Low-carbon foam concrete with excellent stability and preparation method thereof

Abstract

The application discloses low-carbon foam concrete with excellent stability and a preparation method thereof, and the preparation method is as follows: 1) raw materials are weighed according to a proportioning ratio; 2) paper pulp fibers are mixed with water to obtain a paper pulp fiber suspension; 3) a physical foaming agent, a foam stabilizer and water are uniformly mixed and stirred to obtain a foaming liquid, and carbon dioxide gas is introduced into the foaming liquid to obtain foam; 4) the paper pulp fiber suspension, low-calcium clinker, fly ash and the rest of water are uniformly mixed, then the obtained foam is poured into the mixture, and carbon dioxide gas is continuously introduced into the system while stirring to obtain a foam concrete slurry; 5) the foam concrete slurry is cast and shaped, and is placed at room temperature for demolding, pre-curing and carbonization in a carbonization chamber, and thus finished products are obtained. The carbon dioxide foaming and the secondary introduction of carbon dioxide gas into the low-calcium clinker enable the carbonization reaction of the low-calcium clinker, and a stable pore structure can be formed in the concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of porous mortar, concrete, artificial stone or ceramic products, and particularly relates to a low-carbon foam concrete with excellent stability and a preparation method thereof. Background Art

[0002] CO2 mineralization hardening technology is a typical green manufacturing technology, which uses CO2 as the curing atmosphere of the gel material. 2+ The reaction forms calcium carbonate, which causes the product to strengthen and harden rapidly.

[0003] However, the technology of preparing foamed concrete by foaming with carbon dioxide has not been widely promoted and applied. The main reason is that the water-cement ratio of foamed concrete is relatively large. If the early maintenance is improper, the water evaporates too quickly, which can easily lead to volume shrinkage and cracking. The foam stability of carbon dioxide foaming is poor and it is easy to dissolve during the mixing process, which has a certain impact on the forming of foamed concrete. CN2024102465967 discloses a method for preparing ultra-stable CO2 foamed concrete, which comprises mixing a foaming agent with a nano foam stabilizer, dissolving the foam in a calcium hydroxide solution, preparing a foaming liquid, placing the foaming liquid in a foaming machine, introducing carbon dioxide to prepare foam, mixing red mud, lime and deionized water, and then adding slag powder, cement and fly ash in sequence, stirring evenly to obtain a red mud mixture, and then introducing foam into the red mud mixture to obtain CO2 foamed concrete. However, this foamed concrete introduces a large amount of red mud and lime, and the hydration reaction is rapid and violent, which easily causes the concrete to shrink, and then cracking occurs, affecting the performance of the concrete. At the same time, under this system, cement will preferentially undergo hydration reaction, the carbonization reaction rate is low, the CO2 absorbed is limited, and the contribution to the enhancement of concrete hardness is also limited. CN2023105636296 discloses a pulp fiber-doped carbonized foam concrete, in which a cementitious material with γ-C2S as the main component is used. This mineral has poor hydration ability and is prone to carbonization reaction with carbon dioxide, causing the CO2 foam to defoam and rupture prematurely, resulting in an impact on the performance of the foam concrete. In addition, the current conventional foam concrete itself has many pores and a relatively high content of cementitious materials, which causes it to absorb and lose water quickly, and has a large drying shrinkage, which seriously affects its durability. Therefore, the development of high-strength, low-carbon foam concrete with good formability and stability is a difficult problem in the industry. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies in the prior art and provide a low-carbon foamed concrete with excellent stability and a preparation method thereof. The present invention uses low-calcium cement and fly ash as main components, supplemented by pulp fiber, etc., and utilizes physical foaming of CO2 gas to prepare foamed concrete with good volume stability and high carbon fixation capacity.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0006] A low-carbon foamed concrete with excellent stability, the preparation method of which is as follows:

[0007] 1) Weigh the raw materials according to the mass ratio: 60-100 parts of low-calcium clinker, 10-40 parts of fly ash, 2-8 parts of pulp fiber, 0.4-0.9 parts of physical foaming agent, 0.1-0.2 parts of foam stabilizer, and 90-120 parts of water;

[0008] 2) Mixing pulp fibers with 20 to 40 parts of water, stirring evenly to fully disperse the pulp fibers, and letting it stand for 2 to 4 hours to obtain a pulp fiber suspension;

[0009] 3) mixing a physical foaming agent, a foam stabilizer and 50 parts of water, stirring to obtain a foaming liquid, and introducing carbon dioxide gas into the foaming liquid to foam to obtain foam;

[0010] 4) uniformly mixing the pulp fiber suspension obtained in step 2), low-calcium clinker, fly ash, and remaining water, and then pouring the foam obtained in step 3) into the mixture, while continuously introducing carbon dioxide gas into the system while stirring, to obtain a foamed concrete slurry;

[0011] 5) The foamed concrete slurry obtained in step 4) is cast into shape, placed at room temperature for 1 day, and then demolded. The slurry is then moved into a standard curing room for pre-curing, and then placed in a carbonization room for carbonization to obtain low-carbon foamed concrete with excellent stability.

[0012] According to the above scheme, the mineral composition and mass percentage of the low-calcium clinker in step 1) are: CS 12-18%, C3S2 30-48%, C2S 18-25%, and the remainder is impurities; the 45μm sieve residue is less than 15%, and the specific surface area is 500-550m 2 / kg.

[0013] According to the above scheme, in step 1), the fly ash 45μm sieve residue is 10-13%, and the specific surface area is 600-700m 2 / kg.

[0014] According to the above solution, the pulp fiber in step 1) is one or more of wood pulp fiber, bamboo pulp fiber, and straw pulp fiber, and has a length of 1 to 5 mm and a diameter of 11 to 45 μm.

[0015] According to the above scheme, the physical foaming agent in step 1) is dodecylamine polyoxyethylene ether, and its effective mass fraction is ≥99.5%.

[0016] According to the above scheme, the foam stabilizer in step 1) is a hydroxypropyl methylcellulose aqueous solution with a viscosity of 40 to 50 mPa·s.

[0017] According to the above scheme, the stirring process conditions of step 3) are as follows: stirring at a speed of 60±5 r / min for 180-300 s.

[0018] According to the above scheme, the method for foaming the foaming liquid by introducing carbon dioxide gas in step 3) is as follows: the foaming liquid is placed in a foaming machine, and carbon dioxide gas is introduced into the foaming liquid at an output pressure of 0.2-0.4 MPa.

[0019] According to the above scheme, the purity of the carbon dioxide gas in steps 3) and 4) is greater than 99 vol%.

[0020] According to the above scheme, the rate of continuously introducing carbon dioxide gas into the system in step 4) is 3-5 L / min, and the time for introducing carbon dioxide gas is 3-5 min.

[0021] According to the above scheme, the pre-curing time in step 5) is 3 d. If the pre-curing time is short, the early strength of the concrete is insufficient. If the pre-curing time is more than 3 d, the hydration components in the low-calcium cement begin to hydrate, the hydration products are wrapped on the surface of the carbonation components, the carbonation is prevented, the subsequent carbonation curing is not conducive, and the production efficiency is low.

[0022] According to the above scheme, the carbonation conditions in step 5) are as follows: carbonation curing is carried out at a CO2 concentration of 20-100%, a gas pressure of 0.1-0.3 MPa, and a temperature of 50-70 ℃ for 8-20 h.

[0023] The application also provides a preparation method of the low-carbon foam concrete with excellent stability.

[0024] 1) The raw materials are weighed according to the mass ratio: 60-100 parts of low-calcium clinker, 10-40 parts of fly ash, 2-8 parts of paper pulp fiber, 0.4-0.9 parts of physical foaming agent, 0.1-0.2 parts of foam stabilizer, and 90-120 parts of water;

[0025] 2) The paper pulp fiber is mixed with 20-40 parts of water, stirred uniformly, and allowed to stand for 2-4 h to obtain a paper pulp fiber suspension;

[0026] 3) The physical foaming agent, the foam stabilizer, and 50 parts of water are mixed uniformly to obtain a foaming liquid, and carbon dioxide gas is introduced into the foaming liquid to obtain foam;

[0027] 4) The paper pulp fiber suspension obtained in step 2), the low-calcium clinker, the fly ash, and the remaining water are mixed uniformly, then the foam obtained in step 3) is poured into the mixture, and carbon dioxide gas is continuously introduced into the system while stirring to obtain a foam concrete slurry;

[0028] 5) The foam concrete slurry obtained in step 4) is cast and formed, and after being placed at room temperature for 1d, the mold is removed, and then the foam concrete is moved into a standard curing chamber for pre-curing, and then into a carbonation chamber for carbonation, thereby obtaining low-carbon foam concrete with excellent stability.

[0029] The application also provides application of the low-carbon foam concrete with excellent stability in the field of building thermal insulation materials.

[0030] The low-carbon foam concrete with excellent stability provided by the application takes low-calcium clinker as a main carbon fixation component, and the main mineral components are CS, C3S2 and γ-C2S, which have weak hydration capacity in general and long setting time under conventional curing conditions. Since carbon dioxide is slightly soluble in water and is prone to carbonation reaction with low-calcium clinker, the foam prepared by using carbon dioxide for foaming is prone to decomposition during the mixing process with the powder (the reaction equation is: CaO·SiO2+CO2+H2O→CaCO3+H2SiO3, 3CaO·2SiO2+3CO2+2H2O→3CaCO3+2H2SiO3). In the application, carbon dioxide gas is secondarily introduced as a foam stabilizer during the mixing process, so as to partially carbonate with the low-calcium clinker in advance, thereby improving the stability of the carbon dioxide foam and shortening the setting time of the foam concrete. After being cast and formed, the foam concrete shrinks and is separated from the mold, so that the subsequent demolding is facilitated, and the finished product is quickly obtained, with the calcium silicate in the clinker and the carbon dioxide in the foam further carbonating.

[0031] The low-carbon foam concrete with excellent stability provided by the application is mixed with an appropriate amount of paper pulp fiber. The paper pulp fiber has good water retention and can form an interwoven network structure to strengthen the stability of the slurry during pre-curing, so as to make up for the cracking problem caused by the insufficient cementation of the low-calcium clinker during pre-curing. Meanwhile, the microporous characteristics of the paper pulp fiber can provide a channel for the transmission of carbon dioxide, so as to increase the carbonation degree of the concrete. Under the action of carbon dioxide, the low-calcium clinker generates calcium carbonate and silica gel. The calcium carbonate can be filled into the small pores in the foam concrete, and the silica gel has good water retention, which greatly improves the water retention performance of the foam concrete, reduces the drying shrinkage of the foam concrete, and improves the durability of the foam concrete.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The low-carbon foamed concrete with excellent stability provided by the present invention uses low-calcium clinker as a cementitious material and CO2 gas as a foaming gas. Through the improvement of the preparation process, that is, by introducing carbon dioxide into the low-calcium clinker through carbon dioxide foaming and secondary introduction of carbon dioxide gas, the low-calcium clinker undergoes a carbonization reaction, which can form a stable pore structure in the concrete and seal a large amount of CO2 gas in the form of physical carbon fixation. The carbon fixation amount can reach 18.6-25.1%, which is much higher than the foamed concrete prepared from ordinary Portland cement (carbon fixation amount of 10-15%), thereby achieving the purpose of energy conservation and emission reduction. In addition, the prepared concrete has high strength and durability, meeting the use requirements in the field of building insulation materials. 2. The preparation process of the present invention is simple in steps and easy to industrialize and apply. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the embodiments.

[0034] The low calcium clinker used in the embodiment of the present invention is provided by Huaxin Cement Factory. The mineral composition of the low calcium clinker is as follows: CS 12-18%, C3S2 30-48%, C2S 18-25% by mass, the remainder is impurities, the 45 μm sieve residue is less than 15%, and the specific surface area is 500-550 m 2 / kg.

[0035] The fly ash used in the embodiment of the present invention has a 45 μm sieve residue of 10 to 13% and a specific surface area of ​​600 to 700 m 2 / kg.

[0036] Example 1

[0037] A low-carbon foamed concrete with excellent stability, the preparation method of which is as follows:

[0038] 1) Weigh 70 parts of low-calcium clinker, 20 parts of fly ash, 6 parts of wood pulp fibers (length 1-5 mm, diameter 11-45 μm), and 40 parts of water according to the mass ratio, mix the wood pulp fibers with 20 parts of the water, stir evenly to fully disperse the wood pulp fibers, and let it stand for 2 hours to obtain a wood pulp fiber suspension;

[0039] 2) 0.4 parts of dodecylamine polyoxyethylene ether (effective mass fraction 99.5%), 0.1 parts of hydroxypropyl methylcellulose aqueous solution (viscosity 40 mPa·s), and 50 parts of water were mixed uniformly and stirred at 60±5 r / min for 300 s to obtain a foaming solution. The foaming solution was placed in a foaming machine, and carbon dioxide gas (purity 99 vol%) was introduced into the foaming solution at an output pressure of 0.2 MPa to obtain foam;

[0040] 3) The low-calcium clinker, fly ash, wood pulp fiber suspension, and remaining water from step 1) were uniformly mixed, and the foam obtained from step 2) was poured into the mixture. While stirring, carbon dioxide gas (99 vol% purity) was continuously introduced into the system at a rate of 5 L / min, and stirred for 4 minutes to obtain a foamed concrete slurry.

[0041] 4) The foamed concrete slurry obtained in step 3) is cast and formed, and after being placed at room temperature for 1 day, the mold is removed, and the slurry is moved into a standard curing room for pre-curing for 3 days, and then placed in a carbonization chamber for carbonization curing for 20 hours under the conditions of a CO2 concentration of 100%, an air pressure of 0.3 MPa, and a temperature of 50°C, to obtain low-carbon foamed concrete with excellent stability.

[0042] Example 2

[0043] A low-carbon foamed concrete with excellent stability, the preparation method of which is as follows:

[0044] 1) Weigh 90 parts of low-calcium clinker, 30 parts of fly ash, 8 parts of wood pulp fiber, and 60 parts of water according to the mass ratio, mix the wood pulp fiber with 30 parts of water, stir evenly to fully disperse the wood pulp fiber, and let it stand for 2 hours to obtain a wood pulp fiber suspension;

[0045] 2) 0.4 parts of laurylamine polyoxyethylene ether, 0.1 parts of a hydroxypropyl methylcellulose aqueous solution (viscosity 40 mPa·s), and 50 parts of water were mixed uniformly and stirred at a speed of 60±5 r / min for 300 s to obtain a foaming solution. The foaming solution was placed in a foaming machine, and carbon dioxide gas was introduced into the foaming solution at an output pressure of 0.2 MPa to obtain foam;

[0046] 3) The low-calcium clinker, fly ash, wood pulp fiber suspension, and remaining water from step 1) were uniformly mixed, and the foam obtained from step 2) was poured into the mixture. While stirring, carbon dioxide gas was continuously introduced into the system at a rate of 5 L / min, and stirred for 3 minutes to obtain a foamed concrete slurry.

[0047] 4) The foamed concrete slurry obtained in step 3) is cast and formed, and after being placed at room temperature for 1 day, the mold is removed, and the slurry is moved into a standard curing room for pre-curing for 3 days, and then placed in a carbonization chamber for carbonization curing for 20 hours under the conditions of a CO2 concentration of 100%, an air pressure of 0.3 MPa, and a temperature of 50°C, to obtain low-carbon foamed concrete with excellent stability.

[0048] Example 3

[0049] A low-carbon foamed concrete with excellent stability, the preparation method of which is as follows:

[0050] 1) Take low calcium clinker 70 parts, fly ash 20 parts, wood pulp fiber 6 parts, and water 40 parts according to the mass ratio, mix the wood pulp fiber with 20 parts of water, stir uniformly, make the wood pulp fiber fully dispersed, and stand for 2h to obtain a wood pulp fiber suspension;

[0051] 2) Take dodecylamine polyoxyethylene ether 0.4 parts, hydroxypropyl methyl cellulose aqueous solution (viscosity 40 mPa·s) 0.1 parts, and water 50 parts, mix uniformly, stir at a speed of 60±5 r / min for 300s to obtain a foaming liquid, place the foaming liquid in a foaming machine, and introduce carbon dioxide gas into the foaming liquid at an output pressure of 0.2 MPa to obtain a foam;

[0052] 3) Mix the low calcium clinker, fly ash, wood pulp fiber suspension, and the remaining water of step 1) uniformly, then pour the foam obtained in step 2) into it, continuously introduce carbon dioxide gas into the system at a speed of 5 L / min while stirring, and stir for 3 min to obtain a foam concrete slurry;

[0053] 4) Pour the foam concrete slurry obtained in step 3) into a mold, stand at room temperature for 1d, then remove the mold, move into a standard curing room for 3d of pre-curing, and then place it in a carbonation room under the conditions of CO2 concentration 20%, air pressure 0.1 MPa, and temperature 50℃ for carbonation curing for 20h to obtain low-carbon foam concrete with excellent stability.

[0054] Comparative Example 1

[0055] A kind of low-carbon foam concrete, its preparation method is different from the embodiment 1 in curing condition, specific steps are as follows:

[0056] 1) Take low calcium clinker 70 parts, fly ash 20 parts, wood pulp fiber 6 parts, and water 40 parts according to the mass ratio, mix the wood pulp fiber with 20 parts of water, stir uniformly, make the wood pulp fiber fully dispersed, and stand for 2h to obtain a wood pulp fiber suspension;

[0057] 2) Take dodecylamine polyoxyethylene ether 0.4 parts, hydroxypropyl methyl cellulose aqueous solution (viscosity 40 mPa·s) 0.1 parts, and water 50 parts, mix uniformly, stir at a speed of 60±5 r / min for 300s to obtain a foaming liquid, place the foaming liquid in a foaming machine, and introduce carbon dioxide gas into the foaming liquid at an output pressure of 0.2 MPa to obtain a foam;

[0058] 3) Mix the low calcium clinker, fly ash, wood pulp fiber suspension, and the remaining water of step 1) uniformly, then pour the foam obtained in step 2) into it, continuously introduce carbon dioxide gas into the system at a speed of 5 L / min while stirring, and stir for 3 min to obtain a foam concrete slurry;

[0059] 4) The foamed concrete slurry obtained in step 3) was cast and formed, and after being placed at room temperature for 1 day, the mold was removed and then placed in a carbonization chamber for carbonization curing for 20 hours under the conditions of a CO2 concentration of 100%, an air pressure of 0.3 MPa, and a temperature of 50°C to obtain low-carbon foamed concrete.

[0060] Comparative Example 2

[0061] The only difference between this comparative example and Example 1 is that P.O42.5 cement of equal mass is used to replace low-calcium clinker, and the remaining steps are the same as in Example 1.

[0062] Comparative Example 3

[0063] The only difference between this comparative example and Example 1 is that in the foaming process of step 2), air is used instead of carbon dioxide gas for foaming, and the remaining steps are the same as those in Example 1.

[0064] Comparative Example 4

[0065] The only difference between this comparative example and Example 1 is that carbon dioxide gas is not introduced during stirring in step 3, and the remaining steps are the same as in Example 1.

[0066] The foamed concrete slurry obtained in this comparative example collapsed during the curing process of 1 day at room temperature after being cast and formed, and could not be formed.

[0067] The compressive strength (f), carbon fixation (α) and dry density (ρ) of the samples prepared in Examples 1-3 and Comparative Examples 1-4 were tested. d ), foaming volume ratio (V), the test method for the carbon fixation of foam concrete is: the foam concrete is crushed, ground, and dried to a constant weight M, and then calcined at a temperature of 550°C to a constant weight M1, and then heated to 950°C and calcined to a constant weight M2, and the carbon fixation of the foam concrete is calculated according to the formula (M1-M2) / M.

[0068] The stability testing methods for foamed concrete are: 1) Appearance, primarily observing whether the foamed concrete surface is smooth and cracked after hardening; 2) Foaming Volume Ratio Test: A high foaming volume ratio after hardening indicates good stability. The foaming volume ratio (V) is tested by taking the volume of the unfoamed foamed concrete slurry (the concrete slurry obtained in step 3 without adding foam) as the reference volume (V0), and the volume of the hardened slurry as the foamed concrete volume (V1). The ratio of V1 to V0 is recorded as the foaming volume ratio (V). According to the test results of appearance and foaming volume ratio, the stability of foam concrete slurry is divided into 4 levels: excellent (foaming volume ratio is above 4, the slurry has no collapse, the slurry surface is smooth, no bubbles emerge, and no cracks); good (foaming volume ratio is 3-4, the slurry has no collapse, the slurry surface is OK, a small amount of bubbles emerge, and no cracks); general (foaming volume ratio is 2-3, the slurry collapses slightly, the slurry surface is general, a small amount of bubbles are generated, and a small amount of cracks appear); poor (foaming volume ratio is below 2, the slurry drops significantly, the slurry surface is uneven, bubbles of varying sizes are generated, and cracks of varying sizes are generated).

[0069] The test results are shown in Table 1:

[0070] Table 1

[0071]

[0072] From the data comparison of Example 1 and Comparative Example 2 in Table 1, it can be found that the strength and carbon fixation of the foamed concrete prepared using PO 42.5 cement are much lower than those of the low-carbon foamed concrete in Example 1. By comparing the data of Example 1 with Comparative Example 3, it can be found that using air instead of CO2 gas for foaming will reduce the carbon fixation and strength of the foamed concrete, and the volume stability is also poor. By comparing Example 1 with Comparative Example 1, it can be found that after the foamed concrete is cured at room temperature for 1 day and then demolded, a certain period of standard curing and re-carbonization can improve the final carbonization efficiency and strength. The results of Comparative Example 4 show that if CO2 gas is not introduced in step 3), the foam will defoam severely, the slurry cannot be formed, and the concrete stability is extremely poor.

[0073] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art who, within the technical scope disclosed by the present invention, makes equivalent substitutions or changes based on the technical solutions and improved concepts of the present invention shall be covered by the scope of protection of the present invention.

Claims

1. A low-carbon foamed concrete with excellent stability, characterized in that: The preparation method is as follows: 1) Weigh the raw materials according to the mass ratio: 60-100 parts of low-calcium clinker, 10-40 parts of fly ash, 2-8 parts of pulp fiber, 0.4-0.9 parts of physical foaming agent, 0.1-0.2 parts of foam stabilizer, and 90-120 parts of water. The mineral composition and mass percentage of the low-calcium clinker are as follows: CS 12-18%, C3S2 30-48%, C2S 18-25%, and the remainder is impurities; the 45μm sieve residue is less than 15%, and the specific surface area is 500-550 m 2 / kg; 2) Mix the pulp fibers with 20-40 parts of water, stir evenly to fully disperse the pulp fibers, and let stand for 2-4 hours to obtain a pulp fiber suspension; 3) Mix a physical foaming agent, a foam stabilizer, and 50 parts of water, stir to obtain a foaming liquid, and introduce carbon dioxide gas into the foaming liquid to foam to obtain foam; 4) uniformly mixing the pulp fiber suspension obtained in step 2), low-calcium clinker, fly ash, and remaining water, and then pouring the foam obtained in step 3) into the mixture, while continuously introducing carbon dioxide gas into the system while stirring, to obtain a foamed concrete slurry; 5) The foamed concrete slurry obtained in step 4) is cast into a mold, left at room temperature for 1 day, and then removed from the mold. The slurry is then moved into a standard curing room for pre-curing, and then placed in a carbonization chamber for carbonization, thereby obtaining low-carbon foamed concrete with excellent stability.

2. The low-carbon foamed concrete with excellent stability according to claim 1, characterized in that Step 1) The fly ash has a 45 μm sieve residue of 10-13% and a specific surface area of ​​600-700 m 2 / kg.

3. The low-carbon foamed concrete with excellent stability according to claim 1, characterized in that The pulp fiber in step 1) is one or more of wood pulp fiber, bamboo pulp fiber, and straw pulp fiber, and has a length of 1-5 mm and a diameter of 11-45 μm. The physical foaming agent in step 1) is dodecylamine polyoxyethylene ether, and its effective mass fraction is ≥99.5%. The foam stabilizer in step 1) is a hydroxypropyl methylcellulose aqueous solution, and its viscosity is 40-50 mPa·s.

4. The low-carbon foamed concrete with excellent stability according to claim 1, characterized in that The stirring process conditions of step 3) are: stirring at a speed of 60±5 r / min for 180-300 s; the method of step 3) introducing carbon dioxide gas into the foaming liquid for foaming is: placing the foaming liquid in a foaming machine, and introducing carbon dioxide gas into the foaming liquid at an output pressure of 0.2-0.4 MPa.

5. The low-carbon foamed concrete with excellent stability according to claim 1, characterized in that: The purity of the carbon dioxide gas in step 3) and step 4) is above 99 vol%.

6. The low-carbon foamed concrete with excellent stability according to claim 1, characterized in that: Step 4) Carbon dioxide gas is continuously introduced into the system at a rate of 3 to 5 L / min, and the time for introducing carbon dioxide gas is 3 to 5 minutes.

7. The low-carbon foamed concrete with excellent stability according to claim 1, characterized in that: Step 5) pre-curing time is 3 days; Step 5) carbonization conditions are: carbonization curing for 8 to 20 hours under the conditions of CO2 concentration of 20 to 100%, air pressure of 0.1 to 0.3 MPa, and temperature of 50 to 70°C.

8. A method for preparing low-carbon foamed concrete with excellent stability according to any one of claims 1 to 7, characterized in that: The specific steps are as follows: 1) Weigh the raw materials according to the mass ratio: 60-100 parts of low-calcium clinker, 10-40 parts of fly ash, 2-8 parts of pulp fiber, 0.4-0.9 parts of physical foaming agent, 0.1-0.2 parts of foam stabilizer, and 90-120 parts of water; 2) Mix the pulp fibers with 20-40 parts of water, stir evenly to fully disperse the pulp fibers, and let stand for 2-4 hours to obtain a pulp fiber suspension; 3) Mix a physical foaming agent, a foam stabilizer, and 50 parts of water, stir to obtain a foaming liquid, and introduce carbon dioxide gas into the foaming liquid to foam to obtain foam; 4) uniformly mixing the pulp fiber suspension obtained in step 2), low-calcium clinker, fly ash, and remaining water, and then pouring the foam obtained in step 3) into the mixture, while continuously introducing carbon dioxide gas into the system while stirring, to obtain a foamed concrete slurry; 5) The foamed concrete slurry obtained in step 4) is cast into a mold, left at room temperature for 1 day, and then removed from the mold. The slurry is then moved into a standard curing room for pre-curing, and then placed in a carbonization chamber for carbonization, thereby obtaining low-carbon foamed concrete with excellent stability.

9. Use of the low-carbon foamed concrete with excellent stability according to any one of claims 1 to 7 in the field of building thermal insulation materials.

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