Cement-based wave-absorbing material and preparation method thereof

Abstract

The application relates to the technical field of composite functional building materials, in particular to a cement-based wave-absorbing material and a preparation method thereof. Raw materials of the cement-based wave-absorbing material include cement, wave-absorbing functional SAP, tap water and a water reducing agent, and the wave-absorbing functional SAP is prepared by modifying nano Fe3O4. The wave-absorbing agent nano Fe3O4 is used to modify the polyacrylamide type SAP, the wave-absorbing agent is loaded in the internal network structure of the SAP, and the wave-absorbing functional SAP is mixed into the cement-based material, so that the wave-absorbing performance of the cement-based material is improved, and the mechanical performance of the cement-based material is not obviously damaged, thereby enabling the cement-based material to have good wave-absorbing performance and high strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite functional building materials, and particularly relates to a cement-based wave-absorbing material and a preparation method thereof. BACKGROUND

[0002] With the progress of human science and technology, modern electronic information technology has made breakthrough progress, and the application of electronic information technology in the military field is also more and more widely. In the running process, electronic information equipment will use electromagnetic wave as information carrier to realize information transmission in the form of electromagnetic radiation.

[0003] Cement-based material is one of the most widely used building materials in the military engineering industry, and is also the most commonly used material for constructing fixed military facilities, which has excellent structural bearing capacity. Existing research shows that using cement-based material for building construction can make the building have a certain absorption and attenuation effect on electromagnetic waves. However, due to the poor electromagnetic loss performance of cement-based material itself, and the dense internal structure formed after cement hardening, the low porosity and poor impedance matching characteristics, it is difficult to make the electromagnetic wave transmitted to the surface of the cement incident into the cement-based body, so the electromagnetic wave is easy to reflect on the surface of the cement. Generally, the RL of the cement-based material to the electromagnetic wave is only about -3dB, and the electromagnetic protection effect is poor. Therefore, the cement-based wave-absorbing material formed by modifying the cement-based material to have electromagnetic wave-absorbing property has gradually become the research focus in the field of structural wave-absorbing materials.

[0004] However, the current methods for improving the electromagnetic wave absorbing properties of cement-based materials have various problems. The commonly used methods are to introduce high-performance electromagnetic wave absorbing functional components or to introduce wave-transparent aggregates (such as expanded perlite, vitrified microbeads, foamed polystyrene particles, porous ceramic particles, etc.) into the cement-based materials. For example, patent CN107311555A discloses a cement-based wave-absorbing material containing graphene oxide and a preparation method thereof. The method uses nano-Fe3O4 and graphene oxide as the wave-absorbing functional components. However, the hardened cement-based material has a dense internal structure, low porosity, and poor impedance matching characteristics, making it difficult for the electromagnetic waves transmitted to the surface of the cement to be incident into the cement-based material. The wave-absorbing improvement effect of simply introducing high-performance electromagnetic wave absorbing functional components is not obvious. In addition, due to the high cost of graphene oxide, the popularization and application of this method are limited. Patent CN107032703A discloses a cement-based wave-absorbing material containing Fe3O4 and fly ash hollow microspheres and a preparation method thereof. The wave-transparent aggregates such as expanded perlite and hollow microspheres are introduced into the cement-based material to increase the number of electromagnetic wave reflections and prolong the transmission distance of the electromagnetic waves in the cement-based material, thereby greatly enhancing the wave-absorbing performance of the cement-based material. However, this will cause a significant decrease in the mechanical properties of the cement-based material, making it difficult to meet the requirements of military infrastructure for mechanical properties and durability. Therefore, how to ensure that the cement-based material has good wave-absorbing performance while also having good mechanical properties is a technical difficulty currently faced. SUMMARY

[0005] Therefore, the present application provides a cement-based wave-absorbing material and a preparation method thereof to solve the technical problem that the current cement-based materials are difficult to balance the wave-absorbing performance and the mechanical properties. The present application is based on the synthesis method of polyacrylamide-type SAP. The wave-absorbing agent nano-Fe3O4 is used to modify the polyacrylamide-type SAP, and the wave-absorbing agent is loaded in the SAP network structure and the wave-absorbing functional SAP is introduced into the cement-based material. This method can improve the wave-absorbing performance of the cement-based material without significantly damaging the mechanical properties of the cement-based material, so that the cement-based material can have good wave-absorbing performance and high strength.

[0006] The technical scheme of the present application is as follows:

[0007] In one aspect, the present application provides a cement-based wave-absorbing material. The raw materials of the cement-based wave-absorbing material include cement, wave-absorbing functional SAP, tap water, and water reducing agent. The wave-absorbing functional SAP is prepared by modifying with nano-Fe3O4.

[0008] Based on the above scheme, preferably, the preparation method of the wave-absorbing functional SAP includes the following steps:

[0009] S1, acrylamide and deionized water are added into a beaker, stirring until the acrylamide is completely dissolved, then adding nano Fe3O4 for ultrasonic treatment;

[0010] S2, the mixed solution in step S1 is heated under N2 atmosphere, adding N, N'-methylene bisacrylamide and ammonium persulfate, stirring until the system becomes viscous, then stopping stirring and incubating for 2~4h;

[0011] S3, the hydrogel obtained in step S2 is cut into small pieces and soaked in deionized water and then in anhydrous ethanol until the hydrogel becomes a hard white blocky particle;

[0012] S4, the blocky particles obtained in step S3 are dried to constant weight, crushed, ground and sieved to obtain wave-absorbing functional SAP particles.

[0013] On the basis of the above scheme, preferably, according to the mass fraction, the acrylamide is 12~24 parts, and the nano Fe3O4 is 75~105 parts.

[0014] On the basis of the above scheme, further preferably, the mass ratio of nano Fe3O4 to acrylamide is (4~7):1.

[0015] On the basis of the above scheme, preferably, according to the mass fraction, the N, N'-methylene bisacrylamide is 1.44~1.80 parts, the ammonium persulfate is 0.12~0.24 parts, and the anhydrous ethanol is 1440~1560 parts.

[0016] On the basis of the above scheme, preferably, in step S1, the stirring speed is 200~500 rpm / min, and the ultrasonic power is 600~800 W; further preferably, the stirring speed is 300~400 rpm / min, and the ultrasonic power is 650~750 W.

[0017] On the basis of the above scheme, further preferably, 18 parts of acrylamide and 162 parts of deionized water are added into a beaker, stirred at room temperature 25℃ for 15 min, the stirring speed is 300 rpm / min; 90 parts of nano Fe3O4 is added into the acrylamide solution for ultrasonic treatment, the ultrasonic power is 750 W, the ultrasonic time is 15 min; the mixed solution is transferred to a three-necked flask, the water bath temperature is increased to 70℃ under N2 atmosphere, 1.62 parts of N,N'-methylene bisacrylamide and 0.18 parts of ammonium persulfate are added and slowly stirred, until the system becomes viscous, stop stirring and keep for 3 h; the hydrogel is cut and soaked with 1200 parts of deionized water for 2 h, to remove the unreacted monomers; the hydrogel is replaced with 1500 parts of anhydrous ethanol for 48 h to replace the internal moisture of the hydrogel, until the hydrogel becomes a hard white blocky particle; the blocky particle is placed in a 70℃ air drying oven and dried to constant weight, after crushing and grinding, the particle is passed through a standard sieve of 100 mesh to obtain the wave-absorbing functional SAP particle.

[0018] On the basis of the above scheme, preferably, according to the mass fraction, the cement is 900-1100 parts, the wave-absorbing functional SAP is 48-72 parts, the tap water is 400-460 parts, and the water reducing agent is 2.8-3.2 parts.

[0019] On the basis of the above scheme, preferably, the mass ratio of the cement to the wave-absorbing functional SAP is (13-20):1.

[0020] On the basis of the above scheme, further preferably, according to the mass fraction, the cement is 1100 parts, the wave-absorbing functional SAP is 72 parts, the tap water is 430 parts, and the water reducing agent is 3 parts.

[0021] In the second aspect, a preparation method of the cement-based wave-absorbing material is provided, preferably, the cement and the wave-absorbing functional SAP are stirred uniformly, then the tap water and the water reducing agent are added and stirred uniformly, to obtain the cement-based wave-absorbing material.

[0022] On the basis of the above scheme, preferably, the particle size distribution of the wave-absorbing functional SAP is between 100 mesh and 200 mesh, the water reducing agent is a polycarboxylic acid type water reducing agent, the SAP is a polyacrylamide type, and the cement is ordinary portland cement.

[0023] The cement-based wave-absorbing material and the preparation method thereof have the following beneficial effects compared with the prior art:

[0024] (1) The application is based on the demand of considering the mechanical and wave absorbing performance of cement-based materials, and wave absorbing functional SAP is added in the process of preparing the cement-based materials, the water release of SAP enhances the wave absorbing capacity of the cement-based materials, and the wave absorbing agent nano Fe3O4 is loaded in the internal structure of the SAP network, so that the wave absorbing agent exists in the hole after the water release of SAP, the electromagnetic wave is reflected in the hole for many times, the contact times with the wave absorbing agent are increased, and the transmission distance in the cement-based materials is prolonged, so that the wave absorbing capacity of the cement-based materials is greatly improved; the cement-based materials mixed with the wave absorbing functional SAP have good wave absorbing capacity, and the mechanical properties are not obviously decreased, and the mechanical properties are better than those of the cement-based wave absorbing materials on the market, so that the prepared cement-based materials have good wave absorbing and mechanical properties;

[0025] (2) The synthesis method of the wave absorbing functional SAP provided by the application has low cost and stable product performance, does not need too many types of organic reagents, and does not need high temperature and high pressure synthesis conditions, so that the environmental problems caused by chemical reagents and energy consumption can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0027] Figure 1 The preparation process flow chart of the cement-based wave absorbing material of the application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the application will be clearly and completely described in combination with the embodiments of the application. Obviously, the described embodiments are only some 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 are within the protection scope of the application.

[0029] In the application, acrylamide and ammonium persulfate are purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., N,N'-methylenebisacrylamide is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., nano Fe3O4 is purchased from Shanghai Maikelin Biochemical Technology Co., Ltd., cement is purchased from Huaxin Cement Co., Ltd., and polycarboxylic acid type water reducing agent is purchased from Jiangsu Subo New Material Co., Ltd.

[0030] Example 1

[0031] The embodiment prepares a cement-based material with high strength and good wave absorption performance, and the preparation method comprises the following steps:

[0032] 18 g of acrylamide and 162 g of deionized water are added to a beaker, stirred at room temperature 25℃ for 15 min, and the stirring speed is 300 rpm / min; 90 g of nano Fe3O4 is added to the acrylamide solution for ultrasonic treatment, the ultrasonic power is 750 W, and the ultrasonic time is 15 min; the mixed solution is transferred to a three-necked flask, the temperature of the water bath is increased to 70℃ under N2 atmosphere, 1.62 g of N,N'-methylene bisacrylamide and 0.18 g of ammonium persulfate are added and slowly stirred, until the system becomes viscous, stop stirring and keep for 3 h; the hydrogel is cut and soaked with 1200 g of deionized water for 2 h to remove the unreacted monomers; the hydrogel is soaked with 1500 g of anhydrous ethanol for 48 h to replace the internal moisture of the hydrogel, until the hydrogel becomes a hard white blocky particle; the blocky particle is placed in a 70℃ air drying oven and dried to constant weight, after crushing and grinding, the particle is passed through a standard sieve with a mesh number of 100 to obtain the wave absorption functional SAP particle;

[0033] 1100 g of cement and 72 g of the wave absorption functional SAP are stirred uniformly, 430 g of tap water and 3 g of polycarboxylic acid type water reducing agent are added and stirred to prepare the cement-based material with high strength and good wave absorption performance.

[0034] Example 2

[0035] The embodiment prepares a cement-based material with high strength and good wave absorption performance, and the preparation method comprises the following steps:

[0036] 12 g of acrylamide and 150 g of deionized water are added to a beaker, stirred at room temperature 25℃ for 10 min, and the stirring speed is 200 rpm / min; 75 g of nano Fe3O4 is added to the acrylamide solution for ultrasonic treatment, the ultrasonic power is 600 W, and the ultrasonic time is 10 min; the mixed solution is transferred to a three-necked flask, the temperature of the water bath is increased to 70℃ under N2 atmosphere, 1.44 g of N,N'-methylene bisacrylamide and 0.12 g of ammonium persulfate are added and slowly stirred, until the system becomes viscous, stop stirring and keep for 3 h; the hydrogel is cut and soaked with 1080 g of deionized water for 2 h to remove the unreacted monomers; the hydrogel is soaked with 1440 g of anhydrous ethanol for 48 h to replace the internal moisture of the hydrogel, until the hydrogel becomes a hard white blocky particle; the blocky particle is placed in a 70℃ air drying oven and dried to constant weight, after crushing and grinding, the particle is passed through a standard sieve with a mesh number of 100 to obtain the wave absorption functional SAP particle;

[0037] The 900 g cement is uniformly stirred with 48 g of the wave-absorbing functional SAP, 400 g of tap water and 2.8 g of polycarboxylic acid type water reducing agent are added and stirred to prepare a high-strength cement-based material with good wave-absorbing performance.

[0038] Example 3

[0039] The high-strength cement-based material with good wave-absorbing performance is prepared, and the preparation method comprises the following steps:

[0040] The 24 g of acrylamide and 174 g of deionized water are added to a beaker and stirred at room temperature of 25℃ for 20 min at a stirring speed of 500 rpm / min. The 105 g of nano Fe3O4 is added to the acrylamide solution for ultrasonic treatment at an ultrasonic power of 800 W for 20 min. The mixed solution is transferred to a three-necked flask, the temperature of the water bath is increased to 70℃ under N2 atmosphere, 1.80 g of N,N'-methylene bisacrylamide and 0.24 g of ammonium persulfate are added and slowly stirred until the system becomes viscous, then the stirring is stopped and the system is kept for 4 h. The hydrogel is cut and soaked in 1320 g of deionized water for 2 h to remove the unreacted monomers. The hydrogel is soaked in 1560 g of anhydrous ethanol for 48 h to replace the internal moisture of the hydrogel until the hydrogel becomes a hard white blocky particle. The blocky particle is placed in a 70℃ air drying oven for drying to constant weight. After crushing and grinding, the particle is passed through a standard sieve of 100 mesh to obtain the wave-absorbing functional SAP particle.

[0041] The 1000 g of cement is uniformly stirred with 60 g of the wave-absorbing functional SAP, 460 g of tap water and 3.2 g of polycarboxylic acid type water reducing agent are added and stirred to prepare a high-strength cement-based material with good wave-absorbing performance.

[0042] Example 4

[0043] The high-strength cement-based material with good wave-absorbing performance is prepared, and the preparation method comprises the following steps:

[0044] Put 12 g of acrylamide and 174 g of deionized water into a beaker, stir at room temperature 25℃ for 15 min, the stirring speed is 400 rpm / min; 105 g of nano Fe3O4 is added into the acrylamide solution for ultrasonic treatment, the ultrasonic power is 750 W, and the ultrasonic time is 15 min; the mixed solution is transferred to a three-necked flask, the water bath temperature is raised to 70℃ under N2 atmosphere, 1.80 g of N,N'-methylene bisacrylamide and 0.24 g of ammonium persulfate are added and slowly stirred, until the system becomes sticky, stop stirring and keep for 3 h; the hydrogel is cut and soaked with 1320 g of deionized water for 2 h to remove the unreacted monomers; replace the internal moisture of the hydrogel with 1560 g of anhydrous ethanol for 48 h, until the hydrogel becomes a hard white blocky particle; the blocky particles are placed in a 70℃ air drying oven to dry to constant weight, after crushing and grinding, the particles are passed through a standard sieve of 100 mesh to obtain wave-absorbing functional SAP particles;

[0045] Stir 1100 g of cement and 60 g of wave-absorbing functional SAP uniformly, then add 460 g of tap water and 3.2 g of polycarboxylic acid type water reducer for stirring, to prepare a high-strength cement-based material with good wave-absorbing performance.

[0046] Example 5

[0047] This example prepares a high-strength cement-based material with good wave-absorbing performance, and the preparation method comprises the following steps:

[0048] Put 24 g of acrylamide and 150 g of deionized water into a beaker, stir at room temperature 25℃ for 20 min, the stirring speed is 350 rpm / min; 75 g of nano Fe3O4 is added into the acrylamide solution for ultrasonic treatment, the ultrasonic power is 650 W, and the ultrasonic time is 20 min; the mixed solution is transferred to a three-necked flask, the water bath temperature is raised to 70℃ under N2 atmosphere, 1.44 g of N,N'-methylene bisacrylamide and 0.12 g of ammonium persulfate are added and slowly stirred, until the system becomes sticky, stop stirring and keep for 4 h; the hydrogel is cut and soaked with 1080 g of deionized water for 2 h to remove the unreacted monomers; replace the internal moisture of the hydrogel with 1440 g of anhydrous ethanol for 48 h, until the hydrogel becomes a hard white blocky particle; the blocky particles are placed in a 70℃ air drying oven to dry to constant weight, after crushing and grinding, the particles are passed through a standard sieve of 100 mesh to obtain wave-absorbing functional SAP particles;

[0049] Stir 1000 g of cement and 48 g of wave-absorbing functional SAP uniformly, then add 400 g of tap water and 2.8 g of polycarboxylic acid type water reducer for stirring, to prepare a high-strength cement-based material with good wave-absorbing performance.

[0050] Example 6

[0051] The embodiment prepares a cement-based material with high strength and good wave absorption performance. The preparation method is the same as that in Embodiment 1, except that 12 g of acrylamide and 105 g of nano-Fe3O4 are added.

[0052] Embodiment 7

[0053] The embodiment prepares a cement-based material with high strength and good wave absorption performance. The preparation method is the same as that in Embodiment 1, except that 24 g of acrylamide and 75 g of nano-Fe3O4 are added.

[0054] Embodiment 8

[0055] The embodiment prepares a cement-based material with high strength and good wave absorption performance. The preparation method is the same as that in Embodiment 1, except that 48 g of wave absorption functional SAP is added.

[0056] Embodiment 9

[0057] The embodiment prepares a cement-based material with high strength and good wave absorption performance. The preparation method is the same as that in Embodiment 1, except that 60 g of wave absorption functional SAP is added.

[0058] Comparative Example 1

[0059] 1100 g of cement is uniformly stirred with 12 g of ordinary polyacrylamide type SAP, and then 430 g of tap water and 3 g of polycarboxylic acid type water reducer are added and stirred to prepare a cement-based material.

[0060] Comparative Example 2

[0061] 1100 g of cement is uniformly stirred with 60 g of nano-Fe3O4, and then 430 g of tap water and 3 g of polycarboxylic acid type water reducer are added and stirred to prepare a cement-based material.

[0062] Comparative Example 3

[0063] The cement-based material prepared in this comparative example has the same preparation method as in Embodiment 1, except that 9 g of acrylamide and 111 g of nano-Fe3O4 are added.

[0064] Comparative Example 4

[0065] The cement-based material prepared in this comparative example has the same preparation method as in Embodiment 1, except that 27 g of acrylamide and 72 g of nano-Fe3O4 are added.

[0066] Comparative Example 5

[0067] The cement-based material prepared in the present comparative example has the same preparation method as that of Example 1, except that the added wave-absorbing functional SAP is 84 g.

[0068] Comparative Example 6

[0069] The cement-based material prepared in the present comparative example has the same preparation method as that of Example 1, except that the added wave-absorbing functional SAP is 36 g.

[0070] The cement-based materials prepared in Examples 1-9 and Comparative Examples 1-6 are subjected to wave-absorbing and mechanical property tests, respectively, and the results are shown in Table 1.

[0071] Table 1 Wave-absorbing and mechanical property test data of the cement-based materials of Examples 1-9 and Comparative Examples 1-6

[0072]

[0073] As shown in Table 1, the cement-based material prepared in the optimal example of the present application has a maximum reflection loss of -12.5 dB in the frequency range of 8-18 GHz, an effective wave-absorbing bandwidth of 10.0 GHz (RL<-7 dB), and a 28-day compressive strength of 36.4 MPa, which indicates that the cement-based wave-absorbing material prepared in the present application can effectively solve the technical problem that the existing cement-based wave-absorbing materials cannot simultaneously have good wave-absorbing performance and mechanical properties.

[0074] When the ordinary polyacrylamide type SAP without nano-Fe3O4 modification or only nano-Fe3O4 is added, the wave-absorbing performance of the prepared cement-based material is greatly reduced; when the proportion of acrylamide and nano-Fe3O4 added during the synthesis of the wave-absorbing functional SAP is too low or too high, the wave-absorbing performance of the cement-based material is poor; when the content of the added wave-absorbing functional SAP is too low, the wave-absorbing performance of the cement-based material is poor due to its poor wave-transmitting ability; when the content of the added wave-absorbing functional SAP is too high, the mechanical properties of the cement-based material are greatly reduced despite its good wave-absorbing performance.

[0075] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A cement-based absorbing material, characterized by: The raw materials of the cement-based absorbing material include cement, absorbing functional SAP, tap water and a water reducer; in terms of mass, the cement is 900-1100 parts, the absorbing functional SAP is 48-72 parts, the tap water is 400-460 parts, and the water reducer is 2.8-3.2 parts; The preparation method of the wave-absorbing functional SAP comprises the following steps: S1, add acrylamide and deionized water into a beaker, stir until the acrylamide is completely dissolved, then add nano-Fe3O4 and perform ultrasonic treatment; S2, heating the mixed solution in step S1 under a nitrogen atmosphere, adding N,N'-methylenebisacrylamide and ammonium persulfate, stirring until the system becomes viscous, stopping stirring and keeping warm for 2-4 hours; S3, cutting the hydrogel obtained in step S2 into pieces, and soaking them in deionized water and then in anhydrous ethanol until the hydrogel becomes hard white block particles; S4, drying the block particles obtained in step S3 to a constant weight, crushing, grinding, and sieving to obtain wave-absorbing functional SAP particles; In step S1, the amount of acrylamide is 12 to 24 parts by mass, and the amount of nano-Fe3O4 is 75 to 105 parts by mass.

2. The cement-based absorbing material according to claim 1, wherein: In step S1, the mass ratio of the nano-Fe3O4 to acrylamide is (4-7):

1.

3. The cement-based absorbing material according to claim 1, wherein: In steps S2 and S3, based on parts by mass, the amount of N,N'-methylenebisacrylamide is 1.44-1.80 parts, the amount of ammonium persulfate is 0.12-0.24 parts, and the amount of anhydrous ethanol is 1440-1560 parts.

4. The cement-based absorbing material according to claim 1, wherein: In step S1, the stirring speed is 200-500 rpm / min, the time is 10-20 min, the ultrasonic power is 600-800 W, and the time is 10-20 min.

5. The cement-based absorbing material according to claim 1, wherein: The mass ratio of the cement to the wave-absorbing functional SAP is (13-20):

1.

6. The method for preparing a cement-based wave absorbing material according to any one of claims 1 to 5, wherein: The cement and the wave-absorbing functional SAP are mixed evenly, and then tap water and a water-reducing agent are added and mixed evenly to obtain a cement-based wave-absorbing material.

7. The method for preparing a cement-based wave absorbing material according to claim 6, wherein: The particle size of the wave-absorbing functional SAP is distributed between 100 meshes and 200 meshes, and the water reducer is a polycarboxylic acid water reducer.

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