High-crack-resistance self-repairing sprayed concrete composition as well as preparation method and application thereof

Abstract

The invention discloses a high-crack-resistance self-repairing sprayed concrete composition as well as a preparation method and application thereof. The composition comprises the following components in percentage by mass: 40%-50% of cement, 50%-60% of aggregate, 1%-2% of composite microfibers, 3%-5% of modified polymer emulsion, 1%-2% of an additive, 0.5%-1.5% of a nano reinforced phase and 2%-3% of a self-repairing microcapsule, and also comprises an anti-corrosion additive. The composite microfiber is a mixture of polypropylene and basalt microfiber, and the nano reinforced phase is a compound system of nano calcium carbonate and silicon dioxide. The preparation method comprises the steps of aggregate pretreatment, dry material mixing, wet material preparation, microcapsule introduction and injection molding, the aggregate is pretreated through a silane coupling agent, the cement is formed by compounding ordinary Portland cement and aluminate cement, and the modified polymer emulsion is modified through a siloxane monomer. According to the composition, through the synergistic effect of the composite microfibers, the self-repairing microcapsules and the nano reinforced phase, the crack resistance and the self-repairing capacity are improved, the composition is particularly suitable for a corrosive environment, and the service life of a structure can be prolonged.

Description

TECHNICAL FIELD

[0001] The application relates to the field of building materials, and in particular to a high-anti-cracking self-repairing shotcrete composition and a preparation method and application thereof. BACKGROUND

[0002] As an important construction material in the modern building field, shotcrete is widely used in tunnel lining, underground engineering and structure reinforcement, and its performance directly affects the durability and safety of the engineering structure. With the increasing demand for material functions in the building industry, shotcrete with anti-cracking performance and self-repairing capability has become a research hotspot. Although the existing technology realizes a certain degree of performance improvement by adding fibers or microcapsules, there is still room for improvement in the long-term stability and repair efficiency under complex stress environment.

[0003] The single type of fiber reinforcement system in common concrete is difficult to build a multi-scale crack resistance network, resulting in limited crack propagation inhibition capacity; the triggering mechanism of traditional self-repairing microcapsules depends on a single environmental factor, and under low temperature or variable temperature conditions, repair lag or failure may occur; although nanomaterials can optimize the matrix density, the interface compatibility with fibers and microcapsules is insufficient, and it is difficult to form stable synergistic effect; the functions of various components are relatively independent, and there is a lack of systematic integration of physical crack resistance, chemical repair and interface strengthening, so that the material still faces problems such as fast damage accumulation, short repair effect and weak environmental adaptability during long-term service, and cannot meet the performance requirements in high-cold regions or complex stress scenarios, and cannot meet the working requirements of building material applications. Therefore, a high-anti-cracking self-repairing shotcrete composition and a preparation method and application thereof are proposed. SUMMARY

[0004] The application provides the following technical scheme: a high-anti-cracking self-repairing shotcrete composition, comprising: cement 40%-50%, aggregate 50%-60%, composite microfiber 1%-2%, modified polymer emulsion 3%-5%, additive 1%-2%, nano-enhanced phase 0.5%-1.5% and self-repairing microcapsule 2%-3%, wherein the additive comprises at least one of a water reducing agent and an early strength agent, and the cement comprises at least one of Portland cement or slag Portland cement; The composite microfiber is a mixture of polypropylene microfiber and basalt microfiber, and the nano-enhanced phase is a compounding system of nano calcium carbonate and nano silicon dioxide.

[0005] The application provides a preparation method of a high-anti-cracking self-repairing shotcrete composition, based on the high-anti-cracking self-repairing shotcrete composition, comprising the following steps: S1 aggregate pretreatment: Firstly, the 5mm-8mm and 8mm-10mm size aggregates are mixed in a mass ratio of 6:4, and 0.2%-0.5% silane coupling agent is added to the aggregates, then constant temperature stirring is carried out at 50-60°C for 30-40 minutes to form surface modified aggregates; S2 dry material mixing: The ordinary Portland cement and the aluminate cement are compounded in a mass ratio of 8:2-7:3, and the pretreated aggregates, polypropylene microfibers and basalt microfibers are added, then stirring is carried out in a stirrer for 5-10 minutes; S3 wet material preparation: The polyvinyl acetate-butyl acrylate copolymer emulsion and the siloxane monomer are mixed in a mass ratio of 9:1, then the nano calcium carbonate and the nano silicon dioxide are added, and the modified polymer slurry is formed after ultrasonic dispersion for 30-40 minutes; S4 microcapsule introduction: The water reducing agent, early strength agent and self-repairing microcapsules are added in sequence in the dry material mixture, and stirring is carried out for 8-15 minutes; S5 spray forming: The wet material slurry and the dry material mixture are mixed in a double-shaft stirrer at 30-60 revolutions per minute for 2-6 minutes, then the spray pressure is adjusted to 0.4MPa-0.6MPa, the spray distance is 0.8m-1.2m, and the layering spray thickness is 30mm-50mm, and after the data adjustment is completed, the spray is carried out to the construction surface.

[0006] The application further provides application of the high-anti-crack self-repairing spray concrete composition in building engineering, and the building engineering comprises one of tunnel lining, underground engineering and structure reinforcement.

[0007] Preferably, the cement is a composite cement system compounded by the ordinary Portland cement and the aluminate cement in a mass ratio of 8:2-7:3, the aggregates are designed by gradient grading, and the 5mm-8mm size particles and the 8mm-10mm size particles are mixed in a mass ratio of 6:4, the surface of the aggregates is provided with a silane coupling agent pretreatment layer, the pretreatment agent of the pretreatment layer accounts for 0.2%-0.5% of the mass of the aggregates, the composite cement system compounded by the ordinary Portland cement and the aluminate cement is combined with the gradient grading aggregate design, the early strength and long-term stability of the concrete matrix are improved by optimizing the cement hydration rate and the aggregate interlocking effect, the surface of the aggregates is pretreated by the silane coupling agent, the interface bonding between the aggregates and the cement stone is enhanced, and the generation of pores and microcracks is reduced.

[0008] Preferably, the modified polymer emulsion is a polyvinyl acetate-butyl acrylate copolymer emulsion, which is modified by introducing siloxane monomers, the inside of the self-repairing microcapsule is filled with a repairing agent, the repairing agent is at least one of an epoxy resin or a urea-formaldehyde resin, and the polyvinyl acetate-butyl acrylate copolymer emulsion modified by the siloxane monomers cooperates with the nano calcium carbonate-silica composite system, which not only improves the flexibility of the matrix through the polymer film-forming property, but also optimizes the microstructure through the nano material filling effect, and the epoxy resin or urea-formaldehyde resin repairing agent of the self-repairing microcapsule ensures the recovery of mechanical properties after crack healing.

[0009] Preferably, in the step S1, when the silane coupling agent is added to the aggregate, the silane coupling agent is first diluted with anhydrous ethanol and stirred until dissolved, then uniformly applied to the surface of the aggregate in the form of atomized spraying, and the wet state of the surface of the aggregate is continuously monitored during stirring. The silane coupling agent is atomized and sprayed after being diluted with anhydrous ethanol, which, combined with the wet state monitoring during stirring, realizes uniform coating of the surface of the aggregate, avoids interface defects caused by local excess or deficiency, and improves the compatibility of the aggregate and the cement matrix, providing a stable substrate for subsequent fiber reinforcement and microcapsule distribution.

[0010] Preferably, in the step S2, the mixer adopts a step-by-step stirring process, which initially stirs at a low speed to preliminarily mix the cement and aggregate, and then increases the stirring speed after the fibers are uniformly dispersed. A sealing film cover is used outside the stirring bin during the stirring process, and the inner wall and bottom of the stirring bin are cleaned simultaneously after the stirring is completed. The step-by-step stirring process controls the initial mixing at a low speed and the fiber dispersion at a high speed, combined with the sealing film cover and the simultaneous cleaning of the bin wall, ensures uniform dispersion of the fibers without agglomeration, and avoids material waste during stirring, improving the consistency of preparation efficiency and concrete performance.

[0011] Preferably, in the step S3, when the polyvinyl acetate-butyl acrylate copolymer emulsion is mixed with the siloxane monomers, the polyvinyl acetate-butyl acrylate copolymer emulsion is first preheated in a constant-temperature container, and then the siloxane monomers are added after the emulsion stability is stable. In the step S4, when the self-repairing microcapsule is added, it is first dried to remove the surface adsorbed water, and then added to the dry mixture in a layered manner. The preheating of the polymer emulsion and the mixing with the siloxane monomers, combined with the layered addition of the dried self-repairing microcapsule, avoid the problems of poor emulsion fluidity caused by low temperature and microcapsule rupture caused by water absorption, ensuring the uniform distribution of the modified polymer and the microcapsule in the dry material, and improving the mixing effect and the reliability of the self-repairing function.

[0012] Preferably, the step S5 is preceded by a pretreatment of the construction surface before the spray forming, the floating dust, loose particles and oil stains on the construction surface are removed, then the construction surface is blown by high pressure airflow, and for the parts with cracks or depressions, the repair material is filled and leveled in advance, and after the repair material is dried and formed, the spray is carried out, the construction surface pretreatment is blown by high pressure airflow and the cracks are repaired, the weak layer such as floating dust and loose particles is eliminated, the close adhesion of the sprayed concrete and the base surface is ensured, the stress concentration and peeling risk caused by surface defects are avoided, and the structural integrity and durability are improved.

[0013] Preferably, the composition further comprises an anti-corrosion additive, the anti-corrosion additive is zinc phosphate, and the addition amount is 0.5%-1.5%, the introduction of the zinc phosphate anti-corrosion additive forms a dense protective layer in the concrete, inhibits the penetration of corrosive media such as sulfate and chloride ion, slows down the corrosion rate of steel bars and the degradation rate of the matrix, is especially suitable for corrosive environments such as ocean and chemical industry, and prolongs the service life of the structure.

[0014] In summary, compared with the prior art, the present application provides a high-anti-cracking self-repairing sprayed concrete composition, a preparation method and application thereof, and has the following beneficial effects: 1、The present application introduces a composite reinforcing system of polypropylene microfiber and basalt microfiber, combined with self-repairing microcapsules, forming a multi-scale synergistic mechanism, constructing a three-dimensional network structure in the concrete through composite microfibers, effectively inhibiting the initiation and expansion of cracks, and at the same time, through the interfacial adhesion between the fibers and the matrix, the overall toughness of the material is improved, and the self-repairing microcapsules can actively sense the stress change caused by crack expansion in low temperature environment, and timely rupture and release the repair agent, realizing the rapid filling and curing of the cracks, the synergistic effect of the two significantly reduces the damage accumulation rate of the concrete in the service process, not only delays the development of cracks through physical crack resistance, but also realizes the active healing of damage through chemical repair, thereby greatly prolonging the service life of the structure, and the nano-enhanced phase can fill the material micro-pores, optimize the structure of the interface transition zone, improve the matrix density and mechanical properties, and provide a more stable action environment for the microfibers and microcapsules, under the synergistic action of the three, the material not only has greatly enhanced crack resistance, but also has synchronous improvement of self-repairing efficiency and durability, effectively reducing the engineering maintenance cost; 2、The self-repairing microcapsule inside the repair agent ensures good combination with the concrete matrix, the repaired area can restore the mechanical properties close to the original matrix, the composite microfiber provides support for the uniform distribution of the microcapsule by the performance complementation of the two fibers, avoids the influence of the repair effect caused by the local aggregation of the microcapsule, and the nano-enhanced phase strengthens the interface bonding of the cement matrix, the microfiber and the microcapsule by the nano-scale effect, reduces the interface defects, so that the repair agent can more uniformly penetrate and diffuse in the healing process. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is the preparation method flow chart of the application. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0017] Embodiment one Take by mass percentage: cement 45% (ordinary Portland cement and aluminate cement are compounded according to the mass ratio of 8:2), aggregate 53% (5mm-8mm and 8mm-10mm particle size particles are mixed according to the mass ratio of 6:4, the surface silane coupling agent pretreatment agent of the aggregate is 0.3% of the mass of the aggregate), composite microfiber 1.5% (a mixture of polypropylene microfiber and basalt microfiber), modified polymer emulsion 4% (polyvinyl acetate-butyl acrylate copolymer emulsion, modified by introducing siloxane monomer), additive 1.5% (water reducing agent and early strength agent are mixed according to the mass ratio of 1:1), nano-enhanced phase 1% (a compounded system of nano-calcium carbonate and nano-silicon dioxide), self-repairing microcapsule 2.5% (filled with epoxy resin inside); When preparing, the S1 aggregate pretreatment is stirred at 50 DEG C for 30 minutes; the S2 dry material mixing is stirred for 7 minutes; the S3 wet material preparation is ultrasonically dispersed for 35 minutes; the S4 microcapsule introduction is stirred for 10 minutes; the S5 spray forming is mixed by a double-shaft stirrer for 4 minutes, the spray pressure is 0.5MPa, the spray distance is 1.0m, and the layering spray thickness is 40mm; Embodiment two By mass percentage: cement 42% (ordinary Portland cement and aluminate cement are compounded at a mass ratio of 7.5:2.5), aggregate 57% (5mm-8mm and 8mm-10mm particle size particles are mixed at a mass ratio of 6:4, and the amount of silane coupling agent pretreatment agent on the surface of the aggregate is 0.2% of the mass of the aggregate), composite microfiber 1.2% (a mixture of polypropylene microfiber and basalt microfiber), modified polymer emulsion 3.5% (polyvinyl acetate-butyl acrylate copolymer emulsion modified by introducing siloxane monomer), additive 1.2% (only water reducing agent), nano-enhanced phase 0.8% (a compounded system of nano-calcium carbonate and nano-silicon dioxide), self-repairing microcapsule 2.3% (filled with urea-formaldehyde resin inside); When prepared, the S1 aggregate pretreatment is stirred at a constant temperature of 55°C for 35 minutes; the S2 dry material mixing is stirred for 5 minutes; the S3 wet material preparation is ultrasonically dispersed for 30 minutes; the S4 microcapsule introduction is stirred for 12 minutes; the S5 spray forming is mixed by a double-shaft stirrer for 3 minutes, the spray pressure is 0.4MPa, the spray distance is 0.8m, and the layered spray thickness is 30mm; Example Three By mass percentage: cement 48% (ordinary Portland cement and aluminate cement are compounded at a mass ratio of 7:3), aggregate 51% (5mm-8mm and 8mm-10mm particle size particles are mixed at a mass ratio of 6:4, and the amount of silane coupling agent pretreatment agent on the surface of the aggregate is 0.5% of the mass of the aggregate), composite microfiber 1.8% (a mixture of polypropylene microfiber and basalt microfiber), modified polymer emulsion 4.5% (polyvinyl acetate-butyl acrylate copolymer emulsion modified by introducing siloxane monomer), additive 1.8% (only early strength agent), nano-enhanced phase 1.4% (a compounded system of nano-calcium carbonate and nano-silicon dioxide), self-repairing microcapsule 2.8% (filled with a mixture of epoxy resin and urea-formaldehyde resin at a mass ratio of 1:1 inside); When prepared, the S1 aggregate pretreatment is stirred at a constant temperature of 60°C for 40 minutes; the S2 dry material mixing is stirred for 10 minutes; the S3 wet material preparation is ultrasonically dispersed for 40 minutes; the S4 microcapsule introduction is stirred for 15 minutes; the S5 spray forming is mixed by a double-shaft stirrer for 6 minutes, the spray pressure is 0.6MPa, the spray distance is 1.2m, and the layered spray thickness is 50mm; Example Four By mass percentage: cement 46% (ordinary Portland cement and aluminate cement are compounded at a mass ratio of 7.8:2.2), aggregate 54% (5mm-8mm and 8mm-10mm particle size particles are mixed at a mass ratio of 6:4, the surface of the aggregate is pretreated with a silane coupling agent, and the amount of the silane coupling agent is 0.4% of the mass of the aggregate), composite microfiber 1.6% (a mixture of polypropylene microfiber and basalt microfiber), modified polymer emulsion 3.8% (polyvinyl acetate-butyl acrylate copolymer emulsion, modified by introducing siloxane monomers), additive 1.2% (water reducing agent and early strength agent are mixed at a mass ratio of 3:2), nano-enhanced phase 1.1% (a compounded system of nano-calcium carbonate and nano-silicon dioxide), and self-repairing microcapsule 2.3% (filled with epoxy resin inside); When prepared, the S1 aggregate is pretreated at a constant temperature of 55°C for 35 minutes; the S2 dry materials are mixed and stirred for 8 minutes; the S3 wet materials are prepared and ultrasonically dispersed for 35 minutes; the S4 microcapsules are introduced and stirred for 12 minutes; and the S5 spray forming is mixed by a double-shaft stirrer for 5 minutes, the spray pressure is 0.5MPa, the spray distance is 1.1m, and the layered spray thickness is 45mm; Comparative example By mass percentage: cement 45% (only ordinary Portland cement, without aluminate cement compounding), aggregate 55% (only 5mm-8mm particle size particles, without silane coupling agent pretreatment), single polypropylene microfiber 1.5% (without basalt microfiber), unmodified polyvinyl acetate emulsion 4% (without the introduction of siloxane monomers), additive 1.5% (water reducing agent and early strength agent are mixed at a mass ratio of 1:1), no nano-enhanced phase, and no self-repairing microcapsule; When prepared, the S1 aggregate is not pretreated; the S2 dry materials are mixed and stirred for 7 minutes; the S3 wet materials are not ultrasonically dispersed; the S4 microcapsules are not introduced; and the S5 spray forming is mixed by a double-shaft stirrer for 4 minutes, the spray pressure is 0.5MPa, the spray distance is 1.0m, and the layered spray thickness is 40mm.

[0018] As described above, the present application provides a technical solution, a high-anti-cracking self-repairing spray concrete composition, comprising: cement 40%-50%, aggregate 50%-60%, composite microfiber 1%-2%, modified polymer emulsion 3%-5%, additive 1%-2%, nano-enhanced phase 0.5%-1.5%, and self-repairing microcapsule 2%-3%, the additive comprising at least one of water reducing agent and early strength agent, and the cement comprising at least one of Portland cement or slag Portland cement; The composite microfiber is a mixture of polypropylene microfiber and basalt microfiber, and the nano-enhanced phase is a compounded system of nano-calcium carbonate and nano-silicon dioxide; The cement is a composite cement system, which is compounded by ordinary Portland cement and aluminate cement at a mass ratio of 8:2-7:3, the aggregate is mixed by 5mm-8mm particle size particles and 8mm-10mm particle size particles at a mass ratio of 6:4, a left and right silane coupling agent pretreatment layer is arranged on the surface of the aggregate, and the pretreatment agent of the pretreatment layer accounts for 0.2%-0.5% of the mass of the aggregate; The modified polymer emulsion is a polyvinyl acetate-butyl acrylate copolymer emulsion, and is modified by introducing a siloxane monomer, the inside of the self-repairing microcapsule is filled with a repairing agent, and the repairing agent is at least one of an epoxy resin or a urea-formaldehyde resin.

[0019] Please refer to Figure 1 The application provides a preparation method of high-anti-crack self-repairing shotcrete composition, and the high-anti-crack self-repairing shotcrete composition comprises the following steps: S1 aggregate pretreatment: First, the 5mm-8mm and 8mm-10mm particle size aggregates are mixed at a mass ratio of 6:4, and 0.2%-0.5% of the silane coupling agent is added to the aggregate, and then constant temperature stirring is carried out at 50-60 DEG C for 30-40 minutes to form the surface modified aggregate; When the silane coupling agent is added to the aggregate, the silane coupling agent is first diluted with anhydrous ethanol and stirred until dissolved, and then uniformly applied to the surface of the aggregate in the form of atomized spraying, and the wet state of the surface of the aggregate is continuously monitored during the stirring process, and the specific implementation process of the above method is as follows: First, clean and dry aggregate is selected, and the particle size range is divided into two categories: one is smaller particle size particles, and the other is larger particle size particles. The two types of aggregate are mixed at a predetermined mass ratio, which is determined by multiple tests, and the purpose is to form a gradient grading structure. The smaller particle size particles can fill the voids between the larger particles, reducing the internal porosity of the concrete, while the larger particle size particles provide skeleton support, and the synergistic effect of the two can significantly improve the density and mechanical properties of the concrete; The silane coupling agent and anhydrous ethanol are mixed at a specific volume ratio, placed in a container with stirring function, and slowly stirred at room temperature until completely dissolved to form a uniform diluent. The diluted coupling agent is uniformly covered on the surface of the mixed aggregate in the form of fine mist droplets through a special atomizing spraying device. Atomizing spraying can ensure that the coupling agent contacts the aggregate in the form of small droplets, avoiding local excess or deficiency, and realizing uniform surface coating; The sprayed aggregate is transferred to a forced mixer with constant temperature control function, and the appropriate temperature range is maintained during the mixing process. The constant temperature environment can accelerate the chemical reaction between the silane coupling agent and the surface of the aggregate, promote the formation of chemical bonds between the active groups in the coupling agent molecules and the hydroxyl groups on the surface of the aggregate, and thus form a dense organic film layer on the surface of the aggregate. The stirring is carried out at medium speed to ensure that the aggregate is fully rolled during the stirring process, and the coupling agent is uniformly distributed on the surface of each aggregate; During the stirring process, the wetting state of the aggregate surface is continuously monitored through a transparent observation window or intermittent stop inspection. If it is found that some areas are dry or the coupling agent is aggregated, the spraying amount of the atomizing spraying device or the rotation direction of the mixer is immediately adjusted to ensure that all the aggregate surfaces remain moderately wet. This step aims to avoid interface defects caused by uneven distribution of the coupling agent and ensure the consistency of the modification effect; After constant temperature stirring for a certain period of time, a modified layer with reactivity is formed on the surface of the aggregate, at which point the stirring is stopped and the aggregate is discharged. The modified aggregate is in a uniform wet state, and there is no obvious liquid droplet residue on the surface. Through touch inspection, it can be felt that a smooth organic film layer is formed on the surface of the aggregate; through microscope observation, it can be seen that the microstructure of the aggregate surface is more dense, and the porosity is significantly reduced. The finally obtained surface modified aggregate has excellent interface bonding performance, which provides reliable guarantee for the subsequent compounding with the cement matrix; S2 dry material mixing: The ordinary Portland cement and the aluminate cement are compounded according to the mass ratio of 8:2-7:3, and the pretreated aggregate, polypropylene microfiber and basalt microfiber are added, and then stirred in the mixer for 5-10 minutes; The mixer adopts a step-by-step stirring process, which stirs at a low speed in the initial stage to preliminarily mix the cement and the aggregate, and increases the stirring speed after the fibers are uniformly dispersed. A sealing film cover is used outside the stirring bin during the stirring process, and the inner wall and bottom of the stirring bin are cleaned synchronously after the stirring is completed; S3 wet material preparation: The polyvinyl acetate-butyl acrylate copolymer emulsion and the siloxane monomer are mixed according to the mass ratio of 9:1, then the nano calcium carbonate and the nano silicon dioxide are added, and the modified polymer slurry is formed after ultrasonic dispersion for 30-40 minutes; When the polyvinyl acetate-butyl acrylate copolymer emulsion and the siloxane monomer are mixed, the polyvinyl acetate-butyl acrylate copolymer emulsion is first placed in a constant temperature container for preheating, and then the siloxane monomer is added after the emulsion flowability is stable. The specific implementation process of the above method is as follows: First, select polyvinyl acetate-butyl acrylate copolymer emulsion, which is transferred to the container with constant temperature control function, through water bath or electric heating method to maintain the appropriate temperature range. Preheating process continuously observe the emulsion state, when the emulsion viscosity significantly reduced, flow significantly improved, indicating that it has reached a stable state. This step is designed to eliminate the viscosity fluctuations that may occur during storage of emulsion, to ensure uniformity of subsequent mixing with siloxane monomer; After confirming the flow stability of the copolymer emulsion, the siloxane monomer is slowly added to the emulsion in a dropwise manner. Low-speed stirring (about 100-200 rpm) is used during the dropwise process to ensure uniform dispersion of the monomer in the emulsion system and to avoid gelation or stratification caused by excessive local concentration. The introduction of siloxane monomer can react with active groups in the copolymer emulsion to form a modified polymer with a three-dimensional network structure, thereby improving the bonding strength and water resistance of the emulsion; Select nano calcium carbonate and nano silicon dioxide powder and mix them in the predetermined mass ratio. To avoid agglomeration of nano materials, pre-dispersion treatment is needed: add the mixed powder to an aqueous solution containing a dispersant and stir it with a high-speed shearing machine (3000-5000 rpm) for 10-15 minutes to form a uniform nano suspension. This step can effectively break the van der Waals forces between nano particles, ensuring that they exist in a monodisperse state, which lays the foundation for subsequent uniform embedding in the polymer matrix; Slowly pour the pre-treated nano suspension into the modified polymer emulsion and start the ultrasonic dispersion device at the same time. Ultrasonic dispersion uses a combination of high frequency (20-40 kHz) and low power (100-300 W) to further break up nano particle agglomerates and promote their interface bonding with polymer molecules through cavitation and mechanical effects. During the dispersion process, the system state should be continuously observed. When the nano particles are uniformly distributed in the emulsion without sedimentation, it indicates that the dispersion effect meets the standard; After a certain period of ultrasonic dispersion, turn off the ultrasonic device and continue low-speed stirring for 5-10 minutes to stabilize the system. The modified polymer slurry obtained at this time should have the following characteristics: moderate viscosity (can be pumped smoothly), good flowability (no gel or stratification), and uniform distribution of nano particles (no agglomeration observed under a microscope). The final modified polymer slurry can effectively fill the internal pores of concrete and improve the toughness of the matrix through the bridging effect of nano materials, providing an ideal environment for uniform embedding of self-healing microcapsules; S4 microcapsule introduction: Add water reducing agent, early strength agent, and self-healing microcapsules to the dry mixture in sequence and stir for 8-15 minutes. When adding self-healing microcapsules, first dry them to remove surface-adsorbed water, and then add them to the dry mixture in a layered manner; S5 spray forming: The wet slurry body and the dry material mixture are mixed in a double-shaft mixer at 30-60 revolutions per minute for 2-6 minutes, then the spray pressure is adjusted to 0.4-0.6 MPa, the spray distance is 0.8-1.2 m, the layered spray thickness is 30-50 mm, and the spray is performed on the construction surface after the data adjustment is completed; the construction surface is pretreated before spray forming, and the floating dust, loose particles and oil stains on the construction surface are removed, then the construction surface is blown by high-pressure airflow, and for the positions with cracks or depressions, the repair material is filled and leveled in advance, and then the spray is performed after the repair material is dried and formed.

[0020] The application also provides a use of the high-anti-cracking self-repairing spray concrete composition in a construction engineering, and the construction engineering comprises one of a tunnel lining, an underground engineering and a structure reinforcement.

[0021] The scheme introduces a composite reinforcing system of polypropylene microfibers and basalt microfibers, and combines self-repairing microcapsules to form a multi-scale synergistic mechanism, a three-dimensional network structure is constructed in the concrete by the composite microfibers to effectively inhibit the initiation and expansion of cracks, the overall toughness of the material is improved through the interfacial adhesion of the fibers and the matrix, the self-repairing microcapsules can actively sense the stress change caused by crack expansion in a low-temperature environment, and timely rupture and release the repair agent to realize the rapid filling and curing of the cracks, and the synergistic effect of the two significantly reduces the damage accumulation rate of the concrete in the service process, not only delays the crack development through physical crack resistance, but also realizes the active healing of damage through chemical repair, thereby greatly prolonging the service life of the structure, and the nano-enhanced phase can improve the matrix density and mechanical properties by filling the material micro-pores and optimizing the interface transition zone structure, and provide a more stable action environment for the microfibers and the microcapsules, and under the synergistic action of the three, the material not only has a significantly enhanced crack resistance, but also has a synchronous improved self-repairing efficiency and durability, thereby effectively reducing the engineering maintenance cost.

[0022] The scheme ensures that the repair agent in the self-repairing microcapsule is well combined with the concrete matrix, the mechanical properties of the repaired area can be restored close to those of the original matrix, the composite microfibers complement the properties of the two fibers to inhibit macroscopic cracks and provide support for the uniform distribution of the microcapsules to avoid affecting the repair effect due to local aggregation, and the nano-enhanced phase strengthens the interfacial adhesion of the cement matrix and the microfibers and the microcapsules by virtue of the nano-scale effect, reduces the interface defects, and enables the repair agent to more uniformly penetrate and diffuse during the healing process, and this multi-component synergistic mechanism not only enables the material to have excellent crack resistance and self-repairing ability during construction and use, but also can adapt to the diversified needs of the material properties in complex engineering environments, thereby providing a reliable guarantee for the long-term stability of various building structures.

[0023] It has to be noted that, in the present document, the terms "first", "second", etc. merely serve to identify different entities or actions from each other, without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprising", "containing", or any other similar term are intended to encompass non-exclusive inclusions, such that a process, method, article, or apparatus that comprises a list of elements does not necessarily include only those elements, but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0024] While embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, combinations, and variations can be undertaken by those skilled in the art without departing from the spirit and scope of the present application, which is defined by the appended claims and their equivalents.

Claims

1. A highly crack-resistant self-repairing shotcrete composition, characterized in that: The highly crack-resistant self-repairing sprayed concrete composition comprises, in percentage by mass: 40%-50% cement, 50%-60% aggregate, 1%-2% composite microfiber, 3%-5% modified polymer emulsion, 1%-2% additive, 0.5%-1.5% nano-reinforcement phase and 2%-3% self-repairing microcapsule, wherein the additive comprises at least one of a water reducer and an early strength agent, and the cement comprises at least one of Portland cement or Portland slag cement; The composite microfiber is a mixture of polypropylene microfiber and basalt microfiber, and the nano-reinforcement phase is a compound system of nano-calcium carbonate and nano-silicon dioxide.

2. A highly crack-resistant self-repairing sprayed concrete composition according to claim 1, characterized in that: The cement is a composite cement system, which is compounded by ordinary Portland cement and aluminate cement in a mass ratio of 8:2-7:

3. The aggregate adopts a gradient grading design, which is a mixture of 5mm-8mm particle size particles and 8mm-10mm particle size particles in a mass ratio of 6:

4. The surface of the aggregate is provided with left and right silane coupling agent pretreatment layers, and the pretreatment agent dosage of the pretreatment layers is 0.2%-0.5% of the aggregate mass.

3. The highly crack-resistant self-repairing sprayed concrete composition according to claim 1, characterized in that: The modified polymer emulsion is a polyvinyl acetate-butyl acrylate copolymer emulsion, which is modified by introducing a siloxane monomer. The interior of the self-repairing microcapsule is filled with a repair agent, which is at least one of an epoxy resin or a urea-formaldehyde resin.

4. A method for preparing a highly crack-resistant self-repairing sprayed concrete composition, based on the highly crack-resistant self-repairing sprayed concrete composition according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1 Aggregate Pretreatment: First, aggregates with particle sizes of 5mm-8mm and 8mm-10mm are mixed in a mass ratio of 6:4, and a silane coupling agent is added at a mass ratio of 0.2%-0.5% of the aggregate mass. Then, the mixture is stirred at a constant temperature of 50-60°C for 30-40 minutes to form a surface-modified aggregate. S2 dry material mixing: Ordinary Portland cement and aluminate cement are compounded in a mass ratio of 8:2-7:3, and pretreated aggregate, polypropylene microfiber and basalt microfiber are added, followed by stirring in a mixer for 5-10 minutes; S3 wet material preparation: The polyvinyl acetate-butyl acrylate copolymer emulsion and the siloxane monomer are mixed in a mass ratio of 9:1, and then nano-calcium carbonate and nano-silicon dioxide are added, and ultrasonic dispersion is performed for 30-40 minutes to form a modified polymer slurry; S4 microcapsules are introduced: Add water reducer, early strength agent and self-repairing microcapsules to the dry material mixture in sequence and stir for 8-15 minutes; S5 Injection Molding: Mix the wet material slurry and dry material mixture in a twin-shaft mixer at 30-60 revolutions per minute for 2-6 minutes, then adjust the spraying pressure to 0.4MPa-0.6MPa, the spraying distance to 0.8m-1.2m, and the layered spraying thickness to 30mm-50mm. After the data adjustment is completed, spray it onto the construction surface.

5. The method for preparing a highly crack-resistant self-repairing sprayed concrete composition according to claim 4, characterized in that: In step S1, when the silane coupling agent is added to the aggregate, it is first diluted with anhydrous ethanol and stirred until dissolved, and then evenly applied to the surface of the aggregate by atomization spraying, while continuously monitoring the wetness of the aggregate surface during the stirring process.

6. The method for preparing a highly crack-resistant self-repairing sprayed concrete composition according to claim 4, characterized in that: In step S2, the mixer adopts a stepped stirring process, wherein the cement and aggregate are initially mixed at a low stirring rate, and the stirring rate is increased after the fibers are evenly dispersed. At the same time, a sealing film cover is used to cover the outside of the stirring chamber during the stirring process, and the inner wall and bottom of the stirring chamber are cleaned synchronously after the stirring is completed.

7. The method for preparing a highly crack-resistant self-repairing sprayed concrete composition according to claim 4, characterized in that: In step S3, when the polyvinyl acetate-butyl acrylate copolymer emulsion is mixed with the siloxane monomer, the polyvinyl acetate-butyl acrylate copolymer emulsion is first placed in a constant temperature container for preheating, and the siloxane monomer is added after the fluidity of the emulsion is stabilized. At the same time, in step S4, when the self-repairing microcapsules are added, they are first dried to remove surface adsorbed moisture and then added to the dry material mixture in a layered manner.

8. The method for preparing a highly crack-resistant self-repairing sprayed concrete composition according to claim 4, characterized in that: In step S5, the construction surface is pre-treated before injection molding to remove dust, loose particles and oil stains on the construction surface, and then the construction surface is blown with high-pressure airflow. For areas with cracks or depressions, they are filled and leveled with repair materials in advance, and then injection is performed after the repair materials are dried and formed.

9. Use of the highly crack-resistant self-repairing sprayed concrete composition according to any one of claims 1 to 3 in construction engineering, characterized in that: The construction works include one of tunnel lining, underground works and structural reinforcement.

10. The use according to claim 9, characterized in that: The composition further comprises an anti-corrosion additive, which is zinc phosphate and is added in an amount of 0.5% to 1.5%.

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