Pickering emulsions, methods of making and using the same

Abstract

The application relates to the technical field of building material repair, in particular to a Pickering emulsion and a preparation method and application thereof. The Pickering emulsion is an oil-in-water emulsion, the water phase of the Pickering emulsion comprises water and colloidal particles and water-soluble cellulose ethers, and the colloidal particles and the water-soluble cellulose ethers are dispersed in the water; the oil phase of the Pickering emulsion comprises a fatty acid ester; at least part of the colloidal particles and the water-soluble cellulose ethers are distributed on the surfaces of the liquid droplets of the oil phase, and the two cooperate to play the role of an emulsifier, wherein the colloidal particles and the water-soluble cellulose ethers form hydrogen bonds and / or are both negatively charged, so that the colloidal particles are uniformly dispersed in the water phase, so that the liquid droplets of the oil phase are uniformly and stably dispersed in the water phase and cannot contact and coalesce. Therefore, the Pickering emulsion of the application does not need a surfactant or an organic modifier, still has good storage stability and coalescence stability, and also has biocompatibility and environmental friendliness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building material repair, in particular to a Pickering emulsion and a preparation method and application thereof. BACKGROUND

[0002] Concrete is prone to cracks of different degrees due to various factors such as material properties, construction technology, load action and external environment, which weakens the overall strength and stability, and may also cause harmful substances such as chloride ions and sulfate ions to penetrate into the concrete, accelerating the deterioration of the concrete and the corrosion of the steel bars, so it is particularly important to repair the cracks in the concrete and improve its durability.

[0003] To this end, people have proposed pipeline self-repairing concrete, which embeds pipelines in the concrete by simulating the distribution and material transmission form of the vascular network in the body, and when the concrete cracks, the cracks extend to the internal pipelines, and under the action of capillary force, gravity, surface tension and negative pressure, the repair agent is released into the cracks for repair, and the pipeline can also be used to pump repair materials from the outside to achieve multiple self-repairing. For example, brittle materials such as glass are pre-embedded before the concrete is poured, for example, a pipeline template is constructed in situ by 3D printing technology before the cement is solidified after pouring, and the hydrophobic pipeline is formed after the cement hydration is completed.

[0004] Among them, the latter method often needs Pickering emulsion as 3D printing ink, Pickering emulsion is a kind of emulsion stabilized by solid particles adsorbed on the contact surface of water phase and oil phase, and the solid particles can prevent droplets from coalescing, so that the emulsion remains stable. However, due to the surface wettability of the solid particles, these Pickering emulsions often need to be chemically modified or use surfactants to maintain stability, which is expensive and time-consuming, and may also cause harm to human health and the environment. Moreover, the rheological properties (shear thinning properties, storage modulus and loss modulus, and yield stress) of the existing Pickering emulsions, self-supporting strength, and emulsion stability are still not ideal, which cannot meet the needs of pipeline self-repairing concrete. SUMMARY

[0005] The purpose of the present application is to provide a Pickering emulsion and a preparation method thereof, aiming to solve the technical problem in the prior art that the Pickering emulsion used for self-repairing concrete needs to be chemically modified or use surfactants to maintain stability.

[0006] To achieve the above application purpose, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a Pickering emulsion, which is an oil-in-water emulsion, the water phase of which comprises water and colloidal particles, and water-soluble cellulose ether, and the colloidal particles and water-soluble cellulose ether are dispersed in water; the oil phase of which comprises a fatty acid ester;

[0008] At least part of the colloidal particles and the water-soluble cellulose ether are distributed on the surface of the droplets of the oil phase, wherein the colloidal particles and the water-soluble cellulose ether form hydrogen bonds and / or are both negatively charged.

[0009] The present application is an oil-in-water emulsion containing colloidal particles in the water phase, the water phase is the continuous phase, the water phase is the dispersed phase, and a Pickering emulsion is formed. Moreover, the colloidal particles in the water phase form hydrogen bonds with the water-soluble cellulose ether and / or are both negatively charged, so that the colloidal particles are uniformly dispersed in the water phase, and at the same time, at least part of the colloidal particles and the water-soluble cellulose ether are distributed on the surface of the droplets of the oil phase, both of which act as emulsifiers, so that the droplets of the oil phase are uniformly and stably dispersed in the water phase without contacting and coalescing. Therefore, the Pickering emulsion of the present application does not require a surfactant or an organic modifier, still has good storage stability and coalescence stability, and also has biocompatibility and environmental friendliness.

[0010] In a second aspect, the present application provides a preparation method of the above Pickering emulsion, comprising the following steps:

[0011] The raw materials of the oil phase are added to the solution of the water phase for emulsification treatment.

[0012] The preparation method of the present application emulsifies the above-mentioned raw materials of the oil phase and the solution of the water phase, the colloidal particles and the water-soluble cellulose ether in the water phase act as emulsifiers, the oil phase will form droplets, and at least part of the colloidal particles and the water-soluble cellulose ether are distributed on the surface of the droplets of the oil phase, so that the droplets of the oil phase are uniformly and stably dispersed in the water phase without contacting and coalescing, thereby the above-mentioned Pickering emulsion can be prepared without a surfactant or an organic modifier, and can be used for pipeline self-repairing concrete. The preparation method is controllable, and the prepared Pickering emulsion has good storage stability and coalescence stability, and also has biocompatibility and environmental friendliness.

[0013] In a third aspect, the present application provides a pipeline self-repairing concrete product, comprising a product base and a hydrophobic pipeline, the hydrophobic pipeline is arranged inside the product base and communicates with the outside, and the hydrophobic pipeline is formed by solidification of the above-mentioned Pickering emulsion.

[0014] The pipeline self-repairing concrete product of the present application comprises a product base and a hydrophobic pipeline inside, when a crack appears in the product base, a crack repair agent can be transported into the hydrophobic pipeline, so that the crack repair agent flows into the inside of the product base along the hydrophobic pipeline, penetrates to the crack and fills it, and the crack repair agent can repair the crack of the product base in time. Since the hydrophobic pipeline is formed by solidification of the above-mentioned Pickering emulsion, the pipeline formed is hydrophobic, the crack repair agent will not leak and lose during transportation, and can directly reach the crack. The pipeline self-repairing concrete product of the present application also has biocompatibility and environmental friendliness.

[0015] In a fourth aspect, the application provides a method for preparing a pipe self-repairing concrete product, comprising the following steps:

[0016] Constructing a pipe template in the concrete slurry, wherein the pipe template is prepared by forming treatment of the Pickering emulsion prepared by the Pickering emulsion or the method for preparing the Pickering emulsion described above;

[0017] Carrying out a hydration reaction on the concrete slurry containing the pipe template to obtain the pipe self-repairing concrete product.

[0018] The method for preparing the application first prepares a concrete slurry, which is a typical porous material containing many interconnected micropores. The Pickering emulsion can be subjected to forming treatment in the concrete slurry before the concrete slurry is solidified. Since the Pickering emulsion described above has a certain self-supporting strength, it can fill and combine to construct a pipe template in the concrete slurry. Then, a hydration reaction is carried out. The water phase of the Pickering emulsion will be consumed until the oil-in-water emulsion structure is destroyed, and the fatty acid ester of the oil phase will penetrate into the surrounding concrete. After the temperature decreases, the fatty acid ester solidifies to form a hydrophobic pipe in the matrix of the concrete product, thereby obtaining the pipe self-repairing concrete product. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0020] Figure 1 is a preparation process of the Pickering emulsion of Example 1;

[0021] Figure 2 is an infrared spectrum test result graph of the water phase composition of the Pickering emulsion of Example 3 and Example 9;

[0022] Figure 3 is a water phase Zeta potential test result graph of the Pickering emulsion of Example 3, Example 6 to Example 11;

[0023] Figure 4 is a schematic diagram of the relationship between the viscosity and the shear rate of the Pickering emulsion of Example 1 to Example 5;

[0024] Figure 5 is a schematic diagram of the storage modulus and the loss modulus of the Pickering emulsion of Example 1 to Example 5 under shear stress scanning;

[0025] Figure 6 is a schematic diagram of the relationship between the viscosity and the shear rate of the Pickering emulsion of Example 9, 10, 3, 11;

[0026] Figure 7 is a schematic diagram of the storage modulus and loss modulus of the Pickering emulsion of Example 9, 10, 3, 11 under shear stress sweep;

[0027] Figure 8 is a schematic diagram of the viscosity versus shear rate of the Pickering emulsion of Example 12, 3, 13, 14;

[0028] Figure 9 is a schematic diagram of the storage modulus and loss modulus of the Pickering emulsion of Example 12, 3, 13, 14 under shear stress sweep;

[0029] Figure 10 is a schematic diagram of the preparation process of the Pickering emulsion of Example 3 for preparing the pipe self-repairing concrete product;

[0030] Figure 11 is a schematic diagram of the Pickering emulsion of Example 3 for forming pipes with different diameters in concrete by 3D printing;

[0031] Figure 12 is a comparison diagram of the pipe self-repairing concrete product before and after crack repair. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved in the present application more clear and explicit, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0033] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0034] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one" or similar expressions mean any combination of these items, including any combination of single item or multiple items.

[0035] It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0036] The weight of the related components mentioned in the embodiment specification of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the related components in the embodiment specification of the present application is proportionally enlarged or reduced, it is within the scope disclosed in the embodiment specification of the present application. Specifically, the mass in the embodiment specification of the present application can be μg, mg, g, kg, and other mass units commonly known in the chemical industry.

[0037] The terms "first", "second" are only for descriptive purposes and are used to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0038] Glossary in the present application:

[0039] Storage stability: whether the oil and water layering occurs when the emulsion is stored for a long time.

[0040] Coalescence stability: for example, whether the oil droplets in the oil-in-water emulsion will contact and combine to form large droplets.

[0041] Oil-water ratio: the oil-water ratio in the present application is the volume ratio of the oil phase to the water phase.

[0042] The first aspect of the embodiment of the present application provides a Pickering emulsion, which is an oil-in-water emulsion, the water phase of which comprises water and colloidal particles, water-soluble cellulose ether, and the colloidal particles and water-soluble cellulose ether are dispersed in water; the oil phase of which comprises a fatty acid ester;

[0043] At least part of the colloidal particles and water-soluble cellulose ether are distributed on the surface of the droplets of the oil phase, wherein the colloidal particles and water-soluble cellulose ether form hydrogen bonds and / or both have negative charges.

[0044] The embodiment of the present application is an oil-in-water emulsion containing colloidal particles in the water phase, the water phase is the continuous phase, and the water phase is the dispersed phase, which constitutes the Pickering emulsion. Moreover, the colloidal particles in the water phase form hydrogen bonds with the water-soluble cellulose ether and / or both have negative charges, so that the colloidal particles are uniformly dispersed in the water phase, at the same time, at least part of the colloidal particles and water-soluble cellulose ether are distributed on the surface of the droplets of the oil phase, which play the role of emulsifiers together, so that the droplets of the oil phase are uniformly and stably dispersed in the water phase without coalescence. Therefore, the Pickering emulsion of the embodiment of the present application does not need a surfactant or an organic modifier, and still has good storage stability and coalescence stability, and also has biocompatibility and environmental friendliness.

[0045] The Pickering emulsion also has good shear thinning, thixotropy, anti-deformation performance, and certain self-supporting strength, so the subsequent forming performance is good. When applied to pipeline self-repairing concrete, the fatty acid ester of the oil phase will seep out and solidify to form a hydrophobic pipeline in communication with the outside after the water phase of the Pickering emulsion is consumed.

[0046] Regarding the water phase:

[0047] The water phase coats the oil phase, and the water phase contains water, colloidal particles, and water-soluble cellulose ether. In some embodiments, the colloidal particles include at least one of montmorillonite, kaolin, nano-silicon dioxide, hectorite, and sepiolite, which can be sodium-based montmorillonite. These colloidal particles are dispersed in the water phase and at least partially distributed on the surface of the oil phase droplets, acting as an emulsifier to stabilize the oil phase droplets, so that the water phase and the oil phase form a Pickering emulsion. At the same time, the colloidal particles can form hydrogen bonds with the water-soluble cellulose ether, cooperatively stabilizing the oil phase droplets, improving the storage stability and coalescence stability of the emulsion. The colloidal particles and the water-soluble cellulose ether can also both have negative charges, reducing the Zeta potential of the water phase, improving the stability and dispersibility of the colloidal particles in the water phase, achieving improved storage stability and coalescence stability of the emulsion without the need for surfactants or organic modifiers, and also having biocompatibility and environmental friendliness.

[0048] In some embodiments, the Dv50 particle size of the colloidal particles can be 1-1000 nm, and in exemplary embodiments, can include but not limited to any one value or a range between any two values of 1 nm, 10 nm, 50 nm, 100 nm, and 1000 nm. These particle sizes of colloidal particles are conducive to uniform dispersion in the water phase, while improving the desorption energy of the colloidal particles at the oil-water interface, improving the stability of the oil phase droplets, and further improving the storage stability and coalescence stability of the emulsion.

[0049] In some embodiments, the contact angle of the colloidal particles is 20°-25°. The contact angle of the colloidal particles reflects its wetting performance at the oil-water interface, which in turn affects the stability of the oil-in-water emulsion. In exemplary embodiments, it can include but not limited to any one value or a range between any two values of 20°, 22°, 24°, and 25°. These contact angles of colloidal particles are conducive to being wetted by the water phase first, thereby forming a stable oil-in-water emulsion and improving the storage stability and coalescence stability of the Pickering emulsion.

[0050] In some embodiments, the concentration of the colloidal particles in the aqueous phase is 1wt% to 5wt%, and in exemplary embodiments, can include but not limited to any one of 1wt%, 2wt%, 3wt%, 4wt%, 5wt% or a range between any two of them, and optionally 3wt%. The concentration of the colloidal particles can affect the number of colloidal particles distributed on the surface of the oil phase droplets, and these concentrations can enable the colloidal particles to form a monolayer film-like morphology on the surface of the oil phase droplets, thereby fully exerting the emulsifier effect, forming a stable oil-in-water emulsion, and improving the storage stability and coalescence stability of the Pickering emulsion. In addition, the colloidal particles at these concentrations can also endow the Pickering emulsion with shear thinning, thixotropy, and deformation resistance, which is beneficial for subsequent molding.

[0051] In some embodiments, the water-soluble cellulose ether can include anionic, cationic and non-ionic types, and can include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and ethyl cellulose. These water-soluble cellulose ethers can form hydrogen bonds with the above-mentioned colloidal particles and / or both contain negative charges, and can synergistically act as emulsifiers, synergistically enhance the uniform and stable dispersion of the oil phase droplets in the aqueous phase, and can still improve the storage stability and coalescence stability of the Pickering emulsion without surfactants and organic modifiers, and also have biocompatibility and environmental friendliness.

[0052] In some embodiments, the concentration of the water-soluble cellulose ether in the aqueous phase is 0.1wt% to 4wt%, and in exemplary embodiments, can include but not limited to any one of 0.1wt%, 0.25wt%, 0.5wt%, 1wt%, 3wt%, 4wt% or a range between any two of them, and optionally 3wt%. These proportions of water-soluble cellulose ethers can form hydrogen bonds with the above-mentioned colloidal particles and / or both contain negative charges, and can further synergistically act as emulsifiers, and improve the storage stability and coalescence stability of the Pickering emulsion. In addition, the water-soluble cellulose ethers at these concentrations can also synergistically endow the Pickering emulsion with shear thinning, thixotropy, and deformation resistance, which is beneficial for subsequent molding.

[0053] In some embodiments, the pH value of the aqueous phase is 6 to 8. Changes in the pH value can affect the hydrophobicity of the colloidal particles and can adjust the adsorption of the colloidal particles on the surface of the oil phase droplets. The aqueous phase at these pH values can improve the storage stability and coalescence stability of the Pickering emulsion.

[0054] In some embodiments, the Zeta potential of the aqueous phase is ≤﹣20mV, that is, the Zeta potential is negative and the absolute value is not less than 20. In exemplary embodiments, can include but not limited to any one of ﹣20mV, ﹣30mV, ﹣35mV or a range between any two of them. The aqueous phase at these Zeta potentials can be beneficial to improve the stability and dispersibility of the colloidal particles in the aqueous phase, and improve the storage stability and coalescence stability of the emulsion.

[0055] Regarding the oil phase:

[0056] The oil phase containing fatty acid ester makes the oil-water interface have a suitable tension, and is conducive to the interaction with the colloidal particles, so that at least part of the colloidal particles are distributed on the surface of the oil phase droplets. In some embodiments, the solid-liquid phase transition temperature of the fatty acid ester is 25-50°C, and in the exemplary embodiment, it can include but is not limited to any value or range between any two values of 25°C, 30°C, 35°C, 45°C, 50°C. When applied to self-healing concrete, the fatty acid ester of the oil phase of the Pickering emulsion will solidify to form a hydrophobic pipeline connected to the outside world after the water phase of the Pickering emulsion is consumed. Therefore, these fatty acid esters need to remain in a liquid state in the emulsion and remain in a solid state in the pipeline self-healing concrete use scenario. When formulating and storing the emulsion, the temperature needs to be higher than the solid-liquid phase transition temperature, and the temperature in the use scenario needs to be lower than the solid-liquid phase transition temperature.

[0057] As an example, the solid-liquid phase transition temperature of the fatty acid ester is 28°C. When formulating and storing the emulsion, the temperature needs to be kept above 28°C to remain in a liquid state. In the application, the final use scenario temperature is less than 28°C to maintain a solid hydrophobic pipeline. Therefore, the above-mentioned solid-liquid phase transition temperature is suitable for commonly used use scenarios. When it is necessary to be applied to extremely hot scenarios, a fatty acid ester with a higher solid-liquid phase transition temperature needs to be selected to ensure that the fatty acid ester is in a solid state at the temperature in the use scenario, and the temperature during the formulation and storage of the emulsion also needs to be adjusted accordingly.

[0058] In some embodiments, the fatty acid ester includes at least one of methyl palmitate, methyl heptadecanoate, methyl octadecanoate, methyl eicosanoate, ethyl hexadecanoate, ethyl heptadecanoate, ethyl octadecanoate. These fatty acid esters can be used in the oil phase of the Pickering emulsion and can form a hydrophobic pipeline after solidification. Among them, the solid-liquid phase transition temperature of methyl palmitate is 28°C, and the self-healing concrete is suitable for use scenarios with a temperature less than 28°C; the solid-liquid phase transition temperature of methyl heptadecanoate is 30°C; the solid-liquid phase transition temperature of methyl octadecanoate is 37-41°C; the solid-liquid phase transition temperature of methyl eicosanoate is 45-48°C; the solid-liquid phase transition temperature of ethyl hexadecanoate is 24-26°C; the solid-liquid phase transition temperature of ethyl heptadecanoate is 28°C; the solid-liquid phase transition temperature of ethyl octadecanoate is 34-38°C. In addition to these fatty acid esters, other homologues can also be used. According to the corresponding solid-liquid phase transition temperature, they can be applied to different pipeline self-healing concrete use scenarios.

[0059] In some embodiments, the Dv50 particle size of the droplets of the oil phase is 10-30 μm, and in exemplary embodiments, can include but not limited to any one of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm or a range between any two of them. The droplets of the oil phase with these particle sizes are beneficial for the uniform dispersion of the droplets in the water phase, reducing the occurrence of coalescence, and can also cooperate with the water phase to endow the Pickering emulsion with shear thinning, thixotropy, and deformation resistance, which is beneficial for subsequent molding.

[0060] Regarding the emulsion:

[0061] The Pickering emulsion formed by the above-mentioned water phase and oil phase has good stability without adding surfactants and organic modifiers. In some embodiments, the oil-water ratio of the Pickering emulsion is 1:(2-5), and in exemplary embodiments, can include but not limited to any one of 1:2, 1:3, 1:4, 1:5 or a range between any two of them, and can be optionally 1:3. The oil-water ratio with these proportions is beneficial for improving the storage stability and coalescence stability of the Pickering emulsion. At the same time, the oil-water ratio with these proportions is also beneficial for improving the shear thinning, thixotropy, and deformation resistance, and has a certain self-supporting strength, thereby improving the molding performance of the Pickering emulsion.

[0062] The second aspect of the embodiments of the present application provides a preparation method of the Pickering emulsion of the above-mentioned embodiments of the present application, which includes the following steps:

[0063] S10. Adding the raw material of the oil phase to the solution of the water phase for emulsification treatment.

[0064] The preparation method of the embodiments of the present application emulsifies the above-mentioned raw material of the oil phase and the solution of the water phase. The colloidal particles and water-soluble cellulose ethers in the water phase cooperate to play the role of emulsifiers. The oil phase will form droplets. At least part of the colloidal particles and water-soluble cellulose ethers are distributed on the surface of the droplets of the oil phase, so that the droplets of the oil phase are uniformly and stably dispersed in the water phase without coalescence. Therefore, the above-mentioned Pickering emulsion can be prepared without surfactants and organic modifiers, and can be used for pipeline self-repairing concrete. The preparation method is controllable, and the prepared Pickering emulsion has good storage stability and coalescence stability, and also has biocompatibility and environmental friendliness.

[0065] In the above-mentioned embodiments, the solution of the water phase can be prepared first. The colloidal particles can be added to water first, and then the water-soluble cellulose ether is added after uniform dispersion, and then uniformly dispersed to obtain the solution of the water phase. The types and amounts of the colloidal particles and the water-soluble cellulose ether can refer to the related descriptions in the Pickering emulsion above. Then, the heated liquid fatty acid ester is added as the raw material of the oil phase to the solution of the water phase, and the oil-water ratio can be matched according to the above-mentioned oil-water ratio. Finally, emulsification treatment is performed.

[0066] The emulsification treatment can adopt high-pressure homogenization, ultrasonic method, microfluidic technology, membrane emulsification technology, electric field emulsification, or the like. Optionally, the emulsification treatment is performed by a high-pressure homogenizer. The rotation speed of the high-pressure homogenizer can be 10,000-20,000 rpm, and the homogenization time can be 5-20 min. The initial emulsion is prepared into a Pickering emulsion through cavitation, turbulence, and shearing of the machine.

[0067] The third aspect of the embodiments of the present application provides a pipeline self-repairing concrete product, which comprises a product base and a hydrophobic pipeline. The hydrophobic pipeline is arranged in the interior of the product base and is in communication with the outside. The hydrophobic pipeline is formed by solidification of the Pickering emulsion of the above embodiments of the present application.

[0068] The pipeline self-repairing concrete product of the embodiments of the present application comprises a product base and a hydrophobic pipeline in the interior. When a crack occurs in the product base, a crack repairing agent, such as a polyurethane crack repairing agent, can be delivered into the hydrophobic pipeline, so that the crack repairing agent flows into the interior of the product base along the hydrophobic pipeline, penetrates into the crack, and fills the crack. The crack repairing agent can repair the crack of the product base in time. Since the hydrophobic pipeline is formed by solidification of the Pickering emulsion described above, the pipeline is hydrophobic, and the crack repairing agent will not leak out during delivery and can reach the crack directly. The pipeline self-repairing concrete product of the embodiments of the present application also has biocompatibility and environmental friendliness.

[0069] In some embodiments, the hydrophobic pipeline can be a common three-dimensional regular shape, such as a matrix shape, a honeycomb shape, a grid shape, a spiral shape, and the like, or can be a non-regular shape pipeline, and can also contain many capillary pipelines in addition to the main pipeline. In some embodiments, the diameter of the hydrophobic pipeline is 0.6-3.5 mm, and in exemplary embodiments, can include but is not limited to any one of 0.6 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm or a range between any two values. The hydrophobic pipeline with these diameters is conducive to the delivery of the repairing agent.

[0070] The fourth aspect of the embodiments of the present application provides a preparation method of a pipeline self-repairing concrete product, which comprises the following steps:

[0071] S01. Constructing a pipeline template in a concrete slurry, wherein the pipeline template is prepared by molding treatment of the Pickering emulsion of the above embodiments of the present application or the Pickering emulsion prepared by the preparation method of the above embodiments of the present application;

[0072] S02. Performing a hydration reaction on the concrete slurry containing the pipeline template to obtain a pipeline self-repairing concrete product.

[0073] The preparation method of the embodiments of the present application first prepares a concrete slurry. The concrete slurry is a typical porous material and contains many interconnected micropores. The Pickering emulsion can be formed and processed in the concrete slurry before the concrete slurry is solidified. Since the Pickering emulsion has a certain self-supporting strength, it can be filled and combined in the concrete slurry to construct a pipeline template. Then, a hydration reaction is performed. The water phase of the Pickering emulsion is consumed until the oil-in-water emulsion structure is destroyed, and the fatty acid ester of the oil phase penetrates into the surrounding concrete. After the temperature decreases, the fatty acid ester solidifies to form a hydrophobic pipeline in the concrete product matrix, thereby obtaining a pipeline self-repairing concrete product.

[0074] [Step S01]

[0075] The concrete slurry in step S01 can be a cement-based slurry. The cement can be ordinary Portland cement, and the strength can be PO 42.5 grade. The concrete slurry can also contain aggregate, auxiliary cementitious material, water reducing agent, etc. The concrete slurry can be prepared according to a water-cement ratio of 0.3-0.5.

[0076] In some embodiments, the forming and processing of the emulsion includes 3D printing processing. The Pickering emulsion is used as printing ink, and the 3D printing processing is beneficial to the forming of the pipeline template and the formation of a preset shape and size of the pipeline template. Finally, the pipeline in the pipeline self-repairing concrete product can have a preset shape and size, thereby improving the self-repairing effect. Since the Pickering emulsion has a certain self-supporting strength, it can be filled and combined in the concrete slurry to construct a pipeline template.

[0077] During the 3D printing processing, the printing needle can be inserted into the concrete slurry. While the Pickering emulsion is extruded, the air pressure, needle moving speed, and needle inner diameter are adjusted according to the predetermined program to control the direction, shape, size, etc. of the pipeline template. After the printing is completed, the pipeline template with internal and external communication is formed.

[0078] In addition, the emulsion can also be formed and processed to construct a pipeline template first, and then the concrete slurry is poured on the pipeline, so that the pipeline template is arranged in the concrete slurry and is in communication with the outside.

[0079] [Step S02]

[0080] In step S02, a hydration reaction is performed. During the process, the water phase of the Pickering emulsion is continuously consumed, the oil-in-water emulsion structure is destroyed, the fatty acid ester of the oil phase flows out, and penetrates into the surrounding concrete. In the early stage of the hydration reaction, the fatty acid ester remains in a liquid state due to the heat generated by the hydration reaction. In the later stage of the hydration reaction, the temperature decreases, the fatty acid ester solidifies to form a hydrophobic pipeline, thereby obtaining a pipeline self-repairing concrete product.

[0081] The specific embodiments will be described below.

[0082] Example 1

[0083] This example provides a Pickering emulsion and a method for preparing the Pickering emulsion, the Pickering emulsion is an oil-in-water emulsion, the water phase contains water, sodium-based montmorillonite (colloidal particles) with a concentration of 1wt%, carboxymethyl cellulose (water-soluble cellulose ether) with a concentration of 3wt%, at least part of the montmorillonite and carboxymethyl cellulose are distributed on the surface of the oil droplets in the oil phase. The oil phase is methyl palmitate, and the oil-water volume ratio is 1:3.

[0084] The preparation method comprises the following steps:

[0085] As shown in Figure 1 , the montmorillonite is added to 4.5mL of deionized water, and the montmorillonite is uniformly dispersed in the water under magnetic stirring for 10min, then the carboxymethyl cellulose is added, so that the mixed solution contains 1wt% of montmorillonite and 3wt% of carboxymethyl cellulose. Then 1.5mL of heated and dissolved methyl palmitate is added, the oil-water volume ratio is 1:3, and then the homogenizer is added, and the Pickering emulsion is obtained by homogenizing at a speed of 13400rpm for 10min.

[0086] Example 2

[0087] This example provides a Pickering emulsion and a method for preparing the Pickering emulsion, which is different from example 1 only in that the concentration of montmorillonite in the water phase is changed to 2wt%, and the others are the same.

[0088] Example 3

[0089] This example provides a Pickering emulsion and a method for preparing the Pickering emulsion, which is different from example 1 only in that the concentration of montmorillonite in the water phase is changed to 3wt%, and the others are the same.

[0090] Example 4

[0091] This example provides a Pickering emulsion and a method for preparing the Pickering emulsion, which is different from example 1 only in that the concentration of montmorillonite in the water phase is changed to 4wt%, and the others are the same.

[0092] Example 5

[0093] This example provides a Pickering emulsion and a method for preparing the Pickering emulsion, which is different from example 1 only in that the concentration of montmorillonite in the water phase is changed to 5wt%, and the others are the same.

[0094] Example 6

[0095] This example provides a Pickering emulsion and a method for preparing the Pickering emulsion, which is different from example 3 only in that the concentration of carboxymethyl cellulose in the water phase is changed to 0.1wt%, and the others are the same.

[0096] Example 7

[0097] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the concentration of carboxymethyl cellulose in the aqueous phase is changed to 0.25 wt%, and others are the same.

[0098] Example 8

[0099] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the concentration of carboxymethyl cellulose in the aqueous phase is changed to 0.5 wt%, and others are the same.

[0100] Example 9

[0101] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the concentration of carboxymethyl cellulose in the aqueous phase is changed to 1 wt%, and others are the same.

[0102] Example 10

[0103] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the concentration of carboxymethyl cellulose in the aqueous phase is changed to 2 wt%, and others are the same.

[0104] Example 11

[0105] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the concentration of carboxymethyl cellulose in the aqueous phase is changed to 4 wt%, and others are the same.

[0106] Example 12

[0107] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the volume ratio of oil to water is changed to 1:2, and others are the same.

[0108] Example 13

[0109] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the volume ratio of oil to water is changed to 1:4, and others are the same.

[0110] Example 14

[0111] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that the volume ratio of oil to water is changed to 1:5, and others are the same.

[0112] Comparative Example 1

[0113] This example provides a Pickering emulsion and a method for preparing the same, which is identical to that of Example 3 except that a sodium alginate solution with a concentration of 3 wt% is used as the aqueous phase, and Tween 80 is used as the oil-water contact surface stabilizer, and others are the same.

[0114] Comparative Example 2

[0115] The present example provides a Pickering emulsion and a method for preparing the same, which is different from example 3 only in that a 3wt% solution of laponite is used as the water phase, and didodecyldimethylammonium bromide is used as the oil-water interface stabilizer, and the rest is the same.

[0116] The differences between the examples and the comparative examples are shown in Table 1 below:

[0117] Table 1

[0118]

[0119]

[0120] Performance tests and result analysis

[0121] 1. Infrared spectrum test

[0122] The colloidal aqueous solution of montmorillonite, the aqueous solution of carboxymethyl cellulose, and the water phase in example 3 and example 9 were tested by infrared spectrum, and the results are shown in Figure 2 Figure 2 In the above table, MMT represents montmorillonite, and CMC represents carboxymethyl cellulose.

[0123] It can be seen that montmorillonite has an absorption peak caused by the stretching vibration of —OH of surface water molecules near 3617cm -1 , an absorption peak caused by the stretching of interlayer water molecules near 3448cm -1 , and a bending vibration of interlayer water molecules at 1641cm -1 , which indicates that the MMT plate contains crystal water. Absorption peaks caused by Si—O stretching and bending vibration appear near 1030cm -1 and 525cm -1 .

[0124] The absorption peak of CMC near 2920cm -1 is the asymmetric stretching vibration mode of CH2, the absorption peak at 1603cm -1 is the C=O stretching vibration mode, the absorption peak at 1422cm -1 is the CH2 bending vibration mode, and the absorption peak at 1333cm -1 is the CH2 out-of-plane rocking vibration mode.

[0125] When the water phase contains both 3wt% MMT and 1wt% CMC, the intensity of the Si—O stretching peak at 1030cm -1 is significantly weakened, the peak at 525cm -1 disappears, and the characteristic peaks of CMC about CH2 also almost disappear. With the amount of CMC increasing to 3wt%, the Si—O stretching peak at 1030cm​-1 The Si—O stretching peak almost disappeared. These results show that there is a strong hydrogen bond interaction between the CH2group on the CMC chain and the Si—O bond on the MMT, in other words, the CMC molecules are adsorbed on the edge of the MMT plate in this way, and the CMC as a high molecular agent with many branches can be combined on the surface of the montmorillonite colloidal particles. From this result, it can be shown that the CMC can assist the MMT particles to stabilize the emulsion in the Pickering emulsion system, and under the synergistic action of the two, the oil phase droplets will not easily coagulate, and there is no need for the surfactant or organic modifier in the comparative example 1 and comparative example 2, which has biocompatibility and environmental friendliness.

[0126] 2. Zeta potential analysis

[0127] The aqueous phase in the Pickering emulsion of example 3, example 6 to example 11 was tested for Zeta potential, and the results are shown in Figure 3 Figure 3 In the formula, MMT represents montmorillonite, and CMC represents carboxymethyl cellulose. The surface of the sheet layer of montmorillonite has a negative charge, and carboxymethyl cellulose also exhibits a negative charge in an aqueous solution due to the large number of carboxyl groups in its chemical structure. The Zeta potential of the MMT solution alone is -3.4 mV, and the Zeta potential of the CMC solution alone is -25.6 mV.

[0128] Figure 3 As can be seen from the Zeta potential of the mixed solution of 3wt% MMT and different amounts of CMC, compared with the pure MMT solution, the Zeta potential of the MMT and CMC mixed solution decreases significantly, and with the continuous addition of CMC, the Zeta potential decreases significantly, that is, the Zeta potential is negative, and the absolute value becomes larger and larger, representing better dispersibility and stability. When the concentration of CMC increases to 4wt%, the Zeta potential of the solution reaches -36.2 mV, indicating that it has good colloidal stability and dispersibility. This test analysis proves that the two negatively charged substances in the aqueous phase can further improve the stability of the Pickering emulsion.

[0129] 3. Stability test

[0130] The Pickering emulsion stabilized by montmorillonite / carboxymethyl cellulose has good storage stability. The Pickering emulsion with an oil-water ratio of 1:3 prepared from the Pickering emulsion of example 6 to example 9, which contains 3wt% montmorillonite and 0.1wt%, 0.25wt%, 0.5wt%, and 1wt% carboxymethyl cellulose respectively in the aqueous phase, can be stored for more than 2 months without delamination.

[0131] ​The Pickering emulsions of Example 3, Example 9 to 14 were centrifuged at 5000 rpm for 5 min, the water phase contained 3 wt% of montmorillonite and 1 wt% or more of carboxymethyl cellulose prepared Pickering emulsion did not delaminate.

[0132] 4. Thixotropy test

[0133] The shear viscosity and modulus of the emulsion samples of Example 1 to 14, Comparative Example 1, 2 were measured using a rheometer (nton Pr MCR 302) at a controlled temperature of 50°C. All samples were measured at 10 s -1 Pre-shear was performed. The apparent shear viscosity was monitored by increasing the shear rate from 0.01 s -1 to 100 s -1 at 1 Hz. For dynamic viscoelasticity measurements, the linear viscoelastic range was determined at a fixed frequency of 10 rad / s by shear stress (0.01 to 1000), and the storage modulus (G’) and loss modulus (G”) were recorded.

[0134] In which the content of montmorillonite in Example 1 to Example 5 is 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% respectively, gradually increasing, and the others are the same. Figure 4 The viscosity of these emulsion samples versus shear rate is shown, Figure 5 The storage modulus and loss modulus of these emulsion samples under shear stress sweep are shown, Figure 4 , Figure 5 In which MMT represents montmorillonite.

[0135] The content of carboxymethyl cellulose in Example 9, 10, 3, 11 is 1 wt%, 2 wt%, 3 wt%, 4 wt% respectively, gradually increasing, and the others are the same. Figure 6 The viscosity of these emulsion samples versus shear rate is shown, Figure 7 The storage modulus and loss modulus of these emulsion samples under shear stress sweep are shown, Figure 6 , Figure 7 In which CMC represents carboxymethyl cellulose.

[0136] The oil to water ratio in Example 12, 3, 13, 14 is 1:2, 1:3, 1:4, 1:5 respectively, the specific gravity of the oil phase gradually decreases, and the others are the same. Figure 8 The viscosity of these emulsion samples versus shear rate is shown, Figure 9 The storage modulus and loss modulus of these emulsion samples under shear stress sweep are shown, Figure 8 , Figure 9 In which O:W represents the oil to water ratio.

[0137] From Figures 4 to 9It can be seen that the rheological properties of the Pickering emulsion will change when the amount of montmorillonite, the amount of carboxymethyl cellulose and the oil-water ratio are adjusted. As shown in Figure 4 , Figure 6 , Figure 8 , all the Pickering emulsions have shear thinning behavior, and the viscosity will decrease rapidly with the increase of shear rate. This property can ensure the smooth extrusion of the emulsion during the subsequent 3D printing process without blocking the needle port. As can be seen from the respective comparison in each figure, with the increase of the amount of montmorillonite, the increase of carboxymethyl cellulose, and the increase of the oil-water ratio, the initial viscosity of the Pickering emulsion is continuously increased, and the highest is more than 10 3 Pa·s. The initial high viscosity can ensure the shaping ability of the emulsion.

[0138] At the same time, the emulsion also has obvious thixotropy, as shown in Figure 5 , Figure 7 , Figure 9 , the storage modulus G' is obviously greater than the loss modulus G" under low shear stress. The stress at which the first intersection point of the storage modulus and the loss modulus curves appears is the yield stress. With the increase of the amount of montmorillonite, the increase of carboxymethyl cellulose, and the increase of the oil-water ratio, the modulus value of the Pickering emulsion increases, and the yield stress also increases. These characteristics show that the Pickering emulsion has a certain resistance to external shear, that is, deformation, and has a self-supporting performance. Subsequently, the Pickering emulsion ink can be extruded from the needle port while maintaining the integrity of the ink structure, preventing deformation and collapse.

[0139] Pipe self-repairing concrete product embodiment

[0140] The Pickering emulsion of the above embodiment 3 is used as a printing ink to prepare a pipe self-repairing concrete product, as shown in Figure 10 , a three-dimensional model is designed and converted into g code, and then a 3D printer is controlled to print in the cement slurry. The cement is ordinary Portland cement (PO 42.5), and the water-cement ratio is 0.4 to prepare the slurry. The needle of the 3D printer is inserted into the cement matrix slurry to form a pipe template.

[0141] Then, hydration treatment is carried out. In the early stage of cement hydration, the hydration heat temperature exceeds the solid-liquid phase transition temperature of methyl palmitate (28℃), the cement hydration continuously absorbs water, the oil-in-water structure of the Pickering emulsion is gradually destroyed, and the methyl palmitate remains in a liquid state and penetrates into the surrounding cement matrix. As the hydration proceeds to the later stage, the temperature inside the cement decreases, the methyl palmitate changes into a solid state to form a hydrophobic pipe wall, and the pipe is connected to the outside. Finally, the inside of the pipe is washed with clean water for 10 minutes to wash away the montmorillonite and carboxymethyl cellulose, and a pipe self-repairing concrete product is obtained.

[0142] As shown in Figure 11As shown, when the pipe shape is constructed inside the concrete by 3D printing, the size of the pipe can be controlled by adjusting the air pressure, needle moving speed and needle inner diameter to obtain different sizes of pipe diameter, the minimum being 0.6mm and the maximum being 3.5mm.

[0143] In order to verify the hydrophobicity and connectivity of the hydrophobic pipe, water is pumped from the outside to the pipe, water is added from one end and water is discharged from the other end to verify the loss rate, and it is found that the volume loss rate of the pumped water is less than 2%, which shows that the methyl palmitate has hydrophobically modified the cement matrix around the pipe, and thus the internal pipe can pump different types of liquid repair agents from the outside to repair the cracks.

[0144] A cement test piece with a size of 40mm*40mm*160mm is made, a single straight-through pipe with a diameter of 2mm is printed in the middle position, the 3D printing parameters are as follows: the needle type is 21G (inner diameter 0.51mm), the air pressure is 0.2MPa, and the needle moving speed is 20mm / s, after printing, the pipe self-repairing concrete piece is obtained after 28 days of hydration reaction and curing. The cement test piece is cracked by three-point bending loading, the internal pipe is connected with a peristaltic pump, and polyurethane is pumped for 10min, and then cured for one day. As shown in Figure 12 Figure 12 The left graph in the figure is the state before crack repair, and the right graph is the state after crack repair, and by comparison, it can be seen that the crack gap is filled, and the polyurethane has a repairing effect on the crack.

[0145] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a self-healing concrete component for pipelines, characterized in that, Includes the following steps: A pipe template is constructed in concrete slurry, the pipe template being made of Pickering emulsion through 3D printing. The concrete slurry containing the pipe template is subjected to a hydration reaction to obtain a self-healing concrete component for the pipe. The Pickering emulsion is an oil-in-water emulsion, wherein the aqueous phase comprises water, colloidal particles, and water-soluble cellulose ethers, and the colloidal particles and water-soluble cellulose ethers are dispersed in water; and the oil phase comprises fatty acid esters. At least a portion of the colloidal particles and the water-soluble cellulose ether are distributed on the surface of the droplets in the oil phase, wherein the colloidal particles and the water-soluble cellulose ether form hydrogen bonds and / or both are negatively charged; The concentration of the water-soluble cellulose ether in the aqueous phase is 0.1 wt% to 4 wt%. The concentration of the colloidal particles in the aqueous phase is 1 wt% to 5 wt%. The oil-to-water ratio of the Pickering emulsion is 1:(2-5); The preparation method of the Pickering emulsion includes the following steps: The colloidal particles and the water-soluble cellulose ether are sequentially added to water and mixed to obtain the aqueous solution. The raw material, including the oil phase, is added to the aqueous phase solution for emulsification.

2. The preparation method according to claim 1, characterized in that: The water-soluble cellulose ether includes at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and ethyl cellulose.

3. The preparation method according to claim 1 or 2, characterized in that: The contact angle of the colloidal particles is 20° to 25°; And / or, the Dv50 particle size of the colloidal particles can be 1 to 1000 nm; And / or, the colloidal particles include at least one of montmorillonite, kaolinite, nano-silica, lithium saponite, and sepiolite.

4. The preparation method according to claim 1 or 2, characterized in that: The pH value of the aqueous phase is 6 to 8; And / or, the Zeta potential of the aqueous phase is ≤ -20 mV.

5. The preparation method according to claim 1 or 2, characterized in that: The solid-liquid phase transition temperature of the fatty acid ester is 25–50°C. And / or, the fatty acid ester includes at least one of methyl palmitate, methyl heptanoate, methyl octadecanoate, methyl eicosanoate, ethyl hexadecanoate, and ethyl octadecanoate; And / or, the Dv50 particle size of the oil phase droplets is 10–30 μm.

6. A self-healing concrete component for pipelines, characterized in that: The invention includes a concrete component substrate and a drainage channel, wherein the drainage channel is disposed in the component substrate and communicates with the outside, and the self-healing concrete component is prepared by the preparation method according to any one of claims 1 to 5.

7. The self-healing concrete component for pipelines according to claim 6, characterized in that: The diameter of the drainage pipe is 0.6 to 3.5 mm.

Images