A salt-tolerant concrete material prepared from waste felt carbon fibers and a preparation method thereof

Abstract

The application discloses a kind of salt-tolerant concrete prepared by waste felt carbon fiber and a preparation method thereof, and relates to the technical field of waste felt carbon fiber resource utilization.The application mixes waste felt carbon fiber with cement and other materials to prepare salt-tolerant concrete material with electric conduction function, and on this basis, the surface of carbon fiber is modified to improve the bonding performance between carbon fiber material and concrete, and the components of concrete raw materials are adjusted, thereby effectively improving the salt-tolerant erosion resistance of the concrete.

Description

Technical Field

[0001] This invention relates to the field of waste felt carbon fiber resource utilization technology, specifically a salt-alkali resistant concrete material prepared from waste felt carbon fiber and its preparation method. Background Technology

[0002] Carbon fiber felt is a thermal insulation material formed by bonding carbon fibers with resin. It is an engineering material specifically used for thermal insulation in high-temperature kilns, playing a crucial role in maintaining the stable operation of thermal equipment. However, due to the inherent properties of the resin, the resin in the carbon fiber felt inevitably deteriorates after prolonged high-temperature operation, causing the felt to fail to meet operational requirements and become unusable. Simply landfilling or incinerating the waste felt would undoubtedly result in enormous waste; therefore, it is necessary to research the reuse of carbon fibers from waste felt. Summary of the Invention

[0003] The purpose of this invention is to provide a salt-alkali resistant concrete material prepared from waste felt carbon fiber and its preparation method, so as to solve the problems raised in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a salt-alkali resistant concrete prepared using waste felt carbon fiber, having the following technical features: by weight, the salt-alkali resistant concrete comprises 260-280 parts cement, 35-55 parts fly ash, 40-65 parts slag, 25-55 parts silica fume, 1050-1150 parts coarse aggregate, 800-850 parts fine aggregate, 26-125 parts waste felt carbon fiber, 10-30 parts carbon powder, 10-15 parts high-performance water-reducing agent, 1.5-4.5 parts air-entraining agent, 1.2-4.8 parts retarder, and 150-180 parts mixing water.

[0005] Furthermore, the cement is high-belite cement; the fly ash is at least one of grade I or grade II fly ash.

[0006] Furthermore, the coarse aggregate is 5-20mm gravel; the fine aggregate is river sand.

[0007] Furthermore, the high-performance water-reducing agent is a naphthalene-based water-reducing agent; the air-entraining agent is an alkylbenzene sulfonate air-entraining agent; and the retarder is tartaric acid.

[0008] Furthermore, the method for preparing the waste felt carbon fiber includes the following steps:

[0009] a. After disassembling the recycled waste carbon fiber felt into block structures, wash it with clean water, mix it with a saturated zinc chloride solution, dry and evaporate the excess solvent, place the dried waste carbon fiber felt in an oxygen-free environment, heat it to 480~550℃, keep it at the temperature for 25~45min, then cool it to 320~350℃, introduce air, continue to keep it at the temperature for 5~10min, then stop heating, cool it to room temperature, take out the calcined product, and wash it again with deionized water by ultrasonication for 30~45min, then dry it to obtain calcined waste felt carbon fiber.

[0010] b. Add the calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5-10 minutes, then add KH-550 and deionized water, stir and treat for 1-4 hours, filter out the calcined waste felt carbon fiber, dry its surface, add it to an aqueous solution of sodium 3-carboxybenzenesulfonate, heat to 85-92℃, continue ultrasonic vibration reaction for 4-8 hours, filter out, dry to constant weight, and obtain waste felt carbon fiber.

[0011] Furthermore, in step a, the length of the block structure in each direction is 5~40mm.

[0012] Furthermore, in step a, the amount of each component added, by weight, is 1 part of waste carbon fiber felt and 0.01 to 0.05 parts of zinc chloride.

[0013] Furthermore, in step b, the amount of each component added, by weight, is 1 part of calcined waste felt carbon fiber, 0.05~0.08 parts of KH-550 and 0.05~0.15 parts of deionized water.

[0014] Furthermore, a method for preparing salt-alkali resistant concrete using waste felt carbon fiber includes the following steps:

[0015] S1. Weigh the corresponding raw materials according to the formula, and dry mix the weighed cement, fly ash, slag, silica fume, coarse aggregate, fine aggregate, waste felt carbon fiber, and carbon powder evenly to obtain a dry mix.

[0016] S2. Mix the mixing water with the high-performance water-reducing agent, air-entraining agent, and retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at a speed of 200-300 rpm for 2-3 minutes. Then add the second part of the liquid mixture and continue mixing for 2-3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] In order to realize the reuse of waste felt carbon fiber, this invention mixes it with cement and other materials to prepare a salt and alkali resistant concrete material with conductive function. Chloride penetration in the marine environment is the main cause of corrosion of steel bars in marine concrete. Traditional marine concrete cannot conduct electricity and cannot form an electronic conductive path. Therefore, adding carbon fiber can apply anodic protection to it, thereby inhibiting the steel bars in the concrete from losing electrons and corroding.

[0019] Furthermore, to improve the bonding strength between carbon fiber materials and concrete, this invention modifies the surface of the carbon fiber. First, the surface resin is initially removed by anaerobic heating, then cooled to below 500°C and subjected to anaerobic heating again to remove residual resin on the carbon fiber surface, thereby improving the bonding strength with concrete. In addition, this invention further treats the carbon fiber surface with KH550 hydrolysis grafted amino groups, followed by treatment with sodium 3-carboxybenzenesulfonate, introducing sulfonic acid groups onto the surface. This creates a water-reducing agent-like effect, allowing the carbon fiber to be better dispersed in the concrete matrix during mixing, improving electrical conductivity and tensile strength.

[0020] Furthermore, to further improve the salt and alkali resistance of concrete, this invention limits its raw materials, using high-belite cement as the main cementitious material. High-belite cement has low heat of hydration, which can effectively reduce the micro-cracks generated during the initial solidification stage of hydration, thereby preventing the intrusion of external salt and alkali into the concrete in the later stage. In order to further reduce the heat of hydration, this invention also adds admixtures with pozzolanic activity and retarder, thereby further reducing the addition of cement clinker, improving the later hydration strength and salt and alkali resistance of concrete. In addition, the air-entraining agent added in this invention can also introduce micro-bubbles into the concrete, thereby preventing the formation of channels for the intrusion of external salt, alkali and water vapor, further improving the salt and alkali resistance of concrete. Detailed Implementation

[0021] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The high-belite cement used in this invention is Polar Bear 42.5 type high-belite cement; the high-performance water-reducing agent used is commercially available FDN naphthalene-based water-reducing agent; the air-entraining agent used is alkylbenzene sulfonate air-entraining agent; and the retarder used is tartaric acid.

[0023] Example 1. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0024] S1. Weigh and mix 260 parts of high-belite cement, 35 parts of grade 1 fly ash, 40 parts of slag, 25 parts of silica fume, 1050 parts of coarse aggregate, 800 parts of fine aggregate, 26 parts of waste felt carbon fiber, and 10 parts of carbon powder by weight to obtain a dry mix.

[0025] The method for preparing the waste felt carbon fiber includes the following steps:

[0026] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0027] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 0.25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0028] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0029] Example 2. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0030] Compared with Example 1, this example increases the amount of silica fume added in step S1;

[0031] S1. Weigh and mix 260 parts of high-belite cement, 35 parts of grade 1 fly ash, 40 parts of slag, 55 parts of silica fume, 1050 parts of coarse aggregate, 800 parts of fine aggregate, 26 parts of waste felt carbon fiber, and 10 parts of carbon powder by weight to obtain a dry mix.

[0032] The method for preparing the waste felt carbon fiber includes the following steps:

[0033] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0034] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 0.25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0035] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0036] Example 3. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0037] Compared with Example 2, this example increases the amount of slag and fly ash added in step S1;

[0038] S1. Weigh and mix 260 parts of high-belite cement, 55 parts of grade 1 fly ash, 65 parts of slag, 55 parts of silica fume, 1050 parts of coarse aggregate, 800 parts of fine aggregate, 26 parts of waste felt carbon fiber, and 10 parts of carbon powder by weight to obtain a dry mix.

[0039] The method for preparing the waste felt carbon fiber includes the following steps:

[0040] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0041] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 0.25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0042] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0043] Example 4. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0044] Compared with Example 3, this example increases the amount of waste felt carbon fiber added in step S1;

[0045] S1. Weigh and mix 260 parts of high-belite cement, 55 parts of grade 1 fly ash, 65 parts of slag, 55 parts of silica fume, 1050 parts of coarse aggregate, 800 parts of fine aggregate, 125 parts of waste felt carbon fiber, and 10 parts of carbon powder by weight to obtain a dry mix.

[0046] The method for preparing the waste felt carbon fiber includes the following steps:

[0047] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0048] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 0.25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0049] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0050] Example 5. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0051] Compared with Example 4, this example increases the concentration of sodium 3-carboxybenzenesulfonate in step b;

[0052] S1. Weigh and mix 260 parts of high-belite cement, 55 parts of grade 1 fly ash, 65 parts of slag, 55 parts of silica fume, 1050 parts of coarse aggregate, 800 parts of fine aggregate, 125 parts of waste felt carbon fiber, and 10 parts of carbon powder by weight to obtain a dry mix.

[0053] The method for preparing the waste felt carbon fiber includes the following steps:

[0054] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0055] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0056] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0057] Example 6. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0058] S1. Weigh and mix 280 parts of high-belite cement, 55 parts of grade 1 fly ash, 65 parts of slag, 55 parts of silica fume, 1150 parts of coarse aggregate, 850 parts of fine aggregate, 125 parts of waste felt carbon fiber, and 30 parts of carbon powder by weight to obtain a dry mix.

[0059] The method for preparing the waste felt carbon fiber includes the following steps:

[0060] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0061] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0062] S2. By weight, mix 180 parts of mixing water with 15 parts of high-performance water-reducing agent, 4.5 parts of air-entraining agent and 4.8 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0063] Comparative Example 1. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0064] Compared to Example 1, this example replaces high-belite cement with ordinary Portland cement;

[0065] S1. Weigh and mix 260 parts ordinary Portland cement, 35 parts grade I fly ash, 40 parts slag, 25 parts silica fume, 1050 parts coarse aggregate, 800 parts fine aggregate, 26 parts waste felt carbon fiber, and 10 parts carbon powder by weight to obtain a dry mix.

[0066] The method for preparing the waste felt carbon fiber includes the following steps:

[0067] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a zinc chloride saturated solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then cooled to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain calcined waste felt carbon fiber.

[0068] b. By weight, add 1 part of calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5 min, then add 0.05 parts of KH-550 and 0.15 parts of deionized water, stir and treat for 3 h, filter out the calcined waste felt carbon fiber, dry its surface, add it to a 0.25 g / L sodium 3-carboxybenzenesulfonate aqueous solution, heat to 90 °C, continue ultrasonic vibration reaction for 8 h, filter out, dry to constant weight, and obtain waste felt carbon fiber;

[0069] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0070] Comparative Example 2. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber, comprising the following steps:

[0071] Compared with Example 1, this comparative example did not undergo step b.

[0072] S1. Weigh and mix 260 parts of high-belite cement, 35 parts of grade 1 fly ash, 40 parts of slag, 25 parts of silica fume, 1050 parts of coarse aggregate, 800 parts of fine aggregate, 26 parts of waste felt carbon fiber, and 10 parts of carbon powder by weight to obtain a dry mix.

[0073] The method for preparing the waste felt carbon fiber includes the following steps:

[0074] a. By weight, 1 part of the recycled waste carbon fiber felt is broken into block structures with a length of 5-40mm, washed with water, mixed with a saturated zinc chloride solution containing 0.01 parts of zinc chloride, dried to evaporate excess solvent, and then placed in an oxygen-free environment. The temperature is raised to 480℃, kept at that temperature for 25 minutes, then lowered to 320℃, air is introduced, and the reaction is continued for 5 minutes. The heating is then stopped, and the product is cooled to room temperature. The calcined product is then removed and ultrasonically washed again with deionized water for 30 minutes, and then dried to obtain waste felt carbon fiber.

[0075] S2. By weight, mix 160 parts of mixing water with 10 parts of high-performance water-reducing agent, 1.5 parts of air-entraining agent and 1.5 parts of retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at 250 rpm for 3 minutes. Then add the second part of the liquid mixture and continue mixing for 3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

[0076] Testing: The salt-alkali resistant concrete prepared in Examples 1-6 and Comparative Examples 1-2 were poured as test samples and placed in a curing room with a temperature of 20±2℃ and a relative humidity of 95±2%. The compressive strength of the samples was tested at 7 days and 28 days according to GB / T50081-2002. The test samples after 28 days of curing were placed in seawater and their compressive strength was tested again after 120 days.

[0077] Its resistivity was tested using the voltmeter-ammeter method;

[0078] The test results are shown in the table below;

[0079]

[0080] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A salt-alkali resistant concrete prepared using waste felt carbon fiber, characterized in that: By weight, the salt-alkali resistant concrete consists of 260-280 parts cement, 35-55 parts fly ash, 40-65 parts slag, 25-55 parts silica fume, 1050-1150 parts coarse aggregate, 800-850 parts fine aggregate, 26-125 parts waste felt carbon fiber, 10-30 parts carbon powder, 10-15 parts high-performance water-reducing agent, 1.5-4.5 parts air-entraining agent, 1.2-4.8 parts retarder, and 150-180 parts mixing water. The method for preparing the waste felt carbon fiber includes the following steps: a. After disassembling the recycled waste carbon fiber felt into block structures, wash it with clean water, mix it with a saturated zinc chloride solution, dry and evaporate the excess solvent, place the dried waste carbon fiber felt in an oxygen-free environment, heat it to 480~550℃, keep it at the temperature for 25~45min, then cool it to 320~350℃, introduce air, continue to keep it at the temperature for 5~10min, then stop heating, cool it to room temperature, take out the calcined product, and wash it again with deionized water by ultrasonication for 30~45min, then dry it to obtain calcined waste felt carbon fiber. b. Add the calcined waste felt carbon fiber to anhydrous ethanol, stir and mix for 5-10 minutes, then add KH-550 and deionized water, stir and treat for 1-4 hours, filter out the calcined waste felt carbon fiber, dry its surface, add it to an aqueous solution of sodium 3-carboxybenzenesulfonate, heat to 85-92℃, continue ultrasonic vibration reaction for 4-8 hours, filter out, dry to constant weight, and obtain waste felt carbon fiber.

2. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: The cement is high-belite cement; the fly ash is at least one of grade I or grade II fly ash.

3. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: The coarse aggregate is 5-20mm gravel; the fine aggregate is river sand.

4. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: The high-performance water-reducing agent is a naphthalene-based water-reducing agent; the air-entraining agent is an alkylbenzene sulfonate air-entraining agent; and the retarder is tartaric acid.

5. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: In step a, the length of the block structure in each direction is 5~40mm.

6. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: In step a, by weight, the amount of each component added is 1 part of waste carbon fiber felt and 0.01~0.05 parts of zinc chloride.

7. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: In step b, the amount of each component added, by weight, is 1 part of calcined waste felt carbon fiber, 0.05~0.08 parts of KH-550 and 0.05~0.15 parts of deionized water.

8. The salt-alkali resistant concrete prepared using waste felt carbon fiber according to claim 1, characterized in that: In step b, the sodium 3-carboxybenzenesulfonate in the aqueous solution is 0.25~25 g / L.

9. A method for preparing salt-alkali resistant concrete using waste felt carbon fiber as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Weigh the corresponding raw materials according to the formula, and dry mix the weighed cement, fly ash, slag, silica fume, coarse aggregate, fine aggregate, waste felt carbon fiber, and carbon powder evenly to obtain a dry mix. S2. Mix the mixing water with the high-performance water-reducing agent, air-entraining agent, and retarder. After mixing evenly, divide the mixture into two equal parts. Add the first part of the liquid mixture to the dry mix and stir at a speed of 200-300 rpm for 2-3 minutes. Then add the second part of the liquid mixture and continue mixing for 2-3 minutes. Finally, pour the mixture to obtain the salt-alkali resistant concrete.

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