Preparation method of light high-strength foam cement-based material with densified pore wall

Abstract

The invention discloses a preparation method of a light high-strength foam cement-based material with a densified pore wall, which comprises the following steps: (1) dispersing surface-treated aluminum oxide particles in water, mixing with molten paraffin, and heating and stirring for reaction; after the reaction is finished, cooling to room temperature, and washing the obtained solid product to obtain paraffin amp; the invention discloses aluminum oxide modified powder. (2) mixing a silane coupling agent, ethanol and water, stirring and reacting under a heating condition, and then adding the paraffin amp; and continuously reacting the aluminum oxide modified powder. And adding the obtained solid product into a paraffin dissolving agent, uniformly mixing, standing, separating out the solid product, washing, and drying to obtain the modified foam stabilizer. And (3) mixing the modified foam stabilizer with a foaming agent and water, foaming, and uniformly mixing the obtained modified foam with the cement-based material to obtain the foamed cement-based material. By utilizing the modified foam stabilizer, the problems that foam is quickly killed, the foam stability is poor, the porosity is large, and the mechanical property of a cement-based material is easily degraded are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cement-based material preparation, and particularly relates to a preparation method of a light-weight high-strength foam cement-based material with dense pore wall. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant or the like that the information forms part of the prior art that is already known in this field.

[0003] The insufficient density of the pore wall of the existing foam cement-based material is a key factor restricting the mechanical properties and durability of the foam cement-based material. The ordinary foam has the problems of poor stability and easy breakage. The drainage of the foam water film into the cement slurry hinders the cement hydration near the pore wall, so that the internal microstructure of the pore wall is loose, and the density and strength of the pore wall are significantly reduced. At the same time, the existing foam cement-based material also has the problems of insufficient foam stability and low bubble interface film strength, which leads to the easy merging and breakage of the foam in the mixing process, the gradual evolution of the pore structure into a large-size defect hole, and finally the uneven distribution of the pores, the weak pore wall and the deterioration of the pore structure, which seriously affects the strength and stability of the foam cement-based material.

[0004] The addition of a foam stabilizer (such as hydroxypropyl methyl cellulose) in the cement-based material can stabilize the bubble structure to a certain extent. However, these traditional foam stabilizers do not participate in the formation of enhanced hydration products, and are difficult to stabilize at the gas-liquid-solid interface at the same time, resulting in poor density of the pore wall structure. At the same time, their cracking effect on the bubbles leads to low foam stabilization efficiency, which weakens the stability of the pore wall structure, thereby affecting the stability of the foam and the mechanical properties of the foam concrete. SUMMARY

[0005] The present application provides a preparation method of a light-weight high-strength foam cement-based material with dense pore wall, which effectively overcomes the problems of fast foam elimination, poor foam stability, large porosity and easy mechanical property deterioration of the cement-based material by using the prepared modified foam stabilizer. Specifically, the technical scheme of the present application is as follows.

[0006] A preparation method of a light-weight high-strength foam cement-based material with dense pore wall, comprising the following steps: (1) mixing a nano-alumina dispersion liquid and an oleic acid solution, then stirring and reacting under heating conditions, separating out the solid product after completion, washing and drying to obtain surface-treated alumina particles, which are ready for use.

[0007] (2) The surface-treated alumina particles were dispersed in water, then mixed with melted paraffin and stirred under heating conditions. After completion, the mixture was cooled to room temperature, and the resulting solid product was washed to obtain paraffin & alumina modified powder.

[0008] (3) Mix the silane coupling agent, ethanol, and water and stir under heating conditions. After the reaction is completed, add the paraffin and alumina modified powder and continue the reaction. Then add the obtained solid product to the paraffin solvent, mix well, and let stand. Then separate the solid product, wash and dry it to obtain the modified foam stabilizer.

[0009] (4) The modified foam stabilizer is mixed with foaming agent and water and then foamed. The resulting modified foam is mixed with silicate cement-based material containing gypsum to obtain foamed cement-based material.

[0010] Further, in step (1), the mass ratio of oleic acid to nano-alumina is 1:3~3.5. Optionally, the nano-alumina dispersion is formed by nano-alumina particles dispersed in anhydrous ethanol, and the ratio between the two is not particularly limited. The oleic acid solution is formed by dissolving oleic acid in anhydrous ethanol, and the ratio between the two is not particularly limited.

[0011] Further, in step (1), the heating temperature is 70~85℃, and the stirring reaction time is 10~12 hours. During this process, the carboxyl group (-COOH) on the oleic acid molecule undergoes an esterification reaction with the hydroxyl group (Al-OH) on the surface of the nano-alumina to form a hydrophobic aluminum ester bond (Al-O-CO-R).

[0012] Further, in step (1), the drying temperature is 60~80℃, and the drying time is 18~24 hours. Optionally, the solid product is washed with a substance identical to the solvent in the oleic acid solution to remove oleic acid molecules that are not bonded to the nano-alumina, thus avoiding interference with the subsequent encapsulation effect of paraffin on the nano-alumina.

[0013] Further, in step (2), the ratio of the surface-treated alumina particles, water, and paraffin is 3g: 150~180mL: 6~7g.

[0014] Furthermore, in step (2), the heating temperature is lower than the melting temperature of paraffin. Optionally, the stirring reaction time is 45-60 minutes.

[0015] Further, in step (3), the ratio of the silane coupling agent, ethanol, and water is 1g: 135~150mL: 15~30mL. Optionally, the silane coupling agent includes at least one of KH550, KH560, etc.

[0016] Further, in step (3), the heating temperature is 60~70℃, and the stirring reaction time is 50~60min. During this process, the silane coupling agent is hydrolyzed into silanol (-Si(OH)3).

[0017] Further, in step (3), the mass ratio of the silane coupling agent to the paraffin & alumina modified powder is 1:9~10.

[0018] Further, in step (3), the reaction continues for 1-2 hours. During this process, the silanol groups formed by the hydrolysis of the silane coupling agent dehydrate with the Al-OH residue on the surface of the alumina-modified powder to form Si-O-Al bonds, while the terminal amino group (-NH2) faces outward, and forms Si-O-Al bonds through hydrogen bonding or protonation (-NH3). + To achieve hydrophilicity.

[0019] Further, in step (3), the paraffin solvent includes at least one of carbon tetrachloride, chloroform, and diethyl ether. Optionally, the standing time is 40-60 minutes to allow the paraffin on the surface of the solid product to fully dissolve and expose the particles.

[0020] Furthermore, in step (3), the drying temperature is 60~80℃ and the drying time is 20~24 hours.

[0021] Further, in step (4), the ratio of the modified foam stabilizer, the foaming agent, and water is 0.1g: 2~3g: 120~150g. Optionally, the foaming agent includes at least one of the following: sodium fatty alcohol polyoxyethylene ether sulfate, cocamidopropyl betaine, etc.

[0022] Further, in step (4), the modified foam is 15-35% of the mass of the cement-based material.

[0023] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: This invention first treats nano-alumina particles with oleic acid to make them hydrophobic. After adding melted paraffin, the resulting particles are distributed in water containing the surface-treated alumina particles. At this point, the alumina particles coat the surface of the paraffin particles, forming a paraffin & alumina modified powder. This invention further modifies this special structure using a silane coupling agent. During this process, the surfaces of the alumina particles and paraffin coated are sealed, thus preventing modification by the silane coupling agent, while the remaining exposed surfaces of the alumina particles are modified by the silane coupling agent. When the paraffin particles are dissolved using a paraffin solvent, the alumina particles are released, resulting in a modified foam stabilizer with anisotropic properties. Modified foam prepared using this modified foam stabilizer effectively alleviates problems such as easy breakage and uneven pore distribution in cement-based materials. This is because: (1) The modified foam utilizes its hydrophobic side to form a directional arrangement structure at the bubble interface, inhibiting bubble coalescence and making the pore size distribution more uniform. By utilizing its hydrophilic side to adapt to the alkaline cement environment, it ensures cracking during the mid-to-late stages of cementitious material hardening, and induces cement hydration at the pore walls to generate reinforced CAH, CASH gel, and high aspect ratio ettringite products, constructing a highly dense pore wall structure and improving the strength of cementitious materials. This is because the modified foam provides active Al at the pore walls through its alumina-modified powder. 3+ And nucleation sites, promoting the densification growth of CAH and CASH gels, forming enhanced CAH and CASH, while Al 3+ SO4 provided by the gypsum in the silicate cement 2- The reaction produces ettringite with a high aspect ratio, whose needle-like structure can form a good reinforcing skeleton in the gel network. Through the synergistic effect of "hydrophilic anchoring and hydrophobic foam stabilization", the compressive strength and pore size uniformity of the foamed cement-based material prepared by this invention are simultaneously optimized, improving the density and strength of the pore walls and achieving a high foam stabilization effect.

[0024] (2) The modified foam forms pore walls in cement-based materials with better interfacial adhesion to the matrix. Therefore, it can be evenly distributed in the double electric layer of the foam to stabilize the water film, thereby effectively suppressing the problem of the pore structure gradually evolving into large-size defect pores due to foam rupture and coarsening, which leads to the deterioration of the strength of cement-based materials. This is because: on the one hand, the modified foam stabilizer can utilize its exposed Al 3+The -Si(OH)3 generated by the hydrolysis of silane serves as an active site, and its bonding with cement can better promote the formation of the aforementioned reinforced CAH and CASH gels. On the other hand, the modified foam stabilizer can utilize its oleic acid-modified side to form a hydrophobic barrier at the pore interface and a side that forms chemical bonds (Si-O-Ca bonds and Al-O-Ca bonds), both of which are dispersed in the foam pore wall and ultimately bond with the hardened pore wall. This synergistic effect allows the modified foam stabilizer to be oriented at the pore wall, stabilizing the pore wall structure of the bubbles and effectively overcoming the problem of foam cracking and coarsening caused by insufficient foam pore wall strength. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0026] Figure 1 The image shows a sample of the modified foam stabilizer prepared in Example 1 below.

[0027] Figure 2 The image shows a SEM image of the modified foam stabilizer prepared in Example 1 below.

[0028] Figure 3 The test diagram shows the bifacial anisotropy of the modified foam stabilizer prepared in Example 1 below.

[0029] Figure 4 The image shows a specimen prepared from the foamed cement-based material of Example 1 below.

[0030] Figure 5 The image shows a specimen prepared from the foamed cement-based material of Example 4 below. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0032] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. All reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0033] Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the method of this invention. The technical solution of this invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0034] Example 1: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain an oleic acid solution. Nano-alumina and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain a nano-alumina dispersion. The nano-alumina dispersion and oleic acid solution were mixed at a mass ratio of nano-alumina to oleic acid of 3:1, and then heated in an oil bath to 80 °C and magnetically stirred for 12 hours. The solid product was then separated by centrifugation, washed 5 times with anhydrous ethanol, and dried in an oven at 60 °C for 24 hours to obtain surface-treated alumina particles for later use.

[0035] (2) The surface-treated alumina particles were added to water and magnetically stirred for 15 minutes. Then, they were added to molten paraffin at 70°C, with the ratio of surface-treated alumina particles, water, and paraffin being 3g:150ml:6g. The reaction was then continued to be stirred at 70°C for 45 minutes. After the reaction was completed, the mixture was cooled to room temperature, and the resulting solid product was washed three times with water to obtain paraffin and alumina modified powder for later use.

[0036] (3) Mix silane coupling agent (KH550), ethanol, and water in a ratio of 1g:135mL:15mL, then heat in an oil bath to 60℃ and stir for 1 hour. Then add the paraffin & alumina modified powder, with a mass ratio of 9:1 to the silane coupling agent. Continue the reaction at 60℃ for 2 hours. Then add the obtained solid product to carbon tetrachloride, stir evenly, let stand for 50 minutes, then centrifuge to separate the solid product, wash it 5 times with anhydrous ethanol, and finally dry it at 80℃ for 24 hours to obtain the modified foam stabilizer. Figure 1 , Figure 2 As shown.

[0037] (4) First, mix the modified foam stabilizer with water and stir magnetically for 12 hours. Then, ultrasonically disperse the mixture for 30 minutes and add the foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) while stirring with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water is 0.1g:2g:120g. Inject the resulting mixture into a high-speed shear foaming machine and shear for 5 minutes to obtain the modified foam for later use.

[0038] (5) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 20% of the modified foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0039] Performance testing: (1) Figure 3The test diagram of the anisotropic properties of the modified foam stabilizer prepared in this embodiment shows that the modified foam stabilizer is stably distributed at the interface between kerosene (hydrophobic phase) and water, and is neither dispersed in kerosene nor in water, indicating that the modified foam stabilizer has good anisotropic properties. (2) The stability of the modified foam prepared in this embodiment was tested according to "Foamed Concrete" (JGT266-2011), including the foaming ratio, 1-hour bleeding volume and 1-hour settling distance. Among them, the higher the foaming ratio, the better the foam stability, and the lower the bleeding volume and settling distance, the better the foam stability (the same below). (3) The specimens prepared by the foamed cement-based material prepared in this embodiment (such as Figure 4 The compressive strength test was performed (as shown in the image). The results are shown in the table below:

[0040] Example 2: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain an oleic acid solution. Nano-alumina and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain a nano-alumina dispersion. The nano-alumina dispersion and oleic acid solution were mixed at a mass ratio of nano-alumina to oleic acid of 3.2:1, and then heated in an oil bath to 70 °C and magnetically stirred for 12 hours. The solid product was then separated by centrifugation, washed 5 times with anhydrous ethanol, and dried in an oven at 70 °C for 20 hours to obtain surface-treated alumina particles for later use.

[0041] (2) The surface-treated alumina particles were added to water and magnetically stirred for 15 minutes. Then, they were added to molten paraffin at 70°C, with the ratio of surface-treated alumina particles, water, and paraffin being 3g:180ml:7g. The reaction was then continued to be stirred at 70°C for 60 minutes. After completion, the mixture was cooled to room temperature, and the resulting solid product was washed three times with water to obtain paraffin & alumina modified powder for later use.

[0042] (3) Mix silane coupling agent (KH560), ethanol, and water in a ratio of 1g:140mL:20mL, then heat in an oil bath to 70℃ and stir for 50min. Then add the paraffin & alumina modified powder, with a mass ratio of 9:1 to the silane coupling agent. Continue the reaction at 70℃ for 1 hour. Then add the obtained solid product to carbon tetrachloride, stir evenly, let stand for 40min, then centrifuge to separate the solid product, wash 5 times with anhydrous ethanol, and finally dry at 60℃ for 24 hours to obtain the modified foam stabilizer.

[0043] (4) First, mix the modified foam stabilizer with water and stir magnetically for 12 hours. Then, ultrasonically disperse the mixture for 30 minutes and add the foaming agent (cocamidopropyl betaine) while stirring with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water is 0.1g:2.5g:130g. Inject the resulting mixture into a high-speed shear foaming machine and shear for 5 minutes to obtain the modified foam for later use.

[0044] (5) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 15% of the modified foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0045] Performance testing: The stability of the modified foam prepared in this example and the compressive strength of the specimens prepared from the foamed cement-based material were tested using the same method as in Example 1 above. The results are shown in the table below:

[0046] Example 3: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain an oleic acid solution. Nano-alumina and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain a nano-alumina dispersion. The nano-alumina dispersion and oleic acid solution were mixed at a mass ratio of nano-alumina to oleic acid of 3.5:1, and then heated in an oil bath to 85°C and magnetically stirred for 10 hours. The solid product was then separated by centrifugation, washed 5 times with anhydrous ethanol, and dried in an oven at 80°C for 18 hours to obtain surface-treated alumina particles for later use.

[0047] (2) The surface-treated alumina particles were added to water and magnetically stirred for 15 minutes. Then, they were added to molten paraffin at 80°C, with the ratio of surface-treated alumina particles, water, and paraffin being 3g:160ml:6.5g. The reaction was then continued to be stirred at 80°C for 50 minutes. After the reaction was completed, the mixture was cooled to room temperature, and the resulting solid product was washed three times with water to obtain paraffin and alumina modified powder for later use.

[0048] (3) Mix silane coupling agent (KH560), ethanol, and water in a ratio of 1g:150mL:30mL, then heat in an oil bath to 70℃ and stir for 50min. Then add the paraffin & alumina modified powder, with a mass ratio of 9:1 to the silane coupling agent. Continue the reaction at 70℃ for 2 hours. Then add the obtained solid product to carbon tetrachloride, stir evenly, let stand for 60min, then centrifuge to separate the solid product, wash it 5 times with anhydrous ethanol, and finally dry it at 70℃ for 20 hours to obtain the modified foam stabilizer.

[0049] (4) First, mix the modified foam stabilizer with water and stir magnetically for 12 hours. Then, ultrasonically disperse the mixture for 30 minutes and add the foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) while stirring with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water is 0.1g:3g:150g. Inject the resulting mixture into a high-speed shear foaming machine and shear for 6 minutes to obtain the modified foam for later use.

[0050] (5) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 35% of the modified foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0051] Performance testing: The stability of the modified foam prepared in this example and the compressive strength of the specimens prepared from the foamed cement-based material were tested using the same method as in Example 1 above. The results are shown in the table below:

[0052] Example 4: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Mix the foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) with water at a ratio of 0.1g:120g and stir with a glass rod. Then inject the mixture into a high-speed shear foaming machine for shearing treatment for 5 minutes to obtain foam for later use.

[0053] (2) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 20% of the foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0054] Performance testing: The stability of the foam prepared in this embodiment and the specimens prepared from the foamed cement-based material (such as...) were tested using the same method as in Example 1 above. Figure 5 The compressive strength of the material (as shown in the figure) was tested, and the results are shown in the table below. Figure 5 As can be seen, its pores are large and uneven, and loosely distributed. And... Figure 4The specimens prepared in Example 1, as shown, exhibit fine, dense, and uniformly distributed pores. This indicates that the addition of the modified foam stabilizer effectively alleviates the problems of easy foam breakage and uneven pore distribution in cement-based materials. Therefore, the stability and compressive strength of the foam in Example 1 are significantly better than those in Example 4.

[0055] Example 5: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Nano-alumina was added to water and magnetically stirred for 15 min. Then it was added to molten paraffin at 70°C, with the ratio of surface-treated alumina particles, water, and paraffin being 3 g: 150 ml: 6 g. The reaction was then continued to be stirred at 70°C for 45 min. After completion, the mixture was cooled to room temperature, and the resulting solid product was washed three times with water to obtain paraffin & alumina modified powder for later use.

[0056] (2) Mix silane coupling agent (KH550), ethanol, and water in a ratio of 1g:135mL:15mL, then heat in an oil bath to 60℃ and stir for 1 hour. Then add the paraffin & alumina modified powder, with a mass ratio of 9:1 to the silane coupling agent. Continue the reaction at 60℃ for 2 hours. Then add the obtained solid product to carbon tetrachloride, stir evenly, let stand for 50 minutes, then centrifuge to separate the solid product, wash it 5 times with anhydrous ethanol, and finally dry it at 80℃ for 24 hours to obtain the modified foam stabilizer.

[0057] (3) First, mix the modified foam stabilizer with water and stir magnetically for 12 hours. Then, after ultrasonic dispersion for 30 minutes, add the foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) and stir with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water is 0.1g:2g:120g. Inject the resulting mixture into a high-speed shear foaming machine and shear for 5 minutes to obtain the modified foam for later use.

[0058] (4) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 20% of the modified foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0059] Performance testing: The stability of the modified foam prepared in this example and the compressive strength of the specimens prepared from the foamed cement-based material were tested using the same method as in Example 1 above. The results are shown in the table below:

[0060] Example 6: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain an oleic acid solution. Nano-alumina and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain a nano-alumina dispersion. The nano-alumina dispersion and oleic acid solution were mixed at a mass ratio of nano-alumina to oleic acid of 3.2:1, and then heated in an oil bath to 70 °C and magnetically stirred for 12 hours. The solid product was then separated by centrifugation, washed 5 times with anhydrous ethanol, and dried in an oven at 70 °C for 20 hours to obtain surface-treated alumina particles for later use.

[0061] (2) Mix silane coupling agent (KH560), ethanol, and water in a ratio of 1g:140mL:20mL, then heat in an oil bath to 70℃ and stir for 50min. Then add the surface-treated alumina particles, with a mass ratio of 9:1 to the silane coupling agent. After standing for 40min, centrifuge to separate the solid product, wash five times with anhydrous ethanol, and finally dry at 60℃ for 24 hours to obtain the modified foam stabilizer.

[0062] (3) First, mix the modified foam stabilizer with water and stir magnetically for 12 hours. Then, ultrasonically disperse the mixture for 30 minutes and add the foaming agent (cocamidopropyl betaine) while stirring with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water is 0.1g:2.5g:130g. Inject the resulting mixture into a high-speed shear foaming machine and shear for 5 minutes to obtain the modified foam for later use.

[0063] (4) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 15% of the modified foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0064] Performance testing: The stability of the modified foam prepared in this example and the compressive strength of the specimens prepared from the foamed cement-based material were tested using the same method as in Example 1 above. The results are shown in the table below:

[0065] Example 7: A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, comprising the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain an oleic acid solution. Nano-alumina and anhydrous ethanol were mixed at a ratio of 1 g: 50 mL and magnetically stirred for 30 min to obtain a nano-alumina dispersion. The nano-alumina dispersion and oleic acid solution were mixed at a mass ratio of nano-alumina to oleic acid of 3.5:1, and then heated in an oil bath to 85°C and magnetically stirred for 10 hours. The solid product was then separated by centrifugation, washed 5 times with anhydrous ethanol, and dried in an oven at 80°C for 18 hours to obtain surface-treated alumina particles for later use.

[0066] (2) The surface-treated alumina particles were added to water and magnetically stirred for 15 minutes. Then, they were added to molten paraffin at 80°C, with the ratio of surface-treated alumina particles, water, and paraffin being 3g:160ml:6.5g. The reaction was then continued to be stirred at 80°C for 50 minutes. After the reaction was completed, the mixture was cooled to room temperature, and the resulting solid product was washed three times with water to obtain paraffin and alumina modified powder for later use.

[0067] (3) First, mix the paraffin and alumina modified powder with water and stir magnetically for 12 hours. Then, ultrasonically disperse the mixture for 30 minutes and add the foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) while stirring with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water is 0.1g:3g:150g. Inject the resulting mixture into a high-speed shear foaming machine and shear for 6 minutes to obtain the modified foam for later use.

[0068] (4) Mix silicate cement (P·O 42.5) with water at a water-cement ratio of 0.5 and stir for 3 minutes. Then add 35% of the modified foam by mass of the silicate cement and stir for 2 minutes to obtain foamed cement-based material.

[0069] Performance testing: The stability of the modified foam prepared in this example and the compressive strength of the specimens prepared from the foamed cement-based material were tested using the same method as in Example 1 above. The results are shown in the table below:

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls, characterized in that, Includes the following steps: (1) Mix the nano alumina dispersion with oleic acid solution, and then stir the reaction under heating conditions. After the reaction is completed, separate the solid product, wash and dry it to obtain surface-treated alumina particles for later use. (2) The surface-treated alumina particles are dispersed in water, then mixed with melted paraffin and stirred under heating conditions; after completion, the mixture is cooled to room temperature, and the resulting solid product is washed to obtain paraffin & alumina modified powder. (3) Mix silane coupling agent, ethanol and water and stir under heating conditions. After the reaction is completed, add the paraffin & alumina modified powder and continue the reaction. Then add the obtained solid product to the paraffin solvent, mix well and let stand. Then separate the solid product, wash and dry it to obtain the modified foam stabilizer. (4) The modified foam stabilizer is mixed with foaming agent and water and then foamed. The resulting modified foam is mixed with silicate cement-based material containing gypsum to obtain foamed cement-based material.

2. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (1), the mass ratio of nano-alumina to oleic acid is 1:3~3.5; Optionally, in step (1), the nano-alumina dispersion is formed from nano-alumina particles dispersed in anhydrous ethanol; Optionally, in step (1), the oleic acid solution is formed by dissolving oleic acid in anhydrous ethanol.

3. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (1), the heating temperature is 70~85℃, and the stirring reaction time is 10~12 hours; Optionally, in step (1), the drying temperature is 60~80℃ and the drying time is 18~24 hours; Optionally, in step (1), the solid product is washed with the same substance as the solvent in the oleic acid solution.

4. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (2), the ratio of the surface-treated alumina particles, water, and paraffin is 3g: 150~180mL: 6~7g; Optionally, in step (2), the temperature of the heating conditions is not less than the melting temperature of paraffin; Optionally, in step (2), the stirring reaction time is 45~60 min.

5. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (3), the ratio of the silane coupling agent, ethanol and water is 1g: 135~150mL: 15~30mL.

6. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (3), the silane coupling agent includes at least one of KH550 and KH560; Optionally, in step (3), the heating temperature is 60~70℃ and the stirring reaction time is 50~60min.

7. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (3), the mass ratio of the silane coupling agent to the paraffin and alumina modified powder is 1:9~10; optionally, in step (3), the reaction continues for 1~2 hours.

8. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (3), the paraffin solvent includes at least one of carbon tetrachloride, chloroform, and diethyl ether; Optionally, in step (3), the settling time is 40~60 minutes; Optionally, in step (3), the drying temperature is 60~80℃ and the drying time is 20~24 hours.

9. The method for preparing the pore-wall-densified lightweight high-strength foamed cement-based material according to claim 1, characterized in that, In step (4), the ratio of the modified foam stabilizer, foaming agent, and water is 0.1g: 2~3g: 120~150g; Optionally, the foaming agent includes at least one of: sodium fatty alcohol polyoxyethylene ether sulfate and cocamidopropyl betaine.

10. The method for preparing a pore-wall-densified lightweight high-strength foamed cement-based material according to any one of claims 1-9, characterized in that, In step (4), the modified foam is 15-35% of the mass of the cement-based material.

Images