A high-strength, low-rebound shotcrete and a method for producing the same

Abstract

The present application relates to the technical field of concrete preparation, in particular to a kind of high-strength, low rebound rate's shotcrete and its preparation method.The present application prepares shotcrete by composite modified fiber, modified montmorillonite, so that the prepared concrete has high crack resistance, high durability performance, the present application also simultaneously utilizes the characteristics of small particle size, large specific surface area of liquid SiO2, not only directly reduces the rebound rate of shotcrete, when it is evenly dispersed to the crosslinking network system of composite modified fiber and modified montmorillonite, but also can enhance the chemical bonding ability of modified montmorillonite and composite modified fiber, further reduce the rebound rate of shotcrete, improve its crack resistance and durability, so as to better limit the deformation of tunnel structure, improve the service life of tunnel lining under complex environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete preparation, in particular to a high-strength and low-rebound-rate shotcrete and a preparation method thereof. BACKGROUND

[0002] Shotcrete is widely used in the railway, highway, water conservancy, mining and other industries. Shotcrete is a kind of concrete that is formed into a permanent lining instantly by high-speed spraying of high-slump concrete onto the sprayed surface under the action of air pressure. High-performance shotcrete needs to have good pumpability and sprayability, high strength and excellent durability at the same time. Good sprayability is the key to reducing the rebound rate of concrete and increasing the one-time spraying thickness, while high strength and durability are the protection of the surrounding rock deformation of complex environment tunnels and the improvement of the service life of the tunnel lining. Shotcrete is composed of cement, mineral admixtures, additives, water and other components, and has special requirements for water-cement ratio, cementitious material dosage, sand ratio and other factors. Therefore, the selection of shotcrete composition, ratio and preparation method is very important.

[0003] The shotcrete disclosed in patent document CN 117886575 mainly improves its strength and reduces its rebound rate by adding modified additives and functional agents. The shotcrete preparation method disclosed in patent document CN 118084437 improves the dispersion effect of steel fibers and reduces its rebound rate by modifying the accelerator. However, the shotcrete preparation method in the prior art has the following defects: on the one hand, only the high strength of shotcrete is considered, but the rebound rate is not considered; on the other hand, the low rebound rate of shotcrete is considered, but the durability is not considered.

[0004] Therefore, it is an urgent problem to be solved to seek a new shotcrete preparation method to solve the above-mentioned defects. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a high-strength and low-rebound-rate shotcrete and a preparation method thereof. The present application prepares shotcrete by using composite modified fibers and modified montmorillonite, so that the prepared concrete has high crack resistance and high durability. The present application also utilizes the characteristics of liquid SiO2, such as small particle size and large specific surface area, to not only directly reduce the rebound rate of shotcrete, but also enhance the chemical bonding ability of modified montmorillonite and composite modified fibers when it is uniformly dispersed in the crosslinking network system of composite modified fibers and modified montmorillonite, thereby further reducing the rebound rate of shotcrete, improving its crack resistance and durability, and thus better limiting the deformation of tunnel structure and improving the service life of tunnel lining in complex environment.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] A high-strength and low-rebound-rate shotcrete, comprising the following components in parts by mass: ordinary Portland cement 420-450 parts, liquid nano-SiO2 10-60 parts, fine aggregate 850-950 parts, coarse aggregate 700-800 parts, composite modified fiber 30-80 parts, modified montmorillonite 100-200 parts, coupling agent 5-10 parts, crosslinking agent 5-8 parts, water reducing agent 10-30 parts, cellulose 3-5 parts, and water 170-190 parts.

[0008] Preferably, the modified montmorillonite is prepared by the following steps:

[0009] S11. Acidolysis: immerse 250-300 parts of montmorillonite in a concentrated hydrochloric acid solution with a concentration of 0.5-2 mol / L for 1-2 h;

[0010] S12. Cation intercalation: immerse the montmorillonite treated in step S11 in a FeCl3 solution with a concentration of 3-4 mol / L, stand for 1-2 h, and then take it out, calcine at 1000-1200℃ for 3-4 h to obtain the modified montmorillonite.

[0011] Preferably, the composite modified fiber is a mixture of basalt fiber, PE fiber and glass fiber with a mass ratio of 2-3:0.5-1:1-2.

[0012] Preferably, the composite modified fiber is prepared by the following steps:

[0013] S21. Mix basalt fiber, PE fiber and glass fiber into a fiber bundle according to a set ratio;

[0014] S22. Immerse 40-90 parts of the fiber bundle in an aqueous ammonia solution with a concentration of 1-3 mol / L according to parts by mass, stand for 0.5-2 h at 40-50℃, take it out, and dry;

[0015] S23. Immerse 40-90 parts of the fiber bundle treated in step S22 in 100-150 parts of bisphenol A type epoxy resin for 1-2 h, take it out, and obtain the composite modified fiber.

[0016] Preferably, the strength grade of the ordinary Portland cement is ≥42.5 grade; and the liquid nano-SiO2 is spherical particles with a particle size of 50-200 nm.

[0017] Preferably, the coupling agent is a mixture of gamma-methacryloxypropyltrimethoxysilane, 3-epoxypropyltriethoxysilane, and isopropyl tri(dilauryl) titanate in a mass ratio of 3-4:1-3:1; the crosslinking agent is a mixture of hexamethylene diisocyanate and diethylenetriamine in a mass ratio of 2:1.

[0018] Preferably, the basalt fiber has a diameter of 100-400 mu m, an elastic modulus of 8000-10000 MPa, and a tensile strength of 3500-4500 MPa; the glass fiber has a diameter of 200-300 mu m, an elastic modulus of 70-85 GPa, and a tensile strength of 2000-3000 MPa; and the PE fiber has a diameter of 100-400 mu m, an elastic modulus of 20-30 GPa, and a tensile strength of 3000-4000 MPa.

[0019] Preferably, the fine aggregate is artificial sand, and the fineness modulus is 2.5-2.8; and the coarse aggregate is natural pumice, and the particle size is 5-10 mm.

[0020] Preferably, the cellulose is one of carboxymethyl cellulose and hydroxypropyl cellulose; and the viscosity of the cellulose is 50-100 million.

[0021] A preparation method of high-strength and low-rebound-rate sprayed concrete, for preparing the sprayed concrete, comprising the following steps:

[0022] S1. The composite modified fiber, modified montmorillonite, coupling agent, and crosslinking agent are weighed according to the set proportion relationship, and are poured into a mixer for mixing for 60-90 s;

[0023] S2. The ordinary portland cement, liquid nano-SiO2, fine aggregate, coarse aggregate, and cellulose are weighed according to the corresponding proportion, are uniformly mixed, and are added into the mixer for stirring for 1-2 min;

[0024] S3. The water reducing agent and water are weighed according to the corresponding proportion, are uniformly mixed, and are added into the mixer for uniform stirring, so as to prepare the high-strength and low-rebound-rate sprayed concrete.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] 1. The present application utilizes the composite modified fiber to improve the bonding strength of the sprayed concrete, so as to reduce the rebound rate of the sprayed concrete.

[0027] 2.The application increases the interlayer spacing and porosity of montmorillonite by cation intercalation modification, and improves the adsorption capacity of montmorillonite, so that when the modified montmorillonite is applied to concrete, it can effectively fill the pore structure of the concrete, thereby improving the durability of the concrete; in addition, after calcination, the interlayer structure of the modified montmorillonite is partially released, and active MgO is released, which continuously absorbs water in the later use process and is converted into Mg(OH)2 to fill in the concrete system, thereby further improving the compactness of the concrete.

[0028] 3.The application improves the tensile strength of the whole fiber bundle by compounding the composite fiber bundle, so that the dispersibility of the composite fiber in the concrete is improved, and the modified fiber bundle and the montmorillonite can further improve the compactness of the shotcrete by forming a crosslinked network system, thereby greatly improving the durability of the shotcrete.

[0029] 4.The application utilizes the characteristics of liquid SiO2, such as small particle size and large specific surface area, to directly increase the instantaneous adhesion of shotcrete, and when it is uniformly dispersed in the crosslinked network system of the composite modified fiber and the modified montmorillonite, it can also enhance the chemical bonding ability of the modified montmorillonite and the composite modified fiber, thereby further reducing the rebound rate of the shotcrete, improving its crack resistance and durability, and better limiting the deformation of the tunnel structure, thereby improving the service life of the tunnel lining in complex environments. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Preparation process flow chart of the high-strength, low-rebound shotcrete according to the application;

[0031] Figure 2 Preparation process flow chart of the modified montmorillonite according to the application;

[0032] Figure 3 Preparation process flow chart of the composite modified fiber according to the application. DETAILED DESCRIPTION

[0033] The application will be described in detail below with reference to the embodiments thereof, and obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0034] Please refer to Figures 1-3 The application provides a technical solution:

[0035] Embodiment 1

[0036] A preparation method of high-strength, low-rebound shotcrete:

[0037] S1. Take the composite modified fiber, modified montmorillonite, coupling agent, and crosslinking agent in a set proportion, respectively, and pour them into a blender for mixing for 60s;

[0038] S2. Take the ordinary Portland cement, liquid nano-SiO2, fine aggregate, coarse aggregate, and cellulose in a corresponding proportion, uniformly mix them, and then add them to the blender for stirring for 1min;

[0039] S3. Take the water reducing agent and water in a corresponding proportion, uniformly mix them, and then add them to the blender for stirring until uniform, thereby obtaining the high-strength and low-rebound-rate shotcrete.

[0040] In the above process, the dosages of the raw materials are as follows:

[0041] Component Amount (kg) Composite modified fiber 3 Modified montmorillonite 10 Coupling agent 0.5 Crosslinking agent 0.5 Ordinary Portland cement 42 Liquid nano-SiO2 1 Fine aggregate (artificial sand) 85 Coarse aggregate (natural pumice) 70 Cellulose (carboxymethyl cellulose) 3 Water reducing agent (polycarboxylic acid water reducing agent) 10 Water 170

[0042] In the above process, the strength grade of the ordinary Portland cement is ≥42.5 grade;

[0043] The liquid nano-SiO2 is spherical particles with a particle size ranging from 50nm to 200nm;

[0044] The coupling agent is a mixture of γ-methacryloxypropyltrimethoxysilane, 3-epoxypropyltriethoxysilane, and isopropyl tris(dilauryl) titanate in a mass ratio of 3:1:1;

[0045] The crosslinking agent is a mixture of hexamethylene diisocyanate and diethylenetriamine in a mass ratio of 2:1;

[0046] The fine aggregate is artificial sand with a fineness modulus of 2.5;

[0047] The coarse aggregate is natural pumice with a particle size of 5-10mm;

[0048] The viscosity of the cellulose is 50,000;

[0049] The composite modified fiber is a mixture of basalt fiber, PE fiber, and glass fiber in a mass ratio of 2:0.5:1;

[0050] The diameter of the basalt fiber is 100μm, the elastic modulus is 8000MPa, and the tensile strength is 3500MPa;

[0051] The diameter of the glass fiber is 200μm, the elastic modulus is 70GPa, and the tensile strength is 2000MPa; the diameter of the PE fiber is 100μm, the elastic modulus is 20GPa, and the tensile strength is 3000MPa;

[0052] The composite modified fiber is prepared by the following steps:

[0053] S21. Mix basalt fiber, PE fiber, glass fiber into a fiber bundle in a ratio of 2:0.5:1;

[0054] S22. Dip 4 kg of the fiber bundle into an ammonia solution with a concentration of 3 mol / L, and take it out after standing at 40°C for 0.5 h, and dry it;

[0055] S23. Dip 4 kg of the fiber bundle treated in step S22 into 10 kg of bisphenol A type epoxy resin for 1 h, and take it out to prepare the composite modified fiber;

[0056] The bisphenol A type epoxy resin has a brand of E-12 (604) and is purchased from Hubei Shixing Chemical Co., Ltd.;

[0057] The modified montmorillonite is prepared by the following steps:

[0058] S11. Acidolysis: dip 25 kg of montmorillonite into a concentrated hydrochloric acid solution with a concentration of 2 mol / L for 1 h;

[0059] S12. Cationic intercalation: dip the montmorillonite treated in step S11 into a FeCl3 solution with a concentration of 3 mol / L, stand for 2 h, take it out, and calcine it at 1000°C for 4 h to obtain the modified montmorillonite.

[0060] Example 2: Example 2 differs from Example 1 in that, in Example 2, the composite modified fiber is a mixture of basalt fiber, PE fiber, and glass fiber in a mass ratio of 3:0.5:2, and the remaining steps are completely the same in Example 2 and Example 1.

[0061] Example 3: Example 3 differs from Example 1 in that, in Example 3, the composite modified fiber is prepared by the following steps:

[0062] S21. Mix basalt fiber, PE fiber, glass fiber into a fiber bundle in a ratio of 2:0.5:1;

[0063] S22. Dip 4 kg of the fiber bundle into an ammonia solution with a concentration of 1 mol / L, and take it out after standing at 40°C for 2 h, and dry it;

[0064] S23. Dip 4 kg of the fiber bundle treated in step S22 into 10 kg of bisphenol A type epoxy resin for 1.5 h, and take it out to prepare the composite modified fiber;

[0065] The remaining steps are completely the same in Example 3 and Example 1.

[0066] Example 4: Example 4 differs from Example 1 in that, in Example 4, the modified montmorillonite is prepared by the following steps:

[0067] S11. Acidolysis: 25 kg of montmorillonite is immersed in a concentrated hydrochloric acid solution having a concentration of 0.5 mol / L for 2 h;

[0068] S12. Cation intercalation: The montmorillonite treated in step S11 is immersed in a FeCl3solution having a concentration of 4 mol / L and left to stand for 1 h, then removed, and calcined at 1200°C for 3 h to obtain a modified montmorillonite;

[0069] The remaining steps are identical in Example 4 and Example 1.

[0070] Example 5: Example 5 differs from Example 1 in that, in Example 5, the amounts of the components are as shown below:

[0071] Component Amount (kg) Composite modified fiber 8 Modified montmorillonite 20 Coupling agent 0.5 Crosslinking agent 0.5 Ordinary Portland cement 42 liquid nano-SiO2 1 Fine aggregate (artificial sand) 85 Coarse aggregate (natural pumice) 70 Cellulose (carboxymethyl cellulose) 3 Water reducing agent (polycarboxylic acid water reducing agent) 10 Water 170

[0072] The remaining steps are identical in Example 5 and Example 1.

[0073] Example 6: Example 6 differs from Example 1 in that, in Example 6, the amounts of the components are as shown below:

[0074]

[0075]

[0076] The remaining steps are identical in Example 6 and Example 1.

[0077] Example 7: Example 7 differs from Example 1 in that, in Example 7, the amounts of the components are as shown below:

[0078] Component Amount (kg) Composite modified fiber 3 Modified montmorillonite 10 Coupling agent 0.5 Crosslinking agent 0.5 Ordinary Portland cement 42 Liquid nano-SiO2 6 Fine aggregate (artificial sand) 85 Coarse aggregate (natural pumice) 70 Cellulose (carboxymethyl cellulose) 3 Water reducing agent (polycarboxylic acid water reducing agent) 10 Water 170

[0079] The remaining steps are identical in Example 7 and Example 1.

[0080] Comparative Example:

[0081] Comparative Example 1: Comparative Example 1 differs from Example 1 in that, in Comparative Example 1, the raw material components for preparing the shotcrete described in Example 1 are partially omitted, and thus the use of the composite modified fiber is omitted, and the remaining steps are identical in Comparative Example 1 and Example 1.

[0082] Comparative Example 2: Comparative Example 2 has the following difference from Example 1, the difference is only that in Comparative Example 2, the raw material components for preparing the sprayed concrete described in Example 1 are partially omitted, thereby omitting the use of modified montmorillonite, and the remaining steps are completely the same in Comparative Example 2 and Example 1.

[0083] Comparative Example 3: Comparative Example 3 has the following difference from Example 1, the difference is only that in Comparative Example 3, the raw material components for preparing the sprayed concrete described in Example 1 are partially omitted, thereby omitting the use of liquid nano-SiO2, and the remaining steps are completely the same in Comparative Example 3 and Example 1.

[0084] Comparative Example 4: Comparative Example 4 has the following difference from Example 1, the difference is only that in Comparative Example 4, the raw material components for preparing the sprayed concrete described in Example 1 are partially omitted, thereby omitting the use of modified montmorillonite, composite modified fiber, and the remaining steps are completely the same in Comparative Example 4 and Example 1.

[0085] Comparative Example 5: Comparative Example 5 has the following difference from Example 1, the difference is only that in Comparative Example 5, the raw material components for preparing the sprayed concrete described in Example 1 are partially omitted, thereby omitting the use of modified montmorillonite, composite modified fiber, and liquid nano-SiO2, and the remaining steps are completely the same in Comparative Example 5 and Example 1.

[0086] According to the experimental requirements of GB 50204-2015, GB / T 50081-2019, GB / T 50082-2009, GB / T 50081-2002, and JGJ / T 23-2011, the compressive strength, bending resistance, one-time spraying thickness, and rebound rate of the sprayed concrete prepared in Examples 1-3 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1:

[0087] Table 1. Concrete performance test data

[0088]

[0089]

[0090] As can be seen from the above, the high-strength and low-rebound-rate shotcrete provided by the application has a compressive strength of all greater than or equal to 72.3 MPa and a maximum of 82.1 MPa, a bending strength of all greater than or equal to 9.2 MPa and a maximum of 11.2 MPa, and no strength reduction phenomenon occurs in long-term use, the performance of which is far superior to that of ordinary concrete, meets the technical requirements of shotcrete, and also meets the high-performance requirements of concrete for tunnel engineering; secondly, the rebound rate is all less than 6%, and the one-time shot thickness is all greater than or equal to 22 cm, which further indicates that the shotcrete prepared by the application is a kind of excellent and stable concrete material with low rebound rate, which can be mass-produced industrially.

[0091] Meanwhile, as shown in Table 1, the significant difference in performance between Example 1 and Comparative Examples 1, 2, 4 and 5 is a powerful proof that the cation intercalation modification of montmorillonite increases the interlayer spacing and porosity of montmorillonite and improves its adsorption capacity, and when it is applied to concrete, it can effectively fill the pore structure of the concrete, thereby improving the durability of the concrete, and through the compounding of the composite fiber bundle, the advantages of different fibers are complementary, thereby improving the tensile strength of the whole fiber bundle, and further improving the dispersity of the composite fiber in the concrete, and the modified fiber bundle and montmorillonite can further improve the compactness of the shotcrete by forming a crosslinked network system, thereby greatly improving the mechanical properties and durability of the shotcrete.

[0092] The significant difference in performance between Example 1 and Comparative Examples 3 and 4 proves that the liquid SiO2 has the characteristics of small particle size and large specific surface area, which not only directly reduces the rebound rate of the shotcrete, but also enhances the chemical bonding ability of the modified montmorillonite and the composite modified fiber by uniformly dispersing in the crosslinked network system of the composite modified fiber and the modified montmorillonite, thereby further reducing the rebound rate of the shotcrete, improving its crack resistance and durability, and thereby better limiting the deformation of the tunnel structure and improving the service life of the tunnel lining in complex environments.

[0093] Although embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the above-described embodiments, and that various changes, modifications, substitutions and alterations can be made thereto without departing from the spirit and scope of the application, which are defined by the appended claims and their equivalents.

Claims

1. A high-strength, low-rebound-rate shotcrete, characterized in that, The composition by weight is as follows: 420-450 parts of ordinary silicate cement, 10-60 parts of liquid nano-SiO2, 850-950 parts of fine aggregate, 700-800 parts of coarse aggregate, 30-80 parts of composite modified fiber, 100-200 parts of modified montmorillonite, 5-10 parts of coupling agent, 5-8 parts of crosslinking agent, 10-30 parts of water-reducing agent, 3-5 parts of cellulose, and 170-190 parts of water.

2. The high-strength, low-rebound shotcrete according to claim 1, characterized in that, The modified montmorillonite is prepared through the following steps: S11. Acid hydrolysis: Immerse 250-300 parts by weight of montmorillonite in a concentrated hydrochloric acid solution with a concentration of 0.5-2 mol / L for 1-2 hours; S12. Cation intercalation: The montmorillonite treated in step S11 is immersed in a FeCl3 solution with a concentration of 3-4 mol / L and left to stand for 1-2 hours. Then it is taken out and calcined at 1000-1200℃ for 3-4 hours to obtain modified montmorillonite.

3. The high-strength, low-rebound shotcrete according to claim 1, characterized in that, The composite modified fiber is a mixture of basalt fiber, PE fiber and glass fiber in a mass ratio of 2-3:0.5-1:1-2.

4. The high-strength, low-rebound shotcrete according to claim 3, characterized in that, The composite modified fiber is prepared by the following steps: S21. Mix basalt fiber, PE fiber and glass fiber into fiber bundles according to a set ratio; S22. Immerse 40-90 parts by weight of the fiber bundle in an ammonia solution with a concentration of 1-3 mol / L, let it stand at 40-50°C for 0.5-2 hours, then remove and dry. S23. Immerse 40-90 parts by weight of the fiber bundle treated in step S22 into 100-150 parts by weight of bisphenol A type epoxy resin for 1-2 hours and then remove it to obtain the composite modified fiber.

5. The high-strength, low-rebound shotcrete according to claim 1, characterized in that, The ordinary silicate cement has a strength grade ≥ 42.5; the liquid nano-SiO2 consists of spherical particles with a particle size of 50-200 nm.

6. The high-strength, low-rebound shotcrete according to claim 1, characterized in that, The coupling agent is a mixture of γ-methacryloyloxypropyltrimethoxysilane, 3-epoxypropyltriethoxysilane, and isopropyltris(dilauryl)titanate in a mass ratio of 3-4:1-3:1; the crosslinking agent is a mixture of hexamethylene diisocyanate and diethylenetriamine in a mass ratio of 2:

1.

7. The high-strength, low-rebound shotcrete according to claim 4, characterized in that, The basalt fibers have a diameter of 100-400 μm, an elastic modulus of 8000-10000 MPa, and a tensile strength of 3500-4500 MPa; the glass fibers have a diameter of 200-300 μm, an elastic modulus of 70-85 GPa, and a tensile strength of 2000-3000 MPa; the PE fibers have a diameter of 100-400 μm, an elastic modulus of 20-30 GPa, and a tensile strength of 3000-4000 MPa.

8. The high-strength, low-rebound shotcrete according to claim 1, characterized in that, The fine aggregate is artificial sand with a fineness modulus of 2.5-2.8; the coarse aggregate is natural pumice with a particle size of 5-10 mm.

9. The high-strength, low-rebound shotcrete according to claim 1, characterized in that, The cellulose is one of carboxymethyl cellulose and hydroxypropyl cellulose; the viscosity of the cellulose is 50,000 to 100,000.

10. A method for preparing high-strength, low-resilience shotcrete, used to prepare the shotcrete according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Weigh out the composite modified fiber, modified montmorillonite, coupling agent, and crosslinking agent according to the set ratio, and pour them into a mixer and mix for 60-90 seconds; S2. Weigh out the appropriate proportions of ordinary silicate cement, liquid nano-SiO2, fine aggregate, coarse aggregate, and cellulose, mix them evenly, and then add them to a mixer and stir for 1-2 minutes. S3. Weigh out the appropriate proportions of water-reducing agent and water, mix them evenly, and then add them to a mixer to stir evenly to obtain the high-strength, low-rebound sprayed concrete.

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