A calcined clay-based cementitious material and method of making the same

Abstract

This invention relates to the field of building materials technology, and discloses a cementitious material based on calcined clay and its preparation method. The cementitious material includes calcined clay, steel slag, blast furnace slag, cement clinker, gypsum, and an alkaline activator. This invention employs a multi-component composite activation method, utilizing the rational combination of calcined clay, steel slag, blast furnace slag, cement clinker, and gypsum, and the organic coordination of various chemical alkaline activators. This not only provides a high-value-added resource utilization method for industrial by-products but also reduces the amount of cement clinker used, effectively improving the early compressive strength of the cementitious material and ensuring its later-stage strength. This method has wide applications, a simple process flow, and significant potential application value.

Description

Technical Field

[0001] This invention relates to the field of building materials, specifically to a cementitious material based on calcined clay and its preparation method. Background Technology

[0002] Calcined clay is an industrial clay produced by firing waste mud and slag at temperatures between 700°C and 850°C. Utilizing it in the preparation of cementitious materials not only achieves efficient use of waste mud and slag, but also reduces energy consumption and CO2 emissions during production compared to traditional cement clinker. Furthermore, calcined clay exhibits high pozzolanic activity, and the interaction between calcined clay and ordinary silicate cement or clinker promotes the formation of additional CO3-AFM phases and C-(A)-SH gels within the system. Consequently, the prepared calcined clay cementitious materials have smaller pore sizes than ordinary silicate cement, thus benefiting their mechanical properties.

[0003] To address this, Chinese patent document CN 116409948 A provides a low-carbon composite cementitious material based on recycled micro powder, its preparation method, and its application. The low-carbon composite cementitious material is prepared by adding a small amount of calcined clay and recycled micro powder to cement clinker. However, although adding calcined clay to cement can significantly improve its later strength, it faces the problem of reduced early strength.

[0004] Therefore, it is necessary to provide a cementitious material that combines low energy consumption and high early strength, which can fully utilize the characteristics of calcined clay, such as low carbon and low energy consumption and high pozzolanic activity. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a cementitious material based on calcined clay and its preparation method, thereby solving the problems of low early strength and narrow application range of existing calcined clay-based cementitious materials.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A cementitious material based on calcined clay and its preparation method, comprising the following steps:

[0008] Weigh each component in the base material, mix it with an alkaline activator, and grind it to obtain a cementitious material based on calcined clay.

[0009] The base material is selected from one or more of calcined clay, steel slag, slag powder, cement clinker, and gypsum; and / or the alkaline activator is selected from one or more of calcium formate, calcium lignosulfonate, sodium sulfate, calcium chloride, sodium carbonate, sodium silicate, and sodium hydroxide.

[0010] Preferably, the alkaline activator comprises calcium formate, sodium hydroxide, and sodium silicate in a mass ratio of 1~3:9~11:0.3~0.8.

[0011] The alkaline activator accounts for 0.1-10% of the mass of the base material; preferably, the alkaline activator accounts for 5-7% of the mass of the base material; and / or, the alkaline activator is in solid form, and the solid content of the alkaline activator is 95-100%.

[0012] The base material is made from the following raw materials in the indicated weight percentages: 30-60% calcined clay, 3-30% steel slag, 30-60% blast furnace slag, 4-25% cement clinker, and 0-5% gypsum.

[0013] Preferably, the base material is made from the following raw materials in the indicated mass percentages: 30-60% calcined clay, 3-5% steel slag, 30-60% blast furnace slag, 4-6% cement clinker, and 0.5-2% gypsum.

[0014] The calcined clay contains Al2O3 > 15%, Al / Si > 0.3, CaO < 3%, and SO3 < 3%. Preferably, the calcined clay contains Al2O3 ≥ 20% and has a 28-day compressive strength activity index higher than 80%. More preferably, the chemical composition of the calcined clay, by mass percentage, includes: Al2O3: 25~40%, SiO2: 60~75%, K2O + Na2O ≤ 3%, CaO + MgO ≤ 5%, and SO3 < 3%.

[0015] The steel slag is a blocky waste slag produced by steelmaking, composed of oxides of calcium, iron, silicon, and magnesium. The steel slag contains 30-60% CaO, 10-30% SiO2, 2-20% MgO, and 10-40% Fe2O3 by mass. Preferably, the chemical composition of the steel slag, by mass percentage, includes: CaO: 38-50%, Fe2O3: 25-35%, SiO2: 14-20%, MgO: 4.5-12%, MnO: ≤5%, Al2O3: 1-10%, CaF2 ≤2%, and SO3 ≤5%.

[0016] The slag is water-quenched or air-cooled blast furnace slag; and / or, the cement clinker is silicate cement clinker, conforming to the requirements of GB / T 21372 "Silicate Cement Clinker"; and / or, the gypsum is selected from at least one of desulfurized gypsum, mirabilite gypsum, phosphogypsum, and titanium gypsum.

[0017] The base material is dried before mixing; and / or the powder obtained from the grinding process needs to be sieved through a 60-100 μm square hole, and the residue of the powder is 0-10%.

[0018] The cement clinker and calcined clay mentioned are both dry materials, and the moisture content of commercially available products is less than 1%, which does not require special explanation.

[0019] The alkaline activator is also in solid form, and its water content is mainly water of crystallization and chemically bound water / hydroxyl groups. The amount used is also very low, so there is no need to control the water content.

[0020] The present invention also provides a cementitious material based on calcined clay.

[0021] Beneficial effects of the invention

[0022] 1. This invention provides a cementitious material based on calcined clay, comprising a base material and an alkaline activator. By mass percentage, the base material comprises: 30-70% calcined clay, 0-30% steel slag, 10-70% slag powder, 0-25% cement clinker, and 0-5% gypsum. Through the combined use of the above-mentioned specific proportions of calcined clay and slag powder, along with the use of an alkaline activator, the synergistic effect of multiple raw materials and the alkaline activator results in a cementitious material with advantages such as rapid strength formation and high final strength. This overcomes the shortcomings of other calcined clay-based cementitious materials, such as long setting time and slow hydration reaction rate. The compressive strength of the prepared cementitious material is significantly improved.

[0023] 2. This invention provides a calcined clay cementitious material, wherein the alkaline activator is selected from one or more of calcium formate, calcium lignosulfonate, sodium sulfate, calcium chloride, sodium carbonate, sodium silicate, and sodium hydroxide, especially when calcium formate, sodium hydroxide, and sodium silicate are used in a mass ratio of 1~3:9~11:0.3~0.8.

[0024] 3. This invention provides a calcined clay-based cementitious material in which the alkaline activator accounts for 0.1-10% of the mass of the base material; in particular, controlling the alkaline activator to account for 5-7% of the mass of the base material can further promote the reaction between the cementitious components, thereby further improving the flexural strength and compressive strength of the cementitious material.

[0025] 4. This invention provides a calcined clay-based cementitious material, wherein the percentage content of each component in the base material is controlled as follows: 30-60% calcined clay, 3-30% steel slag, 30-60% blast furnace slag, 4-25% cement clinker, and 0-5% gypsum. Preferably, the percentage content of each component in the base material is controlled as follows: 30-60% calcined clay, 3-30% steel slag, 30-60% blast furnace slag, 4-25% cement clinker, and 0-5% gypsum, which can further improve the performance of the cementitious material. More preferably, controlling the percentage content of each component in the base material to be: 30-60% calcined clay, 3-5% steel slag, 30-60% blast furnace slag, 4-6% cement clinker, and 0.5-2% gypsum can significantly improve the compressive strength of the cementitious material, as shown by the compressive strength after 3 days, 7 days, and 34.5-65.8 MPa after curing in water for 3 days, 7 days, and 34 days, respectively.

[0026] 5. This invention provides a calcined clay-based cementitious material. By controlling the chemical composition and content of the base material, the chemical substances in the cementitious material components are promoted to be in an optimal proportion, thereby further improving the compressive strength and stability of the cementitious material.

[0027] 6. The method for preparing cementitious materials based on calcined clay provided by the present invention is simple, with low consumption during the preparation process; it hardens quickly, has high strength, and is widely applicable; the preparation method is easy, low-cost, energy-saving, low-carbon, and environmentally friendly; from the perspectives of technology, economy, and environmental protection, the present invention will have significant social, economic, and environmental benefits, is highly practical, and is suitable for widespread use. Detailed Implementation

[0028] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0029] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0030] Examples 1-10 each provide a cementitious material based on calcined clay, the formulation of which is shown in Table 1. The cementitious materials of each example are prepared according to the following steps:

[0031] Weigh each component in the base material according to Table 1, mix it with the alkaline activator, and grind the prepared material evenly until the powder has a residue of no more than 10% on an 80μm square hole sieve. This will yield a cementitious material based on calcined clay.

[0032] Table 1. Formulation of cementitious materials (kg)

[0033]

[0034] The chemical composition of the calcined clay used in the examples and comparative examples is shown in Table 2.

[0035] Table 2 Chemical composition (%) of calcined clay

[0036]

[0037] The chemical composition of the steel slag used in Examples 1-9 and Comparative Examples 1-2 is shown in Table 3.

[0038] Table 3 Chemical composition of steel slag (%)

[0039]

[0040] The chemical composition of the slag powder used in the examples and comparative examples is shown in Table 4.

[0041] Table 4 Chemical composition (%) of slag powder

[0042]

[0043] The chemical composition of the cement clinker used in the examples and comparative examples is shown in Table 5.

[0044] Table 5 Chemical composition of cement clinker (%)

[0045]

[0046] The chemical composition of the gypsum used in the examples and comparative examples is shown in Table 6.

[0047] Table 6 Chemical composition of gypsum (%)

[0048]

[0049] Test case

[0050] The compressive strength and stability of the cementitious materials prepared in Examples 1-10 and Comparative Examples 1-2 were tested respectively.

[0051] Compressive strength test: The mortar was mixed and molded according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)" and cured in water: The mortar specimens were cured in a curing box at 20℃±2℃ and relative humidity not less than 90% for 1 day, and then demolded. The demolded specimens were placed in water at 20℃±1℃ for 28 days to test the compressive strength.

[0052] Soundness test: According to the "Test Method for Standard Consistency Water Requirement, Setting Time and Soundness of Cement" (GB / T1346-2011), the setting time and soundness of the cementitious materials in Examples 1-10 were tested using the Le Chatelier method.

[0053] The test results are shown in Tables 7 and 8.

[0054] Table 7 shows the compressive strength of the cementitious materials prepared in Examples 1-10 and Comparative Examples 1-2 at 3d, 7d, and 28d.

[0055]

[0056] The embodiments of the present invention yielded a cementitious material based on calcined clay, which exhibited a compressive strength >20.0 MPa after 3 days of water curing, a compressive strength >24.0 MPa after 7 days, and a compressive strength >35.0 MPa after 28 days.

[0057] Table 8 shows the setting time and stability of the cementitious materials prepared in Examples 1-10.

[0058]

[0059] The results show that Examples 1-10 all meet the requirements of the national standard GB175-2020 and can be used as cement.

[0060] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A cementitious material based on calcined clay, characterized in that, The base material includes a base material and an alkaline activator. By mass percentage, the base material includes: 30-60% calcined clay, 4% steel slag, 30-60% slag powder, 5% cement clinker, and 1% gypsum. The alkaline activator comprises calcium formate, sodium hydroxide, and sodium silicate in a mass ratio of 1:2:10; The chemical composition of the steel slag, by mass percentage, includes: CaO: 38~50%, Fe2O3: 25~35%, SiO2: 14~20%, MgO: 4.5~12%, MnO: ≤5%, Al2O3: 1-10%, CaF2 ≤2%, SO3 ≤5%.

2. The cementitious material based on calcined clay according to claim 1, characterized in that, The alkaline activator accounts for 0.1-10% of the mass of the base material.

3. The cementitious material based on calcined clay according to claim 1, characterized in that, The alkaline activator accounts for 5-7% of the mass of the base material.

4. The cementitious material based on calcined clay according to claim 1, characterized in that, The base material is made from the following raw materials in the indicated weight percentages: 60% calcined clay, 4% steel slag, 30% blast furnace slag, 5% cement clinker, and 1% gypsum.

5. The cementitious material based on calcined clay according to claim 4, characterized in that, The base material is made from the following raw materials in the indicated weight percentages: 30% calcined clay, 4% steel slag, 60% blast furnace slag, 5% cement clinker, and 1% gypsum.

6. The cementitious material based on calcined clay according to claim 1, characterized in that, The calcined clay contains Al2O3 > 15%, Al / Si > 0.3, CaO < 3%, and SO3 < 3%.

7. The cementitious material based on calcined clay according to claim 1, characterized in that, The calcined clay has an Al2O3 content of ≥20% and a 28-day compressive strength activity index of over 80%.

8. The cementitious material based on calcined clay according to claim 1, characterized in that, The chemical composition of the calcined clay, by mass percentage, includes: Al2O3: 25~40%, SiO2: 60~75%, K2O+Na2O≤3%, CaO+MgO≤5%, SO3<3%.

9. The cementitious material based on calcined clay according to claim 1, characterized in that, The slag is water-quenched or air-cooled blast furnace slag; and / or, the cement clinker is silicate cement clinker; and / or, the gypsum is selected from at least one of desulfurized gypsum, mirabilite gypsum, phosphogypsum, and titanium gypsum.

10. A method for preparing a cementitious material based on calcined clay according to any one of claims 1-9, characterized in that, Weigh each component in the base material, mix it with an alkaline activator, and grind it to obtain a cementitious material based on calcined clay.

11. The method for preparing cementitious materials based on calcined clay according to claim 10, characterized in that, The powder obtained from the grinding process also needs to be sieved through a 60-100μm square mesh, and the residue of the powder on the sieve is 0-10%.

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