Preparation method and application of novel anti-cracking and anti-freezing inorganic thermal insulation mortar

Abstract

The invention belongs to the technical field of building materials, and particularly relates to novel anti-cracking and anti-freezing inorganic thermal insulation mortar as well as a preparation method and application thereof. The thermal insulation mortar is prepared from the following raw materials in parts by weight: 30-50 parts of ordinary Portland cement, 10-20 parts of ground calcium carbonate, 0.1-0.5 part of hydroxypropyl methyl cellulose, 1-3 parts of redispersible latex powder, 20-30 parts of glass beads, 0.5-1.5 parts of polypropylene fibers and 0.01-0.05 part of an air entraining agent. According to the preparation method, through the steps of premixing, step-by-step addition of the thermal insulation aggregate, the fiber and the additive, high-speed homogenization and the like, uniform dispersion and synergistic effect of all the components are ensured. Through compounding of specific functional components and targeted process optimization, the technical problems that traditional inorganic thermal insulation mortar is prone to cracking and poor in anti-freezing durability are solved. The obtained product integrates excellent crack resistance, high freezing resistance, good bonding strength and constructability, and is especially suitable for projects with harsh requirements on thermal insulation and durability, such as building exterior walls, roofs and old house energy-saving reconstruction in severe cold areas.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a novel crack-resistant and frost-resistant inorganic thermal insulation mortar, its preparation method, and its application. Background Technology

[0002] In the field of building energy conservation and engineering protection, external wall insulation systems are crucial for improving building energy efficiency and enhancing living comfort, especially in extremely cold and frigid regions where the crack resistance and freeze-thaw resistance of materials are placed on extremely high standards. Inorganic insulating mortar, due to its high fire resistance, good durability, and strong adhesion to the base wall, has become an important component of building external wall insulation. However, in practical engineering applications, this type of material has long faced two core technical challenges: cracking and freeze-thaw damage.

[0003] Currently, most inorganic thermal insulation mortars on the market use cement as a binder, supplemented with lightweight aggregates such as vitrified microspheres. The inherent drying shrinkage of cement-based materials, along with the significant difference in elastic modulus between the insulation aggregates and the binder, makes the mortar prone to shrinkage stress during hardening, leading to shrinkage cracking. Furthermore, the pore structure of traditional inorganic thermal insulation mortars is not ideal. Under freeze-thaw cycles, the expansion stress generated by the freezing of internal moisture continuously damages its microstructure, resulting in decreased strength, surface powdering, and even overall peeling, severely impacting the safety and service life of the insulation system.

[0004] To improve the aforementioned properties, existing technologies typically employ physical addition of fibers (such as polypropylene fibers) or chemical introduction of polymer emulsions (such as redispersible latex powder) to enhance crack resistance. While these measures can inhibit crack development to some extent, they often have limitations: the addition of a single fiber has limited effect on improving early plastic shrinkage cracking, and excessive addition can easily lead to fiber agglomeration, which in turn reduces mortar strength; while the introduction of polymers may sacrifice some of the material's fire resistance and increase costs. Regarding freeze protection, conventional methods often rely on introducing air-entraining agents to create closed, fine pores to buffer ice crystal stress. However, the structure, distribution, and stability of the pores are difficult to control precisely, and air-entraining agents often negatively impact the mechanical strength of the mortar, making it difficult to simultaneously achieve both compressive strength and bond strength.

[0005] Existing technical solutions suffer from significant performance imbalances: pursuing multifunctionality through simple physical blending of multiple additives often results in poor compatibility and uneven dispersion among the components, leading to a lack of synergistic performance and even mutual constraints. For example, crack-resistant and antifreeze components may lack effective synergy, failing to form a consistent toughness network and optimized pore structure. Consequently, either crack resistance meets standards but antifreeze durability is insufficient, or antifreeze performance is acceptable but the mortar is brittle and prone to cracking, making it difficult to simultaneously meet the engineering requirements of high strength, high crack resistance, and high antifreeze resistance under harsh environments.

[0006] Therefore, there is an urgent need in this field to develop a novel inorganic thermal insulation mortar. This material should fundamentally resolve the contradiction between crack resistance and frost resistance through innovative raw material formulations and targeted preparation processes, achieving synergistic effects among its components. The goal is to enable the material to possess inherent high toughness, low shrinkage characteristics, and an optimized frost-resistant pore structure without relying on excessive external additives. This would provide a long-lasting, stable, and reliable integrated thermal insulation and protection solution for demanding projects such as buildings in frigid regions, high-humidity environments, and energy-saving renovations of existing buildings. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing and applying a novel crack-resistant and frost-resistant inorganic thermal insulation mortar.

[0008] This invention includes the following technical solutions: A method for preparing a novel crack-resistant and frost-resistant inorganic thermal insulation mortar includes the following steps: (1) Premixing: Add 30-50 parts by weight of ordinary silicate cement, 10-20 parts by weight of heavy calcium carbonate, 0.1-0.5 parts by weight of hydroxypropyl methylcellulose and 1-3 parts by weight of redispersible latex powder to a mixer and stir at a speed of 200-400 rpm for 5-10 minutes to make it initially uniformly mixed. (2) Add thermal insulation aggregate: Under stirring, add 20-30 parts by weight of vitrified microspheres to the mixture obtained in step (1), and stir at a speed of 100-200 rpm for 5-10 minutes to ensure that the thermal insulation aggregate is evenly dispersed; (3) Add fiber and additives: Add 0.5-1.5 parts by weight of polypropylene fiber and 0.01-0.05 parts by weight of air-entraining agent to the mixture obtained in step (2), and stir at a speed of 300-500 rpm for 10-15 minutes to fully disperse the fiber and additives. (4) Homogenization: Increase the rotation speed to 400-600 rpm and disperse at high speed for 10-20 minutes until the mixture is uniform in fineness and free of lumps; (5) Discharge: Let stand for 10-20 minutes to mature, then discharge and package to obtain the new type of crack-resistant and frost-resistant inorganic thermal insulation mortar.

[0009] In the above scheme, the step-by-step feeding and targeted mixing process of "premixed cementitious materials → low-speed addition of aggregates → medium-speed introduction of fibers / air-entraining agents → high-speed homogenization" ensures that each functional component is evenly dispersed and structurally intact, thereby achieving synergistic effects.

[0010] Furthermore, in the above preparation method, the ordinary Portland cement mentioned in step (1) is grade 42.5 ordinary Portland cement. Using grade 42.5 cement ensures that the mortar obtains appropriate early and late strength, providing a stable and reliable mechanical basis for the entire insulation system.

[0011] Furthermore, in the above preparation method, the bulk density of the vitrified microspheres in step (2) is 80-120 kg / m³. 3 The particle size ranges from 0.5 to 1.5 mm. In the above scheme, controlling the bulk density and particle size of vitrified microspheres is the key to balancing the dry density, thermal insulation performance (thermal conductivity) and compressive strength of the mortar.

[0012] Furthermore, in the above preparation method, the polypropylene fibers in step (3) have a length of 3-6 mm and a diameter of 10-20 μm. Polypropylene fibers with a specific aspect ratio can efficiently overlap in the mortar matrix to form a three-dimensional network, effectively transferring and dispersing stress, and inhibiting the generation and development of microcracks.

[0013] Furthermore, in the above preparation method, the air-entraining agent mentioned in step (3) is a rosin thermal polymer air-entraining agent. The rosin thermal polymer air-entraining agent can generate a large number of fine, closed, and stable microbubbles, effectively blocking the water migration channels and providing buffer space for ice crystal expansion, thereby significantly improving the antifreeze properties.

[0014] Furthermore, in the above preparation method, the high-speed dispersion time in step (4) is 15 minutes, and the rotation speed is 500 rpm. Stirring at 500 rpm for 15 minutes during the homogenization stage is the optimal process window to achieve uniform dispersion of each component, eliminate agglomeration, and avoid damage to the vitrified microsphere particles due to excessive stirring.

[0015] This invention discloses a novel crack-resistant and frost-resistant inorganic thermal insulation mortar, prepared by any of the above-mentioned methods. The product, prepared by the aforementioned specific methods, possesses a microstructure (such as fiber distribution and bubble morphology) that determines its comprehensive superior properties, including crack resistance, frost resistance, and high strength.

[0016] Furthermore, the aforementioned novel crack-resistant and frost-resistant inorganic thermal insulation mortar has a dry density ≤250kg / m³. 3 It has a compressive strength ≥0.5MPa, a thermal conductivity ≤0.065W / (m·K), and a mass loss rate ≤5% after 25 freeze-thaw cycles. Based on the excellent comprehensive performance of this mortar in terms of crack resistance and frost protection, its application to specific building parts with extremely high durability requirements can maximize its technical advantages.

[0017] This invention discloses the application of the above-mentioned novel crack-resistant and frost-resistant inorganic thermal insulation mortar in building exterior wall insulation, roof insulation in cold regions, or energy-saving renovation of old buildings.

[0018] Furthermore, for the above applications, the application should be carried out by smearing or spraying, with a thickness of 20-50mm, and the ambient temperature should not be lower than -5℃.

[0019] Compared with the prior art, the present invention has the following outstanding advantages: 1. Excellent crack resistance: Polypropylene fibers form a three-dimensional network in the mortar matrix to withstand shrinkage stress; redispersible latex powder and hydroxypropyl methylcellulose work together to enhance the cohesion of the mortar and reduce plastic shrinkage caused by rapid water evaporation. The three work together to significantly improve the crack resistance of the material from both physical toughening and chemical water retention aspects.

[0020] 2. Excellent freeze-thaw resistance and durability: The use of a specific air-entraining agent introduces a large number of uniform and closed microbubbles into the mortar, which effectively blocks and buffers the expansion stress caused by water freezing; at the same time, the optimized matrix structure enhances the ability to resist freeze-thaw damage, so that the product can maintain structural integrity and stable performance even in harsh environments.

[0021] 3. Balanced Comprehensive Performance: Through precise formulation of raw materials and step-by-step preparation process, this invention achieves a perfect balance of multiple properties such as lightweight, heat preservation, high strength, strong adhesion and smooth construction. It overcomes the bottleneck of mutual restriction between function and performance in traditional technology, and provides a high-performance integrated solution that extends the service life of the insulation system. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 A novel crack-resistant and frost-resistant inorganic thermal insulation mortar is made from the following raw materials in parts by weight: 30 parts ordinary silicate cement, 10 parts heavy calcium carbonate, 0.1 parts hydroxypropyl methylcellulose, 1 part redispersible latex powder, 20 parts vitrified microspheres, 0.5 parts polypropylene fiber, and 0.01 parts rosin thermal polymer air-entraining agent.

[0024] Its preparation method includes the following steps: (1) Premixing: Add ordinary silicate cement, heavy calcium carbonate, hydroxypropyl methylcellulose and redispersible latex powder to a mixer and stir at 200 rpm for 10 minutes to make them initially uniform; (2) Add thermal insulation aggregate: Under stirring, add vitrified microspheres to the mixture obtained in step (1) and stir at a speed of 100 rpm for 10 minutes to ensure that the thermal insulation aggregate is evenly dispersed; (3) Add fiber and additives: Add polypropylene fiber and air-entraining agent to the mixture obtained in step (2), and stir at 300 rpm for 15 minutes to fully disperse the fiber and additives. (4) Homogenization: Increase the rotation speed to 400 rpm and disperse at high speed for 20 minutes until the mixture is uniform in fineness and free of lumps; (5) Discharge: Let stand for 20 minutes to mature, then discharge and package to obtain the new type of crack-resistant and freeze-resistant inorganic thermal insulation mortar.

[0025] Example 2 A novel crack-resistant and frost-resistant inorganic thermal insulation mortar is made from the following raw materials in parts by weight: 40 parts ordinary silicate cement, 15 parts heavy calcium carbonate, 0.3 parts hydroxypropyl methylcellulose, 2 parts redispersible latex powder, 25 parts vitrified microspheres, 1.0 part polypropylene fiber, and 0.03 parts rosin thermal polymer air-entraining agent.

[0026] Its preparation method includes the following steps: (1) Premixing: Add ordinary silicate cement, heavy calcium carbonate, hydroxypropyl methylcellulose and redispersible latex powder to a mixer and stir at 300 rpm for 7 minutes to make them initially uniform; (2) Add thermal insulation aggregate: Under stirring, add vitrified microspheres to the mixture obtained in step (1) and stir at a speed of 150 rpm for 7 minutes to ensure that the thermal insulation aggregate is evenly dispersed; (3) Add fiber and additives: Add polypropylene fiber and air-entraining agent to the mixture obtained in step (2), and stir at a speed of 400 rpm for 12 minutes to fully disperse the fiber and additives. (4) Homogenization: Increase the rotation speed to 500 rpm and disperse at high speed for 15 minutes until the mixture is uniform in fineness and free of lumps; (5) Discharge: Let stand for 15 minutes to mature, then discharge and package to obtain the new type of crack-resistant and antifreeze inorganic thermal insulation mortar.

[0027] Example 3 A novel crack-resistant and frost-resistant inorganic thermal insulation mortar is made from the following raw materials in parts by weight: 50 parts ordinary silicate cement, 20 parts heavy calcium carbonate, 0.5 parts hydroxypropyl methylcellulose, 3 parts redispersible latex powder, 30 parts vitrified microspheres, 1.5 parts polypropylene fiber, and 0.05 parts rosin thermal polymer air-entraining agent.

[0028] Its preparation method includes the following steps: (1) Premixing: Add ordinary silicate cement, heavy calcium carbonate, hydroxypropyl methylcellulose and redispersible latex powder to a mixer and stir at 400 rpm for 5 minutes to make them initially uniform; (2) Add thermal insulation aggregate: Under stirring, add vitrified microspheres to the mixture obtained in step (1) and stir at a speed of 200 rpm for 5 minutes to ensure that the thermal insulation aggregate is evenly dispersed; (3) Add fiber and additives: Add polypropylene fiber and air-entraining agent to the mixture obtained in step (2), and stir at a speed of 500 rpm for 10 minutes to fully disperse the fiber and additives. (4) Homogenization: Increase the rotation speed to 600 rpm and disperse at high speed for 10 minutes until the mixture is uniform in fineness and free of lumps; (5) Discharge: Let stand for 10 minutes to mature, then discharge and package to obtain the new type of crack-resistant and antifreeze inorganic thermal insulation mortar.

[0029] Comparative Example 1 A thermal insulation mortar, made from the following raw materials in parts by weight: 40 parts ordinary silicate cement, 15 parts heavy calcium carbonate, 0.3 parts hydroxypropyl methylcellulose, 2 parts redispersible latex powder, 25 parts vitrified microspheres, and 0.03 parts rosin thermal polymer air-entraining agent. (Excluding polypropylene fiber) The preparation method is the same as in Example 2.

[0030] Comparative Example 2 A thermal insulation mortar, made from the following raw materials in parts by weight: 40 parts ordinary silicate cement, 15 parts heavy calcium carbonate, 0.3 parts hydroxypropyl methylcellulose, 2 parts redispersible latex powder, 25 parts vitrified microspheres, and 1.0 part polypropylene fiber. (Excluding air-entraining agent) The preparation method is the same as in Example 2.

[0031] Comparative Example 3 A thermal insulation mortar, made from the following raw materials in parts by weight: 40 parts ordinary silicate cement, 15 parts heavy calcium carbonate, 25 parts vitrified microspheres, 1.0 part polypropylene fiber, and 0.03 parts rosin thermal polymer air-entraining agent. (Excludes hydroxypropyl methylcellulose and redispersible latex powder) The preparation method is the same as in Example 2.

[0032] Comparative Example 4 A thermal insulation mortar, the formula of which is exactly the same as that in Example 2.

[0033] In its preparation method, steps (1) to (4) are omitted in sequence. All raw materials are added to the mixer at once and stirred at a speed of 500 rpm for 20 minutes, and then discharged. (A one-time mixing process is used, and the step-by-step feeding and optimized stirring process of the present invention is not used).

[0034] Comparative Example 5 A commercially available common inorganic thermal insulation mortar (taking a certain brand of product as an example, the main components are cement and vitrified microspheres, without specific fibers, polymer powder and air-entraining agent system).

[0035] Test Example 1 Crack resistance performance comparison experiment Objective: To verify the shrinkage and cracking resistance of the thermal insulation mortar of the present invention and the synergistic effect of its key components.

[0036] method: Specimen preparation: Mortar specimens were prepared according to the national standard GB / T 20473-2021 Building Thermal Insulation Mortar. The dry powder mortars prepared in Example 2 and Comparative Examples 1-5 were mixed evenly at a water-cement ratio of 0.65 and poured into molds with dimensions of 160mm × 40mm × 40mm. They were cured for 28 days under standard curing conditions (temperature 20±2℃, relative humidity ≥95%).

[0037] Testing equipment: PTI-1 mortar shrinkage and expansion meter with an accuracy of 0.001mm.

[0038] Test Procedure: After curing, the specimens were placed in a constant temperature and humidity chamber (20±2℃, 60±5%RH), and their initial length L0 was measured. Subsequently, the specimens were moved to a dry environment (20±2℃, 50±5%RH), and the length L was measured continuously after 7, 14, and 28 days. t .

[0039] Calculation of drying shrinkage rate ε t = (L0 - L t ) / 160 × 100%. The average value of 5 specimens in each group of data is ± standard deviation.

[0040] The results are shown in Table 2.

[0041] Conclusion: The drying shrinkage rate of Example 2 at all time points was significantly lower than that of all comparative examples (P<0.01). The shrinkage rates of Comparative Example 1 (no fiber) and Comparative Example 3 (no cellulose ether and adhesive powder) increased significantly, proving that the physical toughening effect of polypropylene fiber and the effects of polymer adhesive powder and cellulose ether in improving the cohesion of the mortar and reducing the stress of water evaporation formed an effective synergy, jointly inhibiting the plastic shrinkage and drying shrinkage of the mortar, which is the key to the excellent crack resistance of this invention.

[0042] Test Example 2 Objective: To evaluate the durability of the thermal insulation mortar of the present invention under severe cold conditions and the key role of the air-entraining agent.

[0043] method: Specimen preparation and curing: Prepare cubic specimens of 70.7mm × 70.7mm × 70.7mm and cure for 28 days according to standard.

[0044] Freeze-thaw cycle: The rapid freezing test was conducted according to GB / T 50082-2009 Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete. Each freeze-thaw cycle consisted of freezing at (-20±2)℃ for 4 hours, followed by thawing in water at (20±2)℃ for 4 hours.

[0045] Testing indicators: After every 25 cycles, the mass of the specimen is measured and the mass loss rate is calculated. Simultaneously, its compressive strength is tested and the strength loss rate is calculated.

[0046] The results are shown in Table 3.

[0047] Conclusion: Example 2 exhibited the lowest loss of mass and strength after 25 freeze-thaw cycles. Comparative Example 2 (without air-entraining agent) showed a sharp decline in performance, demonstrating that the uniform, closed microbubble system introduced by the air-entraining agent is the core component resisting freeze-thaw stress. Meanwhile, the performance degradation in Comparative Examples 1 and 3 indicates that the addition of fibers and polymers enhanced the matrix toughness of the mortar, working synergistically with the porous structure generated by the air-entraining agent to improve the material's resistance to freeze-thaw damage.

[0048] Test Example 3 Bond strength and flexibility test Objective: To verify the bonding performance and flexibility of the mortar of the present invention with the base wall, and to assess the risk of cracking and falling off.

[0049] method: Bond strength test: According to the "JGJ / T 70-2009 Standard for Test Methods of Basic Performance of Building Mortar", the test mortar is bonded to the base mortar using an "8" shaped cement mortar mold, and the tensile bond strength is tested after 28 days of curing.

[0050] Compression-to-flexural ratio test: According to GB / T 20473-2021, the compressive strength and flexural strength of 40mm × 40mm × 160mm prism specimens cured for 28 days in the same batch were tested, and the compression-to-flexural ratio (compressive strength / flexural strength) was calculated. The lower the compression-to-flexural ratio, the better the material flexibility.

[0051] The results are shown in Table 4.

[0052] Conclusions: Example 2 exhibited the highest bond strength and the lowest compression-to-flexure ratio, indicating strong adhesion to the substrate and optimal toughness. Comparative Example 3 (without cellulose ether and adhesive powder) showed a sharp decrease in bond strength, demonstrating the crucial role of redispersible latex powder and cellulose ether in enhancing bond strength. Comparative Example 1 (without fibers) showed a significantly increased compression-to-flexure ratio, proving the significant contribution of polypropylene fibers to improving flexibility and inhibiting brittle fracture. The synergistic effect of these three elements ensures that the mortar is less prone to cracking or detachment under temperature changes or slight structural deformation.

[0053] Test Example 4 Construction and Sagging Resistance Tests Objective: To evaluate the improvement of mortar workability by the optimized preparation process of this invention.

[0054] method: Consistency and Segregation: According to JGJ / T 70-2009, the consistency (mm) of mortar is measured using a mortar consistency meter. The well-mixed mortar is poured into a segregation meter, allowed to stand for 30 minutes, and the consistency difference between the upper and lower layers is measured; this difference is the segregation (mm). A small segregation indicates good water retention and stable workability.

[0055] Anti-sagging property: Apply the mixed mortar evenly to a vertically placed concrete slab to a thickness of 20mm. After standing for 5 minutes, observe whether the mortar slides down or shows signs of sagging.

[0056] The results are shown in Table 5.

[0057] Conclusion: Example 2, benefiting from stepwise feeding and optimized mixing processes, ensured the uniform dispersion and full dissolution of water-retaining components such as hydroxypropyl methylcellulose, forming a stable slurry structure. Therefore, it exhibited suitable consistency, low stratification, and excellent anti-sagging properties. Comparative Example 4 (one-time mixing) showed increased stratification and sagging, proving that the preparation process of this invention is necessary and effective in ensuring the final product's application performance.

[0058] Test Case Summary: The above tests verify the technological advancements of this invention. Regarding crack resistance, the 28-day drying shrinkage rate of the present invention is as low as 0.06%, far lower than the comparative example and commercially available products, demonstrating its excellent resistance to shrinkage cracking. In the freeze-thaw resistance test, after 25 freeze-thaw cycles, the mass loss rate of this invention is only 2.5%, and the compressive strength loss rate is 10.2%, with performance degradation far lower than the comparative example lacking key components (such as air-entraining agents and fibers), highlighting its superior durability. In terms of mechanical and construction properties, the tensile bond strength of this invention reaches 0.25 MPa, and the compression-flexure ratio is as low as 3.2, while also exhibiting good anti-sagging properties, indicating strong adhesion to the base wall, good flexibility, and ease of construction. All the above test data clearly show that there is a significant synergistic effect among the key components of this invention (fibers, polymers, and air-entraining agents).

[0059] It is worth noting that the above description of the embodiments focuses on illustrating the technical solution of the present invention, rather than precisely defining its scope of protection. Those skilled in the art should understand that appropriate adjustments and optimizations can be made based on the technical details disclosed in the embodiments of the present invention, or equivalent substitutions can be implemented for individual or even all technical elements. Such adjustments and substitutions will not deviate from the core essence of the technical solution of the present invention and should be included within the technical protection scope of the embodiments of the present invention. In short, the protection of the present invention should not be limited to the concrete presentation of the above embodiments, but broadly covers all equivalent changes and improvements that do not depart from its basic concept. In summary, the protection definition of the present invention should be based on the statement of the claims, and the above embodiments are only used as a reference guide for understanding the present invention.

Claims

1. A method for preparing a novel crack-resistant and frost-resistant inorganic thermal insulation mortar, characterized in that, Includes the following steps: (1) Premixing: Add 30-50 parts by weight of ordinary silicate cement, 10-20 parts by weight of heavy calcium carbonate, 0.1-0.5 parts by weight of hydroxypropyl methylcellulose and 1-3 parts by weight of redispersible latex powder to a mixer and stir at a speed of 200-400 rpm for 5-10 minutes to make it initially uniformly mixed. (2) Add thermal insulation aggregate: Under stirring, add 20-30 parts by weight of vitrified microspheres to the mixture obtained in step (1), and stir at a speed of 100-200 rpm for 5-10 minutes to ensure that the thermal insulation aggregate is evenly dispersed; (3) Add fiber and additives: Add 0.5-1.5 parts by weight of polypropylene fiber and 0.01-0.05 parts by weight of air-entraining agent to the mixture obtained in step (2), and stir at a speed of 300-500 rpm for 10-15 minutes to fully disperse the fiber and additives. (4) Homogenization: Increase the rotation speed to 400-600 rpm and disperse at high speed for 10-20 minutes until the mixture is uniform in fineness and free of lumps; (5) Discharge: Let stand for 10-20 minutes to mature, then discharge and package to obtain the new type of crack-resistant and frost-resistant inorganic thermal insulation mortar.

2. The preparation method according to claim 1, characterized in that, The ordinary silicate cement mentioned in step (1) is grade 42.5 ordinary silicate cement.

3. The preparation method according to claim 1, characterized in that, The bulk density of the vitrified microspheres mentioned in step (2) is 80-120 kg / m3, and the particle size range is 0.5-1.5 mm.

4. The preparation method according to claim 1, characterized in that, The polypropylene fibers mentioned in step (3) have a length of 3-6 mm and a diameter of 10-20 μm.

5. The preparation method according to claim 1, characterized in that, The air-entraining agent mentioned in step (3) is a rosin thermal polymer air-entraining agent.

6. The preparation method according to claim 1, characterized in that, The high-speed dispersion time mentioned in step (4) is 15 minutes, and the rotation speed is 500 rpm.

7. A novel crack-resistant and frost-resistant inorganic thermal insulation mortar, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The novel crack-resistant and frost-resistant inorganic thermal insulation mortar according to claim 7, characterized in that, The mortar has a dry density ≤250kg / m3, compressive strength ≥0.5MPa, thermal conductivity ≤0.065W / (m•K), and a mass loss rate ≤5% after 25 freeze-thaw cycles.

9. The application of the novel crack-resistant and frost-resistant inorganic thermal insulation mortar as described in claim 7 in building exterior wall insulation, roof insulation in cold regions, or energy-saving renovation of old buildings.

10. The application according to claim 9, characterized in that, Application should be done by smearing or spraying, with a thickness of 20-50mm, and the ambient temperature should not be lower than -5℃.

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