Low-calcium carbon sequestration cementing material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to a low-calcium carbon sequestration cementing material as well as a preparation method and application thereof. The low-calcium carbon sequestration cementing material disclosed by the invention is prepared from the following main mineral components in percentage by weight: 55 to 80 percent of calcium silicate, 15 to 35 percent of tricalcium disilicate and 5 to 15 percent of gehlenite. The low-calcium carbon-sequestration cementing material has excellent carbonization activity, can seal a large amount of carbon dioxide, can obtain excellent mechanical properties in a short time, and provides a new way for solving the problem of carbon emission in the cement industry and recycling industrial solid wastes such as magnesium slag and fly ash.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a low-calcium carbon fixation cementitious material and a preparation method and application thereof. BACKGROUND

[0002] China is a traditional large cement producer, and the cement output has been ranked first in the world for a long time. In the future, the cement output of China will remain at a high level for a period of time. As a traditional high energy consumption and high carbon emission enterprise, the carbon dioxide emission of cement accounts for more than 13% of the total emission. The mineral composition of cement clinker mainly includes tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. Tricalcium silicate, as the main mineral composition of cement, has a high sintering temperature, usually above 1450 DEG C, and requires a high calcium content in the raw material. The high sintering temperature and the decomposition of a large amount of calcium carbonate are the main reasons for the long-term high carbon emission of the cement industry.

[0003] On the other hand, China is a large magnesium metal producer, and more than 8 million tons of magnesium slag are produced every year. As a solid waste in the process of magnesium metal smelting or magnesium compound production, the main mineral composition of magnesium slag is dicalcium silicate and a small amount of magnesium oxide. The calcium oxide content is generally more than 50%, so it can be used as a calcium source in the preparation of cement raw materials. However, in the preparation process of traditional Portland cement, the magnesium oxide content in the raw material is strictly required to ensure the stability of the cement, so there are limitations in replacing Portland cement with magnesium slag as a calcium source. Fly ash, as a solid waste in the process of coal-fired power generation, is usually in the form of powder or microbeads. The annual output of fly ash in China is more than 600 million tons, accounting for more than 15% of the total output of industrial solid waste. The energy characteristics of China determine that thermal power generation will still dominate in the future, and the production of fly ash will remain high. Fly ash can be divided into Grade I, Grade II and Grade III according to its chemical composition and physical properties. Fly ash has a good promoting effect on the mechanical properties and working performance of concrete materials due to its own pozzolanic effect and ball effect, so it has been widely used in concrete materials. However, there is still an urgent need for effective methods to deal with low-grade fly ash.

[0004] Therefore, it is necessary to provide an improved technical solution to overcome the above-mentioned deficiencies of the prior art. SUMMARY

[0005] The purpose of the present application is to provide a low-calcium carbon fixation cementitious material and a preparation method and application thereof, so as to help solve or improve the problem of limited application of magnesium slag and fly ash.

[0006] In order to achieve the above object, the present application provides the following technical scheme: a low calcium carbon sequestration cementing material, the main mineral composition of the low calcium carbon sequestration cementing material includes: calcium silicate 55wt.%-80wt.%, tricalcium silicate 15wt.%-35wt.% and calcium aluminum melilite 5wt.%-15wt.%.

[0007] The present application also provides a preparation method of a low calcium carbon sequestration cementing material, which adopts the following technical scheme: the preparation method of the low calcium carbon sequestration cementing material as described above, including the following steps: (1) mixing magnesium slag, fly ash and water to obtain mixed wet material, extruding the mixed wet material into a green material sheet, drying to obtain the green material sheet; (2) calcining the green material sheet; (3) after the calcination is completed, cooling and grinding, thereby obtaining the low calcium carbon sequestration cementing material.

[0008] Preferably, in step (1), the mass ratio of the magnesium slag and the fly ash is (70-80):(20-30); the particle size of the magnesium slag and / or the fly ash is <150μm.

[0009] Preferably, in step (1), the pressure during the extrusion molding is 10-20MPa, and the pressure maintaining time during the extrusion molding is 30-180s.

[0010] Preferably, in step (2), during the calcination, first, the temperature is raised to 250-400℃ at a first temperature raising rate; then the temperature is raised to 900℃ at a second temperature raising rate, and the temperature is maintained for a first time; finally, the temperature is raised to 1150-1250℃ at a third temperature raising rate, and the temperature is maintained for a second time.

[0011] Preferably, the first temperature raising rate is 3-7℃ / min; the second temperature raising rate is 5-10℃ / min, and the first time is 30min; the third temperature raising rate is 10℃ / min, and the second time is 30-120min.

[0012] Preferably, in step (3), the cooling rate is >100℃ / min.

[0013] Preferably, in step (3), after the grinding is completed, the particle size of the low calcium carbon sequestration cementing material is <150μm.

[0014] Preferably, the chemical components of the magnesium slag mainly include CaO, SiO2, Fe2O3, Al2O3 and MgO, wherein CaO and SiO2 are the main components, and the content of each is not less than 20%; the chemical components of the fly ash mainly include CaO, SiO2, Fe2O3, Al2O3 and MgO, wherein SiO2 and Al2O3 are the main components, and the content of each is not less than 20%.

[0015] The application further provides a carbonized product, which is prepared by carbonizing the low-calcium carbon sequestration cementing material.

[0016] Beneficial effects: The low-calcium carbon sequestration cementing material (main components include calcium silicate, tricalcium disilicate, and has high carbonization activity) developed by taking magnesium slag and fly ash as raw materials and performing low-temperature sintering and taking calcium silicate as the main mineral composition can not only greatly reduce carbon dioxide emission in the raw material stage and preparation process, but also can sequestrate a large amount of carbon dioxide by using the excellent carbonization activity in the maintenance stage, and excellent mechanical properties are obtained in a short time, thereby providing a new way for solving the carbon emission problem of the cement industry and the resource utilization of industrial solid wastes such as magnesium slag and fly ash, and since magnesium oxide is also an excellent carbonizable phase, the low-calcium carbon sequestration cementing material of the application does not need to consider the influence of too high magnesium oxide content on the stability.

[0017] The raw material of the application is industrial solid waste (magnesium slag and fly ash), and impurity ions contained in the industrial solid waste can promote the phase reconstruction of the low-calcium carbon sequestration cementing material, reduce the sintering temperature, and save energy consumption; in addition, the application can reduce the consumption of natural raw materials, promote the large-scale consumption of industrial solid waste, and reduce the pollution of industrial solid waste to the natural environment. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings accompanying the specification of this application serve to provide further understanding of the application, and the illustrative embodiments of the application and their descriptions serve to explain the application, and do not constitute improper limitations on the application. Among them: Figure 1 The XRD pattern of the low-calcium carbon sequestration cementing material prepared by taking different proportions of magnesium slag and fly ash as raw materials in Example 1-4 of the application and maintaining at 1200 DEG C for 120 min; Figure 2 The carbonization weight gain of the low-calcium carbon sequestration cementing material prepared by taking different proportions of magnesium slag and fly ash as raw materials in Example 1-4 of the application and maintaining at 1200 DEG C for 120 min after carbonization for different time; Figure 3 The compressive strength of the low-calcium carbon sequestration cementing material prepared by taking different proportions of magnesium slag and fly ash as raw materials in Example 1-4 of the application and maintaining at 1200 DEG C for 120 min after carbonization for different time.

[0019] Figure 4 The carbon sequestration amount of the low-calcium carbon sequestration cementing material of Example 5 of the application after carbonization for 24 h and the compressive strength test results of the carbonized product prepared; Figure 5Carbonation capacity of the low calcium carbonation cementitious material of embodiment 6 of the present application and the compressive strength of the carbonated product prepared by carbonation for 24 hours. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0021] The present application will be described in detail below with reference to the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0022] The present application aims at the problem that the application of magnesium slag and fly ash in the prior art is limited, and provides a low calcium carbonation cementitious material.

[0023] The main mineral composition of the low calcium carbonation cementitious material of the embodiments of the present application includes: calcium silicate 55wt.%-80wt.%, tricalcium disilicate 15wt.%-35wt.% and calcium aluminum melilite 5wt.%-15wt.%. If the content of calcium aluminum melilite is too high, it will adversely affect the carbonation performance of the low calcium carbonation cementitious material of the present application.

[0024] The low calcium carbonation cementitious material of the present application can seal a large amount of carbon dioxide by using its excellent carbonation activity in the curing stage, and excellent mechanical properties can be obtained in a short time, which provides a new way for solving the carbon emission problem of the cement industry and the resource utilization of industrial solid wastes such as magnesium slag and fly ash.

[0025] The present application also provides a preparation method of the low calcium carbonation cementitious material as described above, and the preparation method of the low calcium carbonation cementitious material of the embodiments of the present application includes the following steps: (1) mixing magnesium slag, fly ash and water to obtain mixed wet material, extruding and drying the mixed wet material to obtain green material pieces; (2) calcining the green material pieces; (3) after the calcination is completed, cooling and grinding, to obtain the low calcium carbonation cementitious material.

[0026] The present application uses magnesium slag and fly ash as raw materials, and performs low-temperature sintering to develop a low calcium carbonation cementitious material with calcium silicate as the main mineral composition (main components include calcium silicate and tricalcium disilicate, and has high carbonation activity). The low calcium carbonation cementitious material not only can greatly reduce the carbon dioxide emission in the raw material stage and the preparation process, but also can seal a large amount of carbon dioxide by using its excellent carbonation activity in the curing stage, and excellent mechanical properties can be obtained in a short time, which provides a new way for solving the carbon emission problem of the cement industry and the resource utilization of industrial solid wastes such as magnesium slag and fly ash.

[0027] The raw material of the present application is industrial solid waste (magnesium slag and fly ash), and the impurity ions contained in the industrial solid waste can promote the phase reconstruction of the low-calcium carbon sequestration cementing material, reduce the sintering temperature, and save energy consumption. In addition, the present application can reduce the consumption of natural raw materials, promote the large-scale consumption of industrial solid waste, and reduce the pollution of industrial solid waste to the natural environment. In addition, low-grade fly ash is also suitable for the present application, and the application of fly ash of different grades in the present application has little effect on the composition of the prepared product, which can effectively realize the resource utilization of low-grade fly ash.

[0028] In the preferred embodiment of the preparation method of the low-calcium carbon sequestration cementing material of the present application, in step (1), the mass ratio of magnesium slag and fly ash is (70-80):(20-30) (for example, 70:20, 70:25, 70:30, 75:20, 75:25, 75:30, 80:20, 80:25 or 80:30); and the particle size of the magnesium slag and / or fly ash is <150 μm. If the particle size of the magnesium slag and / or fly ash is too large, it will cause insufficient reaction in step (2).

[0029] In the preferred embodiment of the preparation method of the low-calcium carbon sequestration cementing material of the present application, in step (2), the pressure during extrusion molding is 10-20 MPa (for example, 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa or 20 MPa), and the pressure holding time during extrusion molding is 30-180 s (for example, 30 s, 50 s, 70 s, 90 s, 110 s, 130 s, 150 s, 170 s or 180 s). The appropriate pressure during extrusion molding can promote the combination of calcareous raw materials and siliceous raw materials, and promote the progress of the later sintering reaction. If the pressure is too large, the energy consumption is high. If the pressure during extrusion molding is too small, the green block is relatively loose, and the particles cannot effectively react.

[0030] In the preferred embodiment of the preparation method of the low-calcium carbon sequestration cementing material of the present application, in step (3), during calcination, first, the temperature is raised to 250-400℃ (for example, 250℃, 280℃, 310℃, 340℃, 370℃ or 400℃) at a first heating rate; then the temperature is raised to 900℃ at a second heating rate, and the temperature is held for a first time; finally, the temperature is raised to 1150-1250℃ (for example, 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃ or 1250℃) at a third heating rate, and the temperature is held for a second time. The holding of the temperature at 900℃ for the first time helps to ensure that the calcium carbonate in the green piece can be completely decomposed and the carbon dioxide can be completely removed.

[0031] In a preferred embodiment of the preparation method of the low-calcium carbon sequestration cementitious material, the first temperature increasing rate is 3-7℃ / min (for example, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min or 7℃ / min); the second temperature increasing rate is 5-10℃ / min (for example, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min), and the first time is 30 min; the third temperature increasing rate is 10℃ / min, and the second time is 30-120 min (for example, 30 min, 50 min, 70 min, 90 min, 100 min or 120 min). In the embodiment, the second time has a greater influence on the composition and performance of the product. If the second time is too short, the product performance will be reduced due to insufficient time for crystal type conversion and grain growth. If the second time is too long, not only the energy consumption will be increased, but also the grain growth will not be facilitated.

[0032] In a preferred embodiment of the preparation method of the low-calcium carbon sequestration cementitious material, in step (4), the cooling rate is >100℃ / min. In the embodiment, by setting the cooling rate to be >100℃ / min, the conversion of calcium silicate in the prepared low-calcium carbon sequestration cementitious material to a crystal type with low carbonation activity can be avoided.

[0033] In a preferred embodiment of the preparation method of the low-calcium carbon sequestration cementitious material, in step (4), after the grinding is completed, the particle size of the low-calcium carbon sequestration cementitious material is <150μm.

[0034] In a preferred embodiment of the preparation method of the low-calcium carbon sequestration cementitious material, the chemical components of the magnesium slag mainly include CaO, SiO2, Fe2O3, Al2O3 and MgO, wherein CaO and SiO2 are the main components and the content of each is not less than 20%; the chemical components of the fly ash mainly include CaO, SiO2, Fe2O3, Al2O3 and MgO, wherein SiO2 and Al2O3 are the main components and the content of each is not less than 20%.

[0035] The application further provides a carbonized product, which is prepared by carbonizing the low-calcium carbon sequestration cementitious material as described above.

[0036] The low-calcium carbon sequestration cementitious material, the preparation method and the application thereof will be described in detail below through specific embodiments.

[0037] In the following examples, the magnesium slag and the fly ash used are obtained from magnesium slag produced by the Pijiang method and fly ash produced by a thermal power plant in Yulin City, Shaanxi Province. The chemical components of the magnesium slag and the fly ash are shown in Table 1.

[0038] Table 1 Chemical components of magnesium slag and fly ash (wt.%)

[0039] Example 1 The preparation method of the low-calcium carbon-fixing cementitious material in this embodiment includes the following steps: (1) Magnesium slag and fly ash were ground separately using a crushing and grinding device to grind them to a particle size of less than 150 micrometers; (2) Weigh 73 parts of magnesium slag and 27 parts of fly ash and mix them with water at a mass ratio of 10:1 (the amount of water is 10 parts, and the total amount of magnesium slag and fly ash is mixed with the mass ratio of water at 10:1). Then mix them evenly using a ball mill. (3) The wet material obtained in step (2) is extruded using an extrusion molding device at 15 MPa. Extrude it under forming pressure for 1 minute to obtain raw material sheets; (4) Place the raw material sheets obtained in step (3) into an oven and dry them at 105°C for 12 hours; (5) The raw material sheets obtained in step (4) are placed in a calcining device for calcination. The calcination program is set as follows: 1) The temperature is raised from room temperature to 300℃ at a rate of 5℃ / min for 60 min; 2) The temperature is raised from 300℃ to 900℃ at a rate of 10℃ / min for 60 min; 3) The temperature is held at 900℃ for 30 min to ensure that carbon dioxide is completely removed from the raw material; 4) The temperature is raised from 900℃ to the target temperature of 1200℃ at a rate of 10℃ / min for 30 min; 5) The temperature is held at the target temperature of 1200℃ for 120 min; then the material is rapidly cooled by air cooling (cooling rate > 100℃ / min) to obtain blocky low-calcium carbon-fixing cementitious material. (6) The blocky low-calcium carbon-fixing cementitious material obtained in step (5) is ground into powder with a particle size of less than 150 micrometers by a crushing and grinding device to obtain the low-calcium carbon-fixing cementitious material (powder) of this embodiment.

[0040] The preparation method of the carbonized product in this embodiment includes the following steps: weigh the powdered low-calcium solid carbon cementitious material prepared in step (6) above, mix it with water at a mass ratio of 10:1, extrude it under a molding pressure of 6MPa for 1 minute, and then place it in a carbonization sealed device and carbonize it at 20℃ and 0.2MPa for 4 hours and 24 hours to obtain the carbonized product of this embodiment.

[0041] The XRD, carbonation weight gain, and compressive strength test results of the low-calcium carbon-fixing cementitious material in this embodiment are as follows: Figure 1 , Figure 2 , Figure 3 As shown.

[0042] Example 2 The preparation method of the low-calcium carbon-fixing cementitious material in this embodiment includes the following steps: (1) Magnesium slag and fly ash were ground separately using a crushing and grinding device to make them into micro powder with a particle size of less than 150 micrometers. (2) Weigh 75 parts of magnesium slag powder and 25 parts of fly ash powder and mix them with water at a mass ratio of 10:1. Then mix them evenly using a ball mill. (3) The wet material obtained in step (2) is extruded for 1 minute under a molding pressure of 15 MPa using an extrusion molding device to obtain raw material sheets; (4) Place the raw material sheets obtained in step (3) into an oven and dry them at 105°C for 12 hours; (5) The raw material sheets obtained in step (4) are placed in a calcining device for calcination. The calcination program is set as follows: 1) The room temperature is raised to 300℃, and the temperature is increased at a rate of 5℃ / min for 60min; 2) The temperature is raised from 300℃ to 900℃, and the temperature is increased at a rate of 10℃ / min for 60min; 3) The temperature is held at 900℃ for 30min to ensure that the carbon dioxide in the raw material is completely removed; 4) The temperature is raised from 900℃ to the target temperature of 1200℃, the heating rate is 10℃ / min, and the heating time is 30min; 5) The temperature is held at the target temperature of 1200℃ for 120min; then the material is rapidly cooled by air cooling (cooling rate > 100℃ / min) to obtain blocky low-calcium carbon-fixing cementitious material. (6) The blocky low-calcium carbon-fixing cementitious material obtained in step (5) is ground into powder with a particle size of less than 150 micrometers by a crushing and grinding device to obtain the low-calcium carbon-fixing cementitious material (powder) of this embodiment.

[0043] The preparation method of the carbonized product in this embodiment includes the following steps: weigh the powdered low-calcium solid carbon cementitious material prepared in step (6) above, mix it with water at a mass ratio of 10:1, press it under a molding pressure of 6MPa for 1 minute to form it, and then put it into a carbonization sealed device and carbonize it at 20℃ and 0.2MPa for 4h and 24h to obtain the carbonized product of this embodiment.

[0044] The XRD, carbonation weight gain, and compressive strength test results of the low-calcium carbon-fixing cementitious material in this embodiment are as follows: Figure 1 , Figure 2 , Figure 3 As shown.

[0045] Example 3 The preparation method of the low-calcium carbon-fixing cementitious material in this embodiment includes the following steps: (1) Magnesium slag and fly ash were ground separately using a crushing and grinding device to make them into micro powder with a particle size of less than 150 micrometers. (2) Weigh 76 parts of magnesium slag powder and 24 parts of fly ash powder and mix them with water at a mass ratio of 10:1. Then mix them evenly using a ball mill. (3) The wet material obtained in step (2) is extruded for 1 minute under a molding pressure of 15 MPa using an extrusion molding device to obtain raw material sheets; (4) Place the raw material sheets obtained in step (3) into an oven and dry them at 105°C for 12 hours; (5) The raw material sheets obtained in step (4) are placed in a calcining device for calcination. The calcination program is set as follows: 1) The room temperature is raised to 300℃, and the temperature is increased at a rate of 5℃ / min for 60min; 2) The temperature is raised from 300℃ to 900℃, and the temperature is increased at a rate of 10℃ / min for 60min; 3) The temperature is held at 900℃ for 30min to ensure that the carbon dioxide in the raw material is completely removed; 4) The temperature is raised from 900℃ to the target temperature of 1200℃, the heating rate is 10℃ / min, and the heating time is 30min; 5) The temperature is held at the target temperature of 1200℃ for 120min; then the material is rapidly cooled by air cooling (cooling rate > 100℃ / min) to obtain blocky low-calcium carbon-fixing cementitious material. (6) The blocky low-calcium carbon-fixing cementitious material obtained in step (5) is ground into powder with a particle size of less than 150 micrometers by a crushing and grinding device to obtain the low-calcium carbon-fixing cementitious material (powder) of this embodiment.

[0046] The preparation method of the carbonized product in this embodiment includes the following steps: weigh the powdered low-calcium solid carbon cementitious material prepared in step (6) above, mix it with water at a mass ratio of 10:1, press it under a molding pressure of 6MPa for 1 minute to form it, and then put it into a carbonization sealed device and carbonize it at 20℃ and 0.2MPa for 4h and 24h to obtain the carbonized product of this embodiment.

[0047] The XRD, carbonation weight gain, and compressive strength test results of the low-calcium carbon-fixing cementitious material in this embodiment are as follows: Figure 1 , Figure 2 , Figure 3 As shown.

[0048] Example 4 The preparation method of the low-calcium carbon-fixing cementitious material in this embodiment includes the following steps: (1) Magnesium slag and fly ash were ground separately using a crushing and grinding device to make them into micro powder with a particle size of less than 150 micrometers. (2) Weigh 77 parts of magnesium slag powder and 23 parts of fly ash powder and mix them with water at a mass ratio of 10:1. Then mix them evenly using a ball mill. (3) The wet material obtained in step (2) is extruded for 1 minute under a molding pressure of 15 MPa using an extrusion molding device to obtain raw material sheets; (4) Place the raw material sheets obtained in step (3) into an oven and dry them at 105°C for 12 hours; (5) The raw material sheets obtained in step (4) are placed in a calcining device for calcination. The calcination program is set as follows: 1) The room temperature is raised to 300℃, and the temperature is increased at a rate of 5℃ / min for 60min; 2) The temperature is raised from 300℃ to 900℃, and the temperature is increased at a rate of 10℃ / min for 60min; 3) The temperature is held at 900℃ for 30min to ensure that the carbon dioxide in the raw material is completely removed; 4) The temperature is raised from 900℃ to the target temperature of 1200℃, the heating rate is 10℃ / min, and the heating time is 30min; 5) The temperature is held at the target temperature of 1200℃ for 120min; then the material is rapidly cooled by air cooling (cooling rate > 100℃ / min) to obtain blocky low-calcium carbon-fixing cementitious material. (6) The blocky low-calcium carbon-fixing cementitious material obtained in step (5) is ground into powder with a particle size of less than 150 micrometers by a crushing and grinding device to obtain the low-calcium carbon-fixing cementitious material (powder) of this embodiment.

[0049] The preparation method of the carbonized product in this embodiment includes the following steps: weigh the powdered low-calcium solid carbon cementitious material prepared in step (6) above, mix it with water at a mass ratio of 10:1, press it under a molding pressure of 6MPa for 1 minute to form it, and then put it into a carbonization sealed device and carbonize it at 20℃ and 0.2MPa for 4h and 24h to obtain the carbonized product of this embodiment.

[0050] The XRD, carbonation weight gain, and compressive strength test results of the low-calcium carbon-fixing cementitious material in this embodiment are as follows: Figure 1 , Figure 2 , Figure 3 As shown.

[0051] from Figure 1 As can be seen from the examples, the main mineral composition of the low-calcium carbon-fixing cementitious materials prepared by magnesium slag and fly ash in Examples 1-4 is CS, C3S2, and C2AS minerals.

[0052] Example 5 The preparation method of the low-calcium carbon-fixing cementitious material in this embodiment includes the following steps: (1) Magnesium slag and fly ash were ground separately using a crushing and grinding device to make them into micro powder with a particle size of less than 150 micrometers. (2) Weigh 75 parts of magnesium slag powder and 25 parts of fly ash powder and mix them with water according to the mass ratio. Then mix them evenly using a ball mill. (3) The wet material obtained in step (2) is extruded for 1 minute under a molding pressure of 15 MPa using an extrusion molding device to obtain raw material sheets; (4) Place the raw material sheets obtained in step (3) into an oven and dry them at 105°C for 12 hours; (5) The raw material sheets obtained in step (4) are placed in a calcining device for calcination. The calcination program is set as follows: 1) The room temperature is raised to 300℃, and the temperature is increased at a rate of 5℃ / min for 60min; 2) The temperature is raised from 300℃ to 900℃, and the temperature is increased at a rate of 10℃ / min for 60min; 3) The temperature is held at 900℃ for 30min to ensure that the carbon dioxide in the raw material is completely removed; 4) The temperature is raised to the target temperature at 900℃, and the heating rate is 10℃ / min; 5) The temperature is held at the target temperature for 120min; then the material is rapidly cooled by air cooling (cooling rate > 100℃ / min) to obtain blocky low-calcium carbon-fixing cementitious material. (6) The blocky low-calcium carbon-fixing cementitious material obtained in step (5) is ground into powder with a particle size of less than 150 micrometers by a crushing and grinding device to obtain the low-calcium carbon-fixing cementitious material (powder) of this embodiment.

[0053] The preparation method of the carbonized product in this embodiment includes the following steps: weigh the powdered low-calcium solid carbon cementitious material prepared in step (6) above, mix it with water at a mass ratio of 10:1, press it under a molding pressure of 6MPa for 1 minute to form it, put it into a carbonization sealed device, and carbonize it at 20℃ and 0.2MPa for 24 hours to obtain the carbonized product of this embodiment.

[0054] In step (5), the target temperatures are set to 1150℃ (heating time is 25 min), 1175℃ (heating time is 27.5 min), 1200℃ (heating time is 30 min), 1225℃ (heating time is 32.5 min), and 1250℃ (heating time is 35 min), respectively. Accordingly, the low-calcium carbon-fixing cementitious materials in this embodiment are 5-1, 5-2, 5-3, 5-4 and 5-5 in sequence.

[0055] The test results of carbonization weight gain and compressive strength of the low-calcium solid carbon cementitious material in this embodiment after 24 hours of carbonization curing are as follows: Figure 4 As shown.

[0056] Example 6 The preparation method of the low-calcium carbon-fixing cementitious material in this embodiment includes the following steps: (1) Magnesium slag and fly ash were ground separately using a crushing and grinding device to make them into micro powder with a particle size of less than 150 micrometers. (2) Weigh 75 parts of magnesium slag powder and 25 parts of fly ash powder and mix them with water at a mass ratio of 10:1. Then mix them evenly using a ball mill. (3) The wet material obtained in step (2) is extruded for 1 minute under a molding pressure of 15 MPa using an extrusion molding device to obtain raw material sheets; (4) Place the raw material sheets obtained in step (3) into an oven and dry them at 105°C for 12 hours; (5) The raw material sheets obtained in step (4) are placed in a calcining device for calcination. The calcination program is set as follows: 1) The room temperature is raised to 300℃, and the temperature is increased at a rate of 5℃ / min for 60min; 2) The temperature is raised from 300℃ to 900℃, and the temperature is increased at a rate of 10℃ / min for 60min; 3) The temperature is held at 900℃ for 30min to ensure that the carbon dioxide in the raw material is completely removed; 4) The temperature is raised from 900℃ to the target temperature of 1200℃, the heating rate is 10℃ / min, and the heating time is 30min; 5) The temperature is held at the target temperature; then the material is rapidly cooled by air cooling (cooling rate > 100℃ / min) to obtain blocky low-calcium carbon-fixing cementitious material. (6) The blocky low-calcium carbon-fixing cementitious material obtained in step (5) is ground into powder with a particle size of less than 150 micrometers by a crushing and grinding device to obtain the low-calcium carbon-fixing cementitious material (powder) of this embodiment.

[0057] The preparation method of the carbonized product in this embodiment includes the following steps: weigh the powdered low-calcium solid carbon cementitious material prepared in step (6) above, mix it with water at a mass ratio of 10:1, press it under a molding pressure of 6MPa for 1 minute to form it, put it into a carbonization sealed device, and carbonize it at 20℃ and 0.2MPa for 24 hours to obtain the carbonized product of this embodiment.

[0058] In step (5), the holding times at the target temperature are 30 min, 60 min, 90 min, and 120 min, respectively; Accordingly, the low-calcium carbon-fixing cementitious materials in this embodiment are 6-1, 6-2, 6-3 and 6-4 in sequence.

[0059] The test results of carbonation weight gain and compressive strength of the low-calcium solid carbon cementitious material in this embodiment are as follows: Figure 5 As shown.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-calcium carbon-fixing cementitious material, characterized in that, The main mineral composition of the low-calcium carbon-fixing cementitious material includes: calcium silicate 55wt.%-80wt.%, tricalcium disilicate 15wt.%-35wt.%, and calcium aluminum feldspar 5wt.%-15wt.%.

2. The preparation method of the low-calcium carbon-fixing cementitious material as described in claim 1, characterized in that, Includes the following steps: (1) Mix magnesium slag, fly ash and water to obtain a mixed wet material, extrude the mixed wet material into a mold, and dry it to obtain raw material sheets; (2) Calcining the raw material sheets; (3) After calcination, the material is cooled and ground to obtain the low-calcium carbon-fixing cementitious material.

3. The preparation method of the low-calcium carbon-fixing cementitious material as described in claim 2, characterized in that, In step (1), the mass ratio of magnesium slag to fly ash is (70-80):(20-30); The particle size of the magnesium slag and / or fly ash is <150μm.

4. The preparation method of the low-calcium carbon-fixing cementitious material as described in claim 2, characterized in that, In step (1), the pressure during extrusion molding is 10-20 MPa, and the pressure stabilization time during extrusion molding is 30-180 s.

5. The preparation method of the low-calcium carbon-fixing cementitious material as described in claim 2, characterized in that, In step (2), during calcination, the temperature is first raised to 250-400℃ at the first heating rate; then raised to 900℃ at the second heating rate and held for the first time; finally raised to 1150-1250℃ at the third heating rate and held for the second time.

6. The method for preparing the low-calcium carbon-fixing cementitious material as described in claim 5, characterized in that, The first heating rate is 3-7℃ / min; The second heating rate is 5-10℃ / min, and the first time is 30min; The third heating rate is 10℃ / min, and the second time is 30-120min.

7. The method for preparing the low-calcium carbon-fixing cementitious material as described in claim 2, characterized in that, In step (3), the cooling rate is >100℃ / min.

8. The method for preparing the low-calcium carbon-fixing cementitious material as described in claim 2, characterized in that, In step (3), after grinding, the particle size of the low-calcium carbon-fixing cementitious material is <150μm.

9. The method for preparing the low-calcium carbon-fixing cementitious material as described in claim 2, characterized in that, The chemical composition of magnesium slag mainly includes CaO, SiO2, Fe2O3, Al2O3, and MgO, among which CaO and SiO2 are the main components, with each containing no less than 20%. The main chemical components of fly ash include CaO, SiO2, Fe2O3, Al2O3, and MgO, among which SiO2 and Al2O3 are the main components, with a content of not less than 20%.

10. A carbonized product, characterized in that, The carbonized product is prepared by carbonizing the low-calcium solid carbon cementitious material as described in claim 1.

Images