as calcium in the fly ash, breaking down the oxide shell and exposing the internal active substances, thus enhancing activity. Moreover, the hydrophilicity and permeability of the PCA molecules help dissolve and peel off the oxide shell on the fly ash surface, further exposing active substances and providing a reinforcing effect.

[0013] In addition, the polycarboxylate prepared in this application has good compatibility with water and the above-mentioned alkanolamine, which allows the polycarboxylate to be effectively mixed with other components in the cement system, promoting the uniformity of the overall reaction. This allows the activator in this application to not only effectively enhance the pozzolanic activity of fly ash, but also to significantly improve the compressive strength and flexural strength of fly ash products through electrostatic repulsion dispersion, so that it can maintain sufficient strength and stability during long-term use and improve durability.

[0014] In addition, the good compatibility of polycarboxylate and the steric hindrance of polycarboxylate adsorbed on fly ash particles in this application can prevent agglomeration, thereby maintaining good dispersibility and reducing water demand. The activator for finely ground fly ash in this application can meet the requirement of a significant reduction in water demand without changing the gelation time of finely ground fly ash, thereby improving the application effect of finely ground fly ash in cement products and improving the quality control requirements of cement products.

[0015] Optionally, the activated activator for finely ground fly ash comprises the following raw materials in parts by weight:

[0016] 4 parts polycarboxylic acid additive, 3 parts anhydrous sodium sulfate, 4 parts glucose monohydrate and 16 parts alcoholamine.

[0017] By adopting the above technical solution, the addition of glucose monohydrate in this application utilizes its hygroscopic properties to eliminate the bleeding phenomenon when water seepage occurs in fly ash-cement slurry. Furthermore, the active functional groups of hydroxyl and carboxyl groups in glucose monohydrate are adsorbed onto the surface of fly ash through hydrogen bonding and other interactions, thereby reducing the water demand of fly ash and ultimately lowering the water demand of the slurry.

[0018] Optionally, the alkanolamine includes one or more of triethanolamine, diethanol monoisopropanolamine, and triisopropanolamine.

[0019] Optionally, the alcoholamine includes triethanolamine and diethanol monoisopropanolamine in a mass ratio of 1:(1.1-1.3).

[0020] By adopting the above technical solution, this application selects triethanolamine-enhanced alkanolamine and diethanolamine monoisopropanolamine-promoted alkanolamine. Both have good grinding aid effects, can refine fly ash particles, increase specific surface area, and expose more active sites. In addition, the alkaline environment of both promotes the breaking of Si-O-Si, Si-O-Al, and Al-O-Al bonds in the glass matrix, releasing active silica and alumina, which then react with calcium hydroxide formed by cement hydration to generate hydrated calcium silicate and hydrated calcium aluminate gel products, significantly enhancing the activity of fly ash and playing a reinforcing role. When using the two alkanolamines in the ratio of this application, the activation effect on finely ground fly ash is better. If the amount of triethanolamine is too small, it will not achieve a good emulsification and exfoliation effect and metal complexation effect, affecting the 28-day compressive strength and 28-day flexural strength of fly ash. If the amount of diethanolamine monoisopropanolamine added is too small, the grinding efficiency will be low, and good dispersibility will not be achieved, thus reducing water demand and failing to meet the process economy requirements.

[0021] Optionally, the polycarboxylate additive is prepared by the following method:

[0022] Diethylene glycol monovinyl ether is mixed with an initiator and preheated to 15-20°C. Acrylic acid is then added dropwise under stirring over 40-60 minutes. After reacting for 30-60 minutes, the mixture is cooled and neutralized to obtain a polycarboxylic acid additive.

[0023] By adopting the above technical solution, the polycarboxylate obtained by the method provided in this application has a chain-like comb-like morphology, high surface activity, good compatibility with water and alkanolamines, and is easy to adsorb onto fly ash and cementitious materials to generate steric hindrance. Moreover, in this application, acrylic acid is added dropwise at low temperature and polymerized under the action of an initiator to form a polycarboxylate additive, which reduces the generation of side reactions.

[0024] Optionally, in the preparation process of the polycarboxylic acid additive, the molar ratio of diethylene glycol monovinyl ether to acrylic acid is (1-1.2):5, and the amount of initiator added is 1-3 wt% of the amount of diethylene glycol monovinyl ether added.

[0025] By adopting the above technical solution and using the above ratio, the polycarboxylate additive has a better effect on activating fly ash activity.

[0026] Optionally, the active activator further includes 2-5 parts by weight of polyethyleneimine. When preparing the polycarboxylic acid additive, N,N'-methylenebisacrylamide and hydroxyethyl acrylate are added dropwise together with acrylic acid, and the amount of hydroxyethyl acrylate added is 20-30 wt% of the amount of acrylic acid added, and the amount of N,N'-methylenebisacrylamide added is 5-10 wt% of the amount of acrylic acid added.

[0027] By adopting the above technical solution, the active activator in this application also includes polyethyleneimine, and N,N'-methylenebisacrylamide and hydroxyethyl acrylate are added during the preparation of polycarboxylic acid. N,N'-methylenebisacrylamide, as a crosslinking agent, can react with the copolymer of diethylene glycol monovinyl ether and acrylic acid to form a network structure with greater steric hindrance. The functional monomer of hydroxyethyl acrylate introduces hydroxyl groups into the polycarboxylic acid molecular chain, increasing the active sites for adsorption and interaction with fly ash, further improving the activation effect of fly ash. Polyethyleneimine, as an organic amine compound, has amino groups in its molecule that interact with fly ash... The surface silicon and oxygen functional groups react to form chemical bonds, which helps to disrupt the dense surface structure of fly ash, promote the dissolution of internal active components, and improve the activity of fly ash. Furthermore, the positive charge of polyethyleneimine interacts with the negative charge on the fly ash surface, preventing particle agglomeration and contributing to the uniform distribution and reaction of active components. The combination of polyethyleneimine and polycarboxylate, with the chemical modification and charge effect of polyethyleneimine synergistically working with the dispersion and chelation effects of polycarboxylate, disrupts the surface structure of fly ash, releasing active components, while polycarboxylate promotes the reaction between fly ash and the activator through dispersion and chelation, jointly enhancing the activity of fly ash. In addition, the polyethyleneimine added to the activator, as a highly branched polymer containing primary and secondary amines, and possibly a small amount of amino groups forming amide bonds with the carboxyl and hydroxyl groups in the polycarboxylate, achieves polymeric linkage between polyethyleneimine and polycarboxylate, thereby generating an activator with greater steric hindrance effect, further improving the dispersion of fly ash, helping to expose more fly ash surface, improving subsequent fine grinding, and also increasing the contact area with the activator, thus enhancing the activation effect.

[0028] Optionally, the active activator further includes 1-3 parts by weight of nano-silica powder-carboxymethyl cellulose composite microspheres, which are prepared by the following method:

[0029] 1) Dissolve carboxymethyl cellulose powder in a carboxymethyl cellulose solution with a mass concentration of 35-45 wt%;

[0030] 2) A nano-silicon powder suspension was prepared by mixing nano-silicon powder and water at a mass ratio of 1:(4-6) and ultrasonically dispersing the mixture.

[0031] 3) The carboxymethyl cellulose solution obtained in step 1) is added dropwise to the nano-silicon powder suspension obtained in step 2), stirred, heated to 45-55℃, and then calcium chloride solution is added dropwise. The mixture is kept at 45-55℃ for 10-12 hours, then filtered and dried to obtain nano-silicon powder-carboxymethyl cellulose composite microspheres.

[0032] The mass ratio of carboxymethyl cellulose powder to nano-silica powder is 1:(2-3), and the amount of calcium chloride added is 3-5 wt% of carboxymethyl cellulose powder.

[0033] By employing the above-mentioned technical solution, nano-silica powder acts as a reaction site, promoting the dissolution and recrystallization of aluminosilicate minerals in fly ash. This recrystallization process generates more hydration products, such as calcium silicate hydrate, which significantly improve the strength and durability of fly ash. The nano-sized particles of nano-silica powder possess extremely high specific surface area and surface activity, enabling it to more effectively contact aluminosilicate minerals in fly ash, thereby accelerating the hydration reaction and making it easier to participate in chemical reactions, thus lowering the activation energy. Furthermore, the silicon element in nano-silica powder can react chemically with the aluminum element in fly ash to generate new aluminosilicate minerals or hydration products with higher stability and strength, further enhancing the performance of fly ash. In addition, nano-silica powder may also indirectly promote the hydration reaction by influencing the distribution and migration of ions in the reaction system through adsorption and complexation. Therefore, the addition of nano-silica powder has a positive effect on improving the activity of fly ash.

[0034] Carboxymethyl cellulose can react with metals such as calcium on the surface of fly ash to form a hydrogel structure with a three-dimensional network structure. This structure helps to increase the active surface area of ​​fly ash and promote its reaction with cement hydration products. In this application, nano-silica powder and carboxymethyl cellulose are combined to form composite microspheres for addition. On the one hand, compared with the direct addition of nano-silica powder, it overcomes the disadvantage of easy agglomeration and poor dispersion. On the other hand, the silicate ions generated by the hydrolysis reaction of nano-silica powder in water can chemically react with the active components in fly ash, promote the pozzolanic effect of fly ash, and generate new hydration products, thereby improving the activity of fly ash. Moreover, the calcium ions introduced by the addition of calcium chloride during the preparation of composite microspheres react with the active components in fly ash to generate more hydration products, further stimulating the activity of fly ash.

[0035] Secondly, this application provides a method for preparing an active activator for finely ground fly ash, using the following technical solution:

[0036] A method for preparing an active activator for finely ground fly ash includes the following steps:

[0037] The active activator for finely ground fly ash is prepared by mixing the raw materials evenly according to the formula.

[0038] By adopting the above technical solution, the preparation method provided by this application is simple and convenient, the raw materials are readily available, and it is easy to achieve industrialization.

[0039] Thirdly, this application provides an application of an active activator for finely ground fly ash, employing the following technical solution:

[0040] An application of an active activator for grinding fly ash involves mixing the active activator with fly ash at a mass ratio of 1:(900-1000) and then grinding the fly ash.

[0041] By adopting the above technical solution, the active activator prepared in this application is mixed with fly ash and then ground to work synergistically, effectively improving the pozzolanic activity of fly ash and increasing the compressive strength and flexural strength of fly ash products.

[0042] In summary, this application has the following beneficial effects:

[0043] 1. The polycarboxylic acid obtained by polymerization of diethylene glycol monovinyl ether and acrylic acid as monomers in this application has a chain-like comb-like morphology, which has a large steric hindrance effect and high surface activity. This makes the polycarboxylic acid readily adsorbed onto the surface of fly ash gel material. The polycarboxylic acid molecules adsorbed on the fly ash surface can prevent the agglomeration between fly ash particles through their long chain structure and steric hindrance effect, thereby improving the dispersibility of fly ash. This not only helps to expose more fly ash surface, but also facilitates the mechanical action during the subsequent mechanical grinding of fly ash to destroy the oxide shell on the fly ash surface and expose active substances. Furthermore, the carboxylic acid in the polycarboxylic acid molecule forms a chemical bond with the oxide on the fly ash surface, reducing its surface energy and increasing its reactivity. Moreover, the carboxyl group can also complex with metal ions such as calcium in fly ash, destroying the oxide shell on the fly ash surface and exposing the active substances inside, thereby improving the activity. In addition, the hydrophilicity and permeability of the polycarboxylic acid molecule help to dissolve and peel off the oxide shell on the fly ash surface, further exposing the active substances and playing a reinforcing role.

[0044] 2. The polycarboxylate prepared in this application has good compatibility with water and the above-mentioned alkanolamine, which enables the polycarboxylate to be effectively mixed with other components in the cement system, promoting the uniformity of the overall reaction. This allows the activity activator in this application to not only effectively enhance the pozzolanic activity of fly ash, but also significantly improve the compressive strength and flexural strength of fly ash products through electrostatic repulsion dispersion, so that it can maintain sufficient strength and stability during long-term use and improve durability.

[0045] 3. The good compatibility of polycarboxylate and the steric hindrance of polycarboxylate adsorbed on fly ash particles in this application can prevent agglomeration, thereby maintaining good dispersibility and reducing water demand. The activator for finely ground fly ash in this application can meet the requirement of significantly reducing water demand without changing the gelation time of finely ground fly ash, thereby improving the application effect of finely ground fly ash in cement products and improving the quality control requirements of cement products. Detailed Implementation

[0046] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0047] Preparation Example 1

[0048] A method for preparing a polycarboxylic acid additive includes the following steps:

[0049] Diethylene glycol monovinyl ether was mixed with ammonium persulfate as an initiator, preheated to 18°C, and acrylic acid was added dropwise under stirring. The addition was completed within 50 minutes. After reacting for 40 minutes, the mixture was cooled and neutralized to obtain a polycarboxylic acid additive.

[0050] The molar ratio of diethylene glycol monovinyl ether to acrylic acid is 1.1:5, and the amount of initiator added is 2 wt% of the amount of diethylene glycol monovinyl ether added.

[0051] Preparation Example 2

[0052] A method for preparing a polycarboxylic acid additive includes the following steps:

[0053] Diethylene glycol monovinyl ether was mixed with ammonium persulfate as an initiator, preheated to 15°C, and acrylic acid was added dropwise under stirring. The addition was completed within 40 minutes. After reacting for 60 minutes, the mixture was cooled and neutralized to obtain a polycarboxylic acid additive.

[0054] The molar ratio of diethylene glycol monovinyl ether to acrylic acid is 1:5, and the amount of initiator added is 1 wt% of the amount of diethylene glycol monovinyl ether added.

[0055] Preparation Example 3

[0056] A method for preparing a polycarboxylic acid additive includes the following steps:

[0057] Diethylene glycol monovinyl ether was mixed with ammonium persulfate as an initiator, preheated to 20°C, and acrylic acid was added dropwise under stirring. The addition was completed within 60 minutes. After reacting for 30 minutes, the mixture was cooled and neutralized to obtain a polycarboxylic acid additive.

[0058] The molar ratio of diethylene glycol monovinyl ether to acrylic acid is 1.2:5, and the amount of initiator added is 3 wt% of the amount of diethylene glycol monovinyl ether added.

[0059] Preparation Example 4

[0060] A method for preparing a polycarboxylic acid additive is carried out according to the method in Preparation Example 1, except that N,N'-methylenebisacrylamide and hydroxyethyl acrylate are added dropwise along with acrylic acid, and the amount of hydroxyethyl acrylate added is 25 wt% of the amount of acrylic acid added, and the amount of N,N'-methylenebisacrylamide added is 8 wt% of the amount of acrylic acid added.

[0061] Preparation Example 5

[0062] A method for preparing a polycarboxylic acid additive is carried out according to the method in Preparation Example 1, except that N,N'-methylenebisacrylamide and hydroxyethyl acrylate are added dropwise along with acrylic acid, and the amount of hydroxyethyl acrylate added is 20 wt% of the amount of acrylic acid added, and the amount of N,N'-methylenebisacrylamide added is 5 wt% of the amount of acrylic acid added.

[0063] Preparation Example 6

[0064] A method for preparing a polycarboxylic acid additive is carried out according to the method in Preparation Example 1, except that N,N'-methylenebisacrylamide and hydroxyethyl acrylate are added dropwise at the same time as acrylic acid, and the amount of hydroxyethyl acrylate added is 30 wt% of the amount of acrylic acid added, and the amount of N,N'-methylenebisacrylamide added is 10 wt% of the amount of acrylic acid added.

[0065] Example 1

[0066] A method for preparing an active activator for finely ground fly ash includes the following steps:

[0067] 4 kg of the polycarboxylic acid additive prepared in Example 1, 3 kg of anhydrous sodium sulfate and 16 kg of alkanolamine were mixed evenly to prepare an activity activator. The alkanolamine was selected as a mixture of triethanolamine and diethanol monoisopropanolamine in a mass ratio of 1:1.2.

[0068] Example 2

[0069] A method for preparing an active activator for finely ground fly ash includes the following steps:

[0070] 3 kg of the polycarboxylic acid additive prepared in Preparation Example 2, 2 kg of anhydrous sodium sulfate and 15 kg of alkanolamine were mixed evenly to prepare an activity activator. The alkanolamine was selected as a mixture of triethanolamine and diethanol monoisopropanolamine in a mass ratio of 1:1.1.

[0071] Example 3

[0072] A method for preparing an active activator for finely ground fly ash includes the following steps:

[0073] 7 kg of the polycarboxylic acid additive prepared in Preparation Example 3, 4 kg of anhydrous sodium sulfate and 18 kg of alkanolamine were mixed evenly to prepare an activity activator. The alkanolamine was selected as a mixture of triethanolamine and diethanol monoisopropanolamine in a mass ratio of 1:1.3.

[0074] Example 4

[0075] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that the polycarboxylic acid additive is the polycarboxylic acid additive obtained in Preparation Example 4.

[0076] Example 5

[0077] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that the polycarboxylic acid additive is the polycarboxylic acid additive obtained in Preparation Example 4, and 3 kg of polyethyleneimine is also added.

[0078] Example 6

[0079] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that the polycarboxylic acid additive is the polycarboxylic acid additive obtained in Preparation Example 5, and 2 kg of polyethyleneimine is also added.

[0080] Example 7

[0081] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that the polycarboxylic acid additive is the polycarboxylic acid additive obtained in Preparation Example 6, and 5 kg of polyethyleneimine is also added.

[0082] Example 8

[0083] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that 2 kg of nano-silica powder-carboxymethyl cellulose composite microspheres are added along with the polycarboxylic acid additive. The nano-silica powder-carboxymethyl cellulose composite microspheres are prepared by the following method:

[0084] 1) Dissolve carboxymethyl cellulose powder in a solution with a mass concentration of 40 wt% to obtain a carboxymethyl cellulose solution;

[0085] 2) A nano-silicon powder suspension was prepared by mixing nano-silicon powder and water at a mass ratio of 1:5 and then ultrasonically dispersing the mixture.

[0086] 3) The carboxymethyl cellulose solution obtained in step 1) is added dropwise to the nano-silicon powder suspension obtained in step 2), stirred, heated to 50°C, and then calcium chloride solution with a mass concentration of 12wt% is added dropwise. The mixture is kept at 50°C for 11 hours, filtered, and then dried to obtain nano-silicon powder-carboxymethyl cellulose composite microspheres.

[0087] The mass ratio of carboxymethyl cellulose powder to nano-silica powder is 1:2.5, and the amount of calcium chloride added is 3-5 wt% of carboxymethyl cellulose powder.

[0088] Example 9

[0089] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that 1 kg of nano-silica powder-carboxymethyl cellulose composite microspheres are added along with the polycarboxylic acid additive. The nano-silica powder-carboxymethyl cellulose composite microspheres are prepared by the following method:

[0090] 1) Dissolve carboxymethyl cellulose powder in a solution with a mass concentration of 35 wt% to obtain a carboxymethyl cellulose solution;

[0091] 2) A nano-silicon powder suspension was prepared by mixing nano-silicon powder and water at a mass ratio of 1:4 and then ultrasonically dispersing the mixture.

[0092] 3) The carboxymethyl cellulose solution obtained in step 1) is added dropwise to the nano-silicon powder suspension obtained in step 2), stirred, heated to 45°C, and then a calcium chloride solution with a mass concentration of 10wt% is added dropwise. The mixture is kept at 45°C for 12 hours, filtered, and then dried to obtain nano-silicon powder-carboxymethyl cellulose composite microspheres.

[0093] The mass ratio of carboxymethyl cellulose powder to nano-silica powder is 1:2, and the amount of calcium chloride added is 3 wt% of carboxymethyl cellulose powder.

[0094] Example 10

[0095] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that 3 kg of nano-silica powder-carboxymethyl cellulose composite microspheres are added along with the polycarboxylic acid additive. The nano-silica powder-carboxymethyl cellulose composite microspheres are prepared by the following method:

[0096] 1) Dissolve carboxymethyl cellulose powder in a solution with a mass concentration of 45 wt% to obtain a carboxymethyl cellulose solution;

[0097] 2) A nano-silicon powder suspension was prepared by mixing nano-silicon powder and water at a mass ratio of 1:6 and then ultrasonically dispersing the mixture.

[0098] 3) The carboxymethyl cellulose solution obtained in step 1) is added dropwise to the nano-silicon powder suspension obtained in step 2), stirred, heated to 55°C, and then a calcium chloride solution with a mass concentration of 15wt% is added dropwise. The mixture is kept at 55°C for 10 hours, then filtered and dried to obtain nano-silicon powder-carboxymethyl cellulose composite microspheres.

[0099] The mass ratio of carboxymethyl cellulose powder to nano-silica powder is 1:3, and the amount of calcium chloride added is 5 wt% of carboxymethyl cellulose powder.

[0100] Example 11

[0101] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 8, except that nano-silica powder-carboxymethyl cellulose composite microspheres are replaced with an equal amount of nano-silica powder.

[0102] Example 12

[0103] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 8, except that the nano-silica powder-carboxymethyl cellulose composite microspheres are replaced with carboxymethyl cellulose in equal amounts.

[0104] Example 13

[0105] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 8, except that the nano-silica powder-carboxymethyl cellulose composite microspheres are replaced in equal amounts with a mixture of nano-silica powder and carboxymethyl cellulose, and the nano-silica powder and carboxymethyl cellulose are added after being mixed at a mass ratio of 2.5:1.

[0106] Comparative Example 1

[0107] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that no polycarboxylic acid additive is added to the raw materials.

[0108] Comparative Example 2

[0109] A method for preparing an active activator for finely ground fly ash is carried out according to the method in Example 1, except that glucose monohydrate is not added to the raw materials.

[0110] Application Example 1

[0111] An application of an active activator for finely ground fly ash involves mixing the active activator prepared in Example 1 with fly ash at a mass ratio of 1:950 and then grinding the mixture. The resulting ultrafine fly ash has a median particle size D50 of 25 μm and a particle size range of 20-35 μm.

[0112] The specific composition of the above-mentioned fly ash is: 25 wt% red mud, 40 wt% limestone, 25 wt% clay, 6 wt% aluminum ash and 4 wt% copper sulfate.

[0113] Application Example 2

[0114] An application of an active activator for grinding fly ash is carried out according to the method in Application Example 1, except that the active activator obtained in Example 2 is mixed with fly ash at a mass ratio of 1:900 and then ground to obtain ultrafine fly ash.

[0115] Application Example 3

[0116] An application of an active activator for finely ground fly ash is carried out according to the method in Application Example 1, except that the active activator obtained in Example 3 is mixed with fly ash at a mass ratio of 1:1000 and then ground to obtain ultrafine fly ash.

[0117] Application Example 4-13

[0118] An application of an active activator for finely ground fly ash is carried out according to the method in Application Example 1, except that the active activator is selected from the active activators prepared in Examples 4-13.

[0119] Comparative Application Example 1

[0120] An application of an active activator for finely ground fly ash is carried out according to the method in Application Example 1, except that the active activator is the active activator prepared in Comparative Example 1.

[0121] Comparative Application Example 2

[0122] An application of an active activator for finely ground fly ash is carried out according to the method in Application Example 1, except that the active activator is the active activator prepared in Comparative Example 2.

[0123] Performance testing

[0124] The ultrafine fly ash, silicate cement clinker (PI 42.5), and gypsum prepared in the above application examples and comparative application examples were mixed at a mass ratio of 50:45:5. Then, cement mortar was formed according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)", and then cured. The 3-day compressive strength, flexural strength, and 28-day compressive strength and flexural strength were tested. In addition, ultrafine fly ash obtained by directly grinding fly ash without adding active activator was selected as a blank control group. The above compressive strength and flexural strength were also tested on the blank control group. The test results are shown in Table 1 below.

[0125] Table 1:

[0126]

[0127]

[0128] Continued from Table 1:

[0129]

[0130] Based on the test results in Table 1 above, compared with the test results of the blank control group, which was prepared by directly mixing fly ash and cement clinker without adding an activator, it can be seen that the 3-day strength and 28-day strength of Example 1 are significantly increased compared with the blank control group. Referring to the test results of Example 1 and Example 4, it can be seen that when preparing polycarboxylate additives in Example 4, when N,N'-methylenebisacrylamide and hydroxyethyl acrylate were added along with acrylic monomers, the 28-day strength was enhanced, but the effect was small. Combining the test results of Examples 5-7, when polyethyleneimine was added, the mechanical properties were significantly improved and the fly ash activity was significantly enhanced.

[0131] Referring to the test results of Examples 1 and 8-10, it can be seen that when nano-silica powder-carboxymethyl cellulose composite microspheres are added to the activator, the strength of the cementitious material is significantly improved. Combining this with Examples 11 and 12, where only nano-silica powder is added, it can be seen that the strength actually decreases, possibly due to the tendency of nano-silica powder to agglomerate. The strengthening effect is limited when carboxymethyl cellulose is added. In Example 13, when nano-silica powder and carboxymethyl cellulose are directly mixed and added, although there is some strengthening, it is still limited compared to Example 8. The activation effect is better when nano-silica powder and carboxymethyl cellulose are combined and added. Furthermore, comparing the test results of Application Example 1, the activation performance is significantly reduced when polycarboxylic acid additives are not added to the activator.

[0132] Furthermore, according to GB / T1346-2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", the standard consistency water requirement in Example 1, the blank control group, and Comparative Application Example 1 and Comparative Application Example 2 was tested. It can be seen that when the initial setting time and final setting time meet the requirements, the standard consistency water requirement in the blank control group is 25%, the water requirement in Example 1 is 24%, and the water requirement in Comparative Application Example 1 without the addition of polycarboxylate additive reaches 30%. The activator provided in this application greatly reduces the water requirement while maintaining the requirements for initial setting time and final setting time, thus meeting the requirements. Referring to Comparative Application Example 2, it was found that the cement mortar prepared in Comparative Example 2 showed water bleeding, while the cement mortar prepared in the application examples of this application and Comparative Application Example 1 with the addition of glucose monohydrate did not show water bleeding.

[0133] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An active activator for finely ground fly ash, characterized in that, Including the following parts by weight of raw materials: 3-7 parts polycarboxylate additive, 2-4 parts anhydrous sodium sulfate, 15-18 parts alkanolamine, and 2-6 parts glucose monohydrate; The polycarboxylic acid additive is obtained by polymerization of diethylene glycol monovinyl ether, acrylic acid, N,N'-methylenebisacrylamide and hydroxyethyl acrylate as monomers. The active activator also includes 2-5 parts by weight of polyethyleneimine. When preparing the polycarboxylic acid additive, N,N'-methylenebisacrylamide and hydroxyethyl acrylate are added together with acrylic acid, and the amount of hydroxyethyl acrylate added is 20-30 wt% of the amount of acrylic acid added, and the amount of N,N'-methylenebisacrylamide added is 5-10 wt% of the amount of acrylic acid added.

2. The active activator for finely ground fly ash according to claim 1, characterized in that: The alkanolamine includes one or more of triethanolamine, diethanol monoisopropanolamine, and triisopropanolamine.

3. The active activator for finely ground fly ash according to claim 1, characterized in that: The alkanolamines include triethanolamine and diethanol monoisopropanolamine in a mass ratio of 1:(1.1-1.3).

4. The active activator for finely ground fly ash according to claim 1, characterized in that: The polycarboxylic acid additive is prepared by the following method: Diethylene glycol monovinyl ether was mixed with an initiator and preheated to 15-20°C. Acrylic acid, N,N'-methylenebisacrylamide and hydroxyethyl acrylate were added dropwise under stirring over 40-60 minutes. After reacting for 30-60 minutes, the mixture was cooled and neutralized to obtain a polycarboxylic acid additive.

5. An active activator for finely ground fly ash according to claim 4, characterized in that: In the preparation process of the polycarboxylic acid additive, the molar ratio of diethylene glycol monovinyl ether to acrylic acid is (1-1.2):5, and the amount of initiator added is 1-3 wt% of the amount of diethylene glycol monovinyl ether added.

6. The active activator for finely ground fly ash according to claim 1, characterized in that: The active activator also includes 1-3 parts by weight of nano-silica powder-carboxymethyl cellulose composite microspheres, which are prepared by the following method: 1) Dissolve carboxymethyl cellulose powder in water to obtain a carboxymethyl cellulose solution with a mass concentration of 35-45 wt%; 2) A nano-silicon powder suspension was prepared by mixing nano-silicon powder and water at a mass ratio of 1:(4-6) and ultrasonically dispersing the mixture. 3) The carboxymethyl cellulose solution obtained in step 1) is added dropwise to the nano-silicon powder suspension obtained in step 2), stirred, heated to 45-55℃, and then calcium chloride solution is added dropwise. The mixture is kept at 45-55℃ for 10-12 hours, filtered, and then dried to obtain nano-silicon powder-carboxymethyl cellulose composite microspheres. The mass ratio of carboxymethyl cellulose powder to nano-silica powder is 1:(2-3), and the amount of calcium chloride added is 3-5 wt% of carboxymethyl cellulose powder.

7. A method for preparing an active activator for finely ground fly ash as described in any one of claims 1-6, characterized in that: Includes the following steps: The active activator for finely ground fly ash is prepared by mixing the raw materials evenly according to the formula.

8. The application of an active activator for finely ground fly ash as described in any one of claims 1-6, characterized in that: The active activator is mixed with fly ash at a mass ratio of 1:(900-1000) and then ground for application.

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