Micro-nano self-healing type rebound loss reducing and enhancing agent for shotcrete, preparation method and production equipment

Abstract

The present application provides a kind of micro-nano self-healing type reduces shotcrete rebound amount enhancer, preparation method and production equipment, according to weight percentage, raw material includes nano composite material 30-40%, double fast cement 45-50%, early strength agent 3-8%, mineral activator 2-10%, healing crystallization catalyst 8-15%, nanometer carbon fiber 0.1-2%, the total of each raw material is 100%, utilize the high adsorption of micro-nano material to improve the cohesion of shotcrete, increase the compactness of concrete, further let mineral activator activate micro-nano powder and accelerate cementitious material to accelerate hydration, shorten the setting time of concrete, improve early strength;Nanometer carbon fiber increases the adhesion of cement and aggregate, improves the volume stability of concrete, reduces the rebound amount of shotcrete, ensures early and late strength.Shotcrete service process, such as if not dense, water seepage appears, self-healing crystallization catalyst meets water and activates unhydrated cement hydration, generates crystal to block leakage point, which can reduce the maintenance cost in later period.

Description

Technical Field

[0001] This invention relates to admixtures for building concrete, and in particular, to a micro-nano self-healing shotcrete rebound enhancer, its preparation method, and production equipment. Background Technology

[0002] Shotcrete is a commonly used material for the initial support and reinforcement of tunnels, and it relies on the self-bonding and compressive strength of concrete to support the structure.

[0003] Shotcrete is applied by spraying concrete onto rock layers or steel mesh using external machinery, and then solidifies in a very short time with the help of quick-setting agents and other admixtures. The absence of vibration during this process will affect the density of the concrete. In addition, the short setting time means that a large amount of cementitious material is not hydrated. These defects will affect the strength and durability of the concrete. During the shotcrete application process, it can cause concrete to fall off, increase the amount of concrete rebound, and increase the cost of the project.

[0004] Currently, most techniques involve adding thickeners to increase concrete viscosity, thereby improving concrete bond strength and reducing rebound. However, this overlooks the risk that thickeners may interact negatively with water-reducing agents. Inaccurate control of the amount of thickener added can prevent water-reducing agents from effectively increasing the flowability of concrete, thus affecting later construction performance. Other techniques increase concrete strength by adding ultrafine or nano-powders, but neglect the non-vibration process of shotcrete. In addition, the short setting time means that a large amount of cementitious material remains unhydrated, failing to improve the density of concrete later and affecting its serviceability in humid environments. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides an admixture that reduces concrete rebound and increases density. By adding this admixture, the hydration of cementitious materials can be accelerated, the bond between cement and aggregate can be increased, the rebound of shotcrete can be reduced, and early and late strength can be guaranteed. At the same time, the self-healing crystallization catalyst can stimulate the hydration of unhydrated cement to generate crystals, thereby improving the structural density.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a micro-nano self-healing sprayed concrete rebound enhancer, which, by weight percentage, comprises 30% to 40% nanocomposite materials, 45% to 50% quick-setting cement, 3% to 8% early-strength agent, 2% to 10% mineral activator, 8% to 15% healing crystallization catalyst, and 0.1% to 2% nano carbon fiber, with the total of all raw materials being 100%.

[0007] As a preferred embodiment of the present invention, the early strength agent includes one or a mixture of potassium sulfate, sodium sulfate, calcium formate, calcium nitrate, calcium nitrite, sodium carbonate, lithium carbonate, or calcium carbonate.

[0008] As a preferred embodiment of the present invention, the fast-acting cement includes one of sulfoaluminate cement, aluminate cement, or 72.5 grade high-strength sulfoaluminate cement.

[0009] As a preferred embodiment of the present invention, the mineral activator includes one or a mixture of several of potassium silicate, sodium silicate, sodium fluorosilicate, potassium hydroxide, or sodium hydroxide.

[0010] As a preferred embodiment of the present invention, the healing crystallization catalyst comprises one or a mixture of several of ethylenediaminetetraacetic acid, ethylenediaminetetramethylene phosphoric acid, sodium citrate, or sodium aluminate.

[0011] As a preferred embodiment of the present invention, the diameter of the carbon nanofiber is 50-200 nm and the length is distributed in the range of 50-100 μm.

[0012] As a preferred embodiment of the present invention, all the above materials are mixed uniformly in a certain proportion to prepare the product, and the dosage is 6 to 10% of the weight of the cementitious material.

[0013] The present invention also discloses a preparation method, wherein the raw material components of the nanocomposite material include 30%–40% nano-calcium carbonate, 10%–20% silica fume, 25%–35% ultrafine slag powder, 8%–12% nano-silica, and 0.5%–3% dispersant; The nanocomposite material is prepared by a two-stage air separation filtration method, and the specific preparation method includes the following steps: S1. The ultrafine slag powder is blown into the ball mill by a blower, a dispersant is added, and the ball milling time is controlled at 30min to 70min. The ground powder is then classified by the first air classification to separate the powder with a particle size of less than 2um. S2. The three raw materials, nano-calcium carbonate, silica fume and nano-silica, are blown into the mixing silo and mixed evenly using a high-speed mixer. The mixer speed is controlled at 5000 r / min and the mixing time is controlled at 50 min to 80 min. Then, the powder with a particle size of less than 0.1 μm is screened out by an air classifier. S3. Blow the powder prepared in steps S1 and S2 into the mixing chamber, stir at high speed for 30 minutes, with the speed controlled at 3500 r / min and the time controlled at 30 minutes, to obtain the nanocomposite material.

[0014] The present invention also discloses a production device, including a workbench, a rotating frame, a fixed frame, and a feeding hopper. The rotating frame is rotatably connected to the workbench, and the fixed frame is fixed to the side wall of the rotating frame and used to clamp and store bags. The feeding hopper is slidably connected to the workbench. The rotating frame is connected to a drive ring through an adjustment mechanism. A limiting groove is formed on the surface of the drive ring. A transmission wheel is rotatably connected to the side wall of the feeding hopper. The transmission wheel is rolled on the surface of the drive ring. A feeding assembly is provided on the side wall of the workbench. The lower end of the feeding hopper has a feeding port. A sealing plate is provided on the side wall of the feeding hopper. When the transmission wheel moves into the limiting groove, the feeding assembly moves the sealing plate away from the feeding port.

[0015] In a preferred embodiment of the present invention, the adjusting mechanism includes a fixed rod, a screw sleeve, a positioning disc, an elastic pressure plate, and a positioning ring. The positioning ring is fixed on the rotating frame and located outside the drive ring, and the positioning ring is coaxially arranged with the rotating frame. The fixed rod is fixedly connected to the rotating frame and is coaxially arranged with the rotating frame. The positioning disc is sleeved on the fixed rod. A plurality of elastic pressure plates are fixed to the edge of the positioning disc and are evenly distributed along the axis of the positioning disc. The screw sleeve is threadedly connected to the fixed rod and, after being pressed against the positioning disc, the end of the elastic pressure plate is pressed against the inner wall of the drive ring.

[0016] In summary, the present invention has the following beneficial effects: (1) Avoid using thickeners and use micro-nano composite materials to increase the viscosity of concrete, reduce the rebound of shotcrete, and reduce the incompatibility problem with concrete water-reducing agents; (2) The nucleation effect of micro and nano materials can be used to improve the early and late strength of concrete. At the same time, the addition of healing crystallization catalyst can stimulate the unreacted cementitious materials to continue to hydrate, fill the pores in the spraying process, and increase the density of concrete. This has a positive effect on reducing engineering costs and improving the service life of buildings. Attached Figure Description

[0017] Figure 1 To illustrate the structural diagram of the workbench; Figure 2 for Figure 1 Enlarged view of point A; Figure 3 To illustrate the structural diagram of the rotating frame; Figure 4 for Figure 3 Enlarged view of point B; Figure 5 This is a schematic diagram illustrating the position of the servo motor.

[0018] Reference numerals: 11. Workbench; 12. Rotating frame; 13. Fixed frame; 131. Fixed plate; 132. Clamping plate; 133. Clamping cylinder; 14. Feed hopper; 141. Feed port; 15. Servo motor; 2. Slide rod; 3. Drive ring; 31. Limiting groove; 32. Transmission wheel; 4. Adjustment mechanism; 41. Fixed rod; 42. Screw sleeve; 43. Positioning plate; 44. Elastic pressure plate; 45. Positioning ring; 5. Sealing plate; 6. Feeding assembly; 61. Elastic element; 62. Gear; 63. Rack; 64. Crossbar; 65. Linkage rod; 66. Guide slope; 7. Connecting rod. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, so that the technical solution of the present invention can be more easily understood and mastered.

[0020] A micro-nano self-healing sprayed concrete rebound enhancer, by weight percentage, comprises nanocomposite materials, fast-acting cement, early strength agent, mineral activator, healing crystallization catalyst, and nano carbon fiber, with the total of all raw materials being 100%.

[0021] The raw material components of nanocomposite materials include nano-calcium carbonate, silica fume, ultrafine slag powder, nano-silica, and dispersant.

[0022] The nanocomposite material is prepared by a two-stage air separation filtration method, and the specific preparation method includes the following steps: S1. The ultrafine slag powder is blown into the ball mill by a blower, a dispersant is added, and the ball milling time is controlled at 45 minutes. The ground powder is then classified by the first air classification to separate the powder with a particle size of less than 2 μm.

[0023] S2. The three raw materials, nano-calcium carbonate, silica fume, and nano-silica, are blown into the mixing silo and mixed evenly using a high-speed mixer. The mixer speed is controlled at 5000 r / min and the mixing time is controlled at 50 min. Then, the powder with a particle size of less than 0.1 μm is screened out by an air classifier.

[0024] S3. Blow the powder prepared in steps S1 and S2 into the mixing chamber, stir at high speed for 30 minutes, with the speed controlled at 3500 r / min and the time controlled at 30 minutes, to obtain the nanocomposite material.

[0025] The above materials are mixed evenly in a certain proportion to prepare the product, with an admixture amount of 6-10% of the weight of the cementitious material.

[0026] Early strength agents include one or a mixture of potassium sulfate, sodium sulfate, calcium formate, calcium nitrate, calcium nitrite, sodium carbonate, lithium carbonate, or calcium carbonate.

[0027] Dual-fast cement includes one of sulfoaluminate cement, aluminate cement, or 72.5 grade high-strength sulfoaluminate cement.

[0028] Mineral activators include one or a mixture of potassium silicate, sodium silicate, sodium fluorosilicate, potassium hydroxide, or sodium hydroxide.

[0029] The healing crystallization catalyst includes one or a mixture of several of ethylenediaminetetraacetic acid, ethylenediaminetetramethylene phosphoric acid, sodium citrate, or sodium aluminate.

[0030] The diameter of the carbon nanofibers ranges from 50 to 200 nm, and the length ranges from 50 to 100 μm.

[0031] Example 1: A micro / nano self-healing shotcrete rebound enhancer, comprising, by weight percentage, 35% nanocomposite materials, 45% quick-setting cement, 5% sodium sulfate, 4% sodium fluorosilicate, 10% ethylenediaminetetraacetic acid, and 1% nano-carbon fiber, uniformly mixed in a certain proportion. The raw material components of the nanocomposite materials include 37% nano-calcium carbonate, 15% silica fume, 35% ultrafine slag powder, 12% nano-silica, and 1% dispersant.

[0032] Example 2: The difference from Example 1 is the difference in the proportion of components, including: 30% nanocomposite material, 48.5% quick-setting cement, 4% sodium sulfate, 6% sodium fluorosilicate, 10% ethylenediaminetetraacetic acid, and 1.5% carbon nanofibers, which are mixed uniformly in a certain proportion.

[0033] Comparative Example 1: The difference from Example 1 is that Comparative Example 1 does not contain any nanocomposite material components, and includes: 35% silica fume, 45% cement, 5% sodium sulfate, 4% sodium fluorosilicate, 10% ethylenediaminetetraacetic acid, and 1% carbon nanofibers, which are uniformly mixed in a certain proportion.

[0034] Comparative Example 2: The difference from Example 1 is that Comparative Example 2 does not contain a self-healing crystallization catalyst. The remaining components include: 35% nanocomposite material, 45% cement, 5% sodium sulfate, 4% sodium fluorosilicate, 10% inert limestone powder, and 1% carbon nanofibers, which are mixed uniformly in a certain proportion.

[0035] (1) In accordance with the relevant provisions of GB / T35159-2017 "Accelerating Agent for Shotcrete", test the setting time of cement paste and the 1-day compressive strength ratio of cement mortar; conduct a shotcrete test in accordance with the relevant provisions of JGJ372-2016 "Technical Specification for Application of Shotcrete" and test the rebound rate. (2) The self-healing performance of the self-healing, temperature-suppressing, and waterproof composite material was tested according to T / CECS913-2021 "Standard for Test Method of Self-Healing Performance of Cement Concrete". In Examples 1, 2, Comparative Example 1, and 2, the waterproof material was added as an admixture at 1% of the mass fraction of the concrete cementitious material (cement), and the baseline group was the group without the addition of nano-self-healing shotcrete rebound enhancer. The test results are shown in Table 1.

[0036]

[0037] Analysis of the results in Table 1 shows that, compared to the baseline group, the addition of the nano-self-healing shotcrete rebound enhancer in Example 1 resulted in a shorter setting time, a significant increase in the 1-day compressive strength of the cement paste, and a 28-day relative permeability coefficient of 10%, which is superior to the baseline group. Compared to Comparative Example 1, Example 1 without the nano-composite material showed a prolonged cement setting time, increased mass loss leading to a lower rebound rate, and a significant decrease in the strength of the cement paste. Compared to Comparative Example 2, the removal of the self-healing crystallization catalyst significantly reduced the 28-day relative permeability coefficient, indicating that the self-healing crystallization catalyst promotes the hydration of unreacted cementitious materials, which helps to block pores, reduce the permeability rate, and increase density, thus improving the matrix strength.

[0038] The present invention also discloses a production device, including a workbench 11, a rotating frame 12, a fixed frame 13, and a feeding hopper 14. The rotating frame 12 is driven and rotatably connected to the workbench 11 by a servo motor 15, and is placed horizontally. The rotating frame 12 is coaxially arranged with the power shaft of the servo motor 15. The fixed frame 13 is fixed to the side wall of the rotating frame 12 and is used to clamp and store bags; multiple fixed frames 13 are evenly distributed along the axis of the rotating frame 12.

[0039] The fixing frame 13 includes a fixing plate 131, a clamping plate 132, and a clamping cylinder 133. The fixing plate 131 is fixedly connected to the side wall of the rotating frame 12. The ends of the clamping plate 132 are opposite to those of the fixing plate 131. The clamping cylinder 133 is fixedly connected to the fixing plate 131, and its telescopic shaft is fixedly connected to the clamping plate 132. When the clamping cylinder 133 is activated, the clamping plate 132 can move closer to or further away from the fixing plate 131, so that the clamping plate 132 and the fixing plate 131 can clamp the packaging bag or separate the clamping plate 132 and the fixing plate 131 from the packaging bag. Two fixing frames 13 form a group and are used to clamp the two sides of the packaging bag respectively to keep the packaging bag stable.

[0040] After the raw materials are mixed as described above, the finished product is obtained. After being weighed, the finished product is placed in the feeding hopper 14. The finished product is then injected into each packaging bag sequentially from the feeding hopper 14.

[0041] A slide rod 2 is fixedly connected to the workbench 11, and the feed hopper 14 is slidably connected to the slide rod 2. The rotating frame 12 is connected to the drive ring 3 through the adjustment mechanism 4. The drive ring 3 is coaxially arranged with the rotating frame 12. The drive ring 3 is rotated along the axis of the rotating frame 12 to adjust the angle, and then the drive ring 3 is positioned by the adjustment structure.

[0042] The adjustment mechanism 4 includes a fixed rod 41, a screw sleeve 42, a positioning disc 43, elastic pressure plates 44, and a positioning ring 45. The positioning ring 45 is fixed to the rotating frame 12 and located outside the drive ring 3, and is coaxially arranged with the rotating frame 12. The fixed rod 41 is fixedly connected to the rotating frame 12 and is coaxially arranged with it. The positioning disc 43 is sleeved on the fixed rod 41, making the positioning disc 43 coaxial with the fixed rod 41. Multiple elastic pressure plates 44 are fixed to the edge of the positioning disc 43 and are evenly distributed along the axis of the positioning disc 43. The screw sleeve 42 is threaded onto the fixed rod 41 and abuts against the upper surface of the positioning plate 43. As the screw sleeve 42 moves down along the fixed rod 41, the positioning plate 43 drives the elastic pressure plate 44 to move down. The surface of the elastic pressure plate 44 abuts against the upper surface of the rotating frame 12, and then the elastic pressure plate 44 is bent and the end of the elastic pressure plate 44 abuts against the inner wall of the drive ring 3. The resulting friction achieves the positioning of the drive ring 3.

[0043] Because multiple elastic pressure plates 44 simultaneously abut against the inner wall of the drive ring 3, the drive ring 3 can be subjected to more uniform force, and at the same time, the drive ring 3 can be placed more stably.

[0044] Multiple limiting grooves 31 are formed on the upper surface of the drive ring 3, and the multiple limiting grooves 31 are evenly distributed along the axis of the drive ring 3. A transmission wheel 32 is rotatably connected to the side wall of the feeding hopper 14. The transmission wheel 32 is rolled on the surface of the drive ring 3. When the limiting groove 31 corresponds to the transmission wheel 32, due to gravity, the transmission wheel 32 rolls in the limiting groove 31 and drives the feeding hopper 14 to move down synchronously to enter the packaging bag.

[0045] A feeding assembly 6 is provided on the side wall of the workbench 11. The lower end of the feeding hopper 14 has a feeding port 141. A sealing plate 5 is provided on the side wall of the feeding hopper 14. When the transmission wheel 32 moves into the limiting groove 31, the feeding assembly 6 moves the sealing plate 5 away from the feeding port 141, and then the finished product falls into the packaging bag.

[0046] The feeding assembly 6 includes an elastic element 61, a gear 62, a rack 63, a crossbar 64, a linkage rod 65, and a guide ramp 66. The linkage rod 65 is fixedly connected to the worktable 11. The guide ramp 66 is formed at the upper end of the linkage rod 65. The crossbar 64 is fixed to the sealing plate 5, so that the crossbar 64 abuts against the guide ramp 66.

[0047] A connecting rod 7 is fixedly connected to the side wall of the sealing plate 5. A rack 63 is fixed to the connecting rod 7 and placed horizontally. A gear 62 is rotatably connected to the side wall of the hopper 14. Two racks 63 are located on the upper and lower sides of the gear 62 respectively and are both meshed with the gear 62. When one rack 63 moves, through the transmission action of the gear 62, the two racks 63 can move synchronously in opposite directions. This allows the two sealing plates 5 to move simultaneously in opposite directions, achieving a rapid material unloading process. The two ends of the elastic element 61 are fixedly connected to the two sealing plates 5 respectively.

[0048] Following the above, after the hopper 14 is located inside the packaging bag, the guide slope 66 on the linkage rod 65 abuts against the crossbar 64, thereby causing the crossbar 64 to drive one sealing plate 5 to move away from the hopper 14. Then, through the transmission of the gear 62 and the rack 63, the other sealing plate 5 moves synchronously, so that the finished product can quickly fall into the packaging bag from between the two sealing plates 5.

[0049] Subsequently, the servo motor 15 drives the rotating frame 12 to continue rotating, and the transmission wheel 32 moves upward along the limiting groove 31, causing the feeding hopper 14 to move upward synchronously, separating the crossbar 64 from the linkage rod 65. Through the elastic force of the elastic element 61, the ends of the two sealing plates 5 abut against each other, blocking the feeding port 141. As the transmission wheel 32 continues to roll, the feeding hopper 14 moves out of the packaging bag.

[0050] The width of the packaging bag is much larger than the width of the hopper 14. The distance between the two fixing brackets 13 is less than the width of the packaging bag, allowing the packaging bag to remain open.

[0051] By rotating the aforementioned drive ring 3, the timing of the downward movement of the hopper 14 can be adjusted to facilitate equipment debugging.

[0052] As the servo motor 15 drives the rotating frame 12 to rotate continuously, the packaging bags located on the rotating frame 12 can be filled. Compared with the existing technology that requires stopping the machine to fill the packaging bags, this greatly improves production efficiency. Furthermore, relying on gravity for transmission reduces the use of electrical equipment, improves operational stability, and reduces production costs while saving energy.

[0053] Of course, the above are just typical examples of the present invention. In addition, the present invention may have many other specific embodiments. All technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection claimed by the present invention.

Claims

1. A micro / nano self-healing shotcrete rebound enhancer, characterized in that: By weight percentage, the raw materials include 30%–40% nanocomposite materials, 45%–50% fast-setting cement, 3%–8% early-strength agent, 2%–10% mineral activator, 8%–15% healing crystallization catalyst, and 0.1%–2% carbon nanofibers, with the total of all raw materials being 100%. The healing crystallization catalyst includes one or a mixture of several of ethylenediaminetetraacetic acid, ethylenediaminetetramethylene phosphoric acid, sodium citrate, or sodium aluminate. The carbon nanofibers have a diameter of 50–200 nm and a length distribution of 50–100 μm. The mineral activator is sodium fluorosilicate. The fast-setting cement includes one of sulfoaluminate cement and aluminate cement. The raw material components of the nanocomposite material include 30%–40% nano-calcium carbonate, 10%–20% silica fume, 25%–35% ultrafine slag powder, 8%–12% nano-silica, and 0.5%–3% dispersant; The nanocomposite material is prepared by a two-stage air separation filtration method, and the specific preparation method includes the following steps: S1. The ultrafine slag powder is blown into the ball mill by a blower, a dispersant is added, and the ball milling time is controlled at 30min to 70min. The ground powder is then classified by the first air classification to separate the powder with a particle size of less than 2um. S2. The three raw materials, nano-calcium carbonate, silica fume and nano-silica, are blown into the mixing silo and mixed evenly using a high-speed mixer. The mixer speed is controlled at 5000 r / min and the mixing time is controlled at 50 min to 80 min. Then, the powder with a particle size of less than 0.1 μm is screened out by an air classifier. S3. Blow the powder prepared in steps S1 and S2 into the mixing chamber, stir at high speed for 30 minutes, with the speed controlled at 3500 r / min and the time controlled at 30 minutes, to obtain the nanocomposite material.

2. The micro / nano self-healing shotcrete rebound enhancer according to claim 1, characterized in that: The early strength agent includes one or a mixture of several of the following: potassium sulfate, sodium sulfate, calcium formate, calcium nitrate, calcium nitrite, sodium carbonate, and lithium carbonate.

3. The micro / nano self-healing shotcrete rebound enhancer according to any one of claims 1-2, characterized in that: The above materials are mixed evenly in a certain proportion to prepare the product, with an admixture amount of 6-10% of the weight of the cementitious material.

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