Fluorine-containing alkali-free liquid accelerator, and preparation method and application thereof

Abstract

The present application relates to a kind of fluorine-containing alkali-free liquid accelerator and its preparation method and application, it includes the following weight parts components: aluminum sulfate 48-52 parts, magnesium fluorosilicate 7-9 parts, diethanolamine 10-11 parts, composite flocculant 0.91-1.15 parts, oxalic acid 1-3 parts, ethylenediaminetetraacetic acid 1-3 parts, water 20.85-32.09 parts.Preparation method is as follows: (1) aluminum sulfate is added to water, heating, stirring to dissolve;Subsequently, magnesium fluorosilicate is added, stirring to dissolve;(2) composite flocculant and diethanolamine are sequentially added according to weight fraction, continuous stirring;(3) oxalic acid and ethylenediaminetetraacetic acid are added, stirring to liquid clear after natural cooling, obtain the final fluorine-containing alkali-free liquid accelerator.Compared with prior art, the fluorine-containing alkali-free liquid accelerator of the present application improves the solubility of aluminum sulfate, solution stability, rapid setting effect, and significantly reduces the rebound rate of shotcrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and in particular relates to a fluorine-containing alkali-free liquid quick-setting agent, its preparation method and application. Background Technology

[0002] Accelerators are chemical admixtures that enable cement or concrete to set and harden rapidly, and are an essential component of shotcrete. With the continuous development of accelerator technology, engineering projects have placed high demands not only on the rapid setting effect, early strength effect, and later strength guarantee rate of accelerators, but also on strict limits on the alkali content of accelerators. Against this backdrop, alkali-free liquid accelerators have emerged. Compared with sodium aluminate-type high-alkali liquid accelerators, aluminum sulfate-based alkali-free liquid accelerators have significant advantages in ensuring the later compressive strength ratio and durability of concrete, as well as improving the working environment and enhancing the personal safety of construction workers, making them the mainstream of accelerator development today.

[0003] However, aluminum sulfate-based alkali-free liquid accelerators still have problems such as poor solution stability, high concrete rebound rate, slow early strength development, and later strength reduction, affecting practical application results (e.g., CN 102229477A). Statistics show that when using existing alkali-free liquid accelerator products in actual shotcrete construction, the rebound rate consistently remains above 20%, resulting in very low shotcrete construction efficiency and significant material loss.

[0004] Therefore, to address the aforementioned technical issues, it is still necessary to develop a new type of alkali-free liquid accelerator to balance the accelerator's effects of promoting setting and early strength while reducing the rebound rate of shotcrete, thereby improving the efficiency of shotcrete construction. Summary of the Invention

[0005] The purpose of this invention is to overcome the defect of high rebound rate in shotcrete caused by existing aluminum sulfate-based alkali-free liquid accelerators by providing a fluorine-containing alkali-free liquid accelerator, its preparation method, and its application.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A fluorinated, alkali-free liquid quick-setting agent comprises the following components in parts by weight:

[0008]

[0009]

[0010] Furthermore, the composite flocculant comprises the following components in parts by weight:

[0011]

[0012] Furthermore, the composite flocculant increases cohesiveness and reduces the rebound rate of shotcrete.

[0013] Furthermore, the aluminum sulfate is an industrial-grade raw material, and the actual mass percentage of aluminum sulfate in the aluminum sulfate is ≥60%. The function of aluminum sulfate is to provide aluminum ions and sulfate ions, thereby shortening the cement setting time.

[0014] Furthermore, the magnesium fluorosilicate is an industrial-grade raw material, a white crystalline powder. The function of magnesium fluorosilicate is to provide fluoride and magnesium ions, thereby shortening the cement setting time.

[0015] Furthermore, the diethanolamine is an industrial-grade raw material. The role of diethanolamine is to complex aluminum ions, improve the storage stability of the accelerator, and introduce amine groups to promote cement hydration and accelerate the development of early strength.

[0016] Furthermore, the organic polymeric flocculant includes polyacrylamide and its derivatives, which improve the stability of the liquid quick-setting agent, enhance the cohesiveness of the freshly mixed slurry, and reduce the rebound rate.

[0017] Furthermore, the polyacrylamide and its derivatives are industrial-grade raw materials with a molecular weight of 10,000-20,000 g / mol.

[0018] Furthermore, the molecular weight of the chitin is 100-1000 g / mol. Chitin is a plant extract, and its main component is N-acetyl-D-glucosamine, which mainly functions to chelate aluminum ions and improve the stability of liquid quick-setting agents.

[0019] Furthermore, the chitosan is obtained from chitin through a deacetylation reaction, with a molecular weight of 2000-10000 g / mol. Its main function is to complex aluminum ions, improve the stability of liquid accelerators, and when added to concrete, it inhibits the growth of calcium hydroxide crystals during the hydration process of cementitious materials, thereby improving the long-term strength of concrete.

[0020] Furthermore, the microbial flocculant comprises a mixture of glycoproteins, mucopolysaccharides, cellulose, nucleic acids, etc., obtained through microbial fermentation and purification, with a molecular weight of 10,000-300,000 g / mol, and its main function is to improve the stability of the quick-setting agent.

[0021] Furthermore, the oxalic acid is an industrial-grade raw material with a mass percentage ≥99.0%. The role of oxalic acid is to lower the pH value of the liquid phase, increase the solubility of aluminum ions, and improve the stability of aluminum sulfate-based liquid quick-setting agents.

[0022] Furthermore, the ethylenediaminetetraacetic acid (EDTA) is an industrial product and a raw material. EDTA can inhibit Al... 3+ Water crystallization can also occur through interaction with Al. 3+It forms chelates, increases the solubility of aluminum sulfate, and improves the stability of aluminum sulfate-based liquid quick-setting agents.

[0023] This invention also provides a method for preparing a fluorine-containing alkali-free liquid quick-setting agent, which includes the following steps:

[0024] (1) Add aluminum sulfate to water, heat and stir until dissolved; then add magnesium fluorosilicate and stir until dissolved;

[0025] (2) Add the composite flocculant and diethanolamine in the order of weight parts, and stir continuously;

[0026] (3) Add oxalic acid and ethylenediaminetetraacetic acid, stir until the liquid is clear, and then cool naturally to obtain the final fluorine-containing alkali-free liquid quick-setting agent.

[0027] Further, in step (1), the heating temperature is 65-75°C, preferably 70°C.

[0028] Furthermore, the stirring speed is 600-800 rpm, preferably 700 rpm; the stirring time is 1-2 hours.

[0029] Further, in step (2), the stirring rate is 600-800 rpm, preferably 700 rpm.

[0030] Furthermore, in step (2), the stirring time is 1.5-2.5 hours, preferably 2 hours.

[0031] Furthermore, in step (3), the stirring time is 1-2 hours.

[0032] This invention also provides the application of a fluorine-containing alkali-free liquid quick-setting agent in shotcrete construction, wherein the cementitious material of the concrete includes cement, fly ash, slag powder and limestone, wherein the mass proportion of cement in the cementitious material is greater than or equal to 50%.

[0033] Furthermore, the water content in the concrete is 140-180 kg / m³. 3 .

[0034] Furthermore, the concrete also includes one or more of the following: water-reducing agent, retarder, waterproofing agent, expanding agent, sulfate retarder, or other quick-setting agent.

[0035] Furthermore, the fluorinated alkali-free liquid quick-setting agent is added by dripping or spraying and then comes into contact with the sprayed concrete mixture at the injection nozzle.

[0036] The application of the fluorinated alkali-free liquid quick-setting agent of the present invention in shotcrete construction has a wider range of concrete cementitious materials to choose from, a greater variety of other admixtures that can be added, and a wider range of water consumption compared to traditional application technologies. Therefore, it is suitable for shotcrete construction in tunnels, underground engineering, underground engineering and other projects.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) This invention uses formic acid, ethylenediaminetetraacetic acid and diethanolamine to improve the solubility and stability of aluminum sulfate solution; uses magnesium fluorosilicate and diethanolamine to improve the quick-setting effect and overall early strength effect of aluminum sulfate, and enhance the later strength of concrete with quick-setting agent; uses composite flocculant to improve the cohesiveness of concrete and reduce the rebound rate of concrete. Finally, the rebound rate of sprayed concrete with fluorine-containing alkali-free liquid quick-setting agent is significantly reduced and the strength of concrete structure is improved.

[0039] (2) The fluorine-containing alkali-free liquid quick-setting agent prepared by the present invention is a clear and transparent liquid with low dosage, good stability and high later strength guarantee rate, which reduces the rebound rate of concrete and overcomes the shortcomings of traditional alkali-free liquid quick-setting agents such as poor setting effect, low early strength and poor stability.

[0040] (3) The composite flocculant in this invention includes different types such as organic polymer flocculant, chitin, chitosan, and microbial flocculant. Among them, the main function of microbial flocculant is to improve the stability of liquid quick-setting agent by complexing aluminum ions, which is beneficial to improve the cohesiveness of slurry. When combined with chitin, chitosan and polyacrylamide, it is beneficial to further reduce the rebound rate of concrete.

[0041] (4) The oxalic acid in this invention can reduce the pH value of the liquid phase, increase the solubility of aluminum ions, and improve the stability of aluminum sulfate type liquid quick-setting agent.

[0042] (5) The ethylenediaminetetraacetic acid in this invention can inhibit Al 3+ Water crystallization can also occur through interaction with Al. 3+ It forms chelates, increases the solubility of aluminum sulfate, and improves the stability of aluminum sulfate-based liquid quick-setting agents.

[0043] (6) The preparation method of the alkali-free liquid quick-setting agent of the present invention is simple, the raw material cost is low, and it is suitable for large-scale industrial production. Detailed Implementation

[0044] The embodiments of the present invention will be described in detail below. The following embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0045] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0046] The specific steps of the preparation method of the fluorine-containing alkali-free liquid quick-setting agent proposed in the following embodiments of the present invention are as follows:

[0047] (1) Add water to the reaction vessel while stirring and heating. When the temperature reaches 70°C, add aluminum sulfate according to the mass fraction and stir for 1 hour until completely dissolved.

[0048] (2) Add magnesium fluorosilicate under continuous stirring and stir for 1 hour to dissolve it completely.

[0049] (3) Add polyacrylamide, chitin, chitosan, microbial flocculant, and diethanolamine. After stirring continuously for 2 hours, add oxalic acid and ethylenediaminetetraacetic acid.

[0050] (4) Continue stirring for 1 hour until the liquid becomes clear, then stop heating and continue stirring until it cools naturally to form the final product.

[0051] Example 1:

[0052] The fluorinated, alkali-free liquid quick-setting agent of this embodiment has the following components by weight fraction: 48 parts aluminum sulfate, 7 parts magnesium fluorosilicate, 10 parts diethanolamine, 0.7 parts polyacrylamide, 0.15 parts chitosan, 0.15 parts chitosan, 0.05 parts microbial flocculant, 1 part oxalic acid, 3 parts ethylenediaminetetraacetic acid, and water as the balance, with a total of 100 parts. The stirring rate during preparation was 600 rpm. Performance test results are shown in Table 1.

[0053] Example 2:

[0054] The fluorinated, alkali-free liquid quick-setting agent of this embodiment has the following components by weight fraction: 50 parts aluminum sulfate, 8 parts magnesium fluorosilicate, 11 parts diethanolamine, 0.8 parts polyacrylamide, 0.05 parts chitosan, 0.05 parts chitosan, 0.1 parts microbial flocculant, 2 parts oxalic acid, 1 part ethylenediaminetetraacetic acid, and water as the balance, with a total of 100 parts. The stirring rate during preparation was 800 rpm. Performance test results are shown in Table 1.

[0055] Example 3:

[0056] The fluorinated, alkali-free liquid quick-setting agent of this embodiment has the following components by weight fraction: aluminum sulfate 52 parts, magnesium fluorosilicate 9 parts, diethanolamine 10.5 parts, polyacrylamide 0.75 parts, chitin 0.1 parts, chitosan 0.1 parts, microbial flocculant 0.2 parts, oxalic acid 3 parts, ethylenediaminetetraacetic acid 2 parts, and water as the balance, with a total of 100 parts. The stirring rate during preparation was 750 rpm. Performance test results are shown in Table 1.

[0057] Comparative Example 1:

[0058] Compared with Example 2, the alkali-free liquid quick-setting agent of this comparative example has the following weight fractions: 50 parts aluminum sulfate, 8 parts magnesium fluorosilicate, 11 parts diethanolamine, 1 part polyacrylamide, 2 parts oxalic acid, 1 part ethylenediaminetetraacetic acid, and water as the balance, with a total of 100 parts.

[0059] According to the requirements of GB / T 35159-2017 "Accelerating Agents for Shotcrete", the setting time of cement paste and the compressive strength of cement mortar in Examples 1-3 and Comparative Examples 1-3 were tested. The setting time of cement paste was: cement: 400g, water: 140g - water content in the liquid accelerator; the strength of cement mortar was: cement: 900g, standard sand: 1350g, water: 450g - water content in the liquid accelerator. The performance test results are shown in the table below.

[0060] Table 1 Performance Test Results

[0061]

[0062]

[0063] As shown in the table, compared with concrete without accelerator, the rebound rate of concrete with accelerator is significantly lower. Moreover, the rebound rate reduction is even greater in the embodiments of the present invention compared with the comparative example, indicating that the accelerator of the present invention has a significant effect on reducing the rebound rate of concrete. Compared with Comparative Example 1, Examples 1-3 show that the addition of chitin, chitosan, and microbial flocculants can shorten the setting time and improve the early compressive strength to a certain extent. Furthermore, the combined action of chitin, chitosan, microbial flocculants, and polyacrylamide can effectively reduce the rebound rate of concrete. Among them, Example 2, under the optimal component ratio, can reduce the rebound rate of shotcrete to below 9%.

[0064] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A fluorine-containing, alkali-free liquid quick-setting agent, characterized in that, Includes the following components by weight: 48-52 parts aluminum sulfate 7-9 parts magnesium fluorosilicate 10-11 parts of diethanolamine 0.91-1.15 parts of composite flocculant 1-3 parts oxalic acid 1-3 parts of ethylenediaminetetraacetic acid Water 20.85-32.09 parts; The composite flocculant comprises the following components in parts by weight: 0.7-0.8 parts of organic polymer flocculant Chitosan 0.05-0.15 parts Chitosan 0.05-0.15 parts 0.05-0.2 parts of microbial flocculant.

2. The fluorine-containing alkali-free liquid quick-setting agent according to claim 1, characterized in that, The organic polymeric flocculant includes polyacrylamide and its derivatives.

3. The fluorine-containing alkali-free liquid quick-setting agent according to claim 2, characterized in that, The molecular weight of the polyacrylamide and its derivatives is 10,000-20,000 g / mol.

4. The fluorine-containing alkali-free liquid quick-setting agent according to claim 1, characterized in that, The chitin is extracted from the shells of crustaceans and has a molecular weight of 100-1000 g / mol.

5. The fluorine-containing alkali-free liquid quick-setting agent according to claim 1, characterized in that, The chitosan is obtained by deacetylation of chitin and has a molecular weight of 2000-10000 g / mol.

6. The fluorine-containing alkali-free liquid quick-setting agent according to claim 1, characterized in that, The microbial flocculant comprises glycoproteins, mucopolysaccharides, cellulose, and nucleic acids obtained through microbial fermentation and purification, with a molecular weight of 10,000-300,000 g / mol.

7. A method for preparing a fluorine-containing alkali-free liquid quick-setting agent according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Add aluminum sulfate to water, heat and stir until dissolved; then add magnesium fluorosilicate and stir until dissolved; (2) Add the composite flocculant and diethanolamine in the order of their weight parts, and stir continuously; (3) Add oxalic acid and ethylenediaminetetraacetic acid, stir until the liquid is clear and then cool naturally to obtain the final fluorine-containing alkali-free liquid quick-setting agent.

8. The method for preparing a fluorinated, alkali-free liquid quick-setting agent according to claim 7, characterized in that, In step (1), the heating temperature is 65-75℃; The stirring speed is 600-800 rpm and the stirring time is 1-2 hours.

9. The method for preparing a fluorinated, alkali-free liquid quick-setting agent according to claim 7, characterized in that, In step (2), the stirring rate is 600-800 rpm and the stirring time is 1.5-2.5 h; In step (3), the stirring time is 1-2 hours.

10. The application of the fluorinated alkali-free liquid quick-setting agent according to any one of claims 1-6 in shotcrete construction, characterized in that, The cementitious material of the concrete includes cement, fly ash, slag powder and limestone, wherein the mass proportion of cement in the cementitious material is greater than or equal to 50%; The water content in the concrete is 140-180 kg / m³. 3 ; The concrete also includes one or more of the following: water-reducing agent, retarder, waterproofing agent, expanding agent, sulfate-resistant agent, or other quick-setting agent; The fluorinated, alkali-free liquid quick-setting agent is added by dripping or spraying and then comes into contact with the sprayed concrete mixture at the injection nozzle.

Images