A cement grinding aid and preparation method thereof

Abstract

The present application relates to the field of cement additives, and more specifically, it relates to a cement grinding aid and a preparation method thereof. A cement grinding aid comprises the following raw materials in parts by weight: 3-7 parts of diethanolamine, 1-4 parts of ammonium acetate, 5-10 parts of diethanol monoisopropanolamine, 2-5 parts of calcium carbonate, 50-70 parts of water, and 0.2-0.8 parts of cellulose; its preparation method is: adding diethanolamine, ammonium acetate, and diethanol monoisopropanolamine to water and mixing until uniform; continuing to add cellulose and stirring and mixing; continuing to add calcium carbonate and mixing, and obtaining a finished product after uniformity. The present application has the advantage of improving the grinding aid effect of cement added with fly ash.

Description

Technical Field

[0001] The present invention relates to the field of cement additives, and more specifically, to a cement grinding aid and a preparation method thereof. Background Art

[0002] Cement grinding is the biggest energy consumption in cement production. Clinker grinding is mostly carried out in ball mills. When the grinding equipment is in operation, the energy utilization rate is very low. Improving the energy conversion efficiency in the grinding process is equivalent to reducing costs. Therefore, the solution of adding cement grinding aids during cement grinding has been derived. Cement grinding aids can improve the grinding effect, increase cement output per hour, reduce grinding power consumption, and improve the performance of cement to varying degrees.

[0003] In the related art, in order to reduce costs and improve performance during the preparation of cement, the types and quantities of cement admixtures used are becoming more and more diverse. However, the existing grinding aids are usually of a single composition and cannot be adapted to different cements, which has a certain degree of impact on the improvement of grinding effect.

[0004] When preparing cement, fly ash is often added to improve the performance. Therefore, it is necessary to prepare a cement grinding aid specifically for adding fly ash to improve the grinding effect of cement. Summary of the invention

[0005] In order to improve the grinding aid effect of cement added with fly ash, the present application provides a cement grinding aid and a preparation method thereof.

[0006] In the first aspect, the present application provides a cement grinding aid, which adopts the following technical solution:

[0007] A cement grinding aid comprises the following raw materials in parts by weight: 3-7 parts of diethanolamine, 1-4 parts of ammonium acetate, 5-10 parts of diethanol monoisopropanolamine, 2-5 parts of calcium carbonate, 50-70 parts of water and 0.2-0.8 parts of cellulose.

[0008] By adopting the above technical solution, with the cooperation of diethanolamine, ammonium acetate and diethanol monoisopropanolamine, after the grinding aid is added to the material, it is quickly adsorbed on the surface of the fly ash and cement particles to be ground, reducing the surface free energy, and also forming a layer of monomolecular adsorption film to separate the particles and reduce the compaction. After the adsorption film is formed, the three continue to cooperate, enter the cracks on the surface of the particles to be ground, expand the cracks, and continue to open the cracks, so that the grinding process is carried out in an orderly and rapid manner, thereby having a better grinding aid effect.

[0009] During the grinding process, the particles to be ground will break, and the Si-O-Si bonds and Al-O-Si bonds on the fly ash will also be destroyed due to grinding, thereby being stimulated, releasing the activity of the internal soluble silica and alumina, thereby promoting further hydration of the vitreous body, increasing the activity of the fly ash in cement, and thus giving the cement good strength. The inventor found that after diethanolamine, ammonium acetate, and diethanol monoisopropanolamine were co-adsorbed on the surface of the particles to be ground, they also promoted the destruction of the protective layer composed of Si-O-Si and Al-O-Si. The inventor speculated that this may be because the alkalinity in the system was increased. And after destroying the protective layer structure, calcium carbonate appropriately provides calcium ions to the system, increasing the content of calcium ions in the system. Sufficient calcium ions can participate in the volcanic ash reaction of fly ash to generate gelling hydration products, thereby further improving the strength of cement.

[0010] Preferably, the weight ratio of diethanolamine, ammonium acetate and diethanol monoisopropanolamine is 1:(0.4-0.6):(1-1.4).

[0011] By adopting the above technical scheme, the usage ratio of diethanolamine, ammonium acetate and diethanol monoisopropanolamine is further limited, the ability of the grinding aid to be adsorbed on the surface of the particles to be ground is enhanced, and it is also beneficial to keep the toughness of the adsorption film within a good range.

[0012] Preferably, the cellulose is a mixture of one or more of glass fiber, soybean fiber, microcrystalline cellulose, hydroxyethyl cellulose and bamboo fiber.

[0013] By adopting the above technical solution, adding fibers into the grinding aid system is beneficial to the network of various raw materials, enhancing the coordination and connection between the raw materials, and can also give the grinding aid a certain consistency, so that it adheres to the surface of the particles to be ground and does not pass through quickly, but has a certain residence time, so as to better contact with the particles to be ground.

[0014] Preferably, the cellulose is glass fiber or soybean fiber, and the mass ratio of glass fiber to soybean fiber is 1:(0.3-0.6).

[0015] By adopting the above technical solution, specific types of fibers are selected and combined in specific proportions to provide a stronger network structure. Diethanolamine, ammonium acetate, and diethanol monoisopropanolamine can be spread more evenly in the cement along the network structure, and can be evenly distributed in the horizontal and vertical directions; and can quickly reach the surface of the particles to be ground along the network structure.

[0016] Preferably, the modification of calcium carbonate comprises the following steps:

[0017] Mixing calcium carbonate with water to prepare a calcium carbonate suspension;

[0018] Under the protection of carbon dioxide, heat to 80-90°C, add sodium silicate solution and stir to mix;

[0019] Adjust the pH value to 8-9 and keep warm for reaction;

[0020] Wash, filter and dry to obtain modified calcium carbonate.

[0021] By adopting the above technical solution, calcium carbonate is modified using specific means, and silicon dioxide is coated on the surface of calcium carbonate in an amorphous manner, forming a special coating structure, which prolongs the effective period of calcium carbonate to maintain its performance.

[0022] After the grinding aid is put into cement grinding, as the hydration reaction occurs, the coating structure is slowly destroyed, exposing the calcium carbonate, and the calcium ions are free in the system, causing a series of reactions. When the coating structure is destroyed, its silicon-oxygen bonds are also slowly activated, which is conducive to releasing activity. Due to the use of special modified calcium carbonate, the activation time of fly ash in the grinding reaction is extended, which is conducive to improving the strength of cement.

[0023] Preferably, the mass ratio of calcium carbonate to sodium silicate is 1:(0.1-0.2).

[0024] The inventors found that when the amount of sodium silicate added is too high, silicate is prone to self-polymerization and thus affects the coating effect.

[0025] By adopting the above technical solution, the usage amounts of calcium carbonate and sodium silicate are further limited, so that the sodium silicate can be evenly dispersed on the surface of calcium carbonate, thereby achieving a good coating effect.

[0026] In a second aspect, the present application provides a method for preparing a cement grinding aid, using the following technical solution:

[0027] A method for preparing a cement grinding aid comprises the following steps:

[0028] Add diethanolamine, ammonium acetate and diethanol monoisopropanolamine into water and mix until uniform;

[0029] Continue adding cellulose and stirring to mix;

[0030] Continue to add calcium carbonate and mix evenly to obtain the finished product.

[0031] By adopting the above technical solution and using a specific feeding sequence to prepare the grinding aid, a more uniform dispersion effect can be achieved, which is beneficial for the grinding aid to act in the cement.

[0032] Preferably, when the diethanolamine, ammonium acetate and diethanol monoisopropanolamine are added to water and mixed, the temperature is maintained at 80-100°C and the rotation speed is adjusted to 750-850r / min; when cellulose is added, the temperature and rotation speed are maintained unchanged; when calcium carbonate is added, the temperature is adjusted to 50-70°C and the rotation speed is adjusted to 200-400r / min.

[0033] By adopting the above technical solution, the temperature and stirring speed when each raw material is added are further limited, providing a better reaction basis for the coordinated reaction, thereby giving full play to the effect of each raw material.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. With the cooperation of diethanolamine, ammonium acetate and diethanol monoisopropanolamine, after the grinding aid is added to the material, it is quickly adsorbed on the surface of the fly ash and cement particles to be ground, reducing the surface free energy, and also forming a single molecule adsorption film to separate the particles and reduce the hardening. After the adsorption film is formed, the three continue to cooperate, enter the cracks on the surface of the particles to be ground, expand the cracks, and continue to open the cracks, so that the grinding process is orderly and rapid, thus having a better grinding effect.

[0036] 2. After diethanolamine, ammonium acetate and diethanol monoisopropanolamine are co-adsorbed on the surface of the particles to be ground, they also promote the destruction of the protective layer composed of Si-O-Si and Al-O-Si. After destroying the protective layer structure, calcium carbonate appropriately provides calcium ions to the system, increasing the content of calcium ions in the system. Sufficient calcium ions can participate in the pozzolanic reaction of fly ash to generate gelling hydration products, thereby further improving the strength of cement.

[0037] 3. Selecting specific types of fibers and combining them in specific proportions will provide a stronger network structure. Diethanolamine, ammonium acetate, and diethanol monoisopropanolamine can be spread more evenly in the cement along the network structure, and can be evenly distributed horizontally and vertically; and can quickly reach the surface of the particles to be ground along the network structure. DETAILED DESCRIPTION

[0038] The present application is further described in detail below with reference to the embodiments.

[0039] The raw materials used in the following examples and comparative examples are all commercially available products.

[0040] Preparation Example

[0041] Preparation Example 1

[0042] A method for modifying calcium carbonate comprises the following steps:

[0043] Step 1): Calcium carbonate and water are mixed in a mass ratio of 1:100 to prepare a calcium carbonate suspension.

[0044] Step 2): Under the protection of carbon dioxide, heat to 80° C., add sodium silicate solution into the calcium carbonate suspension, and then stir and mix at a speed of 600 r / min for 1 hour.

[0045] Step 3): adjust the pH value to 8 with sodium hydroxide solution, and keep warm and age the reaction for 2 hours.

[0046] Step 4): After the reaction is completed, wash and filter, dry in hot air at 80° C. to constant weight, and pass through a 60-mesh sieve to obtain modified calcium carbonate.

[0047] The mass ratio of calcium carbonate to sodium silicate is 1:0.1, and the concentration of the calcium silicate solution is 2%.

[0048] Preparation Example 2

[0049] A method for modifying calcium carbonate, which is different from Preparation Example 1 in that:

[0050] In step 2), the mixture is heated to 90° C. and stirred at a speed of 650 r / min.

[0051] In step 3), the pH is adjusted to 9.

[0052] The mass ratio of calcium carbonate to sodium silicate is 1:0.2, and the concentration of the calcium silicate solution is 2%.

[0053] Preparation Example 3

[0054] A method for modifying calcium carbonate, which is different from Preparation Example 1 in that the mass ratio of calcium carbonate to sodium silicate is 1:1.

[0055] Example

[0056] Example 1

[0057] A cement grinding aid comprises the following raw materials: diethanolamine, ammonium acetate, diethanol monoisopropanolamine, calcium carbonate, water and cellulose.

[0058] Wherein, the calcium carbonate adopts commercially available calcium carbonate.

[0059] The mass ratio of cellulose to glass fiber and soybean fiber is 1:0.3, that is, the amount of glass fiber used is 0.46 kg, and the amount of soybean fiber used is 0.14 kg.

[0060] The specific amounts of various raw materials are shown in Table 1.

[0061] The present application also discloses a method for preparing a cement grinding aid, comprising the following steps:

[0062] Step 01): Pour water into the reactor, then raise the temperature of the reactor to 80°C, then add diethanolamine, ammonium acetate, and diethanol monoisopropanolamine into the water in sequence and mix, adjust the rotation speed to 850r / min, and stir until uniform.

[0063] Step 02): Continue to add cellulose into the reactor, keep the temperature and speed unchanged, and stir to mix;

[0064] Step 03): Lower the temperature to 50°C, adjust the speed to 400r / min, then continue to add calcium carbonate into the reactor and mix. After stirring evenly, keep warm and let stand for 6 hours to obtain the finished product.

[0065] Example 2

[0066] A cement grinding aid, which is different from Example 1 in that the amounts of various raw materials are different, as shown in Table 1 for details.

[0067] A method for preparing a cement grinding aid, which is different from that in Example 1,

[0068] In step 01), the temperature is raised to 100°C and the speed is adjusted to 750r / min.

[0069] In step 03), the temperature is adjusted to 70°C and the speed is reduced to 200r / min.

[0070] Example 3

[0071] A cement grinding aid, which is different from Example 1 in that the amounts of various raw materials are different, as shown in Table 1 for details.

[0072] Table 1

[0073]

[0074] Example 4

[0075] A cement grinding aid, which is different from Example 1 in that the weight ratio of diethanolamine, ammonium acetate and diethanol monoisopropanolamine is 1:0.4:1.4, that is, the usage amount of diethanolamine is 5kg, the usage amount of ammonium acetate is 2kg, and the usage amount of diethanol monoisopropanolamine is 7kg.

[0076] Example 5

[0077] A cement grinding aid, which is different from Example 1 in that the weight ratio of diethanolamine, ammonium acetate and diethanol monoisopropanolamine is 1:0.2:2, that is, the usage amount of diethanolamine is 5kg, the usage amount of ammonium acetate is 1kg, and the usage amount of diethanol monoisopropanolamine is 10kg.

[0078] Example 6

[0079] A cement grinding aid, which is different from Example 1 in that the cellulose is glass fiber and soybean fiber, and the mass ratio of the glass fiber to the soybean fiber is 1:0.6, that is, the amount of glass fiber used is 0.38 kg, and the amount of soybean fiber used is 0.23 kg.

[0080] Example 7

[0081] A cement grinding aid, which is different from Example 1 in that the cellulose is glass fiber and soybean fiber, and the mass ratio of the glass fiber to the soybean fiber is 0.3:1, that is, the amount of glass fiber used is 0.14 kg, and the amount of soybean fiber used is 0.46 kg.

[0082] Example 8

[0083] A cement grinding aid, which is different from that in Example 1 in that the cellulose is microcrystalline cellulose.

[0084] Example 9

[0085] A cement grinding aid, which is different from Example 1 in that the calcium carbonate is the modified calcium carbonate prepared in Preparation Example 1.

[0086] Example 10

[0087] A cement grinding aid, which is different from Example 1 in that the calcium carbonate is the modified calcium carbonate prepared in Preparation Example 2.

[0088] Embodiment 11

[0089] A cement grinding aid, which is different from Example 1 in that the calcium carbonate is the modified calcium carbonate prepared in Preparation Example 3.

[0090] Example 12

[0091] A method for preparing a cement grinding aid, which is different from Example 1 in that the temperature in step 1) is adjusted to 50°C and the rotation speed is adjusted to 400 r / min; in step 3), the temperature is adjusted to room temperature and the rotation speed is adjusted to 50 r / min.

[0092] Comparative Example

[0093] Comparative Example 1

[0094] A cement grinding aid, which is different from Example 1 in that diethanolamine is replaced by triethanolamine of equal mass.

[0095] Comparative Example 2

[0096] A cement grinding aid, which is different from Example 1 in that ammonium acetate is replaced by an equal mass of sodium acetate.

[0097] Comparative Example 3

[0098] A cement grinding aid, which is different from Example 1 in that diethanol monoisopropanolamine is replaced by monoethanolamine of equal mass.

[0099] Comparative Example 4

[0100] A cement grinding aid, which is different from Example 1 in that calcium carbonate is replaced by an equal mass of calcium hydroxide.

[0101] Comparative Example 5

[0102] A cement grinding aid, which is different from Example 1 in that the usage amount of diethanolamine is 1 kg, the usage amount of ammonium acetate is 10 kg, and the usage amount of diethanol monoisopropanolamine is 1 kg.

[0103] Performance testing

[0104] Preparation of cement:

[0105] The cement raw materials are mixed with cement clinker, gypsum, limestone and fly ash in a mass ratio of 10:1:1:2.

[0106] The cement grinding aids used are those of Examples 1-12 and Comparative Examples 1-5.

[0107] The cement grinding aid and cement were put into a ball mill at a mass ratio of 1:250 for grinding for 30 minutes.

[0108] The blank control is cement obtained by omitting the addition of cement grinding aid.

[0109] 1. Fineness detection: refer to GB / T 1345-2005 "Test method for cement fineness by sieve analysis", take 10g of samples of Examples 1-12 and Comparative Examples 1-5, and pass them through a 45μm square hole sieve for detection. Conduct three equilibrium tests for each example and comparative example, and take the average value as the final sieve residue (%).

[0110] 2. Cement performance testing:

[0111] Compressive strength test: refer to GB / T 17671-1999 "Test method for strength of cement mortar (ISO method)" to conduct 3d and 28d compressive strength tests (MPa) on the cement obtained above.

[0112] The above tests are detailed in Table 2.

[0113] Table 2

[0114]

[0115]

[0116] According to the comparison of the test data of Example 1-4 and Comparative Example 1-3 in Table 2, it can be seen that the cement of Example 1-4 has better fineness than that of Comparative Example 1-3; in terms of compressive strength, whether it is 3d or 28d, it is more significantly improved than that of Comparative Example 1-3. It is explained that under the cooperation of diethanolamine, ammonium acetate, and diethanol monoisopropanolamine, the grinding aid prepared can be used in cement containing fly ash to improve the grinding effect of cement, and cement has better performance. In combination with the test data comparison of Example 5 and Comparative Example 5, it can be seen that diethanolamine, ammonium acetate, and diethanol monoisopropanolamine should maintain a certain input amount in the system, and the three also need to be kept in a certain ratio to cooperate, otherwise the obtained grinding aid can not fully play the effect of the improvement in cement. Combining the test data of comparative example 4, it can be seen that the fineness of comparative example 4 is worse than that of examples 1-4; although the 3d compressive strength of comparative example 4 is different from that of examples 1-4, it is still relatively good, but the 28d compressive strength of comparative example 4 is not strong enough, which is far behind that of examples 1-4. The inventors speculate that there may be a better and longer-lasting coordination effect between diethanolamine, ammonium acetate, diethanol monoisopropanolamine and calcium carbonate.

[0117] According to the comparison of the test data of Examples 1 and 6 with Examples 7 and 8 in Table 2, it can be seen that the grinding aids of Examples 1 and 6 are used in cement, and the obtained cement has better fineness and higher compressive strength than Examples 7 and 8. This shows that the glass fiber and soybean fiber are beneficial to improving the effect of other raw materials of the grinding aid in cement when matched in a specific ratio.

[0118] According to the detection comparison of Example 1 and Example 9-10 in Table 2, it can be seen that the effect of cement can be further improved by acting the specially modified calcium carbonate in the grinding aid. The inventor speculates that it is because the specially modified calcium carbonate has a coating structure, which has a more stable and long-lasting activity. And the coating structure is put into cement, and it needs to undergo a certain hydration reaction before the coating structure is completely removed, which is conducive to releasing activity. In combination with the detection data comparison of Example 8, 9 and Example 11, it can be seen that calcium carbonate and sodium silicate have an impact on the coating structure when they exceed a certain ratio.

[0119] According to the comparison of the test data of Example 1 and Example 12 in Table 2, it can be seen that after changing the temperature and rotation speed, the grinding aid prepared in Example 12 is used in cement, and the effect of cement is improved to a certain extent, but the improvement is not as large as that in Example 1.

[0120] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A cement grinding aid, characterized in that: The invention comprises the following raw materials in parts by weight: 3-7 parts of diethanolamine, 1-4 parts of ammonium acetate, 5-10 parts of diethanol monoisopropanolamine, 2-5 parts of calcium carbonate, 50-70 parts of water and 0.2-0.8 parts of cellulose; the cellulose is glass fiber or soybean fiber, and the mass ratio of the glass fiber to the soybean fiber is 1:(0.3-0.6).

2. The cement grinding aid according to claim 1, characterized in that: The weight ratio of the diethanolamine, ammonium acetate and diethanol monoisopropanolamine is 1:(0.4-0.6):(1-1.4).

3. The cement grinding aid according to claim 1, characterized in that: The modification of the calcium carbonate comprises the following steps: Mixing calcium carbonate with water to prepare a calcium carbonate suspension; Under the protection of carbon dioxide, heat to 80-90°C, add sodium silicate solution and stir to mix; Adjust the pH value to 8-9 and keep warm for reaction; Wash, filter and dry to obtain modified calcium carbonate.

4. The cement grinding aid according to claim 3, characterized in that: The mass ratio of calcium carbonate to sodium silicate is 1:(0.1-0.2).

5. A method for preparing a cement grinding aid according to any one of claims 1 to 4, characterized in that: The following steps are involved: Add diethanolamine, ammonium acetate and diethanol monoisopropanolamine into water and mix until uniform; Continue adding cellulose and stirring to mix; Continue to add calcium carbonate and mix evenly to obtain the finished product.

6. The method for preparing a cement grinding aid according to claim 5, wherein: When the diethanolamine, ammonium acetate and diethanol monoisopropanolamine are added to water for mixing, the temperature is maintained at 80-100°C and the rotation speed is adjusted to 750-850r / min; when cellulose is added, the temperature and rotation speed are maintained unchanged; when calcium carbonate is added, the temperature is adjusted to 50-70°C and the rotation speed is adjusted to 200-400r / min.

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