Magnesium slag artificial aggregate and preparation method thereof

Abstract

The invention discloses a magnesium slag artificial aggregate and a preparation method thereof. The method comprises the following steps: 1, drying magnesium slag, crushing, and grinding into magnesium slag fine powder through a ball mill and a planetary ball mill; 2, adding a binding agent diluent into the magnesium slag fine powder subjected to ball milling in the step 1, stirring, mixing and ageing; step 3, performing compression molding on the aged material in the step 2 by adopting a semi-dry method to obtain a sample; 4, naturally airing the sample obtained in the step 3, and then putting the sample into carbonation equipment for carbonation treatment of the sample; and 5, cooling and crushing the carbonated sample to obtain the artificial aggregate prepared from the magnesium slag. Through CO2 carbonation, the aggregate with the magnesium metal reducing slag as the raw material is prepared, the utilization rate of the magnesium metal reducing slag is increased, and the carbon dioxide emission and the natural aggregate demand are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of building material preparation, and particularly relates to a magnesium slag artificial aggregate and a preparation method thereof. Background Art

[0002] Magnesium reduction slag is a solid waste generated during the production of magnesium. Currently, it is widely used in building materials, rubber fillers, and as a raw material in the metallurgical industry. Magnesium reduction slag, primarily composed of dicalcium silicate and free magnesium oxide, has a high carbonation potential. Preparing it into aggregate, partially or completely replacing natural sand and gravel aggregate, not only improves the utilization rate of magnesium reduction slag and solves the problem of magnesium slag landfill and accumulation, but also reduces the demand for natural sand and gravel aggregate, protecting the ecological environment while achieving resource utilization.

[0003] Current reports have shown that the use of magnesium reduction slag to prepare composite reinforced aggregates can reduce limestone consumption in the cement industry, thereby reducing emissions. Alkaline minerals react with carbon dioxide to generate stable and irreversible carbonate compounds to carbonize and store CO2. This not only allows the carbonation products to act as aggregates in the material, but also further improves the compressive strength and long-term stability of the specimens. Mineral storage converts CO2 into solid carbonates through chemical reactions, achieving long-term storage. This method not only reduces the concentration of CO2 in the atmosphere, but also produces valuable minerals.

[0004] Research has shown that modified magnesium slag can be used to produce materials with dense structure and high mechanical strength. However, current research still shows that the utilization rate of magnesium slag is still low, which cannot quickly solve the problem of magnesium slag accumulation and landfill. Therefore, it is necessary to develop a new method that can use large amounts of magnesium slag as raw material aggregate, while meeting the requirements of environmental protection and sustainable development while ensuring the required strength. Summary of the Invention

[0005] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a magnesium slag artificial aggregate and a preparation method thereof, wherein aggregate using metallic magnesium reduction slag as raw material is prepared by CO2 carbonation, thereby improving the utilization rate of metallic magnesium reduction slag, reducing carbon dioxide emissions and the demand for natural aggregate.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing magnesium slag artificial aggregate comprises the following steps:

[0008] Step 1: After drying the magnesium slag, it is crushed by a jaw crusher and then ground into magnesium slag fine powder by a ball mill and a planetary ball mill;

[0009] Step 2: Add the binder dilution solution to the magnesium slag fine powder ball-milled in step 1, stir and mix, and then slurry;

[0010] Step 3: The material after being slurried in step 2 is pressed into shape using a semi-dry method to obtain a sample;

[0011] Step 4: After the sample obtained in step 3 is naturally dried, it is placed in a carbonation device for carbonation treatment;

[0012] Step 5: Cool and crush the carbonated sample to obtain artificial aggregate prepared from magnesium slag.

[0013] In the step 1, the main chemical components of the magnesium slag are CaO, SiO2, and MgO, and the main mineral components are γ-C2S, β-C2S, and a small amount of periclase and ferrosilicon.

[0014] In the step 1, the magnesium slag is produced by the Pidgeon process for magnesium smelting, the ball milling time is 30 to 120 minutes, the planetary ball milling time is 0 to 90 minutes, and the particle size of the fine powder after ball milling is 0.05 to 100 μm.

[0015] In the step 1, the drying temperature is 90-120° C. and the drying time is 24-48 hours.

[0016] In the step 2, the amount of binder added is 5 to 30% of the amount of the magnesium slag fine powder obtained in the step 1.

[0017] In the step 2, the mixing time of the mixed materials in the mixer is 10 to 20 minutes, and after mixing, the mixed materials are placed in a sealed container or plastic bag and simmered for 2 to 6 hours.

[0018] In the step 3, the molding pressure is 80-200 MPa.

[0019] In the step 4, the product is naturally dried in the sun for 0.5 to 1 day.

[0020] In step 4, a carbonation reaction is carried out in a controllable carbonation device, and CO2 is delivered by a bubbling method. The conditions are: the carbonation device is kept at 40-70°C for 4-72 hours, the CO2 flow rate is 2L / min-10L / min, and the compressive strength of the magnesium slag artificial aggregate is adjusted by adjusting the magnesium slag ball milling time and the CO2 carbonation time. This condition can make the sample have a higher pressure resistance value.

[0021] The particle size of magnesium slag decreases with the increase of ball milling time. The activity of magnesium slag is highest between 60min and 90min, and the compressive strength of magnesium slag artificial aggregate is the highest. When the ball milling time is greater than 90min, the compressive strength of magnesium slag artificial aggregate will gradually decrease.

[0022] As the CO2 carbonation time increases, the compressive strength of magnesium slag artificial aggregate gradually increases and reaches a peak at around 24 hours. As the carbonation time increases, its compressive strength slowly decreases.

[0023] In the step 5, the cooling time is 12 to 48 hours, and the particle size range after crushing is 0.5 to 5 mm.

[0024] A magnesium slag artificial aggregate, in which CaCO3 grows and covers the surface of uncarbonized hydration products and C2S particles, and the generated magnesium carbonate, calcite and aragonite provide compressive strength.

[0025] Beneficial effects of the present invention:

[0026] Aggregates are prepared using magnesium reduction slag and carbonation reaction with CO2 in flue gas, eliminating the need for complex maintenance and preparation techniques. This reduces the difficulty of magnesium slag aggregate preparation while significantly increasing its utilization rate. This also further addresses the issue of CO2 utilization in industrial solid waste and flue gas. By regulating the ball milling time of the magnesium slag raw material and the CO2 carbonation time, temperature, and flow rate, the phase composition of the synthetic material can be controlled. A carbonate solution is generated through a bubbling method, enabling it to undergo a carbonation reaction with the Ca2SiO4 in the sample. The increase in temperature accelerates the diffusion rate of CO2 into the sample. The resulting magnesium carbonate, calcite, and aragonite provide bonding strength, achieving reactive bonding and imparting higher strength to the sample.

[0027] At the same time, the magnesium slag artificial aggregate prepared by the present invention has high strength and can replace natural aggregates such as sand and stone as raw materials for concrete, significantly reducing the mining and use of natural sand and stone aggregates, effectively protecting mines, saving natural resources, and providing a sustainable development method for the concrete construction industry. The method has the advantages of low raw material cost, high magnesium slag utilization rate, simple preparation technology, strong operability, and high cost performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the XRD diagram of the metallic magnesium reduction slag raw material.

[0029] Figure 2 This is the XRD pattern of the magnesium slag artificial aggregate prepared in Example 1.

[0030] Figure 3 This is the microstructure of the product of Example 1.

[0031] Figure 4 This is the microstructure of the product of Example 2.

[0032] Figure 5 This is the microstructure of the product of Example 3.

[0033] Figure 6This is the microstructure of the product of Example 4. DETAILED DESCRIPTION

[0034] The present invention will be described in further detail below with reference to the accompanying drawings.

[0035] This invention discloses a magnesium slag artificial aggregate and its preparation method. Using magnesium reduction slag as raw material, CO2 from waste gas is introduced to initiate a carbonation reaction. By regulating the milling time of the magnesium slag and the CO2 carbonation time, temperature, and flow rate, the phase composition of the synthesized material is controlled. The resulting magnesium carbonate, calcite, and aragonite provide bonding strength, achieving reactive bonding and resulting in a higher strength sample. Compared to natural aggregates and sand and gravel, magnesium slag artificial aggregate offers lower manufacturing costs and higher compressive strength.

[0036] The preparation method of the present invention specifically comprises the following steps:

[0037] a. Abrasive: After drying the magnesium slag, crush it with a jaw crusher, and then grind it into fine powder with a ball mill and a planetary ball mill.

[0038] In the present invention, the ball milling time is 120 minutes, the ball milling time is 0 minutes to 90 minutes, and the particle size of the fine powder after ball milling is 0.05 to 100 μm.

[0039] b. Mixing: The amount of binder added is 20% of the amount of magnesium slag fine powder after ball milling. The mixing time in the mixer is 10 to 20 minutes to ensure that the materials are mixed evenly.

[0040] c. Sleeping material: After mixing, place the mixture in a sealed container or plastic bag and sleep for 2 to 6 hours.

[0041] d. Molding: Use a hydraulic press to press the above-mentioned slurry into a Φ10×10 cylindrical sample with a molding pressure of 100 MPa.

[0042] e. Drying: Allow the formed specimen to dry naturally for 0.5 to 1 day.

[0043] f. CO2 carbonation: Place the air-dried sample into the CO2 carbonation equipment and input CO2 into the equipment by bubbling. Keep the carbonation equipment at 40-70°C for 4-72 hours, and the CO2 flow rate is 2L / min-6L / min.

[0044] g. Cool and crush the carbonated sample to obtain artificial aggregate prepared from magnesium slag.

[0045] The magnesium slag artificial aggregate prepared by the present invention is regulated by controlling the magnesium slag ball milling time, CO2 gas flow rate, carbonation time, and temperature to control the phase composition of the synthesized material. The generated magnesium carbonate, calcite, and aragonite provide bonding strength, achieving reactive bonding and resulting in a high strength sample. The resulting artificial aggregate has low raw material costs, high magnesium slag utilization, simple preparation technology, strong operability, and high cost-effectiveness.

[0046] The following are several optimal embodiments of the present invention. The present invention is not limited to these embodiments. Experiments conducted by the applicant have shown that magnesium slag artificial aggregate can be prepared within the scope given by the present invention.

[0047] Example 1:

[0048] The chemical composition of the magnesium slag raw materials used is shown in Table 1, and the phase composition is as follows: Figure 1 As shown in Table 1, the main chemical components of magnesium slag are CaO, SiO2, and MgO, and its main mineral components are γ-C2S, β-C2S, and a small amount of periclase and ferrosilicon. Table 1 Chemical composition of magnesium slag (wt%)

[0049] raw materials CaO <![CDATA[SiO2]]> MgO <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> <![CDATA[P2O5]]> <![CDATA[Na2O]]> <![CDATA[SO3]]> SrO <![CDATA[K2O]]> LOI magnesium slag 62.76 25.09 7.17 3.67 0.67 0.12 0.07 0.12 0.02 - 0.33

[0050] The magnesium slag is crushed by a jaw crusher and ground into fine powder by a ball mill, and then ball-milled in a planetary ball mill for 0 min. The binder is added in an amount of 20%. After the ingredients are fully mixed, they are formed on a hydraulic press with a molding pressure of 150 MPa. The sample is naturally cooled and dried for 1 day. The dried sample is placed in a carbonation box, and CO2 air flow is introduced. It is heated to 60°C to start carbonation at a CO2 flow rate of 4 L / min. The carbonation is carried out for 24 hours to obtain magnesium slag carbonated artificial aggregate.

[0051] The phase composition of the sample is Figure 2 As shown in the figure, magnesium carbonate, calcite and aragonite were generated in the sample after carbonation, and the main crystal peak intensity of γ-C2S and β-C2S decreased.

[0052] Microstructure Figure 3 As shown in Figure 2, CaCO3 grows and covers the surface of the uncarbonized hydration products and C2S particles, and the generated magnesium carbonate, calcite, and aragonite provide compressive strength. The properties are shown in Table 2.

[0053] Table 2 Performance of magnesium slag artificial aggregate corresponding to Example 1

[0054] Serial number Ball milling time / min Carbonation time / h Compressive strength / MPa 1 0 24 105.9

[0055] Example 2:

[0056] The magnesium slag is crushed by a jaw crusher and ground into fine powder by a ball mill, and then ball milled in a planetary ball mill for 30 minutes. The binder is added in an amount of 20%. After the ingredients are fully mixed, they are formed on a hydraulic press with a molding pressure of 150MPa. The sample is naturally cooled for half a day, and the dried sample is placed in a carbonation box. CO2 airflow is introduced, and the sample is heated to 60°C to start carbonation. The CO2 flow rate is 4L / min and the carbonation is carried out for 8 hours to obtain magnesium slag carbonated artificial aggregate.

[0057] Microstructure Figure 4 As shown in Figure 3, the generated CaCO3 covers the surface of the uncarbonated hydration products and C2S particles, and the generated magnesium carbonate, calcite, and aragonite provide compressive strength. The properties are shown in Table 3.

[0058] Table 3 Performance of magnesium slag artificial aggregate corresponding to Example 2

[0059] Serial number Ball milling time / min Carbonation time / h Compressive strength / MPa 2 30 8 116.0

[0060] Example 3:

[0061] The magnesium slag is crushed into fine powder by a jaw crusher and ground into fine powder by a ball mill, and then ball milled in a planetary ball mill for 30 minutes. The binder is added in an amount of 20%. After the ingredients are fully mixed, they are formed on a hydraulic press with a molding pressure of 150MPa. The sample is naturally cooled and dried for 1 day. The dried sample is placed in a carbonation box, and CO2 air flow is introduced. It is heated to 60°C to start carbonation. The CO2 flow rate is 4L / min and the carbonation is carried out for 24 hours to obtain magnesium slag carbonated artificial aggregate.

[0062] Microstructure Figure 5 As shown in Figure 4, CaCO3 grows and covers the surface of uncarbonized hydration products and C2S particles, and the generated calcite and aragonite provide compressive strength. The properties are shown in Table 4.

[0063] Table 4 Performance of magnesium slag artificial aggregate corresponding to Example 3

[0064] Serial number Ball milling time / min Carbonation time / h Compressive strength / MPa 3 30 24 139.9

[0065] Example 4:

[0066] The magnesium slag is crushed by a jaw crusher and ground into fine powder by a ball mill, and then ball milled by a planetary ball mill for 90 minutes. The binder is added in an amount of 20%. After the ingredients are fully mixed, they are formed on a hydraulic press with a molding pressure of 150MPa. The sample is naturally cooled for half a day to 1 day. The dried sample is placed in a carbonation box, and CO2 air flow is introduced. It is heated to 60°C to start carbonation. The CO2 flow rate is 4L / min and the carbonation is carried out for 24 hours to obtain magnesium slag carbonated artificial aggregate.

[0067] Sample

[0068] Microstructure Figure 6 As shown in Table 5, the uncarbonated hydration products of CaCO3 and the magnesium carbonate, calcite, and aragonite generated on the surface of C2S particles provide compressive strength.

[0069] Table 5 Performance of magnesium slag artificial aggregate corresponding to Example 4

[0070] Serial number Ball milling time / min Carbonation time / h Compressive strength / MPa 4 90 24 117.8

Claims

1. A method for preparing magnesium slag artificial aggregate, characterized in that: The following steps are included: Step 1: After drying the magnesium slag, crush it, and then grind it into magnesium slag fine powder in a ball mill and a planetary ball mill; Step 2: Add the binder dilution solution to the magnesium slag fine powder ball-milled in step 1, stir and mix, and then slurry; Step 3: The material after being slurried in step 2 is pressed into shape using a semi-dry method to obtain a sample; Step 4: After the sample obtained in step 3 is naturally dried, it is placed in a carbonation device for carbonation treatment; Step 5: Cool and crush the carbonated sample to obtain artificial aggregate prepared from magnesium slag.

2. The method for preparing magnesium slag artificial aggregate according to claim 1, wherein: In the step 1, the magnesium slag is produced by the Pidgeon process for magnesium smelting, the ball milling time is 30 to 120 minutes, the planetary ball milling time is 0 to 90 minutes, and the particle size of the fine powder after ball milling is 0.05 to 100 μm.

3. The method for preparing magnesium slag artificial aggregate according to claim 1, characterized in that: In the step 1, the drying temperature is 90-120° C. and the drying time is 24-48 hours.

4. The method for preparing magnesium slag artificial aggregate according to claim 1, wherein: In the step 2, the amount of binder added is 5 to 30% of the amount of the magnesium slag fine powder obtained in the step 1.

5. The method for preparing magnesium slag artificial aggregate according to claim 1, characterized in that: In the step 2, the mixing time of the mixed materials in the mixer is 10 to 20 minutes, and after mixing, the mixed materials are placed in a sealed container or plastic bag and simmered for 2 to 6 hours.

6. The method for preparing magnesium slag artificial aggregate according to claim 1, characterized in that: In the step 3, the molding pressure is 80-200 MPa.

7. The method for preparing magnesium slag artificial aggregate according to claim 1, characterized in that: In the step 4, the product is naturally dried in the sun for 0.5 to 1 day.

8. The method for preparing magnesium slag artificial aggregate according to claim 1, characterized in that: In step 4, a carbonation reaction is carried out in a controllable carbonation device, and CO2 is delivered by bubbling method. The conditions are: the carbonation device is kept at 40-70°C for 4-72 hours, and the CO2 flow rate is 2L / min-10L / min.

9. The method for preparing magnesium slag artificial aggregate according to claim 1, characterized in that: In the step 5, the cooling time is 12 to 48 hours, and the particle size range after crushing is 0.5 to 5 mm.

10. A magnesium slag artificial aggregate obtained by the method according to any one of claims 1 to 9, characterized in that: CaCO3 grows and covers the surface of uncarbonized hydration products and C2S particles, and the generated magnesium carbonate, calcite and aragonite provide compressive strength.

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