A method of producing foamed concrete using carbon dioxide foam

Abstract

The present application relates to the technical field of concrete, and particularly relates to a method for preparing foam concrete by using carbon dioxide foam, which comprises the following steps: preparing super-stable carbon dioxide foam: uniformly dispersing nanoparticles in water to prepare a nanoparticle suspension; adding a surfactant to the nanoparticle suspension and uniformly stirring to prepare a nanoparticle foaming agent; sucking the nanoparticle foaming agent by a foaming machine, and introducing carbon dioxide to prepare stable carbon dioxide foam; uniformly stirring water and a water reducing agent in cement to obtain a cement slurry, introducing carbon dioxide gas into the cement slurry to obtain carbonated cement slurry; adding a foam stabilizer to the carbonated cement slurry and the prepared carbon dioxide foam, and continuously stirring until the carbon dioxide foam is completely introduced into the cement slurry. The foam concrete prepared by the method has a density which is at least one third lower than that of the existing method under the condition of unchanged strength, so that the application scenarios of the foam concrete are increased.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and more specifically to a method for preparing foamed concrete using carbon dioxide foam. Background Technology

[0002] Carbonation curing technology for cement-based materials can achieve safe and permanent carbon dioxide storage, significantly improving the mechanical and physical properties of cement products after curing, and has important application prospects. Enhancing the efficiency of carbonation curing not only increases carbon sequestration but also improves material performance. Currently, common methods for improving this efficiency include increasing the vacuum level of the carbonation curing chamber, increasing the carbon dioxide curing concentration, increasing the carbon dioxide curing pressure, and adjusting the moisture content of the material. However, all of these methods require high curing conditions and consume additional energy, which is detrimental to carbon reduction. Furthermore, the characteristics of carbon-cured cement-based materials make it difficult for carbon dioxide to penetrate deeply into the material, resulting in limited potential for further effective improvement after a certain level.

[0003] Foamed concrete can be made by adding foam to cement paste and then mixing and curing it. If the air in the foam is replaced with carbon dioxide gas, the preparation of foamed concrete using carbon dioxide combines carbon dioxide foaming with carbonation curing, resulting in a curing method that is completely different from traditional carbonation curing of cement-based materials. Traditional carbon dioxide curing involves localized curing from the outside in, and carbon dioxide can only cure the shallow surface layer of cement-based materials, making it difficult to penetrate deep into the material. However, using carbon dioxide to prepare foamed concrete allows for overall and uniform curing from the inside of the material. This fully utilizes carbon dioxide gas, completely solving the problem of shallow and incomplete carbonation curing, while also simplifying the carbonation curing process and improving its feasibility.

[0004] Currently, some inventions utilize carbon dioxide foam to prepare foamed concrete. For example, patent CN115611589A discloses a method for preparing cement-based foamed lightweight soil based on carbonation curing. This method uses a high-pressure carbon dioxide tank and a foaming mechanism to obtain carbon dioxide foam, which is then introduced into a reaction vessel containing cement slurry and stirred evenly to obtain foamed concrete. Another example is patent CN113277787A, which discloses an optimized preparation method for lightweight carbon dioxide foamed cement-based materials based on carbonation. This method selects 4 g / L of tea saponin as a foaming agent and 5 g / L of sodium dodecylbenzenesulfonate as a foam stabilizer. Carbon dioxide foam is prepared using a carbon dioxide water-based foaming machine and mixed with cement slurry with a specific initial water-cement ratio and foam-slurry ratio to produce carbon dioxide foamed lightweight slurry. Subsequently, methods for preparing carbon dioxide foamed concrete using different raw materials have emerged. For example, patent CN116396053A discloses a negative carbon foamed concrete and its preparation method. After wet grinding, carbon dioxide gas is introduced into the steel slag slurry, and it is mixed evenly with steel slag powder and carbon dioxide foam to obtain a carbon-fixing admixture. Then, the carbon-fixing admixture is mixed evenly with industrial solid waste with carbon fixation potential to produce foamed concrete. After carbonization curing, negative carbon foamed concrete is obtained.

[0005] However, current methods for preparing foamed concrete using carbon dioxide foam, such as those mentioned in the patents above, still have the following problems: 1. Because carbon dioxide is much more soluble in water than in air, it more easily passes through the foam liquid film, resulting in extremely poor stability of the carbon dioxide foam. Under normal circumstances, the half-life of the foam (the time required for a certain volume of foam to decay to half) is only about 5 minutes, which cannot meet the basic requirements for preparing foamed concrete. 2. Because cement paste has high alkalinity, the carbon dioxide in the foam will dissolve in water and react rapidly with the cement paste, further reducing the carbon dioxide content in the paste, ultimately resulting in the density of the prepared foamed concrete not being lower than 1200 kg / m³. 3 The following points are addressed: 3. Due to insufficient carbon dioxide introduction, the carbonation efficiency is not significantly improved, ultimately resulting in lower improvements in carbon fixation rate, mechanical properties, and thermal insulation performance of foamed concrete. This means that the application of carbon dioxide foam in foamed concrete has not achieved its full potential. Therefore, designing a method for preparing foamed concrete using carbon dioxide foam that not only stabilizes the carbon dioxide foam but also prevents the carbon dioxide in the foam from immediately reacting with the cement paste, thus producing low-density, high-strength foamed concrete, is a problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0006] This invention provides a method for preparing foamed concrete using carbon dioxide foam, so as to achieve the manufacture of low-density foamed concrete.

[0007] To achieve the above objectives, the basic solution provided by this invention is: a method for preparing foamed concrete using carbon dioxide foam, comprising:

[0008] S1. Formulate ultra-stable carbon dioxide foam;

[0009] S11. Disperse the nanoparticles evenly in water using stirring or ultrasound to prepare a nanoparticle suspension.

[0010] S12. Add a surfactant to the nanoparticle suspension and stir until homogeneous to obtain a nanoparticle foaming agent.

[0011] S13. Using a foaming machine connected to a carbon dioxide cylinder, the nanoparticle foaming agent is drawn in, increasing the outlet pressure of the carbon dioxide cylinder. This allows the carbon dioxide and nanoparticle foaming agent to mix and form continuous carbon dioxide foam. The half-life of the carbon dioxide foam is greater than 30 minutes.

[0012] S2. Preparation of carbon dioxide foamed concrete;

[0013] S21. Add water and water-reducing agent to cement and stir evenly to obtain cement paste.

[0014] S22. Carbon dioxide gas is introduced into the cement paste to completely carbonize it.

[0015] S23. Add the foam stabilizer and the carbon dioxide foam from step S13 to the carbonized cement slurry and continue stirring until all the carbon dioxide foam is incorporated into the cement slurry, thus obtaining carbon dioxide foam concrete slurry.

[0016] S24. Carbon dioxide foamed concrete is obtained by curing carbon dioxide foamed concrete slurry.

[0017] The working principle and advantages of this invention are as follows: In this solution, the preparation of foamed concrete is divided into two parts. First, ultra-stable carbon dioxide foam is prepared, so that carbon dioxide can remain stable in the foam for a long time.

[0018] First, the nanoparticles are prepared into a suspension to ensure that they are evenly dispersed in water and mixed with water to the greatest extent possible. Then, a surfactant is added to slow down the sedimentation of the nanoparticles and provide deformation tension for the subsequent formation of nanoparticle foam.

[0019] Next, carbon dioxide foam is prepared by adding nanoparticles as a foaming agent. The nanoparticles adsorb onto the liquid phase at the gas-liquid interface of the foam, which reduces the contact area between CO2 and the foam film, thereby reducing the rate at which CO2 dissolves in the liquid inside the film. The nanoparticles dispersed in the foam film increase the resistance to foam movement and hinder CO2 from passing through the foam film, reducing the rate at which CO2 diffuses from the foam into adjacent foams or the air, and preventing bubble merging. The nanoparticles dispersed in the foam film also hinder the flow of the foaming liquid inside the foam film due to gravity and other reasons, reducing the drainage of the foam film and keeping the surface tension of the liquid film at a low level, thereby preventing the foam from bursting.

[0020] Carbonizing the cement separately, allowing it to reach a high degree of carbonation first, prevents the carbon dioxide foam from reacting with the cement. This allows the carbon dioxide foam to act only as a filler material. When the cement slurry is mixed with the carbon dioxide foam, the carbon dioxide in the foam will not react with the cement slurry, thus avoiding the large-scale rupture of the carbon dioxide foam during subsequent mixing, which would ultimately prevent the production of low-density carbon dioxide foam concrete.

[0021] In addition, the addition of water-reducing agent during carbonation reduces the fluidity of cement paste, decreasing the paste flowability from 275mm to 95mm. The reduced fluidity of cement paste on the surface of carbon dioxide foam enhances the ability of cement paste to encapsulate carbon dioxide foam. By preparing carbon dioxide foam and cement paste in steps, the content of carbon dioxide foam remaining in the cement paste is greatly increased, thereby producing low-density foamed concrete. After testing, the strength of the prepared foamed concrete can still reach the existing strength.

[0022] After preparation, the foamed concrete needs to undergo carbonation curing. The carbonation curing conditions are: temperature 20℃, humidity 70%, and CO2 concentration 20%. This curing method changes the curing process from localized curing from the outside in to uniform curing from the inside, while simplifying the carbonation curing process and improving its feasibility. Because more carbon dioxide foam remains inside the foamed concrete, the degree of carbonation and the performance of the material are improved.

[0023] Furthermore, in S11, the nanoparticles are one or more of nano-silica, nano-calcium carbonate, nano-alumina, nano-titanium dioxide, and nano-zirconia, with a particle size between 10-200 nm and a mass ratio of nanoparticles to water of (0.1-10):100. Selecting nanoparticles with a particle size between 10-200 nm effectively forms a suspension, and by achieving a reasonable mass ratio with water, reduces the phenomenon of nanoparticle agglomeration.

[0024] Furthermore, in S12, the surfactant is one or more of the following: plant protein surfactant, animal protein surfactant, sodium lauryl alcohol polyoxyethylene ether sulfate, and dodecyltrimethylammonium bromide, and the mass ratio of surfactant to water is (1-10):100. As an effective additive for foam formation, the surfactant further provides the necessary conditions for foam formation and stability.

[0025] Furthermore, in S12, the outlet pressure of the carbon dioxide cylinder is 0.1-0.6 MPa, and the absorption rate of the nanoparticle foaming agent is 1-5 L / min. This scheme uses a structure that simultaneously draws in carbon dioxide and the foaming machine, and adds a foaming tube to the water pump outlet of the foaming machine to make the foaming more uniform. During use, first, the water pump in the foaming machine is turned on to draw in the foaming agent, the CO2 cylinder is opened and the flow rate of the gas valve is controlled, the outlet pressure of the carbon dioxide cylinder is adjusted to 0.1-0.6 MPa, and the absorption rate of the nanoparticle foaming agent is 1-5 L / min. Power is provided by blowing air using the internal pressure of the cylinder; CO2 and the foaming agent mix after passing through the foaming tube to form CO2 foam, which is obtained from the foam outlet.

[0026] Furthermore, in S21, the type of cement is ordinary silicate cement or sulfoaluminate cement, the type of water-reducing agent is polycarboxylate water-reducing agent or naphthalene water-reducing agent, the mass of water is 20-40% of the mass of cement, and the mass of water-reducing agent is 0.01-1% of the mass of cement.

[0027] Furthermore, in S22, the carbon dioxide aeration time required for each kilogram of cement to prepare cement slurry is 3-30 min, and the carbon dioxide flow rate is 0.1-2.0 L / min.

[0028] Furthermore, in S23, the foam stabilizer is one or more of hydroxypropyl methylcellulose, sodium bicarbonate, gum arabic, and polyacrylamide, and the mass of the foam stabilizer is 0.01-5% of the mass of the cement.

[0029] Furthermore, in S23, the amount of carbon dioxide foam added per kilogram of cement is 1-6 liters. Attached Figure Description

[0030] Figure 1 This is a flowchart of an embodiment of the present invention.

[0031] Figure 2 A schematic diagram of a structure for manufacturing carbon dioxide foam by connecting a carbon dioxide cylinder with a foaming tube. Detailed Implementation

[0032] The following detailed explanation illustrates the specific implementation methods:

[0033] Example 1

[0034] The basic implementation examples are as follows: Figure 1 As shown, a method for preparing foamed concrete using carbon dioxide foam includes:

[0035] S1. Formulate ultra-stable carbon dioxide foam;

[0036] S11. Disperse the nanoparticles evenly in water using stirring or ultrasound to prepare a nanoparticle suspension.

[0037] S12. Add a surfactant to the nanoparticle suspension and stir until homogeneous to obtain a nanoparticle foaming agent.

[0038] S13. Using a foaming machine connected to a carbon dioxide cylinder, the nanoparticle foaming agent is drawn in, increasing the outlet pressure of the carbon dioxide cylinder. This allows the carbon dioxide and nanoparticle foaming agent to mix and form continuous carbon dioxide foam. The half-life of the carbon dioxide foam is greater than 30 minutes.

[0039] S2. Preparation of carbon dioxide foamed concrete;

[0040] S21. Add water and water-reducing agent to cement and stir evenly to obtain cement paste.

[0041] S22. Carbon dioxide gas is introduced into the cement paste to completely carbonize it.

[0042] S23. Add the foam stabilizer and the carbon dioxide foam from step S13 to the carbonized cement slurry and continue stirring until all the carbon dioxide foam is incorporated into the cement slurry, thus obtaining carbon dioxide foam concrete slurry.

[0043] S24. Carbon dioxide foamed concrete is obtained by curing carbon dioxide foamed concrete slurry.

[0044] The nanoparticles are one or more of nano-silica, nano-calcium carbonate, nano-alumina, nano-titanium dioxide, and nano-zirconia. The nanoparticles are either hydrophilic or hydrophobic, with a particle size between 10-200 nm. The mass ratio of nanoparticles to water is (0.1-10):100.

[0045] The surfactant is one or more of the following: plant protein surfactant, animal protein surfactant, sodium lauryl alcohol polyoxyethylene ether sulfate, and dodecyltrimethylammonium bromide. The mass ratio of surfactant to water is (1-10):100. The outlet pressure of the carbon dioxide cylinder is 0.1-0.6 MPa, and the absorption rate of the nanoparticle foaming agent is 1-5 L / min.

[0046] The cement is ordinary silicate cement or sulfoaluminate cement, the water-reducing agent is polycarboxylate water-reducing agent or naphthalene water-reducing agent, the water mass is 20-40% of the cement mass, and the water-reducing agent mass is 0.01-1% of the cement mass.

[0047] The required carbon dioxide aeration time for each kilogram of cement slurry is 3-30 minutes, and the carbon dioxide flow rate is 0.1-2.0 L / min. The foam stabilizer is one or more of hydroxypropyl methylcellulose, sodium bicarbonate, gum arabic, and polyacrylamide, and its mass is 0.01-5% of the cement mass. In S2, the amount of carbon dioxide foam added is 1-6 L of foam per kilogram of cement.

[0048] The specific implementation process is as follows:

[0049] Step (1): Preparation of ultra-stable carbon dioxide foam

[0050] 50nm hydrophilic silica nanoparticles were uniformly dispersed in water for 10 minutes using a 20kHz ultrasonic disperser to prepare a nanoparticle suspension. The mass ratio of nanoparticles to water was 1:100. A plant protein surfactant was added to the nanoparticle suspension and stirred evenly to prepare a nanoparticle foaming agent. The mass ratio of surfactant to water was 2.5:100. The nanoparticle foaming agent was drawn into a foaming machine connected to a carbon dioxide cylinder. The liquid absorption rate of the foaming agent was adjusted to 3L / min, and the outlet pressure of the carbon dioxide cylinder was adjusted to 0.4MPa to prepare ultra-stable carbon dioxide foam. The ultra-stable carbon dioxide foam had a half-life of more than 30 minutes.

[0051] Step (2): Preparation of carbon dioxide foamed concrete

[0052] Water and water-reducing agent are added to ordinary silicate cement and stirred evenly to obtain cement slurry. The water mass is 30% of the cement mass and the water-reducing agent mass is 0.3% of the cement mass. Carbon dioxide gas is introduced into the cement slurry. The gas introduction time for each kilogram of cement slurry is 15 min and the gas flow rate is 0.9 L / min. The ultra-stable carbon dioxide foam prepared in step (1) is added to the carbonized cement slurry and stirred continuously until all the carbon dioxide foam enters the cement slurry. The amount of carbon dioxide foam added is 4 L of foam per kilogram of cement. The carbon dioxide foam concrete slurry obtained after adding carbon dioxide foam is pre-cured to obtain carbon dioxide foam concrete.

[0053] like Figure 2As shown, the outlet pressure of the carbon dioxide cylinder is 0.1-0.6 MPa, and the absorption rate of the nanoparticle foaming agent is 1-5 L / min. This scheme uses a structure that simultaneously draws in carbon dioxide and the foaming machine, and adds a foaming tube to the water pump outlet of the foaming machine to make the foaming more uniform. During use, first, the water pump in the foaming machine is turned on to draw in the foaming agent, the CO2 cylinder is opened and the flow rate of the gas valve is controlled, adjusting the outlet pressure of the carbon dioxide cylinder to 0.1-0.6 MPa, and the absorption rate of the nanoparticle foaming agent to 1-5 L / min. Power is provided by blowing air using the internal pressure of the cylinder; CO2 and the foaming agent mix after passing through the foaming tube to form CO2 foam, which is obtained from the foam outlet.

[0054] Example 1-1

[0055] A method for preparing foamed concrete using carbon dioxide foam, as shown in Example 1, uses the method in step (1) to prepare ultra-stable carbon dioxide foam.

[0056] Examples 1-2

[0057] As shown in Example 1-1, a carbon dioxide foam was prepared, except that the nanoparticles dispersed in the water were 50 nm hydrophilic nano-calcium carbonate.

[0058] Examples 1-3

[0059] As shown in Example 1-1, a carbon dioxide foam was prepared, except that nano-silica was not added to the water.

[0060] Examples 1-4

[0061] As shown in Example 1-1, a carbon dioxide foam was prepared, except that nano-silica was not added to the water, and the surfactant used was the anionic surfactant sodium dodecyl sulfate (K12).

[0062] Examples 1-5

[0063] As shown in Example 1-1, a carbon dioxide foam was prepared, except that nano-silica was not added to the water, and the surfactant used was the cationic surfactant dodecyltrimethylammonium bromide (DTAB).

[0064] Examples 1-6

[0065] As shown in Example 1-1, a carbon dioxide foam was prepared, except that nano-silica was not added to the water, and the surfactant used was the amphoteric surfactant cocamidopropyl betaine (CAB).

[0066] Examples 1-7

[0067] As shown in Example 1-1, a carbon dioxide foam was prepared, the difference being that no nano-silica was added to the water, and an animal protein surfactant was used.

[0068] The carbon dioxide foams prepared in Examples 1-1 to 1-7 were tested for half-life and expansion ratio, and the results are shown in Table 1.

[0069] Table 1. Half-life and expansion ratio of carbon dioxide foam

[0070]

[0071]

[0072] As shown in Table 1, the carbon dioxide foam prepared by the plant protein foaming agent has the best stability. Although the foaming ratio decreases after adding nanoparticles, the stability of the carbon dioxide foam is further improved. Nano silica can significantly improve the stability of carbon dioxide foam.

[0073] Example 2

[0074] A method for preparing foamed concrete using carbon dioxide foam, as shown in Example 1, differs in that, in step (1), when preparing carbon dioxide foam, nanoparticles are not added to the water, and the surfactant is directly mixed with water to form a foaming agent; in step (2), carbon dioxide gas is not introduced into the cement slurry, and carbon dioxide foam without nanoparticles is directly added to the cement slurry.

[0075] Example 3

[0076] A method for preparing foamed concrete using carbon dioxide foam, as shown in Example 1, differs in that: in step (1), when preparing carbon dioxide foam, the carbon dioxide cylinder connected to the foaming machine is replaced with an air compressor, the outlet pressure of the air compressor pipe is 0.3 MPa, and the prepared foam is air foam; in step (2), the amount of air foam added to the cement slurry is 1 L of foam per kilogram of cement, and the density of the foamed concrete obtained in Example 3 is basically the same as that in Example 1.

[0077] Comparative Example 1

[0078] Ordinary foamed concrete was prepared as a control group. Water was added to ordinary silicate cement and stirred evenly to obtain cement paste, with the water content being 40% of the cement mass. Air foam from Example 3 was added to the cement paste at a rate of 1 L of foam per kilogram of cement. The density of the foamed concrete obtained in Comparative Example 1 was basically the same as that in Example 1.

[0079] Comparative Example 2

[0080] The foamed concrete prepared in Comparative Example 1 was immediately placed in a carbonation curing chamber after demolding until the strength at the corresponding age was tested. The carbonation curing conditions were: temperature 20℃, humidity 70%, and carbon dioxide concentration 20%.

[0081] The compressive strength and density of the five groups of specimens from Examples 1-3 and Comparative Examples 1-2 were tested at the corresponding ages, and the results are shown in Table 2.

[0082] Table 2. Density and compressive strength (MPa) of specimens at corresponding ages.

[0083]

[0084] As can be seen from Table 2, the carbon dioxide foam concrete prepared in Example 2 has a significantly higher density due to the extremely poor stability of the foam without the addition of nanoparticles and the violent reaction between the uncarbonized slurry and the carbon dioxide in the foam. Although the final strength is 13.3% higher than that of this scheme, the density increases by 500 kg / m³. 3 The strength of the air-foamed concrete prepared in this scheme is 19.5% higher than that of the air-foamed concrete prepared in Example 3; the strength of the ordinary foamed concrete prepared in this scheme is 53.1% higher than that of the ordinary foamed concrete prepared in Comparative Example 1; although the ordinary carbonized curing foamed concrete in Comparative Example 2 improves the early strength of the material, the later strength improvement is not significant, and the strength is 18.4% higher than that of Comparative Example 1. The strength of this scheme is 44.5% higher than that of Comparative Example 2.

[0085] The thermal conductivity of Example 1 and Comparative Example 1 was tested at corresponding ages, and the results are shown in Table 3.

[0086] Table 3 Thermal conductivity of specimens at corresponding ages (W / (m·K))

[0087] <![CDATA[Density (kg / m 3 )]]> 1d 7d 28d Example 1 750 0.1044 0.1183 0.1237 Comparative Example 1 750 0.1637 0.1663 0.1669

[0088] As shown in Table 3, the thermal conductivity of the foamed concrete prepared by adding carbon dioxide foam in Example 1 was 36.2% lower than that of the ordinary foamed concrete in Comparative Example 1 at 1 day and 25.9% lower at 28 days. The reason for the low thermal conductivity in the early stage of Example 1 is that the thermal conductivity of carbon dioxide is 0.0137 W / (m·K), while that of air is 0.0242 W / (m·K). The pores in the foamed concrete are occupied by carbon dioxide, resulting in a lower thermal conductivity. In the later stage, the carbon dioxide in the pores of the foamed concrete reacts with the hydration products on the pore walls and is consumed, resulting in negative pressure in the pores and reducing the thermal conductivity of the material.

[0089] In this embodiment, a super-stable carbon dioxide foam was prepared using a foaming agent with added nanoparticles, achieving the goal of successfully applying carbon dioxide foam to the preparation of foamed concrete. Carbonation of the cement paste not only increased the degree of carbonation but also slowed down the reaction rate between carbon dioxide and cement paste, significantly increasing the content of carbon dioxide foam remaining in the cement paste, thus enabling the preparation of low-density carbon dioxide foamed concrete. The curing process was changed from the traditional external-to-inside localized carbonation curing to uniform curing from the inside out, simplifying the curing process and improving feasibility. Because a significant amount of carbon dioxide foam remained inside the foamed concrete, the degree of carbonation and material performance were improved.

[0090] In summary, this solution solves the problem of unstable carbon dioxide foam, slows down the reaction rate between carbon dioxide and cement slurry, allows more carbon dioxide foam to remain in the cement slurry, produces lower density foamed concrete, improves the carbon fixation rate of carbon dioxide foamed concrete, and increases its strength.

[0091] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing foamed concrete using carbon dioxide foam, characterized in that, include: S1. Formulate ultra-stable carbon dioxide foam; S11. Disperse silica nanoparticles uniformly in water using stirring or ultrasound to prepare a silica nanoparticle suspension. S12. Add a surfactant to the silica nanoparticle suspension and stir until homogeneous to obtain a silica nanoparticle foaming agent. S13. Using a foaming machine connected to a carbon dioxide cylinder, silica nanoparticle foaming agent is drawn in, increasing the outlet pressure of the carbon dioxide cylinder. This allows the carbon dioxide and silica nanoparticle foaming agent to mix and form continuous carbon dioxide foam. The half-life of the carbon dioxide foam is greater than 30 minutes. S2. Preparation of carbon dioxide foamed concrete; S21. Add water and water-reducing agent to cement and stir evenly to obtain cement paste. S22. Carbon dioxide gas is introduced into the cement paste to completely carbonize it. S23. Add the foam stabilizer and the carbon dioxide foam from step S13 to the carbonized cement slurry and continue stirring until all the carbon dioxide foam is incorporated into the cement slurry, thus obtaining carbon dioxide foam concrete slurry. S24. Carbon dioxide foamed concrete is obtained by curing carbon dioxide foamed concrete slurry.

2. The method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that: The silica nanoparticles have a particle size between 10 and 200 nm, and the mass ratio of silica nanoparticles to water is (0.1-10):

100.

3. The method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that, In step S12, the surfactant is one or more of plant protein surfactants, animal protein surfactants, sodium fatty alcohol polyoxyethylene ether sulfate, and dodecyltrimethylammonium bromide, and the mass ratio of surfactant to water is (1-10):

100.

4. A method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that, In step S13, the outlet pressure of the carbon dioxide cylinder is in the range of 0.1-0.6 MPa, and the absorption rate of the nanoparticle foaming agent is 1-5 L / min.

5. A method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that, In S21, the cement is ordinary Portland cement or sulfoaluminate cement, and the water content is 20-40% of the cement content.

6. A method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that, In step S21, the water-reducing agent is a polycarboxylate water-reducing agent or a naphthalene-based water-reducing agent, and the mass of the water-reducing agent is 0.01-1% of the mass of the cement.

7. A method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that, In S22, the carbon dioxide aeration time required for each kilogram of cement to prepare cement paste is 3-30 min, and the carbon dioxide flow rate is 0.1-2.0 L / min.

8. A method for preparing foamed concrete using carbon dioxide foam as described in claim 1, characterized in that, In S23, the foam stabilizer is one or more of hydroxypropyl methylcellulose, sodium bicarbonate, gum arabic, and polyacrylamide, and the mass of the foam stabilizer is 0.01-5% of the mass of the cement.

9. A method for preparing foamed concrete using carbon dioxide foam as described in claim 1 or 8, characterized in that, In S23, the amount of carbon dioxide foam added per kilogram of cement is 1-6 liters.

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