Composite cement grinding aid and its preparation method

Abstract

The application discloses a composite cement grinding aid and a preparation method thereof, and comprises the following components in parts by weight: 0.5-5 parts of a high-molecular grinding aid, 20-30 parts of industrial waste residue, 8-12 parts of a silane coupling agent, 5-10 parts of an inorganic salt and 30-40 parts of deionized water, wherein the high-molecular grinding aid is a kind of amphoteric high-molecular substance obtained by esterification of maleic anhydride and triethanolamine, taking the esterification product as a monomer, polymerization with dimethyldiallylammonium chloride and 2-acrylamide-2-methylpropanesulfonic acid, and then hydrolysis. The composite cement grinding aid prepared by the method can produce high-efficiency grinding effect at a lower mixing amount, and the cement after grinding has uniform and stable particle size, and has good compressive strength and flexural strength.

Description

Technical Field

[0001] This application relates to the field of cement grinding aids, and in particular to a composite cement grinding aid and its preparation method. Background Technology

[0002] In the cement preparation process, the grinding step is to transform non-hydraulic lumpy materials such as clinker, gypsum, and admixtures into hydraulic powdery materials, thereby giving the cement better physical properties.

[0003] The principle of grinding is that cement particles are reduced in size from coarse to fine under mechanical force. It can be roughly divided into three stages: 1. Early grinding stage: Overcoming the cohesive force of lumpy material particles, destroying the crystal structure, and causing the particle size to decrease linearly over time; 2. Middle grinding stage: The particle size of the material further decreases, but due to the electrostatic interaction and van der Waals forces between powders, the rate of particle size reduction gradually decreases; 3. Late grinding stage: Under the action of mechanical and chemical forces, the ground particles undergo crystal recrystallization, and the enhanced electrostatic force leads to the formation of agglomerates between particles. In this stage, the particle size of the material increases rather than decreases.

[0004] Therefore, during cement grinding, the powder is easily re-agglomerated due to electrostatic effects, making it difficult to reach a grinding equilibrium. Consequently, in actual production, the energy utilization rate of grinding is only about 20%, with most of the energy being converted into ineffective heat consumption during repeated grinding processes. Therefore, improving the energy utilization rate of cement grinding is a key focus for the cement industry.

[0005] Cement grinding aids are commonly used cement additives. The addition of grinding aids can improve the grindability of materials and reduce the re-agglomeration of cement particles due to electrostatic interactions between particles, thereby improving the grinding efficiency of the mill, improving the fineness of cement, increasing cement production, and reducing the power consumption generated during grinding.

[0006] However, most grinding aids in China are currently alkanolamines and alcohols. But the functional groups of single alkanolamines and alcohols are relatively limited, and their applicability to materials is narrow, which restricts the grinding aid effect. Summary of the Invention

[0007] To address the problem of low grinding efficiency of grinding aids, this application develops a composite cement grinding aid and its preparation method.

[0008] In the first aspect, a composite cement grinding aid comprises, by weight, the following components: 0.5-5 parts of polymeric grinding aid, 20-30 parts of industrial waste residue, 8-12 parts of silane coupling agent, 5-10 parts of inorganic salt and 30-40 parts of deionized water;

[0009] The aforementioned polymeric grinding aid is an amphoteric polymer obtained by esterifying maleic anhydride with triethanolamine, using the esterified product as a monomer, polymerizing it with dimethyl diallyl ammonium chloride and 2-acrylamide-2-methylpropanesulfonic acid, and then hydrolyzing it.

[0010] Typical, but not restrictive, industrial waste residues can include papermaking waste residues, glycerin waste, waste foam plastics, beet molasses, waste peanut oil, etc.

[0011] By adopting the above technical solution, triethanolamine is modified by introducing multiple functional groups such as carboxyl, amino, and sulfonic acid groups, which improves the compatibility of cement grinding aid with cement. The introduced anionic groups can enhance the repulsion between cement particles, while the cationic groups electrostatically bind the negatively charged cement particles to the grinding aid, improving the adhesion of the grinding aid to cement cracks and enhancing its grinding effect. Furthermore, during the grinding process, a large amount of heat is generated, causing the temperature to rise rapidly, leading to the volatilization of the liquid grinding aid and loss of its grinding effect. This application modifies triethanolamine to create a polymeric substance, introducing multiple carbon-carbon single bonds into the molecular chain, thus improving the high-temperature resistance of the grinding aid. Dimethyl diallyl ammonium chloride and 2-acrylamide-2-methylpropanesulfonic acid have relatively small molecular weights; the copolymerized polymer has shorter branched chains and a smaller molecular weight, enabling better adhesion to cement cracks and providing a better grinding effect. During the middle and later stages of grinding, the strong electrostatic attraction between powder particles affects the particle size of cement. Introducing anionic and cationic groups reduces the electrostatic interaction between cement particles, thus improving grinding efficiency. Furthermore, after the polymeric grinding aid adheres to the surface of cement particles, a hydration film forms on the cement surface, transforming the solid-solid friction between cement particles into solid-liquid friction, improving the fluidity of cement clinker and reducing the conversion of mechanical energy into heat energy. The addition of industrial waste reduces the cost of the grinding aid by recycling waste industrial materials, making the composite cement additive of this application suitable for production line manufacturing. Furthermore, the combined use of industrial waste and the polymeric grinding aid further improves the compatibility of the composite cement grinding aid with cement, enhancing the grinding effect. Silane coupling agents are selected because, during the grinding process, they gradually penetrate into the cracks in the cement clinker and gradually hydrolyze to form silanols. On the one hand, silanols can modify the surface of the cement clinker, reducing the surface energy and electrostatic charge, thus making the cement clinker easier to grind and less prone to re-agglomeration. On the other hand, silanols contain a large amount of Si-OH, which forms Si-O-Si bonds with the siloxanes in the cement clinker during condensation and forms a large number of hydrogen bonds with the numerous active groups in the polymer grinding aid. Therefore, the adhesion and high-temperature resistance of the polymer grinding aid in cement cracks are improved, further enhancing the grinding effect of the composite cement grinding aid. Adding inorganic salts has two advantages. First, it improves the applicability to cement clinker. Second, it forms a large amount of electrolytes, creating an electrostatic shielding layer between the molecular chains of the polymer grinding aid. This reduces the molecular chain entanglement of the polymer grinding aid, increases the contact area between the polymer grinding aid and cement cracks, and increases the number of cations and anions on the surface of cement particles per unit area, thereby further enhancing the grinding effect of the polymer grinding aid.Adding deionized water can reduce the high temperature generated during grinding and decrease the volatilization of liquid grinding aids. On the other hand, it makes it easier for cement particles to form a hydration film, increases the degree of hydrolysis of silane coupling agents, improves the dispersibility of industrial waste residues, and makes the anti-polymerization electrolyte effect within high molecular organic matter more obvious (due to the shielding effect of electrolytes, which reduces the degree of intra-chain connection of molecular chains), thus achieving a good grinding aid effect.

[0012] Preferably, the raw materials of the polymeric grinding aid, by weight, include the following components: 10-20 parts triethanolamine, 20-30 parts maleic anhydride, 8-12 parts dimethyl diallyl ammonium chloride, 6-10 parts 2-acrylamido-2-methylpropanesulfonic acid, 0.01-0.02 parts p-toluenesulfonic acid, and 0.01-0.02 parts initiator.

[0013] In polymeric grinding aids, the molecular weight, type and number of functional groups, and the number of anions and cations have a significant impact on the grinding effect of the polymeric grinding aid itself, as well as its compatibility with other components. Therefore, by optimizing the raw material ratio of polymeric grinding aids, the polymeric grinding aids can not only have a good grinding effect but also have a good compatibility with other components, thus exhibiting a significant grinding effect on cement grinding.

[0014] Preferably, the initiator is ammonium persulfate.

[0015] Different initiation systems will result in differences in product yield, including the number of functional groups, which will affect the grinding effect of the final polymer grinding aid. Therefore, ammonium persulfate was selected as the initiator to give the prepared polymer grinding aid a better grinding effect.

[0016] Preferably, the preparation method of the polymeric grinding aid includes:

[0017] Preparation of esterification product: Triethanolamine, maleic anhydride and p-toluenesulfonic acid are mixed and reacted at 100-120℃ for 2.5-3.5h to obtain esterification product;

[0018] Preparation of copolymer: The esterification product, dimethyl diallyl ammonium chloride and 2-acrylamide-2-methylpropanesulfonic acid were dissolved in water to form a monomer solution, and then an initiator was added and heated in a water bath at 45-55℃ for 3-5 hours to obtain the copolymer;

[0019] Preparation of polymeric grinding aid: The copolymer was mixed with sodium hydroxide solution and heated in a water bath at 70-80℃ for 20-28 hours. The mixture was then extracted and dried to obtain the polymeric grinding aid.

[0020] In a typical but not limiting step of preparing polymeric grinding aids, the concentration of sodium hydroxide solution is greater than or equal to 5 mol / L.

[0021] By adopting the above preparation method, the preparation parameters of polymeric grinding aids are further optimized, the yield and grinding effect of polymeric grinding aids are improved, and preparation is carried out with as few processes and as low energy consumption as possible to meet the needs of large-scale industrial production.

[0022] Preferably, the industrial waste includes one or a combination of two of beet molasses and sugarcane molasses.

[0023] By adopting the above technical solutions, sugar beets are one of the main economic crops in northern China. The black residue left after sugar production is called sugar beet molasses. Sugar beet molasses is widely available and inexpensive. When sugar beet molasses is used in combination with polymeric grinding aids, it has been found that sugar beet molasses contains a large number of hydroxyl and amino groups. When used in conjunction with polymeric grinding aids, it can improve the applicability to cement clinker and improve the compressive strength of cement to a certain extent. Sugarcane molasses is also widely available and can be compounded with other components to improve the grinding effect of composite cement grinding aids and further improve the mechanical properties of cement.

[0024] Preferably, the industrial waste residue is a composition of beet molasses and sugarcane molasses, wherein the weight ratio of beet molasses to sugarcane molasses is 1:(1-2).

[0025] By adopting the above technical solution, the raw material ratio of industrial waste residue was optimized, and the resulting composite cement grinding aid has a better grinding effect.

[0026] The silane coupling agent used is KH-550 or KH-560.

[0027] This application does not impose significant restrictions on the type of silane coupling agent. Commonly used KH-550 or KH-560 can produce good compounding effects with polymer grinding aids, saving time and production costs.

[0028] Preferably, the inorganic salt is one or a combination of two of sodium tripolyphosphate and sodium hexapolyphosphate.

[0029] By adopting the above technical solutions, sodium tripolyphosphate and sodium hexapolyphosphate can improve the dispersibility of the system and enhance the uniformity of composite cement grinding aids during the grinding process. In addition, they can also act as chelating agents to reduce the impact of alkali-aggregate reaction on the mechanical properties of cement during hydration, and further improve the mechanical properties of cement when combined with industrial waste residue.

[0030] Preferably, the cement grinding aid is suitable for addition at a dosage of 0.01-0.03% in cement grinding.

[0031] By using the cement grinding aid prepared in this application, a good grinding effect can be obtained with a small dosage. Therefore, it can save costs while reducing the antagonistic effect between admixtures and improving the performance of cement.

[0032] Secondly, a method for preparing a composite cement grinding aid, comprising the following steps:

[0033] S1: Mix deionized water, polymeric grinding aid, and inorganic salt to obtain a premix;

[0034] S2: After the silane coupling agent is mixed evenly with industrial waste residue, it is then mixed with the premix to obtain a composite cement grinding aid.

[0035] Typically, but not limitingly, the mixing temperature in step S1 is controlled between 25 and 40°C.

[0036] By employing the above technical solution, deionized water, polymeric grinding aid, and inorganic salt are first mixed, allowing the molecular chains of the polymeric grinding aid to fully unfold in the presence of a large amount of electrolyte. Furthermore, uniform mixing improves the dispersibility of the polymeric grinding aid and inorganic salt. Next, a silane coupling agent is mixed with industrial waste, enabling the waste to carry a portion of the silane coupling agent. During this process, the silane coupling agent modifies the surface of the waste, improving its grinding performance. Finally, the premix is ​​combined with the silane coupling agent to obtain a composite cement grinding aid. This method is simple to operate, and the resulting composite cement grinding aid exhibits good grinding performance.

[0037] In summary, this application has the following beneficial effects:

[0038] 1. Triethanolamine is modified into a polymer. On the one hand, other functional groups such as carboxyl, amino, and amide groups are introduced to improve the compatibility of cement grinding aid with cement. On the other hand, anionic and cationic groups are introduced into the polymer to reduce the decrease in grinding efficiency caused by the volatilization of grinding aid and the agglomeration of cement particles during cement grinding, thereby improving the efficiency of cement grinding.

[0039] 2. The modified polymer material is used in combination with industrial waste residue, inorganic salts and other materials, which is not only environmentally friendly and reduces costs, but also improves the efficiency of grinding aid and improves the mechanical properties of cement. Detailed Implementation

[0040] The raw materials used in the examples and preparation examples are all commercially available and described in detail below. The present application will be further described in detail below with reference to the examples.

[0041] Preparation examples of raw materials and / or intermediates

[0042] Preparation of polymeric grinding aids

[0043] Preparation Example 1-1: A polymeric grinding aid was prepared by the following steps.

[0044] Preparation of esterification product: 15g triethanolamine, 25g maleic anhydride and 0.015g p-toluenesulfonic acid were mixed and reacted at 110℃ for 3h to obtain esterification product;

[0045] Preparation of copolymer: Take the esterification product, 10g of dimethyl diallyl ammonium chloride and 8g of 2-acrylamide-2-methylpropanesulfonic acid, add water to dissolve to 500mL to form a monomer solution, then add 0.015g of ammonium persulfate and heat in a water bath at 50℃ for 4h to obtain the copolymer;

[0046] Preparation of polymeric grinding aid: The copolymer was mixed with 500 mL of 5 mol / L sodium hydroxide solution, heated in a water bath at 75 °C for 24 h, extracted with ethanol multiple times, and dried in an oven at 60 °C to obtain the polymeric grinding aid.

[0047] Preparation Examples 1-2: A polymeric grinding aid was prepared using the following steps:

[0048] Preparation of esterification product: 20g triethanolamine, 30g maleic anhydride and 0.02g p-toluenesulfonic acid were mixed and reacted at 120℃ for 2.5h to obtain esterification product;

[0049] Preparation of copolymer: Take the esterification product, 12g of dimethyl diallyl ammonium chloride and 10g of 2-acrylamide-2-methylpropanesulfonic acid, add water to dissolve to 500mL to form a monomer solution, then add 0.01g of ammonium persulfate and heat in a water bath at 55℃ for 3h to obtain the copolymer;

[0050] Preparation of polymeric grinding aid: The copolymer was mixed with 500 mL of 6 mol / L sodium hydroxide solution, heated in a water bath at 80 °C for 20 h, extracted with ethanol multiple times, and dried in an oven at 65 °C to obtain the polymeric grinding aid.

[0051] Preparation, 1-3, a polymeric grinding aid, is prepared by the following steps:

[0052] Preparation of esterification product: 10g triethanolamine, 20g maleic anhydride and 0.01g p-toluenesulfonic acid were mixed and reacted at 100℃ for 3.5h to obtain esterification product;

[0053] Preparation of copolymer: Take the esterification product, 8g of dimethyl diallyl ammonium chloride and 6g of 2-acrylamide-2-methylpropanesulfonic acid, add water to dissolve to 500mL to form a monomer solution, then add 0.02g of ammonium persulfate and heat in a water bath at 45℃ for 4h to obtain the copolymer;

[0054] Preparation of polymeric grinding aid: The copolymer was mixed with 500 mL of 5 mol / L sodium hydroxide solution, heated in a water bath at 70 °C for 28 h, extracted with ethanol multiple times, and dried in an oven at 65 °C to obtain the polymeric grinding aid.

[0055] Preparation Examples 1-4, a preparation of a polymeric grinding aid, differ from Preparation Example 1-1 in that ammonium persulfate is replaced by an equal amount of 2,2'-azabis(2-imidazoline) dihydrochloride.

[0056] Preparation Examples 1-5, a preparation of a polymeric grinding aid, differs from Preparation Example 1-1 in that 2-acrylamide-2-methylpropanesulfonic acid is replaced with an equal amount of dimethyldiallylammonium chloride.

[0057] Preparation Examples 1-6, a preparation of a polymeric grinding aid, differ from Preparation Example 1-1 in that 2-acrylamide-2-methylpropanesulfonic acid is replaced with an equal amount of 2-propyloxybutylsulfonic acid.

[0058] Preparation Examples 1-7, a preparation of a polymeric grinding aid, differs from Preparation Example 1-1 in that dimethyl diallyl ammonium chloride is replaced with an equal amount of 2-acrylamido-2-methylpropanesulfonic acid.

[0059] Preparation Examples 1-8: A polymeric grinding aid was prepared using the following steps:

[0060] Preparation of esterification product: 15g triethanolamine, 25g maleic anhydride and 0.015g p-toluenesulfonic acid were mixed and reacted at 110℃ for 3h to obtain esterification product;

[0061] Preparation of copolymer: Take the esterification product, 10g allyl polyoxyethylene ether and 8g methacrylic acid, add water to dissolve to 500mL to form a monomer solution, then add 0.015g ammonium persulfate and heat in a water bath at 50℃ for 4h to obtain the copolymer;

[0062] Preparation of polymeric grinding aid: The copolymer was mixed with 500 mL of 5 mol / L sodium hydroxide solution, heated in a water bath at 75 °C for 24 h, extracted with ethanol multiple times, and dried in an oven at 60 °C to obtain the polymeric grinding aid. Example

[0063] Example 1: A composite cement grinding aid is prepared by the following steps:

[0064] S1: Mix 35g of deionized water, 1.5g of polymeric grinding aid, and 7.5g of sodium tripolyphosphate at 33°C for 4 hours to obtain a premix.

[0065] S2: Mix 10g KH-550, 10g beet molasses and 15g sugarcane molasses evenly, and then mix with the premix to obtain a composite cement grinding aid.

[0066] The polymeric grinding aid is derived from Preparation Example 1-1.

[0067] Example 2: A composite cement grinding aid is prepared by the following steps:

[0068] S1: Mix 40g deionized water, 2g polymer grinding aid, 5g sodium tripolyphosphate and 5g sodium hexapolyphosphate at 25°C for 6 hours to obtain a premix.

[0069] S2: Mix 8g KH-550, 10g beet molasses and 10g sugarcane molasses evenly, and then mix with the premix to obtain a composite cement grinding aid.

[0070] The polymeric grinding aid is derived from preparation examples 1-2.

[0071] Example 3: A composite cement grinding aid is prepared by the following steps:

[0072] S1: Mix 30g of deionized water, 1g of polymeric grinding aid, and 5g of sodium hexapolyphosphate at 45°C for 2 hours to obtain a premix.

[0073] S2: Mix 12g KH-560, 10g beet molasses and 20g sugarcane molasses evenly, and then mix with the premix to obtain a composite cement grinding aid.

[0074] The polymeric grinding aid is derived from preparation examples 1-3.

[0075] Example 4, a composite cement grinding aid, differs from Example 1 in that the polymer grinding aid is derived from Preparation Examples 1-4.

[0076] Example 5, a composite cement grinding aid, differs from Example 1 in that sugarcane molasses is replaced with an equal amount of beet molasses.

[0077] Example 6, a composite cement grinding aid, differs from Example 1 in that sugarcane molasses is replaced with an equal amount of peanut oil.

[0078] Example 7, a composite cement grinding aid, differs from Example 1 in that sodium tripolyphosphate is replaced with an equal amount of sodium silicate.

[0079] Example 8, a composite cement grinding aid, differs from Example 1 in that the mass of the polymer grinding aid is 0.5g.

[0080] Example 9, a composite cement grinding aid, differs from Example 1 in that the mass of the polymer grinding aid is 5g.

[0081] Comparative Example

[0082] Comparative Example 1, a composite cement grinding aid, differs from Example 1 in that the source and preparation of the polymer grinding aid are the same as in Examples 1-5.

[0083] Comparative Example 2, a composite cement grinding aid, differs from Example 1 in that the polymeric grinding aid is derived from Preparation Examples 1-6.

[0084] Comparative Example 3, a composite cement grinding aid, differs from Example 1 in that the polymeric grinding aid is derived from Preparation Examples 1-7.

[0085] Comparative Example 4, a composite cement grinding aid, differs from Example 1 in that the polymeric grinding aid is derived from Preparation Examples 1-8.

[0086] Comparative Example 5: A composite cement grinding aid, prepared by the following steps.

[0087] S1: Mix 35g deionized water, 1.5g grinding aid, and 7.5g sodium tripolyphosphate at 33°C for 4 hours to obtain a premix;

[0088] S2: Mix 10g KH-550, 10g beet molasses and 15g sugarcane molasses evenly, and then mix with the premix to obtain a composite cement grinding aid.

[0089] The grinding aid is prepared by the following steps: 15g of triethanolamine, 25g of maleic anhydride and 0.015g of p-toluenesulfonic acid are mixed and reacted at 110℃ for 3h to obtain the cement grinding aid.

[0090] Comparative Example 6, a cement grinding aid, was prepared by the following steps: 10g of diethanol monoisopropanolamine, 12g of triethanolamine, 12g of glycerol, 8g of diethylene glycol and 35.7g of water were mixed, and then 0.3g of defoamer was added and mixed evenly to obtain the cement grinding aid.

[0091] Comparative Example 7, a composite cement grinding aid, differs from Example 1 in that sodium tripolyphosphate is omitted from the components of the composite cement grinding aid, and the proportion of sodium tripolyphosphate is increased to other components according to the formulation ratio of the composite cement grinding aid, while the operation steps and process parameters remain unchanged.

[0092] Comparative Example 8, a composite cement grinding aid, differs from Example 1 in that beet molasses and sugarcane molasses are omitted from the components of the composite cement grinding aid, and the proportions of beet molasses and sugarcane molasses are increased to other components according to the formulation ratio of the composite cement grinding aid, while the operation steps and process parameters remain unchanged.

[0093] Comparative Example 9, a composite cement grinding aid, differs from Example 1 in that KH-550 is omitted from the components of the composite cement grinding aid, and the amount of KH-550 is increased to other components according to the formulation ratio of the composite cement grinding aid, while the operation steps and process parameters remain unchanged.

[0094] Performance testing

[0095] Examples 1-9 and Comparative Examples 1-9 were added to cement at a dosage of 0.03%wt and ground, and their performance was tested as follows. The results are shown in Table 1.

[0096] Experiment 1: Fineness test: The residue of cement on a 45 sieve was tested according to GB / T 1345—2005 "Cement Fineness Test Method - Sieve Analysis Method".

[0097] Test 2: Cement strength test: The 28-day flexural strength and compressive strength of cement were tested according to GB / T 17671—1999 "Test Method for Strength of Cement Mortar (ISO Method)".

[0098] Table 1: Fineness test and cement strength test results of Examples 1-9 and Comparative Examples 1-9.

[0099]

[0100] As can be seen from Examples 1-4 and Comparative Examples 1-6, and Table 1, the polymeric grinding aid obtained by modifying the amine-type compound using this application exhibits good grinding effect. When compounded with other components, it can provide grinding assistance to various materials in cement. The ground cement has a smaller particle size, better flexural strength, and better compressive strength. This is due to the introduction of abundant functional groups such as carboxyl, amino, and sulfonic acid groups, which gives the polymeric grinding aid stronger adsorption and dispersibility. It can stably adsorb onto cement particles during grinding and accelerate the formation of cracks in cement particles. Furthermore, the introduction of anionic and cationic groups generates an electrostatic shielding effect during grinding, reducing the re-agglomeration of refined particles and increasing the electrostatic repulsion between particles, thus improving the bonding strength between the polymer chain and cement particles. In addition, the polymeric grinding aid has a high boiling point and volatilizes very little during the high-temperature grinding process, preventing the grinding effect from being affected by volatilization. Therefore, only a small amount is needed to provide a significant grinding effect. In addition, the active groups in polymer grinding aids can capture water molecules in cement, causing a hydration film to form on the cement surface, improving the fluidity of cement, reducing the angle of repose, and enhancing the grinding effect of cement. Furthermore, when combined with substances such as beet molasses and sodium tripolyphosphate, they can regulate the hydration rate of cement, increase the hydration activity during the hydration process, promote the conversion of AFt to AFm, thereby optimizing the pore structure, reducing porosity, and further improving the compressive strength and flexural strength of cement.

[0101] As can be seen from Examples 1, 5-9, and Comparative Examples 7-9, and Table 1, the selection of industrial waste type, inorganic salt type, and optimization of polymeric additive ratio all have a certain impact on the prepared composite cement grinding aid. This is because the composite cement grinding aid prepared in this application has the characteristics of high efficiency and low dosage, enabling it to exert a good grinding aid effect at a low dosage. Therefore, it can reduce antagonism with other additives in the later stages, which is the result of optimizing the selection and ratio of each component. When the amount of polymeric grinding aid is too small, it cannot exert its function; when the amount is too large, it will increase the entanglement of molecular chains, causing mutual adsorption and agglomeration with other components, reducing the dispersibility and uniformity of the composite cement grinding aid, thereby reducing the grinding aid effect and the effect of improving mechanical properties. In addition, the selection of beet molasses and sugarcane molasses from industrial waste improves the number of ions and the acid-base environment during the hydration process, which can inhibit the hydration reaction of cement to a certain extent, slow down the hydration rate of cement, and improve the problems of early setting and rapid setting caused by polymer grinding aids, thereby improving the later strength of cement.

[0102] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A composite cement grinding aid, comprising, by weight, the following components: 0.5-5 parts polymeric grinding aid, 20-30 parts industrial waste residue, 8-12 parts silane coupling agent, 5-10 parts inorganic salt, and 30-40 parts deionized water; characterized in that, The polymeric grinding aid is an amphoteric polymer obtained by esterification of maleic anhydride and triethanolamine, followed by polymerization of the esterification product with dimethyldiallyl ammonium chloride and 2-acrylamido-2-methylpropanesulfonic acid, and then hydrolysis. The raw materials of the polymeric grinding aid, by weight, include the following components: 10-20 parts triethanolamine, 20-30 parts maleic anhydride, 8-12 parts dimethyldiallyl ammonium chloride, 6-10 parts 2-acrylamido-2-methylpropanesulfonic acid, 0.01-0.02 parts p-toluenesulfonic acid, and 0.01-0.02 parts initiator; the initiator is persulfuric acid. The preparation methods of the ammonium chloride and polymeric grinding aid include: preparation of esterification products: triethanolamine, maleic anhydride and p-toluenesulfonic acid are mixed and reacted at 100-120℃ for 2.5-3.5h to obtain the esterification products; preparation of copolymers: the esterification products, dimethyl diallyl ammonium chloride and 2-acrylamido-2-methylpropanesulfonic acid are dissolved in water to form a monomer solution, and then an initiator is added and heated in a water bath at 45-55℃ for 3-5h to obtain the copolymers; preparation of polymeric grinding aids: the copolymers are mixed with sodium hydroxide solution and heated in a water bath at 70-80℃ for 20-28h, and then extracted and dried to obtain the polymeric grinding aids.

2. The composite cement grinding aid according to claim 1, characterized in that: Industrial waste includes one or a combination of two of beet molasses and sugarcane molasses.

3. The composite cement grinding aid according to claim 1, characterized in that: The industrial waste residue is a combination of beet molasses and sugarcane molasses, wherein the weight ratio of beet molasses to sugarcane molasses is 1:(1-2).

4. The composite cement grinding aid according to claim 1, characterized in that: The silane coupling agent used is KH-550 or KH-560.

5. The composite cement grinding aid according to claim 1, characterized in that: The inorganic salt is one or a combination of two of sodium tripolyphosphate and sodium hexapolyphosphate.

6. The composite cement grinding aid according to claim 1, characterized in that: The raw materials of the composite cement grinding aid include the following components in parts by weight: 1-2 parts of polymeric grinding aid, 20-30 parts of industrial waste residue, 8-12 parts of silane coupling agent, 5-10 parts of inorganic salt and 30-40 parts of deionized water.

7. A method for preparing a composite cement grinding aid according to any one of claims 1-6, characterized in that, The following steps were used to prepare the premix: S1: Deionized water, polymeric grinding aid, and inorganic salt were mixed to obtain the premix; S2: After the silane coupling agent is mixed evenly with industrial waste residue, it is then mixed with the premix to obtain a composite cement grinding aid.

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