Preparation method and application of new type of UHPC tunnel flue plate counter beam

Abstract

The application provides a preparation method and application of a novel UHPC tunnel flue plate counter beam, and the method comprises the following steps: S1, mixing raw materials; cement 50-55 parts, broken stone 5-7 parts, natural sand 30-34 parts and Ca-Mg-Si composite stone powder 4-5 parts are uniformly mixed, 16-20 parts of water are added, preliminary stirring is carried out, 3-4 parts of modified polyacrylonitrile fiber are added, continuous stirring is carried out, 1.5-2 parts of water reducing agent and 0.08-0.1 parts of defoaming agent are added, and full stirring is carried out until uniform, to obtain a mixture; S2, pouring; the mixture obtained in S1 is poured into a mold, a vibrating table is used for vibrating, so that air bubbles and voids are removed; S3, curing; the curing comprises steam curing and standard curing; S4, demolding; after the curing is completed, demolding is carried out, and the novel UHPC tunnel flue plate counter beam is obtained. The application can synergistically improve the compressive strength and bending tensile strength of the concrete product.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high performance concrete products technology, specifically relating to a method for preparing and applying a novel UHPC tunnel flue slab inverted beam. Background Technology

[0002] Tunnel flue slabs are a crucial component in shield tunnel construction, primarily used to protect the tunnel structure and ventilate flue gases. They play a vital role in shield tunnel construction. The flue layer is the sole smoke exhaust channel for underground vehicular passageways, essential for ensuring safety and ventilation within the tunnel. Selecting appropriate flue slab materials and construction techniques is critical for controlling construction costs. Material durability and strength are key factors to consider during selection. The installation structure of the flue slabs needs to withstand the flue gas emission pressure within the tunnel and facilitate construction and maintenance. A common installation method is the use of precast flue slabs, which accelerates construction and improves efficiency. Construction methods typically include cast-in-place and precast methods; cast-in-place flue slabs require higher technical expertise, necessitating on-site concrete pouring, while precast flue slabs are manufactured in a factory and transported to the site for installation.

[0003] As a supporting structure for the tunnel flue slab, the inverted beams of the tunnel flue slab help maintain the shape and stability of the flue layer. They are usually prefabricated and constructed together with the flue slab to form a robust smoke exhaust channel layer. Therefore, in actual construction, high compressive strength and flexural tensile strength are required for the inverted beams of the tunnel flue slab to ensure excellent safety performance. Summary of the Invention

[0004] To address the problems existing in the background technology, the present invention provides a novel method for preparing and applying a UHPC tunnel flue slab inverted beam, which can synergistically improve compressive strength and flexural tensile strength.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a novel UHPC tunnel flue slab inverted beam, comprising the following steps:

[0006] S1. Raw material mixing: By weight, mix 50-55 parts cement, 5-7 parts crushed stone, 30-34 parts natural sand and 4-5 parts Ca-Mg-Si composite stone powder evenly, add 16-20 parts water, stir initially, then add 3-4 parts modified polyacrylonitrile fiber, continue stirring, then add 1.5-2 parts water-reducing agent and 0.08-0.1 parts defoamer, stir thoroughly to obtain the mixture;

[0007] S2, Casting; Pour the mixture obtained in S1 into the mold and use a vibrating table to compact it to remove air bubbles and voids;

[0008] S3. Maintenance; the maintenance includes steam maintenance and standard maintenance;

[0009] S4. Demolding; After curing, demold to obtain the new type of UHPC tunnel flue slab inverted beam.

[0010] Furthermore, the preparation method of the Ca-Mg-Si composite stone powder is as follows:

[0011] A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 1.5%-2% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of 95±5℃ to obtain modified Ca-Si stone powder.

[0012] A2. Peridot rock was calcined at 1550℃ in a blast furnace, solidified and purified to obtain Mg-Si stone powder;

[0013] A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3-5:1 to obtain Ca-Mg-Si composite stone powder.

[0014] Furthermore, the composite modifier includes stearic acid and a silane coupling agent, and the mass ratio of the two is 2:1.

[0015] Furthermore, the specific operating steps for A2 are as follows:

[0016] A21. The peridotite is washed and crushed to obtain crushed rock;

[0017] A22. The crushed rock is placed in a blast furnace and calcined at a high temperature of 1550℃ for 24 hours to obtain lava.

[0018] A23. The lava is subjected to air cooling, recrystallized, and gravity sorted to obtain pure phase rock;

[0019] A24. The pure phase rock is crushed and passed through an 800-mesh sieve to obtain Mg-Si stone powder.

[0020] Furthermore, the modified polyacrylonitrile fiber is prepared by: immersing the polyacrylonitrile fiber in a 7% NaOH solution at room temperature for 8 hours, removing it, washing it with deionized water until neutral, and air-drying it at room temperature to obtain neutral fiber; immersing the neutral fiber in a 7% polyether aqueous solution at room temperature for 2 hours, removing it, and drying it in a drying oven at 95±2℃ for 2 hours to obtain the modified polyacrylonitrile fiber.

[0021] Furthermore, the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent.

[0022] Furthermore, the cement includes P.O52.5 grade ordinary Portland cement and P.O42.5 grade medium-heat Portland cement, and the mass ratio of the two is 4:1.

[0023] Furthermore, the defoamer is a polyether-modified silicone defoamer.

[0024] Furthermore, the particle size of the crushed stone is 5.5-8.0 mm; the particle size of the natural sand is less than 4.5 mm.

[0025] Secondly, the present invention provides an application of a novel UHPC tunnel flue duct inverted beam, which is prepared by the above-mentioned preparation method and is used in a tunnel smoke exhaust system.

[0026] This application has the following beneficial effects:

[0027] 1. Through testing and verification, the concrete produced by this invention has a compressive strength of over 125MPa and a flexural tensile strength of over 12MPa, which is far superior to the corresponding performance of existing ordinary C40 concrete. This ensures that the final tunnel flue slab inverted beam has excellent compressive and flexural tensile strength, and its safety performance is guaranteed.

[0028] 2. The addition of Ca-Mg-Si composite stone powder can significantly improve the compressive strength of the final concrete. Ca-Mg-Si composite stone powder is prepared by mixing modified Ca-Si stone powder and Mg-Si stone powder, and the two have a synergistic effect on enhancing the compressive strength of concrete. The addition of modified polyacrylonitrile fiber can significantly improve the compressive strength of the final concrete, however, its improving ability is weaker than that of Ca-Mg-Si composite stone powder. Ca-Mg-Si composite stone powder and modified polyacrylonitrile fiber can synergistically improve the compressive strength of concrete.

[0029] 3. The addition of Ca-Mg-Si composite stone powder can significantly improve the flexural tensile strength of the final concrete. Ca-Mg-Si composite stone powder is obtained by mixing modified Ca-Si stone powder and Mg-Si stone powder, and the two have a synergistic effect on enhancing the flexural tensile strength of concrete. The addition of modified polyacrylonitrile fiber can significantly improve the flexural tensile strength of the final concrete, and its improving ability is stronger than that of Ca-Mg-Si composite stone powder. Ca-Mg-Si composite stone powder and modified polyacrylonitrile fiber can synergistically enhance the flexural tensile strength of concrete. Attached Figure Description

[0030] Figure 1 A comparative trend chart of compressive strength test data of C40 concrete in Experiment 1 and concrete prepared in Examples 1-6 of this invention;

[0031] Figure 2A comparative trend chart of the flexural tensile strength test data of C40 concrete in Experiment Example 1 and concrete prepared in Examples 1-6 of this invention;

[0032] Figure 3 A comparative trend chart of concrete compressive strength test data obtained in Example 1 and Comparative Examples 1-14 of this invention;

[0033] Figure 4 A comparative trend chart of concrete flexural tensile strength test data obtained in Example 1 and Comparative Examples 1-14 of this invention;

[0034] Figure 5 A perspective view of the novel UHPC tunnel flue slab inverted beam of the present invention. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments.

[0036] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0037] Example 1

[0038] A novel method for preparing a flue slab inverted beam in a UHPC tunnel includes the following steps:

[0039] S1. Raw material mixing: By weight, mix 50 parts cement, 5 parts crushed stone, 30 parts natural sand, and 4 parts Ca-Mg-Si composite stone powder evenly. Add 20 parts water and stir initially. Then add 3 parts modified polyacrylonitrile fiber and continue stirring. Finally, add 1.5 parts water-reducing agent and 0.08 parts defoamer and stir thoroughly to obtain the mixture. The mixture exhibits good fluidity and homogeneity.

[0040] S2, Pouring: Pour the mixture obtained in S1 into the mold and use a vibrating table to compact it to remove air bubbles and voids, ensuring that the mixture is dense and thus obtaining a concrete component.

[0041] S3. The concrete components obtained in S2 are first steam cured, and then standard cured.

[0042] Steam curing utilizes the high temperature and humidity of steam to accelerate the hardening process of concrete. This method is commonly used in precast component production, bridge construction, winter construction, or other applications requiring rapid increases in concrete strength. Steam curing can achieve the same results as standard curing in a shorter time, improving the turnover efficiency of formwork and equipment.

[0043] The steps of steam curing include:

[0044] Preparation of the curing chamber: Concrete components are placed in a sealable curing chamber or curing room to maintain a certain temperature and humidity.

[0045] Steam generator: Use a steam generator to produce saturated steam, which is then transported to the curing chamber or room through pipelines.

[0046] Heating stage: After the concrete is poured, the steam temperature is gradually increased to allow the temperature of the curing environment to rise slowly; the heating rate is 7℃ / h, and it should not be too fast to avoid cracks on the concrete surface.

[0047] Constant temperature stage: After the temperature reaches the predetermined 70℃, maintain constant temperature for 24 hours to promote the rapid hardening of concrete.

[0048] Cooling stage: After the constant temperature curing time is reached, the steam temperature is gradually reduced to allow the temperature of the curing environment to drop slowly; the cooling rate is 7℃ / h to allow the concrete to cool slowly and avoid cracks caused by a sudden drop in temperature.

[0049] End of curing: When the concrete surface temperature drops to room temperature, end steam curing and remove the concrete components from the curing chamber.

[0050] After steam curing, standard curing is performed to ensure the concrete continues to develop its long-term strength and durability. The standard curing period is 28 days, during which the curing temperature is maintained at approximately 15°C. During curing, the concrete surface should be protected from direct sunlight and wind. Humidity should be maintained during curing by spraying water, covering with damp cloths or plastic film to prevent excessive evaporation that could lead to drying shrinkage and cracking. After the curing period, gradually reduce moisturizing measures to allow the concrete to slowly adapt to the natural environment.

[0051] S4. Demolding: After curing, demold to obtain the new type of UHPC tunnel flue slab inverted beam.

[0052] The inverted beams are located at both ends of the flue slab and can be integrally formed during casting. The flue slab has a certain pre-camber, and connecting steel bars are pre-embedded during casting.

[0053] The preparation method of the Ca-Mg-Si composite stone powder is as follows:

[0054] A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 1.5% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of about 95°C to obtain modified Ca-Si stone powder.

[0055] The needle-shaped wollastonite powder was purchased from Shenzhen Haiyang Powder Technology Co., Ltd., model HY-W10. The composite modifier included stearic acid and silane coupling agent in a mass ratio of 2:1; the stearic acid (industrial grade) was purchased from Hubei Tuobang Chemical Co., Ltd.; and the silane coupling agent KH-792 was purchased from Hubei Hengjingrui Chemical Co., Ltd.

[0056] A2. Peridot rock was calcined in a blast furnace at 1550℃ to solidify and purify it, yielding Mg-Si stone powder.

[0057] The specific operating steps are as follows:

[0058] A21. The peridotite is cleaned and crushed to obtain crushed rock.

[0059] A22. Place the crushed rock into a blast furnace and calcine it at a high temperature of 1550℃ for 24 hours to obtain lava.

[0060] A23. The lava is cooled by air, recrystallized, and then separated by gravity to obtain pure phase rock.

[0061] Gravity separation equipment uses chute separators or shaking table separators. These devices are designed to allow materials to be separated into layers according to density with the help of mechanical vibration or water flow.

[0062] A24. The pure phase rock is crushed and passed through an 800-mesh sieve to obtain Mg-Si stone powder.

[0063] A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0064] The modified polyacrylonitrile fiber is prepared as follows: Polyacrylonitrile fiber is immersed in a 7% (w / w) NaOH solution at room temperature for 8 hours. It is then removed, washed with deionized water until neutral, and air-dried at room temperature to obtain neutral fiber. The neutral fiber is then immersed in a 7% (w / w) polyether aqueous solution at room temperature for 2 hours. It is then removed and dried in a drying oven at approximately 95°C for 2 hours to obtain the modified polyacrylonitrile fiber. The polyacrylonitrile fiber was purchased from Guangzhou Gongshi Chemical Materials Co., Ltd.

[0065] The water-reducing agent used is a polycarboxylate superplasticizer. This CC-AI polycarboxylate superplasticizer was purchased from Shenzhen Shangdao Chemical Co., Ltd., originating in Guangdong, model 001.

[0066] The cement includes P.O52.5 grade ordinary Portland cement and P.O42.5 grade medium-heat Portland cement, and the mass ratio of the two is 4:1.

[0067] The defoamer used is a polyether-modified silicone defoamer. This polyether-modified silicone defoamer was purchased from Guangdong Zhonglianbang Fine Chemical Co., Ltd., manufactured in Dongguan, Guangdong, branded as Zhonglianbang, model B-0518.

[0068] The crushed stone has a particle size of 5.5-8.0 mm. The natural sand has a particle size of less than 4.5 mm.

[0069] Example 2

[0070] The only difference between this embodiment and Example 1 is that in A1, the amount of composite modifier is 2% of the acicular wollastonite powder. In A3, the modified Ca-Si stone powder obtained in A1 and the Mg-Si stone powder obtained in A2 are mixed at a mass ratio of 5:1.

[0071] Specifically, the preparation method of the Ca-Mg-Si composite stone powder is as follows:

[0072] A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 2% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of about 95°C to obtain modified Ca-Si stone powder.

[0073] A2. Peridot rock was calcined in a blast furnace at 1550℃ to solidify and purify it, yielding Mg-Si stone powder.

[0074] A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 5:1 to obtain Ca-Mg-Si composite stone powder.

[0075] Example 3

[0076] The only difference between this embodiment and Example 1 is that in A1, the amount of composite modifier is 1.8% of the acicular wollastonite powder. In A3, the modified Ca-Si stone powder obtained in A1 and the Mg-Si stone powder obtained in A2 are mixed at a mass ratio of 4:1.

[0077] Specifically, the preparation method of the Ca-Mg-Si composite stone powder is as follows:

[0078] A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 1.8% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of about 95°C to obtain modified Ca-Si stone powder.

[0079] A2. Peridot rock was calcined in a blast furnace at 1550℃ to solidify and purify it, yielding Mg-Si stone powder.

[0080] A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 4:1 to obtain Ca-Mg-Si composite stone powder.

[0081] Example 4

[0082] The only difference between this embodiment and Embodiment 1 is: S1, raw material mixing; by weight, 55 parts of cement, 7 parts of crushed stone, 34 parts of natural sand and 5 parts of Ca-Mg-Si composite stone powder are mixed evenly, 16 parts of water are added, and the mixture is initially stirred. Then, 4 parts of modified polyacrylonitrile fiber are added and stirred again. Then, 2 parts of water-reducing agent and 0.1 parts of defoamer are added and stirred evenly to obtain the mixture.

[0083] Example 5

[0084] The difference between this embodiment and Embodiment 1 is only in the following aspects: S1, raw material mixing; by weight, 53 parts of cement, 6 parts of crushed stone, 32 parts of natural sand and 4.5 parts of Ca-Mg-Si composite stone powder are mixed evenly, 18 parts of water are added, and the mixture is initially stirred. Then, 3.5 parts of modified polyacrylonitrile fiber are added and stirred continuously. Then, 1.7 parts of water-reducing agent and 0.09 parts of defoamer are added and stirred thoroughly to obtain the mixture.

[0085] Example 6

[0086] The difference between this embodiment and Embodiment 1 is only in the following aspects: S1, raw material mixing; by weight, 53 parts of cement, 6 parts of crushed stone, 32 parts of natural sand and 5 parts of Ca-Mg-Si composite stone powder are mixed evenly, 18 parts of water are added, and the mixture is initially stirred. Then, 3 parts of modified polyacrylonitrile fiber are added and stirred continuously. Then, 1.5 parts of water-reducing agent and 0.08 parts of defoamer are added and stirred thoroughly to obtain a mixture.

[0087] Comparative Example 1

[0088] The only difference between this comparative example and Example 1 is that, in the preparation of Ca-Mg-Si composite stone powder, needle-shaped wollastonite powder is replaced with calcium carbonate powder.

[0089] Specifically, the preparation method of Ca-Mg-Si composite stone powder is as follows:

[0090] A1. Add a composite modifier to calcium carbonate powder, the amount of which is 1.5% of the calcium carbonate powder by mass; then stir at 700 r / min for 10 min at a temperature of about 95℃ to obtain modified Ca powder.

[0091] A2. Peridot rock was calcined in a blast furnace at 1550℃ to solidify and purify it, yielding Mg-Si stone powder.

[0092] A3. Mix the modified Ca powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0093] Comparative Example 2

[0094] The only difference between this comparative example and Example 1 is that, in the preparation of the Ca-Mg-Si composite stone powder, the needle-shaped wollastonite powder is replaced with talc powder.

[0095] Specifically, the preparation method of Ca-Mg-Si composite stone powder is as follows:

[0096] A1. Add a composite modifier to talc powder, the amount of the composite modifier being 1.5% of the talc powder by mass; then stir at 700 r / min for 10 min at a temperature of about 95℃ to obtain modified talc powder.

[0097] A2. Peridot rock was calcined in a blast furnace at 1550℃ to solidify and purify it, yielding Mg-Si stone powder.

[0098] A3. Mix the modified talc powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0099] Comparative Example 3

[0100] The only difference between this comparative example and Example 1 is that the needle-shaped wollastonite powder is not modified in the preparation of the Ca-Mg-Si composite stone powder.

[0101] Specifically, the preparation method of Ca-Mg-Si composite stone powder is as follows:

[0102] A1. Peridot rock was calcined at 1550℃ in a blast furnace to solidify and purify it, yielding Mg-Si stone powder.

[0103] A1. Mix the needle-shaped wollastonite powder with the Mg-Si stone powder obtained in A1 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0104] Comparative Example 4

[0105] The only difference between this comparative example and Example 1 is that in the preparation of Ca-Mg-Si composite stone powder, a single silane coupling agent is added to the needle-shaped wollastonite powder to obtain modified Ca-Si stone powder.

[0106] Specifically, the preparation method of Ca-Mg-Si composite stone powder is as follows:

[0107] A1. Add silane coupling agent to acicular wollastonite powder. The amount of silane coupling agent is 1.5% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of about 95℃ to obtain modified Ca-Si stone powder.

[0108] A2. Peridot rock was calcined in a blast furnace at 1550℃ to solidify and purify it, yielding Mg-Si stone powder.

[0109] A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0110] Comparative Example 5

[0111] The only difference between this comparative example and Example 1 is that in the preparation of Ca-Mg-Si composite stone powder, the peridotite is not subjected to high-temperature calcination and is directly crushed for use.

[0112] Specifically, the preparation method of Ca-Mg-Si composite stone powder is as follows:

[0113] A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 1.5% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of about 95°C to obtain modified Ca-Si stone powder.

[0114] A2. The peridotite is crushed and passed through an 800-mesh sieve to obtain Mg-Si stone powder.

[0115] A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0116] Comparative Example 6

[0117] The only difference between this comparative example and Example 1 is that in the preparation of Ca-Mg-Si composite stone powder, peridotite is replaced with granite.

[0118] Specifically, the preparation method of Ca-Mg-Si composite stone powder is as follows:

[0119] A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 1.5% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of about 95°C to obtain modified Ca-Si stone powder.

[0120] A2. Granite is calcined in a 1000℃ blast furnace, solidified and purified, and then crushed through an 800-mesh sieve to obtain granite powder.

[0121] A3. Mix the modified Ca-Si stone powder obtained in A1 with the granite powder obtained in A2 at a mass ratio of 3:1 to obtain Ca-Mg-Si composite stone powder.

[0122] Comparative Example 7

[0123] The only difference between this comparative example and Example 1 is that in the preparation of Ca-Mg-Si composite stone powder, modified Ca-Si stone powder is removed, and single Mg-Si stone powder is used directly.

[0124] Specifically, S1, raw material mixing: by weight, 50 parts of cement, 5 parts of crushed stone, 30 parts of natural sand and 4 parts of Mg-Si stone powder are mixed evenly, 20 parts of water are added, and the mixture is initially stirred. Then, 3 parts of modified polyacrylonitrile fiber are added and stirred again. Then, 1.5 parts of water-reducing agent and 0.08 parts of defoamer are added and stirred evenly to obtain the mixture.

[0125] Comparative Example 8

[0126] The only difference between this comparative example and Example 1 is that in the preparation of Ca-Mg-Si composite stone powder, Mg-Si stone powder is removed, and only single modified Ca-Si stone powder is used directly.

[0127] Specifically, S1, raw material mixing: by weight, mix 50 parts of cement, 5 parts of crushed stone, 30 parts of natural sand and 4 parts of modified Ca-Si stone powder evenly, add 20 parts of water, stir initially, then add 3 parts of modified polyacrylonitrile fiber, continue stirring, then add 1.5 parts of water-reducing agent and 0.08 parts of defoamer, and stir thoroughly to obtain the mixture.

[0128] Comparative Example 9

[0129] The only difference between this comparative example and Example 1 is the removal of the Ca-Mg-Si composite stone powder.

[0130] Specifically, S1, raw material mixing: by weight, mix 50 parts of cement, 5 parts of crushed stone and 30 parts of natural sand evenly, add 20 parts of water, stir initially, then add 3 parts of modified polyacrylonitrile fiber, continue stirring, then add 1.5 parts of water-reducing agent and 0.08 parts of defoamer, stir thoroughly to obtain the mixture.

[0131] Comparative Example 10

[0132] The only difference between this comparative example and Example 1 is that the polyacrylonitrile fiber was not modified, that is, the modified polyacrylonitrile fiber was replaced with polyacrylonitrile fiber.

[0133] Specifically, S1, raw material mixing: by weight, mix 50 parts of cement, 5 parts of crushed stone, 30 parts of natural sand and 4 parts of Ca-Mg-Si composite stone powder evenly, add 20 parts of water, stir initially, then add 3 parts of polyacrylonitrile fiber, continue stirring, then add 1.5 parts of water-reducing agent and 0.08 parts of defoamer, and stir thoroughly to obtain the mixture.

[0134] Comparative Example 11

[0135] The only difference between this comparative example and Example 1 is that the modified polyacrylonitrile fiber is replaced with modified polyvinyl alcohol fiber.

[0136] Specifically, S1, raw material mixing: by weight, mix 50 parts of cement, 5 parts of crushed stone, 30 parts of natural sand and 4 parts of Ca-Mg-Si composite stone powder evenly, add 20 parts of water, stir initially, then add 3 parts of modified polyvinyl alcohol fiber, continue stirring, then add 1.5 parts of water-reducing agent and 0.08 parts of defoamer, and stir thoroughly to obtain the mixture.

[0137] Preparation method of modified polyvinyl alcohol fiber: Polyvinyl alcohol fiber is immersed in a 7% (w / w) NaOH solution at room temperature for 8 hours, then removed, washed with deionized water until neutral, and air-dried at room temperature to obtain neutral fiber; the neutral fiber is then immersed in a 7% (w / w) polyether aqueous solution at room temperature for 2 hours, removed, and dried in a drying oven at approximately 95°C for 2 hours to obtain modified polyvinyl alcohol fiber. The polyvinyl alcohol fiber was purchased from Taian Senyang Composite Materials Co., Ltd., with a specification of 6mm.

[0138] Comparative Example 12

[0139] The only difference between this comparative example and Example 1 is that the modified polyacrylonitrile fiber is replaced with polyvinyl alcohol fiber, and the difference from Comparative Example 11 is that the polyvinyl alcohol fiber is not modified.

[0140] Specifically, S1, raw material mixing: By weight, 50 parts cement, 5 parts crushed stone, 30 parts natural sand, and 4 parts Ca-Mg-Si composite stone powder are mixed evenly. 20 parts water are added and initially stirred. Then, 3 parts polyvinyl alcohol fiber are added and stirred further. Finally, 1.5 parts water-reducing agent and 0.08 parts defoamer are added and thoroughly mixed to obtain the final mixture. The polyvinyl alcohol fiber was purchased from Taian Senyang Composite Materials Co., Ltd., with a specification of 6mm.

[0141] Comparative Example 13

[0142] The only difference between this comparative example and Example 1 is that the modified polyacrylonitrile fiber has been removed.

[0143] Specifically, S1, raw material mixing: by weight, mix 50 parts of cement, 5 parts of crushed stone, 30 parts of natural sand and 4 parts of Ca-Mg-Si composite stone powder evenly, add 20 parts of water, stir initially, then add 1.5 parts of water-reducing agent and 0.08 parts of defoamer, stir thoroughly to obtain the mixture.

[0144] Comparative Example 14

[0145] The only difference between this comparative example and Example 1 is the removal of Ca-Mg-Si composite stone powder and modified polyacrylonitrile fiber.

[0146] Specifically, S1, raw material mixing: by weight, mix 50 parts of cement, 5 parts of crushed stone and 30 parts of natural sand evenly, add 20 parts of water, stir initially, then add 1.5 parts of water-reducing agent and 0.08 parts of defoamer, stir thoroughly to obtain the mixture.

[0147] Experimental Example 1

[0148] Test items: compressive strength, flexural tensile strength;

[0149] Test basis: GB / T 50081-2019 Standard for Test Methods of Physical and Mechanical Properties of Concrete;

[0150] Test subjects: Existing C40 concrete, and mixtures (concrete) prepared in Examples 1-6 and Comparative Examples 1-14;

[0151] Experimental results: see Table 1 and Figure 1-4 .

[0152] Table 1. Compressive strength and flexural tensile strength data

[0153] Compressive strength / MPa Flexural tensile strength / MPa C40 concrete 39 2.9 Example 1 128 12.4 Example 2 129 12.5 Example 3 126 12.6 Example 4 128 12.2 Example 5 128 12.6 Example 6 126 12.4 Comparative Example 1 116 11.4 Comparative Example 2 113 11.5 Comparative Example 3 109 11.0 Comparative Example 4 118 11.3 Comparative Example 5 114 11.9 Comparative Example 6 116 11.2 Comparative Example 7 104 10.7 Comparative Example 8 109 11.0 Comparative Example 9 81 9.0 Comparative Example 10 114 9.6 Comparative Example 11 118 9.7 Comparative Example 12 109 8.9 Comparative Example 13 102 7.9 Comparative Example 14 51 4.0

[0154] Results Analysis: Based on Examples 1-6 and the data in Table 1, Figure 1-2 It can be seen that the concrete produced by this invention has a compressive strength of over 125 MPa and a flexural tensile strength of over 12 MPa, which is far superior to the corresponding performance of existing ordinary C40 concrete.

[0155] Based on Example 1 and Comparative Examples 1-9, combined with the data in Table 1 and Figure 3It can be seen that the addition of Ca-Mg-Si composite stone powder can significantly improve the compressive strength of the final concrete. Ca-Mg-Si composite stone powder is obtained by mixing modified Ca-Si stone powder and Mg-Si stone powder, and the two have a synergistic effect on enhancing the compressive strength of concrete. Experiments have verified that the acicular wollastonite powder used to prepare modified Ca-Si stone powder cannot be easily replaced by other stone powders (calcium carbonate powder / talc powder), and the peridotite used to prepare Mg-Si stone powder cannot be easily replaced by other rocks (granite), otherwise the compressive strength of concrete will decrease. Furthermore, the modification process in the preparation of modified Ca-Si stone powder and the high-temperature calcination purification process in the preparation of Mg-Si stone powder are essential. Deleting either of these two processes will lead to a decrease in the compressive strength of concrete.

[0156] Based on Example 1 and Comparative Examples 10-13, combined with the data in Table 1 and Figure 3 It can be seen that the addition of modified polyacrylonitrile fiber can significantly improve the compressive strength of the final concrete; however, its improvement ability is weaker than that of Ca-Mg-Si composite stone powder.

[0157] Experiments have verified that the raw material for preparing modified polyacrylonitrile fibers, polyacrylonitrile fibers, cannot be easily replaced by other fibers (polyvinyl alcohol fibers), otherwise the compressive strength of concrete will decrease; furthermore, modification treatment is essential, and removing modification treatment will also lead to a decrease in the compressive strength of concrete.

[0158] Based on Example 1 and Comparative Examples 9, 13-14, combined with the data in Table 1 and Figure 3 It can be seen that Ca-Mg-Si composite stone powder and modified polyacrylonitrile fiber can produce a synergistic effect in enhancing the compressive strength of concrete, achieving a strengthening effect greater than the sum of its parts, rather than a simple superposition of the two strengthening effects.

[0159] Based on Example 1 and Comparative Examples 1-9, combined with the data in Table 1 and Figure 4 It can be seen that the addition of Ca-Mg-Si composite stone powder can significantly improve the flexural tensile strength of the final concrete. The Ca-Mg-Si composite stone powder is obtained by mixing modified Ca-Si stone powder and Mg-Si stone powder, and their effects on enhancing the flexural tensile strength of concrete are synergistic. Experiments have verified that the acicular wollastonite powder used to prepare modified Ca-Si stone powder cannot be easily replaced by other stone powders (calcium carbonate powder / talc powder), and the olivine rock used to prepare Mg-Si stone powder cannot be easily replaced by other rocks (granite); otherwise, the flexural tensile strength of the concrete will decrease. Furthermore, the modification process in preparing modified Ca-Si stone powder and the high-temperature calcination purification process in preparing Mg-Si stone powder are essential; removing either of these processes will lead to a decrease in the flexural tensile strength of the concrete.

[0160] Based on Example 1 and Comparative Examples 10-13, combined with the data in Table 1 and Figure 4 It can be seen that the addition of modified polyacrylonitrile fiber can significantly improve the flexural tensile strength of the final concrete, and its improving ability is stronger than that of Ca-Mg-Si composite stone powder.

[0161] Experiments have verified that the raw material polyacrylonitrile fiber used to prepare modified polyacrylonitrile fiber cannot be easily replaced by other fibers (polyvinyl alcohol fiber), otherwise it will lead to a decrease in the flexural tensile strength of concrete; furthermore, modification treatment is essential, and removing modification treatment will also lead to a decrease in the flexural tensile strength of concrete.

[0162] Based on Example 1 and Comparative Examples 9, 13-14, combined with the data in Table 1 and Figure 4 It can be seen that Ca-Mg-Si composite stone powder and modified polyacrylonitrile fiber can produce a synergistic effect in enhancing the flexural tensile strength of concrete.

[0163] Experimental Example 2

[0164] This invention prefabricates a novel UHPC tunnel flue slab inverted beam. The inverted beam is located at both ends of the flue slab and can be integrally formed during casting. The flue slab has a certain pre-camber, and connecting steel bars are pre-embedded during casting. Using the products obtained in Examples 1-6 as test objects, the surface fireproof coating can be omitted, and the fireproof function of all products reaches Class A fire resistance.

[0165] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0166] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a novel UHPC tunnel flue slab inverted beam, characterized in that, Includes the following steps: S1. Raw material mixing: By weight, mix 50-55 parts cement, 5-7 parts crushed stone, 30-34 parts natural sand and 4-5 parts Ca-Mg-Si composite stone powder evenly, add 16-20 parts water, stir initially, then add 3-4 parts modified polyacrylonitrile fiber, continue stirring, then add 1.5-2 parts water-reducing agent and 0.08-0.1 parts defoamer, stir thoroughly to obtain the mixture; S2, Casting; Pour the mixture obtained in S1 into the mold and use a vibrating table to compact it to remove air bubbles and voids; S3. Maintenance; the maintenance includes steam maintenance and standard maintenance; S4. Demolding; After curing, demold to obtain the new type of UHPC tunnel flue slab inverted beam; The preparation method of the Ca-Mg-Si composite stone powder is as follows: A1. Add a composite modifier to the acicular wollastonite powder. The amount of the composite modifier is 1.5%-2% of the acicular wollastonite powder by mass. Then, stir at 700 r / min for 10 min at a temperature of 95±5℃ to obtain modified Ca-Si stone powder. A2. Peridot rock was calcined at 1550℃ in a blast furnace, solidified and purified to obtain Mg-Si stone powder; A3. Mix the modified Ca-Si stone powder obtained in A1 with the Mg-Si stone powder obtained in A2 at a mass ratio of 3-5:1 to obtain Ca-Mg-Si composite stone powder.

2. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The composite modifier includes stearic acid and a silane coupling agent, and the mass ratio of the two is 2:

1.

3. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The specific operating steps for A2 are as follows: A21. The peridotite is washed and crushed to obtain crushed rock; A22. The crushed rock is placed in a blast furnace and calcined at a high temperature of 1550℃ for 24 hours to obtain lava. A23. The lava is subjected to air cooling, recrystallized, and gravity sorted to obtain pure phase rock; A24. The pure phase rock is crushed and passed through an 800-mesh sieve to obtain Mg-Si stone powder.

4. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The modified polyacrylonitrile fiber is prepared by immersing the polyacrylonitrile fiber in a 7% NaOH solution at room temperature for 8 hours, removing it, washing it with deionized water until neutral, and air-drying it at room temperature to obtain neutral fiber; then immersing the neutral fiber in a 7% polyether aqueous solution at room temperature for 2 hours, removing it, and drying it in a drying oven at 95±2℃ for 2 hours to obtain the modified polyacrylonitrile fiber.

5. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The water-reducing agent used is a polycarboxylate high-efficiency water-reducing agent.

6. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The cement includes P.O52.5 grade ordinary Portland cement and P.O42.5 grade medium-heat Portland cement, and the mass ratio of the two is 4:

1.

7. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The defoamer used is a polyether-modified silicone defoamer.

8. The method for preparing the novel UHPC tunnel flue slab inverted beam according to claim 1, characterized in that, The crushed stone has a particle size of 5.5-8.0 mm; the natural sand has a particle size of less than 4.5 mm.

9. An application of a novel UHPC tunnel flue slab inverted beam, characterized in that, The novel UHPC tunnel flue plate inverted beam is prepared by the preparation method described in any one of claims 1-8, and the novel UHPC tunnel flue plate inverted beam is used in the tunnel smoke exhaust system.

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