CN116335269A - 3D electromagnetic wave-absorbing concrete super structure based on optimized pavement frequency directional steel fibers - Google Patents

3D electromagnetic wave-absorbing concrete super structure based on optimized pavement frequency directional steel fibers Download PDF

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Publication number
CN116335269A
CN116335269A CN202310359051.2A CN202310359051A CN116335269A CN 116335269 A CN116335269 A CN 116335269A CN 202310359051 A CN202310359051 A CN 202310359051A CN 116335269 A CN116335269 A CN 116335269A
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concrete
steel fibers
printing
electromagnetic wave
frequency
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王翔宇
孙浚博
刘淼
颜建伟
王雨飞
唐玮晨
杨超
雷祖祥
徐星隆
方焘
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Liyang Smart City Research Institute Of Chongqing University
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Liyang Smart City Research Institute Of Chongqing University
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • B33Y70/10—Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/16—Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material
    • E04B1/167—Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material with permanent forms made of particular materials, e.g. layered products
    • 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
    • C04B2111/00034—Physico-chemical characteristics of the mixtures
    • C04B2111/00181—Mixtures specially adapted for three-dimensional printing (3DP), stereo-lithography or prototyping
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention relates to a 3D electromagnetic wave-absorbing concrete super structure based on optimized paving frequency directional steel fibers, wherein the main body of the concrete super structure is obtained by an inner and outer multi-circle concrete strip in a 3D printing mode of a loop-shaped printing path in an up-down multi-layer mode, a plurality of circles of concrete strips are formed after each layer of printing, and the width T of each circle of concrete strip is 11-13mm; the layer height H is less than or equal to 7mm; the value range of the layer number K is as follows: k is more than or equal to 3 and less than or equal to 5; the volume doping amount of the oriented steel fibers is more than or equal to 0.5 percent and less than or equal to 1 percent, and the length l=30-50 mm of the oriented steel fibers; the length direction of the oriented steel fibers is parallel to the running direction of the zigzag printing path, the oriented steel fibers are paved on the surface of the concrete strip of each layer, and each layer of oriented steel fibers are paved according to paving frequency. The concrete super structure with the broadband electromagnetic absorption of 6.95GHz and the strong electromagnetic absorption peak of-17.2 dB (more than 97% of electromagnetic wave absorption) in the C wave band (4-8 GHz) and the X wave band (8-12 GHz) is obtained.

Description

3D electromagnetic wave-absorbing concrete super structure based on optimized pavement frequency directional steel fibers
Technical field:
the invention relates to the technical field of concrete, in particular to a 3D electromagnetic wave-absorbing concrete super structure based on directional steel fibers with optimized paving frequency.
Background
The 3D printing technology is a technology for constructing an object by using a bondable material such as powdered metal or plastic based on a digital model file in a layer-by-layer printing manner. The design concept can be quickly and accurately converted into a prototype or a part with a certain function so as to carry out quick evaluation, modification and functional test, thereby greatly shortening the development period, reducing the development cost and accelerating the progress of new products to the market. At present, the 3D printing technology is widely applied in the building field, and breaks through the traditional building material production mode.
The pollution of various electromagnetic radiation to the environment is increasingly serious, and meanwhile, the electromagnetic radiation pollution has great influence on the health of human bodies. The electromagnetic wave-absorbing concrete is a novel building material which combines the function and the structure of electromagnetic wave protection by modifying common concrete. The electromagnetic wave-absorbing concrete has an improvement and promotion effect on electromagnetic protection, can greatly promote the electromagnetic radiation protection capability of building structures such as television transmitting stations, base stations, microwave laboratories, hospitals, transformer substations and the like, reduces the influence of electromagnetic interference, and promotes the physical and mental health of human beings in an electromagnetic environment.
Disclosure of Invention
The invention aims to provide a 3D electromagnetic wave-absorbing concrete superstructure based on directional steel fibers with optimized paving frequency. The concrete super structure relies on the flexibility of an extrusion type 3D printing process, and combines mechanical pavement to obtain the concrete super structure with high electromagnetic absorption in C wave band (4-8 GHz) and X wave band (8-12 GHz).
In order to achieve the above purpose, the technical scheme of the invention is as follows:
A3D electromagnetic wave-absorbing concrete super structure based on optimized pavement frequency directional steel fibers is characterized in that a main body of the concrete super structure is obtained by an inner concrete strip and an outer concrete strip in a 3D printing mode of a loop-shaped printing path in an up-down multi-layer mode, a plurality of circles of concrete strips are formed after each layer of printing, and the width T of each circle of concrete strip is 11-13mm; the layer height H is less than or equal to 7mm; the value range of the layer number K is as follows: k is more than or equal to 3 and less than or equal to 5;
the volume doping amount of the oriented steel fibers is more than or equal to 0.5 percent and less than or equal to 1 percent, and the length l=30-50 mm of the oriented steel fibers; the length direction of the oriented steel fibers is parallel to the running direction of the zigzag printing path, the oriented steel fibers are paved on the surface of the concrete strip of each layer, and each layer of oriented steel fibers are paved according to paving frequency.
The determination process of the paving frequency is as follows:
according to the formula Vc=v T pi r 2 Calculating the volume Vc of single-layer concrete, wherein v is the printing speed of a spray head, t Total (S) The total duration of printing a layer of the square concrete strip, and r is the radius of the spray head;
knowing the volume doping amount p of the oriented steel fibers, calculating the volume Vf of the oriented steel fibers according to the formula vf=vc×p;
calculating the total number of single-layer oriented steel fibers according to the formula n=int [ Vf/(l a b) ], wherein l is the length of the steel fibers, a and b are the width and length of the cross section of the oriented steel fibers, and INT [ ] is a downward rounding function;
the first directional steel fiber starts to be laid for a time t 1 The time for the second oriented steel fiber to begin to lay is t 2 …, and so on, the time for the N directional steel fiber to begin to be laid is t N The 3D printing equipment prints according to the printing path of the shape of the circle as the start before laying the first directional steel fiber, and prints according to the printing path of the shape of the circle as the end after the last directional steel fiber is laid, the three-dimensional printing equipment comprises the following steps of
stat+t 1 +t 2 +t 3 +t 4 +……t N +end＝t Total (S) ，
Let t n ＝A^ n And take in stat+t 1 +t 2 +t 3 +t 4 +……t N +end＝t Total (S) Obtaining a frequency coefficient A, wherein A is less than 1, N is more than or equal to 1 and less than or equal to N, and N is a positive integer;
carry t according to frequency coefficient A n ＝A^ n The paving time of each directional steel fiber is obtained, namely the paving frequency of the directional steel fiber is determined.
The number of turns of each layer of concrete strip is 8-20; the length l=35-40 mm of the oriented steel fiber, the cross section of the oriented steel fiber is rectangular, the length of the rectangle is 2mm, and the width is 0.5mm; start=3.5s, end=5s; the layer height range is as follows: h is more than or equal to 4mm and less than or equal to 7mm.
The concrete super structure can achieve the effect of high electromagnetic absorption of C wave band (4-8 GHz) and X wave band (8-12 GHz); the concrete superstructure is repeated in a periodic mode, a concrete structure with square bottom surfaces of inner and outer multi-turn layers is formed, a plurality of fiber equivalent microscopic filters are formed by adjacent layers and adjacent-turn directional steel fibers, and periodically arranged wave surface grains are formed on the outer surfaces of the upper and lower multi-layer concrete.
The fiber equivalent micro-filter is a regular prism with the side length of 30mm-80 mm.
The concrete superstructure is an electromagnetic protection brick with different specifications, and the bottom surface of the electromagnetic protection brick is square; preferably, the electromagnetic protection brick has the following model: 400X 400mm, 300X 300mm, 250X 250mm or 330X 330mm.
The equipment used for printing the concrete superstructure comprises a 3D printer and a six-axis mechanical arm, wherein the 3D printer is used for obtaining a concrete strip from electromagnetic wave-absorbing concrete according to a zigzag printing path, the six-axis mechanical arm is used for directional laying of directional steel fibers, the laying of the directional steel fibers follows the printing process of the concrete strip, the concrete strip is printed from the center of a sample, the zigzag printing path is printed outwards in sequence, and the directional steel fibers are laid according to the laying frequency.
The printing parameters of the 3D printer are set as follows: the outlet cross section area of the printing nozzle is 115-120mm 2 The extrusion speed is 0.009-0.035m 3 And/h, the horizontal printing speed is 160-185cm/min, and the vertical printing speed is 0.6-0.85m/h;
when 3D printing is carried out, the electromagnetic wave absorbing concrete capable of 3D printing is pumped into a printing nozzle of a 3D printer, and printing is carried out after standing for 3-6 min.
The composition and the content of the electromagnetic wave-absorbing concrete capable of being printed in 3D are respectively as follows:
6.8-7.2 parts of quick hardening ordinary Portland cement;
6.9-7.1 parts of quartz sand;
1.65-1.75 parts of copper slag;
0.75-0.85 parts of silica fume;
0.09-0.15 part of water reducer;
0.28-0.71 part of copper powder, wherein the copper powder consists of brass powder and red copper powder, and the weight ratio of the brass powder to the red copper powder is 7:2.5-3.5;
0.04-0.07 part of basalt fiber with the length of 11-14 mm;
0.003-0.005 part of hydroxypropyl methyl cellulose with the viscosity of 2-7 ten thousand;
1.70-1.74 parts of water.
The average grain diameter of the brass powder is 55-75 mu m, and the pure copper content is 90-95%; the average grain diameter of the red copper powder is 50-80 mu m, and the pure copper content is 95-98%; the iron oxide content of the copper slag is above 53%, and the average grain diameter range is 100-150 mu m.
Compared with the existing concrete material, the invention has the beneficial effects that:
1) The steel fibers have strong magnetic conductivity and strong electric conductivity, the directional steel fibers are arranged in a three-dimensional space in the form of a super structure, the directional steel fibers form an equivalent micro-filter super structure in the three-dimensional space, because the fiber length is 35mm, the size of each fiber equivalent micro-filter is about 30mm-80mm, an electromagnetic absorption peak of a specific corresponding frequency range can be formed, the micro-filter structure with a local-level frequency selection function is skillfully constructed among the directional steel fibers through the setting of paving frequency, and the integral wave absorbing characteristic of the macroscopic structure is realized.
2) The electromagnetic wave-absorbing concrete surface layer of the concrete super structure forms periodically arranged wave surface lines by a printing process, so that the impedance of the composite material is changed from original stepwise mutation into continuous change, the direction of penetrating into the concrete super structure is changed, the direction of reflecting surface electromagnetic waves is changed, the received electromagnetic waves are reduced, the incidence times and the transmission distance of the electromagnetic waves can be increased, the loss probability is improved, certain probability of interference loss is also generated between multiple rows of reflected waves and refracted waves, and the electromagnetic wave super structure is very beneficial to the full incidence and loss of the electromagnetic waves, particularly oblique incidence electromagnetic waves.
3) The concrete superstructure of the invention can take the copper slag-copper powder wave absorber as a main body, and the copper powder wave absorber-steel fiber superstructure multiple composite electromagnetic wave absorbing consumption mechanism can be formed by matching with paved steel fibers, specifically, when electromagnetic waves propagate to the superstructure through air, partial energy is cancelled by vectors of wave surface lines, the rest electromagnetic waves enter the electromagnetic wave absorbing structure, the steel fibers form an equivalent microscopic filter superstructure to capture electromagnetic wave energy of each frequency section and enter an equivalent cavity, and finally the copper powder wave absorber converts the electromagnetic waves into current and a micro magnetic field through hysteresis loss and dielectric loss. In the frequency band of 1-18GHz, the electromagnetic wave absorption band with the electromagnetic wave absorption of more than 90% can reach 6.95GHz, and an electromagnetic wave extremum with the electromagnetic wave absorption of 97% is created.
4) The 3D printing is rapid and flexible, the degree of automation is high, and the preparation of the loop-type super structure can be realized with zero error. When the doping amount is too high, which is more than 1.5%, the direct reflection of electromagnetic waves is rapidly enhanced due to the fact that the metal property of the super structure is too high, so that the electromagnetic wave absorbing capacity is deteriorated, and when the doping amount is too low, which is less than 0.5%, the fiber aggregation effect is poor, so that an effective microscopic filter structure cannot be formed, and the electromagnetic wave absorbing effect is reduced. Compared with the traditional single-layer plate structure, the invention can lead the steel fibers to be arranged in a three-dimensional space in the form of a super structure, which can cause electromagnetic absorption peaks in a specific frequency band of C wave band (4-8 GHz) and X wave band (8-12 GHz), thereby skillfully constructing a plurality of resonance loops with local frequency selection functions aiming at each frequency band. Manufacturing a super-structure matrix in a mode of printing a cementing material, mine solid wastes and a loop-shaped printing path; and the paving frequency is flexibly controlled by means of a six-axis mechanical arm, and then the paving operation of 35mm steel fibers is carried out on the printed matrix material, so that the equivalent filter superstructure aiming at each frequency band is formed. In the embodiment, in the C wave band (4-8 GHz), the X wave band (8-12 GHz) achieves the concrete super structure with the broadband electromagnetic absorption of 6.95GHz and the strong electromagnetic absorption peak of-17.2 dB (more than 97 percent of electromagnetic absorption).
Drawings
Fig. 1 is a schematic structural diagram of a 3D electromagnetic wave-absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers.
Fig. 2 is a diagram of the construction effect of the 3D electromagnetic wave-absorbing concrete superstructure based on the optimized paving frequency oriented steel fibers of the present invention.
FIG. 3 is a graph showing the effect of electromagnetic wave absorption evaluation test on the concrete superstructure of examples 1-2.
Detailed Description
The present invention is further explained below with reference to examples and drawings, but is not to be construed as limiting the scope of the present application.
The invention relates to a 3D electromagnetic wave-absorbing concrete super structure based on directional steel fibers of optimized paving frequency, wherein a main body of the concrete super structure is obtained by an inner concrete strip and an outer concrete strip in a 3D printing mode of a loop-shaped printing path in an up-down multi-layer mode, a plurality of circles of concrete strips are formed after each layer of printing, and the width T of each circle of concrete strip is 11-13mm; the layer height H is less than or equal to 7mm; the value range of the layer number K is as follows: k is more than or equal to 3 and less than or equal to 5;
the volume doping amount of the oriented steel fibers is more than or equal to 0.5 percent and less than or equal to 1 percent, and the length l=30-50 mm of the oriented steel fibers; the length direction of the oriented steel fibers is parallel to the running direction of the zigzag printing path, the oriented steel fibers are paved on the surface of the concrete strip of each layer, and each layer of oriented steel fibers are paved according to paving frequency.
The determination process of the paving frequency is as follows:
according to the formula Vc=v T pi r 2 Calculating the volume Vc of single-layer concrete, wherein v is the printing speed of a spray head, t Total (S) The total duration of printing a layer of the square concrete strip, and r is the radius of the spray head;
knowing the volume doping amount p of the oriented steel fibers, calculating the volume Vf of the oriented steel fibers according to the formula vf=vc×p;
calculating the total number of single-layer oriented steel fibers according to the formula n=int [ Vf/(l a b) ], wherein l is the length of the steel fibers, a and b are the width and length of the cross section of the oriented steel fibers, and INT [ ] is a downward rounding function;
the first directional steel fiber starts to be laid for a time t 1 The time for the second oriented steel fiber to begin to lay is t 2 …, and so on, the time for the N directional steel fiber to begin to be laid is t N The 3D printing equipment prints according to the printing path of the shape of the circle as the start before laying the first directional steel fiber, and prints according to the printing path of the shape of the circle as the end after the last directional steel fiber is laid, the three-dimensional printing equipment comprises the following steps of
stat+t 1 +t 2 +t 3 +t 4 +……t N +end＝t Total (S) ，
Let t n ＝A^ n And take in stat+t 1 +t 2 +t 3 +t 4 +……t N +end＝t Total (S) Obtaining a frequency coefficient A, wherein A is less than 1, N is more than or equal to 1 and less than or equal to N, and N is a positive integer;
carry t according to frequency coefficient A n ＝A^ n The paving time of each directional steel fiber is obtained, namely the paving frequency of the directional steel fiber is determined.
The paving process is realized by using the six-axis mechanical arm, the length direction of the directional steel fibers is consistent with the 3D printing running direction, and the steel fibers can be paved behind the concrete spray head and paved according to the paving frequency.
In the aspect of paving frequency, because the side length of the loop is gradually enlarged, the process of uniformly blanking and paving is not suitable, the direct reflection of electromagnetic waves is increased due to the excessively strong performance of the steel fiber around the centroid, meanwhile, the direct reflection of the electromagnetic waves is also increased due to the excessively sparse steel fiber in the edge area due to the reduced capability of absorbing electromagnetic waves through electromagnetic loss,
the concrete superstructure provided by the invention is printed, the printed structure is subjected to relevant performance test, namely construction evaluation and electromagnetic wave absorption performance evaluation, the printed structure is tested, the concrete superstructure is printed according to the test, the printed structure is prepared according to the preparation method, the smooth printing process can be ensured on the premise of meeting the proposed printing requirements, and the printed structure is stable and firm.
The electromagnetic wave absorption reflectivity test adopts an arched frame reflection method, and uses a vector network analyzer (Agilent N5232A) to emit electromagnetic waves, and the electromagnetic wave absorption reflectivity of the material is tested through the transmission of a transmitting head and a receiving head. The electromagnetic wave absorbing performance test of the invention refers to the national military standard method for testing the reflectivity of radar absorbing materials (GJB 2038-1994). The concrete involved in the electromagnetic wave-absorbing reflectivity test must undergo standard curing (relative humidity 95.+ -. 5% and curing temperature 20.+ -. 1 ℃) for at least 28 days. After curing, concrete test blocks with the size of 180mm and 180mm are obtained and dried at a low temperature of 60 ℃ to reduce the influence of the moisture content on the reflectivity of electromagnetic waves. A smooth 180mm aluminum plate was then placed under the concrete coupon and tested in the 1-18GHz band.
Example 1:
the 3D electromagnetic wave-absorbing concrete super structure based on the directional steel fibers with optimized paving frequency has the concrete strip width T of 12mm and the mass doping amount V of the directional steel fibers of 0.5%. Printing for pumping or mechanically conveying concrete slurry to 3D printerIn the printing nozzle, standing for 4min, wherein the standing time is the time from the preparation of concrete to the printing start, and the outlet cross section area of the printing nozzle is 120mm 2 The horizontal printing speed is 165cm/min, the vertical printing speed is 0.65m/h, and the extrusion speed is 0.01m 3 And/h, and then printing three layers according to the loop-shaped printing path.
The time start=3.5s that the 3D printing device printed according to the zigzag printing path before laying the first oriented steel fiber, and the time end=5s that the 3D printing device printed according to the zigzag printing path after laying the last oriented steel fiber
Then 3.5s+t 1 +t 2 +t 3 +t 4 +……t N +5＝t Total (S) ，
Let t n ＝A^ n (A is less than 1, N is more than or equal to 1 and less than or equal to N, N is a positive integer), and the frequency coefficient A is obtained to be 0.8 on the premise of knowing the total time length of printing a layer of the square concrete strip and the volume doping amount of the directional steel fibers, so that the time intervals of paving all the directional steel fibers are further obtained, and the paving frequency is determined.
The laying of the directional steel fibers follows the printing process of the concrete strip, the concrete strip starts to be printed from the center of the sample, the concrete strip is printed outwards in turn according to a loop-shaped printing path, and the directional steel fibers are laid according to the laying frequency.
The electromagnetic wave-absorbing concrete capable of being printed in 3D used in the embodiment is copper slag electromagnetic wave-absorbing concrete capable of being printed in 3D, and the concrete comprises the following components in parts by weight:
7.0 parts of 42.5# quick hardening ordinary Portland cement;
7.0 parts of quartz sand;
1.70 parts of copper slag;
0.8 parts of silica fume;
0.12 parts of water reducer;
0.3 parts of brass powder;
0.1 part of red copper powder;
0.05 part of basalt fiber with the length of 12 mm;
0.004 part of HPMC viscosity modifier with the viscosity of 5 ten thousand;
1.72 parts of water.
The mass doping amount V of the oriented steel fiber is 0.5 percent.
The specific surface area of the quick hardening ordinary Portland cement is 348m 2 Per kg, density of 3.0g/cm 3 The water consumption of the standard consistency is 25.9%, the initial setting time is 170min, the final setting time is 210min, the loss on ignition is 3.5%, the magnesium oxide content is 2.18%, the flexural strength in 3 days is 5.7MPa, and the compressive strength in 3 days is 30MPa.
The density of the silica fume is 2.3g/cm 3 Specific surface area of 25-29 m 2 /g；
The water reducer is a polycarboxylic acid water reducer, the water reducing rate is more than 30%, and the solid content is 36.5%;
the density of the copper slag is 2.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The average grain diameter is 106 mu m, and the solid content of ferric oxide is 53%;
the average grain diameter of the brass powder is 60 mu m, D0.5 is 55 mu m, and the pure copper content is 93%;
the average grain diameter of the red copper powder is 65 mu m, the D0.5 is 60 mu m, and the pure copper content is 98%.
The average length of the oriented steel fiber is 35mm, the section width is 0.5mm, the section length is 2mm, and the tensile strength is>2850MPA, density 7.8g/mm 3 。
The preparation method of the copper slag electromagnetic wave-absorbing concrete capable of being printed in 3D mode comprises the following steps:
(1) The raw materials are divided into four groups according to parts by weight, wherein the first group comprises 7.0 parts of quick hardening Portland cement, 1.70 parts of copper slag and 7.0 parts of quartz sand, the second group comprises 0.8 parts of silica fume and 0.05 parts of basalt fiber, the third group comprises 0.12 parts of water reducer, 0.3 parts of brass powder, 0.1 parts of red copper powder and 1.72 parts of water and 0.004 parts of hydroxypropyl methyl cellulose;
(2) Simultaneously feeding the first group of raw materials into a 30L horizontal stirrer for mixing and stirring for 100s at a stirring speed of 45 r/min, then correspondingly simultaneously adding the second group of raw materials into the uniformly mixed mixture, and then mixing and stirring for 200s at a stirring speed of 45 r/min until the raw materials are completely and uniformly mixed;
(3) And (3) respectively and uniformly mixing the raw materials of the third group and the fourth group, then respectively adding the mixed materials of the third group into the finished mixture obtained in the step (2), stirring for 80s, stirring the fourth group, and stirring for 180s again to obtain the concrete.
Electromagnetic wave absorption performance evaluation:
the embodiment tests according to the requirements of the method for testing the reflectivity of radar absorbing materials (GJB 2038-1994). The test results are shown in FIG. 3. A bandwidth below-10 dB of 6.95GHz means that at least 90% of the electromagnetic waves are absorbed, and a peak value of-17.2 dB means that 97% of the electromagnetic waves are absorbed. Because the length of the fiber is 35mm, the size of each fiber equivalent micro-filter is about 30mm-80mm, the corresponding frequency has strong electromagnetic wave absorbing performance in the frequency band of 6GHz-15GHz, from the test result, 90% electromagnetic wave absorbing capability is broken through at the frequency of 4.45GHz (wavelength 67 mm), and the high electromagnetic wave absorbing performance up to 11.4GHz (wavelength 26 mm) is maintained, so that the theory of the equivalent micro-filter superstructure is verified.
Example 2:
the 3D electromagnetic wave-absorbing concrete super structure based on the directional steel fibers with optimized paving frequency has the concrete strip width T of 12mm and the mass doping amount V of the directional steel fibers of 1%. Pumping or mechanically conveying concrete slurry into a printing nozzle of a 3D printer, and standing for 4min, wherein the standing time is the time from concrete preparation to printing start, and the outlet cross section area of the printing nozzle is set to be 120mm 2 The horizontal printing speed is 165cm/min, the vertical printing speed is 0.65m/h, and the extrusion speed is 0.01m 3 And/h then printing three layers. The specific printing process and the determination process of the paving frequency are the same as those of example 1.
The copper slag electromagnetic wave-absorbing concrete capable of being printed in 3D mode comprises the following components in parts by weight:
6.8 parts of 42.5# quick hardening ordinary Portland cement;
6.9 parts of quartz sand;
1.65 parts of copper slag;
0.75 parts of silica fume;
0.14 parts of water reducer;
0.2 parts of brass powder;
0.09 part of red copper powder;
0.06 parts of basalt fiber with the length of 12 mm;
0.004 part of HPMC viscosity modifier with the viscosity of 5 ten thousand;
1.70 parts of water.
The specific surface area of the quick hardening ordinary Portland cement is 348m 2 Per kg, density of 3.0g/cm 3 The water consumption of the standard consistency is 25.9%, the initial setting time is 170min, the final setting time is 210min, the loss on ignition is 3.5%, the magnesium oxide content is 2.18%, the flexural strength in 3 days is 5.7MPa, and the compressive strength in 3 days is 30MPa.
The density of the silica fume is 2.3g/cm 3 Specific surface area of 25-29 m 2 /g；
The water reducer is a polycarboxylic acid water reducer, the water reducing rate is more than 30%, and the solid content is 36.5%;
the density of the copper slag is 2.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The average grain diameter is 106 mu m, and the solid content of ferric oxide is 53%;
the average grain diameter of the brass powder is 60 mu m, D0.5 is 55 mu m, and the pure copper content is 93%;
the average grain diameter of the red copper powder is 65 mu m, the D0.5 is 60 mu m, and the pure copper content is 98%.
The average length of the oriented steel fiber is 35mm, the section width is 0.5mm, the section length is 2mm, and the tensile strength is>2850MPA, density 7.8g/mm 3 。
The preparation method of the copper slag electromagnetic wave-absorbing concrete capable of being 3D printed in the embodiment is the same as that in the embodiment 1.
Electromagnetic wave absorption performance evaluation:
the embodiment tests according to the requirements of the method for testing the reflectivity of radar absorbing materials (GJB 2038-1994). The test results are shown in FIG. 3. A bandwidth below-10 dB of 7GHz means that at least 90% of the electromagnetic wave is absorbed, and a peak value of-14.5 dB means that 93.6% of the electromagnetic wave absorbs the peak. Because the doping amount of the steel fiber is close to 1.5% of the critical value, the whole structure presents stronger metal property, so that the direct surface reflection of electromagnetic waves is increased, the electromagnetic wave absorbing performance is reduced, and the absorption peak is slightly worse than that of the embodiment 1 but slightly stronger than that of the embodiment 1 in the wave absorbing bandwidth. In comparison with a theoretical model, because the length of the oriented steel fiber is 35mm, the size of each fiber equivalent micro-filter is about 30mm-80mm, the corresponding frequency will have strong electromagnetic wave-absorbing performance in the frequency band of 6GHz-15GHz, from the test result, 90% of electromagnetic wave-absorbing capacity is broken through at the frequency of 6.1GHz (the wavelength of 49 mm), and the high electromagnetic wave-absorbing performance up to 13.1GHz (the wavelength of 23 mm) is maintained, so that the theory of the equivalent micro-filter superstructure of the invention is verified.
The invention is applicable to the prior art where it is not described.

Claims (10)

1. The 3D electromagnetic wave-absorbing concrete super structure based on the optimized pavement frequency directional steel fibers is characterized in that a main body of the concrete super structure is obtained by inner and outer multi-ring concrete strips in a 3D printing mode of a loop-shaped printing path in an up-down multi-layer mode, the multi-ring concrete strips are formed after each layer of printing, and the width T of each ring of concrete strips is 11-13mm; the layer height H is less than or equal to 7mm; the value range of the layer number K is as follows: k is more than or equal to 3 and less than or equal to 5;
the volume doping amount of the oriented steel fibers is more than or equal to 0.5 percent and less than or equal to 1 percent, and the length l=30-50 mm of the oriented steel fibers; the length direction of the oriented steel fibers is parallel to the running direction of the zigzag printing path, the oriented steel fibers are paved on the surface of the concrete strip of each layer, and each layer of oriented steel fibers are paved according to paving frequency.
2. The 3D electromagnetic wave absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers of claim 1, wherein the pavement frequency determination process is:
according to the formula Vc=v T pi r 2 Calculating the volume Vc of single-layer concrete, wherein v is the printing speed of a spray head, t Total (S) The total duration of printing a layer of the square concrete strip, and r is the radius of the spray head;
knowing the volume doping amount p of the oriented steel fibers, calculating the volume Vf of the oriented steel fibers according to the formula vf=vc×p;
calculating the total number of single-layer oriented steel fibers according to the formula n=int [ Vf/(l a b) ], wherein l is the length of the steel fibers, a and b are the width and length of the cross section of the oriented steel fibers, and INT [ ] is a downward rounding function;
the first directional steel fiber starts to be laid for a time t 1 The time for the second oriented steel fiber to begin to lay is t 2 …, and so on, the time for the N directional steel fiber to begin to be laid is t N The 3D printing equipment prints according to the printing path of the shape of the circle as the start before laying the first directional steel fiber, and prints according to the printing path of the shape of the circle as the end after the last directional steel fiber is laid, the three-dimensional printing equipment comprises the following steps of
stat+t 1 +t 2 +t 3 +t 4 +……t N +end＝t Total (S) ，
Let t n ＝A^ n And take in stat+t 1 +t 2 +t 3 +t 4 +……t N +end＝t Total (S) Obtaining a frequency coefficient A, wherein A is less than 1, N is more than or equal to 1 and less than or equal to N, and N is a positive integer;
carry t according to frequency coefficient A n ＝A^ n The paving time of each directional steel fiber is obtained, namely the paving frequency of the directional steel fiber is determined.
3. The 3D electromagnetic wave absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers of claim 2, wherein the number of turns of each layer of concrete strip is 8-20; the length l=35-40 mm of the oriented steel fiber, the cross section of the oriented steel fiber is rectangular, the length of the rectangle is 2mm, and the width is 0.5mm; start=3.5s, end=5s; the layer height range is as follows: h is more than or equal to 4mm and less than or equal to 7mm.
4. The 3D electromagnetic wave-absorbing concrete super structure based on the optimized pavement frequency oriented steel fiber according to claim 1, wherein the concrete super structure can achieve the effect of high electromagnetic absorption of C wave band (4-8 GHz) and X wave band (8-12 GHz); the concrete superstructure is repeated in a periodic mode, a concrete structure with square bottom surfaces of inner and outer multi-turn layers is formed, a plurality of fiber equivalent microscopic filters are formed by adjacent layers and adjacent-turn directional steel fibers, and periodically arranged wave surface grains are formed on the outer surfaces of the upper and lower multi-layer concrete.
5. The 3D electromagnetic wave-absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers according to claim 1, wherein the fiber equivalent micro-filter is a regular prism with a side length of 30mm-80 mm.
6. The 3D electromagnetic wave-absorbing concrete superstructure based on the optimized pavement frequency oriented steel fibers, according to claim 1, is characterized in that the concrete superstructure is an electromagnetic protection brick with different specifications, and the bottom surface of the electromagnetic protection brick is square; preferably, the electromagnetic protection brick has the following model: 400X 400mm, 300X 300mm, 250X 250mm or 330X 330mm.
7. The 3D electromagnetic wave absorbing concrete superstructure based on directional steel fibers with optimized pavement frequency according to claim 1, wherein the equipment for printing the concrete superstructure comprises a 3D printer and a six-axis mechanical arm, the 3D printer is used for obtaining concrete strips for electromagnetic wave absorbing concrete according to a loop-shaped printing path, the six-axis mechanical arm is used for directional placement of the directional steel fibers, the placement of the directional steel fibers follows the printing process of the concrete strips, the concrete strips are printed from the center of a sample, the printing is sequentially carried out outwards in the loop-shaped printing path, and the directional steel fibers are placed according to the pavement frequency.
8. The 3D electromagnetic wave absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers of claim 7, wherein the printing parameters of the 3D printer are set as follows: the outlet cross section area of the printing nozzle is 115-120mm 2 The extrusion speed is 0.009-0.035m 3 And/h, the horizontal printing speed is 160-185cm/min, and the vertical printing speed is 0.6-0.85m/h;
when 3D printing is carried out, the electromagnetic wave absorbing concrete capable of 3D printing is pumped into a printing nozzle of a 3D printer, and printing is carried out after standing for 3-6 min.
9. The 3D electromagnetic wave-absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers according to claim 8, wherein the composition and content of the 3D printable electromagnetic wave-absorbing concrete are respectively:
6.8-7.2 parts of quick hardening ordinary Portland cement;
6.9-7.1 parts of quartz sand;
1.65-1.75 parts of copper slag;
0.75-0.85 parts of silica fume;
0.09-0.15 part of water reducer;
0.28-0.71 part of copper powder, wherein the copper powder consists of brass powder and red copper powder, and the weight ratio of the brass powder to the red copper powder is 7:2.5-3.5;
0.04-0.07 part of basalt fiber with the length of 11-14 mm;
0.003-0.005 part of hydroxypropyl methyl cellulose with the viscosity of 2-7 ten thousand;
1.70-1.74 parts of water.
10. The 3D electromagnetic wave-absorbing concrete superstructure based on optimized pavement frequency oriented steel fibers according to claim 9, characterized in that the average particle size of the brass powder is 55-75 μm, and the pure copper content is between 90-95%; the average grain diameter of the red copper powder is 50-80 mu m, and the pure copper content is 95-98%; the iron oxide content of the copper slag is above 53%, and the average grain diameter range is 100-150 mu m.
CN202310359051.2A 2023-04-06 2023-04-06 3D electromagnetic wave-absorbing concrete super structure based on optimized pavement frequency directional steel fibers Pending CN116335269A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116922532A (en) * 2023-07-20 2023-10-24 重庆大学溧阳智慧城市研究院 Electromagnetic wave-absorbing concrete multilayer 3D printing path planning method

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116922532A (en) * 2023-07-20 2023-10-24 重庆大学溧阳智慧城市研究院 Electromagnetic wave-absorbing concrete multilayer 3D printing path planning method
CN116922532B (en) * 2023-07-20 2024-04-16 重庆大学溧阳智慧城市研究院 Electromagnetic wave-absorbing concrete multilayer 3D printing path planning method

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