Alkali-free liquid accelerator and preparation method thereof

Abstract

The invention provides an alkali-free liquid accelerator and a preparation method thereof, and relates to the technical field of concrete admixtures. The alkali-free liquid accelerator is prepared from the following raw materials in percentage by mass: 0.5 to 1.5 percent of alumina monohydrate, 0.1 to 0.25 percent of monocalcium phosphate, 40 to 55 percent of aluminum sulfate, 2 to 4 percent of fluosilicate, 7 to 12 percent of diethanol amine, 3 to 10 percent of modified nano C-S-H early strength agent and the balance of water. The accelerator provided by the invention is moderate in viscosity, excellent in early strength performance and relatively short in setting time.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to a non-alkali liquid accelerating agent and a preparation method thereof. Background Art

[0002] The non-alkali liquid accelerating agent takes aluminum sulfate as the main component. In order to achieve higher early strength, the dosage of aluminum sulfate in the non-alkali liquid accelerating agent is usually high. For example, in patent CN116693229B, according to the sum of the mass percentages of each raw material component being 100%, 60-70% of aluminum sulfate, 8-12% of diethanolamine, 0.3-1% of sepiolite, and the balance being water, the prepared accelerating agent has the characteristics of being alkali-free, fluorine-free, high aluminum ion content, low-temperature resistance, and ultra-early strength. The 6-hour compressive strength of the mortar reaches 2.82 MPa, and the 1-day strength reaches 14.81 MPa. However, the dosage of aluminum sulfate in such accelerating agents is high, and the solubility of aluminum sulfate is greatly affected by temperature. Under normal temperature conditions, the viscosity of such accelerating agents is large. When used in shotcrete, it has high requirements for the pump for extracting the accelerating agent. When the suction of the pump is insufficient, it will cause the inability to extract the accelerating agent or the insufficient extraction amount, thereby affecting the spraying effect. How to solve the problem of high viscosity of such accelerating agents is a technical problem to be solved urgently at present. Summary of the Invention

[0003] Based on the technical problems existing in the background art, the present invention proposes a non-alkali liquid accelerating agent and a preparation method thereof.

[0004] A non-alkali liquid accelerating agent proposed by the present invention comprises the following raw materials in mass percentages: 0.5-1.5% of aluminum hydroxide monohydrate, 0.1-0.25% of calcium dihydrogen phosphate, 40-55% of aluminum sulfate, 2-4% of fluorosilicate, 7-12% of diethanolamine, 3-10% of modified nano C-S-H early strength agent, and the balance being water.

[0005] Preferably, the fluorosilicate is selected from one or more of magnesium fluorosilicate and sodium fluorosilicate.

[0006] Preferably, the mass fraction of the diethanolamine is 80-90%.

[0007] Preferably, the modified nano C-S-H early strength agent comprises solution A, solution B, and seed emulsion. Among them, solution A is an aqueous calcium nitrate solution, solution B is silica sol, and the seed emulsion comprises water, silica sol, styrene-butadiene latex, and polycarboxylate water reducer.

[0008] More preferably, the concentration of the aqueous calcium nitrate solution is 13-16%.

[0009] More preferably, the particle size of the silica sol is 20-40 nm, the concentration is 20-40%, and the pH value is 9.0-10.5.

[0010] More preferably, the mass ratio of the water, silica sol, styrene-butadiene latex, and polycarboxylate superplasticizer is (150 - 200):200:10:(8 - 10).

[0011] More preferably, the preparation of the seed emulsion includes heating and stirring the water, silica sol, styrene-butadiene latex, and polycarboxylate superplasticizer evenly to obtain it.

[0012] More preferably, the heating temperature is 25 - 35 °C.

[0013] More preferably, the concentration of the polycarboxylate superplasticizer is 35 - 40%, and the pH value is 6 - 8.

[0014] Preferably, the preparation method of the modified nano C-S-H early strength agent includes simultaneously dropping solution A and solution B into the seed emulsion, stirring evenly to obtain it.

[0015] The present invention also proposes a preparation method of an alkali-free liquid accelerator, including the following steps:

[0016] S1. Heat and stir the water, aluminum hydroxide monohydrate, and calcium dihydrogen phosphate evenly to obtain mixture A;

[0017] S2. Add aluminum sulfate and fluorosilicate to mixture A, stir evenly to obtain mixture B;

[0018] S3. Add the modified nano C-S-H early strength agent and diethanolamine to mixture B, stir evenly to obtain it.

[0019] Preferably, in S1, the heating temperature is 50 - 70 °C.

[0020] Preferably, in S2, after adding aluminum sulfate and mixing evenly, then add fluorosilicate.

[0021] Preferably, in S3, the stirring time is 0.5 - 1 h.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention uses nano-silica sol as the silicon source, calcium nitrate as the calcium source, styrene-butadiene emulsion and a small amount of polycarboxylate superplasticizer as the dispersant to prepare a low calcium-silicon ratio modified nano C-S-H early strength agent. The present invention utilizes the early strength performance of the prepared nano C-S-H with a low calcium-silicon ratio to improve the early strength effect of the accelerator in concrete. Applying it to the alkali-free liquid accelerator can reduce the dosage of aluminum sulfate, thereby reducing the viscosity of the early strength type alkali-free liquid accelerator and improving the low-temperature stability. At the same time, it can both accelerate setting and play an early strength role.

[0024] The present invention mainly uses silica sol to prepare a modified nano C-S-H early-strength material. First, the sol-gel reaction of silica sol itself is utilized, that is, it has a certain coagulation-promoting and early-strength effect by itself. At the same time, its particle size is uniform and its viscosity is small, and adding it to the accelerator system will not cause the instability of the accelerator system. Second, the property of silica sol combined with metal Ca 2+ is used to prepare nano-scale C-S-H. While further bringing about a coagulation-promoting and early-strength effect, new chemical bonds are formed with higher stability, which can ensure the stability of the prepared material itself. Third, the dispersibility of silica sol is used to further stabilize nano C-S-H particles, avoiding the retarding effect caused by using a large amount of polycarboxylate superplasticizer as a dispersant. The nano C-S-H prepared by the present invention can be directly added during the synthesis of the accelerator. Specific embodiments

[0025] The materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial channels without special instructions.

[0026] Example 1

[0027] A preparation method of an alkali-free liquid accelerator includes the following steps:

[0028] S1. Heat 313 g of water, 10 g of aluminum oxide monohydrate, and 2 g of calcium dihydrogen phosphate to 60 °C and stir for 1 h to obtain mixture A;

[0029] S2. Add 500 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 25 g of magnesium fluorosilicate and stir evenly to obtain mixture B;

[0030] S3. Add 50 g of modified nano C-S-H early-strength agent and 100 g of diethanolamine to mixture B and stir evenly to obtain the product.

[0031] The preparation method of the modified nano C-S-H early-strength agent includes: simultaneously dripping solution A and solution B into the seed emulsion, with a dripping time of 3 h. After the dripping is completed, continue to stir for 30 min and then discharge. Among them, solution A is obtained by mixing 40 g of calcium nitrate and 290 g of water evenly; solution B is 300 g of silica sol JN30 (30%); the preparation of the seed emulsion includes: stirring 200 g of water and 200 g of silica sol JN30 (30%) for 10 min, adding 10 g of styrene-butadiene latex StyrofanECO7623 and 10 g of 40% polycarboxylate superplasticizer (KH-4) while stirring, adjusting the temperature to 30 °C, and stirring for 30 min to disperse evenly to obtain the product.

[0032] Example 2

[0033] A preparation method of an alkali-free liquid accelerator includes the following steps:

[0034] S1. Heat 354 g of water, 5 g of aluminum hydroxide monohydrate, and 1 g of calcium dihydrogen phosphate to 60 °C and stir for reaction for 1 h to obtain mixture A;

[0035] S2. Add 450 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 30 g of magnesium fluorosilicate, and stir evenly to obtain mixture B;

[0036] S3. Add 70 g of modified nano C-S-H early strength agent and 90 g of diethanolamine to mixture B, and stir evenly to obtain the product.

[0037] The preparation method of the modified nano C-S-H early strength agent is the same as that in Example 1.

[0038] Example 3

[0039] A preparation method of an alkali-free liquid accelerating agent includes the following steps:

[0040] S1. Heat 372.5 g of water, 15 g of aluminum hydroxide monohydrate, and 2.5 g of calcium dihydrogen phosphate to 60 °C and stir for reaction for 1 h to obtain mixture A;

[0041] S2. Add 400 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 40 g of magnesium fluorosilicate, and stir evenly to obtain mixture B;

[0042] S3. Add 90 g of modified nano C-S-H early strength agent and 80 g of diethanolamine to mixture B, and stir evenly to obtain the product.

[0043] The preparation method of the modified nano C-S-H early strength agent is the same as that in Example 1.

[0044] Comparative Example 1

[0045] A preparation method of an accelerating agent includes the following steps:

[0046] S1. Heat 213 g of water, 10 g of aluminum hydroxide monohydrate, and 2 g of calcium dihydrogen phosphate to 60 °C and stir for reaction for 1 h to obtain mixture A;

[0047] S2. Add 650 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 25 g of magnesium fluorosilicate, and stir evenly to obtain mixture B;

[0048] S3. Add 100 g of diethanolamine to mixture B, and stir evenly to obtain the product.

[0049] Comparative Example 2

[0050] A preparation method of an accelerating agent includes the following steps:

[0051] S1. Heat 363 g of water, 10 g of aluminum hydroxide monohydrate, and 2 g of calcium dihydrogen phosphate to 60 °C and stir for 1 h to obtain mixture A;

[0052] S2. Add 500 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 25 g of magnesium fluorosilicate and stir evenly to obtain mixture B;

[0053] S3. Add 100 g of diethanolamine to mixture B and stir evenly to obtain the product.

[0054] Comparative Example 3

[0055] A preparation method of a quick-setting agent, comprising the following steps:

[0056] S1. Heat 313 g of water, 10 g of aluminum hydroxide monohydrate, and 2 g of calcium dihydrogen phosphate to 60 °C and stir for 1 h to obtain mixture A;

[0057] S2. Add 500 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 25 g of magnesium fluorosilicate and stir evenly to obtain mixture B;

[0058] S3. Add 50 g of commercial nano C-S-H early strength agent (solid content 12.5%) and 100 g of diethanolamine to mixture B and stir evenly to obtain the product.

[0059] Comparative Example 4

[0060] A preparation method of a quick-setting agent, comprising the following steps:

[0061] S1. Heat 313 g of water, 10 g of aluminum hydroxide monohydrate, and 2 g of calcium dihydrogen phosphate to 60 °C and stir for 1 h to obtain mixture A;

[0062] S2. Add 500 g of aluminum sulfate to mixture A, stir for 0.5 h, then add 25 g of magnesium fluorosilicate and stir evenly to obtain mixture B;

[0063] S3. Add 50 g of silica sol and 100 g of diethanolamine to mixture B and stir evenly to obtain the product.

[0064] Test the viscosity of the quick-setting agent prepared above, test its strength and setting time according to the standard of GB / T 35159-2017, the dosage of the quick-setting agent is 8%, and the test results are shown in Table 1.

[0065] Table 1

[0066]

[0067] As can be seen from the data in Table 1, the setting accelerator prepared by the present invention has a moderate viscosity, excellent early strength performance, and a short setting time. From the data of Comparative Example 1, it can be seen that when the modified nano C-S-H early strength agent is not added and the content of aluminum sulfate increases, although the early strength performance can meet the requirements, the viscosity of the setting accelerator system is large, it is easy to agglomerate, the stability is poor, and the state is not good. From the data of Comparative Example 2, it can be seen that when nano C-S-H is not used and the dosage of aluminum sulfate is controlled, although the viscosity is improved, it will result in insufficient strength. From the data of Comparative Example 3, it can be seen that when a commercial nano C-S-H early strength agent is used to replace the modified nano C-S-H early strength agent of the present invention, the setting time of the prepared setting accelerator is unqualified. Due to the retarding effect, its early 6-hour strength does not meet the requirements, and the 1-day strength meets the requirements. From the data of Comparative Example 4, it can be seen that when silica sol is used alone, it has a certain accelerating and early strength effect, but its effect is not enough, and the system is not stable enough; both the strength and the setting time do not meet the requirements.

[0068] In summary, the setting accelerator provided by the present invention has a moderate viscosity, excellent early strength performance and a short setting time.

[0069] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A non-alkali liquid accelerator, characterized in that, It includes raw materials with the following mass percentages: 0.5 - 1.5% of aluminum hydroxide monohydrate, 0.1 - 0.25% of calcium dihydrogen phosphate, 40 - 55% of aluminum sulfate, 2 - 4% of fluorosilicate, 7 - 12% of diethanolamine, 3 - 10% of modified nano C-S-H early strength agent, and the balance is water.

2. The alkali-free liquid accelerator according to claim 1, wherein, The mass fraction of the diethanolamine is 80 - 90%.

3. The alkali-free liquid accelerating admixture according to claim 1, wherein The modified nano C-S-H early strength agent includes solution A, solution B, and seed emulsion. Among them, solution A is an aqueous solution of calcium nitrate, solution B is silica sol, and the seed emulsion includes water, silica sol, styrene-butadiene latex, and polycarboxylate water reducer.

4. The alkali-free liquid accelerator according to claim 3, characterized in that, The concentration of the aqueous solution of calcium nitrate is 13 - 16%.

5. The alkali-free liquid accelerating admixture according to claim 3, wherein, The mass ratio of the water, silica sol, styrene-butadiene latex, and polycarboxylate water reducer is (150 - 200):200:10:(8 - 10).

6. The alkali-free liquid accelerator according to claim 1, wherein, The preparation method of the modified nano C-S-H early strength agent includes simultaneously dropping solution A and solution B into the seed emulsion, stirring evenly, and then obtaining it.

7. A preparation method of the alkali-free liquid accelerator according to any one of claims 1 to 6, characterized in that, It includes the following steps: S1. Heat and stir evenly water, aluminum hydroxide monohydrate, and calcium dihydrogen phosphate to obtain mixture A; S2. Add aluminum sulfate and fluorosilicate to mixture A, stir evenly to obtain mixture B; S3. Add the modified nano C-S-H early strength agent and diethanolamine to mixture B, stir evenly, and then obtain it.

8. The preparation method according to claim 7, characterized in that In S1, the heating temperature is 50 - 70°C.

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