Concrete raw material, top-surface bubble-free concrete sleeper pouring method and application

Abstract

This invention belongs to the field of building materials technology, and specifically provides a concrete raw material. By mass percentage, the concrete raw material includes 20-33% sulfoaluminate cement, 2-8% silica fume, 0.5-3% polymer emulsion, 0.05-0.15% water-reducing agent, 0.01-0.06% retarder, 0.03-0.10% early-strength agent, 0.01-0.06% expansion agent, 0.01-0.09% defoamer, 0.04-0.11% anti-settling agent, 0.05-0.13% fiber, 27-33% sand, and 29-40% crushed stone. The concrete raw materials and the method for pouring concrete sleepers with no air bubbles on the top surface provided by this invention not only ensure the performance requirements of the concrete material in the treatment project of sleeper defects in double-block ballastless track of high-speed railway, but also achieve the construction effect of zero air bubbles on the surface of the cast-in-place sleeper concrete after demolding. This meets the stringent requirements of rail fastener installation on the size and density of the sleeper bearing platform surface, while improving the durability and aesthetics of the sleeper concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to concrete raw materials, a method for pouring concrete sleepers with no air bubbles on the top surface, and their application. Background Technology

[0002] Concrete is a building material made by mixing various raw materials in a certain proportion. During the mixing process, a certain number of air bubbles are inevitably introduced. These air bubbles exist in different sizes: those larger than 100μm are considered large harmful bubbles, those between 100-50μm are moderately harmful bubbles, those between 50-20μm are low-harm or harmless bubbles, and those smaller than 20μm are considered beneficial bubbles. From a concrete structural theory perspective, the voids formed by these tiny air bubbles smaller than 50μm fall into the capillary range, or are considered harmless or low-harm pores. They not only do not reduce strength but also greatly improve the durability of concrete. Therefore, in general concrete production, by selecting superior raw materials, adjusting the mixing process, and adding admixtures (defoamers), harmful air bubbles larger than 50μm can be effectively eliminated, ensuring stable concrete quality.

[0003] However, some projects with special requirements for the smoothness and flatness of concrete surfaces, such as fair-faced concrete, have even stricter requirements regarding the number of air bubbles in the concrete, demanding a "zero-bubble" effect on the concrete surface after demolding. This is generally achieved by using specialized molds, specialized release agents, and special fair-faced concrete formulations. However, due to the rising and aggregation effect of air bubbles, a "zero-bubble" effect on the surface of fair-faced concrete can only be achieved on the sides or bottom of the concrete; demolding the top surface of the concrete cannot achieve a "zero-bubble" effect. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that the existing technology cannot achieve a "zero-bubble" effect after demolding of the concrete top surface.

[0005] Therefore, the present invention provides a concrete raw material, which, by weight percentage, comprises 20-33% sulfoaluminate cement, 2-8% silica fume, 0.5-3% polymer emulsion, 0.05-0.15% water-reducing agent, 0.01-0.06% retarder, 0.03-0.10% early-strength agent, 0.01-0.06% expansion agent, 0.01-0.09% defoamer, 0.04-0.11% anti-settling agent, 0.05-0.13% fiber, 27-33% sand, and 29-40% crushed stone.

[0006] Specifically, the aforementioned early strength agents include one or more of lithium carbonate, calcium formate, or sodium sulfate.

[0007] Specifically, the aforementioned fibers include one or more of polypropylene fibers, glass fibers, or basalt fibers.

[0008] Specifically, the particle size of the aforementioned crushed stone is 4.75-9.5mm.

[0009] The present invention also provides a method for pouring concrete sleepers with no air bubbles on the top surface, comprising the following steps:

[0010] (1) Prepare a sleeper mold, fix it on the existing rail and seal it;

[0011] (2) Prepare the above concrete raw materials according to the specified proportions;

[0012] (3) Mix the concrete raw materials with water, stir evenly, and let stand to defoam;

[0013] (4) After defoaming, the concrete is poured into the sleeper mold. After molding, the sleeper mold is removed and the fastening device is installed.

[0014] Specifically, in step (1) above, the top surface of the sleeper mold is made of breathable steel.

[0015] Specifically, within 10 minutes after the defoamed concrete in step (4) is poured into the sleeper mold, the surface of the mold is evacuated by a vacuum pump to help remove air.

[0016] Specifically, in step (3) above, the mass ratio of water to concrete raw materials is (0.11-0.15):1.

[0017] Specifically, in step (3) above, the stirring time is 3-5 min and the stirring rate is 20-30 r / min.

[0018] The concrete raw materials and the method for pouring concrete sleepers with no air bubbles on the top surface provided by this invention can be used for cast-in-place sleepers in high-speed railways, especially for the repair of double-block ballastless track sleepers.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] The concrete raw materials and the method for pouring concrete sleepers with no air bubbles on the top surface provided by this invention not only ensure the performance requirements of the concrete material in the treatment project of sleeper defects in double-block ballastless track of high-speed railway, but also achieve the construction effect of zero air bubbles on the surface of the cast-in-place sleeper concrete after demolding. This meets the stringent requirements of rail fastener installation on the size and density of the sleeper bearing platform surface, while improving the durability and aesthetics of the sleeper concrete.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a front view of the sleeper mold in Embodiment 2 of the present invention.

[0023] Figure 2 This is a top view of the sleeper mold in Embodiment 2 of the present invention.

[0024] Figure 3 This is a schematic diagram of the funnel-shaped attention device structure in Embodiment 2 of the present invention.

[0025] Figure 4 This is a schematic diagram of the concrete sleeper in Embodiment 2 of the present invention.

[0026] Figure 5 This is a schematic diagram of concrete sleeper laying in Embodiment 2 of the present invention.

[0027] Figure 6 This is a schematic diagram of the concrete sleeper prepared according to Comparative Example 1 of the present invention.

[0028] Figure 7 This is a schematic diagram of the concrete sleeper prepared in Comparative Example 2 of the present invention.

[0029] Reference numerals: 1. Rail; 2. Sleeper mold; 201. Ventilated steel top surface; 202. Feed inlet; 203. Overflow outlet; 3. Bolt; 4. Storage hopper; 5. Control valve; 6. Hoist. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0031] This invention provides a concrete raw material, which, by weight percentage, comprises 20-33% sulfoaluminate cement, 2-8% silica fume, 0.5-3% polymer emulsion, 0.05-0.15% water-reducing agent, 0.01-0.06% retarder, 0.03-0.10% early-strength agent, 0.01-0.06% expansion agent, 0.01-0.09% defoamer, 0.04-0.11% anti-settling agent, 0.05-0.13% fiber, 27-33% sand, and 29-40% crushed stone.

[0032] Optionally, the polymer emulsion is a styrene-butadiene emulsion; the water-reducing agent is a powdered polycarboxylate water-reducing agent; the retarder is one or more of boric acid, tartaric acid, or citric acid; the early strength agent is one or more of lithium carbonate, calcium formate, or sodium sulfate; the expanding agent is one or more of gypsum, calcium oxide, or calcium sulfoaluminate; the defoamer is an organosilicon defoamer or a mineral oil defoamer; the anti-settling agent is one or more of cellulose ether, bentonite, or silica fume; the fiber is one or more of polypropylene fiber, glass fiber, or basalt fiber, with a length of 3-9 mm; the sand is ordinary river sand or Zone II sand; and the crushed stone is clean crushed stone with a particle size range of 4.75-9.5 mm.

[0033] The performance indicators of concrete raw materials were tested, and the results are shown in Table 1.

[0034] Table 1 Performance Indicators

[0035]

[0036] The present invention also provides a method for pouring concrete sleepers with no air bubbles on the top surface, comprising the following steps:

[0037] (1) Prepare a sleeper mold, fix it on the existing rail and seal it.

[0038] The top surface of the sleeper mold is preferably made of 3D printed breathable steel material, while other parts are made of Cr12 mold steel. The top surface of the sleeper mold is provided with a feed port and an overflow port.

[0039] (2) Prepare the above concrete raw materials according to the proportion.

[0040] (3) Mix the concrete raw materials with water, and control the water-to-material ratio at 0.11-0.15. Use a forced mixer to mix for 3-5 minutes at a mixing speed of 20-30 r / min. After mixing evenly, let it stand to defoam.

[0041] (4) After defoaming, the concrete is poured into the sleeper mold. Within 10 minutes after the pouring stops, the surface of the mold is evacuated using a vacuum pump to help remove air. After molding, the sleeper mold is removed and the fasteners are installed.

[0042] The effects of the concrete raw materials and the concrete sleeper pouring method with no air bubbles on the top surface of the present invention will be studied through specific embodiments below.

[0043] Example 1:

[0044] This embodiment provides a concrete raw material, which, by mass percentage, comprises 28% sulfoaluminate cement (42.5 grade), 4% silica fume (Grade I), 1.6% styrene-butadiene emulsion, 0.08% powdered polycarboxylate superplasticizer, 0.04% boric acid, 0.05% lithium carbonate, 0.03% gypsum, 0.04% organosilicon defoamer, 0.06% cellulose ether, 0.1% polypropylene fiber (length 3-9 mm), 30% ordinary river sand (Zone II sand), and 36% clean crushed stone with a particle size range of 4.75-9.5 mm.

[0045] The above raw materials are mixed with water, and the water-to-material ratio is controlled at 0.13. The concrete is mixed for 3 minutes using a forced mixer at a mixing speed of 25 r / min. The mixing volume for each pour can be controlled at about 100L. The properties of the prepared concrete are shown in Table 2.

[0046] Table 2 Concrete Material Properties

[0047]

[0048] Example 2:

[0049] This embodiment provides a method for pouring concrete sleepers with no air bubbles on the top surface, including the following steps:

[0050] (1) As Figure 1-2 A sleeper mold 2 is prepared. The top surface of the mold is made of 3D-printed breathable steel material to form a breathable steel top surface 201, while other parts are made of Cr12 mold steel. A feed port 202 and an overflow port 203 are opened on the top surface of the sleeper mold 2. The sleeper mold 2 is fixed to the existing rail 1 with bolts 3, and the bottom of the sleeper mold 2 is sealed to the top surface of the track bed slab using a sealant.

[0051] (2) Configure the concrete raw materials in Example 1 according to the proportion.

[0052] (3) Mix the concrete raw materials with water, and control the water-to-material ratio at 0.13. Use a forced mixer with a volume of 150-200L to mix for 3 minutes at a mixing speed of 25r / min. The amount of concrete mixed each time can be controlled at about 100L depending on the amount of concrete poured. After mixing evenly, add a sloping chute at the discharge port of the mixer to transfer the freshly mixed concrete to a container and let it stand for 6 minutes to defoam.

[0053] (4) A funnel-type grouting device is used for grouting. A control valve 5 is added to the bottom of the storage hopper 4 to facilitate grout discharge and control the flow rate. The grouting flow rate is controlled at 5L / min. At the same time, a 60mm diameter hose 6 is connected to the bottom grout outlet. The other end of the hose 6 is inserted into the feed inlet 202 of the sleeper mold 2. The storage hopper 4 has a capacity of 50L and an overall height of 1 meter. The structure is as follows: Figure 3As shown.

[0054] After defoaming is complete, pour the settled concrete material into the storage hopper 4 of the grouting equipment. During the feeding process, keep the control valve 5 closed. Once the slurry reaches the designated liquid level, open the lower control valve 5 to release the material. Control the slurry flow rate through the control valve 5.

[0055] After slurry flows out of the overflow port 203 on the shoulder side, close the control valve 5 to stop the injection, remove the feed hose 6, and continue to add an appropriate amount of slurry to the feed port 202 and the overflow port 203 to keep the feed port 202 and the overflow port 203 fully filled.

[0056] Within 10 minutes after the concrete pouring of sleeper mold 2 is stopped, a vacuum pump is used to vent air from the surface of sleeper mold 2. The sleeper mold is removed 3 days later, completing the concrete sleeper pouring and installing the fastening devices.

[0057] The concrete sleeper prepared in this embodiment is as follows: Figure 4-5 As shown, in accordance with the "CRTS Double-Block Ballastless Track Concrete Sleeper" TB / T 3397-2015, the appearance quality and dimensions of the cured concrete sleeper were inspected. The inspection results met all the requirements of the standard, and the concrete surface of the rail bearing part was free of air bubbles and defects, with a smooth and even surface and uniform color, meeting the requirements of functional use and aesthetic appearance.

[0058] Comparative Example 1:

[0059] This comparative example provides a method for pouring concrete sleepers, including the following steps:

[0060] (1) As Figure 1-2 The sleeper mold is prepared by using 3D-printed breathable steel for the top surface and Cr12 mold steel for other parts. A feed inlet and an overflow outlet are provided on the top surface of the sleeper mold. The sleeper mold is then bolted to the existing rail, and a sealant is used to seal the bottom of the sleeper mold to the top surface of the track bed slab.

[0061] (2) Prepare concrete materials, 1m 3 The concrete composition comprises: water: cement: mineral admixtures: sand: crushed stone: admixtures = 129.6 kg: 432 kg: 47 kg: 729 kg: 1189 kg: 5.64 kg. The water is ordinary tap water, the cement is PO42.5 ordinary Portland cement, the fly ash is Grade I fly ash, the sand is river sand (fineness modulus 2.7, Zone II medium sand), the crushed stone is 5-20mm continuously graded crushed stone, and the admixture is polycarboxylate superplasticizer (solid content 21%).

[0062] (3) Mix the concrete raw materials in step (2) and use a forced mixer with a volume of 150-200L to mix for 3 minutes. The mixing speed is 25r / min. The amount of mixing each time can be controlled at about 100L according to the amount of pouring. After mixing evenly, add a sloping chute at the discharge port of the mixer to transfer the freshly mixed concrete to the container and let it stand for 6 minutes to defoam.

[0063] (4) A funnel-type injection device is used for injection. A control valve is added to the bottom of the storage hopper to facilitate slurry discharge and control the flow rate. The injection flow rate is controlled at 5L / min. At the same time, a 60mm diameter hose is connected to the bottom slurry outlet, and the other end of the hose is inserted into the mold inlet. The storage hopper has a capacity of 50L and an overall height of 1 meter. The structure is as follows: Figure 3 As shown.

[0064] After defoaming, pour the settled concrete material into the hopper of the grouting equipment. During the feeding process, keep the control valve closed. Once the slurry reaches the designated liquid level, open the lower control valve to release the material. Control the slurry flow rate through the control valve.

[0065] After slurry flows out of the overflow port on one side of the shoulder, close the control valve to stop the injection, remove the feed hose, and continue to add an appropriate amount of slurry to the feed port and overflow port to keep them fully filled.

[0066] Within 10 minutes of stopping the pouring of the sleeper mold, a vacuum pump is used to vent air from the surface of the mold. Three days later, the sleeper mold is removed, and fastening devices are installed to complete the concrete sleeper pouring.

[0067] The concrete sleepers prepared in this comparative example are as follows: Figure 6 As shown, in accordance with the "CRTS Double-Block Ballastless Track Concrete Sleeper" TB / T 3397-2015, the appearance quality and dimensions of the cured concrete sleeper were inspected. The inspection results showed that the maximum length and depth of the air pores on the concrete surface of the rail bearing part exceeded the standard requirements and could not meet the standard requirements. In addition, there were a large number of air pore defects of different sizes on the concrete surface of the rail bearing part, resulting in poor appearance and failing to meet the on-site requirements.

[0068] Comparative Example 2:

[0069] This comparative example provides a method for pouring concrete sleepers, including the following steps:

[0070] (1) The sleeper mold is made of Cr12 mold steel, and the feed port and overflow port are opened on the top surface of the sleeper mold. The sleeper mold is fixed to the existing rail with bolts, and the bottom of the sleeper mold and the top surface of the track bed are sealed with a sealant.

[0071] (2) Configure the concrete raw materials in Example 1 according to the proportion.

[0072] (3) Mix the concrete raw materials with water, and control the water-to-material ratio at 0.13. Use a forced mixer with a volume of 150-200L to mix for 3 minutes at a mixing speed of 25r / min. The amount of concrete mixed each time can be controlled at about 100L depending on the amount of concrete poured. After mixing evenly, add a sloping chute at the discharge port of the mixer to transfer the freshly mixed concrete to a container and let it stand for 6 minutes to defoam.

[0073] (4) A funnel-type injection device is used for injection. A control valve is added to the bottom of the storage hopper to facilitate slurry discharge and control the flow rate. The injection flow rate is controlled at 5L / min. At the same time, a 60mm diameter hose is connected to the bottom slurry outlet, and the other end of the hose is inserted into the mold inlet. The storage hopper has a capacity of 50L and an overall height of 1 meter. The structure is as follows: Figure 3 As shown.

[0074] After defoaming, pour the settled concrete material into the hopper of the grouting equipment. During the feeding process, keep the control valve closed. Once the slurry reaches the designated liquid level, open the lower control valve to release the material. Control the slurry flow rate through the control valve.

[0075] After slurry flows out of the overflow port on one side of the shoulder, close the control valve to stop the injection, remove the feed hose, and continue to add an appropriate amount of slurry to the feed port and overflow port to keep them fully filled.

[0076] After 3 days, the sleeper molds are removed, and fasteners are installed to complete the concrete sleeper pouring.

[0077] The concrete sleepers prepared in this comparative example are as follows: Figure 7 As shown, in accordance with the "CRTS Double-Block Ballastless Track Concrete Sleeper" TB / T 3397-2015, the appearance quality and dimensions of the cured concrete sleeper were inspected. The inspection results showed that the maximum length and depth of the air pores on the concrete surface of the rail bearing part exceeded the standard requirements and could not meet the standard requirements. In addition, there were a large number of air pore defects of different sizes on the concrete surface of the rail bearing part, resulting in poor appearance and failing to meet the on-site requirements.

[0078] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for pouring concrete sleepers with no air bubbles on the top surface, characterized in that, Includes the following steps: (1) Prepare a sleeper mold, fix it on the existing rail and seal it; the top surface of the sleeper mold is made of breathable steel; (2) Concrete raw materials are prepared in proportion; by mass percentage, the concrete raw materials include 20-33% sulfoaluminate cement, 2-8% silica fume, 0.5-3% polymer emulsion, 0.05-0.15% water-reducing agent, 0.01-0.06% retarder, 0.03-0.10% early strength agent, 0.01-0.06% expansion agent, 0.01-0.09% defoamer, 0.04-0.11% anti-settling agent, 0.05-0.13% fiber, 27-33% sand and 29-40% crushed stone; the sand is river sand from Zone II; the particle size of the crushed stone is 4.75-9.5mm; (3) Mix the concrete raw materials with water, stir evenly, and let stand to defoam; (4) Within 10 minutes after the defoamed concrete is poured into the sleeper mold, the surface of the mold is vented by a vacuum pump. After molding, the sleeper mold is removed and the fastener device is installed.

2. The method for pouring concrete sleepers with no air bubbles on the top surface as described in claim 1, characterized in that: The early strength agent includes one or more of lithium carbonate, calcium formate, or sodium sulfate.

3. The method for pouring concrete sleepers with no air bubbles on the top surface as described in claim 1, characterized in that: The fiber includes one or more of polypropylene fiber, glass fiber, or basalt fiber.

4. The method for pouring concrete sleepers with no air bubbles on the top surface as described in claim 1, characterized in that: In step (3), the mass ratio of water to concrete raw materials is (0.11-0.15):

1.

5. The method for pouring concrete sleepers with no air bubbles on the top surface as described in claim 1, characterized in that: In step (3), the stirring time is 3-5 min and the stirring rate is 20-30 r / min.

6. The application of the concrete sleeper pouring method with no air bubbles on the top surface as described in any one of claims 1-5 in the repair of double-block ballastless track sleepers.

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