Preparation method of modified organosilicon superhydrophobic material, preparation method of superhydrophobic aggregate and adaptive cement-based material

Abstract

The present invention discloses a method for preparing a modified organosilicon super-hydrophobic material, a method for preparing a super-hydrophobic aggregate, and an adaptive cement-based material. The method for preparing a modified organosilicon super-hydrophobic material provided by the present invention comprises the following steps: a siloxane polymer and a fluorinated nano-SiO2 are dissolved in an organic solvent respectively to obtain a siloxane polymer solution and a fluorinated nano-SiO2 dispersion, and then the two solutions are mixed to obtain a mixed solution; under a strong stirring state, anhydrous ethanol and a curing agent are sequentially added to the mixed solution to obtain a modified organosilicon super-hydrophobic material. The modified organosilicon super-hydrophobic material has super-hydrophobic properties due to its special structure, is uniformly stirred with cement-based aggregate, and the super-hydrophobic modification of cement-based aggregate can be achieved, and cement-based material is prepared using the modified cement-based aggregate, and the adaptive regulation of cement-based structures to freeze-thaw complex environments can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of cement-based materials, and in particular to a method for preparing a modified organosilicon super-hydrophobic material, a method for preparing a super-hydrophobic aggregate, and an adaptive cement-based material. Background Art

[0002] "Self-cleaning" refers to the ability to maintain a surface's cleanliness over time despite natural forces like rain. Inspired by the natural "lotus effect," superhydrophobic surfaces with micro- and nanostructures possess numerous unique surface properties, including self-cleaning, water repellency, low friction, and anti-icing properties. Superhydrophobic coatings have broad applications across a wide range of fields.

[0003] Studies on the surface structure of hydrophobic materials such as lotus leaves and feathers have shown that super-hydrophobic coatings are composed of surface micro-nano materials providing rough structures and low surface energy chemicals. At present, researchers have conducted extensive research on the preparation methods and applications of super-hydrophobic coatings and prepared various hydrophobic materials with excellent performance. However, due to mechanical friction, climate aging and other reasons, especially during the freeze-thaw cycle of melting ice and ice formation, expansion and contraction lead to damage and movement of the mastoid structure, the surface roughness decreases, resulting in reduced hydrophobic properties, making it difficult to achieve long-term effective hydrophobic properties, which is a technical bottleneck currently limiting the application of super-hydrophobic coatings. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for preparing a modified organosilicon super-hydrophobic material, a method for preparing a super-hydrophobic aggregate and an adaptive cement-based material.

[0005] The present invention solves the technical problem by adopting the following technical solutions.

[0006] The present invention provides a method for preparing a modified organosilicon super-hydrophobic material, comprising the following steps:

[0007] Dissolving a siloxane polymer and fluorinated nano-SiO2 in an organic solvent respectively to obtain a siloxane polymer solution and a fluorinated nano-SiO2 dispersion, and then mixing the two solutions to obtain a mixed solution;

[0008] Under strong stirring, anhydrous ethanol and a curing agent are sequentially added to the mixed solution to obtain a modified organosilicon superhydrophobic material.

[0009] The present invention also provides a method for preparing a super-hydrophobic aggregate, which comprises spraying the modified organosilicon super-hydrophobic material onto cement-based aggregate to obtain the super-hydrophobic aggregate.

[0010] The present invention also provides an adaptive cement-based material, which replaces fine aggregate with the superhydrophobic aggregate prepared by the above preparation method, is mixed evenly with cement particles in advance, and then an appropriate amount of water is added, stirred and vibrated, poured and demolded, and then the surface is covered with a 100-mesh copper mesh to obtain an adaptive cement-based material.

[0011] The present invention has the following beneficial effects:

[0012] The present invention provides a preparation method of a modified organosilicon super-hydrophobic material, a preparation method of a super-hydrophobic aggregate and an adaptive cement-based material. The super-hydrophobic aggregate after modification using the modified organosilicon super-hydrophobic material has an obvious micro-nano rough structure on its surface. These rough structures are composed of the micron-sized papillae formed by cross-linking and curing of siloxane polymers and the nano-microspheres formed by the embedded fluorinated nano-SiO2. This micro-nano composite rough structure is conducive to the direct capture of air by the solid-liquid contact surface, thereby improving super-hydrophobicity. Meanwhile, the adaptive cement-based material prepared using the modified super-hydrophobic modified aggregate has an adaptive super-hydrophobic control function under a freeze-thaw complex environment, ensures that the newly exposed structural surface after local destruction of the structure still has good super-hydrophobic performance, and realizes the adaptive control of cement-based structures to a freeze-thaw complex environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 A flow chart for preparing the monolithic superhydrophobic mortar provided in an embodiment of the present invention;

[0015] Figure 2 The wettability of water droplets on the surface of superhydrophobic modified quartz sand (a), the wettability of superhydrophobic modified quartz sand in water (b1), the wettability of ordinary quartz sand in water (b2), the state of superhydrophobic modified quartz sand soaked in water before freezing at -20°C for 12 hours (c1), the state of ordinary quartz sand soaked in water before freezing at -20°C for 12 hours (c2), the state of superhydrophobic modified quartz sand soaked in water after freezing at -20°C for 12 hours and then being taken out upside down (c3), the state of ordinary quartz sand soaked in water after being frozen at -20°C for 12 hours and then being taken out upside down (c4);

[0016] Figure 3 SEM images of superhydrophobic modified quartz sand at different sizes: 30 μm (a), 50 μm (b), 20 μm (c), and 1 μm (d);

[0017] Figure 4 EDS spectrum of superhydrophobic modified quartz sand (a) and ordinary quartz sand (b);

[0018] Figure 5 FTIR spectra of superhydrophobic modified quartz sand and ordinary quartz sand (a), XPS full spectrum of F-SiO2 (b), XPS full spectrum of SiO2 (c), XPSC1s fine spectrum of F-SiO2 (d), XPSF1s fine spectrum of F-SiO2 (e), XPSC1s fine spectrum of SiO2 (f), XPS full spectrum of superhydrophobic modified quartz sand (g), XPS full spectrum of ordinary quartz sand (h);

[0019] Figure 6 Surface morphology characteristics of the monolithic superhydrophobic mortar: surface morphology image under industrial camera (a) and surface morphology image under SEM (b);

[0020] Figure 7 SEM images of ordinary mortar, hydrophobic modifier mortar and integral superhydrophobic mortar: SEM image of the interior of ordinary mortar (×1000) (a), SEM image of the interior of hydrophobic modified mortar (×1000) (b), SEM image of the interior of integral superhydrophobic mortar (×1000) (c), SEM image of the interior of integral superhydrophobic mortar (×5000) (d);

[0021] Figure 8 The results of the wear cycle test of the monolithic superhydrophobic mortar are shown;

[0022] Figure 9 The overall wettability results of the monolithic superhydrophobic mortar are: wettability of the cracked specimen surface (a); wettability inside the crack (b); wettability of the exposed surface of the damaged specimen (c);

[0023] Figure 10 The anti-icing test results of ordinary mortar and integral super-hydrophobic mortar at -10°C and the cumulative icing test results at -20°C are as follows: the anti-icing test results of the integral super-hydrophobic mortar at -10°C (a), the anti-icing test results of the ordinary mortar at -10°C (b); the cumulative icing test results of the integral super-hydrophobic mortar at -20°C (c1-c2); the low cumulative icing test results of the ordinary mortar at -20°C (c3-c4);

[0024] Figure 11 Schematic diagram of deicing residue test of ordinary mortar and monolithic superhydrophobic mortar at -20℃ environment (a), deicing residue test result of ordinary mortar at -20℃ environment (b), deicing residue test of monolithic superhydrophobic mortar at -20℃ environment (c);

[0025] Figure 12This is a graph showing the relationship between the compressive strength of ordinary mortar and integral superhydrophobic mortar and the number of freeze-thaw cycles. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0027] The following is a detailed description of a method for preparing a modified organosilicon-based superhydrophobic material, a method for preparing a superhydrophobic aggregate, and an adaptive cement-based material provided in embodiments of the present invention.

[0028] In a first aspect, an embodiment of the present invention provides a method for preparing a modified organosilicon-based super-hydrophobic material, comprising the following steps:

[0029] Dissolving a siloxane polymer and fluorinated nano-SiO2 in an organic solvent respectively to obtain a siloxane polymer solution and a fluorinated nano-SiO2 dispersion, and then mixing the two solutions to obtain a mixed solution;

[0030] Under strong stirring, anhydrous ethanol and a curing agent are sequentially added to the mixed solution to obtain a modified organosilicon superhydrophobic material.

[0031] In an optional embodiment, the siloxane polymer is polydimethylsiloxane or polymethylhydrogensiloxane.

[0032] In an optional embodiment, the organic solvent includes one or more of acetone and butyl acetate.

[0033] In an alternative embodiment, the organic solvent is butyl acetate.

[0034] In an optional embodiment, the fluorinated nano-SiO2 is selected from nano-SiO2 containing fluorine silane chains.

[0035] In an optional embodiment, the fluorinated nano-SiO2 is prepared by the following preparation method:

[0036] Dispersing nano-SiO2 into a mixed solution of anhydrous ethanol and ammonia water, stirring and mixing uniformly to obtain a nano-SiO2 dispersion;

[0037] Then, heptadecafluorodecyltriethoxysilane and tetraethoxysilane are mixed with the nano-SiO2 dispersion to form a SiO2 suspension;

[0038] The SiO2 suspension was then mixed with ethyl acetate, stirred and dispersed evenly, allowed to stand, and the supernatant was separated and removed to obtain a white suspension containing butyl acetate;

[0039] After centrifuging the white suspension containing butyl acetate, fluorinated nano-SiO2 was obtained;

[0040] The mass ratio of heptafluorodecyltriethoxysilane to tetraethoxysilane to nano-SiO2 is 1:(0.8-1.0):(3-4).

[0041] In an optional embodiment, the following steps are included:

[0042] adding polydimethylsiloxane to butyl acetate and stirring to completely dissolve the polydimethylsiloxane in the butyl acetate to obtain a polydimethylsiloxane solution;

[0043] Dispersing the fluorinated nano-SiO2 in anhydrous ethanol, vigorously stirring to evenly disperse the fluorinated nano-SiO2, to obtain a fluorinated nano-SiO2 dispersion;

[0044] The two solutions are mixed and dispersed to obtain a mixed solution;

[0045] Under vigorous stirring, add anhydrous ethanol dropwise to the mixed solution and stir vigorously;

[0046] Finally, a curing agent is added and stirred again to prepare a modified organosilicon superhydrophobic material.

[0047] In a second aspect, an embodiment of the present invention provides a method for preparing a superhydrophobic aggregate, which comprises: spraying the above-mentioned modified organosilicon superhydrophobic material on a cement-based aggregate to obtain a superhydrophobic aggregate.

[0048] In an optional embodiment, the spraying step includes: using a spray gun with a caliber of 1mm-2mm to spray the modified silicone super-hydrophobic material on the surface of the cement-based aggregate, during spraying, the modified silicone super-hydrophobic material is sprayed uniformly on the 40-70 mesh cement-based aggregate at a speed of 1m / s-3m / s and a distance of 15cm-30cm under a compressor pressure of 5kPa-10kPa. The thickness of each spraying is preferably 2mm, and after spraying once, the cement-based aggregate particle layer is turned over; repeating the spraying and turning the cement-based aggregate particle layer 2-3 times, and then curing it at room temperature for 3-5 days to prepare a super-hydrophobic aggregate, wherein the cement-based aggregate includes at least one of quartz sand and machine-made sand.

[0049] In an optional embodiment, the average static contact angle of the superhydrophobic aggregate surface is 150.3 ° above.

[0050] In a third aspect, an embodiment of the present invention provides an adaptive cement-based material, which replaces ordinary fine aggregate with the superhydrophobic aggregate prepared by the above-mentioned preparation method, is mixed evenly with cement particles in advance, and then an appropriate amount of water is added, stirred and vibrated, poured and demolded, and then the surface is covered with a 100-mesh copper mesh to obtain an adaptive cement-based material.

[0051] As can be seen from the above, the present invention first prepares a modified organic silicon super-hydrophobic material, which is composed of micron-sized papillae formed by cross-linking and curing of siloxane polymers and nano-microspheres formed by embedded fluorinated nano-SiO2. This micro-nano composite rough structure is beneficial for the solid-liquid contact surface to directly capture air, thereby improving super-hydrophobicity. The modified organic silicon super-hydrophobic material is uniformly stirred with quartz sand to achieve super-hydrophobic modification of quartz sand, and an adaptive cement-based material is prepared using the super-hydrophobic modified quartz sand to ensure that the newly exposed structural surface after local destruction still has good super-hydrophobic performance, thereby achieving the adaptive regulation of the adaptive cement-based material to the complex environment of freeze-thaw.

[0052] The present invention will be further described below with reference to the embodiments.

[0053] Preparation of ordinary mortar, hydrophobic modifier mortar and integral superhydrophobic mortar

[0054] Preparation of ordinary mortar

[0055] Table 1 shows the basic physical parameters of the M32.5 masonry cement used in the following experiments, and Table 2 shows the mix ratio of the prepared mortar samples.

[0056] Table 1 Basic physical parameters of M32.5 masonry cement

[0057]

[0058] Table 2 Mortar mix ratio (1kg)

[0059]

[0060] Preparation of hydrophobic modifier mortar

[0061] Preparation of hydrophobic modifier mortar: cement and sand are taken in corresponding proportions according to the mortar mix ratio, and placed in a mortar mixer for pre-stirring to mix the cement and sand particles evenly; water is taken in corresponding proportions according to the water amount in the mortar mix ratio and placed in a beaker, and 1.2% of the water mass of polydimethylsiloxane (PDMS) is mixed with the water in the beaker, and a magnetic stirrer is used to stir strongly for 3 hours to evenly disperse the PDMS in the aqueous solution to obtain a PDMS solution; the PDMS solution is poured into the mixer and stirred thoroughly for 180r; the mortar is placed in a 70.7mm test mold, and the sample is vibrated with a vibration table, and the upper surface of the sample is covered with a 100-mesh copper mesh to control the micromorphology; after curing for 3 days, the sample is demoulded and placed in a standard curing box for curing for 28 days to prepare a hydrophobic modifier mortar.

[0062] Preparation of monolithic superhydrophobic mortar

[0063] Preparation of monolithic superhydrophobic mortar: First, fluorinated nano-SiO2 is prepared, and then a superhydrophobic precursor solution is prepared using the fluorinated nano-SiO2; the prepared superhydrophobic precursor solution is then sprayed onto quartz sand to prepare superhydrophobic modified quartz sand; the superhydrophobic modified quartz sand is then used to replace ordinary fine aggregate in the mortar, and the microstructure is controlled by a 100-mesh copper mesh on the surface to prepare an adaptive cement-based material. Figure 1 The preparation method of the integral super-hydrophobic mortar comprises the following steps:

[0064] (1) Preparation of fluorinated nano-SiO2: ① Weigh 5 g of nano-SiO2 and disperse it in a mixed solution of 230 mL of anhydrous ethanol and 20 mL of ammonia water; stir magnetically for 60 minutes to disperse it evenly; ② Continue strong magnetic dispersion and drop 1.5 g of heptafluorodecyltriethoxysilane (PFDTES) and 1.5 mL of tetraethoxysilane (TEOS) into the mixture while stirring; stir for 90 minutes to form a PDMS / PFDTES@SiO2 suspension; ③ Add 250 mL of butyl acetate to the PDMS / PFDTES@SiO2 suspension, stir magnetically for 60 minutes to disperse it evenly, let it stand for 3 hours, and separate the supernatant by decantation to obtain a white suspension containing butyl acetate; ④ Place the white suspension containing butyl acetate in a centrifuge, and centrifuge at 4000 r / min for 5 minutes to obtain a semi-solid white solid product fluorinated nano-SiO2 containing butyl acetate (abbreviated as F-SiO2).

[0065] (2) Prepare a superhydrophobic precursor solution: ① Take 5.25g of PDMS and dissolve it in 2.4mL of butyl acetate, and stir it magnetically for 1h to obtain a PDMS solution; ② Weigh 6.25g of semi-solid F-SiO2 and dissolve it in 9mL of butyl acetate, and stir it strongly magnetically for 3h to obtain a F-SiO2 dispersion; ③ Mix the above-mentioned PDMS solution and F-SiO2 dispersion, and continue to disperse for 2h to obtain a mixed solution; ④ Under strong magnetic stirring, add 2mL of anhydrous ethanol to the mixed solution, and stir it strongly magnetically for 1h; ⑤ Finally, add 0.525g of curing agent and stir it magnetically for 20min to prepare a superhydrophobic precursor solution (abbreviated as PDMS / F-SiO2).

[0066] (3) Preparation of superhydrophobic modified quartz sand: The superhydrophobic precursor solution prepared above was sprayed uniformly on 40-70 mesh quartz sand at a speed of 1 m / s and a distance of 20 cm under 6 kPa compressor pressure, and after spraying once, the 2 mm thick sand layer was turned over; the spraying and turning over sand layer steps were repeated 3 times to ensure that the superhydrophobic precursor solution was evenly adhered to the surface of the quartz sand particles. The superhydrophobic modified quartz sand (abbreviated as PDMS / F-SiO2@quartz sand) was cured at room temperature (25±0.4℃, 24±2% humidity) for 3 days.

[0067] (4) Preparation of integral superhydrophobic mortar: Substitute the fine aggregate with the superhydrophobic modified quartz sand prepared above, mix it evenly with cement particles in advance, add an appropriate amount of water, stir and compact it, and prepare an integral superhydrophobic mortar.

[0068] As can be seen above, in the present embodiment, the superhydrophobic modified quartz sand is prepared by spraying the prepared superhydrophobic precursor solution onto quartz sand. This superhydrophobic modified quartz sand replaces the fine aggregate in the mortar, thereby ensuring that the hydrophobic micro-nanostructures are evenly distributed within the mortar. Furthermore, the incorporation of the superhydrophobic modified quartz sand does not affect the hydration process of cement and water, thereby ensuring that the overall adaptive cement-based material has both superwetting properties and high compressive strength.

[0069] The following is a study on the performance of integral superhydrophobic mortar

[0070] Performance test of superhydrophobic modified quartz sand

[0071] First, SiO2 was grafted with PFDTES and TEOS to produce fluorinated nano-SiO2. A superhydrophobic precursor solution was then prepared using fluorinated nano-SiO2 and PDMS. This solution was sprayed onto 40-70 mesh quartz sand to create superhydrophobic-modified quartz sand, which can replace fine aggregate in mortar. To examine the surface wetting properties of the superhydrophobic-modified quartz sand, the macroscopic hydrophobicity test, microscopic morphology characterization, and wetting stability under different temperature environments were performed.

[0072] Superhydrophobic modified quartz sand exhibits significant water repellency at the macroscopic level. When a 10 μL droplet is dropped on the surface of superhydrophobic modified quartz sand, the droplet and the surface of superhydrophobic modified quartz sand show a 150.3 ° The contact angle ( Figure 2 (Figure a in the figure), while when a droplet falls on the surface of ordinary quartz sand, it will instantly wet the surface of the sand grains and penetrate into the interior from the gaps between the particles. This is mainly because the surface of superhydrophobic modified quartz sand has a lower surface energy. Compared with the solid-liquid contact surface of ordinary quartz sand, the droplets on the solid-liquid contact surface of superhydrophobic modified quartz sand are subject to smaller solid-liquid surface tension. The droplets shrink and approach a spherical shape due to the attraction of internal molecules. Under the combined action of gravity and tension, the droplets appear ellipsoidal in macroscopic form. A small amount of superhydrophobic modified quartz sand and ordinary sand were sprinkled on the water surface respectively. The water-repellent properties of superhydrophobic modified quartz sand made it float on the water surface ( Figure 2 b1 in the figure), while ordinary quartz sand sinks to the bottom of the water due to gravity and hydrophilicity ( Figure 2 The same mass of super-hydrophobic modified quartz sand and ordinary quartz sand were placed in a beaker and 50 mL of water was added. The states were respectively as shown in Figure b2. Figure 2 Figure c1 and c2 in the figure, then put the two beakers into a -20℃ constant temperature box and freeze them for 12 hours. Then, take out the contents of the beakers upside down. It can be seen that even in a low temperature environment of -20℃, the superhydrophobic modified quartz sand still has stable water repellency. The sand pile and 50mL water are clearly separated. After freezing, the sand particles are dispersed and the ice cubes are independent ( Figure 2 (Figure c3 in the figure), while ordinary quartz sand is wetted by water and freezes into one with pore water under low temperature environment ( Figure 2 This shows that the hydrophobicity of superhydrophobic modified quartz sand is stable under low temperature environment.

[0073] Microscopic characterization of superhydrophobic modified quartz sand

[0074] The surface morphologies of ordinary quartz sand and superhydrophobic-modified quartz sand were characterized using SEM. While the surface of unmodified ordinary quartz sand is relatively smooth, the surface of superhydrophobic-modified quartz sand modified with the superhydrophobic precursor solution exhibits a distinct micro- and nano-rough structure. Figure 3 SEM images of super-hydrophobic modified quartz sand at different sizes: 30 μm ( Figure 3 Figure a), 50μm( Figure 3 b), 20 μm ( Figure 3 Figure c), 1μm( Figure 3 d in Figure ), from Figure 3It can be seen from the SEM image under a high-power electron microscope that these rough structures are composed of micron-sized papillae formed by cross-linking and curing of PDMS and nano-microspheres formed by embedded nano-F-SiO2. This micro-nano composite rough structure is conducive to the direct capture of air at the solid-liquid interface, thereby improving superhydrophobicity. This is because the PDMS in the superhydrophobic precursor solution contains CH2 and CH3 hydrophobic groups, and the F-SiO2 contains CF2 and CF3 hydrophobic groups. These hydrophobic groups have lower surface energy and smaller solid-liquid surface tension coefficients, which makes the droplets have a lower energy state when they tend to be spherical on the solid surface, thereby showing water-repellent properties at the macro level. From the EDS energy spectrum of superhydrophobic modified quartz sand ( Figure 4 Figure a) and the EDS spectrum of ordinary quartz sand ( Figure 4 From the analysis of Figure b), it can be seen that the F element content of 0.94% was detected in the superhydrophobic modified quartz sand after fluorosilane grafting, which proves that F-SiO2 was successfully cured and bonded to the quartz sand surface with the PDMS adhesive, and can improve the hydrophobic properties of the superhydrophobic modified quartz sand surface.

[0075] The FTIR spectrum transmittance of super hydrophobic modified quartz sand and ordinary quartz sand is shown in Figure 5 Figure a in Figure 3600 -1 -3400cm -1 The position of the OH group has a broad and strong stretching vibration absorption peak at 2960 cm -1 、2930cm -1 and 2855cm -1 The position is due to the absorption peak caused by the stretching vibration of the CH bond in the CH2 and CH3 groups. -1 The two samples have significant differences in the position, which is mainly due to the vibration of Si-CH3 groups in PDMS molecules and CF bond vibration in F-SiO2 molecules modified by PFDTES and TEOS grafting on the surface of superhydrophobic modified quartz sand. -1 The position of the superhydrophobic modified quartz sand is also significantly different from that of ordinary sand. This is due to the absorption peak caused by the vibration of the Si-O group in the PDMS molecule, which also proves that PDMS is successfully bonded to the quartz sand surface.

[0076] In order to explore the grafting of fluorosilane and nano-SiO2, XPS characterization experiments were carried out on nano-SiO2, F-SiO2, ordinary quartz sand particles and super-hydrophobic modified quartz sand particles, and the element composition and element chemical state before and after hydrophobic modification were compared. The element potential state peak distribution of F1s (689eV), O1s (533eV), C1s (285eV), Si2s (155eV), and Si2p (104eV) is characterized in Figure 5In Figure b, there is a significant F element electronic state in the fluorinated nano-SiO2 molecules, and the F element content accounts for 21.92% of the total element content, which proves that more fluorosilanes are successfully grafted onto the nano-SiO2, and the low surface energy F-SiO2 molecules show super hydrophobicity. Correspondingly, the element electronic state distribution of the unmodified nano-SiO2 is characterized in Figure 5 In Figure c, no F element electronic state energy is detected. Comparative analysis of the C1s peak spectra of SiO2 and F-SiO2 shows that C1s has the same peaks composed of CC (284.5eV), CO (284.7eV) and C=O (285.7eV) before and after modification. The modified F-SiO2 molecule also has an additional CF peak composed of CF2-CF2 (291.8eV) and CF3-CF2 (293.9eV). Figure 5 In the F1s peak spectrum, it can be seen that the F element only forms the CF bond energy with the C element in the molecular bond energy composition ( Figure 5 Figure e in the figure), Figure 5 Panel f has the same CC (284.5 eV), CO (284.7 eV), and C=O (285.7 eV) peaks as those in panel d.

[0077] XPS spectrum analysis of super hydrophobic modified quartz sand is shown in Figure 5 In Figure g, the presence of F1s element can be detected in the element peak spectrum of superhydrophobic modified quartz sand. Compared with the F element content in F-SiO2 molecules, the F element content is significantly reduced, accounting for only 0.37%, while the F element content is not detected in ordinary quartz sand particles ( Figure 5 This is mainly because the surface coverage of the nano-F-SiO2 bonded to the 40-70 mesh quartz sand by PDMS is relatively low. Although the surface has only a very small F element content, it still gives the superhydrophobic modified quartz sand superhydrophobic properties.

[0078] Microscopic morphology of monolithic superhydrophobic mortar

[0079] According to the Cassie-Baxter contact model, increasing the roughness of low surface energy surfaces can improve the surface superwetting properties. In order to improve the surface roughness of the monolithic superhydrophobic mortar, a 100-mesh copper mesh was covered on the upper surface during the preparation stage to control the surface micromorphology. Figure 6 Figure a is a close-up shot of the copper mesh-controlled, integrated super-hydrophobic mortar surface taken with an industrial camera. The surface, modified by the copper mesh, has a regularly distributed, densely arranged, micron-scale papillary structure. The surface morphology of the copper mesh-modified integrated super-hydrophobic mortar was further characterized by SEM. Scanning electron microscopy revealed that the papillary structure modified with a 100-mesh copper mesh was 150×150×50μm. 3The cubic structure is evenly distributed on the surface ( Figure 6 (Figure b in the figure). The copper mesh-modulated papillary structure provides an additional micron-scale roughness structure. These micron-sized papillary structures are composed of superhydrophobic modified quartz sand, F-SiO2, and hydrated calcium silicate. The protrusions and depressions of the papillary structure are filled with nano-rough components. This micro-nano composite structure gives the monolithic superhydrophobic mortar its superhydrophobic properties.

[0080] Figure 7 Contains ordinary mortar samples ( Figure 7 Figure a in the figure), hydrophobic modifier mortar sample ( Figure 7 b) and the internal SEM image of the monolithic superhydrophobic mortar sample ( Figure 7 Figures c and d in the figure). The SEM images of the three groups of samples show that the images of the ordinary mortar samples clearly show flower-like / flaky Ca(OH)2 crystals (CH) and needle-like ettringite. This is because the cement contains large amounts of dicalcium silicate (C2S), tricalcium silicate (C3S), and tricalcium aluminate (C3A). As the cement hydration reaction proceeds, the resulting hydrated calcium silicate gel becomes the main structure of the mortar. C2S and C3S are hydrated to form flaky calcium hydroxide CH, which quickly precipitates out in the aqueous solution upon saturation, forming a flower-like / flaky structure. C3A reacts with gypsum to form needle-like ettringite. The chemical equation for the hydration reaction is as follows:

[0081] (1)

[0082] (2)

[0083] (3)

[0084] From the SEM images of the two groups of super-hydrophobic modified samples, we can see that: the Si-O-Si flexible skeleton structure and micron-sized microspheres of hydrophobic groups are formed by the self-crosslinking and curing of hydrolyzed PDMS-OH molecules. There are also micro-nano layers formed by PDMS-OH and SiO2-OH on the surface of super-hydrophobic modified quartz sand. The roughness of the overall super-hydrophobic mortar sample is significantly higher than that of the ordinary mortar sample. Figure 7 In Figure d, we can see numerous anchor-like hydrated calcium silicate gels, blocky / flaky calcium hydroxide, and rough-surfaced PDMS / F-SiO2@quartz sand, which are bonded and coated with the hydration products, thus ensuring that the integral superhydrophobic mortar has both high strength and hydrophobicity.

[0085] Wear resistance of monolithic superhydrophobic mortar

[0086] In actual engineering applications, the surface of construction projects is often damaged by external forces such as friction and collision during its service life. In order to test the mechanical durability of the integral superhydrophobic mortar sample, a wear cycle test was carried out on the surface controlled by the metal copper mesh, and the degree of wettability damage was judged based on the static contact angle of the surface. In the wear cycle test, an integral superhydrophobic mortar sample with a thickness of 70.7mm×70.7mm×20mm was cut out in advance and the modified surface of the copper mesh was used as the wear test surface. A 500g weight was placed as a heavy load at the center of the integral superhydrophobic mortar sample slice. The integral superhydrophobic mortar sample was moved at a uniform speed of 20cm along the ruler direction at one end of 800 mesh sandpaper, and then worn 20cm in the opposite direction as a wear cycle. After every two wear cycles, the static contact angle of the worn surface was measured, and the average value of the 5 test points was taken as the test data value and plotted. Figure 8 In. By Figure 8 The test results show that the static contact angle of the test sample, that is, the monolithic superhydrophobic mortar sample, at 0 wear cycle is between 145-152 ° This is due to the hydrophobic properties of the superhydrophobic modified quartz sand and the rough structure of the micron-scale papillae on the surface discussed above. After the monolithic superhydrophobic mortar sample experienced 6 wear cycles, the micron-scale papillae regulated by the metal copper mesh were obviously damaged, exposing the rough structure of the monolithic superhydrophobic mortar sample composed of superhydrophobic modified quartz sand and hydration products. Even if the droplet did not contact the regularly arranged micron grid, the droplet still had 150 ° The static contact angle is around 1.5, which proves that the newly exposed internal mortar still has good hydrophobic properties, rather than relying on the grid structure regulated by the metal copper mesh on the surface.

[0087] The interior of the monolithic superhydrophobic mortar sample has superhydrophobic properties, so even if the surface is damaged or the sample is broken, the exposed cement base inside still has superwetting properties. Figure 9 The hydrophobicity of the monolithic super-hydrophobic mortar sample with cracked surface was tested using an aqueous solution containing methylene blue. The test results showed that the droplet fell on the micro-crack with a width of 200 μm on the surface of the monolithic super-hydrophobic mortar sample ( Figure 9 (a in the figure), the droplet on the solid-liquid interface still has significant superhydrophobic properties; even if the crack destroys the surface micron-scale papillary grid structure ( Figure 9 The droplet remains spherical and remains on the surface of the monolithic superhydrophobic mortar sample. This is mainly because the superhydrophobic modified quartz sand has a small particle size and can be evenly dispersed inside the monolithic superhydrophobic mortar sample. The surface of PDMS / F-SiO2@quartz sand has CF2, CF3, CH2, and CH3 groups, providing low surface energy and high-level micro-nano rough structure. The droplet is dropped into the monolithic superhydrophobic mortar sample with a broken corner ( Figure 9(Figure c in the figure), the internal cement-based and superhydrophobic modified quartz sand can still maintain the superwetting state of the droplets, which shows that the interior of the integral superhydrophobic mortar sample also has superhydrophobic properties.

[0088] Anti-icing performance of integral superhydrophobic mortar

[0089] The superwettability of the surface imparts a large contact angle to the solid-liquid interface. The rough solid surface also creates an air layer within the interface. This contact model effectively reduces the solid-liquid contact area, thereby slowing the rate of heat transfer between the solid and liquid, and also slowing the formation of ice nuclei and the growth of ice crystals. The air-filled contact surface provides additional stress concentration sites, reducing ice adhesion strength and imparting anti-icing and deicing properties to the superhydrophobic surface. The anti-icing and deicing properties of the prepared monolithic superhydrophobic mortar and conventional mortar samples were tested using ice condensation time tests, cumulative ice condensation tests, and deicing tests, respectively.

[0090] Low temperature environment anti-icing test

[0091] In the ice freezing time test, the monolithic super-hydrophobic mortar sample and the ordinary mortar sample were placed in a -10℃ constant temperature environment box and pre-cooled to ambient temperature. A 10μL droplet was dropped on the surface of the test sample, and the ice nucleation time, frost layer development time and ice cone complete formation time of the two groups of samples were recorded. On the surface of the monolithic super-hydrophobic mortar sample, the droplet still had a nearly 150 ° The solid-liquid contact model is consistent with the Cassie-Baxter theoretical model, which makes the droplets of the same volume have a significant ice condensation delay phenomenon on the surface of the monolithic superhydrophobic mortar sample. As the droplet stays on the solid surface for a longer time, the contact angle of the droplet gradually decreases to 120 ° This is because a part of the droplets come into contact with the hydrophilic calcium silicate hydrate component on the surface, and a small amount of droplets penetrate into the interior of the integral superhydrophobic mortar sample along the structure of the hydration product itself, resulting in a decrease in the droplet volume, while the length of the solid-liquid-gas three-phase line remains unchanged, resulting in a decrease in the contact angle. When the droplets on the surface of the overall modified sample are in contact with the low temperature environment for 339 seconds, the water molecules are oriented to form ice nuclei, and in the subsequent 40 seconds, the frost layer develops along the contact surface to the top end. Finally, at 395 seconds, the dendritic structure inside the ice crystal is fully developed, and the transparency of the ice crystal is significantly reduced ( Figure 10 Under the same test conditions, the contact angle between a 10 μL droplet on the ordinary mortar sample and the surface is only 40 °Because the surface mortar components are all hydrophilic, the contact model between the droplet and the solid surface is a Wenzel contact model. This contact model will have a very high heat transfer rate between the solid and liquid media. After only 14 seconds, the flat droplet has formed an ice nucleus. In the following 13 seconds, the frost layer quickly develops to the top of the droplet, forming a spike-shaped ice cone. Finally, at 67 seconds, the dense ice crystal structure is fully formed ( Figure 10 (b) Compared with ordinary mortar samples, the monolithic superhydrophobic mortar sample has significant anti-icing properties, and the freezing time is delayed by 5.9 times compared with ordinary mortar samples.

[0092] In the cumulative ice accumulation test, two groups of samples, the monolithic super-hydrophobic mortar sample and the ordinary mortar sample, were pre-cooled to ambient temperature at -20°C. The two groups of samples were placed on a flat surface 30 ° On a platform with an angle of 1 / 4, a 100 mL droplet is uniformly dropped at a rate of 75 mL / h at a height of 10 cm just above the surface to be tested onto the center of the top surface of the test block. When all the 100 mL droplet has dropped, the amount of ice on the top surface of the ordinary mortar sample and the integral superhydrophobic mortar sample is observed. Figure 10 The test results in Figures c1-c2 and c3-c4 show that the surface of the monolithic superhydrophobic mortar specimens has similar accumulated ice as the surface of the ordinary mortar specimens. This is mainly due to the large rolling angle of the monolithic superhydrophobic mortar specimens caused by the low temperature environment, which easily forms accumulated ice on the surface with weaker wettability. However, the difference is that the droplets dripping on the surface of the ordinary mortar specimens wet the surface and form an ice layer in the form of Wenzel contact. This ice layer is difficult to completely remove mechanically, while the surface of the monolithic superhydrophobic mortar specimens only has a significant accumulation of semi-cylindrical ice blocks, and the location of the dripping droplets is not wetted, making these accumulated ice blocks easier to remove.

[0093] Low temperature environment deicing test

[0094] Figure 11 The residual morphology of ice removal of two groups of samples in low temperature environment. In a -20℃ constant temperature test chamber, ice condensation molds were used to condense 70.7×70.7×10mm ice on the monolithic super-hydrophobic mortar sample and the ordinary mortar sample. 3 The ice layer of the two groups of samples was condensed for 24 hours, and a 500g weight was used to fall freely from a height of 1m to hit the ice layer on the upper surface of the two groups of samples. The residual morphology of the damaged ice layer was observed ( Figure 11 The test results show that the ice layer on the monolithic super-hydrophobic mortar sample is broken and detached by the impact of heavy objects ( Figure 11 c in Figure 3), while the ice layer on the ordinary mortar sample with the same impact force only created a groove with a depth of 3 mm ( Figure 11(Figure b) This indicates that the ice layer on the monolithic superhydrophobic mortar sample has lower ice bonding strength. The bonding force between the ice layer and the cement base, as well as the internal interaction force of the ice layer, is smaller than the horizontal force transferred to the ice layer by the weight impact force, causing the ice layer to break and detach from the surface. These test results demonstrate that the monolithic superhydrophobic mortar sample has excellent anti-icing and de-icing properties, making this modified material suitable for engineering construction applications in cold regions.

[0095] Antifreeze performance

[0096] To examine the effects of different hydrophobic modification measures on the degree of degradation of the mortar's compressive mechanical properties, the compressive strength of two groups of cubic specimens (conventional mortar and monolithic superhydrophobic mortar) was measured after 28 days of standard curing. Three specimens were tested in each group, and the average compressive strength (AVE) was calculated for each group. The formula for calculating the compressive strength of the mortar cube is shown in Equation 1:

[0097] (1)

[0098] in: is the compressive strength of mortar cube in MPa; is the ultimate load of specimen failure N; The pressure bearing area of ​​the specimen ; is the conversion factor, ;

[0099] The calculation formula for the average compressive strength AVE of each group of samples is shown in Formula 2:

[0100] (2)

[0101] in: The sum of the compressive strength of the mortar cubes of Samples 1, 2, and 3;

[0102] The calculation formula of the compressive strength damage rate of the sample is shown in formula 3:

[0103] (3)

[0104] in: is the compressive strength loss rate (%) at the corresponding stage when undergoing a single freeze-thaw cycle; I Is the corresponding experience m 、 n Compressive strength loss rate after freeze-thaw cycles (%); m 、 n is the number of freeze-thaw cycles (when m When the freeze-thaw cycles are 0, 15, 30, 45, and 60, the corresponding n for 15, 30, 45, 60, and 75 freeze-thaw cycles).

[0105] Figure 12 Figure 2 shows the compressive strength loss of monolithic superhydrophobic mortar and conventional mortar samples after 75 freeze-thaw cycles. The compressive strength of both samples decreased over the 75 freeze-thaw cycles, and the percentage loss rate increased with the number of freeze-thaw cycles. This indicates that freeze-thaw damage and performance degradation accelerate the rate of damage progression. The conventional mortar sample experienced the greatest strength loss after 75 freeze-thaw cycles, retaining only 32.2% of its initial strength. This indicates that conventional cement-based materials exhibit weak frost resistance under freeze-thaw conditions. The combined effects of hydrostatic and osmotic pressures increase the volume of pore ice phase transitions and lead to severe frost heave damage. Conversely, the monolithic superhydrophobic mortar sample exhibited significantly less strength loss after 75 freeze-thaw cycles, retaining 42.5% of its original strength. This corresponds to the strength loss rate of the conventional mortar sample after 63 freeze-thaw cycles. This indicates that the monolithic superhydrophobic mortar sample improves the frost resistance of cement-based materials by 1.2 times. Furthermore, the rate of strength loss of the monolithic superhydrophobic mortar specimens was significantly lower than that of the conventional mortar specimens. This is primarily due to the significantly reduced water absorption capacity of the monolithic superhydrophobic mortar specimens, which results in a significantly lower initial pore moisture content within the monolithic superhydrophobic mortar specimens than that of the conventional mortar specimens. When the pore water within the conventional mortar specimens undergoes a phase transition and freezes, it reaches critical saturation before the monolithic superhydrophobic mortar specimens, generating hydrostatic and osmotic pressures earlier and causing freeze-thaw failure.

[0106] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an adaptive cement-based material, characterized in that: Super-hydrophobic aggregate is used instead of fine aggregate, which is evenly mixed with cement particles in advance, and then an appropriate amount of water is added. The mixture is stirred and vibrated, cast and demoulded, and then covered with a 100-mesh copper mesh on the surface to obtain an adaptive cement-based material. The super-hydrophobic aggregate is obtained by spraying a modified organic silicon super-hydrophobic material on the cement-based aggregate, wherein the cement-based aggregate includes at least one of quartz sand and machine-made sand. The preparation of the modified organic silicon super-hydrophobic material includes the following steps: Dissolving a siloxane polymer and fluorinated nano-SiO2 in an organic solvent respectively to obtain a siloxane polymer solution and a fluorinated nano-SiO2 dispersion, and then mixing the two solutions to obtain a mixed solution; Under strong stirring, anhydrous ethanol and a curing agent are sequentially added to the mixed solution to obtain a modified organosilicon super-hydrophobic material. The siloxane polymer is polydimethylsiloxane or polymethylhydrogensiloxane, and the organic solvent includes one or more of acetone and butyl acetate.

2. The preparation method according to claim 1, characterized in that The fluorinated nano-SiO2 is selected from nano-SiO2 containing fluorine silane chains.

3. The preparation method according to claim 2, characterized in that The fluorinated nano-SiO2 is prepared by the following preparation method: Dispersing nano-SiO2 into a mixed solution of anhydrous ethanol and ammonia water, stirring and mixing uniformly to obtain a nano-SiO2 dispersion; Then, heptadecafluorodecyltriethoxysilane and tetraethoxysilane are mixed with the nano-SiO2 dispersion to form a SiO2 suspension; The SiO2 suspension was then mixed with ethyl acetate, stirred and dispersed evenly, allowed to stand, and the supernatant was separated and removed to obtain a white suspension containing butyl acetate; After centrifuging the white suspension containing butyl acetate, fluorinated nano-SiO2 is obtained; Wherein, the mass ratio of the heptafluorodecyltriethoxysilane to the tetraethoxysilane to the nano-SiO2 is 1:(0.8-1.0):(3-4).

4. The preparation method according to claim 1, characterized in that The following steps are involved: adding polydimethylsiloxane to butyl acetate and stirring to completely dissolve the polydimethylsiloxane in the butyl acetate to obtain a polydimethylsiloxane solution; Dispersing the fluorinated nano-SiO2 in anhydrous ethanol, vigorously stirring to evenly disperse the fluorinated nano-SiO2, to obtain a fluorinated nano-SiO2 dispersion; The two solutions are mixed and dispersed to obtain a mixed solution; Under vigorous stirring, anhydrous ethanol was added dropwise to the mixed solution and stirred vigorously; Finally, a curing agent is added and stirred again to prepare a modified organosilicon superhydrophobic material.

5. The preparation method according to claim 1, characterized in that The spraying step includes: using a spray gun with a caliber of 1mm-2mm to spray the modified organic silicon super-hydrophobic material on the surface of the cement-based aggregate, during spraying, the modified organic silicon super-hydrophobic material is uniformly sprayed on the 40-70 mesh cement-based aggregate at a speed of 1m / s-3m / s and a distance of 15cm-30cm under a 5kPa-10kPa compressor pressure, each spraying thickness is preferably 2mm, and after spraying once, the cement-based aggregate particle layer is turned over; repeating the spraying and turning the cement-based aggregate particle layer 2-3 times, and then curing it at room temperature for 3-5 days to prepare the super-hydrophobic aggregate.

6. The preparation method according to claim 1, characterized in that The average static contact angle of the super hydrophobic aggregate surface is 150.3 ° above.

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