A micro-expansion shrinkage-inhibiting cement aerogel material and a method for preparing the same

Abstract

The application discloses a cement aerogel material with micro-expansion and shrinkage inhibition and a preparation method thereof. The cement aerogel material is prepared by mixing, foaming, pore forming and drying of a first component, cement and a second component. The first component comprises a hydrogel polymer, an expansion component, water and a dispersing agent. The second component comprises a foaming agent. The weight ratio of the hydrogel polymer, the expansion component, water and the cement is 0.08-0.3:0.04-0.3:8-15:1. By introducing the expansion component with a proper proportion, the expansion component expands, the intermediate-state skeleton strength is improved, and the shrinkage is resisted. The expansion volume is not less than the shrinkage volume in the drying process, the drying shrinkage is effectively offset, the overall structure integrity is maintained, and finally an additional active reinforcement effect is generated.

Description

Technical Field

[0001] This invention relates to an engineering material, more particularly to a cement aerogel material, and also to a method for preparing the material. Background Technology

[0002] Aerogel materials, as a novel type of nanoporous material, have shown great application potential in the field of pipeline lining due to their ultra-low thermal conductivity (down to below 0.02 W / (m·K)), high porosity (>90%), and excellent thermal insulation properties. However, while the inherent nanoporous structure of aerogel materials endows them with excellent thermal insulation performance, it also leads to serious deficiencies in their mechanical properties—low strength and high brittleness. When subjected to internal medium pressure, external mechanical loads, and stress caused by temperature changes, they are extremely prone to damage and cracking, seriously threatening the long-term safe and stable operation of pipeline systems.

[0003] Cement aerogel, a novel material combining inorganic cement and hydrogel polymers, retains the porous, low-density, and low-thermal-conductivity properties of aerogels while addressing the challenges of high brittleness in pure cement and low strength in pure aerogels through a polymer network. However, existing cement aerogel materials face a critical bottleneck in their preparation: volume shrinkage during drying. This shrinkage occurs because moisture evaporates from the pores during drying, causing the skeletal structure to loosen and generating capillary forces that induce shrinkage. Excessive shrinkage can lead to microcracks in the internal structure, damaging the insulating pore structure, severely weakening the material's strength, and causing unexpected increases in density, pore collapse, and deterioration of thermal conductivity.

[0004] To improve the strength of cement aerogel and suppress drying shrinkage, researchers have made various attempts, such as introducing fibers (carbon fiber, glass fiber, polymer fiber) to disperse the stress caused by pore concentration. However, fibers have problems such as poor dispersibility and weak interfacial bonding. Uneven dispersion can easily cause problems such as local density increase and thermal conductivity increase, which have limited effect on suppressing shrinkage. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a cement aerogel material that can reduce drying volume shrinkage, and this invention also provides a method for preparing this cement aerogel material.

[0006] Technical solution: The cement aerogel material of the present invention is made by mixing, foaming, pore-forming and drying a first component, cement and a second component. The first component includes a hydrogel polymer, an expanding component, water and a dispersant. The second component includes a foaming agent. The weight ratio of the hydrogel polymer, the expanding component, water and cement is 0.08~0.3:0.04~0.3:8~15:1.

[0007] This invention introduces an appropriate proportion of expansion component. The expansion component expands, enhances the strength of the intermediate skeleton, resists shrinkage, and maintains the stability and integrity of the material structure. The amount of expansion component is 0.04 to 0.3 parts. This range can generate sufficient expansion stress to inhibit shrinkage and achieve reinforcement, while avoiding excessive expansion that could lead to material cracking or pore damage.

[0008] Preferably, the weight ratio of hydrogel polymer, expanding component, and cement is 0.15~0.3 : 0.04~0.18 : 1. Most preferably, in order to maintain the best thermal insulation effect and avoid excessive expansion compressing the skeleton and increasing the pores, the weight ratio of expanding component and cement is 0.04~0.15 : 8~15 : 1.

[0009] Preferably, the expanding component is selected from at least one or more combinations of ettringite forming agent, magnesium oxide expanding agent, and calcium sulfoaluminate expanding agent. The ettringite forming agent consists of an aluminum source (such as aluminum sulfate or sodium aluminate) and a calcium source (such as calcium oxide or calcium hydroxide). During hydration, it generates ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O), expanding in volume by approximately 120%–150%. The expansion reaction mainly occurs in the early stages of hydration, closely matching the drying shrinkage window. The magnesium oxide expanding agent works by reacting MgO with water to generate Mg(OH)₂, expanding in volume by approximately 100%–120%, and can play a role during material drying. The calcium sulfoaluminate expanding agent works by reacting calcium sulfoaluminate with water to generate ettringite, expanding in volume by approximately 80%–100%. The expansion reaction is mild and easily controlled.

[0010] Preferably, the hydrogel polymer is selected from at least one of sodium alginate, agarose, chitosan, hyaluronic acid, polyvinyl alcohol, sodium polyacrylate, polyacrylamide, and polyethylene glycol. An appropriate amount of hydrogel polymer ensures material molding while providing a uniformly dispersed network environment for the expanding components. Too little polymer results in a powdery material, while too much leads to decreased strength and increased thermal conductivity.

[0011] Preferably, the cement is rapid-hardening sulfoaluminate cement or a mixture thereof with silicate cement. Rapid-hardening sulfoaluminate cement has high early strength and a fast hydration rate, which can accelerate the hydration process of the expansive components, allowing the expansive components to hydrate synchronously with the cement to improve structural stability and enable the expansion stress to fully exert its effect before drying shrinkage occurs. More preferably, the silicate cement mass fraction is ≤30%.

[0012] Preferably, the dispersant is a polycarboxylate superplasticizer, a sulfonate superplasticizer, or a naphthalene superplasticizer, and the weight ratio of the dispersant to cement is 0.015~0.06:1. The dispersant effectively reduces cement particle agglomeration, improves slurry fluidity, and ensures that the expansion component is uniformly mixed with the cement.

[0013] Preferably, the foaming agent is hydrogen peroxide or sodium bicarbonate, and the weight ratio of foaming agent to cement is 0.15~0.5:1. The foaming agent decomposes in the slurry to generate gas, which, combined with directional freezing technology, forms a uniform directional pore structure.

[0014] Preferably, the second component further includes a hydrophobic component, which is a silane compound, and the weight ratio of the hydrophobic component to water is 0.08~0.3:1. The hydrophobic component is added before the foaming agent, and the hydrophobic component is preferably methyltrimethoxysilane or methyltriethoxysilane. The hydrophobic component forms a hydrophobic layer on the material surface and pore walls, improving water resistance and durability.

[0015] The preparation method of the above-mentioned cement aerogel material includes the following steps:

[0016] (1) Dissolve the hydrogel polymer, swelling component, and dispersant in water to form the first component;

[0017] (2) Add cement to the first component in batches and stir to hydrate the cement;

[0018] (3) Add the second component to obtain a mixed slurry. Shape the mixed slurry, create holes, and dry it to obtain cement aerogel material.

[0019] Preferably, in step (2), the cement is added in two batches. Adding it in batches helps control the release of heat of hydration and avoids localized overheating that could affect the uniformity of the expansion component's reaction. The stirring time for the first batch of cement is longer than the stirring and reaction time for the second batch. Taking rapid-hardening sulfoaluminate cement as an example, the stirring time for the first batch of cement is 15-30 minutes, allowing the material to have the gas confinement capacity of the pore-forming agent, facilitating the uniform dispersion of the subsequent initiator and foaming agent. The stirring time for the second batch of cement is 1-2 minutes, used to strengthen the material, and it can be dispersed in the system. During the addition process, the stirring speed is 300-500 r / min. Adding the expansion component before the first batch of cement helps the expansion component and cement hydration reaction to occur simultaneously, improving structural stability.

[0020] Preferably, in order to avoid the temperature affecting the function of the expansion component, the temperature of the first component in step (2) is 25~35℃.

[0021] Preferably, in step (3), directional freezing is used to create pores at a freezing temperature of -150℃ to -120℃ for 30 to 60 minutes. After freezing, the sample is thawed at room temperature and dried after it returns to room temperature. Directional freezing uses liquid nitrogen as a cold source. By controlling the direction of the cold source, ice crystals are induced to grow in a directional manner, ultimately forming a directionally arranged pore structure. This reduces density and enhances mechanical anisotropy, adapting to the stress characteristics of the pipe lining.

[0022] Preferably, in step (3), the mold is placed entirely in an oven at a drying temperature of 50–95°C. More preferably, to promote the function of the expanding component, the drying temperature is 60–95°C. Most preferably, the drying temperature is 85–95°C.

[0023] Preferably, in step (3), the second component is added for 2 to 10 minutes. More preferably, the duration is 2 to 6 minutes. Controlling the addition time of the second component reduces the hydration difference between the expansive component and the cement, avoiding increased drying shrinkage and damage to structural integrity.

[0024] This invention uses a hydrogel polymer as a continuous skeleton and cement as the inorganic phase, introducing specific expansion components (such as ettringite generating agent, magnesium oxide expansion agent, calcium sulfoaluminate, etc.). By controlling the dosage, reaction rate, and expansion timing of the expansion components, the adverse effects of drying shrinkage are offset. The expansion components work synchronously with cement hydration, pre-strengthening the intermediate skeleton, avoiding pore collapse and volume shrinkage. After shrinkage is suppressed, the original porous structure is completely preserved, improving overall strength and durability, reducing material density, effectively blocking heat conduction paths, and thus significantly reducing thermal conductivity. After curing, the expanded volume is no less than the shrinkage volume during the drying process, effectively offsetting drying shrinkage and maintaining the integrity of the overall structure, producing an additional active reinforcing effect.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) Suppressing shrinkage to achieve lower density and thermal conductivity: Compared with cement aerogel without expansion components, the drying shrinkage rate is reduced by more than 50%, the density is reduced by 5% to 10%, the thermal conductivity is reduced by 8% to 15%, and the compressive strength is increased by 80% to 120%; (2) Controlling the timing and total amount of expansion reaction to make the expansion curve highly matched with the drying shrinkage curve, ensuring the stability and repeatability of low density and low thermal conductivity; (3) Simple composition: No need to cooperate with reinforcing fibers, a single expansion agent can suppress shrinkage, reduce density, reduce thermal conductivity, and actively enhance; (4) Lightweight and excellent thermal insulation performance: The material retains a more complete directional pore structure, so that the density can be as low as 80 to 85 kg / m³, and the thermal conductivity can be as low as 0.032 to 0.034 W / (m·K), which is far lower than traditional porous materials, meeting the high-efficiency thermal insulation requirements of pipelines. Attached Figure Description

[0026] Figure 1 Scanning electron microscope images of the samples obtained in Example 1 and Comparative Example 1;

[0027] Figure 2 The compressive strength test curves of the samples obtained in Example 1 and Comparative Example 1 are shown.

[0028] Figure 3This is a comparison chart of the drying shrinkage curves of Example 1 and Comparative Example 1;

[0029] Figure 4 This is a comparison of the physical objects of Example 1 and Comparative Example 1, with the upper part being Comparative Example 1. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to these embodiments. Experimental methods not specified in the embodiments were performed according to conventional conditions or manufacturer recommendations. All reagents used were commercially available analytical grade or industrial grade products.

[0031] Example 1

[0032] (1) Weigh 0.24 parts of sodium alginate (accounting for 0.24 / 1.2=20% of cement) and dissolve it in 12 parts of deionized water. Heat to 70°C and stir until completely dissolved. Cool to room temperature to obtain a polymer solution.

[0033] (2) Weigh 0.1 part of magnesium oxide expansion agent (MgO, activity index 200s) and add it to the polymer solution, stir evenly to obtain a polymer solution containing expansion component;

[0034] (3) Add 0.03 parts of polycarboxylate superplasticizer (Subote 801) and stir well;

[0035] (4) Slowly add 0.6 parts of sulfoaluminate cement (Polar Bear 62.5 grade) to the above solution and stir at 500 r / min for 30 minutes under a 30°C water bath.

[0036] (5) Add the remaining 0.6 parts of sulfoaluminate cement and continue stirring for 1 minute;

[0037] (6) Add 0.15 parts of methyltrimethoxysilane and stir for 2 minutes;

[0038] (7) Add 0.4 parts of 30% hydrogen peroxide and stir quickly for 1 minute;

[0039] (8) Immediately pour the mixed slurry into a polytetrafluoroethylene mold and place it on a liquid nitrogen cold source at -150℃ for directional freezing for 45 minutes;

[0040] (9) After freezing, thaw at room temperature, and then put the mold into a 90°C oven to dry to constant weight to obtain sample S1.

[0041] Example 2

[0042] (1) Weigh 0.3 parts of agarose (accounting for 0.3 / 1.2=25% of cement) and dissolve it in 12 parts of deionized water. Heat to 95°C and stir until completely dissolved. Cool to room temperature to obtain a polymer solution.

[0043] (2) Weigh 0.08 parts of aluminum sulfate and 0.06 parts of calcium hydroxide (calcium hydroxide forming agent) and add them to the polymer solution. Stir evenly to obtain a polymer solution containing the swelling component.

[0044] (3) Add 0.03 parts of polycarboxylate superplasticizer and stir until homogeneous;

[0045] (4) Slowly add 0.6 parts of sulfoaluminate cement to the above solution and stir at 500 r / min for 15 minutes at 30°C;

[0046] (5) Add the remaining 0.6 parts of sulfoaluminate cement and continue stirring for 2 minutes;

[0047] (6) Add 0.15 parts of methyltrimethoxysilane and stir for 2 minutes;

[0048] (7) Add 0.4 parts of 30% hydrogen peroxide and stir quickly for 1 minute;

[0049] (8) Immediately pour the mixed slurry into the mold and place it on a liquid nitrogen cold source at -150℃ for directional freezing for 45 minutes;

[0050] (9) After freezing, thaw at room temperature, and then put the mold into a 90°C oven to dry to constant weight to obtain sample S2.

[0051] Example 3

[0052] (1) Weigh 0.2 parts of polyacrylamide (molecular weight 5 million, accounting for 0.2 / 1.2≈16.7% of cement) and dissolve it in 12 parts of deionized water. Stir until completely dissolved to obtain a polymer solution.

[0053] (2) Weigh 0.12 parts of calcium sulfoaluminate expansion agent and add it to the polymer solution, stir evenly to obtain a polymer solution containing expansion component;

[0054] (3) Add 0.03 parts of polycarboxylate superplasticizer and stir until homogeneous;

[0055] (4) Slowly add 0.6 parts of sulfoaluminate cement to the above solution and stir at 500 r / min for 30 minutes at 30°C;

[0056] (5) Add the remaining 0.6 parts of sulfoaluminate cement and continue stirring for 2 minutes;

[0057] (6) Add 0.15 parts of methyltrimethoxysilane and stir for 2 minutes;

[0058] (7) Add 0.4 parts of 30% hydrogen peroxide and stir quickly for 1 minute;

[0059] (8) Immediately pour the mixed slurry into the mold and place it on a liquid nitrogen cold source at -150℃ for directional freezing for 45 minutes;

[0060] (9) After freezing, thaw at room temperature, and then put the mold into a 90°C oven to dry to constant weight to obtain sample S3.

[0061] Example 4

[0062] (1) Weigh 0.24 parts of sodium alginate and dissolve it in 12 parts of deionized water. Heat to 70°C and stir until completely dissolved. Cool to room temperature to obtain a polymer solution.

[0063] (2) Weigh 0.06 parts of magnesium oxide expansion agent and 0.04 parts of calcium sulfoaluminate expansion agent (composite expansion agent) and add them to the polymer solution. Stir evenly to obtain a polymer solution containing expansion components.

[0064] (3) Add 0.03 parts of polycarboxylate superplasticizer and stir until homogeneous;

[0065] (4) Slowly add 0.6 parts of sulfoaluminate cement to the above solution and stir at 500 r / min for 15 minutes at 30°C;

[0066] (5) Add the remaining 0.6 parts of sulfoaluminate cement and continue stirring for 2 minutes;

[0067] (6) Add 0.15 parts of methyltrimethoxysilane and stir for 2 minutes;

[0068] (7) Add 0.4 parts of 30% hydrogen peroxide and stir quickly for 1 minute;

[0069] (8) Immediately pour the mixed slurry into the mold and place it on a liquid nitrogen cold source at -150℃ for directional freezing for 45 minutes;

[0070] (9) After freezing, thaw at room temperature, and then put the mold into a 90°C oven to dry to constant weight to obtain sample S4.

[0071] Example 5 The difference between this example and Example 1 is that the amount of magnesium oxide expanding agent is adjusted to 0.05 parts, while the other steps are the same, and sample S5 is obtained.

[0072] Example 6 The difference between this example and Example 1 is that the amount of magnesium oxide expanding agent is adjusted to 0.2 parts, while the other steps are the same, and sample S6 is obtained.

[0073] Example 7 The difference between this example and Example 1 is that the drying temperature is adjusted to 60°C and the drying time is extended accordingly, while the other steps are the same, to obtain sample S7.

[0074] Comparative Example 1: The difference between this comparative example and Example 1 is that no expansion component is added, but the other steps are the same, resulting in sample D1.

[0075] Comparative Example 2: This comparative example differs from Example 1 in that no hydrogel polymer is added. The remaining steps are the same, but the material cannot be molded and becomes powdery after drying, making performance testing impossible.

[0076] Comparative Example 3: The difference between this comparative example and Example 1 is that the amount of polymer used is 0.1 parts (accounting for 8.3% of the cement), while the other steps are the same, resulting in sample D3.

[0077] Comparative Example 4: The difference between this comparative example and Example 1 is that ordinary silicate cement (Helin 42.5 grade) was used instead of sulfoaluminate cement. The other steps were the same, and sample D4 was obtained.

[0078] Comparative Example 5: The difference between this comparative example and Example 1 is that directional freezing is not used. Instead, the mold is directly placed in a -30°C freezer for freezing (non-directional). The other steps are the same, and sample D5 is obtained.

[0079] Comparative Example 6 The difference between this comparative example and Example 1 is that the magnesium oxide expanding agent in step (2) is added in step (5) to obtain sample D6.

[0080] Comparative Example 7: The difference between this comparative example and Comparative Example 4 is that heating is performed when the expanding agent is added to promote hydration. The operations in steps (4) and (5) are as follows:

[0081] (4) Slowly add 0.6 parts of silicate cement to the above solution, stir at 500 r / min for 5 minutes, then heat to 50℃ and stir for 30 minutes;

[0082] (5) Stop heating, cool down quickly, and after the temperature stabilizes at room temperature, add the remaining 0.6 parts of silicate cement and continue stirring for 1 minute to obtain sample D7.

[0083] Comparative Example 8 The difference between this comparative example and Comparative Example 4 is that in step (6), the stirring time is 30 minutes.

[0084] Performance testing was conducted on the samples obtained from the above embodiments and comparative examples, including microstructure and mechanical property tests. The mechanical testing methods are as follows:

[0085] Compressive strength: Tested according to GB / T 34336-2017 "Nanoporous Aerogel Composite Thermal Insulation Products", with sample size of 30 mm × 30 mm × 30 mm;

[0086] Thermal conductivity: Tested according to GB / T 10295-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials by heat flow meter method";

[0087] Density: Calculated using the mass-volume method;

[0088] Drying shrinkage rate: The test was conducted according to JC / T 603-2004 "Test Method for Drying Shrinkage of Cement Mortar", and the linear shrinkage rate after drying to constant weight was recorded. The test results are shown in Table 1.

[0089] Figure 1 The images show SEM comparisons of the samples from Example 1 (left) and Comparative Example 1 (right). Example 1 is a dense polymer-cement composite structure, while Comparative Example 1 shows a large number of micropores and interfacial cracks.

[0090] Figure 2 The stress-strain curves of Example 1 and Comparative Example 1 are compared. The compressive strength of Example 1 is 1.48 MPa, which is 72% higher than that of Comparative Example 1 (0.86 MPa). It also has a larger failure strain and enhanced toughness.

[0091] Figure 3 The drying shrinkage curves of Example 1 and Comparative Example 1 are shown. Comparative Example 1 shrinks rapidly in the initial drying stage (0-24 hours), with a final shrinkage rate of 0.68%, resulting in a significant reduction in volume. In Example 1, the shrinkage slows down significantly in the initial drying stage, and the shrinkage tends to stabilize after 24 hours, with a final shrinkage rate of only 0.32%. This difference in curves confirms that the expansion generated by the expanding component in the early stage of drying effectively resists the drying shrinkage, preventing an increase in density and a deterioration in thermal conductivity.

[0092] Figure 4 Cross-sectional views of samples prepared in Example 1 (bottom) and Comparative Example 1 (top) are shown. As can be seen from the figures, the sample prepared in Example 1 has a larger volume, smaller pore size, and more uniform skeleton structure and pores. The sample in Comparative Example 1 showed significant shrinkage after drying, with more large pores and poor uniformity in pore size and skeleton. During the experiment, it was found that compared with before drying, the volume of the sample in Example 1 increased significantly, while the sample in Comparative Example 1 shrank significantly. The large pore structure in Comparative Example 1 may have been caused by skeleton collapse.

[0093] Table 1 Performance Test Results

[0094]

[0095] *Note: The density reduction rate and thermal conductivity reduction rate are calculated based on Comparative Example 1 (without expansion components), and negative values ​​indicate a reduction.

[0096] As shown in Table 1, the cement aerogel materials with synergistic enhancement of micro-expansion and shrinkage inhibition obtained in Examples 1-7 of this invention maintain high compressive strength (1.31-1.55 MPa) while significantly reducing density to 83.8-86.5 kg / m³, a decrease of 4.9%-7.9% compared to Comparative Example 1 (91.0 kg / m³); the thermal conductivity is significantly reduced to 0.0328-0.0340 W / (m·K), a decrease of 8.1%-11.4% compared to Comparative Example 1 (0.0370 W / (m·K)). Simultaneously, the drying shrinkage rate decreases from 0.68% to 0.25%-0.45%, a reduction of 34%-63%. This data confirms that the expansion component, by inhibiting shrinkage, not only improves strength but also achieves dual optimization of density and thermal conductivity reduction.

[0097] Comparative Example 1, without any expanding components, exhibited the highest drying shrinkage rate (0.68%), highest density (91.0 kg / m³), and highest thermal conductivity (0.0370 W / (m·K)). Figure 4 The mid-section diagram illustrates that drying shrinkage leads to volume reduction, pore collapse, increased density, and deterioration of thermal insulation performance. In Example 5, with a small amount of expanding component (0.05 parts), the drying shrinkage rate decreased to 0.45%, the density decreased to 86.5 kg / m³, and the thermal conductivity decreased to 0.0340 W / (m·K), confirming that partial suppression of shrinkage can improve density and thermal conductivity. In Example 1, increasing the expanding component to 0.1 parts further reduced the drying shrinkage rate to 0.32% and the density to 84.5 kg / m³. 3 The thermal conductivity decreased to 0.0332 W / (m·K), confirming that when the expansion was sufficient to fully compensate for the shrinkage, the material maintained a more complete pore structure, and the density and thermal conductivity reached a better level. In Example 6, the amount of expansion component added was increased to 0.2 parts. Compared with Example 1, the compressive strength of the sample in Example 6 continued to increase, and the drying shrinkage decreased. However, the thermal conductivity and density did not decrease significantly. This may be because the expansion component reduced the thermal insulation capacity of the skeleton by increasing the density and strength of the skeleton. The pores inside the sample increased slightly, and ultimately the thermal conductivity and density did not decrease significantly.

[0098] Examples 2 to 4 used different types of expanding components. Example 2 used ettringite forming agent, which had the lowest shrinkage rate (0.28%), lowest density (83.8 kg / m³), lowest thermal conductivity (0.0328 W / (m·K)), and highest strength (1.55 MPa). This was attributed to the optimal matching between the expansion reaction of the ettringite forming agent and the drying shrinkage window, thus preserving the original porous structure to the greatest extent. Example 1 used magnesium oxide expanding agent with a density of 84.5 kg / m³ and a thermal conductivity of 0.0332 W / (m·K). Magnesium oxide reaction expansion has a delayed characteristic, continuing to play a role during the drying process, but its effect is secondary. Example 3 used calcium sulfoaluminate expanding agent with a density of 85.2 kg / m³ and a thermal conductivity of 0.0335 W / (m·K). The expansion reaction was mild, but the effect of inhibiting shrinkage was slightly lower. Example 4 is a composite expanding agent with a density of 84.1 kg / m³ and a thermal conductivity of 0.0330 W / (m·K). The expansion time can be segmented and controlled through compounding, and the effect is between that of Example 1 and Example 2.

[0099] Comparative Example 2, lacking polymer, resulted in a powdery material that could not be molded, verifying that the hydrogel polymer is a necessary component for cement aerogel molding. Comparative Example 3, with a polymer content of 0.1 parts (8.3% of cement), had a strength of only 0.95 MPa and was partially powdery. Its density and thermal conductivity were higher than the example, indicating that insufficient polymer content led to severe shrinkage and an inability to achieve low density and low thermal conductivity. Comparative Example 4 used ordinary silicate cement with a density as high as 166.5 kg / m³ and a thermal conductivity as high as 0.0715 W / (m·K), far exceeding the example. This was attributed to its slow hydration rate, asynchronous reaction of the expansion components, severe shrinkage, and poor pore structure. In Comparative Example 7, increasing the temperature to accelerate the hydration reaction of ordinary silicate cement was ineffective. Comparative Example 5 employed non-directional freezing, resulting in a density of 130.2 kg / m³ and a thermal conductivity of 0.0582 W / (m·K), both inferior to the example, demonstrating that directional freezing is crucial for maintaining low density and low thermal conductivity. Comparative Example 6 adjusted the timing of the expansion agent addition, leading to a decrease in mechanical and thermal insulation properties. Comparative Example 8 showed a significant decrease in performance when the time interval before pore formation was adjusted.

[0100] In summary, this invention uses hydrogel polymers as the molding framework and expansion components as shrinkage inhibitors to successfully prepare cement aerogel materials with lower density (≤85 kg / m³), lower thermal conductivity (≤0.034 W / (m·K)), and higher strength (≥1.45 MPa).

Claims

1. A cement aerogel material, characterized in that, The cement aerogel material is made by mixing, foaming, pore-forming, and drying a first component, cement, and a second component. The first component includes a hydrogel polymer, an expanding component, water, and a dispersant. The second component includes a foaming agent. The weight ratio of the hydrogel polymer, expanding component, water, and cement is 0.08~0.3:0.04~0.3:8~15:

1.

2. The cement aerogel material according to claim 1, characterized in that, The weight ratio of hydrogel polymer, expanding component, and cement is 0.15~0.3 : 0.04~0.18 :

1.

3. The cement aerogel material according to claim 1, characterized in that, The expansion component is selected from at least one or more combinations of ettringite forming agent, magnesium oxide expansion agent, and calcium sulfoaluminate expansion agent, and the cement is rapid-hardening sulfoaluminate cement or a mixture thereof with silicate cement.

4. The cement aerogel material according to claim 1, characterized in that, The hydrogel polymer is selected from at least one of sodium alginate, agarose, chitosan, hyaluronic acid, polyvinyl alcohol, sodium polyacrylate, polyacrylamide, and polyethylene glycol.

5. The cement aerogel material according to claim 1, characterized in that, The dispersant is a polycarboxylate superplasticizer, a sulfonate superplasticizer, or a naphthalene superplasticizer, and the weight ratio of the dispersant to cement is 0.015~0.06:1; the foaming agent is hydrogen peroxide or sodium bicarbonate, and the weight ratio of the foaming agent to cement is 0.15~0.5:

1.

6. The cement aerogel material according to claim 1, characterized in that, The second component also includes a hydrophobic component, which is a silane compound, and the weight ratio of the hydrophobic component to water is 0.08~0.3:

1.

7. A method for preparing the cement aerogel material according to any one of claims 1 to 6, comprising the following steps: (1) Dissolve the hydrogel polymer, swelling component, and dispersant in water to form the first component; (2) Add cement to the first component in batches and stir to hydrate the cement; (3) Add the second component to obtain a mixed slurry. Shape the mixed slurry, create holes, and dry it to obtain cement aerogel material.

8. The preparation method according to claim 7, characterized in that, In step (2), the temperature of the first component is 25~35℃, and the cement is added in two batches. The mixing time of the first batch of cement is 15~30 minutes, and the mixing time of the second batch of cement is 1~2 minutes. The mixing speed is 300~500 r / min.

9. The preparation method according to claim 7, characterized in that, In step (3), directional freezing is used to create holes. The freezing temperature is -150℃ to -120℃ and the freezing time is 30 to 60 minutes. The drying step involves placing the mold as a whole into an oven and drying at a temperature of 50 to 95℃.

10. The preparation method according to claim 7, characterized in that, In step (3), the second component is added for 2 to 10 minutes.

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