Low-carbon early-strength gypsum slag cement and preparation method thereof

Abstract

The invention relates to the technical field of slag cement materials, in particular to low-carbon early-strength gypsum slag cement and a preparation method thereof. The low-carbon early-strength gypsum slag cement is prepared from the following components in parts by weight: 40 to 50 parts of semi-hydrated phosphogypsum, 45 to 55 parts of slag powder, 3 to 8 parts of modified metakaolin, 1 to 4 parts of quick lime, 4 to 10 parts of cement clinker, 0.2 to 0.8 part of accelerator, 0.1 to 0.3 part of water reducing agent and 0.5 to 2.5 parts of water glass, the modified metakaolin is prepared by firstly carrying out surface treatment on 3-methacryloxypropyltrimethoxysilane and then carrying out copolymerization reaction on the modified metakaolin, methyl methacrylate, modified organic silicon and methacrylamide. The low-carbon early-strength gypsum slag cement prepared by the invention not only has excellent mechanical properties, but also has excellent water resistance.

Description

Technical Field

[0001] This invention relates to the field of slag cement materials technology, specifically to a low-carbon, early-strength gypsum slag cement and its preparation method. Background Technology

[0002] With increasing global emphasis on environmental protection and sustainable development, traditional silicate cement faces pressure to transform due to its high energy consumption and large carbon dioxide emissions during production. Gypsum-slag cement, a cementitious material primarily made from industrial waste (slag) and gypsum, has attracted attention due to its low-carbon and resource-recycling characteristics. Slag is a byproduct of steel production; large-scale stockpiling not only occupies land but can also cause environmental pollution. Gypsum is widely found in the chemical and building materials industries, but some types (such as phosphogypsum) are difficult to utilize directly due to their high impurity content.

[0003] By combining slag and gypsum, and through the action of a suitable activator, the active components in the slag can undergo a hydration reaction with the gypsum to form a cement material with cementing properties. This type of cement not only reduces dependence on natural resources (such as limestone) and lowers carbon emissions during the production process, but also achieves high-value utilization of industrial waste, aligning with the development direction of a low-carbon economy and a circular economy.

[0004] However, existing technologies still have some specific problems in achieving low-carbon, early-strength gypsum slag cement:

[0005] 1. Insufficient early strength: Although the combination of gypsum and slag can provide certain cementitious properties, its early strength development is slower compared with traditional Portland cement, making it difficult to meet the requirements of some engineering application scenarios with high early strength requirements (such as emergency repairs, rapid construction, etc.).

[0006] 2. Difficulty in controlling the hydration reaction: The activation of slag and the hydration reaction of gypsum require precise control of conditions (such as the type and dosage of activator, curing environment, etc.). In existing technologies, the precision of controlling the hydration reaction is insufficient, which may lead to uneven hydration products and affect the overall performance stability of cement.

[0007] 3. Durability needs improvement: Some gypsum slag cements may experience durability problems such as strength reduction and insufficient water resistance during long-term use due to issues such as gypsum dissolution and secondary reactions of slag, especially in harsh environments such as humid and high-salt conditions.

[0008] Therefore, we propose a low-carbon, early-strength gypsum slag cement and its preparation method. Summary of the Invention

[0009] The purpose of this invention is to provide a low-carbon, early-strength gypsum slag cement and its preparation method, so as to solve the problems raised in the prior art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A method for preparing low-carbon, early-strength gypsum slag cement includes the following steps:

[0012] Hemihydrate phosphogypsum, slag powder, modified metakaolin, quicklime, cement clinker, accelerator, water-reducing agent and water glass are mixed evenly to obtain low-carbon early-strength gypsum slag cement.

[0013] Furthermore, the low-carbon, early-strength gypsum-slag cement comprises the following components by weight: 40-50 parts hemihydrate phosphogypsum, 45-55 parts slag powder, 3-8 parts modified metakaolin, 1-4 parts quicklime, 4-10 parts cement clinker, 0.2-0.8 parts quick-setting agent, 0.1-0.3 parts water-reducing agent, and 0.5-2.5 parts water glass.

[0014] Furthermore, the preparation method of the accelerator is as follows:

[0015] Aluminum sulfate octahydrate, diethanolamine, water, and lysine are mixed evenly to obtain a quick-setting agent.

[0016] Further, the quick-setting agent comprises the following components by weight: 0.5-0.7 parts aluminum sulfate octahydrate, 0.05-0.08 parts diethanolamine, 0.2-0.4 parts water, and 0.03-0.05 parts lysine.

[0017] Furthermore, the preparation method of the modified metakaolin is as follows:

[0018] Step 1: Add metakaolin to a mixed solution of anhydrous ethanol and deionized water, sonicate for 10-30 min, add 3-methacryloyloxypropyltrimethoxysilane and mix, adjust the pH of the system to 4-5, react at 60-70℃ for 4-6 h, centrifuge, wash and dry to obtain metakaolin containing double bonds.

[0019] Step 2: Mix cashew phenol glycidyl ether and isopropanol evenly, add terminal amino-containing fluorinated organosilicon, react at 45-55℃ for 1-3h, add tetraethyl orthosilicate, hexadecanetriethoxysilane and deionized water, heat to 70-80℃, continue to react for 2-4h, cool to room temperature, wash and distill under reduced pressure to obtain modified organosilicon;

[0020] Step 3: Mix the double-bonded metakaolin and deionized water evenly, add methyl methacrylate, modified organosilicon and methacrylamide, purge with nitrogen gas, add potassium persulfate, and react at 70-80℃ for 10-12 hours. After centrifugation, washing and drying, the modified metakaolin is obtained.

[0021] Furthermore, in step one, the mass ratio of metakaolin, anhydrous ethanol, deionized water and 3-methacryloyloxypropyltrimethoxysilane is 1:(15-20):(3-5):(1-3).

[0022] Furthermore, in step two, the mass ratio of cashew phenol glycidyl ether, isopropanol, and terminal amino-containing fluorinated organosilicon is 1:(4-6):(0.5-1.0), and the mass of tetraethyl orthosilicate is 0.4-0.8 times the mass of terminal amino-containing fluorinated organosilicon.

[0023] Furthermore, the preparation method of the terminal amino-containing fluorinated organosilicon is as follows:

[0024] Under nitrogen protection, octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide pentahydrate were mixed evenly and reacted at 110-120℃ for 10-12 h to obtain an amino-terminated fluorinated organosilicon.

[0025] Further, the mass ratio of the octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide pentahydrate is 1:(2.5-3.0):(0.5-0.6):(0.03-0.05).

[0026] Furthermore, in step two, the mass ratio of tetraethyl orthosilicate, hexadecanetriethoxysilane, and deionized water is 1:(1.0-1.5):(3-5).

[0027] Furthermore, in step three, the mass ratio of double-bonded metakaolin, deionized water, methyl methacrylate, modified organosilicon and methacrylamide is 1:(15-20):(2-4):(0.5-1.5):(1-2).

[0028] Furthermore, the amount of potassium persulfate used is 1-3% of the total mass of metakaolin containing double bonds, methyl methacrylate, modified organosilicon and methacrylamide.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. The present invention relates to a low-carbon, early-strength gypsum slag cement and its preparation method, which uses hemihydrate phosphogypsum and slag powder as the main raw materials, modified metakaolin and quicklime as alkaline activators, and externally adds cement clinker and various additives. After uniform mixing, the low-carbon, early-strength gypsum slag cement is obtained. By synergistically combining the potential activity of slag powder, the promoting effect of alkaline activators and the early strength contribution of cement clinker, the early strength is rapidly developed while ensuring low carbon emissions, thus meeting the requirements for the use of early-strength cement.

[0031] The method first involves surface modification of metakaolin with 3-methacryloyloxypropyltrimethoxysilane to obtain metakaolin containing double bonds. Then, the epoxy groups in cashew phenol glycidyl ether undergo a ring-opening reaction with the amino groups of the terminal amino-containing fluorinated organosilicon. Following this, a hydrolysis-condensation reaction is carried out with tetraethyl orthosilicate and hexadecanetriethoxysilane to introduce hydrophobic fluorocarbon chains, long-chain alkyl groups, and low-surface-energy polysiloxane segments, resulting in modified organosilicon containing double bonds. Finally, under the action of an initiator, the metakaolin containing double bonds, methyl methacrylate, modified organosilicon, and methacrylamide undergo a copolymerization reaction to obtain modified metakaolin, forming a robust hydrophobic film on the material surface. This effectively prevents moisture intrusion, reduces strength reduction and cracking caused by moisture erosion, and extends the service life of cement products.

[0032] 2. The present invention relates to a low-carbon, early-strength gypsum slag cement and its preparation method, which uses lysine as a complexing component to combine with aluminum sulfate to form an aluminum-containing complex, thereby increasing the Al content in the liquid phase of the accelerator. 3+ The content of H, at the same time + Inhibit Al 3+ Hydrolysis is used to achieve the effects of promoting setting and early strength, ensuring that it is released quickly and centrally when mixed with cement paste and participates in the hydration reaction. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Unless otherwise specified, all quantities below are by weight. It should be noted that there are no special restrictions on the suppliers of any of the raw materials involved in this invention. Exemplary examples include (in this embodiment) hemihydrate phosphogypsum: sourced from Anhui Senke New Materials Co., Ltd.; slag powder: S95 grade slag powder, sourced from Shandong Kefa Building Materials Co., Ltd.; metakaolin: particle size of 1250 mesh; quicklime: particle size of 500 mesh; cement clinker: PO 42.5 ordinary silicate cement clinker; water-reducing agent: polycarboxylate water-reducing agent, model PC-1030; water glass: potassium silicate WLK-3.2, sourced from Guangzhou Fuer Chemical Technology Co., Ltd.

[0035] Example 1: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0036] 40 parts hemihydrate phosphogypsum, 45 parts slag powder, 3 parts modified metakaolin, 1 part quicklime, 4 parts cement clinker, 0.2 parts quick-setting agent, 0.1 parts water-reducing agent and 0.5 parts water glass are mixed evenly to obtain low-carbon early-strength gypsum slag cement.

[0037] The preparation method of the quick-setting agent is as follows:

[0038] Mix 0.5 parts aluminum sulfate octahydrate, 0.05 parts diethanolamine, 0.2 parts water and 0.03 parts lysine evenly to obtain a quick-setting agent;

[0039] The preparation method of modified metakaolin is as follows:

[0040] Step 1: Add 3 parts metakaolin to a mixed solution of 45 parts anhydrous ethanol and 9 parts deionized water, sonicate for 10 min, add 3 parts 3-methacryloyloxypropyltrimethoxysilane, adjust the pH of the system to 4, react at 60℃ for 4 h, centrifuge, wash and dry to obtain metakaolin containing double bonds.

[0041] Step 2: Under nitrogen protection, 1 part of octamethylcyclotetrasiloxane, 2.5 parts of trifluoropropyltrimethylcyclotrisiloxane, 0.5 parts of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 0.03 parts of tetramethylammonium hydroxide pentahydrate were mixed evenly and reacted at 110°C for 10 h to obtain fluorinated organosilicon with terminal amino groups;

[0042] Two parts of cashew phenol glycidyl ether and eight parts of isopropanol were mixed evenly, and one part of terminal amino-containing fluorinated organosilicon was added. The mixture was reacted at 45°C for 1 hour. Then, 0.4 parts of tetraethyl orthosilicate, 0.4 parts of hexadecanetriethoxysilane and 1.2 parts of deionized water were added. The mixture was heated to 70°C and reacted for another 2 hours. The mixture was then cooled to room temperature, washed and distilled under reduced pressure to obtain the modified organosilicon.

[0043] Step 3: Mix 3 parts of double-bonded metakaolin and 45 parts of deionized water evenly, add 6 parts of methyl methacrylate, 1.5 parts of modified organosilicon and 3 parts of methacrylamide, purge with nitrogen gas, add 0.13 parts of potassium persulfate, react at 70℃ for 10 hours, centrifuge, wash and dry to obtain modified metakaolin.

[0044] Example 2: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0045] 45 parts hemihydrate phosphogypsum, 50 parts slag powder, 5 parts modified metakaolin, 3 parts quicklime, 6 parts cement clinker, 0.4 parts quick-setting agent, 0.2 parts water-reducing agent and 1 part water glass are mixed evenly to obtain low-carbon early-strength gypsum slag cement.

[0046] The preparation method of the quick-setting agent is as follows:

[0047] Mix 0.6 parts aluminum sulfate octahydrate, 0.06 parts diethanolamine, 0.3 parts water and 0.04 parts lysine evenly to obtain a quick-setting agent;

[0048] The preparation method of modified metakaolin is as follows:

[0049] Step 1: Add 5 parts metakaolin to a mixed solution of 90 parts anhydrous ethanol and 20 parts deionized water, sonicate for 20 min, add 10 parts 3-methacryloyloxypropyltrimethoxysilane, adjust the pH of the system to 4.5, react at 65℃ for 5 h, centrifuge, wash and dry to obtain metakaolin containing double bonds.

[0050] Step 2: Under nitrogen protection, 2 parts of octamethylcyclotetrasiloxane, 5.6 parts of trifluoropropyltrimethylcyclotrisiloxane, 0.4 parts of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 0.08 parts of tetramethylammonium hydroxide pentahydrate were mixed evenly and reacted at 115°C for 11 h to obtain fluorinated organosilicon with terminal amino groups.

[0051] Mix 1 part of cashew phenol glycidyl ether and isopropanol evenly, add 5 parts of terminal amino-containing fluorinated organosilicon, react at 50°C for 2 hours, add 3 parts of tetraethyl orthosilicate, 3.6 parts of hexadecanetriethoxysilane and 12 parts of deionized water, heat to 75°C, continue to react for 3 hours, cool to room temperature, wash and distill under reduced pressure to obtain modified organosilicon.

[0052] Step 3: Mix 5 parts of double-bonded metakaolin and 90 parts of deionized water evenly, add 15 parts of methyl methacrylate, 5 parts of modified organosilicon and 7.5 parts of methacrylamide, purge with nitrogen gas, add 0.65 parts of potassium persulfate, react at 75°C for 11 hours, and after centrifugation, washing and drying, obtain modified metakaolin.

[0053] Example 3: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0054] Mix 50 parts hemihydrate phosphogypsum, 55 parts slag powder, 8 parts modified metakaolin, 4 parts quicklime, 10 parts cement clinker, 0.8 parts quick-setting agent, 0.3 parts water-reducing agent and 2.5 parts water glass evenly to obtain low-carbon early-strength gypsum slag cement.

[0055] The preparation method of the quick-setting agent is as follows:

[0056] Mix 0.7 parts aluminum sulfate octahydrate, 0.08 parts diethanolamine, 0.4 parts water and 0.05 parts lysine evenly to obtain a quick-setting agent;

[0057] The preparation method of modified metakaolin is as follows:

[0058] Step 1: Add 8 parts of metakaolin to a mixed solution of 160 parts of anhydrous ethanol and 40 parts of deionized water, sonicate for 30 min, add 24 parts of 3-methacryloyloxypropyltrimethoxysilane, adjust the pH of the system to 5, react at 70℃ for 6 h, centrifuge, wash and dry to obtain metakaolin containing double bonds.

[0059] Step 2: Under nitrogen protection, 4 parts of octamethylcyclotetrasiloxane, 12 parts of trifluoropropyltrimethylcyclotrisiloxane, 2.4 parts of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 0.2 parts of tetramethylammonium hydroxide pentahydrate were mixed evenly and reacted at 120°C for 12 hours to obtain fluorinated organosilicon with terminal amino groups.

[0060] Two parts of cashew phenol glycidyl ether and 40 parts of isopropanol were mixed evenly, and 12 parts of terminal amino-containing fluorinated organosilicon were added. The mixture was reacted at 55°C for 3 hours. Then, 9.6 parts of tetraethyl orthosilicate, 14.4 parts of hexadecanetriethoxysilane and 48 parts of deionized water were added. The temperature was raised to 80°C and the reaction was continued for 4 hours. The mixture was cooled to room temperature, washed and distilled under reduced pressure to obtain the modified organosilicon.

[0061] Step 3: Mix 8 parts of double-bonded metakaolin and 160 parts of deionized water evenly, add 32 parts of methyl methacrylate, 12 parts of modified organosilicon and 16 parts of methacrylamide, purge with nitrogen gas, add 2 parts of potassium persulfate, react at 80℃ for 12 hours, and after centrifugation, washing and drying, obtain modified metakaolin.

[0062] Comparative Example 1: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0063] 45 parts hemihydrate phosphogypsum, 50 parts slag powder, 5 parts metakaolin, 3 parts quicklime, 6 parts cement clinker, 0.4 parts quick-setting agent, 0.2 parts water-reducing agent and 1 part water glass are mixed evenly to obtain low-carbon early-strength gypsum slag cement.

[0064] Mix 0.6 parts aluminum sulfate octahydrate, 0.06 parts diethanolamine, 0.3 parts water and 0.04 parts lysine evenly to obtain a quick-setting agent;

[0065] Compared with Example 2, Comparative Example 1 replaced the modified metakaolin with the same mass of metakaolin, and the other steps were the same as in Example 2.

[0066] Comparative Example 2: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0067] 45 parts hemihydrate phosphogypsum, 50 parts slag powder, 5 parts modified metakaolin, 3 parts quicklime, 6 parts cement clinker, 0.4 parts quick-setting agent, 0.2 parts water-reducing agent and 1 part water glass are mixed evenly to obtain low-carbon early-strength gypsum slag cement.

[0068] The preparation method of the quick-setting agent is as follows:

[0069] Mix 0.6 parts aluminum sulfate octahydrate, 0.06 parts diethanolamine, 0.3 parts water and 0.04 parts lysine evenly to obtain a quick-setting agent;

[0070] The preparation method of modified metakaolin is as follows:

[0071] Step 1: Add 5 parts metakaolin to a mixed solution of 90 parts anhydrous ethanol and 20 parts deionized water, sonicate for 20 min, add 10 parts 3-methacryloyloxypropyltrimethoxysilane, adjust the pH of the system to 4.5, react at 65℃ for 5 h, centrifuge, wash and dry to obtain metakaolin containing double bonds.

[0072] Step 2: Mix 5 parts of double-bonded metakaolin and 90 parts of deionized water evenly, add 15 parts of methyl methacrylate and 7.5 parts of methacrylamide, purge with nitrogen gas, add 0.65 parts of potassium persulfate, react at 75°C for 11 hours, and after centrifugation, washing and drying, obtain modified metakaolin.

[0073] Compared with Example 2, Comparative Example 2 did not introduce modified organosilicon, but the other steps were the same as in Example 2.

[0074] Comparative Example 3: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0075] Compared with Example 2, Comparative Example 3 replaced the accelerator with the same mass of commercially available accelerator (model J85, from Jinan Dewen Chemical Co., Ltd.), and the other steps were the same as in Example 2.

[0076] Comparative Example 4: A method for preparing low-carbon, early-strength gypsum slag cement, comprising the following processes:

[0077] The preparation method of modified metakaolin is as follows:

[0078] Step 1: Add 5 parts metakaolin to a mixed solution of 90 parts anhydrous ethanol and 20 parts deionized water, sonicate for 20 min, add 10 parts 3-methacryloyloxypropyltrimethoxysilane, adjust the pH of the system to 4.5, react at 65℃ for 5 h, centrifuge, wash and dry to obtain metakaolin containing double bonds.

[0079] Step 2: Under nitrogen protection, 2 parts of octamethylcyclotetrasiloxane, 5.6 parts of trifluoropropyltrimethylcyclotrisiloxane, 0.4 parts of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 0.08 parts of tetramethylammonium hydroxide pentahydrate were mixed evenly and reacted at 115°C for 11 h to obtain fluorinated organosilicon with terminal amino groups.

[0080] Mix 1 part of cashew phenol glycidyl ether and isopropanol evenly, add 5 parts of terminal amino-containing fluorinated organosilicon, react at 50°C for 2 hours, add 3 parts of tetraethyl orthosilicate, 3.6 parts of hexadecanetriethoxysilane and 12 parts of deionized water, heat to 75°C, continue to react for 3 hours, cool to room temperature, wash and distill under reduced pressure to obtain modified organosilicon.

[0081] Step 3: Mix 5 parts of double-bonded metakaolin and 90 parts of deionized water evenly, add 15 parts of methyl methacrylate, 1 part of modified organosilicon and 7.5 parts of methacrylamide, purge with nitrogen gas, add 0.65 parts of potassium persulfate, react at 75°C for 11 hours, centrifuge, wash and dry to obtain modified metakaolin.

[0082] Compared with Example 2, in step three of Comparative Example 4, the mass ratio of double-bonded metakaolin, methyl methacrylate, modified organosilicon and methacrylamide was 1:3:0.2:1.5, and the other steps were the same as in Example 2.

[0083] Experiment: Samples were prepared from the low-carbon, early-strength gypsum slag cement obtained in Examples 1-3 and Comparative Examples 1-4. Their properties were tested and the results were recorded.

[0084] Compressive and flexural strength: In accordance with the provisions of standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)", mortar specimens were prepared, and the compressive and flexural strength of the specimens were determined using a fully automatic pressure testing machine.

[0085] Water absorption rate: The sample cured for 28 days was placed in a 50℃ oven and dried for 48 hours. After being taken out, it was placed at room temperature to cool down, weighed, and the dry mass W1 of the sample was recorded. Then the sample was immersed in water for 24 hours. The sample was taken out and the surface moisture was wiped off with a damp towel. The water content mass W2 of the sample was weighed and recorded. The formula for calculating the water absorption rate is: (W2-W1) / W1×100%.

[0086] The test results are shown in Table 1.

[0087] Table 1. Test results of relevant properties of low-carbon, early-strength gypsum slag cement

[0088]

[0089] Based on the data in the table above, the following conclusions can be clearly drawn:

[0090] Based on Examples 1-3 and Comparative Examples 1-4, it can be seen that the low-carbon, early-strength gypsum slag cement prepared by this invention not only possesses excellent mechanical properties but also excellent water resistance. Compared with Examples 1-3, the flexural strength and compressive strength of the products obtained in Comparative Examples 1 and 2 decreased, while the water absorption rate increased. This indicates that the modified metakaolin prepared by this invention has better hydrophobicity and compatibility than metakaolin, thereby effectively improving the mechanical properties and water resistance of the material. At the same time, this invention further improves the hydrophobicity of the material by introducing modified organosilicon. The mechanical properties of the product obtained in Comparative Example 3 decreased, indicating that the accelerator prepared by this invention performs better than commercially available accelerators. The water absorption rate of the product obtained in Comparative Example 4 increased, indicating that reducing the amount of modified organosilicon added will decrease the water resistance of the material.

[0091] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing low-carbon, early-strength gypsum slag cement, characterized in that: Includes the following steps: Hemihydrate phosphogypsum, slag powder, modified metakaolin, quicklime, cement clinker, accelerator, water-reducing agent and water glass are mixed evenly to obtain low-carbon early-strength gypsum slag cement. The modified metakaolin was first surface-treated with 3-methacryloyloxypropyltrimethoxysilane, and then copolymerized with methyl methacrylate, modified organosilicon and methacrylamide.

2. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 1, characterized in that: The low-carbon, early-strength gypsum-slag cement comprises the following components by weight: 40-50 parts hemihydrate phosphogypsum, 45-55 parts slag powder, 3-8 parts modified metakaolin, 1-4 parts quicklime, 4-10 parts cement clinker, 0.2-0.8 parts quick-setting agent, 0.1-0.3 parts water-reducing agent, and 0.5-2.5 parts water glass.

3. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 2, characterized in that: The preparation method of the accelerator is as follows: Aluminum sulfate octahydrate, diethanolamine, water, and lysine are mixed evenly to obtain a quick-setting agent.

4. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 3, characterized in that: The quick-setting agent comprises the following components by weight: 0.5-0.7 parts aluminum sulfate octahydrate, 0.05-0.08 parts diethanolamine, 0.2-0.4 parts water, and 0.03-0.05 parts lysine.

5. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 1, characterized in that: The preparation method of the modified metakaolin is as follows: Step 1: Add metakaolin to a mixed solution of anhydrous ethanol and deionized water, sonicate for 10-30 min, add 3-methacryloyloxypropyltrimethoxysilane and mix, adjust the pH of the system to 4-5, react at 60-70℃ for 4-6 h, centrifuge, wash and dry to obtain metakaolin containing double bonds. Step 2: Mix cashew phenol glycidyl ether and isopropanol evenly, add terminal amino-containing fluorinated organosilicon, react at 45-55℃ for 1-3h, add tetraethyl orthosilicate, hexadecanetriethoxysilane and deionized water, heat to 70-80℃, continue to react for 2-4h, cool to room temperature, wash and distill under reduced pressure to obtain modified organosilicon; Step 3: Mix the double-bonded metakaolin and deionized water evenly, add methyl methacrylate, modified organosilicon and methacrylamide, purge with nitrogen gas, add potassium persulfate, and react at 70-80℃ for 10-12 hours. After centrifugation, washing and drying, the modified metakaolin is obtained.

6. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 5, characterized in that: In step one, the mass ratio of metakaolin, anhydrous ethanol, deionized water and 3-methacryloyloxypropyltrimethoxysilane is 1:(15-20):(3-5):(1-3).

7. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 5, characterized in that: In step two, the mass ratio of cashew phenol glycidyl ether, isopropanol, and terminal amino-containing fluorinated organosilicon is 1:(4-6):(0.5-1.0), and the mass of tetraethyl orthosilicate is 0.4-0.8 times the mass of terminal amino-containing fluorinated organosilicon.

8. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 7, characterized in that: The preparation method of the amino-terminated fluorinated organosilicon is as follows: Under nitrogen protection, octamethylcyclotetrasiloxane, trifluoropropyltrimethylcyclotrisiloxane, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide pentahydrate were mixed evenly and reacted at 110-120℃ for 10-12 h to obtain an amino-terminated fluorinated organosilicon.

9. The method for preparing low-carbon, early-strength gypsum slag cement according to claim 5, characterized in that: In step three, the mass ratio of double-bonded metakaolin, deionized water, methyl methacrylate, modified organosilicon and methacrylamide is 1:(15-20):(2-4):(0.5-1.5):(1-2).

10. A low-carbon, early-strength gypsum slag cement prepared by the preparation method according to any one of claims 1-9.

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