Recycled concrete with self-repairing function and preparation method thereof

Abstract

The invention belongs to the technical field of constructional engineering, and particularly discloses recycled concrete with a self-repairing function and a preparation method of the recycled concrete. The concrete comprises a base material, a function regulator and a microbial self-repairing agent, the base material comprises cement and recycled aggregate from construction waste, the function regulator comprises a water reducing agent, a mineral admixture and a composite fiber material, and the microbial self-repairing agent is microbial self-repairing slurry. The composite fiber material comprises esterified modified cellulose and polypropylene fiber, and a modifier of the esterified modified cellulose comprises S-acetyl mercaptosuccinic anhydride and 4-phenoxy phthalic anhydride. The internal structure of the concrete is optimized through the composite fiber material, and in cooperation with the in-situ deposition effect of microbial mineralization products, the compactness and defect self-repairing capacity of a matrix are remarkably improved. According to the technology, efficient resource utilization of the construction waste is achieved, and an environment-friendly material solution is provided for green construction engineering.

Description

Technical Field

[0001] This invention belongs to the field of building engineering technology, specifically relating to a self-healing recycled concrete and its preparation method. Background Technology

[0003] Recycled aggregates, obtained by crushing and screening waste concrete, are considered an important way to alleviate the depletion of natural sand and gravel resources, reduce construction waste landfill, and promote sustainable development in the building materials industry. However, due to their complex origins, fluctuating performance, and the presence of attached old mortar, the application of recycled aggregates still faces many technical bottlenecks. Traditional high-performance concrete preparation methods often lack adaptability when dealing with the performance differences brought about by recycled aggregates.

[0004] Therefore, developing a recycled concrete and its preparation method that can effectively utilize recycled aggregates, meet performance requirements, is environmentally friendly and economically feasible is of great practical significance and strategic value for promoting the resource utilization of construction waste, driving the development of green building materials, and supporting large-scale infrastructure construction. Summary of the Invention

[0005] The purpose of this invention is to provide a self-healing recycled concrete and its preparation method.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows: A type of concrete includes a matrix material, a functional modifier, and a microbial self-healing agent, wherein, The microbial remediation agent is a microbial self-healing slurry, which includes Pasteurella multocida liquid and a binding liquid, with a volume ratio of 0.5-2:1 between the binding liquid and the Pasteurella multocida liquid.

[0007] Preferably, the matrix material includes cement and aggregate.

[0008] Preferably, the mass ratio of cement to aggregate is 150-200:1500.

[0009] Preferably, the aggregate includes coarse aggregate and fine aggregate.

[0010] Preferably, the coarse aggregate includes one or more of natural coarse aggregate and recycled coarse aggregate.

[0011] Preferably, the average particle size of the coarse aggregate is 5-20 mm.

[0012] Preferably, the functional regulator includes water-reducing agents and mineral admixtures.

[0013] Preferably, the mass ratio of water-reducing agent to cement is 2-5:198.

[0014] Preferably, the mass ratio of mineral admixtures to cement is 200-240:198.

[0015] Preferably, the functional modifier includes composite fiber materials.

[0016] Preferably, the mass ratio of composite fiber material to cement is 3-10:198.

[0017] Preferably, the composite fiber material includes esterified modified cellulose and polypropylene fiber.

[0018] Preferably, the mass ratio of esterified modified cellulose to polypropylene fiber is 10-30:75.

[0019] Preferably, the modifiers in the esterified modified cellulose include S-acetyl thiosuccinic anhydride and 4-phenoxy phthalic anhydride.

[0020] Preferably, the mass ratio of S-acetyl thiosuccinic anhydride to 4-phenoxy phthalic anhydride is 1-4:2.

[0021] S-acetylmercaptosuccinic anhydride and 4-phenoxyphthalic anhydride, as hydrophobic modifiers, covalently bond with cellulose molecular chains, not only enhancing the chemical stability of cellulose but also reducing the adsorption and penetration of water molecules on the fiber surface through hydrophobic groups. The rigid structure enhances the mechanical strength of the fiber, synergistically constructing a dense molecular network that fills microcracks inside the concrete and blocks interconnected pores, reducing chloride ion penetration channels. Together, they optimize the compatibility of the composite fiber with the cement matrix, enabling the fiber to be evenly dispersed to inhibit crack propagation. Combined with microbial mineralization deposition, this significantly improves the concrete's resistance to salt erosion and carbonation.

[0022] Preferably, the water-reducing agent includes a polycarboxylate superplasticizer.

[0023] Preferably, the water reduction efficiency of the polycarboxylate superplasticizer is 20-30%.

[0024] Preferably, the mineral admixture includes fly ash and mineral powder.

[0025] Preferably, the mass ratio of fly ash to mineral powder is 100-110:118.

[0026] Preferably, the cementing solution comprises calcium acetate and urea.

[0027] Preferably, the mass ratio of calcium acetate to urea is 150-200:60.

[0028] More preferably, the modifier in the esterified modified cellulose includes (-)-diacetyl-D-tartaric anhydride.

[0029] More preferably, the mass ratio of (-)-diacetyl-D-tartaric anhydride to 4-phenoxyphthalic anhydride is 1-4:2. The introduction of hydrophobic groups by (-)-diacetyl-D-tartaric anhydride further enhances the hydrophobic properties of the esterified modified cellulose, reduces the adsorption and penetration of water molecules by the composite fiber material, thereby reducing the migration rate of chloride ions with water inside the concrete; synergistically with S-acetyl mercaptosuccinic anhydride and 4-phenoxyphthalic anhydride, it optimizes the spatial arrangement of cellulose molecular chains, making the modified cellulose more uniformly dispersed in the composite fiber, filling microcracks inside the concrete and refining the pore structure, blocking the penetration paths of chloride ions and carbon dioxide, and further improving the salt erosion resistance of the concrete.

[0030] The present invention also provides a method for preparing a cementing liquid, comprising: Preparation of cementing solution: Dissolve calcium acetate in deionized water, add urea, mix well to obtain cementing solution.

[0031] Preferably, the mass-to-volume ratio of calcium acetate to deionized water is 150-200 g: 1 L.

[0032] Preferably, the mass ratio of calcium acetate to urea is 150-200:60.

[0033] This invention also provides a method for preparing a microbial self-healing slurry, comprising: Preparation of microbial self-healing slurry: Dissolve the lyophilized powder of Bacillus pasteurellii in the dissolving solution, inoculate it onto a solid slant culture medium, and incubate it in a constant temperature incubator at 29-31℃ for 20-25 hours. Then scrape it off and inoculate it into a new sterile liquid culture medium, and incubate it in a constant temperature shaker at 29-31℃ and 140-160 rpm for 20-25 hours to obtain Bacillus pasteurellii liquid. Mix the cementing solution and Bacillus pasteurellii liquid evenly to obtain the microbial self-healing slurry.

[0034] Preferably, the Bacillus pasteurellii strain is designated ATCC-11859.

[0035] Preferably, the volume ratio of the cementing solution to the Bacillus pasteurellium solution is 0.5-2:1.

[0036] This invention also provides a method for preparing esterified modified cellulose, comprising: Preparation of esterified modified cellulose: cellulose is dispersed in a 4-6 wt% sodium hydroxide solution and activated for 1-3 h under stirring. After filtration, it is washed with deionized water and vacuum dried at 35-45℃ for 0.5-1.5 h to obtain activated cellulose. The activated cellulose is dispersed in dimethyl sulfoxide and stirred for 0.5-1.5 h to mix evenly. A modifier is added and stirred for 15-45 min to mix evenly. Concentrated sulfuric acid is added and reacted at 75-85℃ under stirring for 1-3 h. After filtration, it is washed alternately with acetone and deionized water and vacuum dried at 55-65℃ for 10-15 h to obtain esterified modified cellulose.

[0037] Preferably, the mass-to-volume ratio of cellulose to sodium hydroxide solution is 1-5 g: 100 mL.

[0038] Preferably, the mass-to-volume ratio of activated cellulose to dimethyl sulfoxide is 1-5 g: 100 mL.

[0039] Preferably, the modifiers include S-acetylmercaptosuccinic anhydride and 4-phenoxyphthalic anhydride.

[0040] Preferably, the mass ratio of S-acetyl succinic anhydride to activated cellulose is 1-4:2.

[0041] Preferably, the mass ratio of 4-phenoxyphthalic anhydride to activated cellulose is 1-4:2.

[0042] Preferably, the mass ratio of concentrated sulfuric acid to activated cellulose is 0.1-0.4:2.

[0043] More preferably, the modifier includes (-)-diacetyl-D-tartaric anhydride.

[0044] More preferably, the mass ratio of (-)-diacetyl-D-tartaric anhydride to activated cellulose is 1-4:2.

[0045] This invention also provides a method for preparing a composite fiber material, comprising: Preparation of composite fiber materials: Esterified modified cellulose, polypropylene fiber and compatibilizer are stirred at 1000-1400 rpm for 3-10 min to mix evenly, added to a twin-screw extruder for co-extrusion, air-cooled pelletizing and then dried at 55-65℃ for 10-15 h to obtain composite fiber materials.

[0046] Preferably, the compatibilizer is polypropylene grafted with maleic anhydride.

[0047] Preferably, the mass ratio of esterified modified cellulose to polypropylene fiber is 10-30:75.

[0048] Preferably, the mass ratio of compatibilizer to esterified modified cellulose is 2.5-7.5:20.

[0049] Preferably, the temperature of the feeding section of the twin-screw extruder is 98-104℃, the temperature of the compression section is 158-162℃, the temperature of the melting section is 178-182℃, and the temperature of the die head section is 158-162℃.

[0050] Preferably, the screw speed is 50-70 rpm.

[0051] Preferably, the particle size of the composite fiber material is 2-4 mm.

[0052] Preferably, the length of the composite fiber material is 3-5 mm.

[0053] This invention also provides a method for preparing concrete specimens, comprising: Preparation of concrete specimens: Dissolve the water-reducing agent in deionized water and stir evenly to obtain a water-reducing agent solution; pre-mix coarse and fine aggregates for 20-40 seconds, add cement and stir for 40-80 seconds, add water-reducing agent solution and stir for 90-120 seconds, put into molds, vibrate on a vibrating table until slurry appears on the surface, scrape the surface smooth, cover with plastic film, let stand at 21-23℃ for 15-25 hours, then remove the mold, and cure in a standard curing room for 26-30 days to obtain concrete specimens.

[0054] Preferably, the water-reducing agent is a polycarboxylate superplasticizer with a water-reducing efficiency of 20-30%.

[0055] Preferably, the coarse aggregate includes natural coarse aggregate.

[0056] Preferably, the average particle size of the coarse aggregate is 5-20 mm.

[0057] Preferably, the natural coarse aggregate is continuously graded granite crushed stone.

[0058] Preferably, the fine aggregate is continuously graded river sand with a fineness modulus of 2.5-2.8 and a particle size distribution zone II.

[0059] Preferably, the cement is ordinary Portland cement of type PO with a strength grade of 32.5-52.5.

[0060] Preferably, the fly ash is Class II fly ash.

[0061] Preferably, the mineral powder is S95 mineral powder.

[0062] Preferably, the mass ratio of water-reducing agent to deionized water is 2-5:160.

[0063] Preferably, the mass of the water-reducing agent solution is measured by the mass of the water-reducing agent therein, and the mass ratio of the water-reducing agent to the cement is 2-5:198.

[0064] Preferably, the mass ratio of fine aggregate to coarse aggregate is 700-800:995.

[0065] Preferably, the mass ratio of cement to coarse aggregate is 150-200:995.

[0066] Preferably, the mass ratio of fly ash to cement is 100-120:198.

[0067] Preferably, the mass ratio of mineral powder to cement is 100-120:198.

[0068] More preferably, coarse aggregate includes natural coarse aggregate and recycled coarse aggregate.

[0069] More preferably, the recycled coarse aggregate is continuously graded crushed stone made from construction waste from demolished houses after crushing and screening.

[0070] More preferably, the mass ratio of recycled coarse aggregate to natural coarse aggregate is 200-300:700.

[0071] More preferably, the concrete specimens include composite fiber materials.

[0072] More preferably, the mass ratio of composite fiber material to cement is 3-10:198.

[0073] The present invention also provides a method for preparing coated concrete, comprising: Preparation of recycled concrete: A negative pressure coating process is adopted. First, the surface of the concrete specimen is moistened with deionized water. The microbial self-healing slurry is dripped onto the surface of the concrete specimen and spread evenly with a brush soaked in the microbial liquid. After coating, the specimen is placed in a vacuum container, and the negative pressure is adjusted to -0.05~-0.15MPa. After 10-20 minutes, it is taken out and left to stand for 2-4 hours. Then, the binder is dripped onto the surface of the concrete specimen and spread evenly with a brush soaked in the binder. After coating, the specimen is placed in a vacuum container, and the negative pressure is adjusted to -0.05~-0.15MPa. After 10-20 minutes, it is taken out and left to stand for 2-4 hours. The microbial self-healing slurry and binder are repeatedly coated at 10-14 hours every day for 6-8 days to obtain recycled concrete.

[0074] This invention provides a recycled concrete composed of a matrix material, a functional modifier, and a microbial self-healing agent, and its preparation method. The matrix material consists of cement and recycled aggregate from construction waste; the functional modifier includes a water-reducing agent, mineral admixtures, and a composite fiber material, comprising esterified modified cellulose and polypropylene fibers. The modifiers for the esterified modified cellulose include S-acetylmercaptosuccinic anhydride and 4-phenoxyphthalic anhydride; the microbial self-healing agent is a microbial active slurry. By physically filling and constructing a dense network through the composite fibers, the internal structure of the concrete is optimized. This, combined with the directional deposition of microbial mineralization products, significantly improves the microstructure density and self-healing ability of the matrix, while simultaneously achieving efficient recycling of construction waste resources, providing an innovative material solution for green building projects. Attached Figure Description

[0075] Figure 1 This is a schematic diagram of a transmission electron microscope image of esterified modified cellulose.

[0076] Figure 2 This is a schematic diagram showing the moisture absorption rate test results of composite fiber materials.

[0077] Figure 3 This is a schematic diagram of the test results for the chloride ion penetration resistance of concrete. Detailed Implementation

[0078] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0079] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0080] Example 1: Preparation of the cementing solution: Calcium acetate was dissolved in deionized water, urea was added, and the mixture was stirred evenly to obtain the cementing solution. The mass-to-volume ratio of calcium acetate to deionized water was 176 g: 1 L, and the mass ratio of calcium acetate to urea was 176: 60.

[0081] Preparation of the microbial self-healing slurry: Lyophilized *Pasteurella multocida* powder was dissolved in a dissolving solution and inoculated onto a solid slant culture medium. After static incubation at 30°C for 24 hours, the slurry was scraped and inoculated onto a fresh sterile liquid culture medium. The medium was then incubated at 30°C and 150 rpm for 24 hours to obtain the *Pasteurella multocida* liquid. The cementing solution and the *Pasteurella multocida* liquid were then uniformly mixed to obtain the microbial self-healing slurry. The *Pasteurella multocida* designation was ATCC-11859, and the volume ratio of the cementing solution to the *Pasteurella multocida* liquid was 1:1.

[0082] Preparation of concrete specimens: The water-reducing agent was dissolved in deionized water and stirred evenly to obtain a water-reducing agent solution. Coarse and fine aggregates were pre-mixed for 30 seconds, cement was added and stirred for 60 seconds, the water-reducing agent solution was added and stirred for 100 seconds, the mixture was poured into molds, and compacted on a vibrating table until slurry appeared on the surface. The surface was smoothed, covered with plastic film, and allowed to stand at 22℃ for 20 hours before demolding. The specimens were then cured in a standard curing room for 28 days to obtain concrete specimens. The water-reducing agent was a polycarboxylate high-efficiency water-reducing agent with a water-reducing efficiency of 28%. The coarse aggregate was continuously graded granite crushed stone with an average particle size of 10 mm. The fine aggregate was river sand with a fineness modulus of 2.63, a particle size distribution of zone II, and a continuous gradation. The cement was PO type 42.5 strength grade ordinary Portland cement. The fly ash was grade II fly ash. The mineral powder was S95 mineral powder. The mass ratio of water-reducing agent to deionized water is 4.2:160; the mass of the water-reducing agent solution is measured by the mass of the water-reducing agent in it; the mass ratio of water-reducing agent to cement is 4.2:198; the mass ratio of fine aggregate to coarse aggregate is 721:995; the mass ratio of cement to coarse aggregate is 194:995; the mass ratio of fly ash to cement is 109:198; and the mass ratio of mineral powder to cement is 118:198.

[0083] Preparation of recycled concrete: A negative pressure coating process was adopted. First, the surface of the concrete specimen was moistened with deionized water. The microbial self-healing slurry was dripped onto the surface of the concrete specimen and spread evenly with a brush soaked in the microbial liquid. After coating, the specimen was placed in a vacuum container, and the negative pressure was adjusted to -0.1 MPa. After 15 minutes, it was taken out and left to stand for 3 hours. Then, the binder was dripped onto the surface of the concrete specimen and spread evenly with a brush soaked in the binder. After coating, the specimen was placed in a vacuum container, and the negative pressure was adjusted to -0.1 MPa. After 15 minutes, it was taken out and left to stand for 3 hours. The microbial self-healing slurry and binder were repeatedly coated at 12-hour intervals every day for 7 consecutive days to obtain recycled concrete.

[0084] Example 2: The only difference between this example and Example 1 is the preparation of the concrete specimen.

[0085] Preparation of esterified modified cellulose: Cellulose was dispersed in a 5 wt% sodium hydroxide solution and activated for 2 h under stirring. After filtration, it was washed with deionized water and dried under vacuum at 40 °C for 1 h to obtain activated cellulose. The activated cellulose was dispersed in dimethyl sulfoxide and stirred for 1 h to mix evenly. S-acetyl thiosuccinic anhydride and 4-phenoxy phthalic anhydride were added and stirred for 30 min to mix evenly. Concentrated sulfuric acid was added, and the mixture was reacted at 80 °C under stirring for 2 h. After filtration, it was washed alternately with acetone and deionized water and dried under vacuum at 60 °C for 12 h to obtain esterified modified cellulose. The mass-to-volume ratio of cellulose to sodium hydroxide solution was 2 g:100 mL, the mass-to-volume ratio of activated cellulose to dimethyl sulfoxide was 2 g:160 mL, the mass ratio of S-acetyl thiosuccinic anhydride to activated cellulose was 2:2, the mass ratio of 4-phenoxy phthalic anhydride to activated cellulose was 2:2, and the mass ratio of concentrated sulfuric acid to activated cellulose was 0.2:2.

[0086] Preparation of composite fiber material: Esterified modified cellulose, polypropylene fiber, and compatibilizer were stirred at 1200 rpm for 5 min to achieve uniform mixing. The mixture was then fed into a twin-screw extruder for co-extrusion. After air cooling and pelletizing, the mixture was dried at 60℃ for 12 h to obtain the composite fiber material. The compatibilizer was polypropylene grafted with maleic anhydride. The mass ratio of esterified modified cellulose to polypropylene fiber was 20:75, and the mass ratio of compatibilizer to esterified modified cellulose was 5:20. The twin-screw extruder had the following temperatures: feeding section temperature 100℃, compression section temperature 160℃, melting section temperature 180℃, die head section temperature 160℃, screw speed 60 rpm, particle size of the composite fiber material 3 mm, and length of the composite fiber material 4 mm.

[0087] Preparation of concrete specimens: The water-reducing agent was dissolved in deionized water and stirred evenly to obtain a water-reducing agent solution; natural coarse aggregate, recycled coarse aggregate, composite fiber material and fine aggregate were pre-mixed for 30s, cement was added and stirred for 60s, water-reducing agent solution was added and stirred for 100s, the mixture was put into a mold, and compacted on a vibrating table until slurry appeared on the surface. The surface was smoothed, covered with plastic film, and left to stand at 22℃ for 20h before demolding. The concrete specimens were then cured in a standard curing room for 28d to obtain concrete specimens. The water-reducing agent is a polycarboxylate high-efficiency water-reducing agent with a water reduction efficiency of 28%; the coarse aggregate is continuously graded granite crushed stone with an average particle size of 10mm; the recycled coarse aggregate is continuously graded crushed stone from demolished buildings after crushing and screening, with an average particle size of 10mm; the fine aggregate is river sand with a fineness modulus of 2.63, particle size distribution zone II, continuous gradation, and qualified gradation; the cement is PO type 42.5 strength grade ordinary Portland cement; the fly ash is grade II fly ash; and the mineral powder is S95 mineral powder. The mass ratio of water-reducing agent to deionized water is 4.2:160, and the mass of the water-reducing agent solution is measured by the mass of the water-reducing agent in it. The mass ratio of water-reducing agent to cement is 4.2:198. The mass ratio of recycled coarse aggregate to natural coarse aggregate is 295:700, the mass ratio of fine aggregate to natural coarse aggregate is 721:700, the mass ratio of composite fiber material to fine aggregate is 6:721, the mass ratio of cement to fine aggregate is 194:721, the mass ratio of fly ash to cement is 109:198, and the mass ratio of mineral powder to cement is 118:198.

[0088] Example 3: The only difference between this example and Example 2 is the preparation of esterified modified cellulose.

[0089] Preparation of esterified modified cellulose: Cellulose was dispersed in a 5 wt% sodium hydroxide solution and activated for 2 h under stirring. After filtration, it was washed with deionized water and dried under vacuum at 40 °C for 1 h to obtain activated cellulose. The activated cellulose was dispersed in dimethyl sulfoxide and stirred for 1 h to mix evenly. S-acetyl thiosuccinic anhydride and 4-phenoxy phthalic anhydride were added and stirred for 30 min to mix evenly. Concentrated sulfuric acid was added, and the mixture was reacted at 80 °C under stirring for 2 h. After filtration, it was washed alternately with acetone and deionized water and dried under vacuum at 60 °C for 12 h to obtain esterified modified cellulose. The mass-to-volume ratio of cellulose to sodium hydroxide solution was 2 g:100 mL, the mass-to-volume ratio of activated cellulose to dimethyl sulfoxide was 2 g:160 mL, the mass ratio of S-acetyl thiosuccinic anhydride to activated cellulose was 2:2, the mass ratio of 4-phenoxy phthalic anhydride to activated cellulose was 3:2, and the mass ratio of concentrated sulfuric acid to activated cellulose was 0.2:2.

[0090] Example 4: The only difference between this example and Example 2 is the preparation of esterified modified cellulose.

[0091] Preparation of esterified modified cellulose: Cellulose was dispersed in a 5 wt% sodium hydroxide solution and activated for 2 h under stirring. After filtration, it was washed with deionized water and dried under vacuum at 40 °C for 1 h to obtain activated cellulose. The activated cellulose was dispersed in dimethyl sulfoxide and stirred for 1 h to mix evenly. S-acetyl thiosuccinic anhydride, 4-phenoxy phthalic anhydride and (-)-diacetyl-D-tartaric anhydride were added and stirred for 30 min to mix evenly. Concentrated sulfuric acid was added and reacted at 80 °C under stirring for 2 h. After filtration, it was washed alternately with acetone and deionized water and dried under vacuum at 60 °C for 12 h to obtain esterified modified cellulose. The mass-to-volume ratio of cellulose to sodium hydroxide solution is 2 g:100 mL, the mass-to-volume ratio of activated cellulose to dimethyl sulfoxide is 2 g:160 mL, the mass ratio of S-acetyl thiosuccinic anhydride to activated cellulose is 2:2, the mass ratio of 4-phenoxy phthalic anhydride to activated cellulose is 2:2, the mass ratio of (-)-diacetyl-D-tartaric anhydride to activated cellulose is 1:2, and the mass ratio of concentrated sulfuric acid to activated cellulose is 0.2:2.

[0092] Example 5: The only difference between this example and Example 2 is the preparation of esterified modified cellulose.

[0093] Preparation of esterified modified cellulose: Cellulose was dispersed in a 5 wt% sodium hydroxide solution and activated for 2 h under stirring. After filtration, it was washed with deionized water and dried under vacuum at 40 °C for 1 h to obtain activated cellulose. The activated cellulose was dispersed in dimethyl sulfoxide and stirred for 1 h to mix evenly. S-acetyl thiosuccinic anhydride, 4-phenoxy phthalic anhydride and (-)-diacetyl-D-tartaric anhydride were added and stirred for 30 min to mix evenly. Concentrated sulfuric acid was added and reacted at 80 °C under stirring for 2 h. After filtration, it was washed alternately with acetone and deionized water and dried under vacuum at 60 °C for 12 h to obtain esterified modified cellulose. The mass-to-volume ratio of cellulose to sodium hydroxide solution is 2 g:100 mL, the mass-to-volume ratio of activated cellulose to dimethyl sulfoxide is 2 g:160 mL, the mass ratio of S-acetyl thiosuccinic anhydride to activated cellulose is 2:2, the mass ratio of 4-phenoxy phthalic anhydride to activated cellulose is 2:2, the mass ratio of (-)-diacetyl-D-tartaric anhydride to activated cellulose is 2:2, and the mass ratio of concentrated sulfuric acid to activated cellulose is 0.2:2.

[0094] Comparative Example 1: The only difference between this comparative example and Example 2 is that S-acetylthiosuccinic anhydride was not used in the preparation of the esterified modified cellulose.

[0095] Comparative Example 2: The only difference between this comparative example and Example 2 is that 4-phenoxyphthalic anhydride was not used in the preparation of the esterified modified cellulose.

[0096] Comparative Example 3: The only difference between this comparative example and Example 2 is the preparation of the composite fiber material.

[0097] Preparation of composite fiber material: Cellulose, polypropylene fiber, and compatibilizer were stirred at 1200 rpm for 5 min to achieve uniform mixing. The mixture was then fed into a twin-screw extruder for co-extrusion. After air cooling and pelletizing, the mixture was dried at 60℃ for 12 h to obtain the composite fiber material. The compatibilizer was polypropylene grafted with maleic anhydride. The mass ratio of cellulose to polypropylene fiber was 20:75, and the mass ratio of compatibilizer to cellulose was 5:20. The twin-screw extruder had a feeding section temperature of 100℃, a compression section temperature of 160℃, a melting section temperature of 180℃, a die head section temperature of 160℃, a screw speed of 60 rpm, a particle size of 3 mm, and a length of 4 mm.

[0098] Experimental Example 1: Microstructural characterization of esterified modified cellulose.

[0099] Test sample: Esterified modified cellulose prepared in Example 2.

[0100] Test method: Esterified modified cellulose was dispersed in anhydrous ethanol and sonicated for 30 min to obtain a dispersion. 5 μL was dropped onto a copper grid, allowed to stand for 2 min, excess liquid was absorbed with filter paper, and the mixture was vacuum dried at 40 °C for 1 h. The mixture was then observed using a transmission electron microscope.

[0101] Transmission electron microscopy (TEM) image of the esterified modified cellulose prepared in this invention is shown below. Figure 1 As shown, the cellulose exhibits a fibrous structure and increased surface roughness, indicating that the esterified modified cellulose shown in the figure was successfully obtained.

[0102] Experimental Example 2: Moisture Absorption Rate Test of Composite Fiber Materials

[0103] Test samples: Composite fiber materials prepared in Examples 2-5 and Comparative Examples 1-3.

[0104] Test method: Cut the composite fiber into 1cm segments, vacuum dry them and weigh them as m0. Immerse them completely in deionized water for 24 hours. Take out the composite fiber, absorb the surface moisture with filter paper and weigh it as m1. Calculate the moisture absorption rate according to the formula: moisture absorption rate (%) = (m1-m0) / m0×100%.

[0105] The moisture absorption rate test results of the composite fiber material obtained by this invention are as follows: Figure 2As shown, Example 2, by adding S-acetylmercaptosuccinic anhydride and 4-phenoxyphthalic anhydride as hydrophobic modifiers for cellulose, prepared a composite fiber material with low moisture absorption. Example 3 increased the amount of 4-phenoxyphthalic anhydride, introducing more hydrophobic groups containing benzene rings, enhancing the hydrophobicity of esterified modified cellulose, and further reducing the moisture absorption. Example 4 introduced (-)-diacetyl-D-tartaric anhydride in the preparation of esterified modified cellulose, and its moisture absorption further decreased compared to Example 3. The acetyl group in (-)-diacetyl-D-tartaric anhydride is a hydrophobic group, which works synergistically with S-acetylmercaptosuccinic anhydride and 4-phenoxyphthalic anhydride to improve the hygroscopicity of cellulose molecules. A denser hydrophobic layer is formed on the chain surface; Example 5 increased the amount of (-)-diacetyl-D-tartaric anhydride, reducing the adsorption and penetration of water molecules, further optimizing the hydrophobicity of the composite fiber material, and achieving the lowest moisture absorption rate; Comparative Example 1 did not use S-acetyl mercaptosuccinic anhydride in the preparation of esterified modified cellulose, and Comparative Example 2 did not use 4-phenoxyphthalic anhydride, and its moisture absorption rate was higher than that of Example 2; Comparative Example 3 did not use esterified modified cellulose, and could not effectively construct a hydrophobic network. The hydrophilicity of the composite fiber surface was enhanced, and water was more easily penetrated, resulting in the highest moisture absorption rate. This verified the key role of S-acetyl mercaptosuccinic anhydride and 4-phenoxyphthalic anhydride in reducing the moisture absorption rate of the composite fiber material.

[0106] Experimental Example 3: Chloride Ion Permeability Test of Recycled Concrete.

[0107] Test samples: Recycled concrete obtained from each embodiment and comparative example.

[0108] Test method: The recycled concrete was cut into cylindrical specimens with a diameter of 100 mm and a height of 50 mm. The specimens were vacuum-saturated with water and fixed in the test tank. The sides were sealed. A 0.3 mol / L sodium hydroxide solution was poured into the positive electrode tank and a 3.0% sodium chloride solution was poured into the negative electrode tank. Positive and negative wires were connected. The total amount of charge passing through the concrete within 6 hours under an applied voltage of 60 V was tested. The lower the current flux, the stronger the resistance to chloride ion penetration.

[0109] The chloride ion penetration resistance test results of the recycled concrete obtained by this invention are as follows: Figure 3As shown, compared with Example 1, Example 2 introduces composite fiber materials and recycled coarse aggregate. The esterified modified cellulose and polypropylene fibers in the composite fiber material work synergistically to fill micro-cracks inside the concrete and reduce pore connectivity. After pretreatment, the recycled coarse aggregate bonds more tightly to the matrix interface, reducing chloride ion penetration channels and significantly reducing its electrical flux. Example 3 increases the amount of 4-phenoxyphthalic anhydride to enhance the hydrophobicity of the composite fiber, making the pores more fully filled and further improving the impermeability. Example 4 adds (-)-diacetyl-D-tartaric anhydride. The hydrophobic groups in the resulting composite fiber work synergistically to form a stronger hydrophobic layer on the concrete surface, while optimizing fiber dispersion, reducing local pore concentration, and further reducing chloride ion penetration. The permeability and electrical flux of Example 5 were lower than those of Example 2. Example 5 increased the amount of (-)-diacetyl-D-tartaric anhydride, and the more acetyl groups strengthened the hydrophobic barrier effect. The interface transition zone between the fiber and the matrix was denser, the chloride ion penetration resistance was significantly increased, and the salt erosion resistance was optimal. Comparative Example 1 did not use S-acetyl mercaptosuccinic anhydride in the preparation of esterified modified cellulose, Comparative Example 2 did not use 4-phenoxyphthalic anhydride in the preparation of esterified modified cellulose, and Comparative Example 3 did not esterify and modify cellulose and use it in composite fiber materials. The electrical flux of the concrete prepared was higher than that of Example 2, indicating that after the hydrophobic and filling effects were lost, the sealing effect of the composite fiber on the pores was weakened, and the hydrophilicity of the concrete surface was enhanced, which accelerated the migration of chloride ions and reduced the impermeability.

[0110] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any way. Any person skilled in the art can make some modifications or alterations to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as the technology or embodiments that are substantially the same as the present invention.

[0111] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A type of concrete, comprising a matrix material, a functional modifier, and a microbial self-healing agent, wherein, The microbial remediation agent is a microbial self-remediation slurry, which includes Pasteurella multocida liquid and a binding agent, wherein the volume ratio of the binding agent to the Pasteurella multocida liquid is 0.5-2:

1.

2. The concrete according to claim 1, characterized in that, The matrix material includes cement and aggregate, and the mass ratio of cement to aggregate is 150-200:1500.

3. The concrete according to claim 2, characterized in that, The aggregate includes coarse aggregate and fine aggregate. The coarse aggregate includes one or more of natural coarse aggregate and recycled coarse aggregate, and the average particle size of the coarse aggregate is 5-20 mm.

4. The concrete according to claim 1, characterized in that, The functional regulator includes a water-reducing agent and a mineral admixture. The mass ratio of the water-reducing agent to cement is 2-5:198, and the mass ratio of the mineral admixture to cement is 200-240:

198.

5. The concrete according to claim 1, characterized in that, The functional regulator includes a composite fiber material, and the mass ratio of the composite fiber material to cement is 3-10:

198.

6. The concrete according to claim 5, characterized in that, The composite fiber material comprises esterified modified cellulose and polypropylene fiber, wherein the mass ratio of esterified modified cellulose to polypropylene fiber is 10-30:

75.

7. The concrete according to claim 6, characterized in that, The modifiers in the esterified modified cellulose include S-acetyl thiosuccinic anhydride and 4-phenoxy phthalic anhydride, wherein the mass ratio of S-acetyl thiosuccinic anhydride to 4-phenoxy phthalic anhydride is 1-4:

2.

8. The concrete according to claim 1, characterized in that, The water-reducing agent includes a polycarboxylate superplasticizer, which has a water-reducing efficiency of 20-30%.

9. The concrete according to claim 1, characterized in that, The mineral admixture includes fly ash and mineral powder, and the mass ratio of fly ash to mineral powder is 100-110:

118.

10. The concrete according to claim 1, characterized in that, The cementing solution comprises calcium acetate and urea, wherein the mass ratio of calcium acetate to urea is 150-200:60.

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