Anti-cracking and anti-freezing fiber composite concrete and preparation method thereof

Abstract

The invention discloses anti-cracking and anti-freezing fiber composite concrete and a preparation method thereof, and relates to the field of concrete. The preparation method comprises the following steps: immersing bionic spider silk into a microbial mineralization solution, adding a photoresponse nano material, and adjusting illumination, so that calcium carbonate crystals are arranged in a honeycomb shape on the surface of the spider silk, bionic spider silk fibers and microbial mineralization layers are alternately deposited, and a'fiber-mineralization layer-fiber 'sandwich structure is constructed. The structure cooperates with a spider silk spiral and honeycomb mineralization layer, the concrete interface strength is greatly improved, shrinkage cracks are effectively inhibited, microorganisms are activated and mineralized in the cracks to repair the cracks, and the concrete is endowed with high crack resistance and self-repairing capacity. Meanwhile, the self-made nano-composite fiber takes polyvinyl alcohol and ethylene glycol copolymer as main materials, polylactic acid micro-cavities containing anhydrous calcium chloride are connected to two ends of the self-made nano-composite fiber, and the freezing resistance of the concrete is improved by the hydrophilicity of the polyvinyl alcohol and the heat release of the anhydrous calcium chloride. The anti-cracking and anti-freezing fiber composite concrete prepared by the invention has the effects of high cracking resistance and high freezing resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and particularly to a crack-resistant and freeze-resistant fiber composite concrete and a preparation method thereof. Background Art

[0002] In the field of construction engineering, concrete, as the most widely used basic material, its performance directly affects the quality and safety of building structures. Especially in cold regions, concrete structures are constantly subjected to severe freeze-thaw cycles. There are a large number of pores inside ordinary concrete. In a low-temperature environment, the water in the pores will freeze and expand. The repeated freeze-thaw action is like applying a periodic destructive force inside the concrete, resulting in diseases such as cracking and spalling of the concrete, greatly weakening the durability of the structure.

[0003] At the same time, due to its own characteristics, concrete is extremely prone to cracking under the action of factors such as temperature change and dry shrinkage. These cracks not only reduce the bearing capacity of the concrete structure but also damage its waterproof performance, providing a channel for the intrusion of external corrosive media and accelerating the deterioration of the structure. In this context, developing fiber composite concrete with excellent freeze-resistant and crack-resistant properties has become an urgent task in the industry. This material can effectively improve the performance of concrete in cold environments, significantly enhance the stability and service life of building structures, and meet the stringent requirements of construction projects in complex environments. Summary of the Invention

[0004] The purpose of the present invention is to provide a crack-resistant and freeze-resistant fiber composite concrete and a preparation method thereof to solve the problems existing in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: A crack-resistant and freeze-resistant fiber composite concrete, and the preparation method of the crack-resistant and freeze-resistant fiber composite concrete includes the following steps:

[0006] (1) After hydroxylating the bionic spider silk with a silane coupling agent, soak it in a mineralization solution of microorganisms with a mass fraction of 2% according to a mass ratio of 1:100 - 200, add a photo-responsive nanomaterial with 0.01 - 0.03 times the mass of the bionic spider silk, and use a mixed LED light source with a ratio of blue light, green light, and red light of 3:2:1, a light intensity of 1000 lux, and parallel light at 25 - 35 °C for 30 min, and perform a "30-min light irradiation - 90-min static" mineralization cycle until a honeycomb-like mineralization layer is formed, and then in a "deposition - adsorption" manner until a bionic spider silk with a "fiber - mineralization layer - fiber" sandwich structure is formed, and dry it at 30 - 40 °C to constant weight to obtain a self-made solid bionic spider silk;

[0007] (2) Mix polylactic acid containing microchambers, anhydrous calcium chloride, and an organic solvent in a mass ratio of 10:1:100 uniformly. After ultrasonic treatment at 30 - 35 °C and 40 - 50 kHz for 30 min, dry at 40 °C for 6 h to obtain polylactic acid filled with anhydrous calcium chloride. Then mix polyvinyl alcohol - ethylene glycol copolymer, polylactic acid filled with anhydrous calcium chloride, a catalyst, and an organic solvent in a mass ratio of 10:5:0.5:150, stir and react at 30 - 35 °C and 300 - 400 rpm for 4 - 6 h, then perform electrospinning for 2 - 6 h, and dry at 40 °C for 6 h to obtain a self - made composite nanofiber;

[0008] (3) Mix 300 - 400 parts by weight of cement, 600 - 800 parts by weight of sand, 1100 - 1300 parts by weight of stone, 160 - 200 parts by weight of water, 5 parts by weight of an admixture, 3 - 5 parts by weight of self - made bionic spider silk solid, 3 - 5 parts by weight of self - made composite fiber, and 60 - 100 parts by weight of admixture evenly at 500 rpm to obtain crack - resistant and frost - resistant fiber - reinforced concrete.

[0009] Further, the preparation steps of the bionic spider silk in step (1) are as follows: Dissolve the wet recombinant Escherichia coli expressing recombinant spider silk protein in a resuspension containing 300 mM sodium chloride at a mass ratio of 1:10, stir at 4 °C and 300 rpm for 1 h, then perform cell wall breaking treatment with a high - pressure homogenizer, centrifuge at a centrifugation speed of 8000 - 12000 rpm for 10 min, then collect the supernatant. Separate and purify the supernatant through a nickel - column affinity layer, elute the impurity proteins with a buffer solution of pH 8.0 containing 70 mM imidazole, and then elute the target protein with a buffer solution of pH 8.0 containing 250 mM imidazole to obtain a recombinant spider silk protein solution. Transfer the obtained solution to a dialysis bag with a cut - off molecular weight of 10 kD, dialyze in deionized water for 72 h, changing the deionized water once every 8 h. Freeze - dry the dialyzed spider silk protein solution at - 80 °C to obtain bionic spider silk freeze - dried powder; Take the bionic spider silk freeze - dried powder and dissolve it in hexafluoroisopropanol at a mass ratio of 1:4, stir at 100 rpm for 15 min, then perform ultrasonic treatment at 40 kHz for 15 min to obtain a spinning solution; Load the spinning solution into a syringe with a metal needle of an outer diameter of 0.9 mm and an inner diameter of 0.6 mm, connect it to an electrospinning device, set the distance between the nozzle and the receiving plate to 15 cm, the voltage to 20 kV, the solution flow rate to 0.5 mL / h, place a rotating cylinder collection device on the receiving plate, with the rotation speed of the cylinder being 500 rpm, so that the fibers form a spiral shape during collection; Dry the collected spiral fibers in an oven at 40 °C for 24 h to obtain spiral nano - scale bionic spider silk.

[0010] Further, the silane coupling agent in step (1) is: γ - glycidoxypropyltrimethoxysilane (KH560).

[0011] Further, the hydroxylation step in step (1) is as follows: Add KH560 to deionized water at a volume ratio of 1:3, and carry out a hydrolysis reaction by stirring at 250 rpm for 2 h at 35°C; Mix the helical nanoscale biomimetic spider silk with the hydrolysis solution of KH560 at a mass ratio of 1:5, stir and mix at 300 rpm at 60°C for 8 h, take out the biomimetic spider silk, wash it with absolute ethanol 2 - 4 times, and dry it at 40°C to constant weight to obtain hydroxylated biomimetic spider silk.

[0012] Further, the photo-responsive nanomaterial in step (1) is: molybdenum sulfide particles with a diameter of 20 nm.

[0013] Further, the microorganism in step (1) is: Sarcina pasteurii.

[0014] Further, the mineralization solution in step (1) is: a solution composed of 6 g of yeast extract, 5 g of sodium chloride, 6 g of urea, 2 g of bran, 12 g of calcium chloride and 1000 ml of deionized water.

[0015] Further, the preparation process of the polylactic acid containing microchambers in step (2) is as follows: Add lactic acid with a purity ≥98% to the reaction kettle, add p-toluenesulfonic acid according to the mass ratio of lactic acid to p-toluenesulfonic acid of 100:3, and carry out a prepolymerization reaction at 100 - 120°C for 2 h; After the prepolymerization reaction is completed, gradually raise the reaction temperature to 180 - 220°C, and carry out a polycondensation reaction under a vacuum of 10 -3 kPa. As the reaction proceeds, the low-molecular-weight polylactic acid continues to polycondense, and the molecular weight continuously increases, so that the molecular weight of the polylactic acid reaches 100,000 - 150,000; Dissolve the polylactic acid with a molecular weight of 100,000 - 150,000 in dichloromethane at a volume ratio of 1:15 to obtain a polylactic acid solution; Use polyvinyl alcohol as a surfactant, dissolve polyvinyl alcohol in deionized water, and prepare an aqueous polyvinyl alcohol solution with a mass concentration of 1 - 3% as the aqueous phase solution; Inject the polylactic acid solution and the aqueous phase solution into the flow channel of the microfluidic chip through an injection pump at a flow rate ratio of 1:5. At the intersection or specific structure of the flow channel, the two fluids interact, and the polylactic acid solution forms droplets under the action of the aqueous phase solution, and then shrinks under the action of surface tension and other forces to form microchambers with a particle size of 20 μm.

[0016] Further, the preparation process of the polyvinyl alcohol and ethylene glycol copolymer in step (2) is as follows: Add polyvinyl alcohol into a three-necked flask, add deionized water, and stir at a stirring rate of 150 - 250 rpm in a water bath at a temperature of 80 - 90 °C until it is completely dissolved to obtain a uniform polyvinyl alcohol aqueous solution; wait for the polyvinyl alcohol aqueous solution to cool to 40 - 50 °C, add ethylene glycol, continue to stir for 15 - 20 min to make them fully mixed, then continue to add potassium persulfate, and adjust the pH value of the reaction system to 7 - 8 with sodium hydroxide solution (0.1 mol / L), then raise the temperature to 65 - 75 °C, and carry out a polymerization reaction at a stirring rate of 200 - 300 rpm until the molecular weight of the target product reaches 5000 - 10000; distill the reaction product to remove unreacted raw materials and moisture, and then dry the product in an oven at 40 - 50 °C to constant weight to obtain a polyvinyl alcohol and ethylene glycol copolymer with a molecular weight of 5000 - 10000 and in the nanoscale; among them, the mass ratio of polyvinyl alcohol with a polymerization degree of 1700 : ethylene glycol : deionized water : potassium persulfate is 1 : 1 : 15 : 0.02.

[0017] Further, the organic solvent in step (2) is a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3 : 1.

[0018] Further, the electrospinning device in step (2) consists of a spinneret with a diameter of 0.6 - 1.6 mm, a high-voltage power supply of 20 - 50 kV, and a roller rotating at 500 rpm - 1500 rpm.

[0019] Further, the admixture in step (3) is a polycarboxylate superplasticizer, and the admixture is a fly ash admixture.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] The present invention combines a bionic spider silk fiber and a microbial mineralization technology and adds a self-made composite nanofiber to achieve the effects of crack resistance and frost resistance.

[0022] First, the pretreated bionic spider silk of the present invention is hydroxylated by a silane coupling agent and then immersed in a mineralization solution containing microorganisms capable of secreting urease. A light-responsive nanomaterial is added, and by adjusting the light parameters, calcium carbonate crystals are induced to form a honeycomb arrangement on the surface of the bionic spider silk. Then, by alternately depositing bionic spider silk fibers and microbial mineralization layers, a "fiber - mineralization layer - fiber" sandwich structure is formed. Under the combined action of this structure, the helical structure of the bionic spider silk, and the honeycomb mineralization layer deposited by microorganisms on the fiber surface, the interfacial strength of the concrete can be greatly improved, effectively inhibiting shrinkage cracks in the concrete. The mineralization layer can also improve the corrosion resistance and frost resistance of the fiber, and the microorganisms will be activated in the cracks and fill the cracks through mineralization reactions, enabling the concrete to not only have strong crack resistance but also self-repairing properties.

[0023] Secondly, the composite fiber used in the present invention uses a copolymer of polyvinyl alcohol and ethylene glycol as the main material of the nanofiber. The two ends of the copolymer molecular chain are linked with polylactic acid. Since polylactic acid contains microchambers filled with anhydrous calcium chloride, the terminal carboxyl groups on the polylactic acid chambers react with the hydroxyl groups of the copolymer of polyvinyl alcohol and ethylene glycol to form ester bonds under the action of a catalyst, thereby realizing the chemical bonding between the polylactic acid microchambers and the linear copolymer main body. Then, it is made into a self-made nanofiber membrane by electrospinning technology and added to the concrete. Polyvinyl alcohol itself has good hydrophilicity, and the hydroxyl groups on the molecular chain can form hydrogen bonds with water molecules, making it easy for the fiber surface to adsorb water molecules. When the fiber absorbs the free water in the concrete and transports it to both ends, it reacts with the anhydrous calcium chloride in the microchamber to generate heat, improving the frost resistance of the concrete; and calcium chloride is a commonly used substance to lower the freezing point of water, and the freezing point of its aqueous solution can be significantly lower than that of pure water, further enhancing the effect of the nanofiber as a whole in lowering the freezing point of water, greatly improving the frost resistance of the concrete; the hydroxyl groups of ethylene glycol can complex with calcium ions in the concrete, further enhancing the strength of the concrete and increasing crack resistance. The nanofiber structure of the fiber membrane, due to its high specific surface area, forms a mechanical interlock with the cement hydration product (C-S-H gel), reducing the interfacial transition zone and effectively inhibiting the expansion of cracks. Detailed implementation manners

[0024] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] To more clearly illustrate the method provided by the present invention, it is described in detail through the following embodiments. The test methods for each index of the crack-resistant and frost-resistant fiber composite concrete prepared in the following embodiments are as follows:

[0026] Anti-cracking performance: The examples and the concrete were made into corresponding sizes, cured for 28 days under the conditions of a temperature of 22 °C and a relative humidity of 95%, and then the splitting tensile strength test was carried out. The test method was the same as that in "GB / T 50081-2019", and the results were averaged.

[0027] Anti-freezing performance: Using the method of "4 Freezing Resistance Test" in "GB / T50082—2009 Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete", first the examples and the concrete were made into corresponding sizes, and then measured after curing for 28 days under the conditions of a temperature of 22 °C and a relative humidity of 95%.

[0028] Durability performance: According to the step-by-step pressure method in "GB / T50082-2009 Standard Test Method for Long-Term Performance and Durability of Ordinary Concrete", the examples and the concrete were made into corresponding sizes, and after curing for 28 days under the conditions of a temperature of 22 °C and a relative humidity of 95%, their impermeability grades were tested.

[0029] Example 1

[0030] (1) The wet cells of recombinant Escherichia coli expressing recombinant spider silk protein were dissolved in a resuspension containing 300 mM sodium chloride at a mass ratio of 1:10, stirred at 300 rpm for 1 h at 4 °C, then subjected to cell wall breaking treatment by a high-pressure homogenizer, centrifuged at a centrifugal speed of 8000 rpm for 10 min, and then the supernatant was collected. The supernatant was separated and purified by nickel column affinity chromatography. The impurity proteins were eluted with a buffer solution containing 70 mM imidazole at pH 8.0, and then the target protein was eluted with a buffer solution containing 250 mM imidazole at pH 8.0 to obtain a recombinant spider silk protein solution. The obtained solution was transferred to a dialysis bag with a molecular weight cut-off of 10 kD and dialyzed in deionized water for 72 h, and the deionized water was changed once every 8 h. The dialyzed spider silk protein solution was freeze-dried at -80 °C to obtain freeze-dried bionic spider silk powder; The freeze-dried bionic spider silk powder was dissolved in hexafluoroisopropanol at a mass ratio of 1:4, stirred at 100 rpm for 15 min, and then sonicated at 40 kHz for 15 min to obtain a spinning solution; The spinning solution was loaded into a syringe with a metal needle with an outer diameter of 0.9 mm and an inner diameter of 0.6 mm, connected to an electrospinning device, the distance between the nozzle and the receiving plate was set to 15 cm, the voltage was 20 kV, the solution flow rate was 0.5 mL / h, and a rotating cylinder collection device was placed on the receiving plate. The rotation speed of the cylinder was 500 rpm, so that the fibers formed a helix during collection; The collected helical fibers were dried in an oven at 40 °C for 24 h to obtain helical nano-scale bionic spider silk;

[0031] (2) Add KH560 to deionized water at a volume ratio of 1:3, and carry out a hydrolysis reaction by stirring at 250 rpm for 2 h at 35 °C; mix the helical nanoscale biomimetic spider silk with the hydrolysis solution of KH560 at a mass ratio of 1:5, stir and mix at 300 rpm at 60 °C for 8 h, take out the biomimetic spider silk, wash it twice with absolute ethanol, and dry it at 40 °C to constant weight to obtain hydroxylated biomimetic spider silk;

[0032] (3) Immerse the hydroxylated biomimetic spider silk in the mineralization solution of Sporosarcina pasteurii with a mass fraction of 2% at a mass ratio of 1:100. The mineralization solution consists of 6 g of yeast extract, 5 g of sodium chloride, 6 g of urea, 2 g of bran, 12 g of calcium chloride and 1000 ml of deionized water. Add molybdenum disulfide at the nanoscale with a mass 0.01 times that of the biomimetic spider silk. Use a parallel light source with a mixed LED light source with a ratio of blue light, green light, and red light of 3:2:1, a light intensity of 1000 lux, and irradiate at 25 °C for 30 min, and perform a cycle of "irradiation for 30 min - standing for 90 min" 4 times until a honeycomb-like mineralized layer is formed;

[0033] (4) After completing one round of light-induced mineralization, take out the biomimetic spider silk from the mineralization solution, rinse the surface with deionized water, and then immerse it in the above-mentioned new spinning solution to allow the fiber to adsorb on the surface of the mineralized layer. Take out the biomimetic spider silk adsorbed with the fiber, and remove the excess fiber dispersion liquid on the surface with deionized water to form a biomimetic spider silk with a "fiber - mineralized layer - fiber" sandwich structure, and dry it at 30 °C to constant weight to obtain a self-made helical biomimetic spider silk solid with a particle size of 10 nm;

[0034] (5) Add lactic acid with a purity ≥ 98% to the reaction kettle, add p-toluenesulfonic acid at a mass ratio of lactic acid to p-toluenesulfonic acid of 100:3, and carry out a prepolymerization reaction at 100 °C for 2 h; after the prepolymerization reaction is completed, gradually raise the reaction temperature to 180 °C, and carry out a polycondensation reaction under a vacuum of 10 -3 kPa. As the reaction proceeds, the low-molecular-weight polylactic acid continues to polycondense, and the molecular weight continuously increases until the molecular weight of the polylactic acid reaches 100,000; dissolve the above-mentioned polylactic acid with a molecular weight of 100,000 in dichloromethane at a volume ratio of 1:15 to obtain a polylactic acid solution; use polyvinyl alcohol as a surfactant, dissolve polyvinyl alcohol in deionized water, and prepare an aqueous polyvinyl alcohol solution with a mass concentration of 1% as the aqueous phase solution; respectively inject the polylactic acid solution and the aqueous phase solution into the flow channel of the microfluidic chip through an injection pump at a flow rate ratio of 1:5. At the intersection or specific structure of the flow channel, the two fluids interact, and the polylactic acid solution forms droplets under the action of the aqueous phase solution, and then shrinks under the action of surface tension and other forces to form microchambers with a particle size of 20 μm, and obtain polylactic acid containing microchambers;

[0035] (6) Add polyvinyl alcohol to a three-necked flask, add deionized water, and stir at a water bath temperature of 80° C. at a stirring rate of 150 rpm until the polyvinyl alcohol is completely dissolved to obtain a uniform polyvinyl alcohol aqueous solution; after the polyvinyl alcohol aqueous solution is cooled to 40° C., add ethylene glycol, continue to stir for 15 minutes to fully mix, continue to add potassium persulfate, adjust the pH value of the reaction system to 7 with sodium hydroxide solution (0.1 mol / L), then raise the temperature to 65° C., and carry out polymerization reaction at a stirring rate of 200 rpm until the molecular weight of the target product reaches 5000; distill the reaction product to remove unreacted raw materials and water, and then dry the product in a drying oven at 40° C. to constant weight to obtain a nano-scale polyvinyl alcohol and ethylene glycol copolymer with a molecular weight of 5000; wherein the mass ratio of polyvinyl alcohol with a degree of polymerization of 1700: ethylene glycol: deionized water: potassium persulfate is 1:1:15:0.02;

[0036] (7) The polylactic acid containing microcavities, anhydrous calcium chloride, and a mixed solvent of dichloromethane and N,N-dimethylformamide in a volume ratio of 3:1 were mixed in a mass ratio of 10:1:100, and after ultrasonication at 40kHz for 30 minutes at 30°C, the polylactic acid filled with anhydrous calcium chloride was obtained. Then, polyvinyl alcohol and ethylene glycol copolymer, polylactic acid filled with anhydrous calcium chloride, p-toluenesulfonic acid, and a mixed solvent of dichloromethane and N,N-dimethylformamide in a volume ratio of 3:1 were mixed in a mass ratio of 10:5:0.5:150, and stirred at 30°C and 300 rpm for 4 hours, and then electrospinning was continued for 2 hours. The equipment parameters of the spinning device were: 30 kV high voltage power supply, 0.6 mm needle and 1000 rpm roller. The obtained nanofiber membrane was dried at 40°C for 6 hours to obtain self-made composite nanofibers with a particle size of 50 nm.

[0037] (8) 300 parts by weight of cement, 600 parts by weight of sand, 1100 parts by weight of stone, 160 parts by weight of water, 5 parts by weight of polycarboxylic acid-based water reducer, 3 parts by weight of homemade bionic spider silk solid, 3 parts by weight of homemade composite fiber, and 60 parts by weight of fly ash admixture are stirred evenly at 500 rpm to obtain crack-resistant and frost-resistant fiber composite concrete.

[0038] Example 2

[0039] (1) The wet recombinant Escherichia coli expressing recombinant spider silk protein was dissolved in a resuspension containing 300 mM sodium chloride at a mass ratio of 1:10. After stirring at 300 rpm for 1 h at 4°C, it was subjected to cell wall breaking treatment by a high-pressure homogenizer, centrifuged at 10,000 rpm for 10 min, and then the supernatant was collected. The supernatant was separated and purified by nickel column affinity chromatography. The impurity proteins were eluted with a buffer solution containing 70 mM imidazole at pH 8.0, and the target protein was eluted with a buffer solution containing 250 mM imidazole at pH 8.0 to obtain a recombinant spider silk protein solution. The obtained solution was transferred to a dialysis bag with a molecular weight cut-off of 10 kD and dialyzed in deionized water for 72 h, with the deionized water replaced once every 8 h. The dialyzed spider silk protein solution was freeze-dried at -80°C to obtain a freeze-dried bionic spider silk powder. The freeze-dried bionic spider silk powder was dissolved in hexafluoroisopropanol at a mass ratio of 1:4, stirred at 100 rpm for 15 min, and then sonicated at 40 kHz for 15 min to obtain a spinning solution. The spinning solution was loaded into a syringe equipped with a metal needle with an outer diameter of 0.9 mm and an inner diameter of 0.6 mm, connected to an electrospinning device. The distance between the nozzle and the receiving plate was set to 15 cm, the voltage was 20 kV, the solution flow rate was 0.5 mL / h, and a rotating cylindrical collecting device was placed on the receiving plate with a rotation speed of 500 rpm to form a spiral shape when the fibers were collected. The collected spiral fibers were dried in an oven at 40°C for 24 h to obtain spiral nano-scale bionic spider silk;

[0040] (2) KH560 was added to deionized water at a volume ratio of 1:3, and a hydrolysis reaction was carried out by stirring at 250 rpm for 2 h at 35°C. The spiral nano-scale bionic spider silk was mixed with the hydrolysis solution of KH560 at a mass ratio of 1:5, stirred at 300 rpm at 60°C for 8 h, and then the bionic spider silk was taken out, washed 3 times with absolute ethanol, and dried to constant weight at 40°C to obtain hydroxylated bionic spider silk;

[0041] (3) The hydroxylated bionic spider silk was soaked in a mineralization solution of Sporosarcina pasteurii with a mass fraction of 2% at a mass ratio of 1:150. The mineralization solution was composed of 6 g of yeast extract, 5 g of sodium chloride, 6 g of urea, 2 g of bran, 12 g of calcium chloride and 1000 ml of deionized water. Nano-scale molybdenum sulfide with 0.02 times the mass of the bionic spider silk was added. A parallel light source was used with a mixed LED light source with a blue, green, and red light ratio of 3:2:1, a light intensity of 1000 lux, and illuminated at 30°C for 30 min. The cycle of "illuminated for 30 min - standing for 90 min" was carried out 5 times until a honeycomb-shaped mineralization layer was formed;

[0042] (4) After completing one round of light-induced mineralization, the bionic spider silk is taken out of the mineralization solution, and its surface is rinsed with deionized water. Then it is immersed in the above-mentioned new spinning solution to allow the fiber to adsorb on the surface of the mineralized layer. The bionic spider silk adsorbed with the fiber is taken out, and the excess fiber dispersion liquid on the surface is removed with deionized water to form a bionic spider silk with a "fiber-mineralized layer-fiber" sandwich structure. It is dried at 35 °C to constant weight to obtain a self-made bionic spider silk solid with a helical shape and a particle size of 10 nm.

[0043] (5) Lactic acid with a purity of ≥98% is added to the reaction kettle, and p-toluenesulfonic acid is added according to the mass ratio of lactic acid to p-toluenesulfonic acid of 100:3. The prepolymerization reaction is carried out at 110 °C for 2 h. After the prepolymerization reaction is completed, the reaction temperature is gradually increased to 200 °C, and the polycondensation reaction is carried out under a vacuum of 10 -3 kPa. As the reaction proceeds, the low-molecular-weight polylactic acid continues to polycondense, and the molecular weight continuously increases until the molecular weight of the polylactic acid reaches 125,000. The above-mentioned polylactic acid with a molecular weight of 125,000 is dissolved in dichloromethane according to a volume ratio of 1:15 to obtain a polylactic acid solution. Polyvinyl alcohol is used as a surfactant, and polyvinyl alcohol is dissolved in deionized water to prepare an aqueous polyvinyl alcohol solution with a mass concentration of 2% as the aqueous phase solution. The polylactic acid solution and the aqueous phase solution are respectively injected into the flow channel of the microfluidic chip through a syringe pump at a flow rate ratio of 1:5. At the intersection or specific structure of the flow channel, the two fluids interact, and the polylactic acid solution forms droplets under the action of the aqueous phase solution, and then shrinks under the action of surface tension and other forces to form microchambers with a particle size of 20 μm, and polylactic acid containing microchambers is prepared.

[0044] (6) Polyvinyl alcohol is added to a three-necked flask, and deionized water is added. At a water bath temperature of 85 °C, it is stirred at a stirring rate of 200 rpm until it is completely dissolved to obtain a uniform aqueous polyvinyl alcohol solution. After the aqueous polyvinyl alcohol solution is cooled to 45 °C, ethylene glycol is added, and stirring is continued for 18 min to make them fully mixed. Potassium persulfate is continuously added, and the pH value of the reaction system is adjusted to 7.5 with sodium hydroxide solution (0.1 mol / L). Then the temperature is raised to 70 °C, and the polymerization reaction is carried out at a stirring rate of 250 rpm until the molecular weight of the target product reaches 7500. The reaction product is distilled to remove the unreacted raw materials and water, and then the product is dried in an oven at 45 °C to constant weight to obtain a polyvinyl alcohol and ethylene glycol copolymer with a molecular weight of 7500 and a nanoscale. Among them, the mass ratio of polyvinyl alcohol with a degree of polymerization of 1700:ethylene glycol:deionized water:potassium persulfate is 1:1:15:0.02.

[0045] (7) Mix polylactic acid containing microchambers, anhydrous calcium chloride, and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 evenly at a mass ratio of 10:1:100. After ultrasonic treatment at 33 °C for 30 min at 45 kHz, dry it at 40 °C for 6 h to obtain polylactic acid filled with anhydrous calcium chloride. Then mix polyvinyl alcohol and ethylene glycol copolymer, polylactic acid filled with anhydrous calcium chloride, p-toluenesulfonic acid, and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 at a mass ratio of 10:5:0.5:150. After stirring and reacting at 33 °C at 350 rpm for 5 h, continuously electrospin for 4 h. The equipment parameters of the electrospinning device are: a 30 kV high-voltage power supply, a 0.6 mm needle, and a roller with a rotation speed of 1000 rpm. Dry the obtained nanofiber membrane at 40 °C for 6 h to obtain self-made composite nanofibers with a particle size of 50 nm;

[0046] (8) Mix 350 parts by weight of cement, 700 parts by weight of sand, 1200 parts by weight of stone, 180 parts by weight of water, 5 parts by weight of polycarboxylate superplasticizer, 4 parts by weight of self-made bionic spider silk solid, 4 parts by weight of self-made composite fiber, and 80 parts by weight of fly ash admixture evenly at 500 rpm to obtain crack-resistant and frost-resistant fiber-reinforced concrete.

[0047] Example 3

[0048] (1) The wet recombinant Escherichia coli expressing recombinant spider silk protein was dissolved in a resuspension containing 300 mM sodium chloride at a mass ratio of 1:10. After stirring at 300 rpm for 1 h at 4°C, it was subjected to cell wall breaking treatment with a high-pressure homogenizer, centrifuged at 12,000 rpm for 10 min, and then the supernatant was collected. The supernatant was separated and purified by nickel column affinity chromatography. The impurity proteins were eluted with a buffer solution containing 70 mM imidazole at pH 8.0, and the target protein was eluted with a buffer solution containing 250 mM imidazole at pH 8.0 to obtain a recombinant spider silk protein solution. The obtained solution was transferred to a dialysis bag with a molecular weight cut-off of 10 kD and dialyzed in deionized water for 72 h, with the deionized water replaced every 8 h. The dialyzed spider silk protein solution was freeze-dried at -80°C to obtain a freeze-dried bionic spider silk powder. The freeze-dried bionic spider silk powder was dissolved in hexafluoroisopropanol at a mass ratio of 1:4, stirred at 100 rpm for 15 min, and then sonicated at 40 kHz for 15 min to obtain a spinning solution. The spinning solution was loaded into a syringe equipped with a metal needle with an outer diameter of 0.9 mm and an inner diameter of 0.6 mm, connected to an electrospinning device. The distance between the nozzle and the receiving plate was set to 15 cm, the voltage was 20 kV, the solution flow rate was 0.5 mL / h, and a rotating cylindrical collecting device was placed on the receiving plate with a rotation speed of 500 rpm to form a spiral shape when the fibers were collected. The collected spiral fibers were dried in an oven at 40°C for 24 h to obtain spiral nano-scale bionic spider silk;

[0049] (2) KH560 was added to deionized water at a volume ratio of 1:3, and a hydrolysis reaction was carried out by stirring at 250 rpm for 30 min at 35°C. The spiral nano-scale bionic spider silk was mixed with the hydrolysis solution of KH560 at a mass ratio of 1:5, stirred at 300 rpm at 60°C for 8 h, and then the bionic spider silk was taken out, washed 4 times with absolute ethanol, and dried to constant weight at 40°C to obtain hydroxylated bionic spider silk;

[0050] (3) The hydroxylated bionic spider silk was soaked in a mineralization solution of Sporosarcina pasteurii with a mass fraction of 2% at a mass ratio of 1:200. The mineralization solution consisted of 6 g of yeast extract, 5 g of sodium chloride, 6 g of urea, 2 g of bran, 12 g of calcium chloride, and 1000 ml of deionized water. Nano-scale molybdenum sulfide with 0.03 times the mass of the bionic spider silk was added, and a parallel light source was used with a mixed LED light source with a blue, green, and red light ratio of 3:2:1, a light intensity of 1000 lux, and light irradiation at 35°C for 30 min. The cycle of "light irradiation for 30 min - standing for 90 min" was carried out 6 times until a honeycomb-like mineralized layer was formed;

[0051] (4) After completing one round of light-induced mineralization, the biomimetic spider silk is taken out of the mineralization solution, the surface is rinsed with deionized water, and then it is immersed in the above-mentioned new spinning solution so that the fibers are adsorbed on the surface of the mineralized layer. The biomimetic spider silk adsorbed with fibers is taken out, and the excess fiber dispersion liquid on the surface is removed with deionized water to form a biomimetic spider silk with a "fiber-mineralized layer-fiber" sandwich structure. It is dried at 40 °C to constant weight to obtain a self-made biomimetic spider silk solid with a helical shape and a particle size of 10 nm;

[0052] (5) Add lactic acid with a purity of ≥98% into the reaction kettle, add p-toluenesulfonic acid according to the mass ratio of lactic acid to p-toluenesulfonic acid of 100:3, and carry out a prepolymerization reaction at 120 °C for 2 h; after the prepolymerization reaction is completed, gradually raise the reaction temperature to 220 °C, and carry out a polycondensation reaction under a vacuum of 10 -3 kPa. As the reaction proceeds, the low-molecular-weight polylactic acid continues to polycondense, and the molecular weight continuously increases, so that the molecular weight of the polylactic acid reaches 150,000; the polylactic acid with the above-mentioned molecular weight of 150,000 is dissolved in dichloromethane according to a volume ratio of 1:15 to obtain a polylactic acid solution; use polyvinyl alcohol as a surfactant, dissolve polyvinyl alcohol in deionized water, and prepare an aqueous polyvinyl alcohol solution with a mass concentration of 3% as the aqueous phase solution; through an injection pump, the polylactic acid solution and the aqueous phase solution are respectively injected into the flow channel of the microfluidic chip at a flow rate ratio of 1:5. At the intersection or specific structure of the flow channel, the two fluids interact, and the polylactic acid solution forms droplets under the action of the aqueous phase solution, and then shrinks under the action of surface tension and other forces to form microchambers with a particle size of 20 μm, and a polylactic acid containing microchambers is prepared;

[0053] (6) Add polyvinyl alcohol into a three-necked flask, add deionized water, and stir at a stirring rate of 250 rpm in a water bath at 90 °C until completely dissolved to obtain a uniform aqueous polyvinyl alcohol solution; wait for the aqueous polyvinyl alcohol solution to cool to 50 °C, add ethylene glycol, and continue stirring for 20 min to make it fully mixed. Continue to add potassium persulfate, adjust the pH value of the reaction system to 8 with sodium hydroxide solution (0.1 mol / L), then raise the temperature to 75 °C, and carry out a polymerization reaction at a stirring rate of 300 rpm until the molecular weight of the target product reaches 10,000; distill the reaction product to remove unreacted raw materials and moisture, and then dry the product in a drying oven at 50 °C to constant weight to obtain a polyvinyl alcohol and ethylene glycol copolymer with a molecular weight of 10,000 and a nanoscale; the mass ratio of polyvinyl alcohol with a degree of polymerization of 1700:ethylene glycol:deionized water:potassium persulfate is 1:1:15:0.02;

[0054] (7) Mix polylactic acid containing microchambers, anhydrous calcium chloride, and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 evenly at a mass ratio of 10:1:100. After ultrasonic treatment at 35 °C and 50 kHz for 30 min, dry it at 40 °C for 6 h to obtain polylactic acid filled with anhydrous calcium chloride. Then, mix polyvinyl alcohol and ethylene glycol copolymer, polylactic acid filled with anhydrous calcium chloride, p-toluenesulfonic acid, and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 at a mass ratio of 10:5:0.5:150. Stir and react at 35 °C at 400 rpm for 6 h, and then continuously electrospin for 6 h. The equipment parameters of the electrospinning device are: a 30 kV high-voltage power supply, a 0.6 mm needle, and a roller with a rotation speed of 1000 rpm. Dry the obtained nanofiber membrane at 40 °C for 6 h to obtain self-made composite nanofibers with a particle size of 50 nm;

[0055] (8) Mix 400 parts by weight of cement, 800 parts by weight of sand, 1300 parts by weight of stone, 200 parts by weight of water, 5 parts by weight of polycarboxylate superplasticizer, 5 parts by weight of self-made bionic spider silk solid, 5 parts by weight of self-made composite nanofibers, and 100 parts by weight of fly ash admixture evenly at 500 rpm to obtain crack-resistant and frost-resistant fiber-reinforced concrete.

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 2 lies in step (1), that is, the bionic spider silk does not become helical during collection, and the remaining steps are the same as those in Example 2;

[0058] Comparative Example 2

[0059] The difference between Comparative Example 2 and Example 2 lies in step (2), that is, the bionic spider silk is not hydroxylated, and the remaining steps are the same as those in Example 2;

[0060] Comparative Example 3

[0061] The difference between Comparative Example 3 and Example 2 lies in step (3), that is, the mineralized layer of the bionic spider silk is not induced to be honeycomb-shaped, and the remaining steps are the same as those in Example 2;

[0062] Comparative Example 4

[0063] The difference between Comparative Example 4 and Example 2 lies in step (3). The difference is that in step (3), the hydroxylated biomimetic spider silk is added to a mixed solution of 0.1 mol / L calcium chloride solution and 0.1 mol / L sodium carbonate solution at a mass ratio of 1:21. Similarly, the pH value is adjusted to 7 with a tris(hydroxymethyl)aminomethane hydrochloride buffer solution (0.1 mol / L), and the reaction is carried out in a constant temperature incubator at 37 °C for 48 h. During the reaction process, the solution is gently stirred every 12 h. After the reaction is completed, the mineralized biomimetic spider silk is taken out, rinsed 3 times with deionized water, and then the sample is placed in an oven at 60 °C and dried for 24 h. The remaining steps are the same as those in Example 2;

[0064] Comparative Example 5

[0065] The difference between Comparative Example 5 and Example 2 lies in step (4). The difference is that the "fiber-mineralized layer-fiber" sandwich structure is not formed, and the remaining steps are the same as those in Example 2;

[0066] Comparative Example 6

[0067] The difference between Comparative Example 6 and Example 2 lies in steps (5) and (7). The difference is that step (5) is removed, and step (7) is changed to mixing a copolymer of polyvinyl alcohol and ethylene glycol and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 at a mass ratio of 10:150, and continuously spinning for 4 h in an electrospinning device composed of a 30 kV high-voltage power supply, a 0.6 nm needle, and a roller rotating at 1000 rpm. The obtained nanofiber membrane is dried at 40 °C for 6 h to obtain self-made nanofibers with a particle size of 50 nm. The remaining steps are the same as those in Example 2;

[0068] Comparative Example 7

[0069] The difference between Comparative Example 7 and Example 2 lies in steps (6) and (7). The difference is that step (6) is removed, and step (7) is changed to uniformly mixing polylactic acid containing microchambers, anhydrous calcium chloride, and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 at a mass ratio of 10:1:100, sonicating at 50 kHz for 30 min at 35 °C, and then drying at 40 °C for 6 h to obtain polylactic acid filled with anhydrous calcium chloride; mixing the polylactic acid filled with anhydrous calcium chloride, p-toluenesulfonic acid, and a mixed solvent of dichloromethane and N,N-dimethylformamide with a volume ratio of 3:1 at a mass ratio of 5:0.5:150, stirring and reacting at 35 °C at 400 rpm for 6 h, and then continuously spinning for 6 h by electrospinning. The equipment parameters of the spinning device are: a 30 kV high-voltage power supply, a 0.6 nm needle, and a roller rotating at 1000 rpm. The obtained nanofiber membrane is dried at 40 °C for 6 h to obtain self-made nanofibers with a particle size of 50 nm. The remaining steps are the same as those in Example 2;

[0070] Comparative Example 8

[0071] The difference between Comparative Example 8 and Example 2 lies in step (8). Specifically, in step (8), 350 parts by weight of cement, 700 parts by weight of sand, 1200 parts by weight of stone, 180 parts by weight of water, 5 parts by weight of polycarboxylate superplasticizer, 4 parts by weight of self-made composite fiber, and 80 parts by weight of fly ash admixture are stirred evenly at 500 rpm to obtain crack-resistant and freeze-resistant fiber-reinforced concrete. The remaining steps are the same as those in Example 2;

[0072] Comparative Example 9

[0073] The difference between Comparative Example 9 and Example 2 lies in step (8). Specifically, in step (8), 350 parts by weight of cement, 600 parts by weight of sand, 1200 parts by weight of stone, 180 parts by weight of water, 5 parts by weight of polycarboxylate superplasticizer, 4 parts by weight of self-made bionic spider silk solid, and 80 parts by weight of fly ash admixture are stirred evenly at 500 rpm to obtain crack-resistant and freeze-resistant fiber-reinforced concrete. The remaining steps are the same as those in Example 2;

[0074] Comparative Example 10

[0075] The difference between Comparative Example 10 and Example 2 lies in steps (1) to (8). Specifically, steps (1) to (7) are removed, and in step (8), 350 parts by weight of cement, 700 parts by weight of sand, 1200 parts by weight of stone, 180 parts by weight of water, 5 parts by weight of polycarboxylate superplasticizer, and 80 parts by weight of fly ash admixture are stirred evenly at 500 rpm to obtain crack-resistant and freeze-resistant fiber-reinforced concrete.

[0076] Effect Example

[0077] The following Table 1 shows the performance analysis results of the crack-resistant and freeze-resistant fiber-reinforced concrete using Examples 1 to 3 and Comparative Examples 1 to 10 of the present invention.

[0078] Table 1

[0079]

[0080]

[0081] From the comparison of the experimental data of the splitting tensile strength between the examples and the comparative examples, it can be found that for this product, after hydroxylating the pretreated bionic spider silk with a silane coupling agent, it is immersed in a mineralization solution containing microorganisms that can secrete urease, and a photo-responsive nanomaterial is added. By adjusting the light parameters, calcium carbonate crystals are induced to form a honeycomb arrangement on the surface of the bionic spider silk. Then, by alternately depositing bionic spider silk fibers and microbial mineralization layers, a "fiber - mineralization layer - fiber" sandwich structure is formed. Under the combined action of this structure, the helical structure of the bionic spider silk, and the honeycomb mineralization layer deposited by microorganisms on the fiber surface, the interfacial strength of the concrete can be greatly improved, effectively inhibiting the shrinkage cracks of the concrete. The mineralization layer can also improve the corrosion resistance and frost resistance of the fibers. From the comparison of the experimental data of the mass loss rate between the examples and the comparative examples, it can be found that the self-made nanocomposite fiber used in this product uses a copolymer of polyvinyl alcohol and ethylene glycol as the main material of the nanofiber. The two ends of the copolymer molecular chain are linked with polylactic acid containing microchambers, and anhydrous calcium chloride is filled in the chambers. Polyvinyl alcohol has good hydrophilicity, and the hydroxyl groups on the molecular chain are easy to form hydrogen bonds with water molecules, causing water to be adsorbed on the fiber surface. The fiber absorbs the free water in the concrete and transports it to both ends, reacting with the anhydrous calcium chloride in the microchambers to release heat, and calcium chloride lowers the freezing point of water, improving the frost resistance of the concrete. The hydroxyl groups of ethylene glycol complex with calcium ions, enhancing the strength and crack resistance of the concrete. The large specific surface area of the nanofiber membrane structure of the fiber mechanically interlocks with the C-S-H gel, reducing the interfacial transition zone and inhibiting crack propagation. From the comparison of the experimental data of the impermeability grade between the examples and the comparative examples, it can be found that the microorganisms on the surface of the bionic spider silk will be activated in the cracks and fill the cracks through mineralization reactions, making the concrete not only have strong crack resistance but also self-healing properties.

[0082] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

Claims

1. A crack-resistant and frost-resistant fiber composite concrete, characterized in that: The preparation method of the anti-cracking and anti-freezing fiber composite concrete comprises the following steps: (1) After the bionic spider silk is hydroxylated by a silane coupling agent, it is immersed in a mineralization solution of a microorganism with a mass fraction of 2% at a mass ratio of 1:100-200, and a light-responsive nanomaterial with a mass fraction of 0.01-0.03 times that of the bionic spider silk is added. A mixed LED light source with a ratio of blue light, green light, and red light of 3:2:1, a light intensity of 1000 lux, and parallel illumination at 25-35°C for 30 minutes is used. A "30-minute illumination-90-minute standing" mineralization cycle is performed until a honeycomb mineralization layer is formed. Then, a "deposition-adsorption" method is used until a bionic spider silk with a sandwich structure of "fiber-mineralization layer-fiber" is formed, and the bionic spider silk is dried at 30-40°C to a constant weight to obtain a homemade bionic spider silk solid; (2) The polylactic acid containing microcavities, anhydrous calcium chloride, and an organic solvent were uniformly mixed in a mass ratio of 10:1:100, and after ultrasonication at 30-35°C and 40-50kHz for 30 minutes, the polylactic acid filled with anhydrous calcium chloride was obtained by drying at 40°C for 6 hours; then, polyvinyl alcohol and ethylene glycol copolymer, polylactic acid filled with anhydrous calcium chloride, a catalyst, and an organic solvent were mixed in a mass ratio of 10:5:0.5:150, stirred at 30-35°C and 300-400rpm for 4-6 hours, electrospun for 2-6 hours, and dried at 40°C for 6 hours to obtain self-made composite nanofibers; (3) 300-400 parts by weight of cement, 600-800 parts by weight of sand, 1100-1300 parts by weight of stone, 160-200 parts by weight of water, 5 parts by weight of admixture, 3-5 parts by weight of homemade bionic spider silk solid, 3-5 parts by weight of homemade composite fiber, and 60-100 parts by weight of admixture are stirred evenly at 500 rpm to obtain crack-resistant and frost-resistant fiber composite concrete.

2. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The bionic spider silk in step (1) is in a spiral shape with a diameter of 10 nm.

3. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The microorganism in step (1) is Sporosarcina pasteurianum.

4. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The light-responsive nanomaterial in step (1) is molybdenum sulfide particles with a diameter of 20 nm.

5. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The "illumination for 30 minutes - standing for 90 minutes" mineralization cycle and "deposition-adsorption" method in step (1) are as follows: under the above-mentioned illumination parameters, the mineralization solution is illuminated for 30 minutes to induce the mineralization direction, and the solution is allowed to stand for 90 minutes to allow the mineralization growth to proceed, and this cycle is repeated 4 to 6 times until a honeycomb mineralization layer is formed; the bionic spider silk with a layer of mineralized layer deposited is placed in a new spinning solution to adsorb a new layer of bionic spider silk, thereby forming a bionic spider silk with a sandwich structure of "fiber-mineralized layer-fiber".

6. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The polylactic acid containing microcavities in step (2) has a molecular weight of 100,000 to 150,000, and a particle size of the microcavities is 20 μm.

7. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The organic solvent in step (2) is a mixed solvent of dichloromethane and N,N-dimethylformamide in a volume ratio of 3:

1.

8. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The polyvinyl alcohol and ethylene glycol copolymer in step (2) has a molecular weight of 5000 to 10000 and is nanometer-level.

9. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The catalyst in step (2) is p-toluenesulfonic acid.

10. The anti-cracking and anti-freezing fiber composite concrete according to claim 1, characterized in that: The particle size of the homemade nanofiber membrane in step (2) is 50 nm.

Images