Nano C-S-H early strength agent and preparation method thereof

Abstract

The invention provides a nano C-S-H early strength agent and a preparation method thereof, and relates to the technical field of concrete admixtures. The nano C-S-H early strength agent is prepared from the following raw materials in percentage by mass: 3 to 5 percent of calcium source, 0.5 to 1 percent of triethanolamine, 45 to 55 percent of silica sol, 0.8 to 1.2 percent of styrene-butadiene latex, 0.8 to 1.2 percent of polycarboxylate superplasticizer and 39 to 47 percent of water. The nano C-S-H with high stability and low calcium-silicon ratio is prepared by taking silica sol as a silicon source, introducing a small amount of calcium source and taking a small amount of PCE, styrene-butadiene emulsion and triethanolamine as a composite stable dispersant.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and particularly relates to a nano C-S-H early strength agent and a preparation method thereof. Background Art

[0002] At present, for the cutting-edge early strength material, nano C-S-H early strength agent, such as in patent CN202410881909.6, mainly uses sodium silicate and calcium nitrate as the main synthetic raw materials, and uses a relatively high amount of polycarboxylate water reducer as a dispersant. Its dispersing effect will greatly affect the setting acceleration effect of the setting accelerator; in addition, if it is simply added directly during the synthesis of the setting accelerator, the two are incompatible, and it will react with aluminum sulfate to precipitate silicon dioxide particles. Therefore, conventional nano C-S-H cannot be directly used as an early strength supplementary component of the setting accelerator. Summary of the Invention

[0003] Based on the technical problems existing in the background art, the present invention proposes a nano C-S-H early strength agent and a preparation method thereof.

[0004] A nano C-S-H early strength agent, comprising the following raw materials in mass percentages: calcium source 3-5%, triethanolamine 0.5-1%, silica sol 45-55%, styrene-butadiene latex 0.8-1.2%, polycarboxylate water reducer 0.8-1.2%, water 39-47%.

[0005] In the present invention, the function of triethanolamine is firstly as an auxiliary dispersing component, which complexes with calcium ions to control its reaction with silica sol to form nano-scale C-S-H. Secondly, as an auxiliary early strength component, it exerts the early strength effect of triethanolamine.

[0006] Preferably, the calcium source is selected from one or more of calcium nitrate tetrahydrate, calcium formate, calcium hydrogen phosphate, and calcium lactate.

[0007] Preferably, the silica sol is an alkaline silica sol, with a particle size of 10-50 nm and a pH of 9.0-10.5.

[0008] Preferably, the styrene-butadiene latex is Styrofan ECO 7623.

[0009] Preferably, the polycarboxylate water reducer is a commercially available water-reducing polycarboxylate water reducer.

[0010] A preparation method of a nano C-S-H early strength agent, comprising the following steps:

[0011] S1. Preparation of solution A: Mix the calcium source, water, and triethanolamine evenly to obtain solution A;

[0012] S2. Preparation of solution B: Use silica sol as solution B;

[0013] S3. Preparation of seed emulsion: Heat and mix water, styrene-butadiene latex, and polycarboxylate water reducer evenly to obtain the seed emulsion;

[0014] S4. Dropwise add solution A and solution B to the seed emulsion simultaneously, and stir evenly to obtain the product.

[0015] Preferably, in S1, the mass ratio of calcium source, water, and triethanolamine is (3 - 5):(23 - 27):(0.5 - 1).

[0016] Preferably, in S2, the concentration of silica sol is 20 - 40%.

[0017] Preferably, in S3, the mass ratio of water, styrene-butadiene latex, and polycarboxylate water reducer is (16 - 20):(0.8 - 1.2):(0.8 - 1.2).

[0018] Preferably, in S3, the heating temperature is 25 - 45°C.

[0019] The heating temperature within a certain range is helpful for the formation of early strength agent, making the particle size of the early strength agent uniform, and contributing to promoting its early strength effect.

[0020] Preferably, in S4, the mass ratio of seed emulsion, solution A, and solution B is (17.6 - 22.4):(26.5 - 33):(45 - 55).

[0021] Preferably, in S4, the dropping time is 2.5 - 3.5 h.

[0022] Preferably, in S4, the stirring time is 30 - 60 min.

[0023] Preferably, the calcium-silicon molar ratio in the calcium source and silica sol is (0.04 - 0.1):1.

[0024] More preferably, the calcium-silicon molar ratio in the calcium source and silica sol is (0.06 - 0.08):1.

[0025] The present invention also proposes an application of the above-mentioned nano C-S-H early strength agent in a setting accelerator.

[0026] The beneficial effects of the present invention are as follows:

[0027] The nano C-S-H early strength agent provided by the present invention includes a calcium source, triethanolamine, silica sol, styrene-butadiene latex, polycarboxylate water reducer, and water. The various raw materials act synergistically, and the prepared nano C-S-H early strength agent has excellent early strength effect.

[0028] In the system of the present invention, the nano C-S-H is prepared by the synergistic action of three dispersants, namely triethanolamine, PCE, and styrene-butadiene emulsion, to control the formation of nano C-S-H. The styrene-butadiene emulsion and PCE first undergo emulsification in the reaction vessel to form tiny emulsion droplets. Before dropping, calcium ions are masked and modified by triethanolamine. At the same time, silica sol and the modified calcium source are dropped. The dropped calcium source and silica source react with the dispersant in the formed emulsion to form stable nano C-S-H with a low calcium-silicon ratio.

[0029] The polycarboxylate superplasticizer in the system of the present invention is a commercially available conventional high-water-reducing polycarboxylate superplasticizer, with no specific requirements for the molecular structure. Its water reduction rate is ≥25%, and the effective mass fraction is 40-50%.

[0030] The present invention uses silica sol to replace the commonly used sodium silicate as the silicon source, and the prepared nano C-S-H has a low calcium-silicon molar ratio, only (0.06-0.08):1. The common calcium-silicon molar ratio is between (0.9-1.3):1. Applying it to the alkali-free liquid accelerating agent can reduce the dosage of aluminum sulfate, which has both accelerating and early strength enhancing effects. Description of the Drawings

[0031] Figure 1 It is the particle size distribution diagram of the nano C-S-H early strength agent prepared in Example 1 proposed by the present invention. Detailed Description of the Invention

[0032] The technical solution of the present invention will be described in detail through specific examples.

[0033] The materials, reagents, etc. used in the following examples can be obtained from commercial channels without special instructions.

[0034] Example 1

[0035] A preparation method of a nano C-S-H early strength agent includes the following steps:

[0036] S1. Preparation of solution A: Dissolve 40 g of calcium nitrate tetrahydrate and 254 g of water, and after stirring and dissolving, add 6 g of triethanolamine, and continue to stir for 30 min to dissolve evenly to obtain solution A;

[0037] S2. Preparation of solution B: Take 500 g of silica sol JN30 (30%) as solution B; the silica sol is alkaline silica sol with a nano particle size of 30 nm;

[0038] S3. Preparation of seed emulsion: Heat and stir 180 g of water, 10 g of styrene-butadiene latex, and 10 g of 40% polycarboxylate superplasticizer at 35 °C for 30 min to obtain the seed emulsion;

[0039] S4. Simultaneously add solution A and solution B to the seed emulsion dropwise over a period of 4 h. After the addition is complete, continue stirring for 30 min to obtain the product.

[0040] The polycarboxylate water reducer used is the 131 mother liquor produced by Anhui Zhongtie Engineering Materials Technology Co., Ltd., with a mass fraction of 50% and a water reduction rate of 31%. The polyether used in the synthesis is vinyl polyethylene glycol with a molecular weight of 3000, and the molar ratio of acid to ether is 3:1.

[0041] Example 2

[0042] A preparation method of a nano C-S-H early strength agent includes the following steps:

[0043] S1. Preparation of solution A: Dissolve 35 g of calcium nitrate tetrahydrate and 270 g of water by stirring, then add 7 g of triethanolamine and continue stirring for 30 min to dissolve evenly to obtain solution A;

[0044] S2. Preparation of solution B: Take 464 g of silica sol JN30 (30%) as solution B; the silica sol is an alkaline silica sol with a nano-particle size of 30 nm;

[0045] S3. Preparation of the seed emulsion: Heat and stir 200 g of water, 12 g of styrene-butadiene latex, and 12 g of 40% polycarboxylate water reducer at 35 °C for 30 min to obtain the seed emulsion;

[0046] S4. Simultaneously add solution A and solution B to the seed emulsion dropwise over a period of 4 h. After the addition is complete, continue stirring for 30 min to obtain the product.

[0047] The polycarboxylate water reducer is the same as that in Example 1.

[0048] Example 3

[0049] A preparation method of a nano C-S-H early strength agent includes the following steps:

[0050] S1. Preparation of solution A: Dissolve 45 g of calcium nitrate tetrahydrate and 250 g of water by stirring, then add 5 g of triethanolamine and continue stirring for 30 min to dissolve evenly to obtain solution A;

[0051] S2. Preparation of solution B: Take 520 g of silica sol JN30 (30%) as solution B; the silica sol is an alkaline silica sol with a nano-particle size of 30 nm;

[0052] S3. Preparation of the seed emulsion: Heat and stir 160 g of water, 10 g of styrene-butadiene latex, and 10 g of 40% polycarboxylate water reducer at 35 °C for 30 min to obtain the seed emulsion;

[0053] S4. Simultaneously dropwise add Solution A and Solution B into the seed emulsion over a period of 4 h. After the dropwise addition is completed, continue stirring for 30 min to obtain the product.

[0054] The polycarboxylate water reducer used is the 125 mother liquor produced by Anhui Zhongtie Engineering Materials Technology Co., Ltd. Its effective solid content is 45%, the water reducer content is 29%, the polyether used in the synthesis is isopentenyl alcohol polyoxyethylene ether with a molecular weight of 2400, and the molar ratio of acid to ether is 4.4:1.

[0055] Apply the above nano C-S-H early strength agent to the accelerating agent. The specific scheme is as follows: Mix the nano C-S-H early strength agent and alkanolamine substances (ethanolamine, diethanolamine, triethanolamine or triisopropanolamine) evenly at a mass ratio of 10:1 to obtain a mixed solution for standby. After the preparation of the accelerating agent is completed, add 10% of the above mixed solution based on the mass of the accelerating agent and stir evenly to obtain the modified accelerating agent.

[0056] According to the standard of GB / T 35159-2017 "Accelerating Agent for Shotcrete", add the modified accelerating agent to the cement paste in an amount of 8% by weight of the cement, and test the setting time of the cement paste and the compressive strength of the cement mortar.

[0057] The mixing ratio for testing the setting time of the cement paste is: reference cement: water = 400:140.

[0058] The mixing ratio for testing the compressive strength of the cement mortar is: reference cement: standard sand: water = 900:1350:450.

[0059] The test results are shown in Table 1.

[0060] Table 1

[0061] Item 6h Strength (Mpa) 1d Strength (Mpa) Initial Setting Time Final Setting Time Reference Accelerator 0.75 7.56 2min 15s 3min 45s Example 1 1.64 12.78 2min 30s 4min 25s Example 2 1.42 11.56 2min 25s 4min 00s Example 3 1.82 13.25 2min 35s 4min 45s

[0062] It can be seen from the data in Table 1 that the nano C-S-H early strength agent prepared by the present invention has excellent early strength effect, can significantly improve the 6 h and 1 d compressive strengths of the accelerating agent mortar, and solve the problem of unqualified early strength caused by insufficient cement adaptability of the accelerating agent; at the same time, when applied to the accelerating agent, it has little influence on the setting time.

[0063] Figure 1 This is the particle size distribution diagram of the nano C-S-H early strength agent prepared in Example 1 of the present invention. The D50 particle size of the nano C-S-H early strength agent is 326 nm.

[0064] The above is only the preferred specific implementation manner 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 all should be covered within the protection scope of the present invention.

Claims

1. A nano C-S-H early strength agent, characterized in that, It includes raw materials with the following mass percentages: calcium source 3 - 5%, triethanolamine 0.5 - 1%, silica sol 45 - 55%, styrene-butadiene latex 0.8 - 1.2%, polycarboxylate water reducer 0.8 - 1.2%, and water 39 - 47%.

2. The nano C-S-H early strength agent according to claim 1, characterized in that, The silica sol is alkaline silica sol, with a particle size of 10 - 50 nm and a pH of 9.0 - 10.

5.

3. The nano C-S-H early strength agent according to claim 1, wherein, The calcium source is selected from one or more of calcium nitrate tetrahydrate, calcium formate, calcium hydrogen phosphate, and calcium lactate.

4. A preparation method of the nano C-S-H early strength agent according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Preparation of solution A: Mix the calcium source, water, and triethanolamine evenly to obtain solution A; S2. Preparation of solution B: Use silica sol as solution B; S3. Preparation of seed emulsion: Heat and mix water, styrene-butadiene latex, and polycarboxylate water reducer evenly to obtain the seed emulsion; S4. Dropwise add solution A and solution B to the seed emulsion simultaneously, stir evenly, and then it is obtained.

5. The preparation method according to claim 4, characterized in that, In the above S1, the mass ratio of the calcium source, water, and triethanolamine is (3 - 5):(23 - 27):(0.5 - 1).

6. The preparation method according to claim 4, characterized in that, In the above S2, the concentration of the silica sol is 20 - 40%.

7. The preparation method according to claim 4, wherein In the above S3, the mass ratio of water, styrene-butadiene latex, and polycarboxylate water reducer is (16 - 20):(0.8 - 1.2):(0.8 - 1.2).

8. The preparation method according to claim 4, characterized in that, In the above S3, the heating temperature is 25 - 45 °C.

9. The preparation method according to claim 4, characterized in that, In the above S4, the mass ratio of the seed emulsion, solution A, and solution B is (17.6 - 22.4):(26.5 - 33):(45 - 55).

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