A preparation method and application method of conductive concrete

Abstract

A method for preparing conductive concrete comprises the following steps: firstly, evenly mixing expandable graphite, concrete raw materials and carbon fibers to obtain an initial mixture, then adding water to the initial mixture and stirring to obtain concrete slurry, then curing the concrete slurry to obtain a solidified body, and then heating the solidified body to expand the expandable graphite, thereby obtaining the conductive concrete, and the heating temperature is 200°C-600°C. This design not only has better conductivity and lower production cost, but also can improve mechanical properties, and has a wide range of applications, such as indoor climate control, road deicing or cooking.

Description

Technical Field

[0001] The invention relates to a conductive technology for concrete, belongs to the field of concrete, and in particular to a preparation method and an application method of conductive concrete. Background Art

[0002] Concrete is one of the most important inorganic non-metallic materials widely used in building and civil engineering construction due to its unique properties, such as reliable strength, durability, mobility and low cost. However, the poor electrical conductivity of concrete limits its application in fields such as mechanical sensing, humidity sensing, crack detection or Joule heating, especially in the development of smart building materials.

[0003] In order to improve the conductivity of concrete, there is a technology in the prior art that introduces conductive fillers (such as carbon fiber) into concrete to obtain carbon fiber-based concrete, but this technology of adding carbon fiber has the following defects:

[0004] (1) The improvement in the conductivity of carbon fiber-based concrete is limited, and its minimum resistance is still too high (even if more carbon fibers are added, the permeation threshold will not be exceeded), making it difficult to use in areas such as electrothermal conversion;

[0005] (2) The cost of carbon fiber is too high. To obtain carbon fiber-based concrete, excessive amounts of carbon fiber need to be added, which greatly increases the production cost.

[0006] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the application, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to ordinary technicians in this field. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects and problems of limited improvement in conductivity and high production cost in the prior art, and to provide a preparation method and application method of conductive concrete with better conductivity improvement and lower production cost.

[0008] To achieve the above purpose, the technical solution of the present invention is: a method for preparing conductive concrete, the preparation method comprising the following steps: firstly, expandable graphite, concrete raw materials, and carbon fibers are uniformly mixed to obtain an initial mixture, then water is added to the initial mixture and stirred to obtain concrete slurry, then the concrete slurry is solidified to obtain a solidified body, and then the solidified body is heated to expand the expandable graphite, thereby obtaining the conductive concrete, and the heating temperature is 200°C-600°C.

[0009] The termination criterion for heating the solidified body is that the resistance of the conductive concrete no longer changes.

[0010] The amount of expandable graphite used accounts for 1wt%-10wt% of the weight of the concrete raw material.

[0011] The size of the expandable graphite is 0.1mm-1mm.

[0012] The amount of the carbon fiber is 1wt%-3wt% of the weight of the concrete raw material.

[0013] The carbon fiber is chopped carbon fiber with a length of 1mm-5mm.

[0014] The step of uniformly mixing the expandable graphite, concrete raw materials and carbon fibers to obtain an initial mixture means that the expandable graphite and concrete raw materials are uniformly mixed by ball milling, and then the ball milled product is uniformly mixed with the carbon fibers by stirring to obtain the initial mixture.

[0015] The curing of the concrete slurry to obtain a cured body refers to: leaving the concrete slurry to stand at room temperature for 3-30 days to obtain a cured body.

[0016] In the initial mixture, the amount of expandable graphite is two to five times the weight of the carbon fiber.

[0017] An application method of conductive concrete, wherein the conductive concrete is obtained according to the above preparation method;

[0018] The application method comprises: using the conductive concrete as a heating element, wherein the application field of the heating element is any one of indoor climate control, road deicing or cooking.

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

[0020] 1. In the preparation method and application method of a conductive concrete of the present invention, expandable graphite, concrete raw materials, and carbon fibers are first mixed uniformly, and then water is added for stirring and mixing to obtain concrete slurry, and then the concrete slurry is cured to obtain a cured body, and finally the cured body is heated (i.e., heat treated) to expand the expandable graphite, thereby obtaining the final conductive concrete, wherein when the expandable graphite expands, the volume of the expandable graphite increases, and the adjacent carbon fibers can be bridged to form a new conductive path, thereby obtaining a larger number of conductive paths with a wider coverage, greatly reducing the resistance of the concrete, and improving the conductive performance. In addition, the price of expandable graphite is extremely low, and therefore, the addition of expandable graphite can reduce the use of carbon fibers and reduce the production cost. Even if the amount of carbon fibers used remains unchanged, the additionally added expandable graphite is also conducive to breaking through the permeation threshold of the carbon fibers and improving the overall cost performance. Therefore, the present invention not only has better conductive performance improvement, but also has a lower production cost.

[0021] 2. In the preparation method and application method of a conductive concrete of the present invention, carbon fiber is added during preparation to improve the conductive performance. At the same time, the increase of carbon fiber will also improve the mechanical properties of concrete. In addition, during the curing process of concrete, certain bubbles and voids will be formed, and these bubbles and voids will cause the mechanical properties to decrease. However, in this design, when the expandable graphite is expanded after heat treatment, the increased volume will occupy some pores or voids, eliminating the defects of these pores or voids, thereby improving the overall mechanical strength of concrete. Therefore, the present invention can improve the mechanical properties.

[0022] 3. In the preparation method and application method of the conductive concrete of the present invention, the concrete slurry needs to be solidified before heat treatment, rather than directly heat treated, because the solidification of concrete requires a certain amount of water. If the concrete slurry is directly heat treated, the water will be consumed quickly, which is not conducive to the final molding of the concrete, and may even crack, greatly reducing the mechanical strength. Therefore, the present invention can ensure strong mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an operation flow chart of the present invention.

[0024] Figure 2 It is the position comparison between the expandable graphite and the adjacent carbon fibers before and after expansion in the present invention.

[0025] Figure 3 This is a graph showing the electrothermal conversion performance of the conductive concrete produced in Example 2 of the present invention.

[0026] Figure 4 It is a schematic diagram of the heating effect of the conductive concrete produced in Example 2 of the present invention when the power is turned on and off.

[0027] Figure 5 It is a schematic diagram comparing the mechanical strength of the conductive concrete produced in Example 3 of the present invention.

[0028] Figure 6 It is a comparative schematic diagram of the conductive properties (ie, resistance values) of the conductive concrete produced in Example 3 of the present invention. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0030] See also Figure 1 — Figure 6A method for preparing conductive concrete, the method comprising the following steps: firstly, uniformly mixing expandable graphite, concrete raw materials and carbon fibers to obtain an initial mixture, then adding water to the initial mixture and stirring to obtain concrete slurry, then curing the concrete slurry to obtain a solidified body, and then heating the solidified body to expand the expandable graphite, thereby obtaining the conductive concrete, and the heating temperature is 200°C-600°C.

[0031] The termination criterion for heating the solidified body is that the resistance of the conductive concrete no longer changes.

[0032] The amount of expandable graphite used accounts for 1wt%-10wt% of the weight of the concrete raw material.

[0033] The size of the expandable graphite is 0.1mm-1mm.

[0034] The amount of the carbon fiber is 1wt%-3wt% of the weight of the concrete raw material.

[0035] The carbon fiber is chopped carbon fiber with a length of 1mm-5mm.

[0036] The step of uniformly mixing the expandable graphite, concrete raw materials and carbon fibers to obtain an initial mixture means that the expandable graphite and concrete raw materials are uniformly mixed by ball milling, and then the ball milled product is uniformly mixed with the carbon fibers by stirring to obtain the initial mixture.

[0037] The curing of the concrete slurry to obtain a cured body refers to: leaving the concrete slurry to stand at room temperature for 3-30 days to obtain a cured body.

[0038] In the initial mixture, the amount of expandable graphite is two to five times the weight of the carbon fiber.

[0039] An application method of conductive concrete, wherein the conductive concrete is obtained according to the above preparation method;

[0040] The application method comprises: using the conductive concrete as a heating element, wherein the application field of the heating element is any one of indoor climate control, road deicing or cooking.

[0041] The principle of the present invention is described as follows:

[0042] The concrete raw material in the present invention refers to a substance that can be left to solidify after adding water, such as any one of cement, stone, sand, and aggregate or any mixture thereof.

[0043] The curing environment in the present invention is preferably room temperature and 98% humidity. Generally, the curing is basically completed in 28 days, and further curing no longer affects the mechanical properties.

[0044] The reason why the amount of expandable graphite in the present invention is preferably 1wt%-10wt% of the weight of the concrete raw material is that if the weight proportion is less than 1wt%, it will affect the formation of new conductive paths and the conductivity will be poor. If the weight proportion is greater than 10wt%, it will affect the strength of the final product and reduce the mechanical properties.

[0045] The reason why the amount of carbon fiber preferably accounts for 1wt%-3wt% of the weight of the concrete raw material in the present invention is that if the weight proportion is less than 1wt%, the conductivity is poor, and if the weight proportion is greater than 3wt%, the permeation threshold is exceeded, resulting in a waste of carbon fiber.

[0046] In the present invention, the carbon fiber is preferably chopped carbon fiber with a length of 1 mm to 5 mm because: if the carbon fiber is too long, it is not easy to mix evenly, while if the length is too short, the conductivity is poor.

[0047] After the expandable graphite in the present invention is heat treated, the expandable graphite expands, the volume of the expandable graphite increases, and the expandable graphite can bridge adjacent carbon fibers to form a new conductive path (such as Figure 2 as shown).

[0048] Embodiment 1:

[0049] See also Figure 1 — Figure 6 , a method for preparing conductive concrete, the preparation method comprising the following steps: firstly, expandable graphite, concrete raw materials (such as cement powder), and carbon fibers are uniformly mixed to obtain an initial mixture, wherein the amount of the expandable graphite accounts for 1wt%-10wt% of the weight of the concrete raw materials, and the amount of the carbon fibers accounts for 1wt%-3wt% of the weight of the concrete raw materials, and then water is added to the initial mixture and stirred to obtain concrete slurry, and then the concrete slurry is cured to obtain a cured body (cement composite material), and then the cured body is heated to expand the expandable graphite, thereby obtaining the conductive concrete (preferably, the end standard of heating the cured body is: the resistance of the conductive concrete no longer changes), and the heating temperature is 200°C-600°C.

[0050] Embodiment 2:

[0051] The basic content is the same as that of Example 1, except that:

[0052] The amount of expandable graphite is 3wt% of the weight of the concrete raw material, and the amount of carbon fiber is 1wt% of the weight of the concrete raw material. The expandable graphite and the concrete raw material are firstly mixed by ball milling for 2 hours, and then the carbon fiber is added and mixed for 5 minutes to obtain an initial mixture, and then an appropriate amount of water is added to the initial mixture of the powder to obtain a concrete slurry, and then the concrete slurry is cured to obtain a cured body, and the curing time is 14 days, and then the cured body is placed in an oven at a temperature of 300° C. for heat treatment for 10 minutes to obtain the conductive concrete.

[0053] First, the conductive concrete is coated with conductive silver glue at both ends, then clamped with steel clamps, and then powered on to heat it for observation.

[0054] like Figure 3 As shown (showing the heating effect under voltages of 6 volts, 8 volts, 10 volts, and 12 volts), the conductive concrete (5x3cm) can be heated to 160°C under a voltage of 12 volts, and has extremely strong electrothermal conversion performance.

[0055] like Figure 4 As shown in the figure, with the continuous progress of heating, the heating effect of the conductive concrete becomes better and better, and finally reaches 160°C. At the same time, after the power is turned off at 160°C, it can be found that within 60S, it still has a relatively high temperature and a strong heat storage effect.

[0056] Embodiment 3:

[0057] The basic content is the same as that of Example 1, except that:

[0058] A method for applying conductive concrete, wherein the conductive concrete is obtained according to the above-mentioned preparation method; the method for applying comprises: using the conductive concrete as a heating element, wherein the application field of the heating element is any one of indoor climate control, road deicing or cooking.

[0059] The indoor climate control refers to using conductive concrete as a heating element on a wall or floor, such as wall tiles, floor tiles, etc.

[0060] The road deicing method refers to using conductive concrete as a component of the pavement surface for deicing in cold weather.

[0061] The cooking method is to use the conductive concrete as a dedicated heating area in a park, campground or other picnic site to facilitate cooking food during a picnic.

[0062] Embodiment 4:

[0063] The basic content is the same as that of Example 1, except that:

[0064] In the initial mixture, the amount of expandable graphite is two to five times the weight of the carbon fiber. For example, the amount of carbon fiber is 1.5wt%, and the amount of expandable graphite is 4wt%, 5wt%, and 6wt%, respectively, as shown below:

[0065] CC-0: Conductive concrete made by mixing carbon fiber with concrete raw materials, with carbon fiber accounting for 1.5wt%.

[0066] ECC-4: Conductive concrete made by mixing carbon fiber, expandable graphite and concrete raw materials, with carbon fiber accounting for 1.5wt% and expandable graphite accounting for 4wt%.

[0067] ECC-5: Conductive concrete made by mixing carbon fiber, expandable graphite and concrete raw materials, with carbon fiber accounting for 1.5wt% and expandable graphite accounting for 5wt%.

[0068] ECC-6: Conductive concrete made by mixing carbon fiber, expandable graphite and concrete raw materials, with carbon fiber accounting for 1.5wt% and expandable graphite accounting for 6wt%.

[0069] See also Figure 5 , the figure shows the strength comparison of four kinds of conductive concrete. It can be found that the mechanical strength of the conductive concrete containing expandable graphite is significantly greater than that of the conductive concrete containing only carbon fiber, and the mechanical strength of the conductive concrete containing only carbon fiber is greater than that of the conventional concrete (cement) without carbon fiber.

[0070] See also Figure 6 The figure shows the resistance value comparison of four types of conductive concrete. It can be found that the resistance value of the conductive concrete containing expandable graphite after the graphite is expanded after heat treatment is significantly lower than that of the conductive concrete containing only carbon fiber, and the conductive performance is significantly improved.

[0071] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. A method for preparing conductive concrete, characterized in that The preparation method comprises the following steps: First, expandable graphite, concrete raw materials and carbon fibers are uniformly mixed to obtain an initial mixture, water is added to the initial mixture and stirred to obtain concrete slurry, the concrete slurry is then cured to obtain a cured body, and the cured body is heated to expand the expandable graphite, the expansion increases the volume of the graphite, so as to bridge adjacent carbon fibers and form a new conductive path, thereby obtaining the conductive concrete, and the heating temperature is 200°C-600°C.

2. The method for preparing conductive concrete according to claim 1, characterized in that: The termination criterion for heating the solidified body is that the resistance of the conductive concrete no longer changes.

3. A method for preparing conductive concrete according to claim 1 or 2, characterized in that: The amount of expandable graphite used accounts for 1wt%-10wt% of the weight of the concrete raw material.

4. The method for preparing conductive concrete according to claim 3, characterized in that: The size of the expandable graphite is 0.1mm-1mm.

5. The method for preparing conductive concrete according to claim 1 or 2, characterized in that: The amount of the carbon fiber is 1wt%-3wt% of the weight of the concrete raw material.

6. The method for preparing conductive concrete according to claim 1 or 2, characterized in that: The carbon fiber is chopped carbon fiber with a length of 1mm-5mm.

7. A method for preparing conductive concrete according to claim 1 or 2, characterized in that: The step of uniformly mixing expandable graphite, concrete raw materials and carbon fibers to obtain an initial mixture refers to: First, the expandable graphite and the concrete raw material are uniformly mixed by ball milling, and then the ball milled product is uniformly mixed with the carbon fiber by stirring to obtain an initial mixture.

8. The method for preparing conductive concrete according to claim 1 or 2, characterized in that: The curing of the concrete slurry to obtain a cured body refers to: leaving the concrete slurry to stand at room temperature for 3-30 days to obtain a cured body.

9. The method for preparing conductive concrete according to claim 1 or 2, characterized in that: In the initial mixture, the amount of expandable graphite is two to five times the weight of the carbon fiber.

10. A method for applying conductive concrete, characterized in that: The conductive concrete is prepared according to claim 1 or 2; The application method comprises: using the conductive concrete as a heating element, wherein the application field of the heating element is any one of indoor climate control, road deicing or cooking.

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