Preparation method of basalt powder fireproof modified thermal insulation mortar

Abstract

The invention provides a preparation method of basalt powder fireproof modified thermal insulation mortar, and belongs to the technical field of building materials. The basalt powder fireproof modified thermal insulation mortar comprises the following components: Portland cement, gypsum, an alkali activator, modified basalt powder, microencapsulated aluminum hypophosphite, layered double hydroxides, glass beads, expanded vermiculite, fly ash, redispersible latex powder and an organosilicon modified emulsion. The thermal insulation mortar has the beneficial technical effects that through interface modification and multi-stage flame-retardant body design, the problem that strength, thermal insulation and fire prevention of traditional thermal insulation mortar are difficult to consider at the same time is solved, breakthrough of fire resistance, mechanical strength and constructability of the thermal insulation mortar is realized, and the thermal insulation mortar has relatively high environmental protection property.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for preparing basalt powder fireproof modified thermal insulation mortar. Background Art

[0002] Functional mortar, a building material based on cementitious materials like cement and gypsum, is enhanced with specialized properties through the addition of specialized materials, aggregates, and admixtures. It plays a crucial role in modern construction. While conventional mortars, which only fulfill basic functions like masonry and plastering, can achieve specific properties such as fire protection, thermal insulation, waterproofing, high strength, corrosion resistance, and repair and reinforcement, tailored to project requirements, they are widely used in a variety of fields, including construction, transportation, and energy.

[0003] In building wall construction, thermal insulation mortars, by adding lightweight aggregates like expanded perlite and vitrified microspheres, reduce thermal conductivity, achieving efficient insulation and energy conservation. Suitable for both interior and exterior insulation systems, they help buildings meet green energy conservation standards. Waterproof mortars, with their polymers and waterproofing agents, form a dense waterproof layer, effectively resisting rainwater and groundwater infiltration. They are commonly used in humid environments like basements, kitchens, and bathrooms. Furthermore, in road and bridge construction, high-strength repair mortars can quickly repair damaged concrete structures and improve their durability. Anti-corrosion mortars resist attack by chemicals like acids and alkalis, extending the service life of facilities like industrial plants and sewage treatment tanks.

[0004] Among the many types of functional mortars, those containing basalt powder stand out due to their unique advantages. Basalt, a volcanic extrusive rock, is crushed and ground into a powder and then introduced into the mortar system as a functional material, imparting multiple excellent properties.

[0005] Fire resistance is one of the outstanding advantages of functional mortars containing basalt powder. Basalt powder, primarily composed of silicates, is naturally non-combustible and can withstand fire temperatures exceeding 1000°C. Its application in fire-resistant mortars allows the mortar to meet the A1 non-combustibility standard (GB 8624-2012), preventing combustion and toxic gas release when exposed to fire. In high-temperature environments, the skeletal structure formed by basalt powder effectively blocks heat conduction and slows the spread of flames. Adding additives such as flame retardants and refractory fibers further enhances the fireproofing effect. This makes it widely applicable to locations with stringent fire protection requirements, such as high-rise buildings, hospitals, schools, tunnels, and subways, providing reliable protection for building fire safety.

[0006] In terms of thermal insulation performance, basalt powder functional mortar also performs well. The basalt powder in the mortar works synergistically with lightweight thermal insulation aggregates (such as expanded perlite and closed-cell ceramsite) to form a large number of closed pores. Air, as a poor conductor of heat, forms an insulating layer in these pores, greatly reducing the thermal conductivity of the mortar, which can usually be controlled between 0.06-0.10W / (m·K), meeting the requirements of building energy-saving design. In addition, basalt powder has strong chemical stability and can still maintain good physical properties in extreme temperature environments of -40℃-800℃. It has excellent resistance to freeze-thaw cycles, effectively extending the service life of the insulation layer and reducing subsequent maintenance costs.

[0007] Environmental friendliness is also a notable feature of functional mortars containing basalt powder. Basalt, a common rock resource in the Earth's crust, is abundant, has low mining costs, and is highly sustainable. Functional mortars made from basalt powder are inorganic materials and do not release harmful substances such as formaldehyde and volatile organic compounds (VOCs) during production and use. They meet green building material standards and align with the current green and low-carbon development trends in the construction industry. Furthermore, these mortars are recyclable after disposal, reducing the environmental impact of construction waste.

[0008] Basalt powder functional mortar also offers advantages in terms of construction performance and overall durability. By properly blending additives, the mortar possesses excellent workability, facilitating various construction methods such as troweling and spraying. It also provides a strong bond with the base wall, effectively reducing the risk of hollowing and cracking. Furthermore, basalt's resistance to acid and alkali corrosion, UV rays, and electromagnetic radiation significantly enhances the mortar's durability, making it suitable for use in a variety of complex environments, such as industrial plants and coastal structures, providing long-term assurance of project quality. Summary of the Invention

[0009] The purpose of the present invention is to provide a basalt powder fireproof modified thermal insulation mortar, which comprises the following components in parts by mass:

[0010]

[0011]

[0012] The modified basalt powder is obtained by grafting basalt fiber with tannic acid.

[0013] Preferably, the preparation method of the modified basalt powder is:

[0014] S1: Basalt fiber was soaked in acetone and then ultrasonicated; then washed with ethanol and water in sequence and dried;

[0015] S2: soaking basalt fiber in alkaline solution and then plasma treating;

[0016] S3: dissolving tannic acid in Tirs buffer and oxidizing with air;

[0017] S4: soaking the basalt fiber in tannic acid solution and heating and ultrasonic treatment;

[0018] S5: Soak the basalt fiber in Fe 3+ solution, remove and dry.

[0019] Preferably, in step S1, the solid-liquid ratio of basalt fiber to acetone is 1: at least 3;

[0020] In step S2, the alkaline solution is a strong alkaline solution with a concentration of at least 3%; the soaking time is at least 30 minutes;

[0021] In step S3, the concentration of the tannic acid solution is at least 5%; the air oxidation time is at least 4 hours; and stirring is maintained during the air oxidation;

[0022] In step S4, heating to at least 80° C. and soaking for at least 5 hours;

[0023] In the step S5, Fe 3+ The total iron concentration in the solution should be at least 1M; the soaking time should be at least 2 minutes.

[0024] Preferably, the redispersible latex powder is a VAE / VeoVa copolymer type.

[0025] Preferably, the microencapsulated aluminum hypophosphite is aluminum hypophosphite coated with melamine formaldehyde resin or its derivatives.

[0026] Preferably, the layered double hydroxides are zinc-aluminum-based LDHs.

[0027] Preferably, the alkaline activator is a strong alkaline activator or a silicate activator.

[0028] Preferably, the organosilicon-modified emulsion is an acrylic acid-modified organosilicon emulsion.

[0029] Preferably, 0.5-0.8 parts of hydroxypropyl methylcellulose is also included.

[0030] The present invention also provides a method for preparing the aforementioned basalt powder fireproof modified thermal insulation mortar, comprising the following steps:

[0031] S1 Dry powder premixing: dry mix Portland cement, gypsum, alkali activator, fly ash, and redispersible latex powder until uniform to obtain dry powder;

[0032] S2 flame retardant premix: premix microcapsule aluminum hypophosphite and layered double hydroxide to obtain a mixed flame retardant;

[0033] S3: Mix the silicone modified emulsion with water at a water-binder ratio of 0.28-0.32; then add the dry powder and stir; then add the modified basalt powder, glass beads, and expanded vermiculite and stir evenly;

[0034] S4: injection into the mold for molding and curing;

[0035] If the ingredients contain hydroxypropyl methylcellulose, add it during the dry powder premixing in step S1;

[0036] If the water in step S3 contains a water reducer, the water reducer is added to the water in advance, and the water-binder ratio is still 0.28-0.32.

[0037] The components of the present invention can be divided into several categories according to the following:

[0038] 1. Cementitious material system

[0039] Portland cement: As the main cementitious material, it provides basic bonding and early strength, forming a calcium silicate hydrate (CSH) gel skeleton.

[0040] Gypsum: It regulates cement setting time, reduces shrinkage and deformation, and assists in the formation of ettringite (AFt) to enhance early crack resistance. It can also be used in conjunction with alkali activators to promote the release of fly ash activity.

[0041] Alkali activator: Strong alkali or silicate activates the active silica and alumina in fly ash to generate geopolymer gel (NASH), which partially replaces cement and reduces carbon emissions.

[0042] Fly ash: solid waste utilization, rich in active SiO2 and Al2O3, forms geopolymer after alkali activation, enhancing durability; microbead effect improves slurry rheology.

[0043] 2. Functional modified ingredients

[0044] Modified basalt powder: tannic acid and Fe3 + Complex modification roughens the fiber surface, improving mechanical adhesion and flexural strength. Basalt has a melting point of >1500°C, and at high temperatures, it forms a silicate skeleton that slows structural collapse, providing excellent fire-resistant support.

[0045] Redispersible latex powder: VAE / VeoVa copolymer latex powder covers micro-cracks after film formation, improving toughness and reducing shrinkage cracking. It forms a "rigid-flexible" composite reinforcement network with modified basalt fiber.

[0046] Silicone-modified emulsion: Acrylic-modified silicone migrates to the surface to form a hydrophobic film, reducing water absorption and improving freeze-thaw resistance. It can also reduce the surface tension of the slurry and improve workability.

[0047] Hydroxypropyl methylcellulose: It can retain water and thicken, extend the open time, and reduce stratification.

[0048] 3. Fire retardant system

[0049] Microencapsulated aluminum hypophosphite: wrapped in melamine formaldehyde resin to delay decomposition, releases phosphorus free radicals when exposed to fire, interrupting the combustion chain reaction and suppressing smoldering.

[0050] Layered double hydroxide: Zinc-aluminum-based LDHs layers decompose and absorb heat, releasing H2O / CO2 to dilute oxygen, forming a porous metal oxide thermal insulation barrier, which greatly reduces smoke density.

[0051] 4. Thermal insulation system

[0052] Glass beads: Lightweight thermal insulation material with a closed-cell structure that reduces mortar density. The surface is vitrified and sealed, with low water absorption and resistance to freeze-thaw cycles.

[0053] Expanded vermiculite: It is a high-temperature thermal insulation material. After calcination, its volume expands 15-20 times, forming micro-nano pores, which improves the fire resistance limit.

[0054] The beneficial technical effect of the present invention is that through interface modification and multi-stage flame retardant design, it solves the pain point of traditional thermal insulation mortar that is difficult to balance strength, thermal insulation and fire protection, achieves a breakthrough in the fire protection performance, mechanical strength and construction performance of the thermal insulation mortar, and has high environmental protection. DETAILED DESCRIPTION

[0055] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0056] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the specified features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0057] In the description of the present invention, the term "for example" is used to mean "used as an example, illustration or illustration". Any embodiment of the present invention described as "for example" is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any person skilled in the art to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes are not elaborated in detail to avoid obscuring the description of the present invention with unnecessary details. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed herein.

[0058] Unless otherwise specified, the experimental methods used in the specific embodiments are all conventional methods, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0059] In the present invention, unless otherwise specified, “%” represents mass percentage; the raw materials, reagents, etc. used are all conventional commercially available products.

[0060] Example 1

[0061] The preparation of modified basalt powder includes the following steps:

[0062] S1: Soak the basalt fiber in acetone with a mass ratio of basalt fiber to acetone of 1:3; superheat for 30 minutes, then soak for another 12 hours; then wash with ethanol three times, deionized water three times, and then dry in an oven;

[0063] S2: soaking the basalt fiber in 3% NaOH solution for 30 min, and then plasma treating it for 30 min;

[0064] S3: Dissolve tannic acid in Tirs buffer to prepare a 5% tannic acid solution, and then oxidize in air at 30°C for 4 h;

[0065] S4: basalt fibers were immersed in tannic acid solution and ultrasonically treated at 80 °C for 5 h;

[0066] S5: Soak the basalt fiber in Fe3 + 2min in solution, Fe3 + The total iron concentration in the solution is at least 1M; remove and dry.

[0067] Example 2

[0068] The preparation of fireproof modified thermal insulation mortar includes the following steps:

[0069] S1 Weighing: Weigh the raw materials according to the ingredients and amounts in Table 1. The amounts in Table 1 are calculated by mass.

[0070] S2 dry powder premix: dry mix Portland cement, gypsum, alkali activator, fly ash, and redispersible latex powder until uniform to obtain dry powder;

[0071] S3 flame retardant premix: premix microcapsule aluminum hypophosphite and zinc-aluminum-based LDHs complex to obtain a mixed flame retardant;

[0072] S4: Mix the silicone modified emulsion with water (including water reducer) at a water-binder ratio of 0.28; then add the dry powder and stir; then add the modified basalt powder, glass beads, and expanded vermiculite and stir evenly;

[0073] S5: Inject into the mold for molding and curing.

[0074] If the ingredients contain hydroxypropyl methylcellulose, add it during the dry powder premixing in step S1.

[0075] Table 1 Composition of fire-resistant modified thermal insulation mortar

[0076] Ingredients / Serial Number (parts by mass) 1 2 3 4 5 Portland cement 22 24 25 22 22 plaster 2.0 2.5 3.0 2.0 2.0 NaOH 4 5 0 4 4 Water glass activator 0 0 6 0 0 Modified basalt powder 35 37 40 0 0 Basalt fiber 0 0 0 35 0 Wollastonite 0 0 0 0 35 Microencapsulated aluminum hypophosphite 2.0 2.5 3.0 2.0 2.0 Zinc-aluminum-based LDHs 6 7 9 6 6 Glass beads 25 26 28 25 25 Expanded vermiculite 8 9 10 8 8 fly ash 10 13 15 10 10 VAE / VeoVa copolymer redispersible latex powder 4.0 4.5 5.0 4.0 4.0 Acrylic modified silicone emulsion 5 6 7 5 5 Hydroxypropyl methylcellulose 0 0.5 0.8 0 0

[0077] In Table 1, the microencapsulated aluminum hypophosphite is aluminum hypophosphite coated with melamine formaldehyde resin or its derivatives; the zinc-aluminum-based LDHs is zinc-aluminum hydrotalcite.

[0078] Performance Testing

[0079] The performance tests of the fire-resistant modified thermal insulation mortars of each serial number prepared in Example 2 were carried out as follows:

[0080] Bond strength and compressive strength: refer to JGJ70-2009 Test method for basic properties of building mortar;

[0081] Thermal conductivity: measured with reference to GB / T10297 thermal conductivity of non-metallic solid materials;

[0082] Fire resistance time: refer to GB14907-2018 Test method for fire resistance performance of steel structure fire retardant coatings for testing;

[0083] Combustion performance grade: Tested with reference to GB 8624-2012, Classification of Combustion Performance of Building Materials and Products, and the test standard is flat-plate building materials.

[0084] The results are shown in Table 2 below.

[0085] Table 2 Fire-resistant modified thermal insulation mortar performance test

[0086] Project / Serial Number 1 2 3 4 5 Bonding strength (Mpa) 1.30 1.45 1.25 0.94 0.76 Compressive strength (Mpa 16.4 18.2 17.3 11.6 12.8 Thermal conductivity W / (m·K) 0.036 0.038 0.034 0.049 0.078 Refractory time min 305 315 340 285 260 Combustion performance level A1 A1 A2 A1 A1

[0087] Modified basalt powders No. 1, 2, and 3 were prepared by tannic acid-Fe3 + The coordination and plasma treatment significantly improve the mechanical bite force and chemical bonding force between the fiber and the cement matrix. Combined with the redispersible latex powder, the bonding strength can reach a high level. However, the bonding strength of No. 3 has decreased to a certain extent. The present invention believes that although the use of water glass activator promotes early hydration, the excessive lightweight aggregate (38 parts of vermiculite and glass beads) weakens the density, resulting in weak interface bonding. The surface of the unmodified basalt fiber No. 4 is smooth, and the interface is easy to slip, and the bonding strength is lower than that of No. 1. No. 5 uses wollastonite without fiber reinforcement and relies only on latex powder for bonding, with the lowest bonding strength.

[0088] Regarding compressive strength, the differences in compressive strength between No. 1, 2, and 3 are due to the same reasons as in the bond strength analysis. No. 4 exhibits a significant decrease in compressive strength due to the unmodified fibers' tendency to agglomerate and uneven stress distribution. No. 5 is due to the inherently high compressive strength of wollastonite.

[0089] Since No. 3 has the highest proportion of glass microspheres and expanded vermiculite, and the thermal conductivity of basalt powder itself is only 1.5W / (m·K), it has the lowest thermal conductivity. At the same time, the proportion of microencapsulated aluminum hypophosphite and zinc-aluminum hydrotalcite is also the highest, and the two synergistically flame retardant. When heated, aluminum phosphate is released to inhibit combustion, and the hydrotalcite decomposes and absorbs heat, resulting in the longest fire resistance time. However, due to the presence of the organic component hydroxypropyl methylcellulose, the combustion smoke density is slightly higher, so the combustion performance level is A2.

[0090] Basalt No. 4, unmodified, has a smooth surface and strong chemical inertness, resulting in weak bonding with the cement matrix. This leads to three key issues: numerous micro-air gaps at the interface, forming localized thermal barriers; uneven fiber dispersion leading to localized heat accumulation; and interfacial debonding at high temperatures, creating heat conduction pathways, which macroscopically increase thermal conductivity. These heat conduction pathways can form localized high-density areas, leading to localized heat accumulation and premature softening or decomposition of the matrix, ultimately reducing refractory time.

[0091] In No. 5, wollastonite is used instead of basalt. Wollastonite has a higher thermal conductivity (≈1.6W / (m·K)), which leads to fast heat transfer and high thermal conductivity; the refractory time is greatly shortened.

[0092] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A fireproof modified thermal insulation mortar made of basalt powder, characterized in that: The following components are included in parts by mass: The modified basalt powder is obtained by grafting basalt fiber with tannic acid.

2. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: The preparation method of the modified basalt powder is: S1: Basalt fiber was soaked in acetone and then ultrasonicated; then washed with ethanol and water in sequence and dried; S2: soaking basalt fiber in alkaline solution and then plasma treating; S3: dissolving tannic acid in Tirs buffer and oxidizing with air; S4: soaking the basalt fiber in tannic acid solution and heating and ultrasonic treatment; S5: Soak the basalt fiber in Fe 3+ solution, remove and dry.

3. The fireproof modified basalt powder thermal insulation mortar according to claim 2, characterized in that: In step S1, the solid-liquid ratio of basalt fiber to acetone is 1: at least 3; In step S2, the alkaline solution is a strong alkaline solution with a concentration of at least 3%; the soaking time is at least 30 minutes; In step S3, the concentration of the tannic acid solution is at least 5%; the air oxidation time is at least 4 hours; and stirring is maintained during the air oxidation; In step S4, heating to at least 80° C. and soaking for at least 5 hours; In the step S5, Fe 3+ The total iron concentration in the solution should be at least 1M; the soaking time should be at least 2 minutes.

4. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: The redispersible latex powder is of VAE / VeoVa copolymer type.

5. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: The microencapsulated aluminum hypophosphite is aluminum hypophosphite wrapped with melamine formaldehyde resin or its derivatives.

6. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: The layered double hydroxides are zinc-aluminum-based LDHs.

7. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: The alkaline activator is a strong alkaline activator or a silicate activator.

8. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: The organosilicon-modified emulsion is an acrylic acid-modified organosilicon emulsion.

9. The fireproof modified basalt powder thermal insulation mortar according to claim 1, characterized in that: It also includes 0.5-0.8 parts of hydroxypropyl methylcellulose.

10. The method for preparing the fireproof modified thermal insulation mortar of basalt powder according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1 Dry powder premixing: dry mix Portland cement, gypsum, alkali activator, fly ash, and redispersible latex powder until uniform to obtain dry powder; S2 flame retardant premix: premix microcapsule aluminum hypophosphite and layered double hydroxide to obtain a mixed flame retardant; S3: Mix the silicone modified emulsion with water at a water-binder ratio of 0.28-0.32; then add the dry powder and stir; then add the modified basalt powder, glass beads, and expanded vermiculite and stir evenly; S4: injection into the mold for molding and curing; If the ingredients contain hydroxypropyl methylcellulose, add it during the dry powder premixing in step S1; If the water in step S3 contains a water reducer, the water reducer is added to the water in advance, and the water-binder ratio is still 0.28-0.32.

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