Putty for external wall thermal insulation and method for preparing the same

Abstract

The application belongs to the technical field of building thermal insulation materials, and particularly relates to putty for external wall thermal insulation and a preparation method thereof. The method comprises the following steps: 1) dosing; 2) pre-mixing nano aerogel, ceramic fiber, calcium sulfate whisker, basalt fiber and calcium stearate in proportion to prepare a composite powder after the dosing is completed; 3) uniformly dry mixing cement-based cementitious material, cellulose ether and water reducing agent, and then mixing the composite powder to prepare a base material; 4) slowly adding water to the base material, and continuously stirring to prepare a precursor; and 5) dynamically pre-aging the precursor, and then crushing and grinding the precursor into putty powder after the dynamic pre-aging. The application has the advantages that no curing agent is designed to reduce cracking and improve construction safety; a pre-aging process widens the adaptability of a construction environment, and significantly reduces the requirements for humidity and temperature; the microstructure is uniform, the thermal conductivity coefficient is low, and the mechanical properties are stable; the cost is controllable, and the application is suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of building insulation materials technology, specifically relating to a putty for exterior wall insulation and its preparation method. Background Technology

[0002] With the global trend of extreme climate change, building exterior wall insulation materials are facing increasingly severe environmental challenges.

[0003] In existing technologies, ordinary exterior wall insulation putty commonly suffers from problems such as a sharp decline in insulation performance, reduced mechanical strength, cracking, and peeling under extreme temperature (below -30 ℃ or above 70 ℃), high humidity, and salt spray corrosion environments. For example, traditional cement-based putty will suffer structural damage due to ice crystal expansion below -20 ℃, and the strength loss rate exceeds 40% after 50 freeze-thaw cycles; organic modified putty is prone to polymer chain breakage under long-term ultraviolet radiation, and its thermal conductivity can increase by more than 20% after 2000 hours of aging. These problems lead to high maintenance costs for exterior wall insulation putty.

[0004] Existing patented technologies, such as CN114933822A, improve water resistance and mildew resistance, but do not address extreme temperature adaptability. While aerogel composite putty possesses excellent thermal insulation properties, it loses its workability below -15°C. Therefore, developing an exterior wall insulation putty that can operate stably in a wide temperature range of -50 to 80°C while resisting extreme environmental erosion such as salt spray and high humidity has become a pressing technical problem. Summary of the Invention

[0005] The present invention addresses the problems of severe performance degradation and poor construction adaptability of existing exterior wall insulation putty under extreme temperatures, salt spray, ultraviolet radiation, and other environments, and provides a putty for exterior wall insulation and its preparation method.

[0006] The main objective of this invention is: I. To provide an exterior wall insulation putty that maintains excellent thermal insulation and mechanical stability within a wide temperature range of -50 to 80 ℃; II. Improve the durability of putty in extreme environments such as salt spray, high humidity, and ultraviolet radiation through component optimization and process innovation; Third, it achieves the workability and rapid curing of putty in low-temperature environments, overcoming the limitations of winter construction.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A method for preparing putty for exterior wall insulation. The method includes: 1) mixing the ingredients according to the following mass percentages: 45-55 wt% cementitious material, 5-10 wt% nano-aerogel, 3-5 wt% ceramic fiber, 2-4 wt% calcium sulfate whiskers, 1-3 wt% basalt fiber, 0.5-1.0 wt% calcium stearate, 0.3-0.5 wt% cellulose ether, 0.5-1.0 wt% water-reducing agent, with the balance being water.

[0009] 2) After the ingredients are prepared, nano-aerogel, ceramic fiber, calcium sulfate whiskers, basalt fiber and calcium stearate are premixed in proportion to form composite powder.

[0010] 3) After the cement-based cementitious material, cellulose ether and water-reducing agent are dry-mixed evenly, they are mixed with the composite powder to form a base material.

[0011] 4) Slowly add water to the substrate and continue stirring to prepare the precursor.

[0012] 5) The precursor is dynamically pre-aged, and then crushed and ground into putty powder.

[0013] As a preferred option Step 1) The nano-aerogel is a silica aerogel modified by secondary grafting with methyltrimethoxysilane; Step 1) The ceramic fibers are 3-6 mm in length and have an aspect ratio of 30-50; Step 1) The calcium sulfate whiskers are 50-100 μm in length and have an aspect ratio of 20-30; Step 1) The basalt fibers are 3-6 mm in length.

[0014] As a preferred option Step 1) The nano-aerogel is prepared by the following method: Silica aerogel and methyltrimethoxysilane were mixed evenly at a mass ratio of (8–12):1, dispersed in anhydrous ethanol, and reacted at 60–70 °C and pH 4–5 for 4–6 h. After washing and drying, a product with a specific surface area ≥600 m² was obtained. 2 / g.

[0015] As a preferred option Step 2) The premixed mixture is ultrasonically treated for 20 to 40 minutes at a temperature of 20 to 30 ℃, a fluctuation frequency of 40 to 50 kHz, and a power of 600 to 700 W.

[0016] As a preferred option Step 1) The cement-based cementitious material is a compound system of sulfoaluminate cement and silicate cement. The sulfoaluminate cement and silicate cement are mixed in a mass ratio of (3-4):6, and 1-2 wt% of nano-silica is added by mass of silicate cement.

[0017] As a preferred option Step 3) The prepared substrate is stirred for 5 to 10 minutes at a temperature of 15 to 25 ℃ and a rotation speed of 30 to 70 rpm.

[0018] As a preferred option Step 4) involves stirring for 10 to 20 minutes at a stirring temperature of 15–25 °C and a stirring speed of 300–500 rpm.

[0019] As a preferred option Step 5) The dynamic pre-aging is a gradient aging process, with the first stage aging at a temperature of -5 to 5 ℃ for 2 to 3 hours and the second stage aging at a temperature of 20 to 25 ℃ for 4 to 5 hours. Step 4) The crushing and grinding process results in a product with a mesh size of 240-300 mesh.

[0020] A type of putty used for exterior wall insulation.

[0021] The core of this invention lies in the comprehensive improvement of the thermal insulation putty in terms of thermal insulation performance, mechanical strength, construction adaptability and environmental durability by constructing a synergistic platform of methyltrimethoxysilane modified aerogel compatibility mediator system, nano-modified compound cementitious materials, ultrasonic premixed dynamic aging process and controllable fiber fracture technology.

[0022] The core of this scheme for modifying silica aerogel with methyltrimethoxysilane lies in constructing a bifunctional surface chemical environment to achieve molecular-level bridging of the organic-inorganic interface. The methyltrimethoxysilane molecule contains both a hydrophobic methyl group and a hydrolyzable methoxy group, making it an ideal surface modifier. During modification, methyltrimethoxysilane forms covalent bonds with the silanol groups on the aerogel surface through a hydrolysis-condensation reaction. The hydrolysis reaction first occurs under acidic or alkaline catalytic conditions, where the methoxy group reacts with water molecules to generate silanol groups and methanol. Subsequently, the newly generated silanol groups undergo condensation with the silanol groups on the aerogel surface, removing water molecules to form stable Si-O-Si covalent bonds. This chemical bonding not only ensures the stability of the modified layer but also constructs a high-density distribution of functional groups on the aerogel surface. The modified aerogel surface exhibits a gradient chemical environment: the outer layer is rich in methyl groups, providing hydrophobicity and compatibility with organic components; the inner layer retains some silanol groups, maintaining affinity for inorganic components. This gradient surface chemistry provides the molecular basis for the compatibility of multi-component systems, enabling aerogels to form effective interfacial bonds with both fiber fillers and inorganic cementing materials. The bifunctional groups on the aerogel surface achieve a directional molecular bridging effect. Methyl groups interact with the hydrophobic surface of the fiber filler through van der Waals forces, forming a physical adsorption layer. Although the individual bond energies are relatively low, the overall binding force is considerable due to the aerogel's large specific surface area. Silanol groups form hydrogen bonds and chemical bonds with hydration products such as calcium silicate gel and calcium hydroxide in the inorganic cementing material. Silanol groups act as hydrogen bond donors, forming a hydrogen bond network with oxygen atoms in the hydration products; simultaneously, under alkaline conditions, silanol groups may deprotonate, forming ionic or coordinate bonds with calcium ions. This multi-faceted interaction ensures a strong bond between the aerogel and the cementing matrix. The key to directional bridging lies in controlling molecular orientation. By adjusting the modification conditions and the dispersion state of the aerogel, functional groups can be arranged in an ordered manner at the interface, maximizing the efficiency of interfacial interactions. This molecular-level interfacial engineering significantly improves the compatibility and stability of multiphase systems.

[0023] Another important function of aerogels as compatibility mediators is to promote the uniform distribution of components at the microscale. The porous network structure of aerogels provides a dispersion carrier for other components. Fiber fillers can be partially embedded in the macropores of the aerogel, while fine particles of the cementitious material can fill the small and medium pores. This multi-scale spatial distribution avoids macroscopic separation and aggregation of components. The realization of synergistic distribution also relies on the regulatory effect of aerogel surface chemistry. Modified aerogels have differentiated affinities for different components, enabling selective adsorption and dispersion of specific components to form an ordered microstructure. This selective dispersion mechanism not only improves dispersion uniformity but also optimizes the spatial configuration of each component, allowing them to fully exert their respective functional characteristics. The formation of the fiber network, the hydration of the cementitious material, and the thermal insulation effect of the aerogel are organically unified at the microscale.

[0024] In this invention, the compounded cementitious material employs a synergistic ratio of sulfoaluminate cement and silicate cement, fully utilizing the complementary characteristics of the two cementitious materials. Sulfoaluminate cement is characterized by rapid hardening and early strength; its main mineral phases react rapidly in the early stages of hydration, generating ettringite and aluminum hydroxide gel, providing early strength to the system. Silicate cement, on the other hand, provides long-term strength development; the hydration of its tricalcium sulfate and dicalcium sulfate mineral phases produces calcium silicate gel, forming a dense cementitious structure. The synergistic hydration of the two cements follows a time-sequential reaction mechanism. In the early stages of hydration, sulfoaluminate cement dominates, rapidly consuming water and sulfate ions in the system, forming the initial structural framework. As the reaction progresses, silicate cement gradually participates in hydration; the formation of CSH gel fills and strengthens the initial structure, achieving a smooth transition from early strength to long-term strength. The optimization of the compounding ratio is based on hydration kinetics and strength development laws. By adjusting the mass ratio of sulfoaluminate to silicate (usually 3:7 to 4:6), the optimal balance between hydration rate and strength development can be achieved. Excessive sulfoaluminate content leads to excessively rapid hydration, affecting workability; too low a content fails to provide sufficient early strength. The introduction of nano-silica powder is based on its unique micro-filling effect and pozzolanic activity. Nano-silica particles can fill the tiny voids between cementitious material particles, increasing the packing density and compactness of the system. This micro-filling effect not only reduces porosity but also optimizes pore size distribution, transforming harmful macropores into harmless gel pores. The pozzolanic activity of nano-silica manifests in its secondary reaction with the hydration product calcium hydroxide. Under alkaline conditions, the silicon-oxygen bonds on the surface of nano-silica break, releasing silicate ions, which combine with calcium ions to form additional CSH gel. This secondary hydration reaction not only consumes calcium hydroxide that may lead to carbonization but also increases the total amount of cementitious products, improving the strength and durability of the matrix. Meanwhile, the improvement of aerogel encapsulation by nano-silica stems from its surface chemical properties. The abundant silanol groups on the surface of nano-silica have good chemical compatibility with the silanol groups on the surface of aerogel, which can form a hydrogen bond network, enhancing the encapsulation and protection of the aerogel by the gel matrix. This encapsulation effect prevents the aerogel from being damaged during construction and use, and maintains the long-term stability of its thermal insulation performance.

[0025] Nano-modified composite cementitious materials maintain good hydration activity even at low temperatures, mainly due to the nano-effect and the synergistic effect of the composite. The high specific surface area and surface energy of nano-silica provide additional nucleation sites for the hydration reaction, lowering the activation energy. At low temperatures, these nucleation sites promote the formation and crystallization of hydration products, maintaining the hydration reaction. The low-temperature adaptability of the composite system is also reflected in the reasonable distribution of hydration heat. The heat released by the rapid hydration of sulfoaluminate cement provides temperature compensation for the subsequent hydration of silicate cement, forming a self-heating effect. This endogenous heat helps maintain the system temperature and prevents the stagnation of the hydration reaction under low-temperature conditions. The improved low-temperature hydration performance is of great significance for construction adaptability. Under winter construction conditions, the modified cementitious materials can still maintain good fluidity and workability, and after curing, they can reach the design strength requirements, expanding the temperature window for construction.

[0026] Furthermore, in this invention, ultrasonic premixing technology utilizes the cavitation effect and mechanical vibration of ultrasound to achieve efficient dispersion and mixing of components. When ultrasound propagates in a liquid medium, it generates alternating compression and rarefaction waves. When the negative pressure of the rarefaction wave exceeds the cavitation threshold of the liquid, a large number of microbubbles are generated. These bubbles collapse rapidly under the action of the compression wave, generating localized high temperature and pressure and intense microjets, which strongly disperse particle aggregates. For lightweight porous materials such as aerogels, low-to-medium frequency ultrasound can effectively break up aggregates without damaging their internal structure. For dense particles such as nano-silica, higher ultrasonic intensity is required to overcome the van der Waals forces and electrostatic forces between particles. The mechanical action of ultrasound enhances the wetting of the liquid onto the solid surface, reduces interfacial tension, and is beneficial for the formation and stabilization of interfaces between components. This wetting enhancement effect is particularly important for improving the compatibility of hydrophobic aerogels with aqueous gelation systems.

[0027] Dynamic pre-aging technology, by controlling temperature, humidity, and time parameters, allows cementitious materials to complete partial hydration reactions and preliminary reorganization of their microstructure before formal construction. The key to this pretreatment process lies in precisely controlling the degree of hydration, achieving both pre-organization of the structure and maintaining sufficient workability. During pre-aging, hydration reactions begin on the surface of cementitious material particles, generating thin layers of hydration products. These initial hydration products act as "cementing agents," initially connecting the components into a network structure, improving the system's cohesion and stability. Simultaneously, aerogel particles are gradually encapsulated during this process, forming a protective layer to prevent damage during subsequent processing. The "dynamic" characteristic of dynamic aging is reflected in the periodic changes in temperature and humidity. By simulating temperature and humidity fluctuations in actual use environments, the material adapts to environmental changes during the pretreatment stage, improving its stability in practical applications. This environmental adaptability training significantly improves the material's crack resistance and long-term durability.

[0028] The synergistic effect of ultrasonic premixing and dynamic aging achieves rapid curing, with initial setting in 4–6 minutes and reaching the strength required for the next process in 4–6 hours. This rapid curing mechanism is based on the time-series optimization of the hydration reaction and the acceleration of structural development. The uniformly dispersed system formed during premixing provides ideal conditions for rapid hydration. The high dispersion of each component increases the reaction interface, shortens the ion diffusion distance, and accelerates the hydration reaction. The initial structure formed during pre-aging provides skeletal support for subsequent rapid strength development. Rapid curing also benefits from the fast-hardening characteristics of sulfoaluminate cement and the nucleation-promoting effect of nano-silica. Under optimized mix proportions and process conditions, these factors work synergistically to achieve the best match between hydration rate and strength development, ensuring both workability and meeting project deadlines.

[0029] In this invention, controlled fiber fracture technology involves the controlled mechanical treatment of long fibers during crushing and grinding, breaking them into short fibers with a high aspect ratio. This method offers unique advantages over directly using short fibers or nanofibers: it maintains the basic mechanical properties of the fibers, avoids performance loss due to excessive crushing, and effectively controls costs. Controlled fiber fracture is based on a precise match between mechanical force and fiber properties. Different types of fibers have different fracture characteristics and critical stresses. By adjusting grinding parameters, precise control over the fracture length and aspect ratio can be achieved. Too low an aspect ratio reduces the reinforcement effect, while too high an aspect ratio may affect dispersibility and workability. Controlled fracture technology optimizes fiber length distribution through multi-stage grinding and sieving, resulting in a fiber-reinforced system with optimal performance.

[0030] Short fibers, after controlled fracture treatment, form a three-dimensional network structure in the putty matrix. This network formation follows the principles of permeation theory and fiber orientation distribution. When the fiber content exceeds the permeation threshold, the fibers begin to contact and overlap, forming a continuous network structure. This network not only provides mechanical reinforcement but also effectively prevents crack propagation. The reinforcement mechanism of the fiber network includes load transfer, crack bridging, and energy dissipation. Load transfer is achieved through shearing at the fiber-matrix interface, dispersing concentrated stress over a larger area; crack bridging prevents crack propagation by allowing fibers to cross crack surfaces; and energy dissipation dissipates destructive energy through fiber pull-out and fracture. Compared to long fibers, short fiber networks exhibit better isotropy and dispersion uniformity. Long fibers tend to entangle during mixing, forming an oriented distribution and leading to anisotropy in performance. Short fibers, on the other hand, can be more uniformly distributed in the matrix, forming an isotropic reinforcing network and improving the overall performance stability of the material. Simultaneously, the fiber network enhances the cohesion of the putty primarily by increasing the toughness and ductility of the matrix. The presence of fibers alters the material's failure mode, transforming it from brittle fracture to ductile fracture. Under external force, the fibers first undergo elastic deformation, absorbing some strain energy. When the stress exceeds the fiber-matrix interface strength, interfacial debonding occurs, further consuming energy. Finally, the fibers are pulled out or break, achieving ultimate energy dissipation. Improved crack resistance not only prevents crack initiation but, more importantly, controls crack propagation. The fiber network breaks down large cracks into multiple microcracks, reducing stress concentration. The bridging effect of the fibers maintains a certain bonding force on the crack surface, preventing rapid crack propagation. This synergistic reinforcement effect allows the putty to maintain good integrity under drying shrinkage, temperature changes, and external forces, significantly improving its reliability and durability in practical applications.

[0031] In this invention, the material's performance stability across a wide temperature range of -50 to 80 °C stems from the synergistic effect of its multiphase composite structure. The ultra-low thermal conductivity of the aerogel provides excellent thermal insulation properties, reducing the impact of temperature gradients on the internal structure. The presence of the fiber network prevents temperature stress-induced cracking through stress dispersion and crack prevention mechanisms. Increased brittleness at low temperatures is a major challenge. This invention improves toughness while maintaining strength by optimizing the matrix formulation and fiber content. The micro-filling effect of nano-silica reduces defects in the matrix and lowers stress concentration; the porous structure of the aerogel provides space for thermal stress release; and the fiber network absorbs stress energy through deformation. At high temperatures, the material faces the risk of thermal decomposition and performance degradation. The high-temperature stability of the inorganic components provides fundamental protection, while the selection of organic components considers their thermal stability and decomposition temperature to ensure stability within the operating temperature range. In high-humidity environments, the material faces the challenge of moisture absorption expansion and strength loss. The hydrophobic modification of the aerogel significantly reduces its moisture adsorption, maintaining the stability of its thermal insulation performance. The densification of the cementitious matrix and the micro-filling effect of nano-silica reduce the water penetration path and improve impermeability. In salt spray environments, chloride ion corrosion is the main threat. The presence of sulfoaluminate in the compound cementitious material can combine with chloride ions to form Friedel salt, which solidifies chloride ions and reduces their corrosion of metal components such as steel bars. The pozzolanic reaction of nano-silica consumes calcium hydroxide that is susceptible to carbonization, improving the carbonization resistance of the matrix.

[0032] This invention achieves low-temperature construction adaptability by optimizing the low-temperature hydration and rheological properties of the cementitious material. The modified compound cementitious material maintains sufficient hydration activity at low temperatures, ensuring strength development. The use of thixotropic modifiers improves the scraping performance at low temperatures, reducing construction difficulty. Rapid curing capability allows the material to meet tight construction schedules, improving construction efficiency. The stability of construction performance is also reflected in its adaptability to environmental changes. The material maintains consistent construction performance under different temperature and humidity conditions, reducing quality fluctuations caused by environmental changes and improving the controllability and reliability of construction.

[0033] The advantages of this invention are: the curing agent-free design reduces cracking and improves construction safety; the pre-aging process broadens the adaptability to the construction environment and significantly reduces the requirements for humidity and temperature; the microstructure is uniform, the thermal conductivity is low, and the mechanical properties are stable; the cost is controllable and it is suitable for large-scale promotion and application. Detailed Implementation

[0034] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0035] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0036] Example 1: A putty for exterior wall insulation, comprising the following components:

[0037] The preparation method of the putty includes: 1) mixing silica aerogel and methyltrimethoxysilane at a mass ratio of 8:1, dispersing them in anhydrous ethanol, reacting at 60 ℃ and pH 4 for 6 h, and obtaining the putty after washing and drying, with a specific surface area ≥600 m². 2 / g, to prepare nano-aerogels.

[0038] 2) Premix nano-aerogel, ceramic fiber, calcium sulfate whiskers, basalt fiber and calcium stearate according to the proportions in the table above, and ultrasonically treat them for 40 min at a temperature of 20 ℃, a fluctuation frequency of 40 kHz and a power of 600 W to prepare composite powder.

[0039] 3) After dry mixing the cement-based cementitious material, cellulose ether, and water-reducing agent according to the proportions in the table above, mix them with the composite powder and stir for 10 minutes at a temperature of 15 ℃ and a speed of 30 rpm to form a base material. The cement-based cementitious material is a mixture of sulfoaluminate cement and silicate cement in a mass ratio of 3:6, with 1 wt% of nano silica added to the silicate cement.

[0040] 4) Slowly add water to the substrate according to the proportions in the table above, and stir for 20 minutes at a temperature of 15 ℃ and a speed of 300 rpm to prepare the precursor.

[0041] 5) The precursor is dynamically aged. The first stage is aged for 3 hours at -5 ℃, and the second stage is aged for 5 hours at 20 ℃. After dynamic pre-aging, it is crushed and ground to make the product with a mesh size of 240 mesh, and putty powder is made.

[0042] The materials prepared in the examples were subjected to performance testing. Before the performance testing, the putty powder prepared in this example was mixed with deionized water at a ratio of 100:28 to form a putty paste. The specific characterization results are as follows.

[0043] Thermal insulation performance testing: Referring to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials", the steady-state heat flow method was used to evaluate the thermal insulation performance of the materials. Sample preparation: Putty paste was poured into a 300 mm × 300 mm × 30 mm standard mold, smoothed, and cured before drying to constant weight. Testing: The thermal conductivity was measured using a DRPL-III type flat plate thermal conductivity meter at an average temperature of 25 ℃. Simultaneously, the dry density parameter was calculated using the ratio of the dry mass to the volume of the sample.

[0044] Mechanical property testing: Referring to the strength test section of the dynamic crack resistance test in JG / T 157-2009 "Putty for Building Exterior Walls" standard, the compressive strength, flexural strength, and compressive-flexural ratio of the material were evaluated using the standard specimen method. Specimen preparation: Putty paste was injected into a 40 mm × 40 mm × 160 mm triple metal mold for standard forming. Mechanical property testing was conducted using an INSTRON 3365 universal testing machine at a constant loading rate of 2.0 mm / min. Compressive strength and flexural strength were calculated separately according to the corresponding standard methods, and the compressive-flexural ratio was obtained by the ratio of compressive strength to flexural strength.

[0045] Freeze-thaw cycle testing: Referring to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the rapid freeze-thaw method was used to evaluate the durability of materials under alternating temperature environments. Standard test blocks of the same specifications as those used for mechanical properties were used. After curing for 28 days, they were immersed in water for 48 hours to reach saturation, and then placed in a TDR-1 type freeze-thaw test chamber for cyclic testing. Each freeze-thaw cycle included two stages: freezing at -20±2 ℃ for 4 hours and thawing in water at 20±2 ℃ for 4 hours. After 100 cycles, the test blocks were removed, the surface moisture was wiped off, and the compressive strength was measured. The strength retention rate was calculated as (compressive strength after freeze-thaw / compressive strength before freeze-thaw) × 100%.

[0046] Salt spray resistance testing: Referring to GB / T 1771-2007 "Determination of resistance to neutral salt spray in paints and varnishes", the neutral salt spray corrosion method was used to evaluate the corrosion resistance of materials in a marine environment. Sample preparation: Putty paste was applied to a 70mm × 150mm × 4mm asbestos cement board substrate. After curing, all surfaces except the test surface were sealed with epoxy resin to prevent edge effects. Testing: The sample was placed in a YWX-750 salt spray test chamber and continuously sprayed with a 5% (w / w) NaCl solution for 500 hours at a constant temperature of 35±2℃ to simulate a marine atmospheric corrosion environment. After the test, the sample surface was rinsed with deionized water to remove salt and dried to constant weight. The weight loss rate was calculated as [(mass before test - mass after test) / mass before test] × 100%.

[0047] UV resistance testing: Referring to GB / T 1865-2009 "Artificial Climate Aging and Artificial Radiation Exposure of Paints and Varnishes", the durability of materials under ultraviolet radiation was evaluated using the xenon lamp accelerated aging method. Test samples of the same specifications as those used for salt spray resistance were placed in a xenon lamp aging test chamber for accelerated aging. The test conditions were set at an irradiance of 0.51 W / m². 2 The temperature was set at 340 nm, blackboard temperature at 65±3 ℃, chamber temperature at 38±3 ℃, and relative humidity at 50±5%. Natural rainfall was simulated by spraying water for 18 minutes every 120 minutes. After 2000 hours of continuous aging, the change in thermal conductivity of the samples was measured. The rate of change in thermal conductivity was calculated as [(thermal conductivity after aging - thermal conductivity before aging) / thermal conductivity before aging] × 100%.

[0048]

[0049] Based on the above characterization results, this solution achieves a balance between thermal insulation, mechanical strength and environmental durability through component optimization and process innovation, thus meeting the long-term use requirements of external wall insulation materials under complex climatic conditions.

[0050] The performance test results of Example 1 show that the prepared putty material exhibits excellent comprehensive performance. Regarding thermal insulation performance, the dry density is 285.5 kg / m³. 3The thermal conductivity is as low as 0.037 W / (m·K), mainly due to the highly efficient thermal insulation properties of nano-aerogel and the uniform dispersion structure of the composite powder, which is significantly better than the thermal conductivity of traditional external wall insulation materials. In mechanical performance testing, the compressive strength reaches 12.8 MPa, the flexural strength is 4.9 MPa, and the compression-to-flexural ratio is as low as 2.61, which meets the requirement of JG / T 157-2009 standard for flexible putty with a compression-to-flexural ratio ≤3.0. This mechanical property originates from the three-dimensional network structure formed by controllable fracture fibers: the synergistic effect of ceramic fibers, calcium sulfate whiskers, and basalt fibers effectively transfers loads and bridges microcracks, while calcium stearate and cellulose ether optimize the interfacial bonding strength.

[0051] The durability test results are outstanding: after 100 freeze-thaw cycles, the strength retention rate reached 93.3%, indicating that the dynamic aging process significantly improves the structural stability of the material under alternating temperature environments. The weight loss rate in the salt spray test was only 1.1%, verifying the synergistic anti-corrosion mechanism of chloride ions (generating Friedel's salt) from sulfoaluminate cement curing and the filling effect of nano-silica. After 2000 hours of accelerated UV aging, the change rate of thermal conductivity was only +3.2%, indicating that the hydrophobically modified nano-aerogel and fiber network effectively inhibit UV-induced material degradation.

[0052] In addition, construction performance was tested under low-temperature construction conditions. A customized method was used to simulate actual working conditions to evaluate the material's adaptability to construction and early strength in low-temperature environments. Construction performance tests were conducted in an environmental chamber at -15±1 ℃ and relative humidity less than 85%. 500 g of putty paste was placed on a scraper, and the changes in workability were observed over 5 minutes. The criteria for good construction performance were that the paste was soft, easy to apply, and free of curling, excluding adverse construction phenomena such as skinning and hardening. Low-temperature curing strength tests were conducted under the same low-temperature environment. Putty was injected into a standard 40 mm × 40 mm × 160 mm mold, smoothed, and allowed to stand for 24 hours before demolding. The flexural strength was immediately measured using a universal testing machine. The curing strength achievement rate was obtained by calculating the ratio of the 24-hour low-temperature curing strength to the flexural strength of the standard 28-day curing specimen. Specific characterization results are as follows:

[0053] Example 2: A putty for exterior wall insulation, comprising the following components:

[0054] The preparation method of the putty includes: 1) mixing silica aerogel and methyltrimethoxysilane at a mass ratio of 10:1, dispersing them in anhydrous ethanol, reacting at 65 ℃ and pH 4.5 for 5 h, and obtaining the putty after washing and drying, with a specific surface area ≥600 m². 2 / g, to prepare nano-aerogels.

[0055] 2) Premix nano-aerogel, ceramic fiber, calcium sulfate whiskers, basalt fiber and calcium stearate according to the proportions in the table above, and ultrasonically treat them for 30 min at a temperature of 25 ℃, a fluctuation frequency of 45 kHz and a power of 650 W to prepare composite powder.

[0056] 3) After dry mixing the cement-based cementitious material, cellulose ether, and water-reducing agent according to the proportions in the table above, mix them with the composite powder and stir for 7 minutes at a temperature of 20 ℃ and a speed of 50 rpm to form a base material. The cement-based cementitious material is a mixture of sulfoaluminate cement and silicate cement in a mass ratio of 3.5:6, with 1.5 wt% of nano silica added to the silicate cement.

[0057] 4) Slowly add water to the substrate according to the proportions in the table above, and stir for 15 minutes at a temperature of 20 ℃ and a speed of 400 rpm to prepare the precursor.

[0058] 5) The precursor is dynamically aged. The first stage is aged at 0 ℃ for 2.5 h, and the second stage is aged at 23 ℃ for 4.5 h. After dynamic pre-aging, it is crushed and ground to make the product with a mesh size of 270 mesh, and putty powder is made.

[0059] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0060] Thermal insulation performance testing: Referring to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials", the steady-state heat flow method was used to evaluate the thermal insulation performance of the materials. Sample preparation: Putty paste was poured into a 300 mm × 300 mm × 30 mm standard mold, smoothed, and cured before drying to constant weight. Testing: The thermal conductivity was measured using a DRPL-III type flat plate thermal conductivity meter at an average temperature of 25 ℃. Simultaneously, the dry density parameter was calculated using the ratio of the dry mass to the volume of the sample.

[0061] Mechanical property testing: Referring to the strength test section of the dynamic crack resistance test in JG / T 157-2009 "Putty for Building Exterior Walls" standard, the compressive strength, flexural strength, and compressive-flexural ratio of the material were evaluated using the standard specimen method. Specimen preparation: Putty paste was injected into a 40 mm × 40 mm × 160 mm triple metal mold for standard forming. Mechanical property testing was conducted using an INSTRON 3365 universal testing machine at a constant loading rate of 2.0 mm / min. Compressive strength and flexural strength were calculated separately according to the corresponding standard methods, and the compressive-flexural ratio was obtained by the ratio of compressive strength to flexural strength.

[0062] Freeze-thaw cycle testing: Referring to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the rapid freeze-thaw method was used to evaluate the durability of materials under alternating temperature environments. Standard test blocks of the same specifications as those used for mechanical properties were used. After curing for 28 days, they were immersed in water for 48 hours to reach saturation, and then placed in a TDR-1 type freeze-thaw test chamber for cyclic testing. Each freeze-thaw cycle included two stages: freezing at -20±2 ℃ for 4 hours and thawing in water at 20±2 ℃ for 4 hours. After 100 cycles, the test blocks were removed, the surface moisture was wiped off, and the compressive strength was measured. The strength retention rate was calculated as (compressive strength after freeze-thaw / compressive strength before freeze-thaw) × 100%.

[0063] Salt spray resistance testing: Referring to GB / T 1771-2007 "Determination of resistance to neutral salt spray in paints and varnishes", the neutral salt spray corrosion method was used to evaluate the corrosion resistance of materials in a marine environment. Sample preparation: Putty paste was applied to a 70mm × 150mm × 4mm asbestos cement board substrate. After curing, all surfaces except the test surface were sealed with epoxy resin to prevent edge effects. Testing: The sample was placed in a YWX-750 salt spray test chamber and continuously sprayed with a 5% (w / w) NaCl solution for 500 hours at a constant temperature of 35±2℃ to simulate a marine atmospheric corrosion environment. After the test, the sample surface was rinsed with deionized water to remove salt and dried to constant weight. The weight loss rate was calculated as [(mass before test - mass after test) / mass before test] × 100%.

[0064] UV resistance testing: Referring to GB / T 1865-2009 "Artificial Climate Aging and Artificial Radiation Exposure of Paints and Varnishes", the durability of materials under ultraviolet radiation was evaluated using the xenon lamp accelerated aging method. Test samples of the same specifications as those used for salt spray resistance were placed in a xenon lamp aging test chamber for accelerated aging. The test conditions were set at an irradiance of 0.51 W / m². 2 The temperature was set at 340 nm, blackboard temperature at 65±3 ℃, chamber temperature at 38±3 ℃, and relative humidity at 50±5%. Natural rainfall was simulated by spraying water for 18 minutes every 120 minutes. After 2000 hours of continuous aging, the change in thermal conductivity of the samples was measured. The rate of change in thermal conductivity was calculated as [(thermal conductivity after aging - thermal conductivity before aging) / thermal conductivity before aging] × 100%.

[0065]

[0066] Analyzing the above characterization results, this solution, through component ratio adjustment and process optimization, further improves mechanical strength and environmental durability while maintaining excellent thermal insulation performance. Regarding thermal insulation performance, the dry density is 288.9 kg / m³. 3The thermal conductivity of 0.035 W / (m·K) indicates that the material maintains low thermal conductivity, which is attributed to the more complete closed-pore structure formed by the methyltrimethoxysilane-modified nanoaerogel, with a specific surface area ≥600 m². 2 The / g characteristic significantly blocks heat radiation transfer. In mechanical property tests, the compressive strength of 13.5 MPa and the flexural strength of 5.2 MPa were increased by 5.5% and 6.1% respectively compared with Example 1, and the compression-flexural ratio was reduced to 2.60. This is due to the ultrasonic treatment process making the fiber-powder interface more tightly bonded, effectively improving the load transfer efficiency.

[0067] Its durability is particularly outstanding: the freeze-thaw cycle strength retention rate reaches 95.4%, proving that the two-stage dynamic aging process significantly enhances the material's freeze-thaw resistance by regulating the crystal morphology of hydration products; the salt spray weight loss rate is only 0.9%, reflecting the dual anti-corrosion mechanism of the sulfoaluminate cement's ability to solidify chloride ions and the filling of capillary pores by nano-silica; the change rate of thermal conductivity after UV aging is +2.9%, the best in the series, confirming that the hydrophobically modified aerogel maintains a stable pore structure under xenon lamp radiation, and its 7% mass fraction addition forms an effective UV barrier. Therefore, while ensuring ultra-low thermal conductivity, the comprehensive performance indicators of this formula meet the requirements of exterior wall insulation projects in harsh climate zones.

[0068] In addition, construction performance was tested under low-temperature construction conditions. A customized method was used to simulate actual working conditions to evaluate the material's adaptability to construction and early strength in low-temperature environments. Construction performance tests were conducted in an environmental chamber at -15±1 ℃ and relative humidity less than 85%. 500 g of putty paste was placed on a scraper, and the changes in workability were observed over 5 minutes. The criteria for good construction performance were that the paste was soft, easy to apply, and free of curling, excluding adverse construction phenomena such as skinning and hardening. Low-temperature curing strength tests were conducted under the same low-temperature environment. Putty was injected into a standard 40 mm × 40 mm × 160 mm mold, smoothed, and allowed to stand for 24 hours before demolding. The flexural strength was immediately measured using a universal testing machine. The curing strength achievement rate was obtained by calculating the ratio of the 24-hour low-temperature curing strength to the flexural strength of the standard 28-day curing specimen. Specific characterization results are as follows:

[0069] Example 3: A putty for exterior wall insulation, comprising the following components:

[0070] The preparation method of the putty includes: 1) mixing silica aerogel and methyltrimethoxysilane at a mass ratio of 12:1, dispersing them in anhydrous ethanol, reacting at 70 ℃ and pH 5 for 4 h, and obtaining the putty after washing and drying, with a specific surface area ≥600 m². 2 / g, to prepare nano-aerogels.

[0071] 2) Premix nano-aerogel, ceramic fiber, calcium sulfate whiskers, basalt fiber and calcium stearate according to the proportions in the table above, and sonicate them for 20 min at a temperature of 30 ℃, a fluctuation frequency of 50 kHz and a power of 700 W to prepare composite powder.

[0072] 3) After dry mixing the cement-based cementitious material, cellulose ether, and water-reducing agent according to the proportions in the table above, mix them with the composite powder and stir for 5 minutes at a temperature of 25 ℃ and a speed of 70 rpm to form a base material. The cement-based cementitious material is a mixture of sulfoaluminate cement and silicate cement in a mass ratio of 4:6, with 2 wt% nano silica added to the silicate cement.

[0073] 4) Slowly add water to the substrate according to the proportions in the table above, and stir for 10 minutes at a temperature of 25 ℃ and a speed of 500 rpm to prepare the precursor.

[0074] 5) The precursor is dynamically aged. The first stage is aged at 5 ℃ for 2 h, and the second stage is aged at 25 ℃ for 4 h. After dynamic pre-aging, it is crushed and ground to make the product with a mesh size of 300 mesh, and putty powder is made.

[0075] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0076] Thermal insulation performance testing: Referring to GB / T 10294-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials", the steady-state heat flow method was used to evaluate the thermal insulation performance of the materials. Sample preparation: Putty paste was poured into a 300 mm × 300 mm × 30 mm standard mold, smoothed, and cured before drying to constant weight. Testing: The thermal conductivity was measured using a DRPL-III type flat plate thermal conductivity meter at an average temperature of 25 ℃. Simultaneously, the dry density parameter was calculated using the ratio of the dry mass to the volume of the sample.

[0077] Mechanical property testing: Referring to the strength test section of the dynamic crack resistance test in JG / T 157-2009 "Putty for Building Exterior Walls" standard, the compressive strength, flexural strength, and compressive-flexural ratio of the material were evaluated using the standard specimen method. Specimen preparation: Putty paste was injected into a 40 mm × 40 mm × 160 mm triple metal mold for standard forming. Mechanical property testing was conducted using an INSTRON 3365 universal testing machine at a constant loading rate of 2.0 mm / min. Compressive strength and flexural strength were calculated separately according to the corresponding standard methods, and the compressive-flexural ratio was obtained by the ratio of compressive strength to flexural strength.

[0078] Freeze-thaw cycle testing: Referring to GB / T 50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the rapid freeze-thaw method was used to evaluate the durability of materials under alternating temperature environments. Standard test blocks of the same specifications as those used for mechanical properties were used. After curing for 28 days, they were immersed in water for 48 hours to reach saturation, and then placed in a TDR-1 type freeze-thaw test chamber for cyclic testing. Each freeze-thaw cycle included two stages: freezing at -20±2 ℃ for 4 hours and thawing in water at 20±2 ℃ for 4 hours. After 100 cycles, the test blocks were removed, the surface moisture was wiped off, and the compressive strength was measured. The strength retention rate was calculated as (compressive strength after freeze-thaw / compressive strength before freeze-thaw) × 100%.

[0079] Salt spray resistance testing: Referring to GB / T 1771-2007 "Determination of resistance to neutral salt spray in paints and varnishes", the neutral salt spray corrosion method was used to evaluate the corrosion resistance of materials in a marine environment. Sample preparation: Putty paste was applied to a 70mm × 150mm × 4mm asbestos cement board substrate. After curing, all surfaces except the test surface were sealed with epoxy resin to prevent edge effects. Testing: The sample was placed in a YWX-750 salt spray test chamber and continuously sprayed with a 5% (w / w) NaCl solution for 500 hours at a constant temperature of 35±2℃ to simulate a marine atmospheric corrosion environment. After the test, the sample surface was rinsed with deionized water to remove salt and dried to constant weight. The weight loss rate was calculated as [(mass before test - mass after test) / mass before test] × 100%.

[0080] UV resistance testing: Referring to GB / T 1865-2009 "Artificial Climate Aging and Artificial Radiation Exposure of Paints and Varnishes", the durability of materials under ultraviolet radiation was evaluated using the xenon lamp accelerated aging method. Test samples of the same specifications as those used for salt spray resistance were placed in a xenon lamp aging test chamber for accelerated aging. The test conditions were set at an irradiance of 0.51 W / m². 2 The temperature was set at 340 nm, blackboard temperature at 65±3 ℃, chamber temperature at 38±3 ℃, and relative humidity at 50±5%. Natural rainfall was simulated by spraying water for 18 minutes every 120 minutes. After 2000 hours of continuous aging, the change in thermal conductivity of the samples was measured. The rate of change in thermal conductivity was calculated as [(thermal conductivity after aging - thermal conductivity before aging) / thermal conductivity before aging] × 100%.

[0081]

[0082] Analyzing the above characterization results, this solution, through component ratio adjustment and process optimization, further improves mechanical strength and environmental durability while maintaining excellent thermal insulation performance. Regarding thermal insulation performance, the dry density is 293.0 kg / m³. 3The thermal conductivity of 0.039 W / (m·K) indicates that the material maintains good low thermal conductivity, mainly attributed to the closed-pore structure formed by the nano-aerogel effectively blocking heat transfer. In mechanical property testing, the compressive strength of 14.3 MPa and the flexural strength of 5.4 MPa are both improved compared to Example 2, with a compression-to-flexural ratio of 2.65, indicating that the material exhibits a good balance of toughness under load. This is attributed to the ultrasonic treatment process optimizing the interfacial bonding strength between the fibers and the powder.

[0083] In terms of durability: the freeze-thaw cycle strength retention rate reached 91.7%, proving that the two-stage dynamic aging process effectively enhances the stability of the internal structure of the material, enabling it to maintain high strength under repeated freeze-thaw conditions; the salt spray weight loss rate was 1.3%, reflecting the synergistic resistance of the sulfoaluminate cement matrix and nano-silica filler to chloride ion corrosion; the change rate of thermal conductivity after UV aging was +3.8%, confirming that the hydrophobic modified aerogel has good structural stability under long-term UV irradiation, effectively blocking the negative impact of UV radiation on the material's thermal insulation performance.

[0084] In addition, construction performance was tested under low-temperature construction conditions. A customized method was used to simulate actual working conditions to evaluate the material's adaptability to construction and early strength in low-temperature environments. Construction performance tests were conducted in an environmental chamber at -15±1 ℃ and relative humidity less than 85%. 500 g of putty paste was placed on a scraper, and the changes in workability were observed over 5 minutes. The criteria for good construction performance were that the paste was soft, easy to apply, and free of curling, excluding adverse construction phenomena such as skinning and hardening. Low-temperature curing strength tests were conducted under the same low-temperature environment. Putty was injected into a standard 40 mm × 40 mm × 160 mm mold, smoothed, and allowed to stand for 24 hours before demolding. The flexural strength was immediately measured using a universal testing machine. The curing strength achievement rate was obtained by calculating the ratio of the 24-hour low-temperature curing strength to the flexural strength of the standard 28-day curing specimen. Specific characterization results are as follows:

[0085] Comparative Example 1: Based on Example 2, this example only modifies the preparation of the nano-aerogel; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0086] The performance testing method for the comparative product was completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below:

[0087] Analysis of the characterization results showed that group D1-1, using unmodified silica aerogel, exhibited a thermal conductivity increase to 0.046 W / (m·K), decreased strength retention after freeze-thaw cycles, and significant gaps in the interfacial bonding, along with aerogel aggregation. This is attributed to the high hydroxyl activity on the surface of the unmodified aerogel, which readily interacts with moisture during mixing and hydration, leading to self-aggregation between aerogel particles, disrupting the integrity of the closed-cell structure, reducing thermal insulation performance, and simultaneously forming weak interfacial regions with the fibers and matrix, thus weakening freeze-thaw resistance.

[0088] Group D1-2 used aerogels modified with common silane coupling agents, with a thermal conductivity of 0.041 W / (m·K) and a strength retention rate of 85.2% after freeze-thaw cycles. However, some areas showed poor interfacial bonding. This indicates that while common silane coupling agents can improve aerogel dispersibility to some extent, their hydrolytic stability and compatibility with the substrate are inferior to methyltrimethoxysilane. The modified layer is prone to partial failure under dynamic aging or hydration conditions, resulting in slightly poorer stability of the closed-cell structure, insufficient interfacial bonding strength, and lower thermal insulation and durability performance compared to Example 2.

[0089] Groups D1-3, which did not use nano-aerogels, exhibited a significant deterioration in thermal conductivity to 0.089 W / (m·K), a substantial decrease in strength retention after freeze-thaw cycles, and a porous microstructure with exposed fibers. This clearly demonstrates that nano-aerogels are crucial for constructing an efficient thermal insulation network in this system; their absence leads to a sharp decline in the material's thermal resistance. Simultaneously, the aerogel's bridging effect on microcracks and its ability to optimize pore structure are lost, making the material susceptible to structural damage due to moisture intrusion and ice crystal pressure during freeze-thaw cycles, resulting in severely compromised mechanical properties and durability.

[0090] Comparative Example 2: Based on Example 2, this example only modifies the preparation process of the cement-based gel material; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0091] The performance testing method for the comparative product was completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below:

[0092] Analysis of the characterization results shows that group D2-1, using ordinary Portland cement, exhibited a significant decrease in compressive strength to 10.2 MPa, with a low-temperature curing strength achievement rate of only 58.2%. The microstructure was loose and the aerogel encapsulation was poor. This is mainly attributed to the substantial slowdown in the early hydration rate of ordinary Portland cement at low temperatures, resulting in insufficient hydration product formation. This inadequate encapsulation and fixation of the nano-aerogel and other reinforcing components leads to a loose overall material structure, slow strength development, and severely impacts early strength achievement and final mechanical properties after low-temperature construction.

[0093] Group D2-2 used only sulfoaluminate cement, achieving a compressive strength of 11.8 MPa and a low-temperature curing strength attainment rate of 75.1%. However, localized microcracks were observed in the microstructure. This indicates that although sulfoaluminate cement has high early hydration activity, which helps improve low-temperature curing performance, its sole use leads to significant system shrinkage. Under drying or stress, it is prone to microcracks, weakening the material's integrity and strength performance.

[0094] Group D2-3 used a blend of sulfoaluminate cement and silicate cement, but without the addition of nano-silica. Its compressive strength was 12.1 MPa, and the low-temperature curing strength achievement rate was 70.6%. The microstructure showed uneven aerogel dispersion and agglomeration. This confirms the crucial role of nano-silica: as a nanoscale filler, it not only effectively fills the voids between cement particles and refines the pore structure to improve density, but also acts as a nucleus to promote hydration reactions, particularly significantly improving the dispersion stability of the nano-aerogel in the matrix. The absence of nano-silica leads to agglomeration of aerogel particles during mixing, preventing the formation of a uniformly distributed insulating network and reducing the matrix's encapsulation and bonding strength with the aerogel, thus affecting the material's mechanical properties and low-temperature curing efficiency.

[0095] The results of Comparative Example 2 fully verify the necessity of the cement-based cementitious material formulation used in Example 2: This combination not only utilizes the early strength characteristics of sulfoaluminate cement and the later stability of silicate cement by compounding cement, but also optimizes the matrix density, hydration process and dispersion and interfacial bonding of key functional components by adding nano-silica, thereby synergistically ensuring the excellent comprehensive performance of the material, especially the key low-temperature curing ability.

[0096] Comparative Example 3: Based on Example 2, this example only modifies the dynamic aging process; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0097] The performance testing method for the comparative product was completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below:

[0098] Analysis of the above characterization results shows that in group D3-1, the elimination of the pre-aging process and direct grinding resulted in a significantly prolonged curing time (>20 min), a substantial decrease in the low-temperature strength achievement rate, poor surface smoothness, and a shortened construction open time to 15 min. This is attributed to the absence of a pre-aging stage, which disrupts the uniformity of the hydration reaction within the material, leading to a loose microstructure that cannot form an effective support network, resulting in delayed curing, insufficient strength development, and deteriorated workability.

[0099] Group D3-2 underwent single-stage aging, with a curing time of 8 minutes, a low-temperature strength achievement rate of 65.6%, average surface smoothness, and a construction open time of 30 minutes, all of which were inferior to Example 2. This indicates that single-stage aging cannot simulate temperature gradient changes, resulting in insufficient hydration reaction, reduced matrix density, and impact on the early strength development and construction stability of the material.

[0100] Group D3-3 had its grinding mesh adjusted to 180 mesh, a curing time of 6 minutes, a low-temperature strength achievement rate of 72.2%, and average surface smoothness. The open curing time was 35 minutes. While this represents an improvement over D3-1 and D3-2, it is still weaker than Example 2's 5 minutes, 82.7% achievement rate, and excellent smoothness. This is mainly attributed to the reduced grinding mesh leading to increased particle size, which decreases the interfacial bonding efficiency between the fiber and the matrix, limiting the material's strength achievement rate at low temperatures. Furthermore, the rough surface microstructure also affects the smoothness performance.

[0101] Group D3-4 had its grinding mesh adjusted to 420 mesh, with a curing time of 4 minutes, a low-temperature strength achievement rate of 68.9%, average surface smoothness, and an open curing time of 25 minutes. This is attributed to the microscopic inhomogeneity of the distribution of nano-aerogel and fiber filler in the matrix caused by over-grinding. Locally, the molecular bridging density of the methyltrimethoxysilane-modified aerogel was excessively high, forming "rich areas," while adjacent areas lacked sufficient bridging points, resulting in a significant gradient in the interfacial bonding energy distribution. This discontinuity in the distribution of micro-components weakens the overall synergistic strengthening effect of the material at low temperatures, leading to a decrease in the strength achievement rate.

[0102] The two-stage dynamic aging process adopted in this invention significantly improves the low-temperature curing efficiency, strength achievement rate and construction smoothness of the material by precisely controlling the hydration process and particle refinement, while any simplification or adjustment weakens its overall performance.

[0103] Comparative Example 4: Based on Example 2, this example only modifies the dosage of the water-reducing agent; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0104] The performance testing method for the comparative product was completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below:

[0105] Analysis of the above characterization results shows that insufficient water-reducing agent dosage in group D4-1 weakens its dispersion and hydration inhibition effects on cement particles, leading to premature hydration reactions and an earlier rapid hydration exothermic phase in sulfoaluminate cement, thus shortening the system's temperature compensation window. Consequently, the self-heating effect is not adequately maintained, and the early support strength structure is insufficiently constructed at low temperatures, ultimately resulting in a significant decrease in low-temperature strength achievement rate and freeze-thaw stability.

[0106] Excessive water-reducing agent in group D4-2 is over-adsorbed onto the surface of cement particles, significantly prolonging the hydration induction period and inhibiting the early exothermic reaction of sulfoaluminate cement. The self-heating effect is delayed and the strength is weakened. The system cannot obtain sufficient heat compensation during the pre-aging low-temperature stage, resulting in an excessively low hydration reaction rate and slow early structure formation. Consequently, the low-temperature strength achievement rate is low, and the overall mechanical properties and freeze-thaw resistance are affected.

[0107] Comparing the characterization data in this example, the water-reducing agent in this invention not only regulates the workability of the material but also influences the formation of the microstructure and the development of low-temperature performance by precisely controlling the hydration process and the self-heating effect. Its dosage must be strictly controlled within the range of 0.5–1.0 wt% to achieve a balance between hydration inhibition and exothermic compensation, ensuring that the material forms a uniform and dense microstructure during the pre-aging stage, ultimately resulting in excellent workability, mechanical properties, and durability.

Claims

1. A method for preparing putty for exterior wall insulation, characterized in that, The method includes: 1) The ingredients are prepared according to the following mass percentages: cement-based cementitious materials 45-55 wt%, nano-aerogel 5-10 wt%, ceramic fiber 3-5 wt%, calcium sulfate whiskers 2-4 wt%, basalt fiber 1-3 wt%, calcium stearate 0.5-1.0 wt%, cellulose ether 0.3-0.5 wt%, water-reducing agent 0.5-1.0 wt%, and the balance is water; 2) After the ingredients are prepared, nano-aerogel, ceramic fiber, calcium sulfate whiskers, basalt fiber and calcium stearate are premixed in proportion to form composite powder; 3) After the cement-based cementitious material, cellulose ether and water-reducing agent are dry-mixed evenly, they are mixed with the composite powder to form a base material; 4) Slowly add water to the substrate and continue stirring to prepare the precursor; 5) The precursor is dynamically pre-aged, and then crushed and ground into putty powder. Step 1) The nano-aerogel is prepared by the following method: Silica aerogel and methyltrimethoxysilane are mixed uniformly according to a mass ratio of (8-12):1, dispersed in anhydrous ethanol, and reacted at a temperature of 60-70 DEG C and a pH of 4-5 for 4-6 hours, and then washed, dried, and obtained, having a specific surface area of greater than or equal to 600 m 2 / g. Step 1) The cement-based cementitious material is a compound system of sulfoaluminate cement and silicate cement. The sulfoaluminate cement and silicate cement are mixed in a mass ratio of (3-4):6, and 1-2 wt% of nano-silica is added by mass of silicate cement. Step 5) The dynamic pre-aging is a gradient aging process, with the first stage aging at a temperature of -5 to 5 ℃ for 2 to 3 hours and the second stage aging at a temperature of 20 to 25 ℃ for 4 to 5 hours. Step 5) The crushing and grinding process results in a product with a mesh size of 240-300 mesh.

2. The method for preparing putty for exterior wall insulation according to claim 1, characterized in that, Step 1) The nano-aerogel is a silica aerogel modified by secondary grafting with methyltrimethoxysilane; Step 1) The ceramic fibers are 3-6 mm in length and have an aspect ratio of 30-50; Step 1) The calcium sulfate whiskers are 50-100 μm in length and have an aspect ratio of 20-30; Step 1) The basalt fibers are 3-6 mm in length.

3. The method for preparing putty for exterior wall insulation according to claim 1, characterized in that, Step 2) The premixed mixture is ultrasonically treated for 20 to 40 minutes at a temperature of 20 to 30 ℃, a fluctuation frequency of 40 to 50 kHz, and a power of 600 to 700 W.

4. The method for preparing putty for exterior wall insulation according to claim 1, characterized in that, Step 3) The prepared substrate is stirred for 5 to 10 minutes at a temperature of 15 to 25 ℃ and a rotation speed of 30 to 70 rpm.

5. The method for preparing putty for exterior wall insulation according to claim 1, characterized in that, Step 4) The stirring is carried out at a temperature of 15-25 ℃ and a speed of 300-500 rpm for 10-20 minutes.

6. A putty for exterior wall insulation prepared by any one of claims 1 to 5.

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