A surface curing agent for ultra-high performance concrete, a preparation method and application thereof

Abstract

The application discloses a surface curing agent for ultra-high performance concrete and a preparation method and application thereof, and belongs to the technical field of concrete admixtures. The surface curing agent for ultra-high performance concrete is prepared from polyalkyl ester, a silane solution, a small-molecule carbamic acid ester and alcohol ester twelve as raw materials. The hydrophobicity and low density of the surface curing agent can enable the surface curing agent to be simultaneously added during preparation of the ultra-high performance concrete and to migrate to the surface of the concrete during a standing process after completion of stirring and pouring, so that a protective film is formed, water evaporation on the surface is inhibited, and thus the curing effect is achieved. The surface curing agent can be directly added during stirring of the UHPC, the process step of spraying or brushing after molding is reduced, a film with uniform thickness and compactness can be formed on the surface of the concrete, water evaporation is obviously inhibited, and problems such as inconsistent film thickness and discontinuous film formation caused by fluctuation of the external coating process are eliminated.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, and particularly relates to a surface curing agent for ultra-high performance concrete, its preparation method and application. Background Technology

[0002] UHPC is a building material characterized by ultra-high strength (compressive strength ≥120MPa), high durability, and low porosity. Its performance relies on an extremely low water-cement ratio (typically ≤0.25) and a highly dispersible cementitious material system. However, a low water-cement ratio can lead to high concrete viscosity and rapid surface water loss. After concrete pouring, timely covering or watering curing is necessary within a certain timeframe. The curing efficiency of concrete not only affects the early strength development but also its later mechanical properties and durability.

[0003] There are two main types of existing concrete curing agents: one type is inorganic salt-based, which utilizes the silicate in the curing agent to penetrate into the concrete and react chemically with the calcium hydroxide in the cement within a 1-3mm penetration layer on the surface, generating calcium silicate and hydroxides. The hydroxides can activate fly ash and slag, accelerate the hydration of calcium silicate, and improve the surface performance of concrete. This is because calcium silicate is insoluble and can seal various pores on the concrete surface, forming a solid film that prevents premature and excessive evaporation of moisture, thereby ensuring sufficient hydration of cement and achieving the purpose of curing. The other type is organic-based, which, after being sprayed onto the concrete surface, quickly forms a waterproof film that prevents moisture evaporation and achieves immediate curing. Most of the research focuses on improving the film-forming properties of curing agents and increasing water retention. For example, patent CN103253985A proposes an organic / inorganic composite cement concrete curing agent that can achieve a water retention rate of over 90%. Another example is patent CN113416091A, which proposes an emulsion-type curing agent that can improve the water retention rate and surface strength of concrete. Yet another example is patent CN109293277A, which proposes a biodegradable concrete curing agent that can achieve zero pollution to the environment.

[0004] However, the above-mentioned existing technologies are all based on improving the performance of the curing materials themselves. In actual engineering applications, they are usually applied to the surface of the formed concrete by spraying or brushing. Although this process can reduce the construction difficulty and improve efficiency compared with traditional methods such as watering and film covering, it still adds an external coating process and has certain requirements for the uniformity of spraying or brushing, resulting in large fluctuations in application effect. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a surface curing agent for ultra-high performance concrete, its preparation method, and its application. The surface curing agent provided by this invention can be directly added during the mixing process of UHPC, reducing the need for post-molding spraying or brushing. Furthermore, it forms a uniform and dense film on the concrete surface, significantly inhibiting moisture evaporation and eliminating problems such as inconsistent film thickness and discontinuous film formation caused by fluctuations in the external coating process.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an ultra-high performance concrete surface curing agent, the raw materials of which include silane dispersion, polyalkyl ester, small molecule carbamate and alcohol ester dodecyl; the mass ratio of the polyalkyl ester, silane dispersion, small molecule carbamate and alcohol ester dodecyl is 40:(2~5):17:(1~3). The structural formula of the small molecule carbamate is as follows: R1 is selected from phenyl or C5-C6 alkyl, and R2 is selected from C4 alkyl, C8 alkyl or C16 alkyl.

[0007] Furthermore, the polyalkyl ester is selected from polyvinyl acetate and / or polyoctadecyl acrylate.

[0008] Further, the mass concentration of silane in the silane dispersion is 10%; the silane in the silane dispersion is selected from at least one of octyltrimethoxysilane, phenylpropyltrimethoxysilane, methyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane and anilinemethyltriethoxysilane.

[0009] Furthermore, the preparation method of the small molecule carbamate includes the following steps: adding molecular sieves to a long-chain alcohol solution and allowing it to stand, filtering, adding diisocyanate and catalyst, and then performing a reflux reaction to obtain the small molecule carbamate.

[0010] Furthermore, the molar ratio of the long-chain alcohol to the diisocyanate in the long-chain alcohol solution is 2:1.

[0011] Furthermore, the long-chain alcohol is selected from n-butanol, n-octanol, or octadecyl alcohol; The diisocyanate is selected from toluene diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate or diphenylmethane diisocyanate.

[0012] Furthermore, the reflux reaction temperature is (80±5)℃, and the reflux reaction time is 4h.

[0013] The present invention provides a method for preparing the ultra-high performance concrete surface curing agent described in the above technical solution, comprising the following steps: mixing silane dispersion, polyalkyl ester, small molecule carbamate and alcohol ester dodecyl uniformly to obtain the ultra-high performance concrete surface curing agent.

[0014] The present invention also provides an application of the surface curing agent for ultra-high performance concrete described in the above technical solution in the surface curing of ultra-high performance concrete.

[0015] Furthermore, the dosage of the surface curing agent for ultra-high performance concrete is 0.01~0.1% of the mass of the cementitious material in the ultra-high performance concrete.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: This invention uses polyalkyl ester, silane solution, small molecule urethane and 12-ol ester as raw materials to prepare a surface curing agent for ultra-high performance concrete. Utilizing the hydrophobicity and low density of this surface curing agent, it can be added simultaneously during the preparation of ultra-high performance concrete and migrate to the concrete surface during the static setting process after mixing and pouring to form a protective film, inhibiting surface moisture evaporation, thereby achieving the curing effect.

[0017] The components used in the preparation of the surface curing agent of this invention all have a certain degree of hydrophobicity and a density lower than that of water. During the static process of concrete, they will migrate to the concrete surface due to surface tension and gravity. The polyalkyl ester and small molecule carbamate can form a dense and continuous film on the concrete surface, inhibiting the evaporation of water from the concrete surface. The silane dispersion can be hydrolyzed in the cement pore liquid environment to obtain highly active silanol groups. The silanol groups can react with hydration products to obtain CSH gel with a high silica-to-calcium ratio, further sealing the capillaries on the surface, reducing the water migration channels, and improving the surface strength and weather resistance of the concrete.

[0018] Compared with traditional inorganic water glass and organic emulsion surface protectants, the surface protectant provided by this invention is easier to use, has a more uniform film thickness, and a higher rate of water evaporation inhibition. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] This invention provides a surface curing agent for ultra-high performance concrete, comprising silane dispersion, polyalkyl ester, small molecule carbamate, and dodecyl alcohol ester. The mass ratio of the polyalkyl ester, silane dispersion, small molecule carbamate, and dodecyl alcohol ester is 40:(2~5):17:(1~3), more preferably 40:(2~4):17:(1~2). This invention utilizes components with a certain degree of hydrophobicity and a density lower than water to prepare the surface curing agent for ultra-high performance concrete. This allows the agent to be added simultaneously during the preparation of ultra-high performance concrete and to migrate to the concrete surface during the settling process after mixing and pouring, forming a protective film that inhibits surface moisture evaporation, thereby achieving a curing effect.

[0022] In a preferred embodiment, the structural formula of the small molecule carbamate is as follows: Wherein, R1 is selected from phenyl or C5-C6 alkyl, and R2 is selected from C4 alkyl, C8 alkyl, or C16 alkyl. The small molecule urethane and polyalkyl ester in this invention can form a dense, continuous film on the concrete surface, inhibiting moisture evaporation from the concrete surface.

[0023] In a preferred embodiment, the preparation method of the small molecule carbamate includes the following steps: adding molecular sieves to a long-chain alcohol solution and allowing it to stand, filtering, adding diisocyanate and catalyst, and then performing a reflux reaction to obtain the small molecule carbamate.

[0024] In a preferred embodiment, the molar ratio of the long-chain alcohol to the diisocyanate in the long-chain alcohol solution is 2:1; the long-chain alcohol is selected from n-butanol, n-octanol, or octadecyl alcohol; the diisocyanate is selected from toluene diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate, or diphenylmethane diisocyanate; and the solvent of the long-chain alcohol solution is ethyl acetate.

[0025] In a preferred embodiment, the molecular sieve is 4A molecular sieve.

[0026] In a preferred embodiment, the settling time is 24 hours.

[0027] In a preferred embodiment, the filtration process further includes a step of testing the moisture content of the filtrate using the Karl Fischer method; when the moisture content of the filtrate is ≤10ppm, the subsequent steps are continued; when the moisture content of the filtrate is >10ppm, 4A molecular sieve is added again, soaked for 24 hours, and the moisture content is tested again; if the moisture content is ≤10ppm, the 4A molecular sieve is removed.

[0028] In a preferred embodiment, the step of heating to 40-50°C is further included before adding diisocyanate and catalyst.

[0029] In a preferred embodiment, the catalyst is selected from stannous octoate.

[0030] In a preferred embodiment, the reflux reaction temperature is (80±5)℃ and the reflux reaction time is 4h.

[0031] In a preferred embodiment, the reflux reaction is followed by a cooling and vacuum distillation step; the cooling is to a temperature below 50°C; and the vacuum distillation pressure is 133 Pa.

[0032] In a preferred embodiment, the polyalkyl ester is selected from polyvinyl acetate and / or polyoctadecyl acrylate. The polyalkyl esters and small-molecule urethanes of this invention can form a dense, continuous film on the concrete surface, inhibiting moisture evaporation from the concrete surface.

[0033] In a preferred embodiment, the silane dispersion has a silane concentration of 10% by mass; the silane in the silane dispersion is selected from at least one of octyltrimethoxysilane, phenylpropyltrimethoxysilane, methyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and anilinemethyltriethoxysilane, more preferably at least one of octyltrimethoxysilane, phenylpropyltrimethoxysilane, and anilinemethyltriethoxysilane. The silane dispersion of this invention can be hydrolyzed in a cement pore liquid environment to obtain highly active silanol groups. These silanol groups can react with hydration products to obtain a CSH gel with a high silica-to-calcium ratio, further sealing the surface capillaries, reducing moisture migration channels, and simultaneously improving the surface strength and weather resistance of the concrete.

[0034] The present invention provides a method for preparing the ultra-high performance concrete surface curing agent described in the above technical solution, comprising the following steps: mixing silane dispersion, polyalkyl ester, small molecule carbamate and alcohol ester dodecyl uniformly to obtain the ultra-high performance concrete surface curing agent.

[0035] This invention also provides an application of the surface curing agent for ultra-high performance concrete described above in the surface curing of ultra-high performance concrete. The surface curing agent provided by this invention can be directly added during the mixing process of UHPC, reducing the need for spraying or brushing after molding.

[0036] In a preferred embodiment, the dosage of the surface curing agent for ultra-high performance concrete is 0.01 to 0.1% of the mass of the cementitious materials in the ultra-high performance concrete.

[0037] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0038] Example 1 A high-performance concrete surface curing agent is composed of polyvinyl acetate, octyltrimethoxysilane solution, small molecule carbamate-1, and alcohol ester dodecyl in a mass ratio of 40:2:17:1; wherein the octyltrimethoxysilane solution contains 10% octyltrimethoxysilane by mass; the structural formula of small molecule carbamate-1 is: ; The preparation method of small molecule carbamate-1 is as follows: 4A molecular sieve is added to an ethyl acetate solution containing 0.1 mol n-octanol, and after standing for 24 h, it is filtered. The water content of the filtrate is tested by Karl Fischer method and found to be 8 ppm. Then it is added to a flask with magnetic stirring. The temperature is raised to 40℃ and 0.05 mol toluene diisocyanate (TDI) and 0.0001 mol stannous octoate are added. The temperature is raised to (80±5)℃ and refluxed at a constant temperature for 4 h. After the reaction is completed, the temperature is lowered to 50℃ and vacuumed to a pressure of 133 Pa for distillation. After distillation, a light brown liquid is obtained, which is small molecule carbamate-1. The preparation method of the above-mentioned surface curing agent for ultra-high performance concrete is as follows: 200g of polyvinyl acetate, 10g of octyltrimethoxysilane solution, 85g of small molecule urethane-1 and 5g of alcohol ester twelve are added to a mixer and stirred at high speed at 200rpm for 0.5h to obtain the surface curing agent for ultra-high performance concrete.

[0039] Example 2 A high-performance concrete surface curing agent is composed of polyoctadecyl acrylate, aniline methyltriethoxysilane solution, small molecule carbamate-2, and alcohol ester dodecyl in a mass ratio of 40:4:17:2; wherein the mass concentration of aniline methyltriethoxysilane in the aniline methyltriethoxysilane solution is 10%; the structural formula of small molecule carbamate-2 is: ; The preparation method of small molecule carbamate-2 is as follows: 4A molecular sieve is added to an ethyl acetate solution containing 0.1 mol octadecyl alcohol, and after standing for 24 h, it is filtered. The water content of the filtrate is tested by Karl Fischer method and found to be 10 ppm. Then it is added to a flask with magnetic stirring, heated to 40℃, and 0.05 mol toluene diisocyanate (TDI) and 0.0001 mol stannous octoate are added. The temperature is further increased to (80±5)℃, and the reaction is refluxed at a constant temperature for 4 h. After the reaction is completed, the temperature is lowered to 50℃ and vacuumed to a pressure of 133 Pa for distillation. After distillation, a light brown liquid is obtained, which is small molecule carbamate-2. The preparation method of the above-mentioned surface curing agent for ultra-high performance concrete is as follows: 200g of polyoctadecyl acrylate, 20g of aniline methyltriethoxysilane solution, 85g of small molecule urethane-2 and 10g of alcohol ester twelve are added to a mixer and stirred at high speed at 200rpm for 0.5h to obtain the surface curing agent for ultra-high performance concrete.

[0040] Example 3 A high-performance concrete surface curing agent is composed of polyoctadecyl acrylate, phenylpropyltrimethoxysilane solution, small molecule carbamate-3, and alcohol ester dodecyl in a mass ratio of 40:3:17:2; wherein the mass concentration of phenylpropyltrimethoxysilane in the phenylpropyltrimethoxysilane solution is 10%; the structural formula of small molecule carbamate-3 is: ; The preparation method of small molecule carbamate-3 is as follows: 4A molecular sieve is added to an ethyl acetate solution containing 0.1 mol n-butanol, and after standing for 24 h, it is filtered. The water content of the filtrate is tested by Karl Fischer method and found to be 10 ppm. Then it is added to a flask with magnetic stirring, heated to 40℃, and 0.05 mol 1,6-hexamethylene diisocyanate (HDI) and 0.0001 mol stannous octoate are added. The temperature is further increased to (80±5)℃, and the reaction is refluxed at a constant temperature for 4 h. After the reaction is completed, the temperature is lowered to 50℃ and vacuumed to a pressure of 133 Pa for distillation. After distillation, a light brown liquid is obtained, which is small molecule carbamate-3. The preparation method of the above-mentioned surface curing agent for ultra-high performance concrete is as follows: 200g of polyoctadecyl acrylate, 15g of phenylpropyltrimethoxysilane solution, 85g of small molecule urethane-3 and 10g of alcohol ester twelve are added to a mixer and stirred at high speed at 200rpm for 0.5h to obtain the surface curing agent for ultra-high performance concrete.

[0041] Example 4 A high-performance concrete surface curing agent is composed of polyvinyl acetate, styrene-propyltrimethoxysilane solution, small molecule carbamate-4, and alcohol ester dodecyl in a mass ratio of 40:2:17:2; wherein the mass concentration of styrene-propyltrimethoxysilane in the styrene-propyltrimethoxysilane solution is 10%; the structural formula of small molecule carbamate-4 is: ; The preparation method of small molecule carbamate-4 is as follows: 4A molecular sieve is added to an ethyl acetate solution containing 0.1 mol n-octanol, and after standing for 24 h, it is filtered. The water content of the filtrate is tested by Karl Fischer method and found to be 10 ppm. Then it is added to a flask with magnetic stirring, heated to 40℃, and 0.05 mol 1,6-hexamethylene diisocyanate (HDI) and 0.0001 mol stannous octoate are added. The temperature is further increased to (80±5)℃, and the reaction is refluxed at a constant temperature for 4 h. After the reaction is completed, the temperature is lowered to 50℃ and vacuumed to a pressure of 133 Pa for distillation. After distillation, a light brown liquid is obtained, which is small molecule carbamate-4. The preparation method of the above-mentioned surface curing agent for ultra-high performance concrete is as follows: take 200g of polyvinyl acetate, 10g of phenylpropyltrimethoxysilane solution, 85g of small molecule urethane-4 and 10g of alcohol ester twelve and add them to a mixer, and stir at high speed at 200rpm for 0.5h to obtain the surface curing agent for ultra-high performance concrete.

[0042] Comparative Example 1 A surface curing agent for ultra-high performance concrete is composed of polyvinyl acetate, small molecule urethane-1 and alcohol ester twelve in a mass ratio of 40:17:1; The structural formula and preparation method of small molecule carbamate-1, as well as the preparation method of surface curing agent for ultra-high performance concrete, are the same as in Example 1.

[0043] Comparative Example 2 An ultra-high performance concrete surface curing agent is composed of polyoctadecyl acrylate, aniline methyltriethoxysilane solution and small molecule urethane-2 in a mass ratio of 40:4:17; other aspects are the same as in Example 2.

[0044] Comparative Example 3 An ultra-high performance concrete surface curing agent is composed of polyoctadecyl acrylate, phenylpropyltrimethoxysilane solution and alcohol ester twelve in a mass ratio of 40:3:2; other aspects are the same as in Example 3.

[0045] Comparative Example 4 An ultra-high performance concrete surface curing agent is composed of phenylpropyltrimethoxysilane solution, small molecule carbamate-4 and alcohol ester twelve in a mass ratio of 2:17:2; other aspects are the same as in Example 4.

[0046] The surface curing agents prepared in Examples 1-4 and Comparative Examples 1-4 were added to C120 ultra-high performance concrete as admixtures at a dosage of 0.01% of the mass of cementitious materials in the ultra-high performance concrete. The mix proportions of C120 ultra-high performance concrete are shown in Table 1. The admixture was GK-3000 water-reducing agent, purchased from Hebei Chang'an Yucai Technology Co., Ltd. The commercially available emulsion-type surface curing agent ER was used as a control group (ER was added by brushing at a dosage of 50g / m², purchased from Jiangsu Subote New Materials Co., Ltd.).

[0047] The effective water retention rate of the curing agent was tested according to JC901-2002 "Cement Concrete Curing Agent", and the surface rebound strength of the concrete was tested according to JGJ / T23-2011 "Technical Specification for Testing the Compressive Strength of Concrete by Rebound Method". The results are shown in Table 2.

[0048] Table 1. Mix proportions of C120 ultra-high performance concrete (kg / m³) 3 ) Table 2 Test Data As shown in Table 2, the surface curing agent provided by this invention can achieve an effective water retention rate of 86-92%, and the formed film can adhere tightly to the concrete surface and will not dissolve in water; the surface resilience of the concrete can reach 101-106%. However, due to the omission of a certain component, the effective water retention rate of the surface curing agents obtained in Comparative Examples 1-4 decreased, especially in Comparative Example 4, which decreased by 14% compared to Example 4, and the surface resilience of the concrete also decreased.

[0049] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention 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 the present invention should be included within the scope of protection of the present invention.

Claims

1. A surface curing agent for ultra-high performance concrete, characterized in that, The raw materials include silane dispersion, polyalkyl ester, small molecule carbamate, and alcohol ester dodecyl; the mass ratio of the polyalkyl ester, silane dispersion, small molecule carbamate, and alcohol ester dodecyl is 40:(2~5):17:(1~3); The structural formula of the small molecule carbamate is as follows: R1 is selected from phenyl or C5-C6 alkyl, and R2 is selected from C4 alkyl, C8 alkyl or C16 alkyl.

2. The surface curing agent for ultra-high performance concrete according to claim 1, characterized in that, The polyalkyl ester is selected from polyvinyl acetate and / or polyoctadecyl acrylate.

3. The surface curing agent for ultra-high performance concrete according to claim 1, characterized in that, The silane dispersion has a silane mass concentration of 10%; the silane in the silane dispersion is selected from at least one of octyltrimethoxysilane, phenylpropyltrimethoxysilane, methyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane and anilinemethyltriethoxysilane.

4. The surface curing agent for ultra-high performance concrete according to claim 1, characterized in that, The preparation method of the small molecule carbamate includes the following steps: adding molecular sieves to a long-chain alcohol solution and letting it stand, filtering, adding diisocyanate and catalyst, and then carrying out a reflux reaction to obtain the small molecule carbamate.

5. The surface curing agent for ultra-high performance concrete according to claim 4, characterized in that, The molar ratio of the long-chain alcohol to the diisocyanate in the long-chain alcohol solution is 2:

1.

6. The surface curing agent for ultra-high performance concrete according to claim 5, characterized in that, The long-chain alcohol is selected from n-butanol, n-octanol, or octadecyl alcohol; The diisocyanate is selected from toluene diisocyanate, 1,6-hexane diisocyanate, isophorone diisocyanate or diphenylmethane diisocyanate.

7. The surface curing agent for ultra-high performance concrete according to claim 4, characterized in that, The reflux reaction temperature is (80±5)℃, and the reflux reaction time is 4h.

8. A method for preparing a surface curing agent for ultra-high performance concrete according to any one of claims 1 to 7, characterized in that, The process includes the following steps: mixing silane dispersion, polyalkyl ester, small molecule carbamate and alcohol ester twelve evenly to obtain the ultra-high performance concrete surface curing agent.

9. The application of the surface curing agent for ultra-high performance concrete according to any one of claims 1 to 7 in the surface curing of ultra-high performance concrete.

10. The application according to claim 9, characterized in that, The dosage of the surface curing agent for ultra-high performance concrete is 0.01~0.1% of the mass of cementitious materials in ultra-high performance concrete.

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