A high performance concrete composition for repairing tunnel cracks and a method for preparing the same

Abstract

The application relates to the technical field of building materials, and particularly discloses a high-performance concrete composition for repairing tunnel cracks and a preparation method thereof, and the high-performance concrete composition for repairing tunnel cracks comprises the following raw materials in parts by weight: 200-220 parts of Portland cement, 40-50 parts of fly ash, 60-70 parts of mineral powder, 640-660 parts of quartz sand, 700-720 parts of gravel, 6-9 parts of a waterproof agent and 120-130 parts of water; the waterproof agent is composed of microcapsules, nano silicon dioxide and water in a mass ratio of 10-15:3-5:85-90. The high-performance concrete composition provided by the application can repair tunnel cracks and has excellent impermeability.

Description

Technical Field

[0001] This application relates to the field of building materials technology, and more specifically, it relates to a high-performance concrete composition for tunnel crack repair and its preparation method. Background Technology

[0002] As a crucial component of transportation infrastructure, tunnel engineering operates under complex geological and environmental conditions, making it susceptible to various factors such as changes in surrounding rock pressure, temperature stress, vehicle vibration, and groundwater erosion. This leads to defects in the lining structure, including cracks, spalling, and exposed reinforcement, with the problem being particularly pronounced in the curved sections of the tunnel concrete. These defects not only reduce the load-bearing capacity and stability of the tunnel structure but can also cause water leakage, seriously affecting the tunnel's traffic safety and service life.

[0003] In existing technologies, the common approach to repairing cracks in the curved sections of tunnel concrete is to add comb-shaped timbers to adjust the straight cross-section arch frame to fit the curve, then use a pump to deliver concrete into the formwork, and employ a construction scheme of segmented and layered symmetrical pouring, compaction, and sealing the arch ring with either a live or dead seal. However, this type of technology has poor impermeability and is difficult to meet practical requirements. Summary of the Invention

[0004] To address the problems in the prior art, this application provides a high-performance concrete composition for tunnel crack repair and a method for preparing the same.

[0005] This application provides a high-performance concrete composition for tunnel crack repair, which adopts the following technical solution: A high-performance concrete composition for tunnel crack repair comprises the following raw materials in parts by weight: 200-220 parts silicate cement, 40-50 parts fly ash, 60-70 parts mineral powder, 640-660 parts quartz sand, 700-720 parts crushed stone, 6-9 parts waterproofing agent, and 120-130 parts water. The waterproofing agent is composed of microcapsules, nano-silica, and water in a mass ratio of 10-15:3-5:85-90.

[0006] By adopting the above technical solution, a composite waterproofing agent made of cement, fly ash, and mineral powder ternary cementitious materials and microcapsule composite waterproofing agent is combined to achieve an integrated technical effect of targeted crack repair, seepage prevention and waterproofing, and structural reinforcement. Among them, the microcapsules can respond to the stress of tunnel crack propagation to achieve targeted slow release of the core material, quickly forming a hydrophobic film to block seepage channels. Nano-silica has high activity. On the one hand, it undergoes a secondary hydration reaction with calcium hydroxide, a cement hydration product, to generate a large amount of CSH gel, which fills the original pores of the concrete matrix and the gaps at the repair interface. On the other hand, it is adsorbed on the surface of the microcapsules to form a nano-protective layer, reducing the breakage rate of the microcapsules during mixing and grouting, ensuring the stability of the slow-release function of the core material, thereby improving the seepage prevention performance of the concrete composition.

[0007] Optionally, the method for preparing the microcapsules includes the following steps: Sodium alginate was dissolved in water and heated to 70-80℃. Ammonium persulfate was added and stirred for 30-50 minutes. Then methyl methacrylate was added and stirred for 2-3 hours. After cooling to 23-27℃, the core material was added and stirred for 30-50 minutes to form a core-wall material mixed emulsion. The core-wall material mixed emulsion was added dropwise to a crosslinking agent, filtered, washed, and dried to obtain microcapsules.

[0008] By adopting the above technical solution, ammonium persulfate decomposes upon heating to generate free radicals, which initiate the grafting of methyl methacrylate onto the sodium alginate backbone, generating an amphoteric graft polymer with a hydrophilic backbone and hydrophobic side chains. The hydrophobic side chains improve the water resistance and mechanical strength of the capsule wall. When the core-wall material mixed emulsion is dropped into the crosslinking agent solution, the carboxyl groups on the sodium alginate molecular chain rapidly coordinate and crosslink with the crosslinking agent cations, forming a uniform and dense spherical capsule wall on the surface of the emulsion droplet. The capsule wall slowly degrades in the concrete, and the polysaccharide fragments of sodium alginate can participate in the cement hydration reaction, while the side chains fill the capillary pores of the concrete, achieving a synergistic effect of capsule wall degradation and concrete mechanical enhancement.

[0009] Optionally, the mass ratio of sodium alginate, ammonium persulfate, and methyl methacrylate is 1:0.1-0.3:5-8.

[0010] Optionally, the crosslinking agent is one or both of CaCl2 and BaCl2.

[0011] Optionally, the method for preparing the core material includes the following steps: Polyglycerol fatty acid esters are added dropwise to water and mixed evenly to prepare an aqueous phase, wherein the mass ratio of polyglycerol fatty acid esters to water is 1-3:40-50; Span 80, isobutyltriethoxysilane, and PEG2000 are mixed evenly to prepare an oil phase, wherein the mass ratio of Span 80, isobutyltriethoxysilane, and PEG2000 is 20-30:500:1-3; at 40-50℃, the oil phase is added dropwise to the aqueous phase and stirred for 4-5 hours to obtain the core material.

[0012] By adopting the above technical solution, the hydrophobic groups of polyglycerol fatty acid ester face the concrete surface, while the hydrophilic groups face away from the surface. These groups are connected to water via hydrogen bonds to form a water film, hindering further penetration of water. When water flows through the concrete pores, the abundant polyglycerol structure within the pores allows the polyhydroxyl groups to form hydrogen bonds with the water, locking in the moisture and delaying its penetration, thus providing a waterproofing effect. The hydrophilic polyglycerol chains of the polyglycerol fatty acid ester combine with water, while the hydrophobic fatty acid chains interact with the oil phase, enhancing the interfacial stability of the emulsion. Simultaneously, isobutyltriethoxysilane undergoes hydrolysis to generate silanol. The polyhydroxyl groups of the polyglycerol fatty acid ester form intermolecular hydrogen bonds with the Si-OH groups of the silanol. Under constant temperature stirring, the hydrogen bond system further condenses, generating Si-OC covalent bonds and Si-O-Si covalent bonds, forming a cross-linked network. This cross-linked network allows the emulsion to penetrate into the concrete capillaries, forming a dense hydrophobic film and improving the waterproofing effect.

[0013] Optionally, the mineral powder is S95 grade mineral powder.

[0014] By adopting the above technical solution, S95 grade mineral powder has a high activity index and a high specific surface area matching degree with cement, which can fill the gaps between cement particles to form a dense packing structure.

[0015] Optionally, the crushed stone is graded crushed stone, and by mass percentage, the crushed stone with a particle size of 5-10mm accounts for 20-30%, the crushed stone with a particle size of 10-20mm accounts for 35-45%, and the crushed stone with a particle size of 20-30mm accounts for 30-40%.

[0016] By adopting the above technical solution, 20-30mm coarse crushed stone forms the skeleton, forming the main path for load transfer. Its high strength provides basic bearing capacity for the mixture. 10-20mm medium particles fill the gaps between coarse particles, reducing skeleton voids and allowing cement paste to more evenly coat the aggregate surface, accelerating the formation and coagulation of CSH gel. 5-10mm fine particles further fill the remaining voids, increasing density and thus improving the impermeability of the concrete composition.

[0017] Secondly, this application provides a method for preparing a high-performance concrete composition for tunnel crack repair, employing the following technical solution: A method for preparing a high-performance concrete composition for tunnel crack repair includes the following steps: (1) Dry mix silicate cement, fly ash and mineral powder for 2-3 minutes, then add crushed stone and quartz sand and continue to dry mix for 3-5 minutes to obtain a preliminary mixture; (2) Add water and waterproofing agent to the preliminary mixture obtained in step (1) and stir evenly to obtain a high-performance concrete composition for tunnel crack repair.

[0018] In summary, this application has the following beneficial effects: 1. In this application, a preferred compound cement, fly ash, and mineral powder cementitious material system is combined with a microcapsule-nano silica composite waterproofing agent to specifically solve the water seepage problem faced in the repair of concrete cracks in tunnel engineering. The microcapsules have stress-responsive slow release to achieve targeted self-repair of cracks, while the nano silica fills the pores through secondary hydration and adsorbs on the surface of the microcapsules to form a nano protective layer, thereby improving the impermeability of the concrete composition.

[0019] 2. In this application, ammonium persulfate is preferably used to initiate the graft polymerization of methyl methacrylate on the molecular chain of sodium alginate. The resulting composite wall material retains the cross-linking properties of sodium alginate and introduces the alkali-resistant skeleton of polymethyl methacrylate. It can exist stably in the strongly alkaline environment of cement-based materials, effectively preventing premature leakage of the core material.

[0020] 3. In this application, silane-modified emulsion is preferably used as the core material. The ethoxy group in the silane molecule can undergo a hydrolysis-condensation reaction with the hydroxyl group in the concrete hydration products to generate Si-O-Si covalent bonds, firmly grafting the silane molecule onto the pore wall of the concrete matrix. The silane molecule itself also undergoes a cross-linking reaction to form a three-dimensional hydrophobic network structure. At the same time, the hydrophobic groups of the polyglycerol fatty acid ester face the concrete surface, while the hydrophilic groups face away from the surface and are connected to water through hydrogen bonds to form a water film, which prevents further water penetration and plays a waterproof role. When water flows through the concrete pores, the interior contains a large number of polyglycerol structures, and the polyhydroxy groups will form hydrogen bonds with the water to lock in the water, delaying the water penetration and playing a waterproof role. Detailed Implementation

[0021] The following embodiments provide a further detailed description of this application.

[0022] Example of core material preparation

[0023] Source of raw materials: Polyglycerol fatty acid esters are selected from Guangzhou Anrui Food Ingredients Co., Ltd., with an effective substance content of 99%.

[0024] Preparation Example 1-1: 3 kg of polyglycerol fatty acid ester was dropped into 50 kg of water and mixed evenly to prepare an aqueous phase. 30 kg of Span 80, 500 kg of isobutyltriethoxysilane and 3 kg of PEG2000 were mixed evenly to prepare an oil phase. The oil phase was dropped into the aqueous phase and stirred for 5 h to obtain the core material.

[0025] Preparation Example 1-2: 2 kg of polyglycerol fatty acid ester was dropped into 45 kg of water and mixed evenly to prepare an aqueous phase. 25 kg of Span 80, 500 kg of isobutyltriethoxysilane and 2 kg of PEG2000 were mixed evenly to prepare an oil phase. The oil phase was dropped into the aqueous phase and stirred for 4.5 h to obtain the core material.

[0026] Preparation Examples 1-3: 1 kg of polyglycerol fatty acid ester was dropped into 40 kg of water and mixed evenly to prepare an aqueous phase. 20 kg of Span 80, 500 kg of isobutyltriethoxysilane and 1 kg of PEG2000 were mixed evenly to prepare an oil phase. The oil phase was dropped into the aqueous phase and stirred for 4 h to obtain the core material.

[0027] Preparation Example 1-4: The difference from Preparation Example 1-1 is that polyglycerol fatty acid esters were not added. 30 kg of Span 80, 500 kg of isobutyltriethoxysilane and 3 kg of PEG2000 were mixed evenly to prepare an oil phase, and stirred for 5 h to obtain the core material.

[0028] Example of microcapsule preparation

[0029] Source of raw materials: Sodium alginate was selected from Yiwu Guohu Trading Co., Ltd., with an effective content of 99%; methyl methacrylate was selected from Jinan Anqi Chemical Co., Ltd.

[0030] Preparation Example 2-1: 1 kg of sodium alginate was dissolved in 50 kg of water, heated to 80 °C, 0.3 kg of ammonium persulfate was added, and the mixture was stirred for 50 min. Then, 8 kg of methyl methacrylate was added, and the mixture was stirred for 3 h. After cooling to 27 °C, the core material was added, and the mixture was stirred for 50 min to form a core-wall material mixed emulsion. The core-wall material mixed emulsion was added dropwise to a crosslinking agent, filtered, washed three times with water, and dried at 60 °C for 8 h to obtain microcapsules. The core material was prepared in Preparation Example 1-1.

[0031] Preparation Example 2-2: 1 kg of sodium alginate was dissolved in 50 kg of water, heated to 75 °C, 0.2 kg of ammonium persulfate was added, and the mixture was stirred for 40 min. Then, 6 kg of methyl methacrylate was added, and the mixture was stirred for 2.5 h. After cooling to 25 °C, the core material was added, and the mixture was stirred for 40 min to form a core-wall material mixed emulsion. The core-wall material mixed emulsion was added dropwise to a crosslinking agent, filtered, washed three times with water, and dried at 60 °C for 8 h to obtain microcapsules. The core material was prepared in Preparation Example 1-2.

[0032] Preparation Example 2-3: 1 kg of sodium alginate was dissolved in 50 kg of water, heated to 70 °C, 0.1 g of ammonium persulfate was added, and the mixture was stirred for 30 min. Then, 5 kg of methyl methacrylate was added, and the mixture was stirred for 2 h. After cooling to 23 °C, the core material was added, and the mixture was stirred for 30 min to form a core material-wall material mixed emulsion. The core material-wall material mixed emulsion was added dropwise to the crosslinking agent, filtered, washed three times with water, and dried at 60 °C for 8 h to obtain microcapsules. The core material was prepared from Preparation Example 1-3.

[0033] Preparation Example 2-4: The difference from Preparation Example 2-1 is that sodium alginate was not added. The core material was added to methyl methacrylate and stirred for 30 min to form a core material-wall material mixed emulsion. The core material-wall material mixed emulsion was added dropwise to the crosslinking agent, filtered, washed with water three times, and dried at 60°C for 8 h to obtain microcapsules.

[0034] Preparation Example 2-5: The difference from Preparation Example 2-1 is that methyl methacrylate was not added. 1 kg of sodium alginate was dissolved in 50 kg of water, the core material was added, and the mixture was stirred for 50 min to form a core material-wall material mixed emulsion. The core material-wall material mixed emulsion was added dropwise to the crosslinking agent, filtered, washed three times with water, and dried at 60 °C for 8 h to obtain microcapsules.

[0035] Preparation Example 2-6: The difference from Preparation Example 2-1 is that the core material is prepared by Preparation Example 1-4.

[0036] Example of waterproofing agent preparation

[0037] Preparation Example 3-1: 15 kg of microcapsules and 5 kg of nano-silica were added to 90 kg of water and stirred for 50 min to obtain a waterproofing agent. The microcapsules were prepared in Preparation Example 2-1.

[0038] Preparation Example 3-2: 13 kg of microcapsules and 4 kg of nano-silica were added to 88 kg of water and stirred for 50 min to obtain a waterproofing agent. The microcapsules were prepared in Preparation Example 2-2.

[0039] Preparation Example 3-3: 10 kg of microcapsules and 3 kg of nano-silica were added to 85 kg of water and stirred for 50 min to obtain a waterproofing agent. The microcapsules were prepared in Preparation Example 2-3.

[0040] Preparation Example 3-4: The difference from Preparation Example 3-1 is that the microcapsules were prepared by Preparation Example 2-4.

[0041] Preparation Example 3-5: The difference from Preparation Example 3-1 is that the microcapsules were prepared by Preparation Example 2-5.

[0042] Preparation Example 3-6: The difference from Preparation Example 3-1 is that the microcapsules were prepared by Preparation Example 2-6.

[0043] Preparation Example 3-7: The difference from Preparation Example 3-1 is that no microcapsules were added. 5 kg of nano-silica was added to 90 kg of water and stirred for 50 min to obtain a waterproofing agent.

[0044] Preparation Example 3-8: The difference from Preparation Example 2-1 is that no nano-silica was added. 15 kg of microcapsules were added to 90 kg of water and stirred for 50 min to obtain a waterproofing agent.

[0045] Example

[0046] Example 1: A high-performance concrete composition for tunnel crack repair, the raw material composition of which is shown in Table 1. In Table 1, the silicate cement is selected from Hebei Maikemani Mineral Products Co., Ltd., and the type is white cement; the crushed stone is from Jinshi Quarry in Lintao County, Gansu Province, and the crushed stone is divided into three grades: 5-10mm, 10-20mm, and 20-30mm, accounting for 20%, 45%, and 35% respectively; the fly ash is selected from Lingshou Xincheng New Materials Co., Ltd., with the product number XC123; the quartz sand is selected from Shijiazhuang Jiarui Mineral Products Co., Ltd., with the product number SF-Y; the mineral powder is selected from Hebei Kexu Building Materials Co., Ltd., with a purity of 98; and the water is selected from tap water.

[0047] A method for preparing a high-performance concrete composition for tunnel crack repair includes the following steps: (1) Dry mix cement, fly ash and mineral powder for 3 minutes, then add crushed stone and sand and continue to dry mix for 5 minutes to obtain a preliminary mixture; (2) Add water and waterproofing agent to the preliminary mixture obtained in step (1) and stir evenly to obtain a high-performance concrete composition for tunnel crack repair. The waterproofing agent is prepared by preparation example 3-1 and the raw material dosage is shown in Table 1.

[0048] Table 1. Raw material proportions of high-performance concrete compositions in Examples 1-4 Silicate cement 220 210 205 200 fly ash 50 48 45 40 Mineral powder 70 68 65 60 gravel 720 710 705 700 Quartz sand 660 650 645 640 water 130 128 125 120 Waterproofing agent 9 8 7 6 Example 2: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared by Preparation Example 3-2, and the raw material amounts are shown in Table 1.

[0049] Example 3: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared by Preparation Example 3-3, and the raw material amounts are shown in Table 1.

[0050] Example 4: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in the amount of raw materials used, as shown in Table 1.

[0051] Example 5: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared in Examples 3-4.

[0052] Example 6: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared in Examples 3-5.

[0053] Example 7: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared by Examples 3-6.

[0054] Comparative Example

[0055] Comparative Example 1: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared by Examples 3-7.

[0056] Comparative Example 2: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that the waterproofing agent is prepared by Examples 3-8.

[0057] Comparative Example 3: A high-performance concrete composition for tunnel crack repair, which differs from Example 1 in that no waterproofing agent is added.

[0058] Performance testing

[0059] High-performance concrete compositions were prepared according to the methods in the examples and comparative examples, and their performance was tested according to the following methods. The test data are recorded in Table 2.

[0060] 1. Compressive strength and impermeability Concrete specimens were placed in a standard curing chamber for 7 days and 28 days (temperature 20±2℃, relative humidity ≥95%). The compressive strength and impermeability of the high-performance concrete composition were tested at 7 days and 28 days in accordance with the "Standard for Test Methods of Physical and Mechanical Properties of Concrete GB / T 50081-2019".

[0061] Table 2. Test data of the high-performance concrete compositions prepared in the examples and comparative examples.

[0062] Example 1 60.2 63.5 4.6 Example 2 60.0 63.3 4.5 Example 3 59.7 63.1 4.3 Example 4 59.6 63.0 4.2 Example 5 56.2 59.5 3.9 Example 6 55.4 58.7 3.8 Example 7 52.2 55.3 3.5 Comparative Example 1 50.1 53.2 3.2 Comparative Example 2 51.7 54.5 3.3 Comparative Example 3 48.3 51.9 3.0 As can be seen from Examples 1-4 and Table 2, the concrete composition prepared in this application has excellent compressive strength and impermeability.

[0063] As can be seen from Examples 1, 5, and 6, the impermeability of Examples 5 and 6 is reduced, indicating that the grafting of methyl methacrylate onto the sodium alginate backbone can generate a composite wall material that retains the cross-linking properties of sodium alginate while introducing the alkali-resistant skeleton of polymethyl methacrylate. This allows it to exist stably in the strongly alkaline environment of cement-based materials, effectively preventing premature leakage of the core material.

[0064] Combining Examples 1 and 7, it can be seen that the impermeability of Example 7 is reduced, indicating that the hydrophobic groups of the polyglycerol fatty acid ester face the concrete surface, while the hydrophilic groups face away from the surface. Furthermore, the polyglycerol fatty acid ester forms a water film with water through hydrogen bonds, which prevents water from penetrating further and thus plays a waterproof role, thereby improving the impermeability.

[0065] Combining Example 1 and Comparative Examples 1-2, it can be seen that the impermeability of Comparative Examples 1-2 is reduced, indicating that the microcapsules play a stress-relieving role and achieve targeted self-repair of cracks. The nano silica fills the pores through secondary hydration and is adsorbed on the surface of the microcapsules to form a nano protective layer, thereby improving the impermeability of the concrete composition.

[0066] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-performance concrete composition for tunnel crack repair, characterized in that, Including the following parts by weight of raw materials: 200-220 parts silicate cement, 40-50 parts fly ash, 60-70 parts mineral powder, 640-660 parts quartz sand, 700-720 parts crushed stone, 6-9 parts waterproofing agent, and 120-130 parts water. The waterproofing agent is composed of microcapsules, nano-silica, and water in a mass ratio of 10-15:3-5:85-90.

2. The high-performance concrete composition for tunnel crack repair according to claim 1, characterized in that, The method for preparing the microcapsules includes the following steps: Sodium alginate was dissolved in water and heated to 70-80℃. Ammonium persulfate was added and stirred for 30-50 minutes. Then methyl methacrylate was added and stirred for 2-3 hours. After cooling to 23-27℃, the core material was added and stirred for 30-50 minutes to form a core-wall material mixed emulsion. The core-wall material mixed emulsion was added dropwise to a crosslinking agent, filtered, washed, and dried to obtain microcapsules.

3. The high-performance concrete composition for tunnel crack repair according to claim 2, characterized in that, The mass ratio of sodium alginate, ammonium persulfate, and methyl methacrylate is 1:0.1-0.3:5-8.

4. The high-performance concrete composition for tunnel crack repair according to claim 2, characterized in that, The crosslinking agent is one or both of CaCl2 and BaCl2.

5. The high-performance concrete composition for tunnel crack repair according to claim 2, characterized in that, The method for preparing the core material includes the following steps: Polyglycerol fatty acid esters are added dropwise to water and mixed evenly to prepare an aqueous phase, wherein the mass ratio of polyglycerol fatty acid esters to water is 1-3:40-50; Span 80, isobutyltriethoxysilane, and PEG2000 are mixed evenly to prepare an oil phase, wherein the mass ratio of Span 80, isobutyltriethoxysilane, and PEG2000 is 20-30:500:1-3; at 40-50℃, the oil phase is added dropwise to the aqueous phase and stirred for 4-5 hours to obtain the core material.

6. The high-performance concrete composition for tunnel crack repair according to claim 1, characterized in that, The mineral powder is S95 grade mineral powder.

7. The high-performance concrete composition for tunnel crack repair according to claim 1, characterized in that, The crushed stone is graded crushed stone, and by mass percentage, the crushed stone with a particle size of 5-10mm accounts for 20-30%, the crushed stone with a particle size of 10-20mm accounts for 35-45%, and the crushed stone with a particle size of 20-30mm accounts for 30-40%.

8. A method for preparing a high-performance concrete composition for tunnel crack repair according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Dry mix silicate cement, fly ash and mineral powder for 2-3 minutes, then add crushed stone and quartz sand and continue to dry mix for 3-5 minutes to obtain a preliminary mixture; (2) Add water and waterproofing agent to the preliminary mixture obtained in step (1) and stir evenly to obtain a high-performance concrete composition for tunnel crack repair.