A functional additive for fly ash geopolymer and a preparation method thereof

Abstract

The application belongs to the technical field of building material additives, and relates to a functional additive for fly ash geopolymer and a preparation method thereof. The functional additive is prepared by dissolving a first unsaturated polyether monomer and a first unsaturated acrylic acid monomer in water as a base material, heating to 60 DEG C, adding hydrogen peroxide, then adding A material obtained by dissolving a second unsaturated polyether monomer and a second unsaturated acrylic acid monomer in water, chain transfer agent and B material obtained by dissolving ascorbic acid in water, keeping warm for 30 min, and neutralizing the reaction product with sodium hydroxide solution after cooling. The functional additive can improve the workability of fly ash geopolymer, solve the problems of serious loss of fluidity, difficult construction, high water consumption and the like in the preparation of fly ash alkaline activated materials, reduce the cement consumption and energy consumption, improve the environmental pollution and land occupation problems caused by solid waste storage, promote double carbon emission reduction, and promote low-cost engineering application.

Description

Technical Field

[0001] This invention belongs to the field of building material additives technology, and more specifically relates to a functional admixture for fly ash-based polymers and its preparation method. Background Technology

[0002] Some problems and challenges exist with fly ash geopolymers. A particularly prominent issue is rapid setting, a major challenge in their application. Insufficient initial setting time affects product shape and appearance, and hinders construction and long-distance transportation. However, numerous studies have yet to find or design a suitable admixture to address this problem. Analogous to water-reducing agents in cement, there are several types, including lignin sulfonate, naphthalene sulfonate formaldehyde polymers, and polycarboxylate water-reducing agents. However, there is almost no research on water-reducing agents applied to fly ash geopolymer systems, including molecular structure design and application analysis cases. Therefore, it is necessary to improve flowability through specialized structural design, improved formulations, and improved processes to enhance the overall quality and performance of fly ash geopolymers, thereby better adapting them to various application scenarios.

[0003] Currently, the challenge in utilizing fly ash geopolymer systems lies in the lack of precedent for designing the molecular structure of one or more admixture mother liquors through free radical polymerization to ultimately prepare admixtures that meet the requirements. Most of the mature technologies in currently available patents are for various water-reducing agents developed for cement systems. Furthermore, current research on geopolymer water-reducing agents is limited to research articles and reviews, and often studies geopolymer water-reducing agents using the formulation principles of cement water-reducing agents, failing to overcome these conceptual and technological limitations. Summary of the Invention

[0004] The purpose of this invention is to provide a functional admixture for fly ash-based polymers and its preparation method, so as to solve the problems existing in the prior art and achieve the high fluidity retention performance of pure cementitious material system slurry.

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

[0006] One of the technical solutions of this invention is to provide a method for preparing a functional admixture for fly ash-based polymers, comprising the following steps:

[0007] The first unsaturated polyether monomer and the first unsaturated acrylic monomer were dissolved in water to form a base material;

[0008] The second part of unsaturated polyether monomer and the second part of unsaturated acrylic monomer are dissolved in water to form component A.

[0009] Chain transfer agent and ascorbic acid (V) cIt dissolves in water as component B;

[0010] The base material is heated to 60°C and hydrogen peroxide (H2O2) is added. Then, materials A and B are added dropwise. The mixture is kept at this temperature for 30 minutes. After cooling, the reaction product is neutralized with sodium hydroxide solution to obtain the functional additive for fly ash base polymers.

[0011] This reaction process is more efficient. The mixing of the substrate (a mixture of macromonomers and small monomers) with the oxidant results in a more uniform reaction, improving reaction efficiency and molecular structural stability. It also makes it easier to control key parameters such as the molecular weight, polymerization rate, and side chain density of the additive. Furthermore, this method facilitates the synthesis of functional additives with different properties and stable structures, and further improves the dispersibility of alkali-activated slurries, thereby enhancing slurry workability and homogeneity, and making it more adaptable.

[0012] Furthermore, the unsaturated polyether monomer includes at least one of methyl allyl polyoxyethylene ether (TPEG), allyl polyoxyethylene ether (HPEG), and isopentenyl polyoxyethylene ether (IPEG).

[0013] Preferably, the weight-average molecular weight of the TPEG is 2400-4000; the weight-average molecular weight of the HPEG is 2400-4000; and the weight-average molecular weight of the IPEG is 2400-4000.

[0014] Furthermore, the unsaturated acrylic monomer is acrylic acid (AA) and / or methacrylic acid (MAA).

[0015] Furthermore, the chain transfer agent is trimercaptopropionic acid (3-MPA).

[0016] Furthermore, the molar ratio of the unsaturated polyether monomer to the unsaturated acrylic monomer is 1:4 to 40.

[0017] Furthermore, the amount of the chain transfer agent is 0.09% to 0.4% of the sum of the mass of the unsaturated polyether monomer and the unsaturated acrylic monomer.

[0018] Furthermore, the hydrogen peroxide and ascorbic acid are used as initiators, wherein the amount of initiator is 0.55% to 0.65% of the sum of the mass of the unsaturated polyether monomer and the unsaturated acrylic monomer.

[0019] Furthermore, the mass ratio of the first unsaturated polyether monomer, the first unsaturated acrylic monomer, and water in the base material is 4–7.3:0.44–4.2:10.

[0020] Furthermore, the dissolution involves mixing the first unsaturated polyether monomer, the first unsaturated acrylic monomer, and water, and then stirring and pre-dissolving them in a water bath at 30–50°C.

[0021] Furthermore, the mass ratio of the second unsaturated polyether monomer, the second unsaturated acrylic monomer, and water in material A is 6-11:0.66-4.5:10.

[0022] Furthermore, the mass ratio of chain transfer agent, ascorbic acid and water in the B material is 1.1-5:0.16-0.25:100.

[0023] Furthermore, the mass ratio of hydrogen peroxide to substrate is 1:178.3 to 181.

[0024] Furthermore, the dripping process specifically involves using a peristaltic pump to uniformly drip material A and material B, wherein the dripping time for material A is 2 hours and the dripping time for material B is 2.5 hours.

[0025] Furthermore, the sodium hydroxide solution has a mass fraction of 30%; the neutralization is to adjust the pH to 6-8.

[0026] The second technical solution of the present invention provides a functional admixture for fly ash-based polymers prepared by the above preparation method.

[0027] The third technical solution of the present invention provides an application of the above-mentioned functional admixture in improving the high fluidity retention performance of fresh fly ash geopolymer slurry.

[0028] The present invention discloses the following technical effects:

[0029] The functional admixture prepared by this invention can improve the workability of fly ash geopolymers, solving problems such as severe fluidity loss, construction difficulties, and high water consumption in the preparation of alkali-activated materials from fly ash. It is suitable for use in building materials such as road filling, wall interiors, and coal mine subsidence area filling, indirectly improving the utilization rate of fly ash in the construction field. While reducing cement usage and energy consumption, it also mitigates environmental pollution and land occupation caused by solid waste storage, promoting carbon emission reduction and its low-cost engineering application. Increasing the acid-ether ratio in the functional admixture increases the main chain charge density, enhancing the surface adsorption of fly ash particles. The long polyoxyethylene side chains provide steric hindrance, exhibiting strong dispersibility and fluidity retention in the high-alkali environment of fly ash geopolymers.

[0030] The functional admixture prepared by this invention is a high molecular weight polymer with a molecular weight of about 20,000 to 50,000 generated by polymerization reaction. It has a comb-shaped molecular structure and is a polycarboxylic acid polymer with a certain structure and molecular weight by copolymerizing macromonomer polyether (unsaturated polyether monomer) and small monomer (unsaturated acrylic monomer). It is a functional admixture suitable for fly ash geopolymer system.

[0031] The raw materials prepared by this invention are readily available and require few types, with a wide range of monomers to choose from and strong versatility. By adjusting the proportions between the raw materials, functional admixtures with specific molecular structures can be designed, which can effectively alleviate the problems of poor workability and high cost in the construction process of materials such as fly ash geopolymers, and can indirectly improve the utilization rate of fly ash as a geopolymer material.

[0032] The functional admixture of this invention is simple and efficient to prepare and apply, requiring no additional specialized equipment and saving labor and energy costs. By adjusting the appropriate ratio, the prepared functional admixture only needs to be mixed with water in a fly ash geopolymer system, making it convenient, efficient, and effective with low dosage. It significantly increases the utilization rate of solid waste and saves on high-carbon cement usage, achieving energy conservation and emission reduction, and has broad application prospects. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC1 to fresh fly ash geopolymer slurry.

[0035] Figure 2 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC2 to fresh fly ash geopolymer slurry.

[0036] Figure 3 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC3 to fresh fly ash geopolymer slurry.

[0037] Figure 4 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC4 to fresh fly ash geopolymer slurry. Detailed Implementation

[0038] 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.

[0039] 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.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] In the specific testing process, various macromonomers and small monomers can be selected, and the technical effects achieved by using any combination of the types defined in this invention are similar. Therefore, in the specific implementation process, methyl allyl polyoxyethylene ether, allyl polyoxyethylene ether, and isopentenyl polyoxyethylene ether can be substituted equally, and acrylic acid and methacrylic acid can be substituted equally. Among them, the weight average molecular weight of TPEG is 2400-4000, the weight average molecular weight of HPEG is 2400-4000, and the weight average molecular weight of IPEG is 2400-4000. In the specific embodiment of this invention, TPEG is TPEG-2400.

[0044] Example 1

[0045] Preparation of functional admixtures for fly ash-based polymers:

[0046] S1. Mix 29.98g of TPEG, 5.4g of AA and 45g of deionized water in a three-necked flask as the base material, and place it in a water bath at 40°C. Stir and pre-dissolve the mixture for later use.

[0047] S2. Mix 269.78g of TPEG (dissolved), 48.6g of AA, and 270g of deionized water to prepare material A; 1.35g of 3-MPA and 0.117g of V... c Mix with 72g of deionized water to prepare ingredient B;

[0048] S3. After the polyether mixture in the three-necked flask is completely dissolved, heat it to 60°C and add 0.45g of H2O2 at once. At the same time, use a peristaltic pump to add A and B materials dropwise at a uniform rate. Add A material for 2 hours and B material for 2.5 hours. After both A and B materials have been added, keep it at the temperature for 30 minutes.

[0049] S4. After the heat preservation is completed, cool to below 40℃, and neutralize the reaction product with a 30% NaOH solution to a pH of 6-8 to obtain the functional admixture for fly ash-based polymers, denoted as PC1. The ratio of TPEG:AA is 1:6 (molar ratio).

[0050] Example 2

[0051] Preparation of functional admixtures for fly ash-based polymers:

[0052] S1. Mix 26.89g of TPEG, 8.1g of AA and 45g of deionized water in a three-necked flask as the base material, and place it in a water bath at 40°C. Stir and pre-dissolve the mixture for later use.

[0053] S2. Mix 242.8g of TPEG (dissolved), 72.9g of AA, and 270g of deionized water to prepare material A; 1.35g of 3-MPA and 0.117g of V... c Mix with 72g of deionized water to prepare ingredient B;

[0054] S3. After the polyether mixture in the three-necked flask is completely dissolved, heat it to 60°C and add 0.45g of H2O2 at once. At the same time, use a peristaltic pump to add A and B materials dropwise at a uniform rate. Add A material for 2 hours and B material for 2.5 hours. After both A and B materials have been added, keep it at the temperature for 30 minutes.

[0055] S4. After the heat preservation is completed, cool to below 40℃, and neutralize the reaction product with a 30% NaOH solution to a pH of 6-8 to obtain the functional admixture for fly ash-based polymers, denoted as PC2. The ratio of TPEG to AA is 1:10 (molar ratio).

[0056] Example 3

[0057] Preparation of functional admixtures for fly ash-based polymers:

[0058] S1. Mix 22.48g of TPEG, 13.5g of (M)AA and 45g of deionized water in a three-necked flask as the base material, and place it in a water bath at 40°C. Stir and pre-dissolve the mixture for later use.

[0059] S2. Mix 202.33g of TPEG (dissolved), 121.5g of (M)AA, and 270g of deionized water to prepare material A; 1.35g of 3-MPA and 0.117g of V c Mix with 72g of deionized water to prepare ingredient B;

[0060] S3. After the polyether mixture in the three-necked flask is completely dissolved, heat it to 60°C and add 0.45g of H2O2 at once. At the same time, use a peristaltic pump to add A and B materials dropwise at a uniform rate. Add A material for 2 hours and B material for 2.5 hours. After both A and B materials have been added, keep it at the temperature for 30 minutes.

[0061] S4. After the heat preservation is completed, cool to below 40℃, and neutralize the reaction product with a 30% NaOH solution to a pH of 6-8 to obtain the functional admixture for fly ash-based polymers, denoted as PC3. The molar ratio of TPEG:AA is 1:20.

[0062] Comparative Example 1

[0063] Preparation of functional admixtures for fly ash-based polymers:

[0064] S1. Mix 32.97g of TPEG, 1.98g of AA and 45g of deionized water in a three-necked flask as the base material, and place it in a water bath at 40°C. Stir and pre-dissolve the mixture for later use.

[0065] S2. Prepare material A by mixing 296.75g of TPEG (dissolved), 17.82g of AA, and 270g of deionized water; 1.35g of 3-MPA and 0.117g of V... c Mix with 72g of deionized water to prepare ingredient B;

[0066] S3. After the polyether mixture in the three-necked flask is completely dissolved, heat it to 60°C and add 0.45g of H2O2 at once. At the same time, use a peristaltic pump to add A and B materials dropwise at a uniform rate. Add A material for 2 hours and B material for 2.5 hours. After both A and B materials have been added, keep it at the temperature for 30 minutes.

[0067] S4. After the heat preservation is completed, cool to below 40℃, and neutralize the reaction product with a 30% NaOH solution to a pH of 6-8 to obtain the functional admixture for fly ash-based polymers, denoted as PC4. The molar ratio of TPEG:AA is 1:2.

[0068] The admixtures prepared in Examples 1-3 and Comparative Example 1 were used in neat slurry with alkali-activated fly ash as the main cementitious material, with varying dosages of 0.2 wt.%, 0.3 wt.%, 0.5 wt.%, 0.8 wt.%, and 1 wt.%, respectively. Slurry without admixtures served as a control group. The water-cement ratio of the fresh fly ash geopolymer slurry was 0.4, and the NaOH concentration was 3 mol / L.

[0069] The initial and 1-hour flowability of fresh fly ash geopolymer slurry were tested.

[0070] Figure 1 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC1 to fresh fly ash geopolymer slurry.

[0071] Figure 2 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC2 to fresh fly ash geopolymer slurry.

[0072] Figure 3 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC3 to fresh fly ash geopolymer slurry.

[0073] Figure 4 The initial and 1-hour flowability of the slurry were determined by adding different amounts of PC4 to fresh fly ash geopolymer slurry.

[0074] Depend on Figures 1-4 It can be seen that the addition of PC1, PC2, and PC3 to the fresh fly ash-polymer slurry in 3 mol / L NaOH significantly improves the slurry fluidity, and the fluidity increases continuously with the increase of the water-reducing agent dosage. More notably, the slurry fluidity shows a certain degree of reversal after 1 hour, especially with PC3 (TPEG:AA = 1:20), indicating that the synthesized admixtures have good performance and can maintain the high fluidity of pure cementitious material systems such as fly ash-polymer slurries after addition. Although PC4 can slightly improve the slurry fluidity, its improvement is far from sufficient for application in engineering.

[0075] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0076] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The application of a functional admixture in improving the high fluidity retention performance of fresh fly ash geopolymer slurry, characterized in that, The preparation steps of the functional admixture include: The first unsaturated polyether monomer and the first unsaturated acrylic monomer were dissolved in water to form a base material; The second part of unsaturated polyether monomer and the second part of unsaturated acrylic monomer are dissolved in water to form component A. Chain transfer agent and ascorbic acid are dissolved in water as component B; The base material is heated to 60°C and hydrogen peroxide is added. Then, the A material and the B material are added dropwise. The mixture is kept at this temperature for 30 minutes. After cooling, the reaction product is neutralized with sodium hydroxide solution to obtain the functional additive. The unsaturated polyether monomer includes at least one of methyl allyl polyoxyethylene ether, allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether; The unsaturated acrylic monomer is acrylic acid and / or methacrylic acid; The chain transfer agent is trimercaptopropionic acid; The mass ratio of the first unsaturated polyether monomer, the first unsaturated acrylic monomer, and water in the base material is 4~7.3:0.44~4.2:10; The mass ratio of the second unsaturated polyether monomer, the second unsaturated acrylic monomer, and water in material A is 6~11:0.66~4.5:10; The mass ratio of chain transfer agent, ascorbic acid and water in the B component is 1.1~5:0.16~0.25:100; The mass ratio of hydrogen peroxide to substrate is 1:178.3~181; the mass fraction of sodium hydroxide solution is 30%.

2. The application according to claim 1, characterized in that, The weight-average molecular weight of the TPEG is 2400~4000; the weight-average molecular weight of the HPEG is 2400~4000; and the weight-average molecular weight of the IPEG is 2400~4000.

3. The application according to claim 1, characterized in that, The dissolution process involves mixing the first unsaturated polyether monomer, the first unsaturated acrylic monomer, and water, and then stirring and pre-dissolving them in a water bath at 30-50°C.

4. The application according to claim 1, characterized in that, The neutralization refers to adjusting the pH to 6-8.

5. The application according to claim 1, characterized in that, The dripping process specifically involves using a peristaltic pump to uniformly drip material A and material B, wherein the dripping time for material A is 2 hours and the dripping time for material B is 2.5 hours.

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