Self-insulation waterproof alkali-activated fly ash foam concrete and preparation method thereof

Abstract

The invention relates to self-insulation waterproof alkali-activated fly ash foam concrete, which is prepared from the following raw material components: in unit cubic meter of foam concrete, the dosage of superfine fly ash is 341.41-420.69 kg / m < 3 >, the dosage of a binary composite activator is 105.68-214.66 kg / m < 3 >, the alkali equivalent is 0.08-0.11, the water-binder ratio is 0.4-0.6, the dosage of a foaming agent is 3.23-5.18 kg / m < 3 >, the dosage of a foam stabilizer is 1.33-7.36 kg / m < 3 >, the mass of basalt fiber is 3.14-4.21 kg / m < 3 >, the doping amount of calcium hydroxide is 19.36-73.83 kg / m < 3 >, the doping amount of glass beads is 2-4.21 kg / m < 3 >, and the doping amount the dosage of the waterproof agent sodium methyl silicate solution is 6.16-24.20 kg / m < 3 >, and the dosage of the dispersing agent is 4% of the mass of the SiO2 aerogel suspension.

Description

Technical Field

[0001] This invention relates to the field of building energy-saving and thermal insulation materials, and in particular to a self-insulating, waterproof, alkali-activated fly ash foamed concrete and its preparation method. Background Technology

[0002] With global climate change and the increasing demand for sustainable development, the requirements for building energy efficiency are becoming increasingly stringent, ushering in an era of ultra-low energy consumption. Traditional insulation methods and materials are ill-suited to the needs of ultra-low energy buildings, exhibiting problems such as insufficient insulation performance, high thermal conductivity requiring thick insulation layers, poor durability (materials are prone to aging and moisture absorption, rapid performance degradation, and short lifespan), unstable construction quality, and poor compatibility with other systems. Therefore, low-carbon, high-performance building energy-saving self-insulating materials have become a research hotspot. In contrast, the production process of silicate cement is energy-intensive and highly polluting. The preparation process of alkali-activated cementitious materials can reduce carbon emissions by 26% to 45%, and it also has advantages such as high temperature resistance and good durability, hence the name "green cement." Foamed concrete primarily reduces thermal conductivity by increasing porosity. However, increased porosity leads to a decrease in mechanical properties, and the challenge of the trade-off between mechanical and thermal properties remains. Furthermore, as a hydrophilic porous material, foamed concrete has a very high water absorption rate, which significantly increases thermal conductivity, reducing insulation and frost resistance.

[0003] To achieve self-insulating building walls while ensuring the wall thickness is as thin as possible, alkali-activated foamed concrete needs to have a lower thermal conductivity, while also maintaining good waterproof performance to prevent the material properties from being affected by moisture in the environment. This invention is specifically proposed to address the requirements for self-insulating exterior walls of ultra-low energy consumption residential buildings in hot-summer and cold-winter regions. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a self-insulating, waterproof, alkali-activated fly ash foamed concrete and its preparation method, which, with a thickness of 300mm, meets the self-insulating requirements of the exterior walls of ultra-low energy consumption residential buildings in hot-summer and cold-winter regions, i.e., the wall heat transfer coefficient is ≤0.4W / m. 2 • K, with a water absorption rate of less than 5%, thus solving the problem that foamed concrete materials cannot simultaneously achieve thermal insulation and waterproofing performance. The required thermal conductivity for preparing the foamed concrete material is determined by calculation based on the thermal design code for civil buildings, using the following formula:

[0005] K = 1 ( 1⁄h1 + 1⁄h2 + δ⁄ λ )

[0006] In the formula, K represents the heat transfer coefficient of the wall, W / (m²). 2 ·K), with a value of 0.4 W / (m 2 ·K); h1 represents the convective heat transfer coefficient inside the wall, W / (m²).2 ·K), with a value of 8.7 W / (m 2 ·K); h2 represents the convective heat transfer coefficient on the outer side of the wall, W / (m²). 2 ·K), taking the value of 23 W / (m²) under the worst-case scenario. 2 ·K); δ is the wall thickness, mm, taken as 300 mm; λ is the thermal conductivity of alkali-activated fly ash foamed concrete, W / (m·K), and the material's thermal conductivity correction factor α is considered, taken as 1.05. Calculations show that the thermal conductivity of alkali-activated fly ash foamed concrete should not exceed 0.1216 W / (m·K).

[0007] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0008] According to one aspect of the present invention, a self-insulating, waterproof, alkali-activated fly ash foamed concrete is provided, the raw materials comprising the following components:

[0009] The dosage of ultrafine fly ash is 341.41~420.69 kg / m³. 3 The dosage of the binary composite activator (composed of sodium hydroxide and sodium silicate aqueous solution) is 105.68–214.66 kg / m³. 3 The activator modulus is 0.9~1.5, the alkali equivalent is 0.08~0.11, preferably the activator modulus is 1.1, the alkali equivalent is 0.1, the water-cement ratio is 0.4~0.6, and the foam stabilizer dosage is 1.33~7.36 kg / m³. 3 The mass of basalt fiber is 3.14–4.21 kg / m³. 3 The calcium hydroxide content ranges from 19.36 to 73.83 kg / m³. 3 Vitrified microsphere content: 2–4.21 kg / m 3 SiO2 aerogel content 2-8 kg / m 3 The dosage of foaming agent (physical foaming agent) is 3.23–5.18 kg / m³. 3 Waterproofing agent (sodium methylsilicate solution) 6.16~24.20 kg / m 3 The dispersant (silane coupling agent KH550) is 4%.

[0010] The fly ash is ultrafine fly ash. The fineness of the fly ash has a significant impact on the degree of alkali activation reaction. The finer the fly ash, the more complete the alkali activation reaction process. The particle size distribution is 0.662~34.3μm, and the volume average particle size is 9.196 μm.

[0011] The composite activator is prepared by mixing sodium hydroxide and sodium silicate aqueous solution. The modulus of the composite activator can be adjusted by adjusting the ratio of the two.

[0012] The foam stabilizer is hydroxypropyl methylcellulose ether (HPMC) with a molecular weight of 86,000 and a viscosity of 200,000. By adjusting the amount of foam stabilizer, the thickness of the foam film can be increased, the surface tension of the bubble liquid film can be reduced, and the bubble liquid film can be made more hydrophobic, thus slowing down the rate of thinning and deterioration of the foam liquid film and reducing the occurrence of defoaming or bubble merging in foamed concrete.

[0013] The basalt fiber can improve the tensile strength of foamed concrete. The fiber has a length of 6 mm, a diameter of 17 μm, an elastic modulus of 7.6 GPa, and a tensile strength of 1050 MPa.

[0014] The calcium hydroxide is a white powder. Adding calcium hydroxide increases the calcium content of the system, thereby improving the mechanical properties of alkali-activated foamed concrete. The compressive and flexural strengths both decrease and then increase with the amount of calcium hydroxide added. Adding an appropriate amount of calcium hydroxide can improve the mechanical properties. Based on the mass of fly ash, the optimal ratio is 5% of the mass of fly ash.

[0015] The vitrified microspheres are lightweight aggregates that can reduce density and enhance mechanical properties. They have a particle size of 1-3 mm and a bulk density of 116 kg / m³. 3 The compressive strength of the cylinder is 0.52MPa, the thermal conductivity is 0.049W / (m·K), the water absorption rate is 30%, the floating rate is ≥80%, the surface vitrification closed-cell rate is ≥80%, the linear shrinkage rate is 0.29%, and it is used in a fixed proportion, added at 1% of the mass of fly ash used.

[0016] The SiO2 aerogel used was produced by Shenzhen Zhongning Technology Co., Ltd., with a particle size distribution of 15–50 μm and a specific surface area of ​​500–800 m². 2 The thermal conductivity is <0.013 W / (m·K), indicating hydrophobic properties. By utilizing SiO2 aerogel as a lightweight, nanoporous, amorphous solid material, its nanoporous structure can significantly restrict solid-state heat conduction and gaseous heat convection, exhibiting excellent thermal insulation performance. Foamed concrete, as a porous material, has relatively low mechanical strength. Compared to reducing thermal conductivity by increasing the porosity of foamed concrete, incorporating SiO2 aerogel can reduce thermal conductivity at the same porosity, or reduce porosity without changing thermal conductivity, thus reducing the impact on mechanical properties. However, due to the high surface energy and specific surface area of ​​SiO2 aerogel powder, SiO2 aerogel particles easily agglomerate in foamed concrete slurry for uniform dispersion. Furthermore, because SiO2 aerogel powder has a low density, it tends to adhere to the top of the slurry during stirring, making it difficult to achieve its thermal insulation properties. Therefore, this invention proposes a preparation method that first uniformly disperses SiO2 aerogel particles in water before adding other raw materials for mixing. Specifically, the SiO2 aerogel is first dispersed evenly in water using a combination of ultrasound and chemical dispersants before being mixed with other raw materials. The optimal dosage is 6 kg / m³.3 .

[0017] The advantage of using silane coupling agent KH550 as the dispersant is that the surface of SiO2 aerogel contains a large number of silane groups (-Si-CH3) formed by low surface energy hydrophobic methyl (-CH3) groups, which is a key factor causing hydrophobic aggregation of the aerogel. However, its surface also contains highly active silanol groups (-Si-OH), which can react with other groups or form hydrogen bonds. First, the active ingredient of silane coupling agent KH550, 3-aminopropyltriethoxysilane, undergoes a hydrolysis reaction after dissolving in water, and the reaction product is 3-aminopropyltrihydroxysilane (as shown in the following formula).

[0018] Step 1: Hydrolysis

[0019] H2N(CH2)3Si(OC2H5)3 + 3H2O = H2N(CH2)3Si(OH)3 + 3C2H5OH

[0020] Step Two: Replacement

[0021] -Si-OH + H2N(CH2)3Si(OH)3 = -Si-O-Si(OH)2-(CH2)3-NH2 + H2O

[0022] Amino groups (-NH2) can undergo a substitution reaction with the highly active silanol groups (-Si-OH) on the surface of hydrophobic SiO2, adding amino and hydroxyl groups to the surface of SiO2 aerogel particles. Both of these are polar groups that are easily soluble in water, which can improve the hydrophilicity of SiO2 aerogels and enable them to disperse in water. The more thorough the substitution reaction, the better the dispersion effect. However, it is also necessary to determine the optimal amount of dispersant and control the degree of substitution reaction to avoid affecting the performance of SiO2 aerogels.

[0023] The waterproofing agent is a sodium methylsilicate solution, which enhances the waterproofing performance of foamed concrete through internal admixture. Sodium methylsilicate, as a novel rigid building waterproofing material, possesses excellent permeability and crystallinity, with the molecular formula CH5SiO3Na, and is chemically stable. Upon contact with foamed concrete, under the action of water and carbon dioxide, it first forms methylsilicic acid alcohol, which then reacts with Ca²⁺, Mg²⁺, and other substances in the cement hydration products, forming an insoluble network of organosilicon resin waterproofing membrane on the surface and inside the foamed concrete structural material. This membrane can block pores, producing a "reverse capillary effect," forming a hydrophobic layer, and also exhibits micro-expansion to increase density. It is breathable, moisture-proof, and anti-aging, effectively improving the waterproofing performance of foamed concrete.

[0024] According to another aspect of the present invention, a method for preparing the above-mentioned self-insulating, waterproof, alkali-activated fly ash foamed concrete is also provided, comprising:

[0025] Step 1: First, place the ultrafine fly ash in a drying oven and dry it at 200℃. To improve the activity, use a planetary ball mill to spheroidize the fly ash. The grinding media is zirconia balls, the ball-to-material ratio is 15:1, the rotation speed is 600 r / min, and the spheroidizing time is 30 minutes. Add 0.2% of ethylene glycol and triethanolamine composite grinding aid according to the mass of fly ash. Take samples every 15 minutes to avoid over-grinding and particle agglomeration.

[0026] Step 2: Place the four dry materials—activated fly ash, calcium hydroxide, vitrified microspheres, and basalt fiber—in a bucket and stir them thoroughly at a speed of 60 r / min until uniform.

[0027] Step 3: Prepare the binary composite activator. First, place an aqueous solution of sodium silicate with an initial modulus of 3.3 in a glass dissolving vessel, and then place the glass dissolving vessel in a container containing a large amount of water to absorb the heat released during the dissolution of sodium hydroxide solid. Calculate the required mass of NaOH based on the determined modulus, weigh the NaOH particles, add them to a certain amount of water, and stir thoroughly until completely dissolved. After sealing and standing at room temperature, add the NaOH solution to the sodium silicate aqueous solution and stir thoroughly until homogeneous. The stirring time should be no less than 5 minutes. Throughout the process, use a polyethylene plastic film to keep the container sealed to prevent the activator from being carbonized.

[0028] Step 4: Preparation of SiO2 aerogel suspension. The preparation process includes: First, adding silane coupling agent KH550 to deionized water at a mass ratio of 4% and stirring thoroughly with a magnetic stirrer. Then, adding hydrophobic SiO2 aerogel powder to the deionized water, inserting the vibrating rod of an ultrasonic disperser below the liquid surface, and ultrasonically dispersing for 35 minutes at a dispersion power of 540W. This will prepare a uniformly dispersed SiO2 aerogel suspension. During the ultrasonic dispersion process, the entire device is placed in a constant temperature environment of 10℃ to avoid the heat generated during the ultrasonic process causing the temperature of the deionized water to rise, which would affect the dispersion. The magnetic stirrer is kept running throughout the entire ultrasonic dispersion process.

[0029] Step 5: Using HTQ-1 type composite polymer foaming agent, the foam preparation process includes: diluting the foaming agent with water at a weight ratio of 1:40, adding a foam stabilizer (hydroxypropyl methylcellulose ether HPMC) and stirring thoroughly for at least 5 minutes; then foaming using a foaming machine at a pressure of 0.5 MPa; the density of the foam prepared after foaming is approximately 63 kg / m³. 3 .

[0030] Step 6: Add the sodium methyl silicate solution with internal admixture at 5.5% of the amount of ultrafine fly ash. Before use, add the sodium methyl silicate solution to the container according to the set mass ratio and stir thoroughly with a magnetic stirrer for no less than 3 minutes.

[0031] Step 7: Add the binary composite activator with a modulus of 1.1 to the mixture obtained in Step 1 at an alkali equivalent of 0.1. Continue stirring the raw materials until they become flocculent. Add the SiO2 aerogel suspension and stir until uniform. Then add the fully stirred sodium methylsilicate solution and add the required amount of water according to the water-gel ratio. Finally, add the prepared foam and continue stirring until there is no foam in the slurry. Pour the prepared slurry into the mold and vibrate it slightly. Seal the mold with polyethylene film and place it in a curing chamber at a temperature of 55°C and a relative humidity of ≥95% for curing to the set age of 7 days.

[0032] This invention increases the calcium content in the fly ash system by adding calcium hydroxide, thereby increasing the proportion of hydrated calcium silicate in the alkali-activated cementitious material and improving its mechanical properties. Basalt fibers are added to enhance the tensile strength of the foamed concrete, and the addition of SiO2 aerogel, a super-insulating material, improves its thermal performance. However, SiO2 aerogel is difficult to disperse in foamed concrete slurry. This invention proposes a physical-chemical combined dispersion method, specifically using a combination of ultrasound and chemical dispersants to first uniformly disperse SiO2 aerogel particles in water before adding other raw materials. This achieves the goal of reducing porosity while simultaneously improving thermal performance, effectively solving the problem of the mutual constraint between mechanical and thermal properties in conventional alkali-activated foamed concrete preparation methods. The addition of a waterproofing agent addresses the issue of high water absorption in foamed concrete. The invented foamed concrete, with a wall panel thickness of 300mm, can meet the self-insulating requirements of ultra-low energy consumption residential buildings in hot-summer and cold-winter regions (i.e., wall heat transfer coefficient ≤ 0.4W / m²). 2 ·K), which has good engineering application value. Attached Figure Description

[0033] Figure 1 The effect of ultrasonic dispersion time on the absorbance of SiO2 aerogel suspension;

[0034] Figure 2 The variation of absorbance of SiO2 aerogel suspension with dispersant dosage is shown.

[0035] Figure 3 The changes in Zeta potential and pH value of SiO2 aerogel suspension with varying dispersant dosage are shown.

[0036] Figure 4The particle size distribution of SiO2 aerogel suspension varies with the amount of silane coupling agent KH550.

[0037] Figure 5 The cumulative particle size distribution of SiO2 aerogel suspension varies with the amount of silane coupling agent KH550.

[0038] Figure 6 The variation of particle size distribution of SiO2 aerogel suspension with the amount of wetting agent PE-100 is shown.

[0039] Figure 7 The cumulative particle size distribution of SiO2 aerogel suspension varies with the amount of wetting agent PE-100.

[0040] Figure 8 The changes in the state of SiO2 aerogel in water are shown in the figures: (a) original SiO2 aerogel, and (b) dispersed SiO2 aerogel in water. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0042] This invention provides a self-insulating, waterproof, alkali-activated fly ash foamed concrete and its preparation method. The raw materials consist of the following components by weight: ultrafine fly ash produced by Xuzhou Huarun Power Co., Ltd.; a binary composite activator (prepared by mixing water glass (sodium silicate aqueous solution) and sodium hydroxide), the sodium silicate aqueous solution produced by Zhejiang Jiashan Yourui Refractory Materials Co., Ltd.; sodium hydroxide (NaOH) produced by Shandong Binhua Group Co., Ltd. (IS-I type, content ≥0.99%), appearing as flaky crystals; and a foaming agent, HTQ-1 type composite polymer foaming agent, produced by Henan Huatai. The following materials were manufactured by XinCai Technology Co., Ltd.: foam stabilizer (hydroxypropyl methylcellulose ether, HPMC) by Dow Chemical Company, USA; lightweight aggregate - vitrified microspheres by Hebei Yixin Energy-Saving Insulation Building Materials Co., Ltd.; hydrophobic SiO2 aerogel by Shenzhen Zhongning Technology Co., Ltd.; basalt fiber by Changsha Ningxiang Building Materials Co., Ltd.; calcium hydroxide by Nanjing Baore Chemical Co., Ltd.; waterproofing agent sodium methylsilicate solution by Shanxi Jingchen Building Materials Co., Ltd.; dispersant (silane coupling agent KH550) by Jiangsu Chenguang Coupling Agent Co., Ltd.; deionized water; and tap water.

[0043] By selecting and specifying the proportions of the components, this invention achieves a self-insulating alkali-activated foamed concrete that simultaneously maintains mechanical, thermal insulation, and waterproof properties. The technical effects of the aforementioned components and their proportions are described below:

[0044] The first example is the implementation of SiO2 aerogel dispersion in water.

[0045] 1. Optimal duration of ultrasonic dispersion of SiO2 aerogel

[0046] The duration of ultrasonic treatment directly affects the dispersion effect, especially for ultrafine particles. To obtain the optimal process, the output power of the ultrasonic generator was set to a fixed value of 540 W, and only the duration of ultrasonic treatment was varied. The duration of ultrasonic treatment was set to 5 min, 15 min, 25 min, 35 min, 45 min, and 60 min, respectively, with a control group that did not undergo ultrasonic treatment. SiO2 aerogel suspensions were ultrasonically dispersed according to the above durations, and the optimal ultrasonic treatment duration was determined by analyzing the absorbance test results. In the specific experimental procedure, 2 g of SiO2 aerogel powder was weighed and added to 198 g of deionized water to prepare a 1% SiO2 aerogel solution, which was then ultrasonically dispersed for the set durations. The absorbance of the SiO2 aerogel suspensions after ultrasonic dispersion for different durations was measured, and the results are as follows: Figure 1 As shown.

[0047] As the duration of ultrasonic dispersion increases, the absorbance of the suspension, although fluctuating slightly in the middle, shows an overall trend of gradual increase. Figure 1 The results show that extending the ultrasonic dispersion time can improve the dispersion effect. When the dispersion time is 35 min, the absorbance of the suspension reaches 0.977, indicating that the SiO2 aerogel is uniformly dispersed in water. After the time exceeds 35 min, although the absorbance of the suspension fluctuates and increases, the increase is very small and there is basically no significant change. Therefore, the ultrasonic dispersion time can be determined to be 35 min.

[0048] 2. Effect of dispersant dosage on dispersion effect

[0049] To determine the effect of dispersant type and dosage on the dispersion of SiO2 aerogel in water, two dispersants, PE-100 (wetting agent) and KH550 (silane coupling agent), were selected for comparison. The experiments preliminarily determined a suitable dosage range of 4–16 wt%. The dispersant dosage ratio (mass percentage) was calculated based on the total mass of water and aerogel, with a uniform standard of 100 g for each sample group. The concentration of the SiO2 aerogel solution was 6 kg / m³. 3Preparation by dosage. The dosage of dispersant was increased in increments of 2 g to 16 wt%. When preparing the aerogel suspension, the dispersant was first added to water according to the set mass and stirred until uniform. Then, SiO2 aerogel was added, and the aerogel suspension was ultrasonically dispersed for 35 min. Finally, the absorbance, zeta potential and particle size distribution of the prepared SiO2 aerogel suspension were tested.

[0050]

[0051] The absorbance, zeta potential, and particle size distribution of SiO2 aerogel suspensions prepared by two dispersants under different doping conditions are as follows.

[0052] (1) Absorbance

[0053] Combination Figure 2 The higher the absorbance, the more uniform the dispersion. When the silane coupling agent KH550 dosage is 4 wt% (KH-1), the absorbance reaches a high level, then increases very slowly until it reaches a maximum of 0.958 at a dosage of 16 wt% (KH-7). When the wetting agent PE-100 dosage is 6 wt% (PE-2), the absorbance reaches a maximum of 0.86. Under the same dosage conditions, the silane coupling agent KH550 has a better dispersing ability for SiO2 aerogel than the wetting agent PE-100.

[0054] (2) Zeta potential

[0055] Combination Figure 3 The zeta potential of SiO2 aerogel suspension directly reflects the stability of dispersion, and the higher the absolute value, the better. In the dosage range of 4 wt% to 16 wt%, the zeta potential of the suspension dispersed by wetting agent PE-100 is negative, while the zeta potential of the suspension dispersed by silane coupling agent KH550 is positive. When the dosage of both wetting agent PE-100 and silane coupling agent KH550 is 4 wt%, the corresponding zeta potentials of the suspension are -3.185 mV and 4.66 mV, respectively, which are the largest absolute values ​​in their respective test results. This indicates that both dispersants have the best dispersion effect on SiO2 aerogel when the dosage is 4 g.

[0056] (3) Particle size distribution

[0057] Combination Figure 4-5With increasing silane coupling agent KH550 content, the average particle size distribution of SiO2 aerogel suspension particles showed an increasing trend. The average particle sizes corresponding to different dosing levels KH-1, KH-2, KH-3, KH-4, KH-5, KH-6, and KH-7 were 199.5 μm, 198.9 μm, 242.4 μm, 255.4 μm, 278.7 μm, 316.3 μm, and 341.2 μm, respectively. When the dispersant dosing was 4 wt% (KH-1), the first peak appeared at a particle size of 259.7 μm, with a cumulative particle size distribution of 93.3%. When the dispersant dosing was 16 wt% (KH-7), the average particle size of SiO2 aerogel suspension particles increased to 341.2 μm, with a cumulative particle size distribution of 100%, and the first peak point was at 341.7 μm. Compared with a doping amount of 4 wt% (KH-1), the average particle size increased by 71.03% with a doping amount of 16 wt% (KH-7), and the corresponding cumulative particle size distribution D50 increased from 211.54 μm to 304.89 μm.

[0058] Combination Figure 6-7 The effect of varying PE-100 wetting agent dosage on the particle size of SiO2 aerogel in water follows the same pattern as with silane coupling agent KH550: the average particle size distribution of the SiO2 aerogel suspension increases with increasing dosage. Under seven dosage levels (PE-1, PE-2, PE-3, PE-4, PE-5, PE-6, and PE-7), the average particle sizes of the SiO2 aerogel suspension were 587.7 μm, 705.5 μm, 813.3 μm, 840.8 μm, 954.8 μm, 1162 μm, and 1624 μm, respectively. Among these, the PE-100 dosage of 4 wt% (PE-1) resulted in the smallest average particle size, indicating the most uniform dispersion of the aerogel particles in water.

[0059] Comparative analysis showed that when the dosage of silane coupling agent KH550 was 4 wt% (KH-1), the SiO2 aerogel particles exhibited the best dispersion effect in water. Therefore, silane coupling agent KH550 was selected as the dispersant, and the state changes of the aerogel in water after uniform dispersion are as follows: Figure 8 :

[0060] Implementation Case 2: Optimization of mix proportions through orthogonal experimental design.

[0061] Eight variables were selected: alkali equivalent, activator modulus, water-cement ratio, foam content, foam stabilizer content, aerogel content, calcium hydroxide content, and waterproofing agent content. Each variable had four levels. The alkali equivalent values ​​were 0.08, 0.09, 0.10, and 0.11; the activator modulus values ​​were 0.9, 1.1, 1.3, and 1.5; and the water-cement ratio values ​​were 0.4, 0.45, 0.55, and 0.60. Considering foam loss during preparation, the foam content was calculated as a multiple of the theoretical value, specifically 3.0, 3.5, 4.0, and 4.5. The foam stabilizer was added according to the mass ratio of the foaming agent, specifically 1%, 1.5%, 2.5%, and 3.5%. The aerogel content per unit volume of foamed concrete was 2 kg / m³. 3 4 kg / m 3 6 kg / m 3 8 kg / m 3 The dosages of calcium hydroxide and waterproofing agent were calculated based on the mass of fly ash. The calcium hydroxide dosages were 5%, 10%, 15%, and 20%, respectively; the waterproofing agent dosages were 1.5%, 3%, 4.5%, and 5.5%, respectively. Fixed parameters were used for the dosages of vitrified microspheres, basalt fiber, and curing process. Vitrified microspheres and basalt fiber were added at 5% and 1% of the fly ash mass, respectively.

[0062] An orthogonal experimental design was constructed based on the above 8 variables, with each factor set to 4 levels. The corresponding factor level table and orthogonal experimental table are shown below:

[0063]

[0064]

[0065]

[0066] As shown in the table above, the dry density of the 32 mix design samples ranged from 556.83 to 655.77 kg / m³. 3 Only two groups of mix proportion samples had dry densities slightly greater than the target value; the thermal conductivity of the 32nd mix proportion sample was the lowest, at 0.0929 W / (m·K), while only the thermal conductivity of the 1st, 13th, and 31st mix proportion samples was slightly greater than the target value, with the 1st mix proportion sample having the highest thermal conductivity at 0.1377 W / (m·K); the mechanical properties and frost resistance (F25) basically met the target requirements; among the 32 mix proportion samples, the highest mass water absorption rate was only 7.41%.

[0067] Range analysis was performed on the above orthogonal experimental results to analyze the influence of various factors and levels on performance. Based on this, matrix analysis was further used to determine the optimal mix proportion of alkali-activated foamed concrete. The optimal mix proportion was determined by the following factors: alkali equivalent 0.1, alkali activation modulus 1.1, water-cement ratio 0.4, foam content 4.5, foam stabilizer dosage 3.5%, aerogel content 6 kg / m³, calcium hydroxide content 5%, waterproofing agent dosage 5.5%, and vitrified microspheres and basalt fiber added at 5% and 1% of fly ash mass, respectively. The optimal mix proportion had the following mass values ​​for each component: ultrafine fly ash 400.071 kg / m³. 3 The dosage of the binary composite activator with a modulus of 1.1 was 161.29 kg / m³. 3 Water consumption is 74.51 kg / m³ 3 Foam content 3.471m 3 / m 3 (Foaming agent content: 4.957 kg / m³) 3 Foam stabilizer dosage: 1.73 kg / m³ 3 Aerogel content: 6 kg / m³; Calcium hydroxide content: 20.0 kg / m³ 3 Waterproofing agent dosage: 22.0 kg / m² 3 The amount of vitrified microspheres used is 2 kg / m³. 3 The amount of basalt fiber used is 4.0 kg / m³. 3 Therefore, based on the above mix proportions, the sample preparation and curing were carried out, and the performance parameters of the optimal mix proportion alkali-activated fly ash foamed concrete were measured as shown in the table below:

[0068]

[0069] Example

[0070] Based on the above experimental results, this invention provides a self-insulating, waterproof, alkali-activated fly ash foamed concrete, the composition of which is: 400.071 kg / m³ of ultrafine fly ash per cubic meter of foamed concrete. 3 Modulus 1.1, binary composite activator dosage 161.29 kg / m³ 3 Water consumption is 74.51 kg / m³ 3 Foam content 3.471m 3 / m 3 (Foaming agent content: 4.957 kg / m³) 3 Foam stabilizer dosage: 1.73 kg / m³ 3 Aerogel content: 6 kg / m³; Calcium hydroxide content: 20.0 kg / m³ 3 Waterproofing agent sodium methylsilicate solution dosage: 22.0 kg / m² 3 The amount of vitrified microspheres used is 2 kg / m³. 3The amount of basalt fiber used is 4.0 kg / m³. 3 The amount of dispersant used is 4% of the mass of the SiO2 aerogel suspension.

[0071] The binary composite activator is composed of sodium hydroxide and sodium silicate aqueous solution, with an activator modulus of 1.1 and an alkali equivalent of 0.1. The fly ash is ultrafine fly ash with a particle size distribution of 0.662~34.3μm and a volume average particle size of 9.196 μm. The foam stabilizer is hydroxypropyl methylcellulose ether (HPMC) with a molecular weight of 86,000 and a viscosity of 200,000. The basalt fiber has a length of 6mm, a diameter of 17μm, an elastic modulus of 7.6GPa, and a tensile strength of 1050MPa. The vitrified microspheres have a particle size of 1~3mm, a bulk density of 116kg / m³, a compressive strength of 0.52MPa, a thermal conductivity of 0.049W / (m·K), a water absorption rate of 30%, a floating rate ≥80%, a surface vitrification closed-cell rate ≥80%, and a linear shrinkage rate of 0.29%. The SiO2 aerogel has a particle size distribution of 15–50 μm, a specific surface area of ​​500–800 m² / g, and a thermal conductivity of <0.013 W / (m·K). The dispersant used is silane coupling agent KH550.

[0072] Step 1: First, place the ultrafine fly ash in a drying oven and dry it at 200℃. To improve the activity, use a planetary ball mill to spheroidize the fly ash. The grinding media is zirconia balls, the ball-to-material ratio is 15:1, the rotation speed is 600 r / min, and the spheroidizing time is 30 minutes. Add 0.2% of ethylene glycol and triethanolamine composite grinding aid according to the mass of fly ash. Take samples every 15 minutes to avoid over-grinding and particle agglomeration.

[0073] Step 2: Place the four dry materials—activated fly ash, calcium hydroxide, vitrified microspheres, and basalt fiber—in a bucket and stir them thoroughly at a speed of 60 r / min until uniform.

[0074] Step 3: Prepare the binary composite activator. First, place an aqueous solution of sodium silicate with an initial modulus of 3.3 in a glass dissolving vessel, and then place the glass dissolving vessel in a container containing a large amount of water to absorb the heat released during the dissolution of sodium hydroxide solid. Calculate the required mass of NaOH based on the determined modulus, weigh the NaOH particles, add them to a certain amount of water, and stir thoroughly until completely dissolved. After sealing and standing at room temperature, add the NaOH solution to the sodium silicate aqueous solution and stir thoroughly until homogeneous. The stirring time should be no less than 5 minutes. Throughout the process, use a polyethylene plastic film to keep the container sealed to prevent the activator from being carbonized.

[0075] Step 4: Preparation of SiO2 aerogel suspension. The preparation process includes: First, adding silane coupling agent KH550 to deionized water at a mass ratio of 4% and stirring thoroughly with a magnetic stirrer. Then, adding hydrophobic SiO2 aerogel powder to the deionized water, inserting the vibrating rod of an ultrasonic disperser below the liquid surface, and ultrasonically dispersing for 35 minutes at a dispersion power of 540W. This will prepare a uniformly dispersed SiO2 aerogel suspension. During the ultrasonic dispersion process, the entire device is placed in a constant temperature environment of 10℃ to avoid the heat generated during the ultrasonic process causing the temperature of the deionized water to rise, which would affect the dispersion. The magnetic stirrer is kept running throughout the entire ultrasonic dispersion process.

[0076] Step 5: Using HTQ-1 type composite polymer foaming agent, the foam preparation process includes: diluting the foaming agent with water at a weight ratio of 1:40, adding a foam stabilizer (hydroxypropyl methylcellulose ether HPMC) and stirring thoroughly for at least 5 minutes; then foaming using a foaming machine at a pressure of 0.5 MPa; the density of the foam prepared after foaming is approximately 63 kg / m³. 3 .

[0077] Step 6: Add the sodium methyl silicate solution with internal admixture at 5.5% of the amount of ultrafine fly ash. Before use, add the sodium methyl silicate solution to the container according to the set mass ratio and stir thoroughly with a magnetic stirrer for no less than 3 minutes.

[0078] Step 7: Add the binary composite activator with a modulus of 1.1 to the mixture obtained in Step 1 at an alkali equivalent of 0.1. Continue stirring the raw materials until they become flocculent. Add the SiO2 aerogel suspension and stir until uniform. Then add the fully stirred sodium methylsilicate solution and add the required amount of water according to the water-gel ratio. Finally, add the prepared foam and continue stirring until there is no foam in the slurry. Pour the prepared slurry into the mold and vibrate it slightly. Seal the mold with polyethylene film and place it in a curing chamber at a temperature of 55°C and a relative humidity of ≥95% for curing to the set age of 7 days.

[0079] This invention increases the calcium content in the fly ash system by adding calcium hydroxide, thereby increasing the proportion of hydrated calcium silicate in the alkali-activated cementitious material and improving its mechanical properties. Basalt fibers are added to enhance the tensile strength of the foamed concrete, and the addition of SiO2 aerogel, a super-insulating material, improves its thermal performance. However, SiO2 aerogel is difficult to disperse in foamed concrete slurry. This invention proposes a physical-chemical combined dispersion method, specifically using a combination of ultrasound and chemical dispersants to first uniformly disperse SiO2 aerogel particles in water before adding other raw materials. This achieves the goal of reducing porosity while simultaneously improving thermal performance, effectively solving the problem of the mutual constraint between mechanical and thermal properties in conventional alkali-activated foamed concrete preparation methods. The addition of a waterproofing agent addresses the issue of high water absorption in foamed concrete. The invented foamed concrete, with a wall panel thickness of 300mm, can meet the self-insulating requirements of ultra-low energy consumption residential buildings in hot-summer and cold-winter regions (i.e., wall heat transfer coefficient ≤ 0.4W / m²). 2 ·K), which has good engineering application value.

[0080] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A self-insulating, waterproof, alkali-activated fly ash foamed concrete, characterized in that, The dosage of ultrafine fly ash in foamed concrete is 341.41~420.69 kg / m³. 3 The dosage of the binary composite activator is 105.68–214.66 kg / m³. 3 The alkali equivalent is 0.08~0.11, the water-cement ratio is 0.4~0.6, and the foaming agent dosage is 3.23~5.18 kg / m³. 3 The dosage of foam stabilizer is 1.33–7.36 kg / m³. 3 The mass of basalt fiber is 3.14–4.21 kg / m³. 3 The calcium hydroxide content ranges from 19.36 to 73.83 kg / m³. 3 Vitrified microsphere content: 2–4.21 kg / m 3 SiO2 aerogel content 2-8 kg / m 3 The dosage of the waterproofing agent sodium methylsilicate solution is 6.16–24.20 kg / m². 3 The amount of dispersant used is 4% of the mass of the SiO2 aerogel suspension.

2. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The binary composite activator is composed of sodium hydroxide and sodium silicate aqueous solution, with an activator modulus of 0.9~1.5 and an alkali equivalent of 0.08~0.

11.

3. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The fly ash is ultrafine fly ash with a particle size distribution of 0.662~34.3μm and a volume average particle size of 9.196 μm.

4. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The foam stabilizer is hydroxypropyl methylcellulose ether (HPMC) with a molecular weight of 86,000 and a viscosity of 200,000.

5. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The basalt fiber has a length of 6 mm, a diameter of 17 μm, an elastic modulus of 7.6 GPa, and a tensile strength of 1050 MPa.

6. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The vitrified microspheres have a particle size of 1-3 mm and a bulk density of 116 kg / m³. 3 The cylinder compressive strength is 0.52 MPa, the thermal conductivity is 0.049 W / (m·K), the water absorption rate is 30%, the floating rate is ≥80%, the surface vitrification closed-cell rate is ≥80%, and the linear shrinkage rate is 0.29%.

7. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The SiO2 aerogel has a particle size distribution of 15–50 μm and a specific surface area of ​​500–800 m². 2 / g, thermal conductivity <0.013W / (m·K).

8. The self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, The dispersant used is silane coupling agent KH550.

9. The method for preparing self-insulating, waterproof, alkali-activated fly ash foamed concrete according to claim 1, characterized in that, Its preparation steps include: Step 1: First, place the ultrafine fly ash in a drying oven and dry it at 200℃. Then, use a planetary ball mill to spheroidize the fly ash with zirconium oxide balls as the grinding media. The ball-to-material ratio is 15:1, the rotation speed is 600 r / min, and the spheroidizing time is 30 minutes. Add 0.2% of a composite grinding aid of ethylene glycol and triethanolamine according to the mass of the fly ash. Take samples for testing every 15 minutes. Step 2: Mix the four dry materials—ultrafine fly ash, calcium hydroxide, vitrified microspheres, and basalt fiber—at a speed of 60 r / min until homogeneous. Step 3: Prepare the binary composite activator. First, place an aqueous solution of sodium silicate with an initial modulus of 3.3 in a glass dissolving vessel, and then place the glass dissolving vessel in a container containing water to absorb the heat released during the dissolution of solid sodium hydroxide. Calculate the required mass of NaOH based on the determined modulus, weigh the NaOH particles, add them to the water and stir thoroughly until completely dissolved. After sealing and standing at room temperature, add the NaOH solution to the aqueous solution of sodium silicate and stir thoroughly until homogeneous. The stirring time should be no less than 5 minutes. Throughout the process, use a polyethylene plastic film to keep the container sealed. Step 4: Preparation of SiO2 aerogel suspension. The preparation process includes: adding deionized water to a plastic container in a certain proportion, then adding a dispersant to the deionized water. The amount of dispersant is 4% of the total mass of the suspension. Stir the mixture thoroughly with a magnetic stirrer for 5 minutes until homogeneous. Add hydrophobic SiO2 aerogel, then insert the vibrating rod of an ultrasonic disperser below the liquid surface. Set the dispersion power to 540W and perform ultrasonic dispersion for 35 minutes. During the ultrasonic dispersion process, keep the magnetic stirrer stirring consistently to obtain the aerogel suspension. Step 5: Prepare foam using HTQ-1 type composite polymer foaming agent. The foam preparation process includes: diluting the foaming agent with water at a weight ratio of 1:40, adding a foam stabilizer and stirring thoroughly for at least 5 minutes; then foaming using a foaming machine at a pressure of 0.5 MPa. The density of the foam prepared after foaming is approximately 63 kg / m³. 3 ; Step 6: Add the sodium methylsilicate solution to the container according to the set mass ratio, and stir thoroughly with a magnetic stirrer for no less than 3 minutes; Step 7: Add the binary composite activator with a modulus of 1.1 to the dry mixture obtained in step 2 at an alkali equivalent of 0.

1. Continue stirring the dry mixture until it becomes flocculent. Then add the prepared aerogel suspension and foam, and stir until uniform. Then add the fully stirred sodium methylsilicate solution and add the water as needed according to the water-gel ratio. Finally, add the prepared foam and continue stirring until there is no foam in the slurry. The appropriate stirring time is 3 minutes. Step 8: Pour the prepared slurry into the mold, vibrate it slightly, seal the mold with plastic film, and place it in a constant temperature and humidity chamber for curing until the set age. The curing temperature of the concrete is 55℃, the relative humidity of the curing environment is ≥95%, and the curing period is 7 days.

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