Concrete member with electric heating characteristic and preparation method

Abstract

The invention discloses a concrete member with an electric heating characteristic and a preparation method thereof. The concrete member comprises concrete and an electrode mesh arranged in the concrete, wherein the concrete is prepared from sand, fly ash, mineral powder, carbon fibers and an alkali activator through alkali excitation reaction, molding, curing and water absorption; the surface of the concrete is coated with resin to form a sealing structure; the electrode meshes are pre-buried in the concrete before the concrete is formed, and the plurality of electrode meshes are arranged at intervals; every two adjacent electrode meshes serve as a unit, and a plurality of units are connected through wires to form a parallel circuit. The prepared carbon fiber-alkali activated concrete converts electric energy into heat energy through the Joule effect, a traditional heating mode can be replaced, consumption of fossil fuel is reduced, and the carbon fiber-alkali activated concrete has great application potential in near-zero-energy-consumption buildings.

Description

Technical Field

[0001] The present invention relates to the technical field of self-heating concrete and building energy conservation and consumption reduction, and in particular to a concrete component with electric heating characteristics and a preparation method thereof. Background Art

[0002] Alkali-activated materials are green, environmentally friendly cementitious materials formed by the reaction of alkaline solutions with aluminosilicates. They feature low carbon emissions, high strength, and high ionic conductivity. The incorporation of carbon fibers allows for the coordination of electronic and ionic conduction, further enhancing the stability of the conductive network. The resulting carbon fiber-alkali-activated composite material can convert electrical energy into thermal energy through the Joule effect, offering broad application prospects in building heating, deicing, and accelerated concrete curing.

[0003] In existing technologies, self-heating concrete typically uses traditional cement as a binder. Its conductivity depends on the addition of conductive fillers, such as carbon fiber, graphite, steel fiber, and carbon nanotubes. Conductive fillers are unevenly dispersed and prone to agglomeration, resulting in uneven heating and significant thermal stress. Traditional self-heating concrete is energized using a two-electrode method, with a single current path: from one electrode through the self-heating concrete to the other electrode. Due to the high impedance at the electrode-concrete interface, heat accumulates there, causing cracks to develop at the interface. Furthermore, when the concrete span is large, the two-electrode method causes the current transmission path to become longer, which can also lead to uneven heating.

[0004] Therefore, there is an urgent need for a concrete with long-term stable electrothermal properties to solve the above problems. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the object of the present invention is to provide a carbon fiber-alkali excited concrete component with electrothermal properties and a preparation method.

[0006] The present invention is implemented by the following technical solutions: In a first aspect, a concrete component having electrothermal properties is provided, comprising: Concrete and an electrode mesh set therein; The concrete is made of sand, fly ash, mineral powder, carbon fiber and alkali activator through alkali activation reaction, followed by molding, curing and water absorption; the surface of the concrete is covered with resin to form a sealed structure; The electrode mesh is embedded in the concrete before it is formed, and multiple pieces are arranged at intervals; two adjacent electrode meshes are regarded as a unit, and multiple units are connected by wires to form a parallel circuit.

[0007] In one possible implementation, the concrete includes the following components: 85-95 parts fly ash, 5-15 parts mineral powder, 3-5 parts sodium hydroxide, 30-40 parts sodium silicate aqueous solution, 10-13 parts water, 50-70 parts standard sand and 3-5 parts carbon fiber.

[0008] In one possible implementation, the modulus of the sodium silicate aqueous solution is 2-2.2, and the solid content of the sodium silicate aqueous solution is 40-45%.

[0009] In one possible implementation, the carbon fibers include carbon fiber powder and carbon fibers of different lengths.

[0010] Furthermore, the carbon fiber includes, by mass, 0.6-1 parts of carbon fiber powder, 0.9-1.5 parts of 3mm carbon fiber, and 1.5-2.5 parts of 6mm carbon fiber.

[0011] Furthermore, the carbon fiber has a length of 6-9 mm, a tensile strength of 4000-5000 MPa, an elastic modulus of 200-250 GPa, and a resistivity of 1.0-1.3 Ω·cm.

[0012] In one possible implementation, a plurality of electrode meshes are arranged in parallel, and the cross-sectional area of ​​each mesh in the concrete accounts for 80% to 90% of the cross-sectional area of ​​the concrete.

[0013] In one possible implementation, the spacing between the electrode meshes is 40-50 mm.

[0014] In a possible implementation, the electrode meshes are alternately connected to the two poles of the power supply in sequence, so that the concrete portion between two adjacent electrode meshes forms a parallel circuit.

[0015] Furthermore, the electrode meshes are connected by wires to form a first connection end, and the remaining electrode meshes are connected to form a second connection end. The first connection end and the second connection end are respectively connected to two poles of the power supply.

[0016] In a second aspect, a method for preparing a concrete component having electrothermal properties as described in the first aspect is provided, comprising: Adding carbon fibers into an alkaline activator and fully dispersing them to obtain a carbon fiber suspension; Fly ash and mineral powder are mixed, carbon fiber suspension is added and mixed, and then standard sand is added and mixed to obtain a carbon fiber-alkali activated composite material; Pour the carbon fiber-alkali activated composite material into a mold, insert the electrode mesh inside, adjust and fix the spacing and position of the electrode mesh, vibrate it fully and then cure it at room temperature; After solidification, demoulding is performed and after curing, a carbon fiber-alkali activated concrete component is obtained; The carbon fiber-alkali activated concrete component is immersed in water, and after being fully saturated with water, the surface is coated with epoxy resin glue; The stainless steel meshes are alternately connected to two levels of an external AC power supply using a wire, so that the concrete portion between two adjacent electrode meshes forms a parallel circuit.

[0017] The present invention has the following technical effects: 1. The concrete component of the present invention uses an alkali-activated material as a cementitious material. Sodium aluminum silicate gel is the main reaction product and is a three-dimensional spatial structure with multiple cavities inside. Sodium ions have greater freedom of movement within the three-dimensional cavities, which can promote ion exchange, resulting in the alkali-activated material having higher ionic conductivity.

[0018] 2. The concrete component of the present invention uses carbon fibers of different lengths as conductive fillers, which can effectively avoid carbon fiber agglomeration and improve the stability of the electronic conduction network.

[0019] 3. The concrete component of the present invention fully absorbs water to saturation and is sealed by coating with epoxy resin, which can achieve sufficient water retention, not only providing a highly conductive environment, but also utilizing the high specific heat capacity of water to achieve heat equalization and thermal insulation.

[0020] 4. The concrete component preparation method of the present invention strictly controls the sand content. Alkali-activated materials and carbon fibers have the characteristics of thermal shrinkage, while standard sand has the characteristics of thermal expansion. Through quality adjustment, the thermal deformation of the component can be greatly reduced, making the electrical and thermal performance of the component more stable.

[0021] 5. The concrete component fabrication method described in this invention modifies the component's electrical circuit, replacing the traditional two-electrode method with a multi-electrode method. This replaces a single series circuit with multiple parallel circuits, shifting current conduction from a single direction to multiple directions. Due to the parallel circuit's characteristics, excellent electrothermal performance can be achieved even with large component spans, eliminating the need for external high-voltage connections. Furthermore, this circuit modification results in more uniform component heating, significantly reducing damage to the component from thermal stress and ensuring long-term, stable electrothermal performance.

[0022] 6. The concrete component of the present invention utilizes the Joule effect to convert electrical energy into thermal energy, which can replace traditional heating methods, reduce the consumption of fossil fuels, and has great application potential in near-zero energy buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the four electrodes of carbon fiber-alkali excited concrete component.

[0024] Figure 2 Schematic diagram of the eight electrodes of carbon fiber-alkali excited concrete component.

[0025] Figure 3 Thermal strain comparison chart for electro-thermal test.

[0026] Figure 4 Temperature distribution comparison chart for electro-thermal test.

[0027] Figure 5 Temperature distribution chart for cyclic electro-thermal test. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments.

[0029] Embodiment 1 The concrete component with electro-thermal characteristics provided by the embodiments of the present application is prepared from the following components: 85 parts of fly ash, 15 parts of mineral powder, 3 parts of sodium hydroxide, 30 parts of sodium silicate aqueous solution, 10 parts of water, 50 parts of standard sand, 0.6 parts of carbon fiber powder, 0.9 parts of 3 mm carbon fiber, and 1.5 parts of 6 mm carbon fiber.

[0030] The mineral powder is S95 granulated blast furnace mineral powder; the modulus of the sodium silicate aqueous solution is 2.2, and the solid content is 40-45%; the carbon fiber is PAN-based carbon fiber with a length of 6-9 mm, a tensile strength of 4000-5000 MPa, an elastic modulus of 200-250 GPa, and an electrical resistivity of 1.0-1.3 Ω·cm.

[0031] Figure 1 The four-electrode schematic diagram of the carbon fiber-alkali-activated concrete component with electro-thermal characteristics provided by the present application comprises the following preparation steps: (1) Each component is weighed according to the raw material ratio, and the sodium hydroxide particles, the sodium silicate aqueous solution, and the water are fully mixed to prepare an alkali activator; (2) Different sizes of carbon fibers are added to the alkali activator, and an ultrasonic dispersing instrument is used for dispersion for 30 min to uniformly disperse the carbon fibers, to obtain a carbon fiber suspension; (3) The fly ash and the mineral powder are poured into a stirrer and stirred for 2 min, then the carbon fiber suspension is added into the stirrer while stirring, and the stirring is first slow for 2 min, then fast for 1 min, and finally the standard sand is added into the stirrer and stirred for 2 min, to obtain a carbon fiber-alkali-activated composite material; (4) The carbon fiber-alkali-activated composite material is poured into a mold, a stainless steel electrode mesh is inserted into the inside, the mold is placed on a vibrating table and vibrated for 30 s, and the position of the stainless steel electrode mesh is fixed, and the spacing of the stainless steel electrode mesh is 40 mm; (5) The vibrated carbon fiber-alkali activated composite material was cured at room temperature for 1 day before demoulding, and then further cured at this environment for 28 days to obtain a carbon fiber-alkali activated concrete component; (6) Soak the carbon fiber-alkali activated concrete components that have reached the curing age in water for 1 day. After they are fully saturated with water, coat the surface with epoxy resin glue.

[0032] (7) Use wires to connect the stainless steel meshes. From left to right, stainless steel electrode meshes A and C are connected, stainless steel electrode meshes B and D are connected, and the stainless steel electrode meshes A and D at both ends are connected to the external AC power supply.

[0033] Example 2 An embodiment of the present invention provides a concrete component with electrothermal properties, wherein the raw materials for preparing the concrete component include the following components: 90 parts of fly ash, 10 parts of mineral powder, 4 parts of sodium hydroxide, 35 parts of sodium silicate, 12 parts of water, 60 parts of standard sand, 0.8 parts of carbon fiber powder, 1.2 parts of 3mm carbon fiber, and 2 parts of 6mm carbon fiber.

[0034] Figure 2 This is a schematic diagram of eight electrodes of a carbon fiber-alkali-excited concrete component with electrothermal properties according to the present invention, which includes the following preparation steps: (1) Weigh each component according to the raw material ratio, and fully mix the sodium hydroxide particles, sodium silicate aqueous solution and water to prepare an alkali activator; (2) Add carbon fibers of different sizes to an alkaline activator and disperse them using an ultrasonic disperser for 30 minutes to uniformly disperse the carbon fibers to obtain a carbon fiber suspension; (3) Pour fly ash and mineral powder into a blender and stir for 2 minutes, then add the carbon fiber suspension into the blender while stirring, first stir slowly for 2 minutes, then stir quickly for 1 minute, and finally add standard sand into the blender and stir for 2 minutes to obtain a carbon fiber-alkali excited composite material; (4) Pour the carbon fiber-alkali activated composite material into the mold and insert the stainless steel electrode mesh inside. Place the mold on a vibration table and vibrate for 30 seconds. Fix the position of the stainless steel electrode mesh. The spacing between the stainless steel electrode meshes is 40 mm. (5) The vibrated carbon fiber-alkali activated composite material was cured at room temperature for 1 day before demoulding, and then further cured at this environment for 28 days to obtain a carbon fiber-alkali activated concrete component; (6) Soak the carbon fiber-alkali activated concrete components that have reached the curing age in water for 1 day. After they are fully saturated with water, coat the surface with epoxy resin glue.

[0035] (7) Use wires to connect the stainless steel meshes. From left to right, stainless steel electrode meshes A, C, E, and G are connected, and stainless steel electrode meshes B, D, F, and H are connected. The stainless steel electrode meshes A and H at the beginning and end are connected to the external AC power supply.

[0036] The carbon fiber-alkali-activated concrete components with electrothermal properties according to the embodiments of the present invention have stable electrothermal performance compared to conventional concrete components. The electrothermal property comparison test and cyclic electrothermal test of the carbon fiber-alkali-activated concrete components according to Example 1 are further described below. 1. Comparative test of electrothermal characteristics: (1) Test subjects: The two-electrode carbon fiber-ordinary concrete component was the control group, and the four-electrode carbon fiber-alkali-activated concrete component (the component prepared in Example 1) was the experimental group.

[0037] (2) The preparation method of the control group components is as follows: Preparation materials: 100 parts of Portland cement, 30 parts of water, 50 parts of standard sand, and 3 parts of 6mm carbon fiber.

[0038] Preparation steps: adding carbon fiber to water, dispersing it with an ultrasonic disperser for 30 minutes to uniformly disperse the carbon fiber to obtain a carbon fiber suspension; pouring cement into a blender, then adding the carbon fiber suspension to the blender, stirring while adding, first slowly stirring for 2 minutes, then rapidly stirring for 1 minute, and finally adding standard sand to the blender and stirring for 2 minutes to obtain a carbon fiber-cement composite material; pouring the carbon fiber-cement composite material into a mold, and inserting a stainless steel electrode mesh at each end, and placing the mold on a vibration table and vibrating it for 30 seconds; the vibrated carbon fiber-cement composite material is demoulded after curing at room temperature for 1 day, and then further cured in this environment for 28 days to obtain a carbon fiber-ordinary concrete component.

[0039] (3) Test process: The components are connected to an external AC power supply, and a 7V AC voltage is applied to each component for 60 minutes. An infrared camera is used to record the temperature changes of the components during the electric heating process, and a strain gauge is used to measure the thermal deformation of the component surface.

[0040] (4) Test results: The results of the electric heating test of the control group and the experimental group are as follows Figure 3 and Figure 4 As shown, it can be seen that the two-electrode carbon fiber-ordinary concrete component has obvious local heating, produces large thermal strain, and damages the conductive network, while the four-electrode carbon fiber-alkali-excited concrete component heats evenly, has small thermal deformation, and almost no thermal stress, which can maintain stable electrothermal characteristics.

[0041] 2. Cyclic electric heating test: (1) Test object: Four-electrode carbon fiber-alkali-activated concrete component (2) Test process: The component is connected to an external AC power supply. A 10V AC voltage is applied to the component for 60 minutes and then the power is turned off. After the component cools to room temperature, the power is turned on again. This process is repeated 12 times. An infrared camera is used to record the temperature changes of the component during the electric heating process.

[0042] (3) Test results: The temperature distribution of the four-electrode carbon fiber-alkali excited concrete component after each cycle is as follows: Figure 5 As shown, it can be seen that the component has long-term and stable electrothermal characteristics. After 12 electrothermal cycles, the maximum temperature of the component is 7.7℃ lower than the first time. The temperature drop is due to the evaporation of free water inside the component during the electrothermal process, which causes a slight increase in resistance. Starting from the 9th cycle, the heating of the component tends to be stable, and the average temperature is maintained at 43.3℃.

[0043] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent replacements and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention should be included in the scope of protection of the invention.

Claims

1. A concrete component with electrothermal properties, characterized in that: include: Concrete and an electrode mesh set therein; The concrete is made of sand, fly ash, mineral powder, carbon fiber and alkali activator through alkali activation reaction, followed by molding, curing and water absorption; the surface of the concrete is covered with resin to form a sealed structure; The electrode mesh is embedded in the concrete before it is formed, and multiple pieces are arranged at intervals; two adjacent electrode meshes are regarded as a unit, and multiple units are connected by wires to form a parallel circuit.

2. The concrete component according to claim 1, characterized in that The concrete includes the following components by mass: 85-95 parts of fly ash, 5-15 parts of mineral powder, 3-5 parts of sodium hydroxide, 30-40 parts of sodium silicate aqueous solution, 10-13 parts of water, 50-70 parts of standard sand and 3-5 parts of carbon fiber.

3. The concrete component according to claim 1, characterized in that The modulus of the sodium silicate aqueous solution is 2-2.2, and the solid content of the sodium silicate aqueous solution is 40-45%.

4. The concrete component according to claim 1, characterized in that The carbon fibers include carbon fiber powder and carbon fibers of different lengths.

5. The concrete component according to claim 4, characterized in that In parts by mass, the carbon fiber includes: 0.6-1 parts of carbon fiber powder, 0.9-1.5 parts of 3mm carbon fiber, and 1.5-2.5 parts of 6mm carbon fiber.

6. The concrete component according to claim 4, characterized in that The carbon fiber has a length of 6-9 mm, a tensile strength of 4000-5000 MPa, an elastic modulus of 200-250 GPa, and a resistivity of 1.0-1.3 Ω·cm.

7. The concrete component according to claim 1, characterized in that The electrode mesh sheets are arranged in parallel, and the cross-sectional area of ​​each mesh sheet in the concrete accounts for 80% to 90% of the cross-sectional area of ​​the concrete.

8. The concrete component according to claim 1, characterized in that The spacing between the electrode meshes is 40-50 mm.

9. The concrete component according to claim 1, characterized in that The electrode meshes are alternately connected to the two poles of the power supply in sequence, so that the concrete portion between two adjacent electrode meshes forms a parallel circuit.

10. A method for preparing a concrete component with electrothermal properties according to any one of claims 1 to 9, characterized in that: include: Adding carbon fibers into an alkaline activator and fully dispersing them to obtain a carbon fiber suspension; Fly ash and mineral powder are mixed, carbon fiber suspension is added and mixed, and then standard sand is added and mixed to obtain a carbon fiber-alkali activated composite material; Pour the carbon fiber-alkali activated composite material into a mold, insert the electrode mesh inside, adjust and fix the spacing and position of the electrode mesh, vibrate it fully and then cure it at room temperature; After solidification, demoulding is performed and after curing, a carbon fiber-alkali activated concrete component is obtained; The carbon fiber-alkali activated concrete component is immersed in water, and after being fully saturated with water, the surface is coated with epoxy resin glue; Use wires to alternately connect the stainless steel mesh to the two poles of an external AC power supply so that the concrete part between two adjacent electrode meshes forms a parallel circuit.

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