Inorganic thin spray mortar for spraying wall surface in wet environment and preparation and application method thereof

Abstract

This invention provides an inorganic thin-film spray coating for wall coating in humid environments, along with its preparation and application methods, belonging to the field of thin-film spray coatings. It addresses the problem that existing thin-film spray materials, when applied in humid environments, cause uneven hydration heat peaks, increased shrinkage stress, and decreased interfacial adhesion, leading to cracking and powdering. This invention comprises white cement, sand (200 mesh), a high-viscosity inorganic polymer material, colloidal silicate, and water. This invention achieves coating curing without cracking or powdering, and maintains good adhesion and durability in humid environments. To enhance performance in specific scenarios, glass fiber is added as an auxiliary component. This invention also provides key points for preparation and curing to overcome shrinkage and porosity control in thin-film spray coatings under humid conditions, and an applicable thickness range of 1mm–5mm.

Description

Technical Field

[0001] This invention relates to the field of thin spray grout technology, and more specifically, to an inorganic thin spray grout for wall spraying in humid environments, and its preparation and application methods. Background Technology

[0002] In the process of mine construction and production, roadway support and sealing are crucial links to ensure the stability of the surrounding rock, prevent the leakage of harmful gases such as methane, sulfur dioxide, and other acidic or oxidizing gases into the working face, protect the safety of mine personnel, and maintain the continuity of production. The quality of support and sealing directly determines the long-term safety and reliability of the shaft and roadways.

[0003] To adapt to the complex geological conditions of mines and the increasing mining pressure, the inorganic non-metallic materials and polymer organic materials in the support materials need to achieve high-strength bonding, excellent density and superior durability with a relatively thin spray coating thickness, while taking into account on-site workability, environmental friendliness and high resource utilization.

[0004] Traditional shotcrete and mortar materials require a large spraying thickness to achieve the desired support strength and sealing effect, resulting in large material consumption, high transportation costs, and extended construction periods. Furthermore, their adhesion is insufficient, failing to bond tightly with the surrounding rock, making them prone to cracking and detachment under geological stress, thus weakening the support effect. Moreover, their high rebound rate, often in the 30%–50% range, leads to significant material waste, increases on-site dust, affects the health of construction workers, and pollutes the mine environment.

[0005] Of particular concern is the fact that mine roadways are generally in high-humidity environments, and these damp conditions significantly degrade the performance of the shotcrete layer. Uneven hydration heat peaks—uneven distribution of moisture within the shotcrete layer leads to regional differences in the hydration reaction rate of cementitious materials such as cement. Locally, rapid hydration concentrates heat release, while other areas experience slower hydration, thus disrupting the internal temperature field and inducing uneven volume deformation. Increased shrinkage stress—the combined effect of moisture difference and chemical shrinkage between the surface and interior of the shotcrete layer causes uncoordinated shrinkage. When the shrinkage tensile stress exceeds the material's tensile strength, microcracks form. Decreased interfacial bonding—the presence of a free water film on the surrounding rock surface weakens the physical adsorption and chemical bonding between the shotcrete and the rock surface. Simultaneously, excessive moisture dilutes the cementitious components at the interface, reducing bond strength. These problems collectively lead to cracking, pulverization, and even flaking of the shotcrete layer, severely compromising the sealing and support reliability of the roadway.

[0006] Thin-film spraying materials based on polymers are expensive and uneconomical, limiting their large-scale application. Furthermore, they require advanced construction techniques, equipment, and personnel skills, making them difficult to implement smoothly in confined underground spaces and complex environments.

[0007] In summary, the development of inorganic thin-film sprayed grout is essentially a systematic integration of the advantages and avoidance of the shortcomings of traditional inorganic materials and organic polymer thin-film sprayed materials, aiming to provide a more economical, efficient, and reliable solution for the complex environment of mines. Developing a novel inorganic thin-film sprayed grout that combines the economic and safety advantages of inorganic materials with the high performance advantages of organic materials, and can achieve high-strength bonding and excellent sealing effects at thin thicknesses, is of significant practical importance for solving the technical challenges of mine roadway support and sealing. Summary of the Invention

[0008] The technical problem to be solved by this invention is:

[0009] To address the problems that existing thin-film spraying materials cause uneven hydration heat peaks, increased shrinkage stress, and decreased interfacial adhesion in humid environments, leading to cracking and pulverization; and that thin-film spraying materials based on polymers are expensive, uneconomical, and require high-level operating equipment, construction methods, and technology, making them difficult to implement smoothly in confined spaces and complex environments downhole.

[0010] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0011] This invention provides an inorganic thin-film spray coating for wall application in damp environments, comprising the following percentages of raw materials:

[0012] 14%-16% white cement, 24%-26% sand, 4%-6% high-viscosity inorganic polymer materials, 4%-6% colloidal silicon steel, 0.2%-0.5% auxiliary components, and the balance is water.

[0013] Furthermore, the high-viscosity inorganic polymer material is magnesium aluminum silicate.

[0014] Furthermore, it also includes auxiliary components, which include one or more of the following: water-reducing agent, retarder, air-entraining agent, air-entraining agent, modifier, and trace additives.

[0015] Furthermore, the auxiliary component is glass fiber, and the mass of the glass fiber is 0.2%–0.5% of the total mass of the inorganic thin spray slurry.

[0016] Furthermore, the white cement is 525 type grade 1 white cement; the sand is white sand with a particle size of 200 mesh; and the glass fiber is chemically reinforced glass fiber with a length of 6 mm–12 mm and a diameter of 10 μm–20 μm.

[0017] A method for preparing an inorganic thin-film spray coating for wall application in damp environments includes the following steps:

[0018] S1. Mix white cement and sand evenly in a dry state to obtain the base material;

[0019] S2. Gradually add water while stirring to obtain the initial slurry;

[0020] S3. Add magnesium aluminum silicate and silicon steel, and continue stirring until homogeneous;

[0021] S4. Add glass fiber as an auxiliary reinforcing material and stir until the inorganic thin spray slurry reaches the target consistency to obtain the mixed inorganic thin spray slurry.

[0022] An application method for an inorganic thin-film spray coating for wall painting in damp environments includes the following steps:

[0023] S100. Inject the prepared inorganic thin spray slurry into the tank of the spraying machine and adjust the tank pressure to 0.4 MPa to 0.6 MPa to prepare for spraying.

[0024] S200. Open the discharge valve at the bottom of the tank and the air pipe valve of the spray gun in sequence. After the air is sprayed out, open the material pipe valve of the spray gun until the slurry is sprayed out from the spray gun. Then construction can begin.

[0025] S300: After spraying, the wall surface is treated with rapid wet curing or wet-pack moisturizing curing to ensure that the hydration process of the thin spray layer is stable within 24h–72h after construction, thereby reducing the risk of later cracking.

[0026] S400. After the construction is completed, immediately clean the spray gun and other spraying equipment, as well as the inner wall of the mixing tank.

[0027] Furthermore, the thickness of a single spray application of the inorganic thin spray paste is 1 mm–5 mm.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. Excellent interface adaptability and substrate universality: This invention breaks through the dependence of traditional coating materials on substrate material. Experiments have proven that the inorganic thin-film spray coating of this invention can maintain excellent adhesion on substrates with a certain degree of water absorption, such as wood panels (Example 1), and can also effectively fill the defects of rough substrates with loose, porous, and low surface energy characteristics, such as coal blocks, through a multi-pass spraying process (Example 2). This flexible substrate adaptability provides a wide range of applications for this technology in complex industrial scenarios and building repair fields.

[0030] 2. Unique rheological regulation mechanism (synergistic enhancement): This invention introduces a composite formula of magnesium aluminum silicate (high viscosity thixotropic agent) and silicon steel, which makes the inorganic thin spray slurry exhibit excellent thixotropy during construction. It can ensure the fluidity during spraying and thicken rapidly after adhesion, effectively suppressing the slurry from sag on vertical or complex irregular surfaces, and significantly improving the forming thickness and surface density of the sprayed coating.

[0031] 3. Crack resistance and durability of the fiber-reinforced skeleton: This invention constructs a three-dimensional cross-reinforcement network within the hardened matrix by adding chemically strengthened glass fibers (Example 3). This network effectively counteracts the internal stress caused by the mismatch in thermal expansion coefficients between the substrate (e.g., coal block) and the slurry layer, significantly reducing the drying shrinkage crack rate of the cured layer from a physical perspective. Compared to the fiber-free control group, the fiber-containing coating maintains extremely high integrity and durability under cyclic temperature and humidity fluctuations, greatly alleviating the problems of easy cracking and peeling of traditional hard coatings. Attached Figure Description

[0032] Figure 1 is a flowchart of a method for preparing an inorganic thin spray slurry for wall spraying in a humid environment according to an embodiment of the present invention.

[0033] Figure 2 shows the effect of fiber-free spraying on the surface of a wooden board in Example 1;

[0034] Figure 3 shows the effect of fiber-free spraying on the surface of a cement wall in Example 2;

[0035] Figure 4 shows the effect of glass fiber spraying on the surface of coal blocks in Example 3. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] Specific Implementation Scheme 1: This invention provides an inorganic thin spray coating for wall application in humid environments, comprising the following percentages of raw materials:

[0038] 14%-16% white cement (Type 525), 24%-26% sand (200 mesh), 4%-6% high-viscosity inorganic polymer material, 4%-6% colloidal silicon steel, 0.2%-0.5% auxiliary components, balance water;

[0039] It also includes auxiliary components for improving workability and durability, including but not limited to one or more of water-reducing agents, retarders, air-entraining agents, air-entraining agents, modifiers, and trace additives, and the amount of these additives is expressed in volume or mass ratio within the formulation range.

[0040] Preferably, the auxiliary component is glass fiber, and the volume or mass of the glass fiber is 0.2%–0.5% of the total slurry mass, and the glass fiber is uniformly dispersed in the inorganic thin sprayed slurry in the form of monofilaments or chopped strands; the glass fiber is chemically strengthened glass fiber with a length of 6 mm–12 mm and a diameter of 10 μm–20 μm;

[0041] The white cement is 525 type grade 1 white cement, which is used to improve the early strength and adhesion of grade 5 thin spray grout. It hardens quickly and can meet the needs of decoration projects with high requirements for wall load-bearing capacity and construction efficiency. This is because white cement has a clean and uniform white color, good weather resistance and stability, is not easy to fade or yellow, and has relatively low alkalinity during hydration and good compatibility with other additives.

[0042] The white sand (200 mesh) is an inorganic non-metallic mineral material with high-purity silica as its main component, and its fineness is approximately 0.075 mm. It is refined from natural quartz or marble through multiple processes including crushing, grinding, and sieving. This high-fineness white sand possesses high purity and chemical stability; high-quality white sand can have a silica content of over 95%, even over 99%, and extremely low levels of impurities such as iron oxide. This gives it excellent acid resistance and weather resistance; it does not readily react chemically with acids or alkalis at room temperature, and its performance is very stable.

[0043] In addition, white sand possesses excellent physical and chemical properties and versatility in applications. Its Mohs hardness is approximately 7, and its melting point reaches 1730-1750℃, exhibiting good wear resistance and high-temperature resistance. In terms of appearance, its whiteness can reach over 90, with a pure white color that is not easily faded. Due to these characteristics, white sand (200 mesh) has wide applications in high-end decorative building materials and fine chemical industries. As a natural inorganic material, 200 mesh white sand is non-toxic and odorless, meeting green environmental protection requirements. However, precautions should still be taken during construction. It is recommended that workers wear dust masks and gloves to prevent health risks from dust inhalation or skin contact, and the storage environment should be kept dry.

[0044] The high-viscosity inorganic polymer material is magnesium aluminum silicate. This is because magnesium aluminum silicate has excellent thickening and thixotropic properties. Under static or low shear force conditions, it can form a high-viscosity gel network with water, keeping the thin spray grout in a stable suspension state and effectively preventing the solid particles of the thin spray grout from settling and stratifying. When subjected to shearing action such as stirring or pumping, its viscosity will drop rapidly, and its fluidity will increase significantly, making it easier to operate. When the shear force is removed, it can recover its original viscosity in a very short time. This "shear thinning and static thickening" characteristic gives the material excellent anti-sagging and smoothness of construction, which is especially suitable for the use of the thin spray grout of this invention and reduces the difficulty of operation. In addition, magnesium aluminum silicate is selected in this invention because of its stable chemical properties, good compatibility with various organic thickeners, emulsions and pigments, and it does not contain heavy metals and is non-irritating, which can significantly improve the storage stability and construction experience of the thin spray grout.

[0045] In summary, the inorganic thin-film spray slurry of the present invention can achieve the following effects:

[0046] (1) Target performance: The thin spray coating does not crack or powder after curing in a humid environment, and has good bonding strength, low shrinkage, dense pore structure and excellent water resistance;

[0047] (2) Mechanism: Through strict particle size distribution and hydration heat management, shrinkage stress is reduced and interfacial adhesion is improved. At the same time, the stability of the slurry and the interfacial bonding efficiency are improved by using appropriate high viscosity components.

[0048] (3) Auxiliary components: Glass fiber is considered as an auxiliary reinforcing material in this formulation, and is dispersed in the slurry as a dispersing additive to improve toughness and crack resistance;

[0049] (4) Spraying thickness: 1 mm-5 mm, to ensure a dense and uniform coating in a humid environment.

[0050] Specific Implementation Plan Two: Combining Figure 1 As shown, the present invention provides a method for preparing an inorganic thin-film spray coating for wall coating in humid environments, comprising the following steps:

[0051] S1. Mix white cement and sand evenly in a dry state to obtain the base material;

[0052] S2. Gradually add water while stirring to obtain the initial slurry;

[0053] S3. Add magnesium aluminum silicate (high viscosity) and silicon steel, and continue stirring until uniform;

[0054] S4. Add glass fiber as an auxiliary reinforcing material and stir at a speed of 10000 r / min-2000 r / min for 10 min-15 min until the slurry reaches the target consistency to obtain the mixed inorganic thin spray slurry.

[0055] Specific Implementation Scheme 3: This invention provides an application method for an inorganic thin-film spray coating for wall spraying in humid environments, including the following steps:

[0056] S100. Inject the prepared inorganic thin spray slurry into the tank of the spraying machine and adjust the tank pressure to 0.4 MPa to 0.6 MPa to prepare for spraying.

[0057] S200. Open the discharge valve at the bottom of the tank and the air pipe valve of the spray gun in sequence. After the air is sprayed out, open the material pipe valve of the spray gun until the slurry is sprayed out from the spray gun. The slurry is then ready for construction. The thickness of a single spray is 1 mm to 5 mm to ensure a dense and uniform coating in a humid environment, while achieving good interfacial adhesion.

[0058] S300: After spraying, the wall surface is treated with rapid wet curing or wet-pack moisturizing curing to ensure that the hydration process of the thin spray layer is stable within 24h–72h after construction, thereby reducing the risk of later cracking.

[0059] S400. After the construction is completed, immediately clean the spray gun and other spraying equipment, as well as the inner wall of the mixing tank; to prevent the slurry from solidifying and clogging the mixing tank or the inner nozzle of the spray gun, causing irreversible damage to the equipment, or contaminating the mixing tank.

[0060] Example 1: Fiber-free spraying on the surface of a wood board

[0061] Base material: Dried wood board

[0062] Composition and proportion: 15% white cement (525), 25% sand (200 mesh), 5% magnesium aluminum silicate (high viscosity), 5% colloidal silicon steel, and the balance is water.

[0063] Preparation steps:

[0064] S1: Weigh out white cement, sand, magnesium aluminum silicate, and silicon steel according to the proportions, and mix the raw materials evenly;

[0065] S2; Add a certain proportion of water to the mixed raw materials and stir at a speed of 1000 r / min to 2000 r / min for 15 min to obtain a mixed slurry;

[0066] S3: Inject the slurry into the tank of the spraying machine and adjust the tank pressure to 0.5 MPa to prepare for spraying.

[0067] S4: Open the discharge valve at the bottom of the tank and the air pipe valve of the spray gun in sequence. After the air is sprayed out, open the material pipe valve of the spray gun until the slurry is sprayed out from the spray gun. Then construction can be carried out. The thickness of a single spray of slurry is 1 mm to 3 mm.

[0068] S5: After the construction is completed, immediately clean the spray gun and other spraying equipment, as well as the inner wall of the mixing tank.

[0069] The wood surface has a certain degree of water absorption, and this method exhibits good adhesion on the wood. After curing, the surface is smooth, without obvious shrinkage cracks, and the interlayer bond is stable. See the experimental images below. Figure 2 .

[0070] Example 2: Fiber-free spraying on cement wall surface

[0071] Substrate material: Rough coal block surface

[0072] Composition and proportion: 14%-16% white cement (525), 24%-26% sand (200 mesh), 4%-6% magnesium aluminum silicate (high viscosity), 4%-6% colloidal silicon steel, and the balance is water.

[0073] Preparation steps:

[0074] Clean the surface of the coal blocks of loose dust beforehand;

[0075] The slurry was prepared according to the method in Example 1;

[0076] The spraying process of Example 1 is used to cover the rough porous structure of the coal block surface, with the thickness controlled between 1 mm and 3 mm.

[0077] Because cement walls are porous and have low surface energy, this formula effectively fills the grooves on the surface of coal blocks, forming a dense protective shell. However, strict monitoring of moisture retention is necessary during the initial drying stage to prevent microcracks caused by shrinkage stress at the rough interface. See the experimental diagram below. Figure 3 .

[0078] Example 3: Applying glass fiber coating to the surface of coal blocks

[0079] Base material: Rough coal block surface.

[0080] Composition and proportion: Based on the formulation of Example 2, add 0.3% (mass fraction) of glass fiber (8–10 mm in length and 10 μm–20 μm in diameter).

[0081] Preparation steps:

[0082] Clean the surface of the coal blocks of loose dust beforehand;

[0083] The slurry was prepared according to the method in Example 1;

[0084] During the slurry mixing stage, glass fibers are added in stages to ensure that the fibers are three-dimensionally and cross-dispersed in the slurry without clumping.

[0085] The application is carried out using spraying equipment, with the thickness controlled between 1 mm and 3 mm.

[0086] The addition of glass fiber significantly improved the crack resistance of the slurry on the coal surface, as shown in the experimental figures. Figure 4 .

[0087] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. An inorganic thin-film spray coating for wall application in damp environments, characterized in that: Including the following percentages of raw materials, 14%-16% white cement, 24%-26% sand, 4%-6% high-viscosity inorganic polymer materials, 4%-6% colloidal silicon steel, 0.2%-0.5% auxiliary components, and the balance is water.

2. The inorganic thin-film spray coating for wall coating in humid environments according to claim 1, characterized in that: The high-viscosity inorganic polymer material is magnesium aluminum silicate.

3. The inorganic thin-film spray slurry for wall coating in humid environments according to claim 1, characterized in that: It also includes auxiliary components, which include one or more of the following: water-reducing agent, retarder, air-entraining agent, air-entraining agent, modifier, and trace additives.

4. The inorganic thin-film spray coating for wall coating in humid environments according to claim 1, characterized in that: The auxiliary component is glass fiber, and the mass of the glass fiber is 0.2%–0.5% of the total mass of the inorganic thin spray slurry.

5. An inorganic thin-film spray coating for wall application in humid environments according to claim 4, characterized in that: The white cement is 525 type grade 1 white cement; the sand is white sand with a particle size of 200 mesh; the glass fiber is chemically reinforced glass fiber with a length of 6 mm–12 mm and a diameter of 10 μm–20 μm.

6. A method for preparing an inorganic thin-film spray slurry for wall coating in humid environments as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Mix white cement and sand evenly in a dry state to obtain the base material; S2. Gradually add water while stirring to obtain the initial slurry; S3. Add magnesium aluminum silicate and silicon steel, and continue stirring until homogeneous; S4. Add glass fiber as an auxiliary reinforcing material and stir until the inorganic thin spray slurry reaches the target consistency to obtain the mixed inorganic thin spray slurry.

7. A method for applying the inorganic thin-film spray mortar for wall spraying in humid environments as described in any one of claims 1-5, characterized in that, Includes the following steps: S100. Inject the prepared inorganic thin spray slurry into the tank of the spraying machine and adjust the tank pressure to 0.4MPa~0.6MPa to prepare for spraying. S200. Open the discharge valve at the bottom of the tank and the air pipe valve of the spray gun in sequence. After the air is sprayed out, open the material pipe valve of the spray gun until the slurry is sprayed out from the spray gun. Then construction can begin. S300: After spraying, the wall surface is treated with rapid wet curing or wet-pack moisturizing curing to ensure that the hydration process of the thin spray layer is stable within 24h–72h after construction, thereby reducing the risk of cracking later. S400. After the construction is completed, immediately clean the spray gun and other spraying equipment, as well as the inner wall of the mixing tank.

8. The application method of the inorganic thin-film spray mortar for wall spraying in humid environments according to claim 7, characterized in that: The thickness of a single spray application of the inorganic thin spray paste is 1 mm–5 mm.

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