High electromagnetic shielding concrete and application thereof in transformer substation enclosure wall

Abstract

The invention discloses high-electromagnetic-shielding concrete and application thereof in a transformer substation enclosure wall, and belongs to the technical field of concrete.The high-electromagnetic-shielding concrete comprises a reinforcement cage and concrete for pouring the reinforcement cage, and an electromagnetic shielding net is bound to the outer surface of the reinforcement cage; the electromagnetic shielding net is an iron gauze with an electromagnetic shielding admixture attached to the surface, and the electromagnetic shielding admixture comprises the following components in parts by weight: 20-40 parts of magnetic metal, 10-30 parts of a carbon material, 10-20 parts of a polymer, 3-10 parts of a cross-linking agent and 0.01-0.1 part of an initiator. The polymer is a copolymer of methacrylic acid-1-pyrene methyl ester, a CMC-MA (Carboxy Methyl Cellulose-Methyl Acrylate) macromonomer and methoxyl polyethylene glycol methacrylate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a high electromagnetic shielding concrete and application thereof in the surrounding wall of a transformer substation. BACKGROUND

[0002] In the field of information dissemination, electromagnetic waves are extremely common and fast carriers, which are applied in our life. However, the wide application of electromagnetic waves also brings new problems-electromagnetic radiation. Long-term exposure to electromagnetic radiation environment can cause serious damage to the nervous system of human body, resulting in functional reduction of immune and circulatory systems, and even inducing cancer. Therefore, in the environmental protection technical requirements of power transmission and transformation construction projects, it is clearly required that the electromagnetic environmental impact factors such as power frequency electric field and power frequency magnetic field generated by engineering design should be checked and calculated, and corresponding protection measures should be taken to ensure that the electromagnetic environmental impact meets the requirements of national standards.

[0003] In the field of building materials, cement-based materials are the most widely used building materials. It has a broad market prospect to introduce electromagnetic shielding function into cement-based materials to prepare building mortar, block, foam concrete and other materials. However, the electromagnetic shielding efficiency of ordinary traditional concrete materials is low, and they basically do not have conductivity. Therefore, if we want to give the concrete good electromagnetic shielding performance, we must add other functional fillers. Electromagnetic shielding materials can be generally divided into: ferromagnetic and good conductor metal materials, intrinsic conductive polymers, carbon-based electromagnetic shielding materials and composite electromagnetic shielding materials. For example, ferromagnetic metal materials can reduce the space magnetic flux density by using the low impedance and high magnetic permeability of ferromagnetic materials to form a magnetic shield inside the shielding body. Carbon fibers can give concrete electromagnetic shielding function by affecting the reflection and absorption loss of electromagnetic waves by concrete. However, when the cement-based composite material is mixed with conductive materials to form a conductive network inside, the cement-based composite material has a certain conductive capacity, and a large amount of electromagnetic shielding material is required and evenly dispersed. However, too high a content of carbon-based electromagnetic shielding material will have a negative impact on the mechanical properties of concrete, and the specific gravity of ferromagnetic and good conductor metal materials is too high, which can cause problems such as settlement, bleeding rate increase and strength decrease when the content is too high. SUMMARY

[0004] In order to solve the above problems, the present application provides a high electromagnetic shielding concrete, which improves the electromagnetic shielding effect of the concrete by adding an electromagnetic shielding net, and avoids the technical problems of uneven dispersion of electromagnetic shielding materials in traditional electromagnetic shielding concrete, too large specific gravity, poor electromagnetic shielding effect, easy settlement of heavy aggregate and water separation in concrete.

[0005] The technical scheme for achieving the object of the present application is as follows: A high electromagnetic shielding concrete comprises a reinforcement cage and a concrete casted in the reinforcement cage, an outer surface of the reinforcement cage is bound with an electromagnetic shielding net, the electromagnetic shielding net is a wire mesh with a surface attached electromagnetic shielding admixture, the electromagnetic shielding admixture comprises the following components in terms of weight parts: 20-40 parts of magnetic metal, 10-30 parts of carbon material, 10-20 parts of polymer, 3-10 parts of crosslinking agent, and 0.01-1 part of initiator, the polymer is a copolymer of 1-pyrromethylenyl methacrylate, CMC-MA macromonomer and methoxy polyethylene glycol methacrylate.

[0006] In a specific embodiment, the magnetic metal comprises at least one of iron powder, cobalt powder, nickel powder, a magnetic alloy containing any one of iron, cobalt and nickel, and an oxide ferrite; and the carbon material comprises at least one of graphene, carbon nanotube, graphite and carbon black.

[0007] In a specific embodiment, the wire mesh has a mesh number of 80-200.

[0008] In a specific embodiment, the crosslinking agent is at least one of N,N'-methylene bisacrylamide, ethylene glycol dimethacrylate and trimethylolpropane triacrylate; and the initiator is ammonium persulfate or azobisisobutyronitrile.

[0009] In a specific embodiment, the concrete has a mix proportion of: 800-1000 kg / m 3 of coarse aggregate, 600-800 kg / m 3 of fine aggregate, 300-500 kg / m 3 of cement, 40-60 kg / m 3 of iron tailing powder, 40-60 kg / m 3 of fly ash, 40-60 kg / m 3 of silica ash, 5-15 kg / m 3 of water reducing agent, and 100-200 kg / m 3 of water.

[0010] In a specific embodiment, the coarse aggregate is barite, the fine aggregate is natural river sand or machine-made sand, the cement is ordinary portland cement, and the water reducing agent is polycarboxylic acid type water reducing agent.

[0011] In a specific embodiment, the iron tailing powder has a specific gravity of 4400 kg / m 3 and a particle size of 0.1-1.5 mm.

[0012] In a specific embodiment, the 1-pyrromethylenyl methacrylate has a structure as shown in formula (1): Formula 1.

[0013] In one specific embodiment, the CMC-MA macromonomer is prepared by acid catalyzed ring opening reaction of carboxymethylcellulose sodium after acidification with glycidyl methacrylate, and the degree of substitution of the glycidyl methacrylate is 5-30%.

[0014] In one specific embodiment, the polymer is prepared by free radical polymerization, and the mass ratio of 1-pyrenemethyl methacrylate, CMC-MA macromonomer and methoxypolyethylene glycol methacrylate is (1-2):4:(2-4).

[0015] In one specific embodiment, the degree of substitution of the carboxymethylcellulose sodium is 0.7-1.2, and the molecular weight is 70k-120k.

[0016] In one specific embodiment, the molecular weight of the methoxypolyethylene glycol methacrylate is 300-2000.

[0017] In one specific embodiment, the preparation method of the electromagnetic shielding net is mixing magnetic metal, carbon material, polymer, crosslinking agent, initiator and water to obtain electromagnetic shielding mixture, testing the apparent viscosity at 25℃ and shear rate 10s -1 -1 at 8000-15000 mPa·s, then soaking the wire mesh in the electromagnetic shielding mixture, taking out and standing or radiation crosslinking at 60-70℃, drying to obtain the electromagnetic shielding net.

[0018] In one specific embodiment, the preparation method of the high electromagnetic shielding concrete is: after the steel reinforcement cage is tied, a layer of electromagnetic shielding net is tied on the outer surface of the steel reinforcement cage, coarse aggregate, fine aggregate, cement, iron tailing powder, silica fume and fly ash are put into the mixing station, stirred for 1-2min, then water is added, stirred for 2-5min, then water reducing agent is added, and continue stirring until the ice block is fully melted; pouring the concrete in the steel formwork, and vibrating until the concrete surface presents that the cement paste does not sink and the surface basically does not bubble; covering the plastic film on the surface of the vibrated and leveled concrete, and demolding after hardening, and standard curing for at least 28d.

[0019] The application also protects the application of the high electromagnetic shielding concrete in the substation fence.

[0020] Beneficial effects

[0021] The application provides a kind of high electromagnetic shielding concrete, by binding electromagnetic shielding net on the outer surface of the reinforcement cage of concrete, so that incident electromagnetic waves are reflected, absorbed and consumed by multiple reflections inside the concrete wall, thereby achieving high electromagnetic shielding effect. The electromagnetic shielding net is made by adhering magnetic metal and carbon material to iron wire after polymer cross-linking, wherein the magnetic metal and iron wire itself have magnetic adsorption, and the carboxymethyl cellulose in the polymer has thickening and tackifying effect, which can attract the magnetic metal and iron wire through hydrogen bonding, thereby improving the adhesion. In addition, the pyrene group and the carbon material are attracted to each other through π-π stacking, and the long-chain steric hindrance of methoxy polyethylene glycol methacrylate ensures the dispersibility of the magnetic metal and the carbon material, so that the magnetic metal, the carbon material and the polymer can form an electromagnetic shielding admixture with moderate viscosity and strong adhesion. After the iron wire mesh is immersed in the electromagnetic shielding admixture, the polymer and the cross-linking agent react under the action of the initiator to form a tight three-dimensional cross-linked network, which firmly fixes the magnetic metal and the carbon material on the iron wire mesh, so that it can withstand the impact during concrete pouring. The double-loss synergistic network formed by the magnetic metal and the carbon material plus the iron wire mesh as a whole is equivalent to a continuous conductive film with a magnetic hysteresis loop, which greatly improves the electromagnetic shielding effect of the concrete, reduces the use of heavy aggregate and high-cost carbon fiber in traditional electromagnetic shielding concrete, and is suitable for lightweight building material wall surfaces and any complex geometric wall surfaces. The introduction of iron wire mesh and cellulose gel also improves the mechanical properties of the concrete. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is an infrared spectrum of polymer 1.

[0023] Figure 2 It is a schematic diagram of the electromagnetic shielding mechanism of high electromagnetic shielding concrete. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0025] In the embodiments, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0026] The raw materials used in the examples and comparative examples are described as follows: Cement: ordinary Portland cement, P·O 42.5; composition and chemical properties are shown in Table 1: Table 1

[0027] Fine aggregate: Mechanically produced sand from Guangxi; Coarse aggregate: Heavy spar from Guangxi; Water reducing agent: PCA Type I polycarboxylate high performance water reducing agent (HRWR) from Jiangsu Subote; Iron tailings powder: From the iron mine factory in Songxi County, Fujian Province; Silicon powder: From Guizhou Haitian Environmental Protection Science and Technology New Material Co., Ltd.; Fly ash: From the Lingshou County Detong Mineral Product Processing Factory; Iron wire mesh: 100 mesh, Guangzhou Mingwan Sieve Mesh Co., Ltd.; Magnetic metal 1: Neodymium iron boron alloy powder, 325 mesh, Shijiazhuang Ruixiang Mineral Products Co., Ltd.; Magnetic metal 2: Iron powder, 400 mesh, Shijiazhuang Zhenxing Building Material Co., Ltd.; Magnetic metal 3: Iron-silicon-chromium alloy powder, 25-35 μm, Sichuan Xinjinxun Metal Material Co., Ltd.; Magnetic metal 4: Nickel powder, 10,000 mesh, Hebei Wenlun Metal Material Co., Ltd.; Carbon material 1: Flake graphite, 2,000 mesh, Qingdao Mingrun Chen Yue Graphite Co., Ltd.; Carbon material 2: Multi-walled carbon nanotube, tube diameter 9.5 nm, length 1.5 μm, Fosman Technology (Beijing) Co., Ltd.; Crosslinking agent: N,N'-methylenebisacrylamide, commercially available; Initiator: Ammonium persulfate, commercially available; Sodium carboxymethylcellulose: DS = 0.7, molecular weight 90,000, Shanghai Ke'eer Chemical Technology Co., Ltd.; Methoxy polyethylene glycol methacrylate: Molecular weight 450-500, Hubei Shengwei New Material Co., Ltd.; Methacrylic acid-1-pyrenemethyl ester: self-made, the preparation method is as follows: 30g 1-pyrenemethyl alcohol is dissolved in 280ml freshly distilled tetrahydrofuran, 28ml triethylamine and 18ml pyridine are added, the mixture is cooled to 0°C, and then 19ml methacryloyl chloride is added dropwise. After the dropwise addition is completed, the ice water bath is removed, and stirring is continued for 1 hour reaction. After the reaction is completed, 75ml water is added to the reaction bottle, and the solution is transferred to a separatory funnel and extracted with 500ml diethyl ether. The extract is washed with 150ml 1 mol / L hydrochloric acid aqueous solution, 150ml 5% sodium bicarbonate aqueous solution and 150ml saturated brine in sequence. After the solvent is evaporated in vacuum, recrystallization is performed with methanol to obtain the product, and the yield is 90%. Nuclear magnetic resonance hydrogen spectrum test is 1H NMR (500 MHz, CDCl3): δ 8.35 (d, J=9.2 Hz, 1H), 8.25 (t, J=6.6 Hz, 2H), 8.21 (d, J=9.8 Hz, 2H), 8.12 (t, J=4.6 Hz, 3H), 8.06 (m, 1H), 6.18 (s, 1H), 5.95 (s, 2H), 5.59 (s, 1H), 2.00 (s, 3H) ppm.

[0028] CMC-MA macromonomer: 5g sodium carboxymethyl cellulose is dissolved in water, 0.5mol / L HCl is added dropwise to pH 3.0, ethanol is added for precipitation, filtration, and vacuum drying to obtain acid type CMC. 2g acid type CMC is dissolved in a mixed solution of 30ml water and 10ml tetrahydrofuran, nitrogen is bubbled for 15 min, 0.56g glycidyl methacrylate and 0.02g 4-dimethylaminopyridine are added, and ring opening reaction is carried out at 60°C for 2h. After the reaction is completed, 3 times of acetone is added for precipitation, filtration, washing with 50% ethanol for 2 times, and vacuum drying at 40°C to obtain white flocculent product, which is CMC-MA, and the yield is 90%.

[0029] Polymer 1: 2g CMC-MA macromonomer, 1g methacrylic acid-1-pyrenemethyl ester and 2g methoxy polyethylene glycol methacrylate are dissolved in a mixed solution including 40ml water and 10ml tetrahydrofuran, nitrogen is bubbled for 15 min; 30mg ammonium persulfate is added, and reaction is carried out at 70°C for 8h; after the reaction is completed, acetone is added for precipitation, filtration, 50% ethanol is used for washing for 3 times to remove homopolymer, and vacuum drying to obtain brush-like terpolymer, GPC detection shows that the weight average molecular weight is 120k, and the yield is 82%. Fourier infrared transform spectrometer (Nicolet Summit) is used for infrared spectrum test of the polymer, and the results are as shown in Figure 1 The test conditions are: resolution 4cm -1 , scanning 32 times, and the spectrum range is 4000-500cm -1 .

[0030] Polymer 2: Compared with Polymer 1, the difference is that the amount of methyl methacrylate-1-pyrene, CMC-MA macromonomer and methoxy polyethylene glycol methacrylate added is modified to 4g CMC-MA macromonomer, 1g methyl methacrylate-1-pyrene, and 4g methoxy polyethylene glycol methacrylate. The weight average molecular weight detected by GPC is 128k, and the yield is 85%.

[0031] Polymer 3: Compared with Polymer 1, the difference is that the amount of methyl methacrylate-1-pyrene, CMC-MA macromonomer and methoxy polyethylene glycol methacrylate added is modified to 4g CMC-MA macromonomer, 0g methyl methacrylate-1-pyrene, and 4g methoxy polyethylene glycol methacrylate. The weight average molecular weight detected by GPC is 100k, and the yield is 81%.

[0032] Polymer 4: Compared with Polymer 1, the difference is that the amount of methyl methacrylate-1-pyrene, CMC-MA macromonomer and methoxy polyethylene glycol methacrylate added is modified to 1g methyl methacrylate-1-pyrene and 4g methoxy polyethylene glycol methacrylate. The weight average molecular weight detected by GPC is 50k and the yield is 87%.

[0033] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0034] Preparation Examples 1-11 An electromagnetic shielding dopant was prepared by mixing magnetic metal, carbon material, polymer, crosslinking agent, initiator, water, and ethanol. Then, wire mesh was immersed in the electromagnetic shielding dopant shown in Table 2, and tested at 25°C and a shear rate of 10 s. -1 The apparent viscosity was 12000 mPa·s. Then, the wire mesh was immersed in the electromagnetic shielding admixture, taken out and left to stand at 60~70℃ for 30 min, and dried for 2 h to obtain electromagnetic shielding mesh 1~11. The components and proportions of magnetic metal, carbon material, polymer, crosslinking agent, initiator, water and ethanol are shown in Table 2.

[0035] Table 2. Components and proportions of electromagnetic shielding admixtures

[0036] Examples and Comparative Examples After the reinforcing cage is tied, an electromagnetic shielding mesh is tied to the outer surface of each reinforcing cage. The electromagnetic shielding mesh corresponding to the embodiments and comparative examples is shown in Table 3. Coarse aggregate, fine aggregate, cement, iron tailings powder, silica fume, and fly ash are put into the mixing plant and mixed for 1-2 minutes. Then water is added and mixed for 2-5 minutes. Then water-reducing agent is added and mixed for another 1-2 minutes. Concrete is poured into the reinforcing cage formwork and vibrated until the concrete surface shows cement paste that no longer settles and the surface is basically free of bubbles. The vibrated and leveled concrete surface is covered with plastic film. After hardening, the formwork is removed and the standard curing is carried out for at least 28 days to obtain a concrete sample with dimensions of 300×300×30mm. 3 .

[0037] Table 3. Mix proportions of concrete samples from the examples and comparative examples (kg / m²) 3 )

[0038] The following performance tests were performed on the concrete sample, and the results are shown in Table 4.

[0039] (1) Electromagnetic shielding performance test: The shielding effect in the range of 0.95MHz~10GHz was measured using the "Test Method for Shielding Performance of Military Shielded Rooms". The shielding effectiveness test method is divided into shielded room test method and laboratory method. The shielded room test method is carried out using the "Test Method for Shielding Performance of Military Shielded Rooms" and the test range is between 950MHz and 10GHz. The electromagnetic field signal source is placed outside the shielded room and the receiving equipment is placed inside the shielded room. The sample is placed on the test window and compacted. The opening size of the shielded room is 300mm×300mm. The test antenna is a horn antenna. The test method is carried out according to the "Test Method for Shielding Effectiveness of Electromagnetic Shielded Rooms" GB / T 12190-2006. The distance between the sample and the antennas on both sides is 2m. Multiple measurements are taken in different polarization directions, and the highest shielding effectiveness in the low frequency band of 950MHz~3GHz and the high frequency band of 3 (excluding)~10GHz is recorded.

[0040] (2) 28d compressive strength: The compressive strength of the concrete sample was tested at 28d in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar"; (3) 28d flexural strength: The flexural strength of the concrete sample was tested at 28d in accordance with GB / T 17671-2021 "Test Method for Strength of Cement Mortar".

[0041] Table 4 Performance Tests of High Electromagnetic Shielding Concrete

[0042] As can be seen from the examples and comparative examples, the electromagnetic shielding efficiency of the high electromagnetic shielding concrete prepared by the present invention can reach 62~89dB, and it has good mechanical properties.

[0043] In Comparative Example 1, the polymer lacked methyl methacrylate (1-pyrene), which affected the dispersion of carbon materials and may have led to increased electromagnetic wave transmission in some areas, thus reducing electromagnetic shielding effectiveness. In Comparative Example 2, the polymer lacked CMC-MA macromonomers, resulting in poorer adhesion of magnetic metals and carbon materials to the walls, thus affecting the electromagnetic shielding effect of the mesh. Furthermore, the absence of carboxymethyl cellulose's water-retention and retarding effect reduced the mechanical properties of the concrete. Comparative Examples 3 and 4, lacking carbon materials and magnetic metals respectively, could not form electromagnetic shielding meshes that addressed both high and low frequencies. Comparative Example 6 did not use an electromagnetic shielding mesh; the insufficient amounts of magnetic metals and carbon materials prevented the formation of conductive pathways within the concrete, resulting in limited electromagnetic shielding effectiveness.

[0044] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high electromagnetic shielding concrete, comprising a reinforcing cage and concrete for casting the reinforcing cage, characterized in that, The outer surface of the reinforcing cage is bound with an electromagnetic shielding mesh, which is a wire mesh with an electromagnetic shielding admixture attached to its surface. The electromagnetic shielding admixture, by weight, includes the following components: 20-40 parts magnetic metal, 10-30 parts carbon material, 10-20 parts polymer, 3-8 parts crosslinking agent, and 0.01-1 parts initiator. The polymer is a copolymer of methyl methacrylate-1-pyrene, CMC-MA macromonomer, and methoxy polyethylene glycol methacrylate.

2. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The magnetic metal includes at least one of iron powder, cobalt powder, nickel powder, magnetic alloys containing any one of iron, cobalt, and nickel, and oxide ferrites; the carbon material includes at least one of graphene, carbon nanotubes, graphite, and carbon black.

3. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The crosslinking agent is at least one of N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, and trimethylolpropane triacrylate; the initiator is ammonium persulfate or azobisisobutyronitrile.

4. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The concrete mix proportion is: 800~1000 kg / m³ of coarse aggregate. 3 Fine aggregate 600~800kg / m³ 3 Cement 300~500kg / m 3 Iron tailings powder 40~60kg / m³ 3 40~60kg / m³ of fly ash 3 Silica fume 40~60kg / m 3 Water-reducing agent 5~15kg / m 3 Water 100~200kg / m 3 .

5. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The methyl methacrylate-1-pyrene has the structure shown in formula (1): Formula 1.

6. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The CMC-MA macromonomer is prepared by acidification of sodium carboxymethyl cellulose followed by acid-catalyzed ring-opening reaction with glycidyl methacrylate, wherein the degree of substitution of glycidyl methacrylate is 5-30%.

7. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The polymer is prepared by free radical polymerization, and the mass ratio of methyl methacrylate-1-pyrene, CMC-MA macromonomer and methoxy polyethylene glycol methacrylate is (1~2):4:(2~4).

8. The high electromagnetic shielding concrete as described in claim 1, characterized in that, The electromagnetic shielding mesh is prepared by mixing magnetic metal, carbon material, polymer, crosslinking agent, initiator and water to obtain electromagnetic shielding admixture, then immersing iron wire in electromagnetic shielding admixture, allowing it to stand at 60~70℃ for crosslinking, taking it out and drying it to obtain electromagnetic shielding mesh.

9. The high electromagnetic shielding concrete as described in any one of claims 1 to 8, characterized in that, After the reinforcing cage is tied, tie an electromagnetic shielding mesh to the outer surface of each reinforcing cage. Put coarse aggregate, fine aggregate, cement, iron tailings powder, silica fume and fly ash into the mixing plant and mix for 1-2 minutes. Then add water and mix for 2-5 minutes. Add water-reducing agent and continue mixing for 1-2 minutes. Pour concrete into the reinforcing cage formwork and vibrate until the concrete surface shows cement paste that no longer settles and the surface is basically free of bubbles. Cover the vibrated and leveled concrete surface with plastic film. Remove the formwork after hardening and standard curing for at least 28 days.

10. The application of high electromagnetic shielding concrete as described in any one of claims 1 to 8 in substation perimeter walls.

Images