CN114195452B

CN114195452B - Conductive mortar, high-conductivity conductive cement-based material and preparation method thereof

Info

Publication number: CN114195452B
Application number: CN202111523987.1A
Authority: CN
Inventors: 张蕊; 张立力; 田寅; 蒋涛
Original assignee: SUZHOU CONCRETE CEMENT PRODUCTS RESEARCH INSTITUTE CO LTD; China National Building Material Group Co Ltd CNBM
Current assignee: SUZHOU CONCRETE CEMENT PRODUCTS RESEARCH INSTITUTE CO LTD; China National Building Material Group Co Ltd CNBM
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-01-17
Anticipated expiration: 2041-12-14
Also published as: CN114195452A

Abstract

The invention relates to conductive mortar, a high-conductivity conductive cement-based material and a preparation method thereof, wherein the conductive mortar comprises the following components in percentage by mass: 36 to 41 percent of cement; 19 to 20 percent of water; 0.5 to 1 percent of water reducing agent; 0.5 to 3 percent of graphite; 0.1 to 0.5 percent of carbon fiber; 7 to 8 percent of silica fume; 30-32% of machine-made sand; 0.1 to 0.2 percent of carbon fiber dispersant and 0.01 to 0.08 percent of defoamer; wherein the particle size of the graphite is 800 to 1200 meshes. According to the invention, the low-doping amount of graphite powder with fine granularity is adopted to be mixed with the low-doping amount of carbon fiber, and the use of silica fume is cooperated, so that the graphite powder can be uniformly dispersed in a mortar system and is matched with the carbon fiber uniformly dispersed in the system, the conductivity of the conductive mortar can be obviously improved, and meanwhile, the high-strength cement-based material is obtained by utilizing the filling effect of the fine-granularity graphite powder.

Description

Conductive mortar, high-conductivity conductive cement-based material and preparation method thereof

Technical Field

The invention belongs to the technical field of concrete, and particularly relates to conductive mortar, a high-conductivity conductive cement-based material and a preparation method thereof.

Background

Cement concrete has been widely used in various aspects of construction, transportation and urban construction because of its low cost, excellent plasticity and reliable mechanical properties. Traditionally, cement concrete is an insulating material, and the resistivities of saturated and dry concrete are 10 respectively ⁶ Omega cm and 10 ⁹ Omega cm. As early as the thirties of the last century, scientists began studying how to improve the conductivity of cement concrete materials and develop conductive concrete. Developed to date, conductive concrete hasThe method is widely applied to various fields such as industrial static prevention, electromagnetic interference shielding, power equipment grounding engineering, circuit breaker ground closing resistance, building lightning protection equipment, resistors, building heating ground, environmental heating, automatic monitoring of highways and the like.

The conductivity of the concrete may be increased with the incorporation of the conductive phase material. Conductive phase materials that have been studied more generally to date include powder materials (e.g., graphite, carbon black) and one-dimensional materials (e.g., steel fibers and carbon fibers). In the conductive concrete, the conductive phase materials are various in variety and have different properties. However, the existing conductive phase materials have respective defects in the using process: the corrosion of steel fiber in cement-based materials is an important factor for hindering the development of the steel fiber; the carbon nano tube and the carbon nano fiber are expensive, so that the industrial development is inhibited; the addition of powder materials such as pure carbon black, graphite and the like causes high water requirement of the cement-based material, and the large amount of addition has negative influence on the strength of the cement-based material, for example, the compressive strength of concrete doped with 10% of graphite is reduced by 77% in the document of preparation and performance of graphite conductive concrete, such as Stentand, zhang Jun et al; junbo Sun et al, in The article of Construction and Building Materials, the effect of graphite and slag on electrical and mechanical properties of electrical conductive composites, mention that 6% graphite incorporation reduces The flexural strength of The conductive mortar by 34%; however, if the amount of graphite added is small, the conductivity of the cement-based material is affected.

The study of the electrical properties of carbon fiber conducting concrete began in the 90 s. Practice proves that the chopped carbon fibers with proper quantity are mixed into cement concrete, on one hand, the conductivity of the concrete can be improved, and the resistivity of the concrete is from 10 ⁹ Omega cm is reduced to 10 ² Omega cm or less; on the other hand, the impact resistance and tensile strength of the brittle cement matrix can be enhanced, so that the aims of improving the toughness and reducing the drying shrinkage are fulfilled. However, the price of the carbon fiber is expensive, and the cost is greatly increased along with the increase of the doping amount, so that the industrial requirement cannot be met. Therefore, how to reduce the carbon fiber content and maintain the good conductivity and mechanical property of the conductive concrete becomesThe problems to be solved in the carbon fiber conductive concrete are solved.

When the single-doped conductive phase material is low in doping amount, a conductive cement-based material with low resistivity is difficult to obtain. For example, in the patent of 201811088083, the patent of "a carbon fiber/alkali-activated composite pressure-sensitive material and a preparation method thereof", when the carbon fiber content is 0.7%, the lowest resistivity obtained is 123 Ω · cm; in the patent with the application number of 201910108836.6 "a highly conductive graphite concrete", it is mentioned that when the graphite content is 6-9%, the lowest resistivity is 900 Ω · cm.

The defects caused by the defects of the conductive phase material in the single-doped conductive concrete can be overcome to a certain extent by the complex doping of multiple conductive phases. For example, the lowest resistivity of the steel slag carbon fiber composite-doped conductive concrete reported in the patent application number of 201810102286.2, namely steel slag carbon fiber conductive concrete and the preparation method thereof, is 65 omega cm. For example, chinese patent No. 202110773587.X discloses a conductive leveling layer composition, a preparation method thereof, and a conductive leveling layer, wherein, by adding 60-80 parts by mass of graphite powder and 0.1-0.3 part by mass of carbon fiber into 28-35 parts by mass of cement, the prepared cement composition has conductivity and maintains good physical strength, and can be used as a leveling layer raw material between a concrete substrate and an anticorrosive coating. Although the leveling layer has conductivity, the conductivity is poor, the resistivity is as low as 24 omega cm, the tensile strength is only 3.4MPa at most, the consumption of the graphite powder is more than 2 times of that of the cement, and the cost is high.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the conductive mortar which is obtained by doping the low-doping carbon fiber on the basis of the low-doping graphite so as to obtain high conductivity and high breaking strength and the preparation method thereof.

The second purpose of the invention is to provide a cement-based material with high conductivity and high breaking strength.

In order to achieve the purpose, the invention adopts the technical scheme that:

the conductive mortar comprises the following raw materials in percentage by mass:

wherein the particle size of the graphite is 800-1200 meshes.

The traditional method of adding more graphite powder to improve the conductivity of the cement-based material is adopted, and the excessive addition of the graphite powder can improve the water absorption of the cement-based material, so that the strength of the cement-based material is reduced. Through a large number of experimental researches, the inventor of the invention discovers that the graphite powder with fine granularity can utilize the size effect within a reasonable mixing amount range to play a good physical filling effect and optimize the pore structure, thereby improving the mechanical strength of the cement-based material.

However, graphite powder with a fine particle size is difficult to disperse in a system and is easy to agglomerate, the inventor further finds that a certain amount of silica fume is added in the system to help the graphite powder to disperse in the system, the graphite powder can be uniformly dispersed in the system, and simultaneously, carbon fibers with a low doping amount are doped, so that the carbon fibers can be well lapped between the graphite powder to form a conductive path, the resistivity of the cement-based material is greatly reduced, and the conductivity is greatly improved.

In some preferred and specific embodiments, the amount of graphite is 1.5 to 6.5% by mass of the total mass of the cement and the silica fume. Preferably, the using amount of the graphite is 1.5-6% of the total mass of the cement and the silica fume.

Further, the graphite is crystalline flake graphite with the purity of 95-99.5%.

In some preferred and specific embodiments, the carbon fibers are used in an amount of 0.3 to 1.5% by mass of the total mass of the cement and the silica fume. Preferably, the using amount of the carbon fiber is 0.8-1.2% of the total mass of the cement and the silica fume.

In some preferred and specific embodiments, the amount of the graphite is 1.8 to 2.5% of the total amount of the cement and the silica fume, and the amount of the carbon fiber is 0.8 to 1.2% of the total mass of the cement and the silica fume.

In still other preferred and specific embodiments, the graphite is used in an amount of 5.5 to 6% of the total amount of cement and silica fume, and the carbon fibers are used in an amount of 0.8 to 1.2% of the total mass of the cement and silica fume.

Further, the carbon fiber is polyacrylonitrile-based carbon fiber.

In some preferred and specific embodiments, the carbon fibers have a length of 3 to 6mm and a diameter of 7 ± 0.5 μm.

Furthermore, the carbon fiber has the resistivity of 2.5-3 omega cm, the tensile strength of 3000-3500Mpa, the tensile modulus of 200-220Gpa and the carbon content of more than or equal to 83 percent.

According to some embodiments of the invention, the silica fume is silica fume, the mass content of the silicon is greater than or equal to 95%, the average particle size is 0.1-0.15 μm, and the specific surface area is 15-27m ² /g。

According to some embodiments of the invention, the machine-made sand has a particle size of 22 to 40 mesh.

According to some embodiments of the invention, the carbon fiber dispersant is sodium methyl cellulose. The carbon fiber dispersing agent is added to help the carbon fibers to be uniformly dispersed in the mortar, so that the fibers can be well lapped, and a complete power-on network is further formed.

According to some embodiments of the invention, the defoamer is tributyl phosphate, which has an acid value of 0.1mgKOH/g or less and a density of 0.974 to 0.98g/mL. The addition of the defoaming agent is helpful for eliminating bubbles caused by the addition of the carbon fibers, so that the mortar structure is more compact, and the mechanical strength of the mortar matrix is improved.

The second technical scheme adopted by the invention is as follows: the preparation method of the conductive mortar comprises the following steps:

(1) Heating water accounting for 30-40% of the total amount of the water to dissolve the carbon fiber dispersing agent to obtain a mixed solution;

(2) Premixing carbon fibers and machine-made sand to obtain premix;

(3) And (2) stirring and mixing cement, graphite, a water reducing agent, a defoaming agent and water accounting for 30-40% of the total amount of water, then adding the premix obtained in the step (2) and stirring, then adding the mixed solution obtained in the step (1) and stirring, then adding the rest of water and stirring to obtain the conductive mortar.

The third technical scheme adopted by the invention is as follows: the conductive cement-based material is prepared by adopting the conductive mortar or the conductive mortar prepared by the preparation method.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

according to the invention, the low-doping amount of graphite powder with fine granularity is adopted to mix the low-doping amount of carbon fiber, and the graphite powder can be uniformly dispersed in a mortar system in cooperation with the use of silica fume, so that the conductivity of the conductive mortar can be obviously improved, and meanwhile, the high-strength cement-based material is obtained by utilizing the filling effect of the fine-granularity graphite powder.

The invention uses less conductive phase materials, achieves the aims of improving the conductive performance of the conductive mortar and the mechanical strength of the conductive mortar, has the lowest resistivity of 13 omega cm, greatly reduces the cost, and is expected to further promote the industrial application of the carbon fiber conductive concrete.

Drawings

FIG. 1 is a schematic diagram of the optical microscope imaging principle;

in fig. 1: 1. a reflector; 2. an objective lens; 3. a light source; 4. an imaging system.

FIG. 2 (a) is a diagram of the graphite powder at a microscope magnification of 50 times; (b) The morphology of the cement-based material of comparative example 3 was magnified 50 times under a microscope; (c) The morphology of the cement-based material of example 4 was magnified 50 times under a microscope; (d) Is the morphology of the cement-based material of example 4 under a microscope at 20 times magnification.

Detailed Description

The technical solutions of the present invention are described in detail below with reference to specific examples so that those skilled in the art can better understand and implement the technical solutions of the present invention, but the present invention is not limited to the scope of the examples.

The experimental procedures in the following examples are conventional unless otherwise specified. The raw materials used in the following examples were all commercially available products unless otherwise specified.

Example 1

In the cement-based material provided by the embodiment, the conductive mortar adopted by the cement-based material is composed of the following raw materials in percentage by weight: 39.14 percent of Portland cement, 19.54 percent of water, 0.72 percent of polycarboxylic acid water reducing agent, 0.93 percent of graphite powder, 0.23 percent of carbon fiber, 7.39 percent of silica fume, 31.84 percent of sand, 0.19 percent of sodium methyl cellulose and 0.02 percent of tributyl phosphate, wherein,

the graphite powder is crystalline flake graphite with the granularity of 800 meshes and the purity of 99 percent.

The sand has a particle size of 30 mesh.

The silica fume is microsilica, the silicon content is greater than or equal to 95%, the average grain diameter is 0.1-0.15 μm, and the specific surface area is 15-27m ² /g。

The carbon fiber is Polyacrylonitrile (PAN) based carbon fiber, the length of the carbon fiber is 3-6mm, the resistivity of the carbon fiber is 2.5-3 omega cm, the tensile strength is 3000-3500Mpa, the tensile modulus is 200-220Gpa, the diameter is 7 +/-0.5 mu m, and the carbon content is more than or equal to 83 percent.

The invention also provides a preparation method of the low-conductive phase-doped high-conductivity conductive mortar, which is characterized by comprising the following steps of:

(1) Weighing the components according to the weight percentage;

(2) Weighing 1/3 of water in the mixing ratio, heating the water to 70 ℃, and dissolving the carbon fiber dispersing agent;

(3) Pre-mixing the carbon fiber and the sand for 3min according to the weight ratio;

(4) Adding cement, graphite, a polycarboxylic acid water reducing agent, a defoaming agent and 1/3 of water into a stirrer, and stirring for 30s;

(5) Pouring the pre-mixed sand and carbon fiber in the step (3) into a stirrer to continue stirring for 30s;

(6) Pouring the carbon fiber dispersing agent dissolved in the step (2) into a stirrer to continue stirring for 30s;

(7) Finally, adding the rest 2/3 of water, and continuously stirring for 90s to obtain the conductive mortar;

(8) And pouring the conductive mortar into a mold, carrying out vibration molding, demolding after 48 hours, and carrying out standard maintenance.

Example 2

In the cement-based material provided by the embodiment, the conductive mortar adopted by the cement-based material is composed of the following raw materials in percentage by weight: 39.05 percent of Portland cement, 19.50 percent of water, 0.80 percent of polycarboxylic acid water reducing agent, 0.93 percent of graphite powder, 0.46 percent of carbon fiber, 7.34 percent of silica fume, 31.74 percent of sand, 0.1 percent of sodium methyl cellulose and 0.08 percent of tributyl phosphate,

the graphite powder is crystalline flake graphite with the granularity of 1200 meshes and the purity of the graphite of 99 percent.

The rest was the same as in example 1.

Example 3

In the cement-based material provided by the embodiment, the conductive mortar adopted by the cement-based material is composed of the following raw materials in percentage by weight: 38.42 percent of Portland cement, 19.14 percent of water, 0.69 percent of polycarboxylic acid water reducing agent, 2.74 percent of graphite powder, 0.23 percent of carbon fiber, 7.23 percent of silica fume, 31.32 percent of sand, 0.2 percent of sodium methyl cellulose and 0.03 percent of tributyl phosphate, wherein,

The rest is the same as example 1.

Example 4

In the cement-based material provided by the embodiment, the conductive mortar adopted by the cement-based material is composed of the following raw materials in percentage by weight: 38.33 percent of Portland cement, 19.18 percent of water, 0.69 percent of polycarboxylic acid water reducing agent, 2.74 percent of graphite powder, 0.46 percent of carbon fiber, 7.25 percent of silica fume, 31.1 percent of sand, 0.17 percent of sodium methyl cellulose and 0.08 percent of tributyl phosphate,

The rest is the same as example 1.

Comparative example 1

The cement-based material provided by the comparative example comprises the following raw materials in percentage by weight: 35.16% of portland cement, 19.93% of water, 0.91% of polycarboxylic acid water reducing agent, 10% of silica fume and 34% of sand.

The sand has a particle size of 22 mesh.

The rest is the same as example 1.

Comparative example 2

The cement-based material provided by the comparative example comprises the following raw materials in percentage by weight: 39.31 percent of Portland cement, 19.63 percent of water, 0.71 percent of polycarboxylic acid water reducing agent, 0.93 percent of graphite powder, 7.42 percent of silica fume and 32 percent of sand.

The sand has a particle size of 30 mesh.

The rest was the same as in example 1.

Comparative example 3

The cement-based material provided by the comparative example comprises the following raw materials in percentage by weight: 38.51 percent of portland cement, 19.23 percent of water, 0.88 percent of polycarboxylic acid water reducing agent, 2.75 percent of graphite powder, 7.27 percent of silica fume and 31.36 percent of sand.

The graphite powder is crystalline flake graphite with the granularity of 800 meshes and the purity of the graphite of 99 percent.

The sand has a particle size of 30 mesh.

The rest is the same as example 1.

Comparative example 4

The cement-based material provided by the comparative example comprises the following raw materials in percentage by weight: 38.33 percent of portland cement, 26.43 percent of water, 0.69 percent of polycarboxylic acid water reducing agent, 2.73 percent of graphite powder, 0.23 percent of carbon fiber, 31.34 percent of sand, 0.17 percent of sodium methyl cellulose and 0.08 percent of tributyl phosphate.

The graphite powder is crystalline flake graphite with the granularity of 1200 meshes and the purity of 99 percent.

The rest is the same as example 1.

The cement-based materials of examples 1 to 4 and comparative examples 1 to 4 were tested for resistivity by the four-electrode method and for flexural strength by the GBT17671-1999 Cement mortar Strength test method (ISO method), and the results are shown in Table 1.

Table 1 shows the results of the tests on the cement-based materials of examples 1 to 4 and comparative examples 1 to 4

Note: in table 1, the carbon fiber content refers to the percentage of carbon fibers in the total mass of the cementitious material (i.e., cement and silica fume) in the system; the graphite loading refers to the percentage of graphite to the total mass of the cementitious material in the system.

As can be seen from Table 1, the resistivity of the conductive mortar is reduced by 1-2 orders of magnitude by the compound doping of the low-doping carbon fibers and the graphite, wherein when the doping amount of the carbon fibers is 1% and the doping amount of the graphite is 6%, the resistivity of the conductive mortar in 28 days is 13 omega cm; and the comparative conductive mortar with larger resistivity has obvious resistivity increase along with the increase of age, and the resistivity of the conductive mortar has no obvious increase along with the increase of age for the low-doping-amount carbon fiber and graphite complex doping system with lower resistivity. For the mechanical strength, compared with the comparative example, the flexural strength is improved to different degrees, wherein the flexural strength of the conductive concrete doped with 1% of carbon fiber and 2% of graphite is improved by 11% compared with the comparative example 1.

The conductivity of the conductive mortar can be obviously improved by the composite doping of the graphite and the carbon fiber, and the composite doping of the graphite and the carbon fiber can form mutually-lapped network-shaped conductive channels more easily, so that a premise is provided for the conduction of free current carriers. In conductive mortars with only carbon fibers, there are three forms between the fibers and the network of fibers in the cement matrix, interconnected fibers, fibers that are separated from each other, and fibers that are not in contact but are closely spaced. The connected fibers can form a conductive path to effectively conduct current carriers, the unconnected fibers cannot form a conductive channel, an open circuit is formed in the circuit, and the distribution of graphite in the cement-based material enables the fiber networks which are not directly communicated to be communicated, so that a connected conductive network is formed, the network is an important channel for the cement-based material to conduct the current carriers, and the electrical resistivity of the complex doped conductive mortar is reduced rapidly. In the conductive mortar system with low graphite doping amount, the graphite content is low, and the graphite particles are blocked by the cement base to form a barrier, so that the resistivity is high, and the conductivity of the conductive mortar is poor. Because the carbon fiber has good conductivity and large length-diameter ratio, the barrier between the conductive paths of the graphite particles can be effectively weakened by doping the carbon fiber into the concrete to form an effective conductive network, so that in a conductive mortar system with low graphite doping amount, the low-doping carbon fiber can obviously reduce the resistivity of the concrete.

And for the factors influencing the resistivity of the conductive mortar, the residual aqueous solution in the pores of the cement and ions in the solution provide another conductive channel, namely an ion conductive channel. The effect of curing age on resistivity is not trivial. In the early hydration stage of the mortar, a large amount of free water remains in mortar slurry, and the cement structure is loose and a large amount of communicating pores exist, so that more possibility is provided for the ionic conduction of a matrix, and the change of the resistivity of the conductive mortar doped with graphite in the early stage is not obvious along with the increase of the maintenance age; along with the increase of the age, free water in the slurry gradually reacts with clinker to form solid hydrate with higher resistivity, and meanwhile, the structure of cement is more compact, communication holes are reduced, and a free water channel is blocked; and the conductive phase materials such as fibers and powder embedded in the matrix are covered by the hydration product, so that the contact resistance between the conductive phase materials is increased, and finally the resistivity of the conductive mortar is greatly improved. For a carbon fiber and graphite complex doping system, the influence of age on the resistivity of the complex doping system is not obvious, because the system forms a good electrified network at the initial stage, the system is basically not influenced by free water and the reaction degree in the system.

On one hand, because the graphite particles used in the conductive mortar are fine, when the doping amount is low, the size effect can be well played, and under the use of silica fume, fine graphite powder can be well and uniformly dispersed in a system, and a physical filling effect is well played, so that the pore structure of the conductive mortar is compacted, and the hydration product of the conductive mortar is optimized; the carbon fiber has the advantages of high specific strength, high specific modulus and the like, so that the anti-breaking strength of the conductive mortar can be improved by doping the carbon fiber.

Further, in order to determine the lapping condition of the graphite and the carbon fiber in the conductive mortar, the patent uses an optical microscope to observe the microstructure of the conductive mortar. Since graphite is similar to unreacted cement and other particles in the conductive mortar, when the microstructure of the conductive mortar is explored by equipment such as a scanning electron microscope, the graphite and the cement and other particles are difficult to distinguish. However, graphite is structurally crystalline, so that under an optical microscope, graphite is bright white and can be easily found. Carbon fibers are inherently a fibrous structure and are also relatively easy to find.

By using the imaging mechanism of the optical microscope shown in fig. 1, light emitted from the light source 3 is irradiated on the reflective mirror 1, the reflective mirror 1 reflects the light to the sample through the objective lens 2, and the appearance of the sample is observed on the imaging system 4. The results are shown in fig. 2, wherein fig. 2 (a) is a morphology of graphite magnified 50 times under a microscope; FIG. 2 (b) is a morphology of the cement-based material of comparative example 3 magnified 50 times under a microscope; FIG. 2 (c) is a plot of the cement-based material of example 4 at a microscopic magnification of 50; FIG. 2 (d) is a topography of the cement-based material of example 4 under a microscope at 20 times magnification. From fig. 2 (b), which shows the distribution of 6% graphite in the cement matrix, it can be seen that the graphite is uniformly distributed in the cement matrix, but is not directly overlapped, which explains the relatively poor conductivity of the conductive mortar with less graphite content. FIG. 2 (c) is a sample morphology after the graphite and the carbon fiber are re-doped, the graphite is still uniformly distributed in the cement-based material, there is no directly connected part between the graphite individuals, and the carbon fiber plays a role of a conductive bridge; the carbon fibers are distributed in the cement matrix, and the carbon fibers are not directly overlapped, for example, the

carbon fibers

1, 2 and 3 in fig. 2 (c) are not directly overlapped, but the graphite is dispersed in the matrix, so that the distance between the conductive phases is reduced, the conductive phase materials are communicated, and the conductivity of the matrix is improved. Fig. 2 (d) also shows a similar case.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

Claims

1. The conductive mortar is characterized by comprising the following components in percentage by mass:

36 to 41 percent of cement;

19 to 20 percent of water;

0.5 to 1 percent of water reducing agent;

0.5 to 3 percent of graphite;

0.1 to 0.5 percent of carbon fiber;

7 to 8 percent of silica fume;

30-32% of machine-made sand;

0.1 to 0.2 percent of carbon fiber dispersing agent;

0.01 to 0.08 percent of defoaming agent;

wherein the particle size of the graphite is 800 to 1200 meshes;

the length of the carbon fiber is 3 to 6mm, and the diameter of the carbon fiber is 7 +/-0.5 mu m;

the using amount of the graphite is 1.5 to 6.5 percent of the total mass of the cement and the silica fume;

the dosage of the carbon fiber is 0.8 to 1.2 percent of the total mass of the cement and the silica fume;

the preparation method of the conductive mortar comprises the following steps:

(1) Heating water accounting for 30-40% of the total using amount of the water, and dissolving a carbon fiber dispersing agent to obtain a mixed solution;

(2) Premixing carbon fibers and machine-made sand to obtain premix;

(3) Stirring and mixing cement, graphite, a water reducing agent, a defoaming agent and water accounting for 30-40% of the total consumption of the water, then adding the premix obtained in the step (2) and stirring, then adding the mixed solution obtained in the step (1) and stirring, then adding the rest of water and stirring to obtain the conductive mortar.

2. The electrically conductive mortar of claim 1, wherein: the graphite is flake graphite, and the purity is 95 to 99.5 percent.

3. The electrically conductive mortar of claim 1, wherein: the carbon fiber is polyacrylonitrile-based carbon fiber.

4. The electrically conductive mortar of claim 1, wherein: the carbon fiber has the resistivity of 2.5-3 omega cm, the tensile strength of 3000-3500Mpa, the tensile modulus of 200-220Gpa, and the carbon content of more than or equal to 83 percent.

5. The electrically conductive mortar of claim 1, wherein: the silicon ash is micro silicon powder, the mass content of silicon is more than or equal to 95 percent, the average particle size is 0.1-0.15 mu m, and the specific surface area is 15-27m ² /g。

6. The electrically conductive mortar of claim 1, wherein: the grain size of the machine-made sand is 22-40 meshes.

7. The electrically conductive mortar of claim 1, wherein: the carbon fiber dispersing agent is sodium methyl cellulose; and/or the defoaming agent is tributyl phosphate.

8. A preparation method of the conductive mortar of any one of claims 1 to 7, characterized by comprising the following steps:

(2) Premixing carbon fibers and machine-made sand to obtain premix;

9. An electrically conductive cement-based material prepared from the electrically conductive mortar of any one of claims 1 to 7 or the electrically conductive mortar prepared by the preparation method of claim 8.