High-stable enhanced cement-based material hydrophobic admixture, preparation method and application thereof

Abstract

The application discloses a kind of high-stability enhanced cement-based material hydrophobic admixtures and its preparation method and application, by weight percentage, the raw material components of the hydrophobic admixtures include: Janus particle 1~5%, hydrophobic oil phase material 10~50%, water 50~90%;The hydrophobic oil phase material is selected from at least one of siloxane, fatty acid or its salt and alkane compound class.This application has good stability Hydrophobic admixtures, can be evenly distributed in cement-based material, improve the mechanical strength of cement-based material.

Description

Technical Field

[0001] This invention relates to the field of cement admixture technology, and more specifically, to a highly stable reinforced hydrophobic admixture for cement-based materials, its preparation method, and its application. Background Technology

[0002] Overall hydrophobicity of cement-based materials is a key technology for reducing their water / ion permeability and extending their service life. The core implementation method lies in improving the durability of the cement-based material structure by adding hydrophobic agents.

[0003] Traditional hydrophobic agents are essentially lipophilic substances, making them difficult to wet with water. During the mixing and molding of cement-based materials, the hydrophobic components are prone to agglomeration and oil phase floating, resulting in uneven overall hydrophobic effects. For example, CN113880494A uses amphiphilic particles to encapsulate hydrophobic substances to form a core-shell structure, thereby delaying the release of hydrophobic components in the early stages of cement hydration. However, the uniform amphiphilic particles used have two major problems: first, their isotropy leads to low adsorption energy at the oil-water interface and insufficient interfacial film strength, making it difficult to ensure stability in the early hydration stage; second, the particles are prone to hydrophobic association and agglomeration, failing to provide a dense filling effect and making it difficult to compensate for the strength loss caused by the hydrophobic components. Therefore, it fails to fundamentally solve the technical defects of traditional hydrophobic agents, such as poor dispersibility, uneven hydrophobicity, and impact on durability.

[0004] Janus nanoparticles are a class of asymmetric nanomaterials named after the Roman god Janus. Their core characteristic lies in the asymmetry of their spatial structure, chemical composition, or functional properties, integrating two or more distinct physical and chemical structures within a single particle. Currently, there are no reports of Janus particles being used as hydrophobic admixtures in cement. Summary of the Invention

[0005] Addressing the shortcomings of existing slow-release hydrophobic admixtures, such as poor stability and low early-age strength of cement, this invention proposes a highly stable reinforcing hydrophobic admixture for cement-based materials, its preparation method, and its application. The system utilizes spatially asymmetric Janus nanoparticles and hydrophobic organic components as raw materials, and prepares an aqueous dispersion emulsion via the Pickering emulsification method. This system exhibits excellent dispersion stability and can effectively improve the compatibility and uniform distribution of the hydrophobic components in the cement matrix.

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

[0007] In a first aspect, a highly stable reinforced cement-based material hydrophobic admixture, by weight percentage, comprises: 1-5% Janus particles, 10-50% hydrophobic oil phase substance, and 50-90% water; wherein the hydrophobic oil phase substance is selected from at least one of siloxanes, fatty acids or their salts, and alkane compounds.

[0008] Furthermore, the Janus particles are amphiphilic nanoparticles with a spatially asymmetric structure, possessing two regions on their surface with completely different chemical compositions and physical properties: a hydrophilic region on one side and a hydrophobic region on the other. They are modified by topological selection using inorganic nanoparticles, a substance providing hydrophobic groups, and a substance providing hydrophilic groups.

[0009] Furthermore, the inorganic nanoparticles are selected from any one or more of silicon dioxide, titanium dioxide, graphene oxide, zirconium dioxide, hydrated calcium silicate, molybdenum disulfide, zinc oxide, aluminum oxide, and carbon nanotubes; wherein the particle size of the inorganic nanoparticles is 30~200nm.

[0010] Furthermore, the substance providing the hydrophobic group includes saturated fatty acids or unsaturated fatty acids; preferably, the saturated fatty acid includes any one of lauric acid, palmitic acid, and stearic acid, and the unsaturated fatty acid includes any one of oleic acid, linoleic acid, and linolenic acid.

[0011] Further, the substance providing the hydrophilic group includes polyethylene glycol silanes or aminosilanes; preferably, the polyethylene glycol silanes include any one of methoxy polyethylene glycol silanes, amino-polyethylene glycol-silanes, and hydroxy-polyethylene glycol-silanes; the aminosilanes include any one of γ-aminopropyltriethoxysilanes, γ-aminopropyltrimethoxysilanes, and N-β-aminoethyl-γ-aminopropyltrimethoxysilanes.

[0012] Further, the siloxanes include one or more of methyltriethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, n-octyltriethoxysilane, isooctyltriethoxysilane, dodecyltriethoxysilane, polydimethylsiloxane, polymethylhydrosiloxane, 1H,1H,2H,2H-perfluorododecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, trifluoropropyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane; preferably, the fatty acids or their salts include one or more of oleic acid, lauric acid, stearic acid, palmitic acid, calcium stearate, zinc stearate, aluminum stearate, calcium laurate, and zinc laurate; preferably, the alkane compounds include one or more of paraffin oil, paraffin, chlorinated paraffin, and palm oil.

[0013] Secondly, a method for preparing the aforementioned highly stable reinforced cementitious material hydrophobic admixture, characterized in that it comprises:

[0014] Janus particles are dispersed in water, a hydrophobic oil phase is added, and emulsification is carried out by high-speed stirring.

[0015] Furthermore, the high-speed stirring speed is 10,000~18,000 rpm, and the emulsification time is 10~20 min.

[0016] Thirdly, the application of the aforementioned highly stable reinforced cementitious material hydrophobic admixture in the preparation of cementitious materials.

[0017] Furthermore, the amount of the hydrophobic admixture is 0.5wt% to 5wt% of the cement content.

[0018] The technical principle of this invention is as follows:

[0019] In this invention, Janus nanoparticles play multiple functional roles: First, their unique asymmetric structure allows them to irreversibly anchor at the oil-water interface, forming a high-strength interfacial film that ensures hydrophobic substances in the emulsion are not prematurely released during cement hydration, thus preventing hydration from being hindered. Second, Janus particles can achieve directional alignment on the surface of cement particles, with the hydrophilic ends forming hydrogen bonds, coordination, or electrostatic interactions with hydration products, while the hydrophobic ends face the capillary pores, further improving the hydrophobic properties of the matrix. Finally, the groups grafted onto the hydrophilic ends of the Janus particles can achieve uniform dispersion of the nanoparticles in the cement matrix through steric hindrance or electrostatic interactions, effectively preventing particle aggregation. In addition, the incorporation of hydrophilic groups can further enhance the reactivity of the nanoparticles, promote secondary hydration, and achieve synergistic optimization of the hydrophobic and mechanical properties of cement-based materials.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] Based on the differences in physicochemical properties across the surface of Janus particles, this invention successfully prepared a hydrophobic admixture that combines excellent stability with increased strength in cement-based materials, effectively achieving overall hydrophobicity within the cement-based material. This admixture utilizes the significantly higher adsorption energy of Janus particles at the oil-water interface compared to traditional homogeneous particles to prepare a highly stable emulsion-type hydrophobic admixture system. This system effectively suppresses instability phenomena such as aggregation, Ostwald ripening, and flocculation, maintaining structural integrity even under harsh conditions such as high temperature, high salinity, or extreme pH.

[0022] During the cement hydration process, this admixture exhibits a unique release mechanism: In the early stage of hydration, the interfacial barrier formed by Janus particles effectively blocks direct contact between hydrophobic oil phase droplets and cement components, avoiding interference with the hydration process; in the later stage of hydration, the asymmetric structure of Janus nanoparticles achieves directional alignment on the surface of cement particles, and the hydrophilic ends have excellent compatibility with cement particles, which can enhance the reactivity of nanoparticles, achieve secondary hydration, and compact the pore structure of cement stone; the hydrophobic groups are regularly arranged on the surface of hydration products, and work synergistically with the released hydrophobic oil phase components to endow the capillary walls with durable hydrophobic properties, achieving a dual improvement in the mechanical strength and long-term durability of cement-based materials. Attached Figure Description

[0023] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0024] Figure 1 This is a schematic diagram comparing the structures of Janus nanoparticles (A) used in this invention with ordinary amphiphilic nanoparticles (B).

[0025] Figure 2 Photograph (A) and microscopic schematic diagram (B) of the hydrophobic admixture for high-stability strength-growing cement-based materials prepared for the example.

[0026] Figure 3 This is a comparison diagram showing the stability of the emulsions in simulated pore solutions of concrete between the examples and the comparative examples.

[0027] Among them, A) Comparison photos of Example 1 and Comparative Example 1; B) Comparison photos of Example 2 and Comparative Example 2; C) Comparison photos of Example 3 and Comparative Example 3; D) Comparison photos of Example 4 and Comparative Example 4. Detailed Implementation

[0028] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways than those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] 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 this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0030] It should be noted that the raw materials, instruments, etc. involved in this invention are all commercially available products.

[0031] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0032] like Figure 1 As shown, traditional modifications of amphiphilic particles used for emulsion stabilization achieve the amphiphilic effect by adjusting the ratio of hydrophilic and hydrophobic groups, with these groups uniformly distributed on the particle surface. In contrast, Janus particles have hydrophilic and hydrophobic groups distributed on opposite sides of their surface.

[0033] Example 1

[0034] A method for preparing a hydrophobic admixture for high-stability, strength-increasing cementitious materials includes the following steps:

[0035] (1) Weigh 2g of nano-silica and ultrasonically disperse it in 100mL of anhydrous ethanol. Weigh 6g of oleic acid and add it to 200mL of anhydrous ethanol. Gradually add the silica dispersion to the oleic acid solution, maintain 80℃, and react at 800rpm for 12h. Centrifuge to separate the solid particles, wash with ethanol 3 times, and dry.

[0036] (2) Weigh 2g of oleic acid modified silica and ultrasonically disperse it in 100mL of deionized water. Heat 4g of paraffin to 70℃ to melt it and add it to the silica dispersion. Keep it at 70℃ and stir for 30min. After cooling to room temperature, filter it, wash it 3 times with deionized water, and dry it at room temperature.

[0037] (3) Weigh 2g of paraffin-coated nanoparticles and disperse them in 100g of sodium hydroxide solution (2wt%). Stir at room temperature for 2h, and then wash away excess sodium hydroxide with deionized water.

[0038] (4) Prepare 100ml of ethanol-water mixture (ethanol:water = 9:1), add 2g of methoxy polyethylene glycol silane, and pre-hydrolyze at room temperature; weigh 2g of the washed particles and add them to the silane hydrolysis solution, stir until the reaction is complete, and then centrifuge and wash; subsequently, disperse the nanoparticles in 50mL of carbon tetrachloride, dissolve the surface paraffin, and finally centrifuge and dry to obtain Janus nanoparticles.

[0039] (5) Weigh 1g of the above Janus nanoparticles and disperse them in 79mL of deionized water. Then add 20g of octyltriethoxysilane and emulsify at high speed of 12000rpm in an ice-water bath for 10min to obtain a stable organic-inorganic hybrid hydrophobic emulsion of Janus particles.

[0040] like Figure 2 As shown, Janus particles form a high-strength interfacial film on the surface of oil phase droplets, making the prepared emulsion uniform and stable without stratification or precipitation.

[0041] Example 2

[0042] A method for preparing a hydrophobic admixture for high-stability, strength-increasing cementitious materials includes the following steps:

[0043] (1) Weigh 2g of graphene oxide and ultrasonically disperse it in 100mL of anhydrous ethanol. Weigh 6g of lauric acid and add it to 200mL of anhydrous ethanol. Gradually add the graphene oxide dispersion to the oleic acid solution, maintain 80℃, and react at 800rpm for 12h. Centrifuge to separate the solid particles, wash with ethanol 3 times, and dry.

[0044] (2) Weigh 2g of lauric acid modified graphene oxide and ultrasonically disperse it in 100mL of deionized water. Heat 4g of paraffin to 70℃ to melt it and add it to the graphene oxide dispersion. Keep it at 70℃ and stir for 30min. After cooling to room temperature, filter it, wash it 3 times with deionized water, and dry it at room temperature.

[0045] (3) Weigh 2g of paraffin-coated nanoparticles and disperse them in 100g of sodium hydroxide solution (2wt%). Stir at room temperature for 2h, and then wash away excess sodium hydroxide with deionized water.

[0046] (4) Prepare 100ml of ethanol-water mixture (ethanol:water = 9:1), add 2g of amino-polyethylene glycol-silane, and pre-hydrolyze at room temperature; weigh 2g of the washed particles and add them to the silane hydrolysis solution, stir until the reaction is complete, and then centrifuge and wash; subsequently, disperse the nanoparticles in 50mL of carbon tetrachloride, dissolve the surface paraffin, and finally centrifuge and dry to obtain Janus nanoparticles.

[0047] (5) Weigh 1g of the above Janus nanoparticles and disperse them in 79mL of deionized water. Then add 20g of polydimethylsiloxane and emulsify at high speed of 12000rpm in an ice water bath for 10min to obtain a stable organic-inorganic hybrid hydrophobic emulsion of Janus particles.

[0048] Example 3

[0049] A method for preparing a hydrophobic admixture for high-stability, strength-increasing cementitious materials includes the following steps:

[0050] (1) Weigh 2g of nano-titanium dioxide and ultrasonically disperse it in 100mL of anhydrous ethanol. Weigh 6g of stearic acid and add it to 200mL of anhydrous ethanol. Gradually add the titanium dioxide dispersion to the stearic acid solution, maintain 80℃, and react at 800rpm for 12h. Centrifuge to separate the solid particles, wash with ethanol 3 times, and dry.

[0051] (2) Weigh 2g of stearic acid modified titanium dioxide and ultrasonically disperse it in 100mL of deionized water. Heat 4g of paraffin to 70℃ to melt it and add it to the titanium dioxide dispersion. Keep it at 70℃ and stir for 30min. After cooling to room temperature, filter it, wash it 3 times with deionized water, and dry it at room temperature.

[0052] (3) Weigh 2g of paraffin-coated nanoparticles and disperse them in 100g of sodium hydroxide solution (2wt%). Stir at room temperature for 2h, and then wash away excess sodium hydroxide with deionized water.

[0053] (4) Prepare 100ml of ethanol-water mixture (ethanol:water = 9:1), add 2g of γ-aminopropyltriethoxysilane, and pre-hydrolyze at room temperature; weigh 2g of the washed particles and add them to the silane hydrolysis solution, stir until the reaction is complete, and then centrifuge and wash; subsequently, disperse the nanoparticles in 50mL of carbon tetrachloride, dissolve the surface paraffin, and finally centrifuge and dry to obtain Janus nanoparticles.

[0054] (5) Weigh 1g of the above Janus nanoparticles and disperse them in 79mL of deionized water. Then add 20g of calcium stearate and emulsify at high speed of 12000rpm in an ice water bath for 10min to obtain a stable organic-inorganic hybrid hydrophobic emulsion of Janus particles.

[0055] Example 4

[0056] A method for preparing a hydrophobic admixture for high-stability, strength-increasing cementitious materials includes the following steps:

[0057] (1) Weigh 2g of CSH nanofoil and ultrasonically disperse it in 100mL of anhydrous ethanol. Weigh 6g of palmitic acid and add it to 200mL of anhydrous ethanol. Gradually add the CSH nanofoil dispersion to the palmitic acid solution, maintain 80℃, and react at 800rpm for 12h. Centrifuge to separate the solid particles, wash with ethanol 3 times, and dry.

[0058] (2) Weigh 2g of palmitic acid modified CSH nano foil and ultrasonically disperse it in 100mL of deionized water. Heat 4g of paraffin to 70℃ to melt it and add it to the CSH dispersion. Keep it at 70℃ and stir for 30min. After cooling to room temperature, filter it, wash it 3 times with deionized water, and dry it at room temperature.

[0059] (3) Weigh 2g of paraffin-coated nanoparticles and disperse them in 100g of sodium hydroxide solution (2wt%). Stir at room temperature for 2h, and then wash away excess sodium hydroxide with deionized water.

[0060] (4) Prepare 100ml of ethanol-water mixture (ethanol:water = 9:1), add 2g of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and pre-hydrolyze at room temperature; weigh 2g of the washed particles and add them to the silane hydrolysis solution, stir until the reaction is complete, and then centrifuge and wash; subsequently, disperse the nanoparticles in 50mL of carbon tetrachloride, dissolve the surface paraffin, and finally centrifuge and dry to obtain Janus nanoparticles.

[0061] (5) Weigh 1g of the above Janus nanoparticles and disperse them in 79mL of deionized water. Then add 20g of paraffin oil and emulsify at high speed of 12000rpm in an ice water bath for 10min to obtain a stable organic-inorganic hybrid hydrophobic emulsion of Janus particles.

[0062] Comparative Example 1

[0063] The preparation of traditional uniform amphiphilic nanoparticle-stabilized emulsion-type hydrophobic additives includes the following steps:

[0064] (1) Weigh 2g of nano silica particles and ultrasonically disperse them in 100mL of anhydrous ethanol.

[0065] (2) Weigh 2g of hexamethyldisilazane (HMDS) and add it to the above dispersion. Heat it in a water bath to 65°C and keep it warm for 8 hours. After cooling to room temperature, filter it, wash it three times with anhydrous ethanol, and dry it.

[0066] (3) Weigh 1g of the above modified nanoparticles and disperse them in 79mL of deionized water. Then add 20g of octyltriethoxysilane and emulsify at high speed of 12000rpm in an ice-water bath for 10min to obtain a hydrophobic emulsion with stable traditional uniform amphiphilic particles.

[0067] Comparative Example 2

[0068] Compared with Comparative Example 1, the nanoparticles were replaced with graphene oxide, the oil phase was replaced with polydimethylsiloxane, and the rest were the same as Comparative Example 1.

[0069] Comparative Example 3

[0070] Compared with Comparative Example 1, the nanoparticles were replaced with titanium dioxide, the oil phase was replaced with calcium stearate, and the rest were the same as Comparative Example 1.

[0071] Comparative Example 4

[0072] Compared with Comparative Example 1, the nanoparticles were replaced with CSH nanofoil, the oil phase was replaced with paraffin oil, and everything else was the same as Comparative Example 1.

[0073] Characterization of the hydrophobic admixtures obtained in each embodiment and comparative example: The storage stability of the emulsion was characterized by centrifugation. Centrifuge tubes containing the emulsion were placed in a centrifuge at 4000 r / min and rotated for 10 min. The presence of obvious precipitation was observed. The hydrophobic admixtures of each embodiment and comparative example were added to a simulated concrete pore solution with a pH of 12.5 and allowed to stand for 7 days to observe whether stratification occurred. The performance results of the hydrophobic admixtures obtained in each embodiment and comparative example are shown in Table 1.

[0074] The hydrophobic admixtures prepared in the above embodiments and comparative examples were incorporated into cement slurry to prepare hydrophobically modified cement paste. The water-cement ratio of the cement slurry was 0.4, and the hydrophobic admixture accounted for 5% of the cement weight. After thorough mixing, the paste was poured into molds, allowed to harden and solidify, and then demolded. The paste was then cured under standard curing conditions for 28 days. A blank control sample with the same water-cement ratio was also prepared.

[0075] Characterization of the obtained hydrophobic cement paste: The contact angle was measured using a contact angle meter (JC2000D) at 10 points on the inner surface. The average value was taken, and the coefficient of variation for each group was calculated to measure the uniformity of the hydrophobic layer. The capillary water absorption rate of 40×40×40 mm cubic cement paste specimens was determined according to ASTM C1403 standard (C1403, 2015). The hydrophobic performance test results of the hydrophobic cement paste prepared using each example and comparative example are shown in Table 2. Compressive strength tests were conducted according to GB / T 17671-1999 standard (17671-1999, 1999), and the results are shown in Table 3.

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080] Table 3

[0081]

[0082] As shown in Table 1, the hydrophobic admixtures prepared in Examples 1 to 4 of this invention exhibit excellent stability in both centrifugation and alkaline solutions. After centrifugation at 4000 r / min for 10 min, no obvious precipitation or stratification was observed in the emulsions of any of the examples. Example 1, after being left to stand in a simulated concrete pore solution at pH=12.5, also showed no stratification. In contrast, the emulsion in the comparative example, stabilized using conventional uniform amphiphilic nanoparticles, showed obvious stratification under the same test conditions, indicating poor stability. Figure 3This indicates that in the complex environment of high salt and strong alkali in cement paste, traditional Pickering emulsions based on homogeneous amphiphilic particles are prone to instability. In contrast, the Pickering emulsion system based on Janus particles exhibits higher stability than traditional homogeneous modified particles. This is due to the unique spatial asymmetry of Janus particles, which endows them with higher oil-water interface adsorption energy than ordinary homogeneous particles. This effectively inhibits instability behaviors such as emulsion aggregation, Ostwald ripening, and flocculation, and it has excellent salt resistance, acid and alkali resistance, and temperature resistance, effectively preventing the premature release of hydrophobic substances in the early stage of cement hydration.

[0083] As shown in Table 2, the static contact angles of the hydrophobic cement stone samples modified with the hydrophobic admixtures of Examples 1 to 4 of this invention are all greater than 137°, which is significantly higher than that of the blank group (approximately 20°) and the comparative group (109°~128°). Notably, the coefficient of variation of the contact angle in the example group of this invention is much smaller than that in the comparative group, demonstrating that the modification of the cement samples by this invention is more uniform, and the hydrophobic layer distribution is more even. Simultaneously, the capillary water absorption rate is significantly reduced, with a decrease of 77%~84%, indicating that the admixture of this invention can effectively impart overall hydrophobicity to the cement matrix, preventing water from penetrating through capillary pores. While the comparative group also exhibits a certain degree of hydrophobicity, its contact angle is lower and its capillary water absorption rate is higher. This indicates that the stable emulsion droplets of ordinary amphiphilic particles have large differences in size and wide distribution, resulting in local enrichment or absence of hydrophobic components after incorporation into cement, leading to uneven hydrophobic modification. The Janus particles of this invention stabilize the emulsion droplets, resulting in uniform droplet size and narrow distribution, making them less prone to demulsification and enabling the uniform and sustained release of hydrophobic substances with a uniformly distributed hydrophobic layer. Furthermore, after emulsion demulsification, the hydrophilic ends of the Janus particles bond and anchor with hydration products such as CSH and calcium hydroxide, while the hydrophobic ends are uniformly oriented towards the interior of the pores, forming a continuous, dense, low-surface-energy hydrophobic layer on the pore walls, further enhancing the hydrophobic properties of the matrix. Figure 2 ).

[0084] As shown in Table 3, the compressive strength of the cement paste prepared in Examples 1 to 4 of this invention at 3d, 7d, and 28d were all improved compared to the control group, and significantly higher than the comparative example group. For example, the 28-day compressive strength of Example 1 was 62 MPa, which was about 5% higher than the control group, while that of Comparative Example 1 was only 45 MPa, which was significantly lower than the control group. This indicates that traditional homogeneous amphiphilic particle-stabilized emulsion admixtures are prone to demulsification in the high-salt-alkali environment of cement paste, and the hydrophobic components will be released prematurely, inhibiting cement hydration and causing strength loss; moreover, ordinary amphiphilic particles are prone to hydrophobic association between particles, and agglomeration is aggravated in the complex cement environment, which cannot give full play to the filling effect and activity effect of nanoparticles. The hydrophobic admixture of this invention does not prematurely demulsify in cement-based environments. The hydrophobic substances are slowly released during the hardening process, having almost no impact on cement hydration. Furthermore, the hydrophilic side of the Janus particles used is well compatible with the pore solution and hydrated ions in cement slurry, significantly inhibiting the self-aggregation of nanoparticles, improving the pozzolanic activity of nanoparticles, promoting secondary hydration, and increasing the density of CSH gel. Therefore, it can achieve excellent hydrophobic properties while even slightly improving the material strength.

[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A highly stable, enhanced, cementitious material hydrophobing admixture characterized by, By weight percentage, its raw material components include: 1% Janus particles, 20% hydrophobic oil phase substance, and 79% water; the hydrophobic oil phase substance is selected from at least one of siloxanes, fatty acids or their salts, and alkane compounds; the Janus particles are modified by topological selection of inorganic nanoparticles, substances providing hydrophobic groups, and substances providing hydrophilic groups, and its preparation method includes the following steps: (1) Weigh 2g of inorganic nanoparticles and ultrasonically disperse them in 100mL of anhydrous ethanol to obtain dispersion A; weigh 6g of the substance that provides hydrophobic groups and add it to 200mL of anhydrous ethanol, and gradually add dispersion A. Maintain 80℃ and react at 800rpm for 12h. Centrifuge to separate the solid particles, wash with ethanol 3 times, and dry to obtain hydrophobic modified nanoparticles. (2) Weigh 2g of hydrophobic modified nanoparticles and ultrasonically disperse them in 100mL of deionized water to obtain dispersion B; heat 4g of paraffin to 70℃ to melt it and add it to dispersion B, keep it at 70℃ and stir for 30min, cool it to room temperature, filter it, wash it 3 times with deionized water, and dry it at room temperature to obtain paraffin semi-coated nanoparticles. (3) Weigh 2g of paraffin-coated nanoparticles and disperse them in 100g of 2wt% sodium hydroxide solution. Stir at room temperature for 2h, and then wash away excess sodium hydroxide with deionized water. (4) Prepare 100ml of ethanol-water mixture with a volume ratio of 9:1 for alcohol and water, add 2g of the substance that provides hydrophilic groups, pre-hydrolyze at room temperature, add 2g of the particles obtained in step (3), stir the reaction completely, centrifuge and wash; then disperse in 50mL of carbon tetrachloride, dissolve the surface paraffin, and finally centrifuge and dry to obtain Janus nanoparticles.

2. The highly stable reinforced hydrophobic admixture for cement-based materials according to claim 1, characterized in that, The inorganic nanoparticles are selected from any one or more of silicon dioxide, titanium dioxide, graphene oxide, zirconium dioxide, hydrated calcium silicate, molybdenum disulfide, zinc oxide, aluminum oxide, and carbon nanotubes; wherein the particle size of the inorganic nanoparticles is 30~200nm.

3. The highly stable reinforced hydrophobic admixture for cement-based materials according to claim 1, characterized in that, The substance providing the hydrophobic group includes saturated fatty acids or unsaturated fatty acids; wherein the saturated fatty acid includes any one of lauric acid, palmitic acid, and stearic acid, and the unsaturated fatty acid includes any one of oleic acid, linoleic acid, and linolenic acid.

4. The highly stable reinforced hydrophobic admixture for cement-based materials according to claim 1, characterized in that, The substance providing the hydrophilic group includes polyethylene glycol silanes or aminosilanes; wherein the polyethylene glycol silanes include any one of methoxy polyethylene glycol silane, amino-polyethylene glycol-silane, and hydroxy-polyethylene glycol-silane; and the aminosilanes include any one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

5. The highly stable reinforced hydrophobic admixture for cement-based materials according to claim 1, characterized in that, The siloxanes include one or more of the following: methyltriethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, n-octyltriethoxysilane, isooctyltriethoxysilane, dodecyltriethoxysilane, polydimethylsiloxane, polymethylhydrosiloxane, 1H,1H,2H,2H-perfluorododecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, trifluoropropyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane; the fatty acids or their salts include one or more of the following: oleic acid, lauric acid, stearic acid, palmitic acid, calcium stearate, zinc stearate, aluminum stearate, calcium laurate, and zinc laurate; the alkane compounds include one or more of the following: paraffin oil, paraffin wax, chlorinated paraffin, and palm oil.

6. The method for preparing the highly stable reinforced hydrophobic admixture for cement-based materials according to any one of claims 1-5, characterized in that, include: Janus particles are dispersed in water, a hydrophobic oil phase is added, and emulsification is carried out by high-speed stirring.

7. The preparation method according to claim 6, characterized in that, The high-speed stirring speed is 10,000~18,000 rpm, and the emulsification time is 10~20 min.

8. The application of the highly stable reinforced hydrophobic admixture of any one of claims 1-5 in the preparation of cement-based materials.

9. The application according to claim 8, characterized in that, The amount of the hydrophobic admixture is 0.5wt% to 5wt% of the cement content.

Images