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 invention relates to the technical field of cement-based material preparation, and in particular to a method for preparing a lightweight and high-strength foam cement-based material with densified pore walls. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] The lack of pore wall density in existing foamed cementitious materials is a key factor limiting their mechanical properties and durability. Conventional foams suffer from poor stability and easy foam rupture. Drainage of the foam water film into the cement paste hinders cement hydration near the pore walls, loosening the internal microstructure of the pore walls and significantly reducing the density and strength of the pore walls. Furthermore, existing foamed cementitious materials also suffer from insufficient foam stability and low bubble interface film strength. This results in bubbles merging and rupturing easily during mixing, causing the pore structure to gradually evolve into large-scale defective pores. This ultimately leads to uneven pore distribution, fragile pore walls, and a degraded pore structure, severely impacting the strength and stability of the cementitious materials.

[0004] Adding foam stabilizers (such as hydroxypropyl methylcellulose) to cementitious materials 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 simultaneously at the gas-liquid-solid interface, resulting in poor pore wall density. Furthermore, their cracking effect on bubbles leads to low foam stabilization efficiency, weakening the stability of the pore wall structure, thereby affecting the stability of the foam and the mechanical properties of foamed concrete. Summary of the Invention

[0005] The present invention provides a method for preparing a lightweight, high-strength foamed cement-based material with densified pore walls. This method utilizes a modified foam stabilizer to effectively overcome the problems of rapid foam extinction, poor foam stability, high porosity, and the resulting degradation of mechanical properties in cement-based materials. Specifically, the technical solution of the present invention is as follows.

[0006] A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Mix the nano-alumina dispersion with the oleic acid solution, and then stir and react under heating conditions. After the reaction is completed, separate the solid product, wash it, and dry it to obtain surface-treated alumina particles for later use.

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

[0008] (3) Mix the silane coupling agent, ethanol, and water and stir under heating conditions to react. After the reaction is complete, add the paraffin wax and alumina modified powder to continue the reaction. Then, add the obtained solid product to the paraffin wax solvent, mix well, and let it 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 a foaming agent and water to foam, and the obtained modified foam is mixed with a silicate cement-based material containing gypsum to obtain a foamed cement-based material.

[0010] Furthermore, in step (1), the mass ratio of oleic acid to nano-alumina is 1:3 to 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] Furthermore, in step (1), the heating condition is at a temperature of 70-85°C, and the stirring reaction time is 10-12 hours. During this process, the carboxyl groups (-COOH) on the oleic acid molecules react with the hydroxyl groups (Al-OH) on the surface of the nano-alumina to form a hydrophobic aluminum ester bond (Al-O-CO-R).

[0012] Furthermore, in step (1), the drying temperature is 60-80° C. and the drying time is 18-24 hours. Optionally, the solid product is washed with the same solvent as the oleic acid solution to remove oleic acid molecules that are not bonded to the nano-alumina and prevent them from interfering with the subsequent paraffin wax coating effect on the nano-alumina.

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

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

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

[0016] Furthermore, in step (3), the heating condition is a temperature of 60-70° C., and the stirring reaction time is 50-60 min. During this process, the silane coupling agent is hydrolyzed into silanol groups (-Si(OH)3).

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

[0018] Furthermore, in step (3), the reaction is continued for 1 to 2 hours. During this process, the silanol group formed by the hydrolysis of the silane coupling agent dehydrates with the Al-OH group remaining on the surface of the alumina modified powder to form a Si-O-Al bond, while the terminal amino group (-NH2) faces outward and is reacted with the terminal amino group (-NH3) through hydrogen bonding or protonation. + ) to achieve hydrophilicity.

[0019] Furthermore, in step (3), the paraffin dissolving agent includes at least one of carbon tetrachloride, chloroform, ether, etc. Optionally, the standing time is 40 to 60 minutes, so that the paraffin on the surface of the solid product is fully dissolved to expose the particles.

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

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

[0022] Furthermore, 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: The present invention first uses oleic acid to surface-treat the nano-alumina particles to make them hydrophobic as a whole. After adding melted paraffin, the formed particles are distributed in water in which the surface-treated alumina particles are dispersed. At this time, the alumina particles are wrapped on the surface of the paraffin particles to form the paraffin & alumina modified powder. The present invention combines this special structure with a silane coupling agent for further modification. During this process, the surface of the alumina particles and the paraffin-coated surface is in a closed state and will not be modified 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 by a paraffin solvent, the alumina particles are released to obtain a modified foam stabilizer with two-sided anisotropic properties. The modified foam prepared by using this modified foam stabilizer effectively alleviates the problems of easy rupture of foam in cement-based materials and uneven distribution of pores. This is because: (1) The modified foam uses its hydrophobic side to form a directional arrangement structure at the bubble interface, inhibiting bubble merging and making the pore size distribution more uniform. The hydrophilic side is used to adapt to the alkaline cement environment, thereby ensuring the rupture in the middle and late stages of the hardening of the cement-based material, and inducing cement hydration at the pore wall to generate enhanced CAH, CASH gel and high aspect ratio calcium aluminate products, constructing a high-density pore wall structure and improving the strength of the cement-based material. This is because the modified foam provides active Al2O3 at the pore wall through its alumina modified powder. 3+ and nucleation sites, promoting the densification growth of CAH and CASH gels to form enhanced CAH and CASH. 3+ The SO4 provided by the gypsum in the Portland cement 2- The reaction produces high-aspect-ratio ettringite, whose needle-like structure forms a strong reinforcing framework within the gel network. Through the synergistic effect of "hydrophilic anchoring and hydrophobic foam stabilization," the foamed cement-based material prepared by this invention simultaneously optimizes its compressive strength and pore size uniformity, enhancing the density and strength of the pore walls and achieving high foam stabilization.

[0024] (2) The modified foam has better interfacial bonding ability between the pore wall and the matrix formed in the cement-based material, so it can be evenly distributed in the double electric layer of the foam to play the role of stabilizing the water film, thereby effectively inhibiting the problem of the pore structure gradually evolving into large-sized defective pores due to foam rupture and coarsening, which in turn leads to the deterioration of the strength of the cement-based material. This is because: on the one hand, the modified foam stabilizer can utilize its exposed Al 3+The -Si(OH)3 generated by silane hydrolysis serves as an active site, which, when combined with cement, can better promote the formation of the aforementioned enhanced CAH and CASH gels. Furthermore, the modified foam stabilizer utilizes its oleic acid-modified side to form a hydrophobic barrier at the pore interface and a side that forms chemical bonds (Si-O-Ca and Al-O-Ca bonds). These stabilizers are dispersed within the foam pore walls and ultimately bond with the hardened pore walls. This synergistic effect allows the modified foam stabilizer to be localized within the pore walls, stabilizing the bubble wall structure and effectively overcoming the problem of foam rupture and coarsening caused by insufficient pore wall strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a diagram of a modified foam stabilizer sample prepared in Example 1 below.

[0027] Figure 2 The following is an SEM image of the modified foam stabilizer prepared in Example 1.

[0028] Figure 3 This is a test chart of the two-sided anisotropy characteristics of the modified foam stabilizer prepared in the following Example 1.

[0029] Figure 4 The following is a test piece prepared from the foam cement-based material of Example 1.

[0030] Figure 5 The following is a test piece prepared from the foamed cement-based material of Example 4. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0032] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The reagents and raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents and raw materials used in the present invention are used in accordance with conventional methods in the art or in accordance with the product instructions.

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

[0034] Example 1 A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g:50 ml and magnetically stirred for 30 minutes 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 minutes to obtain a nano-alumina dispersion. The nano-alumina dispersion was mixed with the oleic acid solution at a mass ratio of nano-alumina to oleic acid = 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 with anhydrous ethanol five times, 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. The surface-treated alumina particles were then added to melted paraffin wax at 70°C in a ratio of 3 g of the surface-treated alumina particles, 150 ml of water, and 6 g of paraffin wax. The mixture was stirred at 70°C for 45 minutes. After completion, the mixture was cooled to room temperature and the solid product was washed three times with clean water to obtain a paraffin wax and alumina modified powder, which was set aside.

[0036] (3) Silane coupling agent (KH550), ethanol and water were mixed in a ratio of 1g:135mL:15mL, and then heated to 60℃ in an oil bath and stirred for 1 hour. Then the paraffin & alumina modified powder was added, and the mass ratio of the paraffin & alumina modified powder to the silane coupling agent was 9:1. Then the reaction was continued at 60℃ for 2 hours. Then the obtained solid product was added to carbon tetrachloride, stirred evenly and allowed to stand for 50 minutes, and then the solid product was separated by centrifugation and washed with anhydrous ethanol 5 times, and finally dried at 80℃ for 24 hours to obtain a modified foam stabilizer, such as Figure 1 、 Figure 2 shown.

[0037] (4) The modified foam stabilizer was mixed with water and magnetically stirred for 12 hours. The mixture was then ultrasonically dispersed for 30 minutes. A foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) was added and stirred with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water was 0.1 g:2 g:120 g. The resulting mixture was injected into a rapid shear foaming machine and sheared for 5 minutes to obtain the modified foam, which was then set aside.

[0038] (5) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the modified foam was added at 20% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

[0039] Performance test: (1) Figure 3The test diagram of the two-sided anisotropy characteristics of the modified foam stabilizer prepared in this embodiment shows that the modified foam stabilizer is stably distributed on the interface between kerosene (hydrophobic phase) and water, and is neither dispersed into kerosene nor dispersed into water, indicating that the modified foam stabilizer has good two-sided anisotropy characteristics. (2) According to the "Foam Concrete" (JGT266-2011), the stability of the modified foam prepared in this embodiment was tested, including the foaming multiple, 1h water exudation and 1h settlement distance. Among them, the higher the foaming multiple, the better the foam stability, and the lower the water exudation and settlement distance, the better the foam stability (the same below). (3) According to the "Foam Concrete" (JGT266-2011), the test specimens prepared by the foam cement-based material prepared in this embodiment (such as Figure 4 The compressive strength test is shown in the table below.

[0040] Example 2 A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g:50 ml and magnetically stirred for 30 minutes 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 minutes to obtain a nano-alumina dispersion. The nano-alumina dispersion was mixed with the oleic acid solution at a mass ratio of nano-alumina to oleic acid = 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 with anhydrous ethanol five times, 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. The surface-treated alumina particles were then added to melted paraffin at 70°C in a ratio of 3 g of the surface-treated alumina particles, 180 ml of water, and 7 g of paraffin. The reaction was continued at 70°C with stirring for 60 minutes. After completion, the reaction was cooled to room temperature and the solid product was washed three times with clean water to obtain a paraffin and alumina modified powder, which was set aside.

[0042] (3) Silane coupling agent (KH560), ethanol, and water were mixed in a ratio of 1 g: 140 mL: 20 mL, and then heated to 70°C in an oil bath and stirred for 50 minutes. Then, the paraffin wax and alumina modified powder were added in a mass ratio of 9:1 to the silane coupling agent. The reaction was continued at 70°C for 1 hour. The obtained solid product was then added to carbon tetrachloride, stirred evenly, and allowed to stand for 40 minutes. The solid product was then separated by centrifugation and washed with anhydrous ethanol 5 times. Finally, it was dried at 60°C for 24 hours to obtain the modified foam stabilizer.

[0043] (4) The modified foam stabilizer was mixed with water and magnetically stirred for 12 hours. The mixture was then ultrasonically dispersed for 30 minutes, and then a foaming agent (cocamidopropyl betaine) was added and stirred with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water was 0.1 g:2.5 g:130 g. The resulting mixture was injected into a rapid shear foaming machine and sheared for 5 minutes to obtain a modified foam, which was then set aside.

[0044] (5) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the modified foam was added at 15% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

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

[0046] Example 3 A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g:50 ml and magnetically stirred for 30 minutes 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 minutes to obtain a nano-alumina dispersion. The nano-alumina dispersion was mixed with the oleic acid solution at a mass ratio of nano-alumina to oleic acid = 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 with anhydrous ethanol five times, 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. The surface-treated alumina particles were then added to molten paraffin at 80°C in a ratio of 3 g of the surface-treated alumina particles, 160 ml of water, and 6.5 g of paraffin. The reaction was then continued at 80°C with stirring for 50 minutes. After completion, the reaction was cooled to room temperature and the solid product was washed three times with clean water to obtain a paraffin and alumina modified powder, which was set aside.

[0048] (3) Silane coupling agent (KH560), ethanol, and water were mixed in a ratio of 1 g: 150 mL: 30 mL, and then heated in an oil bath to 70°C and stirred for 50 minutes. Then, the paraffin wax and alumina modified powder were added in a mass ratio of 9:1 to the silane coupling agent. The reaction was continued at 70°C for 2 hours. The obtained solid product was then added to carbon tetrachloride, stirred evenly, and allowed to stand for 60 minutes. The solid product was then separated by centrifugation and washed with anhydrous ethanol 5 times. Finally, it was dried at 70°C for 20 hours to obtain the modified foam stabilizer.

[0049] (4) The modified foam stabilizer was mixed with water and magnetically stirred for 12 hours. The mixture was then ultrasonically dispersed for 30 minutes. A foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) was added and stirred with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water was 0.1 g:3 g:150 g. The resulting mixture was injected into a rapid shear foaming machine and sheared for 6 minutes to obtain the modified foam, which was then set aside.

[0050] (5) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the modified foam was added at 35% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

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

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

[0053] (2) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the foam was added at 20% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

[0054] Performance test: The same method as in Example 1 was used to test the stability of the foam prepared in this example, the test pieces prepared from the foam cement-based material (such as Figure 5 The compressive strength of the steel was tested and the results are shown in the following table. Figure 5 It can be seen that the pores are large and uneven, and the distribution is loose. Figure 4The pores in the specimens prepared in Example 1 are small, dense, and evenly distributed. This demonstrates that the addition of the modified foam stabilizer effectively alleviates the problems of foam breakage and uneven pore distribution in cement-based materials. Therefore, the stability and compressive strength of the foam in Example 1 are significantly superior to those in Example 4.

[0055] Example 5 A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Add nano-alumina to water and stir magnetically for 15 minutes. Then add it to melted paraffin at 70°C, with the ratio of the surface-treated alumina particles, water, and paraffin being 3g:150ml:6g. Stir and react at 70°C for 45 minutes. After completion, cool to room temperature and wash the resulting solid product three times with clean water to obtain a paraffin & alumina modified powder, which is set aside.

[0056] (2) Silane coupling agent (KH550), ethanol, and water were mixed in a ratio of 1 g: 135 mL: 15 mL, and then heated to 60°C in an oil bath and stirred for 1 hour. Then, the paraffin wax and alumina modified powder were added in a mass ratio of 9:1 to the silane coupling agent. The reaction was continued at 60°C for 2 hours. The obtained solid product was then added to carbon tetrachloride, stirred evenly, and allowed to stand for 50 minutes. The solid product was then separated by centrifugation and washed with anhydrous ethanol 5 times. Finally, it was dried at 80°C for 24 hours to obtain a modified foam stabilizer.

[0057] (3) The modified foam stabilizer was first mixed with water and magnetically stirred for 12 hours. The mixture was then ultrasonically dispersed for 30 minutes, and then a foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) was added and stirred with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water was 0.1 g:2 g:120 g. The resulting mixture was injected into a rapid shear foaming machine and sheared for 5 minutes to obtain the modified foam, which was then set aside.

[0058] (4) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the modified foam was added at 20% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

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

[0060] Example 6 A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g:50 ml and magnetically stirred for 30 minutes 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 minutes to obtain a nano-alumina dispersion. The nano-alumina dispersion was mixed with the oleic acid solution at a mass ratio of nano-alumina to oleic acid = 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 with anhydrous ethanol five times, and dried in an oven at 70°C for 20 hours to obtain surface-treated alumina particles for later use.

[0061] (2) A silane coupling agent (KH560), ethanol, and water were mixed in a ratio of 1 g:140 mL:20 mL, and then heated in an oil bath to 70°C with stirring for 50 minutes. The surface-treated alumina particles were then added in a mass ratio of 9:1 to the silane coupling agent. After standing for 40 minutes, the solid product was separated by centrifugation and washed five times with anhydrous ethanol. Finally, it was dried at 60°C for 24 hours to obtain a modified foam stabilizer.

[0062] (3) The modified foam stabilizer and water were first mixed and magnetically stirred for 12 hours. After ultrasonic dispersion for 30 minutes, a foaming agent (cocamidopropyl betaine) was added and stirred with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water was 0.1 g:2.5 g:130 g. The resulting mixture was injected into a rapid shear foaming machine and sheared for 5 minutes to obtain the modified foam, which was then set aside.

[0063] (4) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the modified foam was added at 15% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

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

[0065] Example 7 A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls comprises the following steps: (1) Oleic acid and anhydrous ethanol were mixed at a ratio of 1 g:50 ml and magnetically stirred for 30 minutes 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 minutes to obtain a nano-alumina dispersion. The nano-alumina dispersion was mixed with the oleic acid solution at a mass ratio of nano-alumina to oleic acid = 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 with anhydrous ethanol five times, 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. The surface-treated alumina particles were then added to molten paraffin at 80°C in a ratio of 3 g of the surface-treated alumina particles, 160 ml of water, and 6.5 g of paraffin. The reaction was then continued at 80°C with stirring for 50 minutes. After completion, the reaction was cooled to room temperature and the solid product was washed three times with clean water to obtain a paraffin and alumina modified powder, which was set aside.

[0067] (3) The paraffin wax and alumina modified powders were first mixed with water and magnetically stirred for 12 hours. After ultrasonic dispersion for 30 minutes, a foaming agent (sodium fatty alcohol polyoxyethylene ether sulfate) was added and stirred with a glass rod. The ratio of the modified foam stabilizer, foaming agent, and water was 0.1 g:3 g:150 g. The resulting mixture was injected into a rapid shear foaming machine and sheared for 6 minutes to obtain a modified foam, which was then set aside.

[0068] (4) Portland cement (P·O 42.5) and water were mixed at a water-cement ratio of 0.5 and stirred for 3 minutes, and then the modified foam was added at 35% by weight of the Portland cement and stirred for 2 minutes to obtain a foamed cement-based material.

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

[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 aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lightweight and high-strength foam cement-based material with densified pore walls, characterized in that: The steps include: (1) Mixing the nano-alumina dispersion with the oleic acid solution, and then stirring the mixture under heating conditions to react. After the reaction is completed, the solid product is separated, washed, and dried to obtain surface-treated alumina particles for later use; (2) dispersing the surface-treated alumina particles in water, then mixing with melted paraffin and stirring under heating conditions; after completion, cooling to room temperature, and then washing the obtained solid product to obtain paraffin & alumina modified powder; (3) Mixing the silane coupling agent, ethanol, and water, stirring and reacting under heating conditions, adding the paraffin wax and alumina modified powder to continue the reaction; then adding the obtained solid product to the paraffin wax solvent, mixing evenly, and letting it stand, then separating the solid product, washing, and drying to obtain the modified foam stabilizer; (4) The modified foam stabilizer is mixed with a foaming agent and water to foam, and the obtained modified foam is mixed with a silicate cement-based material containing gypsum to obtain a foamed cement-based material.

2. The method for preparing a lightweight and high-strength foam cement-based material with densified pore walls according to claim 1, characterized in that: In step (1), the mass ratio of the nano-alumina to the oleic acid is 1:3-3.5; Optionally, in step (1), the nano-alumina dispersion is formed by 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 a lightweight and high-strength foam cement-based material with densified pore walls according to claim 1, characterized in that: In step (1), the heating temperature is 70-85°C, and the stirring reaction time is 10-12 hours; Optionally, in step (1), the drying temperature is 60-80° C., 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 a lightweight and high-strength foam cement-based material with densified pore walls according to claim 1, characterized in that: In step (2), the ratio of the surface-treated alumina particles, water, and paraffin is 3 g: 150-180 mL: 6-7 g; Optionally, in step (2), the temperature of the heating condition is not less than the melting temperature of paraffin; Optionally, in step (2), the stirring reaction time is 45 to 60 minutes.

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

6. The method for preparing a lightweight and high-strength foam cement-based material with densified pore walls 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° C., and the stirring reaction time is 50-60 min.

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

8. The method for preparing a lightweight and high-strength foam cement-based material with densified pore walls according to claim 1, characterized in that: In step (3), the paraffin dissolving agent includes at least one of carbon tetrachloride, chloroform, and ether; Optionally, in step (3), the standing time is 40 to 60 minutes; Optionally, in step (3), the drying temperature is 60-80° C., and the drying time is 20-24 hours.

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

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