Design method and preparation method of composite low-calcium mineral phase system

Abstract

This invention discloses a design method for a composite low-calcium mineral phase system. The method uses β-C2S, γ-C2S, and α-CS as three design components and conducts seven sets of experiments. The specific experimental method is as follows: First, the value range of each component in each set of experiments is determined according to the constraints. Then, the vertices, midpoints of the three sides, and center point of the triangle are selected as experimental data points to obtain the performance parameters for each data point. Finally, the software Design Expert is used to obtain a triangle contour map within the triangle coordinate system. Based on this map, the mass proportion of each mineral phase in the composite system with good carbon fixation and cementing properties is obtained. This invention also discloses a preparation method for the above-mentioned composite low-calcium mineral phase system.

Description

Technical Field

[0001] This invention relates to a design method for a composite low-calcium mineral phase system, and also to a preparation method for the aforementioned composite low-calcium mineral phase system. Background Technology

[0002] By developing cementitious materials containing low-calcium mineral phase systems, carbon emissions can be effectively reduced.

[0003] Currently, low-calcium mineral phases include C2S, CS, and C3S2. These phases have lower sintering temperatures, consume less limestone, and significantly reduce carbon emissions during clinker preparation. Furthermore, they all exhibit high carbonization activity, allowing for the use of carbon dioxide curing instead of hydration curing, resulting in higher mechanical properties within a shorter curing time. However, current single-phase low-calcium mineral systems, after carbonization curing, suffer from limited carbon fixation, low carbon content, and weak cementing properties. Summary of the Invention

[0004] Objectives of the Invention: One objective of this invention is to provide a design method for a composite low-calcium mineral phase system, which enables the constructed composite low-calcium mineral phase system to have both good carbon fixation performance and good cementing performance; another objective of this invention is to provide a method for obtaining the above-mentioned composite low-calcium mineral phase system, which obtains cement clinker containing four mineral phases by calcining solid waste in one step.

[0005] Technical Solution: The design method for the composite low-calcium mineral phase system described in this invention is based on the simplex centroid design method. The design principle is: when there are n design components, 2 n – The experiment of group 1 yielded the corresponding contour map. The method of this invention uses β-C2S, γ-C2S and α-CS as 3 design components, so n=3, and 7 groups of experiments are required. The experimental method is as follows: First, the value range of each component in each group of experiments is determined according to the constraints. Then, the vertex, midpoint of the three sides and center point of the triangle are selected as experimental data points to obtain the performance parameters of each data point. Finally, the software Design Expert is used to obtain the triangle contour map in the triangle coordinate system. Based on this map, the mass proportion of each mineral phase in the composite system with good carbon fixation and cementation properties is obtained.

[0006] The preparation method of the composite low-calcium mineral phase system of the present invention is as follows: calcining wollastonite tailings powder at 1150-1250℃, and then naturally cooling it with the furnace to obtain the low-calcium mineral phase composite system material.

[0007] The calcination time is 1 to 2 hours.

[0008] In this process, 10% to 20% water by weight of the clinker is added to the clinker, stirred evenly, and then pressed into shape. The pressed pre-formed product is then placed in a carbonization reactor for carbonization curing.

[0009] The process involves pressing the material into shape in a 2cm*2cm*2cm steel mold under a pressure of 2-10 MPa, with a carbonization curing time of no less than 24 hours.

[0010] The wollastonite tailings were ground and passed through an 800-mesh sieve to obtain wollastonite tailings powder. The wollastonite tailings were produced in the wollastonite mining area of ​​Shanggao County, Yichun City, Jiangxi Province. The main mineral components of the wollastonite tailings were wollastonite (Ca3Si3O9) and associated calcium carbonate (CaCO3). The mass percentage of associated calcium carbonate in the wollastonite tailings was 48%. The molar ratio of CaO to SiO2 in the wollastonite tailings was 2.38:1.

[0011] The main mineral phases in the composite low-calcium mineral phase system obtained by the above preparation method are γ-C2S: 44wt%, β-C2S: 34wt%, β-CS: 10wt%, and α-CS: 2wt%.

[0012] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The composite low-calcium mineral phase system of the present invention is mainly composed of β-C2S, γ-C2S, β-CS and α-CS. The clinker is self-pulverized and does not require grinding. That is, the clinker of the present invention is directly in powder form after firing and can be directly used as cement. In addition, the composite low-calcium mineral phase system of the present invention can simultaneously improve carbon fixation and cementing performance. The strength after 1 hour of carbonization curing is above 55 MPa, and the strength after 24 hours of curing can reach above 129 MPa. The carbon fixation amount can reach 217 kg / t, which has excellent mechanical properties and carbon fixation performance. Attached Figure Description

[0013] Figure 1 The XRD pattern of the wollastonite tailings used in this invention;

[0014] Figure 2 Thermogravimetric analysis diagram of the wollastonite tailings used in this invention;

[0015] Figure 3 (a) Compressive strength of the composite low-calcium mineral phase system obtained from 7 sets of tests designed using the simple center of gravity design method; Figure 3 (b) Carbon sequestration of the composite low-calcium mineral phase system obtained from 7 sets of experiments designed using the simple center of gravity design method;

[0016] Figure 4 Contour plots (ternary contour plots) showing the compressive strength and carbon fixation of composite low-calcium mineral phase systems obtained from β-C2S, γ-C2S, and α-CS with different proportions;

[0017] Figure 5 (a) XRD diffraction patterns of composite low-calcium mineral phase system materials prepared at different calcination temperatures; Figure 5 (b) Quantitative analysis of each mineral phase in composite low-calcium mineral phase system materials prepared at different calcination temperatures;

[0018] Figure 6 (a) Compressive strength of composite low-calcium mineral phase system materials prepared at different calcination temperatures; Figure 6 (b) The carbon fixation content of the composite low-calcium mineral phase system materials prepared at different calcination temperatures;

[0019] Figure 7 The mass fractions of β-C2S, γ-C2S, and α-CS in the composite system were obtained using a triangular contour map when the compressive strength reached over 120 MPa and the carbon fixation amount reached over 180 kg / t after 24 hours of carbonization curing. Detailed Implementation

[0020] The raw material used in this invention to prepare the composite low-calcium mineral phase system material is wollastonite tailings (WT), which originates from the wollastonite mining area of ​​Shanggao County, Yichun City, Jiangxi Province. The wollastonite tailings are grayish-white. After grinding and passing through an 800-mesh sieve, they are dried and stored to obtain wollastonite tailings powder. The phase composition of the wollastonite tailings powder is shown below. Figure 1 According to the XRD pattern, the main mineral components of the wollastonite tailings are wollastonite (Ca3Si3O9) and associated calcium carbonate (CaCO3), with minor impurities including magnesium oxide and iron oxide phases. Thermogravimetric analysis of the wollastonite tailings is detailed in [link to documentation]. Figure 2 It can be found that the amount of associated calcium carbonate in wollastonite tailings is about 48%. XRF testing of wollastonite tailings shows that the molar ratio of CaO to SiO2 in wollastonite tailings is 2.38:1.

[0021] Table 1 shows the chemical composition of wollastonite tailings determined by XRF.

[0022]

[0023] The present invention relates to a design method for a composite low-calcium mineral phase system. This method is based on the simplex centroid design method. The composite low-calcium mineral phase system includes β-C2S, γ-C2S, and CS (β-CS and α-CS). CS includes β-CS and α-CS. The carbonization activity of α-CS is slightly higher than that of β-CS, but its carbonization reaction activity is lower than that of β-C2S and γ-C2S. Therefore, α-CS is selected as one of the design components in the design.

[0024] The method of this invention uses β-C2S, γ-C2S and α-CS as three design components, n=3, and conducts 7 sets of experiments. The experimental method is as follows: First, the value range of each component in each set of experiments is determined according to the constraints. Then, the vertex, midpoint of the three sides and center point of the triangle are selected as experimental data points to obtain the performance parameters of each data point. Finally, the software DesignExpert is used to obtain the triangle contour map in the triangle coordinate system. Based on this map, the mass proportion of each mineral phase in the composite system with good carbon fixation and cementation properties is obtained.

[0025] Simultaneously possessing good carbon fixation and cementing properties means that after 24 hours of carbonization curing, the compressive strength reaches over 120 MPa and the carbon fixation amount reaches over 180 kg / t. At this time, the mass fraction of β-C2S in the composite system is 31-70%, the mass fraction of γ-C2S is 28-56%, and the mass fraction of α-CS is 0-31%.

[0026] Table 2 shows the value ranges of each component in each of the seven groups of experiments.

[0027]

[0028] The preparation method of the composite low-calcium mineral phase system of the present invention is as follows: wollastonite tailings powder is placed in an alumina crucible and calcined at 1200℃ for 2 hours, and then naturally cooled with the furnace to obtain the composite low-calcium mineral phase system material (WT-12).

[0029] The prepared composite low-calcium mineral phase system material was mixed with water at a water-binder ratio of 1:10. The mixture was then pressed into 20mm*20mm*20mm cubic blocks using a tablet press and placed in a carbonization reactor for carbonization and curing for 24 hours.

[0030] The composite low-calcium mineral phase system material was subjected to X-ray diffraction testing and carbonization curing to obtain carbonized products. The mechanical properties of the carbonized products were tested according to JGJ / T70-2009 "Standard for Test Methods of Basic Performance of Building Mortar", and the degree of carbonization of the products was evaluated by the lost calcium carbonate ignition method.

[0031] Tests revealed that the main mineral phases in the sintered clinker were γ-C₂S: 44 wt%, β-C₂S: 34 wt%, β-CS: 10 wt%, and α-CS: 2 wt%. (See attached table for details.) Figure 6 After 24 hours of carbonization curing, the compressive strength was 129.75 MPa and the carbon fixation amount was 217 kg / t.

[0032] Figure 6All preparation conditions were completely consistent, with the only difference being the carbon fixation content and compressive strength of the composite low-calcium mineral phase systems (WT-9, WT-10, WT-11, WT-13) obtained by calcination at calcination temperatures of 900℃, 1000℃, 1100℃, and 1300℃.

Claims

1. A method for preparing a composite low-calcium mineral phase system, characterized in that, Specifically, wollastonite tailings powder is calcined at 1150~1250℃ and then naturally cooled in the furnace to obtain a composite low-calcium mineral phase system material. In the wollastonite tailings, the molar ratio of CaO to SiO2 is 2.38:

1. In the obtained composite low-calcium mineral phase system, the main mineral phases are γ-C2S: 44wt%, β-C2S: 34wt%, β-CS: 10wt%, and α-CS: 2wt%.

2. The preparation method of the composite low-calcium mineral phase system according to claim 1, characterized in that: The calcination time is 1-2 hours.

3. The preparation method of the composite low-calcium mineral phase system according to claim 1, characterized in that: Add 10% to 20% water by weight of the material to the material, stir evenly, press into shape, and place the pressed pre-formed product in a carbonization reactor for carbonization curing.

4. The preparation method of the composite low-calcium mineral phase system according to claim 3, characterized in that: It is pressed into shape in a 2cm*2cm*2cm steel mold under a pressure of 2~10Mpa.

5. The preparation method of the composite low-calcium mineral phase system according to claim 3, characterized in that: The carbonization curing time shall be no less than 24 hours.

6. The method for preparing the composite low-calcium mineral phase system according to claim 1, characterized in that: Wollastonite tailings were ground and passed through an 800-mesh sieve to obtain wollastonite tailings powder. The wollastonite tailings were produced in the wollastonite mining area of ​​Shanggao County, Yichun City, Jiangxi Province. The main mineral components of the wollastonite tailings were wollastonite and associated calcium carbonate, with associated calcium carbonate accounting for 48% of the mass of the wollastonite tailings.

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