Low-resilience sprayed concrete admixture as well as preparation method and application thereof

Abstract

The invention discloses a low-resilience sprayed concrete admixture as well as a preparation method and application thereof, and relates to the technical field of engineering materials. The admixture is prepared from the following raw materials in parts by weight: 400 to 500 parts of silica fume, 100 to 250 parts of fluffy ash, 200 to 320 parts of pretreated coal gasification furnace slag micro powder, 20 to 30 parts of disodium dihydrogen pyrophosphate, 10 to 15 parts of sodium dihydrogen phosphate, 20 to 30 parts of sodium hexametaphosphate, 5 to 10 parts of rubber powder and 5 to 10 parts of cellulose ether. The preparation method comprises the following steps: weighing the raw materials in parts by weight, adding the raw materials into a concrete mixer, and uniformly stirring for 15-30 minutes; and bagging the uniformly stirred mixture to obtain the low-resilience sprayed concrete admixture. The obtained admixture is applied to sprayed concrete, and the low-resilience sprayed concrete is obtained. The problems that existing coal gasification slag sprayed concrete is low in construction efficiency, and the engineering quality is difficult to meet the requirements are solved.

Description

Technical Field

[0001] The present application relates to the field of engineering material technology, and in particular to a low-rebound shotcrete admixture, a preparation method thereof, and an application thereof. Background Art

[0002] In underground coal mining projects, shotcrete is a commonly used material for supporting coal mine tunnels. By using a pressure spray gun to spray shotcrete composed of cement, sand, gravel, and accelerator onto the top and side of the tunnel, it plays a supporting role for the coal mine tunnels.

[0003] Coal gasification furnace slag is an industrial solid waste produced in the gasifier during the coal-to-oil process. It usually has a fineness modulus of fine sand, high porosity and high water absorption, and has gelling activity after grinding. Due to the gradual implementation of the national dual-carbon strategy, the requirements for high-value utilization of coal are constantly increasing, and the coal-to-oil industry is booming. The gasification furnace slag directly out of the furnace will cause environmental pollution after being piled up. Coal gasification furnace slag contains a large amount of amorphous gelling active substances. These substances can react secondary with cement hydration products in concrete to generate more hydrated calcium silicate gel, which can improve the density and compressive strength of concrete.

[0004] However, coal gasification furnace slag has high water absorption and potential alkali aggregate activity, so it is difficult to directly apply it to shotcrete, which will cause problems such as large water consumption, high rebound rate, poor early strength and segregation of shotcrete. Therefore, it is necessary to study a low-rebound shotcrete admixture and a preparation method for shotcrete with high coal gasification furnace slag content to improve the consumption of coal gasification furnace slag and solve the problems of low construction efficiency of existing coal gasification furnace slag shotcrete and difficulty in meeting engineering quality requirements. Summary of the invention

[0005] In order to overcome the problems of large water consumption, high rebound rate, poor early strength and segregation when directly using coal gasification furnace slag in shotcrete, and to solve the problem that the existing coal gasification furnace slag shotcrete has low construction efficiency and engineering quality that is difficult to meet the requirements, the application provides a low-rebound shotcrete admixture, its preparation method and application.

[0006] The present application provides a low-rebound shotcrete admixture, which adopts the following technical solution:

[0007] A low-rebound shotcrete admixture comprises raw materials by weight including 400-500 parts of silica fume, 100-250 parts of fluff ash, 200-320 parts of pretreated coal gasification furnace slag powder, 20-30 parts of disodium dihydrogen pyrophosphate, 10-15 parts of sodium dihydrogen phosphate, 20-30 parts of sodium hexametaphosphate, 5-10 parts of rubber powder and 5-10 parts of cellulose ether.

[0008] Preferably, the method for preparing the pretreated coal gasification furnace slag powder comprises the following steps:

[0009] S1. The coal gasification slag is crushed, screened, washed and dried, and then fully immersed in a hydrochloric acid solution, then washed to neutrality, and dried to obtain the hydrochloric acid-treated coal gasification slag;

[0010] S2. The treated gasification slag is mixed with an alkaline activator, water is added to mix and stir evenly, and then dried after sufficient stirring at room temperature to obtain a gasification slag impregnated with an alkaline activator, and then placed in a nitrogen atmosphere for microwave activation, and then washed with water to neutrality and dried to obtain the pretreated gasification slag;

[0011] S3. The pre-treated coal gasification furnace slag is first pre-grinded by a roller press, and then further ground in an ultra-fine ball mill to obtain a specific surface area of ​​≥700m 2 / kg pretreated coal gasification slag powder.

[0012] Preferably, the power of the microwave activation is 650-750 W, and the time is 10-15 min.

[0013] Preferably, the cellulose ether is hydroxypropyl methylcellulose with a viscosity of 100,000-200,000 mPa.s.

[0014] Preferably, the rubber powder is prepared from the following raw materials: polyvinyl alcohol, tert-butyl hydroperoxide solution, sodium formaldehyde sulfoxylate, vinyl acetate, ethylene, sodium bicarbonate, and water.

[0015] Preferably, the method for preparing the rubber powder comprises the following steps:

[0016] S1. Add 6-10 parts of 4.8wt% tert-butyl hydroperoxide solution to the initiator tank and stir to dissolve; stir 2-3 parts of polyvinyl alcohol and 80-120 parts of water at room temperature for 15-25min, heat to 80-90°C and stir for 60-70min to dissolve to obtain a polyvinyl alcohol solution;

[0017] S2. Add polyvinyl alcohol solution, 0.2-0.3 parts of sodium formaldehyde sulfoxylate and 10-15 parts of water to the reactor, stir well, add 50-75 parts of vinyl acetate and stir well, add ethylene and heat to 2.5-3MPa, when the temperature rises to 50-60°C, start dripping tert-butyl hydroperoxide solution, and when the temperature reaches 80-85°C, increase the ethylene pressure to 6.0-6.5MPa; then drip 50-75 parts of vinyl acetate, maintain the reaction temperature and ethylene pressure unchanged until the addition of vinyl acetate is completed;

[0018] S3. Cool down to 50 - 60 °C, carry out defoaming, filtration, and cooling, add 0.3 - 0.4 parts of sodium bicarbonate, and discharge the material; after freeze-drying and screening the product, rubber powder is obtained.

[0019] A preparation method of a low-elasticity shotcrete admixture provided by this application adopts the following technical solution:

[0020] A preparation method of a low-elasticity shotcrete admixture includes the following steps:

[0021] Weigh raw materials such as silica fume, potash, pretreated coal gasification slag micropowder, sodium dihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium hexametaphosphate, rubber powder, and cellulose ether according to parts by weight of the raw materials; add the raw materials into a concrete mixer for stirring, and stir evenly for 15 - 30 min; bag the evenly stirred mixture to obtain the low-elasticity shotcrete admixture.

[0022] An application of a low-elasticity shotcrete admixture provided by this application adopts the following technical solution:

[0023] An application of a low-elasticity shotcrete admixture, the application of the admixture in shotcrete; the raw materials of the shotcrete include 350 - 400 parts of cement, 100 - 150 parts of admixture, 800 - 850 parts of sand, 800 - 850 parts of crushed stone, 4 - 10 parts of water reducing agent, 28 - 30 parts of accelerating agent, and 150 - 200 parts of water by weight.

[0024] Preferably, the sand includes 30 - 50% of pretreated coal gasification slag micropowder and 50 - 70% of natural sand.

[0025] Preferably, the preparation method of the shotcrete includes the following steps:

[0026] S1: Weigh each raw material according to parts by weight, and add cement, admixture, crushed stone, and sand into concrete mixing equipment;

[0027] S2: Stir each component to form a mixture;

[0028] S3: After adding water, water reducing agent, and accelerating agent to the mixture, continue to stir to obtain shotcrete.

[0029] In summary, this application includes at least one of the following beneficial technical effects:

[0030] 1. In this application, the coal gasification slag is crushed, screened, washed with water, dried, impregnated in a hydrochloric acid solution, washed with water until neutral, and then mixed with an alkaline activator and subjected to microwave activation treatment. This reduces the hydrophilicity of the surface of the coal gasification slag and weakens its water absorption capacity, thereby reducing the water consumption of concrete. At the same time, the treatment with the alkaline activator can stimulate the latent activity of the coal gasification slag, enabling it to participate in the secondary hydration reaction in concrete and generating more hydration products, thus improving the early strength of concrete. Moreover, the microwave activation treatment can optimize the pore structure of the coal gasification slag, making it more evenly dispersed in concrete and reducing the segregation phenomenon.

[0031] 2. The low-elasticity shotcrete admixture prepared from raw materials such as silica fume, potash, pretreated coal gasification slag fine powder, sodium dihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium hexametaphosphate, rubber powder, and cellulose ether can effectively overcome the problems of large water consumption, high rebound rate, poor early strength, and segregation existing in directly applying coal gasification slag to shotcrete, and solve the problem that the construction efficiency of the existing coal gasification slag shotcrete is low and the engineering quality is difficult to meet the requirements. Among them, silica fume and pretreated coal gasification slag fine powder can improve the compactness and later strength of concrete and prevent alkali-aggregate reaction. The addition of potash and composite phosphates can promote cement hydration and enhance the early strength and crack resistance of concrete. Rubber powder and cellulose ether, as water retention agents and thickeners, can improve the wrapping performance of concrete slurry on aggregates.

[0032] 3. The coal gasification slag is an industrial solid waste, and this application also solves the problem of resource utilization of industrial solid waste, which conforms to the logic of circular economy development. Specific Embodiments

[0033] The following further elaborates on this application in conjunction with embodiments.

[0034] Preparation Example 1 Preparation of Pretreated Coal Gasification Slag Fine Powder

[0035] Preparation Example 1.1

[0036] S1. The coal gasification slag is crushed and screened to 0.1 mm, washed with water and dried, then fully impregnated in a 0.5 mol / L hydrochloric acid solution for 24 h, and then washed with water until neutral and dried to obtain hydrochloric acid-treated coal gasification slag.

[0037] S2. 1 kg of the treated coal gasification slag is mixed with 2 kg of the alkaline activator sodium carbonate, 9.3 kg of water is added, and the mixture is stirred evenly. After stirring at room temperature for 3 h, it is dried to obtain coal gasification slag impregnated with the alkaline activator, which is placed in a nitrogen atmosphere and microwave-activated at a power of 650 W for 10 min, then washed with water until neutral and dried to obtain the pretreated coal gasification slag.

[0038] S3. First, pre-grind the pretreated coal gasification slag through a roller press, and then further grind it in an ultrafine ball mill to obtain coal gasification slag micropowder with a specific surface area ≥ 700 m 2 / kg of pretreated coal gasification slag.

[0039] Preparation Example 1.2

[0040] S1. Crush and screen the coal gasification slag to 0.1 mm, wash it with water and dry it. Then, fully immerse it in a 0.5 mol / L hydrochloric acid solution for 26 h, and then wash it with water until neutral. After drying, hydrochloric acid-treated coal gasification slag is obtained;

[0041] S2. Mix 1.5 kg of the treated coal gasification slag with 3 kg of the alkaline activator sodium carbonate, add 14 kg of water, mix and stir evenly. Stir at room temperature for 3.5 h and then dry to obtain coal gasification slag impregnated with the alkaline activator. Place it in a nitrogen atmosphere and microwave activate it at a power of 700 W for 13 min, then wash it with water until neutral and dry to obtain the pretreated coal gasification slag;

[0042] S3. First, pre-grind the pretreated coal gasification slag through a roller press, and then further grind it in an ultrafine ball mill to obtain coal gasification slag micropowder with a specific surface area ≥ 700 m 2 / kg of pretreated coal gasification slag.

[0043] Preparation Example 1.3

[0044] S1. Crush and screen the coal gasification slag to 0.1 mm, wash it with water and dry it. Then, fully immerse it in a 0.5 mol / L hydrochloric acid solution for 28 h, and then wash it with water until neutral. After drying, hydrochloric acid-treated coal gasification slag is obtained;

[0045] S2. Mix 2 kg of the treated coal gasification slag with 4 kg of the alkaline activator sodium carbonate, add 18.6 kg of water, mix and stir evenly. Stir at room temperature for 4 h and then dry to obtain coal gasification slag impregnated with the alkaline activator. Place it in a nitrogen atmosphere and microwave activate it at a power of 750 W for 15 min, then wash it with water until neutral and dry to obtain the pretreated coal gasification slag;

[0046] S3. First, pre-grind the pretreated coal gasification slag through a roller press, and then further grind it in an ultrafine ball mill to obtain coal gasification slag micropowder with a specific surface area ≥ 700 m 2 / kg of pretreated coal gasification slag.

[0047] Preparation of rubber powder in Preparation Example 2

[0048] Preparation Example 2.1

[0049] S1. Add 6 g of a 4.8 wt% tert-butyl hydroperoxide solution to the initiator tank and stir to dissolve it; stir 2 g of polyvinyl alcohol and 80 g of water at room temperature for 15 min, then raise the temperature to 80 °C and stir for another 60 min to dissolve it, obtaining a polyvinyl alcohol solution;

[0050] S2. Add the polyvinyl alcohol solution, 0.2 g of sodium formaldehyde sulfoxylate, and 10 g of water to the reaction kettle, stir evenly, then add 50 g of vinyl acetate and stir evenly. When ethylene is introduced and the pressure is raised to 2.5 MPa, heat is applied. When the temperature rises to 50 °C, start dropping the tert-butyl hydroperoxide solution. After the temperature reaches 80 °C, raise the ethylene pressure to 6.0 MPa; then drop in another 50 g of vinyl acetate and maintain the reaction temperature and ethylene pressure unchanged until the addition of vinyl acetate is completed;

[0051] S3. Cool down to 50 °C, carry out degassing, filtration, and cooling, add 0.3 g of sodium bicarbonate, and discharge the product; after subjecting the product to freeze-drying and screening, the rubber powder is obtained.

[0052] Preparation Example 2.2

[0053] S1. Add 8 g of a 4.8 wt% tert-butyl hydroperoxide solution to the initiator tank and stir to dissolve it; stir 2.5 g of polyvinyl alcohol and 100 g of water at room temperature for 20 min, then raise the temperature to 85 °C and stir for another 65 min to dissolve it, obtaining a polyvinyl alcohol solution;

[0054] S2. Add the polyvinyl alcohol solution, 0.25 g of sodium formaldehyde sulfoxylate, and 12.5 g of water to the reaction kettle, stir evenly, then add 62 g of vinyl acetate and stir evenly. When ethylene is introduced and the pressure is raised to 2.7 MPa, heat is applied. When the temperature rises to 55 °C, start dropping the tert-butyl hydroperoxide solution. After the temperature reaches 83 °C, raise the ethylene pressure to 6.3 MPa; then drop in another 62 g of vinyl acetate and maintain the reaction temperature and ethylene pressure unchanged until the addition of vinyl acetate is completed;

[0055] S3. Cool down to 55 °C, carry out degassing, filtration, and cooling, add 0.35 g of sodium bicarbonate, and discharge the product; after subjecting the product to freeze-drying and screening, the rubber powder is obtained.

[0056] Preparation Example 2.3

[0057] S1. Add 10 g of a 4.8 wt% tert-butyl hydroperoxide solution to the initiator tank and stir to dissolve it; stir 3 g of polyvinyl alcohol and 120 g of water at room temperature for 25 min, then raise the temperature to 90 °C and stir for another 70 min to dissolve it, obtaining a polyvinyl alcohol solution;

[0058] S2. Add the polyvinyl alcohol solution, 0.3 g of sodium formaldehyde sulfoxylate, and 15 g of water into the reaction kettle. After stirring evenly, add 75 g of vinyl acetate and stir evenly. Heat when the ethylene pressure is increased to 3 MPa. When the temperature rises to 60 °C, start dropping the tert-butyl hydroperoxide solution. After the temperature reaches 85 °C, increase the ethylene pressure to 6.5 MPa; then drop in another 75 g of vinyl acetate, and maintain the reaction temperature and ethylene pressure unchanged until the addition of vinyl acetate is completed.

[0059] S3. Cool down to 60 °C, carry out defoaming, filtration, and cooling, add 0.4 g of sodium bicarbonate, and discharge the product; after freeze-drying and screening the product, the rubber powder is obtained.

[0060] Example 1

[0061] Weigh 400 g of silica fume, 100 g of potash, 200 g of pretreated pulverized coal gasification slag powder obtained from Preparation Example 1.1, 20 g of sodium dihydrogen pyrophosphate, 10 g of sodium dihydrogen phosphate, 20 g of sodium hexametaphosphate, 5 g of rubber powder obtained from Preparation Example 2.1, and 5 g of hydroxypropyl methylcellulose with a viscosity of 100,000 mPa·s according to the parts by weight of the raw materials; add the raw materials into a concrete mixer and stir for 15 min evenly; bag the evenly stirred mixture to obtain the low-elasticity shotcrete admixture.

[0062] Example 2

[0063] Weigh 450 g of silica fume, 170 g of potash, 260 g of pretreated pulverized coal gasification slag powder obtained from Preparation Example 1.1, 25 g of sodium dihydrogen pyrophosphate, 12.5 g of sodium dihydrogen phosphate, 25 g of sodium hexametaphosphate, 7.5 g of rubber powder obtained from Preparation Example 2.1, and 7.5 g of hydroxypropyl methylcellulose with a viscosity of 150,000 mPa·s according to the parts by weight of the raw materials; add the raw materials into a concrete mixer and stir for 23 min evenly; bag the evenly stirred mixture to obtain the low-elasticity shotcrete admixture.

[0064] Example 3

[0065] Weigh 500 g of silica fume, 250 g of potash, 320 g of pretreated pulverized coal gasification slag powder obtained from Preparation Example 1.1, 30 g of sodium dihydrogen pyrophosphate, 15 g of sodium dihydrogen phosphate, 30 g of sodium hexametaphosphate, 10 g of rubber powder obtained from Preparation Example 2.1, and 10 g of hydroxypropyl methylcellulose with a viscosity of 200,000 mPa·s according to the parts by weight of the raw materials; add the raw materials into a concrete mixer and stir for 30 min evenly; bag the evenly stirred mixture to obtain the low-elasticity shotcrete admixture.

[0066] Example 4

[0067] Example 4 is different from Example 1 in that the pretreated pulverized coal gasification slag powder used in Example 4 is from Preparation Example 1.2.

[0068] Example 5

[0069] Example 5 is different from Example 1 in that the pretreated pulverized coal gasification slag powder used in Example 5 is from Preparation Example 1.3.

[0070] Example 6

[0071] Example 6 is different from Example 1 in that the rubber powder used in Example 6 is from Preparation Example 2.2.

[0072] Example 7

[0073] Example 7 is different from Example 1 in that the rubber powder used in Example 7 is from Preparation Example 2.3.

[0074] Comparative Example 1

[0075] Comparative Example 1 is different from Example 1 in that the pulverized coal gasification slag powder in Comparative Example 1 is ordinary pulverized coal gasification slag powder without pretreatment, and the specific surface area is ≥700 m 2 / kg.

[0076] Comparative Example 2

[0077] Comparative Example 2 is different from Example 1 in that the rubber powder used in Comparative Example 2 is ethylene-vinyl acetate.

[0078] Application Example 1

[0079] S1: Weigh each raw material by weight. Add 350 g of P·O42.5 ordinary Portland cement, 100 g of the admixture prepared in Example 1, 800 g of crushed stone and 800 g of sand to the concrete mixing equipment; in this application example, the sand includes 30% of the pretreated pulverized coal gasification slag powder prepared in Preparation Example 1.1 and 70% of natural sand; the particle size of the crushed stone is ≤10 mm and the mud content is ≤3%;

[0080] S2: Stir each component to form a mixture;

[0081] S3: After adding 150 g of water, 4 g of polycarboxylate superplasticizer and 28 g of accelerating agent aluminum sulfate to the mixture, continue to stir to obtain shotcrete.

[0082] Application Example 2

[0083] S1: Weigh each raw material by weight parts. Add 375 g of P·O42.5 ordinary Portland cement, 125 g of admixture prepared in Example 1, 825 g of crushed stone and 825 g of sand into the concrete mixing equipment. In this application example, the sand includes 30% of pretreated pulverized coal gasification slag micro-powder prepared in Preparation Example 1.1 and 70% of natural sand. The particle size of the crushed stone is ≤10 mm and the mud content is ≤3%.

[0084] S2: Stir each component to form a mixture.

[0085] S3: After adding 175 g of water, 7 g of polycarboxylate superplasticizer and 29 g of accelerator aluminum sulfate into the mixture, continue to stir to obtain shotcrete.

[0086] Application Example 3

[0087] S1: Weigh each raw material by weight parts. Add 400 g of P·O42.5 ordinary Portland cement, 150 g of admixture prepared in Example 1, 850 g of crushed stone and 850 g of sand into the concrete mixing equipment. In this application example, the sand includes 30% of pretreated pulverized coal gasification slag micro-powder prepared in Preparation Example 1.1 and 70% of natural sand. The particle size of the crushed stone is ≤10 mm and the mud content is ≤3%.

[0088] S2: Stir each component to form a mixture.

[0089] S3: After adding 200 g of water, 10 g of polycarboxylate superplasticizer and 30 g of accelerator aluminum sulfate into the mixture, continue to stir to obtain shotcrete.

[0090] Application Example 4

[0091] The difference between Application Example 4 and Application Example 1 is that the admixture used in Application Example 4 is prepared in Example 2.

[0092] Application Example 5

[0093] The difference between Application Example 5 and Application Example 1 is that the admixture used in Application Example 5 is prepared in Example 3.

[0094] Application Example 6

[0095] The difference between Application Example 6 and Application Example 1 is that the admixture used in Application Example 6 is prepared in Example 4.

[0096] Application Example 7

[0097] The difference between Application Example 7 and Application Example 1 is that the admixture used in Application Example 7 is prepared in Example 5.

[0098] Application Example 8

[0099] The difference between Application Example 8 and Application Example 1 is that the admixture used in Application Example 8 is prepared from Example 6.

[0100] Application Example 9

[0101] The difference between Application Example 9 and Application Example 1 is that the admixture used in Application Example 9 is prepared from Example 7.

[0102] Application Example 10

[0103] The difference between Application Example 10 and Application Example 1 is that the sand in Application Example 10 includes 40% of the pretreated fine powder of coal gasification furnace slag prepared from Preparation Example 1.1 and 60% of natural sand.

[0104] Application Example 11

[0105] The difference between Application Example 11 and Application Example 1 is that the sand in Application Example 11 includes 50% of the pretreated fine powder of coal gasification furnace slag prepared from Preparation Example 1.1 and 50% of natural sand.

[0106] Application Example 12

[0107] The difference between Application Example 12 and Application Example 1 is that the sand in Application Example 12 includes 20% of the pretreated fine powder of coal gasification furnace slag prepared from Preparation Example 1.1 and 80% of natural sand.

[0108] Application Example 13

[0109] The difference between Application Example 13 and Application Example 1 is that the sand in Application Example 13 includes 60% of the pretreated fine powder of coal gasification furnace slag prepared from Preparation Example 1.1 and 40% of natural sand.

[0110] Comparative Application Example 1

[0111] The difference between Comparative Application Example 1 and Application Example 1 is that the admixture in Comparative Application Example 1 is replaced with the pretreated fine powder of coal gasification furnace slag prepared from Preparation Example 1.1.

[0112] Comparative Application Example 2

[0113] The difference between Comparative Application Example 2 and Application Example 1 is that the admixture in Comparative Application Example 2 is replaced with silica fume.

[0114] Comparative Application Example 3

[0115] The difference between Comparative Application Example 3 and Application Example 1 is that the admixture used in Comparative Application Example 3 is prepared from Comparative Example 1.

[0116] Comparative Application Example 4

[0117] The difference between Comparative Application Example 4 and Application Example 1 is that the admixture used in Comparative Application Example 4 is prepared from Comparative Example 2.

[0118] Performance Detection Test

[0119] I. The setting time of the shotcrete obtained from Application Examples 1 - 13 and Comparative Application Examples 1 - 4 was detected using GB / T 35159 - 2017 "Accelerators for Shotcrete". The results are shown in Table 1.

[0120] II. The compressive strength of the shotcrete obtained from Application Examples 1 - 13 and Comparative Application Examples 1 - 4 was detected using GB / T 50081 - 2019 "Standard Test Methods for Physical and Mechanical Properties of Concrete". The results are shown in Table 1.

[0121] III. The rebound rate of the shotcrete obtained from Application Examples 1 - 13 and Comparative Application Examples 1 - 4 was detected using NB - T 11535 - 2024 "Test Method for Determining the Rebound Rate of Shotcrete". The results are shown in Table 1.

[0122] The specific detection results are as follows:

[0123] Table 1 Performance Detection Results

[0124]

[0125]

[0126] It can be seen from the detection results in Table 1 that a low - rebound shotcrete admixture, its preparation method, and its application in shotcrete provided by this application can obtain shotcrete with a fast setting speed, high compressive strength, and low rebound rate, effectively improving the construction efficiency and engineering quality.

[0127] This specific embodiment is only an explanation of this application and does not limit this application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A low-rebound shotcrete admixture, characterized in that: The raw materials include 400-500 parts of silica fume, 100-250 parts of fluff ash, 200-320 parts of pretreated coal gasification furnace slag powder, 20-30 parts of disodium dihydrogen pyrophosphate, 10-15 parts of sodium dihydrogen phosphate, 20-30 parts of sodium hexametaphosphate, 5-10 parts of rubber powder and 5-10 parts of cellulose ether by weight.

2. The low-rebound shotcrete admixture according to claim 1, characterized in that: The method for preparing the pretreated coal gasification furnace slag powder comprises the following steps: S1. The coal gasification slag is crushed, screened, washed and dried, and then fully immersed in a hydrochloric acid solution, then washed to neutrality, and dried to obtain the hydrochloric acid-treated coal gasification slag; S2. The treated gasification slag is mixed with an alkaline activator, water is added to mix and stir evenly, and then dried after sufficient stirring at room temperature to obtain a gasification slag impregnated with an alkaline activator, and then placed in a nitrogen atmosphere for microwave activation, and then washed with water to neutrality and dried to obtain the pretreated gasification slag; S3. The pre-treated coal gasification furnace slag is first pre-grinded by a roller press, and then further ground in an ultra-fine ball mill to obtain a specific surface area of ​​≥700m 2 / kg pretreated coal gasification slag powder.

3. The low-rebound shotcrete admixture according to claim 2, characterized in that: The power of the microwave activation is 650-750W, and the time is 10-15min.

4. The low-rebound shotcrete admixture according to claim 1, characterized in that: The cellulose ether is hydroxypropyl methylcellulose, and the viscosity is 100000-200000 mPa.s.

5. The low-rebound shotcrete admixture according to claim 1, characterized in that: The rubber powder is prepared from the following raw materials: polyvinyl alcohol, tert-butyl hydroperoxide solution, sodium formaldehyde sulfoxylate, vinyl acetate, ethylene, sodium bicarbonate and water.

6. The low-rebound shotcrete admixture according to claim 5, characterized in that: The preparation method of the rubber powder comprises the following steps: S1. Add 6-10 parts of 4.8wt% tert-butyl hydroperoxide solution to the initiator tank and stir to dissolve; stir 2-3 parts of polyvinyl alcohol and 80-120 parts of water at room temperature for 15-25min, heat to 80-90°C and stir for 60-70min to dissolve to obtain a polyvinyl alcohol solution; S2. Add polyvinyl alcohol solution, 0.2-0.3 parts of sodium formaldehyde sulfoxylate and 10-15 parts of water to the reactor, stir well, add 50-75 parts of vinyl acetate and stir well, add ethylene and heat to 2.5-3MPa, when the temperature rises to 50-60°C, start dripping tert-butyl hydroperoxide solution, and when the temperature reaches 80-85°C, increase the ethylene pressure to 6.0-6.5MPa; then drip 50-75 parts of vinyl acetate, maintain the reaction temperature and ethylene pressure unchanged until the addition of vinyl acetate is completed; S3. Cool down to 50-60°C, degas, filter, cool, add 0.3-0.4 parts of sodium bicarbonate, and discharge; freeze-dry and sieve the product to obtain rubber powder.

7. A method for preparing a low-resilience shotcrete admixture according to any one of claims 1 to 6, characterized in that: The following steps are involved: Weigh the raw materials of silica fume, fluff ash, pre-treated coal gasification furnace slag powder, disodium dihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium hexametaphosphate, rubber powder and cellulose ether according to their weight; add the raw materials into a concrete mixer and stir them evenly for 15-30 minutes; bag the evenly stirred mixture to obtain a low-rebound shotcrete admixture.

8. The use of a low-rebound shotcrete admixture according to any one of claims 1 to 6, characterized in that: The admixture is used in shotcrete; the raw materials of the shotcrete include 350-400 parts of cement, 100-150 parts of admixture, 800-850 parts of sand, 800-850 parts of crushed stone, 4-10 parts of water reducer, 28-30 parts of accelerating setting agent and 150-200 parts of water by weight.

9. The use of a low-rebound shotcrete admixture according to claim 8, characterized in that: The sand comprises 30-50% pre-treated coal gasification furnace slag powder and 50-70% natural sand.

10. The use of a low-rebound shotcrete admixture according to claim 8, characterized in that: The method for preparing shotcrete, The following steps are involved: S1: Weigh the raw materials according to weight, and add cement, admixture, crushed stone and sand into the concrete mixing equipment; S2: stirring the components to form a mixture; S3: After adding water, water reducing agent and accelerating setting agent into the mixture, continue stirring to obtain shotcrete.

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