A concrete bubble regulating agent suitable for high altitude areas and a preparation method thereof

Abstract

The application discloses a concrete bubble regulating agent suitable for high-altitude areas and a preparation method thereof, and the concrete bubble regulating agent comprises the following raw materials in parts of mass: modified polyvinyl alcohol film coating solution 8-25 parts, rosin modified air entraining agent 62-77 parts, ammonium persulfate 0.5-2 parts and glutaraldehyde 0.1-1 part. The concrete bubble regulating agent has the advantages of low mixing amount, large air entraining amount and good bubble stabilizing effect, can simplify the use steps of the concrete admixture, reduce the comprehensive use cost, and simultaneously solve the problems of low concrete bubble content and high bubble loss rate in high-altitude areas, and has remarkable economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a concrete bubble regulator suitable for high-altitude areas and its preparation method. Background Technology

[0002] Air-entraining agents are commonly used in engineering to improve the pore structure of concrete, thereby enhancing its durability. However, in high-altitude concrete projects, it has been found that with increasing altitude, the low air pressure in high-altitude areas increases the surface tension of air bubbles in the concrete, reducing the quality of air entrainment and bubble formation. This results in larger pores and poorer uniformity of bubble distribution. Consequently, the air-entraining capacity and bubble stabilization ability of air-entraining agents are significantly lower than in plains areas, making air entrainment in fresh concrete increasingly difficult. Compared to concrete in plains areas, with the same dosage of air-entraining agent, fresh concrete in high-altitude areas has a lower air content, an increased bubble spacing coefficient, and reduced freeze-thaw durability after hardening. Increasing the dosage of air-entraining agent, while increasing the air content of concrete, leads to a larger number of bubbles, which in turn deteriorates the pore structure of the concrete, ultimately reducing its durability.

[0003] To address the challenges of air entrainment and low bubble stability in concrete under low-pressure conditions at high altitudes, numerous scholars have conducted related research. Studies have revealed that problems such as cracking and insufficient early strength caused by the complex environment of high-altitude regions require compounding air-entraining agents with other components for effective solutions. Patent CN119430735A discloses a solid air-entraining agent suitable for low-pressure areas at high altitudes. By using rubber powder aggregates with carbon nanotubes and nano-zinc oxide, it improves the interfacial adhesion of the cement matrix, reduces the formation of interconnected pores, and significantly extends the service life of buildings, demonstrating significant practical application value. Patent CN118459148A discloses a composite air-entraining agent. By adding hard water-resistant components and foam stabilizers to the air-entraining agent, it improves the workability of concrete and enhances the construction efficiency of concrete projects in high-altitude regions.

[0004] The aforementioned techniques for improving the applicability of air-entraining agents in high-altitude areas all involve adding specific components to reduce the number of large air bubbles and stabilize small air bubbles that are beneficial to the workability of concrete, thereby improving the adaptability of concrete in high-altitude, low-pressure regions. However, the number of air bubbles in concrete is difficult to control, and relying solely on existing air bubbles is unlikely to improve its workability. Furthermore, studies have found that small air bubbles with a size within 500 μm have a relatively small impact on concrete strength, but a significant effect on improving concrete pumpability; existing research has paid little attention to this type of bubble. Conventional air-entraining agents lack specific engineering application requirements and cannot meet the complex and variable high-altitude environment, leading to severe degradation of concrete performance and seriously affecting project quality. Therefore, there is an urgent need to develop a new type of concrete air bubble regulator suitable for high-altitude areas to improve the pumpability and durability of concrete. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a concrete bubble regulator suitable for high-altitude areas and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, a concrete air bubble regulator suitable for high-altitude areas is provided, comprising the following raw materials by mass parts: 8-25 parts of modified polyvinyl alcohol coating solution, 62-77 parts of rosin-modified air-entraining agent, 0.5-2 parts of ammonium persulfate, and 0.1-1 parts of glutaraldehyde.

[0008] Further, the modified polyvinyl alcohol coating solution comprises the following components by mass parts: 15-20 parts polyvinyl alcohol, 1-5 parts nano silica, 1-4 parts glycerol, 0.8-2 parts vinyl hydroxyl silicone oil, 0.05-1.0 parts polysorbate-80, 0.05-0.3 parts polydimethylsiloxane, and 150-300 parts deionized water;

[0009] The degree of polymerization of the polyvinyl alcohol is 1700 to 2400.

[0010] Furthermore, the modified polyvinyl alcohol coating solution is prepared as follows:

[0011] SA1. Mix polyvinyl alcohol with deionized water and heat to 85-95°C, stirring and dispersing until completely dissolved to form a transparent first solution;

[0012] SA2, Mix polydimethylsiloxane with vinyl hydroxyl silicone oil to form a second solution;

[0013] SA3. Divide polysorbate-80 into two portions. The mass of the first portion is 1 / 5 of the sum of the masses of polydimethylsiloxane and vinyl hydroxyl silicone oil. Use the first portion of polysorbate-80 to pre-emulsify the second solution.

[0014] SA4. After the first solution is cooled to 50-60°C, add glycerin and the second part of polysorbate-80 in sequence and stir for 10 minutes. Then slowly add the pre-emulsified second solution and disperse it under high-speed shear at 2000-3000 rpm for 30 minutes.

[0015] SA5. Reduce the stirring speed to 500-800 rpm and maintain the temperature at 50-60°C for 1-2 hours to obtain a uniform and transparent colloid.

[0016] SA6. Add nano-silica to the colloid and ultrasonically disperse for 20-30 minutes to obtain the modified polyvinyl alcohol coating solution.

[0017] The present invention can control the bubble control ability by adjusting the amount of polydimethylsiloxane in the modified polyvinyl alcohol coating solution and the reaction time.

[0018] Further, the rosin-modified air-entraining agent comprises the following components by mass parts: 50-70 parts rosin resin, 5-15 parts maleic anhydride, 0.5-2.0 parts p-toluenesulfonic acid, 10-20 parts propylene glycol methyl ether acetate, 1-5 parts triethanolamine, 0.5-3.0 parts lignin sulfonate, 0.5-3 parts pH adjuster, 0.1-1% sodium benzoate, and 160-250 parts deionized water.

[0019] Furthermore, the softening point of the rosin resin is 80-100°C, and the pH adjuster is sodium hydroxide or citric acid.

[0020] Furthermore, the preparation method of the rosin-modified air-entraining agent is as follows:

[0021] SB1. Pulverize rosin resin to a particle size ≤100μm and add it to the reaction vessel, then heat to 120~140℃ to melt it;

[0022] SB2. Add maleic anhydride to the reactor, stir at 800-1200 rpm and control the reaction temperature at 120-130℃; add p-toluenesulfonic acid as a catalyst, react for 2-3 hours to produce maleic anhydride-grafted rosin ester.

[0023] SB3. Add propylene glycol methyl ether acetate to the reactor, cool to 80-90°C, reduce the stirring speed to 500-800 rpm, add deionized water dropwise and lignin sulfonate to form a pre-emulsion, and continue stirring for 30 minutes.

[0024] SB4. Add triethanolamine to the reaction vessel, then add sodium benzoate as a stabilizer, and stir for 10-15 minutes; add pH adjuster dropwise, and then emulsify at high speed for 30 minutes to form a stable emulsion with a particle size ≤5μm, which is the rosin modified air-entraining agent.

[0025] Furthermore, in the SB4, the rotational speed of the high-speed shearing is 8000–12000 rpm.

[0026] The present invention can regulate the air-entraining capacity by adjusting the dosage of rosin-modified air-entraining agent.

[0027] On the other hand, a method for preparing a concrete bubble regulator suitable for high-altitude areas is provided, comprising the following steps:

[0028] S1. Add the modified polyvinyl alcohol coating solution to the rosin modified air-entraining agent and maintain the temperature at 50-60℃; then add ammonium persulfate and glutaraldehyde and react for 2-4 hours to form a reaction solution, wherein the reaction solution is a core-shell structure of polyvinyl alcohol coated with rosin resin.

[0029] S2. The reaction solution is centrifuged and filtered to remove impurities, and then spray-dried to adjust the solid content to 20-30 wt%, thus obtaining the concrete bubble regulator.

[0030] Furthermore, in step S2, the parameters for spray drying are as follows: inlet air temperature 160–180°C, outlet air temperature 80–100°C, and atomization pressure 0.2–0.4 MPa.

[0031] Furthermore, the concrete bubble regulator is a powder with a particle size ≤50μm.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The concrete bubble regulator of the present invention has advantages such as low dosage, large air entrainment, and good bubble stabilization effect. It can simplify the use steps of concrete admixtures, reduce the overall cost of use, and solve the problems of low bubble content and high bubble loss rate in concrete in high-altitude areas, resulting in significant economic and social benefits.

[0034] 2. This invention utilizes a modified polyvinyl alcohol (PVA) coating solution to form a dense film layer (i.e., a core-shell structure of PVA-coated rosin resin) on the surface of the rosin resin of the modified air-entraining agent through a cross-linking reaction. This slows down the dissolution rate of the air-entraining agent in concrete and prolongs the bubble stabilization time (≥2 hours). Simultaneously, the introduction of defoaming components (vinyl hydroxyl silicone oil and polydimethylsiloxane) into the modified PVA coating solution can eliminate larger bubbles during concrete mixing, improving the foam stabilization ability of the paste.

[0035] 3. In this invention, nano-silica is embedded in the polyvinyl alcohol coating layer for modification, which enhances the mechanical strength of the film layer and reduces bubble coalescence (average bubble pore size ≤200μm).

[0036] 4. No organic solvents are used in the preparation process of this invention, and the wastewater can be directly discharged after pH adjustment, making it green and environmentally friendly. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1

[0039] As a preferred embodiment of the present invention, the concrete air bubble regulator applicable to high-altitude areas in this embodiment includes the following raw materials by mass: 8 parts of modified polyvinyl alcohol coating solution, 65 parts of rosin modified air-entraining agent, 0.5 parts of ammonium persulfate, and 0.2 parts of glutaraldehyde.

[0040] Example 2

[0041] As a preferred embodiment of the present invention, the concrete air bubble regulator applicable to high-altitude areas in this embodiment includes the following raw materials by mass parts: 15 parts modified polyvinyl alcohol coating solution, 70 parts rosin modified air-entraining agent, 0.6 parts ammonium persulfate, and 0.2 parts glutaraldehyde.

[0042] Comparative Example

[0043] The bubble control agent in this comparative example differs from those in Examples 1 and 2 in that the modified polyvinyl alcohol coating solution is not added to the rosin-modified air-entraining agent, but is directly incorporated into the concrete mixture to exert its air-entraining effect.

[0044] Test case

[0045] Simulating low-pressure environments (80kPa and 50kPa), the air-absorbing agents from Examples 1, 2, and the comparative example were used to prepare reference concrete according to the proportions in Table 1 below. The air content and 28-day strength loss of the concrete were tested according to the national standard GB / T 50080-2016, "Test Method for Performance of Ordinary Concrete Mixtures." The specific operating procedure is as follows: ① Weigh the raw materials according to the proportions and load them into the mixer. Dry mix for 15 seconds in the low-pressure test chamber. Dissolve the air-absorbing agent in water and add it to the water tank. During mixing, the water supply from the tank is controlled by a solenoid valve. ② Close the chamber door, set the specified pressure and temperature, and start the low-pressure test chamber. ③ After the pressure and temperature reach the set values ​​and stabilize for 1 minute, start the mixer and simultaneously open the solenoid valve to add water. Once all the water has been added, start timing. Mix for 120 seconds, then close the mixer and the low-pressure test chamber. The air content of the freshly mixed concrete is tested within 5 minutes. ④ Maintain the pressure and let stand for 30 minutes, then mix again for 120 minutes. After mixing, test the air content of the concrete. The gas content of each group was tested three times and the average value was taken.

[0046] Table 1 Concrete mix proportions (kg / m³) 3 )

[0047] 436 90 701 977 6.05 1.73 170

[0048] Concrete specimens were prepared in a low-pressure test chamber according to Table 1, with concrete specimens prepared without air-filling agents used as the baseline group. The specimens were cured in a standard curing room for 28 days to test their compressive strength, and the 28-day strength loss rate of the concrete was calculated. The test results are shown in Table 2 below:

[0049] Table 2 Test Results of Examples

[0050]

[0051]

[0052] As can be seen from the test results in Table 2, the bubble regulator provided by this invention can increase the air content of concrete under low pressure conditions and keep the air content of concrete at a high level for a period of time, while significantly reducing the 28-day strength loss of concrete, thereby improving the overall performance of concrete.

[0053] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A concrete bubble regulator suitable for high-altitude areas, characterized in that, It includes the following raw materials by mass parts: 8-25 parts modified polyvinyl alcohol coating solution, 62-77 parts rosin modified air-entraining agent, 0.5-2 parts ammonium persulfate, and 0.1-1 parts glutaraldehyde; The modified polyvinyl alcohol coating solution comprises the following components by mass parts: 15-20 parts polyvinyl alcohol, 1-5 parts nano silica, 1-4 parts glycerin, 0.8-2 parts vinyl hydroxyl silicone oil, 0.1-0.5 parts polysorbate-80, 0.05-0.3 parts polydimethylsiloxane, and 150-300 parts deionized water. The degree of polymerization of the polyvinyl alcohol is 1700~2400.

2. The concrete bubble regulator suitable for high-altitude areas according to claim 1, characterized in that, The modified polyvinyl alcohol coating solution is prepared as follows: SA1. Mix polyvinyl alcohol with deionized water and heat to 85~95℃, stirring and dispersing until completely dissolved to form a transparent first solution; SA2, Mix polydimethylsiloxane with vinyl hydroxyl silicone oil to form a second solution; SA3. Divide polysorbate-80 into two portions. The mass of the first portion is 1 / 5 of the sum of the masses of polydimethylsiloxane and vinyl hydroxyl silicone oil. Use the first portion of polysorbate-80 to pre-emulsify the second solution. SA4. After the first solution is cooled to 50~60℃, add glycerin and the second part of polysorbate-80 in sequence and stir for 10 minutes. Then slowly add the pre-emulsified second solution and disperse it under high-speed shear at 2000~3000 rpm for 30 minutes. SA5. Reduce the stirring speed to 500~800 rpm and stir at 50~60℃ for 1~2 hours to obtain a uniform and transparent colloid. SA6. Add nano-silica to the colloid and ultrasonically disperse for 20-30 minutes to obtain the modified polyvinyl alcohol coating solution.

3. The concrete bubble regulator suitable for high-altitude areas according to claim 1, characterized in that, The rosin-modified air-entraining agent comprises the following components by mass parts: 50-70 parts rosin resin, 5-15 parts maleic anhydride, 0.5-2.0 parts p-toluenesulfonic acid, 10-20 parts propylene glycol methyl ether acetate, 1-5 parts triethanolamine, 0.5-3.0 parts lignin sulfonate, 0.5-3 parts pH adjuster, 0.1-1% sodium benzoate, and 160-250 parts deionized water.

4. The concrete bubble regulator suitable for high-altitude areas according to claim 3, characterized in that, The softening point of the rosin resin is 80~100℃, and the pH adjuster is sodium hydroxide or citric acid.

5. A concrete bubble regulator suitable for high-altitude areas according to claim 3, characterized in that, The preparation method of the rosin-modified air-entraining agent is as follows: SB1. Pulverize rosin resin to a particle size ≤100μm and add it to the reaction vessel, then heat to 120~140℃ to melt it; SB2. Add maleic anhydride to the reactor, stir at 800-1200 rpm and control the reaction temperature at 120-130℃; add p-toluenesulfonic acid as a catalyst, react for 2-3 hours to produce maleic anhydride-grafted rosin ester. SB3. Add propylene glycol methyl ether acetate to the reactor, cool to 80-90°C, reduce the stirring speed to 500-800 rpm, add deionized water dropwise and lignin sulfonate to form a pre-emulsion, and continue stirring for 30 minutes. SB4. Add triethanolamine to the reaction vessel, then add sodium benzoate as a stabilizer, and stir for 10-15 minutes; add pH adjuster dropwise, and then emulsify at high speed for 30 minutes to form a stable emulsion with a particle size ≤5μm, which is the rosin modified air-entraining agent.

6. The concrete bubble regulator suitable for high-altitude areas according to claim 5, characterized in that, In the SB4, the high-speed shearing speed is 8000~12000 rpm.

7. A method for preparing a concrete bubble regulator suitable for high-altitude areas according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Add the modified polyvinyl alcohol coating solution to the rosin modified air-entraining agent and maintain the temperature at 50~60℃; then add ammonium persulfate and glutaraldehyde and react for 2~4 hours to form a reaction solution, wherein the reaction solution is a core-shell structure of polyvinyl alcohol coated with rosin resin. S2. The reaction solution is centrifuged and filtered to remove impurities, and then spray-dried to adjust the solid content to 20~30wt%, thus obtaining the concrete bubble regulator.

8. A method for preparing a concrete bubble regulator suitable for high-altitude areas according to claim 7, characterized in that, In S2, the parameters for spray drying are as follows: inlet air temperature 160~180℃, outlet air temperature 80~100℃, and atomization pressure 0.2~0.4 MPa.

9. A method for preparing a concrete bubble regulator suitable for high-altitude areas according to claim 8, characterized in that, The concrete bubble regulator is a powder with a particle size ≤50μm.

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