A carbonized lightweight material and its preparation method

Abstract

This invention discloses a carbonized lightweight material, the raw materials and their weight proportions of which include: 30-35 parts of carbonizable calcareous material, 5-10 parts of pozzolanic material, 0.2-1 part of thickener, 1-3 parts of soluble carbonate, and 60-65 parts of water. Using carbonizable calcareous material, pozzolanic material, and pozzolanic material as the main raw materials, and with the regulating effect of thickener and soluble carbonate, this invention can achieve effective molding of slurry under ultra-high water-to-solid ratio conditions, effectively control the capillary structure, and ensure good mechanical properties and durability while maintaining low bulk density. Furthermore, the preparation method involved is relatively simple, convenient to operate, and low in cost, making it suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a carbonized lightweight material and its preparation method. Background Technology

[0002] Currently, commonly used lightweight building materials (autoclaved aerated concrete, sintered bricks, etc.) emit large amounts of carbon dioxide during production. With increasing global climate change and pollution, the development of low-carbon lightweight materials is imperative. Using industrial waste gas to carbonize and cure lightweight materials, which can absorb carbon dioxide during the material production process, has become an important research direction.

[0003] Existing methods for molding lightweight carbonized materials typically introduce pores through physical or chemical means to control density. However, this approach has certain problems, such as the difficulty in matching the gas generation process with the slurry thickening and hardening process, leading to performance degradation or molding defects. Furthermore, during the carbonization reaction, carbonization products coat the surface of the carbonized material particles, inhibiting the reaction rate and resulting in insufficient carbon absorption. Summary of the Invention

[0004] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a carbonized lightweight material and its preparation method. By adjusting the water-to-solid ratio to control the capillary structure, the material achieves good mechanical and durability properties while maintaining low bulk density. Furthermore, the preparation method is simple, easy to operate, and suitable for widespread application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A carbonized lightweight material, the raw materials and their weight percentages include: 30-35 parts of carbonizable calcareous material, 5-10 parts of volcanic ash material, 0.2-1 part of thickener, 1-3 parts of soluble carbonate, and 60-65 parts of water.

[0007] In the above scheme, the carburizable calcareous material includes, but is not limited to, steel slag, magnesium slag, and calcium carbide sludge, wherein the carburizable components (C3S, C2S, C3S2, CS, CH, etc.) are not less than 75%, and the specific surface area is 400-700 m². 2 / kg.

[0008] Preferably, the total content of C3S and C2S in the carbonizable components of the carbonizable calcareous material is not less than 70%, and the specific surface area is 550-650 m². 2 / kg.

[0009] In the above scheme, the pozzolanic material includes, but is not limited to, fly ash, slag, silica fume, and metakaolin, with a specific surface area of ​​not less than 500 m². 2 / kg, with an activity index of not less than 85%.

[0010] In the above scheme, the thickener is a cellulose ether with a 1% solid content, a room temperature thickening capacity of 2-20 Pa·s, a thixotropic index of 1.5-4.5, and a molecular weight of 100,000-300,000.

[0011] In the above scheme, the soluble carbonate is a normal salt and / or an acid salt (bicarbonate); wherein, the normal salt includes, but is not limited to, one or more of sodium carbonate, potassium carbonate, ammonium carbonate, and lithium carbonate; the acid salt includes, but is not limited to, one or more of sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, and lithium bicarbonate. The effective ingredient content is required to be no less than 85%.

[0012] The above-mentioned method for preparing a carbonized lightweight material includes the following preparation steps:

[0013] (1) Weigh the carbonizable calcium material, pozzolanic material, thickener, soluble carbonate and water according to the proportion and stir evenly to obtain a slurry;

[0014] (2) Under stirring conditions, the resulting slurry is heated and kept warm;

[0015] (3) The heated slurry is poured into the mold and left to stand for curing. After it hardens, it is demolded to obtain the blank.

[0016] (4) The billet is carbonized and cured to obtain carbonized lightweight material finished product.

[0017] In the above scheme, in step (1), the slurry is stirred for 10 to 20 minutes and the stirring rate is 60 to 90 r / min.

[0018] In the above scheme, in step (2), the heating method of the slurry is not limited, such as high-temperature steam heating or high-temperature air heating, with a heating rate of 5-15℃ / min, and holding at 70-80℃ for 5-10min. The stirring rate during the slurry heating process is controlled at 30-60r / min.

[0019] Furthermore, the high-temperature steam temperature is 100–150°C; the high-temperature air temperature is 150–200°C.

[0020] Furthermore, the water-to-solid ratio of the slurry after heat preservation in step (2) is 1.2 to 1.5.

[0021] In the above scheme, in step (3), the static curing time is 2.5 to 3.5 hours, and the temperature in the curing room is 80 to 90°C and the relative humidity is 90 to 100%.

[0022] In the above scheme, the gas used for carbonization curing in step (4) is not limited, such as industrial carbon-containing tail gas or industrial-grade carbon dioxide. The carbon dioxide concentration in the carbonization gas is not less than 15 vol%, the carbonization curing time is 6 to 12 hours, the curing temperature is 60 to 90°C, the curing pressure is 0.3 to 0.7 MPa, and the relative humidity is 40 to 60%.

[0023] The performance optimization mechanism of the carbonized lightweight material described in this invention includes:

[0024] 1) Under the regulating effect of the thickener and the nano-calcium carbonate crystals formed by soluble carbonates, effective molding is achieved under the ultra-high water-to-solid ratio conditions (slurry after heat preservation and heating) described in this invention, without the occurrence of water seepage and stratification. The large number of capillary pores formed by water regulate the bulk density of the material. The small pore size effectively reduces stress concentration at the pore walls of porous materials under load, which is beneficial to improving strength. The cellulose ether thickener contains a large number of -OH groups, which electrostatically interact with Ca... 2+ Coordination enhances local supersaturation, promoting nucleation of calcite products in the early stages of carbonization curing. Furthermore, the alkyl groups in the cellulose ether significantly reduce the surface tension and interfacial energy of water, leading to a decrease in the surface energy of the calcite crystals, which is beneficial for stable crystal growth. The introduced cellulose ether promotes the nucleation and growth of calcite products, thus improving carbonization performance.

[0025] 2) This invention adopts an ultra-high water-to-solid ratio formulation system, which makes the slurry contain a large amount of liquid phase, promotes the metathesis reaction between soluble carbonates and carbonizable calcium materials, and uniformly generates a large amount of nano-calcium carbonate in the liquid phase. Due to its large specific surface area, it further increases the viscosity of the slurry. When used in combination with thickeners, the stability of the slurry is higher and the molding effect is better.

[0026] 3) The uniformly dispersed nano-calcium carbonate in the liquid phase acts as a nucleus, causing partial deposition of carbonization products on its surface. This promotes a more uniform distribution of carbonization products in the liquid phase, further reducing the capillary pore size inside the green body and thus improving carbonization performance. The nucleation effect prevents carbonization products from being mainly concentrated on the surface of carbonizable calcium-based material particles. The thickness of the carbonization product layer on the particle surface is reduced, making it easier for calcium ions to diffuse through the carbonization product layer and react with carbon dioxide to form calcium carbonate. This helps to shorten the carbonization curing time, increase the degree of carbonization, and improve the carbon absorption capacity.

[0027] 4) Soluble carbonates undergo metathesis reactions to generate a large amount of soluble alkali, which can act as an alkali activator to promote the hydration reaction of pozzolanic materials. The presence of a large liquid phase provides ample space for the accumulation of hydration products, and the hydration products and carbonation products bind together, further improving the performance of lightweight materials. In addition, the increased solubility of carbon dioxide in the presence of soluble alkali also promotes the carbonation reaction.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1) The molding process is simple, and the capillary pores in the slurry are evenly distributed, which makes it less prone to problems such as collapse and deformation during the pore-forming process of conventional porous materials, thus ensuring the stability of performance.

[0030] 2) Carbonizable materials are mostly industrial solid wastes, such as steel slag, magnesium slag, and calcium carbide sludge, which have significant economic and environmental benefits.

[0031] 3) During the carbonization curing process of lightweight materials, carbon dioxide in industrial exhaust gas can be absorbed, which helps to reduce carbon emissions. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to embodiments, so as to facilitate a clearer understanding of the present invention, but these embodiments do not constitute a limitation on the present invention.

[0033] In the following examples and comparative examples, the carburizable calcareous material is steel slag, and its main chemical composition and mass percentage include: C2S 58%, C3S 16%, Ca(OH)2 5%, C3S2 5%, Ca2Fe2O5 6%, CaCO3 5%, SiO2 4%, and its specific surface area is 580 m². 2 / kg; the volcanic ash material consists of metakaolin and slag, with metakaolin having a specific surface area of ​​630m². 2 / kg, activity index 92%, slag specific surface area 560m² 2 / kg, activity index 96%. Cellulose ether is produced by Zhengzhou Yuxiang Chemical Products Co., Ltd., with a thickening capacity of 12 Pa·s at 1% solid content, thixotropic index 2.1, and molecular weight 200,000. Soluble carbonate is sodium carbonate, with an active ingredient content of 92%. Carbonation gas is industrial tail gas from cement kilns, at a temperature of 75℃, relative humidity of 45%, and carbon dioxide concentration of 19 vol.

[0034] Example 1

[0035] A carbonized lightweight material based on capillary regulation, the preparation method of which includes the following steps:

[0036] 1) Take 32 parts of steel slag, 6 parts of metakaolin, 0.6 parts of cellulose ether, 2 parts of sodium carbonate, and 60 parts of water and mix them evenly to obtain a slurry. The mixing time is 15 minutes and the mixing speed is 60 r / min.

[0037] 2) The slurry is heated by 120℃ high-temperature steam at a heating rate of 10℃ / min, and held at 75℃ for 10min; the stirring rate is controlled at 30r / min during the heating process; the water-to-solid ratio of the slurry after holding is 1.25.

[0038] 3) After the slurry is poured and formed, it is placed in a static curing room for 3 hours. The temperature in the curing room is 85℃ and the relative humidity is 95%.

[0039] 4) The hardened and demolded green body is carbonized and cured with industrial tail gas from a cement kiln to obtain carbonized lightweight material, wherein the carbonization and curing time is 8 hours and the pressure is 0.5 MPa.

[0040] Example 2

[0041] A carbonized lightweight material based on capillary regulation is prepared in a manner similar to that of Example 1, except that the carbonization curing time is 12 hours and the pressure is 0.5 MPa.

[0042] Example 3

[0043] A carbonized lightweight material based on capillary regulation is prepared in a manner similar to that of Example 1, except that 32 parts of steel slag, 6 parts of ore slag, 0.6 parts of cellulose ether, 2 parts of sodium carbonate, and 60 parts of water are mixed evenly to obtain a slurry.

[0044] Comparative Example 1

[0045] A carbonized lightweight material based on capillary regulation is prepared in a manner similar to that of Example 1, except that the thickener used is triphenylethylphenol polyoxyethylene ether methacrylate, which has a thickening capacity of 9 Pa·s and a thixotropic index of 2.9 at 1% solid content.

[0046] Comparative Example 2

[0047] A carbonized lightweight material based on capillary regulation is prepared in a manner similar to that of Example 1, except that volcanic ash material is not used.

[0048] Comparative Example 3

[0049] A carbonized lightweight material based on capillary regulation is prepared in a manner similar to that of Example 1, except that soluble carbonates are not used.

[0050] Comparative Example 4

[0051] A carbonized lightweight material based on capillary regulation is prepared in a manner similar to that of Example 1, except that: the slurry is heated with high-temperature air (200°C) at a heating rate of 10°C / min and held at 75°C for 10min; the stirring rate is controlled at 30r / min during the heating process; and the water-to-solid ratio of the slurry after holding is 0.9.

[0052] The carbonized aerated concrete obtained in Examples 1-3 and Comparative Examples 1-4 was subjected to performance tests, and the results are shown in Table 1.

[0053] Table 1 Performance test results of carbonized lightweight materials

[0054]

[0055] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations; therefore, any obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A carbonized lightweight material, characterized in that, Its raw materials and their weight percentages include: 30-35 parts of carbideable calcium material, 5-10 parts of pozzolanic material, 0.2-1 part of thickener, 1-3 parts of soluble carbonate, and 60-65 parts of water; The thickener is a cellulose ether; The carbonized lightweight material includes the following preparation steps: (1) Weigh the carbonizable calcium material, pozzolanic material, thickener, soluble carbonate and water according to the proportion and stir evenly to obtain a slurry; (2) Under stirring conditions, the resulting slurry is heated and kept at a constant temperature; (3) The slurry after heat preservation and heating is poured into the mold and left to stand for curing. After it hardens, it is demolded to obtain the green body. (4) The billet is carbonized and cured to obtain carbonized lightweight material finished product; The water-to-solid ratio of the slurry after heat preservation in step (2) is 1.2~1.

5.

2. The carbonized lightweight material according to claim 1, characterized in that, The content of the carburizable component in the carburizable calcareous material is not less than 75 wt%, and the specific surface area is 400~700 m². 2 / kg.

3. The carbonized lightweight material according to claim 1, characterized in that, The specific surface area of ​​the volcanic ash material is not less than 500 m². 2 / kg, with an activity index of not less than 85%.

4. The carbonized lightweight material according to claim 1, characterized in that, The thickener has a 1% solid content and a room temperature thickening capacity of 2~20 Pa·s, with a thixotropic index of 1.5~4.

5.

5. The carbonized lightweight material according to claim 1, characterized in that, The soluble carbonate is a normal salt and / or an acid salt.

6. The method for preparing the carbonized lightweight material according to any one of claims 1 to 5, characterized in that, The preparation steps include the following: (1) Weigh the carbonizable calcium material, pozzolanic material, thickener, soluble carbonate and water according to the proportion and stir evenly to obtain a slurry; (2) Under stirring conditions, the resulting slurry is heated and kept at a constant temperature; (3) The slurry after heat preservation and heating is poured into the mold and left to stand for curing. After it hardens, it is demolded to obtain the green body. (4) The billet is carbonized and cured to obtain carbonized lightweight material finished product.

7. The preparation method according to claim 6, characterized in that, In step (2), the heating temperature is 70~80℃ and the holding time is 5~10min.

8. The preparation method according to claim 6, characterized in that, In step (3), the static curing time is 2.5~3.5h, and the temperature in the curing room is 80~90℃ and the relative humidity is 90~100%.

9. The preparation method according to claim 6, characterized in that, In step (4), the carbonization curing step is characterized by a carbon dioxide concentration of not less than 15 vol% in the carbonization gas, a carbonization curing time of 6 to 12 hours, a curing temperature of 60 to 90 degrees Celsius, a curing pressure of 0.3 to 0.7 MPa, and a relative humidity of 40 to 60%.

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