Composite hydrophobic high-strength constant-temperature anti-dewing paste and preparation method thereof

Abstract

This application relates to the field of building waterproofing materials, and in particular to a composite hydrophobic high-strength constant-temperature anti-condensation slurry and its preparation method. It comprises the following raw materials in parts by weight: 30-40 parts of PO 42.5 cement, 0.5-2 parts of calcium formate, 5-15 parts of active mineral admixtures, 25-35 parts of hydrophobic perlite, 10-15 parts of cenospheres, 2-6 parts of redispersible polymer powder, 0.3-1 part of cellulose ether, 0.5-2 parts of reinforcing fibers, and 0.1-1 parts of additives. The hydrophobic perlite is prepared by using potassium methylsilicate, a silane coupling agent, and nano-SiO2 to form a composite hydrophobic liquid, and a hydrophobic film is formed on the surface of the perlite. The slurry of this application possesses excellent strength, hydrophobicity, and anti-condensation properties.

Description

Technical Field

[0001] This application relates to the field of building waterproofing materials, and in particular to composite water-repellent high-strength constant temperature anti-condensation slurry and its preparation method. Background Technology

[0002] Building energy conservation is a key aspect of reducing societal energy consumption, and the performance of wall insulation materials is crucial. Currently, the building insulation field mainly uses two categories of materials: organic and inorganic. Organic materials, such as EPS polystyrene boards, XPS extruded polystyrene boards, and polyurethane foam boards, are lightweight and have low thermal conductivity, and have been widely used. Inorganic materials are represented by various insulation mortars, such as granulated polystyrene insulation mortar, expanded vitrified microsphere insulation mortar, and polymer cement-based inorganic insulation mortar. These materials typically use cement as a binder, incorporating lightweight aggregates (such as polystyrene particles and vitrified microspheres) and additives. Their principle lies in utilizing the porous structure formed by the lightweight aggregates to impede heat transfer.

[0003] However, existing thermal insulation mortar technologies still face a series of long-standing problems and performance shortcomings in practical engineering applications. First, insufficient waterproofing and water-repellent properties are a common defect. Most thermal insulation mortars have high water absorption, and once cracks appear in the external finishing layer, moisture easily penetrates. After the material absorbs moisture, the water in its pores significantly increases the thermal conductivity, leading to a sharp decline in insulation performance and loss of its temperature-regulating effect. Second, the contradiction between strength and durability is prominent. Water-absorbing insulation layers not only experience increased load but are also more prone to delamination and cracking under freeze-thaw cycles, ultimately leading to large-scale detachment and posing serious safety hazards. Although adding polymer powders can improve bonding strength and toughness, achieving a stable balance between high strength, low water absorption, and excellent insulation performance remains a technical challenge. Finally, the system's crack resistance and anti-condensation capabilities are weak. The existing system relies on multi-layer construction and meticulous construction to release stress. Any mismatch in material properties or improper construction of any layer may lead to cracking, thus creating conditions for moisture intrusion and the formation of thermal bridges. Under the influence of indoor and outdoor temperature differences, condensation is likely to occur inside or on the inner surface of the wall.

[0004] Existing improvement methods mostly employ surface hydrophobic treatment or polymer addition, but fail to achieve a synergistic effect between bulk hydrophobicity and structural reinforcement. Furthermore, these methods are complex, costly, and lack long-term stability. Therefore, a composite hydrophobic high-strength constant-temperature anti-condensation slurry that can fundamentally and synergistically improve hydrophobicity, mechanical strength, and long-term thermal insulation stability is needed to address the high water absorption rate, performance degradation after moisture absorption, and the resulting risks of cracking, detachment, and condensation associated with existing technologies. Summary of the Invention

[0005] Based on the shortcomings of the prior art, the purpose of this invention is to provide a composite hydrophobic high-strength constant temperature anti-condensation slurry and its preparation method, so as to achieve the excellent hydrophobicity, mechanical strength, anti-condensation and heat preservation properties of the anti-condensation slurry.

[0006] In the first aspect, this application provides a composite hydrophobic high-strength constant temperature anti-condensation grout, comprising the following raw materials in parts by weight: 30-40 parts of PO 42.5 cement, 0.5-2 parts of calcium formate, 5-15 parts of active mineral admixture, 25-35 parts of hydrophobic perlite, 10-15 parts of cenospheres, 2-6 parts of redispersible polymer powder, 0.3-1 part of cellulose ether, 0.5-2 parts of reinforcing fiber, and 0.1-1 parts of additives; The hydrophobic perlite is obtained by preparing a composite hydrophobic liquid using potassium methylsilicate, silane coupling agent, and nano-SiO2, and then forming a hydrophobic film on the surface of the perlite.

[0007] PO 42.5 cement provides the main strength of the material, and the calcium silicate hydrate generated during cement hydration can bind components such as perlite and cenospheres. Calcium formate is introduced as a key early-strength component. In the early stages of slurry hydration, calcium formate significantly accelerates the dissolution and hydration reaction rate of cement clinker minerals such as tricalcium silicate, promoting the rapid formation of early hydration products and the initial formation of the network structure. This allows the slurry to achieve high early strength within 24 hours, effectively meeting the requirements of demolding, initial impact resistance, and other construction processes, ensuring project progress. Active mineral admixtures are introduced as core reinforcing and densifying components. Active mineral admixtures, such as silica fume, are rich in highly active amorphous silica. Their pozzolanic effect and micro-aggregate filling effect work synergistically. In the later stages of slurry hydration, silica fume reacts secondaryly with calcium hydroxide released during cement hydration, generating more CSH gel with a low calcium-to-silica ratio. This not only continuously improves the later-stage strength of the slurry but also significantly optimizes its microstructure: its extremely fine particles fill the gaps between cement particles, greatly reducing porosity and making the structure more compact, thereby simultaneously enhancing mechanical properties and impermeability durability. Cenospheres, high-strength spheres with a hollow structure, possess excellent thermal insulation and reinforcing functions. They can fill the gaps between cement and perlite, achieving particle gradation, thus improving strength and reducing shrinkage. Redispersible polymer powder provides certain film-forming and bonding-promoting functions, preventing water penetration, improving slurry flexibility and bonding strength, and preventing cracking. Cellulose ethers act as water-retaining and thickening agents, locking in moisture while preventing sagging and particle settling. Reinforcing fibers can prevent shrinkage and cracking, improve the overall toughness and impact resistance of the slurry, and prevent water penetration caused by cracking.

[0008] The inventors loaded a hydrophobic film onto the surface of perlite and its pores. The hydrophobic film is an organic-inorganic hybrid network structure formed by the solidification of a siloxane pre-hydrolyzed solution and a nano-SiO2 composite hydrophobic solution. The silane coupling agent enables surface grafting of nano-SiO2, enhancing the system's strength while also bonding with the silanol groups of cement hydration products. Similarly, potassium methylsilicate can be grafted onto the nano-SiO2 surface, providing hydrophobicity, and can also bond with the hydration product calcium silicate hydrate. This results in an organic-inorganic hybrid network structure on the perlite surface, exhibiting excellent hydrophobicity and high strength. Furthermore, its interaction with cement hydration products ensures a strong bond within the system, preventing cracking and water penetration, while also providing better insulation.

[0009] Preferably, the preparation process of the hydrophobic perlite includes: Step 1: Perlite pretreatment and activation: Perlite particles are sprayed with NaOH solution and then dried to obtain activated perlite for later use; Step 2: Pre-hydrolysis: Potassium methylsilicate silane, coupling agent KH560 and water-ethanol mixed solvent are mixed to obtain siloxane pre-hydrolysis solution A; nano SiO2 is dispersed in water to obtain nano SiO2 dispersion B; B is slowly added dropwise to A to obtain composite hydrophobic solution; Step 3: Place the activated perlite in the reactor and inject the composite hydrophobic liquid obtained in Step 2 under vacuum; then restore normal pressure, pressurize with nitrogen, and depressurize; continue the vacuum-pressurization-depressurization cycle 2-3 times to obtain the product; Step 4: The product from Step 3 is dried by gradient heating to obtain hydrophobic perlite.

[0010] Preferably, step 1 includes: perlite pretreatment and activation: expanding perlite uniform particles with a particle size of 0.5-1.5 mm are sprayed with a NaOH solution with a mass fraction of 2-5% for 15-20 minutes, and then dried in an oven at 100-110℃ for 1-3 hours to obtain activated perlite for later use.

[0011] Preferably, step 2 includes: pre-hydrolysis: mixing 40-50 parts by weight of 40% potassium methylsilicate solution, 5-10 parts by weight of silane coupling agent KH560 and 40-50 parts by weight of water-ethanol mixed solvent, stirring at 300-500 rpm for 30-60 min to obtain siloxane pre-hydrolysis solution A; dispersing 10-15 parts by weight of nano-SiO2 in 30-40 parts by weight of water, ultrasonically dispersing for 20-40 min to obtain nano-SiO2 dispersion B; slowly adding B dropwise to A under stirring at 500-800 rpm, controlling the reaction temperature at 30-40℃; after the addition is complete, continuing to stir the reaction for 2-4 h to obtain a composite hydrophobic solution.

[0012] Preferably, step 3 includes: placing activated perlite in a reaction vessel, evacuating to below -0.095 MPa and maintaining the vacuum for 10-30 minutes, injecting the composite hydrophobic liquid obtained in step 2 under vacuum, and controlling the mass ratio of perlite to composite hydrophobic liquid to be 4-6:1; then restoring to normal pressure, immediately filling the vessel with nitrogen gas to a pressure of 0.4-0.6 MPa, maintaining the pressure for 10-20 minutes, and then depressurizing; continuing the vacuum-pressurization-depressurization cycle 2-3 times.

[0013] Preferably, in step 4: the product from step 3 is dried at 35-45℃ for 10-12 hours; the temperature is raised to 75-85℃ and dried for 6-8 hours; the temperature is further raised to 95-105℃ and dried for 2-4 hours to obtain hydrophobic perlite.

[0014] This invention prepares a reactive organic-inorganic hybrid hydrophobic liquid using an in-situ sol-gel method, and then utilizes a vacuum-pressurized cyclic impregnation process to force it to penetrate the inner surface of every micropore of perlite. During subsequent curing, the hybrid network is anchored to the activated perlite substrate through strong Si-O-Si chemical bonds. This not only achieves "bulk hydrophobicity," meaning water cannot penetrate the aggregate at all, but more importantly, this hydrophobic film itself becomes a reinforcing phase, forming a strong bond with cement hydration products, transforming the "weak bonding area" in traditional hydrophobic treatment processes into a "reinforced interface area." The special treatment of perlite fundamentally cuts off the capillary transport channels for moisture. Extremely low hygroscopicity ensures the insulation layer remains dry throughout long-term use, with a stable thermal conductivity, improving the thermal inertia of the building walls, and ensuring the inner surface temperature is always above the dew point temperature, achieving true "constant temperature anti-condensation."

[0015] Based on the hydrophobic treatment method of this application, a gradient temperature drying process is used in conjunction. This avoids the agglomeration of nanoparticles due to rapid drying, allowing the hybrid network to shrink gently within the pores. The silanol in the hybrid network undergoes dehydration condensation with the active Si-OH on the perlite surface, forming strong chemical bonds (Si-O-Si). At the same time, the hybrid network itself further cross-links and solidifies, and finally, the temperature rise achieves complete removal of moisture.

[0016] Preferably, the anti-condensation slurry meets one of the following conditions: 1) The active mineral admixture is selected from one or more of silica fume, fly ash, and slag powder, with a particle size of 3-5 μm; 2) The particle size of the cenospheres is 60-200μm; 3) The reinforcing fiber includes one or both of lignin fiber and polypropylene short fiber; 4) The additives include one or both of polycarboxylate powder water-reducing agent and polyacrylamide.

[0017] In this application, the perlite, cenospheres, and silica fume in the slurry have different particle sizes. Perlite provides the main volume support and thermal insulation channels. The cenospheres have a much smaller particle size than perlite and have a certain spherical bearing effect, which provides excellent drag reduction, lubrication, and improved flowability. They can fill the gaps between the perlite skeleton more flexibly, reduce the internal porosity of the material, make the structure more compact, and improve the strength and water resistance. The silica fume has a smaller particle size than cenospheres, which can further fill the gaps and achieve dense packing. The three components work together to synergistically improve the system's strength, water repellency, and thermal insulation effect.

[0018] Secondly, this application provides a method for preparing a composite hydrophobic high-strength constant temperature anti-condensation slurry, comprising the following steps: mixing the raw materials of the first aspect to obtain dry powder, and mixing water and dry powder at a weight ratio of 0.35-0.40:1 to obtain slurry.

[0019] At this ratio, mixing for 3-5 minutes will form a uniform, viscous, and easy-to-apply paste.

[0020] Preferably, the premixed modification treatment of cenospheres and reinforcing fibers includes the following steps: cenospheres and reinforcing fibers are treated with silane respectively, then mixed and heated to react, and then cooled to obtain cenosphere-lignin fiber reinforced material.

[0021] Preferably, the cenospheres are treated with KH560, and the lignin fibers are treated with KH550.

[0022] Preferably, the lignocellulosic fiber reinforcing material is mixed with other components to obtain a dry powder, and the dry powder is mixed with water to obtain a slurry.

[0023] Lignin fiber, as a reinforcing material, is an important component for improving the crack resistance of materials. However, it contains a large number of hydrophilic groups. Uneven dispersion or excessive addition may result in the lignin fiber not being completely encapsulated, adsorbing and guiding water penetration, thus weakening the overall hydrophobic effect. The inventors further improved the solution by premixing and modifying cenospheres and lignin fiber. Epoxy-modified cenospheres can bond to the surface of amino-modified lignin fiber to obtain a cenosphere-lignin fiber reinforced material. The cenospheres have excellent flowability, and their filling of the perlite voids further carries the lignin fiber into the perlite voids, effectively shielding the lignin fiber and reducing its exposure and water absorption. Furthermore, this treatment method further improves the dispersion of lignin fiber, enabling better crack resistance in the overall material, thus optimizing the hydrophobic properties.

[0024] Thirdly, this application provides the application of the thermal insulation mortar in the field of building construction. The application includes a thermal insulation mortar layer formed by applying the mortar to a wall. The thickness of the mortar layer is 10-15 mm, preferably 11-13 mm, and more preferably 12 mm. The volumetric water absorption rate of the thermal insulation mortar can be reduced to below 5%, the dry density of the thermal insulation mortar layer is ≤300 kg / m³, the 28-day compressive strength can reach 0.7-0.9 MPa, and the thermal conductivity of the thermal insulation mortar layer is 0.045-0.060 W / (m·K).

[0025] In summary, this application has at least the following beneficial technical effects: This application utilizes a compound of hydrophobic perlite, calcium formate, silica fume, and cenospheres. The organic-inorganic hybrid network formed on the surface of the hydrophobic perlite not only provides hydrophobicity but also serves as a microscopic reinforcing skeleton, forming chemical bonds with cement hydration products and enhancing interfacial strength. The compound of silica fume and cenospheres achieves a "micron-nano" gradient filling, significantly reducing porosity and increasing density. Calcium formate enhances early strength, forming a time-series-connected and functionally complementary reinforcing network that ensures the slurry exhibits excellent and stable high-strength properties throughout its entire lifespan.

[0026] Traditional plastering mortars often dry out quickly and have short open times due to the water-absorbing properties of perlite, resulting in a poor application experience. The water-repellent lightweight aggregate used in this application, with its non-absorbent properties, makes the mortar smooth and easy to apply, with a long open time, significantly improving construction efficiency and plastering quality. Simultaneously, the introduction of calcium formate significantly accelerates early cement hydration, giving the mortar sufficient early strength, allowing for faster subsequent processes and effectively shortening the construction period.

[0027] This application achieves effective masking of lignin fibers in the slurry through premixing modification treatment with cenospheres and lignin fibers, reducing their exposure and water absorption, further improving the dispersion of lignin fibers, enabling better crack resistance in the overall material, and optimizing water repellency. Detailed Implementation

[0028] The present application will be further described in detail below through examples.

[0029] Silica fume has a particle size of 4μm and a SiO2 content of 95%; cenospheres have a particle size of 100μm and a bulk density of 720kg / m³. 3 Purity 96%; expanded perlite content 98%, density 1.7g / cm³ 3The particle size was 1 mm; the redispersible polymer powder was purchased from Langfang Qizhen Chemical; the cellulose ether was purchased from Shanghai Quanyan Biotechnology, and the hydroxypropyl methylcellulose had an effective content of 99%; the reinforcing fiber was purchased from Shandong Xingmao Engineering Materials Co., Ltd. All examples used lignin fibers, and the additive in the examples was polycarboxylate powder water-reducing agent, purchased from Hebei Kaqi Food Co., Ltd. (PCE). Other components were all conventional brands in the art or obtained through conventional processes. Example Example 1

[0030] Preparation of hydrophobic perlite: Step 1: Perlite pretreatment and activation: Uniform expanded perlite particles with a particle size of 1 mm are sprayed with a 3% NaOH solution for 18 minutes. The activated perlite is then dried in a 105℃ oven for 2 hours to remove physically adsorbed water and obtain activated perlite. Step 2: Pre-hydrolysis: Mix 45 parts by weight of 40% potassium methylsilicate solution, 8 parts by weight of silane coupling agent KH560, and 45 parts by weight of deionized water-ethanol mixed solvent (water:ethanol volume ratio 9:1). React in a reactor at 400 rpm for 45 min until the system changes from turbid to semi-transparent, obtaining siloxane pre-hydrolysis solution A. Disperse 12 parts by weight of nano-SiO2 (particle size 20 nm) in 35 parts by weight of deionized water and ultrasonically disperse for 30 min to obtain nano-SiO2 dispersion B. Slowly add solution B to solution A under high-speed stirring at 650 rpm, controlling the reaction temperature at 35℃. After the addition is complete, continue stirring and reacting for 3 h to obtain a composite hydrophobic solution. Step 3: Place the activated perlite in a pressure-bearing reactor, evacuate to below -0.095 MPa and maintain for 20 minutes to completely remove pore air. Inject the composite hydrophobic liquid prepared in Step 2 under vacuum, controlling the mass ratio of perlite to composite hydrophobic liquid to be 5:1. After restoring normal pressure, immediately fill the reactor with nitrogen to a pressure of 5 MPa and maintain the pressure for 15 minutes. Then depressurize. This "vacuum-pressurization-depressurization" cycle is repeated twice, that is, the process of evacuating, restoring normal pressure, pressurizing, and depressurizing is repeated. During this period, no more composite hydrophobic liquid is added.

[0031] Step 4: Place the product from Step 3 into an oven with an initial temperature of 40℃ and dry for 11 hours to slowly remove moisture. After initial drying, raise the temperature to 80℃ and dry for 7 hours. Finally, raise the temperature to 100℃ and dry for 3 hours to obtain hydrophobic perlite.

[0032] A composite hydrophobic high-strength constant temperature anti-condensation slurry, comprising (parts by weight): 35 parts of PO 42.5 cement, 8 parts of silica fume, 1 part of calcium formate, 30 parts of hydrophobic perlite, 12 parts of cenospheres, 4 parts of redispersible polymer powder, 0.5 parts of cellulose ether, 1 part of reinforcing fiber, and 0.5 parts of additives. Slurry preparation process: According to the formula, put cement, water-repellent perlite, cenospheres, and silica fume into a zero-gravity mixer and mix for 4 minutes until uniform. While stirring, add redispersible adhesive powder, cellulose ether, reinforcing fiber, calcium formate, and additives in sequence, and continue to dry mix for 6 minutes to ensure that each component is evenly distributed, thus obtaining thermal insulation mortar dry powder. When using, mix the above water and dry powder in a mixer at a water-cement ratio of 0.40:1 (by weight) for 4 minutes until a uniform, viscous, and easy-to-apply slurry is formed. Example 2

[0033] The difference between Example 2 and Example 1 lies in the component content, as follows: A composite hydrophobic high-strength constant temperature anti-condensation slurry, comprising (parts by weight): 38 parts of PO 42.5 cement, 10 parts of silica fume, 1.5 parts of calcium formate, 28 parts of hydrophobic perlite, 10 parts of cenospheres, 5 parts of redispersible polymer powder, 0.6 parts of cellulose ether, 1.2 parts of reinforcing fiber, and 0.5 parts of additives. Example 3

[0034] The difference between Example 3 and Example 1 is that the cenospheres and reinforcing fibers underwent premixing modification treatment. The specific slurry preparation process is as follows: Premixed modification treatment of celery beads and reinforcing fibers was carried out: celery beads were added to a 3% NaOH solution and stirred for 2 hours, then filtered, washed with water, and dried for later use. KH560 was added to an ethanol-water solution (water-ethanol volume ratio 9:1) to form a 3wt% solution. The pH was adjusted to 4.5 with acetic acid and stirred for 45 minutes to obtain a silane solution. Celery beads were then added to the solution and reacted at 65℃ for 2 hours. After filtration, washing with ethanol, and drying, KH560-treated celery beads were obtained. KH550 was added to an ethanol-water solution (water-ethanol volume ratio 9:1) to form a 3wt% solution. The pH was adjusted to 4.5 with acetic acid and stirred for 45 min to obtain a silane solution. Lignin fibers were then added and reacted at 65°C for 2 h. The mixture was filtered, washed with ethanol, and dried to obtain KH550-treated lignin fibers. The treated cenospheres and treated lignin fibers were added to 100 parts by weight of acetone, heated to 80°C and refluxed for 4 hours. The mixture was then filtered, washed with acetone, and dried to obtain cenosphere-lignin fiber reinforced material.

[0035] According to the formula, cement, water-repellent perlite, cenosphere-lignin fiber reinforcement material, and silica fume are put into a zero-gravity mixer and mixed for 4 minutes until uniform. While stirring, redispersible adhesive powder, cellulose ether, calcium formate, and additives are added in sequence, and dry-mixed for another 6 minutes to ensure that each component is evenly distributed, thus obtaining thermal insulation slurry dry powder. When using, water and the above dry powder are mixed in a mixer at a water-cement ratio of 0.40 (by weight) for 4 minutes until a uniform, viscous, and easy-to-apply slurry is formed.

[0036] Comparative Example 1 Comparative Example 1 replaced the hydrophobic perlite of Example 1 with an equal amount of ordinary expanded perlite; the formula is as follows: A composite hydrophobic high-strength constant temperature anti-condensation slurry, comprising (parts by weight): 35 parts PO 42.5 cement, 8 parts silica fume, 1 part calcium formate, 30 parts expanded perlite, 12 parts cenospheres, 4 parts redispersible polymer powder, 0.5 parts cellulose ether, 1 part reinforcing fiber, and 0.5 parts additives.

[0037] Comparative Example 2 Comparative Example 2 replaced the hydrophobic perlite of Example 1 with potassium methylsilicate-impregnated modified perlite. The specific difference was in step 2: pre-hydrolysis: 45 parts by weight of a 40% potassium methylsilicate solution and 45 parts by weight of a deionized water-ethanol mixed solvent (water:ethanol volume ratio 9:1) were mixed and reacted in a reactor at 400 rpm for 45 min to obtain pre-hydrolyzed solution A. 12 parts by weight of nano-SiO2 (particle size 20 nm) were dispersed in 35 parts by weight of deionized water and ultrasonically dispersed for 30 min to obtain nano-SiO2 dispersion B. Solution B was slowly added dropwise to solution A under high-speed stirring at 650 rpm, controlling the reaction temperature at 35°C. After the addition was complete, stirring and reaction continued for 3 h to obtain a composite hydrophobic solution. The recipe is as follows A composite hydrophobic high-strength constant temperature anti-condensation slurry, comprising (parts by weight): 35 parts of PO 42.5 cement, 8 parts of silica fume, 1 part of calcium formate, 30 parts of hydrophobic perlite, 12 parts of cenospheres, 4 parts of redispersible polymer powder, 0.5 parts of cellulose ether, 1 part of reinforcing fiber, and 0.5 parts of additives.

[0038] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is the removal of calcium formate and silica fume, and a corresponding increase in the amount of cement used; otherwise, they are the same as in Example 1. The formula is as follows: A composite hydrophobic high-strength constant temperature anti-condensation slurry, comprising (parts by weight): 44 parts of PO 42.5 cement, 30 parts of hydrophobic perlite, 12 parts of cenospheres, 4 parts of redispersible polymer powder, 0.5 parts of cellulose ether, 1 part of reinforcing fiber, and 0.5 parts of additives.

[0039] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the hydrophobic perlite was replaced with KH560 modified perlite; the specific difference lies in step 2: pre-hydrolysis: 8 parts by weight of silane coupling agent KH560 were mixed with 45 parts by weight of deionized water-ethanol mixed solvent (water:ethanol volume ratio 9:1), and reacted in a reactor at 400 rpm for 45 min to obtain siloxane pre-hydrolysis solution A; 12 parts by weight of nano-SiO2 (particle size 20 nm) were dispersed in 35 parts by weight of deionized water and ultrasonically dispersed for 30 min to obtain nano-SiO2 dispersion B. Under high-speed stirring at 650 rpm, solution B was slowly added dropwise to solution A, and the reaction temperature was controlled at 35°C. After the addition was complete, the reaction was continued for 3 h to obtain a composite hydrophobic solution; Comparative Example 5 Commercially available thermal insulation mortar has a water-cement ratio of 0.45.

[0040] Performance Testing: The performance testing items for the hydrophobic perlite-based composite thermal insulation mortar include compressive strength, thermal conductivity, and volumetric water absorption. Performance testing was conducted according to GB / T 20473-2021 "Building Thermal Insulation Mortar". Thermal conductivity was determined according to JGJ51-2002 "Technical Specification for Lightweight Aggregate Concrete". Specimens were naturally cured and dried to constant weight, and the thermal conductivity was measured using a thermal pulse method.

[0041] In this invention, the anti-condensation performance of the composite hydrophobic high-strength constant-temperature anti-condensation slurry is assessed using a programmable cooling platform (accuracy ±0.5℃) as the core temperature control unit, with an integrated thermally conductive ceramic coating on the surface to ensure temperature uniformity. The cooling platform is equipped with a PID temperature control module, which can stably maintain a temperature range of 0℃-5℃. A slurry sample is coated onto its surface and allowed to dry and solidify. The test environment is at a temperature of 25℃±1℃ and a humidity of 50%±5%. This method achieves the condensation effect through the temperature difference between the cooling platform and the ambient temperature, and the anti-condensation performance of the slurry is measured by the time it takes for condensation to cease on the surface of slurries with different formulations.

[0042] The performance test results of the examples and comparative examples are shown in Table 1.

[0043] Table 1 Performance Test Table performance Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Dry density (kg / m3) 285 295 281 290 305 310 303 305 Thermal conductivity, W / (m·K) 0.0480 0.0520 0.0450 0.0761 0.0682 0.0625 0.0671 0.0653 28-day compressive strength, MPa 0.82 0.88 0.89 0.45 0.65 0.58 0.68 0.50 Volumetric water absorption rate, % 5.2 4.8 4.7 32 12 7.5 10 18 Anti-condensation time, h 5 4 5 1 3 4 2 2 Analysis of the experimental examples and comparative examples shows that the strength, hydrophobicity, and anti-condensation effect of Examples 1-3 are all better than those of Comparative Examples 1-5. The volume water absorption rate of this application can be reduced to below 5% in 24 hours, the dry density is ≤300 kg / m³, the compressive strength in 28 days can reach 0.8-0.9 MPa, and the thermal conductivity is 0.045~0.060W / (m·k).

[0044] In Comparative Example 1, the volumetric water absorption rate of ordinary expanded perlite was as high as 32%, the lowest 28-day compressive strength was 0.45 MPa, and the anti-condensation time was only 1 hour. The porous structure of ordinary perlite became a channel for rapid water intrusion. After water intrusion, it not only significantly increased the thermal conductivity and reduced the insulation performance, but also formed internal stresses that could cause freeze-thaw damage in the pores, and significantly hindered cement hydration, resulting in a loose paste structure and low strength. This confirms that achieving self-hydrophobicity of the aggregate is a fundamental prerequisite for solving a series of problems. This invention, through hydrophobic perlite, cuts off the main channel for water transmission at the source.

[0045] Although the water absorption rate of sodium methylsilicate-impregnated perlite in Comparative Example 2 was better than that of ordinary perlite, it was far inferior to that of Example 1, and its 28-day strength was also significantly lower than that of Example 1. The bonding force between the sodium methylsilicate-impregnated film and the substrate was weak and easily damaged. The present invention uses sodium methylsilicate, KH560 and silica to form a hybrid network combined with an "in-situ hybridization-vacuum pressure impregnation" process. By venting the air in the pores through vacuum, pressure is applied to allow the hybrid sol to penetrate into the inner wall of each micropore, and then chemically bonded and cured to form a strong "bulk hydrophobic + interface-reinforced" structure.

[0046] Comparative Example 3, which did not use calcium formate or silica fume, had a 28-day strength of 0.58 MPa, indicating that both are crucial for early strength development and later densification. In this invention, calcium formate accelerates early hydration, while silica fume provides continuous reinforcement through the pozzolanic effect and micro-filling, forming a time-series-connected strength development system.

[0047] The water absorption rate and 28-day strength of the slurry prepared by KH560 impregnated perlite in Comparative Example 4 were also inferior to those of Example 1. Compared with Example 1, the hydrophobicity of KH560 impregnated perlite was deteriorated, the hybrid network bonding was weak, and the bonding with cement hydration products was deteriorated.

[0048] Compared with the commercially available product in Comparative Example 5, the composite hydrophobic high-strength constant temperature anti-condensation slurry of the present invention has increased compressive strength by more than 64%, reduced water absorption by more than 72%, reduced thermal conductivity by more than 26%, and has a longer anti-condensation time, achieving a synergistic breakthrough in high strength, low water absorption, and low thermal conductivity.

[0049] This invention not only achieves synergistic performance through formula compounding, but also realizes the transformation from "interfacial hydrophobicity" to "bulk phase hydrophobicity + reinforcement" through innovative preparation process of hydrophobic perlite. It successfully unifies the performance indicators of high strength, low water absorption, excellent thermal insulation and anti-condensation, and achieves a synergistic breakthrough in comprehensive performance, solving a long-standing pain point in the field of building insulation materials.

[0050] This invention is not limited to the specific details of the above embodiments. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of this invention, and all such modifications fall within the protection scope of this invention. Furthermore, it should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this invention will not describe the various possible combinations separately. Moreover, different embodiments of this invention can also be arbitrarily combined, as long as they do not violate the spirit of this invention, and should also be considered as part of the disclosure of this invention.

Claims

1. A composite hydrophobic high-strength constant-temperature anti-condensation slurry, characterized in that, The raw materials include the following parts by weight: 30-40 parts of PO 42.5 cement, 0.5-2 parts of calcium formate, 5-15 parts of active mineral admixture, 25-35 parts of hydrophobic perlite, 10-15 parts of cenospheres, 2-6 parts of redispersible polymer powder, 0.3-1 part of cellulose ether, 0.5-2 parts of reinforcing fiber, and 0.1-1 parts of additives; The hydrophobic perlite is obtained by preparing a composite hydrophobic liquid using potassium methylsilicate, silane coupling agent, and nano-SiO2, and then forming a hydrophobic film on the surface of the perlite.

2. The composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 1, characterized in that, The preparation process of the hydrophobic perlite includes: Step 1: Perlite pretreatment and activation: Perlite particles are sprayed with NaOH solution and then dried to obtain activated perlite for later use; Step 2: Pre-hydrolysis: Potassium methylsilicate silane, coupling agent KH560 and water-ethanol mixed solvent are mixed to obtain siloxane pre-hydrolysis solution A; nano SiO2 is dispersed in water to obtain nano SiO2 dispersion B; B is slowly added dropwise to A to obtain composite hydrophobic solution; Step 3: Place the activated perlite in the reactor and inject the composite hydrophobic liquid obtained in Step 2 under vacuum; then restore normal pressure, pressurize with nitrogen, and depressurize; continue the vacuum-pressurization-depressurization cycle 2-3 times to obtain the product; Step 4: The product from Step 3 is dried by gradient heating to obtain hydrophobic perlite.

3. The composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 2, characterized in that, Step 1 includes: perlite pretreatment and activation: uniform expanded perlite particles with a particle size of 0.5-1.5 mm are sprayed with a 2-5% NaOH solution for 15-20 minutes, and then dried in an oven at 100-110℃ for 1-3 hours to obtain activated perlite for later use.

4. The composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 2, characterized in that, Step 2 includes: pre-hydrolysis: 40-50 parts by weight of 40% potassium methylsilicate solution, 5-10 parts by weight of silane coupling agent KH560 and 40-50 parts by weight of aqueous ethanol mixed solvent are mixed and stirred at 300-500 rpm for 30-60 min to obtain siloxane pre-hydrolysis solution A; 10-15 parts by weight of nano-SiO2 are dispersed in 30-40 parts by weight of deionized water and ultrasonically dispersed for 20-40 min to obtain nano-SiO2 dispersion B; under stirring at 500-800 rpm, B is slowly added dropwise to A, and the reaction temperature is controlled at 30-40℃; after the addition is complete, the reaction is continued to be stirred for 2-4 h to obtain composite hydrophobic solution.

5. The composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 2, characterized in that, Step 3 includes: placing activated perlite in a reaction vessel, evacuating to below -0.095 MPa and maintaining the vacuum for 10-30 minutes, injecting the composite hydrophobic liquid obtained in step 2 under vacuum, and controlling the mass ratio of perlite to composite hydrophobic liquid to be 4-6:1; then restoring to normal pressure, immediately filling the vessel with nitrogen gas to a pressure of 0.4-0.6 MPa, maintaining the pressure for 10-20 minutes, and then depressurizing; continuing the vacuum-pressurization-depressurization cycle 2-3 times.

6. The composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 2, characterized in that, Step 4 includes: drying the product from step 3 at 35-45℃ for 10-12 hours, raising the temperature to 75-85℃ and drying for 6-8 hours, and continuing to raise the temperature to 95-105℃ and drying for 2-4 hours to obtain hydrophobic perlite.

7. The composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 1, characterized in that, The anti-condensation slurry meets one of the following conditions: 1) The active mineral admixture is selected from one or more of silica fume, fly ash, and slag powder, with a particle size of 3-5 μm; 2) The particle size of the cenospheres is 60-200μm; 3) The reinforcing fiber includes one or both of lignin fiber and polypropylene short fiber; 4) The additives include one or both of polycarboxylate powder water-reducing agent and polyacrylamide.

8. The method for preparing the composite hydrophobic high-strength constant-temperature anti-condensation slurry according to any one of claims 1-7, characterized in that, The process includes the following steps: mixing the components to obtain a dry powder, and mixing water and the dry powder at a weight ratio of 0.35-0.40:1 to obtain a slurry.

9. The preparation method of the composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 8, characterized in that, The premixed modification treatment of cenospheres and reinforcing fibers includes the following steps: cenospheres and reinforcing fibers are treated with silane respectively, then mixed and heated to react, and then cooled to obtain cenosphere-lignin fiber reinforced material.

10. The preparation method of the composite hydrophobic high-strength constant-temperature anti-condensation slurry according to claim 9, characterized in that, The cenosphere-lignin fiber reinforcing material and other components are mixed to obtain a dry powder, and the dry powder is mixed with water to obtain a slurry.