Magnesium slag and stone powder normal-temperature carbon fixation artificial aggregate and preparation method thereof

Abstract

The application belongs to the technical field of concrete, and particularly relates to a magnesium-slag-stone-powder normal-temperature carbon-fixing artificial aggregate and a preparation method thereof. The preparation method of the magnesium-slag-stone-powder normal-temperature carbon-fixing artificial aggregate comprises the following steps: (1) adding water into magnesium slag and stone powder and stirring to obtain a mixture; (2) pouring the mixture into a disc granulator, starting the disc granulator, and spraying water to prepare an aggregate blank; (3) pre-curing the aggregate blank to reduce the water content of the aggregate blank; and (4) making the aggregate blank obtained in step (3) react with CO2 gas to obtain the magnesium-slag-stone-powder normal-temperature carbon-fixing artificial aggregate. The magnesium-slag-stone-powder normal-temperature carbon-fixing artificial aggregate meets various performance requirements of high-strength aggregate in the standard GB-T-17431.1-2010, and can replace natural aggregate such as sand and stone to be used as a raw material of concrete.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete, and particularly relates to a magnesium slag and stone powder normal-temperature carbon fixation artificial aggregate and a preparation method thereof. BACKGROUND

[0002] Sand and stone aggregate is a material indispensable to the largest amount of national infrastructure construction. With the rapid development of China's infrastructure, the problem of "sand and stone supply shortage" has become increasingly urgent. China, as the world's largest sand and stone producer and consumer, according to statistics, about 10 billion tons of sand and stone aggregate are needed for infrastructure construction every year. Such a large demand can only be met by mining, which will inevitably lead to overconsumption of limited natural resources and damage to the sustainable development of the ecological environment. It is urgent to seek green alternatives to sand and stone aggregate.

[0003] In addition, global warming has brought a series of climate disasters, and carbon dioxide gas is the main source of greenhouse gases. Carbon dioxide capture and storage technology (CCS) is considered the most economical and feasible technical approach to reducing carbon dioxide emissions and mitigating global warming. Carbon dioxide storage technology includes geological storage, ocean storage, and mineral carbonization storage, and mineral carbonization storage is considered the safest storage approach.

[0004] China's magnesium smelting enterprises are large in scale, accounting for more than 70% of the world's magnesium production. The Pidgeon process for smelting magnesium has low equipment investment and cost, but produces 6.5-8.0 tons of magnesium slag per ton of magnesium produced. Currently, the enterprise's magnesium treatment slag is mainly landfilled and stacked, polluting the land and hindering crop growth, and causing resource waste and damage to the ecological environment. In 2019, 2020, and 2021, China's metal magnesium production was 968,500 tons, 961,000 tons, and 960,000 tons, respectively. According to the calculation of 6.5-8.0 tons of slag per ton of magnesium produced, nearly 6.24-7.68 million tons of magnesium slag were produced each year in the past three years. However, the overall utilization rate of magnesium slag in the magnesium smelting industry is only about 30%, and the cumulative amount of stacked magnesium slag is at least 60 million tons and is still increasing year by year. Mechanically produced sand and stone powder is collected and stored during the production of mechanically produced sand, but the storage of these powders not only occupies a large amount of space, but also causes air and water pollution, and also wastes resources. The comprehensive utilization of magnesium slag and stone powder has become a key research direction.

[0005] If the above solid waste is treated and used to prepare aggregate by a disc granulator, partially or completely replacing natural sand and stone aggregate, not only can the resource utilization of magnesium slag and stone powder be realized, but also the problem of magnesium slag occupying farmland and polluting the environment can be solved from the source, and the huge demand for natural sand and stone in infrastructure construction can be met, which meets the demand of the national sustainable development strategy.

[0006] Therefore, it is necessary to provide an improved technical solution to overcome the deficiencies of the prior art. SUMMARY

[0007] The present application aims to provide a magnesium slag and stone powder normal temperature carbon fixation artificial aggregate and a preparation method thereof, so as to solve or improve at least one of the problems of occupying arable land, polluting the environment and natural sand and stone not being able to meet the actual demand caused by magnesium slag and stone powder in the prior art.

[0008] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: a preparation method of a magnesium slag and stone powder normal temperature carbon fixation artificial aggregate, comprising the following steps: (1) adding water to magnesium slag and stone powder and stirring uniformly to obtain a mixture; (2) pouring the mixture into a disc granulator, starting the disc granulator, and spraying water to prepare an aggregate blank; (3) pre-curing the aggregate blank to reduce the water content of the aggregate blank; (4) making the aggregate blank obtained by step (3) undergo a carbonation reaction with CO2 gas to obtain the magnesium slag and stone powder normal temperature carbon fixation artificial aggregate.

[0009] Preferably, the magnesium slag is magnesium slag produced by the Pidgeon process, and the stone powder is powder produced in the process of machine-made sand production; before step (1), the magnesium slag is further dried; the drying temperature is 90-105℃, and the drying time is 3-5h.

[0010] Preferably, the particle size of the magnesium slag is: passing through a 200-mesh sieve and the residue amount is <10%; the particle size of the stone powder is ≤200 mesh.

[0011] Preferably, in step (1), the mass ratio of the magnesium slag to the stone powder is 1:1; in the mixture, the water-material ratio is 5%-10%.

[0012] Preferably, in step (2): the angle of the disc granulator is set to 40°-45°; the amount of water sprayed is 10%-15% of the mixture; the particle size of the aggregate blank is 4.75-15mm.

[0013] Preferably, before step (3), step A of adding magnesium slag into the disc granulator is further included; in step A, the amount of magnesium slag added is 5%-10% of the mixture.

[0014] Preferably, the pre-curing temperature is 35-50℃; the water content of the aggregate blank obtained after the pre-curing is 9%-11%.

[0015] Preferably, in the carbonation reaction, the volume fraction of CO2 in the CO2 gas is 50%-99%, and the carbonation reaction time is 8-24h.

[0016] Preferably, the gas pressure of the CO2 gas is 0.1-0.3MPa; the carbonation reaction is carried out in a steam autoclave.

[0017] The application also provides a magnesium slag stone powder normal-temperature carbon fixation artificial aggregate, which is prepared by the above method. 3 3 .

[0018] Beneficial effects:

[0019] The application makes full use of the carbonation active components such as β-2CaO·SiO2, γ-2CaO·SiO2, CaO and MgO contained in the Pidgeon magnesium slag, so that the artificial aggregate blank has high strength; the stone powder achieves the CaCO3 seed effect and improves the raw material particle size distribution; through carbonization, the CaO and MgO in the magnesium slag are converted into CaCO3 and MgCO3, avoiding the reaction with water to generate Ca(OH)2 and Mg(OH)2, so that the magnesium slag avoids the occurrence of stability defects; the greenhouse gas CO2 is captured and utilized through the aggregate carbonization method to achieve the carbon fixation effect, which reduces the concentration of CO2 in the natural environment while producing the product, and helps to achieve the double carbon target.

[0020] The high-strength carbonized artificial aggregate prepared by the application has a cylinder compressive strength of 14-16 MPa, a water absorption rate of 7%-9%, a bulk density of 1100-1200 kg / m 3 , and an apparent density of 1950-2000 kg / m 3 . The strength is high, the water absorption rate is low, and it fully meets the various performance requirements of high-strength aggregate in the standard GB-T-17431.1-2010, and can replace natural aggregate such as sand and stone as raw material for concrete, greatly reducing the mining and use of natural sand and stone aggregate, effectively protecting the mine and saving natural resources, and providing a sustainable development method for the concrete construction industry. BRIEF DESCRIPTION OF DRAWINGS

[0021] 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 an improper limitation on the application. Among them:

[0022] Figure 1 The XRD graph of the magnesium slag sieved through a 200-mesh screen used in the embodiment of the application;

[0023] Figure 2 The XRD graph of the magnesium slag sieved through a 100-mesh screen used in the comparative example; ​

[0024] Figure 3 XRD pattern of the stone powder with a mesh size of 200 used in the embodiment of the present application;

[0025] Figure 4 A graph of the relationship between the carbonation reaction time and the cylinder compressive strength of the artificial aggregate prepared in the process of preparing the artificial aggregate;

[0026] Figure 5 A graph of the relationship between the water content of the aggregate blank after the pre-curing ends and the carbonation rate of the artificial aggregate prepared;

[0027] Figure 6 A photo of the artificial aggregate prepared in Comparative Example 8;

[0028] Figure 7 A photo of the artificial aggregate prepared in Comparative Example 9;

[0029] Figure 8 A photo of the artificial aggregate prepared in Comparative Example 10;

[0030] Figure 9 A photo of the magnesium slag stone powder room temperature carbonation artificial aggregate prepared in Example 2;

[0031] Figure 10 An XRD pattern of the magnesium slag carbonated on the surface of the magnesium slag stone powder room temperature carbonation artificial aggregate of Example 1;

[0032] Figure 11 An XRD pattern of the magnesium slag carbonated inside the magnesium slag stone powder room temperature carbonation artificial aggregate of Example 1. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0034] 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.

[0035] The present application aims at at least one of the problems of occupying arable land, polluting the environment and natural sand and stone not meeting actual demand caused by magnesium slag and stone powder at present, and provides a preparation method of magnesium slag stone powder normal temperature carbon fixation artificial aggregate. The preparation method of the magnesium slag stone powder normal temperature carbon fixation artificial aggregate of the present application comprises the following steps: (1) adding water to the magnesium slag and stone powder and stirring uniformly to obtain a mixture; (2) pouring the mixture into a disc granulator, starting the disc granulator, and spraying water to prepare an aggregate blank; (3) pre-curing the aggregate blank to reduce the water content of the aggregate blank; (4) making the aggregate blank obtained by step (3) and CO2 gas undergo carbonation reaction to obtain the magnesium slag stone powder normal temperature carbon fixation artificial aggregate.

[0036] The present application makes full use of the components with carbonation activity contained in the Pidgeon magnesium slag, such as β-2CaO·SiO2, γ-2CaO·SiO2, CaO, MgO, etc., uses stone powder to achieve CaCO3 seed effect, and perfects the particle size distribution of raw materials. After carbonation of the magnesium slag, the calcium carbonate crystal form is aragonite and calcite ( Figure 10 ), and the calcium carbonate crystal form in the stone powder is also calcite type ( Figure 3 ). In the carbonation process of the magnesium slag, the calcite type calcium carbonate in the stone powder plays a directional induction role to a certain extent. Through carbonation, CaO and MgO in the magnesium slag are converted into CaCO3 and MgCO3, avoiding the reaction with water to generate Ca(OH)2 and Mg(OH)2, so that the magnesium slag avoids the occurrence of stability defects. The greenhouse gas CO2 is captured and utilized through the carbonation of the aggregate to achieve the effect of carbon fixation, which reduces the concentration of CO2 in the natural environment (the aggregate blank can fix and absorb 10%-15% of its own mass of CO2) while producing the product, helping to achieve the double carbon goal. The CO2 gas can come from industrial waste gas containing carbon dioxide and having no pollution to the environment, such as waste gas discharged in the process of chemical synthesis of urea (containing 90-98% of carbon dioxide).

[0037] In addition, if the magnesium slag is used alone for the preparation of artificial aggregate, the magnesium slag is not easy to shape during granulation. The present application can improve the granulation effect by adding stone powder, which helps to prepare artificial aggregate with good granulation effect and complete form. It should be noted that if the magnesium slag is used alone for the preparation of artificial aggregate, the magnesium slag needs to be dried before being used for the preparation of artificial aggregate, which consumes a large amount of heat and causes waste of energy. By compounding the stone powder (which does not need to be dried when used for the preparation of artificial aggregate in the present application) with the magnesium slag, the amount of magnesium slag can be reduced, and the preparation of an equal amount of artificial aggregate can be realized with significantly reduced energy consumption.

[0038] In the preferred embodiment of the present application, the magnesium slag is the magnesium slag produced by the Pidgeon process, and the stone powder is the fine dust produced in the process of producing machine-made sand; before step (1), the magnesium slag is dried; the drying temperature is 90-105 DEG C, and the drying time is 3-5 h. The magnesium slag used in the present application is the magnesium slag produced by the Pidgeon process, and a large amount of γ-2CaO·SiO2 is produced after cooling, which causes self-pulverization after volume expansion, resulting in that the fine powder with a particle size of less than 150 μm accounts for more than 60% in the magnesium slag; the stone powder used is the fine dust produced in the production of machine-made sand, and 70%-80% of the stone powder can reach a particle size of less than 75 μm in different production cycles.

[0039] In the preferred embodiment of the present application, the particle size of the magnesium slag is: passing through a 200-mesh sieve and the residue is less than 10%; and the particle size of the stone powder is less than or equal to 200 mesh (i.e., passing through a 200-mesh sieve).

[0040] In the preferred embodiment of the present application, in step (1), the mass ratio of the magnesium slag to the stone powder is 1:1; and in the mixture, the water-to-material ratio (the ratio of water to the total mass of the magnesium slag and the stone powder) is 5%-10%. By adding an appropriate amount of water to the mixture of the magnesium slag and the stone powder in step (1), it is helpful to avoid the environmental problems caused by the direct pouring of the magnesium slag and the stone powder into the granulator, and the fine powder flies around with the rotation of the rotating disc due to the insufficient water in the early stage; in addition, it is helpful to reduce the problem of poor uniformity of the water in the aggregate caused by water spraying in the later stage of granulation.

[0041] In the preferred embodiment of the present application, in step (2), the angle of the disc granulator is set to 40-45 DEG; the amount of water sprayed is 10%-15% of the mixture; and the particle size of the aggregate blank body is 4.75-15 mm. In the granulation process, if the amount of water sprayed is too large, the mixture becomes a mud ball in the later stage of granulation, which is not easy to be granulated into regular spherical shape; if the amount of water sprayed is too small, the granulation formed in the later stage is a ball with low density, which has no strength in the early stage and is not easy to be maintained, and the strength of the aggregate obtained after maintenance is low. Preferably, in step (2), the particle size of the water sprayed is less than 0.1 mm (in the granulation process, the nozzle aperture of the watering can is less than 0.1 mm).

[0042] In the preferred embodiment of the present application, before step (3), step A of adding the magnesium slag into the disc granulator is further included; in step A, the amount of the magnesium slag added is 5%-10% (for example, 5%, 6%, 7%, 8%, 9% or 10%) of the mixture. Since the aggregate blank body obtained by granulation has a high water content and a serious surface adhesion, the addition of the magnesium slag can separate different aggregate blank bodies, so that the aggregate blank body formed in the subsequent rotation tends to be a spherical shape.

[0043] In the preferred embodiment of the present application, the temperature of the pre-curing is 35-50℃ (for example, 35℃, 40℃, 45℃ or 50℃); and the water content of the obtained aggregate blank after the pre-curing is 9%-11% (for example, 9%, 10% or 11%).

[0044] In the preferred embodiment of the present application, the volume fraction of CO2 in the CO2 gas during the carbonization reaction is 50%-99% (for example, 50%, 60%, 70%, 80%, 90% or 99%), and the carbonization reaction time is 8-24h (for example, 8h, 12h, 16h, 20h or 24h).

[0045] In the preferred embodiment of the present application, the gas pressure of the CO2 gas is 0.1-0.3MPa (for example, 0.1Mpa, 0.2MPa or 0.3MPa); and the carbonization reaction is carried out in a steam autoclave.

[0046] The present application also provides a magnesium slag stone powder normal-temperature carbon fixation artificial aggregate, which is prepared by the method as described above.

[0047] In the preferred embodiment of the present application, the cylinder compressive strength of the magnesium slag stone powder normal-temperature carbon fixation artificial aggregate is 14-16MPa (for example, 14Mpa, 15Mpa or 16Mpa), the water absorption is 7%-10% (for example, 7%, 8%, 9% or 10%), the bulk density is 1100-1200kg / m 3 (for example, 1100kg / m 3 , 1120kg / m 3 , 1140kg / m 3 , 1160kg / m 3 , 1180kg / m 3 or 1200kg / m 3 ), and the apparent density is 1950-2000kg / m 3 (for example, 1950kg / m 3 , 1960kg / m 3 , 1970kg / m 3 , 1980kg / m 3 , 1990kg / m 3 or 2000kg / m 3 ).

[0048] The magnesium slag stone powder normal-temperature carbon fixation artificial aggregate and the preparation method thereof will be described in detail through specific embodiments.

[0049] The XRD pattern of the magnesium slag passing through a 200-mesh sieve used in the following embodiments is shown in Figure 1 ; and the XRD pattern of the magnesium slag passing through a 100-mesh sieve used in the following embodiments is shown inFigure 2 XRD pattern of the stone powder sieved by a 200-mesh sieve is shown in Figure 1. Figure 3

[0050] Example 1

[0051] The preparation method of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the present example comprises the following steps:

[0052] (1) The wet magnesium slag produced by the Pidgeon process is dried at 105℃ for 3h, then cooled to room temperature in a dryer, and weighed again after 1h. If the weight remains unchanged or the error is less than or equal to 0.4mg, the sample is then ground using a ball mill until the residue on a 200-mesh sieve is less than 10%.

[0053] The stone powder produced by the production of machine-made sand needs to be filtered through a 200-mesh sieve.

[0054] The magnesium slag and the stone powder are mixed in a mass ratio of 1:1, and water is added (water to material ratio of 5%, which refers to the ratio of water to the total amount of magnesium slag and stone powder) to obtain a mixture;

[0055] (2) The mixture obtained in step (1) is fed into a disc granulator to form granules, and the particle size range of the artificial aggregate blank body is 4.75-15mm. The water spraying amount is controlled at 14.4% of the mass of the mixture, the angle of the disc granulator is controlled at 45°, and the rotation speed is controlled at 35r / min. The diameter of the disc granulator is 0.5m. 10% of the mass of the mixture is added to the aggregate blank body before it leaves the granulator;

[0056] (3) The aggregate blank body obtained in step (2) is pre-cured in an environment at a temperature of 40℃ until the water content of the aggregate blank body is 9.96%;

[0057] (4) The aggregate blank body obtained after pre-curing in step (3) is placed in a steam autoclave at room temperature, and CO2 gas is introduced to cause a carbonation reaction between the aggregate blank body obtained after pre-curing in step (3) and the CO2 gas. The volume fraction of CO2 in the CO2 gas is 99.9%, the gas pressure is 0.3MPa, and the carbonation time is 24h. After carbonation, the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the present example is obtained.

[0058] The various properties of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the present example are tested in accordance with GB / T-17431.2-2010 "Lightweight Aggregate and Test Methods Part 2: Test Methods for Lightweight Aggregate". The test results are shown in Table 1 below:

[0059] Table 1

[0060] Bulk density (kg / m 3 )]]> Water absorption (%) Apparent density (kg / m 3 )]]> Cylinder pressure strength (MPa) 1186.27 8.66％ 1979.46 14.678

[0061] ​Example 2

[0062] The preparation method of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the embodiment comprises the following steps:

[0063] (1) The wet magnesium slag produced by the Pidgeon process is placed at 105°C for drying for 3 hours, then cooled to room temperature in a dryer, and weighed again after 1 hour. If the weight remains unchanged or the error is less than or equal to 0.4 mg, the whole is cooled to room temperature and then ground by a ball mill until the residue on a 200-mesh screen is less than 10%.

[0064] The stone powder produced by the production of machine-made sand needs to be filtered through a 200-mesh screen to remove excess impurities.

[0065] The mixture is prepared by mixing magnesium slag and stone powder in a mass ratio of 1:1 and adding water in a water-to-material ratio (the ratio of water to the total mass of magnesium slag and stone powder) of 10%.

[0066] (2) The uniformly mixed mixture of step (1) is fed into a disc granulator for granulation to obtain artificial aggregate blanks with a particle size range of 4.75-15 mm. The water spraying amount is controlled at 8.83% of the mass of the mixture, the angle of the disc granulator is controlled at 45°, and the rotation speed is controlled at 35 r / min. The diameter of the disc granulator is 0.5 m. 10% of the mass of the mixture is added to the aggregate blanks before they leave the granulator.

[0067] (3) The aggregate blanks obtained by step (2) are pre-cured in an environment at a temperature of 40°C until the water content of the aggregate blanks is 9.88%.

[0068] (4) The aggregate blanks obtained after pre-curing in step (3) are placed in a steam autoclave at room temperature, and CO2 gas is introduced to cause a carbonation reaction between the aggregate blanks obtained after pre-curing in step (3) and the CO2 gas. The volume fraction of CO2 in the CO2 gas is 99.9%, the gas pressure is 0.3 MPa, and the carbonation time is 24 hours. After carbonation, the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the embodiment is obtained.

[0069] The various properties of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the embodiment are tested in accordance with GB / T-17431.2-2010 "Lightweight Aggregate and Test Methods Part 2: Test Methods for Lightweight Aggregate". The test results are shown in Table 2 below:

[0070] Table 2

[0071] Bulk density (kg / m 3 )]]> Water absorption (%) Apparent density (kg / m 3 )]]> Cylinder pressure strength (MPa) 1174.87 9.05 1953.40 15.285

[0072] Example 3

[0073] The preparation method of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of the embodiment comprises the following steps:

[0074] (1) The wet magnesium slag produced by the Pidgeon process is dried at 105°C for 3 hours, then placed in a desiccator to cool to room temperature and weighed. The same operation is repeated 1 hour later. If the weighed mass remains unchanged or the error is ≤0.4 mg, the residue is ground in a ball mill until the residue on a 200-mesh sieve is less than 10%.

[0075] The stone powder produced by the production of machine-made sand needs to be filtered through a 200-mesh screen to remove excess impurities;

[0076] The magnesium slag and the stone powder are prepared in a mass ratio of 1:1, water is added in a water-to-material ratio (the ratio of water to the total mass of the magnesium slag and the stone powder) of 5%, and the mixture is uniformly mixed to obtain a mixture;

[0077] (2) the mixed material obtained in step (1) is fed into a disc granulator for granulation to obtain an artificial aggregate blank having a particle size range of 4.75-15 mm, wherein the uniform water spraying amount is controlled at 14.52% of the mass of the mixed material, the angle of the disc granulator is controlled at 45°, the speed is controlled at 45 r / min, and the diameter of the disc granulator is 0.5 m; magnesium slag is added at 10% of the mass of the mixed material before the aggregate blank leaves the granulator;

[0078] (3) pre-curing the aggregate body obtained by the treatment in step (2) in an environment at a temperature of 40° C. until the moisture content of the aggregate body reaches 9.88%;

[0079] (4) placing the aggregate body obtained after pre-curing in step (3) into an autoclave at room temperature, introducing CO2 gas, and causing the aggregate body obtained after pre-curing in step (3) to undergo a carbonization reaction with the CO2 gas; wherein the volume fraction of CO2 in the CO2 gas is 99.9%, the gas pressure is 0.3 MPa, and the carbonization time is 24 h; after the carbonization is completed, the magnesium slag stone powder room temperature carbonization artificial aggregate of this embodiment is obtained.

[0080] The various properties of the magnesium slag and stone powder room temperature carbon fixation artificial aggregate of this embodiment were tested in accordance with GB / T-17431.2-2010 "Lightweight Aggregate and Its Test Methods Part 2: Lightweight Aggregate Test Methods". The test results are shown in Table 3 below:

[0081] Table 3

[0082] Bulk density (kg / m 3 )]]> Water absorption (%) Apparent density (kg / m 3 )]]> Cylinder pressure strength (MPa) 1185.32 9.11％ 1974.16 15.310

[0083] Example 4

[0084] The preparation method of magnesium slag stone powder room temperature carbon fixation artificial aggregate of this embodiment comprises the following steps:

[0085] (1) The wet magnesium slag produced by the Pidgeon process is dried at 105°C for 3h, then cooled to room temperature in a desiccator, weighed, and then the same operation is repeated after 1h. The mass is unchanged or the error is ≤0.4mg. Then, the ball mill is used to grind the magnesium slag until the residue on a 200 mesh screen is <10% when the magnesium slag is cooled to room temperature;

[0086] The stone powder produced by the production of machine-made sand needs to be filtered through a 200 mesh screen to remove excess impurities.

[0087] The mixed material is obtained by mixing the magnesium slag and the stone powder at a mass ratio of 1:1, adding water at a water-to-material ratio (the ratio of water to the total mass of magnesium slag and stone powder) of 10%, and mixing uniformly.

[0088] (2) The mixed material obtained in step (1) is put into a disc granulator to be granulated, and artificial aggregate blanks with a particle size range of 4.75-15mm are obtained. The water spraying amount is controlled at 9.07% of the mass of the mixed material, the angle of the disc granulator is controlled at 45°, and the rotation speed is controlled at 45r / min. The diameter of the disc granulator is 0.5m. 10% of the mass of the mixed material is added to the aggregate blanks before they leave the granulator.

[0089] (3) The aggregate blanks obtained in step (2) are pre-cured in an environment with a temperature of 40°C until the water content of the aggregate blanks is 9.64%.

[0090] (4) The aggregate blanks obtained after pre-curing in step (3) are placed in a steam autoclave at room temperature, and CO2 gas is introduced to cause a carbonation reaction between the aggregate blanks obtained after pre-curing in step (3) and the CO2 gas. The volume fraction of CO2 in the CO2 gas is 99.9%, the gas pressure is 0.3MPa, and the carbonation time is 24h. After the carbonation is completed, the magnesium slag stone powder carbonation artificial aggregate at room temperature of this embodiment is obtained.

[0091] The properties of the magnesium slag stone powder carbonation artificial aggregate at room temperature of this embodiment are tested according to GB / T-17431.2-2010 "Lightweight Aggregate and Test Methods Part 2: Test Methods for Lightweight Aggregate". The test results are shown in Table 4.

[0092] Table 4

[0093] Bulk density (kg / m 3 )]]> Water absorption (%) Apparent density (kg / m 3 )]]> Cylinder pressure strength (MPa) 1201.94 8.58 1997.08 14.617

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 2 is only that the carbonation reaction time in step (4) is 2h, 4h, 6h, 8h and 12h respectively; the rest is the same as Example 2.

[0096] Comparative Example 2

[0097] The difference between the present comparative example and Example 1 is only that in step (3), the water content of the aggregate blank body after the pre-curing is 5.95%, 7.01%, 7.55% and 8.93% respectively, and the rest is consistent with Example 1.

[0098] Comparative Example 3

[0099] The difference between the present comparative example and Example 2 is only that:

[0100] In step (3), the pre-curing time is 0h (the water content of the aggregate blank body is 18.89%), 1h (the water content of the aggregate blank body after the pre-curing is 16.93%), 2h (the water content of the aggregate blank body after the pre-curing is 10.97%), 2.5h (the water content of the aggregate blank body after the pre-curing is 7.44%), 3h (the water content of the aggregate blank body after the pre-curing is 10.18%), 3.5h (the water content of the aggregate blank body after the pre-curing is 5.75%), 4h (the water content of the aggregate blank body after the pre-curing is 6.80%) and 6h (the water content of the aggregate blank body after the pre-curing is 5.20%);

[0101] In step (4), the carbonization time is 8h;

[0102] The rest is consistent with Example 2.

[0103] Comparative Example 4

[0104] The difference between the present comparative example and Example 1 is only that the magnesium slag and the stone powder are respectively passed through a 100-mesh sieve; the rest is consistent with Example 1.

[0105] Comparative Example 5

[0106] The difference between the present comparative example and Example 2 is only that the magnesium slag and the stone powder are respectively passed through a 100-mesh sieve; the rest is consistent with Example 2.

[0107] Comparative Example 6

[0108] The difference between the present comparative example and Example 3 is only that the magnesium slag and the stone powder are respectively passed through a 100-mesh sieve; the rest is consistent with Example 3.

[0109] Comparative Example 7

[0110] The difference between the present comparative example and Example 4 is only that the magnesium slag and the stone powder are respectively passed through a 100-mesh sieve; the rest is consistent with Example 4.

[0111] Comparative Example 8

[0112] The difference between the present comparative example and Example 2 is only that the stone powder is omitted, and only the magnesium slag is used to prepare the artificial aggregate; the rest is consistent with Example 2.

[0113] Comparative Example 9

[0114] The difference between the present comparative example and Example 2 is only that the mass ratio of magnesium slag to stone powder is 9:1; the rest is consistent with Example 2.

[0115] Comparative Example 10

[0116] The difference between the present comparative example and Example 2 is only that the mass ratio of magnesium slag to stone powder is 7:3; the rest is consistent with Example 2.

[0117] Experimental Example

[0118] 1. Investigation of the influence of carbonization reaction time in step (4) on the performance of artificial aggregate:

[0119] According to GB / T-17431.2-2010 "Lightweight Aggregate and Its Test Methods Part 2: Test Methods for Lightweight Aggregate", the performance of the magnesium slag stone powder carbonation artificial aggregate of Comparative Example 1 at room temperature was tested. The test results are shown in Table 5 and Figure 4

[0120] Table 5

[0121]

[0122] Through data analysis of Table 5 and Figure 4 it can be seen that within 0-8h, with the extension of carbonization reaction time, the cylinder compressive strength of the artificial aggregate is rapidly improved; within 8-24h, with the extension of carbonization reaction time, the cylinder compressive strength of the artificial aggregate is slowly improved.

[0123] 2. Investigation of the influence of water content of aggregate blank after pre-curing in step (3) on the performance of artificial aggregate:

[0124] According to GB / T-17431.2-2010 "Lightweight Aggregate and Its Test Methods Part 2: Test Methods for Lightweight Aggregate", the performance of the artificial aggregate of Comparative Example 2 was tested. The test results are shown in Table 6:

[0125] Table 6

[0126]

[0127] Data analysis of Table 6 shows that the water content of aggregate blank after pre-curing has a significant influence on the cylinder compressive strength, water absorption, apparent density and bulk density of the artificial aggregate prepared; if the water content of aggregate blank after pre-curing is less than 9%, the cylinder compressive strength and apparent density and bulk density of the artificial aggregate prepared are significantly reduced, and the water absorption is increased.

[0128] 3. Investigation of the influence of water content of aggregate blank after pre-curing in step (3) on the performance of artificial aggregate (carbonization time in step (4) is 8h):​

[0129] After step (4) is completed, the carbon sequestration rate of the artificial aggregate of Comparative Example 3 is detected; the detection result is shown in Table 6. Figure 5

[0130] Data analysis of Table 6 shows that after the pre-curing is completed, when the water content of the aggregate blank increases from 5% to 10%, the carbon sequestration rate increases accordingly (carbon sequestration rate formula: x = (y-z) / y, wherein x is the carbon sequestration rate, y is the mass of the sample aggregate blank after removing the water content before carbonation, and z is the mass of the aggregate sample after carbonation and 105° drying for 24 hours); when the water content of the aggregate blank increases from 10% to 18% after the pre-curing is completed, the carbon sequestration rate decreases accordingly. Figure 5 Data analysis of Table 6 shows that after the pre-curing is completed, when the water content of the aggregate blank increases from 5% to 10%, the carbon sequestration rate increases accordingly (carbon sequestration rate formula: x = (y-z) / y, wherein x is the carbon sequestration rate, y is the mass of the sample aggregate blank after removing the water content before carbonation, and z is the mass of the aggregate sample after carbonation and 105° drying for 24 hours); when the water content of the aggregate blank increases from 10% to 18% after the pre-curing is completed, the carbon sequestration rate decreases accordingly.

[0131] 4. Investigate the influence of the particle size of magnesium slag and stone powder on the performance of the artificial aggregate prepared:

[0132] According to GB / T-17431.2-2010 "Lightweight Aggregate and Test Methods Part 2: Test Methods for Lightweight Aggregate", the properties of the magnesium slag stone powder room temperature carbonation artificial aggregate of Comparative Examples 4-7 are tested. The test results are shown in Table 7:

[0133] Table 7

[0134]

[0135] Analysis of the corresponding data in Table 7 shows that the cylinder compressive strength of the aggregate prepared by using stone powder and magnesium slag with a mesh size of 100 is greatly reduced, the water absorption is increased, and the apparent density and bulk density are reduced.

[0136] 5. Investigate the influence of the amount ratio of magnesium slag and stone powder on the artificial aggregate prepared:

[0137] (1) According to GB / T-17431.2-2010 "Lightweight Aggregate and Test Methods Part 2: Test Methods for Lightweight Aggregate", the properties of the magnesium slag stone powder room temperature carbonation artificial aggregate of Comparative Examples 8-10 are tested. The test results are shown in Table 8:

[0138] Table 8

[0139]

[0140] Data analysis of Table 8 shows that when the amount ratio of magnesium slag and stone powder changes (the amount of magnesium slag is greater than that of stone powder), the cylinder compressive strength, apparent density and bulk density of the artificial aggregate prepared are significantly reduced, and the water absorption is increased.

[0141] (2) Influence of the amount ratio of magnesium slag and stone powder on the granulation effect:

[0142] ​​The photos of the artificial aggregate prepared in Comparative Examples 8-10 and Example 2 are shown in sequence as Figure 6-9

[0143] It can be seen from Figure 6-9 that when only magnesium slag is used to prepare the artificial aggregate, the aggregate green body has different shapes and low sphericity, and is prone to form flat spheres or deformed spheres, which can cause the strength of the aggregate to decrease. With the increase of the amount of stone powder (gradually increased to 50%), the forming effect of the aggregate green body is gradually improved, the sphericity of the artificial aggregate prepared is gradually increased, and the performance of the artificial aggregate is also obviously improved.

[0144] 6. The magnesium slag carbonized product on the surface and inside of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of Example 1 was analyzed by XRD respectively:

[0145] The XRD pattern of the magnesium slag carbonized product on the surface of the magnesium slag stone powder room temperature carbon fixation artificial aggregate of Example 1 is shown in Figure 10 ; and the XRD pattern of the magnesium slag carbonized product inside the magnesium slag stone powder room temperature carbon fixation artificial aggregate of Example 1 is shown in Figure 11

[0146] It can be seen from Figure 10-11 that the surface layer magnesium slag has been completely carbonized, and mainly has two (calcite, aragonite) crystal forms of calcium carbonate; the degree of carbonization of the inner layer magnesium slag is lower than that of the surface layer magnesium slag, and in addition to showing a strong calcite type calcium carbonate peak, it also shows the existence of γ-C2S and β-C2S.

[0147] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​​

Claims

1. A method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate, characterized in that: The steps include: (1) Add water to magnesium slag and stone powder and stir evenly to obtain a mixture; (2) pouring the mixed material into a disc granulator, starting the disc granulator, spraying water, and preparing an aggregate body; (3) Pre-curing the aggregate blank to reduce the moisture content of the aggregate blank; the moisture content of the aggregate blank obtained after the pre-curing is 9%-11%; (4) allowing the aggregate blank obtained by the treatment in step (3) to undergo a carbonization reaction with CO2 gas to obtain the magnesium slag stone powder room temperature carbon fixation artificial aggregate; In step (1), the mass ratio of the magnesium slag to the stone powder is 1:1; the particle size of the magnesium slag is: passing through a 200-mesh sieve with a sieve residue of less than 10%; and the particle size of the stone powder is ≤200 mesh.

2. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 1, characterized in that: The magnesium slag is the magnesium slag produced by the Pidgeon process of magnesium smelting, and the stone powder is the powder produced in the process of machine-made sand production; Before step (1), the method further includes the step of drying the magnesium slag; The drying temperature is 90-105° C., and the drying time is 3-5 hours.

3. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 1, characterized in that: In step (1), the ratio of water to the total mass of magnesium slag and stone powder in the mixture is 5%-10%.

4. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 1, characterized in that: In step (2): the angle of the disc granulator is set at 40°-45°; The amount of water sprayed is 10%-15% of the mixture; The particle size of the aggregate blank is 4.75-15 mm.

5. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 1, characterized in that: Before step (3), the method further includes step A: adding magnesium slag to the disc granulator; In step A, the amount of magnesium slag added is 5%-10% of the mixture.

6. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 1, characterized in that: The pre-curing temperature is 35-50°C.

7. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 1, characterized in that: During the carbonization reaction, the volume fraction of CO2 in the CO2 gas is 50%-99%, and the carbonization reaction time is 8-24 hours.

8. The method for preparing magnesium slag stone powder room temperature carbon fixation artificial aggregate according to claim 7, characterized in that: The gas pressure of the CO2 gas is 0.1-0.3 MPa; The carbonization reaction is carried out in an autoclave.

9. A magnesium slag stone powder room temperature carbon fixation artificial aggregate, characterized in that: Prepared by the method according to any one of claims 1 to 8; The cylinder compressive strength of the magnesium slag stone powder carbon-fixing artificial aggregate at room temperature is 14-16MPa, the water absorption rate is 7%-9%, and the bulk density is 1100-1200kg / m 3 , apparent density is 1950-2000kg / m 3 .

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