High-porosity nano-modified aerated concrete block and preparation process thereof

Abstract

The invention relates to the field of supply and demand interaction of an electric power system, and discloses a high-porosity nano-modified aerated concrete block and a preparation process of the high-porosity nano-modified aerated concrete block. 10 to 30 parts of fly ash; 3 to 7 parts of gypsum; 0.1 to 3 parts of nano silicon; 0.3 to 0.8 part of a foaming agent; 25 to 45 parts of water; 10 to 25 parts of sand; the nano silicon is silicon dioxide particles with the particle size of 20-50 nanometers, and the specific surface area of the nano silicon is 200-300 m < 2 > / g; the foaming agent is a foaming agent containing aluminum powder, and the particle size of the aluminum powder is not greater than 50 microns; the fly ash is low-sulfur fly ash from a thermal power plant, and the particle size is less than 100 microns. According to the invention, nano-silicon is cooperated with microwave foaming and steam curing, so that the effects of uniform and closed pore structure, compact pore wall and remarkable improvement of the overall heat insulation performance of the material are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of interactive supply and demand of power systems, and in particular to a high-porosity nano-modified aerated concrete block and a preparation process thereof. Background Art

[0002] With growing attention paid to building energy conservation and green building materials, materials with multifunctional properties such as lightweight, thermal insulation, and heat preservation have become a hot topic in current research and application. Especially in cold or hot regions, the sensitivity of exterior walls, roofs, and other building envelopes to heat conduction directly affects indoor energy consumption. Such applications require materials that combine thermal insulation and structural stability to reduce energy loss, enhance living comfort, and lower the building's operational energy burden.

[0003] Existing technologies often use cement as a matrix, with foaming agents introduced to achieve lightweighting. Some technologies incorporate mineral admixtures such as microsilica fume, improving the material's mechanical properties and a certain degree of impermeability. Other studies have attempted to use conventional thermal curing or chemical admixtures to adjust pore structure morphology, aiming to improve pore uniformity and closure to a certain extent. These technologies exhibit a certain degree of engineering adaptability under specific environments, are easy to form, meet basic performance standards, and have relatively manageable costs, suggesting potential for widespread adoption.

[0004] However, there are still some problems in the existing technology. First, the traditional foaming method has a narrow operating window, the bubbles are very easy to break or merge, and the pore structure is unstable. To put it bluntly, it is difficult to control. Secondly, although microsilica powder can improve strength, it cannot deeply participate in the construction of the pore wall, the control accuracy is poor, and it is difficult to fundamentally improve the density. Then there is the problem of maintenance methods. Under conventional conditions, the reaction is not sufficient, the pore wall is weak, and it collapses when stepped on, and the later thermal insulation performance cannot hold up. Overall, these shortcomings directly affect the actual application of materials in high-performance green building materials scenarios. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a high-porosity nano-modified aerated concrete block and its preparation process. The present invention solves the problems of unstable bubble structure, high pore connectivity, loose pore wall and insufficient reaction in existing cement-based thermal insulation materials.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: a high-porosity nano-modified aerated concrete block, the concrete block comprising the following components in parts by weight:

[0007] Cement: 40-60 parts. Cement is the main binder material of aerated concrete blocks. In the present invention, the overall performance of the material is optimized by adjusting the proportion of cement and the ratio of other components. Cement provides basic strength support for the structure of aerated concrete. The main chemical components of cement - tricalcium silicate (C3S) and belite (C2S) can form cementing products during the hydration process. These cementing substances improve the durability and mechanical strength of the blocks through interaction with other components. By reasonably proportioning cement and other components, the porosity and structural properties of aerated concrete can be effectively controlled to avoid its strength loss;

[0008] Fly ash: 10-30 parts. The fly ash is low-sulfur fly ash from thermal power plants, with a particle size of less than 100 microns, and its chemical composition contains 70%-85% of silicon dioxide and bauxite minerals. Fly ash is a common industrial waste. The addition of fly ash can not only effectively reduce the amount of cement used and reduce production costs, but also improve the microstructure of aerated concrete. The addition of fly ash helps to improve the workability of aerated concrete, and reacts with the calcium components in cement to form relatively stable hydration products, thereby improving the compressive strength and impermeability of the blocks. In particular, in the application of low-sulfur fly ash, its lower content of harmful substances helps to optimize the overall performance of the blocks and enhances the long-term effectiveness and stability of aerated concrete.

[0009] Gypsum: 3-7 parts. The main function of gypsum is to regulate the setting time of aerated concrete and prevent excessive hydration. During the production of aerated concrete, gypsum reacts with the aluminates in the cement, regulating the cement hydration process. The addition of gypsum slows down the cement hydration process, helps to generate and control bubbles, thereby stabilizing the porosity of the concrete and avoiding shrinkage problems caused by excessive hydration reactions. Gypsum can also effectively reduce the thermal expansion difference between cement and other components, improving the overall thermal stability of the material.

[0010] Nano silicon: 0.1-3 parts, the nano silicon is silicon dioxide particles with a particle size of 20-50 nanometers and a specific surface area of 200-300m 2 / g; Nanosilicon, as a new type of high-efficiency reinforcing material, is used in aerated concrete primarily to enhance the strength of the blocks and improve their water resistance. Nanosilicon particles have a large specific surface area and can be fully dispersed in the cement paste, forming a chemical reaction with the cement hydration products and promoting the formation of CSH gel in the cement, thereby effectively improving the compressive strength and durability of the blocks. At the same time, the addition of nanosilicon particles can improve the microstructure of the blocks, making the pores evenly distributed, and can effectively enhance the anti-freeze properties of the blocks, further improving their long-term stability.

[0011] Foaming agent: 0.3-0.8 parts, the foaming agent is a foaming agent containing aluminum powder, and the particle size of the aluminum powder is not more than 50 microns; the main function of the foaming agent is to control the pore structure of aerated concrete and provide the necessary porosity. The foaming agent generates gas by reacting with water, so that the concrete slurry forms a uniform foam, and then forms a large number of closed pores in the aerated concrete. The quality of the foaming agent and the method of adding it directly affect the uniformity and stability of the pores, thereby affecting the thermal conductivity, sound insulation and compressive strength of the aerated concrete. In the present invention, a foaming agent containing aluminum powder is selected, and gas is generated by the reaction of aluminum powder with water to control the stability and uniformity of the bubbles, thereby providing a guarantee for the production of high-porosity blocks;

[0012] Water: 25-45 parts. Water acts as a lubricant and reaction medium during the preparation of aerated concrete. Water reacts with cement and other ingredients to produce hydration products, which combine with other components such as nanosilicon to form a strong and durable structure. In the present invention, by properly controlling the amount of water added, the proper fluidity of the slurry can be ensured, the molding effect is guaranteed, and it helps to form the desired cell structure during the foaming process.

[0013] Sand: 10-25 parts. Sand is one of the aggregates in aerated concrete, primarily providing the building block's skeleton structure. The sand's particle size and distribution have a significant impact on the final performance of the building block. In this invention, the sand's proportion and particle size are precisely controlled to ensure uniform distribution within the aerated concrete, preventing the formation of pores and thereby ensuring the stability and durability of the finished building block.

[0014] The present invention also provides a process for preparing a high-porosity nano-modified aerated concrete block, comprising the following steps:

[0015] S1, pre-treating the nano-silicon by ultrasonic dispersion, wherein the processing time of the nano-silicon is 5-10 minutes;

[0016] S2. Dry mix cement, fly ash, gypsum, sand and pretreated nano-silicon according to the following parts by weight:

[0017] Cement: 40-60 parts;

[0018] Fly ash: 10-30 parts;

[0019] Gypsum: 3-7 parts;

[0020] Sand: 10-25 parts;

[0021] Nano silicon: 0.1-3 parts;

[0022] S3, adding water and foaming agent in proportion, stirring to form a uniform slurry;

[0023] S4, pouring the stirred slurry into a mold and foaming it by microwave radiation to form a closed-cell structure, wherein the microwave radiation power is 500-800W, the frequency is 2450MHz, and the foaming time is 5-15 minutes;

[0024] S5. Place the foamed mixture in a curing environment with a temperature of 60-80°C and a humidity of 85%-95% for 24-48 hours;

[0025] S6. After curing is completed, the cured concrete blocks are cut into standard sizes using cutting equipment. The size of the blocks is 600 mm×200 mm×100 mm.

[0026] Preferably, said S1 comprises the following steps:

[0027] During the ultrasonic dispersion process of nano silicon, a polycarboxylic acid dispersant is added as an auxiliary agent, and the amount of the dispersant is 0.5%-1% of the mass of the nano silicon;

[0028] The ultrasonic frequency is 20-40 kHz, so that the nanoparticles do not aggregate in the solution and can be evenly distributed in the cement slurry system;

[0029] Nanosilicon is pretreated by ultrasonic dispersion, with the treatment time controlled within 5-10 minutes. As a nanoscale material, nanosilicon has a small particle size, a large specific surface area, and excellent activity. In cement systems, nanosilicon can be better dispersed in the cement paste to form a more uniform hydration product. Ultrasound is used to evenly disperse the nanosilicon particles in the paste to prevent aggregation due to small particle size. The use of polycarboxylic acid dispersants further enhances dispersibility, ensuring that nanosilicon can fully participate in the cement hydration reaction and promote the formation of CSH gel. This process helps to improve the compressive strength and durability of the blocks, and by precisely controlling the distribution of nanosilicon, the pore structure of aerated concrete can be effectively optimized, improving its thermal and sound insulation properties.

[0030] Preferably, said S3 comprises the following steps:

[0031] The foaming agent is aluminum powder with a particle size of less than 40 μm. When adding, it is first prepared into a sodium hydroxide solution and then slowly stirred and added to control the reaction rate and cell uniformity.

[0032] The mass fraction of the sodium hydroxide solution is 0.1%-0.3%, and the aluminum powder accounts for 0.3%-0.8% of the total mass of the slurry;

[0033] The role of a foaming agent in aerated concrete is to form a fine, evenly distributed bubble structure, thereby increasing the porosity of the blocks. The foaming agent used contains aluminum powder, which reacts with sodium hydroxide in water to produce hydrogen, driving the foaming process. This process is strictly controlled by adjusting the aluminum powder particle size and the mass fraction of the sodium hydroxide solution to ensure the stability of the foaming process and the uniformity of the bubbles. This controlled process results in aerated concrete blocks with an ideal pore structure, enhancing their thermal conductivity, sound insulation, and compressive strength.

[0034] Preferably, the S5 comprises the following steps:

[0035] The curing environment adopts steam curing mode, and the steam pressure is controlled at 0.1-0.2MPa to accelerate the cement hydration reaction and microstructure setting;

[0036] The curing process includes two stages: pre-curing stage and high temperature and wet heat curing stage, and the total duration is controlled within 24-48 hours;

[0037] To further enhance the performance of aerated concrete blocks, particularly in terms of strength and durability, steam curing is employed. This method promotes cement hydration and accelerates the formation of the aerated concrete microstructure by controlling steam pressure and curing temperature. During curing, the steam pressure is controlled between 0.1 and 0.2 MPa, effectively accelerating the cement hydration rate and ensuring more uniform hardening of the blocks. The phased curing process, combining a pre-curing phase with a high-temperature, moist heat curing phase, not only ensures the overall performance of the blocks but also improves production efficiency and reduces curing time.

[0038] Preferably, the S4 comprises the following steps:

[0039] The internal heating rate is controlled by continuous radiation, so that the temperature rise is controlled at 5-10℃ per minute;

[0040] 2 minutes before the end of foaming, reduce the microwave power to 200W for slow cooling to stabilize the bubble structure and form a dense closed-cell system;

[0041] During the foaming process, the present invention heats the slurry by microwave radiation, precisely controlling the foaming temperature and time. Microwave radiation heating has the advantages of rapid heating, concentrated energy, and good uniformity, which helps to form a small and stable bubble structure in a short period of time. During the foaming process, the control of microwave radiation power is particularly critical, which can regulate the rate of increase of the internal temperature to avoid bubble bursting caused by excessive heating. The slow cooling process carried out before the end of foaming effectively stabilizes the bubble structure, making the formed bubbles more dense and uniform. The innovation of the microwave foaming method enables the aerated concrete blocks of the present invention to save time and improve production efficiency during the manufacturing process.

[0042] Preferably, the S6 comprises the following steps:

[0043] Block cutting uses diamond saw blade precision cutting equipment, and the cutting speed is controlled at 0.5-1.5m / min;

[0044] After cutting, the blocks are placed in a ventilated and dry area for 7 days of air stabilization to allow the residual moisture to evaporate, ultimately obtaining finished blocks with stable dimensions and excellent mechanical properties;

[0045] After steam curing, aerated concrete blocks require precision cutting to achieve standard dimensions. In this method, diamond saw blades are used for precision cutting, with a strictly controlled cutting speed to ensure a smooth surface and precise dimensions. The cut blocks are then placed in a ventilated, dry area for seven days for air stabilization to remove any residual moisture, thus preventing deformation or cracking caused by uneven evaporation. This process ensures the dimensional stability and excellent mechanical properties of the final product.

[0046] The present invention provides a high-porosity nano-modified aerated concrete block and its preparation process. It has the following beneficial effects:

[0047] 1. This invention significantly improves the early reactivity and microstructural density of the gelling system by introducing nanosilicon materials. Due to their high specific surface area and interfacial activity, the nanoparticles are evenly distributed in the slurry, forming a dense skeleton during the hydration reaction, enhancing the overall stability of the material and laying the foundation for the construction of lightweight, high-strength structures.

[0048] 2. This invention uses microwave radiation as the energy input, effectively achieving rapid and uniform control of the foaming process, avoiding the problems of uneven pore size and bubble fusion that occur with traditional foaming methods. Microwave technology possesses penetrating and instantaneous heating properties, allowing for simultaneous regulation of slurry state and gas release behavior, resulting in a foam structure with a high closed-cell ratio and low connectivity.

[0049] 3. This invention establishes a synergistic process path for microwave foaming and steam curing, achieving an organic coupling between pore structure regulation and pore wall densification. The steam environment not only promotes the formation of hydration products at the pore interface, but also enhances the stability of the bubble structure and the overall durability of the material, resolving the technical challenges of easy bubble collapse and loose pore walls.

[0050] 4. This invention achieves a breakthrough in balancing multiple performance indicators, including strength, thermal insulation, and durability, in lightweight, high-porosity materials through the collaborative design of component optimization and energy field control. This invention forms a composite control system that integrates material modification and process control, suitable for the promotion and application of green building materials and energy-saving building envelopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0053] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0054] The sources of the raw materials used in the following examples and comparative examples are as follows:

[0055] Nanosilicon was purchased from Qingdao Ocean Science and Technology Development Co., Ltd.;

[0056] The polymer foaming agent was purchased from Suzhou Alpha Chemical Co., Ltd., model AF-300;

[0057] Please see the attached Figure 1 :

[0058] Example 1:

[0059] Component ratio: cement: 45 parts, fly ash: 15 parts, gypsum: 5 parts, nano silicon: 1 part, foaming agent: 0.4 parts, water: 30 parts, sand: 20 parts.

[0060] Preparation steps:

[0061] S1. Pretreatment of nano-silicon:

[0062] Nano-silicon was mixed with an appropriate amount of water, and ultrasonic treatment was performed with an ultrasonic frequency of 25 kHz for 8 minutes. A polycarboxylic acid dispersant was added in an amount of 1% of the mass of the nano-silicon.

[0063] S2. Dry mixing of raw materials:

[0064] Cement, fly ash, gypsum, sand and pre-treated nano-silicon are dry-mixed according to the proportions to ensure that all ingredients are evenly distributed.

[0065] S3. Add water and foaming agent:

[0066] Add 30 parts of water and 0.4 parts of a foaming agent containing aluminum powder, stir evenly to form a uniform slurry.

[0067] S4, Foaming and Molding:

[0068] The uniformly stirred slurry was poured into a mold and foamed by microwave radiation with a microwave power of 700 W, a frequency of 2450 MHz, and a foaming time of 10 minutes.

[0069] S5. Steam curing:

[0070] The foamed mixture was placed in a steam curing chamber with a steam pressure of 0.15 MPa, a temperature controlled at 75° C., a humidity of 90%, and a curing time of 36 hours.

[0071] S6, cutting and stabilization:

[0072] After curing, use a diamond saw blade to cut the blocks into pieces of 600mm×200mm×100mm. After cutting, place them in a ventilated area for 7 days to ensure dimensional stability.

[0073] Example 2:

[0074] Component ratio: cement: 50 parts, fly ash: 20 parts, gypsum: 6 parts, nano silicon: 1.5 parts, foaming agent: 0.6 parts (containing aluminum powder, the aluminum powder particle size is less than 40 μm), water: 28 parts, sand: 18 parts.

[0075] Preparation steps:

[0076] S1. Pretreatment of nano-silicon:

[0077] The same method as in Example 1 was used to treat 1.5 parts of nano-silicon by ultrasonic dispersion, using a polycarboxylic acid dispersant, the treatment time was 10 minutes, and the ultrasonic frequency was 28 kHz.

[0078] S2. Dry mixing of raw materials:

[0079] Cement, fly ash, gypsum, sand and pre-treated nano-silicon are dry-mixed according to the above ratio to ensure uniform mixing.

[0080] S3. Add water and foaming agent:

[0081] Add 28 parts of water and 0.6 parts of foaming agent according to the ratio, stir evenly to form a uniform slurry.

[0082] S4, Foaming and Molding:

[0083] The slurry was poured into a mold and foamed by microwave radiation. The microwave power was set to 750 W, the frequency was 2450 MHz, and the foaming time was 12 minutes.

[0084] S5. Steam curing:

[0085] The foamed slurry was placed in a steam curing environment, with the steam pressure controlled at 0.18 MPa, the temperature at 80° C., the humidity at 95%, and the curing time at 40 hours.

[0086] S6, cutting and stabilization:

[0087] After curing, the blocks are precisely cut using diamond saw blades to a standard size of 600mm×200mm×100mm. After cutting, they are placed in a drying area for stabilization for 7 days to ensure the stability of the block structure.

[0088] Example 3:

[0089] Group allocation ratio:

[0090] Cement: 55 parts, fly ash: 12 parts, gypsum: 5 parts, nano silicon: 2 parts (particle size 20-50 nanometers, specific surface area 300m 2 / g), foaming agent: 0.5 parts, water: 32 parts, sand: 15 parts.

[0091] Preparation steps:

[0092] S1. Pretreatment of nano-silicon:

[0093] The same ultrasonic dispersion method as in the previous two embodiments was used to mix the nano-silicon with water and then treat the mixture. The treatment time was 8 minutes, the frequency was 30 kHz, and 0.8% of a polycarboxylic acid dispersant was added to ensure uniform dispersion of the nano-silicon.

[0094] S2. Dry mixing of raw materials:

[0095] Cement, fly ash, gypsum, sand and pre-treated nano-silicon are dry-mixed according to the proportions to ensure uniform distribution of the components.

[0096] S3. Add water and foaming agent:

[0097] 32 parts of water and 0.5 parts of a foaming agent containing aluminum powder were added to the dry mixture and stirred until uniform to form a slurry with moderate fluidity.

[0098] S4, Foaming and Molding:

[0099] The uniformly stirred slurry was poured into a mold and foamed by microwave radiation with a microwave power of 800 W, a frequency of 2450 MHz, and a foaming time of 15 minutes.

[0100] S5. Steam curing:

[0101] The foamed slurry was placed in a steam curing chamber with a steam pressure of 0.2 MPa, a temperature set at 85°C, a humidity of 95%, and a curing time of 48 hours.

[0102] S6, cutting and stabilization:

[0103] After curing, use diamond saw blades to cut the blocks into standard sizes of 600mm×200mm×100mm. After cutting, place them in a stable area with air circulation for 7 days of natural drying to ensure the stability and strength of the blocks.

[0104] Comparative Example 1:

[0105] Compared with Example 1, the difference is that no nano-silicon is added, and the other components and process parameters are the same.

[0106] Comparative Example 2:

[0107] Compared with Example 1, the difference is that the microwave radiation foaming is cancelled and the natural static foaming is replaced with the static foaming for 30 minutes. The other components and parameters are the same.

[0108] Comparative Example 3:

[0109] Compared to Example 2, the difference is that the aluminum powder in the foaming agent is replaced with sodium bicarbonate, the amount used remains unchanged (0.6 parts), and the other components and processes remain the same. This comparative example is used to verify the key role of the dedicated foaming agent (aluminum powder) in forming a closed-cell structure and increasing porosity.

[0110] Comparative Example 4:

[0111] Compared with Example 2, the difference is that steam curing is eliminated and replaced with room temperature curing (25°C, 70% humidity, time 72 hours). The other processes and components remain unchanged. This comparative example is used to compare the contribution of steam curing to early strength development and structural stability.

[0112] Comparative Example 5:

[0113] Compared with Example 3, the difference is that the nano-silicon is replaced by ordinary micro-silicon powder of the same mass (particle size of about 5 μm, specific surface area <30m 2 / g), while the other components and processes remained the same. This comparative example was used to verify the core role of nanoscale materials in enhancing reaction activity and microstructure regulation.

[0114] Comparative Example 6:

[0115] Compared to Example 3, the microwave foaming and steam curing steps were omitted, and a traditional static foaming and room temperature curing method (foaming for 30 minutes and curing for 72 hours at 25°C) was adopted. The other proportions remained unchanged. This comparative example represents the "completely energy-free" condition group and is used to comprehensively compare the comprehensive performance improvements achieved by the integrated process pathway of the present invention.

[0116] Experiment 1:

[0117] Experimental purpose: By comparing the 28-day compressive strength of the high-porosity aerated concrete blocks prepared in Examples 1-3 and corresponding Examples 1-6, verify the effect of the nano-admixture material, foaming method and steam curing technology in the present invention on improving the material structural strength.

[0118] Experimental steps:

[0119] Sample preparation:

[0120] The specimens in each group that have been prepared and stabilized (curing period expired) are numbered and marked.

[0121] Use a vernier caliper to confirm whether the sample size error is within the range of ±2mm.

[0122] Equipment debugging:

[0123] Start the press, preheat the system for 5 minutes, and calibrate the load unit;

[0124] Adjust the position of the lower pressing plate to ensure that the indenter contacts the top of the specimen evenly.

[0125] Test operation:

[0126] Align the center of the specimen with the loading platform;

[0127] Continue loading at the standard loading rate until the specimen fails;

[0128] Record the ultimate failure load P and convert the compressive strength σ=P / A (unit: MPa).

[0129] Results statistics:

[0130] Each group recorded three test results and took the average value;

[0131] Keep at least one decimal place and make notes on test abnormalities when necessary (see Table 1 for experimental results).

[0132] Table 1: Comparative data of compressive strength

[0133]

[0134] From Table 1, we can get:

[0135] Comparison of compressive strength results shows that the specimens exhibit significantly higher mechanical properties after the introduction of nanosilica. This is primarily due to the extremely high specific surface area of nanosilica particles, which promotes the hydration reaction within the system while filling the micropores within the cement matrix and increasing the density of the slurry. The nanoparticles generate a large amount of CSH gel at an early stage, forming a dense skeleton structure, thereby enhancing the overall load-bearing capacity. Compared to microsilica fume, nanoparticles are more easily involved in the reaction and are evenly distributed, effectively improving the microscopic stability of the structure.

[0136] In terms of pore formation, microwave radiation is used to achieve rapid and uniform foaming, allowing gas release and simultaneous solidification of the slurry structure, effectively avoiding problems such as pore clustering and through-pore formation. The static foaming group exhibited a significant decrease in compressive strength due to uneven porosity and weak wall thickness, demonstrating the critical role of the microwave foaming process in regulating pore size and uniform bubble distribution. Furthermore, microwave input can rapidly elevate the internal temperature of the system, further promoting the formation of early hydration products and improving early-stage strength.

[0137] Steam curing plays a dual role in regulating temperature and humidity during the material hardening process, significantly accelerating the reaction rate of mineral admixtures and allowing reaction products such as CSH to form a densely packed structure, significantly improving strength and stability. Experimental results show that in the absence of steam curing, the system strength is generally low, indicating that the process has a positive coupling effect on the activation of nanomaterials and the densification of pore wall structures. Overall, nano-modification, microwave control, and steam synergistically construct the "dense skeleton-uniform pore structure" composite system required for high-strength, lightweight materials.

[0138] Experiment 2:

[0139] Experimental Objective: To evaluate the effects of different formulations and molding processes on cell structure, specifically parameters such as porosity, average pore size, and pore size distribution uniformity. The focus was on verifying the synergistic effects of microwave foaming, nano-silicon, and steam curing in forming a closed-cell structure and controlling pore size distribution.

[0140] Experimental steps:

[0141] Sample drying:

[0142] The specimens were placed in a constant temperature oven (105°C) and dried for 24 hours until constant weight was reached, and the dry mass was measured.

[0143] Porosity measurement:

[0144] The dried sample was immersed in degassed deionized water, the drainage volume was measured, and the porosity (%) was calculated based on the volume.

[0145] Mercury intrusion pore size test:

[0146] Paraffin was applied to the sample surface to seal micro cracks;

[0147] Mercury pressure (5–300 MPa) was loaded in the order of low pressure → high pressure;

[0148] The volume change of the liquid entering different pore size ranges was recorded, and the pore size distribution range and the dominant pore size were calculated.

[0149] SEM+ image analysis:

[0150] Cross section of sample treated with metal spraying;

[0151] Take images of the pore structure (magnification 500x–1000x);

[0152] ImageJ was used to measure and count ≥200 pore sizes, and their distribution frequency and standard deviation were analyzed (the experimental results are shown in Table 2).

[0153] Table 2: Comparison of porosity and pore size distribution data of different samples

[0154]

[0155]

[0156] From Table 2, we can get:

[0157] Experimental results show that the introduction of nanosilicon components results in a more concentrated overall pore size distribution and a more uniform pore structure. This structural improvement stems from the excellent dispersibility and interface control capabilities of nanoscale particles in the slurry. Nanosilicon can significantly enhance the reactivity of the concrete system, accelerating the rate of CSH gel formation in the early stages, thereby forming a dense coating at the bubble interface, inhibiting bubble coalescence and escape, and effectively controlling pore size. In contrast, the pore size distribution span of the group without nanosilicon was significantly widened, indicating that micron-scale or unmodified systems struggle to achieve fine-grained control of bubble structure at the microscopic level.

[0158] Microwave foaming technology also plays a key role in controlling pore structure. Its non-contact, synchronized internal and external heating energy input method enables the slurry to quickly solidify and set during the foaming process, releasing gas in a short period of time, thus avoiding the pore merging and segregation caused by long-term static standing. In comparison, the pore structure formed by traditional static foaming is more unstable, with a larger pore size standard deviation and a trend of increasing through-porosity. The rapid heating characteristics of microwave heating not only promote the early formation of a spatial network structure in the slurry, but also suppress bubble deformation, thereby obtaining a more ideal closed-cell structure.

[0159] Steam curing also plays an important role in pore stability. The steam environment can provide the moist and hot conditions required for the subsequent pore wall structure to undergo a continuous hydration reaction, prompting more reaction products to form at the bubble interface, thereby improving the density and strength of the pore wall. Compared with the room temperature curing group, it can be seen that the materials that have not undergone steam curing perform poorly in terms of pore size concentration, and are prone to problems such as pore penetration and collapse. This shows that the synergy of energy input and chemical reaction is necessary to achieve structural uniformity. Overall, the combined effect of nano-admixtures and energy field input enables the material to establish a stable pore wall network and continuously closed pores during the formation process, forming an excellent microstructure control system.

[0160] Experiment 3:

[0161] Purpose: This experiment aims to evaluate the effects of different components and molding processes on the thermal conductivity of the material, especially to verify the contribution of foaming uniformity, porosity structure, and closed-cell ratio to thermal insulation performance, and to analyze the role of nano-modification and microwave-steam coupling technology in improving thermal performance.

[0162] Experimental procedures

[0163] Sample preparation:

[0164] Cut standard size samples from the prepared blocks, keeping the edges neat and the surface free of cracks;

[0165] Oven the samples to constant weight to ensure dry conditions.

[0166] Equipment debugging:

[0167] Start the heat flow meter equipment and calibrate the thermocouple and heat flow sensor;

[0168] Place the sample between the hot plate and the cold plate, adjusting them to achieve full contact and avoid air gaps.

[0169] Testing process:

[0170] Start the program and record the heat flux and temperature difference data after the steady-state heat flow is established; automatically calculate the thermal conductivity;

[0171] Each group of samples was tested three times and the average was taken after excluding the abnormal fluctuation values.

[0172] Summarize the average thermal conductivity of each group;

[0173] A comparative analysis was conducted in combination with porosity and structural characteristics.

[0174] Table 3: Comparison of thermal conductivity coefficients of samples in each group

[0175]

[0176]

[0177] From Table 3 we can get:

[0178] Test results show that materials modified with nanosilicon exhibit lower thermal conductivity in terms of thermal conductivity. This is attributed to the fact that it promotes hydration reactions in the system and generates a high-density CSH gel, making the pore wall structure more uniform and continuous, reducing the formation of thermal bridges. Nanosilicon also has a good filling effect and can be embedded in the micropores of traditional cement-ash systems, further blocking the conduction path of gaseous or solid heat flow, thereby improving the overall thermal insulation capacity of the material. In comparison, samples using microsilica powder have difficulty effectively penetrating into the micropores due to their larger particle size, resulting in a significantly increased thermal conductivity.

[0179] The microwave foaming process significantly improves the distribution of pores, making them more uniform and highly closed. Under the rapid excitation of microwave energy, the foaming process can be completed before the initial solidification of the slurry, avoiding the merging and escape of bubbles, and forming closed pores with stable structure and similar size. This type of structure is equivalent to a large number of gas microcavities in heat conduction, and its thermal conductivity is much lower than that of the solid matrix, thereby significantly reducing the overall thermal conductivity coefficient of the material. In contrast, static foaming leads to large fluctuations in pore size and high opening rate, enhanced connectivity of the airflow path, and the heat flow conduction path is opened up, which significantly reduces the thermal insulation effect.

[0180] Steam curing provides a stable hydrothermal environment for the material during the pore-forming process, promoting a more complete hydration reaction and further improving the density of the pore walls. This process not only improves the structural strength, but also significantly inhibits the formation of capillary channels within the pore walls, making it difficult for heat to be conducted along the capillaries or microcracks. Although the room temperature curing group can maintain a certain porosity, the pore wall structure is loose, the connection parts are not fully reacted, and there is almost no obstruction to the heat conduction path. Therefore, from the perspective of material thermal performance, nano-silicon reinforcement, microwave shaping, and steam stabilization constitute the key path for regulating the "low thermal conductivity-high closed porosity-low connectivity" structure.

[0181] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high-porosity nano-modified aerated concrete block, characterized in that: The concrete block comprises the following components in parts by weight: Cement: 40-60 parts; Fly ash: 10-30 parts; Gypsum: 3-7 parts; Nano silicon: 0.1-3 parts; Foaming agent: 0.3-0.8 parts; Water: 25-45 parts; Sand: 10-25 parts.

2. The high-porosity nano-modified aerated concrete block according to claim 1, characterized in that: The nano-silicon is a silicon dioxide particle with a particle size of 20-50 nanometers and a specific surface area of 200-300m 2 / g.

3. The high-porosity nano-modified aerated concrete block according to claim 1, characterized in that: The foaming agent is a foaming agent containing aluminum powder, and the particle size of the aluminum powder is not greater than 50 microns.

4. The high-porosity nano-modified aerated concrete block according to claim 1, characterized in that: The fly ash is low-sulfur fly ash from a thermal power plant, has a particle size of less than 100 microns, and contains 70%-85% of silicon dioxide and bauxite minerals in its chemical composition.

5. A process for preparing high-porosity nano-modified aerated concrete blocks, characterized in that: The method for preparing a high-porosity nano-modified aerated concrete block according to any one of claims 1 to 4 comprises the following steps: S1, pre-treating the nano-silicon by ultrasonic dispersion, wherein the processing time of the nano-silicon is 5-10 minutes; S2. Dry mix cement, fly ash, gypsum, sand and pretreated nano-silicon according to the following parts by weight: Cement: 40-60 parts; Fly ash: 10-30 parts; Gypsum: 3-7 parts; Sand: 10-25 parts; Nano silicon: 0.1-3 parts; S3, adding water and foaming agent in proportion, stirring to form a uniform slurry; S4, pouring the stirred slurry into a mold and foaming it by microwave radiation to form a closed-cell structure, wherein the microwave radiation power is 500-800W, the frequency is 2450MHz, and the foaming time is 5-15 minutes; S5, placing the foamed mixture in a curing environment with a temperature of 60-80°C and a humidity of 85%-95% for 24-48 hours; S6. After curing is completed, the cured concrete blocks are cut into standard sizes using cutting equipment. The size of the blocks is 600 mm×200 mm×100 mm.

6. The process for preparing a high-porosity nano-modified aerated concrete block according to claim 5, characterized in that: The S3 includes the following steps: The foaming agent is aluminum powder with a particle size of less than 40 μm. When adding, it is first prepared into a sodium hydroxide solution and then slowly stirred and added to control the reaction rate and cell uniformity. The mass fraction of the sodium hydroxide solution is 0.1%-0.3%, and the aluminum powder accounts for 0.3%-0.8% of the total mass of the slurry.

7. The process for preparing a high-porosity nano-modified aerated concrete block according to claim 5, characterized in that: Said S1 comprises the following steps: During the ultrasonic dispersion process of nano silicon, a polycarboxylic acid dispersant is added as an auxiliary agent, and the amount of the dispersant is 0.5%-1% of the mass of the nano silicon; The ultrasonic frequency is 20-40 kHz, so that the nanoparticles do not aggregate in the solution and can be evenly distributed in the cement slurry system.

8. The process for preparing a high-porosity nano-modified aerated concrete block according to claim 5, characterized in that: The S5 comprises the following steps: The curing environment adopts steam curing mode, and the steam pressure is controlled at 0.1-0.2MPa to accelerate the cement hydration reaction and microstructure setting; The curing process includes two stages: pre-curing stage and high temperature and wet heat curing stage, and the total duration is controlled within 24-48 hours.

9. The process for preparing a high-porosity nano-modified aerated concrete block according to claim 5, wherein: The S4 comprises the following steps: The internal heating rate is controlled by continuous radiation, so that the temperature rise is controlled at 5-10℃ per minute; Two minutes before the end of foaming molding, the microwave power was reduced to 200 W for slow cooling to stabilize the bubble structure and form a dense closed-cell system.

10. The process for preparing a high-porosity nano-modified aerated concrete block according to claim 5, characterized in that: The S6 comprises the following steps: Block cutting uses diamond saw blade precision cutting equipment, and the cutting speed is controlled at 0.5-1.5m / min; After cutting, the blocks are placed in a ventilated and dry area for 7 days of air stabilization to evaporate the residual moisture, ultimately obtaining finished blocks with stable dimensions and excellent mechanical properties.

Images