Conductive fiber reinforced concrete and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to conductive fiber reinforced concrete and a preparation method thereof. The conductive fiber reinforced concrete is prepared from 350 to 450 parts of cement, 500 to 900 parts of fly ash, 400 to 800 parts of iron tailing sand, 3 to 20 parts of a water reducing agent, 15 to 40 parts of modified aragonite whisker and 200 to 400 parts of water, wherein the water-binder ratio of the conductive fiber reinforced concrete is 0.2 to 0.35; graphene oxide is loaded on the surface of the modified aragonite whisker. According to the invention, the graphene oxide is coated on the surface of the aragonite whisker through the silane coupling agent, so that the conductivity of the aragonite whisker is improved; meanwhile, the concrete adopts iron tailing sand as fine aggregate, so that the conductivity of the concrete is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly to a conductive fiber-reinforced concrete and a preparation method thereof. Background Art

[0002] As a new type of intelligent building material, conductive concrete significantly improves the electrical conductivity of traditional concrete by incorporating conductive phase materials (such as carbon fiber, graphite, or metal components), forming a multifunctional composite material with excellent mechanical properties and electrical response. It realizes the synergistic effect of the "structure - circuit" dual attributes, providing an innovative technical solution for intelligent transportation systems.

[0003] In the prior art, a patent application with the patent publication number CN 11623167 A, a preparation method and application method of conductive concrete, discloses a preparation method of conductive concrete, including the following steps: first, uniformly mix expandable graphite, concrete raw materials, and carbon fiber to obtain an initial mixture, then add water to the initial mixture and stir to obtain concrete slurry, then cure the concrete slurry to obtain a cured body, and then heat the cured body to cause the expandable graphite to expand, thereby obtaining the conductive concrete, and the heating temperature is 200°C - 600°C.

[0004] Again, for example, a patent application with the patent publication number JP1991174342A provides an inorganic building material that can be used for new purposes, an inorganic hardened body characterized by carbon whiskers obtained by a mixed vapor phase method. It can not only produce carbon whiskers produced by the vapor phase method at low cost, but also replace the use of traditional carbon fibers. The carbon whiskers used in the present invention have a spiral diameter of about 0.1 to 10μm, preferably about 1 - 5μm; preferably a length of about 100μm to 3mm.

[0005] However, when using carbon fiber, pure carbon conductive components, and metal components to make conductive concrete, the prices of carbon fiber and metal components are relatively expensive compared to the total cost of concrete; while using graphite as the conductive component, the conductive effect is not good, and at the same time, high-temperature heating is required, with high process difficulty and cost.

[0006] In addition, materials such as carbon fiber, carbon whiskers grown by the vapor phase method, and conductive polymer materials are all soft and easily curled conductive materials, which are not easily unfolded to form a conductive network during the mixing process of concrete; therefore, the conductivity of the final concrete is not good, especially manifested in uneven conductivity.

[0007] Therefore, it is necessary to provide a conductive fiber-reinforced concrete and a preparation method thereof to solve the above problems. Summary of the Invention

[0008] The main object of the present invention is to provide a conductive fiber reinforced concrete and a preparation method thereof, so as to solve the above technical problems proposed in the background art.

[0009] To achieve the above object, a conductive fiber reinforced concrete provided by the present invention includes: 350 - 450 parts of cement, 500 - 900 parts of fly ash, 400 - 800 parts of iron tailing sand, 3 - 20 parts of water reducing agent, 15 - 40 parts of modified aragonite whiskers, and 200 - 400 parts of water; wherein, the water - binder ratio of the conductive fiber reinforced concrete is 0.2 - 0.35; the surface of the modified aragonite whiskers of the modified aragonite whiskers is loaded with graphene oxide, the aspect ratio of the modified aragonite whiskers is 10 - 20, the diameter is 0.5 - 1.5 μm, and the length is 20 - 30 μm.

[0010] Preferably, the cement is composite Portland cement; the fly ash is low - calcium fly ash with a calcium content of less than 10%; the particle size of the iron tailing sand is 100 - 600 microns; the water reducing agent is a polycarboxylate - based water reducing agent, and the water reducing rate of the water reducing agent is not less than 20%.

[0011] The present invention also provides a preparation method of the conductive fiber reinforced concrete, including the steps: S1, dry - mix 500 - 900 parts of fly ash and 350 - 450 parts of cement; then add 400 - 800 parts of iron tailing sand and continue dry - mixing. S2, in the mixture obtained by dry - mixing in step S1, add 3 - 20 parts of water reducing agent and 200 - 400 parts of water and stir, then add 15 - 40 parts of modified aragonite whiskers with graphene oxide loaded on the surface, and continue to stir evenly to obtain fiber - reinforced concrete. The preparation method of the modified aragonite whiskers with graphene oxide loaded on the surface includes: S31, mix desulfurized gypsum 100 - 300 g, ammonia water with a concentration of 10% - 30% 150 - 250 ml, and water 1000 ml according to the ratio, stir at a temperature of 70 - 90 °C and a rotation speed of 300 - 500 rpm, and react for 4 - 10 min. S32, introduce industrial tail gas containing 10% - 30% carbon dioxide, continuously stir and react at a temperature of 70 - 90 °C for 0.5 - 1 h to generate aragonite whiskers. S331, in the solution after the reaction in step S32, add 100 - 500 ml of silane coupling agent with a mass fraction of 0.2% - 2% according to the ratio in step S31, stir for 1 - 3 hours, and dry the centrifuged solid matter in an oven. S332. Add the product obtained in step S331 in an amount of 100 - 200 g to 1000 ml of a graphene oxide solution with a mass fraction of 0.02% - 0.05% at a ratio, stir for 1 - 3 hours, dry the solid material obtained after centrifuging the slurry in an oven to obtain modified aragonite whiskers. The aspect ratio of the modified aragonite whiskers is 10 - 20, the diameter is 0.5 - 1.5 μm, and the length is 20 - 30 μm.

[0012] Preferably, the desulfurized gypsum is CaSO4·2H2O with a purity of over 95%. The specific surface area of the desulfurized gypsum powder is about 264 m 2 / kg.

[0013] Preferably, in step S331, the concentration of the silane coupling agent is 1.0%; in step S332, the concentration of graphene oxide is 0.03%; in step S2, the amount of modified aragonite whiskers is 30 - 40 parts.

[0014] Preferably, the reaction temperature in steps S31 and S32 is 80°C.

[0015] Preferably, in step S2, first add 3 - 20 parts of a water - reducing agent to 200 - 400 parts of water, then add it to the mixture obtained by dry mixing in step S1, stir for more than 3 min to obtain a mixture; then add 15 - 40 parts of modified aragonite whiskers with graphene oxide loaded on the surface and continue to stir for more than 10 min to obtain fiber - reinforced concrete.

[0016] Preferably, the cement is composite Portland cement; the fly ash is low - calcium fly ash with a calcium content of less than 10%; the iron tailings sand has a particle size of 100 - 600 microns; the water - reducing agent is a polycarboxylate - based water - reducing agent with a water - reducing rate of not less than 20%.

[0017] The present invention also provides a conductive fiber - reinforced concrete prepared by using the preparation method described in any one of the above.

[0018] In the present invention, aragonite whiskers are generated by carbonizing desulfurized gypsum, and graphene oxide is coated on the surface of aragonite whiskers through a silane coupling agent to increase the conductivity of aragonite whiskers.

[0019] The desulfurized gypsum is carbonized under the action of ammonia water and high temperature: CaSO4·2H2O(S)+CO2(g)+2NH4OH(l)→CaCO3(S)+(NH4)2SO4(aq); Among them, the reaction temperature is about 80°C, and the generated calcium carbonate is aragonite whiskers.

[0020] Then, a silane coupling agent is added to the solution, which undergoes a condensation reaction with aragonite as shown below: RSi(OR')3+3H2O→RSi(OH)3+3 R'OH, RSi(OH)3+CaCO3-OH→RSi(OH)2O-CaCO3+H2O; After the condensed and dried aragonite whiskers are added with graphene oxide solution, the CO- on their surface undergoes a condensation reaction with the R-bond of the above product (RSi(OH)2O-CaCO3), thereby binding to the aragonite surface and increasing conductivity.

[0021] At the same time, the concrete uses iron tailings sand as fine aggregate to further improve the conductivity of the concrete.

[0022] Compared with the prior art, this application has at least the following beneficial effects: (1) Low cost. Desulfurized gypsum, industrial exhaust gas, and iron ore tailings are all wastes. The use of aragonite whiskers coated with graphene oxide instead of expensive carbon fibers can effectively reduce material costs.

[0023] (2) Carbon fixation. Desulfurized gypsum reacts with carbon dioxide in industrial exhaust gas to produce aragonite whiskers, which can fix carbon and reduce carbon emissions, thereby reducing the greenhouse effect.

[0024] (3) Good electrical conductivity. Aragonite whiskers are loaded with silane coupling agents and graphene oxide. The modified aragonite whiskers are inorganic whisker structures with certain strength, aspect ratio of about 10-20, and certain electrical conductivity. They are not easy to bend and agglomerate during mixing with other components of concrete. They can form a three-dimensional conductive network by overlapping, thereby improving the electrical conductivity of concrete. At the same time, since 400-800 parts of iron tailings are added to the concrete, which accounts for a large proportion of the overall components and contains a small amount of iron, it can be used as a supplement to the conductive agent and embedded in the three-dimensional conductive network formed by the modified aragonite whiskers, further improving the electrical conductivity of the concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the accompanying drawings: Figure 1 It is a schematic diagram of the preparation process of the conductive fiber reinforced concrete in the present invention.

[0026] Figure 2Schematic diagram of the preparation process of the modified aragonite whiskers in the present invention.

[0027] Figure 3 Figure showing the resistivity comparison of the electrically conductive fiber-reinforced concrete prepared in Examples 1-7 and the comparative example.

[0028] The realization, functional features and advantages of the objectives of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0029] The following clearly and completely describes the technical problems to be solved, the technical solutions adopted and the technical effects achieved by the embodiments of the present invention in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of them. Based on the embodiments in the present application, all other equivalent or apparently variant embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The embodiments of the present invention can be embodied in many different ways as defined and covered in the claims.

[0030] It should be noted that, for the convenience of understanding, many specific details are given in the following description. However, it is obvious that the implementation of the present invention can be carried out without these specific details.

[0031] It should be noted that, without clear definition or conflict, the various embodiments and the technical features therein in the present invention can be combined with each other to form technical solutions.

[0032] Please also combine Figures 1-3 with specific embodiments to describe the electrically conductive fiber-reinforced concrete in the present invention.

[0033] First, the sources and characteristics of some components in the present invention are described: Desulfurized gypsum, using the flue gas desulfurized gypsum provided by a coal-fired power plant in Changsha, light yellow powder, with a purity of more than 95%, the contents of calcium oxide and sulfur trioxide higher than 86%, the impurity content lower than 4%, the loss on ignition of 8-9%, and the specific surface area of 264 m 2 / kg.

[0034] The cement is composite Portland cement (P.O.42.5), in which the contents of tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium ferroaluminate are 58%, 15%, 7%, and 14% respectively.

[0035] Fly ash is fly ash from Changsha, which is low-calcium fly ash, and the calcium content of the fly ash is 5%.

[0036] Iron tailings sand comes from a construction site in Tai'an, Shandong, with a particle size of 100-600 microns.

[0037] Each of the following has a mass of 1 g.

[0038] Comparative example: Preparation of aragonite whiskers: 100 g of desulfurized gypsum, 200 ml of 20% ammonia water, and 1000 ml of distilled water were added to a magnetic stirrer and stirred at a speed of 400 rpm. The temperature was controlled at 80 °C. After reacting for 5 minutes; Industrial waste gas containing 20% carbon dioxide was introduced, and stirring was continued at 80 °C for 1 h to produce aragonite whiskers.

[0039] Preparation of fiber-reinforced concrete (each portion is 1 g): (1) Weigh 400 portions of cement and 800 portions of fly ash and mix them dry; then add 400 portions of iron tailings sand and continue stirring to obtain a dry mixture; (2) Slowly add 10 portions of water reducer to 300 portions of water, add it to the dry mixture, and stir for 5 minutes to obtain a uniform mixture; (3) Add 20 portions of aragonite whiskers, put them into the mixture and stir for 10 minutes until uniform to obtain concrete.

[0040] Example 1: Preparation of modified aragonite whiskers: Preparation of A-aragonite whiskers: 100 g of desulfurized gypsum, 200 ml of 20% ammonia water, and 1000 ml of distilled water were added to a magnetic stirrer and stirred at a speed of 400 rpm. The temperature was controlled at 80 °C. After reacting for 5 minutes; Industrial waste gas containing 20% carbon dioxide was introduced, and stirring was continued at 80 °C for 1 h to produce aragonite whiskers; B-modification: Add 250 ml of 0.5% silane coupling agent by mass fraction, stir for 1 h, centrifuge the solid substance, and dry it in an oven at 105 °C for 24 h; 100 g of the dried solid substance was added to 1000 ml of 0.02% graphene oxide solution by mass fraction, stirred for 1 h, then the slurry was centrifuged, and the solid substance was dried in an oven at 105 °C for 24 h to obtain modified aragonite whiskers.

[0041] Preparation of fiber-reinforced concrete (each portion is 1 g): (1) Weigh 400 portions of cement and 800 portions of fly ash and mix them dry; then add 400 portions of iron tailings sand and continue stirring to obtain a dry mixture; (2) Slowly add 10 portions of water reducer to 300 portions of water, add it to the dry mixture, and stir for 5 minutes to obtain a uniform mixture; (3) Add 20 parts of modified aragonite whiskers, put them into the mixture and stir for 10 minutes until uniform to obtain electrically conductive fiber-reinforced concrete.

[0042] Example 2: The steps are the same as those in Example 1, except that the mass fraction of the silane coupling agent is 1.0%.

[0043] Example 3: Similar to Example 1, except that the mass fraction of the silane coupling agent is 2.0%.

[0044] Example 4: Similar to Example 2, except that the mass fraction of graphene oxide is 0.03%.

[0045] Example 5: Similar to Example 2, except that the mass fraction of graphene oxide is 0.05%.

[0046] Example 6: Similar to Example 4, except that the amount of modified aragonite whiskers is 25 parts.

[0047] Example 7: Similar to Example 4, except that the amount of modified aragonite whiskers is 40 parts.

[0048] Conduct electrical conductivity tests on the concrete prepared in the comparative example and the electrically conductive fiber-reinforced concrete prepared in Examples 1-7 using a resistivity meter. The test results are as Figure 3 shown.

[0049] It can be seen from Figure 3 that the resistivity of the comparative example is relatively high, reaching about 3500 Ω•cm, which does not meet the requirements for road snow melting and ice melting (below 1000 Ω•cm). Although iron tailings sand is added, the iron tailings sand is relatively dispersed and cannot play a good electrical conductivity role.

[0050] The aspect ratio of the aragonite whiskers prepared in the comparative example and Examples 1-5 is about 10-20, the diameter is about 0.5-1.5 μm, and the length is 20-30 μm. Modifying it will not significantly change the overall morphology and size of the aragonite whiskers.

[0051] The electrical conductivity of the modified aragonite whiskers prepared in the comparative example and Examples 1-5 was measured by the four-probe method: The resistivity of the unmodified aragonite whiskers in the comparative example is 3×10 7 Ω•cm; The resistivity of the modified aragonite whiskers in Example 1 is 5×10 5 Ω•cm; The resistivity of the modified aragonite whiskers in Example 2 is 6×10 3Ω·cm; The resistivity of the modified aragonite whiskers in Example 3 is 4×10 3 Ω·cm; The resistivity of the modified aragonite whiskers in Example 4 is 8×10 -1 Ω·cm; The resistivity of the modified aragonite whiskers in Example 5 is 5×10 -1 Ω·cm.

[0052] Compared with the comparative example, when modified aragonite whiskers are added to the concrete in Example 1, the resistivity is significantly decreased to about 1250 Ω·cm. In Examples 1-3, by increasing the concentration of the silane coupling agent, the resistivity of the modified aragonite whiskers and the resistivity of the final concrete are further decreased, but the resistivity of the final concrete in Examples 2 and 3 is approximate. Using the concentration of the silane coupling agent in Example 2, about 1.0% is better.

[0053] In Examples 4-5, by increasing the concentration of graphene oxide, the resistivity of the modified aragonite whiskers and the resistivity of the final conductive concrete are also decreased, but the decreasing amplitude is not very large. Using the concentration of graphene oxide in Example 4, about 0.03% is more appropriate.

[0054] The examples prove that by loading aragonite whiskers with a silane coupling agent and graphene oxide, the modified aragonite whiskers are inorganic whisker structures with certain strength, an aspect ratio of about 10-20, and certain conductivity. During the mixing process with other components of the concrete, a three-dimensional conductive network can be formed in a lapping manner. The modified aragonite whiskers have good dispersibility in the concrete, are not easy to bend and agglomerate, and improve the conductivity of the concrete. At the same time, since 400-800 parts of iron tailing sand are also added to the concrete, which accounts for a relatively large proportion in the overall components and contains a small amount of iron, it can be used as a supplement to the conductive agent and is embedded and distributed in the three-dimensional conductive network formed by the modified aragonite whiskers, further improving the conductivity of the concrete.

[0055] In Examples 6-7, by increasing the content of the modified aragonite whiskers, the resistivity is further decreased. When the modified aragonite whiskers are 40 parts, the resistivity is decreased to about 200 Ω·cm. Continuing to increase the content of the aragonite whiskers will not have an obvious impact on the resistivity, and the fibers are not easy to be uniformly dispersed. Therefore, according to the above results, the content of the modified aragonite whiskers is 30-40 parts, which has better cost advantages and effects.

[0056] The above-described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A conductive fiber reinforced concrete, characterized in that, It includes: 350 - 450 parts of cement, 500 - 900 parts of fly ash, 400 - 800 parts of iron tailings sand, 3 - 20 parts of water reducer, 15 - 40 parts of modified aragonite whiskers, and 200 - 400 parts of water; among them, the water - binder ratio of the electrically conductive fiber - reinforced concrete is 0.2 - 0.35; the surface of the aragonite whiskers of the modified aragonite whiskers is loaded with graphene oxide, the aspect ratio of the modified aragonite whiskers is 10 - 20, the diameter is 0.5 - 1.5 μm, and the length is 20 - 30 μm.

2. The conductive fiber reinforced concrete according to claim 1, characterized in that, The cement is composite portland cement; the fly ash is low - calcium fly ash with a calcium content of less than 10%; the particle size of the iron tailings sand is 100 - 600 microns; the water reducer is a polycarboxylate - based water reducer with a water - reducing rate of not less than 20%.

3. A preparation method of conductive fiber reinforced concrete, characterized in that, It includes the steps: S1. Dry - mix 500 - 900 parts of fly ash with 350 - 450 parts of cement; then add 400 - 800 parts of iron tailings sand and continue dry - mixing to obtain a dry - mix material. S2. In the dry - mix material, add 3 - 20 parts of water reducer and 200 - 400 parts of water and stir, then add 15 - 40 parts of modified aragonite whiskers with graphene oxide loaded on the surface, and continue to stir evenly to obtain fiber - reinforced concrete. Among them, the preparation method of the modified aragonite whiskers with graphene oxide loaded on the surface includes the steps: S31. Mix desulfurized gypsum, ammonia water, and water in the proportions of 100 - 300 g of desulfurized gypsum, 150 - 250 ml of ammonia water with a concentration of 10% - 30%, and 1000 ml of water, stir at a temperature of 70 - 90 °C and a rotation speed of 300 - 500 rpm, and react for 4 - 10 min. S32. Introduce industrial waste gas containing 10% - 30% carbon dioxide, continuously stir and react at a temperature of 70 - 90 °C for 0.5 - 1 h to generate aragonite whiskers. S331. In the solution after the reaction in step S32, add 100 - 500 ml of silane coupling agent with a mass fraction of 0.2% - 2% according to the proportion in step S31, stir for 1 - 3 hours, and dry the centrifuged solid matter in an oven. S332. According to the proportion of 100 - 200 g of the product obtained in step S331 and 1000 ml of graphene oxide solution with a mass fraction of 0.02% - 0.05%, add the product obtained in step S331 to the graphene oxide solution, stir for 1 - 3 hours, centrifuge the slurry, and dry the solid matter in an oven to obtain modified aragonite whiskers, and the aspect ratio of the modified aragonite whiskers is 10 - 20, the diameter is 0.5 - 1.5 μm, and the length is 20 - 30 μm.

4. The preparation method of the conductive fiber reinforced concrete according to claim 3, characterized in that, In step S331, the concentration of the silane coupling agent is 1.0%; in step S332, the concentration of graphene oxide is 0.03%; in step S2, the amount of modified aragonite whiskers is 30 - 40 parts.

5. The preparation method of the conductive fiber reinforced concrete according to claim 3, characterized in that, The reaction temperature in steps S31 and S32 is 80 °C.

6. The preparation method of the conductive fiber reinforced concrete according to claim 3, wherein, In the step S2, first add 3 to 20 parts of water reducing agent into 200 to 400 parts of water, then add the mixture into the dry mix, and stir for more than 3 minutes to obtain a mixture; then add 15 to 40 parts of modified aragonite whiskers with graphene oxide loaded on the surface, and continue to stir for more than 10 minutes to obtain fiber reinforced concrete.

7. The preparation method of the conductive fiber reinforced concrete according to claim 3, wherein The cement is composite portland cement; the fly ash is low-calcium fly ash with a calcium content of less than 10%; the iron tailing sand has a particle size of 100 - 600 microns; the water reducing agent is a polycarboxylate-based water reducing agent, and the water reducing rate of the water reducing agent is not less than 20%.

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