Preparation method and application of liquid alkali-free accelerator

Abstract

The invention discloses a preparation method and application of a liquid alkali-free accelerator, and belongs to the technical field of rapid-setting materials in the building industry. The preparation method comprises the following steps: uniformly mixing a solution containing aluminum sulfate and a fluosilicic acid solution to obtain a first mixed solution, then adding a second mixed solution containing a sodium metaaluminate additive and sodium hydroxide into the first mixed solution, and reacting at 100-110 DEG C for 1-2 hours to obtain the liquid alkali-free accelerator, wherein the second mixed solution containing the sodium metaaluminate additive and the sodium hydroxide is prepared by gradually adding aluminum hydroxide solid into a sodium hydroxide solution for reaction, and the molar ratio of the sodium hydroxide to the aluminum hydroxide is (1.35-1.45): 1; the solid content of the obtained liquid alkali-free accelerator is 40-50%, and the pH value of the liquid alkali-free accelerator is 1.5-3.0. The method is easy to operate, raw materials are easy to obtain, and the obtained accelerator is high in stability, good in concrete setting effect and high in setting strength and has a wide application market.

Description

Technical Field

[0001] The invention belongs to the technical field of quick-setting materials in the construction industry, and in particular relates to a preparation method and application of a liquid alkali-free quick-setting agent. Background Art

[0002] As my country's infrastructure construction enters a stable development stage, the use of shotcrete has reached a peak. In the construction of infrastructure tunnel projects, accelerators are admixtures that can quickly solidify and harden cement or concrete. At present, the use of accelerators in my country is very large, but most of them are powdered accelerators made of highly alkaline materials. In the actual construction process, it will damage the skin, eyes and other parts of the workers, and the strength of the concrete will decrease. At the same time, it is very easy to add unevenly during the construction of accelerators. Therefore, it is of great significance to produce liquid, alkali-free, and excellent performance accelerators.

[0003] The main raw material of alkali-free accelerator is aluminum sulfate, because the aluminum ions in aluminum sulfate can not only significantly accelerate the hydration rate of cement, but also play a significant role in the rapid setting of cement. However, when aluminum sulfate is used to prepare accelerator, it is necessary to use materials containing fluoride ions for compounding.

[0004] The Chinese invention patent with application publication number CN113480226A discloses a liquid alkali-free accelerating agent and its preparation method and application: it uses the difference in the solubility of aluminum salts and the difference in the dispersion in cement, and uses tartaric acid group to coordinate aluminum ions as the active center. Although this accelerating agent has a short accelerating time and can make concrete have good strength, it is constructed at low temperature in the actual production and preparation process, has large shrinkage deformation and large parameters, and thus cannot ensure the final effect of the product.

[0005] The Chinese invention patent application publication number CN109650761A discloses a preparation method and application of a liquid alkali-free accelerating setting agent: the accelerating setting agent has good rapid setting effect, high compressive strength, and reduces alkali corrosion in concrete structures. However, the accelerating setting agent requires many auxiliary materials to be added during the preparation process, resulting in high cost and poor product stability.

[0006] The Chinese invention patent with application publication number CN111662035A discloses a preparation method and application of a liquid alkali-free accelerator: the liquid alkali-free accelerator is synthesized from sodium aluminate, aluminum sulfate and fluorosilicic acid as raw materials, and a complex stabilizer needs to be added to maintain the stability of the accelerator product. Summary of the invention

[0007] In view of the shortcomings and deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing a liquid alkali-free accelerating setting agent and its application. The method is simple to operate, the raw materials are readily available, the obtained accelerating setting agent has high stability, can be widely used in the construction industry, and has good setting effect and high setting strength when used as a cement concrete additive, and has a broad application market.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] Provided is a method for preparing a liquid alkali-free accelerating setting agent, comprising the following steps:

[0010] The solution containing aluminum sulfate and the fluosilicic acid solution are mixed evenly to obtain a first mixed solution, and then a second mixed solution containing sodium metaaluminate additive and sodium hydroxide is added to the first mixed solution, and the mixture is reacted at 100-110° C. for 1-2 hours to obtain a liquid alkali-free accelerating setting agent; wherein:

[0011] The second mixed solution containing sodium aluminate additive and sodium hydroxide is prepared by gradually adding aluminum hydroxide solid into sodium hydroxide solution for reaction, wherein the molar ratio of sodium hydroxide to aluminum hydroxide is (1.35-1.45):1;

[0012] The obtained liquid alkali-free quick-setting agent has a solid content of 40-50% and a pH value of 1.5-3.0.

[0013] According to the above scheme, the temperature of the first mixed solution is regulated to 70-80°C, and the second mixed solution containing sodium aluminate additive and sodium hydroxide is quickly added thereto, and the final reaction temperature is controlled to 100-110°C by reaction heat, and the reaction is kept warm for 1-2 hours. Controlling the reaction temperature by reaction heat can effectively reduce heating energy consumption.

[0014] According to the above scheme, the mass ratio of the fluorosilicic acid in the fluorosilicic acid solution to the aluminum sulfate in the solution containing aluminum sulfate is 1:4.4-5.0.

[0015] According to the above scheme, the mass ratio of fluorosilicic acid to aluminum hydroxide in the fluorosilicic acid solution is 1:1.0-1.5; wherein the aluminum hydroxide is the raw material used to prepare the second mixed solution containing sodium aluminate auxiliary agent and sodium hydroxide, and the aluminum hydroxide is completely converted into sodium aluminate during the reaction.

[0016] According to the above scheme, the concentration of aluminum sulfate in the acidic solution containing aluminum sulfate is 42-48%; the concentration of the fluorosilicic acid solution is greater than 35%; and the concentration of sodium aluminate in the mixed solution of sodium aluminate and sodium hydroxide is 30-35%.

[0017] According to the above scheme, the solution containing aluminum sulfate is an aqueous solution containing aluminum sulfate, or a sulfuric acid solution containing aluminum sulfate.

[0018] Preferably, the method for preparing the sulfuric acid solution containing aluminum sulfate is: gradually adding aluminum hydroxide solid into the sulfuric acid solution to carry out an acid-base neutralization reaction to generate a solution containing aluminum sulfate and sulfuric acid.

[0019] More preferably, the reaction temperature in the preparation of the acidic solution containing aluminum sulfate is 100-110° C., and the reaction time is 1.0-1.5 h.

[0020] More preferably, the concentration of sulfuric acid solution in the preparation of the acidic solution containing aluminum sulfate is 47-53%.

[0021] More preferably, the pH value at the reaction endpoint is controlled at 1.5-2.5 during the preparation of the acidic solution containing aluminum sulfate.

[0022] According to the above scheme, the reaction temperature in the second mixed solution containing sodium aluminate auxiliary agent and sodium hydroxide is 105-115° C., and the reaction time is 0.5-1.0 h.

[0023] Provided is an application of the liquid alkali-free quick-setting agent prepared by the method as a quick-setting agent in concrete.

[0024] According to the above scheme, the amount of the liquid alkali-free accelerating setting agent in the concrete is 2.5-3.0%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention provides a method for preparing a liquid alkali-free accelerator. The method comprises the following steps: using an acidic solution containing aluminum sulfate, a mixed solution of a sodium aluminate auxiliary and sodium hydroxide, and a fluorosilicic acid solution as raw materials, and controlling the pH value of the aluminum sulfate solution to be 1.5-2.5; gradually adding aluminum hydroxide solid to an excess sodium hydroxide solution to obtain a mixed solution of a sodium aluminate auxiliary and sodium hydroxide (simply adding sodium aluminate will result in an excess of aluminum element in the final reaction, resulting in an incomplete double decomposition reaction and affecting the performance of the accelerator product); and then, through a reasonable addition sequence, temperature and pH control, in the process of acid-base reaction and double decomposition reaction, elements such as fluorine, aluminum and silicon form a more stable structure, and a stable liquid alkali-free accelerator can be prepared without adding a complex stabilizer.

[0027] 2. The liquid alkali-free quick-setting agent obtained by the present invention can be added to concrete in a low dosage to effectively shorten the setting time and improve the strength of the shotcrete; at the same time, it solves the problems of strong corrosiveness and low strength in the later stage of traditional quick-setting agents, and the quick-setting agent product obtained has higher stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a production flow chart of a liquid alkali-free quick-setting agent in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0030] Example 1

[0031] Provided is a method for preparing a liquid alkali-free accelerating setting agent, comprising the following steps:

[0032] (1) Weigh 440 g of 50% sulfuric acid into a reactor, start stirring and heat to 55° C., add 115.60 g of aluminum hydroxide solid, heat the system to 103° C. by reaction heat, and keep warm for 1.2 h until the solution is completely dissolved, to obtain a solution containing aluminum sulfate with a pH of 2.2.

[0033] (2) Weigh 140.63 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 96° C., add 64.29 g of aluminum hydroxide solid, heat the system to 110° C. by reaction heat, and keep warm for 0.8 h until the auxiliary agent solution is completely dissolved, thereby obtaining a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0034] (3) Weigh 130 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, heat to 78° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 110° C. by reaction heat, and keep warm for 1.5 hours until the solution presents a stable suspension state, thereby obtaining a liquid alkali-free quick-setting agent product. The product indicators are as follows: solute content is 46%, pH value is 2.5, and it can be stably stored for 1-2 months.

[0035] application:

[0036] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.5%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 2.5min; final setting time is 7min; 1d compressive strength is 8.10Mpa; 28d compressive strength ratio is 95%; 90d compressive strength retention rate is 103%.

[0037] Example 2

[0038] Provided is a preparation method and application of a liquid alkali-free accelerating setting agent, comprising the following steps:

[0039] (1) 704 g of 50% sulfuric acid was weighed into a reactor, stirred and heated to 57° C., 184.96 g of aluminum hydroxide solid was added thereto, and the system was heated to 105° C. by reaction heat and kept warm for 1.3 h until the solution was completely dissolved, thereby obtaining a solution containing aluminum sulfate with a pH of 2.3.

[0040] (2) Weigh 225 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 95° C., add 102.90 g of aluminum hydroxide solid, heat the system to 110° C. by reaction heat, and keep warm for 0.9 h until the auxiliary agent solution is completely dissolved, thereby obtaining a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0041] (3) Weigh 208 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, raise the temperature to 76° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 110° C. by reaction heat, and keep warm for 1.6 hours until the solution presents a stable suspension state, thereby obtaining a liquid alkali-free quick-setting agent product. The product indicators are as follows: the solute content is 47%, the pH value is 2.8, and it can be stably stored for 1-2 months.

[0042] application:

[0043] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.6%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 3.0min; final setting time is 8min; 1d compressive strength is 8.00Mpa; 28d compressive strength ratio is 93%; 90d compressive strength retention rate is 102%.

[0044] Example 3

[0045] Provided is a preparation method and application of a liquid alkali-free accelerating setting agent, comprising the following steps:

[0046] (1) 396 g of 50% sulfuric acid was weighed into a reactor, stirred and heated to 57° C., 104.08 g of aluminum hydroxide solid was added thereto, and the system was heated to 104° C. by reaction heat and kept warm for 1.2 h until the solution was completely dissolved, thereby obtaining a solution containing aluminum sulfate with a pH of 2.2.

[0047] (2) Weigh 126.60 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 95° C., add 57.90 g of aluminum hydroxide solid, heat the system to 108° C. by reaction heat, and keep warm for 0.8 h until the auxiliary agent solution is completely dissolved, thereby obtaining a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0048] (3) Weigh 117 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, heat to 75° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 110° C. by reaction heat, and keep warm for 1.5 h until the solution presents a stable suspension state, thereby obtaining a liquid alkali-free quick-setting agent product. The product indicators are as follows: solute content is 46%, pH value is 2.9, and it can be stably stored for 1-2 months.

[0049] application:

[0050] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.4%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 2.8min; final setting time is 7.8min; 1d compressive strength is 8.05Mpa; 28d compressive strength ratio is 94%; 90d compressive strength retention rate is 102%.

[0051] Example 4

[0052] Provided is a method for preparing a liquid alkali-free accelerating setting agent, comprising the following steps:

[0053] (1) 440 g of 50% sulfuric acid was weighed into a reactor, stirred and heated to 55° C., 115.68 g of aluminum hydroxide solid was added thereto, and the system was heated to 103° C. by reaction heat and kept warm for 1.2 h until the solution was completely dissolved, thereby obtaining a solution containing aluminum sulfate with a pH of 2.2.

[0054] (2) Weigh 140.67 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 96° C., add 64.34 g of aluminum hydroxide solid, heat the system to 108° C. by reaction heat, and keep warm for 0.8 h until the auxiliary agent solution is completely dissolved, thereby obtaining a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0055] (3) Weigh 130 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, heat to 78° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 107° C. by reaction heat, and keep warm for 1.5 h until the solution presents a stable suspension state, thereby obtaining a liquid alkali-free quick-setting agent product. The product indicators are as follows: solute content is 46%, pH value is 2.5, and it can be stably stored for 1-2 months.

[0056] application:

[0057] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.5%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 2.6min; final setting time is 7.2min; 1d compressive strength is 8.06Mpa; 28d compressive strength ratio is 94%; 90d compressive strength retention rate is 103%.

[0058] Comparative Example 1

[0059] Provided is a preparation method and application of a liquid alkali-free accelerating setting agent, comprising the following steps:

[0060] (1) 440 g of 50% sulfuric acid was weighed into a reactor, stirred and heated to 55° C., 115.60 g of aluminum hydroxide solid was added thereto, and the system was heated to 103° C. by reaction heat. The temperature was kept at this temperature for 1.2 h until the solution was completely dissolved, thereby obtaining a solution containing aluminum sulfate with a pH of 2.3.

[0061] (2) Weigh 140.63 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 96° C., add 64.29 g of aluminum hydroxide solid, heat the system to 110° C. by reaction heat, and keep warm for 0.8 h until the auxiliary agent solution is completely dissolved, thereby obtaining a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0062] (3) Weigh 130 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, raise the temperature to 60° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 90° C. by reaction heat, and keep warm for 1.5 h until the solution becomes stable, to obtain a liquid alkali-free accelerating setting agent product, the detection indicators of which are: the product is unstable, with obvious precipitation, the solute content is 46%, and the pH value is 2.5.

[0063] application:

[0064] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.5%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 8.0min; final setting time is 20.0min; 1d compressive strength is 4.3Mpa; 28d compressive strength ratio is 85%; 90d compressive strength retention rate is 90%.

[0065] Comparative Example 2

[0066] Provided is a preparation method and application of a liquid alkali-free accelerating setting agent, comprising the following steps:

[0067] (1) Weigh 440 g of 50% sulfuric acid into a reactor, start stirring and heat to 55° C., add 115.60 g of aluminum hydroxide solid, raise the system temperature to 103° C. by reaction heat, and keep warm for 1.2 h until the solution is completely dissolved to obtain a solution containing aluminum sulfate with a pH of 2.3.

[0068] (2) Weigh 140.63 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 96° C., add 64.29 g of aluminum hydroxide solid, heat to 110° C. through a reaction heat system, and keep warm for 0.8 h until the auxiliary agent solution is completely dissolved to obtain a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0069] (3) Weigh 150 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, heat to 78° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 110° C. by reaction heat, and keep warm for 1.5 h until the solution is stable, to obtain a liquid alkali-free accelerating setting agent product, the detection indicators of which are: the product is unstable, with obvious precipitation, the solute content is 47.3%, and the pH value is 1.0.

[0070] application:

[0071] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.5%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 8.5min; final setting time is 22.4min; 1d compressive strength is 4.7Mpa; 28d compressive strength ratio is 83%; 90d compressive strength retention rate is 92%.

[0072] Comparative Example 3

[0073] Provided is a preparation method and application of a liquid alkali-free accelerating setting agent, comprising the following steps:

[0074] (1) 440 g of 50% sulfuric acid was weighed into a reactor, stirred and heated to 55° C., 115.60 g of aluminum hydroxide solid was added thereto, the system temperature was raised to 103° C. by the heat of reaction, and the temperature was kept at this temperature for 1.2 h until the solution was completely dissolved, thereby obtaining a solution containing aluminum sulfate with a pH of 2.2.

[0075] (2) Weigh 140.63 g of 32% sodium hydroxide solution into a reactor, start stirring and heat to 96° C., add 64.29 g of aluminum hydroxide solid, heat the system to 110° C. by reaction heat, and keep warm for 0.8 h until the auxiliary agent solution is completely dissolved, thereby obtaining a mixed solution of sodium aluminate auxiliary agent and sodium hydroxide.

[0076] (3) Weigh 120 g of a 40% fluorosilicic acid solution into a reactor, start stirring, and add the aluminum sulfate solution synthesized in the above step (1), mix well, raise the temperature to 78° C., quickly add the mixed solution of sodium aluminate and sodium hydroxide synthesized in step (2), raise the system temperature to 110° C. by reaction heat, and keep warm for 1.5 h until the solution becomes stable, thereby obtaining a liquid alkali-free accelerating setting agent product. The detection indicators are: the product is unstable, with obvious precipitation, the solute content is 47.3%, and the pH value is 4.0.

[0077] application

[0078] The liquid alkali-free accelerator is added to the concrete at a ratio of 2.5%. The concrete is made by mixing sand, cement and water in a mass ratio of 3:2:1. Referring to GB / T 35159-2017 General requirements for accelerators for shotcrete, the corresponding setting indicators of the above accelerator are tested: initial setting time is 8.8min; final setting time is 24.3min; 1d compressive strength is 4.2Mpa; 28d compressive strength ratio is 80%; 90d compressive strength retention rate is 89%.

[0079] Table 1. Setting effect of the quick-setting agent obtained in Examples 1-3 and Comparative Examples 1-4

[0080] Serial number Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Reaction temperature (℃) 110 110 110 107 90 110 110 pH 2.5 2.8 2.9 2.5 2.5 1.0 4.0 Accelerator dosage (%) 2.5 2.6 2.4 2.5 2.5 2.5 2.5 Initial setting time (min) 2.5 3.0 2.8 2.6 8.0 8.5 8.8 Final setting time (min) 7.0 8 7.8 7.2 20.0 22.4 24.3 1d compressive strength(Mpa) 8.10 8.00 8.05 8.06 4.3 4.7 4.2 28d compressive strength ratio (%) 95 93 94 94 85 83 80 90d compressive strength retention rate (%) 103 102 102 103 90 92 89

[0081] From the test results in Table 1, the reaction temperature of the accelerator provided by Examples 1 to 4 of the present invention is 100-110° C., the pH value is between 2.0 and 3.0, and the setting time of the cement paste can be shortened to 2 to 3 min and the final setting time is 7 to 8 min at a dosage of 2.5% to 3.0%, which is much lower than the requirements of initial setting time ≤5 min and setting time ≤12 min specified in GB / T 35159-2017. The mortar strength: 1d compressive strength is greater than 7.0 MPa, 28d compressive strength ratio is greater than 90%, and 90d compressive strength retention rate is maintained at more than 100%, all of which are higher than the values ​​required by the national standard. The reaction temperature of the accelerator provided in Comparative Example 1 of the present invention is less than 100°C, and the pH value is 2.5. At a dosage of 2.5%, the initial setting time, final setting time, 1d compressive strength, 28d compressive strength ratio and 90d compressive strength retention rate of the cement paste do not meet the index requirements of GB / T 35159-2017. The reaction temperature of the accelerator provided in Comparative Examples 2-3 of the present invention is 100°C, and the pH value is outside the range of 1.5 to 3.0. At a dosage of 2.5%, the initial setting time, final setting time, 1d compressive strength, 28d compressive strength ratio and 90d compressive strength retention rate of the cement paste do not meet the index requirements of GB / T35159-2017.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for the technical requirements of this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a liquid alkali-free accelerating setting agent, characterized in that: The following steps are involved: The solution containing aluminum sulfate and the fluosilicic acid solution are mixed evenly to obtain a first mixed solution, and then a second mixed solution containing sodium metaaluminate additive and sodium hydroxide is added to the first mixed solution, and the mixture is reacted at 100-110° C. for 1-2 hours to obtain a liquid alkali-free accelerating setting agent; wherein: The second mixed solution containing sodium aluminate additive and sodium hydroxide is prepared by gradually adding aluminum hydroxide solid into sodium hydroxide solution for reaction, wherein the molar ratio of sodium hydroxide to aluminum hydroxide is (1.35-1.45):1; The obtained liquid alkali-free quick-setting agent has a solid content of 40-50% and a pH value of 1.5-3.

0.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the fluorosilicic acid in the fluorosilicic acid solution to the aluminum sulfate in the solution containing aluminum sulfate is 1:4.4-5.

0.

3. The preparation method according to claim 1, characterized in that: The mass ratio of fluorosilicic acid to aluminum hydroxide in the fluorosilicic acid solution is 1:1.0-1.

5.

4. The preparation method according to claim 1, characterized in that: The concentration of aluminum sulfate in the acidic solution containing aluminum sulfate is 42-48%; the concentration of sodium aluminate in the mixed solution of sodium aluminate and sodium hydroxide is 30-35%; and the concentration of the fluorosilicic acid solution is greater than 35%.

5. The preparation method according to claim 1, characterized in that: The solution containing aluminum sulfate is an aqueous solution containing aluminum sulfate, or a sulfuric acid solution containing aluminum sulfate.

6. The preparation method according to claim 5, characterized in that: The method for preparing the sulfuric acid solution containing aluminum sulfate is: gradually adding aluminum hydroxide solid into the sulfuric acid solution to carry out acid-base neutralization reaction to generate a solution containing aluminum sulfate and sulfuric acid.

7. The preparation method according to claim 6, characterized in that: The reaction temperature in the preparation of the acidic solution containing aluminum sulfate is 100-110° C., the reaction time is 1.0-1.5 h, and the pH value at the reaction end point is controlled at 1.5-2.

5.

8. The preparation method according to claim 1, characterized in that: The reaction temperature in the second mixed solution containing sodium aluminate additive and sodium hydroxide is 105-115° C., and the reaction time is 0.5-1.0 h.

9. Use of the liquid alkali-free accelerating setting agent prepared by the preparation method according to any one of claims 1 to 8 in concrete.

10. The use according to claim 9, characterized in that: The liquid alkali-free quick-setting agent is added in an amount of 2.5-3.0% in concrete.

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