Mineral coated glass fiber, high and low temperature resistant foam concrete and preparation methods thereof

Abstract

The invention relates to the technical field of building materials, in particular to mineral-coated glass fibers, high-temperature-resistant and low-temperature-resistant foam concrete and preparation methods thereof. The preparation method comprises the following steps: carrying out impurity removal, acid pickling and calcination pretreatment on mineral admixtures such as diatomite, metakaolin or fly ash, cleaning glass fibers, chemically grafting the mineral admixtures and the glass fibers by using a silane coupling agent, and carrying out hydrolysis, polymerization and vacuum curing to uniformly coat the surfaces of the fibers with minerals so as to prepare the mineral-coated glass fibers. When the mineral admixture is doped into foam concrete, the combination of a pore structure and an interface can be remarkably improved, the mechanical property and durability of the material at an extreme temperature are enhanced, and a new way is provided for high-valued application of the mineral admixture and the glass fiber.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a mineral-coated glass fiber, high and low temperature resistant foamed concrete, and their preparation methods. Background Technology

[0002] Fiber-reinforced cementitious composites, by introducing discontinuous short fibers or continuous long fibers, can to some extent compensate for the inherent defects of traditional cementitious materials, such as low tensile strength, high brittleness, and susceptibility to cracking. In recent years, foamed concrete has been widely used in building envelopes, roof insulation layers, and lightweight infill projects due to its low density, good thermal insulation properties, and light weight. However, the presence of numerous interconnected or semi-connected pores within foamed concrete leads to lower matrix strength and weak early crack resistance. During long-term service, it is susceptible to the coupled effects of environmental factors such as moisture migration, freeze-thaw cycles, and temperature gradients, resulting in degradation of mechanical properties and insufficient durability.

[0003] To improve the overall performance of foamed concrete, researchers have attempted to combine it with fiber reinforcement technology to develop fiber-reinforced foamed concrete. Glass fiber, due to its low cost, high tensile strength, and ease of dispersion, has become a potential reinforcing phase. However, the application of glass fiber in cement-based systems still faces significant challenges: on the one hand, the porous structure of foamed concrete provides penetration channels for corrosive media such as chloride and sulfate ions, accelerating material degradation; on the other hand, the cement hydration process releases a large number of hydroxide ions, causing the pore fluid pH to reach as high as 12–14. This highly alkaline environment easily leads to the destruction of the silica network structure on the glass fiber surface, triggering alkaline corrosion and strength decay, thereby weakening its reinforcing effectiveness and even causing debonding at the fiber-matrix interface, seriously affecting the long-term service reliability of the composite material.

[0004] To improve the interfacial properties between fibers and cementitious matrices, existing technologies have proposed various fiber surface modification methods. These include coating fibers with inorganic or organic coatings such as nano-silica, aluminum hydroxide, and graphene oxide, or incorporating nanoparticles into the slurry to optimize the density of the interfacial transition zone (ITZ). Some studies have applied these methods to foamed concrete systems to improve their stability under high-temperature or freeze-thaw conditions. However, these modification strategies generally suffer from complex preparation processes, high raw material costs, harsh reaction conditions, and the potential introduction of organic byproducts, making it difficult to meet the requirements of economic efficiency, environmental friendliness, and operability for large-scale engineering applications.

[0005] For example, Chinese patent CN116969727A discloses a foamed concrete board and its preparation method. This technology uses a silane coupling agent to treat the surface of alkali-resistant glass fibers, ceramic fibers, and basalt fibers, and incorporates solid waste such as diatomaceous earth and red brick powder to improve bonding performance and crack resistance. This approach focuses on multi-fiber synergistic reinforcement and solid waste resource utilization, mainly targeting the improvement of room temperature mechanical properties. It does not form a novel fiber reinforcement with independent functions, nor does it systematically solve the problems of alkali resistance stability and interface durability of glass fibers under extreme high / low temperature service environments.

[0006] It is worth noting that commonly used mineral admixtures such as diatomaceous earth, metakaolin, and fly ash are not only widely available, inexpensive, and environmentally friendly, but also rich in active functional groups such as silanol groups (Si–OH) on their surfaces, sharing certain similarities with glass fibers in chemical composition. From a material compatibility perspective, there may be a potential basis for interfacial interactions between the two. Currently, these mineral admixtures are mostly used as substitutes for cementitious materials or as functional fillers, incorporated alone into ordinary concrete or foamed concrete to reduce density, improve thermal insulation performance, or refine pore structure. However, there are no research reports on combining mineral admixtures with the surface functionalization of glass fibers. Although exploring the regulatory role of mineral components on the fiber-matrix interface from a materials design perspective has certain theoretical significance, there is still a lack of systematic research and technical pathways to support how to effectively achieve stable adhesion of mineral phases on the fiber surface, the interfacial bonding mechanism, and whether this strategy can synergistically improve the mechanical stability and long-term durability of foamed concrete under harsh environments such as high and low temperature alternation and freeze-thaw cycles.

[0007] Therefore, developing a resource-rich, low-cost, and environmentally friendly mineral admixture for simple and engineerable surface modification of glass fiber, and organically combining it with foamed concrete systems to significantly improve its durability in extreme high and low temperature environments while ensuring lightweight and thermal insulation properties, remains a pressing technical problem to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides mineral-coated glass fibers, high- and low-temperature resistant foamed concrete, and their preparation methods. The aim is to construct an inorganic coating layer composed of mineral admixtures in situ on the surface of glass fibers using interface modifiers such as silane coupling agents. This produces mineral-coated glass fibers that provide both fiber protection and matrix reinforcement. When incorporated into foamed concrete, this significantly improves the interfacial bonding between the mineral-coated glass fibers and the foamed concrete matrix, enhancing the strength and durability of the material under high-temperature and freeze-thaw conditions. Furthermore, it fully leverages the advantages of abundant mineral admixture resources, environmental friendliness, and low cost, demonstrating promising engineering application prospects and environmental benefits.

[0009] Specifically, the present invention provides a method for preparing mineral-coated glass fibers, characterized by comprising the following preparation steps:

[0010] S1. Mix the silane coupling agent with an alcohol solvent to obtain a mixed solution; adjust the mixed solution to an acidic state, and perform a hydrolysis reaction on the mixed solution to obtain a silane coupling agent hydrolysate;

[0011] S2. Add the mineral admixture powder to the silane coupling agent hydrolysate and disperse it evenly to obtain a mineral admixture dispersion;

[0012] S3. Contact the glass fiber with the mineral admixture dispersion to allow the mineral admixture to adhere to and be fixed on the surface of the glass fiber, thereby obtaining glass fiber loaded with mineral admixture;

[0013] S4. The glass fiber loaded with mineral admixture is dried under reduced pressure and cross-linked with the surface of the glass fiber by a silane coupling agent to form a mineral admixture-glass fiber composite layer on the surface of the glass fiber, thereby obtaining mineral-coated glass fiber.

[0014] In some specific embodiments of the present invention, the silane coupling agent is a coupling agent for fiber reinforcement that can both condense with inorganic surfaces and contain reactive organic functional groups.

[0015] In some specific embodiments of the present invention, the silane coupling agent is selected from one or more of aminosilanes, epoxysilanes, and vinylsilanes.

[0016] In some specific embodiments of the present invention, the silane coupling agent is silane coupling agent KH-560.

[0017] In some specific embodiments of the present invention, the glass fiber in S3 needs to be pretreated. The pretreatment steps include: washing the glass fiber in anhydrous ethanol to remove surface impurities and sizing agent, and drying it for later use.

[0018] In some specific embodiments of the present invention, the volume ratio of the silane coupling agent to the alcohol solvent is 1:(6-15); the hydrolysis reaction is carried out under acidic conditions with a pH of 4.0 to 5.0; the hydrolysis reaction is carried out at a temperature of 30 to 50°C; and the hydrolysis reaction takes 0.5 to 2 hours.

[0019] In some specific embodiments of the present invention, the hydrolysis reaction is carried out under acidic conditions with a pH of 4.5; the hydrolysis reaction is carried out at a temperature of 40°C; and the hydrolysis reaction takes 0.5 to 2 hours.

[0020] In some specific embodiments of the present invention, the alcohol solvent is ethanol, methanol, or isopropanol.

[0021] In some specific embodiments of the present invention, the mineral admixture is at least one of diatomaceous earth, metakaolin, silica fume or fly ash; the mass fraction of the mineral admixture in the mineral admixture dispersion is 9-15 wt%.

[0022] In some specific embodiments of the present invention, the mineral admixture is a mineral admixture that has been purified by acid washing and activated by high-temperature calcination; after treatment, the mineral admixture has an average particle size of 45-75 μm and a specific surface area of ​​5-25 m² / g.

[0023] In some specific embodiments of the present invention, the contact method in S3 is at least one of impregnation-stirring and spray coating; the mass ratio of the mineral admixture to the glass fiber is (0.9-1.5):1; the glass fiber is alkali-resistant glass fiber with a diameter of 11-12 μm and a length of 11-12 mm.

[0024] In some specific embodiments of the present invention, the impregnation-stirring step involves adding glass fiber into a mineral admixture dispersion and continuously stirring at 35–45°C for 2–4 hours to complete the impregnation-stirring treatment.

[0025] In some specific embodiments of the present invention, the drying temperature in step S4 is 60-80°C; the drying time is 12-24 hours.

[0026] In some specific embodiments of the present invention, the drying temperature in step S4 is 80°C; the drying time is 12 to 24 hours.

[0027] In some specific embodiments of the present invention, the decompression condition is a vacuum condition.

[0028] The present invention also provides a mineral-coated glass fiber, which is prepared by any of the above-described methods for preparing mineral-coated glass fibers.

[0029] The present invention also provides mineral-coated glass fibers prepared by any of the above-described methods, or the application of the above-described mineral-coated glass fibers in the preparation of foamed concrete.

[0030] The present invention also provides a high and low temperature resistant foamed concrete, which is prepared from the following components in parts by weight: 652 to 662 parts of cement, 20 to 21 parts of foam, 3.25 to 9.75 parts of mineral-coated glass fiber prepared by any of the above methods, and 326 to 336 parts of water.

[0031] This invention also provides a method for preparing high and low temperature resistant foamed concrete, which includes the following preparation steps:

[0032] A method for preparing mineral-coated glass fibers, characterized by comprising the following preparation steps:

[0033] S1. Mix the silane coupling agent with an alcohol solvent to obtain a mixed solution; adjust the mixed solution to an acidic state, and perform a hydrolysis reaction on the mixed solution to obtain a silane coupling agent hydrolysate;

[0034] S2. Add the mineral admixture powder to the silane coupling agent hydrolysate and disperse it evenly to obtain a mineral admixture dispersion;

[0035] S3. Contact the glass fiber with the mineral admixture dispersion to allow the mineral admixture to adhere to and be fixed on the surface of the glass fiber, thereby obtaining glass fiber loaded with mineral admixture;

[0036] S4. The glass fiber loaded with mineral admixture is dried under reduced pressure and cross-linked with the surface of the glass fiber by a silane coupling agent to form a mineral admixture-glass fiber composite layer on the surface of the glass fiber, thereby obtaining mineral-coated glass fiber.

[0037] The present invention also provides a high and low temperature resistant foamed concrete specimen, which is prepared by the following steps:

[0038] (1): Weigh the raw materials according to the following parts by weight: 652 to 662 parts of cement, 20 to 21 parts of foam, 3.25 to 9.75 parts of mineral-coated glass fiber prepared by the preparation method of mineral-coated glass fiber described above, and 326 to 336 parts of water.

[0039] (2): Mix cement, water and mineral-coated glass fiber and stir evenly to form a uniform slurry;

[0040] (3): Add foam to the slurry and continue stirring until the slurry and foam are fully and evenly mixed to obtain high and low temperature resistant foamed concrete;

[0041] (4): The high and low temperature resistant foamed concrete is poured into a mold and cured for 28 to 30 days at a temperature of 20℃±2℃ and a relative humidity of not less than 95%. After demolding, the high and low temperature resistant foamed concrete specimen is obtained.

[0042] The present invention has the following significant advantages and effects compared with the prior art:

[0043] (1) Significantly improved interfacial bonding performance: Through the mediation of interfacial modifiers such as silane coupling agents, an inorganic coating composed of mineral admixtures such as diatomaceous earth, metakaolinite, silica fume, and fly ash is constructed in situ on the surface of glass fibers, forming an independent "mineral-coated fiber" functional unit. This mineral coating forms a strong chemical bond and physical anchor with the surface of the glass fibers. At the same time, its own inorganic properties have excellent compatibility with the foamed concrete matrix. Compared with the existing technology where "the fiber surface is only treated with silane and the mineral powder is separately incorporated into the matrix", this invention completely solves the technical problems of poor interfacial bonding between the fiber and the matrix and easy agglomeration of mineral powder. It significantly improves the interfacial bonding strength between the fiber and the concrete matrix, realizes the synergistic stress of the fiber and the matrix, and provides a core guarantee for improving the mechanical properties and durability of the material.

[0044] (2) Enhanced service performance under extreme temperatures: The mineral coating layer constructed by the present invention has both excellent thermal stability and freeze-thaw resistance, enabling the composite material to maintain high mechanical strength and structural integrity under high temperature (such as fire environment) and repeated freeze-thaw cycles. Unlike the simple physical blending method of "fiber and mineral powder are added separately" in the prior art, the present invention forms a mineral-coated fiber unit with a clear structure and integrated function through the strategy of "coating first and then composite", which solves the key problem of performance degradation of foamed concrete under extreme environment.

[0045] (3) Realize the high-value utilization of solid waste resources: Using industrial by-products or natural minerals such as diatomaceous earth, fly ash, and metakaolin as coating materials not only reduces the cost of raw materials, but also promotes the green recycling of bulk solid waste, which is in line with the concept of sustainable development.

[0046] In summary, this invention not only achieves a breakthrough in material performance, but also demonstrates significant advantages in environmental benefits and engineering applicability, providing an innovative technical path for the development of high-performance, durable foamed concrete. Detailed Implementation

[0047] The present invention will be further described in conjunction with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0048] According to the present invention, a method for preparing mineral-coated glass fibers is provided, comprising the following steps:

[0049] ① Clean the glass fiber in anhydrous ethanol to remove surface impurities and sizing agent, and then dry it for later use;

[0050] ② Mix silane coupling agent with anhydrous ethanol at a volume ratio of 1:(6~15) to obtain a mixed solution; adjust the pH of the mixed solution to an acidic state of 4.0 to 5.0, and carry out a hydrolysis reaction at a temperature of 40°C for 0.5 to 2 hours to obtain a silane coupling agent hydrolysate;

[0051] ③ The mineral admixture is at least one of diatomaceous earth, metakaolin, silica fume, or fly ash. The mineral admixture is a mineral admixture that has been purified by acid washing and activated by high-temperature calcination. After treatment, the average particle size of the mineral admixture is 45-75 μm, and the specific surface area is 5-25 m² / g. The mineral admixture powder is added to the silane coupling agent hydrolysate and dispersed evenly to obtain a mineral admixture dispersion. The mass fraction of the mineral admixture in the mineral admixture dispersion is 9-15 wt%.

[0052] ④ The glass fiber is added to the mineral admixture dispersion and stirred continuously at 35–45℃ for 2–4 hours to complete the impregnation-stirring treatment; the mineral admixture is attached and fixed to the surface of the glass fiber to obtain glass fiber loaded with mineral admixture; the mass ratio of the mineral admixture to the glass fiber is (0.9–1.5):1; the glass fiber is alkali-resistant glass fiber with a diameter of 11–12 μm and a length of 11–12 mm;

[0053] ⑤ The glass fiber loaded with mineral admixture is dried under reduced pressure at a temperature of 80°C for 12-24 hours. The mineral admixture is cross-linked with the glass fiber surface under the action of a silane coupling agent to form a mineral admixture-glass fiber composite layer on the glass fiber surface, thus obtaining mineral-coated glass fiber.

[0054] According to the present invention, a method for preparing high and low temperature resistant foamed concrete is provided, comprising the following steps:

[0055] Step (1): Weigh the raw materials according to the following parts by weight: 652 to 662 parts of cement, 20 to 21 parts of foam, 3.25 to 9.75 parts of mineral-coated glass fiber prepared by the preparation method of mineral-coated glass fiber of the present invention, and 326 to 336 parts of water;

[0056] Step (2): Mix cement, water and mineral-coated glass fiber and stir evenly to form a uniform slurry;

[0057] Step (3): Add foam to the slurry and continue stirring until the slurry and foam are fully mixed and homogeneous to obtain composite foam concrete.

[0058] This invention provides a method for evaluating the high and low temperature resistance of foamed concrete, using the changes in the mass and compressive strength of the foamed concrete before and after high and low temperature damage as the evaluation criteria, including the following steps:

[0059] a) Pre-curing and grouping of specimens

[0060] The high and low temperature resistant foamed concrete slurry prepared according to the present invention is poured into a mold to form a shape, preventing the fibers from floating or settling significantly. The cast specimens are cured for 28 to 30 days at 20℃±2℃ and relative humidity not less than 95%. The specimens are then divided into a high temperature test group and a freeze-thaw test group.

[0061] b) High-temperature performance evaluation

[0062] The specimens in the high-temperature test group were heated from room temperature to the target temperature in a muffle furnace at a set heating rate. The target temperatures were room temperature, 200℃, 400℃, 600℃, and 800℃, respectively. After being held at each target temperature for 2 hours, the specimens were naturally cooled to room temperature. The masses m0 and m of the specimens before and after the high-temperature treatment were measured. i and compressive strength e0, e i Calculate the mass loss rate according to the following formula. And compressive strength loss rate S:

[0063]

[0064]

[0065] c) Evaluation of freeze-thaw performance

[0066] The specimens in the freeze-thaw test group were subjected to freeze-thaw cycles within a temperature range of −15℃ to 15℃, with the number of cycles being 0, 25, 50, 75, and 100, respectively. The control group with 0 cycles was the non-freeze-thaw control group. After each stage of freeze-thaw treatment, the mass and compressive strength of the specimens were measured, and the mass loss rate and compressive strength loss rate before and after freeze-thaw were calculated according to the above formula.

[0067] d) Comprehensive evaluation and mechanism analysis

[0068] By comparing the mass loss rate, compressive strength loss rate, and apparent damage of foamed concrete under high temperature and freeze-thaw conditions with different mineral-coated glass fiber content, and combining the changes in pore structure parameters and micromorphology, the effect of mineral-coated glass fiber on improving the high and low temperature resistance of foamed concrete was evaluated, and the modification scheme with the best comprehensive performance was determined.

[0069] Example 1 Preparation of mineral-coated glass fiber A

[0070] Mineral-coated glass fiber A was prepared according to the following preparation steps and the preparation conditions in Table 1:

[0071] (i) Clean the glass fiber in anhydrous ethanol to remove surface impurities and sizing agent, and dry it for later use.

[0072] (ii) Mix silane coupling agent KH560 with ethanol to obtain a mixed solution; adjust the mixed solution to an acidic state and perform a hydrolysis reaction on the mixed solution to obtain a silane coupling agent hydrolysate;

[0073] (iii) Add the mineral admixture powder (diatomaceous earth powder) to the silane coupling agent hydrolysate and disperse it evenly to obtain a mineral admixture dispersion;

[0074] (iv) Contact the glass fiber with the mineral admixture dispersion to allow the mineral admixture to adhere to and fix on the surface of the glass fiber, thereby obtaining glass fiber loaded with mineral admixture;

[0075] (v) The glass fiber loaded with mineral admixture is dried under reduced pressure and cross-linked with the surface of the glass fiber under the action of silane coupling agent to form a mineral admixture-glass fiber composite layer on the surface of the glass fiber, thereby obtaining mineral-coated glass fiber.

[0076] Table 1. Preparation conditions of mineral-coated glass fiber A

[0077]

[0078] Example 2 Preparation of mineral-coated glass fiber B

[0079] The preparation steps are the same as in Example 1, and the preparation conditions are shown in Table 2.

[0080] Table 2 Preparation conditions of mineral-coated glass fiber B

[0081]

[0082] Example 3 Preparation of mineral-coated glass fiber C

[0083] The preparation steps are the same as in Example 1, and the preparation conditions are shown in Table 3.

[0084] Table 3 Preparation conditions of mineral-coated glass fiber C

[0085]

[0086] Example 4: Preparation of foamed concrete with different fiber content

[0087] Prepare the foamed concrete (excluding the C-SG group) according to the following preparation steps and the mix proportions in Table 4:

[0088] (I) Mix cement, water and mineral-coated glass fiber A or alkali-resistant glass fiber and stir evenly to form a uniform slurry;

[0089] (II) Prepare a foaming solution by mixing foaming agent and water in a certain proportion, and prepare stable foam by mechanical stirring. Add the foam to the slurry and continue stirring until the slurry and foam are fully mixed and uniform to obtain foamed concrete with different mineral-coated glass fiber A content or different ordinary glass fiber content.

[0090] C-SG group foamed concrete was prepared according to the following preparation steps and the mix proportions in Table 4:

[0091] (i) Mix cement, water, diatomaceous earth and modified glass fiber (a mixture of silane coupling agent and alkali-resistant glass fiber in a mass ratio of 1:5) and stir evenly to form a uniform slurry;

[0092] (ii) Prepare a foaming solution by mixing foaming agent and water in a certain proportion, and prepare stable foam by mechanical stirring. Add the foam to the slurry and continue stirring until the slurry and foam are fully mixed and uniform to obtain foamed concrete with different mineral-coated glass fiber A content or different ordinary glass fiber content.

[0093] Table 4 Mix proportions of foamed concrete with different fiber content

[0094]

[0095] Performance tests were conducted on foamed concrete with different mineral-coated glass fiber A content or different ordinary glass fiber content prepared in this embodiment. The test results are shown in Table 5.

[0096] Table 5 Performance of foamed concrete with different mineral-coated glass fiber A content or different ordinary glass fiber content

[0097]

[0098] As shown in this embodiment, under the same foamed concrete mix proportion and dry density, the 28-day room temperature compressive strength of group C-0 is 6.8–7.3 MPa, while the compressive strengths of groups C-DE, C-GF, and C-DG are 6.6–7.2 MPa, 7.1–7.7 MPa, and 7.0–7.7 MPa, respectively. The 28-day room temperature compressive strength of groups FC-1 to FC-3 is further increased to 7.5–8.5 MPa, with group FC-2 exhibiting the highest strength. These results indicate that, without changing the matrix mix proportion, constructing a mineral coating on the surface of glass fiber can significantly improve the synergistic load-bearing capacity of the fiber and the foamed concrete matrix, achieving a higher strength level. This provides a foundation for maintaining high residual strength and low strength loss under high-temperature and freeze-thaw cycles.

[0099] Example 5: Evaluation of freeze-thaw performance of foamed concrete with different fiber content

[0100] The evaluation method, based on the changes in the mass and compressive strength of foamed concrete before and after low-temperature damage, includes the following steps:

[0101] a) Pre-curing of specimens

[0102] The foamed concrete slurry with different fiber content prepared in Example 4 was poured into a mold to form a specimen, preventing the fibers from floating or settling significantly. The cast specimens were then cured for 28 days at 20℃±2℃ and relative humidity not less than 95%.

[0103] b) Evaluation of freeze-thaw performance

[0104] The specimens in the freeze-thaw test group underwent freeze-thaw cycles within a temperature range of −15℃ to 15℃, with the number of cycles being 0, 25, 50, 75, and 100, respectively. The control group (0 cycles) was the non-freeze-thaw control group. After each freeze-thaw treatment, the specimen masses m0 and m2 were measured. i and compressive strength e0, e i The mass loss rate and compressive strength loss rate before and after freeze-thaw are calculated according to the following formula.

[0105]

[0106]

[0107] d) Comprehensive evaluation and mechanism analysis

[0108] By comparing the mass loss rate, compressive strength loss rate, and apparent damage of foamed concrete with different fiber content under freeze-thaw conditions, and combining the changes in pore structure parameters and micromorphology, the effect of mineral-coated glass fiber on improving the low-temperature resistance of foamed concrete was evaluated.

[0109] The parameters / conditions for freeze-thaw performance evaluation are shown in Table 7; the freeze-thaw performance evaluation data are shown in Table 8.

[0110] Table 7. Test conditions for evaluating the freeze-thaw performance of foamed concrete with different fiber contents.

[0111]

[0112] Table 7. Evaluation data of freeze-thaw performance of foamed concrete with different fiber contents

[0113]

[0114] Example 6: Evaluation of the high-temperature performance of foamed concrete with different fiber content

[0115] The evaluation method, based on the changes in the mass and compressive strength of foamed concrete before and after high-temperature damage, includes the following steps:

[0116] a) Pre-curing and grouping of specimens

[0117] The foamed concrete slurry with different fiber content prepared in Example 4 was poured into a mold to form a specimen, preventing the fibers from floating or settling significantly. The cast specimens were then cured for 28 days at 20℃±2℃ and relative humidity not less than 95%.

[0118] b) High-temperature performance evaluation

[0119] The specimens were heated from room temperature to target temperatures in a muffle furnace at a set heating rate. The target temperatures were room temperature, 200℃, 400℃, 600℃, and 800℃, respectively. After being held at each target temperature for 2 hours, the specimens were allowed to cool naturally to room temperature. The specimen masses m0 and m2 before and after the high-temperature treatment were measured. i and compressive strength e0, e i Calculate the mass loss rate according to the following formula. And compressive strength loss rate S:

[0120]

[0121]

[0122] c) Comprehensive evaluation and mechanism analysis

[0123] By comparing the mass loss rate, compressive strength loss rate, and apparent damage of foamed concrete under high temperature conditions with different fiber content, and combining the changes in pore structure parameters and micromorphology, the effect of mineral-coated glass fiber on improving the high and low temperature resistance of foamed concrete was evaluated.

[0124] The parameters / conditions for high-temperature performance evaluation are shown in Table 8, and the high-temperature performance evaluation data are shown in Table 9.

[0125] Table 8. Test conditions for evaluating the high-temperature performance of foamed concrete with different fiber contents.

[0126]

[0127] Table 9. High-Temperature Performance Evaluation Data of Foamed Concrete with Different Fiber Contents

[0128] Group Compressive strength loss rate after 800℃ mass loss rate after 800℃ C-0 (Blank Group) 47.83%-49.18% 32.49%-35.72% C-DE (medium-doped diatomite group) 46.13%-48.35% 31.33%-34.81% C-GF (Ordinary Fiberglass Group) 40.87%-43.92% 28.17%-31.73% C-DG (diatomaceous earth + ordinary glass fiber) 40.31%-43.66% 27.92%-31.82% C-SG (Silane Coupling Agent Modified Glass Fiber Assembly) 39.13%-40.72% 27.37%-30.68% FC-2 (dosage in this invention) 35.31%-38.43% 24.33%-27.26%

[0129] Example 7: Evaluation of the comprehensive durability of foamed concrete with different fiber content after freeze-thaw cycles and then high temperatures.

[0130] The evaluation method assesses the difference in durability between the material of this invention and the control group under conditions of freeze-thaw damage followed by high-temperature exposure, including the following steps:

[0131] a) Pre-curing and grouping of specimens

[0132] The foamed concrete slurry with different fiber content prepared in Example 4 was poured into a mold to form a mold, so as to prevent the fibers from floating or settling significantly. The cast specimens were cured for 28 days at 20℃±2℃ and relative humidity not less than 95%, and then taken out of the curing room and wiped dry.

[0133] b) Freeze-thaw

[0134] The cured specimens were placed in a freeze-thaw test chamber within a temperature range of -15℃ to 15℃ and subjected to freeze-thaw treatment for a predetermined number of cycles (e.g., 0, 50, 100 times). Each cycle included four stages: cooling, low-temperature isothermal treatment, heating, and high-temperature isothermal treatment. After each cycle, the specimens were removed, weighed, and their compressive strength was tested and recorded. The freeze-thawed specimens were then allowed to air dry at room temperature for approximately 24 hours to allow surface moisture to evaporate. For the high-temperature test group, the specimens were heated in a muffle furnace from room temperature to the target temperature at a set heating rate. The target temperatures were room temperature, 200℃, 400℃, 600℃, and 800℃, respectively. After holding at each target temperature for 2 hours, the specimens were allowed to cool naturally to room temperature. The specimen masses m0 and m2 before and after the high-temperature treatment were measured. i and compressive strength e0, e i Calculate the mass loss rate according to the following formula. And compressive strength loss rate S:

[0135]

[0136]

[0137] c) High temperature

[0138] The specimen was then placed in a resistance furnace and heated to the target temperature (e.g., 400℃ or 800℃) at a heating rate of approximately 10℃ / min. After holding at this temperature for 2 hours, the specimen was cooled to room temperature in the furnace. After cooling, the specimen masses m0 and m2 before and after the high-temperature treatment were measured. i and compressive strength e0, e i Calculate the mass loss rate according to the following formula. And compressive strength loss rate S:

[0139]

[0140]

[0141] d) Comprehensive evaluation and mechanism analysis

[0142] By comparing the mass loss rate, compressive strength loss rate, and apparent damage of foamed concrete under freeze-thaw and high-temperature conditions with different mineral-coated glass fiber content, and combining the changes in pore structure parameters and micromorphology, the effect of mineral-coated glass fiber on improving the high and low temperature resistance of foamed concrete was evaluated.

[0143] The parameters / conditions for evaluating the overall durability performance of the freeze-thaw cycle followed by high temperature are shown in Table 10, and the data for evaluating the overall durability performance of the freeze-thaw cycle followed by high temperature are shown in Table 11.

[0144] Table 10 Test conditions for comprehensive durability performance evaluation after freeze-thaw cycle followed by high temperature.

[0145] project Parameter / Condition Description Specimen type Mineral-coated glass fiber foam concrete specimens and comparative specimens of this invention Specimen size 100mm×100mm×100mm Pre-maintenance conditions 20℃±2℃, relative humidity ≥95%, standard curing for 28 days Freeze-thaw temperature range −15℃～15℃ Single freeze-thaw cycle Freeze at -15℃ for 2-4 hours, then thaw at +15℃ for 2-4 hours. Freeze-thaw cycle number setting 0 times, 50 times, 100 times High temperature level setting after freeze-thaw 400℃、800℃ High temperature heating equipment muffle furnace High temperature heating rate 10℃ / min High temperature constant temperature time Hold the temperature at each target temperature for 2 hours. Cooling method Air cooling, allowing it to cool naturally to room temperature. Specimen grouping method The specimens are grouped according to the combination of freeze-thaw cycles and high temperature levels, with each combination corresponding to a group of specimens, and each group consisting of no fewer than 3 specimens. Test time point Before freeze-thaw, before high-temperature treatment, after high-temperature treatment Test Project Specimen quality and compressive strength at each stage Evaluation content The durability difference between the material of this invention and the control group was evaluated under conditions of freeze-thaw damage followed by high-temperature treatment.

[0146] Table 11 Comprehensive durability performance evaluation data after freeze-thaw cycle followed by high temperature.

[0147] Group Compressive strength loss rate after 50 freeze-thaw cycles and then at 400℃ Mass loss rate after 50 freeze-thaw cycles and then at 400℃ Compressive strength loss rate after 100 freeze-thaw cycles and then at 800℃ Compressive strength loss rate after 100 freeze-thaw cycles and then at 800℃ C-0 (Blank Group) 64.15%-69.80% 26.40%-31.75% 80.25%-85.60% 44.90%-49.85% C-DE (medium-doped diatomite group) 62.93%-68.84% 25.80%-30.92% 79.61%-84.13% 43.72%-48.61% C-GF (Ordinary Fiberglass Group) 58.19%-63.21% 23.41%-28.17% 74.53%-79.02% 40.18%-45.35% C-DG (diatomaceous earth + ordinary glass fiber) 57.62%-62.87% 23.16%-27.92% 73.97%-78.34% 39.81%-44.94% C-SG (Silane Coupling Agent Modified Glass Fiber Assembly) 57.82%-61.17% 22.85%-26.88% 71.27%-76.39% 38.03%-43.22% FC-2 (dosage in this invention) 52.41%-59.73% 21.69%-25.37% 69.22%-75.46% 36.36%-41.12%

[0148] As can be seen from the above embodiments, the present invention constructs a protective layer by loading mineral admixtures on the surface of glass fibers and incorporates the mineral-coated glass fibers into foamed concrete. Under the premise of not significantly increasing density and construction complexity, it improves the interfacial bond between fibers and cement matrix, inhibits pore connectivity and crack propagation, and helps reduce mass loss and strength decay under high temperature and freeze-thaw effects. This improves the service stability of foamed concrete in high and low temperature coupled environments, and provides a simple and scalable modification method for the engineering application of foamed concrete under harsh environmental conditions.

[0149] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing mineral-coated glass fibers, characterized in that, The preparation steps include the following: S1. Mix the silane coupling agent with an alcohol solvent to obtain a mixed solution; adjust the mixed solution to an acidic state, and perform a hydrolysis reaction on the mixed solution to obtain a silane coupling agent hydrolysate; S2. Add the mineral admixture powder to the silane coupling agent hydrolysate and disperse it evenly to obtain a mineral admixture dispersion; S3. Contact the glass fiber with the mineral admixture dispersion to allow the mineral admixture to adhere to and be fixed on the surface of the glass fiber, thereby obtaining glass fiber loaded with mineral admixture; S4. The glass fiber loaded with mineral admixture is dried under reduced pressure and cross-linked with the surface of the glass fiber by a silane coupling agent to form a mineral admixture-glass fiber composite layer on the surface of the glass fiber, thereby obtaining mineral-coated glass fiber.

2. The method for preparing mineral-coated glass fibers as described in claim 1, characterized in that, The volume ratio of the silane coupling agent to the alcohol solvent is 1:(6-15); the hydrolysis reaction is carried out under acidic conditions with a pH of 4.0 to 5.0; the hydrolysis reaction is carried out at a temperature of 30 to 50°C; and the hydrolysis reaction takes 0.5 to 2 hours.

3. The method for preparing mineral-coated glass fibers as described in claim 1, characterized in that, The mineral admixture is at least one of diatomaceous earth, metakaolin, silica fume, or fly ash; the mass fraction of the mineral admixture in the mineral admixture dispersion is 9–15 wt%.

4. The method for preparing mineral-coated glass fibers as described in claim 1, characterized in that, The mineral admixture is a mineral admixture that has been purified by acid washing and activated by high-temperature calcination; after treatment, the average particle size of the mineral admixture is 45-75 μm and the specific surface area is 5-25 m² / g.

5. The method for preparing mineral-coated glass fibers as described in claim 1, characterized in that, The contact method in S3 is at least one of impregnation-stirring and spray coating; the mass ratio of the mineral admixture to the glass fiber is (0.9-1.5):1; the glass fiber is alkali-resistant glass fiber with a diameter of 11-12 μm and a length of 11-12 mm.

6. The method for preparing mineral-coated glass fibers according to any one of claims 1-5, characterized in that, The drying temperature in S4 is 60–80°C; the drying time is 12–24 hours.

7. A mineral-coated glass fiber, characterized in that, It is prepared by the method for preparing mineral-coated glass fibers according to any one of claims 1-6.

8. The mineral-coated glass fiber prepared by the method of preparing mineral-coated glass fiber as described in any one of claims 1-6, or the mineral-coated glass fiber as described in claim 7, in the preparation of foamed concrete.

9. A type of high and low temperature resistant foamed concrete, characterized in that, It is prepared from the following components in parts by weight: 652 to 662 parts cement, 20 to 21 parts foam, 3.25 to 9.75 parts mineral-coated glass fiber prepared by the method of preparing mineral-coated glass fiber according to any one of claims 1-6 or as described in claim 7, and 326 to 336 parts water.

10. A method for preparing high and low temperature resistant foamed concrete, characterized in that, The preparation includes the following steps: Step 1: Weigh the raw materials according to the following parts by weight: 652 to 662 parts of cement, 20 to 21 parts of foam, 3.25 to 9.75 parts of mineral-coated glass fiber prepared by the method of mineral-coated glass fiber preparation according to any one of claims 1-5 or as described in claim 6, and 326 to 336 parts of water. Step 2: Mix and stir the cement, water, and mineral-coated glass fibers to form a homogeneous slurry; Step 3: Add foam to the slurry and continue stirring until the slurry and foam are fully mixed and homogeneous to obtain high and low temperature resistant foamed concrete.

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