Self-repairing overall super-hydrophobic concrete material and preparation method thereof

Abstract

The invention provides a self-repairing overall super-hydrophobic concrete material and a preparation method thereof, and belongs to the technical field of concrete.The self-repairing overall super-hydrophobic concrete material contains modified hollow SiO2 microspheres, the size of the microspheres is 100-300 nm, the wall thickness of the microspheres is 30-80 nm, a shell layer of the microspheres is of a pore structure, organosiloxane is loaded on the surface and in a cavity of the microspheres, and the modified hollow SiO2 microspheres are hollow SiO2 microspheres. And the microspheres have relatively small apparent density. According to the scheme, the density difference between the hollow SiO2 microspheres and the concrete is ingeniously utilized, after the concrete is vibrated, a lotus leaf-like surface rough structure is formed outside, and the internal compactness and the microstructure are improved; according to the scheme, the problem that low-surface-energy substances such as organosiloxane easily lose efficacy in a concrete high-alkali environment is solved, the problem that the strength becomes low due to the fact that cement hydration is affected by direct addition of a hydrophobic modifier is also avoided, the concrete has the advantages of being small in modified material dosage and low in cost, and the self-repairing capacity and durability of the concrete are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a self-repairing integral super-hydrophobic concrete material and a preparation method thereof. BACKGROUND

[0002] Concrete is widely used in civil engineering fields such as roads, bridges, and building construction due to its high mechanical properties and excellent plasticity. However, the surface of ordinary concrete has a large number of hydroxyl groups generated by cement hydration and exhibits porous characteristics, making the concrete have strong hydrophilic properties. Corrosive ions such as chloride ions and sulfates can easily penetrate the interior along with water migration, severely affecting the durability and service life of concrete. In cold regions of the north, the repeated freezing and thawing of water trapped in the interior of concrete leads to concrete expansion and pulverization. In coastal areas, corrosive ions enter the interior of concrete to rust and reinforce steel, damaging the safety and quality of buildings. Therefore, enhancing the ability of concrete to resist water intrusion can improve the service life of concrete.

[0003] Both surface super-hydrophobic modification and integral super-hydrophobic modification of concrete materials can improve the impermeability, chloride ion resistance, and frost resistance of concrete materials. The impermeability of integral super-hydrophobic modification is superior to that of surface super-hydrophobic modification. The rough structure of integral super-hydrophobic components has good adhesion and is integrated with the cement base material, unlike surface super-hydrophobic concrete which is prone to falling off and can restore super-hydrophobic properties by simply removing the surface. In addition, when new cracks occur in concrete during service, it still has waterproof properties due to the presence of low surface energy substances in the interior.

[0004] There are two main ways to modify the integral super-hydrophobicity of concrete: directly adding a hydrophobic agent and adding a hydrophobic modified cementitious material. However, directly adding a hydrophobic agent will inevitably inhibit the hydration of cement, resulting in slightly lower mechanical strength of concrete than ordinary concrete. Adding a hydrophobic modified cementitious material or filler requires a large amount and is costly, making it unsuitable for the popularization and application of super-hydrophobic concrete. The invention patent application with the publication number CN11746601A and the name of a simple and environmentally friendly integral super-hydrophobic concrete preparation method and product discloses a technical solution of adding super-hydrophobic modified silica powder to the cement system to obtain integral super-hydrophobic concrete. However, the amount of hydrophobic modified material used is also large, and the low surface energy substance is sensitive to alkaline environments and can easily fail when in contact with the high alkalinity environment of concrete for a long time. Therefore, there is an urgent need to develop an integral super-hydrophobic concrete material with small material usage, low cost, and high durability to solve this problem. SUMMARY

[0005] Therefore, the present application provides a self-repairing integral super-hydrophobic concrete material and a preparation method thereof, aiming to solve the technical problems of low strength, large amount of modified material, and poor durability of existing integral super-hydrophobic modification of concrete.

[0006] In a first aspect, the present application provides a self-repairing monolithic super-hydrophobic concrete material, which contains modified hollow SiO2 microspheres in raw materials, the modified hollow SiO2 microspheres have a size of 100-300 nm and a wall thickness of 30-80 nm, the shell layer has micropore and mesopore structures and the surface and cavity of the modified hollow SiO2 microspheres are loaded with organosiloxane; the apparent density of the modified hollow SiO2 microspheres is 1.8-2.1 g / cm 3 , and the apparent density of the self-repairing monolithic super-hydrophobic concrete material is 2.2-2.5 g / cm 3 .

[0007] In the present application, when the organosiloxane on the surface of the modified hollow SiO2 microspheres is invalid due to long-term contact with the high-alkali environment of the concrete, the organosiloxane in the cavity of the SiO2 microspheres is slowly released and supplemented through the pore structure on the shell layer under the driving force of the internal and external concentration difference, so that the concrete material has excellent self-repairing performance; the test data also show that the contact angle between the concrete material prepared by the present application and water is 156-160°, and the super-hydrophobic property is still exhibited after the wear resistance test and the durability test. In addition, the hollow SiO2 microspheres loaded with a low-surface-energy substance (i.e., organosiloxane) can move to the surface of the concrete under the influence of the density difference, form a rough structure similar to the surface of a lotus leaf, and achieve super-hydrophobic property.

[0008] Preferably, in the above self-repairing monolithic super-hydrophobic concrete material, the organosiloxane includes but is not limited to one or more of hexadecyltrimethoxysilane, octadecyltrichlorosilane, polydimethylsiloxane, dimethyldimethoxysilane, isobutyltrimethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, tetramethoxysilane, phenyltrimethoxysilane, chlorotrimethylsilane, trimethylchlorosilane, and dimethylchlorosilane.

[0009] Preferably, in the above self-repairing monolithic super-hydrophobic concrete material, the preparation method of the modified hollow SiO2 microspheres includes the following steps: mixing a polyacrylic acid aqueous solution and an ammonia solution and then pouring into ethanol to obtain a polyacrylic acid microsphere template; slowly adding tetraethyl orthosilicate under stirring, centrifuging and washing after the reaction is completed, and high-temperature calcination to obtain hollow SiO2 microspheres; mixing the hollow SiO2 microspheres and organosiloxane in an organic solvent, and vacuum impregnation to make the organosiloxane penetrate into the cavity of the hollow SiO2 microspheres, thereby obtaining the modified hollow SiO2 microspheres.

[0010] More preferably, in the self-repairing monolithic super-hydrophobic concrete material, the concentration of the polyacrylic acid aqueous solution is 50wt%, the concentration of the ammonia aqueous solution is 25wt%, and the mass ratio of the two is (3-4):20; the mass ratio of the total mass of the polyacrylic acid aqueous solution and the ammonia aqueous solution to the mass of the ethanol is 1:(15-20). It can be understood that, in the present application, the hollow SiO2 microspheres are prepared by hydrolysis and condensation of tetraethyl orthosilicate on the surface of polyacrylic acid, so the size of the template determines the size of the cavity, which in turn affects the size and apparent density of the modified hollow SiO2 microspheres.

[0011] More preferably, in the self-repairing monolithic super-hydrophobic concrete material, the mass ratio of the tetraethyl orthosilicate to the polyacrylic acid is (6-8):1. By adjusting the amount of tetraethyl orthosilicate, the size and wall thickness of the modified hollow SiO2 microspheres can be controlled; test data show that a too thin wall thickness will result in a decrease in the wear resistance and durability of the concrete material.

[0012] More preferably, in the self-repairing monolithic super-hydrophobic concrete material, the high-temperature calcination temperature is 500-600℃, and the calcination time is 4-7h.

[0013] More preferably, in the self-repairing monolithic super-hydrophobic concrete material, the organic solvent includes but is not limited to one or more of hexane, cyclohexane, ethanol, toluene, dichloromethane, trichloromethane, ethyl acetate, tetrahydrofuran, and acetone; the vacuum impregnation conditions are 40-60℃, 0.1-1kPa, and a duration of 10-30 minutes.

[0014] Preferably, in the self-repairing monolithic super-hydrophobic concrete material, the raw materials further include cement, sand, stone, water, and a water reducing agent, and the mass ratio of the cement, sand, stone, modified hollow SiO2 microspheres, water, and water reducing agent is (150-350):(700-900):(950-1050):(2-7):(150-190):(3-10). More preferably, in some embodiments of the present application, the cement is a 42.5 ordinary portland cement, the sand has a particle size of 0.15-4.75mm and a fineness modulus of 2.5-3.0, the stone has a particle size of 5-31.5mm, and the water reducing agent is a polycarboxylic acid water reducing agent with a solid content of 8%-20%.

[0015] In a second aspect, the present application provides a method for preparing the self-repairing monolithic super-hydrophobic concrete material, which specifically comprises: uniformly mixing cement, sand, stone, modified hollow SiO2 microspheres, water, and a water reducing agent in a certain proportion, forming and vibrating, and obtaining the self-repairing monolithic super-hydrophobic concrete material after hardening and curing. The vibration can be an inserted vibration or an attached vibration, and the vibration process should avoid over-vibration and missed vibration. When the inserted vibration is used, it is recommended to sequentially vibrate from the edge to the center of the template to avoid excessive upward movement of the hollow SiO2 microspheres.

[0016] Compared with the prior art, the application has the following beneficial effects: The low surface energy substance is filled into the cavity of the hollow SiO2 microspheres, and due to the small density of the SiO2 hollow spheres, the application ingeniously utilizes the gravity difference, and through concrete vibration, the SiO2 microspheres are affected by the small density of the cement paste and move to the surface of the concrete to form a rough structure similar to the surface of a lotus leaf, realizing the super-hydrophobic property; at the same time, the low surface energy substance is loaded in the hollow SiO2 microspheres, avoiding long-term contact with the alkaline cement paste, and after slow release, the super-hydrophobic property of the concrete can be greatly prolonged, and the durability is improved. In addition, the SiO2 microspheres in the concrete material can significantly improve the internal pore structure, reduce the pore size and pore volume, and improve the impermeability of the concrete, and due to the improvement of the pore structure, the mechanical properties of the concrete are not obviously reduced. The application utilizes the gravity difference to more easily construct a rough structure on the surface, thereby effectively reducing the amount of hydrophobic modified filler used, and the cost is lower, which is conducive to wide application and promotion. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0018] Figure 1 It is the transmission electron microscope graph of the modified hollow SiO2 microspheres in Example 1; Figure 2 It is the surface scanning electron microscope graph of the self-repairing super-hydrophobic concrete material in Example 1; Figure 3 It is the internal scanning electron microscope graph of the self-repairing super-hydrophobic concrete material in Example 1; Figure 4 It is the surface scanning electron microscope graph of the concrete material in Comparative Example 1; Figure 5 It is the wetting property test graph of the self-repairing super-hydrophobic concrete material in Example 1 Figure 6 It is the super-hydrophobic effect graph of the self-repairing super-hydrophobic concrete material surface on the methylene blue dyed water in Example 1; Figure 7 It is the super-hydrophobic effect graph of the self-repairing super-hydrophobic concrete material internal on the methylene blue dyed water in Example 1; Figure 8 It is the super-hydrophobic effect graph of the self-repairing super-hydrophobic concrete material after wear resistance test on the methylene blue dyed water in Example 2. DETAILED DESCRIPTION

[0019] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the present document are intended to cover non-exclusive inclusion.

[0021] The overall super-hydrophobic modification of the concrete material is the key to improve the service life of the concrete, and then there are respective limitations whether it is modified by adding a hydrophobic agent or adding a hydrophobic modified cementitious material or filler. In order to solve this technical problem, the present application first prepares hollow SiO2 microspheres with polyacrylic acid as a template, then fills the hollow SiO2 microspheres with organosiloxane by vacuum impregnation, and then cleverly uses the density difference to make the modified hollow SiO2 microspheres move to the surface of the concrete and form a rough structure similar to the surface of a lotus leaf, realizing super-hydrophobicity. The overall super-hydrophobic concrete prepared by the present application scheme not only has a small amount of hydrophobic modified filler, has no effect on the strength of the concrete, but also has super-hydrophobic self-repairing performance, and the wear resistance and durability are improved.

[0022] In a first aspect, the present application provides a self-repairing overall super-hydrophobic concrete material, which raw materials include cement, sand, stone, modified hollow SiO2 microspheres, water and water reducing agent in a mass ratio of (150-350):(700-900):(950-1050):(2-7):(150-190):(3-10), wherein the modified hollow SiO2 microspheres have a size of 100-300 nm and a wall thickness of 30-80 nm, the shell layer has a pore structure and the surface and cavity are loaded with organosiloxane, and the apparent density of the modified hollow SiO2 microspheres is 1.8-2.1 g / cm 3 The apparent density of the self-repairing overall super-hydrophobic concrete material is 2.2-2.5 g / cm 3 .

[0023] In a second aspect, the present application provides a method for preparing a self-repairing overall super-hydrophobic concrete material, comprising the following steps: S1, preparing hollow SiO2 microspheres with polyacrylic acid as a template; S2, loading organosiloxane on the surface and cavity of the hollow SiO2 microspheres by vacuum impregnation; S3, mixing and stirring cement, sand, stone, modified hollow SiO2 microspheres, water and water reducing agent according to the proportion, vibrating the mixture after molding, and obtaining the self-repairing integral super-hydrophobic concrete material after hardening and curing.

[0024] In some embodiments of the present application, step S1 is specifically: mixing the polyacrylic acid aqueous solution and the ammonia solution, then pouring into ethanol to obtain a polyacrylic acid microsphere template; slowly adding tetraethyl orthosilicate under stirring, centrifuging and washing after the reaction is completed, and high-temperature calcination to obtain the hollow SiO2 microspheres. The mass ratio of tetraethyl orthosilicate to polyacrylic acid is preferably (6-8):1, and the high-temperature calcination conditions are preferably 500-600℃ for 4-7h.

[0025] In some embodiments of the present application, step S2 is specifically: mixing the hollow SiO2 microspheres and organosiloxane in an organic solvent, and vacuum impregnating to make the organosiloxane penetrate into the hollow SiO2 microspheres, thereby obtaining the modified hollow SiO2 microspheres. The organic solvent is preferably one or more of hexane, cyclohexane, ethanol, toluene, dichloromethane, trichloromethane, ethyl acetate, tetrahydrofuran, and acetone; and the vacuum impregnation conditions are preferably 40-60℃, 0.1-1kPa, and 10-30min.

[0026] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are used to explain the present application, and cannot be understood as limiting the present application. If the specific technology or conditions are not specified in the embodiments, the technology or conditions described in the literature in the art or according to the product manual are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be obtained by market purchase.

[0027] In the following examples and comparative examples, the same cement, sand, stone and water reducing agent are used, wherein the cement is 42.5 ordinary portland cement, the particle size of the sand is 0.15-4.75mm, the particle size of the stone is 5-31.5mm and continuously graded, and the water reducing agent is a polycarboxylic acid water reducing agent.

[0028] Example 1 This example provides a self-repairing integral super-hydrophobic concrete material, and the preparation process is as follows: (1) Preparation of hollow SiO2 microspheres.

[0029] At room temperature, 16.8 g of polyacrylic acid aqueous solution (50 wt% concentration) was dissolved in 90 g of ammonia solution (25 wt% concentration), stirred to a transparent solution, and then poured into 1800 g of ethanol. The solution turned milky white, forming a polyacrylic acid microsphere template. Under magnetic stirring, 60 g of tetraethyl orthosilicate was added dropwise within 40 min. After stirring for 10 h, the tetraethyl orthosilicate was hydrolyzed and polycondensed on the surface of the polyacrylic acid template to form a SiO2 shell layer. After centrifugal washing, calcination was carried out at 550°C in a muffle furnace for 5 h to obtain hollow SiO2 microspheres.

[0030] (2) Preparation of modified hollow SiO2 microspheres.

[0031] 6 g of hexadecyltrimethoxysilane was mixed with acetone in a mass ratio of 3:100 and stirred until uniformly mixed. Then, the obtained hollow SiO2 microspheres were mixed and placed in a vacuum pressure impregnation chamber, with the temperature adjusted to 40°C and the pressure set to 0.3 kPa. The process was continued for 20 min to ensure that the hollow SiO2 microspheres were fully impregnated with hexadecyltrimethoxysilane. The mixture was then dried for use.

[0032] (3) Preparation of concrete material.

[0033] 3 kg of cement, 8 kg of sand, 10 kg of stone, 40 g of modified hollow SiO2 microspheres, 1.68 kg of water, and 70 g of water reducing agent were mixed and stirred for 150 s. After uniform stirring, the concrete mixture was molded into a 150*150*150 compression-resistant mold using an insert-type vibrator, which was sequentially vibrated from the edge to the center. After hardening and curing, a self-repairing overall super-hydrophobic concrete test block was obtained.

[0034] Example 2 This example provides a self-repairing overall super-hydrophobic concrete material, which is prepared as follows: (1) Preparation of hollow SiO2 microspheres.

[0035] At room temperature, 19.2 g of polyacrylic acid aqueous solution (50 wt% concentration) was dissolved in 100 g of ammonia solution (25 wt% concentration), stirred to a transparent solution, and then poured into 2100 g of ethanol. The solution turned milky white, forming a polyacrylic acid microsphere template. Under magnetic stirring, 70 g of tetraethyl orthosilicate was added dropwise within 30 min. After stirring for 10 h, the tetraethyl orthosilicate was hydrolyzed and polycondensed on the surface of the polyacrylic acid template to form a SiO2 shell layer. After centrifugal washing, calcination was carried out at 600°C in a muffle furnace for 5 h to obtain hollow SiO2 microspheres.

[0036] (2) Preparation of modified hollow SiO2 microspheres.

[0037] Mix 10 g of methyl triethoxysilane with ethyl acetate at a mass ratio of 1:20 and stir until uniformly mixed; then mix with the obtained hollow SiO2microspheres and place in a vacuum pressure impregnation chamber, adjust the temperature to 60°C, the pressure to 0.1 kPa, and continue for 30 minutes, so that the hollow SiO2microspheres cavities are completely infiltrated with methyl triethoxysilane, and dry for use.

[0038] (3) Preparation of the concrete material.

[0039] Mix 2 kg of cement, 8.5 kg of sand, 9.8 kg of stone, 30 g of modified hollow SiO2microspheres, 1.75 kg of water, and 60 g of water reducing agent, and stir for 120 s. After stirring uniformly, the concrete mixture is molded in a 175*185*150 impermeable test mold, and a plug-in vibrator is used to vibrate from the edge to the center in sequence, and after hardening and curing, a self-repairing overall super-hydrophobic concrete test block is obtained.

[0040] Example 3 This example provides a self-repairing overall super-hydrophobic concrete material, and the preparation process is as follows: (1) Preparation of hollow SiO2microspheres.

[0041] At room temperature, 150 g of polyacrylic acid aqueous solution (50 wt% concentration) is dissolved in 1000 g of ammonia solution (25 wt% concentration), and stirred until a transparent solution is obtained. Pour the solution into 20 kg of ethanol, and the solution turns milky white to form a polyacrylic acid microsphere template. Under stirring, 600 g of tetraethyl orthosilicate is added dropwise within 60 min. After stirring for 10 h, the tetraethyl orthosilicate is hydrolyzed and polycondensed on the surface of the polyacrylic acid template to form a SiO2shell layer. After centrifugal washing, calcine at 500°C in a muffle furnace for 7 h to obtain hollow SiO2microspheres.

[0042] (2) Preparation of modified hollow SiO2microspheres.

[0043] Mix 40 g of dimethyl dimethoxysilane with ethanol at a mass ratio of 1:50 and stir until uniformly mixed; then mix with the hollow SiO2microspheres and place in a vacuum pressure impregnation chamber, adjust the temperature to 50°C, the pressure to 0.3 kPa, and continue for 25 minutes, so that the hollow SiO2microspheres cavities are completely infiltrated with dimethyl dimethoxysilane, and dry for use.

[0044] (3) Preparation of the concrete material.

[0045] Mix 32 kg of cement, 83 kg of sand, 102 kg of stone, 500 g of modified hollow SiO2microspheres, 16.0 kg of water, and 800 g of water reducing agent, and stir for 180 s. After uniform stirring, the concrete mixture is molded in a prefabricated component outer wall plate test mold, and an attached vibrator is used for vibration, with a vibration time of 30 s. After hardening and curing, a self-repairing overall super-hydrophobic concrete outer wall plate is obtained.

[0046] Comparative Example 1 This example provides a concrete material, and the preparation method is as follows: Mix 3 kg of cement, 8 kg of sand, 10 kg of stone, 1.68 kg of water, and 70 g of water reducing agent, and stir for 150 s. After uniform stirring, the concrete mixture is molded in a 150*150*150 compression test mold, and an inserted vibrator is used for vibration, with sequential vibration from the edge to the center. After hardening and curing, a self-repairing overall super-hydrophobic concrete test block is obtained.

[0047] Comparative Example 2 This example provides a concrete material, and the preparation method is as follows: (1) Hydrophobic modification of solid SiO2microspheres.

[0048] The same mass and similar size solid SiO2microspheres are used to replace the hollow SiO2microspheres in the reaction with hexadecyltrimethoxysilane, under the same conditions as step (2) of Example 1.

[0049] (2) Preparation of the concrete material.

[0050] Mix 3 kg of cement, 8 kg of sand, 10 kg of stone, 40 g of SiO2microspheres obtained in step (1), 1.68 kg of water, and 70 g of water reducing agent, and stir for 150 s. After uniform stirring, the concrete mixture is molded in a 150*150*150 compression test mold, and an inserted vibrator is used for vibration, with sequential vibration from the edge to the center. After hardening and curing, a self-repairing overall super-hydrophobic concrete test block is obtained.

[0051] Comparative Example 3 This example provides a concrete material, and the preparation method is as follows: (1) Hydrophobic modification of solid SiO2microspheres.

[0052] The same mass and similar size solid SiO2microspheres are used to replace the hollow SiO2microspheres in the reaction with hexadecyltrimethoxysilane, under the same conditions as step (1) of Comparative Example 2.

[0053] (2) Preparation of the concrete material.

[0054] Unlike Comparative Example 2, the amount of SiO2microspheres is increased to 400 g (i.e., ten times the amount), and the other steps are the same as step (2) of Comparative Example 2.

[0055] Comparative Example 4 The example provides a concrete material, and the preparation method is as follows: (1) Preparation of hollow SiO2 microspheres.

[0056] The step (1) is completely consistent with that of the example 1.

[0057] (2) Preparation of modified hollow SiO2 microspheres.

[0058] 6 g of hexadecyltrimethoxysilane is mixed with acetone at a mass ratio of 3:100, and stirred until uniformly mixed, and then stirred with the hollow SiO2 microspheres. Compared with the example 1, the vacuum impregnation process is omitted, that is, the hollow SiO2 microspheres are only surface hydrophobic modified, and the cavity is not loaded with low surface energy substances.

[0059] (3) Preparation of the concrete material.

[0060] The step (3) is consistent with that of the example 1.

[0061] Comparative example 5 The example provides a concrete material, and the difference from the example 1 is that only a hydrophobic modifier is added, and no hydrophobic modified filler is added, and the specific preparation method is as follows: 3 kg of cement, 8 kg of sand, 10 kg of stone, 20 g of hexadecyltrimethoxysilane solution (3 wt%), 1.68 kg of water, and 70 g of water reducing agent are mixed and stirred, and the stirring time is 150 s. After uniform stirring, the concrete mixture is molded in a 150*150*150 compression test mold, and an insertion type vibration is used, and the vibration is sequentially vibrated from the edge to the center, and a self-repairing overall super-hydrophobic concrete test block is obtained after hardening and curing.

[0062] Comparative example 6 The example provides a concrete material, and the preparation method is as follows: (1) Preparation of hollow SiO2 microspheres.

[0063] The difference from the example 1 is that the amount of tetraethyl orthosilicate is reduced from 60 g to 30 g, and the other steps are consistent with those of the example 1.

[0064] (2) and (3) are completely consistent with the steps (2) and (3) of the example 1.

[0065] The wall thickness of the hollow SiO2 microspheres obtained in the example is thinned, and the apparent density of the modified hollow SiO2 microspheres obtained is only 1.3 g / cm 3 .

[0066] The materials prepared in the above examples and comparative examples are detected as follows: 1. Structure detection of modified hollow SiO2 microspheres.

[0067] The microstructure of the modified hollow SiO2 microspheres was observed using a FEI Tecnai G2 F20 transmission electron microscope. During sample preparation, the hollow SiO2 microsphere powder was dispersed in anhydrous ethanol using an ultrasonic disperser, dropped onto a carbon film copper mesh, and dried.

[0068] Figure 1 This is a transmission electron micrograph of the hollow SiO2 microspheres loaded with hexadecyltrimethoxysilane prepared in Example 1. It can be seen from the figure that the size of the hollow SiO2 microspheres is about 200 nm, the wall thickness is about 50 nm, and the cavity is completely filled with hexadecyltrimethoxysilane.

[0069] 2.Structure and performance testing of concrete materials.

[0070] (1) Scanning electron microscopy.

[0071] The surface and internal microstructure of the concrete material were observed using a Nanosem430 field emission scanning electron microscope from Philips of the Netherlands.

[0072] Figure 1 and Figure 4 The figures are scanning electron microscope images of the surface of the concrete materials prepared in Example 1 and Comparative Example 1, respectively. By comparing the two images, it can be seen that due to the density difference, the surface of the concrete material in the scheme of the present invention is completely covered with modified hollow SiO2 spheres, forming a nano-protrusion structure. This structure is similar to the protrusions on the surface of "lotus leaves" in nature, providing a structural basis for superhydrophobic properties.

[0073] Figure 3 This is a scanning electron microscope image of the interior of the concrete material prepared in Example 1. It can be seen from the image that the number of spheres is significantly reduced compared to the surface. Figure 4 It can be seen that SiO2 spheres can effectively fill the pores and gaps between large cement particles, making the concrete structure denser. At the same time, the addition of SiO2 microspheres promotes the hydration reaction of cement, resulting in a large number of needle-shaped or columnar calcium aluminate hydrate structures, which enhances the mechanical properties of concrete. The combination of needle-shaped and spherical structures constitutes a micro-nano rough structure, which makes the interior of the concrete also have superhydrophobic properties.

[0074] (2) Testing of concrete material strength, hydrophobicity, wear resistance and durability.

[0075] The static water contact angle test (WCA) was used to test the hydrophobicity of concrete: the static WCA and sliding angle of the sample surface were measured using a contact angle goniometer (DCA35, Dataphysics, Germany) at room temperature.

[0076] The compressive strength of the self-repairing integral super-hydrophobic concrete was tested by using an electronic universal testing machine. The compressive strength was tested according to the Standard for Testing Methods of Physical and Mechanical Properties of Concrete (GBT 50081-2019), and the sample size was 150 mm x 150 mm x 150 mm.

[0077] Super-hydrophobic wear resistance test: the concrete member was rubbed with a steel wire brush at a force of 1000 N, and each rubbing cycle referred to 15 cm of transverse and longitudinal rubbing. After 1000 polishing cycles, the contact angle of water droplets on the surface of the super-hydrophobic concrete sample was tested.

[0078] Super-hydrophobic durability test: the prepared concrete sample was placed in an outdoor environment and continuously observed for 1 year. After the concrete was subjected to the action of natural climate, the hydrophobic performance of the concrete member at the time points of 6 months and 1 year was tested.

[0079] The test results of the concrete materials prepared in Examples 1-3 and Comparative Examples 1-6 are shown in Table 1 and Figures 5-8 .

[0080] Table 1 Test results of the performance of the concrete materials

[0081] Figure 5 The test results of the wetting performance of the surface of the concrete material prepared in Example 1 are shown in the figure, and the hydrophobic angle is measured to be 158.7°; Figures 6-7 The super-hydrophobic effect figures of the surface and the interior of the concrete material on the methylene blue dyed water are shown in the figures, respectively. It can be seen that the methylene blue dyed water droplets can only stay in the large pores or recesses on the surface, and it can be seen that the surface and the interior of the concrete material both have good hydrophobic performance. Moreover, after the wear resistance test and the durability test, the concrete material still has super-hydrophobic performance.

[0082] The concrete material prepared in Example 2 also has high hydrophobic performance, and the surface hydrophobic angle is 158.5°, and strong wear resistance, and the hydrophobic angle is still 153.7° after the wear resistance test; Figure 8 is the super-hydrophobic effect figure after the wear resistance test, the concrete test block is rubbed to form longitudinal and transverse grooves, and the water droplets on the surface are still nearly spherical; moreover, it still has super-hydrophobic effect after being placed for one year.

[0083] The concrete material prepared in Example 3 also has high hydrophobic angle, strong wear resistance and durability, and the hydrophobic angle is 152.8° after being placed for one year.

[0084] The strength of the concrete prepared in Comparative Example 1 is 37.9 MPa, which is slightly lower than that of Example 1. This is mainly due to the fact that the pores are not filled with SiO2 microspheres, and the needle-like calcium aluminate hydrate cannot be generated. This shows that the scheme of the present application does not adversely affect the strength.

[0085] As can be seen from Table 1, the hydrophobic performance is not achieved when the same mass of solid SiO2 microspheres is used to replace the modified hollow SiO2 microspheres in the present application in Comparative Example 2. This is because the solid SiO2 microspheres have a large density, and cannot take advantage of the density difference, resulting in most of the SiO2 microspheres still being coated inside the concrete, and not being able to form a dense protrusion on the surface. At the same time, the solid SiO2 microspheres cannot load organosiloxane, and cannot modify the surrounding concrete material, so the durability also decreases sharply.

[0086] Compared with Comparative Example 2, the amount of hydrophobic modified SiO2 microspheres is increased in Comparative Example 3. As can be seen from Table 1, when the amount is greatly increased, a higher superhydrophobic performance can be achieved. However, the increase in the amount causes the organosiloxane to come into contact with the cement too much, resulting in a slight decrease in strength; and, since the organosiloxane is not loaded, the low-surface-energy substance quickly fails in the alkaline environment of the concrete, and the hydrophobic angle is only 75.2° after one year.

[0087] In the preparation scheme of Comparative Example 4, the hollow SiO2 microspheres are not loaded with organosiloxane. As can be seen from Table 1, the concrete material prepared in Comparative Example 4 can achieve superhydrophobic performance, but in the abrasion test, a small part of the SiO2 spheres will be damaged, and there will be no leakage of low-surface-energy substances, so the superhydrophobic performance is not achieved after the abrasion test, and the durability is also significantly reduced.

[0088] In Comparative Example 5, only a hydrophobic modifier is added, and the strength of the concrete material prepared is decreased by 9-10 MPa; and, since no SiO2 spheres are added, the roughness cannot be increased, and the surface hydrophobic angle is only 138.2°.

[0089] Compared with Example 1, the wall thickness of the hollow SiO2 spheres used in Comparative Example 6 is thinned, and some of them will be damaged during the mixing and vibrating of the concrete, resulting in a slight decrease in the hydrophobic angle, and the proportion of the damaged thin spheres is increased in the abrasion test, the rough structure is damaged, and the abrasion resistance is decreased. At the same time, as the wall thickness is thinned, the release rate of organosiloxane is accelerated, and the hydrophobic performance of the coating is lost quickly after six months.

[0090] In summary, the overall superhydrophobic concrete provided by the present application has the advantages of small amount of SiO2 microspheres, high strength, and excellent hydrophobic self-repairing performance.

[0091] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and achieving the same effects within the scope of the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments or by combining part of the constituent elements of the embodiments are also included in the scope of the present application without departing from the spirit of the present application.

Claims

1. A self-repairing integral super-hydrophobic concrete material, characterized in that: The raw materials contain modified hollow SiO2 microspheres, the size of which is 100-300 nm, the wall thickness is 30-80 nm, the shell has a porous structure, and the surface and cavity of the modified hollow SiO2 microspheres are loaded with organosiloxane; the apparent density of the modified hollow SiO2 microspheres is 1.8-2.1 g / cm 3 , and the apparent density of the self-repairing integral super-hydrophobic concrete material is 2.2~2.5g / cm 3 .

2. The self-repairing integral super-hydrophobic concrete material according to claim 1, characterized in that: The organosiloxane includes one or more of hexadecyltrimethoxysilane, octadecyltrichlorosilane, polydimethylsiloxane, dimethyldimethoxysilane, isobutyltrimethoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, tetramethoxysilane, phenyltrimethoxysilane, trimethylsilyl chloride, trimethylchlorosilane, and dimethylchlorosilane.

3. The self-repairing integral super-hydrophobic concrete material according to claim 1, characterized in that: The preparation method of the modified hollow SiO2 microspheres comprises the following steps: The polyacrylic acid aqueous solution and the ammonia aqueous solution were mixed and poured into ethanol, and ethyl orthosilicate was slowly added under stirring. After the reaction was completed, the mixture was centrifuged and washed, and then calcined at high temperature to obtain hollow SiO2 microspheres. The hollow SiO2 microspheres are mixed with organosiloxane in an organic solvent, and the organosiloxane is allowed to penetrate into the cavity of the hollow SiO2 microspheres by vacuum impregnation, thereby obtaining the modified hollow SiO2 microspheres.

4. The self-repairing integral super-hydrophobic concrete material according to claim 3, characterized in that: The mass ratio of the tetraethyl orthosilicate to polyacrylic acid is (6-8):

1.

5. The self-repairing integral super-hydrophobic concrete material according to claim 3, characterized in that: The high temperature calcination conditions are: 500-600° C., 4-7 hours.

6. The self-repairing integral super-hydrophobic concrete material according to claim 3, characterized in that: The concentration of the polyacrylic acid aqueous solution is 50wt%, the concentration of the ammonia aqueous solution is 25wt%, and the mass ratio of the two is (3-4):20; the mass ratio of the total mass of the polyacrylic acid aqueous solution and the ammonia aqueous solution to ethanol is 1:(15-20).

7. The self-repairing integral super-hydrophobic concrete material according to claim 3, characterized in that: The organic solvent includes, but is not limited to, one or more of hexane, cyclohexane, ethanol, toluene, dichloromethane, chloroform, ethyl acetate, tetrahydrofuran, and acetone.

8. The self-repairing integral super-hydrophobic concrete material according to claim 1, characterized in that: The raw materials also include cement, sand, stone, water and water reducing agent, and the mass ratio of the cement, sand, stone, modified hollow SiO2 microspheres, water and water reducing agent is (150~350):(700~900):(950~1050):(2~7):(150~190):(3~10).

9. The self-repairing integral super-hydrophobic concrete material according to claim 8, characterized in that: The cement is ordinary Portland cement with a grade of 42.5, the particle size of the sand is 0.15-4.75 mm and the fineness modulus is 2.5-3.0, the particle size of the stone is 5-31.5 mm, and the water reducer is a polycarboxylate water reducer with a solid content of 8%-20%.

10. A method for preparing the self-repairing integral super-hydrophobic concrete material according to any one of claims 1 to 9, characterized in that: The raw materials including the modified hollow SiO2 microspheres are mixed evenly, molded and vibrated, and a self-repairing integral super-hydrophobic concrete material is obtained after hardening and curing.

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