Gypsum-based cementitious material and method of making same

Abstract

The present application relates to the technical field of inorganic non-metallic materials, and particularly relates to a gypsum-based cementing material and a preparation method thereof, the gypsum-based cementing material comprising the following components in percentage by mass: 25-50% of type 2 anhydrite powder, 10-30% of hemihydrate gypsum powder, 10-20% of cement clinker powder, 20-25% of active micro powder, 3-5% of quicklime, and 1-5% of an activator. The gypsum-based cementing material of the present application is based on type 2 anhydrite and hemihydrate gypsum, and cement clinker powder is added thereto, so that the hydration performance of the cementing material can be significantly improved; the active micro powder and quicklime powder are further added, so that the cementing structure of the cementing material can be improved, a multi-element cementing system is formed, and the stability and durability of the cementing system are significantly improved; and the activator is further added, so that a calcium aluminate cementing body can be quickly formed during the hydration of the cementing material, the hydration conditions are further optimized, and the gypsum-based cementing material is more suitable for construction.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, and in particular to a gypsum-based cementitious material and its preparation method. Background Technology

[0002] As an important branch of inorganic non-metallic materials, gypsum-based cementitious materials have gained widespread attention and application in various fields such as construction engineering, building materials products, and mine filling due to their advantages such as wide availability of raw materials, low energy consumption, and good environmental performance.

[0003] However, existing gypsum-based cementitious materials mostly employ a single gypsum system or a single cementitious system, resulting in several drawbacks: First, the performance of cementitious materials with a single gypsum system is significantly limited; either the hydration rate is too fast but the water resistance is poor, or the strength is high but the hydration and setting efficiency is low, making it difficult to balance setting speed, strength, and water resistance. Second, the strength level of traditional gypsum-based materials is generally lower than that of cement products, making it unable to replace cement in many fields with high strength requirements, thus limiting the expansion of its application range. Third, existing formulations are mostly single cementitious systems with relatively simple cementitious structures, insufficient stability and durability, and a lack of efficient integration and utilization solutions for industrial solid waste, failing to fully leverage the synergistic effect of multiple components. Fourth, some gypsum-based materials have low hydration reaction efficiency, requiring specific environmental conditions to achieve the expected performance, resulting in poor construction adaptability.

[0004] Therefore, it is urgently needed in this field to develop a gypsum-based cementitious material that can efficiently dispose of industrial by-product gypsum slag, take into account setting speed, high strength, high water resistance, and can replace cement in some fields, while optimizing its preparation process to make it a stable and efficient multi-component cementitious material. Summary of the Invention

[0005] In order to take into account various properties such as setting speed, setting strength, water resistance and hydration efficiency, in one aspect of the present invention, a gypsum-based cementitious material is proposed, comprising: components in the following mass percentages: 25%~50% type 2 anhydrous gypsum powder, 10%~30% hemihydrate gypsum powder, 10%~20% cement clinker powder, 20%~25% activated micro powder, 3%~5% quicklime and 1%~5% activator.

[0006] In one or more embodiments, the cement clinker includes: silicate cement clinker or calcium sulfoaluminate cement clinker.

[0007] In one or more embodiments, the specific surface area of ​​silicate cement clinker is greater than or equal to 350 m² / kg, and the specific surface area of ​​calcium sulfoaluminate cement clinker is greater than or equal to 380 m² / kg.

[0008] In one or more embodiments, the active micro powder includes: blast furnace slag micro powder, Class F II fly ash, or titanium extraction tailings micro powder.

[0009] In one or more embodiments, the gypsum-based cementitious material further includes quicklime.

[0010] In one or more embodiments, the activator includes a sulfate-based activator or an aluminum-based activator.

[0011] In one or more embodiments, the sulfate-based activator includes: industrial-grade sodium sulfate with a purity ≥98%; or industrial-grade ferrous sulfate, FeSO4. 7H2O content ≥90%.

[0012] In one or more embodiments, the aluminum-based activator includes: industrial-grade potassium aluminum sulfate with a purity ≥95%; or industrial-grade aluminum sulfate with an Al2(SO4)3 content ≥96%.

[0013] In one or more embodiments, the mass percentage of each component in the gypsum-based cementitious material further includes: 30% to 45% of type 2 anhydrous gypsum powder, 15% to 30% of hemihydrate gypsum powder, 15% to 20% of cement clinker powder, 20% to 25% of active micro powder, 3% to 5% of quicklime, and 1% to 5% of activator.

[0014] In a second aspect of the present invention, a method for preparing the gypsum-based cementitious material as described above is provided. The method includes: drying gypsum slag at 100-200°C and then grinding it to 200 mesh to obtain hemihydrate gypsum powder; heat-treating the hemihydrate gypsum powder at 800-1200°C and then grinding it to 200 mesh to obtain type 2 anhydrous gypsum powder; mixing anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker, activated micro powder, quicklime, and activator according to a preset mass ratio; transferring the uniformly mixed material to a ball mill for grinding to achieve a specific surface area of ​​400 m² / kg or more, thereby obtaining the gypsum-based cementitious material.

[0015] The beneficial effects of this invention include: the gypsum-based cementitious material of this invention is based on type 2 anhydrous gypsum and hemihydrate gypsum, achieving a balance between hydration reaction rate, high matrix strength, and water resistance, ensuring the basic performance of the gypsum-based cementitious material. On this basis, the addition of cement clinker powder can significantly improve the hydration performance of the cementitious material. The addition of active micro powder and quicklime powder can improve the cementitious structure of the cementitious material, forming a multi-component cementitious system, thereby significantly improving the stability and durability of the cementitious system. The addition of an activator can quickly form an ettringite-based cement during the hydration of the cementitious material, further optimizing the hydration conditions and making it easier to construct. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for preparing gypsum-based cementitious materials according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0019] In one embodiment, the present invention provides a gypsum-based cementitious material comprising the following components in weight percentages: 25% to 50% anhydrous gypsum powder of type II, 10% to 30% hemihydrate gypsum powder, 10% to 20% cement clinker powder, 20% to 25% activated micro powder, 3% to 5% quicklime, and 1% to 5% activator. Specifically, in this embodiment, gypsum slag is processed into type 2 anhydrous gypsum and hemihydrate gypsum, with type 2 anhydrous gypsum as the main component and hemihydrate gypsum as the auxiliary component. This is because type 2 anhydrous gypsum has a slower hydration reaction rate, but forms a matrix with high strength and good water resistance, while hemihydrate gypsum has a faster hydration reaction, but forms a matrix with poor water resistance. Combining the two achieves complementary advantages and addresses their weaknesses. Furthermore, adding cement clinker powder to the gypsum-based cementitious material can significantly improve its hydration performance, bringing its strength close to that of cement products. Adding active micro-powder and quicklime powder can further improve the cementitious structure of the material, forming a multi-component cementitious system. This includes gypsum cementitious systems, cement cementitious systems, and ettringite cementitious systems to improve the stability and durability of the cementitious system; the activators used are sulfate activators (sodium sulfate, ferrous sulfate) and aluminum-based activators (potassium aluminum sulfate, aluminum sulfate). The introduction of these activators can quickly form ettringite-based cementitious bodies during the hydration of cementitious materials, optimize hydration conditions, and make them easier to construct; in addition, anhydrous gypsum and hemihydrate gypsum can be sourced from industrial by-products such as titanium gypsum, desulfurized gypsum, and phosphogypsum slag, which has important practical significance and application value for realizing the resource utilization of industrial solid waste, reducing the building materials industry's dependence on cement, and reducing carbon emissions.

[0020] In one embodiment, quicklime can be added to the above-mentioned gypsum-based cementitious material to further accelerate the setting speed.

[0021] In one embodiment, the cement clinker includes: silicate cement clinker or calcium sulfoaluminate cement clinker. Optionally, the specific surface area of ​​the silicate cement clinker is greater than or equal to 350 m² / kg, and the specific surface area of ​​the calcium sulfoaluminate cement clinker is greater than or equal to 380 m² / kg.

[0022] In one embodiment, the active micro-powder includes: blast furnace slag micro-powder, Class F Grade II fly ash, or titanium extraction tailings micro-powder. Optionally, the 7-day activity index of the blast furnace slag micro-powder is ≥75%, and the 7-day activity index of the titanium extraction tailings micro-powder is ≥80%.

[0023] In one embodiment, the activator includes a sulfate-based activator or an aluminum-based activator. Optionally, the sulfate-based activator includes: industrial-grade sodium sulfate with a purity ≥98%; or industrial-grade ferrous sulfate, FeSO4. 7H2O content ≥90%; aluminum-based activators include: industrial grade potassium aluminum sulfate, purity ≥95%; or industrial grade aluminum sulfate, Al2(SO4)3 content ≥96%.

[0024] In one embodiment, the mass percentage of each component in the gypsum-based cementitious material further includes: 30% to 45% of type 2 anhydrous gypsum powder, 15% to 30% of hemihydrate gypsum powder, 15% to 20% of cement clinker powder, 20% to 25% of active micro powder, 3% to 5% of quicklime, and 1% to 5% of activator.

[0025] In a second aspect of the invention, a method for preparing a gypsum-based cementitious material as described in the invention is also provided, such as... Figure 1 As shown, the method includes: Step S1, drying gypsum slag at 100~200℃ and then grinding it to 200 mesh to obtain hemihydrate gypsum powder; Step S2, heat-treating the hemihydrate gypsum powder at 800~1200℃ and then grinding it to 200 mesh to obtain type 2 anhydrous gypsum powder; Step S3, mixing anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker, active micro powder, quicklime and activator according to a preset mass ratio; Step S4, transferring the uniformly mixed material to a ball mill for grinding until the specific surface area of ​​the mixture reaches 400m² / kg or more to obtain gypsum-based cementitious material. The gypsum-based cementitious material prepared using the method of this embodiment has a specific surface area of ​​400 m² / kg or more, making it suitable for building materials and mine backfilling. Furthermore, tests have verified that the standard mortar using this cementitious material achieves a 28-day strength of over 35 MPa, the backfill material achieves a 7-day strength of over 2.5 MPa, and a 28-day strength of over 4 MPa. Moreover, the preparation method of this embodiment can dispose of a large amount of industrial solid waste, and the product can completely replace cement in some fields.

[0026] The following examples will compare the performance of gypsum-based cementitious materials obtained under different preparation parameters and component ratios: Example 1 Type 2 anhydrous gypsum powder, prepared from titanium gypsum, was selected as the main raw material, accounting for 40% by mass. The titanium gypsum contained 75% calcium sulfate dihydrate. Hemihydrate gypsum powder, which is derived from the same source as Type 2 anhydrous gypsum powder, accounted for 20% by mass. Cement clinker powder, with a specific surface area of ​​350 m² / kg, was selected as silicate cement clinker, accounting for 10% by mass. Activated micro powder, using blast furnace slag micro powder with a 7-day activity index ≥75%, accounted for 20% by mass. Quicklime powder, with an effective calcium oxide content ≥85% and a fineness of 200 mesh, accounted for 5% by mass. Sulfate-based activator, using industrial-grade sodium sulfate with a purity ≥98%, accounted for 3% by mass. Aluminum-based activator, using industrial-grade potassium aluminum sulfate with a purity ≥95%, accounted for 2% by mass. In the preparation process, titanium gypsum slag is first fed into a drying kiln and dried at 150℃ for 2 hours to remove free moisture. Then, it is ground to 200 mesh (sieve residue ≤5%) through a ball mill to obtain hemihydrate gypsum powder. The hemihydrate gypsum powder is then fed into a rotary kiln and heat-treated at 1000℃ for 3 hours. After cooling, it is ground to 200 mesh again to obtain type 2 anhydrous gypsum powder. The raw materials are weighed according to the above mass percentages. The type 2 anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker powder, active micro powder, and quicklime powder are first added to a mixer for premixing for 15 minutes. Then, sulfate-based activators and aluminum-based activators are added, and the mixture is transferred to a ball mill for grinding for 1.5 hours. The specific surface area of ​​the material is measured to be 420 m² / kg. The gypsum-based cementitious material product is then discharged. Performance tests were conducted on the product. According to GB / T 17671-2021 standard, the standard mortar had a 3-day compressive strength of 22.5 MPa, a 7-day compressive strength of 30.2 MPa, and a 28-day compressive strength of 38.6 MPa, with a water resistance coefficient (28-day saturated strength / 28-day dry strength) of 0.82. According to MT / T 420-2010 standard, the filling body had a 7-day compressive strength of 3.1 MPa and a 28-day compressive strength of 5.2 MPa.

[0027] Example 2 Type II anhydrous gypsum powder and hemihydrate gypsum powder were prepared using desulfurized gypsum as raw material. Type II anhydrous gypsum powder comprised 25% by mass, and the desulfurized gypsum contained 72% calcium sulfate dihydrate. The hemihydrate gypsum powder, derived from the same source as Type II anhydrous gypsum powder, accounted for 30%. Cement clinker powder was selected from calcium sulfoaluminate cement clinker with a specific surface area of ​​380 m² / kg, comprising 20% ​​by mass. The activated micro-powder used was Class F, Grade II fly ash, accounting for 20%. In this embodiment, no quicklime powder or aluminum-based activator was added; the sulfate-based activator used was industrial-grade ferrous sulfate (FeSO₄). The content of 7H2O is ≥90%, and the mass percentage is 5%. The preparation process is as follows: Desulfurized gypsum slag is fed into a drying kiln and dried at 120℃ for 3 hours. It is then ground to 200 mesh (sieve residue ≤4%) to obtain hemihydrate gypsum powder. The hemihydrate gypsum powder is fed into an electric kiln and heat-treated at 850℃ for 4 hours. After cooling, it is ground to 200 mesh to obtain type 2 anhydrous gypsum powder. The raw materials are weighed according to the formula, mixed evenly, and then fed into a ball mill for 2 hours of grinding. The specific surface area of ​​the material is measured to be 410m² / kg. The discharged material is the cementitious material product. Performance test results show that, according to GB / T 17671-2021 standard, the standard mortar has a 3-day compressive strength of 25.3 MPa, a 7-day compressive strength of 32.8 MPa, and a 28-day compressive strength of 36.4 MPa, with a water resistance coefficient of 0.78; according to MT / T 420-2010 standard, the filling body has a 7-day compressive strength of 2.8 MPa and a 28-day compressive strength of 4.5 MPa. Furthermore, the product has an initial setting time of 18 minutes and a final setting time of 35 minutes under standard consistency water content, indicating a relatively fast setting speed.

[0028] Example 3 Type 2 anhydrous gypsum powder and hemihydrate gypsum powder were prepared using phosphogypsum as raw material. The phosphogypsum contained 78% calcium sulfate dihydrate, accounting for 50% by mass. The hemihydrate gypsum powder was derived from the same source as the Type 2 anhydrous gypsum powder, accounting for 10% by mass. The cement clinker powder was silicate cement clinker with a specific surface area of ​​360 m² / kg, accounting for 10% by mass. The active micro powder was titanium extraction tailings micro powder with an activity index of ≥80% after 7 days, accounting for 25% by mass. The quicklime powder had an effective calcium oxide content of ≥88% and a fineness of 200 mesh, accounting for 3% by mass. The sulfate-based activator was industrial-grade sodium sulfate with a purity of ≥98%, accounting for 2% by mass. The aluminum-based activator was industrial-grade aluminum sulfate with an Al2(SO4)3 content of ≥96%, accounting for 1% by mass. In the preparation process, phosphogypsum slag is first sent to a drying kiln and dried at 180℃ for 1.5 hours. It is then ground to 200 mesh (with ≤3% residue on the sieve) to obtain hemihydrate gypsum powder. The hemihydrate gypsum powder is then sent to a tunnel kiln and heat-treated at 1100℃ for 2.5 hours. After cooling, it is ground to 200 mesh to obtain type 2 anhydrous gypsum powder. The raw materials are weighed according to the formula, premixed for 20 minutes, and then transferred to a ball mill for 1 hour of grinding. The specific surface area of ​​the material is measured to be 430 m² / kg. The discharged material is the cementitious material product. Performance test results show that, according to GB / T 17671-2021 standard, the standard mortar has a 3-day compressive strength of 20.1 MPa, a 7-day compressive strength of 28.5 MPa, and a 28-day compressive strength of 40.2 MPa, with a water resistance coefficient of 0.85; according to MT / T420-2010 standard, the filling body has a 7-day compressive strength of 3.3 MPa and a 28-day compressive strength of 5.8 MPa, indicating that the product exhibits the best strength and water resistance performance.

[0029] All three embodiments strictly adhere to the raw material selection range and preparation process parameters of this invention. The specific surface area of ​​all products is ≥400m² / kg, the 28-day compressive strength of standard mortar is ≥35MPa, and the strength of the filling body meets the requirements of ≥2.5MPa at 7 days and ≥4MPa at 28 days, fully meeting the usage requirements of building materials and mine filling fields. Among them, the formulation of Example 1 has a balanced comprehensive performance, excellent water resistance coefficient and strength, and is suitable for building structural components, road base courses and other scenarios with high requirements for both water resistance and strength. In Example 2, the proportion of hemihydrate gypsum reaches the upper limit (30%) specified by this invention, and no quicklime or aluminum-based activator is added, resulting in a faster setting speed. It is suitable for scenarios with high construction efficiency requirements, such as rapid mine filling and emergency repairs. In Example 3, the proportion of type 2 anhydrous gypsum reaches the upper limit (50%) specified by this invention, and the active micro powder is selected from highly active titanium tailings micro powder. The product has the best strength and water resistance, and is suitable for building materials in high humidity environments, such as exterior wall brick adhesives and underground engineering filling materials. In addition, all embodiments have made extensive use of industrial solid waste, including gypsum slag, blast furnace slag powder, fly ash, and titanium extraction tailings, with the amount of solid waste added being ≥60%. This not only realizes the resource utilization of industrial solid waste and reduces environmental pressure, but also makes the product performance replace cement in some scenarios, effectively reducing carbon emissions and resource consumption in the building materials industry.

[0030] Comparative Example 1 The main raw material is only type 2 anhydrous gypsum powder, which accounts for 60% by mass. The calcium sulfate dihydrate content in this titanium gypsum is 75%. The cement clinker powder is silicate cement clinker with a specific surface area of ​​350 m² / kg, accounting for 10%. The active micro powder is blast furnace slag micro powder with a 7-day activity index ≥75%, accounting for 20% by mass. The effective calcium oxide content of quicklime powder is ≥85%, and the fineness is 200 mesh, accounting for 5%. The sulfate-based activator is industrial-grade sodium sulfate with a purity ≥98%, accounting for 3% by mass. The aluminum-based activator is industrial-grade potassium aluminum sulfate with a purity ≥95%, accounting for 2%. In the preparation process, titanium gypsum slag is first fed into a drying kiln and dried at 150℃ for 2 hours to remove free moisture. Then, it is ground to 200 mesh (sieve residue ≤5%) through a ball mill to obtain hemihydrate gypsum powder. The hemihydrate gypsum powder is then fed into a rotary kiln and heat-treated at 1000℃ for 3 hours. After cooling, it is ground to 200 mesh again to obtain type 2 anhydrous gypsum powder. The raw materials are weighed according to the above mass percentages. The type 2 anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker powder, active micro powder, and quicklime powder are first added to a mixer for premixing for 15 minutes. Then, sulfate-based activators and aluminum-based activators are added, and the mixture is transferred to a ball mill for grinding for 1.5 hours. The specific surface area of ​​the material is measured to be 420 m² / kg. The gypsum-based cementitious material product is then discharged. Performance tests were conducted on the product. According to GB / T 17671-2021 standard, the standard mortar had a 3-day compressive strength of 20.4 MPa, a 7-day compressive strength of 28.6 MPa, and a 28-day compressive strength of 38.7 MPa, with a water resistance coefficient (28-day saturated strength / 28-day dry strength) of 0.85. According to MT / T 420-2010 standard, the filling body had a 7-day compressive strength of 2.8 MPa and a 28-day compressive strength of 5.3 MPa.

[0031] Comparative Example 2 The main raw material is hemihydrate gypsum, accounting for 60% by mass, and the calcium sulfate dihydrate content in this titanium gypsum is 75%. The cement clinker powder is silicate cement clinker with a specific surface area of ​​350 m² / kg, accounting for 10%. The active micro powder is blast furnace slag micro powder with a 7-day activity index ≥75%, accounting for 20% by mass. The quicklime powder has an effective calcium oxide content ≥85% and a fineness of 200 mesh, accounting for 5%. The sulfate-based activator is industrial-grade sodium sulfate with a purity ≥98%, accounting for 3% by mass. The aluminum-based activator is industrial-grade potassium aluminum sulfate with a purity ≥95%, accounting for 2%. In the preparation process, titanium gypsum slag is first fed into a drying kiln and dried at 150℃ for 2 hours to remove free moisture. Then, it is ground to 200 mesh (sieve residue ≤5%) through a ball mill to obtain hemihydrate gypsum powder. The hemihydrate gypsum powder is then fed into a rotary kiln and heat-treated at 1000℃ for 3 hours. After cooling, it is ground to 200 mesh again to obtain type 2 anhydrous gypsum powder. The raw materials are weighed according to the above mass percentages. The type 2 anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker powder, active micro powder, and quicklime powder are first added to a mixer for premixing for 15 minutes. Then, sulfate-based activators and aluminum-based activators are added, and the mixture is transferred to a ball mill for grinding for 1.5 hours. The specific surface area of ​​the material is measured to be 420 m² / kg. The gypsum-based cementitious material product is then discharged. Performance tests were conducted on the product. According to GB / T 17671-2021 standard, the standard mortar had a 3-day compressive strength of 23.1 MPa, a 7-day compressive strength of 31.5 MPa, and a 28-day compressive strength of 37.6 MPa, with a water resistance coefficient (28-day saturated strength / 28-day dry strength) of 0.75. According to MT / T 420-2010 standard, the filling body had a 7-day compressive strength of 3.2 MPa and a 28-day compressive strength of 5.0 MPa.

[0032] As can be seen from the above Comparative Examples 1 and 2, if only hemihydrate gypsum is used as the main raw material, its strength in the early stage is high due to its fast setting speed, but its strength in the later stage is insufficient and its water resistance is greatly reduced. On the other hand, if only type 2 anhydrous gypsum powder is used as the main raw material, its strength in the early stage is low due to its slow setting speed, which is not conducive to improving construction efficiency.

[0033] Comparative Example 3 Type 2 anhydrous gypsum powder, prepared from titanium gypsum, was selected as the main raw material, accounting for 50% by mass. The titanium gypsum contained 75% calcium sulfate dihydrate. Hemihydrate gypsum powder, which is of the same origin as Type 2 anhydrous gypsum powder, accounted for 30% by mass. Cement clinker powder, with a specific surface area of ​​350 m² / kg, was selected as silicate cement clinker, accounting for 10%. Quicklime powder, with an effective calcium oxide content of ≥85% and a fineness of 200 mesh, accounted for 5%. Sulfate-based activator, industrial-grade sodium sulfate with a purity of ≥98%, accounted for 3% by mass. Aluminum-based activator, industrial-grade potassium aluminum sulfate with a purity of ≥95%, accounted for 2%. In the preparation process, titanium gypsum slag is first fed into a drying kiln and dried at 150℃ for 2 hours to remove free moisture. Then, it is ground to 200 mesh (sieve residue ≤5%) through a ball mill to obtain hemihydrate gypsum powder. The hemihydrate gypsum powder is then fed into a rotary kiln and heat-treated at 1000℃ for 3 hours. After cooling, it is ground to 200 mesh again to obtain type 2 anhydrous gypsum powder. The raw materials are weighed according to the above mass percentages. The type 2 anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker powder, active micro powder, and quicklime powder are first added to a mixer for premixing for 15 minutes. Then, sulfate-based activators and aluminum-based activators are added, and the mixture is transferred to a ball mill for grinding for 1.5 hours. The specific surface area of ​​the material is measured to be 420 m² / kg. The gypsum-based cementitious material product is then discharged. Performance tests were conducted on the product. According to GB / T 17671-2021 standard, the standard mortar had a 3-day compressive strength of 20.1 MPa, a 7-day compressive strength of 25.5 MPa, and a 28-day compressive strength of 33.7 MPa, with a water resistance coefficient (28-day saturated strength / 28-day dry strength) of 0.80. According to MT / T 420-2010 standard, the filling body had a 7-day compressive strength of 2.9 MPa and a 28-day compressive strength of 4.8 MPa.

[0034] As can be seen from the above Comparative Example 3, the removal of active micro powder led to an overall decline in the material performance of this embodiment, especially in terms of strength. This is because active micro powder helps to form a multi-component gel system. If it is removed, the stability of the multi-component gel system will be reduced, making it difficult to achieve the effect of 1+1 being greater than 2. It is even less effective than using type 2 anhydrous gypsum powder and hemihydrate gypsum alone.

[0035] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. The embodiment numbers disclosed above are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0036] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A gypsum-based cementitious material, characterized in that, It includes the following components by weight percentage: 25%~50% type 2 anhydrous gypsum powder, 10%~30% hemihydrate gypsum powder, 10%~20% cement clinker powder, 20%~25% activated micro powder, 3%~5% quicklime, and 1%~5% activator.

2. The gypsum-based cementitious material according to claim 1, characterized in that, The cement clinker includes: silicate cement clinker or calcium sulfoaluminate cement clinker.

3. The gypsum-based cementitious material according to claim 2, characterized in that, The specific surface area of ​​the silicate cement clinker is greater than or equal to 350 m² / kg, and the specific surface area of ​​the calcium sulfoaluminate cement clinker is greater than or equal to 380 m² / kg.

4. The gypsum-based cementitious material according to claim 1, characterized in that, The active micro powders include: blast furnace slag micro powder, Class F II fly ash, or titanium extraction tailings micro powder.

5. The gypsum-based cementitious material according to claim 4, characterized in that, Also includes: quicklime.

6. The gypsum-based cementitious material according to claim 1, characterized in that, The activator includes: sulfate-based activators or aluminum-based activators.

7. The gypsum-based cementitious material according to claim 6, characterized in that, The sulfate-based activator includes: Industrial grade sodium sulfate, purity ≥98%; or Industrial grade ferrous sulfate, FeSO4 7H2O content ≥90%.

8. The gypsum-based cementitious material according to claim 6, characterized in that, The aluminum-based activator includes: Industrial grade potassium aluminum sulfate, purity ≥95%; or Industrial grade aluminum sulfate, with an Al2(SO4)3 content ≥96%.

9. The gypsum-based cementitious material according to claim 1, characterized in that, The mass percentage of each component in the gypsum-based cementitious material also includes: 30%~45% Type 2 anhydrous gypsum powder, 15%~30% hemihydrate gypsum powder, 15%~20% cement clinker powder, 20%~25% active micro powder, 3%~5% quicklime, and 1%~5% activator.

10. A method for preparing a gypsum-based cementitious material according to any one of claims 1-9, characterized in that, The method includes: The gypsum residue is dried at 100~200℃ and then ground to 200 mesh to obtain hemihydrate gypsum powder. Hemihydrate gypsum powder is heat-treated at 800~1200℃ and then ground to 200 mesh to obtain type 2 anhydrous gypsum powder; Anhydrous gypsum powder, hemihydrate gypsum powder, cement clinker, activated micro powder, quicklime, and activator were mixed according to the preset mass ratio. The uniformly mixed materials are transferred to a ball mill for further grinding until the specific surface area of ​​the mixture reaches 400 m². 2 Gypsum-based cementitious materials are obtained at a concentration of / kg or above.

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