Spraying concrete material as well as preparation method and application thereof

Abstract

The invention discloses a sprayed concrete material as well as a preparation method and application thereof. The preparation method comprises the following steps: preparing foamed slurry; preparing to obtain a mortar material; and spraying the mortar material to the surface of the condensed foamed slurry to obtain the sprayed concrete material. The strength and stability of a traditional sprayed concrete material can be improved, and the low temperature resistance, freeze-thaw cycle resistance, corrosion resistance and heat insulation performance of the traditional sprayed concrete material can be enhanced.

Description

Technical Field

[0001] The present application relates to a composite material, and particularly to a shotcrete material, a preparation method thereof, and an application thereof. Background Art

[0002] In the construction of projects such as tunnels, especially in special environmental conditions in the Sichuan-Tibet region, the deficiencies of traditional shotcrete materials in terms of low-temperature resistance are particularly obvious. Traditional shotcrete materials often exhibit low toughness and impact resistance in low-temperature environments, and are prone to cracks and peeling. Since traditional shotcrete materials are mainly composed of cement, sand, and gravel, among which, cement is prone to slow hydration reaction or incomplete reaction in low-temperature environments, resulting in incomplete hardening of the shotcrete material, thereby affecting its strength and durability. In addition, in low-temperature environments, the shotcrete material itself lacks good heat insulation performance, resulting in the inability to effectively maintain the temperature in mines or tunnels. Moreover, in low-temperature environments, the workability of traditional shotcrete materials will be affected, and problems such as poor adhesion and extended drying time often occur during spraying.

[0003] Therefore, for tunnels in cold regions, it is particularly important to develop spraying materials with good low-temperature tolerance, excellent heat insulation, low density, and easy construction. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the main purpose of the present application is to provide a shotcrete material, a preparation method thereof, and an application thereof. The present application aims to solve the problem that the performance of traditional shotcrete materials is poor in low-temperature environments, which affects effective construction.

[0005] To achieve the above purposes, the present application provides the following technical solutions:

[0006] A shotcrete material, the material comprising: a foamed slurry and a mortar material. Among them, by mass, the foamed slurry comprises: magnesium chloride hexahydrate: 200 to 240 parts; magnetized water: 124 to 150 parts; nano magnesium oxide: 260 to 280 parts; alkali-activated fly ash: 60 to 70 parts; bio-based aerogel foaming agent: 12 to 15 parts; sodium carbonate-calcium peroxide complex: 25 to 35 parts; nano-crystal nucleus composite early strength agent: 1 to 1.5 parts; phase change microcapsules: 5 to 8 parts; carbon nanotube dispersion: 0.2 to 0.4 parts; by mass, the mortar material comprises: sulfoaluminate cement: 180 to 200 parts; lithium silicate-graphene oxide composite gelling agent: 70 to 80 parts; hydrated lime-nano calcium hydroxide: 55 to 65 parts; ultrafine mineral powder-steel slag micro powder mixture: 300 to 320 parts; hydrophobic cerium oxide@silane: 10 to 12 parts; recycled glass sand-ceramic microspheres: 350 to 375 parts; self-healing fiber: 1 to 2 parts.

[0007] The present application also provides a method for preparing shotcrete material, and the preparation method includes: preparing a foamed slurry; preparing a mortar material; spraying the mortar material onto the surface of the condensed foamed slurry to obtain the shotcrete material.

[0008] Optionally, the preparation of the foamed slurry includes: weighing magnesium chloride hexahydrate, magnetized water, and nano-magnesium oxide according to a set amount, stirring and mixing them to obtain a magnesium chloride mixed solution; sequentially adding alkali-activated fly ash and sodium carbonate-calcium peroxide complex to the magnesium chloride mixed solution, and stirring to obtain a pre-foamed slurry; adding a bio-based aerogel foaming agent and a nano-crystalline nucleus early strength agent pre-dispersion liquid to the pre-foamed slurry, and stirring at a low speed to obtain a preliminary foamed slurry; adding phase change microcapsules and carbon nanotubes to the preliminary foamed slurry, and stirring to obtain the foamed slurry.

[0009] Optionally, before the stirring and mixing, the magnesium chloride hexahydrate and the nano-magnesium oxide are pretreated.

[0010] Optionally, the magnesium chloride mixed solution is allowed to stand for aging.

[0011] Optionally, the preparation of the mortar material includes: weighing sulphoaluminate cement, a mixture of ultrafine mineral powder and steel slag powder, and dry mixing of hydrated lime-nano-calcium hydroxide according to a set amount to obtain a dry-mixed cement-based material; adding a lithium silicate-graphene oxide composite gelling agent and hydrophobic cerium oxide@silane to the dry-mixed cement-based material, and stirring to obtain a gelled slurry; adding recycled glass sand-ceramic microspheres to the gelled slurry, and stirring to obtain the mortar material. [[ID=))

[0012] Optionally, before the dry mixing, the hydrated lime-nano-calcium hydroxide is activated.

[0013] Optionally, the adding of the recycled glass sand-ceramic microspheres to the gelled slurry includes: adding the recycled glass sand-ceramic microspheres to the gelled slurry in batches.

[0014] Optionally, the preparation of the mortar material further includes: adding self-healing fibers to the mortar material.

[0015] The present application also provides an application of the shotcrete material, and the shotcrete material is applied to the lining of a tunnel in a cold region.

[0016] The present application can bring the following beneficial effects:

[0017] By combining specific proportions of various components and utilizing the synergistic effect among the components, the present application can not only improve the strength and stability of the shotcrete material, but also significantly enhance its anti-low temperature, anti-freeze-thaw cycle, anti-corrosion and heat insulation properties. In addition, the shotcrete material has a low density and excellent construction adaptability, and can solve the problems of high transportation cost and poor construction environment of traditional shotcrete materials under complex geological conditions. Description of the Drawings

[0018] Figure 1 FIG. is a schematic flow chart of a method for preparing shotcrete materials provided by an embodiment of the present application. Detailed Embodiments

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0020] It should be noted that all directional indications (such as up, down, left, right, front, back,...) in the embodiments of the present application are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0021] In the present application, unless otherwise clearly defined and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0022] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, such descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution where A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present application.

[0023] In an exemplary embodiment, the present application provides a shotcrete material, which includes: a foamed slurry and a mortar material. Among them, by mass parts, the foamed slurry includes: magnesium chloride hexahydrate: 200 to 240 parts; magnetized water: 124 to 150 parts; nano magnesium oxide: 260 to 280 parts; alkali-activated fly ash: 60 to 70 parts; bio-based aerogel foaming agent (tea saponin / lignin composite system): 12 to 15 parts; sodium carbonate-calcium peroxide complex: 25 to 35 parts; nano-crystalline nucleus composite early strength agent (containing C-S-H crystal seeds + sulphoaluminate): 1 to 1.5 parts; phase change microcapsules: 5 to 8 parts; carbon nanotube dispersion: 0.2 to 0.4 parts. By mass parts, the mortar material includes: sulphoaluminate cement: 180 to 200 parts; lithium silicate-graphene oxide composite gelling agent: 70 to 80 parts; hydrated lime-nano calcium hydroxide: 55 to 65 parts; ultra-fine mineral powder-steel slag powder mixture: 300 to 320 parts; hydrophobic cerium oxide@silane: 10 to 12 parts; recycled glass sand (70%)-ceramic microbeads (30%): 350 to 375 parts; self-healing fiber (microbial spores@polylactic acid fiber): 1 to 2 parts.

[0024] Figure 1 FIG. is a schematic flow chart of a method for preparing a shotcrete material provided in another exemplary embodiment of the present application, as Figure 1 shown, the preparation method includes the following steps:

[0025] S100: Prepare and obtain a foamed slurry;

[0026] S200: Prepare and obtain a mortar material;

[0027] S300: Spray the mortar material onto the surface of the foamed slurry to obtain a shotcrete material.

[0028] Next, the present application combines Figure 1 and details the preparation method of the shotcrete material through specific Examples 1 to 3.

[0029] Example 1

[0030] Step 1: Prepare and obtain a foamed slurry, specifically including:

[0031] Step 1.1: Weigh 200 parts of magnesium chloride hexahydrate, 124 parts of magnetized water and 260 parts of nano magnesium oxide, and stir them at a low speed (the stirring speed is, for example, 200 rpm) in a stirring kettle, and use the alternating action of ultrasonic waves and microwaves to assist in mixing. After stirring and mixing, a magnesium chloride mixed solution is obtained;

[0032] In this step, before stirring and mixing, it is necessary to pre-treat magnesium chloride hexahydrate and nano-magnesium oxide first. The pre-treatment includes drying magnesium chloride hexahydrate (drying magnesium chloride hexahydrate in an oven at 60 °C for 2 hours to remove the surface moisture, and then crushing and sieving it to avoid caking) and dispersing nano-magnesium oxide (mixing it with magnetized water and treating it with an ultrasonic disperser for 20 minutes to prevent agglomeration).

[0033] It should be noted that due to its large specific surface area, nano-magnesium oxide is prone to agglomeration. The cavitation effect of ultrasonic waves can generate tiny bubbles in the liquid. The local high temperature and high pressure environment generated when these bubbles burst helps to break the agglomeration between nano-particles and make them better dispersed in the solution. Microwave heating is an internal heating method that can directly act on the substance molecules and make them heat up rapidly. Compared with the traditional external heating method, microwave heating can accelerate the chemical reaction rate and make the reaction more uniform, which helps to speed up the dissolution process and the speed of subsequent chemical reactions. In this application, by alternately using ultrasonic waves and microwaves, the advantages of both can be utilized. It can not only effectively disperse nano-particles (ultrasonic waves), but also accelerate the dissolution and reaction processes (microwaves), which not only helps to form a uniform mixture, but also ensures that the subsequent added components can react fully with it, thus affecting the performance of the final product.

[0034] It should also be noted that after obtaining the magnesium chloride mixture, it needs to be left standing for aging, and the Baume degree of the mixture is measured with a Baume hydrometer. When the Baume degree is greater than 28 (this is an important indicator to ensure the appropriate concentration and density of the magnesium chloride solution), a qualified magnesium chloride solution is obtained.

[0035] It is worth noting that after stirring, ultrasonic wave and microwave treatments, there may still be an incomplete reaction between some chemical substances in the magnesium chloride mixture, and it takes a certain amount of time to complete the chemical reaction. If the steps of standing and aging are omitted, the chemical reaction cannot be completed thoroughly, thus affecting the quality and performance of the foaming slurry.

[0036] Step 1.2: Add 60 parts of alkali-activated fly ash and 25 parts of sodium carbonate-calcium peroxide complex to the magnesium chloride solution in sequence. After each component is added, it needs to be stirred slowly and fully for 10 minutes to ensure the full chemical reaction between the components. After stirring, a pre-foaming slurry is obtained.

[0037] In this step, alkali-activated fly ash is an alkali-activated material that gradually releases alkaline substances in the magnesium chloride solution, helping to adjust and stabilize the pH of the mixture. The sodium carbonate-calcium peroxide complex, however, is highly alkaline and oxidizing. Adding this strongly alkaline material first can cause the pH of the magnesium chloride solution to rise rapidly, thereby affecting the dissolution and dispersion of subsequent ingredients. Adding the alkali-activated fly ash first can, on the one hand, buffer and adjust the pH of the magnesium chloride solution to a certain extent, providing a milder reaction environment for subsequent ingredients. On the other hand, it can enhance the activity of the alkali-activated fly ash, allowing it to better participate in subsequent chemical reactions, thereby enhancing the strength and durability of the final material. The sodium carbonate-calcium peroxide complex not only provides an alkaline environment but may also introduce oxidizing or other chemically active factors. Adding the sodium carbonate-calcium peroxide complex too early can trigger unwanted side reactions, such as adverse interactions with ingredients that have not yet fully dispersed or reacted, thus affecting the quality and performance of the slurry. Therefore, these adverse effects can be reduced by allowing the alkali-activated fly ash to be fully dispersed and to undergo necessary reactions with other components in the solution before adding the sodium carbonate-calcium peroxide complex.

[0038] Step 1.3: Add 12 parts of bio-based aerogel foaming agent and 1 part of nanocrystalline core early strength agent pre-dispersion liquid to the pre-foamed slurry, and stir at a low speed (for example, a stirring speed of 150 rpm) to obtain a preliminary foamed slurry.

[0039] In this step, the main function of the bio-based aerogel foaming agent is to introduce gas into the slurry to form a stable foam structure, which is crucial for the thermal insulation performance of the final material. However, if the foaming process is too intense or out of control, it may cause the pores to be too large, uneven or unstable, thereby affecting the overall strength and durability of the sprayed concrete material. By stirring at a low speed, the foaming speed can be slowed down, making the foam more delicate and uniform, which helps to form an ideal pore structure. In addition, the nanocrystalline core early strength agent pre-dispersion liquid contains ingredients that can accelerate the cement hydration reaction and increase the early strength. Slow-speed stirring helps these fine particles to be evenly dispersed throughout the slurry, ensuring that they can play the best effect in the entire system, rather than being concentrated locally and causing uneven effects.

[0040] Step 1.4: Add 5 parts of phase change microcapsules and 0.2 parts of carbon nanotubes to the preliminary foaming slurry, stir for 5 minutes, and maintain the temperature ≤30° C. After stirring, obtain a foaming slurry.

[0041] In this step, the phase change microcapsule is a kind of tiny particle formed by wrapping a core containing a phase change material (PCM) with a protective shell, which can absorb or release heat within a specific temperature range, thereby helping to regulate the ambient temperature and further improving the heat insulation performance of the shotcrete material. Carbon nanotubes have extremely high strength and excellent electrical conductivity. Adding a small amount can significantly enhance the mechanical properties of the shotcrete material, such as tensile strength, compressive strength, etc. In addition, in order to ensure good dispersion and interfacial bonding force of the carbon nanotubes in the matrix, the carbon nanotubes need to be surface-treated with a surfactant before adding to prevent their agglomeration phenomenon, so that they can be more evenly distributed in the foamed slurry.

[0042] Step 2: Prepare the mortar material, specifically including:

[0043] Step 2.1: Dry-mix 180 parts of sulfoaluminate cement, 10 parts of a mixture of ultrafine mineral powder and steel slag powder, and 55 parts of hydrated lime-nano calcium hydroxide to obtain a dry-mixed cement-based material;

[0044] In this step, hydrated lime-nano calcium hydroxide, as an alkaline activator or active filler, needs to have high reactivity when reacting with other components (such as cement, lithium silicate, etc.). Therefore, in this embodiment, before dry-mixing, it is activated. Through the activation treatment, the passivation layer on its surface can be removed or its crystal structure can be changed, making the hydrated lime-nano calcium hydroxide more likely to participate in the hydration reaction or other chemical reactions, thereby accelerating the setting and hardening process and enhancing the mechanical properties of the final product. In addition, after the activation treatment, the hydrated lime-nano calcium hydroxide needs to be ground to a particle size ≤ 10 μm to increase its specific surface area. A larger specific surface area means more reaction contact surfaces, which is conducive to accelerating the reaction rate with other components and promoting the formation of a denser microstructure, thereby improving the overall strength and durability of the shotcrete material.

[0045] Step 2.2: Add 70 parts of a lithium silicate-graphene oxide composite gelling agent and 10 parts of hydrophobic cerium oxide@silane to the dry-mixed cement-based material and stir at a medium speed (the stirring speed is, for example, 400 rpm). After stirring, a gelling slurry is obtained;

[0046] In this step, graphene, as a two-dimensional nanomaterial, has extremely high strength and modulus. The composite gelling agent formed by combining it with lithium silicate can significantly improve the compressive, flexural strength and toughness of the mortar material. Lithium silicate, as an alkaline activator, can accelerate the cement hydration reaction and help improve the early strength of concrete or mortar. In addition, the presence of graphene further promotes this effect, enabling the shotcrete material to reach a relatively high strength level in a short time.

[0047] Hydrophobic cerium oxide is treated by surface modification (such as using silane coupling agent), which endows it with good hydrophobicity. When it is evenly dispersed in mortar materials, it can effectively reduce the water absorption rate of the materials, enhance the waterproof performance, and prevent problems such as corrosion caused by water penetration. In addition, cerium oxide itself is an excellent ultraviolet absorber and antioxidant, which can resist the aging phenomenon caused by ultraviolet radiation. At the same time, the introduction of silane can also enhance the resistance of shotcrete materials to environmental erosion, thereby extending the service life.

[0048] Step 2.3: Incorporate 350 parts of recycled glass sand-ceramic microspheres (for example, it can be divided into 5 parts, each part is 70 parts) into the cementitious paste in batches. The ratio of glass sand to ceramic microspheres is 7:3, and the particle size is controlled within 0.1 - 1 mm. Stir until the recycled glass sand-ceramic microsphere particles evenly wrap the cementitious material to obtain the mortar material.

[0049] In this step, the density of the recycled glass sand-ceramic microspheres is different from that of the cementitious paste. If all the recycled glass sand-ceramic microspheres are added at one time, it will cause the recycled glass sand-ceramic microspheres to sink to the bottom of the cementitious material under the action of gravity, or agglomerate due to the electrostatic interaction between them, which is not conducive to the formation of a uniform mortar structure. By adopting the method of adding in batches, each batch of particles has enough time to be wrapped by the cementitious paste and be dispersed by stirring, thereby improving the uniformity and stability of the mortar material.

[0050] Step 3: Spray the mortar material onto the surface of the foamed paste after condensation to obtain the shotcrete material.

[0051] In this step, the present embodiment adopts a layered spraying process, that is, spraying the mortar material onto the surface of the foamed paste after condensation in layers, which specifically includes: using a high-pressure airless spraying device to evenly spray the mortar material onto the surface of the foamed paste after condensation, and controlling the single-layer thickness ≤ 30 mm (which can effectively reduce the mortar shrinkage stress and reduce the generation of cracks). Keep the distance between the nozzle and the surface of the foamed paste at 30 - 50 cm during spraying, and the spraying pressure is 0.5 - 0.8 MPa to ensure that the mortar evenly covers. During the initial setting period of the first layer of mortar, slightly moisten and cure the surface of the mortar to prevent cracking after the mortar solidifies. After the first layer of mortar completely solidifies, repeat the above spraying steps and stack layer by layer until the designed thickness is reached. It should be noted that before each layer of spraying, the surface of the previous layer of mortar needs to be slightly polished to remove the floating slurry and uneven parts to ensure that the bonding between each mortar layer is tight. After spraying, immediately cover with a water retention film or spray water mist, and spray a curing agent containing nano-calcium hydroxide (once every 6 hours) to ensure the full development of the strength of the shotcrete material.

[0052] By adopting layered spraying, firstly, the bonding between each layer of mortar can be made tight, avoiding delamination or debonding. After inspection, compared with one-time spraying, layered spraying can increase the adhesion between mortar layers to more than 2.5 MPa, significantly enhancing the overall mechanical properties of the shotcrete material. Secondly, the mortar material can fully fill the pores of the foamed slurry, forming a dense protective layer, thereby improving the impermeability and durability of the shotcrete material.

[0053] Example 2

[0054] Step 1: Prepare the foamed slurry, specifically including:

[0055] Step 1.1: Weigh 240 parts of magnesium chloride hexahydrate, 150 parts of magnetized water, and 280 parts of nanoscale magnesium oxide, and stir them at a low speed (the stirring speed is, for example, 200 rpm) in a stirring kettle, and use the alternating action of ultrasonic waves and microwaves to assist in mixing. After stirring and mixing, a magnesium chloride mixed solution is obtained;

[0056] Step 1.2: Add 70 parts of alkali-activated fly ash and 35 parts of sodium carbonate-calcium peroxide complex to the magnesium chloride solution in sequence. After each component is added, it needs to be stirred at a low speed for 10 minutes to ensure the full chemical reaction between the components. After stirring, a pre-foamed slurry is obtained;

[0057] Step 1.3: Add 15 parts of bio-based aerogel foaming agent and 1.5 parts of nanocrystalline nucleus early strength agent pre-dispersion liquid to the pre-foamed slurry, and stir at a low speed (the stirring speed is, for example, 150 rpm) to obtain a preliminary foamed slurry;

[0058] Step 1.4: Add 8 parts of phase change microcapsules and 0.4 parts of carbon nanotubes to the preliminary foamed slurry, stir for 5 minutes, and keep the temperature ≤ 30 °C. After stirring is completed, a foamed slurry is obtained.

[0059] Step 2: Prepare the mortar material, specifically including:

[0060] Step 2.1: Dry-mix 200 parts of sulfoaluminate cement, 15 parts of ultrafine mineral powder - steel slag micro powder mixture, and 65 parts of grey calcium - nano calcium hydroxide to obtain a dry-mixed cement-based material;

[0061] Step 2.2: Add 80 parts of lithium silicate - graphene oxide composite gelling agent and 12 parts of hydrophobic cerium oxide @ silane to the dry-mixed cement-based material and stir at a medium speed (the stirring speed is, for example, 400 rpm). After stirring is completed, a gelled slurry is obtained;

[0062] Step 2.3: Batchwise incorporate 375 parts of recycled glass sand - ceramic microspheres (the ratio of glass sand to ceramic microspheres is 7:3, and the particle size is controlled within 0.1 - 1 mm) into the gelled slurry, and stir until the recycled glass sand - ceramic microsphere particles evenly wrap the gelling material to obtain the mortar material;

[0063] Step 3: Spray the mortar material onto the surface of the foamed slurry after condensation to obtain the shotcrete material.

[0064] In this step, the spraying process used is as described in Example 1 and will not be elaborated here.

[0065] It should be noted that, different from Example 1, after obtaining the mortar material in this example, 1 part of self-healing fiber is further added to the mortar material and stirred at a low speed (150 rpm), so as to obtain the mortar material containing self-healing fiber. Self-healing fibers are usually composed of materials such as microbial spores and polylactic acid fibers. When tiny cracks appear in the mortar material, the self-healing fibers can help the cracks heal themselves through physical filling or chemical reactions. For example, the fibers wrapped with the repair agent break when the crack forms, releasing the repair agent, and these repair agents can react with carbon dioxide or other substances in the air to form precipitates, thus sealing the cracks. Further, the self-healing fibers can also improve the toughness and tensile strength of the mortar material, reducing the cracking risk caused by factors such as temperature changes and dry shrinkage. This is because the self-healing fibers can form a three-dimensional network structure inside the mortar material, effectively dispersing stress and preventing the expansion of cracks.

[0066] Example 3

[0067] Step 1: Prepare the foamed slurry, specifically including:

[0068] Step 1.1: Weigh 220 parts of magnesium chloride hexahydrate, 137 parts of magnetized water and 270 parts of nano-magnesium oxide, stir at a low speed (the stirring speed is, for example, 200 rpm) in a stirring kettle, and use the alternating action of ultrasonic waves and microwaves to assist mixing. After stirring and mixing, obtain the magnesium chloride mixed solution;

[0069] Step 1.2: Add 65 parts of alkali-activated fly ash and 30 parts of sodium carbonate-calcium peroxide complex to the magnesium chloride solution in sequence. After each component is added, it is necessary to stir at a low speed and fully for 10 minutes to ensure the full chemical reaction between the components. After stirring, obtain the pre-foamed slurry;

[0070] Step 1.3: Add 13.5 parts of bio-based aerogel foaming agent and 1.25 parts of nano-crystalline nucleus early strength agent pre-dispersion liquid to the pre-foamed slurry, and stir at a low speed (150 rpm) to obtain the preliminary foamed slurry;

[0071] Step 1.4: Add 6.5 parts of phase change microcapsules and 0.3 parts of carbon nanotubes to the preliminary foamed slurry, stir for 5 minutes, and keep the temperature ≤ 30 °C. After stirring is completed, obtain the foamed slurry.

[0072] Step 2: Prepare the mortar material, specifically including:

[0073] Step 2.1: Dry-mix 190 parts of sulfoaluminate cement, 12 parts of ultrafine mineral powder - steel slag powder mixture, and 60 parts of hydrated lime - nano-calcium hydroxide to obtain a dry-mixed cement-based material;

[0074] Step 2.2: Add 75 parts of lithium silicate - graphene oxide composite gelling agent and 11 parts of hydrophobic cerium oxide @ silane to the dry-mixed cement-based material and stir at a medium speed (the stirring speed is, for example, 400 rpm). After stirring is completed, a gelling slurry is obtained;

[0075] Step 2.3: Batchwise incorporate 360 parts of recycled glass sand - ceramic microbeads (the ratio of glass sand to ceramic microbeads is 7:3, and the particle size is controlled within 0.1 - 1 mm) into the gelling slurry, and stir until the recycled glass sand - ceramic microbead particles evenly coat the gelling material to obtain a mortar material;

[0076] Step 2.4: Add 2 parts of self-healing fibers to the mortar material and stir at a low speed (150 rpm) to obtain a mortar material containing self-healing fibers.

[0077] Step 3: Spray the mortar material onto the surface of the foamed slurry after condensation to obtain a shotcrete material.

[0078] Different from Example 1 and Example 2, before spraying the mortar material onto the foamed slurry after condensation, in this example, the surface of the incompletely condensed foamed slurry is subjected to plasma bombardment treatment, that is, a low-temperature plasma device (such as an atmospheric pressure plasma jet) is used to uniformly bombard the surface of the foamed slurry after initial setting for 30 s to 60 s. And during the bombardment process, nanoparticles (such as boron nitride nanosheets) are synchronously injected onto the surface of the foamed slurry, so that the nanoparticles are embedded in the surface of the foamed slurry to further improve its mechanical properties. Among them, the step of synchronously injecting nanoparticles is implemented as follows:

[0079] First, modify the boron nitride nanosheets, that is, place the boron nitride nanosheets in a reaction vessel, add an appropriate amount of ethanol or deionized water as a solvent, then add a silane coupling agent (such as KH-550, KH-560, etc.), stir and heat to 50 - 60 °C, react for 2 - 4 hours. After the reaction is completed, centrifuge and wash to remove the unreacted silane coupling agent. Then, add the modified boron nitride nanosheets to ethanol or deionized water to prepare a suspension with a concentration of 0.5% - 1%, and use an ultrasonic disperser (power 300 - 500 W) to treat for 30 - 60 minutes to ensure that the nanosheets are evenly dispersed. By modifying the boron nitride nanosheets, their surface can have better hydrophilicity and be easily dispersed in the solvent. In addition, ultrasonic dispersion can further break the aggregation of the nanosheets, thus forming a stable boron nitride nanosheet suspension.

[0080] Secondly, a nanoparticle injection system is set in the plasma bombardment device, and the boron nitride nanosheet suspension is evenly sprayed onto the surface of the foaming slurry through an atomizing nozzle. During the plasma bombardment process, the boron nitride nanosheet suspension is embedded in the surface of the foaming slurry under the action of high temperature and high-energy particles, forming a dense nano-scale reinforcement layer, which can further improve the surface adhesion of the foaming slurry, making it easier for the mortar material to adhere to the surface of the foaming slurry.

[0081] The present application compared the shotcrete materials prepared in Examples 1 to 3, and the comparison results are shown in Table 1:

[0082] Table 1

[0083]

[0084] In Table 1, Example 3 (F600) shows the best performance and the highest number of freeze-thaw cycles, indicating its best durability in low-temperature environments. In terms of heat insulation performance, all three examples reach Class A (non-combustibility), indicating excellent heat insulation performance and the ability to effectively maintain the temperature in tunnels or mines. Example 3 shows the best chemical corrosion resistance and the strongest chemical corrosion resistance. Example 3 has the highest compressive strength, indicating its best structural strength. Example 3 has the highest flexural strength, indicating its best crack resistance. Among them, the chemical corrosion resistance is shown in Table 2:

[0085] Table 2

[0086]

[0087] Based on the comprehensive judgment of the above data, Example 3 shows the best performance among the above indicators, so it can be used as the best embodiment of the present application.

[0088] Next, the present application compares the performance of the shotcrete materials prepared in the present application and the existing shotcrete materials according to GB / T 50082-2009 "Standard Test Methods for Long-Term Performance and Durability of Ordinary Concrete". In order to verify the superiority of the freeze-thaw cycle resistance, corrosion resistance and heat insulation performance of the materials described in the present application compared with some existing materials, according to standards such as GB / T 50082-2009 "Standard Test Methods for Long-Term Performance and Durability of Ordinary Concrete" and GB8624-1997 "Classification Method for Combustion Performance of Building Materials", the applicant conducted relevant tests on the spraying materials described in the present application and the existing shotcrete materials (in order to avoid sensitivity, the present application uses Material A, Material B and Material C to replace the existing shotcrete materials), and the test results are shown in Table 3:

[0089] Table 3

[0090]

[0091] As can be seen from the data shown in Table 3, the shotcrete material prepared by the method described in this application can maintain high strength and durability under low-temperature conditions. By spraying a foamed spraying material as the inner-layer material of the tunnel for heat insulation and heat preservation, and spraying a high-strength sealing mortar on the outer layer as the sealing material, the foaming multiple of the foamed spraying material in this application is 3-5 times, which can effectively reduce the environmental burden during the transportation and construction of traditional cement materials.

[0092] In another exemplary embodiment, this application also provides an application of the shotcrete material, and the shotcrete material is applied to the lining of a tunnel in a cold region.

[0093] In this embodiment, the shotcrete material prepared by the method described in this application has excellent freeze-thaw cycle resistance (F600 is achieved in Example 3) and good heat insulation performance (meeting Class A non-combustibility), which can effectively solve the problems of cracking and peeling of traditional shotcrete materials in low-temperature environments, and at the same time can help maintain the internal temperature of the tunnel and improve the overall durability and safety of the project.

[0094] The above are only the preferred embodiments of this application, and do not limit the patent scope of this application accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of this application.

Claims

1. A shotcrete material, characterized in that, The materials include: foamed slurry and mortar materials, where By mass, the foamed slurry includes: Magnesium chloride hexahydrate: 200 to 240 parts; Magnetized water: 124 to 150 parts; Nanoscale magnesium oxide: 260 to 280 parts; Alkali-activated fly ash: 60 to 70 parts; Bio-based aerogel foaming agent: 12 to 15 parts; Sodium carbonate-calcium peroxide complex: 25 to 35 parts; Nanocrystalline nucleus composite early strength agent: 1 to 1.5 parts; Phase change microcapsules: 5 to 8 parts; Carbon nanotube dispersion: 0.2 to 0.4 parts; By mass, the mortar materials include: Sulfoaluminate cement: 180 to 200 parts; Lithium silicate-graphene oxide composite gelling agent: 70 to 80 parts; Hydrated lime-nano calcium hydroxide: 55 to 65 parts; Ultra-fine mineral powder-steel slag micro-powder mixture: 300 to 320 parts; Hydrophobic cerium oxide@silane: 10 to 12 parts; Recycled glass sand-ceramic microspheres: 350 to 375 parts; Self-healing fiber: 1 to 2 parts.

2. A preparation method of shotcrete material, characterized in that, The preparation method includes: Preparing to obtain the foamed slurry; Preparing to obtain the mortar materials; Spraying the mortar materials onto the surface of the condensed foamed slurry to obtain shotcrete materials.

3. The preparation method of the shotcrete material according to claim 2, wherein, The preparation to obtain the foamed slurry includes: Weighing magnesium chloride hexahydrate, magnetized water and nanoscale magnesium oxide according to the set amount and stirring and mixing them to obtain a magnesium chloride mixed solution; Sequentially adding alkali-activated fly ash and sodium carbonate-calcium peroxide complex to the magnesium chloride mixed solution, and stirring to obtain a pre-foamed slurry; Adding a bio-based aerogel foaming agent and a pre-dispersed solution of a nanocrystalline nucleus early strength agent to the pre-foamed slurry, and slowly stirring to obtain a preliminary foamed slurry; Adding phase change microcapsules and carbon nanotubes to the preliminary foamed slurry, and stirring to obtain the foamed slurry.

4. The preparation method of the shotcrete material according to claim 3, characterized in that, Before stirring and mixing, pre-treat the magnesium chloride hexahydrate and the nanoscale magnesium oxide.

5. The preparation method of the shotcrete material according to claim 3, characterized in that, Let the magnesium chloride mixed solution stand for aging.

6. The preparation method of the shotcrete material according to claim 2, characterized in that, The preparation to obtain the mortar materials includes: Weighing sulfoaluminate cement, ultra-fine mineral powder-steel slag micro-powder mixture and hydrated lime-nano calcium hydroxide according to the set amount and dry-mixing them to obtain a dry-mixed cement-based material; Adding a lithium silicate-graphene oxide composite gelling agent and hydrophobic cerium oxide@silane to the dry-mixed cement-based material, and stirring to obtain a gelled slurry; Incorporating recycled glass sand-ceramic microspheres into the gelled slurry, and stirring to obtain the mortar materials.

7. The preparation method of the shotcrete material according to claim 6, wherein, Before dry-mixing, activate the hydrated lime-nano calcium hydroxide.

8. The preparation method of the shotcrete material according to claim 6, characterized in that, The incorporation of the recycled glass sand-ceramic microspheres into the gelled slurry includes: Incorporating the recycled glass sand-ceramic microspheres into the gelled slurry in batches.

9. The preparation method of the shotcrete material according to claim 6, characterized in that The preparation to obtain the mortar materials also includes: Adding self-healing fiber to the mortar materials.

10. Application of shotcrete material, characterized in that, The shotcrete materials are applied to the lining of tunnels in cold regions.

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