Preparation method of carbon nanotube cement-based waterproof material

Abstract

The invention discloses a preparation method of a carbon nanotube cement-based waterproof material, belonging to the field of building waterproof concrete materials. The preparation method includes multi-walled carbon nanotube filling, preparation of carbon nanotube composite silica sol, and preparation of waterproof materials. The waterproof material prepared by the invention has excellent mechanical properties. According to the method in GB / T50081-2019, the compressive strength, flexural strength, splitting tensile strength, and static compressive elastic modulus of the waterproof material are detected. The compressive strength is 47.4-48.8 MPa, the flexural strength is 17.1-17.5 MPa, the splitting tensile strength is 4.3-4.5 MPa, and the static compressive elastic modulus is 52.3-53.0 GPa.

Description

Technical Field

[0001] The present invention relates to a preparation method of a carbon nanotube cement-based waterproof material, belonging to the field of building waterproof concrete materials. Background Art

[0002] Concrete has abundant raw materials. It not only has good plasticity and durability, but also can meet the needs of various structural engineering projects. It is currently the engineering material with the widest application range and the largest usage amount. However, factors such as the design of concrete structure and mix ratio, the selection of concrete materials, and concrete construction and on-site maintenance are likely to cause the generation of concrete cracks, affecting the strength of the entire building structure. Therefore, research scholars have considered adding materials such as particles, fibers, and reactive powders to concrete to improve its performance, and more attention has been paid to the research on nanomaterials.

[0003] Concrete is composed of cement, water, etc. admixed with high-quality same-sized or gap-graded aggregates. There are inevitably micropores and microcracks on its surface, with a certain porosity. These structural defects provide channels for water molecules to penetrate into the interior of the concrete. If it is applied to roads, it can achieve certain drainage, sound absorption, and noise reduction functions, but it does not have waterproof effect and cannot be used as a building waterproof material. If certain substances are added to the concrete material to make it have a certain waterproof effect, then the low-cost advantage of concrete as a waterproof material can enable it to obtain a wider application.

[0004] Nanomaterials have a smaller volume, better optical, thermal, and electrical properties, and stronger mechanical properties. It is this series of excellent properties that provides strong theoretical and technical support for the research on the application of nanomaterials in cement-based composites. It has been found that the addition of nanomaterials such as carbon nanotubes effectively improves the performance of cement-based composites. It can not only fill the microporous structure of cement, but also carbon nanotubes can generate chemical interactions with the surface of concrete hydration products, restricting the diffusion of nanoscale cracks, making the microstructure of concrete more dense, and thus improving the waterproof performance of concrete.

[0005] CN102603235A discloses a carbon nanotube cement-based waterproof material and its preparation method. Adding carbon nanotubes to the concrete raw material components can endow the concrete with high waterproof performance. The carbon nanotubes used in this invention are multi-walled carbon nanotubes. Compared with single-walled carbon nanotubes, they have a lower price and better performance in some aspects. For example, multi-walled carbon nanotubes have more defects in the axial direction and unevenness to varying degrees, which can increase the strength of the concrete material, and the increased degree is higher than that of adding single-walled carbon nanotubes. However, at the same time, due to the structural defects of multi-walled carbon nanotubes, the elastic and tensile properties of single-walled carbon nanotubes themselves are better than those of multi-walled carbon nanotubes. When multi-walled carbon nanotubes are added to the concrete, the elastic modulus and tensile strength of the concrete will be relatively low. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects existing in the prior art. By filling multi-walled carbon nanotubes with rare earth elements, then compounding them with aluminum elements and silica sol, and adding them as raw material components to the waterproof concrete material, while ensuring the waterproof performance of the material, the elastic modulus and tensile strength of the material are improved.

[0007] To solve the above technical problem, this invention adopts the following technical solutions:

[0008] A preparation method of a carbon nanotube cement-based waterproof material, the preparation method includes filling multi-walled carbon nanotubes, preparing carbon nanotube composite silica sol, and preparing the waterproof material.

[0009] The following is a further improvement of the above technical solution:

[0010] The method for filling multi-walled carbon nanotubes is as follows: Place the multi-walled carbon nanotubes in a nitrogen atmosphere, control the heating rate at 4.5 - 5.5 °C / min, raise the temperature to 405 - 425 °C, perform heat treatment on the multi-walled carbon nanotubes, the heat treatment time is 85 - 95 min, after the treatment is completed, control the cooling rate at 2.5 - 3.5 °C / min, cool the multi-walled carbon nanotubes to 60 - 70 °C, keep them warm, then immerse the warm multi-walled carbon nanotubes in a cerium sulfate solution, control the frequency at 50 - 70 kHz, perform ultrasonic treatment, the ultrasonic treatment time is 12 - 20 min, after the ultrasonic treatment ends, perform suction filtration and drying to obtain rare earth element-filled multi-walled carbon nanotubes;

[0011] The mass ratio of the multi-walled carbon nanotubes to the cerium sulfate solution is 1:4.5 - 5.5;

[0012] The diameter of the multi-walled carbon nanotubes is 70 - 100 nm, and the length is 200 - 300 μm;

[0013] The concentration of cerium element in the cerium sulfate solution is 8 - 12 g / L, and the solvent of the solution is sulfuric acid with a concentration of 0.15 mol / L.

[0014] The method for preparing the carbon nanotube composite silica sol is as follows: under a nitrogen atmosphere, the multi-walled carbon nanotubes filled with rare earth elements are mixed with trimethylaluminum solution and stirred for 18 - 25 min. After stirring, the nitrogen atmosphere is maintained, the heating rate is controlled at 4.5 - 5.5 °C / min, and the temperature is raised to 825 - 870 °C for sintering for 110 - 130 min. After sintering, the multi-walled carbon nanotubes coated with alumina are obtained. After cooling to room temperature, they are mixed with silica sol and stirred at a speed of 50 - 90 r / min. While stirring, the temperature is controlled at 100 °C, and the water in the silica sol is evaporated until the water content is 0, obtaining the carbon nanotube composite silica sol;

[0015] The mass ratio of the multi-walled carbon nanotubes filled with rare earth elements to the trimethylaluminum solution is 5:10 - 14;

[0016] The concentration of the trimethylaluminum solution is 20 - 30 wt%, and the solvent is n-hexane;

[0017] The mass ratio of the multi-walled carbon nanotubes coated with alumina to the silica sol is 5:6.5 - 7.5;

[0018] The concentration of the silica sol is 15 - 25 wt%, the particle size of the colloidal particles is 12 - 20 nm, and the solvent is deionized water.

[0019] The method for preparing the waterproof material is as follows: cement, fine sand, quartz sand, and fly ash are poured into a mortar mixer for dry stirring for 8 - 12 min. Then, water, water reducer, and defoamer are added to the mixer and stirring is continued for 13 - 17 min. Finally, the carbon nanotube composite silica sol is added and stirring is continued for 22 - 28 min. After stirring, it is poured into a mold and then cured to obtain a carbon nanotube cement-based waterproof material;

[0020] The mass ratio of cement, fine sand, quartz sand, fly ash, water, water reducer, defoamer, and carbon nanotube composite silica sol is 700 - 800:575 - 625:325 - 375:110 - 130:475 - 550:10 - 12:4.5 - 5.5:8 - 10;

[0021] The type of the cement is P·O 42.5 grade ordinary Portland cement;

[0022] The fineness modulus of the fine sand is 2.37 and the apparent density is 2587 g / m 3 ;

[0023] The particle size of the quartz sand is 0.45-0.55 mm;

[0024] The particle size of the fly ash is 150-200 μm;

[0025] The water reducer is a polycarboxylic acid water reducer, model number is XCA-100;

[0026] The defoamer is a silicone polyether defoamer, and its model is Deqian Defom6800.

[0027] Compared with the prior art, the present invention achieves the following beneficial effects:

[0028] The waterproof material prepared by the present invention has excellent mechanical properties. According to the method in GB / T50081-2019, the compressive strength, flexural strength, splitting tensile strength, and static compressive elastic modulus of the waterproof material are tested. The compressive strength is 47.4-48.8MPa, the flexural strength is 17.1-17.5MPa, the splitting tensile strength is 4.3-4.5MPa, and the static compressive elastic modulus is 52.3-53.0GPa;

[0029] The waterproof material prepared by the present invention has excellent waterproof performance. According to the method in GB / T50081-2019, the water absorption rate of the waterproof material is detected, and the water absorption rate is 0.54-0.58%; according to the method in GB / T50082-2024, the step-by-step pressurization method is adopted to detect the water permeability resistance of the waterproof material, and the maximum pressure when water seepage occurs is used as an indicator, and the water permeability resistance is 1.7-1.8MPa; according to the method in GB / T50082-2024, the electric flux method is adopted to detect the chloride ion permeability resistance of the waterproof material, and the electric flux is used as an indicator, and the 28d electric flux is 37-41C;

[0030] The waterproof material prepared by the present invention has good wear resistance. According to the method in GB / T50081-2019, the wear resistance of the waterproof material is tested by the abrasion method, and the abrasion is 0.011-0.014 kg / m 2 ;

[0031] The waterproof material prepared by the present invention has a low expansion coefficient and is less affected by thermal expansion and contraction. According to the method in GB / T50081-2019, the linear expansion coefficient of the waterproof material is tested, and the linear expansion coefficient is (0.7-0.8)×10 -6 ;

[0032] The waterproof material prepared by the present invention has good gas impermeability. According to the method in GB / T50082-2024, the apparent gas permeability coefficient of nitrogen at a pressure of 0.4 MPa is measured, and the gas permeability coefficient is (4.1-4.4)×10 -18 . Detailed implementation mode

[0033] Example 1

[0034] (1) Multi-walled carbon nanotube filling

[0035] Place the multi-walled carbon nanotubes in a nitrogen atmosphere, control the heating rate at 5°C / min, raise the temperature to 415°C, perform heat treatment on the multi-walled carbon nanotubes for 90 min, after the treatment is completed, control the cooling rate at 3°C / min, cool the multi-walled carbon nanotubes to 65°C, keep them warm, and then immerse the warm multi-walled carbon nanotubes in a cerium sulfate solution, control the frequency at 60 kHz, perform ultrasonic treatment for 15 min, after the ultrasonic treatment is completed, perform suction filtration and drying to obtain multi-walled carbon nanotubes filled with rare earth elements;

[0036] The mass ratio of the multi-walled carbon nanotubes to the cerium sulfate solution is 1:5;

[0037] The diameter of the multi-walled carbon nanotubes is 80 nm and the length is 240 μm;

[0038] The concentration of cerium element in the cerium sulfate solution is 10 g / L, and the solvent of the solution is 0.15 mol / L sulfuric acid.

[0039] (2) Preparation of carbon nanotube composite silica sol

[0040] Under a nitrogen atmosphere, mix the multi-walled carbon nanotubes filled with rare earth elements with trimethylaluminum solution and stir for 20 min. After the stirring is completed, maintain the nitrogen atmosphere, control the heating rate at 5°C / min, raise the temperature to 850°C, perform sintering for 120 min. After the sintering is completed, obtain multi-walled carbon nanotubes coated with alumina. After cooling it to room temperature, mix it with silica sol and stir at a speed of 60 r / min. While stirring, control the temperature at 100°C to evaporate the water in the silica sol until the water content is 0 to obtain carbon nanotube composite silica sol;

[0041] The mass ratio of the multi-walled carbon nanotubes filled with rare earth elements to the trimethylaluminum solution is 5:12;

[0042] The concentration of the trimethylaluminum solution is 25 wt%, and the solvent is n-hexane;

[0043] The mass ratio of the multi-walled carbon nanotubes coated with alumina to the silica sol is 5:7;

[0044] The concentration of the silica sol is 20wt%, the particle size of the colloidal particles is 15nm, and the solvent is deionized water.

[0045] (3) Preparation of waterproof materials

[0046] Pour cement, fine sand, quartz sand and fly ash into a mortar mixer and dry-mix them for 10 minutes, then add water, a water reducing agent and a defoaming agent into the mixer and continue to stir for 15 minutes, finally add carbon nanotube composite silica sol and continue to stir for 25 minutes, after stirring, pour into a mold, and then obtain a carbon nanotube cement-based waterproof material after curing;

[0047] The mass ratio of the cement, fine sand, quartz sand, fly ash, water, water reducing agent, defoaming agent and carbon nanotube composite silica sol is 750:600:350:120:520:11:5:9;

[0048] The model of the cement is P·O42.5 grade ordinary Portland cement;

[0049] The fineness modulus of the fine sand is 2.37 and the apparent density is 2587 g / m 3 ;

[0050] The particle size of the quartz sand is 0.50 mm;

[0051] The particle size of the fly ash is 170 μm;

[0052] The water reducer is a polycarboxylic acid water reducer, model number is XCA-100;

[0053] The defoamer is a silicone polyether defoamer, and its model is Deqian Defom6800.

[0054] Example 2

[0055] (1) Multi-walled carbon nanotube filling

[0056] The multi-walled carbon nanotubes are placed in a nitrogen atmosphere, the heating rate is controlled to be 4.5°C / min, the temperature is raised to 425°C, the multi-walled carbon nanotubes are heat-treated, the heat treatment time is 85 minutes, and after the treatment is completed, the cooling rate is controlled to be 2.5°C / min, the multi-walled carbon nanotubes are cooled to 60°C, and the heat is kept, and then the heat-preserved multi-walled carbon nanotubes are immersed in a cerium sulfate solution, the frequency is controlled to be 50kHz, and the ultrasound is performed for 20 minutes. After the ultrasound is completed, the multi-walled carbon nanotubes are filtered and dried to obtain rare earth element-filled multi-walled carbon nanotubes;

[0057] The mass ratio of the multi-walled carbon nanotubes to the cerium sulfate solution is 1:4.5;

[0058] The diameter of the multi-walled carbon nanotubes is 70 nm and the length is 200 μm;

[0059] The concentration of cerium element in the cerium sulfate solution is 8 g / L, and the solvent of the solution is sulfuric acid with a concentration of 0.15 mol / L.

[0060] (2) Preparation of carbon nanotube composite silica sol

[0061] Under a nitrogen atmosphere, the multi-walled carbon nanotubes filled with rare earth elements are mixed with trimethylaluminum solution and stirred for 18 min. After stirring, the nitrogen atmosphere is maintained, the heating rate is controlled at 4.5 °C / min, and the temperature is raised to 870 °C for sintering for 110 min. After sintering, multi-walled carbon nanotubes coated with alumina are obtained. After cooling to room temperature, they are mixed with silica sol and stirred at a speed of 50 r / min. While stirring, the temperature is controlled at 100 °C to evaporate the water in the silica sol until the water content is 0, obtaining carbon nanotube composite silica sol;

[0062] The mass ratio of the multi-walled carbon nanotubes filled with rare earth elements to the trimethylaluminum solution is 5:10;

[0063] The concentration of the trimethylaluminum solution is 30 wt%, and the solvent is n-hexane;

[0064] The mass ratio of the multi-walled carbon nanotubes coated with alumina to the silica sol is 5:6.5;

[0065] The concentration of the silica sol is 25 wt%, the particle size of the colloidal particles is 12 nm, and the solvent is deionized water.

[0066] (3) Preparation of waterproof material

[0067] Cement, fine sand, quartz sand, and fly ash are poured into a mortar mixer for dry stirring for 8 min. Then, water, water reducer, and defoamer are added to the mixer and stirring is continued for 17 min. Finally, carbon nanotube composite silica sol is added and stirring is continued for 22 min. After stirring is completed, it is poured into a mold and then cured to obtain a carbon nanotube cement-based waterproof material;

[0068] The mass ratio of cement, fine sand, quartz sand, fly ash, water, water reducer, defoamer, and carbon nanotube composite silica sol is 700:575:325:110:475:10:4.5:8;

[0069] The type of cement is P·O42.5 ordinary Portland cement;

[0070] The fineness modulus of the fine sand is 2.37, and the apparent density is 2587 g / m3 ;

[0071] The particle size of the quartz sand is 0.45 mm;

[0072] The particle size of the fly ash is 150 μm;

[0073] The water reducer is a polycarboxylic acid water reducer, model number is XCA-100;

[0074] The defoamer is a silicone polyether defoamer, and its model is Deqian Defom6800.

[0075] Example 3

[0076] (1) Multi-walled carbon nanotube filling

[0077] The multi-walled carbon nanotubes are placed in a nitrogen atmosphere, the heating rate is controlled to be 5.5°C / min, the temperature is raised to 405°C, the multi-walled carbon nanotubes are heat-treated, the heat treatment time is 95 minutes, and after the treatment, the cooling rate is controlled to be 3.5°C / min, the multi-walled carbon nanotubes are cooled to 70°C, and the heat is kept, and then the heat-preserved multi-walled carbon nanotubes are immersed in a cerium sulfate solution, the frequency is controlled to be 70kHz, and the ultrasound is performed for 12 minutes. After the ultrasound is completed, the multi-walled carbon nanotubes are filtered and dried to obtain rare earth element-filled multi-walled carbon nanotubes;

[0078] The mass ratio of the multi-walled carbon nanotubes to the cerium sulfate solution is 1:5.5;

[0079] The multi-walled carbon nanotube has a diameter of 100 nm and a length of 300 μm;

[0080] The concentration of cerium element in the cerium sulfate solution is 12 g / L, and the solvent of the solution is 0.15 mol / L sulfuric acid.

[0081] (2) Preparation of carbon nanotube composite silica sol

[0082] In a nitrogen atmosphere, a rare earth element-filled multi-walled carbon nanotube is mixed with a trimethylaluminum solution and stirred for 25 minutes. After stirring, the nitrogen atmosphere is maintained and the heating rate is controlled to be 5.5°C / min. The temperature is raised to 825°C for sintering. The sintering time is 130 minutes. After sintering, alumina-coated multi-walled carbon nanotubes are obtained. After cooling to room temperature, the multi-walled carbon nanotubes are mixed with silica sol and stirred at a speed of 90 r / min. While stirring, the temperature is controlled to be 100°C to evaporate the water in the silica sol until the water content is 0, thereby obtaining a carbon nanotube composite silica sol.

[0083] The mass ratio of the rare earth element-filled multi-walled carbon nanotubes to the trimethylaluminum solution is 5:14;

[0084] The concentration of the trimethylaluminum solution is 20wt%, and the solvent is n-hexane;

[0085] The mass ratio of the alumina-coated multi-walled carbon nanotubes to the silica sol is 5:7.5;

[0086] The concentration of the silica sol is 15 wt %, the particle size of the colloidal particles is 20 nm, and the solvent is deionized water.

[0087] (3) Preparation of waterproof materials

[0088] Pour cement, fine sand, quartz sand and fly ash into a mortar mixer and dry-mix them for 12 minutes, then add water, a water reducing agent and a defoaming agent into the mixer and continue to stir for 13 minutes, finally add carbon nanotube composite silica sol and continue to stir for 28 minutes, after stirring, pour into a mold, and then obtain a carbon nanotube cement-based waterproof material after curing;

[0089] The mass ratio of the cement, fine sand, quartz sand, fly ash, water, water reducing agent, defoaming agent and carbon nanotube composite silica sol is 800:625:375:130:550:12:5.5:10;

[0090] The model of the cement is P·O42.5 grade ordinary Portland cement;

[0091] The fineness modulus of the fine sand is 2.37 and the apparent density is 2587 g / m 3 ;

[0092] The particle size of the quartz sand is 0.55 mm;

[0093] The particle size of the fly ash is 200 μm;

[0094] The water reducer is a polycarboxylic acid water reducer, model number is XCA-100;

[0095] The defoamer is a silicone polyether defoamer, and its model is Deqian Defom6800.

[0096] Comparative Example 1

[0097] Different from Example 1, the multi-walled carbon nanotube filling step is omitted, and the untreated multi-walled carbon nanotubes are directly used for the step of preparing carbon nanotube composite silica sol. When the dosage remains unchanged, the remaining steps remain unchanged to prepare the waterproof material.

[0098] Comparative Example 2

[0099] Different from Example 1, the step of preparing carbon nanotube composite silica sol is omitted, and the rare earth element-filled multi-walled carbon nanotubes obtained in the multi-walled carbon nanotube filling step are directly used as raw materials for the waterproof material. Without changing the dosage, the remaining steps are kept unchanged to prepare the waterproof material.

[0100] Test Example 1 Mechanical Property Test of Waterproof Material

[0101] The waterproof materials prepared in Examples 1-3 and Comparative Examples 1-2 were used to detect the compressive strength, flexural strength, splitting tensile strength, and static compressive elastic modulus of the waterproof materials according to the method in GB / T50081-2019. The results are shown in Table 1.

[0102] Table 1

[0103]

[0104] In Examples 1-3, rare earth element multi-walled carbon nanotubes were used for filling, and then they were compounded with aluminum elements and silica sol, and used as raw material components to be added to the waterproof concrete material. The prepared waterproof materials have relatively excellent mechanical properties, with high compressive strength, flexural strength, splitting tensile strength, and static compressive elastic modulus.

[0105] In Comparative Example 1, the multi-walled carbon nanotube filling step was omitted, and the untreated multi-walled carbon nanotubes were directly used in the step of preparing carbon nanotube composite silica sol. Finally, the mechanical properties of the prepared waterproof material decreased, especially the compressive strength, splitting tensile strength, and static compressive elastic modulus decreased severely, and the flexural strength also decreased to a large extent.

[0106] In Comparative Example 2, the step of preparing carbon nanotube composite silica sol was omitted, and the rare earth element-filled multi-walled carbon nanotubes obtained in the multi-walled carbon nanotube filling step were directly used as raw materials for the waterproof material to prepare the waterproof material. Finally, the mechanical properties of the prepared waterproof material decreased, especially the flexural strength decreased severely, and the compressive strength, splitting tensile strength, and static compressive elastic modulus also decreased to a large extent.

[0107] Test Example 2 Waterproof Property Test of Waterproof Material

[0108] The waterproof materials prepared in Examples 1-3 and Comparative Examples 1-2 were used to detect the water absorption rate of the waterproof materials according to the method in GB / T50081-2019, and the water impermeability of the waterproof materials was detected by the step-by-step pressure method according to the method in GB / T50082-2024, with the maximum pressure when water seepage occurred as the index. According to the method in GB / T50082-2024, the electrical flux method was used to detect the chloride ion permeability resistance of the waterproof materials, with the electrical flux as the index. The results are shown in Table 2.

[0109] Table 2

[0110]

[0111] Examples 1-3 were filled with rare earth element multi-walled carbon nanotubes, and then compounded with aluminum element and silica sol, and added as raw material components to the waterproof concrete material. The prepared waterproof materials have relatively excellent waterproof performance, with low water absorption rate, can maintain anti-seepage performance under large water pressure, and have good anti-chloride ion permeability and low electric flux;

[0112] In Comparative Example 1, the multi-walled carbon nanotube filling step was omitted, and the untreated multi-walled carbon nanotubes were directly used for the preparation of carbon nanotube composite silica sol step. Finally, the waterproof performance of the prepared waterproof material decreased, especially the water absorption rate increased seriously, the anti-seepage pressure decreased seriously, and in addition, the electric flux also increased to a large extent, and the anti-chloride ion permeability was poor;

[0113] In Comparative Example 2, the step of preparing carbon nanotube composite silica sol was omitted, and the rare earth element-filled multi-walled carbon nanotubes obtained from the multi-walled carbon nanotube filling step were directly used as the raw materials of the waterproof material for the preparation of the waterproof material. Finally, the waterproof performance of the prepared waterproof material decreased, especially the decrease in chloride ion permeability was particularly serious, the electric flux increased seriously, the water absorption rate also increased to a large extent, and the anti-seepage pressure decreased to a large extent.

[0114] Test Example 3 Wear resistance test of waterproof materials

[0115] The wear resistance of the waterproof materials prepared in Examples 1-3 and Comparative Examples 1-2 was detected by the abrasion loss method according to the method in GB / T50081-2019, and the results are shown in Table 3.

[0116] Table 3

[0117]

[0118] Examples 1-3 were filled with rare earth element multi-walled carbon nanotubes, and then compounded with aluminum element and silica sol, and added as raw material components to the waterproof concrete material. The prepared waterproof materials have relatively excellent wear resistance, and the abrasion loss per unit area is low;

[0119] In Comparative Example 1, the multi-walled carbon nanotube filling step was omitted, and the untreated multi-walled carbon nanotubes were directly used for the preparation of carbon nanotube composite silica sol step. Finally, the wear resistance of the prepared waterproof material decreased, and the abrasion loss per unit area increased seriously;

[0120] In Comparative Example 2, the step of preparing the carbon nanotube composite silica sol was omitted, and the multi-walled carbon nanotubes filled with rare earth elements obtained in the multi-walled carbon nanotube filling step were directly used as raw materials for the waterproof material to prepare the waterproof material. Eventually, the wear resistance of the prepared waterproof material decreased, and the wear amount per unit area increased to a large extent.

[0121] Test Example 4 Test on the expansion coefficient of the waterproof material

[0122] The waterproof materials prepared in Examples 1-3 and Comparative Examples 1-2 were used to test the linear expansion coefficient of the waterproof material according to the method in GB / T50081-2019, and the results are shown in Table 4.

[0123] Table 4

[0124]

[0125] In Examples 1-3, by filling with rare earth element multi-walled carbon nanotubes, then compounding them with aluminum element and silica sol, and adding them as raw material components to the waterproof concrete material, the prepared waterproof material has a lower expansion coefficient and is less affected by thermal expansion and contraction;

[0126] In Comparative Example 1, the multi-walled carbon nanotube filling step was omitted, and the untreated multi-walled carbon nanotubes were directly used in the step of preparing the carbon nanotube composite silica sol. Eventually, the expansion coefficient of the prepared waterproof material increased to a certain extent and was greatly affected by thermal expansion and contraction;

[0127] In Comparative Example 2, the step of preparing the carbon nanotube composite silica sol was omitted, and the multi-walled carbon nanotubes filled with rare earth elements obtained in the multi-walled carbon nanotube filling step were directly used as raw materials for the waterproof material to prepare the waterproof material. Eventually, the expansion coefficient of the prepared waterproof material increased more severely and was greatly affected by thermal expansion and contraction.

[0128] Test Example 5 Test on the gas permeability of the waterproof material

[0129] The waterproof materials prepared in Examples 1-3 and Comparative Examples 1-2 were used to test the gas permeability with nitrogen as the test gas according to the method in GB / T50082-2024, the gas path pressure was set at 0.4 MPa, and the apparent gas permeability coefficient under this pressure was tested, and the results are shown in Table 5.

[0130] Table 5

[0131]

[0132] In Examples 1-3, by filling with rare earth element multi-walled carbon nanotubes, then compounding them with aluminum element and silica sol, and adding them as raw material components to the waterproof concrete material, the prepared waterproof material has a lower gas permeability coefficient and the interior of the waterproof material is relatively dense;

[0133] In Comparative Example 1, the multi-walled carbon nanotube filling step was omitted, and the untreated multi-walled carbon nanotubes were directly subjected to the step of preparing the carbon nanotube composite silica sol. As a result, the gas permeability coefficient of the finally prepared material increased to a certain extent, and the density inside the waterproof material was poor.

[0134] In Comparative Example 2, the step of preparing the carbon nanotube composite silica sol was omitted, and the rare earth element-filled multi-walled carbon nanotubes obtained from the multi-walled carbon nanotube filling step were directly used as the raw material of the waterproof material for the preparation of the waterproof material. As a result, the gas permeability coefficient of the finally prepared material increased severely, and the density inside the waterproof material was poor.

Claims

1. A method for preparing a carbon nanotube cement-based waterproof material, characterized in that: The preparation method includes filling with multi-walled carbon nanotubes, preparing carbon nanotube composite silica sol, and preparing waterproof material; The multi-walled carbon nanotube filling method comprises placing the multi-walled carbon nanotube in a nitrogen atmosphere, heating the multi-walled carbon nanotube to 405-425° C., heat-treating the multi-walled carbon nanotube for 85-95 minutes, cooling the multi-walled carbon nanotube to 60-70° C. after the treatment, and keeping the temperature, then immersing the kept multi-walled carbon nanotube in a cerium sulfate solution, performing ultrasound, and after the ultrasound, filtering and drying to obtain the multi-walled carbon nanotube filled with rare earth elements; The mass ratio of the multi-walled carbon nanotubes to the cerium sulfate solution is 1:4.5-5.5; The concentration of cerium element in the cerium sulfate solution is 8-12 g / L; The method for preparing the carbon nanotube composite silica sol comprises: mixing and stirring multi-walled carbon nanotubes filled with rare earth elements and trimethylaluminum solution in a nitrogen atmosphere; maintaining the nitrogen atmosphere, heating to 825-870° C., and sintering for 110-130 minutes; after sintering, alumina-coated multi-walled carbon nanotubes are obtained; cooling the multi-walled carbon nanotubes to room temperature, mixing the multi-walled carbon nanotubes with silica sol, and continuously stirring to evaporate water to obtain the carbon nanotube composite silica sol; The mass ratio of the rare earth element-filled multi-walled carbon nanotubes to the trimethylaluminum solution is 5:10-14; The mass ratio of the alumina-coated multi-walled carbon nanotubes to the silica sol is 5:6.5-7.5; The method for preparing the waterproof material comprises mixing and stirring the raw materials according to the steps, pouring the raw materials into a mold after stirring, and finally curing to obtain a carbon nanotube cement-based waterproof material; The raw materials include cement, fine sand, quartz sand, fly ash, water, water reducing agent, defoaming agent, carbon nanotube composite silica sol, and the mass ratio thereof is 700-800:575-625:325-375:110-130:475-550:10-12:4.5-5.5:8-10; The particle size of the quartz sand is 0.45-0.55 mm.

2. The method for preparing a carbon nanotube cement-based waterproof material according to claim 1, characterized in that: In the multi-walled carbon nanotube filling method, the heating method is to control the heating rate to 4.5-5.5°C / min; the cooling method is to control the cooling rate to 2.5-3.5°C / min; the ultrasonic method is to control the frequency to 50-70kHz, perform ultrasonication, and the ultrasonication time is 12-20min.

3. The method for preparing a carbon nanotube cement-based waterproof material according to claim 1, characterized in that: In the multi-walled carbon nanotube filling method, the solvent of the cerium sulfate solution is 0.15 mol / L sulfuric acid; the diameter of the multi-walled carbon nanotube is 70-100 nm, and the length is 200-300 μm.

4. The method for preparing a carbon nanotube cement-based waterproof material according to claim 1, characterized in that: In the method for preparing carbon nanotube composite silica sol, the heating method is to control the heating rate to 4.5-5.5°C / min; after the multi-walled carbon nanotubes filled with rare earth elements are mixed with the trimethylaluminum solution, the stirring time is 18-25min, and the method for stirring to evaporate water is to stir at a speed of 50-90r / min, and control the temperature to 100°C while stirring, so as to evaporate the water in the silica sol until the water content is 0.

5. The method for preparing a carbon nanotube cement-based waterproof material according to claim 1, characterized in that: In the method for preparing carbon nanotube composite silica sol, the concentration of trimethylaluminum solution is 20-30wt%, and the solvent is n-hexane; the concentration of silica sol is 15-25wt%, the particle size of colloidal particles is 12-20nm, and the solvent is deionized water.

6. The method for preparing a carbon nanotube cement-based waterproof material according to claim 1, characterized in that: In the method for preparing the waterproof material, the cement type is P·O 42.5 grade ordinary Portland cement; the fineness modulus of the fine sand is 2.37, and the apparent density is 2587 kg / m 3 ; The particle size of fly ash is 150-200μm; the water reducer is a polycarboxylic acid type water reducer, model XCA-100; the defoamer is a silicone polyether type defoamer, model Deqian Defom6800.

7. The method for preparing a carbon nanotube cement-based waterproof material according to claim 1, characterized in that: In the method for preparing the waterproof material, the raw materials are mixed and stirred separately according to the steps, cement, fine sand, quartz sand and fly ash are dry-mixed for 8-12 minutes, water, water reducing agent and defoaming agent are added to the mixer, stirring is continued for 13-17 minutes, and finally carbon nanotube composite silica sol is added and stirring is continued for 22-28 minutes.

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