High-disturbance-resistance cement-based material and preparation method thereof

Abstract

The invention discloses a high-disturbance-resistance cement-based material and a preparation method thereof, and belongs to the technical field of cement-based material production. Comprising the following steps: preparing polyvinyl alcohol-sodium borate hydrogel, and performing freeze drying treatment and crushing treatment to obtain particles; the method comprises the following steps: treating a fiber raw material through melt spinning to obtain expanded fibers, and carrying out surface indentation treatment on the expanded fibers to obtain indented expanded fibers; particles are adsorbed on the indented expansion fibers through electrostatic adsorption, and modified indented expansion fibers are obtained; the preparation method comprises the following steps: inoculating bacillus into spontaneous combustion coal gangue to obtain first aggregate, and mixing the first aggregate with quartz sand to obtain second aggregate; and mixing the cementing material, the second aggregate and the modified indented expansion fiber according to a preset proportion, adding water, and uniformly stirring to prepare the high-disturbance-resistance cement-based material. The high-disturbance-resistance cement-based material disclosed by the invention has early strength and high toughness under a dynamic disturbance condition, and damage to the material caused by disturbance can be effectively resisted.

Description

Technical Field

[0001] The present application belongs to the technical field of cement-based material production, and specifically relates to a highly resistant cement-based material and a preparation method thereof. Background Art

[0002] In order to reduce the impact on traffic, bridge construction and road bridge deck repair projects are usually carried out under open or semi-open traffic conditions. Therefore, it is necessary to ensure that cement-based materials can maintain high interfacial bonding strength and structural integrity under complex dynamic loads (such as vehicle impact, temperature changes, and structural deformation transmission) and harsh environments (such as salt corrosion and freeze-thaw cycles).

[0003] Traditional cementitious materials are not adaptable to dynamic disturbances (i.e., transient or periodic disturbances to the cementitious material structure under dynamic external loads, such as vehicle impacts, resulting in changes in internal stress, microstructure, or mechanical properties). This can lead to microcracks in joints or repair interfaces due to repeated vehicle rolling and thermal expansion and contraction. Furthermore, concentrated disturbance stresses can also cause delamination or through-cracks in the cementitious material, leading to repair failure. Therefore, it is necessary to develop a disturbance-resistant cementitious material that exhibits self-healing capabilities and high toughness under dynamic disturbance conditions. Summary of the Invention

[0004] In order to solve the above technical problems, the present application provides a highly resistant cement-based material and a preparation method thereof, which can effectively improve the resistant performance and bearing performance of the cement-based material, as well as the self-repairing ability of the cement-based material.

[0005] To achieve the above objectives, the present application provides a method for preparing a highly resistant cement-based material, comprising the following steps: preparing polyvinyl alcohol-sodium borate hydrogel, and subjecting it to freeze-drying and pulverizing to obtain particles; The fiber raw material is melt-spinned to obtain expanded fiber, and the surface of the fiber is indented to obtain scored expanded fiber; Adsorbing particles onto the scored expanded fiber by electrostatic adsorption to obtain a modified scored expanded fiber; Inoculating Bacillus into spontaneous combustion coal gangue to obtain a first aggregate, and mixing the first aggregate with quartz sand to obtain a second aggregate; The cementitious material, the second aggregate and the modified notched expansion fiber are mixed according to a preset ratio, and water is added and stirred evenly to prepare a high disturbance resistance cement-based material.

[0006] Furthermore, polyvinyl alcohol-sodium borate hydrogel was prepared by the following method: The polyvinyl alcohol solution of 10 wt% and the sodium borate solution of 5 wt% to 20 wt% are mixed in a mass ratio of (2 to 5):1 under stirring, and after the reaction is completed, the mixture is cooled to room temperature and bubbles are removed to obtain the product.

[0007] Furthermore, the freeze-drying treatment temperature is -30°C to -50°C, and the time is 3h to 6h; the particle size of the particles is less than 500 mesh.

[0008] Furthermore, the expanded fiber is obtained by melt spinning the fiber raw material, comprising: Weigh 5 to 8 parts of modified graphene particles, 10 to 15 parts of thermosensitive polyurethane particles, and 15 to 18 parts of polyvinyl alcohol particles and mix them evenly to obtain a mixture; The mixture is processed by melt spinning to obtain expanded fibers; wherein, The parameters of the melt spinning process include: extrusion temperature of 250°C, flow rate of 0.5m / min~0.8m / min, circular spinneret size of 0.3mm, pitch of 15mm, and spinning length of 1m.

[0009] Furthermore, the modified graphene particles are prepared by the following method: Graphene oxide and deionized water were mixed in a ratio of 200 mg:500 mL, and then dispersed in an ultrasonic water bath to obtain a first mixture; 2.0 g of sodium 4-styrenesulfonate was added to the first mixture and stirred for more than 1 h until the sodium 4-styrenesulfonate was completely dissolved to obtain a second mixture; Add 10 g of hydrazine hydrate to the second mixture and heat in a water bath at 95° C. for 24 h to obtain a primary product; The primary product was washed with deionized water and then dried for 24 h to obtain modified graphene particles.

[0010] Furthermore, the temperature-sensitive polyurethane particles are prepared by the following method: Mix 60 g of poly(1,2-propylene glycol) and 35 g of L-lysine ethyl ester diisocyanate, and stir at room temperature for more than 48 hours to obtain an initial product; The initial product was dissolved in 200 mL of methanol solution, and diethyl ether was added as a precipitant. The dissolution-precipitation process was repeated three times. Then, the final precipitate was taken out and placed in an oven to dry for 48 hours to obtain thermosensitive polyurethane particles.

[0011] Furthermore, the fiber length of the scored expanded fiber is 15 mm to 20 mm, and the indentation depth of the scored expanded fiber is 0.4 mm to 0.6 mm.

[0012] Furthermore, the Bacillus is inoculated into the spontaneous combustion coal gangue to obtain the first aggregate, comprising: Crushing spontaneous combustion gangue to a particle size of less than 5 mm to obtain gangue particles; Sterilize the gangue particles and the Bacillus nutrient solution using high-temperature steam and cool to room temperature; Under sterile conditions, Bacillus was inoculated into the cooled Bacillus nutrient solution at a 1% inoculum volume to obtain a concentration of (4-6) × 10 7 cfu / mL of bacterial solution; The cooled coal gangue particles are added to the bacterial solution for vacuum immersion treatment and drying treatment to obtain the first aggregate after constant weight; wherein the pressure of the vacuum immersion treatment is -0.07MPa~-0.03MPa, the time of the vacuum immersion treatment is 25min~40min; the temperature of the drying treatment is 38℃~45℃.

[0013] Furthermore, the mass ratio of the first aggregate to the quartz sand in the second aggregate is (0.5-1):1, and the particle size of the quartz sand is 20-40 mesh.

[0014] Furthermore, in the preset proportion, the mass ratio of the cementitious material, the second aggregate and the modified notched expansion fiber is (0.4~0.6):(0.5~0.6):(0.1~0.2); wherein, the amount of water added is regulated according to a water-cement ratio of 0.3.

[0015] Furthermore, the cementitious material includes the following components in parts by weight: 180 to 220 parts of Portland cement, 280 to 320 parts of sulfoaluminate cement, 40 to 60 parts of silica fume, 15 to 25 parts of fly ash, 0.5 to 1.5 parts of crystallization early strength agent, 0.5 to 1.5 parts of expansion agent and 1 to 3 parts of polycarboxylate water reducer.

[0016] The present application also provides a highly resistant cement-based material, which is prepared using the above-mentioned preparation method.

[0017] In summary, this application has the following advantages: 1. This application incorporates modified notched expansion fibers, which expand and elongate under the action of water and cement hydration heat, thereby increasing the contact points between fibers. Therefore, the self-healing hydrogel attached to its surface can produce a self-healing effect after absorbing water, thereby connecting the fibers into a networked structure. Furthermore, the polyvinyl alcohol-sodium borate hydrogel possesses both certain strength and toughness, effectively inhibiting the initiation of cracks before the initial setting of the cement matrix, significantly improving its anti-disturbance performance. After the cement hydration heat release is complete, a hardened matrix is ​​formed, and the modified notched expansion fibers begin to retract and generate tensile stress. The surface notch design enhances the mechanical locking effect with the cement matrix, further optimizing the load-bearing performance of the anti-disturbance material.

[0018] 2. This application adds a second aggregate. When the cement-based material is vibrated or impacted and cracks are generated, its built-in microbial repair agent can self-sense the internal loss and repair the cracks by generating or releasing repair substances, thereby improving the service life of the cement-based material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the method for preparing a highly resistant cement-based material provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The principles and features of the present invention are described below in conjunction with the examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Where specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0021] The highly resistant cement-based material provided by the present application combines three resistant mechanisms of biological self-repair, fiber reinforcement and energy dissipation, and can achieve multi-dimensional damage resistance under dynamic loads. Among them, the polyvinyl alcohol-sodium borate hydrogel forms a dynamic cross-linked network through reversible borate bonds, which dissipates energy under stress and avoids stress concentration. The surface indentations of the notched expansion fibers provide mechanical bite points, and the electrostatically adsorbed hydrogel particles form a flexible buffer layer at the fiber-matrix interface, thereby inhibiting crack propagation. The second aggregate is a combined aggregate of Bacillus and self-igniting coal gangue, in which the microorganisms can be activated at the cracks and metabolized to generate calcium carbonate crystals, thereby achieving self-repair of the cracks.

[0022] Specifically, the present application provides a method for preparing a highly resistant cement-based material, such as Figure 1 As shown, the following steps are included: S1. Prepare polyvinyl alcohol-sodium borate hydrogel, and freeze-dry and pulverize it to obtain particles.

[0023] In this application, the hydroxyl groups of polyvinyl alcohol (PVA) form reversible covalent bonds (BOC) with the borate groups of sodium borate (Na2B4O7), imparting shear-thickening properties to the hydrogel. This ratio also balances crosslink density and molecular chain mobility, ensuring the material maintains energy dissipation without becoming brittle under dynamic loads. Freeze-drying creates three-dimensional through-holes, increasing the specific surface area of ​​the particles and enhancing electrostatic adsorption and interfacial bonding strength with the fibers.

[0024] Among them, polyvinyl alcohol-sodium borate hydrogel is a self-healing hydrogel formed by the reaction of polyvinyl alcohol solution and sodium borate solution. It has excellent self-healing ability and toughness, can withstand certain external forces without breaking, and can effectively bond the components of cement-based materials during the early strength development stage, significantly resisting damage to the material structure caused by disturbances.

[0025] Specifically, polyvinyl alcohol-sodium borate hydrogel is prepared by the following method: S101, weighing 10 to 20 parts of polyvinyl alcohol, adding it to 100 parts of deionized water, and stirring it at 90° C. using a magnetic stirrer at a speed of 150 rpm to 250 rpm for 1.5 h to 2.5 h; S102, after the stirring is completed, ensure that the polyvinyl alcohol is completely dissolved to obtain a transparent viscous polyvinyl alcohol solution; S103, weighing 5 to 20 parts of sodium borate, adding it to 100 parts of deionized water, and stirring it at a speed of 150 rpm to 250 rpm using a magnetic stirrer at room temperature for 8 min to 12 min to obtain a sodium borate solution; S104, stirring the polyvinyl alcohol solution at 90° C. using a magnetic stirrer, and adding the sodium borate solution during the stirring process. After the addition is completed, stirring is continued for 18 minutes to 25 minutes to fully react to obtain the first product; S105. When the first product is cooled to room temperature, a vacuum ultrasonic machine (ultrasonic power of 20 kHz, ultrasonic time of 5 min) is used to remove bubbles therein, and after standing for 20 min, a colorless and transparent self-healing polyvinyl alcohol-sodium borate hydrogel is obtained.

[0026] In a specific embodiment, the freeze-drying treatment temperature is -30°C to -50°C, and the time is 3h to 6h.

[0027] In a specific embodiment, the particle size of the particles obtained after the crushing process is less than 500 mesh. The particle size less than 500 mesh can ensure that the particles can be embedded in the fiber notches to form a "pinning effect" and thus prevent the fibers from debonding from the matrix.

[0028] S2. Processing the fiber raw material by melt spinning to obtain expanded fiber, and performing surface indentation treatment on the fiber to obtain scored expanded fiber.

[0029] The present application can achieve controllable fiber expansion and high modulus through multi-component gradient melting, wherein the graphene particles provide a heat-conducting network, which can accelerate the temperature uniformity during the melt spinning process and reduce the stress within the fiber.

[0030] In a specific embodiment, the fiber raw material includes: 5 to 8 parts modified graphene particles, 10 to 15 parts thermosensitive polyurethane particles, and 15 to 18 parts polyvinyl alcohol particles. The modified graphene particles have a particle size of 100 to 500 μm, the thermosensitive polyurethane particles have a particle size of 1 to 3 mm, and the polyvinyl alcohol particles have a particle size of 0.1 to 0.5 mm.

[0031] Preferably, the fiber raw material includes: 7 parts of modified graphene particles, 12 parts of temperature-sensitive polyurethane particles and 16 parts of polyvinyl alcohol particles.

[0032] In some optional embodiments of the present application, the melt spinning parameters include: The extrusion temperature is 250°C, the flow rate is 0.5m / min~0.8m / min, the circular spinneret size is 0.3mm, the spacing is 15mm, and the spinning length is 1m.

[0033] S3. Adsorbing the particles onto the notched expansion fiber through electrostatic adsorption to obtain a modified notched expansion fiber.

[0034] In the specific implementation process, the parameters of electrostatic adsorption include: voltage of 20KV, current of 80μA, using a needle-tip discharge corona electrode, and the corona electrode material is stainless steel.

[0035] In this application, to optimize the fiber's reinforcement efficiency and energy absorption path, the scored expansion fiber's length is controlled within the range of 15mm to 20mm to meet the critical fiber length, thereby ensuring effective stress transfer. Furthermore, the indentation depth of the scored expansion fiber is controlled within the range of 0.4mm to 0.6mm, which improves the fiber's extraction work (i.e., the frictional work between the fiber and the substrate during extraction) and increases the fiber's load-bearing capacity.

[0036] S4. Inoculating Bacillus into the spontaneous combustion coal gangue to obtain a first aggregate, and mixing the first aggregate with quartz sand to obtain a second aggregate.

[0037] In this application, the first aggregate is prepared by the following method: S401, crushing spontaneous combustion coal gangue to a particle size of less than 5mm; S402, sterilizing the crushed gangue particles and the Bacillus nutrient solution using high-temperature steam, and cooling to room temperature; wherein the Bacillus nutrient solution comprises the following components: 10 g / L glucose, 5 g / L calcium phosphate, 0.5 g / L ammonium sulfate, 0.2 g / L potassium chloride, 0.1 g / L magnesium sulfate heptahydrate, 0.0001 g / L manganese sulfate, 0.0001 g / L ferrous sulfate, and 0.5 g / L yeast extract; S403. Under sterile conditions, inoculate 1% of the Bacillus into the cooled Bacillus nutrient solution to obtain a concentration of (4-6) × 10 7 cfu / mL of bacterial solution; S404. Add the cooled gangue particles to the bacterial solution for vacuum immersion treatment and drying treatment to obtain the first aggregate after constant weight; wherein, the pressure of the vacuum immersion treatment is -0.07MPa~-0.03MPa, the time of the vacuum immersion treatment is 25min~40min; the temperature of the drying treatment is 38℃~45℃; the temperature of the high-temperature steam sterilization is 100℃~140℃, and the time is 20min~30min.

[0038] The porous structure of the self-combustion coal gangue in this application has the advantages of low density and high porosity, providing ample shelter for Bacillus spores. Furthermore, the alkaline environment of the self-combustion coal gangue can inhibit the growth of other bacteria. Vacuum immersion can displace pore air through negative pressure, increasing the penetration depth of the bacterial solution and thus improving loading efficiency. Finally, the drying process can preserve the dormant state of the Bacillus spores, thereby shortening the time it takes for the Bacillus spores to revive upon contact with water.

[0039] In this application, the mass ratio of the first aggregate to quartz sand in the second aggregate is (0.5-1):1, and the quartz sand has a particle size of 20-40 mesh. This dual-aggregate gradation optimizes the density and microbial activity of cement-based materials. Quartz sand fills the gaps within the first aggregate (which contains gangue coarse aggregate), increasing the packing density. Its surface roughness also enhances mechanical adhesion with the cementitious material, while its chemical inertness prevents interference with microbial metabolism.

[0040] Furthermore, the present application uses self-igniting coal gangue as a component of aggregate, which reduces the amount of natural sand used, achieves the reuse of solid waste, and thus reduces the cost of materials.

[0041] S5. Mix the cementitious material, the second aggregate and the modified notched expansion fiber according to a preset ratio, add water and stir evenly to obtain a high disturbance resistance cement-based material.

[0042] In the preset ratios of this application, the mass ratios of cementitious material, secondary aggregate, and modified scored expansive fiber are (0.4-0.6):(0.5-0.6):(0.1-0.2); the amount of water added is controlled to achieve a water-cement ratio of 0.3. This ratio ensures the formation of a continuous network, enhancing the flexural strength of the cement-based material. Furthermore, the water-cement ratio balances the fluidity and porosity of the slurry, thereby balancing the mechanical properties and self-healing ability of the cement-based material.

[0043] In some optional embodiments of the present application, the cementitious material includes the following components by weight: 180-220 parts of Portland cement, 280-320 parts of sulfoaluminate cement, 40-60 parts of silica fume, 15-25 parts of fly ash, 0.5-1.5 parts of a crystallization accelerator (nano-SiO2 crystallization accelerator, CSH seeds), 0.5-1.5 parts of an expansive agent (including at least one of a calcium-magnesium composite expansive agent, a calcium oxide-calcium sulfoaluminate expansive agent, and a magnesium oxide expansive agent), and 1-3 parts of a polycarboxylate superplasticizer. Portland cement primarily provides the backbone of the CSH gel, while sulfoaluminate cement primarily enhances the strength of the cementitious material. The nano-silica in the silica fume fills pores, thereby reducing the chloride ion diffusion coefficient. The crystallization accelerator accelerates the nucleation of hydration products, rapidly increasing the strength of the cementitious material in a short period of time. Based on this, the composite cementitious system of the present application can achieve rapid hardening, minimal expansion, and high durability.

[0044] In a second aspect, based on a general inventive concept, the present application also provides a highly resistant cement-based material prepared by the above method.

[0045] The highly resistant cement-based material prepared in this application has high toughness and self-healing ability. It has high compressive strength under both disturbed and undisturbed conditions, and can repair the initial crack width of 0.5mm to about 0.1mm within 28 days, greatly improving the service life of the cement-based material and at the same time reducing maintenance costs, thereby improving the economic benefits of the cement-based material.

[0046] The above technical solutions of the present application are described in detail below with reference to specific embodiments.

[0047] The equipment and raw materials used in the embodiments include: Magnetic stirrer: Zhengzhou Rongxiang Instrument Equipment Co., Ltd., thermal collector constant temperature heating magnetic stirrer.

[0048] Melt spinning machine: Sichuan Zhiyan Technology Co., Ltd.

[0049] High temperature steam sterilizer: Shandong Bo Ke Biological Industry Co., Ltd.

[0050] Air bath constant temperature oscillator: Shanghai Bozhen Instrument Manufacturing Factory.

[0051] Bacillus: Guangdong Runhe Biopharmaceutical Technology Co., Ltd.

[0052] Portland cement: P·O 42.5.

[0053] Sulphoaluminate cement: R·SAC 42.5.

[0054] Silica fume: apparent density 2250kg / m 3 , silicon dioxide content ≥90%, specific surface area ≥18000m 2 / kg.

[0055] Fly ash: apparent density 2300kg / m 3 , specific surface area ≥700m 2 / kg.

[0056] Crystal nucleus early strength agent: nano-SiO2 crystal nucleus early strength agent, CSH seed.

[0057] Expansion agent: calcium-magnesium composite expansion agent, calcium oxide-calcium sulfoaluminate expansion agent, magnesium oxide expansion agent.

[0058] Polycarboxylate water reducer: Shandong Jinrong Chemical Technology Co., Ltd.

[0059] The modified graphene particles and temperature-sensitive polyurethane particles used in the examples were obtained by the following method: (1) Modified graphene particles are prepared by the following method: 200 mg of graphene oxide and 500 mL of deionized water were mixed, and then dispersed in an ultrasonic water bath at room temperature for 1 h to obtain a first mixture; 2.0 g of sodium 4-styrenesulfonate was added to the first mixture and stirred for more than 1 h until the sodium 4-styrenesulfonate was completely dissolved to obtain a second mixture; Add 10 g of hydrazine hydrate to the second mixture and heat in a water bath at 95° C. for 24 h to obtain a primary product; The primary product was washed with deionized water and then dried at 105° C. for 24 h to obtain modified graphene particles.

[0060] (2) Thermosensitive polyurethane particles are prepared by the following method: Mix 60 g of poly(1,2-propylene glycol) and 35 g of L-lysine ethyl ester diisocyanate, and stir at 200 rpm for more than 48 h at room temperature to obtain an initial product; The initial product was dissolved in 200 mL of methanol solution (analytical grade, concentration 99%), and 50 mL of ether (analytical grade, concentration 99%) was added as a precipitant. The dissolution-precipitation process was repeated three times. The final precipitate was then taken out and placed in an oven (30°C) to dry for 48 hours to obtain thermosensitive polyurethane particles.

[0061] Example 1 This embodiment provides a method for preparing a highly resistant cement-based material, comprising the following steps: (1) Preparation of polyvinyl alcohol solution Weigh 10 g of polyvinyl alcohol and add it to 100 mL of deionized water. Stir at 90 °C for 2 h at a stirring speed of 200 r / min. After stirring, ensure that the polyvinyl alcohol is completely dissolved to obtain a transparent and viscous polyvinyl alcohol solution.

[0062] (2) Preparation of sodium borate solution Weigh 5 g of sodium borate and add it to 100 mL of deionized water. Stir at room temperature for 10 min at a stirring speed of 200 r / min to obtain a sodium borate solution.

[0063] (3) Preparation of polyvinyl alcohol-sodium borate hydrogel Add the sodium borate solution to the polyvinyl alcohol solution at 90°C while stirring. Continue stirring for 20 minutes to allow for full reaction. After the reaction mixture was cooled to room temperature, it was placed in a vacuum ultrasonic machine (ultrasonic power of 20 kHz, ultrasonic time of 5 minutes, the same below) to remove bubbles in the mixture. After standing for 20 minutes, a colorless and transparent polyvinyl alcohol-sodium borate hydrogel with self-healing function was obtained.

[0064] The polyvinyl alcohol-sodium borate hydrogel was freeze-dried and then crushed into particles with a particle size of less than 500 mesh. The freeze-drying temperature was -30°C and the time was 3 hours.

[0065] (4) Preparation of modified notched expansion fibers 7 g of modified graphene particles (300 μm), 12 g of thermosensitive polyurethane particles (2 mm), and 16 g of polyvinyl alcohol particles (0.3 mm) were mixed to obtain a mixture; The mixture was melt-spun by a melt spinning machine, and the surface of the cooled fiber was indented with a depth of 0.5 mm and a fiber length of 20 mm to obtain a scored expanded fiber; Electrostatic adsorption was used to adsorb particles of polyvinyl alcohol-sodium borate hydrogel onto the scored expanded fibers to produce modified scored expanded fibers. Melt spinning parameters (the same below) included an extrusion temperature of 250°C, a flow rate of 0.8 m / min, a circular spinneret orifice size of 0.3 mm, a pitch of 15 mm, and a spinning path length of 1 m. Electrostatic adsorption parameters (the same below) included a voltage of 20 kV, a current of 80 μA, and a needle-tip discharge corona electrode made of stainless steel.

[0066] (5) Preparation of the first aggregate and the second aggregate The self-igniting coal gangue was crushed to a particle size of less than 5 mm, and the crushed coal gangue particles and the prepared Bacillus nutrient solution were steam sterilized in a high-temperature steam sterilizer with steam at 120°C for 30 minutes; wherein the Bacillus nutrient solution (the same below) comprises the following components: 10 g / L glucose, 5 g / L calcium phosphate, 0.5 g / L ammonium sulfate, 0.2 g / L potassium chloride, 0.1 g / L magnesium sulfate heptahydrate, 0.0001 g / L manganese sulfate, 0.0001 g / L ferrous sulfate, and 0.5 g / L yeast extract; Cool naturally in a sterile environment, and transfer the Bacillus into the cooled Bacillus nutrient solution at a 1% inoculum volume using a pipette. Ensure that no other strains are mixed in during the inoculation process. After the inoculation, the mixture was placed in a 30°C air bath constant temperature shaker at 120 rpm and cultured for 2 days to obtain a concentration of 5×10 7 cfu / mL of bacterial solution; The sterilized gangue is placed in a bacterial solution for vacuum immersion treatment, so that the Bacillus is adsorbed inside the sterilized spontaneous combustion gangue. The vacuum pressure is -0.05 MPa and the immersion time is 30 minutes. The gangue is then dried in a 40°C oven to a constant weight (constant weight means that the mass of the gangue no longer changes) to obtain a first aggregate. The first aggregate and quartz sand are evenly mixed in a mass ratio of 1:1 to obtain the second aggregate; wherein the particle size of the quartz sand is 40 mesh.

[0067] (6) Preparation of cementitious materials Weigh 200g of ordinary Portland cement, 300g of sulphoaluminate cement, 50g of silica fume, 20g of first-grade fly ash, 1g of nano-SiO2 crystal nucleus early strength agent, 1g of calcium-magnesium composite expansion agent and 2g of polycarboxylate water reducer, mix them evenly to obtain a cementitious material.

[0068] (7) Preparation of highly resistant cement-based materials The prepared cementitious material, the second aggregate and the modified notched expansion fiber were added into a mixer at a mass ratio of 0.5:0.5:0.1, and water was added at a water-cement ratio of 0.3. After uniform mixing, a high-disturbance-resistant cement-based material was obtained.

[0069] Example 2 This embodiment provides a method for preparing a highly resistant cement-based material, comprising the following steps: (1) Preparation of polyvinyl alcohol solution Weigh 10 g of polyvinyl alcohol and add it to 100 mL of deionized water. Stir at 90 °C for 2 h at a stirring speed of 250 r / min. After stirring, ensure that the polyvinyl alcohol is completely dissolved to obtain a transparent and viscous polyvinyl alcohol solution.

[0070] (2) Preparation of sodium borate solution Weigh 5 g of sodium borate and add it to 100 mL of deionized water. Stir the mixture at room temperature for 10 min at a stirring speed of 250 r / min to obtain a sodium borate solution.

[0071] (3) Preparation of polyvinyl alcohol-sodium borate hydrogel Add the sodium borate solution to the polyvinyl alcohol solution at 90°C while stirring. Continue stirring for 20 minutes to allow for full reaction. After the reaction mixture is cooled to room temperature, it is placed in a vacuum ultrasonic machine to remove bubbles in the mixture, and after standing, a colorless and transparent polyvinyl alcohol-sodium borate hydrogel with self-repairing function is obtained.

[0072] The polyvinyl alcohol-sodium borate hydrogel was freeze-dried and then crushed into particles with a particle size of less than 500 mesh. The freeze-drying temperature was -50°C and the time was 6 hours.

[0073] (4) Preparation of modified notched expansion fibers 5 g of modified graphene particles, 10 g of thermosensitive polyurethane particles, and 18 g of polyvinyl alcohol particles were mixed to obtain a mixture; The mixture was melt-spun by a melt spinning machine, and the surface of the cooled fiber was indented, with the indentation depth of 0.5 mm and the fiber length of 15 mm to obtain indented expanded fiber; The particles of polyvinyl alcohol-sodium borate hydrogel are adsorbed on the notched expansion fiber by electrostatic adsorption to obtain the modified notched expansion fiber.

[0074] (5) Preparation of the first aggregate and the second aggregate The spontaneous combustion coal gangue was crushed to a particle size of less than 5 mm, and the crushed coal gangue particles and the prepared Bacillus nutrient solution were steam sterilized in a high-temperature steam sterilizer at 120°C for 30 minutes; Cool naturally in a sterile environment, and transfer the Bacillus into the cooled Bacillus nutrient solution at a 1% inoculum volume using a pipette. Ensure that no other strains are mixed in during the inoculation process. After the inoculation, the mixture was placed in a 30°C air bath constant temperature shaker at 120 rpm and cultured for 2 days to obtain a concentration of 5×10 7 cfu / mL of bacterial solution; The sterilized gangue is placed in a bacterial solution for vacuum immersion treatment, so that the Bacillus is adsorbed inside the sterilized spontaneous combustion gangue. The vacuum pressure is -0.05 MPa and the immersion time is 30 minutes. The gangue is then dried in a 40°C oven to a constant weight (constant weight means that the mass of the gangue no longer changes) to obtain a first aggregate. The first aggregate and quartz sand are evenly mixed in a mass ratio of 1:1 to obtain the second aggregate; wherein the particle size of the quartz sand is 20 mesh.

[0075] (6) Preparation of cementitious materials Weigh 210g of ordinary Portland cement, 290g of sulphoaluminate cement, 55g of silica fume, 15g of first-grade fly ash, 1g of nano-SiO2 crystal nucleus early strength agent, 0.5g of magnesium oxide expansion agent and 2.5g of polycarboxylate water reducer, mix them evenly to obtain a cementitious material.

[0076] (7) Preparation of highly resistant cement-based materials The prepared cementitious material, the second aggregate and the modified notched expansion fiber were added into a mixer at a mass ratio of 0.4:0.6:0.1, and water was added at a water-cement ratio of 0.3. After uniform mixing, a high-disturbance-resistant cement-based material was obtained.

[0077] Example 3 This embodiment provides a method for preparing a highly resistant cement-based material, comprising the following steps: (1) Preparation of polyvinyl alcohol solution Weigh 10 g of polyvinyl alcohol and add it to 100 mL of deionized water. Stir at 90 °C for 2 h at a stirring speed of 150 r / min. After stirring, ensure that the polyvinyl alcohol is completely dissolved to obtain a transparent and viscous polyvinyl alcohol solution.

[0078] (2) Preparation of sodium borate solution Weigh 5 g of sodium borate and add it to 100 mL of deionized water. Stir the mixture at room temperature for 10 min at a stirring speed of 150 r / min to obtain a sodium borate solution.

[0079] (3) Preparation of polyvinyl alcohol-sodium borate hydrogel Add the sodium borate solution to the polyvinyl alcohol solution at 90°C while stirring. Continue stirring for 20 minutes to allow for full reaction. After the reaction mixture is cooled to room temperature, it is placed in a vacuum ultrasonic machine to remove bubbles in the mixture, and after standing, a colorless and transparent polyvinyl alcohol-sodium borate hydrogel with self-repairing function is obtained.

[0080] The polyvinyl alcohol-sodium borate hydrogel was freeze-dried and then crushed into particles with a particle size of less than 500 mesh. The freeze-drying temperature was -40°C and the time was 5 hours.

[0081] (4) Preparation of modified notched expansion fibers 8 g of graphene particles, 10 g of thermosensitive polyurethane particles, and 15 g of polyvinyl alcohol particles were mixed to obtain a mixture; The mixture was melt-spun by a melt spinning machine, and the surface of the cooled fiber was indented with a depth of 0.5 mm and a fiber length of 18 mm to obtain a scored expanded fiber; The particles of polyvinyl alcohol-sodium borate hydrogel are adsorbed on the notched expansion fiber by electrostatic adsorption to obtain the modified notched expansion fiber.

[0082] (5) Preparation of the first aggregate and the second aggregate The spontaneous combustion coal gangue was crushed to a particle size of less than 5 mm, and the crushed coal gangue particles and the prepared Bacillus nutrient solution were steam sterilized in a high-temperature steam sterilizer at 120°C for 30 minutes; Cool naturally in a sterile environment, and transfer the Bacillus into the cooled Bacillus nutrient solution at a 1% inoculum volume using a pipette. Ensure that no other strains are mixed in during the inoculation process. After the inoculation, the mixture was placed in a 30°C air bath constant temperature shaker at 120 rpm and cultured for 2 days to obtain a concentration of 5×10 7 cfu / mL of bacterial solution; The sterilized gangue is placed in a bacterial solution for vacuum immersion treatment, so that the Bacillus is adsorbed inside the sterilized spontaneous combustion gangue. The vacuum pressure is -0.05 MPa and the immersion time is 30 minutes. The gangue is then dried in a 40°C oven to a constant weight (constant weight means that the mass of the gangue no longer changes) to obtain a first aggregate. The first aggregate and quartz sand are evenly mixed in a mass ratio of 1:1 to obtain the second aggregate; wherein the particle size of the quartz sand is 40 mesh.

[0083] (6) Preparation of cementitious materials Weigh 220g of ordinary Portland cement, 280g of sulphoaluminate cement, 48g of silica fume, 22g of first-grade fly ash, 1.5g of nano-SiO2 crystal nucleus early strength agent, 1g of calcium-magnesium composite expansion agent and 1g of polycarboxylate water reducer, mix them evenly to obtain a cementitious material.

[0084] (7) Preparation of highly resistant cement-based materials The prepared cementitious material, the second aggregate and the modified notched expansion fiber were added into a mixer at a mass ratio of 0.6:0.5:0.2, and water was added at a water-cement ratio of 0.3. After uniform mixing, a high-disturbance-resistant cement-based material was obtained.

[0085] Comparative Example 1 The difference between this comparative example and Example 1 is that the modified notched expansion fiber is not added, and the remaining steps are consistent with Example 1.

[0086] Comparative Example 2 The difference between this comparative example and Example 1 is that only quartz sand is used as aggregate and the first aggregate is not added. The remaining steps are consistent with Example 1.

[0087] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of the cementitious material, the second aggregate and the modified notched expansion fiber is 0.5:0.5:0.3, and the other steps are consistent with Example 1.

[0088] Comparative Example 4 The difference between this comparative example and Example 1 is that the mass ratio of the cementitious material, the second aggregate and the modified notched expansion fiber is 0.5:0.5:0.06, and the remaining steps are consistent with Example 1.

[0089] Comparative Example 5 The difference between this comparative example and Example 1 is that the mass ratio of the cementitious material, the second aggregate and the modified notched expansion fiber is 0.5:0.7:0.4, and the remaining steps are consistent with Example 1.

[0090] Comparative Example 6 The difference between this comparative example and Example 1 is that the mass ratio of the cementitious material, the second aggregate and the modified notched expansion fiber is 0.5:0.3:0.4, and the other steps are consistent with Example 1.

[0091] The cement-based materials prepared in Example 1 were compared with those in Comparative Examples 1-6, wherein the compressive strength test referred to GBT17671-2021 "Test method for strength of cement mortar (ISO method)"; the disturbance conditions were to use a high-frequency electric vibration table to simulate the disturbance conditions, and the vibration parameters were a vibration frequency of 5 Hz, an amplitude of 5 mm, and continuous vibration for 1 hour; for the crack width test, the crack width was observed using a reading microscope with a magnification of not less than 40 times and a graduation value of not more than 0.01 mm, and the data are shown in Table 1.

[0092] Table 1

[0093] Compared to Comparative Example 1, Example 1 of the present application incorporates modified, notched, expansive fibers, and its 28-day compressive strength is improved, with increases of 21.3% under undisturbed conditions and 37.5% under disturbed conditions. This is likely due to the fact that the fibers effectively transmit stress, while the surface notches also increase the fiber's pull-out work, enabling it to absorb the energy of dynamic loads. Furthermore, the cementitious material of Example 1 exhibits a post-disturbance strength retention rate of 98.8% (determined by comparing the 28-day compressive strength after disturbance with the undisturbed compressive strength), demonstrating that the fiber network can inhibit crack propagation under dynamic loads and dissipate energy through interfacial slip.

[0094] Compared with Comparative Example 2, Example 1 of the present application adds the first aggregate (which is a bacteria-containing aggregate) and has crack self-repairing ability, which can maintain the long-term durability of the cement-based material. As can be seen from Table 1, the crack width of Example 1 is reduced by about 80%, and the reason is that the bacillus metabolism produces calcium carbonate to fill the crack space. Although the initial strength of Comparative Example 2 is slightly higher than that of the cement-based material of Example 1, the strength loss after disturbance is higher, which shows that the quartz sand does not have self-repairing ability, and the microcracks will continue to expand under dynamic load.

[0095] At the same time, as can be seen from Example 1 and Comparative Examples 3-4, only when the proportioning is carried out according to the preset proportioning relationship of the present application, the compressive strength, crack resistance and disturbance resistance of the high-disturbance-resistant cement-based material can be optimized. Among them, the excessive proportion of modified fibers will reduce the bonding strength of the system, and too low will lead to ineffective crack resistance. The proportion of the second aggregate should match the cementitious material, so as to ensure the balance of skeleton support and bonding strength.

[0096] In summary, it can be seen that the modified notch expansion fiber used in the present application is the core to improve the immediate mechanical properties, which can enhance the compressive strength of the cement-based material and reduce the strength loss under dynamic load; the first aggregate used is the key to ensure long-term durability, which can significantly improve the self-repairing ability of the crack. The high-disturbance-resistant cement-based material of the present application can limit the crack width <1mm in the initial stage of the crack through the coupling effect of the fiber and the microorganism, and can repair the crack after the crack appears through the efficient mineralization of the microorganism in the limited crack. At the same time, the fiber can absorb impact energy through plastic deformation to adapt to instantaneous load, and the microorganism therein can repair fatigue microcracks to adapt to cyclic load.

[0097] Although the specific embodiments of the present application are described in detail, it should not be understood as limiting the scope of protection of the present application. Various modifications and variations made by those skilled in the art within the scope described in the claims are still within the scope of protection of the present application.

Claims

1. A method for preparing a highly resistant cement-based material, characterized in that: The following steps are involved: preparing polyvinyl alcohol-sodium borate hydrogel, and subjecting it to freeze-drying and pulverizing to obtain particles; The fiber raw material is melt-spinned to obtain expanded fibers, and the expanded fibers are subjected to surface indentation treatment to obtain scored expanded fibers; Adsorbing the particles onto the scored expanded fiber by electrostatic adsorption to obtain a modified scored expanded fiber; Inoculating Bacillus into spontaneous combustion coal gangue to obtain a first aggregate, and mixing the first aggregate with quartz sand to obtain a second aggregate; The cementitious material, the second aggregate and the modified notched expansion fiber are mixed according to a preset ratio, and water is added and stirred evenly to prepare a high disturbance resistance cement-based material.

2. The preparation method according to claim 1, characterized in that The polyvinyl alcohol-sodium borate hydrogel is prepared by the following method: The polyvinyl alcohol solution of 10 wt% to 20 wt% and the sodium borate solution of 5 wt% to 20 wt% are mixed in a mass ratio of (2 to 5):1 under stirring, and after the reaction is completed, the mixture is cooled to room temperature and bubbles are removed to obtain the product.

3. The preparation method according to claim 1, characterized in that The freeze-drying treatment temperature is -30°C to -50°C, and the time is 3h to 6h; the particle size of the particles is less than 500 mesh.

4. The preparation method according to claim 1, characterized in that The method of obtaining expanded fibers by melt spinning a fiber raw material comprises: Weigh 5 to 8 parts of modified graphene particles, 10 to 15 parts of thermosensitive polyurethane particles, and 15 to 18 parts of polyvinyl alcohol particles and mix them evenly to obtain a mixture; The mixture is processed by melt spinning to obtain expanded fibers; wherein, The parameters of the melt spinning process include: extrusion temperature of 250° C., flow rate of 0.5 m / min to 0.8 m / min, circular spinneret size of 0.3 mm, spacing of 15 mm, and spinning length of 1 m.

5. The preparation method according to claim 1, characterized in that The fiber length of the scored expansion fiber is 15 mm to 20 mm, and the indentation depth of the scored expansion fiber is 0.4 mm to 0.6 mm.

6. The preparation method according to claim 1, characterized in that The method of inoculating Bacillus into spontaneous combustion coal gangue to obtain the first aggregate comprises: Crushing spontaneous combustion coal gangue to a particle size of less than 5 mm to obtain coal gangue particles; Sterilize the gangue particles and the Bacillus nutrient solution using high-temperature steam, and cool to room temperature; Under sterile conditions, Bacillus was inoculated into the cooled Bacillus nutrient solution at a 1% inoculum volume to obtain a concentration of (4-6)×10 7 cfu / mL of bacterial solution; The cooled gangue particles are added to the bacterial solution for vacuum immersion treatment and drying treatment to obtain the first aggregate after constant weight; wherein the pressure of the vacuum immersion treatment is -0.07 MPa to -0.03 MPa, the time of the vacuum immersion treatment is 25 minutes to 40 minutes; and the temperature of the drying treatment is 38° C. to 45° C.

7. The preparation method according to claim 1, characterized in that The mass ratio of the first aggregate to the quartz sand in the second aggregate is (0.5-1):1, and the particle size of the quartz sand is 20-40 mesh.

8. The preparation method according to claim 1, characterized in that In the preset proportion, the mass ratio of the cementitious material, the second aggregate and the modified notched expansion fiber is (0.4-0.6): (0.5-0.6): (0.1-0.2); wherein, the amount of water added is regulated according to a water-cement ratio of 0.

3.

9. The preparation method according to claim 1, characterized in that The cementitious material comprises the following components in parts by weight: 180 to 220 parts of Portland cement, 280 to 320 parts of sulphoaluminate cement, 40 to 60 parts of silica fume, 15 to 25 parts of fly ash, 0.5 to 1.5 parts of a crystallization early strength agent, 0.5 to 1.5 parts of an expansion agent, and 1 to 3 parts of a polycarboxylate water reducer.

10. A highly resistant cement-based material, characterized in that: The method according to any one of claims 1 to 9 is used to prepare the present invention.

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