Process for recycling coal ash of power plant to produce concrete

Abstract

The application relates to the technical field of concrete recycling, and discloses a concrete process prepared by recycling power plant fly ash, wherein the power plant fly ash, cement, mineral powder, basalt crushed stone and river sand are mixed and stirred to obtain a mixture; water reducing agent, modified bamboo fiber, modified steel fiber and water are added to the mixture and stirred to obtain concrete. The modified bamboo fiber can be filled into the pore structure of the concrete by the calcium carbonate crystals induced by the bacillus pasteurii bacterial liquid and urea, the bonding strength of the modified bamboo fiber and the concrete is enhanced, and the mechanical strength of the concrete is further enhanced; the zinc acetate on the surface of the modified steel fiber can form a coating of crosslinked network structure with the polyethylene glycol phosphate, the contact area and the binding force with the concrete aggregate are increased, the steel fiber is more firmly dispersed in the concrete, and the mechanical strength of the concrete is improved.

Description

Technical Field

[0001] This invention relates to the field of recycled concrete technology, specifically a process for reusing coal ash from power plants to prepare concrete. Background Technology

[0002] Concrete is a major material in engineering construction, used in the construction of buildings, structures, roads, bridges, water conservancy facilities, municipal engineering projects, etc. Concrete is mainly composed of fly ash, cement, sand, gravel, admixtures and water. Due to the large demand for concrete, the amount of fly ash used as one of the main admixtures in concrete has also increased dramatically, resulting in a supply shortage and a sharp rise in the price of fly ash and the cost of concrete. In particular, the high cost of fly ash leads to the increase in the cost of concrete. Using fly ash obtained by processing power plant slag to produce concrete not only utilizes the power plant slag as waste, but also helps to protect the environment.

[0003] Using coal ash from power plants to replace part of the cement in concrete preparation can reduce the cost of concrete and produce concrete with good performance. However, coal ash concrete generally has low mechanical strength and contains a large number of microcracks, mortar, and interfacial transition zones between aggregates and mortar. It is characterized by being porous, having high water absorption, and poor mechanical properties, which results in generally low later-stage strength of recycled concrete, limiting its application in important projects such as high-rise buildings and bridges. Summary of the Invention

[0004] This invention provides a process for reusing and re-preparing concrete from power plant fly ash, which solves the problems of low mechanical strength and numerous microcracks commonly found in power plant fly ash concrete.

[0005] The technical solution of the present invention:

[0006] A process for reusing coal ash from power plants to prepare concrete includes the following steps:

[0007] S1. Mix power plant coal ash, cement, mineral powder, basalt crushed stone and river sand, and stir at a speed of 80-120 r / min for 3-5 min to obtain a mixture;

[0008] S2. Add water-reducing agent, modified bamboo fiber, modified steel fiber and water to the mixture, and continue to stir at a rate of 80-120 r / min for 10-15 min to obtain concrete.

[0009] The modified bamboo fiber is obtained by treating bamboo fiber with alkaline solution a, and then reacting it with microcapsules and tetraethyl silicate.

[0010] The microcapsules are made by using a mixture of Bacillus pasteurellium bacterial solution and urea as the core material, and chitosan solution and sodium alginate solution as the encapsulation material.

[0011] The modified steel fiber is obtained by treating steel fiber with alkaline solution b, mixing it with lignin and carbonizing it at high temperature, and then reacting it with zinc acetate and polyethylene glycol phosphate.

[0012] Furthermore, the mass ratio of power plant coal ash, cement, mineral powder, basalt crushed stone, river sand, water-reducing agent, modified bamboo fiber, modified steel fiber and water is (1.5-1.7):(1.6-2):(5-6):(5-6):(4-5):(0.1-0.2):(0.1-0.2):(0.04-0.06):(1.2-1.4).

[0013] Furthermore, the cement is grade 42.5 low-alkalinity sulfoaluminate cement.

[0014] Furthermore, the power plant fly ash is Class F Grade I fly ash, with a fineness of 40-50 μm, a loss on ignition of 2.6-2.9%, and a moisture content of 0.1-0.2%.

[0015] Furthermore, the mineral powder is S95 grade slag powder with a density of 2.5-3.9 g / cm³. 3 Specific surface area is 445-460 m² 2 / kg, with a moisture content of 0.15-0.25%, and an activity index of 94.5-95.6% after 28 days.

[0016] Furthermore, the basalt gravel has a continuous gradation of 5-25mm and a mud content of 0.1-0.3%.

[0017] Furthermore, the apparent density of the river sand is 2660-2690 kg / m³. 3 The fineness modulus is 2.3-2.5, the particle size is 3.3-4.2 mm, and the mud content is 0.8-1.3%.

[0018] Furthermore, the water-reducing agent is any one of PCE-102 polycarboxylate water-reducing agent, PCE-101 polycarboxylate water-reducing agent, and PCE-103 polycarboxylate water-reducing agent.

[0019] Furthermore, the modified bamboo fiber is specifically prepared by the following steps:

[0020] A1. Add Pasteurella multocida bacterial solution and urea to deionized water, stir evenly to obtain core material, mix chitosan solution and sodium alginate solution, stir evenly to obtain capsule material, mix capsule material and core material, stir reaction for 5-10 min, add glutaraldehyde, react at 35-45℃ for 1-3 h, filter and collect reaction product to obtain microcapsules;

[0021] A2. Immerse bamboo fiber in alkaline solution a, stir evenly, stir at 30-40℃ for 30-40 minutes, remove bamboo fiber, wash and dry to obtain pretreated bamboo fiber;

[0022] A3. Add pretreated bamboo fiber to ethanol and deionized water, stir evenly, add microcapsules, continue stirring, add tetraethyl silicate and ammonia, stir and react at 50-60℃ for 3-5 hours, filter, wash and dry to obtain modified carbon fiber.

[0023] Furthermore, in the A1 reaction process described above, the mixture of Bacillus pasteurellium culture and urea is used as the core material, the chitosan solution and sodium alginate solution are used as the encapsulation material, and glutaraldehyde is used as the cross-linking curing agent to form microcapsules loaded with Bacillus pasteurellium culture and urea.

[0024] Furthermore, during the A2 reaction process described above, the bamboo fiber is treated with alkaline solution a. The hemicellulose, lignin, and cellulose in the bamboo fiber can dissolve in alkaline solution a, promoting the removal of some amorphous components, improving surface roughness, and increasing active groups.

[0025] Furthermore, during the A3 reaction process described above, the silanol groups generated by the hydrolysis of tetraethyl silicate can chemically bond with the oxygen-containing functional groups on the surface of the pretreated bamboo fiber to form an inorganic silica layer on the pretreated bamboo fiber. The silanol groups generated by the hydrolysis of tetraethyl silicate can also react with the active groups on the surface of the microcapsules, allowing the microcapsules to be embedded between the inorganic silica layers, thus obtaining modified carbon fibers.

[0026] Further, in step A1, the ratio of the amount of Bacillus pasteurellium culture, urea, deionized water, chitosan solution, sodium alginate solution and glutaraldehyde is (8-12) mL:(1-2) g:(45-55) mL:(20-30) mL:(20-30) mL:(0.1-0.2) g.

[0027] Furthermore, in step A2, the ratio of bamboo fiber to alkaline solution a is (18-22)g:(180-220)mL.

[0028] Further, in step A3, the ratio of the amount of pretreated bamboo fiber, ethanol, deionized water, microcapsules, tetraethyl silicate and ammonia is (10-20)g:(70-90)mL:(70-90)mL:(3-4)g:(6.6-7)g:(4-5)mL.

[0029] Furthermore, the concentration of Bacillus pasteurellium in the culture was 4-6 × 10⁻⁶. 6 CFU / mL.

[0030] Furthermore, the chitosan solution has a mass fraction of 0.5-1.5%; the sodium alginate solution has a mass fraction of 1-2%.

[0031] Furthermore, the bamboo fiber has a length of 70-80mm and a diameter of 0.1-1mm.

[0032] Furthermore, alkaline solution a is a sodium hydroxide solution with a mass fraction of 5-7%.

[0033] Furthermore, the modified steel fibers are specifically prepared by the following steps:

[0034] B1. Immerse the steel fiber in alkaline solution b at 40-50℃ for 30-40 minutes, remove the steel fiber, wash to remove grease and impurities from the surface of the steel fiber, and dry to obtain pretreated steel fiber;

[0035] B2. Add lignin to ethanol and stir evenly. Add pretreated steel fibers and stir at 80-90℃ until the ethanol evaporates. Place in a tube furnace, add potassium hydroxide solution, mix evenly, introduce argon gas, heat to 800-900℃, and perform high-temperature carbonization for 3-5 hours. Cool to room temperature, take out, wash, and dry to obtain steel fibers loaded with porous biochar.

[0036] B3. Add steel fibers loaded with porous biochar to polyethylene glycol phosphate, stir evenly, add zinc acetate, stir and react at 130-150℃ for 20-30 min, cool to room temperature, filter, wash and dry to obtain modified steel fibers.

[0037] Furthermore, during the B1 reaction process described above, the steel fibers are treated with alkaline solution b, which removes grease and impurities from the surface of the steel fibers and forms highly active hydroxyl groups on the surface of the steel fibers, which is beneficial for the synthesis of porous carbon on the surface of the steel fibers.

[0038] Furthermore, in the above B2 reaction process, lignin can adhere to the surface of the pretreated steel fiber in the organic solvent ethanol. With lignin as a carbon source and potassium hydroxide solution as an activator, porous carbon material can be synthesized on the surface of the pretreated steel fiber after high-temperature carbonization, thus obtaining steel fiber loaded with porous biochar.

[0039] Furthermore, during the B3 reaction process described above, the steel fibers loaded with porous biochar exhibit excellent adsorption properties, enabling them to adsorb zinc acetate and polyethylene glycol phosphate onto the surface of the steel fibers. In addition, the zinc ions of zinc acetate can combine with the oxygen-containing functional groups on the polyethylene glycol phosphate molecular chain, thereby forming a cross-linked network coating on the surface of the steel fibers, resulting in modified steel fibers.

[0040] Furthermore, in step B1, the ratio of steel fiber to alkaline solution b is (18-22) g: (180-220) mL.

[0041] Further, in step B2, the ratio of lignin, ethanol, pretreated steel fiber and potassium hydroxide solution is (8-12)g:(140-160)mL:(16-20)g:(4-6)mL.

[0042] Further, in step B3, the ratio of steel fiber loaded with porous biochar, polyethylene glycol phosphate ester and zinc acid is (8-12)g:(140-160)mL:(5-6)g.

[0043] Furthermore, the steel fibers have a diameter of 0.4-0.6 mm, a length of 20-30 mm, and a tensile strength of 1100-1200 MPa.

[0044] Furthermore, alkaline solution b is a sodium hydroxide solution with a mass fraction of 18-22%.

[0045] The present invention has the following beneficial effects:

[0046] (1) In the technical solution of the present invention, the pasteurized bacterial solution and urea are mixed as the core material, and chitosan and sodium alginate are used as the capsule material to form a microcapsule structure. On the one hand, pasteurized bacteria use urea as raw material and then combine with calcium ions in concrete to induce the formation of calcium carbonate crystals, which fill the cracks in the concrete and enhance the mechanical strength of the concrete. On the other hand, the formed microcapsule structure provides a better survival environment for the pasteurized bacterial solution, avoiding the pasteurized bacterial solution from existing in the alkaline environment of the concrete for a long time, which would cause the pasteurized bacterial solution to become inactive and affect the density and mechanical strength of the concrete. Moreover, the microcapsules can fill the gaps in the concrete aggregate and improve the density of the concrete.

[0047] (2) In the technical solution of this invention, bamboo fiber has high strength and toughness, and its addition to concrete can improve the mechanical properties of concrete. Moreover, bamboo fiber is a green, inexpensive, and renewable resource. Bamboo fiber is treated with alkaline solution a to improve the surface roughness and increase active groups. The reaction of pretreated bamboo fiber, microcapsules, and tetraethyl silicate can form an organosilicon layer in the pretreated bamboo fiber, and the microcapsules are embedded in the organosilicon layer. On the one hand, the microcapsules fill the voids on the surface of the pretreated bamboo fiber through the organosilicon, sealing the voids on the surface of the pretreated bamboo fiber and preventing the porous structure of the pretreated bamboo fiber from easily absorbing moisture, which would lead to a decline in fiber performance. This process affects the mechanical strength of concrete and increases the surface roughness of bamboo fibers, thereby increasing the bonding force between bamboo fibers and concrete aggregates. On the other hand, during the mixing process of concrete aggregates or when cracks appear in the concrete, the stress generated causes the microcapsules to rupture, releasing Pasteurella multocida bacterial solution and urea, which can combine with calcium ions in the concrete aggregates to form calcium carbonate crystals. The modified bamboo fibers, along with the calcium carbonate formed, fill the pore structure of the concrete, enhancing the bonding strength between the modified bamboo fibers and the concrete, and thus enhancing the mechanical strength of the concrete. In addition, the calcium carbonate layer formed on the surface of the pretreated bamboo fibers further enhances the moisture resistance of the bamboo fibers.

[0048] (3) In the technical solution of the present invention, the steel fiber is treated with alkaline solution b to form highly active hydroxyl groups on the surface of the steel fiber, which is conducive to the synthesis of porous carbon on the surface of the steel fiber, improving the surface roughness and chloride corrosion resistance of the steel fiber; porous carbon material is synthesized on the surface of the pretreated steel fiber to obtain steel fiber loaded with porous biochar; the porous structure of the synthesized porous biochar can prevent acidic media from contacting the steel fiber, improve the corrosion resistance of the steel fiber, and avoid the decrease in strength of the steel fiber and the impact on the mechanical strength of concrete when a large amount of chloride ions penetrate and corrode the passivation film on the surface of the steel fiber.

[0049] (4) In the technical solution of the present invention, zinc acetate and polyethylene glycol phosphate are adsorbed onto the surface of steel fibers loaded with porous biochar. On the one hand, the adsorption of zinc acetate and polyethylene glycol phosphate onto the surface of steel fibers loaded with porous biochar makes zinc acetate and polyethylene glycol phosphate more firmly adsorbed on the surface of steel fibers, avoiding the migration and precipitation of zinc acetate and polyethylene glycol phosphate. Moreover, the zinc ions of zinc acetate can consume hydroxide ions in concrete, reduce the alkalinity of concrete, and effectively enhance the durability and compressive strength of concrete. On the other hand, the zinc ions of zinc acetate can combine with the functional groups on the molecular chain of polyethylene glycol phosphate, so that polyethylene glycol phosphate forms a cross-linked network coating on the surface of steel fibers, increasing the contact area and bonding force with concrete aggregate, making the steel fibers more firmly dispersed in concrete, improving the mechanical strength of concrete. Moreover, the coating formed by the cross-linked network structure has a good steric hindrance effect, effectively slowing down the penetration of chloride ions, further preventing the corrosion of steel fibers, and reducing the corrosion of steel fibers and concrete by chloride ions. Detailed Implementation

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0051] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0052] The power plant fly ash is Class F, Grade I fly ash, with a fineness of 45μm, a loss on ignition of 2.7%, and a moisture content of 0.15%.

[0053] The mineral powder is S95 grade slag powder with a density of 3.6 g / cm³. 3 Specific surface area is 455 m² 2 / kg, with a moisture content of 0.2%, and an activity index of 95.2% after 28 days.

[0054] The basalt gravel has a continuous gradation of 15mm and a mud content of 0.2%.

[0055] The apparent density of river sand is 2670 kg / m³. 3 The fineness modulus is 2.4, the particle size is 3.8 mm, and the mud content is 1.1%.

[0056] The water-reducing agent is PCE-102 polycarboxylate water-reducing agent.

[0057] The bamboo fiber has a length of 75mm and a diameter of 0.5mm; the steel fiber has a diameter of 0.5mm, a length of 25mm, and a tensile strength of 1150MPa.

[0058] The lignin is dealkalized lignin, produced by Shanghai Maclean Biochemical Technology Co., Ltd.

[0059] Pasteurella multocida was purchased from Wuhan Ruichen Standards Technology Co., Ltd.

[0060] Polyethylene glycol phosphate is prepared by the following steps:

[0061] After mixing polyethylene glycol-200 and polyphosphate at a molar ratio of 1:1.3, the mixture was stirred at 80°C for 3 hours to obtain a mixed solution. The mixed solution was then mixed with water at a mass ratio of 95:5 and the reaction was continued at 80°C for 1 hour to obtain polyethylene glycol phosphate.

[0062] The Bacillus pasteurellium culture is prepared by the following steps:

[0063] Add 5g yeast powder, 5g trimethylglycine, 10g tryptone, 5g ammonium sulfate, 2g glutamic acid, and 10g urea to 1000mL of deionized water. Adjust the pH to 9.5 with 2mol / L sodium hydroxide solution. Sterilize at 120℃ for 30min, cool to room temperature, inoculate with Bacillus pasteurellii, and incubate at 33℃ and 133r / min for 24h to obtain Bacillus pasteurellii bacterial culture.

[0064] Example 1: Modified bamboo fiber was prepared by the following steps:

[0065] A1. Add 10 mL of Bacillus pasteurellium culture and 1.5 g of urea to 50 mL of deionized water and stir until homogeneous to obtain the core material. Mix 25 mL of 1% chitosan solution and 25 mL of 1.5% sodium alginate solution and stir until homogeneous to obtain the capsule material. Mix the capsule material and the core material and stir for 8 min. Add 0.15 g of glutaraldehyde and react at 60 °C for 2 h. Filter and collect the reaction product to obtain microcapsules.

[0066] A2. Immerse 20g of bamboo fiber in 200mL of alkaline solution a, stir evenly, stir at 35℃ for 35min, take out the bamboo fiber, wash it 3 times with deionized water, and dry it in an oven at 70℃ for 8min to obtain pretreated bamboo fiber.

[0067] A3. Add 15g of pretreated bamboo fiber to 80mL of ethanol and 80mL of deionized water, stir evenly, add 3.5g of microcapsules, continue stirring, then add 6.8g of tetraethyl silicate and 4.5mL of 30% ammonia water, stir and react at 40℃ for 4h, filter, wash three times with deionized water, and dry in a 70℃ oven for 10min to obtain modified carbon fiber.

[0068] Comparative Example 1 differs from Example 1 in that the microcapsules are replaced with Bacillus pasteurellium culture and urea, while the remaining steps and raw materials are the same as in Example 1.

[0069] Modified bamboo fiber is prepared by the following steps:

[0070] A1. Immerse 20g of bamboo fiber in 200mL of alkaline solution a, stir evenly, stir at 35℃ for 35min, take out the bamboo fiber, wash it 3 times with deionized water, and dry it in an oven at 70℃ for 8min to obtain pretreated bamboo fiber.

[0071] A2. Add 15g of pretreated bamboo fiber to 80mL of ethanol and 80mL of deionized water, stir well, add 10mL of Bacillus pasteurellium culture and 1.5g of urea, continue stirring, then add 6.8g of tetraethyl silicate and 4.5mL of 30% ammonia water, stir and react at 40℃ for 4h, filter, wash 3 times with deionized water, and dry at room temperature overnight to obtain modified carbon fiber.

[0072] The difference between Comparative Example 2 and Example 1 is that tetraethyl silicate was not added, while the remaining steps and raw materials were the same as in Example 1.

[0073] Modified bamboo fiber is prepared by the following steps:

[0074] A1. Add 10 mL of Bacillus pasteurellium culture and 1.5 g of urea to 50 mL of deionized water and stir until homogeneous to obtain the core material. Mix 25 mL of 1% chitosan solution and 25 mL of 1.5% sodium alginate solution and stir until homogeneous to obtain the capsule material. Mix the capsule material and the core material and stir for 8 min. Add 0.15 g of glutaraldehyde and react at 60 °C for 2 h. Filter and collect the reaction product to obtain microcapsules.

[0075] A2. Immerse 20g of bamboo fiber in 200mL of 6% sodium hydroxide solution, stir evenly, stir at 35℃ for 35min, take out the bamboo fiber, wash it 3 times with deionized water, and dry it in an oven at 70℃ for 8min to obtain pretreated bamboo fiber.

[0076] A3. Add 15g of pretreated bamboo fiber to 80mL of ethanol and 80mL of deionized water, stir well, add 3.5g of microcapsules, continue stirring, filter, wash three times with deionized water, and dry in an oven at 70℃ for 10min to obtain modified carbon fiber.

[0077] Example 2: Modified steel fiber was prepared by the following steps:

[0078] B1. Immerse 20g of steel fiber in 200mL of 6% sodium hydroxide solution and soak at 45℃ for 35min. Remove the steel fiber and wash it 3 times with anhydrous ethanol and 3 times with deionized water to remove grease and impurities from the surface of the steel fiber. Dry it in an oven at 70℃ for 10min to obtain pretreated steel fiber.

[0079] B2. Add 10g of lignin to 150mL of ethanol and stir well. Add 18g of pretreated steel fiber and stir at 85℃ until the ethanol evaporates. Place in a tube furnace, add 5mL of 0.1mol / L potassium hydroxide solution, mix well, introduce argon gas, heat to 850℃, and carbonize at high temperature for 4h. Cool to room temperature, take out, wash 3 times with deionized water, and dry in a 70℃ oven for 10min to obtain steel fiber loaded with porous biochar.

[0080] B3. Add 10g of steel fiber loaded with porous biochar to 150mL of polyethylene glycol phosphate, stir well, add 5.5g of zinc acetate, stir and react at 140℃ for 25min, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10min to obtain modified steel fiber.

[0081] The difference between Comparative Example 3 and Example 2 is that the steel fibers loaded with porous biochar are replaced with pretreated steel fibers, while the remaining steps and raw materials are the same as in Example 2.

[0082] Modified steel fibers are prepared by the following steps:

[0083] B1. Immerse 20g of steel fiber in 200mL of 6% sodium hydroxide solution and soak at 45℃ for 35min. Remove the steel fiber and wash it 3 times with anhydrous ethanol and 3 times with deionized water to remove grease and impurities from the surface of the steel fiber. Dry it in an oven at 70℃ for 10min to obtain pretreated steel fiber.

[0084] B2. Add 10g of pretreated steel fiber to 150mL of polyethylene glycol phosphate, stir well, add 5.5g of zinc acetate, stir and react at 140℃ for 25min, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10min to obtain modified steel fiber.

[0085] The difference between Comparative Example 4 and Example 1 is that zinc acetate was not added, while the remaining steps and raw materials were the same as in Example 1.

[0086] Modified steel fibers are prepared by the following steps:

[0087] B1. Immerse 20g of steel fiber in 200mL of 6% sodium hydroxide solution and soak at 45℃ for 35min. Remove the steel fiber and wash it 3 times with anhydrous ethanol and 3 times with deionized water to remove grease and impurities from the surface of the steel fiber. Dry it in an oven at 70℃ for 10min to obtain pretreated steel fiber.

[0088] B2. Add 10g of lignin to 150mL of ethanol and stir well. Add 18g of pretreated steel fiber and stir at 85℃ until the ethanol evaporates. Place in a tube furnace, add 5mL of 0.1mol / L potassium hydroxide solution, mix well, introduce argon gas, heat to 850℃, and carbonize at high temperature for 4h. Cool to room temperature, take out, wash 3 times with deionized water, and dry in a 70℃ oven for 10min to obtain steel fiber loaded with porous biochar.

[0089] B3. Add 10g of steel fibers loaded with porous biochar to 150mL of polyethylene glycol phosphate, stir evenly, stir and react at 140℃ for 25min, cool to room temperature, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10min to obtain modified steel fibers.

[0090] Example 3: A process for reusing and reprocessing power plant fly ash to prepare concrete, comprising the following steps:

[0091] S1. Mix 1.5 kg of power plant coal ash, 1.6 kg of cement, 5 kg of mineral powder, 5 kg of basalt crushed stone and 4 kg of river sand, and stir at a speed of 80 r / min for 3 min to obtain a mixture;

[0092] S2. Add 0.1 kg of water-reducing agent, 0.1 kg of modified bamboo fiber prepared in Example 1, 0.04 kg of modified steel fiber prepared in Example 2 and 1.2 kg of water to the mixture, and continue stirring at a rate of 80 r / min for 10 min to obtain concrete.

[0093] Example 4: A process for reusing and reprocessing power plant fly ash to prepare concrete, comprising the following steps:

[0094] S1. Mix 1.6 kg of power plant coal ash, 1.8 kg of cement, 5.6 kg of mineral powder, 5.5 kg of basalt crushed stone and 4.5 kg of river sand, and stir at a speed of 100 r / min for 4 min to obtain a mixture;

[0095] S2. Add 0.15 kg of water-reducing agent, 0.15 kg of modified bamboo fiber prepared in Example 1, 0.05 kg of modified steel fiber prepared in Example 2 and 1.3 kg of water to the mixture, and continue stirring at a rate of 100 r / min for 13 min to obtain concrete.

[0096] Example 5: A process for reusing and reprocessing power plant fly ash to prepare concrete, comprising the following steps:

[0097] S1. Mix 1.7 kg of power plant coal ash, 2 kg of cement, 6 kg of mineral powder, 6 kg of basalt crushed stone and 5 kg of river sand, and stir at a speed of 120 r / min for 5 min to obtain a mixture;

[0098] S2. Add 0.2 kg of water-reducing agent, 0.2 kg of modified bamboo fiber prepared in Example 1, 0.06 kg of modified steel fiber prepared in Example 2 and 1.4 kg of water to the mixture, and continue stirring at a rate of 120 r / min for 15 min to obtain concrete.

[0099] The difference between Comparative Example 5 and Example 4 is that the modified bamboo fiber prepared in Example 1 is replaced with the substance prepared in Comparative Example 1, while the other steps are the same as in Example 4.

[0100] The difference between Comparative Example 6 and Example 4 is that the modified bamboo fiber prepared in Example 1 is replaced with the substance prepared in Comparative Example 2, while the other steps are the same as in Example 4.

[0101] The difference between Comparative Example 7 and Example 4 is that the modified steel fiber prepared in Example 2 is replaced with the substance prepared in Comparative Example 3, while the other steps are the same as in Example 4.

[0102] The difference between Comparative Example 8 and Example 4 is that the modified steel fiber prepared in Example 2 is replaced with the substance prepared in Comparative Example 4, while the other steps are the same as in Example 4.

[0103] The performance of the concrete prepared in Examples 3-5 and Comparative Examples 5-8 was then tested.

[0104] Compressive and flexural strength tests: The compressive strength and flexural strength of the concrete prepared above were tested in accordance with the testing standards of GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The compressive strength and flexural strength of the concrete prepared above were tested after standard curing for 7 days and 28 days.

[0105] Chloride ion corrosion resistance test: The concrete prepared above was soaked in a 6% sodium chloride aqueous solution at 20℃ for 12 hours and dried for 12 hours as one corrosion cycle. After 30 corrosion cycles, the compressive strength and flexural strength of the concrete after corrosion cycles were tested according to the testing standards of GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0106] The fracture toughness of the concrete prepared above was tested according to the DL / T 5332-2005 standard.

[0107] The measurement data are shown in Table 1 below:

[0108] Table 1

[0109]

[0110]

[0111] In Comparative Example 5, when the microcapsules were replaced with modified bamboo fiber prepared from Bacillus pasteurellium culture and urea and added to concrete, its mechanical properties decreased. This demonstrates that encapsulating Bacillus pasteurellium culture and urea in microcapsules enhances the activity of the Bacillus pasteurellium culture in concrete. The microcapsules can also fill the gaps in the concrete aggregate, improving the density of the concrete. However, in Comparative Example 5, when Bacillus pasteurellium culture and urea were directly added to the concrete, this effect was not achieved, and its mechanical properties decreased.

[0112] In Comparative Example 6, the modified bamboo fiber prepared without tetraethyl silicate was added to concrete, resulting in a decrease in its mechanical properties. This demonstrates that the microcapsules, through organosilicon, fill the voids in the surface of the pretreated bamboo fiber, sealing the voids and preventing the porous structure of the pretreated bamboo fiber from easily absorbing moisture, which would lead to a decrease in fiber performance and affect the mechanical strength of the concrete. Furthermore, the calcium carbonate induced by Bacillus pasteurization on the surface of the bamboo fiber is also filled into the pore structure of the concrete, enhancing the bond strength between the modified bamboo fiber and the concrete, thereby enhancing the mechanical strength of the concrete. In contrast, Comparative Example 6, lacking tetraethyl silicate, did not achieve this effect, resulting in a decrease in its mechanical properties.

[0113] In Comparative Example 7, the steel fibers loaded with porous biochar were replaced with modified steel fibers prepared from pretreated steel fibers and added to concrete. The mechanical properties of the concrete decreased, demonstrating that the synthesis of porous carbon materials on the surface of pretreated steel fibers can hinder the contact of acidic media with the steel fibers, improve the steel fibers' resistance to chloride ions, and prevent the passivation film on the surface of the steel fibers from being corroded by a large number of chloride ions, which would lead to a decrease in the strength of the steel fibers and affect the mechanical strength of the concrete. Furthermore, zinc acetate and polyethylene glycol phosphate are more firmly adsorbed on the surface of the steel fibers, preventing the migration and precipitation of zinc acetate and polyethylene glycol phosphate. In contrast, the pretreated steel fibers in Comparative Example 7 lacked porous biochar and could not achieve this effect, resulting in a decrease in their mechanical properties.

[0114] In Comparative Example 8, the modified steel fibers prepared without zinc acetate, when added to concrete, exhibited decreased mechanical strength and aging resistance. This demonstrates that zinc ions from zinc acetate can bind with functional groups on the polyethylene glycol phosphate molecular chain, forming a cross-linked network coating on the steel fiber surface. This increases the contact area and bonding force with the concrete aggregate, resulting in more firmly dispersed steel fibers in the concrete and improved mechanical strength. Furthermore, the cross-linked network coating provides good steric hindrance, effectively slowing down chloride ion penetration and further preventing steel fiber corrosion. In contrast, Comparative Example 8, lacking zinc acetate, failed to achieve this effect, resulting in decreased mechanical strength.

[0115] The data in Table 1 show that the concrete prepared in Examples 3-5 met the performance requirements, while the concrete prepared in Comparative Examples 5-8 did not meet the performance requirements. This indicates that the concrete prepared by the present invention has excellent mechanical strength and density.

[0116] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0117] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A process for reusing and reprocessing power plant fly ash to prepare concrete, characterized in that, Includes the following steps: S1. Mix power plant coal ash, cement, mineral powder, basalt crushed stone and river sand, and stir at a speed of 80-120 r / min for 3-5 min to obtain a mixture; S2. Add water-reducing agent, modified bamboo fiber, modified steel fiber and water to the mixture, and continue to stir at a rate of 80-120 r / min for 10-15 min to obtain concrete; The modified bamboo fiber is obtained by treating bamboo fiber with alkaline solution a, and then reacting it with microcapsules and tetraethyl silicate. The microcapsules are made by using a mixture of Bacillus pasteurellium bacterial solution and urea as the core material, and chitosan solution and sodium alginate solution as the encapsulation material. The modified steel fiber is obtained by treating steel fiber with alkaline solution b, mixing it with lignin and carbonizing it at high temperature, and then reacting it with zinc acetate and polyethylene glycol phosphate. The high-temperature carbonization of the steel fibers specifically involves: Lignin was added to ethanol and stirred until homogeneous. Pretreated steel fibers were then added and stirred at 80-90℃ until the ethanol evaporated. The mixture was placed in a tube furnace, potassium hydroxide solution was added, and the mixture was stirred until homogeneous. Argon gas was introduced and the temperature was raised to 800-900℃ for high-temperature carbonization for 3-5 hours. The mixture was then cooled to room temperature, removed, washed, and dried to obtain steel fibers loaded with porous biochar.

2. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The chitosan solution has a mass fraction of 0.5-1.5%; the sodium alginate solution has a mass fraction of 1-2%.

3. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The alkaline solution a is a sodium hydroxide solution with a mass fraction of 5-7%; the concentration of the Bacillus pasteurellium bacterial culture is 4-6 × 10⁻⁶. 6 CFU / mL.

4. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The bamboo fiber has a length of 70-80mm and a diameter of 0.1-1mm.

5. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The steel fiber has a diameter of 0.4-0.6 mm, a length of 20-30 mm, and a tensile strength of 1100-1200 MPa; the alkaline solution b is a sodium hydroxide solution with a mass fraction of 18-22%.

6. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The power plant fly ash is Class F Grade I fly ash, with a fineness of 40-50μm, a loss on ignition of 2.6-2.9%, and a moisture content of 0.1-0.2%; the cement is Grade 42.5 low-alkalinity sulfoaluminate cement.

7. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The mineral powder is S95 grade slag powder with a density of 2.5-3.9 g / cm³. 3 Specific surface area is 445-460 m² 2 / kg, with a moisture content of 0.15-0.25%, and an activity index of 94.5-95.6% after 28 days.

8. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The basalt gravel has a continuous gradation of 5-25mm and a mud content of 0.1-0.3%.

9. The process for reusing and reprocessing power plant fly ash to prepare concrete according to claim 1, characterized in that, The apparent density of the river sand is 2660-2690 kg / m³. 3 The fineness modulus is 2.3-2.5, the particle size is 3.3-4.2 mm, and the mud content is 0.8-1.3%; the water-reducing agent is any one of PCE-102 polycarboxylate water-reducing agent, PCE-101 polycarboxylate water-reducing agent, and PCE-103 polycarboxylate water-reducing agent.

10. Concrete prepared by the process of reusing and reprocessing power plant fly ash as described in any one of claims 1-9.

Images