A thermal insulation mortar admixture and its preparation method

Abstract

This invention discloses an admixture for thermal insulation mortar and its preparation method, belonging to the field of building materials technology. The key technical point is that the admixture comprises the following raw materials in parts by weight: 15-25 parts polymer powder, 1-5 parts nano aerogel, 0.1-0.5 parts nano alumina, 1-5 parts composite fiber, 1-5 parts water-repellent agent, 0.5-3 parts thixotropic agent, 1-5 parts early strength agent, and 5-10 parts microsilica powder, which solves the problems of poor strength, high water absorption, and high shrinkage caused by traditional thermal insulation mortar admixtures.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a thermal insulation mortar admixture and its preparation method. Background Technology

[0002] In the development of building energy systems, the energy consumption of building envelopes has gradually received widespread attention. With increasing demands for building energy conservation, reducing building energy consumption has become a crucial research direction in the construction field. Energy conservation and consumption reduction are of great significance for reducing energy consumption, mitigating environmental pollution, and achieving sustainable development. Against this backdrop, the application of thermal insulation materials in buildings is becoming increasingly important, as they can effectively reduce heat transfer, lower building energy consumption, and improve building energy efficiency.

[0003] To achieve energy conservation and emission reduction in buildings, the use of thermal insulation materials is a common method in the construction industry. Currently, mainstream thermal insulation materials are mainly divided into two categories: organic and inorganic. Organic thermal insulation materials, due to their low thermal conductivity, can meet the thermal insulation needs of buildings to a certain extent. Inorganic thermal insulation materials, such as thermal insulation mortar, are a typical example of inorganic thermal insulation materials. They achieve their insulation function through a scientific ratio of cementitious materials, lightweight aggregates (such as vitrified microspheres, expanded vermiculite, and expanded perlite), and functional additives. Traditional thermal insulation mortar often increases the proportion of lightweight aggregates (such as vitrified microspheres) to reduce thermal conductivity; polymer latex powder is added to increase water retention; and air-entraining agents are used to improve certain properties. Furthermore, most admixtures on the market target only a single property; for example, adding cellulose ethers only improves water retention.

[0004] However, these existing technologies have significant drawbacks. Traditional thermal insulation mortars have a significantly lower thermal conductivity compared to organic materials, making it difficult to meet the insulation performance requirements of modern building standards. Increasing the proportion of lightweight aggregates leads to a decrease in compressive strength (typically ≤1.5MPa), making it difficult to meet the requirements of high-rise buildings or load-bearing structures; polymer latex powder increases water retention but reduces compressive strength (strength decreases by 0.5MPa for every 1% increase in dosage); excessive air-entraining agents can cause a strength loss of over 30%, and are prone to cracking and high water absorption; mortar has large drying shrinkage, easily producing micro-cracks after construction, and the porous structure of lightweight aggregates results in high water absorption (≥10%), affecting thermal insulation performance and freeze-thaw durability. Furthermore, most commercially available admixtures target a single property, making it difficult to address multiple needs such as crack resistance, water repellency, and reinforcement. Meanwhile, the high cost of nanomaterials and imported latex powders limits large-scale application; recycled aggregates have unstable performance and require pretreatment; with the widespread use of manufactured sand, the compounding of thermal insulation mortar admixtures has become more difficult, requiring customized services, further increasing costs. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a thermal insulation mortar admixture and its preparation method, thereby resolving the issues of poor strength, high water absorption, and high shrinkage associated with traditional thermal insulation mortar admixtures.

[0006] The present invention provides a thermal insulation mortar admixture and its preparation method, which adopts the following technical solution: An admixture for thermal insulation mortar, the admixture comprising the following raw materials in parts by weight: 15-25 parts polymer powder, 1-5 parts nano aerogel, 0.1-0.5 parts nano alumina, 1-5 parts composite fiber, 1-5 parts water-repellent agent, 0.5-3 parts thixotropic agent, 1-5 parts early strength agent, and 5-10 parts microsilica powder.

[0007] By adopting the above technical solution, the polymer powder film can enhance the bonding strength between mortar and wall, prevent hollowing and falling off, and also form an adhesive layer on the surface of lightweight aggregate to prevent the aggregate from separating from cement. At the same time, the formed film blocks the capillary pores of the wall, reduces water absorption, avoids freeze-thaw cycles, and can work synergistically with thixotropic agents to improve the workability of mortar, making mortar plastering smoother and reducing adhesion to tools.

[0008] The high porosity of nano-aerogels allows some nano-alumina particles to be adsorbed onto their surface under the influence of surface potential energy, forming an encapsulation structure. This surface modification of the nano-aerogels not only enhances the mechanical strength of the thermal insulation mortar by initiating a secondary hydration reaction through the bonding of more nano-scale hydration products, building upon the original network structure of the hardened mortar (composite fibers are uniformly dispersed in the mortar, forming a three-dimensional network after the matrix hardens, effectively bridging cracks and inhibiting crack propagation), but also enhances the mechanical strength of the thermal insulation mortar by forming a new dense network structure. Simultaneously, the excellent high-temperature resistance of nano-alumina allows it to transform into ceramic materials under high-temperature environments, significantly improving the high-temperature resistance and fire resistance of the thermal insulation mortar.

[0009] Early strength agents can accelerate cement hydration, promote the dissolution and hydration of minerals such as C3S and C3A, accelerate the rapid generation of hydration products (especially ettringite), and improve early strength. Combining early strength agents with microsilica and nano alumina can accelerate the reactivity of early strength agents, thereby effectively improving the strength of mortar. In addition, the large-scale generation of ettringite is accompanied by micro-expansion in volume, which compensates for the hardening shrinkage of mortar, reduces drying shrinkage cracks, and ettringite coats the surface of lightweight aggregates, improves interfacial bonding strength, and prevents aggregates from floating and delaminating.

[0010] In summary, by adjusting the composition and dosage of each component, the admixture obtained in this application can effectively improve the strength of thermal insulation mortar, reduce water absorption, and also effectively reduce the drying shrinkage rate of the mortar.

[0011] Preferably, the polymer powder is an epoxy-modified acrylate copolymer.

[0012] By adopting the above technical solution, when the polymer powder is an epoxy-modified acrylate copolymer, the epoxy groups crosslink with cement hydration products (such as calcium ions) to form a dense network structure, which reduces water absorption and improves the tensile strength of the mortar. In addition, the epoxy segments in the copolymer provide high rigidity, and the acrylate segments impart flexibility, making the copolymer performance stable. The carboxyl and hydroxyl groups in the copolymer can form hydrogen bonds with nano-silica aerogels, micro silica powders, etc., which improves dispersion uniformity and reduces interface defects.

[0013] Preferably, the nano-aerogel is a hydrophobic silica aerogel.

[0014] Preferably, the composite fiber comprises basalt fiber and PVA fiber in a weight ratio of 1:1.

[0015] By adopting the above technical solution, basalt fibers form a three-dimensional network structure in the mortar, effectively bridging microcracks, inhibiting crack propagation, and improving resistance to shrinkage cracking (especially cracks caused by drying shrinkage and temperature stress). PVA fibers are dispersed in the plastic stage of the mortar, reducing plastic shrinkage cracks caused by rapid moisture evaporation and improving early crack resistance. Both technologies balance crack resistance in the plastic stage and long-term impact resistance. Therefore, the combined use of these two technologies can significantly improve the crack resistance, durability, and safety of thermal insulation mortar, while maintaining its lightweight insulation properties throughout the long term.

[0016] Preferably, the hydrophobic agent is an organosilicon resin powder, and more preferably isobutyltriethoxysilane.

[0017] By adopting the above technical solution, after the organosilicon resin powder is dispersed in the mortar, the silanol groups at the end of its molecular chain react with the cement hydration products to form a hydrophobic siloxane network structure, which covers the surface of the capillary wall, making the capillary wall hydrophobic. The organosilicon resin and the hydrophobic silica aerogel work together, with the organosilicon resin providing surface hydrophobicity and the silica aerogel being internally hydrophobic, thereby achieving a dual effect of reducing water absorption.

[0018] Preferably, the thixotropic agent comprises the following raw materials in parts by weight: 50-70 parts sodium bentonite, 0.5-3 parts sodium dodecylbenzenesulfonate, 0.5-3 parts plastic expansion agent, 10-30 parts stone powder, 10-20 parts gypsum, and 0.5-1 parts water-reducing agent.

[0019] By adopting the above technical solution, when the thixotropic agent is composed of the above substances, it can effectively adjust the workability of the entire mortar material, thereby improving pumpability and resolving the contradiction between construction efficiency and operability.

[0020] Preferably, the plastic expanding agent is mainly composed of metallic aluminum powder and azodicarbonamide.

[0021] Preferably, the stone powder is composed of heavy calcium carbonate and talc in a weight ratio of 1:1.

[0022] By adopting the above technical solutions, the addition of heavy calcium carbonate can fill the gaps between cement particles and lightweight aggregates, increasing density and improving mechanical strength; the addition of talc can significantly improve the lubricity and anti-sagging properties of mortar, making scraping easier and the surface smoother. Therefore, the addition of stone powder can improve the workability and workability of mortar, making it smoother and easier to apply.

[0023] Preferably, the early strength agent is a sulfoaluminate activator.

[0024] A second aspect of this application is to provide a method for preparing a thermal insulation mortar admixture as described above, comprising the following preparation steps: S1. Perform plasma surface treatment on the composite fibers; S2. After mixing the polymer powder, nano aerogel, nano alumina, water repellent, thixotropic agent, early strength agent, and micro silica powder, add the composite fiber obtained in step S1 and mix evenly to obtain the mortar admixture.

[0025] In summary, the present invention has the following beneficial effects: 1. This thermal insulation mortar admixture can reduce the thermal conductivity of the thermal insulation mortar, improve its thermal insulation performance, and make it meet the requirements of modern building standards; 2. It can reduce the water absorption rate of thermal insulation mortar, enhance the durability of thermal insulation performance and freeze-thaw resistance, and reduce the weakening of thermal insulation performance due to water intrusion; 3. It takes into account the multiple properties of thermal insulation mortar, such as crack resistance, water repellency, and reinforcement, and avoids the limitation of admixtures that only target a single property. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments. All reagents, unless otherwise specified, are commercially available conventional reagent products.

[0027] In the embodiments and comparative examples of this application, all raw materials used are commercially available, specifically: The thermal conductivity of hydrophobic silica aerogel is less than 0.08 W / (m·K). The silicone resin powder used is isobutyltriethoxysilane; Sodium-based bentonite has a whiteness >70%, viscosity >600 mPa·s, pH value between 7 and 10, moisture content <12%, and a passing rate of >95% on a 45 μm sieve. The plastic expansion agent is mainly composed of metallic aluminum powder and azodicarbonamide, and also includes some stabilizers / dispersants (stearates) and quartz powder, which were purchased from Hubei Guiyi New Building Materials Co., Ltd. The epoxy-modified acrylate copolymer used was EBECREL 3708 from ZNX. Example 1

[0028] A method for preparing a thermal insulation mortar admixture includes the following preparation steps: S1. Mix 1 kg of composite fiber consisting of basalt fiber and PVA fiber in a weight ratio of 1:1, and then perform plasma surface treatment. The plasma power is 200W and the treatment time is 5 minutes. S2. Add 15kg of epoxy-modified acrylate copolymer, 1kg of nano silica aerogel, 0.1kg of nano alumina, 1kg of organosilicon resin powder, 0.5kg of thixotropic agent, 1kg of sulfoaluminate activator, and 5kg of microsilica powder to a high-speed mixer and mix for 10 minutes. Then add the composite fiber obtained in step S1 and mix for 5 minutes until uniform to obtain the mortar admixture. Among them, the nano-aerogel is a hydrophobic silica aerogel; The thixotropic agent comprises 0.5 kg sodium bentonite, 0.005 kg sodium dodecylbenzenesulfonate, 0.005 kg plasticizing agent, 0.1 kg stone powder, 0.1 kg gypsum, and 0.005 kg water-reducing agent. The stone powder is composed of heavy calcium carbonate and talc in a 1:1 weight ratio. The thixotropic agent is prepared by mixing sodium bentonite, stone powder, and gypsum, then adding sodium dodecylbenzenesulfonate, a plasticizing agent, and a water-reducing agent, and stirring until the mixture is homogeneous. Example 2

[0029] A method for preparing a thermal insulation mortar admixture includes the following preparation steps: S1. Mix 3 kg of composite fiber consisting of basalt fiber and PVA fiber in a weight ratio of 1:1, and then perform plasma surface treatment. The plasma power is 200W and the treatment time is 5 minutes. S2. Add 20kg of epoxy-modified acrylate copolymer, 3kg of nano silica aerogel, 0.3kg of nano alumina, 3kg of organosilicon resin powder, 2kg of thixotropic agent, 3kg of sulfoaluminate activator, and 7kg of microsilica powder to a high-speed mixer and mix for 10 minutes. Then add the composite fiber obtained in step S1 and mix for 5 minutes until uniform to obtain the mortar admixture. Among them, the nano-aerogel is a hydrophobic silica aerogel; The thixotropic agent includes 0.5 kg sodium bentonite, 0.005 kg sodium dodecylbenzene sulfonate, 0.005 kg plasticizing agent, 0.1 kg stone powder, 0.1 kg gypsum, and 0.005 kg water-reducing agent; The thixotropic agent is prepared by mixing sodium bentonite, stone powder, and gypsum, then adding sodium dodecylbenzenesulfonate, a plasticizing agent, and a water-reducing agent, and stirring until the mixture is homogeneous. Example 3

[0030] A method for preparing a thermal insulation mortar admixture includes the following preparation steps: S1. Mix 5 kg of composite fiber consisting of basalt fiber and PVA fiber in a weight ratio of 1:1, and then perform plasma surface treatment. The plasma power is 200W and the treatment time is 5 minutes. S2. Add 25kg of epoxy-modified acrylate copolymer, 5kg of nano silica aerogel, 0.5kg of nano alumina, 5kg of organosilicon resin powder, 3kg of thixotropic agent, 5kg of sulfoaluminate activator, and 10kg of microsilica powder to a high-speed mixer and mix for 10 minutes. Then add the composite fiber obtained in step S1 and mix for 5 minutes until uniform to obtain the mortar admixture. Among them, the nano-aerogel is a hydrophobic silica aerogel; The thixotropic agent includes 0.5 kg sodium bentonite, 0.005 kg sodium dodecylbenzene sulfonate, 0.005 kg plasticizing agent, 0.1 kg stone powder, 0.1 kg gypsum, and 0.005 kg water-reducing agent; The thixotropic agent is prepared by mixing sodium bentonite, stone powder, and gypsum, then adding sodium dodecylbenzenesulfonate, a plasticizing agent, and a water-reducing agent, and stirring until the mixture is homogeneous. Example 4

[0031] A method for preparing a thermal insulation mortar admixture differs from Example 2 in that, while the total amount of thixotropic agent remains unchanged, the amounts of each component in the thixotropic agent are varied. Specifically, it includes 0.6 kg sodium bentonite, 0.01 kg sodium dodecylbenzenesulfonate, 0.01 kg plastic expansion agent, 0.2 kg stone powder, 0.15 kg gypsum, and 0.008 kg water-reducing agent. All other components are the same as in Example 2. Example 5

[0032] A method for preparing a thermal insulation mortar admixture differs from Example 2 in that, while the total amount of thixotropic agent remains unchanged, the amounts of each component in the thixotropic agent are varied. Specifically, it includes 0.7 kg sodium bentonite, 0.03 kg sodium dodecylbenzenesulfonate, 0.03 kg plastic expansion agent, 0.3 kg stone powder, 0.2 kg gypsum, and 0.01 kg water-reducing agent. All other components are the same as in Example 2. Comparative Example 1

[0033] A method for preparing a thermal insulation mortar admixture differs from Example 2 in that an equal amount of ethylene-vinyl acetate copolymer is used instead of epoxy-modified acrylate copolymer, while all other aspects are the same as in Example 2. Comparative Example 2

[0034] A method for preparing a thermal insulation mortar admixture differs from Example 2 in that an equal amount of polypropylene fiber is used instead of PVA fiber, while all other aspects are the same as in Example 2. Comparative Example 3

[0035] A method for preparing a thermal insulation mortar admixture differs from Example 2 in that an equal amount of steel fiber is used instead of basalt fiber, while all other aspects are the same as in Example 2. Blank group

[0036] The admixtures obtained in the above embodiments were added to mortar for testing of mortar compressive strength, thermal conductivity, drying shrinkage, water absorption and spread. The mortar formula was: cement: fly ash: admixture: vitrified microspheres = 100:30:6:7.5. The test results are shown in Table 1.

[0037] Table 1. Mortar Performance Test Results project Thermal conductivity (W / m·K) 28-day compressive strength / MPa Drying shrinkage rate / % Water absorption rate (24h, %) Expansion / mm Example 1 0.070 3.2 0.03 4.0 170 Example 2 0.068 3.5 0.02 3.8 172 Example 3 0.069 3.5 0.02 3.8 173 Example 4 0.067 3.6 0.02 3.7 173 Example 5 0.068 3.5 0.03 3.7 172 Comparative Example 1 0.071 2.2 0.03 4.1 167 Comparative Example 2 0.069 2.6 0.03 4.0 166 Comparative Example 3 0.091 4.0 0.02 3.8 170 Blank group 0.088 1.3 0.08 18 140 The blank group consists of mortar without any admixtures, with a cement:fly ash:vitrified microspheres ratio of 100:30:7.5.

[0038] Based on the mortar performance test results in Table 1: In Examples 1-3 of this application, by adjusting the dosage of each component in the admixture, the thermal conductivity of the mortar obtained after application was lower than that of the blank group, and the 28-day compressive strength was significantly higher than that of the blank group. This indicates that the addition of the admixture in this application effectively improved the strength performance of the mortar. Furthermore, the drying shrinkage rate in Examples 1-3 was lower than that in the blank group, indicating that the volume stability of the mortar obtained in Examples 1-3 was better than that of the blank group, and the crack resistance after hardening was superior to that of the blank group. Moreover, the 24-hour water absorption rate in Examples 1-3 was significantly lower than that in the blank group, indicating that the mortar obtained in Examples 1-3 had high density, fewer internal voids, a more compact structure, and certain wear resistance. In contrast, the water absorption rate of the mortar in the blank group was too high, indicating that the mortar had more pores, a loose structure, and was prone to strength reduction or cracking due to water penetration.

[0039] In addition, the addition of admixtures significantly improves the flowability of mortar. For example, the spread in Examples 1-3 of this application is ≥170mm, while the spread of mortar in the blank group is 140mm. It can be seen that the addition of admixtures has a significant impact on the strength, water absorption rate, and flowability of mortar, and effectively improves the service life of mortar after hardening.

[0040] Compared with Example 2, when the total amount of thixotropic agent is the same as in Example 2, by changing the content of each component in the thixotropic agent, the admixtures obtained in Examples 4-5, when applied to mortar, have basically the same properties as those in Example 2. This indicates that when the content of thixotropic agent in this application is within this range, the effect on the performance of the admixture is basically the same.

[0041] Compared with Example 2, when the ethylene-vinyl acetate copolymer was replaced with an equal amount of epoxy-modified acrylate copolymer, the 28-day compressive strength of the mortar obtained in Comparative Example 1 was significantly reduced compared with Example 2. The reason may be that the ethylene-vinyl acetate copolymer is water-soluble / swellable, and it will soften, swell, and lose strength when it comes into contact with water. In contrast, the epoxy-modified acrylate copolymer, due to its high content of polar epoxy and hydroxyl groups, forms stronger chemical bonds and physical adsorption with cement hydration products and the substrate. Moreover, the epoxy groups form a rigid three-dimensional network structure with a higher degree of cross-linking, which plays a better synergistic role with cement, making the overall load-bearing capacity of the composite stronger. Therefore, the epoxy-modified acrylate copolymer adopts a "rigid-flexible" structural design, which can maintain high toughness without sacrificing rigidity, resulting in higher mortar strength.

[0042] Compared with Example 2, when an equal amount of polypropylene fiber was used to replace PVA fiber, or an equal amount of steel fiber was used to replace basalt fiber, the 28-day compressive strength of the mortar obtained in Comparative Example 2 was significantly lower than that of Example 2. In Comparative Example 3, the 28-day compressive strength of the mortar was significantly improved after the use of steel fiber, but the thermal conductivity of the mortar also increased significantly. The higher the thermal conductivity, the worse the thermal insulation performance. Moreover, the cost will increase significantly after the use of steel fiber. Therefore, considering both cost and mortar performance, the combination of basalt fiber and PVA fiber can effectively ensure the performance of the mortar while reducing the cost.

[0043] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A thermal insulation mortar admixture, characterized in that, The additives include the following raw materials in parts by weight: 15-25 parts polymer powder, 1-5 parts nano aerogel, 0.1-0.5 parts nano alumina, 1-5 parts composite fiber, 1-5 parts water-repellent agent, 0.5-3 parts thixotropic agent, 1-5 parts early strength agent, and 5-10 parts microsilica powder.

2. The thermal insulation mortar admixture according to claim 1, characterized in that: The polymer powder is an epoxy-modified acrylate copolymer.

3. The thermal insulation mortar admixture according to claim 1, characterized in that: The nano-aerogel is a hydrophobic silica aerogel.

4. The thermal insulation mortar admixture according to claim 1, characterized in that: The composite fiber comprises basalt fiber and PVA fiber in a weight ratio of 1:

1.

5. The thermal insulation mortar admixture according to claim 1, characterized in that: The hydrophobic agent is an organosilicon resin powder.

6. The thermal insulation mortar admixture according to claim 1, characterized in that: The thixotropic agent comprises the following raw materials in parts by weight: 50-70 parts sodium bentonite, 0.5-3 parts sodium dodecylbenzenesulfonate, 0.5-3 parts plastic expansion agent, 10-30 parts stone powder, 10-20 parts gypsum, and 0.5-1 parts water-reducing agent.

7. The thermal insulation mortar admixture according to claim 6, characterized in that: The plastic expansion agent is mainly composed of metallic aluminum powder and azodicarbonamide.

8. The thermal insulation mortar admixture according to claim 6, characterized in that: The stone powder is composed of heavy calcium carbonate and talc in a weight ratio of 1:

1.

9. The thermal insulation mortar admixture according to claim 1, characterized in that: The early strength agent is a sulfoaluminate activator.

10. A method for preparing a thermal insulation mortar admixture as described in any one of claims 1-9, characterized in that, The preparation steps include the following: S1. Perform plasma surface treatment on the composite fibers; S2. After mixing the polymer powder, nano aerogel, nano alumina, water repellent, thixotropic agent, early strength agent, and micro silica powder, add the composite fiber obtained in step S1 and mix evenly to obtain the mortar admixture.