Aerogel-hollow glass microsphere composite mortar in cold regions and a preparation method thereof

Abstract

This invention belongs to the field of cement-based materials technology, specifically relating to an aerogel-hollow glass microsphere composite mortar for cold regions and its preparation method. The composite mortar, by weight, comprises the following components: 535-560 parts cement, 50-55 parts silica fume, 120-140 parts aerogel-hollow glass microsphere composite aggregate, 3.0-3.5 parts polypropylene fiber, 2.0-2.2 parts polyvinyl alcohol fiber, 4.8-5.3 parts dispersible latex powder, 3.0-3.3 parts hydroxypropyl methylcellulose ether, 5.4-5.7 parts water-reducing agent, and 290-300 parts water. The aerogel-hollow glass microsphere composite aggregate is obtained by activating and modifying hollow glass microspheres, then combining them with hydrophobic aerogel and nano-SiO2 / nano-hydroxyapatite composite sol. This invention overcomes the technical problem in the prior art where the mechanical properties, thermal insulation performance, and freeze-thaw resistance of composite thermal insulation mortars are difficult to improve synergistically.

Description

Technical Field

[0001] This invention belongs to the field of cement-based materials technology, specifically relating to a cold-region aerogel-hollow glass microsphere composite mortar and its preparation method. Background Technology

[0002] Aerogel, an ultralight solid material with a nanoscale porous network structure, is one of the solid materials with the lowest known thermal conductivity. Incorporating aerogel into cement-based materials can significantly reduce the thermal conductivity of mortar and effectively reduce the material's weight, aligning with the trend towards lightweight construction. However, directly incorporating aerogel into cement-based materials leads to poor aerogel-cement matrix compatibility. Furthermore, the significant difference in particle size distribution between the nanoscale aerogel and other materials results in numerous uneven and harmful pores, reducing structural density and lowering the material's mechanical properties. This greatly limits the application of aerogel in cement-based materials.

[0003] In existing technologies, to improve the compatibility between aerogel and cementitious matrix, silane coupling agents or physical mixing methods are often used for modification, without incorporating multi-scale pore structure optimization design. This results in poor compatibility between aggregates and cementitious materials, limiting the improvement in thermal insulation performance. Another approach involves adding hollow glass microspheres to construct a porous structure; however, when the proportion of insulating aggregate is large, while the material's thermal insulation performance improves, its mechanical strength decreases, making it prone to delamination and peeling. Especially in the freeze-thaw cycle environment of cold regions, the expansion of ice crystals caused by moisture intrusion exacerbates interfacial damage, leading to a significant decrease in strength and failing to meet the long-term service requirements of cold-region engineering. Therefore, how to achieve enhanced interfacial bonding between aerogel and cementitious matrix, construct a multi-scale insulation system, and synergistically improve mechanical properties, thermal insulation performance, and freeze-thaw durability has become a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a cold-region aerogel-hollow glass microsphere composite mortar to solve the technical problem in the prior art that the poor compatibility between aggregates and cementitious materials in porous structures and the easy occurrence of water penetration make it difficult to synergistically improve the mechanical properties, thermal insulation properties and freeze-thaw resistance of composite mortar.

[0005] The aforementioned aerogel-hollow glass microsphere composite mortar for cold regions comprises, by weight, the following components: 535-560 parts cement, 50-55 parts silica fume, 120-140 parts aerogel-hollow glass microsphere composite aggregate, 3.0-3.5 parts polypropylene fiber, 2.0-2.2 parts polyvinyl alcohol fiber, 4.8-5.3 parts dispersible latex powder, 3.0-3.3 parts hydroxypropyl methylcellulose ether, 5.4-5.7 parts water-reducing agent, and 290-300 parts water; the aerogel-hollow glass microsphere composite aggregate is obtained by activating and modifying hollow glass microspheres and then combining them with hydrophobic aerogel and nano-SiO2 / nano-hydroxyapatite composite sol.

[0006] Preferably, the preparation method of the aerogel-hollow glass microsphere composite aggregate includes the following steps: S1: Oxalic acid, citric acid, and sodium hexametaphosphate are added to deionized water and stirred to obtain mixture A. Hollow glass microspheres are then added and ultrasonically dispersed to obtain surface-activated hollow glass microspheres. S2: Add γ-aminopropyltriethoxysilane and heptadecafluorodecyltrimethoxysilane to anhydrous ethanol, adjust the pH to acidic with acetic acid, mix and stir to obtain mixture B; S3: Add the activated hollow glass microspheres obtained in step S1 to the mixture B, stir at room temperature first, then heat and continue stirring to obtain modified hollow glass microspheres. S4: Add the hydrophobic aerogel to the ethanol solution and disperse it by ultrasonication to form an aerogel suspension. Add γ-aminopropyltriethoxysilane, chitosan quaternary ammonium salt, and nano-SiO2 / nano-hydroxyapatite composite sol to the aerogel suspension. Heat and stir in a water bath to obtain mixture C. S5: Add the modified hollow glass microspheres obtained in step S3 to the mixture C, stir and react at a constant temperature, then cool to room temperature, filter, wash and dry to obtain the aerogel-hollow glass microsphere composite aggregate.

[0007] Preferably, in step S1, the amount of hollow glass microspheres added is 90-100 parts by mass; the mass ratio of hollow glass microspheres to mixture A is 1:5; the mass fraction of oxalic acid in mixture A is 0.75%, the mass fraction of citric acid is 0.25%, and the mass fraction of sodium hexametaphosphate is 0.07%; the stirring time is 3 minutes, and the ultrasonic dispersion is carried out at 50°C and 100W for 3 minutes.

[0008] Preferably, in step S2, the pH value is adjusted to 4-6 by mass parts, and the mixing time is 3 min.

[0009] Preferably, in step S3, the mass ratio of the activated hollow glass microspheres to the mixed liquid B is 1:3; the stirring at room temperature is 150 rpm for 30 min at 25°C; the temperature after heating is 60°C, and the stirring continues at 200 rpm for 60 min after heating.

[0010] Preferably, in step S4, the amount of hydrophobic aerogel added is 40-60 parts by mass, the amount of ethanol solution added is 220-330 parts by mass, and the mass fraction of the ethanol solution is 80%; the ultrasonic dispersion time is 30 min.

[0011] Preferably, in step S4, the amount of γ-aminopropyltriethoxysilane added is 4.5-6 parts by mass, the amount of chitosan quaternary ammonium salt added is 0.5-0.7 parts, and the amount of nano-SiO2 / nano-hydroxyapatite composite sol added is 12-18 parts; the water bath heating and stirring is carried out in a 50°C water bath at 300 rpm for 60 min.

[0012] Preferably, in step S5, the isothermal stirring reaction is carried out at a constant temperature of 60°C and stirred at 150 rpm for 1-2 hours; the washing is performed three times with anhydrous ethanol; and the drying is carried out at 45°C for 5 hours.

[0013] Preferably, the solid content of the nano-SiO2 / nano-hydroxyapatite composite sol is 10~20wt%, wherein the mass ratio of nano-SiO2 to nano-hydroxyapatite is 3:1.

[0014] This invention also provides a method for preparing the cold-region aerogel-hollow glass microsphere composite mortar as described above, comprising the following steps: (1) Weigh each component raw material according to the designed weight proportions; (2) Mix cement, silica fume, dispersible latex powder, and hydroxypropyl methylcellulose ether evenly to obtain a dry-mixed cementitious material; (3) Add polypropylene fiber and polyvinyl alcohol fiber to the dry-mixed cementitious material and mix evenly; (4) Add water and water-reducing agent to the mixture obtained in step (3), mix evenly, and obtain wet material; (5) Add aerogel-hollow glass microsphere composite aggregate to the wet material and mix evenly to obtain cold region aerogel-hollow glass microsphere composite mortar.

[0015] The technical advantages of this invention are as follows: By constructing a gradient functional structure with an inner amino layer and an outer perfluoroalkyl layer on the surface of hollow glass microspheres, and modifying the surface with hydrophobic SiO2 aerogel, an aerogel-hollow glass microsphere composite thermal insulation aggregate is formed, which enhances the interfacial bonding strength between the composite aggregate and the cement matrix, and constructs a stable and continuous "micron-nano" porous thermal insulation network. While retaining the thermal insulation porosity, the structural density is improved, solving the technical problem that the addition of traditional thermal insulation aggregates leads to serious loss of mechanical properties.

[0016] Meanwhile, the hydrophobic surface layer and aerogel effectively reduce freeze-thaw stress and decrease compressive strength loss during freeze-thaw cycles. The antibacterial component, chitosan quaternary ammonium salt, adhering to the surface of the composite aggregate inhibits bacterial growth to prevent structural damage from hydration products, thus enhancing mortar density and interfacial strength. The addition of nano-SiO2 and nano-hydroxyapatite composite fillers further improves density, helps inhibit the propagation of microcracks between the aggregate and cement matrix, and enhances the mortar's mechanical properties, thermal insulation properties, and freeze-thaw resistance. Attached Figure Description

[0017] Figure 1 The image shows the aerogel-hollow glass microsphere composite mortar specimen prepared in Example 1 of this application. Figure 2 This is a microscopic diagram of the internal structure of the aerogel-hollow glass microsphere composite mortar specimen prepared in Example 1 of this application. Detailed Implementation

[0018] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0019] In existing technologies, hollow glass microspheres are added to thermal insulation mortar to construct a porous structure and improve thermal insulation performance. However, when the proportion of thermal insulation aggregate is large, while the thermal insulation performance of the material is improved, the mechanical strength decreases, and hollowing and peeling are prone to occur. Especially in the freeze-thaw cycle environment of cold regions, the expansion of ice crystals caused by moisture intrusion will aggravate interface damage, resulting in a significant decrease in strength, which cannot meet the long-term service requirements of cold region projects.

[0020] To address the aforementioned technical issues, this invention first activates the surface of hollow glass microspheres, then performs gradient functional modification on the activated hollow glass microspheres. This constructs an "inner layer -NH2 reinforced / outer layer -CF3 hydrophobic" structure on the surface of the hollow glass microspheres. The -NH2 layer can form hydrogen bonds and undergo secondary condensation with CSH gel, enhancing interfacial bonding. The heptadecafluorodecyltrimethoxysilane hydrolysis and condensation to form a -CF3 hydrophobic layer blocks water penetration. Simultaneously, a hydrophobic aerogel (such as SiO2 aerogel) is covalently bonded to its surface (Si-O-Si), and the hydrophobic layer and aerogel synergistically block water intrusion and disperse freeze-thaw stress. Antibacterial components such as chitosan quaternary ammonium salt are anchored to the surface of the composite aggregate through electrostatic adsorption and chemical bonding, inhibiting bacterial growth to avoid structural damage from hydration products and enhancing mortar density and interfacial strength. The three-dimensional network structure system formed by polypropylene fibers and polyvinyl alcohol fibers effectively disperses the aerogel-hollow glass microsphere composite aggregate. Nano-SiO2 / nano-hydroxyapatite composite filler can fill the pores of the matrix and improve its density. On the other hand, in the microcrack area generated by freeze-thaw cycles, it can act as a nucleation site to promote the secondary deposition of CSH gel, which helps to inhibit the propagation of microcracks and further synergistically improves the mechanical properties, thermal insulation properties and freeze-thaw resistance of cement-based materials.

[0021] Based on the above-mentioned inventive concept, the present invention provides a cold-region aerogel-hollow glass microsphere composite mortar and its preparation method. Specific embodiments of the present invention are as follows: Example 1 like Figure 1 , Figure 2 As shown, Example 1 provides a cold-region aerogel-hollow glass microsphere composite mortar, which, by mass parts, includes the following components: 560 parts cement, 55 parts silica fume, 120 parts aerogel-hollow glass microsphere composite aggregate, 3.0 parts polypropylene fiber, 2.0 parts polyvinyl alcohol fiber, 4.8 parts dispersible latex powder, 3.0 parts hydroxypropyl methylcellulose ether, 5.5 parts water-reducing agent, and 290 parts water.

[0022] The cement is P·O 42.5 grade ordinary Portland cement.

[0023] The silica fume contains 98.1% SiO2, has a loss on ignition of 1.48%, and a specific surface area of ​​22.1 m². 2 / g, bulk density 450 kg / m³ 3 .

[0024] The polypropylene fiber density is 0.91 g / cm³. 3 Length 6 mm, diameter 20-31 mm Tensile strength ≥460 MPa, elongation at break 30%.

[0025] The polyvinyl alcohol fibers have a density of 1.2 g / cm³, a length of 6 mm, and a diameter of 15-31 mm. Tensile strength ≥1600MPa, elongation at break 30%.

[0026] The dispersible latex powder is a saponification-resistant redispersible vinyl acetate / ethylene copolymer powder with an apparent density of 540-590 g / L.

[0027] The hydroxypropyl methylcellulose ether has a viscosity of 100,000 mPa·s.

[0028] The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate of 25-30%.

[0029] Aerogel-hollow glass microsphere composite aggregate is obtained by activating and modifying hollow glass microspheres and then combining them with hydrophobic aerogel and nano-SiO2 / nano-hydroxyapatite composite sol.

[0030] The preparation method of the aerogel-hollow glass microsphere composite aggregate includes the following steps: S1: Add oxalic acid, citric acid, and sodium hexametaphosphate to deionized water, mix and stir for 3 min to obtain mixture A, add 90 parts of hollow glass microspheres, and ultrasonically disperse for 3 min at 50℃ and 100W to obtain activated hollow glass microspheres.

[0031] In step S1, the hollow glass microspheres have a standard median particle size of 20 μm and a thermal conductivity ≤0.08 W / (m•K). The mixture A contains 0.75% oxalic acid, 0.25% citric acid, and 0.07% sodium hexametaphosphate. The mass ratio of the hollow glass microspheres to mixture A is 1:5.

[0032] S2: Add 5 parts of γ-aminopropyltriethoxysilane and 2 parts of heptadecafluorodecyltrimethoxysilane to 265 parts of anhydrous ethanol, adjust the pH to 4-6 with acetic acid, mix and stir for 3 min to obtain mixture B.

[0033] S3: Add the activated hollow glass microspheres obtained in step S1 to mixture B, stir at 150 rpm for 30 min at 25°C, then raise the temperature to 60°C and continue stirring at 200 rpm for 60 min to obtain modified hollow glass microspheres.

[0034] In step S3, the mass ratio of the activated hollow glass microspheres to the mixed liquid B is 1:3.

[0035] S4: Add 50 parts of hydrophobic aerogel to 275 parts of ethanol solution and ultrasonically disperse for 30 min to form a uniform aerogel suspension; add 5.5 parts of γ-aminopropyltriethoxysilane, 0.6 parts of chitosan quaternary ammonium salt, and 15 parts of nano-SiO2 / nano-hydroxyapatite composite sol to the suspension and stir at 300 rpm for 60 min in a 50℃ water bath to obtain mixture C.

[0036] In step S4, the hydrophobic aerogel has a pore size of 20-80 nm and a thermal conductivity ≤0.02 W / (m•K). The ethanol solution has a mass fraction of 80%. The nano-SiO2 / nano-hydroxyapatite composite sol has a solid content of 10 wt%, wherein the mass ratio of nano-SiO2 to nano-hydroxyapatite is 3:1.

[0037] S5: Add the modified hollow glass microspheres to the mixture C, and stir at 150 rpm for 1-2 h under constant temperature of 60℃. Cool to room temperature, filter, remove the filtrate, wash 3 times with anhydrous ethanol, and dry at 45℃ for 5 h to obtain the aerogel-hollow glass microsphere composite aggregate.

[0038] Example 1 also provides a method for preparing aerogel-hollow glass microsphere composite mortar for cold regions, comprising the following steps: (1) Weigh each component raw material according to the designed weight proportions.

[0039] (2) Weigh out the cement, silica fume, dispersible latex powder and hydroxypropyl methylcellulose ether and mix them for 2 minutes at a stirring speed of 300 rpm to obtain dry-mixed cementitious material.

[0040] (3) Add polypropylene fiber and polyvinyl alcohol fiber, stir for 3 minutes at a stirring speed of 300 rpm to ensure uniform dispersion.

[0041] (4) Add water and polycarboxylate superplasticizer, stir for 3 minutes at a stirring speed of 500 rpm to obtain wet material.

[0042] (5) Add aerogel-hollow glass microsphere composite aggregate, stir for 2 minutes at a stirring speed of 200 rpm, and mix evenly to obtain aerogel-hollow glass microsphere composite mortar for cold regions.

[0043] After the aerogel-hollow glass microsphere composite mortar for cold regions is formed, it is cured for 28 days in an environment with a temperature of 20±2℃ and humidity >90% to obtain the solidified product. Figure 1 As shown.

[0044] Example 2 Compared with Example 1, Example 2 has the following technical differences: Example 2 provides a cold-region aerogel-hollow glass microsphere composite mortar, which, by mass parts, includes the following components: 535 parts cement, 52 parts silica fume, 125 parts aerogel-hollow glass microsphere composite aggregate, 3.3 parts polypropylene fiber, 2.1 parts polyvinyl alcohol fiber, 5.0 parts dispersible latex powder, 3.1 parts hydroxypropyl methylcellulose ether, 5.7 parts water-reducing agent, and 298 parts water.

[0045] Example 3 Compared with Example 1, Example 3 has the following technical differences: Example 3 provides a cold-region aerogel-hollow glass microsphere composite mortar, which comprises the following components by weight: 540 parts cement, 50 parts silica fume, 140 parts aerogel-hollow glass microsphere composite aggregate, 3.5 parts polypropylene fiber, 2.2 parts polyvinyl alcohol fiber, 5.3 parts dispersible latex powder, 3.3 parts hydroxypropyl methylcellulose ether, 5.4 parts water-reducing agent, and 300 parts water.

[0046] The comparison is provided below, and the details are as follows.

[0047] Comparative Example 1 Comparative Example 1 differs from Example 1 in the following technical aspects: Comparative Example 1 provides an aerogel-hollow glass microsphere composite mortar, wherein the components and amounts are the same as in Example 1, but the preparation method of the aerogel-hollow glass microsphere composite aggregate is different. The preparation method of the aerogel-hollow glass microsphere composite aggregate in Comparative Example 1 includes the following steps: S1: Add oxalic acid, citric acid, and sodium hexametaphosphate to deionized water, mix and stir for 3 min to obtain mixture A, add 90 parts of hollow glass microspheres, and ultrasonically disperse for 3 min at 50℃ and 100W to obtain activated hollow glass microspheres.

[0048] S2: Add 50 parts of hydrophobic aerogel to 275 parts of ethanol solution and ultrasonically disperse for 30 min to form a uniform aerogel suspension; add 5.5 parts of γ-aminopropyltriethoxysilane, 0.6 parts of chitosan quaternary ammonium salt, and 15 parts of nano-SiO2 / nano-hydroxyapatite composite sol to the suspension and stir at 300 rpm for 60 min in a 50℃ water bath to obtain mixture C.

[0049] S3: Add the modified hollow glass microspheres to the mixture C, and stir at 150 rpm for 1-2 h under constant temperature of 60℃. Cool to room temperature, filter, remove the filtrate, wash 3 times with anhydrous ethanol, and dry at 45℃ for 5 h to obtain the aerogel-hollow glass microsphere composite aggregate.

[0050] Compared to Example 1, the difference in this comparative example is that the gradient modification in step S2 of composite aggregate preparation (corresponding to steps S2 and S3 in Example 1) is omitted. The hollow glass microspheres are directly composited with aerogel after surface activation. The remaining components, dosages and preparation methods are the same as in Example 1.

[0051] Comparative Example 2 Comparative Example 2 differs from Example 1 in the following technical aspects: Comparative Example 2 provides an aerogel-hollow glass microsphere composite mortar, wherein the components and dosages are the same as in Example 1, but the preparation method of the aerogel-hollow glass microsphere composite aggregate is different. The preparation method of the aerogel-hollow glass microsphere composite aggregate in Comparative Example 2 includes the following steps: S1: Add oxalic acid, citric acid, and sodium hexametaphosphate to deionized water, mix and stir for 3 min to obtain mixture A, add 90 parts of hollow glass microspheres, and ultrasonically disperse for 3 min at 50℃ and 100W to obtain activated hollow glass microspheres.

[0052] S2: Add 5 parts of γ-aminopropyltriethoxysilane and 2 parts of heptadecafluorodecyltrimethoxysilane to 265 parts of anhydrous ethanol, adjust the pH to 4-6 with acetic acid, mix and stir for 3 min to obtain mixture B.

[0053] S3: Add the activated hollow glass microspheres obtained in step S1 to mixture B, stir at 150 rpm for 30 min at 25°C, then raise the temperature to 60°C and continue stirring at 200 rpm for 60 min to obtain modified hollow glass microspheres.

[0054] S4: Add 50 parts of hydrophobic aerogel to 275 parts of ethanol solution and ultrasonically disperse for 30 min to form a uniform aerogel suspension; add 5.5 parts of γ-aminopropyltriethoxysilane and 0.6 parts of chitosan quaternary ammonium salt to the suspension and stir at 300 rpm for 60 min in a 50℃ water bath to obtain mixture C.

[0055] S5: Add the modified hollow glass microspheres to the mixture C, and stir at 150 rpm for 1-2 h under constant temperature of 60℃. Cool to room temperature, filter, remove the filtrate, wash 3 times with anhydrous ethanol, and dry at 45℃ for 5 h to obtain the aerogel-hollow glass microsphere composite aggregate.

[0056] Compared to Example 1, the difference in this comparative example is that nano-SiO2 / nano-hydroxyapatite composite sol is not added in step S4, while the remaining components, amounts, and preparation methods are the same as in Example 1.

[0057] Comparative Example 3 Comparative Example 3 differs from Example 1 in the following technical aspects: Comparative Example 3 provides a composite mortar comprising the following components by weight: 560 parts cement, 55 parts silica fume, 90 parts hollow glass microspheres, 50 parts hydrophobic aerogel, 3.0 parts polypropylene fiber, 2.0 parts polyvinyl alcohol fiber, 4.8 parts dispersible latex powder, 3.0 parts hydroxypropyl methylcellulose ether, 5.5 parts water-reducing agent, and 290 parts water.

[0058] Comparative Example 3 also provides a method for preparing composite mortar, comprising the following steps: (1) Weigh each component raw material according to the designed weight proportions.

[0059] (2) Weigh out the cement, silica fume, dispersible latex powder and hydroxypropyl methylcellulose ether and mix them for 2 minutes at a stirring speed of 300 rpm to obtain dry-mixed cementitious material.

[0060] (3) Add polypropylene fiber and polyvinyl alcohol fiber, stir for 3 minutes at a stirring speed of 300 rpm to ensure uniform dispersion.

[0061] (4) Add water and polycarboxylate superplasticizer, stir for 3 minutes at a stirring speed of 500 rpm to obtain wet material.

[0062] (5) Add hollow glass microspheres and hydrophobic aerogel by physical blending, stir for 2 minutes at a stirring speed of 200 rpm, and mix evenly to obtain composite mortar.

[0063] Compared to Example 1, the difference in this comparative example is that: no aerogel-hollow glass microsphere composite aggregate is prepared; instead, 90 parts of hollow glass microspheres and 50 parts of hydrophobic aerogel are directly added to the composite mortar by physical blending; the remaining components, dosages, and preparation methods are the same as in Example 1.

[0064] Performance testing: The mortars prepared in Examples 1-3 and Comparative Examples 1-3 were made into specimens and, after standard curing (temperature 20±2℃, humidity >90%, age 28 days), their performance was tested according to the following standards: (1) Dry apparent density: Tested according to the "Test Methods for Inorganic Rigid Thermal Insulation Products" (GB / T 5486-2008); (2) Compressive strength: Tested according to the "Test Method for Strength of Cement Mortar (ISO Method)" (GB / T 17671-1999); (3) Thermal conductivity: Tested according to the Test Methods for Inorganic Rigid Insulation Products (GB / T 5486-2008).

[0065] (4) Compressive strength loss rate: Tested according to "Building Thermal Insulation Mortar" (GB / T 20473-2021). Each freeze-thaw cycle is: freezing at (-20±2)℃ for 4 h, and then thawing in water at (20±5)℃ for 4 h as one freeze-thaw cycle. This freeze-thaw cycle is repeated 15 times, and the compressive strength loss rate is calculated.

[0066] The specimens of Examples 1-3 and Comparative Examples 1-3 underwent performance testing, and the specific results are shown in Table 1.

[0067] Table 1 Performance Test Results

[0068] Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the gradient modification treatment of hollow glass microspheres can significantly improve the mechanical properties and freeze-thaw resistance of mortar. The -NH2 grafted with KH-550 in the inner layer forms hydrogen bonds and secondary condensation with CSH gel, which can enhance the interfacial bonding strength. The hydrophobic layer formed by the outer FAS-17 can block water penetration and reduce the formation of ice crystals during freeze-thaw cycles. At the same time, the nano-SiO2 / nano-hydroxyapatite composite filler can fill the pores of the matrix and improve the density. On the other hand, in the microcrack areas generated by freeze-thaw cycles, it can act as a nucleation site to promote the secondary deposition of CSH gel, which helps to inhibit the propagation of microcracks and further synergistically improves the mechanical properties, thermal insulation properties and freeze-thaw resistance of cement-based materials.

[0069] Comparing Example 1 and Comparative Example 3, it can be seen that during the physical blending process, aerogel and hollow glass microspheres are prone to agglomeration and detachment, resulting in an increase in interfacial cracks and a higher proportion of harmful pores, which significantly reduces mechanical and thermal insulation properties. However, the present invention reduces interfacial cracks and "cavitation" gaps by modifying the aerogel-hollow glass microsphere composite, while maintaining the complete pore structure and improving the structural density, thereby achieving a synergistic improvement in thermal insulation and antifreeze properties.

[0070] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A composite mortar of aerogel and hollow glass microspheres for cold regions, characterized in that, The composition comprises, by weight parts, the following components: 535-560 parts cement, 50-55 parts silica fume, 120-140 parts aerogel-hollow glass microsphere composite aggregate, 3.0-3.5 parts polypropylene fiber, 2.0-2.2 parts polyvinyl alcohol fiber, 4.8-5.3 parts dispersible latex powder, 3.0-3.3 parts hydroxypropyl methylcellulose ether, 5.4-5.7 parts water-reducing agent, and 290-300 parts water; wherein the aerogel-hollow glass microsphere composite aggregate is obtained by activating and modifying hollow glass microspheres and then combining them with hydrophobic aerogel and nano-SiO2 / nano-hydroxyapatite composite sol.

2. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 1, characterized in that, The preparation method of the aerogel-hollow glass microsphere composite aggregate includes the following steps: S1: Oxalic acid, citric acid, and sodium hexametaphosphate are added to deionized water and stirred to obtain mixture A. Hollow glass microspheres are then added and ultrasonically dispersed to obtain surface-activated hollow glass microspheres. S2: Add γ-aminopropyltriethoxysilane and heptadecafluorodecyltrimethoxysilane to anhydrous ethanol, adjust the pH to acidic with acetic acid, mix and stir to obtain mixture B; S3: Add the activated hollow glass microspheres obtained in step S1 to the mixture B, stir at room temperature first, then heat and continue stirring to obtain modified hollow glass microspheres. S4: Add the hydrophobic aerogel to the ethanol solution and disperse it by ultrasonication to form an aerogel suspension. Add γ-aminopropyltriethoxysilane, chitosan quaternary ammonium salt, and nano-SiO2 / nano-hydroxyapatite composite sol to the aerogel suspension. Heat and stir in a water bath to obtain mixture C. S5: Add the modified hollow glass microspheres obtained in step S3 to the mixture C, stir and react at a constant temperature, then cool to room temperature, filter, wash and dry to obtain the aerogel-hollow glass microsphere composite aggregate.

3. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 2, characterized in that, In step S1, the amount of hollow glass microspheres added is 90-100 parts by mass; the mass ratio of hollow glass microspheres to mixture A is 1:5; the mass fraction of oxalic acid in mixture A is 0.75%, the mass fraction of citric acid is 0.25%, and the mass fraction of sodium hexametaphosphate is 0.07%; the stirring time is 3 minutes, and the ultrasonic dispersion is carried out at 50°C and 100W for 3 minutes.

4. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 2, characterized in that, In step S2, the pH value is adjusted to 4-6 by mass parts; the mixing and stirring time is 3 minutes.

5. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 2, characterized in that, In step S3, the mass ratio of the activated hollow glass microspheres to the mixed liquid B is 1:3; the stirring at room temperature is 150 rpm for 30 min at 25°C; the temperature after heating is 60°C, and the stirring continues at 200 rpm for 60 min.

6. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 2, characterized in that, In step S4, the amount of hydrophobic aerogel added is 40-60 parts by mass, the amount of ethanol solution added is 220-330 parts by mass, and the mass fraction of the ethanol solution is 80%; the ultrasonic dispersion time is 30 min.

7. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 2, characterized in that, In step S4, the amount of γ-aminopropyltriethoxysilane added is 4.5-6 parts by mass, the amount of chitosan quaternary ammonium salt added is 0.5-0.7 parts, and the amount of nano-SiO2 / nano-hydroxyapatite composite sol added is 12-18 parts; water bath heating and stirring is carried out in a 50°C water bath at 300 rpm for 60 min.

8. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 2, characterized in that, In step S5, the constant temperature stirring reaction is carried out at a constant temperature of 60°C and stirred at 150 rpm for 1-2 hours; the washing is performed three times with anhydrous ethanol; and the drying is carried out at 45°C for 5 hours.

9. The cold-region aerogel-hollow glass microsphere composite mortar according to claim 1, characterized in that, The solid content of the nano-SiO2 / nano-hydroxyapatite composite sol is 10~20 wt%, wherein the mass ratio of nano-SiO2 to nano-hydroxyapatite is 3:

1.

10. A method for preparing a cold-region aerogel-hollow glass microsphere composite mortar according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Weigh each component raw material according to the designed weight proportions; (2) Mix cement, silica fume, dispersible latex powder, and hydroxypropyl methylcellulose ether evenly to obtain a dry-mixed cementitious material; (3) Add polypropylene fiber and polyvinyl alcohol fiber to the dry-mixed cementitious material and mix evenly; (4) Add water and water-reducing agent to the mixture obtained in step (3), mix evenly, and obtain wet material; (5) Add aerogel-hollow glass microsphere composite aggregate to the wet material and mix evenly to obtain cold region aerogel-hollow glass microsphere composite mortar.

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