Lining concrete for large cross-section tunnel and its preparation method

Abstract

The application discloses a lining concrete for large-section tunnels and a preparation method thereof, and belongs to the technical field of building materials. The lining concrete comprises the following components in parts by weight: cement 300-400 parts, fly ash 40-50 parts, mineral powder 40-70 parts, fine aggregate 600-650 parts, coarse aggregate 1050-1150 parts, water 150-200 parts, water reducing agent 7-11 parts, and air entraining agent 5-10 parts. The water reducing agent comprises the following raw materials in parts by weight: polyether macromonomer 100 parts, unsaturated carboxylic acid monomer 5-7 parts, 3,4-dihydroxybenzoic acid methyl ester 4-6 parts, unsaturated amide 2-4 parts, oxidizing agent 1.0-2.0 parts, reducing agent 0.5-1.0 parts, chain transfer agent 0.5-1.5 parts, and deionized water 300-350 parts. The lining concrete has low bleeding rate, good fluidity, and 1h lossless slump, is beneficial to the discharge of air bubbles, and can solve the problems of bleeding, honeycomb pitted surface, air holes and water bubbles of the tunnel lining concrete in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a lining concrete for large-section tunnels and its preparation method. Background Technology

[0002] Most circular tunnels use full-circular needle beam trolleys for concrete lining due to their advantages such as rapid concrete pouring, one-time full-section molding, high efficiency, and low cost. However, some problems exist in practical applications. For example, during the bottom concrete lining of the tunnel, because the steel formwork of the needle beam trolley is located above the concrete, and air bubbles move from bottom to top, when the air bubbles reach the top of the concrete, the steel formwork obstructs their escape, leading to honeycomb-like pitting, air holes, and water bubbles (such as...). Figure 1 Problems such as those shown in the image occur; furthermore, after a period of pause in pouring, water seeps from the concrete surface, causing blisters, peeling, and watermarks (as shown in the image) to appear on the concrete surface. Figure 2 Defects such as those shown in the image affect the surface smoothness of the concrete, resulting in poor appearance quality and failing to meet the requirements for concrete quality and surface flatness. In actual construction, improvements are generally made by increasing the density of the working windows at the bottom of the trolley and strengthening the control of the vibration process. For example, Chinese patent CN114033436A discloses a full-circular needle beam lining trolley and its construction method, replacing the current full-circular needle beam lining trolley's bottom formwork with a sliding formwork with a very small covering area. During the entire tunnel bottom lining process, except for the sliding formwork covering area, the rest of the tunnel bottom is open, allowing vibration operations to be performed on both longitudinal sides of the sliding formwork. Because the sliding formwork area is small, the concrete under its cover is also within the effective vibration zone. The side formwork, side molds, and top formwork are almost perpendicular to the horizontal plane, and the upper part of the pouring space is open, which is beneficial for inserting vibrators during vibration. Therefore, the entire construction process has no dead angles in vibration and air release, resulting in high concrete density and strength. However, this lining trolley can only accelerate air release to a certain extent, cannot completely eliminate bottom air bubbles, and cannot solve the problem of concrete bleeding. Furthermore, it requires changes to the needle beam trolley's structure, making operation relatively complex.

[0003] Therefore, there is an urgent need to provide a lining concrete for large-section tunnels. By optimizing the material mix ratio, this invention can solve the technical problems of honeycomb, pitting, air holes, and water bubbles that easily occur in the bottom concrete when using a needle beam trolley for tunnel concrete lining in the existing technology. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the purpose of this invention is to provide a lining concrete for large-section tunnels. This concrete has a low bleeding rate, good fluidity, and no slump loss after 1 hour, which facilitates the removal of air bubbles. This solves the problems of bleeding, honeycomb surface defects, air holes, and water bubbles in existing tunnel lining concrete.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0006] A type of lining concrete for large-section tunnels comprises the following components in parts by weight: 300-400 parts cement, 40-50 parts fly ash, 40-70 parts mineral powder, 600-650 parts fine aggregate, 1050-1150 parts coarse aggregate, 150-200 parts water, 7-11 parts water-reducing agent, and 5-10 parts air-entraining agent.

[0007] The water-reducing agent comprises the following raw materials in parts by weight: 100 parts of polyether macromonomer, 5-7 parts of unsaturated carboxylic acid monomer, 4-6 parts of methyl 3,4-dihydroxybenzoate, 2-4 parts of unsaturated amide, 1.0-2.0 parts of oxidant, 0.5-1.0 parts of reducing agent, 0.5-1.5 parts of chain transfer agent, and 300-350 parts of deionized water.

[0008] This invention uses polyether macromonomers, unsaturated carboxylic acids, methyl 3,4-dihydroxybenzoate, and unsaturated amides as raw materials to prepare a water-reducing agent, which is then added to concrete. Utilizing the hydrophilicity of the hydroxyl groups in methyl 3,4-dihydroxybenzoate and the high water absorption of the amide groups, free water is adsorbed and fixed, reducing its release and thus providing water retention and thickening effects. Simultaneously, the steric hindrance of methyl 3,4-dihydroxybenzoate improves the dispersibility of the water-reducing agent in concrete. By employing the above technical solution, the fluidity and slump retention of concrete can be effectively improved, reducing bleeding and resulting in concrete with low bleeding rate, excellent fluidity, and low slump loss over time, which is beneficial for the removal of air bubbles. At the same time, an air-entraining agent introduces an appropriate amount of beneficial small air bubbles, utilizing the ball-bearing effect of these small bubbles to reduce friction between aggregates and improve concrete fluidity. The concrete of this invention is very suitable for construction using needle beam trolleys, effectively avoiding the problems of bleeding, honeycomb pitting, air holes, and water bubbles that occur in concrete when using needle beam trolleys for tunnel lining in existing technologies.

[0009] Preferably, the method for preparing the water-reducing agent includes the following steps:

[0010] S1. Dissolve unsaturated carboxylic acid monomers and methyl 3,4-dihydroxybenzoate in N,N-dimethylacetamide, then add alkali to adjust the pH of the solution to 9-10, react at 80-90℃ for 5-8 hours, and obtain the intermediate after drying;

[0011] S2. Dissolve the intermediate obtained in step S1 in deionized water to obtain solution A; dissolve the unsaturated amide in deionized water to obtain solution B; dissolve the reducing agent and chain transfer agent in deionized water to obtain solution C;

[0012] S3. Dissolve the polyether macromonomer in the remaining deionized water, then add the oxidant and stir until homogeneous. Then add solution A and solution B dropwise in sequence, and add solution C dropwise at the same time as adding solution A and solution B. After the addition is complete, react at 40-60℃ for 2-3 hours. Finally, dilute with water to a solid content of 30-70% to obtain the water-reducing agent.

[0013] This invention involves reacting an unsaturated carboxylic acid monomer with methyl 3,4-dihydroxybenzoate under alkaline conditions to obtain an intermediate, which is then used as a raw material to prepare a water-reducing agent, thereby improving the anti-bleeding effect of the water-reducing agent.

[0014] Preferably, the coarse aggregate comprises two types of crushed stone with particle sizes of 5-10 mm and 10-20 mm, and the weight ratio of crushed stone with a particle size of 5-10 mm to that with a particle size of 10-20 mm is 1:(2-3). The maximum particle size of the coarse aggregate of the present invention is 20 mm, and it uses two types of continuously graded crushed stone of 5-10 mm and 10-20 mm. By optimizing the concrete mix proportion, the fluidity of the concrete can be improved and the bleeding of the concrete can be reduced.

[0015] Preferably, the air-entraining agent is at least one of aliphatic polyoxyethylene ether sodium sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium rosinate.

[0016] Preferably, the polyether macromonomer is isopentenyl alcohol polyoxyethylene ether or ethylene glycol monovinyl glycol ether.

[0017] Preferably, the unsaturated carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid.

[0018] Preferably, the unsaturated amide includes at least one of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, or N-hydroxymethylacrylamide.

[0019] Preferably, the oxidant includes at least one of hydrogen peroxide, ammonium persulfate, and sodium persulfate; the reducing agent includes at least one of ascorbic acid, bisulfite, and thiosulfate; and the chain transfer agent is mercaptopropionic acid or mercaptoacetic acid.

[0020] Preferably, the weight-average molecular weight of the polyether macromonomer is 3000-5000.

[0021] Another object of the present invention is to provide a method for preparing the lining concrete for large-section tunnels, comprising the following steps:

[0022] P1. Weigh each component according to the parts by weight;

[0023] P2. Dry mix the fine aggregate and coarse aggregate evenly, then add cement, fly ash, and mineral powder and continue to dry mix evenly. Then add water-reducing agent, air-entraining agent, and water to obtain the lining concrete for the large-section tunnel.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] The lining concrete of this invention has good fluidity, a slump greater than 200mm, and no loss of slump within 1 hour. The bleeding rate is less than 1.5%, making it very suitable for lining construction using a needle beam trolley. It can effectively avoid the problems of bleeding, honeycomb surface, air holes, and water bubbles that occur in concrete when using a needle beam trolley to line tunnels in the prior art. Attached Figure Description

[0026] Figure 1 A schematic diagram showing blisters appearing on an existing concrete surface;

[0027] Figure 2 This is a schematic diagram showing water ripples appearing on an existing concrete surface. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the following examples and comparative examples, the cement is P·O42.5 ordinary Portland cement, the fly ash is Grade II fly ash, the slag powder is S95 slag powder, the coarse aggregate includes two types of crushed stone with particle sizes of 5-10mm and 10-20mm, and the weight ratio of crushed stone with particle size of 5-10mm to crushed stone with particle size of 10-20mm is 1:(2-3); the fine aggregate is manufactured sand with a fineness modulus of 2.6.

[0030] The method for preparing lining concrete for large-section tunnels according to the present invention includes the following steps:

[0031] P1. Weigh each component according to the parts by weight;

[0032] P2. Dry mix the fine aggregate and coarse aggregate evenly, then add cement, fly ash, and mineral powder and continue to dry mix evenly. Then add water-reducing agent, air-entraining agent, and water to obtain the lining concrete for the large-section tunnel.

[0033] Example 1

[0034] This embodiment provides a lining concrete for large-section tunnels, comprising the following components in parts by weight: 300 parts cement, 50 parts fly ash, 70 parts mineral powder, 600 parts fine aggregate, 1050 parts coarse aggregate, 150 parts water, 7 parts water-reducing agent, and 5 parts sodium dodecyl sulfate.

[0035] The preparation method of the water-reducing agent includes the following steps:

[0036] S1. Dissolve 5 parts of acrylic acid and 4 parts of methyl 3,4-dihydroxybenzoate in 20 parts of N,N-dimethylacetamide, then add ammonia to adjust the pH of the solution to 9, react at 80°C for 8 hours, and obtain the intermediate by evaporation and drying to remove the solvent;

[0037] S2. Dissolve the intermediate obtained in step S1 in deionized water to obtain a solution A with a mass fraction of 30%; dissolve 4 parts of acrylamide in deionized water to obtain a solution B with a mass fraction of 50%; dissolve 0.5 parts of ascorbic acid and 0.5 parts of mercaptoacetic acid in deionized water to obtain a solution C with a mass fraction of 1% ascorbic acid.

[0038] S3. Dissolve 100 parts of isopentenyl alcohol polyoxyethylene ether in the remaining deionized water, then add 1 part of 30% hydrogen peroxide, stir well, and then add solution A and solution B dropwise in sequence. While adding solution A and solution B, add solution C dropwise. The dropwise addition time for solution A is 2 hours, the dropwise addition time for solution B is 1.5 hours, and the dropwise addition time for solution C is 3.5 hours. After the dropwise addition is completed, react at 40°C for 3 hours. Finally, dilute with water to a solid content of 40% to obtain the water-reducing agent.

[0039] Example 2

[0040] This embodiment provides a lining concrete for large-section tunnels, comprising the following components in parts by weight: 400 parts cement, 40 parts fly ash, 50 parts mineral powder, 650 parts fine aggregate, 1150 parts coarse aggregate, 200 parts water, 11 parts water-reducing agent, and 10 parts sodium dodecylbenzenesulfonate.

[0041] The preparation method of the water-reducing agent includes the following steps:

[0042] S1. Dissolve 6 parts of methacrylic acid and 5 parts of methyl 3,4-dihydroxybenzoate in 20 parts of N,N-dimethylacetamide, then add ammonia to adjust the pH of the solution to 10, react at 90°C for 5 hours, and obtain the intermediate by evaporation and drying to remove the solvent;

[0043] S2. Dissolve the intermediate obtained in step S1 in deionized water to obtain a solution A with a mass fraction of 20%; dissolve 4 parts of N-hydroxymethylacrylamide in deionized water to obtain a solution B with a mass fraction of 70%; dissolve 0.75 parts of bisulfite and 0.75 parts of mercaptopropionic acid in deionized water to obtain a solution C with a bisulfite mass fraction of 1.2%.

[0044] S3. Dissolve 100 parts of ethylene glycol monovinyl glycol ether in the remaining deionized water, then add 1.5 parts of ammonium persulfate, stir well, and then add solution A and solution B dropwise in sequence. While adding solution A and solution B, add solution C dropwise. The dropwise addition time for solution A is 1.5 hours, the dropwise addition time for solution B is 1.5 hours, and the dropwise addition time for solution C is 3 hours. After the dropwise addition is completed, react at 60°C for 2 hours. Finally, dilute with water to a solid content of 40% to obtain the water-reducing agent.

[0045] Example 3

[0046] This embodiment provides a lining concrete for large-section tunnels, comprising the following components in parts by weight: 350 parts cement, 45 parts fly ash, 60 parts mineral powder, 625 parts fine aggregate, 1100 parts coarse aggregate, 175 parts water, 9 parts water-reducing agent, and 7 parts sodium rosinate.

[0047] The preparation method of the water-reducing agent includes the following steps:

[0048] S1. Dissolve 7 parts of acrylic acid and 6 parts of methyl 3,4-dihydroxybenzoate in 20 parts of N,N-dimethylacetamide, then add ammonia to adjust the pH of the solution to 10, react at 85°C for 7 hours, and obtain the intermediate by evaporation and drying to remove the solvent;

[0049] S2. Dissolve the intermediate obtained in step S1 in deionized water to obtain a solution A with a mass fraction of 35%; dissolve 2 parts of 2-acrylamide-2-methylpropanesulfonic acid in deionized water to obtain a solution B with a mass fraction of 50%; dissolve 0.5 parts of ascorbic acid and 0.5 parts of mercaptoacetic acid in deionized water to obtain a solution C with a mass fraction of 1% ascorbic acid.

[0050] S3. Dissolve 100 parts of isopentenyl alcohol polyoxyethylene ether in the remaining deionized water, then add 1 part of 30% hydrogen peroxide, stir well, and then add solution A and solution B dropwise in sequence. While adding solution A and solution B, add solution C dropwise. The dropwise addition time for solution A is 2 hours, the dropwise addition time for solution B is 1.5 hours, and the dropwise addition time for solution C is 3.5 hours. After the dropwise addition is completed, react at 40°C for 3 hours. Finally, dilute with water to a solid content of 40% to obtain the water-reducing agent.

[0051] Comparative Example 1

[0052] The concrete in this comparative example is basically the same as that in Example 3, except that the water-reducing agent is prepared using the following method:

[0053] S1. Dissolve acrylic acid in deionized water to obtain a solution A with a mass fraction of 30%; dissolve 2 parts of 2-acrylamide-2-methylpropanesulfonic acid in deionized water to obtain a solution B with a mass fraction of 50%; dissolve 0.5 parts of ascorbic acid and 0.5 parts of mercaptoacetic acid in deionized water to obtain a solution C with a mass fraction of 1% ascorbic acid.

[0054] S2. Dissolve 100 parts of isopentenyl alcohol polyoxyethylene ether in the remaining deionized water, then add 1 part of 30% hydrogen peroxide, stir well, and then add solution A and solution B dropwise in sequence. While adding solution A and solution B, add solution C dropwise. The dropwise addition time for solution A is 2 hours, the dropwise addition time for solution B is 1.5 hours, and the dropwise addition time for solution C is 3.5 hours. After the dropwise addition is completed, react at 40°C for 3 hours. Finally, dilute with water to a solid content of 40% to obtain the water-reducing agent.

[0055] Compared to Example 3, the water-reducing agent in this comparative example lacks methyl 3,4-dihydroxybenzoate.

[0056] Comparative Example 2

[0057] The concrete in this comparative example is basically the same as that in Example 3, except that the water-reducing agent is prepared using the following method:

[0058] S1. Dissolve 7 parts acrylic acid and 6 parts methyl 3,4-dihydroxybenzoate in deionized water to obtain a solution A with a mass fraction of 30%; dissolve 2 parts 2-acrylamide-2-methylpropanesulfonic acid in deionized water to obtain a solution B with a mass fraction of 50%; dissolve 0.5 parts ascorbic acid and 0.5 parts mercaptoacetic acid in deionized water to obtain a solution C with a mass fraction of 1% ascorbic acid.

[0059] S2. Dissolve 100 parts of isopentenyl alcohol polyoxyethylene ether in the remaining deionized water, then add 1 part of 30% hydrogen peroxide, stir well, and then add solution A and solution B dropwise in sequence. While adding solution A and solution B, add solution C dropwise. The dropwise addition time for solution A is 2 hours, the dropwise addition time for solution B is 1.5 hours, and the dropwise addition time for solution C is 3.5 hours. After the dropwise addition is completed, react at 40°C for 3 hours. Finally, dilute with water to a solid content of 40% to obtain the water-reducing agent.

[0060] Compared with Example 3, the preparation method of the water-reducing agent in this comparative example lacks the reaction conditions of step S1.

[0061] Test case

[0062] In accordance with the relevant provisions of GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the slump, air content and bleeding rate of concrete were tested. The performance test results of the concrete are shown in Table 1.

[0063] Table 1. Concrete performance test results As can be seen from the data in Table 1, the concrete of the present invention has a slump greater than 200 mm, good fluidity, and almost no slump loss over time, exhibiting excellent slump retention performance; the bleeding rate is low (less than 1.5%), demonstrating good anti-bleeding effect. Comparative Example 1, lacking methyl 3,4-dihydroxybenzoate, experienced a slump loss exceeding 10% after 1 hour, and a significant increase in bleeding rate; Comparative Example 2, although containing methyl 3,4-dihydroxybenzoate, lacked the reaction conditions of step S1, resulting in a significantly increased slump loss and bleeding rate. This indicates that reacting the unsaturated carboxylic acid monomer with methyl 3,4-dihydroxybenzoate under alkaline conditions can effectively improve the fluidity and slump retention performance of concrete, enhancing the anti-bleeding effect of the water-reducing agent.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A type of lining concrete for large-section tunnels, characterized in that, The following components are included in parts by weight: 300-400 parts cement, 40-50 parts fly ash, 40-70 parts mineral powder, 600-650 parts fine aggregate, 1050-1150 parts coarse aggregate, 150-200 parts water, 7-11 parts water-reducing agent, and 5-10 parts air-entraining agent. The water-reducing agent comprises the following raw materials in parts by weight: 100 parts polyether macromonomer, 5-7 parts unsaturated carboxylic acid monomer, 4-6 parts methyl 3,4-dihydroxybenzoate, 2-4 parts unsaturated amide, 1.0-2.0 parts oxidant, 0.5-1.0 parts reducing agent, 0.5-1.5 parts chain transfer agent, and 300-350 parts deionized water; The preparation method of the water-reducing agent includes the following steps: S1. Dissolve unsaturated carboxylic acid monomers and methyl 3,4-dihydroxybenzoate in N,N-dimethylacetamide, then add alkali to adjust the pH of the solution to 9-10, react at 80-90℃ for 5-8 hours, and obtain the intermediate after drying; S2. Dissolve the intermediate obtained in step S1 in deionized water to obtain solution A; dissolve the unsaturated amide in deionized water to obtain solution B; dissolve the reducing agent and chain transfer agent in deionized water to obtain solution C; S3. Dissolve the polyether macromonomer in the remaining deionized water, then add the oxidant and stir until homogeneous. Then add solution A and solution B dropwise in sequence. While adding solution A and solution B, add solution C dropwise. After the addition is complete, react at 40-60℃ for 2-3 hours. Finally, dilute with water to a solid content of 30-70% to obtain the water-reducing agent.

2. The lining concrete for large-section tunnels according to claim 1, characterized in that, The coarse aggregate includes two types of crushed stone with particle sizes of 5-10mm and 10-20mm, and the weight ratio of crushed stone with a particle size of 5-10mm to crushed stone with a particle size of 10-20mm is 1:(2-3).

3. The lining concrete for large-section tunnels according to claim 1, characterized in that, The air-entraining agent is at least one of aliphatic polyoxyethylene ether sodium sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium rosinate.

4. The lining concrete for large-section tunnels according to claim 1, characterized in that, The polyether macromonomer is either isopentenyl alcohol polyoxyethylene ether or ethylene glycol monovinyl glycol ether.

5. The lining concrete for large-section tunnels according to claim 1, characterized in that, The unsaturated carboxylic acid monomer includes at least one of acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid.

6. The lining concrete for large-section tunnels according to claim 1, characterized in that, The unsaturated amide includes at least one of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and N-hydroxymethylacrylamide.

7. The lining concrete for large-section tunnels according to claim 1, characterized in that, The oxidant includes at least one of hydrogen peroxide, ammonium persulfate, and sodium persulfate; the reducing agent includes at least one of ascorbic acid, bisulfite, and thiosulfate; and the chain transfer agent is mercaptopropionic acid or mercaptoacetic acid.

8. The method for preparing lining concrete for large-section tunnels according to any one of claims 1-7, characterized in that, Includes the following steps: P1. Weigh each component according to the weight percentages; P2. Dry mix the fine aggregate and coarse aggregate evenly, then add cement, fly ash, and mineral powder and continue to dry mix evenly. Then add water-reducing agent, air-entraining agent, and water to obtain the lining concrete for the large-section tunnel.

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