A carbon-fixed, water-resistant gypsum product and its preparation method

Abstract

This invention relates to the field of solid waste resource utilization, and more particularly to a carbon-fixed, water-resistant gypsum product and its preparation method. The raw materials for the carbon-fixed, water-resistant gypsum product include α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, red mud, nano-calcium carbonate, nano-silica, and water; wherein the mass ratio of the α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, and red mud is 50~80:10~25:7.5~15:2.5~10. This invention can reduce the use of organic hydrophobic substances and cementitious materials, lower the cost of gypsum products, and effectively solve the problem of poor water resistance of gypsum, significantly improving the water resistance, strength, and service life of gypsum products.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, and in particular to a carbon-fixing, water-resistant gypsum product and its preparation method. Background Technology

[0002] Industrial waste gypsum is a waste residue mainly composed of calcium sulfate, emitted from coal-fired power plants, chemical plants, and other related industries. Examples include flue gas desulfurization gypsum, phosphogypsum, titanium gypsum, fluorogypsum, citric acid gypsum, and salt gypsum. With the increasing production of industrial by-product gypsum year by year, the large-scale stockpiling of industrial waste gypsum not only occupies land and wastes resources, but its acidic and other harmful substances easily pollute the surrounding environment, seriously affecting and restricting the ecology. Therefore, accelerating the resource utilization of industrial waste gypsum is imperative. Gypsum products made from gypsum have poor water resistance; their strength decreases sharply with increasing humidity. This greatly limits the uses and usage of gypsum products. The fundamental reason for this phenomenon is: 1. Gypsum has a high solubility (2.05g CaSO4 dissolves per liter of water at 20℃). When exposed to moisture, the dissolution of gypsum weakens the bonding force between its crystals, thus reducing its strength. Especially under the influence of moving water, when water flows through or along the surface of gypsum products, it dissolves and separates the gypsum, resulting in an irreversible reduction in strength. 2. Due to the hygroscopic absorption of moisture within the microcracks of the gypsum body, a water film coats the surface of the gypsum crystals, thus separating the micro-units of the individual crystalline structures. This can also be seen as gypsum having an adsorption effect on water. 3. The high porosity of gypsum materials also exacerbates the hygroscopic effect, because hardened gypsum loses strength not only in pure water but also when loaded in saturated and supersaturated gypsum solutions. To solve the problem of poor water resistance in gypsum, it is essential to address the above three issues.

[0003] However, current technologies still have some drawbacks: 1. Coating the surface of gypsum products with silicone waterproof coatings or paraffin wax is problematic because the water resistance of the gypsum product drops sharply when the coating is damaged. 2. Adding organic hydrophobic substances to gypsum products can improve water resistance to some extent, but these organic substances can affect the hydration properties of the gypsum itself, leading to risks such as unstable setting time and reduced product strength. 3. Adding cement or other hydration-active adhesives can improve performance, but it increases costs and carries the risk of expansion and cracking. 4. Using ordinary building gypsum (β-type hemihydrate gypsum) requires a large amount of water during mixing, and the product itself is prone to having many pores.

[0004] There is an urgent need to provide a new carbon-fixed, water-resistant gypsum product and its preparation method. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a carbon-fixed, water-resistant gypsum product and its preparation method. This invention employs a multi-solid waste synergistic reaction and carbonization curing method to prepare the carbon-fixed, water-resistant gypsum product. By optimizing the raw materials—α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, red mud, nano-calcium carbonate, nano-silica, and water—and their dosages, it can reduce the porosity of the gypsum substrate itself, seal the pores of the gypsum product, and protect the gypsum crystals at the microscopic level, thus comprehensively solving the problem of poor water resistance in gypsum.

[0006] In a first aspect, this invention provides a carbon-fixed, water-resistant gypsum product. The raw materials for this product include α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, red mud, nano-calcium carbonate, nano-silica, and water. The mass ratio of the α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, and red mud is 50-80:10-25:7.5-15:2.5-10. In this invention, based on α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, and red mud are used for a synergistic reaction, which not only reduces the use of organic hydrophobic substances and cementitious materials, lowering the cost of gypsum products, but also improves the water resistance, strength, and service life of the gypsum products.

[0007] Preferably, the mass ratio of the α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag and red mud is 50~80:15~25:12~15:6~10, and more preferably 50~60:15~20:12.5~15:7.5~10.

[0008] Preferably, the mass ratio of the α-type short columnar hemihydrate gypsum, nano-calcium carbonate, and nano-silica is 50~80:0~0.05:0~0.03, and more preferably 50~80:0.02~0.05:0.01~0.03.

[0009] Preferably, the mass ratio of the α-type short columnar hemihydrate gypsum to water is 50~80:30~40, more preferably 50~80:30~38. In this invention, by optimizing the proportions of the above raw materials, the water resistance, strength, and service life of the carbon-fixed, high-water-resistant gypsum products can be further improved.

[0010] Preferably, the α-type short columnar hemihydrate gypsum has an aspect ratio of 1:1 to 1.5:1 and a particle size of 20 to 80 μm. In this invention, the α-type short columnar hemihydrate gypsum can be prepared by a pressurized aqueous solution method, and preferably uses α-type short columnar hemihydrate gypsum with an aspect ratio of 1:1 to 1.5:1 and a particle size of 20 to 80 μm.

[0011] Preferably, the carbon-fixed, water-resistant gypsum product comprises the following raw materials in parts by weight: 50-80 parts of α-type short columnar hemihydrate gypsum, 10-25 parts of magnesium slag, 7.5-15 parts of carbide slag, 2.5-10 parts of red mud, 0.02-0.05 parts of nano-calcium carbonate, 0.01-0.03 parts of nano-silica, and 30-38 parts of water. In this invention, by optimizing the amounts of α-type short columnar hemihydrate gypsum, magnesium slag, carbide slag, red mud, nano-calcium carbonate, nano-silica, and water, the porosity of the gypsum substrate itself is further reduced, better sealing the pores of the gypsum product, thereby protecting the gypsum crystals at the microscopic level and comprehensively solving the problem of poor water resistance in gypsum.

[0012] Further optimization includes the following raw materials in parts by weight: 50-80 parts of α-type short columnar hemihydrate gypsum, 15-25 parts of magnesium slag, 12-15 parts of carbide slag, 6-8 parts of red mud, 0.04-0.05 parts of nano-calcium carbonate, 0.02-0.03 parts of nano-silica, and 34-36 parts of water.

[0013] Preferably, the particle size of the α-type short columnar hemihydrate gypsum is 20~80μm.

[0014] Preferably, the particle size of the magnesium slag and carbide slag is 5~20μm.

[0015] Preferably, the red mud has a particle size of 15~30μm.

[0016] Preferably, the particle size of the nano-calcium carbonate is 60-100 nanometers.

[0017] Preferably, the particle size of the nano-silica is 15-30 nanometers.

[0018] Preferably, the mixture also includes a carbonizing gas, wherein the volume concentration of carbon dioxide in the carbonizing gas is 20% to 50%; preferably, the carbonizing gas is waste gas containing carbon dioxide emitted by the factory. In this invention, the specific amount of carbon dioxide gas used is not specifically limited. The carbon dioxide is used for carbonization curing, and the amount commonly used in the art can be adopted. Preferably, the test blocks prepared from the above raw materials are placed in carbon dioxide gas for carbonization curing for at least one day.

[0019] According to this invention, the carbon-fixed, water-resistant gypsum products mainly utilize α-type short columnar hemihydrate gypsum, which has well-developed crystals, low specific surface area, and low water requirement during mixing. When the water requirement is low, the porosity of the gypsum substrate itself is reduced after hydration and hardening, thus reducing the possibility of water entering the interior of the gypsum product. The carbon-fixing reactants (magnesium slag, carbide slag) react with carbon dioxide during carbonization curing; the magnesium slag contains dicalcium silicate, and the chemical equation for the reaction is: γC₂S + 2CO₂ 2CaCO3 + SiO2; Calcium hydroxide is present in carbide slag, and the chemical equation for the reaction is: Ca(OH)2 + CO2 The calcium carbonate and silica gel produced by the reaction CaCO3 + H2O can fill the pores inside the product, further sealing off the entry of external water. Because the calcium carbonate and silica gel produced are smaller than gypsum crystals, they can adhere well to the surface of the gypsum crystals, forming a coating that prevents the gypsum crystals from dissolving upon contact with water.

[0020] Secondly, the present invention provides a method for preparing the above-mentioned carbon-fixed, water-resistant gypsum product, comprising the following steps: premixing magnesium slag, carbide slag, α-type short columnar hemihydrate gypsum, nano-calcium carbonate, and nano-silica to obtain a powder mixture sample; mixing the powder mixture sample with water and stirring to obtain a wet slurry; pouring the wet slurry and then performing standard curing to obtain a test block; and performing carbonization curing on the test block to obtain the carbon-fixed, water-resistant gypsum product.

[0021] Preferably, the carbonization curing time is 24~72h, the carbon dioxide concentration is 20%~50%, and the temperature is 20±2℃.

[0022] Preferably, the premixing time is 5 to 10 minutes.

[0023] Preferably, the stirring time is 120~240s.

[0024] Preferably, the standard curing time is 2 to 8 hours.

[0025] Preferably, the process also includes grinding magnesium slag, carbide slag, and red mud separately for 20-35 minutes using a separate planetary ball mill.

[0026] Preferably, a 40×40×160mm cement mortar triple mold is used for casting, and then the cast cement mortar triple mold is placed in a cement standard curing box for curing.

[0027] The beneficial effects of this invention are at least as follows: The carbon-fixed, water-resistant gypsum product provided by this invention can reduce the porosity of the gypsum substrate itself, seal the pores of the gypsum product, and protect the gypsum crystals at the microscopic level. This invention uses α-type short columnar hemihydrate gypsum to reduce the water demand of the gypsum-based product and decrease the porosity of the product itself. Simultaneously, it employs a synergistic reaction of multiple solid wastes such as magnesium slag, carbide slag, and red mud, followed by carbonization curing. The resulting micro-sized calcium carbonate, silica gel, and hydrated calcium silicate gel, among other carbonization and hydration products, fill the pores between the overlapping gypsum crystals and adhere to the surface of the gypsum crystals. These micro-carbonization and hydration products also bond together through physical and chemical bonding, further enhancing the bonding strength between the gypsum crystals. This invention, utilizing multiple solid wastes and carbonization curing, not only solves the problem of poor water resistance in gypsum products but also provides a new approach for the synergistic treatment of multiple solid wastes and the effective utilization of greenhouse gases. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is an image of α-type short columnar hemihydrate gypsum in an embodiment of the present invention.

[0030] Figure 2 This is a microscopic image of the internal structure of the carbon-fixed, water-resistant gypsum product provided in Embodiment 3 of the present invention.

[0031] Figure 3 This is a microscopic image of the interior of a common gypsum product provided in Comparative Example 4 of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0034] Unless otherwise specified, the techniques or conditions described in the embodiments of this invention shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Devices, instruments, reagents, etc., without specified manufacturers, are all conventional products that can be purchased through legitimate channels. All experimental reagents and raw materials involved are commercially available products, and all reagents are analytical grade products.

[0035] Example 1

[0036] This embodiment provides a carbon-fixed, water-resistant gypsum product. The raw materials for this product are: 10 parts magnesium slag, 7.5 parts carbide slag, 2.5 parts red mud, 80 parts α-type short columnar hemihydrate gypsum, 0.02 parts nano-calcium carbonate, 0.01 parts nano-silica, and 30 parts water. The α-type short columnar hemihydrate gypsum is prepared by a pressurized aqueous solution method, with an aspect ratio of 1:1 to 1.5:1 and a particle size of 20 to 80 μm. Figure 1 The particle size of magnesium slag and carbide slag is 5~20μm; the red mud is Bayer process red mud produced by the factory for alumina production, which is ball-milled and has a particle size of 15~30μm; the particle size of nano calcium carbonate is 60~100 nanometers; the particle size of nano silica is 15~30 nanometers; the water is (room temperature) tap water; the carbonation curing uses waste gas containing carbon dioxide emitted by the factory, with a carbon dioxide volume concentration of 20%.

[0037] This embodiment also provides a method for preparing the above-mentioned carbon-fixed, water-resistant gypsum product, the steps of which are as follows:

[0038] Step 1: Place 10 parts magnesium slag, 7.5 parts calcium carbide slag, and 2.5 parts red mud into a planetary ball mill and grind them for 20 minutes each.

[0039] Step 2: Put the ground magnesium slag, carbide slag, red mud, 80 parts of α-type short columnar hemihydrate gypsum, 0.02 parts of nano calcium carbonate, and 0.01 parts of nano silica into a mixer and premix for 5 minutes to obtain a powder mixture sample.

[0040] Step 3: Put the powder mixture sample obtained in Step 2 and 30 parts of water into a cement mortar mixer and mix for 120 seconds to obtain a wet slurry.

[0041] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold. Then, place the poured cement mortar triple mold into a cement standard curing box (temperature 20±2℃, relative humidity above 95%) for curing for 2 hours. After curing, demold to obtain test blocks.

[0042] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 20% and a temperature of 20±2℃ for 12 hours of curing. After curing, the test block is obtained.

[0043] Example 2

[0044] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0045] Step 1: Put 15 parts magnesium slag, 10 parts calcium carbide slag, and 5 parts red mud into a planetary ball mill and grind them for 25 minutes each.

[0046] Step 2: Place the ground magnesium slag, carbide slag, red mud, 70 parts of α-type short columnar hemihydrate gypsum, 0.03 parts of nano calcium carbonate, and 0.01 parts of nano silica into a mixer and premix for 6 minutes to obtain a powder mixture sample.

[0047] Step 3: Put the powder mixture sample obtained in Step 2 and 32 parts of water into a cement mortar mixer and mix for 160 seconds to obtain a wet slurry.

[0048] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold, then place the poured cement mortar triple mold into a cement standard curing box for 4 hours. After curing, demold to obtain test blocks.

[0049] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 30% and a temperature of 20±2℃ for 24 hours of curing. After curing, carbon-fixed high water-resistant gypsum products are obtained.

[0050] Example 3

[0051] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0052] Step 1: Put 20 parts magnesium slag, 12.5 parts calcium carbide slag, and 7.5 parts red mud into a planetary ball mill and grind them for 30 minutes each.

[0053] Step 2: Put the ground magnesium slag, carbide slag, red mud, 60 parts of α-type short columnar hemihydrate gypsum, 0.04 parts of nano calcium carbonate, and 0.02 parts of nano silica into a mixer and premix for 8 minutes to obtain a powder mixture sample.

[0054] Step 3: Place the powder mixture sample obtained in Step 2 and 34 parts of water into a cement mortar mixer and mix for 200 seconds to obtain a wet slurry.

[0055] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold, then place the poured cement mortar triple mold into a cement standard curing box for 6 hours. After curing, demold to obtain test blocks.

[0056] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 40% and a temperature of 20±2℃ for 56 hours of curing. After curing, carbon-fixed high water-resistant gypsum products are obtained.

[0057] Figure 2 The scanning electron microscope (SEM) image of the carbon-fixed, water-resistant gypsum product in this embodiment shows that tiny carbonization and hydration products, such as calcium carbonate, silica gel, and hydrated calcium silicate gel, fill the pores between the overlapping gypsum crystals and adhere to the surface of the gypsum crystals. These tiny carbonization and hydration products also bond together with each other through physical and chemical bonding, further enhancing the bonding strength between the gypsum crystals.

[0058] Example 4

[0059] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0060] Step 1: Put 25 parts magnesium slag, 15 parts calcium carbide slag, and 10 parts red mud into a planetary ball mill and grind them for 35 minutes respectively.

[0061] Step 2: Put the ground magnesium slag, carbide slag, red mud, 50 parts of α-type short columnar hemihydrate gypsum, 0.05 parts of nano calcium carbonate, and 0.03 parts of nano silica into a mixer and premix for 8 minutes to obtain a powder mixture sample.

[0062] Step 3: Put the powder mixture sample obtained in Step 2 and 38 parts of water into a cement mortar mixer and mix for 240 seconds to obtain a wet slurry.

[0063] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold, then place the poured cement mortar triple mold into a cement standard curing box for 8 hours. After curing, demold to obtain test blocks.

[0064] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 50% and a temperature of 20±2℃ for 64 hours of curing. After curing, carbon-fixed high water-resistant gypsum products are obtained.

[0065] Example 5

[0066] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0067] Step 1: Put 20 parts magnesium slag, 15 parts calcium carbide slag, and 10 parts red mud into a planetary ball mill and grind them for 30 minutes respectively.

[0068] Step 2: Put the ground magnesium slag, carbide slag, red mud, 55 parts of α-type short columnar hemihydrate gypsum, 0.04 parts of nano calcium carbonate, and 0.02 parts of nano silica into a mixer and premix for 8 minutes to obtain a powder mixture sample.

[0069] Step 3: Place the powder mixture sample obtained in Step 2 and 34 parts of water into a cement mortar mixer and mix for 200 seconds to obtain a wet slurry.

[0070] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold, then place the poured cement mortar triple mold into a cement standard curing box for 6 hours. After curing, demold to obtain test blocks.

[0071] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 40% and a temperature of 20±2℃ for 56 hours of curing. After curing, carbon-fixed high water-resistant gypsum products are obtained.

[0072] Example 6

[0073] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0074] Step 1: Put 20 parts magnesium slag, 12.5 parts calcium carbide slag, and 7.5 parts red mud into a planetary ball mill and grind them for 30 minutes each.

[0075] Step 2: Put the ground magnesium slag, carbide slag, red mud, 60 parts of α-type short columnar hemihydrate gypsum, 0.04 parts of nano calcium carbonate, and 0.02 parts of nano silica into a mixer and premix for 8 minutes to obtain a powder mixture sample.

[0076] Step 3: Place the powder mixture sample obtained in Step 2 and 34 parts of water into a cement mortar mixer and mix for 200 seconds to obtain a wet slurry.

[0077] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold, then place the poured cement mortar triple mold into a cement standard curing box for 6 hours. After curing, demold to obtain test blocks.

[0078] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 30% and a temperature of 20±2℃ for 60 hours of curing. After curing, carbon-fixed high water-resistant gypsum products are obtained.

[0079] Comparative Example 1

[0080] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0081] Step 1: Put 100 parts of α-type short columnar hemihydrate gypsum and 30 parts of water into a cement mortar mixer and mix for 120 seconds to obtain a wet slurry.

[0082] Step 2: Pour the wet slurry obtained in Step 1 into a 40×40×160mm cement mortar triple mold. Then, place the poured cement mortar triple mold into a cement standard curing chamber for 2 hours. After curing, demold the molded specimen and continue curing it in the cement standard curing chamber for 70 hours. This yields the gypsum specimen.

[0083] Comparative Example 2

[0084] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0085] Step 1: Put 15 parts magnesium slag, 10 parts calcium carbide slag, and 5 parts red mud into a planetary ball mill and grind them for 25 minutes each.

[0086] Step 2: Place the ground magnesium slag, carbide slag, red mud, 70 parts of α-type short columnar hemihydrate gypsum, 0.03 parts of nano calcium carbonate, and 0.01 parts of nano silica into a mixer and premix for 6 minutes to obtain a powder mixture sample.

[0087] Step 3: Put the powder mixture sample obtained in Step 2 and 32 parts of water into a cement mortar mixer and mix for 160 seconds to obtain a wet slurry.

[0088] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold. Then, place the poured cement mortar triple mold into a cement standard curing chamber for 4 hours. After curing, demold the specimen and continue curing it in the cement standard curing chamber for 68 hours. This yields gypsum-based specimens.

[0089] Comparative Example 3

[0090] The same carbon-fixed, water-resistant gypsum product and preparation method as in Example 1 are used, except that:

[0091] Step 1: Put 25 parts magnesium slag, 15 parts calcium carbide slag, and 10 parts red mud into a planetary ball mill and grind them for 35 minutes respectively.

[0092] Step 2: Put the ground magnesium slag, carbide slag, and 50 parts of α-type short columnar hemihydrate gypsum into a mixer and premix for 8 minutes to obtain a powder mixture sample.

[0093] Step 3: Put the powder mixture sample obtained in Step 2 and 38 parts of water into a cement mortar mixer and mix for 240 seconds to obtain a wet slurry.

[0094] Step 4: Pour the wet slurry obtained in Step 3 into a 40×40×160mm cement mortar triple mold, then place the poured cement mortar triple mold into a cement standard curing box for 8 hours. After curing, demold to obtain test blocks.

[0095] Step 5: Place the test block obtained in Step 4 into a carbonization chamber with a carbon dioxide concentration of 50% and a temperature of 20±2℃ for 64 hours of curing. After curing, carbon-fixed high water-resistant gypsum products are obtained.

[0096] Comparative Example 4

[0097] The gypsum product provided in this comparative example is prepared by the following method:

[0098] Step 1: Put 100 parts of building gypsum (β-type hemihydrate gypsum) and 70 parts of water into a cement mortar mixer and mix for 120 seconds to obtain a wet slurry.

[0099] Step 2: Pour the wet slurry obtained in Step 1 into a 40×40×160mm cement mortar triple mold. Then, place the poured cement mortar triple mold into a cement standard curing box for 2 hours. After curing, demold the mold and continue to place the demolded test block into the cement standard curing box for 70 hours to obtain the gypsum test block.

[0100] Figure 3 To illustrate the microstructure of ordinary building gypsum products in Comparative Example 4, the hydrated gypsum formed without the treatment of this invention exhibits coarse crystals with loose inter-crystal connections and numerous internal pores. External moisture easily penetrates the product, resulting in poor water resistance.

[0101] The strength test of gypsum products shall be conducted in accordance with GB / T 17669.3-1999 "Determination of Mechanical Properties of Building Gypsum"; the softening coefficient of gypsum products is: softening coefficient = compressive strength under saturated water absorption state / compressive strength under dry state.

[0102] Table 1 Performance test results of each embodiment and comparative example

[0103]

[0104] Tests have shown that the embodiments of the present invention can effectively solve the problem of poor water resistance of gypsum. Compared with the comparative example, the embodiments of the present invention can significantly improve the water resistance and strength of gypsum products, thereby extending their service life.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A carbon-fixing, water-resistant gypsum product, characterized in that, The carbon-fixed, water-resistant gypsum product comprises the following raw materials in parts by weight: 50-80 parts of α-type short columnar hemihydrate gypsum, 10-25 parts of magnesium slag, 7.5-15 parts of carbide slag, 2.5-10 parts of red mud, 0.02-0.05 parts of nano-calcium carbonate, 0.01-0.03 parts of nano-silica, and 30-38 parts of water; the raw materials of the carbon-fixed, water-resistant gypsum product also include carbonized gas; the particle size of the α-type short columnar hemihydrate gypsum is 20-80 μm, the particle size of the magnesium slag and carbide slag is 5-20 μm, the particle size of the red mud is 15-30 μm, the particle size of the nano-calcium carbonate is 60-100 nanometers, and the particle size of the nano-silica is 15-30 nanometers.

2. The carbon-fixed, water-resistant gypsum product according to claim 1, characterized in that, The aspect ratio of the α-type short columnar hemihydrate gypsum is 1:1 to 1.5:

1.

3. The carbon-fixed, water-resistant gypsum product according to claim 1, characterized in that, The raw materials include the following parts by weight: 50-80 parts of α-type short columnar hemihydrate gypsum, 15-25 parts of magnesium slag, 12-15 parts of carbide slag, 6-8 parts of red mud, 0.04-0.05 parts of nano calcium carbonate, 0.02-0.03 parts of nano silica, and 34-36 parts of water.

4. The carbon-fixed, water-resistant gypsum product according to any one of claims 1-3, characterized in that, The volume concentration of carbon dioxide in the carbonized gas is 20% to 50%.

5. The method for preparing the carbon-fixed, water-resistant gypsum product according to any one of claims 1-4, characterized in that, The process includes the following steps: premixing magnesium slag, carbide slag, α-type short columnar hemihydrate gypsum, nano-calcium carbonate, and nano-silica to obtain a powder mixture sample; mixing the powder mixture sample with water and stirring to obtain a wet slurry; pouring the wet slurry and then performing standard curing to obtain a test block; and performing carbonization curing on the test block to obtain a carbon-fixed, water-resistant gypsum product.

6. The method for preparing carbon-fixed, water-resistant gypsum products according to claim 5, characterized in that, The carbonization curing time is 24~72h, the carbon dioxide concentration is 20%~50%, and the temperature is 20±2℃.

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