CN114907076A - Method for synergistically improving dynamic property and wave absorption property of concrete by using nano particles - Google Patents
Method for synergistically improving dynamic property and wave absorption property of concrete by using nano particles Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/0076—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials characterised by the grain distribution
- C04B20/008—Micro- or nanosized fillers, e.g. micronised fillers with particle size smaller than that of the hydraulic binder
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00241—Physical properties of the materials not provided for elsewhere in C04B2111/00
- C04B2111/00258—Electromagnetic wave absorbing or shielding materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Dispersion Chemistry (AREA)
- Nanotechnology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
Abstract
The invention discloses a method for improving dynamic property and wave absorption property of concrete by using nano particles in a synergistic manner, which relates to the technical field of concrete processing and comprises the following steps: (1) preparing a nanoparticle dispersion liquid; (2) preparing mixed ash; (3) preparing mortar; (4) preparing nano concrete; (5) and (5) molding. The invention fully utilizes the excellent properties of the nano particles in the aspects of physics, chemistry, magnetism and the like, realizes the synergistic improvement of the static and dynamic mechanical properties and the wave absorption property of the concrete, and promotes the development of the concrete material towards high performance and multifunction. By adopting a multi-component composite optimization mode, two or more nano-particles with complementary advantages are mixed into the concrete together in a proper amount, so that the nano-particles can obtain broadband strong wave absorption characteristics, and the radar reflectivity in a full frequency band range (2 GHz-18 GHz) can be lower than-8 dB.
Description
Technical Field
The invention belongs to the technical field of concrete processing, and particularly relates to a method for improving dynamic characteristics and wave absorption performance of concrete by using nanoparticles in a synergistic manner.
Background
The concrete is the most important basic raw material in building materials, has important strategic guarantee effect on national economy and social development, and is widely applied to the fields of civil buildings and military engineering. Concrete will remain the dominant building material irreplaceable to human society for a considerable period of time in the future.
In civil buildings, on one hand, cement-based materials bear normal design loads and also bear dynamic loads such as different types of rapidly-changing impact and collision in the using process of the cement-based materials. For example, high-rise buildings and bridge structures are occasionally subjected to wind load, airport runways are subjected to impact load when airplanes take off and land, containment vessels of nuclear power plants can be subjected to impact action and explosion influence, and almost all building structures can be subjected to earthquake load. Therefore, in order to meet the requirements of hurricane resistance, strong shock resistance and explosion resistance of civil buildings, the dynamic characteristics of the concrete material need to be further improved. On the other hand, with the development of modern high and new technologies, electromagnetic radiation from computers, mobile phones, communication cables, base stations, and the like has become a new social public nuisance. Electromagnetic pollution caused by electromagnetic radiation is classified as fourth environmental pollution following atmospheric pollution, water source pollution and noise pollution, and the problems of safety protection and effective absorption of electromagnetic waves are more and more concerned and greatly emphasized by people. The adoption of the electromagnetic shielding concrete material is one of effective ways for solving the electromagnetic radiation hazard of civil buildings. In military engineering, first, military engineering is extremely easy to find in enemy radar detection. Secondly, military engineering is extremely easy to destroy under the striking action of high-precision large-equivalent killer weapons of enemies. The building material is a key factor influencing the impact load resistance and electromagnetic radiation resistance of engineering facilities, and the concrete material needs to be continuously improved to adapt to increasingly harsh civil and military requirements, so that the improvement on the dynamic property and the wave absorbing performance of the concrete material is very necessary.
CN202010937305.0 discloses a method for improving concrete dynamic characteristics by applying a multi-scale fiber structure, which is characterized in that nano-level carbon nanotubes are grafted to the surface of micro-level carbon fibers to form a multi-level multi-scale fiber reinforcement which can be well bonded with concrete in a concrete matrix, thereby reducing the development of concrete cracks, improving the concrete strength and obviously improving the dynamic strength of the prepared concrete. However, the use of multi-scale fibrous structures can only improve the dynamic properties of concrete.
CN201510291886.4 discloses an electromagnetic wave-absorbing concrete and a preparation method thereof, wherein the electromagnetic wave-absorbing concrete takes wave-absorbing function ceramsite and wave-absorbing cement slurry as raw materials, the wave-absorbing function ceramsite is taken as aggregate, and a wave-absorbing agent is added into the wave-absorbing cement slurry, so that the electromagnetic wave-absorbing concrete and the wave-absorbing cement slurry jointly play a role in electromagnetic wave absorption and have good electromagnetic wave-absorbing efficacy. However, the effective wave-absorbing frequency band is 8-18 GHz, and the wave-absorbing performance in the frequency band of 2-8 GHz is not good.
In addition, with the continuous development and maturity of nanotechnology, the nanometer materials develop rapidly, and are widely applied to the fields of chemical industry, materials, aerospace, medicine and the like, so that great achievements are achieved. Nanomaterials possess special effects not possessed by macroscopic substances: the small-size effect, the surface and interface effect, the quantum effect and the macroscopic quantum tunneling effect also have a series of unique performances in aspects such as electromagnetism, photochemistry and the like, and further present a plurality of surprising properties. Therefore, the nano materials with a plurality of excellent characteristics are compounded into the concrete as the dispersion reinforcing phase to prepare the nano concrete, thereby synergistically improving the dynamic characteristics and the wave-absorbing performance of the concrete material and promoting the development of the concrete material to high performance and multiple functions, which is a direction with development prospect at present.
Disclosure of Invention
The invention aims to solve the existing problems and provides a method for synergistically improving the dynamic property and the wave absorption property of concrete by using nano particles.
The invention is realized by the following technical scheme:
a method for synergistically improving dynamic characteristics and wave absorption performance of concrete by using nano particles comprises the following steps:
(1) preparing a nanoparticle dispersion liquid:
stirring a water reducing agent and 3/4 water into a solution, adding nanoparticles into the solution, stirring at a high speed for 3min, and performing ultrasonic dispersion for 15min to prepare a nanoparticle dispersion liquid for later use;
(2) preparing mixed ash:
stirring the fly ash and 1/2 cement together to obtain uniformly mixed ash;
(3) preparing mortar:
adding the nanoparticle dispersion liquid into the mixed ash, and stirring for 30s to prepare mortar;
(4) preparing nano concrete:
sequentially adding sand and gravel into mortar, stirring for 30s, adding the residual 1/4 water and 1/2 cement into the mortar, stirring for 120s, and stirring into uniform mixture, namely fresh concrete;
(5) molding:
and (5) forming, vibrating and curing to obtain the nano concrete.
Further, the water reducing agent in the step (1) is a 40% solid content polycarboxylic acid high performance water reducing agent mother liquor produced by the chemical industry company in Shaanxi, and is used as a concrete water reducing agent and a nanoparticle dispersing agent, and the main performance indexes are as follows: the water reducing rate is more than or equal to 25 percent, the bleeding rate ratio is less than or equal to 60 percent, the gas content is less than or equal to 6.0 percent, the difference of the setting time is-210 min, the compressive strength ratio of 7d is more than or equal to 150, the compressive strength ratio of 28d is more than or equal to 140, the shrinkage ratio is less than or equal to 110 percent, and the appearance is brown transparent liquid.
Further, the nanoparticles in the step (1) are one of nano silicon dioxide, nano aluminum oxide and nano iron oxide produced by Hangzhou Wanjing company.
Further, the main part of the nano iron oxideThe performance is as follows: the model VK-E01 is brick red powder, the content is more than or equal to 99.8 percent, and the specific surface area is 80-90 m 2 The water content of the crystal form alpha is less than or equal to 0.1 percent; the main properties of the nano-alumina are as follows: model VK-L20Y, white powder with the content not less than 99.99 percent and the specific surface area of 150-200 m 2 The crystal form is gamma crystal form, the water content is less than or equal to 0.01 percent; the main properties of the nano-silica are as follows: model VK-SP15, white flocculent powder with content not less than 99.8%, specific surface area of 250 + -30 m 2 The crystal form is alpha crystal form, the water content is less than or equal to 0.1 percent;
further, the fly ash in the step (2) is I-grade (F-type) low-calcium fly ash produced from Shanxi Han City power plants.
Further, the cement in the step (2) is Shanxi Qinling brand PC32.5R cement, and the main properties are as follows: specific surface area is 486m 2 The standard consistency is 26.2 percent, the initial setting time is 129min, the final setting time is 209min, the stability is qualified, the breaking strength of 3d is 4.3MPa, and the compressive strength is 19 MPa.
Further, the volume weight of the crushed stone in the step (4) is 2750kg/m 3 The limestone macadam has the grain diameter of 5-10 mm accounting for 15% and the grain diameter of 10-20 mm accounting for 85%.
Further, the sand volume weight in the step (4) is 2730kg/m 3 Fineness modulus of 2.68 and bulk density of 1450kg/m 3 And dam river midsand containing 1.0% of mud.
Compared with the prior art, the invention has the following advantages:
1. the concrete provided by the invention has good dynamic characteristics and wave-absorbing performance, the dynamic compressive strength can be improved by 41.52%, the impact toughness can be increased by 54.38%, and the radar reflectivity in a full frequency band range (2 GHz-18 GHz) can be lower than-8 dB.
2. The invention fully utilizes the excellent physical, chemical, magnetic and other properties of the nano particles, realizes the synergistic improvement of the static and dynamic mechanical properties and the wave absorption property of the concrete, and promotes the development of the concrete material towards high performance and multiple functions.
(1) The physical filling effect of the nano particles reduces initial defects and harmful pores in concrete.
(2) The physical size effect of the nano particles provides crystal nuclei for the crystallization of cement hydration products, so that the crystals are more uniform and compact.
(3) The chemical activity of the nanoparticles can react with cement products to form high strength products, thereby reducing and refining the formation of harmful crystals.
(4) The excellent magnetic property of the nano particles can improve the dielectric constant and the magnetic conductivity of concrete and enhance the dielectric loss and the magnetic loss of the concrete to electromagnetic waves.
Through the advantages (1), (2) and (3) of the nano particles, the static mechanical property and the dynamic property of the concrete can be enhanced. By virtue of the advantages (4) of the nano particles, the wave-absorbing performance of the concrete can be enhanced.
3. The invention adopts a multi-element composite optimization mode, and two or more types of nano-particles with complementary advantages are mixed into the concrete together in a proper amount, so that the nano-particles can obtain broadband strong wave absorption characteristics, and the radar reflectivity in a full frequency band range (2 GHz-18 GHz) can be lower than-8 dB.
Drawings
FIG. 1 is a flow chart of the preparation of the nano concrete of the present application;
FIG. 2 is a graph comparing the dynamic compressive strength of the nano-concrete of the present application;
FIG. 3 is a comparison graph of the wave-absorbing properties of different nano-concretes according to the application;
FIG. 4 is a comparison graph of the wave-absorbing properties of nano concrete with different nano particle doping amounts.
Detailed Description
Example 1:
a method for synergistically improving dynamic characteristics and wave absorption performance of concrete by using nano particles comprises the following steps:
(1) preparing a nanoparticle dispersion liquid:
stirring a water reducing agent and 3/4 water into a solution, adding nanoparticles into the solution, stirring at a high speed for 3min, and performing ultrasonic dispersion for 15min to prepare a nanoparticle dispersion liquid for later use;
(2) preparing mixed ash:
stirring the fly ash and 1/2 cement together to obtain uniformly mixed ash;
(3) preparing mortar:
adding the nanoparticle dispersion liquid into the mixed ash, and stirring for 30s to prepare mortar;
(4) preparing nano concrete:
sequentially adding sand and gravel into mortar, stirring for 30s, adding the residual 1/4 water and 1/2 cement into the mortar, stirring for 120s, and stirring into uniform mixture, namely fresh concrete;
(5) molding:
and (5) forming, vibrating and curing to obtain the nano concrete.
The parameters of each raw material are as follows:
cement: shanxi Qinling ridge PC32.5R cement, the main properties are shown in Table 1 below.
TABLE 1 Property parameters of the cements
Fly ash: class I (class F) low calcium fly ash from Han City, Shaanxi.
Crushing stone: the volume weight is 2750kg/m 3 The limestone macadam (the particle size is 5-10 mm and 15%, and the particle size is 10-20 mm and 85%).
Sand: the volume weight is 2730kg/m 3 Fineness modulus of 2.68 and bulk density of 1450kg/m 3 And dam river sediment with mud content of 1.0%.
Water reducing agent: a40% solid content polycarboxylic acid high-performance water reducing agent mother liquor produced by chemical engineering companies in Shaanxi is used as a concrete water reducing agent and a nanoparticle dispersing agent, and main performance indexes are shown in Table 2 below.
TABLE 2 Performance parameters of Water reducing Agents
Water: tap water.
Nano-particles: 2.0 wt% of nano SiO is doped 2 (Nano SiO) 2 The mass of the inorganic nano material accounts for 2.0 percent of the total mass of the cement and the fly ash), and the concrete is the inorganic nano material modified concrete.
Example 2:
ordinary concrete without nano-particles.
The preparation method and the raw material parameters are the same as those of example 1.
Example 3:
2.0 wt% of nano Al is doped 2 O 3 The concrete of (2) is a nano metal oxide modified concrete.
The preparation method and the raw material parameters are the same as those of example 1.
Example 4:
2.0 wt% of nano Fe 2 O 3 The concrete of (2) is a nano metal oxide modified concrete.
The preparation method and the raw material parameters are the same as those of example 1.
Example 5:
2.0 wt% of nano SiO is doped 2 And 2.0 wt% of nano Fe 2 O 3 The concrete of (2) is a composite modified concrete of inorganic nano materials and nano metal oxides.
The preparation method and the raw material parameters are the same as those of example 1.
The nanoparticles in the above examples were: nanometer SiO produced by Hangzhou Wanjing company 2 Nano Al 2 O 3 Nano Fe 2 O 3 The main performance index of one of the above is shown in Table 3 below.
Wherein the nano Al 2 O 3 Nano Fe 2 O 3 Is a nano metal oxide, nano SiO 2 Is an inorganic nano material.
TABLE 3 type of nanoparticles and corresponding parameters
The raw material blending ratios of the above examples are shown in table 4 below:
TABLE 4 nanometer concrete mix proportion (unit: kg/m) 3 )
Note: PC denotes ordinary concrete without nanoparticles incorporated;
NS represents 2.0 wt% nano SiO 2 (Nano SiO 2) 2 The mass of the cement-fly ash accounts for 2.0 percent of the total mass of the cement and the fly ash; the same below) is inorganic nano-material modified concrete.
NA represents 2.0 wt% of nano Al 2 O 3 The concrete of (2) is a nano metal oxide modified concrete.
NF represents 2.0 wt% of nano Fe 2 O 3 The concrete of (2) is a nano metal oxide modified concrete.
NSF represents the doping of 2.0 wt% nano SiO 2 And 2.0 wt% of nano Fe 2 O 3 The concrete of (2) is a composite modified concrete of inorganic nano materials and nano metal oxides.
In order to compare the technical effects of the application, the concrete is prepared correspondingly by the methods of the above examples 1 to 5, and then the performance test is performed.
(1) Static mechanical properties
The static mechanical properties of the nano concrete are as follows 5:
TABLE 5 static mechanical Properties of the Nanocoretes
As can be seen from Table 5 above, (1) after the nanoparticles are doped, the static mechanical properties of the concrete can be improved. (2) Doped with nano Al 2 O 3 And then, the compressive strength of the concrete reaches 49.4MPa, the flexural strength reaches 4.9MPa, and the compressive strength and the flexural strength are respectively improved by 46.15 percent and 36.11 percent compared with the common concrete. (3) Doped with nano Fe 2 O 3 And then, the compressive strength of the concrete reaches 42.4MPa, the flexural strength reaches 5.2MPa, and the compressive strength and the flexural strength are respectively improved by 25.44% and 44.44% compared with the common concrete.
The nano particles have the following three main reasons for improving the static mechanical property of common concrete: (1) the filling effect of the nano particles is stabilized, and initial defects and harmful pores between a matrix and an aggregate interface are reduced.
(2) The nanoparticles are uniformly dispersed in the matrix and the extremely small size makes it easy to act as nuclei for the hydration products of the cement, making the crystals more uniform and dense, while preventing the formation of particles such as Ca (OH) 2 Etc. produce harmful crystals in the cement matrix. (3) In addition, a part of active particles participate in crystallization reaction, and different products have different effects on improving the strength of concrete.
The improvement effect of the nano particles on the static mechanical property of the concrete is different mainly due to the following three reasons: (1) the nanoparticles have different reactivity and there are different levels of optimum incorporation in the concrete. (2) The different grain diameters of the nano-particles have different filling effects on harmful defects, and the difference of the surface energy also causes the nano-particles to influence the nucleation effect of the crystals. (3) The nanoparticles are also distinguished by their own characteristics in terms of the reaction products.
(2) Dynamic characteristics
A. Dynamic compressive strength
The dynamic compressive strength can be considered as the ultimate strength when the concrete is damaged under the impact load, and is an important parameter for representing the impact resistance and the bearing capacity of the concrete.
The dynamic compressive strength of the nano concrete is shown in figure 2:
as can be seen from FIG. 2, the dynamic compressive strength of the concrete is increased after the nano particles are added under the same strain rate level, wherein the nano Al is 2 O 3 The effect of improving the dynamic compressive strength of the concrete is most obvious.
Selecting the strain rate to be 110-116 s -1 In between, the dynamic compressive strength of each group of nano concrete is shown in the following table 6:
table 6 shows that the strain rate is 110 to 116s -1 Dynamic compressive strength of each group of nano concrete
| Test piece number | Strain rate/s -1 | Dynamic compressive strength/MPa |
| PC | 115.40 | 44.63 |
| NS | 110.79 | 46.87 |
| NA | 114.26 | 63.16 |
| NF | 110.69 | 52.95 |
| NSF | 112.97 | 54.98 |
As can be seen from Table 6, the dynamic compressive strength of the ordinary concrete is 44.63MPa in the strain rate range, and the dynamic compressive strength of the concrete is increased after the nano-particles are added. Doped with nano Al 2 O 3 Then, the dynamic compressive strength of the concrete is increased by 41.52%. Doped with nano Fe 2 O 3 Then, the dynamic compressive strength of the concrete is increased by 18.64%. Simultaneously doping nano SiO 2 And nano Fe 2 O 3 The dynamic compressive strength of the concrete then increased 23.19%.
B. Impact toughness
The impact toughness is the ability of the concrete to absorb energy under the impact load, and is an important index for representing the impact resistance of the concrete. The impact toughness evaluation index can be measured by the specific energy absorption, which represents the energy absorbed by the concrete sample per unit volume during the impact loading process.
Selecting the strain rate to be 110-116 s -1 In between, the dynamic compressive strength of each group of nano concrete is shown in the following table 7:
TABLE 7 strain rate of 110-116 s -1 Dynamic compressive strength of each group of nano concrete
As can be seen from Table 7, the impact toughness of the ordinary concrete is 252.1KJ in the strain rate range, and the impact toughness of the concrete is increased after the nanoparticles are added. Doped with nano Al 2 O 3 After that, the concrete is punchedThe impact toughness is increased by 54.38%, and the amplification is maximum.
According to the dynamic compressive strength index and the impact toughness index, the dynamic property of the concrete can be improved by adding the nano particles.
(6) Wave absorbing property
A. Wave absorbing performance of different nano concrete
When the thickness of the nano concrete is 50mm, the reflectivity is as shown in figure 3:
as can be seen from FIG. 3, (1) nano SiO is simultaneously doped 2 And nano Fe 2 O 3 And then, the radar reflectivity of the concrete in the full frequency band range (2 GHz-18 GHz) is lower than-8 dB. (2) Doped with nano Fe 2 O 3 Later, the concrete has a smaller reflectivity in the low frequency range and a larger reflectivity at higher frequencies. A minimum of-13.56 dB occurs near the 2.56GHz frequency. (3) Independently doped with nano SiO 2 Nano Al 2 O 3 Later, the concrete has a slightly higher reflectivity in the low frequency range and a lower reflectivity at higher frequencies. The radar reflectivity is lower than-5 dB in the full frequency band range (2 GHz-18 GHz).
In conclusion, the inorganic nano material and nano metal oxide composite modified concrete has the best wave-absorbing performance.
The single nano-particle is doped into the concrete to hardly meet the dual requirements of impedance matching and strong absorption, and the inorganic nano-material and the nano-metal oxide are compounded and doped into the concrete in a mode of compounding multi-element materials and complementing various wave-absorbing materials, so that the electromagnetic loss capacity of the concrete can be improved, and the purpose of lower reflectivity of the concrete in a wider frequency range is achieved.
B. Wave absorbing performance of nano concrete with different nano particle mixing amounts
NF-2 means 2.0 wt% of nano Fe 2 O 3 The concrete of (2); NF-5 means doping 5.0 wt% of nano Fe 2 O 3 The concrete of (2). When the thickness of the nano concrete is 50mm, the reflectivity is as shown in figure 4:
as can be seen from fig. 4, (1) the radar reflectivity curve of the nano concrete with different nano particle loadings has a consistent overall trend in the full frequency range. (2) When the frequency is 2.56GHz, the radar reflectivity of the nano concrete reaches the minimum value, and when the doping amount of the nano particles is 2.0% and 5.0%, the radar reflectivity of the nano concrete is respectively-13.6 dB and-16.7 dB. (3) In the full frequency band range (2 GHz-18 GHz), the radar reflectivity of NF-5 is lower than-6 dB. In the frequency range of 2 GHz-14 GHz, the radar reflectivity of NF-5 is lower than-10 dB. (4) By properly increasing the doping amount of the nano particles, the radar reflectivity of the nano concrete can be improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention, and the present invention is not limited to the illustrated embodiments, and all the modifications and equivalents of the embodiments may be made without departing from the spirit and scope of the present invention.
Claims (8)
1. A method for synergistically improving dynamic characteristics and wave absorption performance of concrete by using nano particles is characterized by comprising the following steps:
(1) preparing a nanoparticle dispersion liquid:
stirring a water reducing agent and 3/4 water into a solution, adding nanoparticles into the solution, stirring at a high speed for 3min, and performing ultrasonic dispersion for 15min to prepare a nanoparticle dispersion liquid for later use;
(2) preparing mixed ash:
stirring the fly ash and 1/2 cement together to obtain uniformly mixed ash;
(3) preparing mortar:
adding the nanoparticle dispersion liquid into the mixed ash, and stirring for 30s to prepare mortar;
(4) preparing nano concrete:
sequentially adding sand and gravel into mortar, stirring for 30s, adding the residual 1/4 water and 1/2 cement into the mortar, stirring for 120s, and stirring into uniform mixture, namely fresh concrete;
(5) molding:
and (5) forming, vibrating and curing to obtain the nano concrete.
2. The method for synergistically improving the dynamic property and the wave absorption property of the concrete by using the nanoparticles as claimed in claim 1, wherein the water reducing agent in the step (1) is a 40% solid content polycarboxylic acid high performance water reducing agent mother liquor produced by the chemical industry company of Shaanxi, and is used as a concrete water reducing agent and a nanoparticle dispersing agent, and the main performance indexes are as follows: the water reducing rate is more than or equal to 25 percent, the bleeding rate ratio is less than or equal to 60 percent, the gas content is less than or equal to 6.0 percent, the difference of the setting time is-210 min, the compressive strength ratio of 7d is more than or equal to 150, the compressive strength ratio of 28d is more than or equal to 140, the shrinkage ratio is less than or equal to 110 percent, and the appearance is brown transparent liquid.
3. The method as claimed in claim 1, wherein the nanoparticles used in step (1) are selected from one of nano-silica, nano-alumina and nano-iron oxide manufactured by Hangzhou Wanjing company.
4. The method for synergistically improving the dynamic property and the wave absorption property of the concrete by using the nano-particles as claimed in claim 3, wherein the main properties of the nano-iron oxide are as follows: the model VK-E01 is brick red powder, the content is more than or equal to 99.8 percent, and the specific surface area is 80-90 m 2 The water content is less than or equal to 0.1 percent; the main properties of the nano-alumina are as follows: model VK-L20Y, white powder with the content not less than 99.99 percent and the specific surface area of 150-200 m 2 The crystal form is gamma crystal form, the water content is less than or equal to 0.01 percent; the main properties of the nano-silica are as follows: model VK-SP15, white flocculent powder with content not less than 99.8%, specific surface area of 250 + -30 m 2 The crystal form is alpha crystal form, the water content is less than or equal to 0.1 percent.
5. The method for synergistically improving the dynamic property and the wave absorption property of the concrete by using the nano-particles as claimed in claim 1, wherein the fly ash in the step (2) is I-grade low-calcium fly ash produced from Shanxi Han City power plant.
6. The method for synergistically improving the dynamic properties and the wave absorption properties of concrete by using nanoparticles as claimed in claim 1, wherein the nanoparticles are selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium hydroxideThe cement in the step (2) is Shanxi Qinling brand PC32.5R cement, and the main properties are as follows: specific surface area of 486m 2 The standard consistency is 26.2 percent, the initial setting time is 129min, the final setting time is 209min, the stability is qualified, the breaking strength of 3d is 4.3MPa, and the compressive strength is 19 MPa.
7. The method for synergistically improving the dynamic characteristics and the wave absorption performance of concrete by using nano-particles as claimed in claim 1, wherein the volume weight of the crushed stone in the step (4) is 2750kg/m 3 The limestone macadam has the grain diameter of 5-10 mm accounting for 15% and the grain diameter of 10-20 mm accounting for 85%.
8. The method for synergistically improving the dynamic characteristics and the wave absorption performance of concrete by using nano-particles as claimed in claim 1, wherein the sand volume weight in the step (4) is 2730kg/m 3 The fineness modulus is 2.68, and the bulk density is 1450kg/m 3 And dam river midsand containing 1.0% of mud.
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