Composite dry-mixed waterproof mortar based on nano material, and preparation method and application of composite dry-mixed waterproof mortar

Abstract

The invention belongs to the technical field of mortar, and particularly provides composite dry-mixed waterproof mortar based on a nano-material and a preparation method and application of the composite dry-mixed waterproof mortar based on the nano-material. The composite dry-mixed waterproof mortar comprises the following raw materials: ordinary Portland cement, machine-made sand, the modified nano-material, redispersible latex powder, a water repellent, a water-retaining thickener and a water reducing agent; the modified nano material is prepared by wrapping modified nano silicon dioxide with poly (N-isopropylacrylamide) / polyvinyl alcohol gel; according to the modified nano material, the performance of the mortar is improved by improving the dispersity of nano silicon dioxide in the mortar. The dry-mixed waterproof mortar prepared by the invention has the advantages of permeability resistance and high durability.

Description

Technical Field

[0001] This application belongs to the field of mortar technology, and in particular relates to a composite dry-mixed waterproof mortar based on nanomaterials, its preparation method, and its application. Background Technology

[0002] Waterproof mortar is a crucial line of defense in building waterproofing, commonly used in basements, kitchens, and bathrooms—areas prone to leakage. However, in actual use, ordinary waterproof mortar, during the cement hydration process, fails to form a dense aggregate of products, resulting in numerous pores that further develop into capillary channels. This allows moisture to penetrate the building's interior, threatening structural safety. Furthermore, prolonged exposure to humid environments allows corrosive media to enter the mortar through these pores, causing cracking, peeling, and other problems, thus reducing the building's lifespan.

[0003] Nanomaterials such as nano-silica, when used in waterproof mortar, can improve the mortar's performance in several ways. Firstly, the extremely small particle size of nano-silica can fill the tiny pores within the mortar and the capillary channels created by hydration. Furthermore, its ability to fill pores and optimize the microstructure enhances the mortar's resistance to erosion. Secondly, the high activity of nano-silica promotes cement hydration and improves the early strength of the mortar. However, the small particle size and large specific surface area of ​​nano-silica make it prone to agglomeration. Agglomerated nano-silica cannot fully utilize its nano-effects and occupies internal space in the mortar, easily leading to structural defects.

[0004] Patent application CN112661461A discloses a high-strength waterproof and seepage-resistant nano-SiO2 mortar and its preparation method. This invention involves preparing a dispersion of nano-silica and polyvinyl alcohol, which is then mixed with cement, sand, and other materials to produce the mortar. This invention utilizes the filling effect and hydration-promoting properties of nano-silica to improve mortar performance, and this method can alleviate the agglomeration problem of nano-silica to some extent. However, in the nano-silica and polyvinyl alcohol system, no chemical grafting modification is used; relying solely on physical dispersion results in poor dispersion stability. Physical dispersion does not change the surface properties of nano-silica, which still possesses high surface energy. Over time, the nanoparticles easily overcome the state maintained by physical dispersion and re-agglomerate. Furthermore, the adsorption between polyvinyl alcohol and nano-silica is mainly through hydrogen bonds and van der Waals forces, resulting in weak adsorption capacity. Nano-silica, being highly polar, preferentially forms hydrogen bonds with water molecules in the solution, making it easy to detach and rapidly agglomerate. Summary of the Invention

[0005] To address the aforementioned problems and further improve the dispersibility of nano-silica, thereby enhancing the impermeability and mechanical properties of mortar, this application provides a composite dry-mix waterproof mortar based on nanomaterials.

[0006] This application first provides a composite dry-mixed waterproof mortar based on nanomaterials. The raw materials of the dry-mixed waterproof mortar include the following: ordinary silicate cement, manufactured sand, modified nanomaterials, redispersible latex powder, water-repellent agent, water-retaining thickener, and water-reducing agent; the modified nanomaterials are obtained by treating modified nano-silica with poly(N-isopropylacrylamide) / polyvinyl alcohol gel.

[0007] The modified nanomaterial is obtained by encapsulating modified nano-silica with poly(N-isopropylacrylamide) / polyvinyl alcohol gel.

[0008] The modified nano-silica is obtained by grafting modified cyclodextrin onto the surface of nano-silica.

[0009] Furthermore, the mass ratio of the modified cyclodextrin to nano silica is 1:(7-9).

[0010] Furthermore, the preparation method of the modified cyclodextrin includes the following steps: S1, reacting cyclodextrin with p-toluenesulfonyl chloride to generate p-toluenesulfonated cyclodextrin; S2, reacting a straight-chain alkyl alcohol with p-toluenesulfonyl chloride to generate p-toluenesulfonic acid alkyl ester; S3, reacting p-toluenesulfonated cyclodextrin with a diamine compound to generate a cyclodextrin derivative; S4, reacting the cyclodextrin derivative with p-toluenesulfonic acid alkyl ester, filtering, and drying to obtain modified cyclodextrin.

[0011] Furthermore, in step S2, the straight-chain alkyl alcohol is one of n-dodecyl alcohol, n-tetradecyl alcohol, and n-hexadecyl alcohol; And / or, in step S3, the diamine compound is one of ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine.

[0012] Furthermore, in step S4, the mass ratio of the cyclodextrin derivative to the alkyl p-toluenesulfonate is (1.5-2):1.

[0013] Furthermore, the preparation method of the modified nanomaterial includes the following steps: dissolving polyvinyl alcohol in deionized water, then adding modified nano-silica and N-isopropylacrylamide, mixing evenly, adding ammonium persulfate and tetramethylethylenediamine to carry out a polymerization reaction, and freeze-drying to obtain the final product.

[0014] Furthermore, the mass ratio of polyvinyl alcohol, N-isopropylacrylamide, and modified nano-silica is 5:10:(1-1.5).

[0015] Furthermore, the cement is ordinary Portland cement with a strength grade of 42.5; Furthermore, the manufactured sand has a fineness modulus of 2.3-3.0, an MB value of ≤1.4, and a stone powder content of ≤10%. Furthermore, the redispersible latex powder is at least one of polyvinyl acetate, polyvinyl acetate-ethylene, polyvinyl acetate-ethylene tert-carbonate, and polyacrylate-styrene.

[0016] Furthermore, the hydrophobic agent is an organosilicon-based hydrophobic agent.

[0017] Furthermore, the water-retaining and thickening material is at least one of hydroxypropyl methylcellulose, methylcellulose, and hydroxyethyl methylcellulose.

[0018] This application also provides a method for preparing a composite dry-mixed waterproof mortar based on nanomaterials, comprising the following steps: premixing cement, manufactured sand, and modified nanomaterials; adding redispersible latex powder, water-repellent agent, and water-retaining thickener; adding polycarboxylate superplasticizer and stirring to obtain a dry powder form of dry-mixed waterproof mortar.

[0019] This application also provides an application of a composite dry-mixed waterproof mortar based on nanomaterials in building waterproofing, water conservancy projects, and industrial facilities.

[0020] Compared with the prior art, this application has the following beneficial effects: 1. The modified nanomaterial prepared in this application is made by encapsulating modified nano-silica with poly(N-isopropylacrylamide / polyvinyl alcohol) gel. After the three-dimensional network structure of the gel encapsulates the modified nano-silica, the physical barrier formed by the gel molecular chains effectively prevents the aggregation of the modified nano-silica, thereby improving its dispersibility in water. 2. The poly(N-isopropylacrylamide) / polyvinyl alcohol gel molecular chain contains hydroxyl and amide bonds, which can form hydrogen bonds with the hydroxyl groups in the β-cyclodextrin of the modified nano-silica structure, forming a more stable fixed gel network and enhancing the overall stability of the gel. Simultaneously, the poly(N-isopropylacrylamide) / polyvinyl alcohol gel has a unique minimum critical dissolution temperature. During mortar hydration, when the temperature exceeds this temperature, the gel transitions from a swollen state to a contracted state, releasing stored water molecules and reacting with cement particles to accelerate the hydration rate. The hydration products cross-link and interpenetrate with poly(N-isopropylacrylamide), improving the mortar's density. As hydration progresses, poly(N-isopropylacrylamide) polymerizes into a thin film network structure, bridging cement hydration products, dispersing and transmitting stress, and improving the mortar's flexural strength. Polyvinyl alcohol contains unhydrolyzed vinyl acetate chains, which hydrolyze in cement to form acetate. The acetate reacts with calcium ions in the cement, prolonging the time for calcium ions to reach supersaturation, reducing the amount of calcium hydroxide formed, improving cement durability and mechanical properties.

[0021] 3. The steric hindrance effect of the hydrophobic long chains in modified nano-silica reduces the aggregation of nano-silica. After dispersion, the nanoparticles fill the capillary pores of the mortar, reducing the mortar porosity. The reduction in porosity makes the internal stress distribution of the mortar more uniform, improving mechanical properties such as compressive strength and flexural strength. In addition, the hydrophobic alkyl long chains attached to the modified nano-silica have low surface energy, repelling water molecule penetration and improving the cement's impermeability. Attached Figure Description

[0022] Figure 1 The infrared spectra of the modified β-cyclodextrin and β-cyclodextrin prepared in Example 3 of this application are shown.

[0023] Figure 2 This is a scanning electron microscope image of nano-silica from Comparative Example 1 of this application.

[0024] Figure 3 Scanning electron microscope image of the modified nano-silica prepared in Example 3 of this application. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0027] Example 1 The composite dry-mixed waterproof mortar based on nanomaterials in this embodiment is composed of the following raw materials by weight: 33kg of ordinary silicate cement, 75kg of manufactured sand, 0.5kg of modified nanomaterials, 3.6kg of redispersible latex powder, 0.5kg of organosilicon water-repellent agent, 0.25kg of water-retaining and thickening material, and 0.12kg of polycarboxylate superplasticizer.

[0028] The cement used is ordinary Portland cement with a strength grade of 42.5. The manufactured sand has a fineness modulus of 2.3-3.0, an MB value ≤1.4, and a stone powder content ≤10%. The redispersible latex powder is model 5010N. The water-repellent agent is model 6034H. The water-retaining and thickening material is hydroxypropyl methylcellulose. The polycarboxylate superplasticizer is model SC-11.

[0029] The modified nanomaterials in this embodiment are prepared as follows: 5g of polyvinyl alcohol is dissolved in a 100mL water bath at 80℃ for 30min, and then naturally cooled to room temperature. 1g of modified nano-silica is added, and the mixture is sonicated for 10min. 10g of N-isopropylacrylamide monomer is added, and the mixture is stirred until the N-isopropylacrylamide is completely dissolved, forming a homogeneous mixture. Ammonium persulfate and tetramethylethylenediamine are added as a redox initiation system, and the mixture is reacted at room temperature for 2h to form N-isopropylacrylamide polymer chains, which are physically entangled / mixed with polyvinyl alcohol molecular chains to obtain a poly(N-isopropylacrylamide / polyvinyl alcohol) blend system containing nanoparticles. This mixture is frozen at -25℃ for 24h and thawed at room temperature for 20min. This process is called a single freeze-thaw cycle (N=1), and a total of 7 cycles (N=7) are performed to obtain a hydrogel. The obtained hydrogel is soaked in distilled water for 48h, during which the distilled water is continuously replaced to remove uncrosslinked polymer chains and impurities. The purified hydrogel was freeze-dried to remove moisture, resulting in a dry poly(N-isopropylacrylamide / polyvinyl alcohol) hydrogel containing nanoparticles, which was then stored for later use.

[0030] The preparation method of modified nano-silica in this embodiment is as follows: 1.5g of dried modified β-cyclodextrin was dissolved in 200mL of anhydrous DMF under stirring. 0.4mL of triethoxy(3-propyl isocyanate)silicon was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 70℃ and reacted for 6h. Then, 10g of nano-silica (average particle size 50±5nm) was added to the above solution, and the temperature was raised to 110℃ and the reaction was continued for 24h. After cooling to room temperature, the mixture was filtered. The crude product was repeatedly washed with DMF, methanol and acetone until the filtrate was clear. Finally, the solid was vacuum dried at 85℃ for 6h to obtain the modified β-cyclodextrin-modified nano-silica material.

[0031] The preparation method of modified β-cyclodextrin in this embodiment includes the following steps: 1.10 g of β-cyclodextrin was added to 100 mL of NaOH aqueous solution (1 wt%) and stirred in an ice-water bath until completely dissolved. 1.68 g of p-toluenesulfonyl chloride was dissolved in 5 mL of acetonitrile and slowly added dropwise to the reaction system using a constant-pressure dropping funnel, gradually resulting in the precipitation of a white precipitate. After continuing stirring for 2 hours, ammonium chloride was added to adjust the pH of the solution to 8, resulting in the precipitation of a large amount of white substance. The solution was washed twice with deionized water and ethanol, respectively, filtered, and the filter cake was vacuum dried to obtain mono-6-p-toluenesulfonated-β-cyclodextrin.

[0032] S2. Dissolve 10g of n-hexadecyl alcohol in a dichloromethane solution. Slowly add a dichloromethane solution containing 7.9g of p-toluenesulfonyl chloride to the solution system in an ice-water bath. The addition is completed in 30 minutes. After reacting in an ice-water bath for 1 hour, react at 30°C for 5 hours. Distill under reduced pressure to obtain a light yellow solid. Wash twice with water, filter, and dry under vacuum to obtain hexadecyl toluenesulfonate.

[0033] S3. In a three-necked flask equipped with a reflux condenser, 5 g of mono-6-p-toluenesulfonated-β-cyclodextrin was added. Under nitrogen protection, excess ethylenediamine was added, and the mixture was heated to 70°C and stirred for 4 h. At this temperature, excess ethylenediamine was removed by vacuum distillation to obtain a light yellow solid. After dissolving it in a small amount of water, it was precipitated with anhydrous ethanol, filtered, and a white powder was obtained. After vacuum drying, mono-[6-(2-aminoethyl)-amino-6-deoxy]-cyclodextrin was obtained.

[0034] S4. In a three-necked flask equipped with a reflux condenser and a dropping funnel, add mono-[6-(2-aminoethyl)-amino-6-deoxy]-β-cyclodextrin, hexadecyl p-toluenesulfonate, and 50 mL of N-methylpyrrolidone (NMP) at a mass ratio of 1.5:1. Stir for 30 min to ensure thorough mixing of the reactants. Heat to 70 °C and stir for 6 h. Filter to obtain a pale yellow solid. Wash away unreacted starting materials with NMP. Filter the remaining pale yellow solid and dry under vacuum to obtain modified cyclodextrin.

[0035] The preparation method of the composite dry-mixed waterproof mortar based on nanomaterials in this embodiment is as follows: weigh ordinary silicate cement, manufactured sand, and modified nanomaterials by weight and add them to a mixer for premixing for 5 minutes at a speed ≤30 r / min; add 5010N redispersible latex powder, 6034H water-repellent agent, and hydroxypropyl methylcellulose and mix for 10 minutes (increase the speed to 45 r / min); add polycarboxylate superplasticizer SC11 and stir at low speed for 5 minutes to obtain dry powder dry-mixed waterproof mortar.

[0036] Example 2 The composite dry-mixed waterproof mortar based on nanomaterials in this embodiment is composed of the following raw materials by weight: 32kg of ordinary silicate cement, 78kg of manufactured sand, 0.6kg of modified nanomaterials, 4.2kg of redispersible latex powder, 0.55kg of water-repellent agent, 0.28kg of water-retaining and thickening material, and 0.15kg of polycarboxylate superplasticizer.

[0037] The cement used is ordinary Portland cement with a strength grade of 42.5. The manufactured sand has a fineness modulus of 2.3-3.0, an MB value ≤1.4, and a stone powder content ≤10%. The redispersible latex powder is model 5010N. The water-repellent agent is model 6034H. The water-retaining and thickening material is hydroxypropyl methylcellulose. The polycarboxylate superplasticizer is model SC-11.

[0038] The modified nanomaterials in this embodiment are prepared as follows: 5g of polyvinyl alcohol is dissolved in a 100mL water bath at 80℃ for 30min, and then naturally cooled to room temperature. 1.5g of modified nano-silica is added, and the mixture is sonicated for 10min. 10g of N-isopropylacrylamide monomer is added, and the mixture is stirred until the N-isopropylacrylamide is completely dissolved, forming a homogeneous mixture. Ammonium persulfate and tetramethylethylenediamine are added as a redox initiation system, and the mixture is reacted at room temperature for 2h to form N-isopropylacrylamide polymer chains, which are physically entangled / mixed with polyvinyl alcohol molecular chains to obtain a poly(N-isopropylacrylamide / polyvinyl alcohol) blend system containing nanoparticles. This mixture is frozen at -25℃ for 24h and thawed at room temperature for 20min. This process is called a single freeze-thaw cycle (N=1), and a total of 7 cycles (N=7) are performed to obtain a hydrogel. The obtained hydrogel is soaked in distilled water for 48h, during which the distilled water is continuously replaced to remove uncrosslinked polymer chains and impurities. The purified hydrogel was freeze-dried to remove moisture, resulting in a dry poly(N-isopropylacrylamide / polyvinyl alcohol) hydrogel containing nanoparticles, which was then stored for later use.

[0039] The preparation method of modified nano-silica in this embodiment is as follows: 1.5g of dried modified β-cyclodextrin was dissolved in 200mL of anhydrous DMF under stirring. 0.4mL of triethoxy(3-propyl isocyanate)silicon was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 70℃ and reacted for 6h. Then, 12g of nano-silica (average particle size 50±5nm) was added to the above solution, and the temperature was raised to 110℃ and the reaction was continued for 24h. After cooling to room temperature, the mixture was filtered. The crude product was repeatedly washed with DMF, methanol and acetone until the filtrate was clear. Finally, the solid was vacuum dried at 85℃ for 6h to obtain the modified β-cyclodextrin-modified nano-silica material.

[0040] The preparation method of modified β-cyclodextrin in this embodiment includes the following steps: 1.10 g of β-cyclodextrin was added to 100 mL of NaOH aqueous solution (1 wt%) and stirred in an ice-water bath until completely dissolved. 1.68 g of p-toluenesulfonyl chloride was dissolved in 5 mL of acetonitrile and slowly added dropwise to the reaction system using a constant-pressure dropping funnel, gradually resulting in the precipitation of a white precipitate. After continuing stirring for 2 hours, ammonium chloride was added to adjust the pH of the solution to 8, resulting in the precipitation of a large amount of white substance. The solution was washed twice with deionized water and ethanol, respectively, filtered, and the filter cake was vacuum dried to obtain mono-6-p-toluenesulfonated-β-cyclodextrin.

[0041] S2. Dissolve 10g of n-hexadecyl alcohol in a dichloromethane solution. Slowly add a dichloromethane solution containing 7.9g of p-toluenesulfonyl chloride to the solution system in an ice-water bath. The addition is completed in 30 minutes. After reacting in an ice-water bath for 1 hour, react at 30°C for 5 hours. Distill under reduced pressure to obtain a light yellow solid. Wash twice with water, filter, and dry under vacuum to obtain hexadecyl toluenesulfonate.

[0042] S3. In a three-necked flask equipped with a reflux condenser, 5 g of mono-6-p-toluenesulfonated-β-cyclodextrin was added. Under nitrogen protection, excess ethylenediamine was added, and the mixture was heated to 70°C and stirred for 4 h. At this temperature, excess ethylenediamine was removed by vacuum distillation to obtain a light yellow solid. After dissolving it in a small amount of water, it was precipitated with anhydrous ethanol, filtered, and a white powder was obtained. After vacuum drying, mono-[6-(2-aminoethyl)-amino-6-deoxy]-cyclodextrin was obtained.

[0043] S4. In a three-necked flask equipped with a reflux condenser and a dropping funnel, add mono-[6-(2-aminoethyl)-amino-6-deoxy]-β-cyclodextrin, hexadecyl p-toluenesulfonate, and 50 mL of N-methylpyrrolidone (NMP) at a mass ratio of 1.5:1. Stir for 30 min to ensure thorough mixing of the reactants. Heat to 70 °C and stir for 6 h. Filter to obtain a pale yellow solid. Wash away unreacted starting materials with NMP. Filter the remaining pale yellow solid and dry under vacuum to obtain modified cyclodextrin.

[0044] The preparation method of the composite dry-mixed waterproof mortar based on nanomaterials in this embodiment is as follows: weigh ordinary silicate cement, manufactured sand, and modified nanomaterials by weight and add them to a mixer for premixing for 5 minutes at a speed ≤30 r / min; add 5010N redispersible latex powder, 6034H water-repellent agent, and hydroxypropyl methylcellulose and mix for 10 minutes (increase the speed to 45 r / min); add polycarboxylate superplasticizer SC11 and stir at low speed for 5 minutes to obtain dry powder dry-mixed waterproof mortar.

[0045] Example 3 The composite dry-mixed waterproof mortar based on nanomaterials in this embodiment is composed of the following raw materials by weight: 34 kg of ordinary silicate cement, 80 kg of manufactured sand, 0.8 kg of modified nanomaterials, 4.5 kg of redispersible latex powder, 0.6 kg of water-repellent agent, 0.3 kg of water-retaining and thickening material, and 0.17 kg of polycarboxylate superplasticizer.

[0046] The cement used is ordinary Portland cement with a strength grade of 42.5. The manufactured sand has a fineness modulus of 2.3-3.0, an MB value ≤1.4, and a stone powder content ≤10%. The redispersible latex powder is model 5010N. The water-repellent agent is model 6034H. The water-retaining and thickening material is hydroxypropyl methylcellulose. The polycarboxylate superplasticizer is model SC-11.

[0047] The modified nanomaterials in this embodiment are prepared as follows: 5g of polyvinyl alcohol is dissolved in a 100mL water bath at 80℃ for 30min, and then naturally cooled to room temperature. 1g of modified nano-silica is added, and the mixture is sonicated for 10min. 10g of N-isopropylacrylamide monomer is added, and the mixture is stirred until the N-isopropylacrylamide is completely dissolved, forming a homogeneous mixture. Ammonium persulfate and tetramethylethylenediamine are added as a redox initiation system, and the mixture is reacted at room temperature for 2h to form N-isopropylacrylamide polymer chains, which are physically entangled / mixed with polyvinyl alcohol molecular chains to obtain a poly(N-isopropylacrylamide / polyvinyl alcohol) blend system containing nanoparticles. This mixture is frozen at -25℃ for 24h and thawed at room temperature for 20min. This process is called a single freeze-thaw cycle (N=1), and a total of 7 cycles (N=7) are performed to obtain a hydrogel. The obtained hydrogel is soaked in distilled water for 48h, during which the distilled water is continuously replaced to remove uncrosslinked polymer chains and impurities. The purified hydrogel was freeze-dried to remove moisture, resulting in a dry poly(N-isopropylacrylamide / polyvinyl alcohol) hydrogel containing nanoparticles, which was then stored for later use.

[0048] The preparation method of modified nano-silica in this embodiment is as follows: 1.5g of dried modified β-cyclodextrin was dissolved in 200mL of anhydrous DMF under stirring. 0.4mL of triethoxy(3-propyl isocyanate)silicon was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 70℃ and reacted for 6h. Then, 10g of nano-silica (average particle size 50±5nm) was added to the above solution, and the temperature was raised to 110℃ and the reaction was continued for 24h. After cooling to room temperature, the mixture was filtered. The crude product was repeatedly washed with DMF, methanol and acetone until the filtrate was clear. Finally, the solid was vacuum dried at 85℃ for 6h to obtain the modified β-cyclodextrin-modified nano-silica material.

[0049] The preparation method of modified β-cyclodextrin in this embodiment includes the following steps: 1.10 g of β-cyclodextrin was added to 100 mL of NaOH aqueous solution (1 wt%) and stirred in an ice-water bath until completely dissolved. 1.68 g of p-toluenesulfonyl chloride was dissolved in 5 mL of acetonitrile and slowly added dropwise to the reaction system using a constant-pressure dropping funnel, gradually resulting in the precipitation of a white precipitate. After continuing stirring for 2 hours, ammonium chloride was added to adjust the pH of the solution to 8, resulting in the precipitation of a large amount of white substance. The solution was washed twice with deionized water and ethanol, respectively, filtered, and the filter cake was vacuum dried to obtain mono-6-p-toluenesulfonated-β-cyclodextrin.

[0050] S2. Dissolve 10g of n-hexadecyl alcohol in a dichloromethane solution. Slowly add a dichloromethane solution containing 7.9g of p-toluenesulfonyl chloride to the solution system in an ice-water bath. The addition is completed in 30 minutes. After reacting in an ice-water bath for 1 hour, react at 30°C for 5 hours. Distill under reduced pressure to obtain a light yellow solid. Wash twice with water, filter, and dry under vacuum to obtain hexadecyl toluenesulfonate.

[0051] S3. In a three-necked flask equipped with a reflux condenser, 5 g of mono-6-p-toluenesulfonated-β-cyclodextrin was added. Under nitrogen protection, excess ethylenediamine was added, and the mixture was heated to 70°C and stirred for 4 h. At this temperature, excess ethylenediamine was removed by vacuum distillation to obtain a light yellow solid. After dissolving it in a small amount of water, it was precipitated with anhydrous ethanol, filtered, and a white powder was obtained. After vacuum drying, mono-[6-(2-aminoethyl)-amino-6-deoxy]-cyclodextrin was obtained.

[0052] S4. In a three-necked flask equipped with a reflux condenser and a dropping funnel, add mono-[6-(2-aminoethyl)-amino-6-deoxy]-β-cyclodextrin, hexadecyl p-toluenesulfonate, and 50 mL of N-methylpyrrolidone (NMP) at a mass ratio of 1.5:1. Stir for 30 min to ensure thorough mixing of the reactants. Heat to 70 °C and stir for 6 h. Filter to obtain a pale yellow solid. Wash away unreacted starting materials with NMP. Filter the remaining pale yellow solid and dry under vacuum to obtain modified cyclodextrin.

[0053] The preparation method of the composite dry-mixed waterproof mortar based on nanomaterials in this embodiment is as follows: weigh ordinary silicate cement, manufactured sand, and modified nanomaterials by weight and add them to a mixer for premixing for 5 minutes at a speed ≤30 r / min; add 5010N redispersible latex powder, 6034H water-repellent agent, and hydroxypropyl methylcellulose and mix for 10 minutes (increase the speed to 45 r / min); add polycarboxylate superplasticizer SC11 and stir at low speed for 5 minutes to obtain dry powder dry-mixed waterproof mortar.

[0054] Comparative Example 1 The nanomaterial-based composite dry-mixed waterproof mortar of this comparative example is composed of the following raw materials by weight: 33 kg of ordinary silicate cement, 75 kg of manufactured sand, 0.4 kg of nano silica (average particle size 50±5 nm), 3.6 kg of redispersible latex powder, 0.5 kg of water-repellent agent, 0.25 kg of water-retaining and thickening material, and 0.12 kg of polycarboxylate superplasticizer.

[0055] The cement used is ordinary Portland cement with a strength grade of 42.5. The manufactured sand has a fineness modulus of 2.3-3.0, an MB value ≤1.4, and a stone powder content ≤10%. The redispersible latex powder is model 5010N. The water-repellent agent is model 6034H. The water-retaining and thickening material is hydroxypropyl methylcellulose. The polycarboxylate superplasticizer is model SC-11.

[0056] The preparation method of the nanomaterial-based composite dry-mixed waterproof mortar in this comparative example is as follows: ordinary silicate cement, manufactured sand, and nano silica are weighed and added to a mixer for premixing for 5 minutes at a speed ≤30 r / min; 5010N redispersible latex powder, 6034H water-repellent agent, and hydroxypropyl methylcellulose are added and mixed for 10 minutes (speed increased to 45 r / min); polycarboxylate superplasticizer SC11 is added and stirred at low speed for 5 minutes to obtain dry powder dry-mixed waterproof mortar.

[0057] Comparative Example 2 The comparative example of a nanomaterial-based composite dry-mixed waterproof mortar consists of the following raw materials by weight: 33 kg of ordinary silicate cement, 75 kg of manufactured sand, 0.4 kg of β-cyclodextrin-modified nano-silica, 3.6 kg of redispersible latex powder, 0.5 kg of water-repellent agent, 0.25 kg of water-retaining and thickening material, and 0.12 kg of polycarboxylate superplasticizer.

[0058] The cement used is ordinary Portland cement with a strength grade of 42.5. The manufactured sand has a fineness modulus of 2.3-3.0, an MB value ≤1.4, and a stone powder content ≤10%. The redispersible latex powder is model 5010N. The water-repellent agent is model 6034H. The water-retaining and thickening material is hydroxypropyl methylcellulose. The polycarboxylate superplasticizer is model SC-11.

[0059] The preparation method of the modified nano-silica in this comparative example is as follows: 1.3 g of dried β-cyclodextrin was dissolved in 200 mL of anhydrous DMF under stirring. 0.4 mL of triethoxy(3-propyl isocyanate)silicon was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 70 °C and reacted for 6 h. Then, 10 g of nano-silica (average particle size 50 ± 5 nm) was added to the above solution, and the temperature was raised to 110 °C and the reaction was continued for 24 h. After cooling to room temperature, the mixture was filtered to obtain a crude product. The crude product was repeatedly washed with DMF, methanol and acetone until the filtrate was clear. Finally, the solid was vacuum dried at 85 °C for 6 h to obtain the β-cyclodextrin modified nano-silica material.

[0060] The preparation method of the nanomaterial-based composite dry-mixed waterproof mortar in this comparative example is as follows: ordinary silicate cement, manufactured sand, and β-cyclodextrin-modified nano-silica are weighed and added to a mixer for premixing for 5 minutes at a speed ≤30 r / min; 5010N redispersible latex powder, 6034H water-repellent agent, and hydroxypropyl methylcellulose are added and mixed for 10 minutes (speed increased to 45 r / min); polycarboxylate superplasticizer SC11 is added and stirred at low speed for 5 minutes to obtain dry powder dry-mixed waterproof mortar.

[0061] Comparative Example 3 The comparative example of a nanomaterial-based composite dry-mixed waterproof mortar consists of the following raw materials by weight: 32 kg of ordinary silicate cement, 78 kg of manufactured sand, 0.6 kg of modified β-cyclodextrin-modified nano-silica, 4.2 kg of redispersible latex powder, 0.55 kg of water-repellent agent, 0.28 kg of water-retaining and thickening material, and 0.15 kg of polycarboxylate superplasticizer.

[0062] The cement used is ordinary Portland cement with a strength grade of 42.5. The manufactured sand has a fineness modulus of 2.3-3.0, an MB value ≤1.4, and a stone powder content ≤10%. The redispersible latex powder is model 5010N. The water-repellent agent is model 6034H. The water-retaining and thickening material is hydroxypropyl methylcellulose. The polycarboxylate superplasticizer is model SC-11.

[0063] The preparation method of the modified β-cyclodextrin-modified nano-silica in this comparative example is as follows: 1.5 g of dried modified β-cyclodextrin was dissolved in 200 mL of anhydrous DMF under stirring. 0.4 mL of triethoxy(3-propyl isocyanate)silicon was slowly added dropwise at room temperature. After the addition was completed, the temperature was raised to 70 °C and reacted for 6 h. Then, 10 g of nano-silica (average particle size 50 ± 5 nm) was added to the above solution, and the temperature was raised to 110 °C and reacted for another 24 h. After cooling to room temperature, the mixture was filtered to obtain a crude product. The crude product was repeatedly washed with DMF, methanol and acetone until the filtrate was clear. Finally, the solid was vacuum dried at 85 °C for 6 h to obtain the modified β-cyclodextrin-modified nano-silica material.

[0064] The preparation method of the modified β-cyclodextrin in this comparative example includes the following steps: 1.10 g of β-cyclodextrin was added to 100 mL of NaOH aqueous solution (1 wt%) and stirred in an ice-water bath until completely dissolved. 1.68 g of p-toluenesulfonyl chloride was dissolved in 5 mL of acetonitrile and slowly added dropwise to the reaction system using a constant-pressure dropping funnel, gradually resulting in the precipitation of a white precipitate. After continuing stirring for 2 hours, ammonium chloride was added to adjust the pH of the solution to 8, resulting in the precipitation of a large amount of white substance. The solution was washed twice with deionized water and ethanol, respectively, filtered, and the filter cake was vacuum dried to obtain mono-6-p-toluenesulfonated-β-cyclodextrin.

[0065] S2. Dissolve 10g of n-hexadecyl alcohol in a dichloromethane solution. Slowly add a dichloromethane solution containing 7.9g of p-toluenesulfonyl chloride to the solution system in an ice-water bath. The addition is completed in 30 minutes. After reacting in an ice-water bath for 1 hour, react at 30°C for 5 hours. Distill under reduced pressure to obtain a light yellow solid. Wash twice with water to remove impurities, filter, and dry under vacuum to obtain hexadecyl toluenesulfonate.

[0066] S3. In a three-necked flask equipped with a reflux condenser, 5 g of mono-6-p-toluenesulfonated-β-cyclodextrin was added. Under nitrogen protection, excess ethylenediamine was added, and the mixture was heated to 70°C and stirred for 4 h. At this temperature, excess ethylenediamine was removed by vacuum distillation to obtain a light yellow solid. After dissolving it in a small amount of water, it was precipitated with anhydrous ethanol, filtered, and a white powder was obtained. After vacuum drying, mono-[6-(2-aminoethyl)-amino-6-deoxy]-cyclodextrin was obtained.

[0067] S4. In a three-necked flask equipped with a reflux condenser and a dropping funnel, add mono-[6-(2-aminoethyl)-amino-6-deoxy]-β-cyclodextrin, hexadecyl p-toluenesulfonate, and 50 mL of N-methylpyrrolidone (NMP) at a mass ratio of 1.5:1. Stir for 30 min to ensure thorough mixing of the reactants. Heat to 70 °C and stir for 6 h. Filter to obtain a pale yellow solid. Wash away unreacted starting materials with NMP. Filter the remaining pale yellow solid and dry under vacuum to obtain modified cyclodextrin.

[0068] The preparation method of the nanomaterial-based composite dry-mixed waterproof mortar in this comparative example is as follows: ordinary silicate cement, manufactured sand, and modified β-cyclodextrin-modified nano-silica are weighed and added to a mixer for premixing for 5 minutes at a speed ≤30 r / min; 5010N redispersible latex powder, 6034H water-repellent agent, and hydroxypropyl methylcellulose are added and mixed for 10 minutes (speed increased to 45 r / min); polycarboxylate superplasticizer SC11 is added and stirred at low speed for 5 minutes to obtain dry powder dry-mixed waterproof mortar.

[0069] Performance testing 1. According to JGJ / T 70-2009 "Standard for Test Methods of Basic Performance of Building Mortar", the impermeability of mortar was determined using a mortar permeability meter. The sample was a truncated cone with dimensions of 70mm×80mm×30mm. After the mortar specimens were cured to standard for 28 days, paraffin wax was heated to seal the circumference of the specimens, and pressure was applied to 0.2MPa. After maintaining constant pressure for 2 hours, the pressure was increased to 0.3MPa, and then increased by 0.1MPa every hour. When water seepage appeared on 3 of the 6 specimens, the test was stopped immediately, and the data was recorded. The test results are shown in Table 1.

[0070] 2. According to the "Test Method for Strength of Cement Mortar (ISO Method)", the compressive and flexural strength of mortar were tested using an integrated cement mortar compressive and flexural strength testing machine. The prepared mortar was filled into 40mm×40mm×160mm molds in two batches, with three test blocks made for each test group. The compressive and flexural strengths were tested. The mortar test blocks were cured for 28 days before strength testing. First, the flexural strength was tested, followed by the compressive strength test on the fractured mortar test blocks. The strength value was calculated and averaged from the three test blocks. The test results are shown in Table 1.

[0071] Table 1. Test data of mortar impermeability and mechanical properties in Examples 1-3 and Comparative Examples 1-3. Analysis of Examples 1-3 and Comparative Examples 1-3, combined with Table 1, shows that the waterproof mortar with modified nano-silica encapsulated in poly(N-isopropylacrylamide) / polyvinyl alcohol gel exhibits good impermeability and mechanical properties. In Comparative Example 1, the added nano-silica was unmodified, resulting in uneven dispersion and lower compressive and flexural strength compared to Examples 1-3. In Comparative Example 2, the added β-cyclodextrin-modified nano-silica showed limited improvement in hydrophobicity compared to Comparative Example 1, with a slight increase in impermeability. In Comparative Example 3, the added β-cyclodextrin-modified nano-silica further improved hydrophobicity compared to Comparative Examples 1-2.

[0072] 3. The anti-permeability and anti-dispersion performance of the mortars in Example 3 and Comparative Example 1 were determined using a mortar permeability analyzer. The specific procedure is as follows: First, mortar was prepared into specimens with dimensions of 210mm × 140mm × 30mm according to the preparation method of Example 3, with a water-cement ratio of 0.40. The specimens were divided into 6 equal parts with dimensions of 70mm × 70mm × 30mm, designated as A1, A2, A3, A4, A5, and A6. After standard curing of the mortar specimens for 28 days, paraffin wax was heated and sealed around the specimens. The pressure was increased to 0.2MPa and stabilized at constant pressure for 2 hours, then increased to 0.3MPa. Thereafter, the pressure was increased by 0.1MPa every hour. When water seepage appeared on the surface of the specimen, the test was stopped immediately, and the data was recorded. The test was repeated 3 times, and the average value was taken. The results are shown in Table 2. The anti-permeability and anti-dispersion performance of the mortar in Comparative Example 1 was tested using the same procedure. The specimens in Comparative Example 1 were divided into 6 equal parts, designated as B1, B2, B3, B4, B5, and B6.

[0073] Table 2. Data on the anti-permeability and dispersibility properties of mortar in Example 3 and Comparative Example 1. Analysis of the mortar impermeability dispersion performance test data of Example 3 and Comparative Example 1, combined with Table 2, shows that the impermeability pressure of specimens A1-A6 fluctuates within a small range and the data is relatively stable, indirectly reflecting that the modified nanomaterials are dispersed relatively evenly in the waterproof mortar. The impermeability pressure of specimens B1-B6 fluctuates within a larger range, indirectly reflecting that the nano-silica added in Comparative Example 1 has poor dispersion.

[0074] 4. The modified β-cyclodextrin and its functional groups prepared in Example 3 were characterized using a BRUKER TENSOR 27 Fourier transform infrared spectrometer. The specific steps are as follows: 200 mg KBr and 1 mg of the analyte were ground finely in an agate mortar and pressed into a thin sheet. The wavelength range for the test was 4000-400 cm⁻¹. -1 The result is as follows Figure 1 As shown.

[0075] The analysis results show that the modified β-cyclodextrin has a concentration of 1650-1550 cm⁻¹. -1 The newly added NH bending vibration peak is due to the attached ethylenediamine structure; 2920 cm⁻¹ -1 The peak intensity was significantly enhanced, which is the peak of the asymmetric stretching vibration of the methylene group in the attached n-hexadecyl alcohol.

[0076] 5. The nano-silica of Comparative Example 1 and the modified nano-silica prepared in Example 3 were observed using a scanning electron microscope. The obtained images are shown below. Figure 2 and Figure 3 As shown.

[0077] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this invention.

Claims

1. A composite dry-mix waterproof mortar based on nanomaterials, characterized in that, The raw materials include: ordinary silicate cement, manufactured sand, modified nanomaterials, redispersible latex powder, water-repellent agent, water-retaining thickener, and water-reducing agent; the modified nanomaterials are prepared by encapsulating modified nano-silica with poly(N-isopropylacrylamide) / polyvinyl alcohol gel.

2. The composite waterproof mortar based on nanomaterials according to claim 1, characterized in that: The modified nano-silica is prepared by grafting modified cyclodextrin onto the surface of nano-silica.

3. The composite waterproof mortar based on nanomaterials according to claim 2, characterized in that: The mass ratio of the modified cyclodextrin to nano silica is 1:(7-9).

4. The composite waterproof mortar based on nanomaterials according to claim 2, characterized in that: The method for preparing the modified cyclodextrin includes the following steps: S1, reacting cyclodextrin with p-toluenesulfonyl chloride to generate p-toluenesulfonated cyclodextrin; S2, reacting a straight-chain alkyl alcohol with p-toluenesulfonyl chloride to generate p-toluenesulfonic acid alkyl ester; S3, reacting p-toluenesulfonated cyclodextrin with a diamine compound to generate a cyclodextrin derivative; S4, reacting the cyclodextrin derivative with p-toluenesulfonic acid alkyl ester, filtering, and drying to obtain the modified cyclodextrin.

5. The composite waterproof mortar based on nanomaterials according to claim 4, characterized in that: In step S2, the straight-chain alkyl alcohol is one of n-dodecyl alcohol, n-tetradecyl alcohol, and n-hexadecyl alcohol; And / or, in step S3, the diamine compound is one of ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine.

6. The composite waterproof mortar based on nanomaterials according to claim 4, characterized in that: In step S4, the mass ratio of the cyclodextrin derivative to the alkyl p-toluenesulfonate is (1.5-2):

1.

7. The composite waterproof mortar based on nanomaterials according to claim 1, characterized in that: The preparation method of the modified nanomaterial includes the following steps: dissolving polyvinyl alcohol in deionized water, then adding modified nano-silica and N-isopropylacrylamide, mixing evenly, adding ammonium persulfate and tetramethylethylenediamine to carry out a polymerization reaction, and freeze-drying to obtain the final product.

8. The composite waterproof mortar based on nanomaterials according to claim 7, characterized in that: The mass ratio of polyvinyl alcohol, N-isopropylacrylamide and modified nano silica is 5:10:(1-1.5).

9. A method for preparing a composite dry-mixed waterproof mortar based on nanomaterials, characterized in that, The process includes the following steps: premixing cement, manufactured sand, and modified nanomaterials; adding redispersible latex powder, water-repellent agent, and water-retaining thickener; adding polycarboxylate superplasticizer and stirring to obtain dry-mixed waterproof mortar in powder form.

10. An application of a composite dry-mix waterproof mortar based on nanomaterials, characterized in that: The mortar according to any one of claims 1-8 or the mortar prepared by the preparation method according to claim 9 may be used for building waterproofing, water conservancy projects, and industrial facilities.

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