A method for regulating a quick-setting carbon dioxide foam concrete

Abstract

This invention provides a method for controlling the yield stress of quick-setting carbon dioxide foamed concrete. The method of this invention establishes the yield stress of carbon dioxide foamed slurry. t 0 Mathematical model and foam stability coefficient S f The mathematical model accurately and efficiently controls the properties of slurry foam and the rheological parameters of cementitious materials, thereby controlling the quality of foam concrete preparation process and mechanical properties. This results in foam concrete materials with high early strength, excellent durability and good carbon sequestration, which can shorten the production cycle, improve product performance and broaden the application scenarios of foam concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and specifically to a method for controlling the setting of rapid-setting carbon dioxide foam concrete. Background Technology

[0002] Foamed concrete is a porous, lightweight inorganic material formed by the physical / chemical action of cementitious materials, water, and foaming agents. Its typical characteristics include low density, high porosity, excellent thermal insulation, and good sound insulation and fire resistance. However, traditional preparation processes rely on alkane-based chemical foaming agents or surfactants for physical foaming, which easily leads to bubble coalescence and rupture, forming a non-uniform pore structure. This results in a material compressive strength generally below 5 MPa and a drying shrinkage rate as high as 0.3%-0.8%. Furthermore, the hydration reaction of silicate cement-based systems is slow, making it difficult to meet the early strength requirements of rapid construction scenarios. In recent years, novel foaming-mineralization synergistic technologies based on the functional utilization of carbon dioxide gas have attracted attention: CO2 can act as a foaming agent, forming micron-sized closed pores through pressure release, and the carbonate ions generated from its dissolution can react with Ca in the cementitious materials. 2+ Mg 2+ After a mineralization reaction occurs, carbonate crystal nuclei are generated, which accelerates condensation and strengthens the pore interface, making it an environmentally friendly and energy-saving building material with development potential.

[0003] As a foaming gas, CO2's solubility varies with pressure under pressure gradient control, allowing for precise control of bubble size. Furthermore, the HCO3 produced by CO2 dissolution... - / CO3 2- With active cations (Ca) in cementitious materials 2+ Mg 2+ A mineralization reaction occurs, generating nano-carbonate crystals (calcite, aragonite, etc.). This process not only releases heat of hydration to accelerate solidification but also improves pore wall density through nucleation and interfacial bonding. By designing the cementing components and optimizing CO2 injection parameters, the CO2 solidification rate can reach over 85%, while simultaneously achieving synergistic optimization of compressive strength and porosity, thus combining carbon sequestration and emission reduction with structural functionality.

[0004] However, this also presents some problems. Because carbon dioxide is far more soluble in water than in air, the stability of CO2 foam in cement paste is significantly reduced. On the one hand, the rapid dissolution of CO2 in alkaline paste (solubility approximately 1.45 g / L, 25℃) causes a sharp drop in internal pressure of the bubbles, exacerbating Oswald curing. On the other hand, the mismatch between the carbonate precipitation rate and the interfacial tension regulation of the bubbles results in insufficient gas-liquid interfacial film strength. Furthermore, due to the high alkalinity of the cement paste, dissolved CO2 rapidly reacts with calcium hydroxide in the paste to form calcium carbonate, which not only accelerates foam collapse but also significantly reduces the CO2 content in the paste, limiting overall carbonation efficiency. Simultaneously, CO2 foam is significantly affected by the liquid film drainage effect. Due to gas diffusion between bubbles, CO2 transfers from smaller bubbles to larger bubbles, exacerbating foam instability and causing large bubbles to expand and rupture rapidly, thus reducing the durability of the foam system. In addition, the slow formation of hydration products results in insufficient encapsulation and support of the foam by the paste, further aggravating foam collapse. Because CO2 bubbles largely disappear before the cementitious material sets and hardens, the carbonation process is not fully realized, resulting in a low carbon fixation rate in foamed concrete, and its mechanical and thermal insulation properties are not effectively improved.

[0005] As the bubble carrier and mineralization reaction medium, the slurry's plastic viscosity and yield stress must satisfy a dynamic balance. If the viscosity is too low, CO2 bubbles will rapidly rise and coalesce due to buoyancy, leading to an increased coefficient of variation in pore size distribution. Conversely, if the viscosity is too high, bubble expansion will be inhibited, limiting porosity. Simultaneously, insufficient thixotropy in the slurry results in a significant shear-thinning effect, causing bubble walls to collapse before the mineralization reaction is complete. An excessively fast thixotropic recovery rate hinders CO2 diffusion, reducing the carbonization depth. Furthermore, the yield stress also determines the slurry's ability to encapsulate bubbles. At low yield stress, bubbles are prone to rupture before the mineralization reaction is complete, while high yield stress hinders CO2 diffusion.

[0006] In summary, the high solubility of CO2, the fragility of the foam film, and the Ostwald curing effect between bubbles lead to insufficient stability of carbon dioxide foam. The rheological parameters and other properties of the cement paste hinder CO2 diffusion, resulting in slow formation of hydration products. The poor stability of carbon dioxide foam and the inadequate bonding between the cement paste and the foam result in poor quality foamed concrete, limiting its application potential in carbon capture and the preparation of high-performance building materials.

[0007] To address the poor stability of carbon dioxide foam, admixtures are typically added. Firstly, nanoparticles can be used as foam stabilizers. During foam prefabrication, these particles adsorb onto the liquid film, forming a substantial solid film surrounding the bubbles. This reduces the contact area between carbon dioxide molecules and the liquid film, weakening the disproportionation reaction that leads to foam collapse. Alternatively, polymers can be added to increase liquid phase viscosity, thereby enhancing foam stability. For the poor bonding between cement paste and carbon dioxide foam, the properties of the cement paste can be optimized. Adjusting the paste's viscosity and yield stress ensures the encapsulation and support of the foam bubbles. Alternatively, optimizing the consistency and alkalinity of the cement paste increases the retention rate of CO2 foam after its introduction, reducing foam breakage. Furthermore, adding admixtures or adjusting the cement paste mix ratio accelerates the formation of hydration products, enhancing the paste's support for the foam and reducing foam collapse. These measures effectively improve the bonding between cement paste and carbon dioxide foam, enhancing the quality and application potential of foamed concrete.

[0008] In the preparation of foamed concrete, there is a certain relationship between foam stability and the rheological parameters of cement paste, but the quantitative relationship between the two remains unclear. Current control methods rely heavily on empirical adjustments, making it difficult to accurately balance the contradiction between bubble structure stability and paste pumpability. The influence of interfacial chemical interactions, shear dilution effects, and hydration processes leads to blind spots in mix design. There is an urgent need to construct a quantitative mathematical model of "rheological parameters-interfacial properties-bubble evolution" through simulation to provide theoretical support for the development of lightweight, high-strength cement-based materials, enabling efficient control of rapid-setting carbon dioxide foamed concrete and improving its quality and application potential. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a method for controlling the yield stress of quick-setting carbon dioxide foamed concrete. The method of this invention establishes the yield stress of carbon dioxide foamed slurry. t 0 Mathematical model and foam stability coefficient S f The mathematical model accurately and efficiently controls the properties of slurry foam and the rheological parameters of cementitious materials, thereby controlling the quality of foam concrete preparation process and mechanical properties. This results in foam concrete materials with high early strength, excellent durability and good carbon sequestration, which can shorten the production cycle, improve product performance and broaden the application scenarios of foam concrete.

[0010] The technical solution of the present invention is as follows:

[0011] A method for controlling the yield stress of quick-setting carbon dioxide foam concrete includes the following steps: adjusting the yield stress of carbon dioxide foam slurry. t 0 Mathematical model and foam stability coefficient S fMathematical models enable the control of rapid-setting carbon dioxide foam concrete;

[0012] Yield stress t 0. Mathematical Model:

[0013]

[0014] in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of carbon dioxide foam is expressed in mN / m.

[0015] Foam stability coefficient S f Mathematical model:

[0016]

[0017] in: t 0 represents the yield stress of the carbon dioxide-added foam slurry, in Pa; γ represents the interfacial tension between the carbon dioxide bubbles and the liquid phase of the slurry (i.e., the gas-liquid interfacial tension), in N / m. Critical shear rate, in seconds. -1 ; α The foam structure strengthening coefficient; r Where is the bubble radius, in meters (m). d The average thickness of the slurry film between adjacent bubbles, in meters; or p The plastic viscosity of carbon dioxide-added foam slurry at a standard temperature of 20℃ is expressed in Pa·s. or w The viscosity of water at 20°C is expressed in Pa·s.

[0018] According to a preferred embodiment of the present invention, the yield stress t In the mathematical model, material constants K The following method was used to determine the conditions under a fixed temperature (20±0.5℃) for preparing bubbles with different carbon dioxide volume fractions and surface tensions. s i Carbon dioxide-added foam slurry; rheological curves of each sample were collected at set time points, and the yield stress at the corresponding time was extracted by fitting with the Bingham model. t ( t j Simultaneously, the reference yield stress of each sample was measured at the same time. tbase ( t j Then, an observation sequence was constructed using the yield stress difference. t ( t j )- t base ( t j ) is the dependent variable, and φ is the dependent variable. i / s i Using K as the independent variable, a linear regression using the least squares method is performed, with the slope being the constant K. This is done to maintain the model's physical interpretability and predictive stability. The final... K The values ​​should be calculated using regression analysis on datasets showing good linearity (R² ≥ 0.90) from multiple independent and repeated experiments (no fewer than three groups) to ensure representativeness and stability. The material constants determined using the above method... K It can accurately reflect the sensitivity of the change in the yield stress of the foam slurry after the addition of carbon dioxide, and provide a reliable theoretical basis and parameter support for the subsequent calculation of the foam stability coefficient and process control.

[0019] According to a preferred embodiment of the present invention, the foam stability coefficient S f In the mathematical model, the average thickness d of the slurry film between adjacent bubbles is obtained by microscopic observation.

[0020] According to a preferred embodiment of the present invention, based on the yield stress of the carbon dioxide-added foam slurry... t A mathematical model was developed to regulate the surface tension of carbon dioxide foam. s To achieve yield stress t The control of 0 allows for the regulation of the preparation process and performance of rapid-setting carbon dioxide foam concrete.

[0021] According to a preferred embodiment of the present invention, based on the foam stability coefficient of the carbon dioxide-added foam slurry... S f Mathematical model, by controlling the yield stress of carbon dioxide-added foam slurry t 0. Interfacial tension γ between carbon dioxide bubbles and the slurry liquid phase; bubble radius r Average thickness of the slurry film between adjacent bubbles d Plastic viscosity of carbon dioxide-added foam slurry or p One or a combination thereof, to achieve the foam stability coefficient S f The control of these parameters allows for the regulation of the preparation process and performance of quick-setting carbon dioxide foam concrete.

[0022] According to a preferred embodiment of the present invention, based on the target yield stress t 0 or foam stability coefficient S f The yield stress of the foam slurry can be increased by adding carbon dioxide. t 0 Mathematical model or foam stability coefficient S f The mathematical model yields specific performance parameters, and the preparation process is adjusted to obtain a product with the target yield stress. t 0 or foam stability coefficient S f Quick-setting carbon dioxide foam concrete.

[0023] According to a preferred embodiment of the present invention, yield stress is a key indicator reflecting the fluidity and bubble stability of foamed concrete slurry: when yield stress t When the Pa is below 100, the concrete performance is poor, the paste is too thin, and it cannot provide effective support for the air bubbles. The air bubbles are prone to floating and agglomerating, resulting in uneven pore size distribution, poor foam stability, and affecting the uniformity and strength of the foamed concrete; yield stress t When the Pa value is within the range of 100-200 Pa, the concrete exhibits good performance, with moderate paste viscosity and strength. This effectively encapsulates air bubbles, inhibiting their rise and aggregation, resulting in uniform dispersion and a stable pore structure. This improves the strength and durability of foamed concrete, making it suitable for conventional applications such as lightweight insulation. Meanwhile, the yield stress... t When the Pa exceeds 200, the concrete performance is poor, the paste becomes too thick, fluidity is poor, pouring is difficult, and air bubbles are hard to distribute evenly, leading to foam rupture and affecting the quality and performance of foamed concrete. (Foam stability coefficient) S f The calculation results are usually in 10 9 -10 10 Within the range: when the foam stability coefficient S f <10 9 When the concrete performance is poor and the foam stability is insufficient, the concrete is prone to collapse and the pore structure is easily deteriorated, leading to a reduction in strength, durability, and construction quality; when the foam stability coefficient is low... S f In 10 9 -10 10 When the foam stability coefficient is between [a certain value], the concrete performance is good and can meet the requirements of general non-load-bearing insulation materials, but the room for performance improvement is limited; when the foam stability coefficient is ... S f >10 10 When the concrete exhibits excellent performance and highly stable foam, it is suitable for high-strength or high-performance applications such as carbon sequestration. It forms a uniform and stable pore structure, significantly improving the material's compressive strength and carbon sequestration efficiency. However, if the yield stress is high or the interfacial tension is low... S fThe value may be further increased, thereby optimizing the performance of foamed concrete.

[0024] Preferably, yield stress t When the Pa is in the range of 100-200 Pa, the yield stress is t The lower the value of 0, the better the concrete performance; foam stability coefficient S f The larger the diameter, the better the concrete performance.

[0025] According to the present invention, an efficient method for preparing quick-setting carbon dioxide foamed concrete is proposed by scientifically controlling the yield stress and foam stability coefficient of cement. Specifically, it includes: selecting sulfoaluminate cement or low-heat silicate cement as the base material, dynamically adding early-strength agents and / or quick-setting agents to optimize the water-cement ratio. Simultaneously, composite surfactants and / or polymeric stabilizers (such as hydroxypropyl methylcellulose) and / or nanoparticles are used to control the surface tension of the foam, inhibit Ostwald curing, extend the foam half-life, and achieve uniform bubble distribution. In terms of process, pre-prepared CO2 foam and slurry are mixed by mechanical stirring, poured, and then allowed to stand to solidify. By dynamically adjusting the admixtures, the material is ensured to possess both high mechanical properties and engineering applicability, making it suitable for building insulation and carbon sequestration. Preferably, the preparation method of the carbon dioxide foamed concrete slurry includes the following steps: uniformly mixing surfactant and water to obtain a foaming solution; using a physical foaming machine to introduce carbon dioxide gas to generate dense foam; uniformly mixing cement and water to obtain cement slurry; adding the above-mentioned foam to the cement slurry and mixing thoroughly to obtain the carbon dioxide foamed concrete slurry. Further preferably, a polymeric stabilizer (such as hydroxypropyl methylcellulose) and / or nanoparticles are added to the foaming solution; and an early-strength agent and / or a quick-setting agent are added to the cement slurry.

[0026] According to the present invention, the yield stress of carbon dioxide-added foam slurry t The method for determining the mathematical model is as follows:

[0027] As a time-varying non-Newtonian fluid, cement paste's rheological parameters significantly influence its strength development. In the preparation of carbon dioxide foamed concrete, rheological parameters (such as yield stress, plastic viscosity, and thixotropy) can directly affect the uniformity of the pore structure and material properties by controlling the dispersion, migration, and stabilization behavior of air bubbles. Appropriate yield stress can inhibit foam buoyancy and breakage, plastic viscosity can delay bubble coalescence, and thixotropy can balance workability and pre-hardening stability. Dynamic matching of rheological properties can be achieved by optimizing the water-cement ratio and admixtures, thereby forming a fine closed-cell and high-porosity structure while ensuring the paste's workability, ultimately balancing the lightweight nature and mechanical strength of the concrete.

[0028] In the preparation of carbon dioxide foamed concrete, the addition of foam reduces the interparticle force of the paste due to the dilution effect, weakening the yield strength. Furthermore, the high admixture may increase the local strength due to the extrusion of air bubbles, altering the yield strength of the cement paste and leading to an imbalance between foam stability and paste fluidity. Therefore, it is necessary to correct the yield strength and balance the rheological properties by adjusting the water-cement ratio, adding thickeners, and optimizing the foam admixture. This will enable the paste to effectively encapsulate air bubbles and inhibit coarsening while maintaining the fluidity required for construction, ultimately forming a foamed concrete structure with uniform pores, lightweight properties, and controllable mechanical properties. This allows for the derivation of a quantitative description of the yield strength of cement paste.

[0029] The yield stress of cement paste reflects the critical stress required for it to begin flowing and is related to the strength of its internal structure. When carbon dioxide foam is introduced, the presence of the bubbles affects this structure. The surface tension of the bubbles (…) s This determines the size and stability of the bubble. When s At higher levels, the bubbles are larger (according to the Weber number). r ∝ s This leads to a reduction in interface area, thereby decreasing the reinforcing effect on the slurry structure. Surface tension s As the bubble size increases, the bubble radius also increases. r ∝ s This leads to a decrease in the total interfacial area A of the bubbles per unit volume. Since the increase in the yield stress of the slurry is proportional to the interfacial area A, the decrease in the interfacial area weakens the reinforcing effect on the slurry structure, ultimately manifesting as... t 0 s Increases and decreases. Therefore, by reducing σ (e.g., using surfactants), the bubble size can be reduced and the interfacial area increased, thereby improving the yield stress of the slurry and optimizing the stability and performance of foamed concrete. That is, A∝1 / s and t 0 ∝ A, therefore t 0 and s Inversely proportional.

[0030] First, based on Weber number analysis, under fixed stirring conditions, the bubble radius... r ∝ s ,Right now r=kσ ( k (where A is a proportionality constant), and the interfacial area of ​​the bubble per unit volume is A = 3 φ / r φ is the percentage of carbon dioxide bubble volume to the total slurry volume. Substituting into... r=kσ Therefore, we can obtain: A = 3 φ / (kσ) Now, assuming that the yield stress increment of the cement paste is proportional to the interfacial area, then: t 0= t 0,base + k`•A= t 0,base + (k` •3φ) / ( ks) Combine the constant terms into K=(k`• 3 ) / k The yield stress of carbon dioxide-added foam slurry was obtained. t 0:

[0031]

[0032] in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of carbon dioxide foam is expressed in mN / m.

[0033] This model shows that the yield stress of cement paste is inversely proportional to the surface tension of carbon dioxide foam. As surface tension increases, the bubble size increases, the interfacial area decreases, leading to a decrease in yield stress. This relationship provides a theoretical basis for optimizing the rheological properties of foamed concrete.

[0034] According to the present invention, the foam stability coefficient of carbon dioxide-added foam slurry S f The method for determining the mathematical model is as follows:

[0035] The stability of CO2 foam plays a crucial role in the strength gain, workability, and durability of foamed concrete. Stable foam ensures that the slurry uniformly encapsulates air bubbles, forming a uniformly structured pore structure, improving early strength and final mechanical properties, while also enhancing carbon sequestration efficiency and thermal insulation performance. However, due to the high solubility of CO2 in water and the influence of carbonation reactions, foam is prone to rupture, leading to slurry collapse and deterioration of the pore structure, thereby reducing the strength, durability, and construction quality of foamed concrete. Therefore, it is necessary to improve the stability of CO2 foam by optimizing the foaming agent formulation and adding polymeric stabilizers, so that foamed concrete possesses superior mechanical and physical properties, ensuring its reliability and applicability in engineering projects.

[0036] Precast foam is a dispersion system in which gas is dispersed in a liquid. Because it contains numerous gas-liquid interfaces, it is not a static equilibrium system, and its structure and properties change over time. Three main factors contribute to foam instability: drainage caused by gravity segregation, bubble coalescence caused by film rupture, and disproportionation caused by gas diffusion. Since the liquid phase density is greater than the gas phase density, gas-liquid separation occurs under gravity, and the liquid film gradually thins, resulting in foam drainage. Furthermore, surface tension is also a significant factor contributing to the hydrophobicity of the foam film. As surface tension decreases, the expansion modulus of elasticity increases, and the expansion viscoelasticity of the liquid film has a crucial impact on the foam's resistance to external disturbances and rupture. Foam stability is affected by factors such as the surface tension of the foam film, drainage rate, and bubble coalescence, while the rheological properties of the cement paste significantly influence these processes. Therefore, foam stability can be characterized by surface tension, paste yield stress, and viscosity, and a mathematical model can be established to describe the relationships between these parameters.

[0037] (1) Theoretical basis and assumptions

[0038] Foam stability is mainly controlled by the following physical mechanisms: the yield stress of the slurry ( t 0), interfacial tension (γ), bubble radius ( r ), slurry film thickness ( d And the foam half-life. Now assume the cement paste is a Bingham fluid, and its yield stress is... t Initial stability is dominated by γ, while the foam bursting rate is driven by interfacial tension and competes with the slurry rheological properties. The driving force for foam bursting comes from the interfacial tension γ, while the resistance comes from the yield stress of the slurry. t 0. When a bubble is subjected to shear, the driving force and the resisting force interact, and when the critical shear rate is reached... (The typical rate characterizing the dynamic deformation of foam is approximately 0.1 s in experiments.) -1 At this point, the foam stabilizes and reaches equilibrium. Because the geometry of the foam and the viscosity of the slurry have a significant impact on stability, small bubbles (low viscosity)... r ) and thick liquid film (high d High viscosity can delay foam bursting, while high viscosity will inhibit liquid film flow.

[0039] (2) Construction of the comprehensive formula:

[0040] Foam stability coefficient S f Mathematical model:

[0041]

[0042] in: t0 represents the yield stress of the carbon dioxide-added foam slurry, in Pa; γ represents the interfacial tension between the carbon dioxide bubbles and the liquid phase of the slurry (i.e., the gas-liquid interfacial tension), in N / m. Critical shear rate, in seconds. -1 ; α The foam structure strengthening coefficient; r Where is the bubble radius, in meters (m). d The average thickness of the slurry film between adjacent bubbles, in meters; or p The plastic viscosity of carbon dioxide-added foam slurry at a standard temperature of 20℃ is expressed in Pa·s. or w The viscosity of water at 20°C is expressed in Pa·s.

[0043] (3) Summary of physical meaning:

[0044] When the yield stress of the slurry t As 0 increases, the slurry's resistance to deformation increases, the interfacial tension γ decreases, which weakens the interfacial driving force and reduces the bubble radius. r Or liquid film thickness d Increasing the viscosity makes the foam structure denser, while increasing the viscosity of the slurry. or p Increasing the volume reduces the fluidity of the slurry, delays drainage and aggregation, all of which can improve the foam stability coefficient.

[0045] The technical features and beneficial effects of this invention are as follows:

[0046] 1. This invention achieves precise design of the pore structure of foamed concrete by modifying the yield stress relationship of cement paste after adding foam. By controlling the synergistic effect of the yield stress of cement paste and the surface tension of carbon dioxide foam, the stability and uniformity of the pore structure of foamed concrete can be optimized. While ensuring lightweight properties, mechanical strength and thermal insulation performance are improved, and construction fluidity and bubble anti-collapse ability are also improved. In addition, the use of carbon dioxide foaming has the benefits of resource utilization and emission reduction, ultimately achieving the goal of preparing high-performance, low-energy-consumption green building materials.

[0047] 2. This invention uses the modified slurry yield stress to determine the stability of carbon dioxide foam, which ensures good foam stability during the preparation of foamed concrete to form a good pore structure. The pore structure of foamed concrete has a decisive influence on its performance. Foam with good stability can form approximately spherical, non-interconnected pores, which has a positive effect on improving the mechanical properties, thermal properties, water absorption and frost resistance of foamed concrete.

[0048] 3. This invention quantifies the relationship between carbon dioxide foam and slurry by defining a foam stability coefficient. This control method not only helps to fix the shape of the foam but also provides favorable conditions for strength growth. When the cement yield stress is precisely controlled, the slurry can rapidly begin to solidify in the stable stage before the foam bursts, thereby locking the foam morphology inside the concrete and forming a uniform and stable pore structure. The stability of this pore structure is crucial for improving the performance and carbon sequestration efficiency of foamed concrete because it reduces pore connectivity and material density unevenness caused by bubble bursts. In terms of strength growth, the shortened initial setting time means that the cement hydration reaction can proceed faster, and hydration products are continuously generated and fill the gaps between the foams, enhancing the overall strength of the material. In addition, this control can optimize construction performance and reduce construction problems caused by excessively long or short initial setting times, such as poor slurry fluidity or limited construction window, thereby improving construction efficiency and the quality of the final product.

[0049] 4. Based on yield stress t A mathematical model was developed to regulate the surface tension of carbon dioxide foam. s To achieve yield stress t The control of 0 allows for the regulation of the preparation process and performance of rapid-setting carbon dioxide foamed concrete. This is based on the foam stability coefficient. S f Mathematical model, by adjusting the yield stress of the slurry t 0, interfacial tension γ, bubble radius r slurry film thickness d slurry viscosity or p One or a combination thereof, to achieve the foam stability coefficient S f The control of this process allows for the regulation of the preparation process and performance of rapid-setting carbon dioxide foamed concrete. This is based on the target yield stress. t 0 or foam stability coefficient S f It can be achieved through yield stress t 0 Mathematical model or foam stability coefficient S f The mathematical model yields specific performance parameters, which are then controlled by adjusting the manufacturing process to produce a product with the target yield stress. t 0 or foam stability coefficient S f Quick-setting carbon dioxide foamed concrete. Yield stress was calculated. t 0 and foam stability coefficient S f It can be used to evaluate the performance of quick-setting carbon dioxide foam concrete.

[0050] 5. The yield stress proposed in this invention t The mathematical model for 0 is flawed because existing technologies primarily rely on empirical formulas or linear models (such as the Bingham model and the Herschel-Bulkley model) to describe the rheological parameters of cement paste, failing to accurately correlate rheological properties with the nonlinear characteristics of the setting process. This invention proposes a yield stress... t A mathematical model can optimize the yield stress of cement paste after adding foam and quantitatively guide the optimization of admixtures. Regarding the foam stability coefficient... S f The mathematical model currently relies mainly on qualitative analysis of a single factor (such as surface tension or viscosity) or empirical formulas for half-life. t 1 / 2 ∝ the / c However, it did not systematically integrate drainage rate, Laplace pressure, and Ostwald ripening effect. This invention establishes the foam radius through multi-parameter simultaneous analysis. r Viscosity or With surface tension c The quantitative relationship is used to achieve dynamic control of CO2 foam stability.

[0051] 6. The yield stress determined in this invention t 0 and foam stability coefficient S f The mathematical model can optimize the ratio of admixtures and evaluate product quality by combining the increase in compressive strength.

[0052] 7. The control method proposed in this invention establishes a systematic path from parameter control to performance optimization based on the mathematical models of yield stress and foam stability coefficient of carbon dioxide-added foam slurry. By controlling the surface tension of carbon dioxide foam, the yield stress of the slurry can be effectively adjusted, thereby affecting the slurry's ability to encapsulate air bubbles and its fluidity, achieving precise control of the rheological properties of foamed concrete. Simultaneously, based on the mathematical model of foam stability coefficient, by controlling parameters such as the yield stress, interfacial tension, bubble radius, slurry film thickness, and slurry plastic viscosity, the stability of foam in the slurry can be systematically optimized, effectively suppressing bubble coalescence and collapse, and improving the uniformity and stability of the pore structure. Verification by examples shows that this control path can control the yield stress within the optimal performance range of 100–200 Pa, and the foam stability coefficient is greater than 10. 9 This results in carbon dioxide foamed concrete products with excellent mechanical properties, high density, and high carbon sequestration efficiency. Detailed Implementation

[0053] The technical solution of the present invention will be further described below with reference to specific embodiments. All raw materials used in the embodiments are commercially available products; all equipment used is conventional equipment; and all testing methods are conventional methods.

[0054] Example 1

[0055] A method for preparing carbon dioxide foamed concrete without admixtures includes the following steps:

[0056] S1. Preparation of carbon dioxide foamed concrete

[0057] S1.1. Take a certain mass of animal protein foaming liquid, add water (the mass of water is 30 times the mass of animal protein foaming liquid), stir evenly to prepare a foaming solution, and use a physical foaming machine to pass carbon dioxide gas to produce dense foam for later use.

[0058] S1.2. Mix 10.71 kg of standard cement and 4.82 kg of water evenly to form a uniform cement paste with a water-cement ratio of 0.45.

[0059] S1.3, Set the target wet density to 800 kg / m³ 3 According to the calculation results, 0.47 kg of precast foam was added to the cement paste in batches and stirred. After stirring, the product was obtained, which is the carbon dioxide foamed concrete paste.

[0060] S2. Comparison of rheological parameter determination results with data fitting results from comparative experiments.

[0061] The yield stress of the slurry obtained in step S1.2 was tested using a rheometer. t 0,base The surface tension of the carbon dioxide foam prepared in step S1.1 was tested using a surface tension meter. s ; Measurement value t 0. The yield stress of the cement paste with added foam (S1.3) was tested using a rheometer; each parameter was tested five times and the average value was taken. The percentage of carbon dioxide bubble volume to the total paste volume (φ) was calculated using existing methods.

[0062] Yield stress t In the mathematical model, material constants K The following method was used to determine the preparation of bubbles with different carbon dioxide bubble volume fractions φ at 20±0.5℃. i With surface tension s i Carbon dioxide-added foam slurry; rheological curves of each sample were collected at set time points, and the yield stress at the corresponding time was extracted by fitting with the Bingham model. t ( t jSimultaneously, the reference yield stress of each sample was measured at the same time. t base ( t j ). Based on the yield stress difference t ( t j )- t base ( t j ) is the dependent variable, and φ is the dependent variable. i / s i Using the least squares method as the independent variable, linear regression was performed. The regression determination coefficient R² ≥ 0.90 and the residual distribution was random, indicating a linear relationship. The slope was taken as the material constant K. The final value of K was the average of multiple independent experiments (no less than 3 groups).

[0063] The surface tension obtained from the above tests s Material constants K Yield stress of grout without added foam (i.e., cement grout) t 0,base Bubble volume fraction φ, using yield stress t 0 Mathematical model calculation of fitted value t 0:

[0064]

[0065] in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of the carbon dioxide foam is expressed in mN / m.

[0066] The test results are shown in the table below.

[0067]

[0068] Comparing the fitting results with the actual measurement results, the fitting results are close to the experimental results, indicating that the model of the present invention has good accuracy.

[0069] S3, Foam Stability Coefficient S f Number calculation

[0070] Stability parameters were tested, with each parameter tested five times and the average value taken. The results are shown in the table below.

[0071]

[0072] The foam structure strengthening coefficient α As a dimensionless parameter, the specific method for determining it is as follows: Prepare thin-layer samples of the aforementioned carbon dioxide foamed concrete and immediately observe them under an optical microscope. Using image analysis software (such as ImageJ), randomly select no fewer than 50 bubbles, measure their equivalent radii, and calculate the average value as the initial average bubble radius. r 0. Keep the sample in a static environment during initial observation. t 0 after 60 seconds ( t 1) At that time, randomly select no fewer than 50 bubbles in the same or adjacent fields of view and measure their average radius, denoted as . r 1. r 0- r 1 is denoted as Δ r Δ t The value is 60s. The strengthening coefficient of the foam structure is... α Calculate using the following formula:

[0073]

[0074] in, k It is 0.01 s - ¹.

[0075] Calculate the foam stability coefficient S f Mathematical model:

[0076]

[0077] S4. Pour the slurry into the mold to about half its capacity. Gently tap the side wall of the mold to distribute it more evenly. Then continue pouring slurry into the mold until it is slightly above the top surface, and use a scraper to smooth the surface of the slurry. Finally, cover the top surface of the mold with plastic wrap and place the mold in a standard curing room (temperature (20±2)℃, relative humidity not less than 95%) for curing for 28 days.

[0078] The average compressive strength of the five groups of specimens was measured using experimental instruments, and the results are shown in the table below:

[0079]

[0080] Example 2

[0081] A method for preparing carbon dioxide foamed concrete using an alkali-free accelerator and nano-stabilizing materials includes the following steps:

[0082] S1. Preparation of quick-setting carbon dioxide foamed concrete

[0083] S1.1. Take a certain mass of animal protein foaming liquid, add water (the mass of water is 25 times the mass of animal protein foaming liquid), and nano silica (particle size is 50nm, the mass of nano silica is 1wt% of the mass of animal protein foaming liquid), stir evenly to prepare a foaming solution, and use a physical foaming machine to pass carbon dioxide gas to produce dense foam for later use.

[0084] S1.2. Mix 10.71 kg of reference cement, 4.82 kg of water and alkali-free quick-setting agent (HQ alkali-free liquid quick-setting agent, the mass of which is 2 wt% of the mass of the reference cement) evenly to form a uniform cement paste.

[0085] S1.3, Set the target wet density to 800 kg / m³ 3 According to the calculation results, 0.47 kg of precast foam was added to the cement paste in batches and stirred. After stirring, the product was obtained, which is the carbon dioxide foamed concrete paste.

[0086] S2. Comparison of rheological parameter determination results with data fitting results from comparative experiments.

[0087] The yield stress of the slurry obtained in step S1.2 was tested using a rheometer. t 0,base The surface tension of the carbon dioxide foam prepared in step S1.1 was tested using a surface tension meter. s ; Measurement value t 0. The yield stress of the cement paste with added foam (S1.3) was tested using a rheometer; each parameter was tested five times and the average value was taken. The percentage of carbon dioxide bubble volume to the total paste volume (φ) was calculated using existing methods.

[0088] Yield stress t In the mathematical model, material constants K The following method was used to determine the preparation of bubbles with different carbon dioxide bubble volume fractions φ at 20±0.5℃. i With surface tension s i Carbon dioxide-added foam slurry; rheological curves of each sample were collected at set time points, and the yield stress at the corresponding time was extracted by fitting with the Bingham model. t ( t j Simultaneously, the reference yield stress of each sample was measured at the same time. t base ( t j ). Based on the yield stress difference t ( t j )- t base (t j ) is the dependent variable, and φ is the dependent variable. i / s i Using the least squares method as the independent variable, linear regression was performed. The regression determination coefficient R² ≥ 0.90 and the residual distribution was random, indicating a linear relationship. The slope was taken as the material constant K. The final value of K was the average of multiple independent experiments (no less than 3 groups).

[0089] The surface tension obtained from the above tests s Material constants K Yield stress of grout without added foam (i.e., cement grout) t 0,base Bubble volume fraction φ, using yield stress t 0 Mathematical model calculation of fitted value t 0:

[0090]

[0091] in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of the carbon dioxide foam is expressed in mN / m.

[0092] The specific results are shown in the table below.

[0093]

[0094] Comparing the fitting results with the actual measurement results, the fitting results are close to the experimental results, indicating that the model of the present invention has good accuracy.

[0095] S3, Foam Stability Coefficient S f Number calculation

[0096] For each stability parameter, test five times and take the average value.

[0097]

[0098] The foam structure strengthening coefficient α As a dimensionless parameter, the specific method for determining it is as follows: Prepare thin-layer samples of the aforementioned carbon dioxide foamed concrete and immediately observe them under an optical microscope. Using image analysis software (such as ImageJ), randomly select no fewer than 50 bubbles, measure their equivalent radii, and calculate the average value as the initial average bubble radius. r0. Keep the sample in a static environment during initial observation. t 0 after 60 seconds ( t 1) At that time, randomly select no fewer than 50 bubbles in the same or adjacent fields of view and measure their average radius, denoted as . r 1. r 0- r 1 is denoted as Δ r Δ t The value is 60s. The strengthening coefficient of the foam structure is... α Calculate using the following formula:

[0099]

[0100] in, k It is 0.01 s - ¹.

[0101] Calculate the foam stability coefficient S f Mathematical model:

[0102]

[0103] S4. Pour the slurry into the mold to about half its capacity. Gently tap the side wall of the mold to distribute it more evenly. Then continue pouring slurry into the mold until it is slightly above the top surface, and use a scraper to smooth the surface of the slurry. Finally, cover the top surface of the mold with plastic wrap and place the mold in a standard curing room (temperature (20±2)℃, relative humidity not less than 95%) for curing for 28 days.

[0104] The average compressive strength of the five groups of specimens was measured using experimental instruments, and the results are shown in the table below:

[0105]

[0106] Example 3

[0107] A method for preparing carbon dioxide foamed concrete using an early-strength agent and a polymeric stabilizer includes the following steps:

[0108] S1. Preparation of carbon dioxide foamed concrete

[0109] S1.1. Take a certain mass of animal protein foaming liquid, add water (the mass of water is 25 times the mass of animal protein foaming liquid), add hydroxypropyl methylcellulose (the mass of hydroxypropyl methylcellulose is 3wt% of the mass of animal protein foaming liquid), stir evenly to prepare a foaming solution, and use a physical foaming machine to pass carbon dioxide gas to produce dense foam for later use.

[0110] S1.2. Mix 10.71 kg of reference cement, 4.82 kg of water, and sodium sulfate accelerator (the mass of the accelerator is 1 wt% of the mass of the reference cement) evenly to form a uniform cement paste.

[0111] S1.3, Set the target wet density to 800 kg / m³ 3 According to the calculation results, 0.47 kg of precast foam was added to the cement paste in batches and stirred. After stirring, the product was obtained, which is the carbon dioxide foamed concrete paste.

[0112] S2. Comparison of rheological parameter determination results with data fitting results from comparative experiments.

[0113] The yield stress of the slurry obtained in step S1.2 was tested using a rheometer. t 0,base The surface tension of the carbon dioxide foam prepared in step S1.1 was tested using a surface tension meter. s ; Measurement value t 0. The yield stress of the cement paste with added foam (S1.3) was tested using a rheometer; each parameter was tested five times and the average value was taken. The percentage of carbon dioxide bubble volume to the total paste volume (φ) was calculated using existing methods.

[0114] Yield stress t In the mathematical model, material constants K The following method was used to determine the preparation of bubbles with different carbon dioxide bubble volume fractions φ at 20±0.5℃. i With surface tension s i Carbon dioxide-added foam slurry; rheological curves of each sample were collected at set time points, and the yield stress at the corresponding time was extracted by fitting with the Bingham model. t ( t j Simultaneously, the reference yield stress of each sample was measured at the same time. t base ( t j ). Based on the yield stress difference t ( t j )- t base ( t j ) is the dependent variable, and φ is the dependent variable. i / s i Using the least squares method as the independent variable, linear regression was performed. The regression determination coefficient R² ≥ 0.90 and the residual distribution was random, indicating a linear relationship. The slope was taken as the material constant K. The final value of K was the average of multiple independent experiments (no less than 3 groups).

[0115] The surface tension obtained from the above tests s Material constants K Yield stress of grout without added foam (i.e., cement grout) t 0,base Bubble volume fraction φ, using yield stress t 0 Mathematical model calculation of fitted value t 0:

[0116]

[0117] in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of the carbon dioxide foam is expressed in mN / m.

[0118] The specific results are shown in the table below.

[0119]

[0120] Comparing the fitting results with the actual measurement results, the fitting results are close to the experimental results, indicating that the model of the present invention has good accuracy.

[0121] S3, Foam Stability Coefficient S f Number calculation

[0122] Stability parameters were tested, with each parameter tested five times and the average value taken. The results are shown in the table below.

[0123]

[0124] The foam structure strengthening coefficient α As a dimensionless parameter, the specific method for determining it is as follows: Prepare thin-layer samples of the aforementioned carbon dioxide foamed concrete and immediately observe them under an optical microscope. Using image analysis software (such as ImageJ), randomly select no fewer than 50 bubbles, measure their equivalent radii, and calculate the average value as the initial average bubble radius. r 0. Keep the sample in a static environment during initial observation. t 0 after 60 seconds ( t 1) At that time, randomly select no fewer than 50 bubbles in the same or adjacent fields of view and measure their average radius, denoted as . r 1. r 0- r 1 is denoted as Δ r Δt The value is 60s. The strengthening coefficient of the foam structure is... α Calculate using the following formula:

[0125]

[0126] in, k It is 0.01 s - ¹.

[0127] Calculate the foam stability coefficient S f Mathematical model:

[0128]

[0129] S4. Pour the slurry into the mold to about half its capacity. Gently tap the side wall of the mold to distribute it more evenly. Then continue pouring slurry into the mold until it is slightly above the top surface, and use a scraper to smooth the surface of the slurry. Finally, cover the top surface of the mold with plastic wrap and place the mold in a standard curing room (temperature (20±2)℃, relative humidity not less than 95%) for curing for 28 days.

[0130] The average compressive strength of the five groups of specimens was measured using experimental instruments, and the results are shown in the table below:

[0131]

[0132] Example 4

[0133] A method for preparing carbon dioxide foamed concrete using an alkali-free quick-setting agent includes the following steps:

[0134] S1. Preparation of quick-setting carbon dioxide foamed concrete

[0135] S1.1 Weigh a certain mass of sodium dodecyl sulfate and prepare an aqueous solution with a concentration of 1.0 wt%. Add hydroxypropyl methylcellulose and nano silica (particle size of 50 nm), wherein the concentration of hydroxypropyl methylcellulose is 2 wt% and the concentration of nano silica is 2 wt%. Stir evenly to prepare a foaming solution. Use a physical foaming machine to pass carbon dioxide gas to produce dense foam for later use.

[0136] S1.2. Mix 10.71 kg of reference cement, 4.82 kg of water, and quick-setting agent (HQ alkali-free liquid quick-setting agent, the mass of the quick-setting agent is 1 wt% of the mass of the reference cement) with sodium sulfate early-strength agent (the mass of the early-strength agent is 1 wt% of the mass of the reference cement) to form a uniform cement paste.

[0137] S1.3, Set the target wet density to 800 kg / m³ 3According to the calculation results, 0.47 kg of precast foam was added to the cement slurry in batches and stirred. After stirring, the product was obtained, which is the target carbon dioxide foam concrete slurry.

[0138] S2. Comparison of rheological parameter determination results with data fitting results from comparative experiments.

[0139] The yield stress of the slurry obtained in step S1.2 was tested using a rheometer. t 0,base The surface tension of the carbon dioxide foam prepared in step S1.1 was tested using a surface tension meter. s ; Measurement value t 0. The yield stress of the cement paste with added foam (S1.3) was tested using a rheometer; each parameter was tested five times and the average value was taken. The percentage of carbon dioxide bubble volume to the total paste volume (φ) was calculated using existing methods.

[0140] Yield stress t In the mathematical model, material constants K The following method was used to determine the preparation of bubbles with different carbon dioxide bubble volume fractions φ at 20±0.5℃. i With surface tension s i Carbon dioxide-added foam slurry; rheological curves of each sample were collected at set time points, and the yield stress at the corresponding time was extracted by fitting with the Bingham model. t ( t j Simultaneously, the reference yield stress of each sample was measured at the same time. t base ( t j ). Based on the yield stress difference t ( t j )- t base ( t j ) is the dependent variable, and φ is the dependent variable. i / s i Using the least squares method as the independent variable, linear regression was performed. The regression determination coefficient R² ≥ 0.90 and the residual distribution was random, indicating a linear relationship. The slope was taken as the material constant K. The final value of K was the average of multiple independent experiments (no less than 3 groups).

[0141] The surface tension obtained from the above tests s Material constants K Yield stress of grout without added foam (i.e., cement grout) t 0,baseBubble volume fraction φ, using yield stress t 0 Mathematical model calculation of fitted value t 0:

[0142]

[0143] in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of the carbon dioxide foam is expressed in mN / m.

[0144] The specific results are shown in the table below:

[0145]

[0146] Comparing the fitting results with the actual measurement results, the fitting results are close to the experimental results, indicating that the model of the present invention has good accuracy.

[0147] S3, Foam Stability Coefficient S f Number calculation

[0148] Stability parameters were tested, with each parameter tested five times and the average value taken. The results are shown in the table below.

[0149]

[0150] The foam structure strengthening coefficient α As a dimensionless parameter, the specific method for determining it is as follows: Prepare thin-layer samples of the aforementioned carbon dioxide foamed concrete and immediately observe them under an optical microscope. Using image analysis software (such as ImageJ), randomly select no fewer than 50 bubbles, measure their equivalent radii, and calculate the average value as the initial average bubble radius. r 0. Keep the sample in a static environment during initial observation. t 0 after 60 seconds ( t 1) At that time, randomly select no fewer than 50 bubbles in the same or adjacent fields of view and measure their average radius, denoted as . r 1. r 0- r 1 is denoted as Δ r Δ t The value is 60s. The strengthening coefficient of the foam structure is... α Calculate using the following formula:

[0151]

[0152] in,k It is 0.01 s - ¹.

[0153] Calculate the foam stability coefficient S f Mathematical model:

[0154]

[0155] S4. Pour the slurry into the mold to about half its capacity. Gently tap the side wall of the mold to distribute it more evenly. Then continue pouring slurry into the mold until it is slightly above the top surface, and use a scraper to smooth the surface of the slurry. Finally, cover the top surface of the mold with plastic wrap and place the mold in a standard curing room (temperature (20±2)℃, relative humidity not less than 95%) for curing for 28 days.

[0156] The average compressive strength of the five groups of specimens was measured using experimental instruments, and the results are shown in the table below:

[0157]

[0158] Example 5:

[0159] S1. Experimental Design and Formulation

[0160] PO 42.5 silicate cement was selected, and the target slurry yield stress was... t The foam stability coefficient is controlled at 170 Pa. S f Controlled at 9.2×10 9 It is used to obtain good strength and foam retention effect.

[0161] After screening experiments, the following scheme was determined:

[0162] S1.1, Preparation of foaming liquid

[0163] Take a certain mass of animal protein foaming solution, add water (the mass of water is 25 times the mass of animal protein foaming solution), add hydroxypropyl methylcellulose (the mass of hydroxypropyl methylcellulose is 2wt% of the mass of animal protein foaming solution) and nano silica (particle size is 50nm, the mass of nano silica is 1wt% of the mass of animal protein foaming solution), stir evenly to prepare a foaming solution, and use a physical foaming machine to introduce carbon dioxide gas to produce dense foam for later use.

[0164] S1.2, Slurry Preparation

[0165] Mix 10.71 kg of cement with 4.82 kg of water and accelerator (HQ alkali-free liquid accelerator, the mass of the accelerator being 1 wt% of the base cement mass) until homogeneous to form a paste;

[0166] S1.3 Add foam with a set wet density of 800 kg / m³, add 0.47 kg of foam in batches and mix evenly to obtain foamed concrete slurry.

[0167] S2. Model Validation and Parameter Testing

[0168] The results are shown in the table below.

[0169]

[0170] The foam structure strengthening coefficient α As a dimensionless parameter, the specific method for determining it is as follows: Prepare thin-layer samples of the aforementioned carbon dioxide foamed concrete and immediately observe them under an optical microscope. Using image analysis software (such as ImageJ), randomly select no fewer than 50 bubbles, measure their equivalent radii, and calculate the average value as the initial average bubble radius. r 0. Keep the sample in a static environment during initial observation. t 0 after 60 seconds ( t 1) At that time, randomly select no fewer than 50 bubbles in the same or adjacent fields of view and measure their average radius, denoted as . r 1. r 0- r 1 is denoted as Δ r Δ t The value is 60s. The strengthening coefficient of the foam structure is... α Calculate using the following formula:

[0171]

[0172] in, k It is 0.01 s - ¹.

[0173] Calculate the foam stability coefficient S f Mathematical model:

[0174]

[0175] The fact that the values ​​are consistent with the design values ​​indicates that a specific preparation scheme can be designed based on the target settings.

[0176] S3. Pour the slurry into the mold to about half its capacity. Gently tap the side wall of the mold to distribute it more evenly. Then continue pouring slurry into the mold until it is slightly above the top surface, and use a scraper to smooth the surface of the slurry. Finally, cover the top surface of the mold with plastic wrap and place the mold in a standard curing room (temperature (20±2)℃, relative humidity not less than 95%) for curing for 28 days.

[0177] The average compressive strength of the five groups of specimens was measured using experimental instruments, and the results are shown in the table below:

[0178]

[0179] Based on the above information, the following table is obtained:

[0180]

[0181] The results show that, through comparative experimental data from the examples, the influence of foam stability coefficient and cement paste yield strength on the performance of carbon dioxide foamed concrete was explored in depth. The experimental results indicate a significant positive correlation between the foam stability coefficient and the compressive strength of the foamed concrete. Specifically, the foam stability coefficient of Example 1 was 5.16 × 10⁻⁶. 9 The corresponding 28-day compressive strength is 1.59 MPa; while the foam stability coefficients of Examples 2-4 are increased to 5.85 × 10⁻⁶ MPa. 9 7.54×10 9 and 9.95×10 9The 28-day compressive strength also increased accordingly to 1.96 MPa, 2.12 MPa, and 2.42 MPa. This phenomenon indicates that the higher the foam stability coefficient, the better the stability of the foam in the cement paste, and the less likely the bubbles are to break, thereby improving the uniformity and density of the foamed concrete and ultimately enhancing the compressive strength of the material. Further analysis revealed that foamed concrete exhibits better performance when the yield strength of the cement paste falls within a certain range (100-200 Pa). This is because the fluidity of the paste and the stability of the air bubbles are balanced at this range. If the yield stress is too low, the paste becomes too thin, failing to effectively support the air bubbles, leading to bubble escape and uneven strength. If the yield stress is too high, the paste becomes too thick, resulting in poor fluidity and affecting the uniform distribution of air bubbles. Within this range, the paste effectively encapsulates the air bubbles while maintaining the required fluidity for construction, ensuring uniform bubble distribution, forming a stable pore structure, and improving the strength and durability of the foamed concrete. This range was determined through rheological testing, data analysis, and model prediction. The yield stress in Example 1 was 206.6 Pa, slightly higher than this range, indicating relatively low compressive strength. In contrast, the yield stresses in Examples 2-4 were 198.216 Pa, 186.086 Pa, and 168.424 Pa, respectively. The compressive strength of foamed concrete is significantly improved when the yield strength is within the ideal range of 100-200 Pa. Yield strength reflects the cement paste's resistance to flow; excessively high yield strength leads to poor paste fluidity and difficulty in uniform foam distribution; excessively low yield strength prevents the paste from effectively supporting the foam, causing foam rupture. Therefore, when the yield strength is between 100-200 Pa, the paste's fluidity and supporting capacity reach an optimal balance, allowing for uniform foam distribution and stable existence, thus significantly improving the compressive strength of foamed concrete. Furthermore, the addition of additives such as nano-silica, hydroxypropyl methylcellulose, accelerators, and early-strength agents significantly improved the compressive strength of foamed concrete by enhancing the rheological properties of the paste and the stability of the foam. These additives not only improved the foam stability coefficient but also optimized parameters such as the paste's plastic viscosity, interfacial tension, bubble radius, and paste film thickness, further refining the foam structure and enhancing the overall material performance.

[0182] In summary, the foam stability coefficient and the yield strength of the cement paste are key factors affecting the performance of carbon dioxide foamed concrete. By rationally controlling the foam stability coefficient and optimizing the yield strength of the cement paste to the ideal range of 100-200 Pa, combined with the use of additives, the compressive strength and overall performance of foamed concrete can be effectively improved. This finding provides important theoretical basis and practical guidance for the preparation and performance optimization of foamed concrete.

[0183] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A method for controlling the setting of rapid-setting carbon dioxide foamed concrete, characterized in that, including the step of incorporating a yield stress of a carbon dioxide foam slurry t 0Mathematical model and foam stability factor S f The mathematical model realizes the regulation of the carbon dioxide foam concrete. Yield stress t 0Mathematical model: ； in: t 0,base The yield stress of the slurry without the addition of carbon dioxide foam is expressed in Pa. K φ is a material constant in Pa·m; φ is the percentage of carbon dioxide bubble volume in the carbon dioxide-added foam slurry to the total volume of the slurry. s The surface tension of carbon dioxide foam is expressed in mN / m. Foam stability coefficient S f Mathematical model: ； in: t 0 represents the yield stress of the carbon dioxide-added foam slurry, in Pa; γ represents the interfacial tension between the carbon dioxide bubbles and the liquid phase of the slurry, in N / m. Critical shear rate, in seconds. -1 ; α The foam structure strengthening coefficient; r Where is the bubble radius, in meters (m). d This represents the average thickness of the slurry film between adjacent air bubbles, in meters (m). or p The plastic viscosity of carbon dioxide-added foam slurry at a standard temperature of 20℃ is expressed in Pa·s. or w The viscosity of water at 20°C is expressed in Pa·s.

2. The method for controlling the setting of rapid-setting carbon dioxide foamed concrete according to claim 1, characterized in that, Foam stability coefficient S f In the mathematical model, the average thickness of the slurry liquid film between adjacent bubbles d It was obtained through microscopic observation.

3. The method for controlling the setting of rapid-setting carbon dioxide foamed concrete according to claim 1, characterized in that, Based on the yield stress of carbon dioxide-added foam slurry t A mathematical model was developed to regulate the surface tension of carbon dioxide foam. s To achieve yield stress t The control of 0 allows for the regulation of the preparation process and performance of rapid-setting carbon dioxide foam concrete.

4. The method for controlling the setting of rapid-setting carbon dioxide foamed concrete according to claim 1, characterized in that, Based on the foam stability coefficient of carbon dioxide-added foam slurry S f Mathematical model, by controlling the yield stress of carbon dioxide-added foam slurry t 0. Interfacial tension γ between carbon dioxide bubbles and the slurry liquid phase; bubble radius r Average thickness of the slurry film between adjacent bubbles d Plastic viscosity of carbon dioxide-added foam slurry or p One or a combination thereof, to achieve the foam stability coefficient S f The control of these parameters allows for the regulation of the preparation process and performance of quick-setting carbon dioxide foam concrete.

5. The method for controlling the setting of rapid-setting carbon dioxide foamed concrete according to claim 1, characterized in that, Based on the target yield stress t 0 or foam stability coefficient S f The yield stress of the foam slurry can be increased by adding carbon dioxide. t 0 Mathematical model or foam stability coefficient S f The mathematical model yields specific performance parameters, and the preparation process is adjusted to obtain a product with the target yield stress. t 0 or foam stability coefficient S f Quick-setting carbon dioxide foam concrete.

6. The method for controlling the setting of rapid-setting carbon dioxide foamed concrete according to claim 1, characterized in that, Yield stress is a key indicator reflecting the fluidity and bubble stability of foamed concrete slurry: when the yield stress... t When the Pa is below 100, the concrete performance is poor, the paste is too thin, and it cannot provide effective support for the air bubbles. The air bubbles are prone to floating and agglomerating, resulting in uneven pore size distribution, poor foam stability, and affecting the uniformity and strength of the foamed concrete; yield stress t When the Pa value is within the range of 100-200, the concrete exhibits good performance, with moderate paste viscosity and strength. This effectively encapsulates air bubbles, inhibiting their rise and aggregation, resulting in uniform dispersion and a stable pore structure, thus improving the strength and durability of the foamed concrete. t When the Pa exceeds 200, the concrete performance is poor, the paste becomes too thick, the fluidity is poor, pouring is difficult, and air bubbles are hard to distribute evenly, leading to foam rupture and affecting the quality and performance of foamed concrete; the foam stability coefficient S f Calculation results: When the foam stability coefficient S f <10 9 When the concrete performance is poor and the foam stability is insufficient, the concrete is prone to collapse and the pore structure is easily deteriorated, leading to a reduction in strength, durability, and construction quality; when the foam stability coefficient is low... S f In 10 9 -10 10 When the foam stability coefficient is between [a certain value], the concrete performance is good and can meet the requirements of general non-load-bearing insulation materials, but the room for performance improvement is limited; when the foam stability coefficient is ... S f >10 10 When the concrete exhibits excellent performance and highly stable foam, it is suitable for high-strength or high-performance carbon sequestration applications. It can form a uniform and stable pore structure, significantly improving the compressive strength and carbon sequestration efficiency of the material.

7. The method for controlling the setting of rapid-setting carbon dioxide foamed concrete according to claim 6, characterized in that, Yield stress t When the Pa is in the range of 100-200 Pa, the yield stress is t The lower the value of 0, the better the concrete performance; the foam stability coefficient S f The larger the diameter, the better the concrete performance.

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