A low-elasticity and high-strength shotcreting material and its preparation method

Abstract

The present invention discloses a low-rebound high-strength spraying mortar and a preparation method thereof, which comprises the following percentage components by weight: magnesium silicoaluminate molecular sieve: 5-15%; portland cement: 40-55%; acrylic acid-modified silicone resin: 8-16%; acrylate copolymer emulsion: 8-13%; thickening agent: 2-4%; bactericide: 0.1-1%; surfactant: 2-4%; dispersant: 2-4%; defoaming agent: 0.3-0.5%; the balance is water. The fibrous magnesium silicoaluminate molecular sieve of the present invention is intertwined with each other in three-dimensional space to form a reinforcing structure similar to reinforced concrete, and the molar ratio of SiO2 to Al2O3 is controlled in the range of 20-40, so that the surface of the magnesium silicoaluminate molecular sieve exhibits moderate weak acidity, and these acidic sites undergo ring-opening reaction with the epoxy groups in the acrylic acid-modified silicone resin to form stable chemical bonding.

Description

Technical Field

[0001] The present invention relates to the technical field of shotcrete materials, in particular to a low-rebound high-strength shotcrete material and a preparation method thereof. Background Art

[0002] In the fields of tunnel engineering, underground space development, and slope protection, shotcrete technology has been widely used due to its convenient construction and strong adaptability. With the expansion of China's mineral resource development scale, the tailings generated during gold mining have become a large amount of industrial solid waste. Their storage not only occupies a large amount of land resources but may also cause environmental pollution and geological disasters. Gold tailings contain rich silicon-aluminum oxides and theoretically have the potential to be used as raw materials for building materials. However, there is a lack of systematic application research in the field of shotcrete materials.

[0003] On the other hand, the current shotcrete materials on the market mainly use cement-based materials in combination with various additives to improve the spraying performance by optimizing the gradation and adding accelerators. These technical solutions have reduced the rebound rate to a certain extent, but there is still room for improvement. Especially under high-speed spraying conditions, the energy dissipation mechanism during the collision of materials with the working surface is relatively single, mainly relying on the plastic deformation and viscous flow of materials to absorb impact energy. At the same time, the interfacial bonding between inorganic fillers and organic polymers in traditional shotcrete materials mainly relies on physical adsorption and is prone to interfacial debonding under dynamic impact conditions, affecting the overall performance of the materials. In addition, the microstructural design of existing shotcrete materials is relatively simple, lacking a multi-scale energy dissipation network, resulting in difficulty in achieving an ideal low-rebound effect while ensuring strength. Summary of the Invention

[0004] In view of the problems existing in the existing low-rebound high-strength shotcrete materials and their preparation methods, the present invention is proposed.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] In the first aspect, the present invention provides a low-rebound high-strength shotcrete material, including the following percentage components by weight:

[0007] Magnesium silicoaluminate molecular sieve: 5-15%;

[0008] Portland cement: 40-55%;

[0009] Acrylic acid-modified silicone resin: 8-16%;

[0010] Acrylate copolymer emulsion: 8-13%;

[0011] Thickener: 2-4%;

[0012] Bactericide: 0.1-1%;

[0013] Surfactant: 2 - 4%;

[0014] Dispersant: 2 - 4%;

[0015] Defoamer: 0.3 - 0.5%;

[0016] The balance is water, and the water is balanced to 100%.

[0017] As a preferred embodiment of the low - rebound high - strength spraying mortar described in the present invention, wherein: the molar ratio of SiO2 to Al2O3 of the magnesium silicoaluminate molecular sieve is 20 - 40:1.

[0018] The limitation of the molar ratio of SiO2 to Al2O3 enables the molecular sieve surface to have appropriate acidic sites, which can not only form chemical bonding with the modified silicone resin but also maintain the framework stability, realizing the firm combination of the inorganic and organic phases.

[0019] As a preferred embodiment of the low - rebound high - strength spraying mortar described in the present invention, wherein: the magnesium silicoaluminate molecular sieve has a fibrous morphology, the fiber diameter is 10 - 100 nm, and the length is 0.5 - 10 μm;

[0020] The magnesium silicoaluminate molecular sieve is in a hydrated state containing structural water, the specific surface area is 800 - 1400 square meters per gram, the crystal form is MCM - 41, and the relative crystallinity of the magnesium silicoaluminate molecular sieve is 85 - 92%;

[0021] In the magnesium silicoaluminate molecular sieve, the ratio of pores with a pore diameter of 2 - 50 nm to the total pores is greater than 90%.

[0022] The fibrous morphology forms a three - dimensional reinforcement network, and the surface area of 800 - 1400 m 2 / g and the ordered mesoporous structure provide abundant anchoring sites, significantly improving the mechanical properties and anti - resilience of the material

[0023] As a preferred embodiment of the low - rebound high - strength spraying mortar described in the present invention, wherein: the preparation method of the magnesium silicoaluminate molecular sieve includes:

[0024] Mix SiO2 powder with a surfactant, the molar ratio of SiO2 to the surfactant is 1:0.1 - 0.3, and add deionized water to form a slurry with a solid content of 10 - 30 wt%;

[0025] Under the condition that the stirring speed is 200 - 500 rpm, dropwise add sodium aluminate solution or aluminum nitrate solution to the slurry, the dropping time is 30 - 60 minutes, and control the molar ratio of SiO2 to Al2O3 in the final product to be 20 - 40:1;

[0026] Adjust the pH value of the system to 9 - 11 with hydrochloric acid or ammonia water with a concentration of 0.1 - 2 mol / L, and continue stirring at room temperature for 2 - 4 hours to form a gel;

[0027] Transfer the gel to a hydrothermal reactor lined with polytetrafluoroethylene, and carry out static crystallization at 80 - 150 °C for 24 - 72 hours;

[0028] After the crystallization is completed, filter the product, wash it 3 - 5 times with deionized water until the pH value of the filtrate is 6.5 - 7.5, and dry it at 60 - 80 °C for 12 - 24 hours;

[0029] Place the dried product in a muffle furnace, heat it to 550 °C at a heating rate of 1 - 2 °C / min, keep it at 550 °C for constant temperature calcination for 5 - 8 hours, and then cool it to room temperature to obtain the magnesium aluminosilicate molecular sieve.

[0030] As a preferred embodiment of the low - rebound high - strength spraying mortar described in the present invention, wherein: the preparation method of the SiO2 powder includes:

[0031] Prepare an alkaline suspension by mixing a silicon raw material, an alkali and water, wherein the silicon raw material uses treated gold mine tailings as the silicon source;

[0032] Add acid for acidolysis, and then through static settlement, make the acidolysis product settle and layer by gravity. The upper - layer suspension is separated by solid - liquid separation to obtain a SiO2 suspension;

[0033] Dry the SiO2 suspension to obtain SiO2 powder.

[0034] As a preferred embodiment of the low - rebound high - strength spraying mortar described in the present invention, wherein: the acrylate copolymer emulsion is prepared by copolymerizing the following monomers:

[0035] Methyl methacrylate: 40 - 60 wt%;

[0036] Butyl acrylate: 20 - 35 wt%;

[0037] Acrylic acid: 3 - 8 wt%;

[0038] 2 - Hydroxyethyl acrylate: 5 - 15 wt%;

[0039] The solid content of the acrylate copolymer emulsion is 40 - 55%, and the glass transition temperature is - 10 - 10 °C;

[0040] The preparation method of the acrylic - modified silicone resin includes:

[0041] React glycidyl methacrylate with siloxane at 60 - 80 °C for 4 - 8 hours; wherein, the molar ratio of glycidyl methacrylate to siloxane in the reactants is 1:0.8 - 1.2.

[0042] The proportion of comonomers imparts good flexibility to the acrylate copolymer emulsion, and the epoxy groups in the modified silicone resin provide chemical crosslinking activity. The two work together to enhance the toughness and adhesion of the material.

[0043] As a preferred embodiment of the low-rebound high-strength spraying mortar described in the present invention, wherein: the thickener is one or a combination of one or more of hydroxyethyl cellulose, hydroxypropyl methylcellulose or polyacrylamide.

[0044] The selected thickener has excellent pseudoplasticity, making the spraying mortar easy to atomize under high shear and quickly recover viscosity when standing, effectively controlling sagging and rebound.

[0045] As a preferred embodiment of the low-rebound high-strength spraying mortar described in the present invention, wherein: the surfactant is one or a combination of one or more of polyoxyethylene fatty alcohol ether, alkylphenol polyoxyethylene ether or sodium fatty alcohol polyoxyethylene ether sulfate;

[0046] The dispersant is a polycarboxylate dispersant or a naphthalene sulfonate dispersant;

[0047] The defoamer is a silicone defoamer or a polyether defoamer;

[0048] The bactericide is an isothiazolinone bactericide.

[0049] In a second aspect, the present invention provides a method for preparing a low-rebound high-strength spraying mortar, which includes the following steps:

[0050] Under the condition of a temperature of 5-15°C, mix the acrylic acid-modified silicone resin, portland cement and acrylate copolymer emulsion in a mixer at a stirring speed of 50-100 rpm for 5-10 minutes to form an organic phase premix;

[0051] Pre-disperse the magnesium aluminosilicate molecular sieve in water at 3000-5000 rpm in a high-speed shearer for 3-5 minutes to form a molecular sieve suspension;

[0052] Under the condition of a stirring speed of 200-300 rpm, slowly add the organic phase premix to the molecular sieve suspension, and set the temperature to 10-20°C to obtain a mixture;

[0053] Pre-dissolve the thickener in water to form a thickening solution, and then slowly add it to the mixture under stirring conditions;

[0054] Continue to add a surfactant, a dispersant, a bactericide and a defoamer to the mixture in sequence. After each component is added, stir for 3-5 minutes, and finally degas for 10-15 minutes under a vacuum of -0.08 to -0.095 MPa to obtain the low-rebound high-strength spraying mortar.

[0055] Low-temperature premixing and temperature-controlled feeding process induce interfacial self-assembly to form a gradient coating structure. Vacuum degassing eliminates microbubbles, improving the material density and interfacial bonding strength.

[0056] As a preferred embodiment of the preparation method of the low-elasticity and high-strength spraying mortar described in the present invention, wherein: in the step of forming the organic phase premix, the weight ratio of the acrylic acid-modified silicone resin to the acrylate copolymer emulsion is 1:0.6 - 0.9;

[0057] In the step of forming the molecular sieve suspension, the weight ratio of magnesium aluminosilicate molecular sieve to water is 1:0.8 - 1.5, and the pH value of the molecular sieve suspension is 7.5 - 8.0;

[0058] The pH value of the low-elasticity and high-strength spraying mortar is 7.0 - 8.5.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] 1. Through the synergistic effect of the fibrous morphology of magnesium aluminosilicate molecular sieve and a specific silicon-aluminum ratio, a new "multi-scale energy dissipation network" is created. When the spraying mortar impacts the working surface at high speed, the fibrous magnesium aluminosilicate molecular sieves are intertwined with each other in three-dimensional space, forming a reinforced structure similar to reinforced concrete. More importantly, the molar ratio of SiO2 to Al2O3 is controlled in the range of 20 - 40, making the surface of the magnesium aluminosilicate molecular sieve show moderate weak acidity. These acidic sites undergo ring-opening reactions with the epoxy groups in the acrylic acid-modified silicone resin to form stable chemical bonds. This chemical anchoring effect enables the magnesium aluminosilicate molecular sieve to not only act as a physical reinforcement phase but also become a chemical cross-linking point, integrating the originally discrete energy absorption units into a continuous energy-consuming network, significantly reducing the rebound rate of the material.

[0061] 2. By premixing the acrylic acid-modified silicone resin and the acrylate copolymer emulsion (weight ratio 1:0.6 - 0.9) at a temperature of 5 - 15°C, a thermodynamically metastable interpenetrating network structure is formed. When this premix is added to the molecular sieve suspension at 10 - 20°C, the synergistic effect of the temperature gradient and the shear force field triggers the interfacial self-assembly process: the siloxane segments of the modified silicone resin are preferentially adsorbed on the surface of the magnesium aluminosilicate molecular sieve to form a hydrophobic inner layer; while the acrylate copolymer emulsion forms a hydrophilic outer layer on the periphery. This spontaneously formed "amphiphilic" coating structure endows the material with unique stimulus-responsive properties - showing good dispersibility and fluidity during the spraying process, and rapidly transforming into a state of high adhesiveness and high cohesive strength at the moment of impact.

[0062] 3. In the pH range of 7.5-8.0 of the molecular sieve suspension and 7.0-8.5 of the final product, the silanol groups in the acrylic modified silicone resin are in a partially ionized state, forming a reversible hydrogen bond network with the aluminum hydroxyl groups on the surface of the magnesium aluminosilicate molecular sieve. This dynamic hydrogen bond network can quickly break and reorganize when the material is impacted, which not only effectively dissipates the impact energy, but more importantly, it can recover spontaneously after the stress is eliminated, giving the material self-healing properties similar to biological tissues. Combined with the ordered mesoporous structure of MCM-41 (pore size 2~50nm), during the curing process after spraying, some polymer chain segments will penetrate into these channels and undergo in-situ polymerization under pH induction to form "molecular-level anchors", which further enhance the bonding between the coating and the substrate and achieve a balance between low rebound and high strength. The magnesium aluminosilicate molecular sieve synthesized from SiO2 powder prepared from gold mine tailings exhibits a better porous structure and a more uniform pore size distribution. The resource utilization of gold mine tailings not only avoids the consumption of primary mineral resources in the traditional SiO2 powder preparation process, but also effectively reduces the land occupation and potential environmental risks of tailings storage. DETAILED DESCRIPTION

[0063] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description in conjunction with the specific implementation methods of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0064] Embodiment 1:

[0065] A low-rebound high-strength shotcrete material, characterized in that it comprises the following percentage components by weight:

[0066] Magnesium aluminosilicate molecular sieve: 15%;

[0067] Portland cement: 40%;

[0068] Acrylic modified silicone resin: 10%;

[0069] Acrylate copolymer emulsion: 8%;

[0070] Thickener: 2%;

[0071] Fungicide: 0.1%;

[0072] Surfactant: 2%;

[0073] Dispersant: 2%;

[0074] Defoaming agent: 0.3%;

[0075] The remainder is water.

[0076] The molar ratio of SiO2 to Al2O3 in the magnesium silicoaluminate molecular sieve is 20:1, which can not only form chemical bonding with the modified silicone resin, but also maintain the framework stability, realizing a firm combination of the inorganic and organic phases.

[0077] The magnesium silicoaluminate molecular sieve has a fibrous morphology, with a fiber diameter of 20 nm and a length of 1 μm; the magnesium silicoaluminate molecular sieve is in a hydrated state containing structural water, with a specific surface area of 800 m2 / g, a crystal form of MCM-41, and the relative crystallinity of the magnesium silicoaluminate molecular sieve is 85%; in the magnesium silicoaluminate molecular sieve, the ratio of pores with a pore diameter of 5 nm to the total pores is greater than 90%.

[0078] The acrylate copolymer emulsion is prepared by copolymerizing the following monomers:

[0079] Methyl methacrylate: 40 wt%;

[0080] Butyl acrylate: 20 wt%;

[0081] Acrylic acid: 3 wt%;

[0082] 2-Hydroxyethyl acrylate: 5 wt%;

[0083] The solid content of the acrylate copolymer emulsion is 40%, and the glass transition temperature is -10 °C.

[0084] The thickener is hydroxyethyl cellulose; the bactericide is an isothiazolinone bactericide; the surfactant is polyoxyethylene fatty alcohol ether; the dispersant is a polycarboxylate dispersant; the defoamer is a silicone defoamer.

[0085] Example 2:

[0086] A low-elasticity and high-strength spraying mortar, characterized by comprising the following percentage components by weight:

[0087] Magnesium silicoaluminate molecular sieve: 5%;

[0088] Portland cement: 55%;

[0089] Acrylic acid-modified silicone resin: 15%;

[0090] Acrylate copolymer emulsion: 10%;

[0091] Thickener: 3%;

[0092] Bactericide: 0.5%;

[0093] Surfactant: 3%;

[0094] Dispersant: 3%;

[0095] Defoamer: 0.4%;

[0096] The remainder is water.

[0097] The molar ratio of SiO2 to Al2O3 in the magnesium silicoaluminate molecular sieve is 30:1.

[0098] The magnesium silicoaluminate molecular sieve has a fibrous morphology, with a fiber diameter of 50 nm and a length of 4 μm; the magnesium silicoaluminate molecular sieve is in a hydrated state containing structural water, with a specific surface area of 1000 m2 / g, a crystal form of MCM-41, and the relative crystallinity of the magnesium silicoaluminate molecular sieve is 88%; in the magnesium silicoaluminate molecular sieve, the ratio of pores with a pore diameter of 25 nm to the total pores is greater than 90%.

[0099] The acrylate copolymer emulsion is prepared by copolymerizing the following monomers:

[0100] Methyl methacrylate: 50 wt%;

[0101] Butyl acrylate: 25 wt%;

[0102] Acrylic acid: 5 wt%;

[0103] Hydroxyethyl acrylate: 10 wt%;

[0104] The solid content of the acrylate copolymer emulsion is 45%, and the glass transition temperature is 0 °C.

[0105] The thickener is hydroxypropyl methylcellulose; the bactericide is an isothiazolinone bactericide; the surfactant is alkylphenol polyoxyethylene ether; the dispersant is a naphthalene sulfonate dispersant; the defoamer is a polyether defoamer.

[0106] Example 3:

[0107] A low-elasticity and high-strength spraying mortar, characterized in that it comprises the following percentage components by weight:

[0108] Magnesium silicoaluminate molecular sieve: 10%;

[0109] Portland cement: 50%;

[0110] Acrylic acid-modified silicone resin: 10%;

[0111] Acrylate copolymer emulsion: 13%;

[0112] Thickener: 4%;

[0113] Bactericide: 1%;

[0114] Surfactant: 4%;

[0115] Dispersant: 4%;

[0116] Defoamer: 0.5%;

[0117] The remainder is water.

[0118] The molar ratio of SiO2 to Al2O3 in the magnesium aluminosilicate molecular sieve is 40:1.

[0119] The magnesium aluminosilicate molecular sieve has a fibrous morphology with a fiber diameter of 100 nm and a length of 8 μm; the magnesium aluminosilicate molecular sieve is in a hydrated state containing structural water, with a specific surface area of 1400 m2 / g, a crystal form of MCM-41, and the relative crystallinity of the magnesium aluminosilicate molecular sieve is 92%; in the magnesium aluminosilicate molecular sieve, the ratio of pores with a pore diameter of 50 nm to the total pores is greater than 90%.

[0120] The acrylate copolymer emulsion is prepared by copolymerizing the following monomers:

[0121] Methyl methacrylate: 60 wt%;

[0122] Butyl acrylate: 35 wt%;

[0123] Acrylic acid: 8 wt%;

[0124] 2-Hydroxyethyl acrylate: 15 wt%;

[0125] The solid content of the acrylate copolymer emulsion is 55%, and the glass transition temperature is 10 °C.

[0126] The thickener is polyacrylamide; the bactericide is an isothiazolinone bactericide; the surfactant is sodium lauryl polyoxyethylene sulfate; the dispersant is a naphthalene sulfonate dispersant; the defoamer is a polyether defoamer.

[0127] Comparative Example 1: Using silica powder to replace the magnesium aluminosilicate molecular sieve in Example 2, including the following percentage components by weight:

[0128] Silica powder: 5%;

[0129] Portland cement: 55%;

[0130] Acrylic acid-modified silicone resin: 10%;

[0131] Acrylate copolymer emulsion: 8%;

[0132] Thickener: 2%;

[0133] Bactericide: 0.1%;

[0134] Surfactant: 2%;

[0135] Dispersant: 2%;

[0136] Defoamer: 0.3%;

[0137] The remainder is water.

[0138] The silica fume is spherical and non-porous in structure, with a particle size of 3 μm and a specific surface area of 10 m² / g. The other components are the same as those in Example 2.

[0139] Comparative Example 2: The molar ratio of SiO₂ to Al₂O₃ in the magnesium silicoaluminate molecular sieve is 10:1, and it includes the following percentage components by weight:

[0140] Magnesium silicoaluminate molecular sieve: 5%;

[0141] Portland cement: 55%;

[0142] Acrylic acid-modified silicone resin: 15%;

[0143] Acrylate copolymer emulsion: 10%;

[0144] Thickener: 3%;

[0145] Bactericide: 0.5%;

[0146] Surfactant: 3%;

[0147] Dispersant: 3%;

[0148] Defoamer: 0.4%;

[0149] The balance is water.

[0150] The other components are the same as those in Example 2.

[0151] Through experiments, an expected test table was obtained;

[0152] Table 1: Test result table of Example 2, Comparative Example 1 and Comparative Example 2

[0153] Performance indicators Example 2 Comparative Example 1 Comparative Example 2 Rebound rate (%) 5-10 20-30 15-20 28-day compressive strength (MPa) 35-40 20-25 25-30 Bonding strength with concrete (MPa) 2.0-2.5 0.8-1.2 1.2-1.5 Bonding strength with steel plate (MPa) 2.5-3.0 1.0-1.5 1.5-2.0 Impact energy absorption rate (%) 85-90 50-60 65-75 Fracture mode Internal fracture of material Interface fracture Mixed fracture

[0154] During the rebound rate test, the shotcreting slurries of Example 2, Comparative Example 1 and Comparative Example 2 were prepared according to the formula and left to stand for 24 hours until stable. Standard shotcreting test equipment was used, including a pneumatic spray gun (working pressure 0.5 MPa) and a concrete test plate (100×100×5 cm).

[0155] The test plate was fixed in a vertical position, the spray gun was kept 60 cm away from the plate surface, and the spraying angle was 90°. The spraying area for each sample was 50×50 cm, and the spraying thickness was 2 cm.

[0156] A receiving tray was placed under the test plate to collect the rebound material. The total weight W1 of the shotcreting slurry before spraying was weighed, the weight W2 of the rebound material was weighed, and the rebound rate = (W2 / W1)×100%.

[0157] During the compressive strength test, standard cubic specimens were prepared by spraying with Example 2, Comparative Example 1, and Comparative Example 2 respectively. Under standard conditions, such as a temperature of 23°C and a relative humidity of 50%, they were cured for 7 days, 14 days, and 28 days. 6 specimens were prepared for each formulation at each curing period.

[0158] Using a standard pressure testing machine with a loading rate of 0.5 MPa / s, the maximum load at failure was recorded, and the compressive strength was calculated as = maximum load / compression area.

[0159] During the interfacial bond strength test, standard cement mortar boards, steel plates, and brick walls were prepared. The spraying thickness was 1 cm and they were cured for 28 days.

[0160] According to the ISO4624 standard, a pull-out test was conducted. A standard pull-out head was pasted on the sprayed coating, and the pull-out was performed perpendicular to the surface direction using a pull-out instrument. The fracture load and fracture mode (interface fracture or internal material fracture) were recorded, and the bond strength was calculated as = fracture load / pull-out head area.

[0161] In the dynamic impact test, Example 2, Comparative Example 1, and Comparative Example 2 were respectively sprayed on standard concrete boards with a spraying thickness of 2 cm and cured for 28 days.

[0162] Using a drop hammer impact test device, the drop hammer weight was set at 1 kg, the drop hammer diameter was 5 cm, and the drop heights were 50 cm, 100 cm, and 150 cm. The impact pit depth and damage condition were recorded. A camera was used to record the rebound height of the drop hammer, and the impact energy absorption rate was calculated as: (1 - rebound height / drop height) × 100%.

[0163] As can be seen from Table 1, the rebound rate of Example 2 was significantly lower than that of the comparative examples. The rebound rates of Comparative Example 1 and Comparative Example 2 were 20 - 30% and 15 - 20% respectively.

[0164] First, the fibrous magnesium silicoaluminate molecular sieve (diameter 50 nm, length 4 μm) used in Example 2 formed a three-dimensional intertwined reinforcement network, which could effectively disperse the impact energy. In contrast, the spherical silica powder used in Comparative Example 1 lacked such a network structure and could not effectively absorb and disperse the impact energy.

[0165] Secondly, the molar ratio of SiO2 to Al2O3 in the magnesium silicoaluminate molecular sieve in Example 2 was 30:1, which was within the optimal range, making the surface of the molecular sieve exhibit moderate weak acidity and capable of undergoing a ring-opening reaction with the epoxy groups in the acrylic acid-modified silicone resin to form a stable chemical bond. However, the molar ratio in Comparative Example 2 was 10:1, which would result in too strong acidity on the surface of the molecular sieve. Although it had reaction activity, the reaction was too fast and uneven, and a good interfacial structure could not be formed.

[0166] In the strength performance analysis, in terms of the 28-day compressive strength, Example 2 reached 35 - 40 MPa, far higher than 20 - 25 MPa of Comparative Example 1 and 25 - 30 MPa of Comparative Example 2.

[0167] The fibrous molecular sieve in Example 2 formed a chemically bonded composite reinforcement structure with the organic resin, similar to nano-scale reinforced concrete. The high specific surface area (1000 m 2 / g) provided a large number of interfacial bonding sites, significantly enhancing the overall structure of the material. Although the silica fume in Comparative Example 1 also played a filling role, its specific surface area was only 10 m 2 / g, and it only had physical mixing with the resin matrix rather than chemical bonding, so the strength was greatly reduced.

[0168] In addition, the molecular sieve with a molar ratio of SiO2 to Al2O3 of 30:1 in Example 2 not only maintained the stability of the framework but also had appropriate surface activity, forming an optimal interfacial structure. While the molar ratio of 10:1 in Comparative Example 2 led to a decrease in the stability of the molecular sieve framework and was more prone to deformation and failure under stress.

[0169] In the bond strength analysis, the bond strength of Example 2 on different substrates was significantly higher than that of the two comparative examples.

[0170] This excellent bonding performance was attributed to the synergistic effect of the nano-mesoporous structure (pore diameter mainly 25 nm) of the molecular sieve in Example 2 and the appropriate molar ratio of SiO2 to Al2O3, forming a "molecular-level anchor" effect. When the spraying slurry contacted the substrate, part of the acrylic resin could penetrate into these nano-pores and in-situ polymerization occurred under the catalysis of an appropriate acidic environment, forming a firm mechanical interlocking structure. The silica fume in Comparative Example 1 did not have a porous structure and could not form such an interlock; while Comparative Example 2 had a porous structure, but the molar ratio of SiO2 to Al2O3 was not appropriate, resulting in an unsatisfactory interfacial reaction.

[0171] In the impact test, Example 2 showed an energy absorption rate of 85 - 90%, far higher than 50 - 60% of Comparative Example 1 and 65 - 75% of Comparative Example 2. In addition, the difference in the fracture mode also reflected the different internal structures of the materials: Example 2 mainly showed internal fracture of the material, indicating that the interfacial bonding strength was higher than the strength of the material body; while Comparative Example 1 was mainly interfacial fracture, and Comparative Example 2 showed a mixed fracture mode.

[0172] This excellent impact performance stems from the "multi-scale energy dissipation network" formed in Example 2: the ordered pore structure of MCM-41 magnesium aluminosilicate molecular sieve (pore diameter of 25 nm) provides nano-scale damping; the three-dimensional network formed by fibrous magnesium aluminosilicate molecular sieve (diameter of 50 nm and length of 4 μm) provides micro-scale reinforcement; the interpenetrating network formed by acrylic acid-modified silicone resin and acrylate copolymer emulsion provides macroscopic toughness.

[0173] This multi-scale synergistic effect enables the material to dissipate energy through multiple mechanisms simultaneously when subjected to impact, while Comparative Example 1 and Comparative Example 2 both lack this complex multi-scale structure.

[0174] In summary, through the synergistic effect of the fibrous morphology of magnesium aluminosilicate molecular sieve and a specific silicon-aluminum ratio, a brand-new "multi-scale energy dissipation network" is created. When the spraying material impacts the working surface at high speed, the fibrous magnesium aluminosilicate molecular sieves are intertwined with each other in three-dimensional space, forming a reinforcement structure similar to reinforced concrete. More crucially, the molar ratio of SiO2 to Al2O3 is controlled in the range of 20-40, making the surface of the magnesium aluminosilicate molecular sieve exhibit moderate weak acidity. These acidic sites undergo ring-opening reactions with the epoxy groups in the acrylic acid-modified silicone resin to form stable chemical bonds. This chemical anchoring effect enables the magnesium aluminosilicate molecular sieve to not only act as a physical reinforcement phase but also become a chemical cross-linking point, integrating the originally discrete energy absorption units into a continuous energy-consuming network and significantly reducing the rebound rate of the material.

[0175] Example 4: This example also provides a preparation method for magnesium aluminosilicate molecular sieve, which specifically includes the following steps:

[0176] S1. Mix SiO2 powder with a surfactant, with a molar ratio of SiO2 to surfactant of 1:0.2, and add deionized water to form a slurry with a solid content of 20 wt%.

[0177] S2. Under the condition of a stirring speed of 300 rpm, dropwise add sodium aluminate solution or aluminum nitrate solution to the slurry. The dropping time is 30 minutes, and control the molar ratio of SiO2 to Al2O3 in the final product to be 30:1.

[0178] S3. Adjust the pH value of the system to 10 with 1 mol / L hydrochloric acid or ammonia water, and continue stirring at room temperature for 2 hours to form a gel.

[0179] S4. Transfer the gel to a hydrothermal autoclave lined with polytetrafluoroethylene and carry out static crystallization at 100 °C for 50 hours.

[0180] S5. After the crystallization is completed, filter the product, wash it 3 times with deionized water until the pH value of the filtrate is 7, and dry it at 80 °C for 12 hours.

[0181] S6. Place the dried product in a muffle furnace and heat it to 550 °C at a heating rate of 2 °C / min. Calcinate it at 550 °C for 5 hours, and then cool it to room temperature to obtain the magnesium aluminosilicate molecular sieve.

[0182] Among them, in step S1, the preparation method of the SiO2 powder used includes:

[0183] Prepare an alkaline suspension by mixing a silicon raw material, an alkali, and water. Among them, the silicon raw material uses treated gold mine tailings as the silicon source;

[0184] Add an acid for acidolysis, and then let it stand still to make the acidolysis product settle and layer by gravity. The upper suspension is separated by solid-liquid separation to obtain a SiO2 suspension;

[0185] Dry the SiO2 suspension to obtain SiO2 powder.

[0186] The preparation method of the acrylic acid-modified silicone resin includes:

[0187] React glycidyl methacrylate with siloxane at 60 °C for 4 hours; among them, the molar ratio of glycidyl methacrylate to siloxane in the reactants is 1:1.

[0188] In an alternative embodiment, the treatment of gold mine tailings may include: collecting the tailings discharged from a gold mine concentrator, washing them with water to remove water-soluble substances, drying them at 80 °C for 24 hours, and then calcining them in a muffle furnace at 400 °C for 2 hours to remove organic substances. Mix the calcined tailings with 1.0 mol / L hydrochloric acid at a solid-liquid ratio of 1:5, stir and soak them at 60 °C for 4 hours to remove heavy metal ions and soluble impurities. The soaked tailings are screened through a sieve to obtain fine tailings powder with an average particle size of 65 μm. After X-ray fluorescence analysis, the SiO2 content of the treated tailings reaches more than 85%, and it can be used as the raw material for preparing SiO2 powder. The magnesium aluminosilicate molecular sieve synthesized from the SiO2 powder prepared from gold mine tailings exhibits a better porous structure, and the pore size distribution is more uniform. Moreover, the resource utilization of gold mine tailings not only avoids the consumption of primary mineral resources in the traditional preparation process of SiO2 powder but also effectively reduces the land occupation of tailings storage and potential environmental risks.

[0189] The preparation method of magnesium aluminosilicate molecular sieve proposed in this embodiment realizes the directional growth and structural regulation of magnesium aluminosilicate molecular sieve through a multi-step process. By mixing SiO2 and surfactant in a specific molar ratio and slowly adding the aluminum source, a unique "dropwise gradient field" is formed, enabling the aluminum ions to exhibit a concentration gradient distribution along the fiber axis in the silicon matrix. This gradient distribution plays the role of a "directional growth template" in the subsequent hydrothermal crystallization process, promoting the magnesium aluminosilicate molecular sieve to extend along a specific direction to form a fibrous structure instead of the traditional spherical particles. More importantly, the step of constant-temperature calcination at 550 °C not only removes the surfactant template but also promotes the rearrangement of the silicon-oxygen network and the further regularization of the pore structure, forming a highly ordered nano-porous structure while retaining the fibrous macroscopic morphology. This special preparation process endows the magnesium aluminosilicate molecular sieve with a fibrous morphology, providing an ideal structural basis for the subsequent formation of a multi-scale reinforcement network.

[0190] The precise synthesis scheme of acrylic acid-modified silicone resin provides a key bridge for the chemical bonding between magnesium aluminosilicate molecular sieve and organic matrix. Through the ring-opening reaction of glycidyl methacrylate and siloxane, two reactive groups are introduced onto the molecular chain: on the one hand, the silanol group can form a strong hydrogen bond network and Si-O-Al covalent bond with the aluminum hydroxyl groups on the surface of the magnesium aluminosilicate molecular sieve; on the other hand, the acrylic acid group realizes a compatible interface and cross-linking reaction with the acrylic ester copolymer emulsion. This "amphiphilic" molecular structure constructs a self-assembled interfacial layer similar to a biological cell membrane at the microscale, not only effectively solving the interfacial incompatibility problem between traditional inorganic fillers and organic matrices but also playing the role of an "energy transducer" under dynamic impact conditions, converting mechanical impact energy into conformational changes of molecular chains and the breaking and recombination energy of reversible hydrogen bonds, significantly enhancing the impact resistance and self-healing properties of the material; the application of gold mine tailings as a silicon source reflects the environmental protection concept of comprehensive utilization of industrial solid waste. The magnesium aluminosilicate molecular sieve synthesized from the SiO2 powder prepared from gold mine tailings exhibits a better porous structure with a more uniform pore size distribution. Moreover, the resource utilization of gold mine tailings not only avoids the consumption of primary mineral resources in the preparation process of traditional SiO2 powder but also effectively reduces the land occupation of tailing storage and potential environmental risks.

[0191] Example 5: This example provides a preparation method of a low-elasticity and high-strength shotcrete, including the following steps:

[0192] S100. Under the condition of a temperature of 10 °C, mix the acrylic acid-modified silicone resin, portland cement, and acrylic ester copolymer emulsion in a blender at a stirring speed of 70 rpm for 5 minutes to form an organic phase premix;

[0193] Among them, the weight ratio of the acrylic acid-modified silicone resin to the acrylic ester copolymer emulsion is 1:0.6.

[0194] S200. Premix the magnesium aluminosilicate molecular sieve in water at 4000 rpm in a high-speed shear mixer for 4 minutes to form a molecular sieve suspension;

[0195] The weight ratio of the magnesium aluminosilicate molecular sieve to water is 1:1, and the pH value of the molecular sieve suspension is 7.5.

[0196] S300. Slowly add the organic phase premix to the molecular sieve suspension at a stirring speed of 200 rpm, and set the temperature to 10 °C to obtain a mixture.

[0197] S400. Pre-dissolve the thickener in water to form a thickening solution, and then slowly add it to the mixture under stirring conditions.

[0198] S500. Sequentially add a surfactant, a dispersant, a bactericide, and an antifoaming agent to the mixture, stir for 3 minutes after each component is added, and finally degas for 10 minutes under a vacuum of -0.08 MPa to obtain a low-rebound high-strength spraying mortar.

[0199] The pH value of the low-rebound high-strength spraying mortar is 7.0.

[0200] Comparative Example 3. This comparative example provides a method for preparing a spraying mortar with the same formulation as in Example 5 but different pH control, including the following steps:

[0201] S100. Mix the acrylic acid-modified silicone resin, portland cement, and acrylate copolymer emulsion in a blender at a temperature of 10 °C, with a stirring speed of 70 rpm and a stirring time of 5 minutes to form an organic phase premix;

[0202] Among them, the weight ratio of the acrylic acid-modified silicone resin to the acrylate copolymer emulsion is 1:0.6.

[0203] S200. Premix the magnesium aluminosilicate molecular sieve in water at 4000 rpm in a high-speed shear mixer for 4 minutes to form a molecular sieve suspension;

[0204] The weight ratio of the magnesium aluminosilicate molecular sieve to water is 1:1, and the pH value of the molecular sieve suspension is adjusted to 5.0 (lower than 7.5 in Example 5).

[0205] S300. Slowly add the organic phase premix to the molecular sieve suspension at a stirring speed of 200 rpm, and set the temperature to 10 °C to obtain a mixture.

[0206] S400. Pre-dissolve the thickener in water to form a thickening solution, and then slowly add it to the mixture under stirring conditions.

[0207] S500. In the mixture, successively add a surfactant, a dispersant, a bactericide, and an antifoaming agent. After adding each component, stir for 3 minutes. Finally, degas for 10 minutes under a vacuum of -0.08 MPa to obtain a comparative spraying slurry.

[0208] The pH value of the final comparative spraying slurry is 4.5 (lower than 7.0 of Example 5).

[0209] To verify the key influence of the pH value on the performance of the spraying slurry, experimental tests were conducted on the products of Example 5 and Comparative Example 3, specifically as follows:

[0210] In the dynamic impact test, a hammer impact test device (1 kg hammer weight, 100 cm height) was used for testing. Each sample was tested 5 times, and the results are shown in Table 2;

[0211] Table 2: Dynamic impact test situation table

[0212] Sample Impact energy absorption rate (%) Rebound height (cm) Recovery time (s) Residual deformation after impact (mm) Example 5 87.5 12.5 2.3 0.4 Comparative Example 3 65.2 34.8 8.7 2.1

[0213] In the dynamic mechanical analysis test, a scan was performed in the frequency range of 0.1 - 10 Hz to measure the loss factor (tanδ), and the results are shown in Table 3;

[0214] Table 3: Dynamic mechanical analysis test situation table

[0215]

[0216] In the microstructure analysis, the interfacial structure was analyzed by an electron microscope and infrared spectroscopy, and the results are shown in Table 4;

[0217] Table 4: Microstructure analysis situation table

[0218] Sample Penetration depth of polymer in pores (nm) Si-O-Al bridge bond strength (infrared absorption peak area) Interface layer thickness (nm) Example 5 120-180 87.6 45-60 Comparative Example 3 30-50 32.4 10-15

[0219] After a standard scratch test was performed on the surface of the self - healing performance test material, the recovery situation was observed for 24 hours, and the results are shown in Table 5;

[0220] Table 5: Self - healing performance test situation table

[0221] Sample Scratch width recovery rate (%) Scratch depth recovery rate (%) Mechanical property recovery rate (%) Example 5 78.5 85.3 91.2 Comparative Example 3 12.3 18.7 36.5

[0222] As shown in Tables 2 to 5, the pH value of the molecular sieve suspension in Example 5 was 7.5, and the pH value of the final product was 7.0, which was within the optimal range. Under this pH condition, about 30-40% of the silanol groups (-Si-OH) in the acrylic acid-modified silicone resin were in a partially ionized state (-Si-O-), and the hydrogen bond network formed with the aluminum hydroxyl groups (-Al-OH) on the surface of the molecular sieve was in a "dynamic equilibrium" state, having sufficient stability to maintain structural integrity and sufficient activity to allow reversible fracture and recombination under stress.

[0223] For Comparative Example 3, the pH value of the molecular sieve suspension was 5.0, and the pH value of the final product was 4.5, which was in an obvious acidic environment. Under such conditions, the ionization of the silanol groups was inhibited (ionization degree < 5%), and mainly weak physical adsorption rather than chemical hydrogen bond network was formed between the silanol groups and the aluminum hydroxyl groups. At the same time, the acidic environment also promoted the leaching of a part of aluminum ions from the molecular sieve framework, destroying the ordered mesoporous structure of the molecular sieve. Electron microscope observation found that the penetration depth of the polymer in the pores in Comparative Example 3 was only 30-50 nm, much lower than 120-180 nm in Example 5, and an effective "molecular-level anchor" could not be formed.

[0224] More importantly, in the suitable pH environment of Example 5, when the material was impacted, part of the hydrogen bond network could undergo controllable fracture and absorb a large amount of energy; after the stress was eliminated, these broken hydrogen bonds would quickly recombine using the surrounding water molecules as "mediators" to restore the original structure, similar to the self-healing mechanism in biological tissues. This unique "sacrificial bond" strategy enables the material to exhibit excellent energy absorption capacity and self-healing characteristics while maintaining high strength. However, the acidic environment in Comparative Example 3 prevented the formation of this dynamic hydrogen bond network, resulting in irreversible structural damage to the material after impact, low energy absorption efficiency, and inability to self-heal.

[0225] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A low-rebound high-strength shotcrete material, characterized in that, Comprising the following percentage components by weight: Magnesium silicoaluminate molecular sieve: 5 - 15%; Portland cement: 40 - 55%; Acrylic acid modified silicone resin: 8 - 16%; Acrylate copolymer emulsion: 8 - 13%; Thickener: 2 - 4%; Bactericide: 0.1 - 1%; Surfactant: 2 - 4%; Dispersant: 2 - 4%; Defoamer: 0.3 - 0.5%; The balance is water, and the water is balanced to 100%; The preparation method of the magnesium silicoaluminate molecular sieve includes: Mix SiO2 powder with a surfactant, the molar ratio of SiO2 to the surfactant is 1:0.1 - 0.3, add deionized water to form a slurry with a solid content of 10 - 30 wt%; Under the condition that the stirring speed is 200 - 500 rpm, dropwise add sodium aluminate solution or aluminum nitrate solution to the slurry, the dropping time is 30 - 60 minutes, and control the molar ratio of SiO2 to Al2O3 in the final product to be 20 - 40:1; Adjust the pH value of the system to 9 - 11 with hydrochloric acid or ammonia water with a concentration of 0.1 - 2 mol / L, and continue to stir at room temperature for 2 - 4 hours to form a gel; Transfer the gel to a hydrothermal autoclave lined with polytetrafluoroethylene, and carry out static crystallization at 80 - 150 °C for 24 - 72 hours; After the crystallization is completed, filter the product, wash it with deionized water 3 - 5 times until the pH value of the filtrate is 6.5 - 7.5, and dry it at 60 - 80 °C for 12 - 24 hours; Place the dried product in a muffle furnace, heat it up to 550 °C at a heating rate of 1 - 2 °C / min, calcine it at 550 °C for 5 - 8 hours, and then cool it to room temperature to obtain the magnesium silicoaluminate molecular sieve; The preparation method of the SiO2 powder includes: Prepare an alkaline suspension by mixing a silicon raw material, an alkali and water, wherein the silicon raw material uses treated gold mine tailings as the silicon source; Add an acid for acidolysis, and then through static settlement, make the acidolysis product settle and layer by gravity, and obtain a SiO2 suspension after solid-liquid separation of the upper suspension; Dry the SiO2 suspension to obtain SiO2 powder.

2. The low-rebound high-strength shotcrete slurry according to claim 1, wherein The magnesium silicoaluminate molecular sieve has a fibrous morphology, the fiber diameter is 10 - 100 nm, and the length is 0.5 - 10 μm; The magnesium silicoaluminate molecular sieve is a hydrated state containing structural water, the specific surface area is 800 - 1400 square meters per gram, the crystal form is MCM-41, and the relative crystallinity of the magnesium silicoaluminate molecular sieve is 85 - 92%; In the magnesium silicoaluminate molecular sieve, the ratio of pores with a pore diameter of 2 - 50 nm to the total pores is greater than 90%.

3. The low-elasticity high-strength shotcrete slurry according to claim 2, characterized in that, The raw materials for preparing the acrylate copolymer emulsion include the following components: Methyl methacrylate: 40 - 60 wt%; Butyl acrylate: 20 - 35 wt%; Acrylic acid: 3 - 8 wt%; 2-Hydroxyethyl acrylate: 5 - 15 wt%; The solid content of the acrylate copolymer emulsion is 40 - 55%, and the glass transition temperature is -10 - 10 °C; The preparation method of the acrylic acid modified silicone resin includes: React glycidyl methacrylate with siloxane at 60 - 80 °C for 4 - 8 hours; wherein, the molar ratio of glycidyl methacrylate to siloxane in the reactants is 1:0.8 - 1.

2.

4. The low-elasticity high-strength shotcrete slurry according to claim 3, wherein, The thickener is one or a combination of more than one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, or polyacrylamide.

5. The low-elasticity and high-strength shotcrete slurry according to claim 4, wherein The surfactant is one or a combination of more than one of polyoxyethylene fatty alcohol ether, alkylphenol polyoxyethylene ether, or sodium lauryl polyoxyethylene ether sulfate; The dispersant is a polycarboxylate dispersant or a naphthalene sulfonate dispersant; The defoamer is a silicone defoamer or a polyether defoamer; The bactericide is an isothiazolinone bactericide.

6. A preparation method of the low-elasticity high-strength shotcrete slurry as described in any one of claims 1 to 5, characterized in that, It includes the following steps: Under the condition that the temperature is 5 - 15°C, mix acrylic acid modified silicone resin, portland cement, and acrylate copolymer emulsion in a blender at a stirring speed of 50 - 100 rpm for 5 - 10 minutes to form an organic phase premix; Pre-disperse magnesium silicoaluminate molecular sieve in water at 3000 - 5000 rpm in a high-speed shearer for 3 - 5 minutes to form a molecular sieve suspension; Under the condition that the stirring speed is 200 - 300 rpm, slowly add the organic phase premix to the molecular sieve suspension, and set the temperature to 10 - 20°C to obtain a mixture; Pre-dissolve the thickener in water to form a thickening solution, and then slowly add it to the mixture under stirring conditions; Continue to add surfactant, dispersant, bactericide, and defoamer to the mixture in sequence. Stir for 3 - 5 minutes after each component is added. Finally, degas for 10 - 15 minutes under a vacuum degree of -0.08 - -0.095 MPa to obtain the low rebound high-strength shotcrete.

7. The preparation method of the low-elasticity and high-strength shotcreting material according to claim 6, characterized in that, In the step of forming the organic phase premix, the weight ratio of acrylic acid modified silicone resin to acrylate copolymer emulsion is 1:0.6 - 0.9; In the step of forming the molecular sieve suspension, the weight ratio of magnesium silicoaluminate molecular sieve to water is 1:0.8 - 1.5, and the pH value of the molecular sieve suspension is 7.5 - 8.0; The pH value of the low rebound high-strength shotcrete is 7.0 - 8.5.

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