Conductive mortar and method for its preparation

Abstract

This invention discloses a conductive mortar and its preparation method. The conductive mortar comprises, by weight, 40-60 parts metakaolin, 15-30 parts steel slag, 20-35 parts calcium carbide slag, 0-10 parts gypsum, 50-100 parts self-igniting coal gangue, 35-50 parts electrolyte solution, 0-1 part activator, 0.5-1 part water-retaining agent, and 0.5-2 parts water-reducing agent. This conductive mortar avoids the use of expensive conductive materials, using simple and readily available materials to reduce mortar resistance, thereby reducing costs and improving the conductive stability of the material.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to a conductive mortar and its preparation method. Background Technology

[0002] With global resource shortages becoming increasingly prominent and energy consumption continuing to rise, the building sector accounts for over 30% of all energy consumption, making the development of energy-saving materials imperative. Conductive mortar, as a cutting-edge technology in the construction field, has attracted widespread attention. It possesses thermoelectric sensing and conversion capabilities and can be applied to areas such as building floor heating, building structural damage detection, electromagnetic interference shielding, and lightning protection grounding.

[0003] Based on different conduction methods, conductive mortars can be divided into ionic conductive and electronic conductive mortars. Ionic conductive mortars involve permeating an electrolyte solution into the mortar specimen through pores, where free ions move directionally under external voltage, thus imparting conductivity to the mortar. Current research on conductive mortars primarily focuses on electronic conductive mortars, which incorporate conductive materials to achieve conductivity. Common conductive materials for electronic conductive mortars include carbon fiber, steel fiber, graphite, and some metal powders. However, carbon fiber is expensive, its mixtures are difficult to apply, and it has poor dispersibility. Steel fiber and metal powders are easily oxidized under alkaline conditions, forming a passivation film that significantly increases resistivity and affects material strength. While graphite has good chemical stability, a large dosage is required to achieve good conductivity in the matrix material, which can lead to a rapid decrease in strength. Due to the inherent characteristics of each conductive material, conductive cementitious materials suffer from high cost, poor conductivity stability, and low strength. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical problems and provide a conductive mortar and its preparation method. This conductive mortar avoids the use of expensive conductive materials and uses simple and readily available materials to reduce the mortar resistance and prepare conductive mortar.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A conductive mortar comprises, by weight, 40-60 parts metakaolin, 15-30 parts steel slag, 20-35 parts calcium carbide slag, 0-10 parts gypsum, 50-100 parts self-igniting coal gangue, 35-50 parts electrolyte solution, 0-1 part activator, 0.5-1 part water-retaining agent, and 0.5-2 parts water-reducing agent.

[0007] Furthermore, the metakaolin composition includes: 45-50 wt.% SiO2, 37-43 wt.% Al2O3, and the metakaolin particle size is 500-700 mesh.

[0008] Furthermore, the steel slag comprises: 34–46 wt.% CaO, 10–20 wt.% SiO2, and 15–24 wt.% FeO, and has a specific surface area of ​​450–550 m². 2 / kg.

[0009] Furthermore, the CaO content in the carbide slag is ≥80wt.%, and the gypsum is desulfurized gypsum.

[0010] Furthermore, the composition of the coal gangue includes: 40-55 wt.% SiO2 and 25-35 wt.% Al2O3.

[0011] Furthermore, the coal gangue is coal gangue sand with a particle size of 0.1 mm to 5.0 mm after being crushed and screened by a crusher, and the fineness modulus of the coal gangue sand is 3.4.

[0012] Furthermore, the electrolyte solution is a solution using one of FeSO4, FeCl3, Na2SO4, and CaCl2 as the solute and tap water as the solvent, and the mass fraction of the electrolyte is 5-15 wt.%.

[0013] Furthermore, the activator is water glass with a modulus of 1.

[0014] Furthermore, the water-retaining agent is hydroxyethyl cellulose ether, and the water-reducing agent is a polycarboxylate superplasticizer.

[0015] This invention also provides a method for preparing conductive mortar, comprising the following steps:

[0016] S1. Soak the coal gangue in an electrolyte solution for 12 hours;

[0017] S2. Mix metakaolin, steel slag, carbide slag, gypsum, activator, water-retaining agent, and water-reducing agent evenly to form a mixture. Pour the electrolyte solution soaked with coal gangue into the mixture and stir thoroughly to obtain a mixed slurry.

[0018] S3. Pour the mixed slurry into the mold, vibrate to form, cure, and demold to obtain the conductive mortar.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. This invention uses industrial waste residue as raw material to realize the comprehensive utilization of solid waste. Steel slag and carbide slag not only exhibit certain hydraulic properties, but also have a synergistic cementing effect with metakaolin. This is because both have strong alkaline characteristics, providing an alkaline environment to promote the depolymerization-condensation process between cementing materials, giving the material excellent mechanical properties, and effectively reducing the amount of activator used, thus reducing costs.

[0021] 2. The conductivity method of the present invention is ionic conductivity. Compared with the traditional electronic conductivity method, ionic conductivity has a wide variety of electrolyte solutions to choose from, and is inexpensive. It can also effectively avoid the problem of uneven distribution of conductive materials.

[0022] 3. As the free water content in the material gradually decreases, the resistivity of the material increases. The water-retaining agent used in this invention is hydroxyethyl cellulose ether, which ensures the free water content in the matrix, prolongs the water evaporation time, and improves the conductive stability of the material.

[0023] 4. This invention uses coal gangue as fine aggregate and pre-soaks it in an electrolyte solution to form conductive coal gangue. The porous structure of the coal gangue allows the electrolyte to penetrate into its interior, ensuring uniform distribution of the electrolyte solution within the mortar and improving the material's conductivity. The porous structure of the coal gangue also retains free water within the matrix, while the alkaline cementitious material forms a denser coating, slowing down the evaporation of free water and enhancing the material's conductive stability. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] The metakaolin used in this embodiment of the invention comprises: 45-50 wt.% SiO2, 37-43 wt.% Al2O3, and the particle size of the metakaolin is 500-700 mesh.

[0026] The steel slag used in this embodiment of the invention comprises: 34–46 wt.% CaO, 10–20 wt.% SiO2, and 15–24 wt.% FeO, and has a specific surface area of ​​450–550 m². 2 / kg.

[0027] The coal gangue used in the embodiments of the present invention comprises: 40-55 wt.% SiO2 and 25-35 wt.% Al2O3.

[0028] The coal gangue used in this embodiment of the invention is coal gangue sand with a particle size of 0.1 mm to 5.0 mm after being crushed and screened by a crusher. The fineness modulus of the coal gangue sand is 3.4.

[0029] The water-retaining agent used in the embodiments of the present invention is hydroxyethyl cellulose ether, and the water-reducing agent used is polycarboxylate superplasticizer.

[0030] Example 1

[0031] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 1.

[0032] Table 1

[0033]

[0034]

[0035] The electrolyte solution used in this embodiment has a mass fraction of 10 wt.%, with CaCl2 as the solute and tap water as the solvent.

[0036] S1. Soak 100 parts of coal gangue in 50 parts of CaCl2 electrolyte solution with a mass fraction of 10 wt.% for 12 hours;

[0037] S2. Mix 50 parts metakaolin, 25 parts steel slag, 25 parts calcium carbide slag, 10 parts gypsum, 1 part activator, 0.5 parts water-retaining agent, and 1 part water-reducing agent evenly to form a mixture. Pour the CaCl2 electrolyte solution soaked with coal gangue into the mixture and stir thoroughly to obtain a mixed slurry.

[0038] S3. Pour the mixed slurry into a 40*40*160mm mold, vibrate and smooth the surface. After that, insert a galvanized iron mesh electrode at each end of a test block 1cm away from the edge of the mold for resistance testing. Then, place it under standard curing conditions of 20℃ and 95% humidity for 1 day before demolding to obtain conductive mortar #1. The demolded specimens continue to be cured under the same conditions, and performance testing will be carried out later.

[0039] Example 2

[0040] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 2.

[0041] Table 2

[0042]

[0043]

[0044] Except for the specific composition of each component, the electrolyte solution and preparation method are the same as in Example 1, resulting in conductive mortar #2.

[0045] Example 3

[0046] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 3.

[0047] Table 3

[0048] Components weight metakaolin 50 steel slag 15 calcium carbide slag 35 plaster 8 Coal gangue 80 Electrolyte solution 35 Activator 1 Water-retaining agent 0.5 Water reducing agent 2

[0049] Except for the specific composition of each component, the electrolyte solution and preparation method in this embodiment are the same as in Example 1, resulting in conductive mortar #3.

[0050] Example 4

[0051] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 4.

[0052] Table 4

[0053] Components weight metakaolin 40 steel slag 30 calcium carbide slag 30 plaster 10 Coal gangue 60 Electrolyte solution 40 Activator 0 Water-retaining agent 0.5 Water reducing agent 1.5

[0054] Except for the specific composition of each component, the electrolyte solution and preparation method are the same as in Example 1, resulting in conductive mortar #4.

[0055] Example 5

[0056] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 5.

[0057] Table 5

[0058] Components weight metakaolin 40 steel slag 30 calcium carbide slag 30 plaster 0 Coal gangue 100 Electrolyte solution 50 Activator 1 Water-retaining agent 0.5 Water reducing agent 1.5

[0059] Except for the specific composition of each component, the electrolyte solution and preparation method in this embodiment are the same as in Example 1, resulting in conductive mortar #5.

[0060] Example 6

[0061] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 6.

[0062] Table 6

[0063] Components weight metakaolin 40 steel slag 30 calcium carbide slag 30 plaster 10 Coal gangue 100 Electrolyte solution 50 Activator 1 Water-retaining agent 0.5 Water reducing agent 1.5

[0064] Except for the specific composition of each component, the electrolyte solution and preparation method in this embodiment are the same as in Example 1, resulting in conductive mortar 6#.

[0065] Example 7

[0066] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 7.

[0067] Table 7

[0068] Components weight metakaolin 60 steel slag 20 calcium carbide slag 20 plaster 10 Coal gangue 100 Electrolyte solution 50 Activator 1 Water-retaining agent 0.5 Water reducing agent 0.5

[0069] Except for the specific composition of each component, the electrolyte solution and preparation method in this embodiment are the same as in Example 1, resulting in conductive mortar #7.

[0070] Example 8

[0071] As a preferred embodiment of the present invention, the conductive mortar disclosed in this embodiment has the specific composition shown in Table 8.

[0072] Table 8

[0073] Components weight metakaolin 60 steel slag 20 calcium carbide slag 20 plaster 5 Coal gangue 100 Electrolyte solution 50 Activator 1 Water-retaining agent 1 Water reducing agent 0.5

[0074] Except for the specific composition of each component, the electrolyte solution and preparation method are the same as in Example 1, resulting in conductive mortar #8.

[0075] Example 9

[0076] Except for the use of FeCl3 as the solute in the electrolyte solution, all other materials and preparation methods in this embodiment are the same as in Example 1, resulting in conductive mortar #9.

[0077] Example 10

[0078] In this embodiment, except that Na2SO4 is used as the solute in the electrolyte solution, all other materials and preparation methods are the same as in Example 1, resulting in conductive mortar 10#.

[0079] Example 11

[0080] Except for the use of FeSO4 as the solute in the electrolyte solution, the other materials and preparation methods in this embodiment are the same as in Example 1, resulting in conductive mortar 11#.

[0081] Example 12

[0082] In this embodiment, except that the mass fraction of the electrolyte solution is replaced with 5 wt.%, the other materials and preparation methods are the same as in Example 1, and conductive mortar 12# is obtained.

[0083] Example 13

[0084] In this embodiment, except that the mass fraction of the electrolyte solution is replaced with 7 wt.%, the other materials and preparation methods are the same as in Example 1, and conductive mortar 13# is obtained.

[0085] Example 14

[0086] In this embodiment, except that the mass fraction of the electrolyte solution is replaced with 12 wt.%, the other materials and preparation methods are the same as in Example 1, and conductive mortar 14# is obtained.

[0087] Example 15

[0088] In this embodiment, except that the mass fraction of the electrolyte solution is replaced with 15 wt.%, the other materials and preparation methods are the same as in Example 1, and conductive mortar 15# is obtained.

[0089] Comparative Example 1

[0090] Except for the use of tap water instead of electrolyte solution and the use of tap water to soak coal gangue, all other materials in this comparative example are the same as those in Example 1. The amount of tap water used in this comparative example is the same as the amount of tap water used in the electrolyte solution in Example 1.

[0091] S1. Soak 100 parts of coal gangue in 50 parts of tap water for 12 hours;

[0092] S2. Mix 50 parts metakaolin, 25 parts steel slag, 25 parts carbide slag, 10 parts gypsum, 1 part activator, 0.5 parts water-retaining agent, and 1 part water-reducing agent evenly to form a mixture. Pour tap water soaked with coal gangue into the mixture and stir thoroughly to obtain a control slurry.

[0093] S3. Pour the comparison mortar into a 40*40*160mm mold, vibrate and smooth the surface. After that, insert a galvanized iron mesh electrode at each end of a test block 1cm away from the edge of the mold for resistance testing. Then, place it under standard curing conditions of 20℃ and 95% humidity for 1 day before demolding to obtain comparison mortar #1. The demolded specimens continue to be cured under the same conditions, and performance tests are carried out later.

[0094] Comparative Example 2

[0095] In this comparative example, except for the absence of a water-retaining agent, all other materials and preparation methods are the same as in comparative example 1, resulting in comparative mortar 2#.

[0096] Test case

[0097] The test blocks formed from the mortars of Examples 1-15 and Comparative Examples 1-2 were subjected to strength tests according to GB / T17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)"; the resistivity was calculated using the following formula: ρ=R·S / L (where R——resistance of the specimen, Ω; S——cross-sectional area of ​​the specimen, m²). 2 L—Specimen length, in meters. Specific test results are shown in Table 2 below:

[0098] Table 2

[0099]

[0100] As can be seen from Table 2 above, the electrolyte solution significantly reduced the resistivity of the mortar, and the water-retaining agent helped stabilize the resistivity. The greater the amount of metakaolin, the higher the activity and strength of the cementitious material. However, with the reduction of the amount of steel slag and carbide slag, the improvement of the mechanical properties of the mortar was not obvious. This is because the reduction of the amount of alkaline material weakened the activation effect on the metakaolin.

[0101] As can be seen from Table 2 above, when CaCl3 is used as a solute to prepare electrolyte solutions with different mass fractions, the resistivity of the mortar continuously decreases as the mass fraction increases. When the mass fraction of the electrolyte is greater than 10 wt.%, the decrease in mortar resistivity becomes smaller, indicating that when the concentration of ions required for conductivity reaches a certain level, the resistivity tends to stabilize. However, as time goes on, the moisture content inside the mortar decreases, and the difference in resistivity gradually becomes more obvious.

[0102] As shown in Table 2 above, the 10 wt.% electrolyte solution significantly reduced the resistivity of the mortar. In the early stage of testing, due to the high moisture content of the specimens, the resistivity was mainly determined by the moisture content, so the difference in resistivity between the groups of specimens was not significant. However, as the age increased, the free water content in the specimens gradually decreased, and the resistivity increased accordingly. FeCl3 and CaCl2 had no significant effect on strength, while FeSO4 and Na2SO4 electrolyte solutions had a greater effect on strength. This is because SO4... 2- It can decompose some of Ca(OH)2 to generate gypsum, which damages the internal structure of the specimen and reduces its strength.

[0103] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. An electrically conductive mortar, characterized in that, The self-combustion coal gangue is 50-100 parts by mass, the electrolyte solution is 35-50 parts by mass, the activator is 0-1 part by mass, the water-retaining agent is 0.5-1 part by mass, and the water-reducing agent is 0.5-2 parts by mass. The steel slag comprises 34-46 wt.% CaO, 10-20 wt.% SiO2, 15-24 wt.% FeO, and the specific surface area of the steel slag is 450-550 m 2 / kg. The self-combustion coal gangue comprises 40-55 wt.% SiO2 and 25-35 wt.% Al2O3. The water-retaining agent is a hydroxyethyl cellulose ether, and the water-reducing agent is a polycarboxylic acid superplasticizer. The preparation method of the conductive mortar comprises the following steps: S1, soaking the self-combustion coal gangue in the electrolyte solution for 12 hours; S2, uniformly stirring metakaolin, steel slag, carbide slag, gypsum, an activator, a water-retaining agent and a water-reducing agent to form a mixture, pouring the electrolyte solution soaked with the self-combustion coal gangue into the mixture, and fully stirring to obtain a mixed slurry; S3, pouring the mixed slurry into a mold, vibrating and compacting, curing and demolding, and thus the conductive mortar is obtained.

2. An electrically conductive mortar according to claim 1, characterized in that The metakaolin comprises 45-50 wt.% SiO2 and 37-43 wt.% Al2O3, and the particle size of the metakaolin is 500-700 mesh.

3. The electrically conductive mortar of claim 1, wherein The CaO content in the carbide slag is greater than or equal to 80 wt.%.

4. The electrically conductive mortar of claim 1, wherein The self-combustion coal gangue is coal gangue sand with a particle size of 0.1-5.0 mm after being crushed and screened by a crusher, and the fineness modulus of the coal gangue sand is 3.

4.

5. The electrically conductive mortar of claim 1, wherein The electrolyte solution is a solution prepared by taking one of FeSO4, FeCl3, Na2SO4 and CaCl2 as a solute and tap water as a solvent, and the mass fraction of the electrolyte solution is 5-15 wt.%.

6. The electrically conductive mortar of claim 1, wherein The activator is water glass with a modulus of 1.

7. A method of preparing a conductive mortar according to any one of claims 1 to 6, characterized in that, The preparation method comprises the following steps: S1, soaking the self-combustion coal gangue in the electrolyte solution for 12 hours; S2, uniformly stirring metakaolin, steel slag, carbide slag, gypsum, an activator, a water-retaining agent and a water-reducing agent to form a mixture, pouring the electrolyte solution soaked with the self-combustion coal gangue into the mixture, and fully stirring to obtain a mixed slurry; S3, pouring the mixed slurry into a mold, vibrating and compacting, curing and demolding, and thus the conductive mortar is obtained.

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