Multifunctional admixture additive based on industrial solid waste and preparation and use method thereof

Abstract

This application belongs to the field of building materials technology, and more particularly relates to a multifunctional admixture additive based on industrial solid waste, and methods for its preparation and use. To address the poor electrical conductivity and hydrophobicity of concrete produced using admixture additives in the prior art, this application provides a multifunctional admixture additive based on industrial solid waste, and a method for its preparation. By utilizing a carbon nanotube-fly ash composite material and modified fly ash, the concrete possesses both electrical conductivity and excellent water resistance, improving the concrete's overall properties.

Description

Technical Field

[0001] The present application belongs to the field of building material technology, and particularly relates to a multifunctional admixture additive based on industrial solid waste and a preparation and use method thereof. Background Art

[0002] Fly ash is one of the main solid wastes generated during the combustion process in coal-fired power plants. When coal is burned in boilers, the minerals within it melt at high temperatures and are discharged with the flue gases. These tiny particles are captured and collected as they pass through dust removal equipment, forming fly ash. The chemical composition of fly ash varies depending on the type of coal burned and region, but generally includes silica, alumina, iron oxide, and calcium oxide. Silica is typically the primary component of fly ash, accounting for over 50% of the total. According to coal consumption in my country, burning one ton of coal produces approximately 250-300 kg of fly ash. If large amounts of fly ash are not controlled or treated, they can cause air pollution and, if they enter water bodies, can clog rivers. It is now widely used in the production of building materials such as concrete.

[0003] Traditional concrete is widely used in the construction industry due to its insulating properties. However, in certain specific application scenarios, such as heated pavements, lightning protection facilities, electromagnetic shielding, etc., ordinary concrete cannot meet the needs. To overcome this limitation, researchers began to explore how to make concrete conductive. In cold areas, conductive concrete can be used for paving roads to prevent snow and ice accumulation through electrical heating, or for building buildings that require electromagnetic shielding effects, such as data centers and laboratories. The lightning protection system of a building can use conductive concrete to improve its efficiency. By integrating sensors, conductive concrete can be used to monitor the health of the structure, such as crack detection, etc. In corrosive environments, conductive concrete can also provide corrosion protection.

[0004] CN107082602B discloses a non-fired concrete and its preparation method, comprising the following components expressed in parts by weight: 160-320 parts of cement; 100-140 parts of admixture; 700-900 parts of non-fired fine aggregate; 950-1150 parts of non-fired coarse aggregate; 1.7-2.3 parts of conductive enhancer; 1.4-1.9 parts of polyacrylonitrile carbon fiber; 5-9.5 parts of composite admixture; and 165-175 parts of water. The conductive enhancer is evenly dispersed in the slurry to form a large conductive network, making the concrete conductive. The conductive enhancer is 10-90nm carbon black powder. If the carbon black powder particle size is too large, it may cause uneven dispersion in the concrete slurry, forming areas with poor or excessive conductivity, affecting the overall conductive performance. Carbon black is inherently hydrophilic, which means that carbon black increases the water absorption of concrete and reduces its durability. Summary of the Invention

[0005] In order to solve the problem of poor conductivity and hydrophobicity of concrete obtained by admixture additives in the prior art, the present application provides a multifunctional admixture additive based on industrial solid waste and its preparation and use method. Through the carbon nanotube-fly ash composite material and the modification of fly ash, the concrete has good conductivity and good waterproof performance, thereby improving the comprehensive performance of the concrete.

[0006] The present application provides a method for preparing a multifunctional admixture additive based on industrial solid waste, comprising the following steps:

[0007] S1. Soak fly ash in a nickel nitrate hexahydrate solution with ethanol as the solute for 10-20 minutes, stir the mixture and heat it at a temperature of 50°C-55°C until the alcohol is completely evaporated.

[0008] S2. Introducing nitrogen and hydrogen into the reactor at 450° C. for 60-80 minutes, then adjusting the temperature to 400-500° C., introducing acetylene, reacting for 45-60 minutes, and then cooling to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material;

[0009] S3. Take untreated fly ash again, add stearic acid, and dry-ball grind for 8-10 hours to obtain component B hydrophobic fly ash.

[0010] Furthermore, the fly ash includes 50%-70% silicon dioxide, 5%-8% calcium oxide, 20%-40% aluminum oxide, and 3%-7% iron oxide.

[0011] Furthermore, the concentration of the nickel nitrate hexahydrate solution in step S1 is 0.05-0.2 mol / L.

[0012] Furthermore, in step S2, the nitrogen usage is 400-600 mL / min, the hydrogen usage is 200-600 mL / min, and the acetylene usage is 100-400 mL / min.

[0013] Furthermore, the dry ball grinding in step S3 uses alumina grinding media with a diameter of 10-19 mm, the ratio of alumina to fly ash is 5-8:1, and the weight ratio of fly ash to stearic acid is 60-80:1.

[0014] According to the above preparation method, a multifunctional admixture additive based on industrial solid waste is obtained, and the ratio of the component A to the component B is 1:1-3.

[0015] The method for using the multifunctional admixture additive based on industrial solid waste comprises the following steps: uniformly mixing component B with admixtures, cement and aggregate, adding component A after adding water, stirring into slurry, pouring, curing, molding and curing to obtain concrete.

[0016] Furthermore, the addition amount of the A and B components is 3%-8% of the total weight of the concrete.

[0017] The beneficial effects of this application are:

[0018] 1. The present application provides a method for preparing a multifunctional admixture additive based on industrial solid waste. By impregnating fly ash, nickel ions are adsorbed on its surface, providing the necessary catalytic active centers for the subsequent growth of carbon nanotubes. This ensures uniform growth of carbon nanotubes on the fly ash surface, improves the bonding strength between the carbon nanotubes and the fly ash, and enhances the activity of the fly ash surface, providing better conditions for subsequent carbon nanotube growth. Nitrogen and hydrogen are introduced into the reactor at high temperature to provide a reducing atmosphere, and acetylene gas is used as a carbon source. Under high temperature and a reducing atmosphere, acetylene decomposes to generate carbon atoms, which are catalyzed by the nickel ions on the fly ash surface and deposited to form carbon nanotubes. The generated carbon nanotubes are tightly bound to the fly ash, forming a conductive network that imparts electrical conductivity to concrete. Stearic acid, a long-chain fatty acid with lipophilicity, chemically adsorbs to functional groups such as hydroxyl groups on the fly ash surface. Stearic acid molecules form a hydrophobic film on the fly ash surface, significantly enhancing the hydrophobicity of the fly ash, reducing water adsorption, and improving the durability of concrete. Through mechanical grinding, the specific surface area of fly ash is increased and the uniform distribution of stearic acid molecules on the surface of fly ash is promoted. Under the action of mechanical force, stearic acid molecules are more firmly adsorbed on the surface of fly ash to form a stable hydrophobic layer, which makes the concrete conductive while also having good waterproof properties, thereby improving the comprehensive performance of concrete.

[0019] 2. After evenly mixing component B with raw materials such as cement and aggregate, add an appropriate amount of water and then component A. Stir to fully disperse the components to ensure that the carbon nanotube-fly ash composite material is evenly distributed in the concrete to form a conductive network. At the same time, the hydrophobic fly ash is well dispersed in the concrete, providing hydrophobic properties, improving the uniformity and performance consistency of the concrete, and reducing local performance differences. Using industrial solid waste fly ash as raw material realizes the recycling of resources and reduces environmental pollution. Compared with pure new materials, the use of industrial waste to prepare additives reduces production costs.

[0020] 3. Fly ash, as a porous material, has a large specific surface area and provides a large number of active sites. When used as a substrate for carbon nanotube growth, fly ash ensures uniform distribution of catalyst particles. The silica in fly ash has a large specific surface area, providing more active sites and favoring the growth of carbon nanotubes on its surface. Alumina, with its high melting point and chemical stability, can maintain its structural stability at high temperatures, providing a stable support platform for carbon nanotube growth and helping to improve the dispersion of fly ash particles, thereby promoting the uniform growth of carbon nanotubes on the fly ash surface. Iron oxide is one of the key catalysts for carbon nanotube growth. By providing iron ions, fly ash promotes the formation of carbon nanotubes, accelerates their growth rate, and helps control their diameter and length. Due to the porosity and high specific surface area of fly ash, carbon nanotubes grown on it can better adhere to the substrate. This enhanced bonding reduces the contact resistance between carbon nanotubes, helping to form a continuous conductive network, thereby improving overall conductivity. The silica and alumina in fly ash can play a certain buffering role, reducing thermal stress at high temperatures and helping to reduce defects in the growth process of carbon nanotubes. Fewer defects mean that electrons can move more smoothly inside the carbon nanotubes, thereby improving conductivity. DETAILED DESCRIPTION

[0021] The following specific examples further illustrate the technical solutions of the present invention and its effects. The following examples are only used to illustrate the content of the present invention and are not intended to limit the scope of protection of the present invention. Simple changes made to the present invention by applying the concept of the present invention are all within the scope of protection claimed in the present invention.

[0022] The equipment used in the preparation method of the present invention can be any known equipment in the art. Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0023] Example 1

[0024] S1. Soak fly ash in a 0.1 mol / L nickel nitrate hexahydrate solution containing ethanol as the solute for 10 minutes. Stir the mixture and heat it at 50° C. until the alcohol is completely evaporated.

[0025] S2. At 450°C, nitrogen and hydrogen were introduced into the quartz tube reactor for 60 min, with a nitrogen flow rate of 400 mL / min and a hydrogen flow rate of 400 mL / min. The temperature was then adjusted to 400°C, and acetylene was introduced at a flow rate of 200 mL / min. The reaction was carried out for 45 minutes, and then the introduction of hydrogen and acetylene was stopped. The mixture was cooled to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material.

[0026] S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 8 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 15 mm, the weight ratio of alumina to fly ash is 8:1, and the weight ratio of fly ash to stearic acid is 60:1, to obtain component B hydrophobic fly ash.

[0027] S4. Mix component B with admixtures, cement and aggregates evenly, add component A after adding water, stir to form a slurry, pour, cure, shape and solidify to obtain concrete, the weight ratio of component A to component B is 1:1, and the total weight of component A and component B is 3% of the total weight of the concrete.

[0028] Example 2

[0029] S1. Soak fly ash in a 0.2 mol / L nickel nitrate hexahydrate solution with ethanol as the solute for 20 minutes. Stir the mixture and heat it at 55° C. until the alcohol is completely evaporated.

[0030] S2. At 450°C, nitrogen and hydrogen were introduced into the quartz tube reactor and maintained for 80 minutes, with a nitrogen flow rate of 500 mL / min and a hydrogen flow rate of 600 mL / min. The temperature was then maintained at 450°C, acetylene was introduced at a flow rate of 100 mL / min, and the reaction was carried out for 60 minutes. The introduction of hydrogen and acetylene was then stopped, and the mixture was cooled to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material.

[0031] S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 10 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 19 mm, a weight ratio of alumina to fly ash of 5:1, and a weight ratio of fly ash to stearic acid of 70:1 to obtain component B hydrophobic fly ash.

[0032] S4. Mix component B with admixtures, cement and aggregates evenly, add component A after adding water, stir to form a slurry, pour, cure, shape and solidify to obtain concrete, the weight ratio of component A to component B is 1:2, and the total weight of component A and component B is 8% of the total weight of the concrete.

[0033] Example 3

[0034] S1. Soak fly ash in a 0.05 mol / L nickel nitrate hexahydrate solution containing ethanol as a solute for 15 minutes. Stir the mixture and heat it at 50° C. until the alcohol is completely evaporated.

[0035] S2. At 450°C, nitrogen and hydrogen were introduced into the quartz tube reactor for 70 minutes, with a nitrogen flow rate of 600 mL / min and a hydrogen flow rate of 200 mL / min. The temperature was then adjusted to 500°C, and acetylene was introduced at a flow rate of 400 mL / min. The reaction was carried out for 55 minutes, and then the introduction of hydrogen and acetylene was stopped. The mixture was cooled to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material.

[0036] S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 9 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 10 mm, the weight ratio of alumina to fly ash is 7:1, and the weight ratio of fly ash to stearic acid is 80:1, to obtain component B hydrophobic fly ash.

[0037] S4. Mix component B with admixtures, cement and aggregates evenly, add component A after adding water, stir to form a slurry, pour, cure, shape and solidify to obtain concrete, the weight ratio of component A to component B is 1:3, and the total weight of component A and component B is 5% of the total weight of the concrete.

[0038] Comparative Example 1

[0039] S1. Take untreated fly ash, add stearic acid, and dry ball grind for 9 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 10 mm. The weight ratio of alumina to fly ash is 7:1, and the weight ratio of fly ash to stearic acid is 80:1 to obtain hydrophobic fly ash of component B.

[0040] S2. Mix component B with admixtures, cement and aggregate evenly, add water and then add component A, where component A is carbon nanotubes sold by Guangzhou Jiushun New Materials Co., Ltd., stir into a slurry, pour, cure, shape and solidify to obtain concrete, wherein the weight ratio of component A to component B is 1:3, and the total weight of component A and component B is 5% of the total weight of the concrete.

[0041] Comparative Example 2

[0042] S1. Soak fly ash in a 0.2 mol / L nickel nitrate hexahydrate solution with ethanol as the solute for 20 minutes. Stir the mixture and heat it at 55° C. until the alcohol is completely evaporated.

[0043] S2. At 450°C, nitrogen and hydrogen were introduced into the quartz tube reactor for 80 min, with a nitrogen flow rate of 500 mL / min and a hydrogen flow rate of 600 mL / min. The temperature was then raised to 600°C, and acetylene was introduced at a flow rate of 100 mL / min. The reaction was carried out for 60 minutes, and then the introduction of hydrogen and acetylene was stopped. The mixture was cooled to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material.

[0044] S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 10 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 19 mm, a weight ratio of alumina to fly ash of 5:1, and a weight ratio of fly ash to stearic acid of 70:1 to obtain component B hydrophobic fly ash.

[0045] S4. Mix component B with admixtures, cement and aggregates evenly, add component A after adding water, stir to form a slurry, pour, cure, shape and solidify to obtain concrete, the weight ratio of component A to component B is 1:2, and the total weight of component A and component B is 8% of the total weight of the concrete.

[0046] Comparative Example 3

[0047] S1. Soak fly ash in a 0.1 mol / L nickel nitrate hexahydrate solution containing ethanol as the solute for 10 minutes. Stir the mixture and heat it at 50° C. until the alcohol is completely evaporated.

[0048] S2. At 450°C, nitrogen and hydrogen were introduced into the quartz tube reactor for 60 min, with a nitrogen flow rate of 400 mL / min and a hydrogen flow rate of 400 mL / min. The temperature was then adjusted to 400°C, and acetylene was introduced at a flow rate of 200 mL / min. The reaction was carried out for 45 minutes, and then the introduction of hydrogen and acetylene was stopped. The mixture was cooled to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material.

[0049] S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 8 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 15 mm, the weight ratio of alumina to fly ash is 8:1, and the weight ratio of fly ash to stearic acid is 60:1, to obtain component B hydrophobic fly ash.

[0050] S4. Mix component B with admixtures, cement and aggregates uniformly, add component A after adding water, stir into a slurry, pour, cure, shape and solidify to obtain concrete, the weight ratio of component A to component B is 1:1, and the total weight of component A and component B is 10% of the total weight of the concrete.

[0051] Comparative Example 4

[0052] S1. Soak fly ash in a 0.2 mol / L nickel nitrate hexahydrate solution with ethanol as the solute for 20 minutes. Stir the mixture and heat it at 55° C. until the alcohol is completely evaporated.

[0053] S2. At 450°C, nitrogen and hydrogen were introduced into the quartz tube reactor and maintained for 80 minutes, with a nitrogen flow rate of 500 mL / min and a hydrogen flow rate of 600 mL / min. The temperature was then maintained at 450°C, acetylene was introduced at a flow rate of 100 mL / min, and the reaction was carried out for 60 minutes. The introduction of hydrogen and acetylene was then stopped, and the mixture was cooled to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material.

[0054] S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 10 hours. The dry ball grinding uses an alumina grinding medium with a diameter of 19 mm, a weight ratio of alumina to fly ash of 5:1, and a weight ratio of fly ash to stearic acid of 70:1 to obtain component B hydrophobic fly ash.

[0055] S4. Mix component B with admixtures, cement and aggregates evenly, add component A after adding water, stir to form a slurry, pour, cure, shape and solidify to obtain concrete, the weight ratio of component A to component B is 1:5, and the total weight of component A and component B is 8% of the total weight of the concrete.

[0056] The concrete obtained in the examples and comparative examples was poured into a mold with a size of 100 mm × 100 mm × 100 mm. Some samples were used for resistivity and water contact angle tests, and the other samples were used for compressive strength tests. The test results are shown in the following table.

[0057] Table 1: Performance test table of samples obtained in specific implementation methods

[0058]

[0059] As can be seen from the data in the table above, the conductivity of Examples 1-3 is superior to that of Comparative Examples 1-3. The difference between Comparative Example 1 and Example 3 is that commercially available carbon nanotubes are used, resulting in a significantly higher resistivity than carbon nanotubes deposited using fly ash as a base. Compared to Example 2, Comparative Example 2, with a reaction temperature of 600°C, exhibits both lower resistivity and hydrophobicity than Example 2. Compared to Example 1, Comparative Example 3, with additives A and B accounting for 10% of the total weight of the concrete, exhibits lower resistivity than Example 1, while maintaining substantially the same hydrophobicity. Compared to Example 2, Comparative Example 4, with a weight ratio of Component A to Component B of 1:5, exhibits lower resistivity than Example 2, but better hydrophobicity than Example 2, due to the increased proportion of hydrophobic fly ash. In terms of compressive strength, there is little difference between Examples 1-3 and Comparative Examples 1, 2, and 4, but the compressive strength of Comparative Example 3 is significantly lower than that of the other embodiments due to the excessive proportion of additives in the total weight of the concrete.

Claims

1. A method for preparing a multifunctional admixture additive based on industrial solid waste, characterized in that: The following steps are involved: S1. Soaking fly ash in a nickel nitrate hexahydrate solution with ethanol as a solvent, wherein the concentration of the nickel nitrate hexahydrate solution is 0.05-0.2 mol / L, for 10-20 minutes, stirring the mixture and heating it at a temperature of 50° C.-55° C. until the ethanol is completely evaporated; S2. Introducing nitrogen and hydrogen into the reactor at 450° C. for 60-80 minutes, then adjusting the temperature to 400-500° C., introducing acetylene, reacting for 45-60 minutes, and then cooling to room temperature under a nitrogen atmosphere to obtain a component A carbon nanotube-fly ash composite material; S3. Take untreated fly ash again, add stearic acid, and dry ball grind for 8-10 hours to obtain hydrophobic fly ash of component B. The dry ball grinding uses an alumina grinding medium with a diameter of 10-19 mm, the ratio of alumina to fly ash is 5-8:1, and the mass ratio of fly ash to stearic acid is 60-80:1; the ratio of component A to component B is 1:1-3.

2. The method for preparing a multifunctional admixture additive based on industrial solid waste according to claim 1, characterized in that: The fly ash comprises 50%-70% silicon dioxide, 5%-8% calcium oxide, 20%-40% aluminum oxide, and 3%-7% iron oxide.

3. The method for preparing a multifunctional admixture additive based on industrial solid waste according to claim 1, characterized in that: In step S2, the nitrogen usage is 400-600 mL / min, the hydrogen usage is 200-600 mL / min, and the acetylene usage is 100-400 mL / min.

4. A multifunctional admixture additive based on industrial solid waste is obtained according to the preparation method of the multifunctional admixture additive based on industrial solid waste according to any one of claims 1 to 3.

5. The method for using the multifunctional admixture additive based on industrial solid waste according to claim 4, characterized in that: Mix component B with admixtures, cement and aggregates evenly, add component A after adding water, stir into slurry, pour, cure, shape and solidify to obtain concrete.

6. The method for using the multifunctional admixture additive based on industrial solid waste according to claim 5, characterized in that: The addition amount of the A and B components is 3%-8% of the total weight of the concrete.

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