A spraying material and its preparation method

Abstract

This invention belongs to the technical field of shotcrete materials, specifically relating to a shotcrete material and its preparation method. The shotcrete material, by weight, comprises the following raw materials: 45-65 parts cement, 30-50 parts aggregate, 11-15 parts fiber composition, 6-8 parts polymer emulsion, and 8-12 parts admixture. The shotcrete material prepared by this invention has low resilience, high compressive strength and flexural strength, and good impermeability.

Description

Technical Field

[0001] This invention belongs to the field of spraying material technology, specifically relating to a spraying material and its preparation method. Background Technology

[0002] In projects such as rapid slope repair, surrounding rock support, tunnel repair and reinforcement, leak sealing, and road emergency repair, shotcrete materials are often used for efficient construction. Shotcrete materials are usually composed of cement, aggregates, water, admixtures, and fibers. However, as people's standards for construction projects have increased, the adhesion between traditional shotcrete materials and the substrate is poor, and they are prone to falling off, which reduces the stability and durability of the building and requires multiple applications. This makes it difficult to meet the needs of efficient and high-quality construction. To solve this problem, people in this field have developed shotcrete materials or shotcrete admixtures with different components.

[0003] Patent CN102826774A describes a nano-grade sprayed concrete modifier admixture, whose mass composition is: 60-95 parts nano-SiO2; 5-40 parts ultrafine mineral admixture; and 0-10 parts surfactant. The nano-SiO2 is a highly active nanoparticle material with a SiO2 content ≥95%. This invention improves the workability and durability of concrete by adding a large amount of nano-silica. However, the admixture requires a large dosage in concrete, and the cost of nano-silica is relatively high, limiting its widespread application.

[0004] Patent CN105110718B discloses a dry-mixed shotcrete material for underground anchor mesh support with high content of fly ash and coal gangue. It is composed of the following raw materials: 800-1800 parts fly ash, 800-1800 parts coal gangue, 50-200 parts cement, 50-150 parts slag powder, 5-10 parts silica, 30-100 parts microsilica, 5-10 parts naphthalene-based water-reducing agent, and 0.1-0.3 parts polypropylene fiber. This material saves resources, reduces environmental pollution, and lowers production costs. It also reduces the number of underground workers and mixing equipment, lowers labor intensity, and improves safety. It has a low rebound rate and a long storage time. However, the material has insufficient permeability, poor filling effect, and relatively poor compressive strength.

[0005] Therefore, there is an urgent need in the market for a shotcrete material that is widely applicable and has high compressive strength. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a sprayed grout material and its preparation method. The sprayed grout material prepared by the present invention has high compressive strength and flexural strength, good impermeability, low resilience, and wide applicability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a spraying material, comprising, by weight, the following raw materials: 45-65 parts cement, 30-50 parts aggregate, 11-15 parts fiber composition, 6-8 parts polymer emulsion, and 8-12 parts admixture.

[0009] In some embodiments, the fiber composition is modified carbon fiber and polypropylene fiber in a mass ratio of (1.2-1.6):1.

[0010] In some embodiments, the method for preparing the modified carbon fiber includes the following steps:

[0011] A1. Soak carbon fibers in nitric acid for 3-5 hours to obtain pretreated carbon fibers;

[0012] A2. Add the pretreated carbon fiber obtained in step A1, silane coupling agent, N-phenylethyl methacrylamide and sodium ethoxide to anhydrous ethanol, stir at 50-60℃ for 3-4 hours, wash and dry to obtain modified carbon fiber.

[0013] Preferably, the silane coupling agent is aminoethylaminopropyltrimethoxysilane.

[0014] Adding fibers to shotcrete materials can significantly improve their mechanical properties, durability, and workability, thereby enhancing the performance of the shotcrete materials and reducing long-term maintenance costs. This invention selects polypropylene fibers to be added to shotcrete materials, which can effectively inhibit plastic shrinkage cracks and drying shrinkage cracks, and is suitable for early crack prevention. However, polypropylene fibers have a low modulus, which leads to a decrease in the flexural strength of the shotcrete materials. The applicant has improved the flexural performance of shotcrete materials by adding carbon fibers, but it is difficult to disperse carbon fibers directly. The applicant has modified carbon fibers to improve their dispersibility in shotcrete materials, thereby improving the flexural strength of shotcrete materials. The possible reason is that pretreated carbon fibers have higher activity and are more likely to react with silane coupling agents. Then, the silane coupling agent is reacted with N-phenylethyl methylacrylamide to increase a certain amount of amide groups, which can coordinate with metals in cement, making them dispersed evenly and increasing the density of shotcrete materials. At the same time, it can compensate for the problem of reduced compressive strength of shotcrete materials caused by excessive rigid groups such as benzene rings.

[0015] In some embodiments, the mass ratio of the pretreated carbon fiber to N-phenylethyl methacrylamide in step A2 is 1:(0.4-0.8).

[0016] This invention increases the dispersibility of carbon fibers by limiting the ratio of pretreated carbon fibers to N-phenylethyl methacrylamide, while avoiding a decrease in the compressive strength of the sprayed material. In addition, it avoids the problem of increased resilience of the sprayed material due to a decrease in the interfacial bonding force with the polymer emulsion.

[0017] In some embodiments, the method for preparing the polymer emulsion includes the following steps:

[0018] B1. Add 3-pentenoic acid, trifluoropentanol, and concentrated sulfuric acid to dichloromethane and react at 70-80℃ for 5-6 hours. Wash and dry to obtain the compound.

[0019] B2. Add the compound obtained in step B1, styrene, and emulsifier to water, stir for 30-40 minutes, then add the initiator and react at 70-80℃ for 1-2 hours to obtain a polymer emulsion.

[0020] Adding polymer emulsions to sprayed grout materials can effectively improve the ease of construction. This invention not only increases the ease of construction by adding polymer emulsions to sprayed grout materials, but also increases the flexural strength of the sprayed grout materials, reduces the resilience of the sprayed grout materials, reduces slump loss, and saves costs. The possible reason is that after a large number of fluorine atoms in the compound polymerize with styrene, the surface energy of the polymer chain segments is reduced. On the one hand, it is easier to mix with other substances evenly and increase the compressive strength. On the other hand, it can better fill the micro-cracks and capillaries of the cement matrix and improve impermeability. In addition, the addition of benzene rings and alkane segments in the polymer emulsion enhances the interaction with carbon fibers, further enhancing the flexural strength of the sprayed grout materials while reducing resilience.

[0021] In some embodiments, the mass ratio of 3-pentenoic acid to trifluoropentanol in step B1 is 1:(1.4-1.7).

[0022] In some embodiments, the mass ratio of the compound to styrene in step B2 is (0.1-0.4):1.

[0023] This invention adds fluorine atoms to a polymer emulsion by limiting the ratio of 3-pentenoic acid and trifluoropentanol, while limiting the mass ratio of the compound to styrene to enhance the impermeability of the sprayed material and avoid the problem of reduced resilience caused by excessive fluorine atoms.

[0024] In some embodiments, the aggregate is ordinary quartz sand with a particle size of 10-40 mesh.

[0025] Preferably, the aggregate is a composition of ordinary quartz sand with an average particle size of 15 mesh and 35 mesh, and the mass ratio of the two is (2-3):1.

[0026] More preferably, the aggregate is a composition of ordinary quartz sand with an average particle size of 15 mesh and 35 mesh, and the mass ratio of the two is 2.5:1.

[0027] In some embodiments, the additive, by weight, comprises the following raw materials: 0.8-1 parts guar gum, 25-30 parts copolymer, 2-5 parts modifier, 0.2-0.4 parts initiator, and 90-100 parts solvent.

[0028] In some embodiments, the method for preparing the copolymer includes the following steps:

[0029] (1) Add pentaerythritol triacrylate, pyromellitic acid, and hydroquinone to dichloromethane, heat to 70-80℃ and add concentrated sulfuric acid, then continue the reaction for 7-8 hours, wash and dry to obtain the compound;

[0030] (2) Add the compound obtained in step (1), pentaerythritol, allyl glycidyl ether and catalyst into a reaction vessel, heat to 160-200℃, and stir at -0.1Kpa to 1Kpa for 3-4h to obtain the copolymer.

[0031] In some embodiments, the mass ratio of pentaerythritol triacrylate to pyromellitic acid is 1:(0.9-1.3).

[0032] In some embodiments, the mass ratio of the compound in step (2) to pentaerythritol is 1:(0.7-1).

[0033] In some embodiments, the mass ratio of the compound in step (2) to allyl glycidyl ether is 1:(0.05-0.15).

[0034] In some embodiments, the preparation method of the modifier includes the following steps: adding resveratrol oxide, sodium gluconate, isocyanate, trans-1,2,3-propenylic acid and butyltin dilaurate to acetone, reacting at 70-80°C for 1-2 hours, and drying to obtain the modifier.

[0035] Preferably, the isocyanate is isophorone diisocyanate.

[0036] In some embodiments, the mass ratio of oxidized resveratrol to isocyanate is (0.1-0.3):1.

[0037] In some embodiments, the sodium gluconate to isocyanate ratio is (0.7-1.2):1.

[0038] In some embodiments, the mass ratio of trans-1,2,3-propenylic acid to isocyanate is (1-1.5):1.

[0039] In some embodiments, the initiator is azobisisobutyrazoline hydrochloride.

[0040] In some embodiments, the method for preparing the admixture includes the following steps:

[0041] S1. Solution preparation: Add guar gum to half the weight of the solvent, heat to 40-60℃ and stir for 60-90 minutes to obtain guar gum solution;

[0042] Add the modifier and copolymer to the remaining solvent and stir for 30-50 minutes to obtain a mixture;

[0043] S2. Add the mixture obtained in step S1 to the guar gum solution, then add the initiator, react at 65-75℃ for 3-4 hours, dry, and pulverize to obtain the spraying material additive.

[0044] The second aspect of the present invention provides a method for preparing a sprayed grout material, comprising the following steps: stirring cement, aggregate, fiber composition, polymer emulsion and additives at 30-45°C for 1-2 hours to obtain the final product.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. This invention prepares a sprayed grout material by means of cement, aggregate, fiber composition, polymer emulsion and additives, which has high compressive strength, flexural strength and impermeability, and can reduce the resilience of the sprayed grout material.

[0047] 2. This invention uses pretreated carbon fibers to react with a silane coupling agent, and then uses the silane coupling agent to react with N-phenylethyl methacrylamide to modify the carbon fibers, thereby improving the dispersibility of carbon fibers in the sprayed material, solving the problem of flexural strength of the sprayed material, and at the same time making up for the defect that the excessive presence of rigid groups such as benzene rings leads to a decrease in the compressive strength of the sprayed material.

[0048] 3. By adding polymer emulsion to the spraying material, this invention not only increases the convenience of construction, but also makes it easier to mix with other substances evenly. It solves the problems of low compressive strength and large resilience after adding conventional polymer emulsion. At the same time, it can better fill the voids in the cement matrix and improve impermeability. Detailed Implementation

[0049] The present invention will be described below with reference to specific embodiments. It should be noted that the examples and comparative examples below are for illustrative purposes only and are not intended to limit the invention. Other combinations and various modifications within the scope of the invention can be made without departing from its spirit or scope.

[0050] To facilitate implementation of this invention by those skilled in the art, some raw materials and manufacturers of the embodiments and comparative examples are described below:

[0051] The compounds and related reagents used in the following examples and comparative examples are all commercially available. The polypropylene fiber has a diameter of 20 μm and was purchased from Taian Hongfang New Material Co., Ltd.; the carbon fiber has a diameter of 7 μm and was purchased from Yancheng Xiangsheng Carbon Fiber Technology Co., Ltd.; the cement is ordinary 425 type cement; and the commercially available admixture is GH-201 type tunnel construction shotcrete admixture, purchased from Guangxi Nanning Gaohong Herun Building Materials Technology Co., Ltd.

[0052] Preparation Example 1

[0053] The method for preparing the copolymer includes the following steps:

[0054] (1) 10g pentaerythritol triacrylate, 11g pyromellitic acid, and 0.01g hydroquinone were added to 200ml dichloromethane, heated to 75℃, and 5ml 95wt% concentrated sulfuric acid was added. The reaction was continued for 7.5h. The mixture was washed and dried to obtain the compound.

[0055] (2) Add 10g of the compound obtained in step (1), 9g of pentaerythritol, 1g of allyl glycidyl ether and 0.1g of tetrabutyl titanate into a reaction vessel, heat to 180℃, and stir at -0.1Kpa for 3.5h to obtain the copolymer.

[0056] Preparation Example 2

[0057] The preparation method of the modifier includes the following steps: 2g of resveratrol oxide, 10g of sodium gluconate, 10g of isophorone diisocyanate, 13g of trans-1,2,3-propenylic acid and 0.2g of butyltin dilaurate are added to 100ml of acetone, reacted at 75℃ for 1.5h, and dried to obtain the modifier.

[0058] Preparation Example 3

[0059] By weight, the additives contain the following raw materials: 0.9 parts guar gum, 28 parts copolymer, 4 parts modifier, 0.3 parts azobisisobutyrazoline hydrochloride, and 95 parts water.

[0060] The preparation method of the admixture includes the following steps:

[0061] S1. Preparation of solution: Add guar gum to half the weight of water, heat to 50°C and stir for 75 minutes to obtain guar gum solution;

[0062] Add the modifier and copolymer to the remaining water and stir for 40 minutes to obtain a mixture;

[0063] S2. Add the mixture obtained in step S1 to the guar gum solution, then add azobisisobutyrazoline hydrochloride, react at 70℃ for 3.5h, dry, and pulverize to obtain the spraying material additive.

[0064] Preparation Example 4

[0065] The preparation method of modified carbon fiber-1 includes the following steps:

[0066] A1. Soak 10g of carbon fiber in 200ml of 75wt% nitric acid solution for 4h to obtain pretreated carbon fiber;

[0067] A2. Add 5g of the pretreated carbon fiber obtained in step A1, 3g of aminoethylaminopropyltrimethoxysilane, 3g of N-phenylethylmethacrylamide, and 0.1g of sodium ethoxide to 100ml of anhydrous ethanol, stir at 55℃ for 3.5h, wash and dry to obtain modified carbon fiber-1.

[0068] Preparation Example 5

[0069] The preparation method of modified carbon fiber-2 is the same as that in preparation example 4, except that the amount of N-phenylethyl methacrylamide added is 5g.

[0070] Preparation Example 6

[0071] The preparation method of polymer emulsion-1 includes the following steps:

[0072] B1. Add 10g of 3-pentenoic acid, 15g of trifluoropentanol, and 5ml of 80wt% concentrated sulfuric acid to 100ml of dichloromethane, react at 75℃ for 5.5h, wash and dry to obtain the compound;

[0073] B2. Add 2g of the compound obtained in step B1, 10g of styrene and 0.5g of sodium dodecyl sulfonate to 200ml of water, stir for 35min, then add 0.1g of azobisisobutyronitrile and react at 75℃ for 1.5h to obtain polymer emulsion-1.

[0074] Preparation Example 7

[0075] The preparation method of polymer emulsion-2 is the same as that of preparation example 6, except that the amount of trifluoropentanol added is 12g.

[0076] Preparation Example 8

[0077] The preparation method of polymer emulsion-3 is the same as that of preparation example 6, except that the amount of compound added in step B2 is 5g.

[0078] Preparation Example 9

[0079] The preparation method of polymer emulsion-4 includes the following steps:

[0080] Add 2g of 3-pentenoic acid, 10g of styrene and 0.5g of sodium dodecyl sulfonate to 200ml of water, stir for 35min, then add 0.1g of azobisisobutyronitrile and react at 75℃ for 1.5h to obtain polymer emulsion 4.

[0081] Example 1

[0082] A spraying material, by weight, comprises the following raw materials: 55 parts cement, 40 parts aggregate, 14 parts fiber composition, 7 parts polymer emulsion-1, and 10 parts admixture;

[0083] The fiber composition includes modified carbon fiber-1 and polypropylene fiber in a mass ratio of 1.4:1; the aggregate is a composition of ordinary quartz sand with an average particle size of 15 mesh and 35 mesh in a mass ratio of 2.5:1.

[0084] The preparation method of the sprayed grout material in this embodiment includes the following steps: stirring cement, aggregate, fiber composition, polymer emulsion-1 and additives at 40°C for 1.5 hours to obtain the final product.

[0085] Example 2

[0086] A spraying material, by weight, comprises the following raw materials: 45 parts cement, 30 parts aggregate, 11 parts fiber composition, 6 parts polymer emulsion-1, and 8 parts admixture;

[0087] The fiber composition includes modified carbon fiber-1 and polypropylene fiber in a mass ratio of 1.2:1; the aggregate is a composition of ordinary quartz sand with an average particle size of 15 mesh and 35 mesh in a mass ratio of 2.5:1.

[0088] The preparation method of the sprayed grout material in this embodiment includes the following steps: stirring cement, aggregate, fiber composition, polymer emulsion-1 and additives at 30°C for 2 hours to obtain the final product.

[0089] Example 3

[0090] A spraying material, by weight, comprises the following raw materials: 65 parts cement, 50 parts aggregate, 15 parts fiber composition, 8 parts polymer emulsion-1, and 12 parts admixture;

[0091] The fiber composition includes modified carbon fiber-1 and polypropylene fiber in a mass ratio of 1.6:1; the aggregate is a composition of ordinary quartz sand with an average particle size of 15 mesh and 35 mesh in a mass ratio of 2.5:1.

[0092] The preparation method of the sprayed grout material in this embodiment includes the following steps: stirring cement, aggregate, fiber composition, polymer emulsion-1 and additives at 45°C for 1 hour to obtain the final product.

[0093] Example 4

[0094] A spraying material and its preparation method are described. The specific implementation method is the same as in Example 1, except that modified carbon fiber-1 is replaced with modified carbon fiber-2 in equal amounts.

[0095] Example 5

[0096] A spraying material and its preparation method are described. The specific implementation method is the same as in Example 1, except that polymer emulsion-1 is replaced with an equal amount of polymer emulsion-2.

[0097] Example 6

[0098] A spraying material and its preparation method are described. The specific implementation method is the same as that in Example 1, except that polymer emulsion-1 is replaced with an equal amount of polymer emulsion-3.

[0099] Example 7

[0100] A spraying material and its preparation method are described. The specific implementation method is the same as that in Example 1, except that polymer emulsion-1 is replaced with an equal amount of polymer emulsion-4.

[0101] Example 8

[0102] A spraying material and its preparation method are described. The specific implementation method is the same as in Example 1, except that the admixture is replaced with an equal amount of commercially available admixture.

[0103] Comparative Example 1

[0104] A spraying material and its preparation method are described. The specific implementation method is the same as in Example 1, except that modified carbon fiber-1 is replaced with an equal amount of carbon fiber.

[0105] Performance testing

[0106] 1. Compressive strength, flexural strength, and impermeability

[0107] The sprayed materials obtained from each embodiment and comparative example were then added into a cube mold with a side length of 100 mm and compacted using an electric vibration table. After 24 hours, the mold was removed and the samples were cured for 28 days at a temperature of 25°C and a relative humidity of 95% to obtain test blocks.

[0108] Compressive strength and flexural strength were tested in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete";

[0109] The impermeability grade was tested using the stepwise pressure method in GB / T 50082-2009 Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete.

[0110] 2. Rebound rate

[0111] The rebound rate was tested in accordance with JGJ / T 372-2016 "Technical Specification for Application of Shotcrete".

[0112] The experimental results are shown in Table 1.

[0113] Table 1

[0114] Group Compressive strength / MPa Flexural strength / MPa impermeability grade Rebound rate % Example 1 55.8 16.1 >P12 5.6 Example 2 53.2 15.4 >P12 5.8 Example 3 54.4 15.8 >P12 5.9 Example 4 51.1 13.2 >P12 6.8 Example 5 52.4 15.6 P11 5.8 Example 6 47.8 11.5 >P12 7.9 Example 7 44.5 10.9 P10 6.3 Example 8 41.6 10.3 P11 7.6 Comparative Example 1 42.1 9.5 P11 9.3

[0115] A comparison of the experimental data from Examples 1-3 in Table 1 shows that the sprayed material obtained by this invention has good compressive strength, flexural strength, and impermeability, with a low resilience. A comparison of Example 4 with Example 1 shows that changing the ratio of pretreated carbon fiber and N-phenylethyl methacrylamide may lead to an excessive rigid structure and a poorer bonding ability with the polymer emulsion, resulting in a decrease in both compressive and flexural strength of the sprayed material, and an increase in resilience. A comparison of Example 5 with Example 1 shows that changing the ratio of 3-pentenoic acid and trifluoropentanol may lead to a decrease in the purity of the prepared compound, a decrease in the uniformity of mixing with other substances, and a decrease in the impermeability of the sprayed material. A comparison of Example 6 with Example 1... It is known that changing the ratio of the compound to styrene may result in an excess of fluorine atoms, altering the viscosity of the sprayed material and affecting the hydration reaction of cement, leading to increased resilience and decreased compressive and flexural strength. A comparison of Example 7 and Example 1 shows that the absence of trifluoropentanol may result in a higher surface energy of the polymer emulsion, leading to decreased compressive strength, flexural strength, and impermeability of the sprayed material, while increasing resilience. A comparison of Example 8 and Example 1 shows that the performance of the sprayed material using common commercially available admixtures is reduced in all aspects. A comparison of Comparative Example 1 and Example 1 shows that without modification of the carbon fiber, the carbon fiber has poor compatibility and weak bonding in the sprayed material, resulting in reduced performance of all aspects of the sprayed material.

[0116] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A spraying material, characterized in that, By weight, it contains the following raw materials: 45-65 parts cement, 30-50 parts aggregate, 11-15 parts fiber composition, 6-8 parts polymer emulsion, and 8-12 parts admixture. The fiber composition is modified carbon fiber and polypropylene fiber, with a mass ratio of (1.2-1.6):1; The method for preparing the modified carbon fiber includes the following steps: A1. Soak carbon fibers in nitric acid for 3-5 hours to obtain pretreated carbon fibers; A2. Add the pretreated carbon fiber obtained in step A1, silane coupling agent, N-phenylethyl methacrylamide and sodium ethoxide to anhydrous ethanol, stir at 50-60℃ for 3-4 hours, wash and dry to obtain modified carbon fiber. The mass ratio of the pretreated carbon fiber to N-phenylethyl methacrylamide in step A2 is 1:(0.4-0.8).

2. The sprayed material according to claim 1, characterized in that, The method for preparing the polymer emulsion includes the following steps: B1. Add 3-pentenoic acid, trifluoropentanol, and concentrated sulfuric acid to dichloromethane and react at 70-80℃ for 5-6 hours. Wash and dry to obtain the compound. B2. Add the compound obtained in step B1, styrene, and emulsifier to water, stir for 30-40 minutes, then add the initiator and react at 70-80℃ for 1-2 hours to obtain a polymer emulsion.

3. The sprayed material according to claim 2, characterized in that, The mass ratio of 3-pentenoic acid and trifluoropentanol in step B1 is 1:(1.4-1.7).

4. The sprayed material according to claim 2, characterized in that, The mass ratio of the compound to styrene in step B2 is (0.1-0.4):

1.

5. The sprayed material according to claim 1, characterized in that, The aggregate is ordinary quartz sand with a particle size of 10-40 mesh.

6. The shotcrete material according to claim 1, characterized in that, By weight, the additive comprises the following raw materials: 0.8-1 parts guar gum, 25-30 parts copolymer, 2-5 parts modifier, 0.2-0.4 parts initiator, and 90-100 parts solvent.

7. A method for preparing the sprayed material according to any one of claims 1-6, characterized in that, The process includes the following steps: mixing cement, aggregate, fiber composition, polymer emulsion and admixtures at 30-45℃ for 1-2 hours to obtain the final product.