Springback inhibitor for sprayed concrete as well as preparation method and application of springback inhibitor

Abstract

The invention discloses a springback inhibitor for sprayed concrete as well as a preparation method and application of the springback inhibitor. The rebound inhibitor is prepared from the following components in percentage by mass: 2-5% of magnesium aluminum silicate, 19.8-29.8% of silica fume, 1-4% of a macromolecular tackifier, 2-5% of aluminum sulfate slag powder, 38-51% of superfine stone powder, 9-16% of fly ash microspheres, 1-2% of a water reducing agent, 2-3% of redispersible milk powder, 2-5% of inorganic mineral fibers and 0.01-0.2% of modified plant fibers. The springback inhibitor disclosed by the invention has a remarkable effect on reducing the springback rate of the sprayed concrete, and can enhance the water dispersibility resistance of the sprayed concrete and improve the cohesiveness of the sprayed concrete. The preparation method disclosed by the invention is simple in industry and easy for large-scale production.

Description

Technical Field

[0001] The invention relates to the field of building materials, and in particular to a rebound inhibitor for shotcrete and a preparation method and application thereof. Background Art

[0002] Shotcrete is a special type of concrete that is made by mixing cementitious materials, aggregates, etc. in a certain proportion into a spraying device, and then sprayed to the sprayed surface at high speed with the help of compressed air or other power. It is quickly solidified into a layer of supporting structure under the action of the accelerator, thereby supporting the surrounding rock. During the construction of shotcrete, due to the influence of the spraying angle, pressure, surrounding rock conditions, concrete setting time, etc., problems such as large rebound and falling blocks are prone to occur in the arch crown, arch waist and other parts. In some cases, the rebound rate exceeds 30%, resulting in a large waste of materials and affecting construction safety. The rebound rate of tunnel shotcrete is mainly related to factors such as the spraying process, concrete ratio and performance, accelerator effect, rock wall conditions and construction level. Among them, for the current more common wet process, the working state of concrete and its adaptability to the accelerator are crucial. To ensure that the concrete can be smoothly sprayed through the pipe and quickly consolidated into one after being sprayed onto the rock wall at high speed, and to reduce the rebound of concrete due to the collision force of aggregates or the falling of concrete due to gravity, the concrete is required to have good fluidity and adhesion, and to be able to solidify quickly and have high early strength.

[0003] A rebound inhibitor is a material that can improve the working state of shotcrete, shorten the setting time, and reduce the rebound rate of shotcrete. The Chinese invention patent with application number CN201910864462.0 discloses a method for preparing a rebound inhibitor for shotcrete, which uses modified acrylamide to increase viscosity and modified sepiolite to inhibit cracking, but acrylamide has potential neurotoxicity, genotoxicity and carcinogenicity, and long-term contact may cause damage to the body. The Chinese invention patent with publication number CN115677264B discloses an admixture for reducing the rebound rate of shotcrete and a preparation method thereof, which includes components such as viscosity increase, coagulation accelerator, and plasticity preservation. Hydroxypropyl methylcellulose, polyvinyl alcohol, and nano-silica are used to significantly improve the cohesiveness of concrete, and tricalcium aluminate is used to promote the setting of concrete. Water reducer and gypsum are added to improve fluidity and plasticity. The main component is nano-silica, which has a high cost. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a rebound inhibitor for shotcrete and a preparation method and application thereof. The rebound inhibitor of the present invention is prepared from magnesium aluminum silicate, silica fume, polymer thickener, aluminum sulfate slag powder, ultrafine stone powder, water reducer, redispersible latex powder, inorganic mineral fiber, and modified plant fiber, and is a fine powder mixture with good homogeneity. The rebound inhibitor of the present invention can solve the problems of large rebound rate, poor water resistance and poor cohesion of shotcrete.

[0005] To achieve the above purpose, the technical solution designed by the present invention is as follows:

[0006] The invention provides a rebound inhibitor for shotcrete. The rebound inhibitor is prepared from 2-5% of magnesium aluminum silicate, 19.8-29.8% of silica fume, 1-4% of polymer viscosity enhancer, 2-5% of aluminum sulfate slag powder, 38-51% of ultrafine stone powder, 9-16% of fly ash microbeads, 1-2% of water reducer, 2-3% of redispersible emulsion powder, 2-5% of inorganic mineral fiber and 0.01-0.2% of modified plant fiber in percentage by mass.

[0007] Furthermore, the rebound inhibitor is prepared from 4-5% magnesium aluminum silicate, 20.8-29.8% silica fume, 2-3% polymer viscosity enhancer, 4-5% aluminum sulfate slag powder, 38-51% ultrafine stone powder, 9-10% fly ash microbeads, 1-2% water reducer, 2-3% redispersible emulsion powder, 2-5% inorganic mineral fiber and 0.2% modified plant fiber.

[0008] Furthermore, the water reducer is any one of a powdered polycarboxylic acid water reducer and a naphthalene water reducer; the silica fume is any one of original silica fume, semi-densified silica fume and densified silica fume; the polymer thickener is any one of methyl cellulose, hydroxymethyl cellulose ether, modified starch ether and polyacrylamide.

[0009] Furthermore, the polyacrylamide is an anionic polyacrylamide with a molecular weight of 5 to 12 million.

[0010] Furthermore, the ultrafine stone powder is any one of tailings powder, limestone powder and machine-made aggregate dust collection powder; the redispersible latex powder is any one of vinyl acetate and ethylene copolymer powder (Vac / E), ethylene, vinyl chloride and vinyl silicate ternary copolymer powder (E / Vc / VL), and vinyl acetate, ethylene and higher fatty acid vinyl ester ternary copolymer powder (Vac / E / VeoVa).

[0011] Furthermore, the inorganic mineral fiber is at least one of wollastonite powder, wollastonite fiber, calcium sulfate whisker and sepiolite powder; and the modified plant fiber is any one of carboxylated cellulose nanofiber and carboxylated cellulose nanowhisker.

[0012] Furthermore, the rebound inhibitor is prepared from 4% magnesium aluminum silicate, 20.8% densified silica fume, 2% modified starch ether, 4% aluminum sulfate slag powder, 51% limestone powder, 10% fly ash microbeads, 1% powdered polycarboxylic acid water reducer, 2% vinyl acetate and ethylene copolymer rubber powder, 5% calcium sulfate whiskers and 0.2% carboxylated cellulose nanofibers.

[0013] The present invention also provides a method for preparing the rebound inhibitor for shotcrete, comprising the following steps:

[0014] (1) Weighing magnesium aluminum silicate, silica fume, polymer thickener, aluminum sulfate slag powder, ultrafine stone powder, fly ash microbeads, water reducer, redispersible emulsion powder, inorganic mineral fiber and modified plant fiber according to mass percentage;

[0015] (2) The components of step (1) are mixed to obtain a rebound inhibitor for shotcrete.

[0016] The present invention also provides an application of the rebound inhibitor for shotcrete in reducing the rebound rate of shotcrete. The mass ratio of the rebound inhibitor in the shotcrete is 4-10%.

[0017] Furthermore, the rebound inhibitor is added in a mass ratio of 6% in the shotcrete.

[0018] Principle of the present invention:

[0019] 1. Magnesium aluminum silicate powder contains a large number of regular flake structure aggregates. In aqueous solution, the cationic charges adsorbed between the flake structure layers will be dragged to the surface of the chip by electrostatic attraction, and water will penetrate between the flake layers to cause swelling, resulting in the depolymerization of the flake structure. The depolymerized flake structures will overlap with each other to form a three-dimensional network structure, which will bind a large number of water molecules and reduce the fluidity of the system, thereby showing a thickening effect. At the same time, the hydroxyl (-OH) in the molecular structure of magnesium aluminum silicate can form hydrogen bonds with water molecules. A large number of hydrogen bonds are connected to each other, which enhances the intermolecular force, so that the water molecules are firmly "locked" in the network structure of magnesium aluminum silicate, further restricting the free movement of water molecules and increasing the viscosity of the system.

[0020] 2. The microstructures of the components of the rebound inhibitor of the present invention include several types: ① granular materials, such as stone powder and silica fume; ② flakes, such as magnesium aluminum silicate; ③ rods, such as silica fume powder. Granular materials have a filling effect, which can improve the compactness of shotcrete, thereby improving strength and anti-permeability; flakes have a water-retaining and thickening effect, which can improve the adhesion of concrete to the rock wall and reduce the falling of small pieces; rods have a linking and toughening effect, which can allow concrete to form a large whole through a network structure, thereby further improving the integrity and adhesion and preventing large pieces from falling. The mixing of these different structural materials can enhance the performance of the rebound inhibitor of the present invention and reduce the rebound rate of shotcrete.

[0021] Beneficial effects of the present invention:

[0022] 1. The present invention introduces magnesium aluminum silicate and methyl cellulose polymer materials in the component design. Magnesium aluminum silicate forms a network structure after dissolving in water, which can increase the viscosity of the material. Methyl cellulose is an organic thickener that can increase the viscosity of the material. The introduction of the two can improve the cohesiveness of the shotcrete and improve the thixotropy of the concrete mixture, so that the slurry and the bone will not separate during the spraying process. The slurry can be sprayed to the rock wall for a short time by relying on the viscosity of the slurry, providing sufficient time for the concrete to solidify, thereby greatly suppressing the dust generated by the slurry spraying during the spraying process and improving the bonding strength between the concrete and the rock wall.

[0023] 2. The present invention introduces industrial solid waste aluminum sulfate slag, fully utilizes the ultrafine SiO2 particles in the aluminum sulfate slag as a filling material to improve strength, and the residual aluminum sulfate component promotes the reaction speed of cement and accelerator, promotes cement hydration, shortens the setting time, and improves early strength, thereby solving the problems of low solubility, limited effective ingredient content, and unstable accelerator effect of aluminum sulfate, the main accelerating component of alkali-free accelerator. At the same time, the use of industrial solid waste aluminum sulfate slag avoids the use of industrial-grade aluminum sulfate slag and reduces costs.

[0024] 3. The present invention adopts a mixed method of inorganic mineral fiber and modified plant fiber to improve the rebound shedding and deformation cracking of shotcrete. The structure of the modified plant fiber is linear, and the inorganic mineral fiber is generally needle-shaped, with an aspect ratio of 5 to 20. The needle-shaped inorganic-organic fiber plays a role similar to that of a micro-steel mesh in shotcrete, which can effectively connect the shotcrete into a whole, reduce the separation and scattering of sand and gravel aggregate particles in the shotcrete, and thus reduce the amount of rebound. At the same time, the microfibers overlap each other into a mesh, which can improve the toughness and crack resistance of the shotcrete, and to a certain extent inhibit the stress concentration cracking caused by concrete shrinkage or slight deformation of the rock wall. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand.

[0026] The specific properties of the materials involved in Examples 1 to 5 are as follows:

[0027] Magnesium aluminum silicate: easy-to-disperse flowing powder, magnesium aluminum silicate content ≥80%, water content ≤8%, specific surface area ≥250cm 2 / g, 45μm sieve pass rate ≥85%, 5% water suspension apparent viscosity ≥500mpa.s;

[0028] Silica ash: An ultra-fine silicon powder material formed by the rapid oxidation and condensation of SiO2 and Si gas produced during the smelting of ferrosilicon alloy and industrial silicon with oxygen in the air;

[0029] Semi-densified silica fume: SiO2 content ≥90%, water requirement ratio ≤110%, specific surface area ≥20000m 2 / kg, 28d activity index ≥90%;

[0030] Aluminum sulfate slag powder: Al2O3 content ≥15%, specific surface area ≥200m 2 / kg;

[0031] Ultrafine stone powder: 45μm sieve residue ≤30%, moisture content ≤1%, MB value ≤1.4, 28d activity index ≥60%;

[0032] Wollastonite powder: SiO2 content ≥50%, aspect ratio ≥15:1, loss on ignition ≤3.0%;

[0033] Calcium sulfate whiskers: CaSO4 content ≥ 95%, average diameter 1-8μm, average length 30-200μm, average aspect ratio 10-100;

[0034] Sepiolite powder: fineness between 100-500 mesh, water absorption ≤180%;

[0035] Example 1

[0036] This embodiment provides a rebound inhibitor for shotcrete and a preparation method thereof, which is prepared by physically homogenizing and mixing the following components in percentage by mass:

[0037] 2% magnesium aluminum silicate, 19.99% original silica fume, 1% hydroxymethyl cellulose ether, 5% aluminum sulfate slag powder, 50% tailings powder, 16% fly ash microbeads, 1% powdered polycarboxylic acid water reducer, 2% vinyl acetate and ethylene copolymer rubber powder (Vac / E), 3% wollastonite powder, and 0.01% carboxylated cellulose nanofiber (CNF-C).

[0038] The rebound inhibitor for shotcrete is prepared by mixing according to the above ratio. The rebound inhibitor is a fine powder mixture with good homogeneity. The mass ratio of the rebound inhibitor in concrete is 5%.

[0039] Example 2

[0040] This embodiment provides a rebound inhibitor for shotcrete and a preparation method thereof, which is prepared by physically homogenizing and mixing the following components in percentage by mass:

[0041] Magnesium aluminum silicate 4%, densified silica fume 20.8%, modified starch ether 2%, aluminum sulfate slag powder 4%, limestone powder 51%, fly ash microspheres 10%, powdered polycarboxylic acid water reducer 1%, vinyl acetate and ethylene copolymer rubber powder (Vac / E) 2%, calcium sulfate whisker 5%, carboxylated cellulose nanofiber (CNF-C) 0.2%.

[0042] The rebound inhibitor for shotcrete is prepared by mixing according to the above ratio. The rebound inhibitor is a fine powder mixture with good homogeneity. The mass ratio of the rebound inhibitor in concrete is 6%.

[0043] Example 3

[0044] This embodiment provides a rebound inhibitor for shotcrete and a preparation method thereof, which is prepared by physically homogenizing and mixing the following components in percentage by mass:

[0045] 5% magnesium aluminum silicate, 29.8% original silica fume, 3% 5 million molecular weight polyacrylamide, 5% aluminum sulfate slag powder, 38% limestone powder, 9% fly ash microbeads, 2% naphthalene water reducer, 3% vinyl acetate and ethylene and higher fatty acid vinyl ester ternary copolymer rubber powder (Vac / E / VeoVa), 2% wollastonite fiber, 3% sepiolite powder, and 0.2% carboxylated cellulose nanowhiskers (C-CNC).

[0046] The rebound inhibitor for shotcrete is prepared by mixing according to the above ratio. The rebound inhibitor is a fine powder mixture with good homogeneity. The mass ratio of the rebound inhibitor in concrete is 8%.

[0047] Example 4

[0048] This embodiment provides a rebound inhibitor for shotcrete and a preparation method thereof, which is prepared by physically homogenizing and mixing the following components in percentage by mass:

[0049] Aluminum magnesium silicate 5%, semi-densified silica fume 20.8%, methyl cellulose 2%, aluminum sulfate slag powder 2%, machine-made aggregate dust collection powder 51%, fly ash microbeads 9%, naphthalene-based water reducer 2%, ethylene, vinyl chloride and vinyl silicate ternary copolymer rubber powder (E / Vc / VL) 2%, calcium sulfate whisker 6%, carboxylated cellulose nanofiber (CNF-C) 0.2%.

[0050] The rebound inhibitor for shotcrete is prepared by mixing according to the above ratio. The rebound inhibitor is a fine powder mixture with good homogeneity. The mass ratio of the rebound inhibitor in concrete is 10%.

[0051] Example 5

[0052] This embodiment provides a rebound inhibitor for shotcrete and a preparation method thereof, which is prepared by physically homogenizing and mixing the following components in percentage by mass:

[0053] Aluminum magnesium silicate 4%, semi-densified silica fume 19.8%, 12 million molecular weight polyacrylamide 4%, aluminum sulfate slag powder 3%, machine-made aggregate dust collection powder 48%, fly ash microbeads 12%, naphthalene water reducer 2%, ethylene, vinyl chloride and vinyl silicate ternary copolymer rubber powder (E / Vc / VL) 2%, calcium sulfate whisker 5%, carboxylated cellulose nano whisker (CNF-C) 0.2%.

[0054] The rebound inhibitor for shotcrete is prepared by mixing according to the above ratio. The rebound inhibitor is a fine powder mixture with good homogeneity. The mass ratio of the rebound inhibitor in concrete is 4%.

[0055] Example 6

[0056] This embodiment provides a rebound inhibitor for shotcrete and a preparation method thereof, which is prepared by physically homogenizing and mixing the following components in percentage by mass:

[0057] 3% magnesium aluminum silicate, 25% densified silica fume, 3% 10 million molecular weight polyacrylamide, 3% aluminum sulfate slag powder, 43.8% limestone powder, 14% fly ash microbeads, 1.5% powdered polycarboxylic acid water reducer, 2.5% ethylene, vinyl chloride and vinyl silicate ternary copolymer rubber powder (E / Vc / VL), 4% wollastonite powder, 0.2% carboxylated cellulose nanowhiskers (CNF-C).

[0058] The rebound inhibitor for shotcrete is prepared by mixing according to the above ratio. The rebound inhibitor is a fine powder mixture with good homogeneity. The mass ratio of the rebound inhibitor in concrete is 4%.

[0059] Example 7

[0060] The rebound inhibitor for shotcrete prepared in Examples 1 to 3 of the present invention was applied to machine-made sand shotcrete, and the comparative example was a blank control group. The prepared concrete was tested for working performance and mechanical properties, respectively, and the test methods were based on GB / T 50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures" and GB / T50081-2019 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete". Rebound rate, 1d strength, and 28d strength were used for evaluation.

[0061] The cement described in the embodiments of the present invention is P.O42.5 cement; the fly ash is first-grade fly ash with a water demand ratio of 95%; the gravel is 5-10 mm continuously graded granite crushed stone; the water reducer is CP-J polycarboxylic acid high-performance water reducer; the fineness modulus of the machine-made sand is 2.8, the stone powder content is 8.2%, the MB value is 1.2, and the water demand ratio is 118%; the accelerator is an alkali-free accelerator with a solid content of 52.1%, an initial setting time of the net paste of 3.6 min, and a final setting time of the net paste of 6.8 min. The mass ratio of the rebound inhibitor for shotcrete in the concrete is 6%.

[0062] The strength grade of shotcrete is C30 and the mix ratio is shown in Table 1.

[0063] Table 1 Shotcrete mix ratio

[0064]

[0065] The wet spraying test data was obtained through actual production. The weight of the rebounded concrete was collected by colored strips of cloth. The concrete cut test pieces were collected by spraying concrete molds to test the compressive strength. The relevant performance results are shown in Table 2.

[0066] Table 2 Related performance results

[0067]

[0068]

[0069] It can be seen from the experimental data that the rebound inhibitor of the present invention has a good effect on reducing the rebound rate of concrete, can improve the fluidity of concrete, and at the same time improve the viscosity of concrete, and improve the workability of concrete, reduce the loss of shotcrete, and improve the 1d and 28d strength of concrete. Among them, the rebound inhibitor of Example 2 has the best effect on reducing the rebound rate of concrete.

[0070] Although the above embodiments have been described in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A rebound inhibitor for shotcrete, characterized in that: The rebound inhibitor is prepared by 2-5% magnesium aluminum silicate, 19.8-29.8% silica fume, 1-4% polymer viscosity enhancer, 2-5% aluminum sulfate slag powder, 38-51% ultrafine stone powder, 9-16% fly ash microbeads, 1-2% water reducer, 2-3% redispersible emulsion powder, 2-5% inorganic mineral fiber and 0.01-0.2% modified plant fiber in percentage by mass.

2. The rebound inhibitor according to claim 1, characterized in that: The rebound inhibitor is prepared from 4-5% magnesium aluminum silicate, 20.8-29.8% silica fume, 2-3% polymer viscosity enhancer, 4-5% aluminum sulfate slag powder, 38-51% ultrafine stone powder, 9-10% fly ash microbeads, 1-2% water reducer, 2-3% redispersible emulsion powder, 2-5% inorganic mineral fiber and 0.2% modified plant fiber.

3. The rebound inhibitor according to claim 2, characterized in that: The water reducer is any one of a powdered polycarboxylic acid water reducer and a naphthalene water reducer; the silica fume is any one of original silica fume, semi-densified silica fume and densified silica fume; the polymer viscosity enhancer is any one of methyl cellulose, hydroxymethyl cellulose ether, modified starch ether and polyacrylamide.

4. The rebound inhibitor according to claim 3, characterized in that: The polyacrylamide is an anionic polyacrylamide with a molecular weight of 5 to 12 million.

5. The rebound inhibitor according to claim 2, characterized in that: The ultrafine stone powder is any one of tailings powder, limestone powder and machine-made aggregate dust powder; the redispersible latex powder is any one of vinyl acetate and ethylene copolymer powder, ethylene, vinyl chloride and vinyl silicate ternary copolymer powder, and vinyl acetate, ethylene and higher fatty acid vinyl ester ternary copolymer powder.

6. The rebound inhibitor according to claim 2, characterized in that: The inorganic mineral fiber is at least one of wollastonite powder, wollastonite fiber, calcium sulfate whisker and sepiolite powder; the modified plant fiber is any one of carboxylated cellulose nanofiber and carboxylated cellulose nanowhisker.

7. The rebound inhibitor according to any one of claims 2 to 6, characterized in that: The rebound inhibitor is prepared from 4% magnesium aluminum silicate, 20.8% densified silica fume, 2% modified starch ether, 4% aluminum sulfate slag powder, 51% limestone powder, 10% fly ash microbeads, 1% powdered polycarboxylic acid water reducer, 2% vinyl acetate and ethylene copolymer rubber powder, 5% calcium sulfate whiskers and 0.2% carboxylated cellulose nanofibers.

8. A method for preparing a rebound inhibitor for shotcrete according to claim 1, characterized in that: The following steps are involved: (1) Weighing magnesium aluminum silicate, silica fume, polymer thickener, aluminum sulfate slag powder, ultrafine stone powder, fly ash microbeads, water reducer, redispersible emulsion powder, inorganic mineral fiber and modified plant fiber according to mass percentage; (2) The components of step (1) are mixed to obtain a rebound inhibitor for shotcrete.

9. Use of the rebound inhibitor for shotcrete as claimed in claim 1 in reducing the rebound rate of shotcrete, characterized in that: The mass ratio of the rebound inhibitor in the shotcrete is 4-10%.

10. The use according to claim 9, characterized in that: The mass ratio of the rebound inhibitor in the shotcrete is 6%.

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