Grinding aid for producing cement from volcanic ash in East African region and preparation method of grinding aid

Abstract

The invention relates to a grinding aid for producing cement from volcanic ash in the East African region and a preparation method of the grinding aid, and belongs to the technical field of cement production. The additive is prepared from the following raw materials in parts by weight: 30-40 parts of oxalic acid modified triethanolamine, 0.5-2 parts of trometamol, 15-20 parts of molasses, 6-10 parts of lithium acetate and the balance of water. 0.1% of the grinding aid is used for cement production, so that the compressive strength of cement can be improved, and the fluidity of cement paste can be increased; the use amount of volcanic ash can be increased by more than 5%, so that the local cement raw material cost is reduced.

Description

Technical Field

[0001] The present invention relates to a grinding aid for producing cement from volcanic ash in the East African region and a preparation method thereof, belonging to the technical field of cement production. Background Art

[0002] The components of the East African volcanic ash are mainly detected to include SiO2, Fe2O3, CaO, Al2O3, MgO, etc., among which SiO2, Fe2O3, and CaO are dominant. In the development of foreign markets, it is found that a large amount of volcanic ash is generally used as a cement admixture in the East African region. However, the local volcanic ash has a higher iron content, a lower aluminum content, poor activity, and poor grindability compared with the domestic volcanic ash, resulting in generally low cement strength. Moreover, other local admixtures are not as abundant as those in China. As a result, local cement enterprises have to use such volcanic ash in order to reduce costs, leading to frequent unqualified cement strength. During the investigation, it was found that international well-known grinding aid enterprises such as Sika and Mapei have conducted many tests locally, but none of them have been able to solve the problem well.

[0003] Based on this, the present invention proposes a grinding aid for producing cement from volcanic ash in the East African region and a preparation method thereof. Summary of the Invention

[0004] The purpose of the present invention is to provide a grinding aid for producing cement from volcanic ash in the East African region and a preparation method thereof, aiming to reduce the cost of cement raw materials and improve the performance of existing volcanic ash blended cement to solve the problems of the prior art.

[0005] The technical solution of the present invention is as follows:

[0006] A grinding aid for producing cement from volcanic ash in the East African region is composed of the following raw materials in parts by weight: 30 - 40 parts of oxalic acid-modified triethanolamine, 0.5 - 2 parts of aminobutanetriol, 15 - 20 parts of molasses, 6 - 10 parts of lithium acetate, and the balance is water.

[0007] The above-mentioned oxalic acid-modified triethanolamine is prepared by the following steps:

[0008] Weigh an appropriate amount of triethanolamine and add it to a four-necked reaction flask at one time. Start the stirrer, then weigh an appropriate amount of oxalic acid, and use a special melting pump to uniformly add the weighed oxalic acid to the four-necked reaction flask within 2 hours. The reaction temperature is 50°C ± 2°C, and the reaction time is 1 hour.

[0009] The preparation method of the above-mentioned grinding aid is as follows:

[0010] Take an appropriate amount of water and add it to the stirrer. Start the stirrer, add lithium acetate, and stir for 15 minutes until it is completely dissolved. Then, add molasses, aminobutanetriol, and oxalic acid-modified triethanolamine in sequence, and continue to stir for 10 minutes to obtain a mixed solution, which is the cement grinding aid described in the invention.

[0011] Mechanism of action:

[0012] In this product, oxalic acid modified triethanolamine is applied to the production of cement from pozzolan. The molecules of oxalic acid modified triethanolamine adhere to the surface, causing Fe 2 O 3 , Al2O3, and CaO 、 in pozzolan to decompose more readily in a weakly acidic environment, thereby weakening the surface energy of pozzolan particles and improving the grinding efficiency of cement grinding. At the same time, due to the decomposition of Fe 2 O 3 , Al2O3, and CaO in pozzolan, it is more conducive to the formation of hydration products such as hydrated silicate, hydrated aluminate, and ferroaluminate during the cement hydration process, thus more conducive to improving the compressive strength of cement. Tromethamine assists in the dissolution of metal ions, which is more beneficial to the progress of the hydration reaction. Lithium acetate, as a strong activator, promotes cement hydration and increases cement strength. The produced grinding aid is weakly acidic, which is beneficial to improving the working performance of cement and improving the compatibility with polycarboxylate water reducer for concrete.

[0013] The beneficial effects of the present invention are as follows:

[0014] The grinding aid of the present invention is a weakly acidic product. The grinding aid molecules wrap around the surface of pozzolan, which is more conducive to the decomposition of iron components, thereby weakening the surface energy of pozzolan particles and improving the cement grinding efficiency. At the same time, it is beneficial to the dissolution and decomposition of Fe2O3, Al2O3, and CaO in pozzolan, and it is more conducive to the formation of hydration products such as hydrated silicate, hydrated aluminate, and ferroaluminate during the cement hydration process, thus more conducive to improving the compressive strength of cement. Specifically as follows:

[0015] 1. For the grinding aid of the present invention, when a 0.1% dosage is used in cement production, it can increase the compressive strength of cement by 3 - 5 mpa;

[0016] 2. The grinding aid of the present invention can increase the dosage of pozzolan by more than 5%, thereby reducing the cost of cement raw materials.

[0017] 3. When using the grinding aid of the present invention, the fluidity of the produced cement paste increases by more than 30 mm, significantly improving the working performance. Specific embodiments

[0018] Example 1

[0019] Weigh 280 g of triethanolamine with a content of 85%, and add it into a 500 ml four-neck reaction flask at one time. Start the stirrer. Then weigh 100 g of oxalic acid with a content of 99%, and use a special melting pump to uniformly add the weighed oxalic acid into the four-neck reaction flask within 2 hours, ensuring that the reaction temperature is controlled at 50°C ± 2°C. React for another 1 hour at 50°C ± 2°C to obtain the oxalic acid-modified triethanolamine required by the present invention.

[0020] Example 2

[0021] A grinding aid for facilitating the production of cement from volcanic ash in the East African region is composed of the following raw materials in parts by weight: 35 parts of oxalic acid-modified triethanolamine, 2 parts of aminobutanetriol, 15 parts of molasses, 10 parts of lithium acetate, and 38 parts of water.

[0022] The preparation method of this grinding aid is as follows: Add 380 kg of water into a stirrer, start the stirrer, add 100 kg of lithium acetate, and stir for 15 minutes until completely dissolved. Then sequentially add 150 kg of molasses, 20 kg of aminobutanetriol, and 350 kg of oxalic acid-modified triethanolamine, and continue to stir for 10 minutes to obtain 1000 kg of mixed solution, which is the cement grinding aid described in the invention.

[0023] Example 3

[0024] A grinding aid for facilitating the production of cement from volcanic ash in the East African region is composed of the following raw materials in parts by weight: 30 parts of oxalic acid-modified triethanolamine, 1 part of aminobutanetriol, 15 parts of molasses, 6 parts of lithium acetate, and 48 parts of water.

[0025] The preparation method of this grinding aid is as follows: Add 480 kg of water into a stirrer, start the stirrer, add 60 kg of lithium acetate, and stir for 15 minutes until completely dissolved. Then sequentially add 150 kg of molasses, 10 kg of aminobutanetriol, and 300 kg of oxalic acid-modified triethanolamine, and continue to stir for 10 minutes to obtain 1000 kg of mixed solution, which is the cement grinding aid described in the invention.

[0026] Example 4

[0027] A grinding aid for facilitating the production of cement from volcanic ash in the East African region is composed of the following raw materials in parts by weight: 40 parts of oxalic acid-modified triethanolamine, 0.5 part of aminobutanetriol, 20 parts of molasses, 6 parts of lithium acetate, and 33.5 parts of water.

[0028] The preparation method of this grinding aid is as follows: Add 335 kg of water into a stirrer, start the stirrer, add 60 kg of lithium acetate, and stir for 15 minutes until completely dissolved. Then sequentially add 200 kg of molasses, 5 kg of aminobutanetriol, and 400 kg of oxalic acid-modified triethanolamine, and continue to stir for 10 minutes to obtain 1000 kg of mixed solution, which is the cement grinding aid described in the invention.

[0029] Example 5 Performance Test of Cement Products

[0030] In the laboratory, a test small mill with a diameter of φ500mm * 500mm was used. For the blank sample, it was composed of: 75% clinker, 5% desulfurized gypsum, 5% limestone, and 15% volcanic ash; for the reference sample, it was composed of: 70% clinker, 5% desulfurized gypsum, 5% limestone, and 20% volcanic ash. With the same grinding time of 30 minutes, two mill samples of cement were prepared respectively without adding grinding aids and adding 0.1% of the cement grinding aids in Examples 2 - 4. The first mill sample was discarded and the second mill sample was retained. The 3-day and 28-day compressive strength tests of the cement were carried out in accordance with GB / T 17671-2021 "Test Method for Cement Mortar Strength (ISO Method)", and the fluidity verification of cement paste was carried out respectively in accordance with GB / T 8077-2000 "Test Method for Homogeneity of Concrete Admixtures".

[0031] The proportion of volcanic ash components in East Africa (%) is as follows in the table:

[0032] Sample Name LOSS SiO2 Al2O3 Fe2O3 <![CDATA CaO > <![CDATA MgO > SO3 East African Pozzolan 5.94 42.3 9.16 16.83 11.24 10.53 0.22

[0033] The test results of physical indexes of different cement samples are as follows:

[0034]

[0035] Note: The test was carried out under the same conditions with fixed operators.

[0036] From the above comparison results, it can be seen that for the cement added with the grinding aids in Examples 2 - 4 of the present invention, without changing the cement mix ratio, compared with the blank cement without adding grinding aids, the residue on the 45um sieve decreased, and the fineness of the cement powder was overall improved. Under the conditions of the same mix ratio and the same grinding time, the fineness of the cement decreased significantly, with a decrease amplitude reaching 30%, and the 3-day and 28-day compressive strengths of the cement increased significantly by at least 3.5MPa or more, and the fluidity of the cement paste increased significantly, with an increase reaching 30mm. When reducing the clinker dosage by 5% and increasing the volcanic ash dosage by 5%, while maintaining the same grinding time, for the cement added with the grinding aids of the present invention, the 3-day and 28-day compressive strengths were significantly improved to varying degrees compared with the cement with reduced clinker dosage, and the working performance of the cement was significantly improved.

[0037] Example 6 Comparative Performance Test of Cement Products

[0038] In the laboratory, a φ500mm*500mm test small mill is used, in accordance with: 70% clinker, 5% desulfurized gypsum, 5% limestone, 20% pozzolan (same as Example 5). With the same grinding time of 30 minutes, cement samples are prepared without adding grinding aids, adding 0.1% of the cement grinding aid in Example 2, and commonly used grinding aids on the market, SC-KZ100A, MB-FH100C, XP-KH100B. Two mill cement samples are prepared for each, the first mill samples are discarded and the second mill samples are retained. The 3-day and 28-day compressive strength tests of the cement are carried out in accordance with GB / T17671-2021 "Test Method for Cement Mortar Strength (ISO Method)", and the fluidity of cement paste is verified respectively in accordance with GB / T8077-2000 "Test Method for Homogeneity of Concrete Admixtures". The grinding aid used is SC-KZ100A

[0039] The properties of the cement prepared by adding different grinding aids are shown in the following table

[0040]

[0041] The indicators of the cement added with the grinding aid of the present invention are significantly better than those of the cement added with other grinding aids on the market. From the above comparison results, it can be seen that adding the grinding aid of the present invention is more suitable for the production of pozzolan cement compared with several common grinding aids on the market.

Claims

1. A grinding aid for cement production from volcanic ash in East Africa, characterized by: The invention is composed of the following raw materials in parts by weight: 30-40 parts of oxalic acid-modified triethanolamine, 0.5-2 parts of tromethamine, 15-20 parts of molasses, 6-10 parts of lithium acetate, and the balance is water.

2. A grinding aid for producing cement from volcanic ash in East Africa according to claim 1, characterized in that: The invention is composed of the following raw materials in parts by weight: 35 parts of oxalic acid-modified triethanolamine, 2 parts of tromethamine, 15 parts of molasses, 10 parts of lithium acetate, and the balance is water.

3. A grinding aid for producing cement from volcanic ash in East Africa according to claim 1, characterized in that: The above oxalic acid-modified triethanolamine is prepared by the following method: S1, add triethanolamine into a four-necked reaction bottle at once, and start the agitator; S1. Use a special melting pump to evenly add oxalic acid into a four-necked reaction bottle within 2 hours. The reaction time is 1 hour.

4. A grinding aid for producing cement from volcanic ash in East Africa according to claim 3, characterized in that: The reaction temperature of S2 is 50°C ± 2°C.

5. A method for preparing a grinding aid as claimed in claim 1, characterized in that: The steps include: Step (1): weigh and prepare the raw materials of oxalic acid-modified triethanolamine, tromethamine, molasses and lithium acetate for later use; Step (2): add water to the stirrer, start the stirrer, add lithium acetate, and stir for 15 minutes; Step (3): After the above raw materials are completely dissolved, molasses, tromethamine, and oxalic acid-modified triethanolamine are added in sequence, and stirring is continued for 10 minutes to obtain a mixed solution, which is the cement grinding aid of the present invention.

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