Multifunctional concrete external curing agent as well as preparation method and application thereof

Abstract

The invention discloses a multifunctional concrete external curing agent and a preparation method and application thereof, and belongs to the technical field of concrete admixtures, the multifunctional concrete external curing agent comprises the following raw materials by weight: 40-85 parts of a water-based resin emulsion, 1-3 parts of thermal expansion microspheres, 0.3-5 parts of a coalescing agent, 0.02-0.06 part of an antifoaming agent, and 0-1 part of a pH regulator. The multifunctional concrete external curing agent provided by the invention has synergistic composite functions, has excellent environmental protection property, and meets the requirements of green and environment-friendly building materials. The product provided by the invention can replace a traditional curing process, is suitable for concrete engineering under severe conditions of high temperature, dryness, strong wind and the like, remarkably improves the construction efficiency, reduces the curing cost, and has a wide market value.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, and particularly relates to a multifunctional concrete external curing agent, its preparation method and application. Background Technology

[0002] If concrete is not cured in a timely manner after construction, its internal moisture will evaporate to the outside through the capillary pores of the system, leading to incomplete hydration of the cementitious materials and a reduction in hydration products, thus causing a decline in a series of concrete properties. In particular, shrinkage cracks and structural loosening caused by excessively rapid moisture evaporation will reduce the strength and durability of the concrete. Therefore, it is particularly important to take effective curing measures to reduce or avoid moisture evaporation during the plastic stage of concrete. Moreover, a large number of engineering practices have shown that the migration and loss of moisture, as well as the strain gradient caused by uneven temperature changes, play an important role in the initiation, cracking, and propagation of concrete cracks or defects. In summer, high temperatures, low humidity, and rapid drying can lead to faster setting and reduced strength in newly poured concrete. During the service life of concrete, drastic diurnal temperature fluctuations caused by strong sunlight can also adversely affect the durability of concrete.

[0003] Traditional maintenance methods (such as covering and watering, and plastic film) have problems such as water waste, low efficiency and high cost. Most commercially available maintenance agents focus on a single function (such as only water retention or only film formation), lack comprehensive performance, and some contain organic solvents or toxic substances, which do not meet the requirements of green environmental protection.

[0004] Therefore, how to provide a multifunctional, environmentally friendly, and efficient external care agent is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a multifunctional concrete external curing agent, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A multifunctional concrete external curing agent, comprising the following raw materials in parts by weight:

[0008] 40-85 parts of water-based resin emulsion, 1-3 parts of thermally expandable microspheres, 0.3-5 parts of film-forming aid, 0.02-0.06 parts of defoamer, and 0-1 parts of pH adjuster.

[0009] Preferably, the solvent of the multifunctional concrete external curing agent is water.

[0010] More preferably, the sum of the amounts of water and other raw materials added is 100 parts.

[0011] Preferably, the aqueous resin emulsion includes styrene-acrylic emulsion or self-crosslinking pure acrylic elastic emulsion.

[0012] Beneficial effects: External curing agents made from these two types of emulsions have excellent elongation and elasticity, can adapt to the movement of cracks in the mortar layer, and make the polymer film layer difficult to break or wrinkle. In particular, the water-based self-crosslinking pure acrylic elastic emulsion can self-crosslink, has excellent adhesion and anti-fouling properties, can effectively resist ultraviolet radiation, and has excellent long-term durability and water retention.

[0013] Preferably, the median particle size of the thermally expandable microspheres is 10-40 μm. This particle size range can improve the solar reflectance and make the film formed with the external curing agent resin more dense.

[0014] More preferably, the thermally expandable microspheres have a core-shell structure, consisting of a thermoplastic polymer shell encapsulating a low-boiling-point solvent (liquid alkanes or other compounds). When heated to a suitable temperature, the polymer shell softens while the core solvent vaporizes, allowing the microspheres to expand to tens of times their initial volume. After cooling, the microspheres retain their expanded volume without shrinking back.

[0015] Beneficial Effects: As a functional filler, thermally expandable microspheres have extremely low density, allowing for a significant increase in the volume solids content of the curing agent without substantially increasing product weight or viscosity. With the same wet film thickness, curing agents with higher volume solids content form a thicker dry film, resulting in lower permeability and better water retention. Simultaneously, during the evaporation of water from the aqueous resin emulsion and the approach of polymer particles to the film formation process, the thermally expandable microspheres act as a "skeleton" or "fulcrum." After film formation, they also form countless closed, water-impermeable micro-barriers within the aqueous resin matrix. When water vapor penetrates this composite film, it must bypass these densely packed microspheres, greatly extending its migration path. This "maze effect" significantly reduces the water vapor permeability of the outer curing agent film layer, ensuring water retention performance.

[0016] Meanwhile, the thermally expandable microspheres in this invention possess superior elasticity and compressibility. When the curing film formed by the external curing agent on the concrete surface experiences shrinkage stress during concrete hydration heat release or diurnal temperature variations, these microspheres can absorb and buffer some of the stress like tiny sponges, preventing stress concentration that could lead to microcracks in the film. This characteristic of synchronous expansion and contraction with the concrete substrate ensures that the external curing agent film remains intact and crack-free despite deformation, guaranteeing high water retention. Furthermore, the hollow structure of the thermally expandable microspheres exhibits low thermal conductivity, significantly improving thermal insulation performance. On the other hand, the refractive index contrast caused by the hollow structure of the thermally expandable microspheres provides excellent reflection of sunlight, including visible and near-infrared wavelengths. This significantly reduces the absorption of direct sunlight by the curing agent, while the shell polymer material effectively radiates heat through atmospheric windows (8-13 μm band) in the infrared band, preventing drastic temperature increases caused by intense sunlight, controlling concrete temperature fluctuations, and ultimately improving the durability and service life of concrete components.

[0017] Preferably, the film-forming aid comprises propylene glycol phenyl ether and / or dodecyl alcohol ester.

[0018] Beneficial effects: The above-mentioned film-forming aids can improve the density and water resistance of the formed external curing film, effectively prevent the evaporation of moisture inside the concrete, and effectively improve the volume shrinkage and crack resistance of the concrete.

[0019] Preferably, the defoamer is an organosilicone defoamer.

[0020] Beneficial effects: Organosilicon defoamers can rapidly break bubbles. The low surface tension of the defoamer droplets propels the organosilicon continuously into the adjacent bubble film, resulting in repeated bubble breaking and a long-lasting foam-suppressing effect. This invention improves the production efficiency of external curing agents and the dispersion effect of thermally expanded microspheres by effectively controlling bubbles, thereby increasing the density of the dried film.

[0021] Preferably, the pH adjuster comprises 2-amino-2-methyl-1-propanol and / or ammonia.

[0022] Beneficial effects: The present invention uses the above-mentioned pH adjuster to control the pH value of the product to 7-9. Within this pH range, the storage stability of the external curing agent can be improved, microbial growth can be inhibited, and the compatibility with the alkalinity of concrete itself can be better.

[0023] A method for preparing a multifunctional concrete external curing agent includes the following steps:

[0024] After dispersing the thermally expanded microspheres in the defoamer solution, water-based resin emulsion, film-forming aid, and pH adjuster are added while stirring, and stirring is continued to obtain the multifunctional concrete external curing agent.

[0025] Preferably, the preparation method specifically includes the following steps:

[0026] Add the defoamer to the water, add the thermally expanded microspheres while stirring at a linear speed of 2 m / s, then increase the linear speed to 10 m / s and continue to disperse for 10 min. After that, reduce the linear speed to 2 m / s and add the water-based resin emulsion, film-forming aid, and pH adjuster while stirring. Continue stirring for 20 min to obtain the multifunctional concrete external curing agent.

[0027] Beneficial effects: The preparation method provided by this invention facilitates thorough and uniform mixing of all components, fully leveraging the performance advantages of each raw material. By controlling the stirring speed and time, the thermally expanded microspheres are well dispersed in the system, avoiding agglomeration, thereby ensuring the quality stability and performance consistency of the external curing agent.

[0028] Application of a multifunctional concrete external curing agent in the curing of concrete structure surfaces.

[0029] Beneficial effects: After drying, the multifunctional external concrete curing agent of this invention forms a dense polymer film on the concrete surface, reducing the evaporation of moisture from the concrete surface. Due to the introduction of radiative cooling, the coating can reduce the temperature rise of concrete in strong sunlight, thereby reducing temperature fluctuations and improving durability. In summary, this external curing agent not only provides curing but also regulates temperature changes, improving the durability of concrete.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] The multifunctional concrete external curing agent provided by this invention features a synergistic composite function. Through the combined effects of dense film formation, radiative cooling, and elastic crack resistance, it achieves "multiple effects in one agent" and possesses excellent environmental friendliness. This invention uses a water-based system and low-VOC components, meeting the requirements for green and environmentally friendly building materials. The product provided by this invention can replace traditional curing processes and is suitable for concrete projects under harsh conditions such as high temperature, dryness, and strong winds. It significantly improves construction efficiency, reduces curing costs, and has broad market value. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0034] This invention discloses a multifunctional concrete external curing agent, comprising the following raw materials in parts by weight:

[0035] 40-85 parts of water-based resin emulsion, 1-3 parts of thermally expandable microspheres, 0.3-5 parts of film-forming aid, 0.02-0.06 parts of defoamer, and 0-1 parts of pH adjuster.

[0036] In a preferred embodiment, the solvent of the multifunctional concrete external curing agent is water.

[0037] In a more preferred embodiment, the total amount of water and other raw materials added is 100 parts.

[0038] In a preferred embodiment, the aqueous resin emulsion includes styrene-acrylic emulsion or self-crosslinking pure acrylic elastic emulsion.

[0039] In a preferred embodiment, the median particle size of the thermally expanded microspheres is 10-40 μm. This particle size range can improve the solar reflectance and make the film formed with the external curing agent resin more dense.

[0040] In a more preferred embodiment, the thermally expandable microspheres have a core-shell structure, consisting of a thermoplastic polymer shell encapsulating a low-boiling-point solvent (liquid alkanes or other compounds). When heated to a suitable temperature, the polymer shell softens while the core solvent vaporizes, allowing the microspheres to expand to tens of times their initial volume. After cooling, the microspheres retain their expanded volume without shrinking back.

[0041] In a preferred embodiment, the film-forming aid comprises propylene glycol phenyl ether and / or dodecyl alcohol ester.

[0042] In a preferred embodiment, the defoamer is an organosilicone defoamer.

[0043] In a preferred embodiment, the pH adjuster comprises 2-amino-2-methyl-1-propanol and / or ammonia.

[0044] This invention also discloses a method for preparing a multifunctional concrete external curing agent, comprising the following steps:

[0045] After dispersing the thermally expanded microspheres in the defoamer solution, water-based resin emulsion, film-forming aid, and pH adjuster are added while stirring, and stirring is continued to obtain the multifunctional concrete external curing agent.

[0046] In a preferred embodiment, the preparation method specifically includes the following steps:

[0047] Add the defoamer to the water, add the thermally expanded microspheres while stirring at a linear speed of 2 m / s, then increase the linear speed to 10 m / s and continue to disperse for 10 min. After that, reduce the linear speed to 2 m / s and add the water-based resin emulsion, film-forming aid, and pH adjuster while stirring. Continue stirring for 20 min to obtain the multifunctional concrete external curing agent.

[0048] This invention also discloses the application of a multifunctional concrete external curing agent in the curing of concrete structure surfaces.

[0049] Unless otherwise specified, "parts" in the embodiments of this invention refers to parts by weight.

[0050] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels;

[0051] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0052] Example 1

[0053] A multifunctional concrete external curing agent includes the following steps:

[0054] Add 0.04 parts of silicone defoamer (BASF FoamStar ED 2522) to 18.66 parts of water. Add 3 parts of thermally expanded microspheres (Nourion 044 WE 20 d36, D50=20μm) while stirring at a linear velocity of 2 m / s. Increase the linear velocity to 10 m / s and disperse for 10 min. Then reduce the linear velocity to 2 m / s and add 73 parts of waterborne styrene-acrylic emulsion (BASF Acronal 4040) and 5 parts of film-forming aid (Dow PPH). At the same time, add 0.3 parts of pH adjuster (Dow AMP-95) to adjust the pH of the system to 8. Continue stirring for 20 min to obtain the multifunctional concrete external curing agent.

[0055] Example 2

[0056] Add 0.02 parts of silicone defoamer (BASF FoamStar SI 2292) to 31.08 parts of water, then add 2 parts of thermally expanded microspheres (Nourion 461 WE 20 d36, D50=30μm) while stirring at a linear speed of 2 m / s. Increase the linear speed to 10 m / s and disperse for 10 min. Then reduce the linear speed to 2 m / s, add 66 parts of self-crosslinking pure acrylic elastic emulsion (Baolijia BLJ-968M), 0.8 parts of film-forming aid (dodecyl alcohol ester), and 0.1 parts of pH adjuster (ammonia water) to adjust the pH of the system to 8. Continue stirring for 20 min to obtain the multifunctional concrete external curing agent.

[0057] Example 3

[0058] Add 0.06 parts of silicone defoamer (BASF FoamStar SI 2292) to 9.04 parts of water, then add 1 part of thermally expanded microspheres (Nourion 920 WE 40 d24, D50=40μm) while stirring at a linear speed of 2 m / s. Increase the linear speed to 10 m / s and disperse for 10 min. Then reduce the linear speed to 2 m / s, add 85 parts of self-crosslinking pure acrylic elastic emulsion (Lubrizol Carbocure TSR-72) and 4.5 parts of film-forming aid (dodecyl alcohol ester), and add 0.4 parts of pH adjuster (Dow AMP-95) to adjust the pH of the system to 8. Continue stirring for 20 min to obtain the multifunctional concrete external curing agent.

[0059] Comparative Example 1

[0060] A commercially available concrete curing liquid produced by a building materials company in Beijing.

[0061] Comparative Example 2

[0062] The raw materials used in Example 1 of CN112143355A using existing technology are: 38 parts of water-based resin emulsion, 14.7 parts of water, 8 parts of thermally expandable microspheres, 2 parts of halogen-free phosphorus flame retardant, 30 parts of inorganic powder, 5 parts of microspheres, 0.15 parts of defoamer, 0.15 parts of pH adjuster, 0.5 parts of dispersant, 0.15 parts of wetting agent, 0.5 parts of film-forming aid, 0.25 parts of ethylene glycol, 0.25 parts of propylene glycol, 0.2 parts of preservative, 0.3 parts of thickener, and 0.05 parts of colorant.

[0063] The preparation method includes the following steps:

[0064] S1. Prepare the raw materials according to the proportions. Add defoamer, pH adjuster, dispersant and wetting agent to water and disperse and stir evenly. Then add phosphorus flame retardant and stir evenly.

[0065] During the coating preparation process, phosphorus-based flame retardants may be added or not, depending on the fire resistance requirements of the material.

[0066] S2. Add inorganic powder to the above mixture and disperse and stir evenly. The inorganic powder is any one of calcium powder, mica powder, sepiolite powder, and talc powder.

[0067] S3. Add the aqueous resin emulsion to the above mixture and disperse and stir evenly. The aqueous resin emulsion is a self-crosslinking pure acrylic elastic emulsion (Lubrizol Carbocure TSR-72).

[0068] S4. Add thermally expanded microspheres (Nouryon 044 WE 20 d36, D50=20μm) to the above mixture and disperse and stir evenly;

[0069] S5. Add microspheres to the above mixture and disperse them evenly, wherein the microspheres are any one of ceramic microspheres or hollow glass microspheres;

[0070] S6. Add film-forming aid, ethylene glycol, and propylene glycol to the above mixture, and disperse and stir evenly;

[0071] S7. Add preservative to the above mixture and stir evenly.

[0072] S8. Thickeners can be used to adjust the viscosity of the coating as needed, wherein the thickener is any one of alkali-swelling thickeners, polyurethane thickeners, and cellulose.

[0073] S9. A colorant can be added as needed to adjust the color and make a coating, wherein the colorant is either a color powder or a color paste.

[0074] During the coating preparation process, dispersion and stirring are carried out using a disperser or a stone paint mixer.

[0075] Comparative Example 3

[0076] The only difference from Example 1 is that it does not include thermally expandable microspheres, and specifically includes the following steps:

[0077] Add 0.04 parts of silicone defoamer (BASF FoamStar ED 2522) to 18.66 parts of water, increase the linear velocity to 10 m / s, disperse for 10 min, then reduce the linear velocity to 2 m / s, add 76 parts of waterborne styrene-acrylic emulsion (BASF Acronal 4040) and 5 parts of film-forming aid (Dow PPH), and add 0.3 parts of pH adjuster (Dow AMP-95) to adjust the pH of the system to 8. Continue stirring for 20 min to obtain the concrete external curing agent.

[0078] Comparative Example 4

[0079] The only difference from Example 1 is that the thermally expandable microspheres are replaced with thermally expandable microspheres of the same mass but larger particle size (Waytop WP80W, D50=80μm). All other process steps and parameters are the same as in Example 1.

[0080] Technical effects:

[0081] Concrete preparation:

[0082] The concrete external curing agents obtained in Examples 1-4 and Comparative Examples 1-4 were used to form concrete specimens and test the effective water retention rate and compressive strength ratio according to Appendix A and Appendix B of the industry standard JC901-2002 "Cement Concrete Curing Agents". During testing, the slump of the concrete mix was 40mm ± 10mm as required by the specification. The concrete mix proportions are shown in Table 1 (GK-3000 concrete admixture was provided by Hebei Chang'an Yucai Technology Co., Ltd.). The volatile organic compound (VOC) content was tested according to GB / T23986.2-2023 standard. In addition, an automatic temperature recorder was used to detect the surface temperature of the concrete specimens under natural outdoor conditions. Specific test results are shown in Table 2.

[0083] Table 1 Concrete mix proportions (kg) for external curing agent testing

[0084]

[0085] Table 2 Concrete Performance Testing Table

[0086]

[0087] Test results show that, compared to ordinary commercially available products, the concrete external curing agent of this invention has significantly better water retention performance and higher compressive strength. It also exhibits a lower surface temperature, mitigating the temperature rise caused by strong sunlight, thereby reducing temperature fluctuations and extending the service life of concrete. Furthermore, the formulation uses a water-based system and low-VOC components, resulting in low volatile organic compound content, meeting the requirements for green and environmentally friendly building materials. In addition, although the existing technology CN112143355A also uses thermally expanding microspheres and resin raw materials, the specific raw material selection differs from that in this invention. Moreover, the raw material composition of this invention is simpler, the raw materials are more readily available, and the resulting product has superior water retention, mechanical properties, and environmental friendliness.

[0088] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A multifunctional concrete external curing agent, characterized in that, The ingredients include the following parts by weight: 40-85 parts of water-based resin emulsion, 1-3 parts of thermally expandable microspheres, 0.3-5 parts of film-forming aid, 0.02-0.06 parts of defoamer, and 0-1 parts of pH adjuster.

2. The multifunctional concrete external curing agent according to claim 1, characterized in that, The solvent for the multifunctional concrete external curing agent is water.

3. The multifunctional concrete external curing agent according to claim 1, characterized in that, The aqueous resin emulsion includes styrene-acrylic emulsion or self-crosslinking pure acrylic elastic emulsion.

4. The multifunctional concrete external curing agent according to claim 1, characterized in that, The median particle size of the thermally expandable microspheres is 10-40 μm.

5. The multifunctional concrete external curing agent according to claim 1, characterized in that, The film-forming aids include propylene glycol phenyl ether and / or dodecyl alcohol ester.

6. The multifunctional concrete external curing agent according to claim 1, characterized in that, The defoamer is an organosilicone defoamer.

7. The multifunctional concrete external curing agent according to claim 1, characterized in that, The pH adjuster includes 2-amino-2-methyl-1-propanol and / or ammonia.

8. A method for preparing a multifunctional concrete external curing agent as described in any one of claims 1-7, characterized in that, Includes the following steps: After dispersing the thermally expanded microspheres in the defoamer solution, water-based resin emulsion, film-forming aid, and pH adjuster are added while stirring, and stirring is continued to obtain the multifunctional concrete external curing agent.

9. The application of a multifunctional concrete external curing agent as described in any one of claims 1-7 in the surface curing of concrete structures.

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