An early-strength super-sulfated cement, a preparation method and application thereof

Abstract

The present application relates to a kind of early strength type supersulfated cement and its preparation method and application, the raw material of the supersulfated cement includes granulated blast furnace slag, fly ash, cement clinker, limestone, alkaline activator and the desulfurization hemihydrate gypsum of specific method control;The present application first controls the crystal form of desulfurization hemihydrate gypsum as core control means, in combination with the collaborative proportioning design of mineral powder, fly ash, can make supersulfated cement have early strength high, setting time short, good fluidity, good durability and other excellent comprehensive performance, can be adapted to pumping, injection, 3D printing and other various construction technology, solve the problem of low fluidity, high viscosity, poor construction adaptability of traditional supersulfated cement.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and more specifically, to an early-strength supersulfate cement, its preparation method, and its application. Background Technology

[0002] Supersulfate cement, as a novel green cementitious material, uses industrial solid waste (such as slag, fly ash, and desulfurized gypsum) as its main raw material. It requires no high-temperature calcination and boasts significant advantages such as low energy consumption and low carbon emissions, aligning with the green transformation and development trend of the cement industry. In 2025, my country's cement production reached 1.693 billion tons, accounting for nearly half of the global total, and the cement industry's carbon emissions accounted for 13% of the country's total carbon emissions. Therefore, developing alternative materials such as supersulfate cement is of great significance for achieving the "dual carbon" goals (carbon reduction and carbon eradication).

[0003] However, the current core formula of supersulfate cement consists of slag powder, natural / dihydrate desulfurized gypsum, a single alkaline activator (NaOH, water glass), and a small amount of silicate cement clinker. Its drawbacks include a 1-day compressive strength <15MPa and a 3-day strength <25MPa, failing to meet the requirements of early-strength projects (such as rapid repairs and C50 pumped concrete); single alkali activation easily leads to excessive expansion of ettringite, with a shrinkage rate >0.03%, and the hardened body is prone to cracking. There are several insurmountable technical bottlenecks: First, the early strength is low, with 3-day compressive strength often below 20MPa, failing to meet the early strength requirements of rapid construction projects such as road repairs and tunnel spraying; second, the setting time is too long, with initial setting times generally exceeding 300 minutes and final setting times exceeding 400 minutes, resulting in extremely low construction efficiency; third, the pure solid wastewater treatment system lacks activity, and ordinary desulfurized hemihydrate gypsum is irregularly granular, dissolving in layers, with few active sites, slow sulfate ion release, and a relatively large particle size (D). 50 Most of them have a particle size of 50μm or more, and a small specific surface area, making it difficult to efficiently activate the hydration activity of slag powder and fly ash; fourth, the addition of a high dosage of a single alkaline activator to improve hydration activity can easily lead to a reduction in the strength of cement in the later stage, and the excessive alkalinity of the slurry can lead to poor workability; fifth, the unreasonable particle size distribution of cement results in low slurry fluidity, which can easily lead to segregation, bleeding, and poor compatibility.

[0004] Existing technologies for improving the above problems mostly involve single methods, such as adding high-belite sulfoaluminate cement clinker or some early-strength admixtures to improve early strength, but without combining with gypsum modification. Excessive clinker dosage can easily increase carbon emissions. Simple drying and dehydration treatment of desulfurized gypsum only changes the crystal water content without controlling the crystal form, resulting in limited improvement in hydration activity. Ultrafine grinding / nanomaterial modification: hydration rate is improved by ultrafine grinding of slag and gypsum, but energy consumption is high, and the synergistic matching problem between gypsum dissolution and ettringite formation is not solved, resulting in limited improvement in early strength.

[0005] The crystal form (morphology and particle size) of gypsum directly affects its hydration and dissolution rate and the formation morphology of ettringite. Current technologies for gypsum crystal form control are mainly applied to high-strength gypsum, gypsum whiskers, and building gypsum. Hemihydrate / anhydrous gypsum preparation technology: This involves converting dihydrate gypsum into hemihydrate / anhydrous gypsum through calcination, utilizing phase change to control the crystal form. However, this technology is only applicable to high-strength gypsum products. Gypsum whisker preparation technology: This involves preparing gypsum whiskers through hydrothermal and melting methods to improve the strength of gypsum materials. However, the preparation process is complex and costly, making it unsuitable for large-scale application in cement-based materials. Gypsum morphology control technology: Existing research often involves adding a single crystallizing agent, citric acid, to control the transformation of platy dihydrate gypsum into needle-like or long columnar shapes, rather than forming hexagonal crystals, especially those with small aspect ratios. The increase in the number of active sites is limited, and it lacks synergistic optimization with the cementitious system of supersulfate cement, and no industrial-scale preparation process has been developed.

[0006] These improvement methods have not fundamentally solved the core problems of low hydration activity, poor crystal morphology, and poor synergy among multiple components of gypsum, making it difficult to achieve comprehensive performance optimization of ultra-high gypsum cement system in terms of early strength, rapid setting, high fluidity, and high durability. Summary of the Invention

[0007] Based on the aforementioned technical problems in the existing technology, the present invention provides an early-strength supersulfate cement, wherein the supersulfate cement comprises granulated blast furnace slag, fly ash, cement clinker, limestone, alkaline activator, and desulfurized hemihydrate gypsum prepared by a specific method; the present invention is the first to use the crystal form regulation of desulfurized hemihydrate gypsum as the core regulation means, combined with the synergistic proportion design of mineral powder and fly ash, so that the supersulfate cement can have excellent comprehensive properties such as high early strength, short setting time, good fluidity, and good durability.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] An early-strength supersulfate cement, the raw materials of which include granulated blast furnace slag, fly ash, desulfurized hemihydrate gypsum, sulfoaluminate cement clinker, limestone and alkaline activator; wherein the desulfurized hemihydrate gypsum is in the form of hexagonal short columnar shape with an aspect ratio ≥1.2;

[0010] The preparation method of the desulfurized hemihydrate gypsum includes the following steps:

[0011] S1. Mix citric acid and triglyceride to obtain a regulator; then add desulfurized hemihydrate gypsum powder, ball mill and mix evenly, then add water and mix evenly to obtain a suspension;

[0012] S2. Mix CaCl2 solution and MgCl2 solution and react them hydrothermally to obtain the first solution;

[0013] S3. Mix maleic anhydride, dodecyl sulfate and acrylate evenly to obtain the second solution;

[0014] S4. Mix the first solution and the second solution thoroughly to obtain the third solution;

[0015] S5. Mix the third solution and the suspension evenly and carry out a hydrothermal reaction to obtain the short columnar desulfurized hemihydrate gypsum.

[0016] In some embodiments, in step S1, the mass ratio of citric acid to triglyceride is 3-5:1.

[0017] In some embodiments, in step S1, the amount of the regulator added is 0.1-3.5% of the dry weight of the desulfurized hemihydrate gypsum.

[0018] In some embodiments, in step S1, the solid content of the suspension is 30-70 wt%.

[0019] In some embodiments, step S1, the preparation of the desulfurized hemihydrate gypsum powder includes the following steps:

[0020] The undisturbed hemihydrate gypsum was dried to a moisture content of ≤0.3wt%, and then pulverized to D50=6.5μm to obtain desulfurized hemihydrate gypsum powder.

[0021] In some embodiments, in step S2, the mass fraction of the CaCl2 solution is 10-20%, and the mass fraction of the MgCl2 solution is 10-20%.

[0022] In some embodiments, the temperature of the hydrothermal reaction in step S2 is 120-150°C.

[0023] In some embodiments, in step S3, the mass ratio of maleic acid, dodecyl sulfate, and acrylate is (0.3-0.5):1:(0.4-0.6).

[0024] In some embodiments, in step S3, the dodecyl sulfate is sodium dodecyl sulfate.

[0025] In some embodiments, in step S4, the mass ratio of the first solution to the second solution is 1-3:1.

[0026] In some embodiments, in step S5, the amount of the third solution added is 0.2-0.5% of the dry weight of the desulfurized hemihydrate gypsum.

[0027] In some embodiments, the temperature of the hydrothermal reaction in step S5 is 120-150°C.

[0028] In some embodiments, after the hydrothermal reaction is completed, the following step S6 is also included: vacuum filtering the reaction product, and drying the filter cake in a spray dryer to obtain short columnar desulfurized hemihydrate gypsum.

[0029] In some embodiments, during step S6, the vacuum degree is -0.08 to -0.06 MPa during vacuum filtration; and during spray drying, the inlet air temperature is controlled at 120 to 140°C and the outlet air temperature at 60 to 70°C.

[0030] In some embodiments, the raw materials of the early-strength supersulfate cement, by mass percentage, include 40-55% granulated blast furnace slag, 10-20% fly ash, 10-20% desulfurized hemihydrate gypsum, 3-8% sulfoaluminate cement clinker, 5-10% limestone, and 0.5-2% alkaline activator.

[0031] In some embodiments, the granulated blast furnace slag has a specific surface area of ​​480~490 m² / kg.

[0032] In some embodiments, the fly ash has a specific surface area of ​​400~420 m² / kg.

[0033] In some embodiments, the desulfurized hemihydrate gypsum is in the form of hexagonal short columns with an aspect ratio ≥1.2, and its particle size satisfies d90=60-70μm, d50=20-30μm, and d10=5-8μm; preferably, the aspect ratio of the desulfurized hemihydrate gypsum is 1.5-3.0:1.

[0034] In some embodiments, the sulfoaluminate cement clinker is a high-belite sulfoaluminate cement clinker with a specific surface area ≥350m² / kg, a 3d compressive strength ≥40MPa, and a mineral composition by mass percentage satisfying C2S≥40%, C4A3S≥25%, CaSO4≤5%, and f-CaO≤1.0%.

[0035] In some embodiments, the limestone is calcite-type limestone obtained by ultrafine grinding, with a CaCO3 content ≥95wt.%, a specific surface area ≥400m² / kg, and a particle size index D. 90 ≤70μm.

[0036] In some embodiments, the alkaline activator is a mixture of water glass and sodium hydroxide; wherein the modulus of the water glass is 1.0 to 1.5, the purity of the sodium hydroxide is ≥96 wt.%, and the mass ratio of water glass to sodium hydroxide is 3 to 5:1.

[0037] The present invention also provides a method for preparing the above-mentioned supersulfate cement, the method comprising the following steps:

[0038] 1) Raw material pretreatment: Granulated blast furnace slag, fly ash, desulfurized hemihydrate gypsum, sulfoaluminate cement clinker, and limestone are dried to a moisture content of ≤0.2wt%;

[0039] 2) Mixing and grinding: Granulated blast furnace slag, fly ash, desulfurized hemihydrate gypsum, sulfoaluminate cement clinker, limestone and alkaline activator are mixed and added to a ball mill for grinding until the specific surface area of ​​the mixture is ≥450m² / kg and the particle size D90≤80μm, to obtain supersulfate cement.

[0040] The present invention also provides a method for applying the supersulfate cement, which is as follows: the supersulfate cement is mixed with water at a water-cement ratio of 0.28-0.35, then a water-reducing agent is added, and the mixture is stirred until a uniform, lump-free slurry is formed. The slurry can be directly used to prepare concrete, mortar, or shotcrete, and is suitable for rapid road / airport repair, tunnel / mine shotcrete support, 3D building printing, mine goaf filling, rapid production of precast components, marine engineering, saline-alkali land engineering, and post-disaster emergency engineering construction.

[0041] In some embodiments, the water-reducing agent is a polycarboxylate water-reducing agent, specifically an ether-type polycarboxylate high-efficiency water-reducing agent with a water reduction rate ≥30% and a solid content of 20wt.%~40wt.%.

[0042] In some embodiments, the amount of water-reducing agent added is 0.1-0.3% of the mass of the supersulfate cement.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] The supersulfate cement provided by this invention is the first to use gypsum crystal form regulation as the core regulation method. It uses hexagonal short columnar desulfurized hemihydrate gypsum as the core sulfate activator, combined with the synergistic proportion of granulated blast furnace slag and fly ash, and compounded with sulfoaluminate cement to achieve rapid early strength synergy, composite alkali activator to enhance solid waste hydration activation, and limestone micro powder to optimize particle size distribution and microstructure. It utilizes the high specific surface area and high active site characteristics of submicron-sized hexagonal short columnar desulfurized hemihydrate gypsum, combined with the synergistic hydration effect of multiple components, to achieve a comprehensive improvement in the early strength, rapid setting, high flowability and high durability of supersulfate cement. Specifically, this invention uses undisturbed hemihydrate gypsum as raw material, a mixture of citric acid and triglyceride as a crystal form regulator, and a mixture of maleic anhydride, dodecyl sulfate, and acrylate as a crystal aspect ratio regulator. By combining the two regulators in a specific way, the crystal form and aspect ratio of the desulfurized hemihydrate gypsum are controlled, so that the specific surface area of ​​the obtained desulfurized hemihydrate gypsum is ≥600m² / kg, the number of active sites increases by more than 100%, and the sulfate ion release rate is increased by 50%. Simultaneously, utilizing the high specific surface area and high active site characteristics of the hexagonal short columnar desulfurized hemihydrate gypsum, combined with the composite activation system and synergistic activation effect, the start time of cement hydration acceleration period is advanced to 1.5~2.0h, the cumulative hydration heat in 96h is ≥55J / g, the amount of ettringite generated is increased by about 60%, and the hydration products are generated faster and more fully; the submicron-sized gypsum and limestone powder form a multi-gradation system, making the cement mortar fluidity ≥185mm, with good workability of the slurry, no segregation or bleeding, and adaptable to various construction processes such as pumping, spraying, and 3D printing, solving the problems of low fluidity, high viscosity, and poor construction adaptability of traditional supersulfate cement. The rapid formation of submicron-sized gypsum crystals of ettringite and CSH gel forms a dense framework, while limestone powder fills the pores, reducing the proportion of harmful pores in the cement stone by more than 70%, thus forming a dense microstructure of "framework + filling". The cement has a sulfate resistance grade of ≥KS150, excellent resistance to chloride ion penetration and freeze-thaw resistance, and is suitable for harsh service environments such as marine and saline-alkali land.

[0045] The early-strength supersulfate cement of this invention combines ultra-high early strength, short setting time, excellent flowability and durability. Its 1-day compressive strength is ≥25MPa, 3-day compressive strength is ≥32MPa, and 28-day compressive strength is ≥56MPa. Its 1-day early strength is more than 3 times higher than that of ordinary supersulfate cement systems, and its later strength continues to increase steadily without shrinkage. The initial setting time is 40~55min, and the final setting time is 60~80min, which can meet the setting requirements of various rapid construction projects and fundamentally solve the core problems of low early strength and slow setting of traditional products.

[0046] In addition, the total amount of granulated blast furnace slag powder, fly ash and desulfurized gypsum in this invention is ≥70%, realizing the high-value resource utilization of industrial solid waste; the production process has no main clinker calcination process, only a low amount of high belite sulfoaluminate cement clinker is added, the CO2 emission per ton of cement is reduced by more than 70% compared with traditional silicate cement, and the production energy consumption is reduced by 60%, which is in line with the national "dual carbon" development goal.

[0047] Finally, the gypsum crystal form control pretreatment process of the present invention adopts conventional drying, crushing, wet ball milling and spray drying equipment, without the need for additional special high-end equipment; the crystal form control agent is a conventional chemical raw material with low cost; the mixing and grinding process is consistent with the traditional cement production process, the proportion of each component is precise and controllable, the production cost is comparable to that of traditional supersulfate cement, and it is easy to promote and apply on a large scale in the industrial sector.

[0048] This invention can flexibly control the early strength, setting time and fluidity of cement by adjusting the ball milling time of gypsum crystal form control pretreatment, the dosage of crystal form control agent, or the dosage of each cementitious material component, so as to meet the needs of various engineering scenarios such as road repair, tunnel shotcrete, 3D building printing, mine filling, precast component production, marine / saline land engineering. Attached Figure Description

[0049] Figure 1 SEM images of the formation process of desulfurized hemihydrate gypsum prepared by the methods in Examples 1 and 4-7; Figure 2 The relationship between the aspect ratio and compressive strength of hexagonal desulfurized hemihydrate gypsum crystals in Examples 1 and 4-7 is shown.

[0050] Figure 3 The initial setting time of the supersulfate cement specimens of Examples 1-7 and Comparative Examples 1-3;

[0051] Figure 4 The 1-day, 3-day, and 28-day compressive strengths of the supersulfate cement specimens in Examples 1-7 and Comparative Examples 1-3;

[0052] Figure 5 This is a diagram illustrating the mechanism of gypsum crystal form regulation and activity activation.

[0053] Figure 6 This is a diagram illustrating the hydration reaction mechanism of supersulfate cement.

[0054] Among them, 1-unmodified virgin hemihydrate gypsum crystals; 2-active sites; 3-sulfate ions (SO4) 2- ); 4-calcium ion (Ca 2+); 5- Hexagonal columnar desulfurized hemihydrate gypsum crystals; 6- Hexagonal columnar desulfurized hemihydrate gypsum crystals with an aspect ratio of 1~3:1; 7- Hexagonal columnar desulfurized hemihydrate gypsum crystals with an aspect ratio of 3~6:1; 8- Microcracks; 9- Granulated blast furnace slag powder particles; 10- Fly ash particles; 11- High belite sulfoaluminate cement clinker particles; 12- Alkaline activator; 13- Aluminum ions (Al 3+ ); 14-Silicon ions (Si 4+ ); 15-Tetracalcium aluminosilicate (C4A3S) and dicalcium silicate (C2S); 16-Electrite crystals (Aft); 17-Hydrated calcium silicate gel (CSH) gel; 18-Unreacted gypsum crystals; 19-Calcium aluminosilicate hydration product particles; 20-Limestone microparticles; 21-Hydrated dense structure. Detailed Implementation

[0055] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0057] All performance tests in the embodiments and comparative examples of this invention were performed in accordance with national standards, and the testing instruments were industry-standard equipment; the relevant performance tests and standards are as follows:

[0058] Compressive strength: 《Test Method for Strength of Cement Mortar (ISO Method)》 (GB / T 17671-2021);

[0059] Setting time: "Standard consistency water requirement, setting time and soundness test method for cement" (GB / T 1346-2011);

[0060] Mortar flowability: "Method for Determination of Flowability of Cement Mortar" (GB / T 2419-2005);

[0061] Specific surface area: "Determination of specific surface area of ​​cement - Blaine method" (GB / T 8074-2008);

[0062] Heat of hydration: According to the "Determination of Heat of Hydration of Cement" (GB / T 12959-2008), the heat of hydration was tested at 20℃ for 96 hours using an isothermal calorimeter (IC-TAMAir 8).

[0063] Hydration product content: Quantitative analysis was performed using XRD-Rietveld and thermogravimetric analysis using TG-DTG.

[0064] Sulfate attack resistance: Test method for sulfate attack resistance of cement (GB / T 749-2008); Particle size distribution: Laser particle size analyzer (Malvern Mastersizer 3000);

[0065] Crystal morphology: Scanning electron microscope (SEM, Hitachi SU8010).

[0066] Example 1

[0067] The preparation of hexagonal short columnar desulfurized hemihydrate gypsum includes the following steps:

[0068] S1. Drying and pulverizing: The raw hemihydrate gypsum, a by-product of industrial production, is dried in an oven at 105℃ for 5 hours, controlling its moisture content to ≤0.3wt.%, and then pulverized using an air jet mill to D. 50 =6.5μm, to obtain desulfurized hemihydrate gypsum fine powder;

[0069] S2. Wet ball milling and crystal form control: Add the desulfurized hemihydrate gypsum fine powder to the ball mill, add grinding media at a ball-to-material ratio of 3:1, mix citric acid and triglyceride at a mass ratio of 4:1 to obtain a regulator, add 0.25% of the regulator by dry basis of the desulfurized hemihydrate gypsum, and add deionized water to adjust the slurry solid content to 60 wt.%, and ball mill for 50 min;

[0070] S3. Crystal Aspect Ratio Control: A mixed solution A was obtained by hydrothermally reacting a 15% CaCl2 solution and a 12% MgCl2 solution at 140℃ for 1 hour. A mixed solution B was obtained by mixing maleic anhydride, sodium dodecyl sulfate, and acrylate in a mass ratio of 0.4:1:0.5 and stirring thoroughly for 0.5 hours. Mixed solutions A and B were then mixed and stirred thoroughly at a mass ratio of 2:1 to obtain mixed solution C. 0.3% (by dry weight) of mixed solution C was added to the ball-milled slurry and stirred thoroughly. The mixture was then hydrothermally reacted at 140℃ for 2 hours to control the crystal aspect ratio of the desulfurized hemihydrate gypsum to 1.5:1, yielding the reaction product.

[0071] S4. Filtration and drying: The obtained reaction product is vacuum filtered at a vacuum degree of -0.07MPa. The filter cake is sent to a spray dryer with the inlet air temperature controlled at 120℃ and the outlet air temperature controlled at 65℃. After drying, it is pulverized and classified to obtain hexagonal short columnar desulfurized hemihydrate gypsum.

[0072] The raw materials for supersulfate cement, by mass percentage, include: 55% granulated blast furnace slag powder, 10% fly ash, 15% crystal form regulating pretreated desulfurized hemihydrate gypsum, 5% high belite sulfoaluminate cement clinker, 8% limestone powder, and 1% composite alkaline activator (a mixture of water glass and sodium hydroxide in a mass ratio of 4:1).

[0073] The preparation of supersulfoaluminate cement includes the following steps:

[0074] 1) Raw material pretreatment: Granulated blast furnace slag powder, fly ash, high belite sulfoaluminate cement clinker, and limestone powder are dried in an oven at 40±2℃ for more than 8 hours; Sodium hydroxide in the alkaline activator is ground into powder with a particle size of 80μm, and premixed with water glass at a mass ratio of 4:1 at room temperature to obtain a composite alkaline activator.

[0075] 2) Mixing and Grinding: Crystalline modified gypsum, granulated blast furnace slag powder, fly ash, high-belite sulfoaluminate cement clinker, limestone powder, and composite alkaline activator are all fed into a ball mill for mixing and grinding. During grinding, the ball-to-material ratio is controlled at 7:1, the grinding time is 50 minutes, the material temperature is 55℃, and the mixture is ground until the specific surface area of ​​the mixture reaches 470 m². 2 / kg, to obtain supersulfate cement.

[0076] Performance testing of supersulfate cement:

[0077] Preparation of test blocks: Mix supersulfate cement powder with water at a water-cement ratio of 0.31, then add polycarboxylate superplasticizer (the mass of superplasticizer is 0.2% of the mass of supersulfate cement powder) to obtain a mixture; put the mixture into a mixer and stir for 3 minutes until a uniform, lump-free slurry is formed; pour the slurry into a standard mold of 40mm×40mm×160mm, place it on a vibrating table and vibrate for 2~3 minutes to remove air, complete the molding, and obtain the test block;

[0078] Curing: Place the molded test blocks in a standard curing environment with a temperature of 20±1℃ and a relative humidity of ≥95% and cure them until the specified age. Then, conduct performance tests in accordance with the relevant test specifications.

[0079] Example 2

[0080] The difference between this embodiment and Embodiment 1 lies in the raw material composition of the supersulfate cement and the amount of water-reducing agent used in preparing the test blocks; all other conditions remain the same. Details are as follows:

[0081] The raw materials, by weight percentage, include 50% granulated blast furnace slag powder, 15% fly ash, 15% crystal form-controlled pretreated desulfurized hemihydrate gypsum, 6% high belite sulfoaluminate cement clinker, 10% limestone powder, and 1.5% composite alkaline activator;

[0082] When preparing the test blocks, the amount of water-reducing agent used was 0.25%.

[0083] Example 3

[0084] The difference between this embodiment and Embodiment 1 lies in the raw material composition of the supersulfate cement and the amount of water-reducing agent used in preparing the test blocks; all other conditions remain the same. Details are as follows:

[0085] The raw materials, by weight percentage, include 45% granulated blast furnace slag powder, 20% fly ash, 18% crystal form-controlled pretreated desulfurized hemihydrate gypsum, 7% high belite sulfoaluminate cement clinker, 7% limestone powder, and 2% composite alkaline activator;

[0086] When preparing the test blocks, the amount of water-reducing agent used was 0.3%.

[0087] Example 4

[0088] The difference between this embodiment and Comparative Example 1 is that the aspect ratio of the desulfurized hemihydrate gypsum used is different, while other conditions are the same; the preparation of the test specimens is also the same as in Example 1. The specific preparation of the hexagonal short columnar desulfurized hemihydrate gypsum in this embodiment is as follows:

[0089] S1. Drying and pulverizing: The raw hemihydrate gypsum, a by-product of industrial production, is dried in an oven at 105℃ for 5 hours, controlling its moisture content to ≤0.3wt.%, and then pulverized using an air jet mill to D. 50 =6.5μm, to obtain desulfurized hemihydrate gypsum fine powder;

[0090] S2. Wet ball milling and crystal form control: Add the desulfurized hemihydrate gypsum fine powder to the ball mill, add grinding media at a ball-to-material ratio of 3:1, mix citric acid and triglyceride at a mass ratio of 4:1 to obtain a regulator, add 0.25% of the regulator by dry basis of the desulfurized hemihydrate gypsum, and add deionized water to adjust the slurry solid content to 60 wt.%, and ball mill for 50 min;

[0091] S3. Crystal Aspect Ratio Control: A mixed solution A was obtained by hydrothermally reacting a 15% CaCl2 solution and a 12% MgCl2 solution at 140℃ for 1 hour. A mixed solution B was obtained by mixing maleic anhydride, sodium dodecyl sulfate, and acrylate in a mass ratio of 0.4:1:0.5 and stirring thoroughly for 0.5 hours. Mixed solutions A and B were then mixed and stirred thoroughly at a mass ratio of 2:1 to obtain mixed solution C. 0.2% (by dry weight of gypsum) of mixed solution C was added to the ball-milled slurry and stirred thoroughly. The mixture was then hydrothermally reacted at 140℃ for 2 hours to control the crystal aspect ratio of the desulfurized hemihydrate gypsum to 2:1, yielding the reaction product.

[0092] S4. Filtration and drying: The obtained reaction product is vacuum filtered at a vacuum degree of -0.07MPa. The filter cake is sent to a spray dryer with the inlet air temperature controlled at 120℃ and the outlet air temperature controlled at 65℃. After drying, it is pulverized and classified to obtain hexagonal short columnar hemihydrate gypsum.

[0093] Example 5

[0094] The difference between this embodiment and Comparative Example 1 is that the aspect ratio of the desulfurized hemihydrate gypsum used is different, while other conditions are the same; the preparation of the test specimens is also the same as in Example 1. The specific preparation of the hexagonal short columnar desulfurized hemihydrate gypsum in this embodiment is as follows:

[0095] S1. Drying and pulverizing: The raw hemihydrate gypsum, a by-product of industrial production, is dried in an oven at 105℃ for 5 hours, controlling its moisture content to ≤0.3wt.%, and then pulverized using an air jet mill to D. 50 =6.5μm, to obtain desulfurized hemihydrate gypsum fine powder;

[0096] S2. Wet ball milling and crystal form control: Add desulfurized hemihydrate gypsum fine powder to a ball mill, add grinding media at a ball-to-material ratio of 3:1, mix citric acid and triglyceride at a mass ratio of 4:1 to obtain a regulator, add 0.25% of the regulator by dry weight of gypsum, and add deionized water to adjust the slurry solid content to 60 wt.%, and ball mill for 50 min;

[0097] S3. Crystal Aspect Ratio Control: A mixed solution A was obtained by hydrothermally reacting a 15% CaCl2 solution and a 12% MgCl2 solution at 140℃ for 1 hour. A mixed solution B was obtained by mixing maleic anhydride, sodium dodecyl sulfate, and acrylate in a mass ratio of 0.4:1:0.5 and stirring thoroughly for 0.5 hours. Mixed solutions A and B were then mixed and stirred thoroughly at a mass ratio of 2:1 to obtain mixed solution C. 0.15% (by dry weight) of mixed solution C was added to the ball-milled slurry and stirred thoroughly. The mixture was then hydrothermally reacted at 140℃ for 2 hours to control the crystal aspect ratio of the desulfurized hemihydrate gypsum to 3.3:1, yielding the reaction product.

[0098] S4. Filtration and drying: The obtained reaction product is vacuum filtered at a vacuum degree of -0.07MPa. The filter cake is sent to a spray dryer with the inlet air temperature controlled at 120℃ and the outlet air temperature controlled at 65℃. After drying, it is pulverized and classified to obtain hexagonal short columnar desulfurized hemihydrate gypsum.

[0099] Example 6

[0100] The difference between this embodiment and Comparative Example 1 is that the aspect ratio of the desulfurized hemihydrate gypsum used is different, while other conditions are the same; the preparation of the test specimens is also the same as in Example 1. The specific preparation of the hexagonal short columnar desulfurized hemihydrate gypsum in this embodiment is as follows:

[0101] S1. Drying and pulverizing: The raw hemihydrate gypsum, a by-product of industrial production, is dried in an oven at 105℃ for 5 hours, controlling its moisture content to ≤0.3wt.%, and then pulverized using an air jet mill to D. 50 =6.5μm, to obtain desulfurized hemihydrate gypsum fine powder;

[0102] S2. Wet ball milling and crystal form control: Add the desulfurized hemihydrate gypsum fine powder to the ball mill, add grinding media at a ball-to-material ratio of 3:1, mix citric acid and triglyceride at a mass ratio of 4:1 to obtain a regulator, add 0.25% of the regulator by dry basis of the desulfurized hemihydrate gypsum, and add deionized water to adjust the slurry solid content to 60 wt.%, and ball mill for 50 min;

[0103] S3. Crystal Aspect Ratio Control: A mixed solution A was obtained by hydrothermally reacting a 15% CaCl2 solution and a 12% MgCl2 solution for 1 hour. A mixed solution B was obtained by mixing maleic anhydride, sodium dodecyl sulfate, and acrylate in a mass ratio of 0.4:1:0.5 and stirring thoroughly for 0.5 hours. Mixed solutions A and B were then mixed and stirred thoroughly in a mass ratio of 2:1 to obtain mixed solution C. 0.1% (by dry weight of gypsum) of mixed solution C was added to the ball-milled slurry and stirred thoroughly. The mixture was then hydrothermally reacted at 140℃ for 2 hours to control the crystal aspect ratio of the desulfurized hemihydrate gypsum to 4.5:1, yielding the reaction product.

[0104] S4. Filtration and drying: The obtained reaction product is vacuum filtered at a vacuum degree of -0.07MPa. The filter cake is sent to a spray dryer with the inlet air temperature controlled at 120℃ and the outlet air temperature controlled at 65℃. After drying, it is pulverized and classified to obtain hexagonal short columnar desulfurized hemihydrate gypsum.

[0105] Example 7

[0106] The difference between this embodiment and Comparative Example 1 is that the aspect ratio of the desulfurized hemihydrate gypsum used is different, while other conditions are the same; the preparation of the test specimens is also the same as in Example 1. The specific preparation of the hexagonal short columnar desulfurized hemihydrate gypsum in this embodiment is as follows:

[0107] S1. Drying and pulverizing: The raw hemihydrate gypsum, a by-product of industrial production, is dried in an oven at 105℃ for 5 hours, controlling its moisture content to ≤0.3wt.%, and then pulverized using an air jet mill to D. 50 =6.5μm, to obtain desulfurized hemihydrate gypsum fine powder;

[0108] S2. Wet ball milling and crystal form control: Add the desulfurized hemihydrate gypsum fine powder to the ball mill, add grinding media at a ball-to-material ratio of 3:1, mix citric acid and triglyceride at a mass ratio of 4:1 to obtain a regulator, add 0.25% of the regulator by dry basis of the desulfurized hemihydrate gypsum, and add deionized water to adjust the slurry solid content to 60 wt.%, and ball mill for 50 min;

[0109] S3. Crystal Aspect Ratio Control: A mixed solution A was obtained by hydrothermally reacting a 15% CaCl2 solution and a 12% MgCl2 solution at 140℃ for 1 hour. A mixed solution B was obtained by mixing maleic anhydride, sodium dodecyl sulfate, and acrylate in a mass ratio of 0.4:1:0.5 and stirring thoroughly for 0.5 hours. Mixed solutions A and B were then mixed and stirred thoroughly at a mass ratio of 2:1 to obtain mixed solution C. 3.5% (by dry weight) of mixed solution C was added to the ball-milled slurry and stirred thoroughly. The mixture was then hydrothermally reacted at 140℃ for 2 hours to control the crystal aspect ratio of the desulfurized hemihydrate gypsum to 1.2:1, yielding the reaction product.

[0110] S4. Filtration and drying: The obtained reaction product is vacuum filtered at a vacuum degree of -0.07MPa. The filter cake is sent to a spray dryer with the inlet air temperature controlled at 120℃ and the outlet air temperature controlled at 65℃. After drying, it is pulverized and classified to obtain hexagonal short columnar desulfurized hemihydrate gypsum.

[0111] Comparative Example 1

[0112] This comparative example is traditional supersulfate cement, whose raw materials, by mass percentage, include 65% granulated blast furnace slag powder, 15% fly ash, and 20% ordinary desulfurized hemihydrate gypsum; with 0.25% polycarboxylate superplasticizer added externally; the raw materials in this comparative example do not contain high belite sulfoaluminate cement clinker, limestone powder, or alkaline activator.

[0113] Its preparation method includes the following steps:

[0114] 1) Ordinary desulfurized hemihydrate gypsum, dried to a moisture content of 0.5 wt.%, and pulverized to D... 50 =55μm;

[0115] 2) All raw materials are directly mixed and ground at a ball-to-material ratio of 7:1 for 45 minutes, resulting in a mixture with a specific surface area of ​​450 m². 2 / kg, D 90 =85μm, thus obtaining traditional supersulfate cement.

[0116] Preparation and curing of test blocks: Same as in Example 1.

[0117] Comparative Example 2

[0118] The raw materials for supersulfate cement, by weight percentage, include 50% granulated blast furnace slag powder, 15% fly ash, 15% wet-milled desulfurized gypsum, 10% limestone powder, and 1.5% composite alkaline activator;

[0119] Its preparation method includes the following steps:

[0120] 1) Drying and pulverizing: The desulfurized gypsum is dried and pulverized to D... 50 =7.5μm, wet ball milling for 55 min, spray drying and then D 50 =7.8μm, D 90 =22μm, specific surface area 650m² 2 / kg;

[0121] 2) Raw material pretreatment: Granulated blast furnace slag powder, fly ash, high belite sulfoaluminate cement clinker, and limestone powder are dried in an oven at 40±2℃ for more than 8 hours; sodium hydroxide in the alkaline activator is ground into powder with a particle size of 80μm, and premixed with water glass at a mass ratio of 4:1 at room temperature to obtain a composite alkaline activator.

[0122] 3) Mixing and Grinding: Hemihydrate gypsum, granulated blast furnace slag powder, fly ash, high-belite sulfoaluminate cement clinker, limestone powder, and composite alkaline activator are all fed into a ball mill for mixing and grinding. During the grinding process, the ball-to-material ratio is controlled at 7:1, the grinding time is 50 minutes, the material temperature is 55℃, and the mixture is ground until the specific surface area of ​​the mixture reaches 470 m². 2 / kg, to obtain supersulfate cement.

[0123] Preparation and curing of test blocks: Same as in Example 1, except that the amount of water-reducing agent added is 0.25%.

[0124] Comparative Example 3

[0125] The raw materials for this comparative example of supersulfate cement, by mass percentage, include 50% granulated blast furnace slag powder, 15% fly ash, 15% high-pressure converted hemihydrate gypsum, 10% limestone powder, and 1.5% composite alkaline activator;

[0126] Its preparation method includes the following steps:

[0127] 1) Crystal form modification of desulfurized hemihydrate gypsum: Using traditional methods, desulfurized hemihydrate gypsum is converted into hexagonal columnar hemihydrate gypsum in a reactor (135℃, 0.45MPa); among which, D 50 =31μm, D 90 =65μm, specific surface area 431m² 2 / kg;

[0128] 2) Raw material pretreatment: Granulated blast furnace slag powder, fly ash, high belite sulfoaluminate cement clinker, and limestone powder are dried in an oven at 40±2℃ for more than 8 hours; sodium hydroxide in the alkaline activator is ground into powder with a particle size of 80μm, and premixed with water glass at a mass ratio of 4:1 at room temperature to obtain a composite alkaline activator.

[0129] 3) Mixing and Grinding: Hemihydrate gypsum, granulated blast furnace slag powder, fly ash, high-belite sulfoaluminate cement clinker, limestone powder, and composite alkaline activator are all fed into a ball mill for mixing and grinding. During the grinding process, the ball-to-material ratio is controlled at 7:1, the grinding time is 50 minutes, the material temperature is 55℃, and the mixture is ground until the specific surface area of ​​the mixture reaches 470 m². 2 / kg, to obtain supersulfate cement.

[0130] Preparation and curing of test blocks: Same as Comparative Example 2.

[0131] The process of controlling the crystal form and aspect ratio of the desulfurized hemihydrate gypsum obtained by the preparation methods in Examples 1 and 4-7 is as follows: Figure 1 As shown, the method of the present invention can effectively control the crystal form and aspect ratio of desulfurized hemihydrate gypsum, and the resulting desulfurized hemihydrate gypsum can be in the form of hexagonal short columnar shape.

[0132] Desulfurized hemihydrate gypsum with the same crystal form but different aspect ratios was applied to supersulfate cement. The compressive strengths of the supersulfate cement specimens at 1d, 3d, and 28d are shown in Table 1. Figure 2 As shown.

[0133] The initial setting times of the specimens prepared from supersulfate cement in Examples 1-7 and Comparative Examples 1-3 are shown in Table 1 and 2. Figure 3 As shown.

[0134] The properties of the desulfurized hemihydrate gypsum obtained in Examples 1-7 and Comparative Examples 1-3, as well as the 1-day, 3-day, and 28-day compressive strength and other properties of the specimens made from supersulfate cement, are shown in Table 1 and 28. Figures 1-4 As shown.

[0135] Table 1. Comprehensive Comparison of Data Between Examples and Comparative Examples

[0136]

[0137] (1) As shown in Table 1 and Figure 2 As shown, desulfurized hemihydrate gypsum with the same crystal form but different aspect ratios exhibits different effects when applied to hypersulfate cement. The aspect ratio of crystals in Example 1 is 1.5, while those in Examples 4-7 are 2, 3.3, 4.5, and 1.2, respectively. With increasing aspect ratio, both early strength and 28-day strength increase, while setting time and fluidity decrease. Compared to Example 6, Examples 7, 1, 4, and 5 show increases in 1-day compressive strength of 54.2%, 51.4%, 31.6%, and 9.6%, respectively; 3-day compressive strength of 39.1%, 37.8%, 22.9%, and 5.4%, respectively; and 28-day compressive strength of 24.8%, 22.3%, 19.7%, and 12.1%, respectively. This demonstrates that controlling the aspect ratio of hexagonal columnar gypsum crystals can effectively regulate the performance of hypersulfate cement. Considering both strength and fluidity, the optimal aspect ratio of gypsum crystals is 1.5-3:1.

[0138] (2) Combining Table 1 and Figures 2-3 In Examples 1-7, the hexagonal short columnar hemihydrate gypsum prepared using the method of the present invention showed that the 1-day compressive strength was increased by more than 168% compared with Comparative Example 1 (conventional gypsum), the 3-day strength was increased by more than 77.9%, the 28-day strength was increased by more than 28.3%, and the initial setting time was shortened by more than 4 times. This proves that the processing technology of the present invention can significantly optimize the morphology and particle size of gypsum crystals, improve hydration activity, and increase the strength of supersulfate cement, especially the early strength.

[0139] (3) Combining Table 1 and Figures 3-4 Comparative Example 2, without the addition of a gypsum crystal form regulator, showed that the gypsum after wet ball milling remained irregularly granular, with a specific surface area 16.9% lower than that of Example 2. Its 1-day strength decreased by more than 43.9%, its 3-day compressive strength decreased by more than 31.7%, its 28-day strength decreased by 25.5%, and its setting time was extended by 237%. This indicates that the desulfurized hemihydrate gypsum preparation method provided by this invention can effectively induce the formation of hexagonal columnar crystals with small aspect ratios and high active sites in hemihydrate gypsum.

[0140] (4) Combining Table 1 and Figures 3-4 The high-pressure converted hemihydrate gypsum of Comparative Example 3 has a much larger particle size than the submicron-sized hemihydrate gypsum of Example 2, and its specific surface area is only 58.7% of that of Example 2. Its 1-day compressive strength decreased by 30.3%, its 3-day compressive strength decreased by 21.6%, and its 28-day compressive strength decreased by 20.1%, proving that the synergistic effect of submicron-sized particle size and hexagonal columnar crystal morphology is better than simple crystal form conversion.

[0141] The specific method of this invention regulates the crystal form and structure of short columnar desulfurized hemihydrate gypsum, activates the activity of desulfurized hemihydrate gypsum, and the reaction mechanism of its application in supersulfate cement are as follows: Figure 5 and Figure 6 As shown. This invention constructs a multi-component synergistic hydration system that combines submicron-sized hexagonal columnar gypsum crystals and high-belite sulfoaluminate cement clinker for composite activation, synergistic activation with "composite alkaline activator + industrial solid waste substrate," and performance enhancement through "multi-gradation optimization + admixture regulation." Combined with the "high-activity site theory" and "directional morphology enhancement mechanism," it achieves a breakthrough improvement in the comprehensive performance of supersulfate cement. Specifically, the method of this application regulates the crystal form and structure of desulfurized hemihydrate gypsum, and the mechanism for activating the activity of desulfurized hemihydrate gypsum is as follows: Figure 5 As shown. Figure 5 Ordinary unprocessed hemihydrate gypsum 1 is irregularly granular with a dense crystal structure and a slow dissolution rate. The hexagonal columnar hemihydrate gypsum 5, modified by wet ball milling and directional induction pretreatment with a crystal form regulator according to the method of this invention, exhibits micro-defects within the crystals, increasing the number of active sites 2 by more than 60% compared to ordinary gypsum. Furthermore, the hexagonal columnar morphology provides a larger specific surface area, leading to rapid hydration upon contact with water. Simultaneously, the crystals crack due to hydration expansion, generating microcracks 8 on the surface and releasing more reactive sites 2. Moreover, the specific surface area of ​​hexagonal gypsum crystals 6 with a small aspect ratio is significantly larger than that of hexagonal gypsum crystals 7 with a large aspect ratio, resulting in a significantly improved effective reaction interface, better dispersion of short columnar crystal particles, and a release rate increase of more than 50%, thus leading to higher reactivity. By controlling the aspect ratio of the hexagonal columnar hemihydrate gypsum crystals, the aspect ratio of gypsum crystals is reduced, providing sufficient raw materials for the rapid formation of ettringite 16.

[0142] The rapid setting and early strength mechanism of the supersulfate cement obtained by combining the desulfurized hemihydrate gypsum of this invention with specific raw material composition during use is as follows: Figure 6 As shown, specifically: high concentrations of SO4 released by submicron-sized gypsum 5. 2- 3. It undergoes a rapid hydration reaction with C4A3S and C2S minerals 15 in high-belite sulfoaluminate cement clinker 11, initiating the accelerated hydration period within 1-1.5 hours and rapidly generating needle-like ettringite crystals 16. Simultaneously, the C2S mineral 15 in the clinker hydrates to generate CSH gel 17, forming an interwoven double-skeleton structure with ettringite 16, significantly improving the early strength and setting speed of the cement. The composite alkaline activator 12, formed by the combination of water glass and sodium hydroxide, precisely controls the alkalinity of the slurry within the optimal range of 12-13, effectively disrupting the glassy structure of granulated blast furnace slag powder 9 and fly ash 10, releasing a large amount of active Ca. 2+ 4. Al 3+ 13. Si 4+14; These active ions react with SO4 released from submicron-sized gypsum. 2- 3. A synergistic hydration reaction occurs, generating more ettringite 16 and CSH gel 17. The compound system avoids excessive damage to the vitreous structure and subsequent strength reduction caused by excessive alkalinity of a single alkali agent. Submicron-grade desulfurized hemihydrate gypsum, limestone powder 20, slag powder 9 / fly ash 10 form a "submicron-micron-submillimeter" multi-gradation system, reducing the water demand of the slurry and improving workability. CaCO3 in limestone powder reacts with the aluminum phase in the hydration products to generate calcium aluminate hydration product 19, which fills the capillary pores of cement stone and reduces the proportion of harmful pores. Polycarboxylate superplasticizer improves the fluidity of the slurry through steric hindrance effect, reduces the water-cement ratio, and further improves the density of the supersulfate cement hydration products. Eettringite 16, CSH gel 17, calcium aluminate 19 and other hydration products intertwine to form a dense skeleton structure. The high activity of submicron-grade gypsum 5 makes the hydration products generate more fully, and limestone powder fills the pores to form a dense hydration product structure 21. This reduces the proportion of harmful pores in supersulfate cement by more than 70%; the dense microstructure effectively prevents the intrusion of corrosive media such as sulfate ions and chloride ions, while improving the freeze-thaw resistance of supersulfate cement, giving it excellent durability.

[0143] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0144] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A type of early-strength supersulfate cement, characterized in that, Its raw materials include granulated blast furnace slag, fly ash, desulfurized hemihydrate gypsum, sulfoaluminate cement clinker, limestone, and alkaline activator; the desulfurized hemihydrate gypsum is in the form of hexagonal short columnar shape with an aspect ratio ≥1.2; The preparation method of the desulfurized hemihydrate gypsum includes the following steps: S1. Mix citric acid and triglyceride to obtain a regulator; then add desulfurized hemihydrate gypsum powder, ball mill and mix evenly, then add water and mix evenly to obtain a suspension; S2. Mix CaCl2 solution and MgCl2 solution and react them hydrothermally to obtain the first solution; S3. Mix maleic anhydride, dodecyl sulfate and acrylate evenly to obtain the second solution; S4. Mix the first solution and the second solution thoroughly to obtain the third solution; S5. Mix the third solution and the suspension evenly and carry out a hydrothermal reaction to obtain the short columnar desulfurized hemihydrate gypsum.

2. The early-strength supersulfate cement according to claim 1, characterized in that, The aspect ratio of the desulfurized hemihydrate gypsum is (1.5-3):

1.

3. The early-strength supersulfate cement according to claim 1, characterized in that, In step S1, the mass ratio of citric acid to triglyceride is 3-5:1; and / or, the amount of regulator added is 0.1-3.5% of the dry weight of the desulfurized hemihydrate gypsum; and / or, the solid content of the suspension is 30-70 wt%.

4. The early-strength supersulfate cement according to claim 1, characterized in that, In step S2, the mass fraction of the CaCl2 solution is 10-20%, the mass fraction of the MgCl2 solution is 10-20%, and / or the temperature of the hydrothermal reaction is 120-150℃.

5. The early-strength supersulfate cement according to claim 1, characterized in that, In step S3, the mass ratio of maleic acid, dodecyl sulfate, and acrylate is (0.3-0.5):1:(0.4-0.6).

6. The early-strength supersulfate cement according to claim 1, characterized in that, In step S4, the mass ratio of the first solution to the second solution is 1-3:

1.

7. The early-strength supersulfate cement according to claim 1, characterized in that, In step S5, the amount of the third solution added is 0.2-0.5% of the dry weight of the desulfurized hemihydrate gypsum; and / or, the temperature of the hydrothermal reaction is 120-150℃.

8. The early-strength supersulfate cement according to any one of claims 1-7, characterized in that, By mass percentage, its raw materials include 40-55% granulated blast furnace slag, 10-20% fly ash, 10-20% desulfurized hemihydrate gypsum, 3-8% sulfoaluminate cement clinker, 5-10% limestone, and 0.5-2% alkaline activator.

9. The method for preparing early-strength supersulfate cement according to any one of claims 1-8, characterized in that, Includes the following steps: 1) Raw material pretreatment: Granulated blast furnace slag, fly ash, desulfurized hemihydrate gypsum, sulfoaluminate cement clinker, and limestone are dried to a moisture content of ≤0.2wt%; 2) Mixing and grinding: Granulated blast furnace slag, fly ash, desulfurized hemihydrate gypsum, sulfoaluminate cement clinker, limestone and alkaline activator are mixed and added to a ball mill for grinding until the specific surface area of ​​the mixture is ≥450m² / kg and the particle size D90≤80μm, to obtain supersulfate cement.

10. The application of the supersulfate cement according to any one of claims 1-8 in road repair, tunnel support, mine support, 3D building printing, mine goaf filling, rapid production of precast components, marine engineering, saline-alkali land engineering and post-disaster emergency engineering construction.

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