A reduced type alkali-free liquid accelerator and a preparation method thereof

Abstract

The application relates to a shrinkage-reducing alkali-free liquid accelerator, which comprises the following raw materials in parts by weight: 10-15 parts of a shrinkage-reducing agent, 1-4 parts of a stabilizer, 30-50 parts of an aluminum salt, 3-15 parts of an alcohol amine and 20-30 parts of water; the shrinkage-reducing agent comprises the following raw materials: an organic amine, a polyhydric alcohol acrylate, an initiator, a chain transfer agent and water; the organic amine comprises at least one of linoleyl ethanolamine, linoleamide, ethylene bisoleic acid amide, linoleic acid diethanol amide, triisopropylamine oleate, arachidonylethanolamine and triisopropylamine linoleate; the prepared accelerator can reduce the late shrinkage of sprayed concrete, and meanwhile, the early accelerating effect of the accelerator is not affected.

Description

Technical Field

[0001] This invention relates to the field of admixtures, and in particular to a shrinkage-reducing alkali-free liquid quick-setting agent and its preparation method. Background Technology

[0002] Shotcrete is concrete formed by spraying concrete at high speed onto a surface using spraying machinery, which then allows it to harden. Compared to ordinary concrete, shotcrete is characterized by its rapid application, early strength, simple construction process, and the elimination of the need for formwork and vibration, often without affecting other production and construction activities. Since its inception, shotcrete has been widely used in underground construction. Due to its material and process characteristics, it quickly expanded beyond underground building support to the reinforcement and strengthening of structures, achieving excellent reinforcement results and economic benefits.

[0003] Shotcrete and cast-in-place concrete share many similarities, but also have many differences. Firstly, the construction process and forming conditions for shotcrete differ from ordinary concrete. Secondly, shotcrete has a higher cement content and sand ratio than ordinary wet-set concrete, and a lower water-cement ratio. Especially after the addition of accelerators, the concrete structure is significantly altered. Therefore, its performance differs somewhat from ordinary concrete. Shotcrete uses a larger amount of cement, has a higher water content, and contains accelerators, resulting in greater shrinkage than ordinary concrete, typically (80-140)×10⁻⁶. -6 The shrinkage rate (cm / cm) of shotcrete is significantly affected by factors such as accelerators and curing conditions. Shotcrete with 3%–4% accelerator shrinks approximately 80% more than shotcrete without accelerator. This is because the addition of accelerators rapidly absorbs the large amount of free water between cement particles, accelerating cement hydration. The longer the shotcrete is cured under moist conditions, the less shrinkage occurs. Excessive moisture evaporation during the early hardening process of shotcrete can lead to noticeable network shrinkage cracks on the surface. Drying shrinkage is a process that gradually develops from the concrete surface inwards, resulting in internal stress and residual deformation. The residual deformation varies depending on the shape and size of the shotcrete. If the thickness of the shotcrete varies greatly, the thinner sections are more prone to cracking due to faster moisture evaporation. Therefore, maintaining a moist surface on the shotcrete can slow down shrinkage and internal stress, thus reducing the risk of cracking.

[0004] Patent CN114455879B discloses a method for preparing a liquid alkali-free accelerator through polycarboxylate esterification. The method involves ring-opening polymerization of cyclic amide monomers followed by esterification with polycarboxylate to synthesize a carboxyamine organic complexing agent, which is then compounded with other components to obtain the liquid alkali-free accelerator. Specifically, the ring-opening polymerization of cyclic amide monomers yields a polymer backbone, which is then esterified with polycarboxylate to obtain a carboxyamine organic complexing agent. This agent is then compounded with aluminum sulfate, montmorillonite powder, and other components to obtain the liquid alkali-free accelerator. This invention utilizes an innovatively designed carboxyamine organic complexing agent component based on molecular structure, combining the performance advantages of cyclic amide polymers and polycarboxylate. The composite multifunctional groups possess excellent ion complexing capabilities, significantly improving problems such as poor stability, low energy efficiency, and insufficient aluminum ion capacity in accelerators. The prepared liquid alkali-free accelerator can significantly shorten the setting time of cement-based materials and improve early strength. While this patent creatively incorporates a carboxylate esterification composite liquid, it does not solve the problem of high shrinkage rate in shotcrete.

[0005] Patent CN113087441B discloses a fluorine-free liquid alkali-free quick-setting agent, its preparation method, and its application. The fluorine-free liquid alkali-free quick-setting agent comprises the following raw materials in parts by weight: 40-60 parts aluminum sulfate, 2-10 parts alkanolamine, 0.5-2 parts phenyl compound, 3-15 parts early-strength agent, 0.5-2 parts stabilizer, 0.05-0.2 parts rheology modifier, and 25-50 parts water. Although this patent describes high early strength, its material composition does not include shrinkage-reducing components, making it difficult to address the problem of high shrinkage in shotcrete.

[0006] Patent CN114685075B discloses a composite modified nano-aluminum sol, its preparation method, and its application in sulfur-free and alkali-free accelerators. The composite modified nano-aluminum sol material of this invention consists of nano-aluminum sol supported by carrier particles with an interlayer structure and a cement hydration reaction-active modifier. It exhibits good stability and accelerating effect; the sol-modified sulfur-free and alkali-free accelerator prepared from it possesses green and environmentally friendly characteristics, being fluorine-free, sulfur-free, and non-corrosive. Its early strength development is rapid, with a 6-hour mortar strength greater than 3.0 MPa and a 24-hour mortar strength greater than 18.0 MPa. However, the excessively high early strength of this accelerator, coupled with the lack of shrinkage-reducing or expansion components, inevitably leads to significant shrinkage in the later stages of shotcrete. Summary of the Invention

[0007] In response to existing technologies, this invention develops a shrinkage-reducing alkali-free liquid accelerator and its preparation method. The prepared accelerator can reduce the later-stage shrinkage of shotcrete without affecting the early-stage accelerating effect of the accelerator.

[0008] Based on this, the present invention provides a shrinkage-reducing alkali-free liquid quick-setting agent, which comprises the following raw materials by weight: 10-15 parts shrinkage-reducing agent, 1-4 parts stabilizer, 30-50 parts aluminum salt, 3-15 parts alkanolamine, and 20-30 parts water.

[0009] The shrinkage reducing agent comprises the following raw materials: organic amine, polyol acrylate, initiator, chain transfer agent, and water; the organic amine comprises at least one of linoleic acid ethanolamine, linoleamide, ethyl dioleylamide, linoleic acid diethanolamide, oleic acid triisopropanolamine, arachidonic acid ethanolamine, and linoleic acid triisopropanolamine.

[0010] Preferably, the organic amine is linoleic acid ethanolamine.

[0011] Furthermore, the molar ratio of the organic amine to the polyol acrylate is 1:(1-3).

[0012] Further, the polyol acrylate includes at least one of triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, diethylene glycol butyl ether acrylate, dipropanediol acrylate, dipropylene glycol monomethyl ether acrylate, diethyl ether methacrylate, dimethyl 2-acrylate, and diethoxy methacrylate.

[0013] Preferably, the polyol acrylate is diethylene glycol butyl ether acrylate.

[0014] Furthermore, the initiator includes at least one of persulfate-hypophosphite-ferrous sulfate, hydrogen peroxide-L-ascorbic acid-ferrous sulfate, and hydrogen peroxide-hypophosphite-ferrous sulfate.

[0015] Further, the transfer agent includes at least one of mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-mercaptosuccinic acid, sodium methacrylate sulfonate, and 2-acrylamide-2-methylpropanesulfonic acid.

[0016] Furthermore, the stabilizer includes at least one of magnesium aluminum silicate, sepiolite, hydroxyethyl carboxymethyl cellulose ether, white carbon black, polyacrylamide, nano silica, and hydrated magnesium silicate.

[0017] Furthermore, the aluminum salt includes at least one of aluminum sulfate, polyaluminum sulfate, nano-alumina, nano-aluminum hydroxide, and magnesium aluminum sulfate.

[0018] Furthermore, the alkanolamine includes at least one of triethanolamine, diethanolamine, triisopropanolamine, diethanolamine, and N,N-dimethylethanolamine.

[0019] A second objective of this invention is to provide a method for using a shrinkage-reducing, alkali-free liquid quick-setting agent, comprising the following steps:

[0020] S1. Copolymerization reaction: Organic amine and polyol acrylate are blended, and then an initiator, chain transfer agent and water are added. The mixture is reacted at 5-15°C for 2-3 hours to obtain the shrinkage reducer.

[0021] S2. Complexation reaction: Water, shrinkage reducer, and stabilizer are added to the reaction vessel and stirred for 2-3 hours. Then, aluminum salt is added and stirred at 45-55°C for 3-4 hours. Finally, alcohol amine is added and the pH value is adjusted to above 2.0 to obtain the shrinkage-reducing alkali-free liquid quick-setting agent.

[0022] In summary, the present invention has the following beneficial effects:

[0023] 1. The present invention provides a shrinkage-reducing alkali-free liquid quick-setting agent, which is synthesized by double-bond opening copolymerization of linoleyl alcohol amine and diethylene glycol butyl ether acrylate. The copolymer product overcomes the hydrophobicity of linoleyl alcohol amine and linoleamide. At the same time, the diethylene glycol dimethacrylate introduced into the chain segment of the quick-setting agent can effectively reduce the surface tension of the quick-setting agent in water molecules, resulting in a good overall shrinkage reduction effect of the quick-setting agent.

[0024] 2. The quick-setting agent prepared by this invention can effectively reduce the 28-day shrinkage rate of concrete and improve the durability of concrete. At the same time, the quick-setting agent is alkali-free and fluorine-free, has high early strength, and retains sufficient compressive strength in the later stage, resulting in good durability for shotcrete structural parts. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the experimental materials and reagents used in the following examples are commercially available. All quantitative experiments in the following examples were performed in triplicate, and the data are the average of the three replicates or the average ± standard deviation.

[0027] Furthermore, the term "and / or" throughout the text includes three solutions. Taking A and / or B as an example, it includes technical solution A, technical solution B, and a technical solution that simultaneously satisfies both A and B. In addition, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0028] Example 1

[0029] A method for preparing a shrinkage-reducing, alkali-free liquid quick-setting agent includes the following steps:

[0030] S1. Copolymerization reaction: Organic amine and polyol acrylate are blended, and then initiator, chain transfer agent and water are added. The mixture is reacted at 10°C for 2 hours to obtain the shrinkage reducer.

[0031] S2. Complexation reaction: Water, shrinkage reducer, and stabilizer are added to the reactor and stirred for 2 hours. Then, aluminum salt is added and stirred at 50°C for 3 hours. Finally, alcohol amine is added and the pH value is adjusted to above 2.0 to obtain the shrinkage-reducing alkali-free liquid quick-setting agent.

[0032] The preparation steps of the shrinkage-reducing alkali-free liquid quick-setting agent in Examples 2-6 are the same as those in Example 1. The raw material amounts of shrinkage-reducing agent and quick-setting agent in Examples 1 to 6 are shown in Table 1 and Table 2.

[0033] Table 1 shows the raw material amounts of the shrinkage reducing agent in each embodiment (by weight).

[0034]

[0035] Table 2 shows the raw material usage (by weight) of the accelerator in each embodiment.

[0036]

[0037]

[0038] The difference between Comparative Example 1 and Example 1 is that no shrinkage reducer is added to the raw materials of the quick-setting agent.

[0039] The difference between Comparative Example 2 and Example 1 is that in the raw materials of the shrinkage reducer, linoleic alcohol ethanolamine is replaced with triethanolamine.

[0040] The difference between Comparative Example 3 and Example 1 is that in the raw materials of the shrinkage agent, linoleic alcohol ethanolamine is replaced with diethanolamine.

[0041] The difference between Comparative Example 4 and Example 1 is that in the raw materials of the shrinkage reducer, diethylene glycol butyl ether acrylate is replaced with ethylene glycol butyl ether acetate.

[0042] The difference between Comparative Example 5 and Example 1 is that in the raw materials of the shrinkage reducer, diethylene glycol butyl ether acrylate is replaced with diethylene glycol butyl ether.

[0043] Accelerator performance test

[0044] The accelerators prepared in Examples 1-6 and Comparative Examples 1-5 were tested for performance at 6% of the cement content according to GB / T 35159-2017. The test results are shown in Table 3.

[0045] Table 3 Comparison of the performance of accelerators

[0046]

[0047]

[0048] As can be seen from the experimental data in Table 3, compared with Comparative Examples 1-5, the shrinkage-reducing alkali-free liquid quick-setting agent of the present invention has a slightly reduced setting time, a slight increase in 1-day strength, a significant increase in 28-day compressive strength ratio and 90-day compressive strength retention rate, and a 28-day shrinkage rate ratio that is reduced by 15% to 22%, showing a significant shrinkage reduction effect.

[0049] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A shrinkage-reducing, alkali-free liquid quick-setting agent, characterized in that, By weight, it includes the following raw materials: 10-15 parts shrinkage reducer, 1-4 parts stabilizer, 30-50 parts aluminum salt, 3-15 parts alkanolamine, and 20-30 parts water; The shrinkage reducing agent comprises the following raw materials: organic amine, polyol acrylate, initiator, chain transfer agent, and water; the organic amine comprises at least one of linoleyl alcohol ethanolamine, linoleamide, ethyl dioleylamide, linoleic acid diethanolamide, triisopropanolamine oleate, arachidonic acid ethanolamine, and triisopropanolamine linoleate. The polyol acrylates include at least one of triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, diethylene glycol butyl ether acrylate, dipropanediol acrylate, dipropylene glycol monomethyl ether acrylate, diethyl ether methacrylate, dimethyl 2-acrylate, and diethoxy methacrylate.

2. The shrinkage-reducing alkali-free liquid quick-setting agent according to claim 1, characterized in that: The molar ratio of the organic amine to the polyol acrylate is 1:(1-3).

3. The shrinkage-reducing alkali-free liquid quick-setting agent according to claim 1, characterized in that: The initiator includes at least one of persulfate-hypophosphite-ferrous sulfate, hydrogen peroxide-L-ascorbic acid-ferrous sulfate, and hydrogen peroxide-hypophosphite-ferrous sulfate.

4. The shrinkage-reducing alkali-free liquid quick-setting agent according to claim 1, characterized in that: The chain transfer agent includes at least one of mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 2-mercaptosuccinic acid, sodium methylpropenesulfonate, and 2-acrylamide-2-methylpropanesulfonic acid.

5. The shrinkage-reducing alkali-free liquid quick-setting agent according to claim 1, characterized in that: The stabilizer includes at least one of magnesium aluminum silicate, sepiolite, hydroxyethyl carboxymethyl cellulose ether, white carbon black, polyacrylamide, nano silica, and hydrated magnesium silicate.

6. The shrinkage-reducing alkali-free liquid quick-setting agent according to claim 1, characterized in that: The aluminum salt includes at least one of aluminum sulfate, polyaluminum sulfate, nano-alumina, nano-aluminum hydroxide, and magnesium aluminum sulfate.

7. The shrinkage-reducing alkali-free liquid quick-setting agent according to claim 1, characterized in that: The alkanolamine includes at least one of triethanolamine, diethanolamine, triisopropanolamine, diethanolamine, and N,N-dimethylethanolamine.

8. A method for preparing a shrinkage-reducing, alkali-free liquid quick-setting agent as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Copolymerization reaction: Organic amine and polyol acrylate are blended, and then an initiator, chain transfer agent and water are added. The mixture is reacted at 5~15℃ for 2~3 hours to obtain the shrinkage reducer. S2. Complexation reaction: Water, shrinkage reducer, and stabilizer are added to the reactor and stirred for 2-3 hours. Then, aluminum salt is added and stirred at 45-55°C for 3-4 hours. Finally, alkanolamine is added and the pH value is adjusted to above 2.0 to obtain the shrinkage-reducing alkali-free liquid quick-setting agent.

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