Phosphate composite material for repairing concrete in extremely cold environment and preparation method thereof

Abstract

The application discloses a phosphate composite material for concrete repair in an extremely cold environment and a preparation method thereof, and belongs to the technical field of concrete repair materials. The composite material comprises a phosphate cementing material, a double-network gel carrier, a slow-release phosphate component, a temperature-sensing deformation microsphere-carbon layer composite, a latent heat release type low-temperature accelerator, a nano-enhancing component, a coagulation regulator and water. Through the multiple effects of double-network gel anchoring, temperature response release of the slow-release component, temperature-sensing deformation anti-freezing and latent heat release low-temperature solidification, the phosphate repair material can realize controllable low-temperature solidification, high toughness, excellent anti-freezing and thawing performance and interface bonding performance improvement in an extremely cold environment.

Description

Technical Field

[0001] This invention belongs to the field of concrete repair materials technology, specifically a phosphate composite material for concrete repair in extremely cold environments and its preparation method. Background Technology

[0002] In high-altitude and frigid regions of Northeast and Northwest my country, the Qinghai-Tibet Plateau, and other special engineering scenarios such as polar scientific research projects, cryogenic storage and transportation facilities, and cold-region wind power foundations, a large number of concrete structures are subjected to long-term service in extremely cold environments. These environments are generally characterized by persistent temperatures below -30°C, extreme minimum temperatures reaching -60°C, large diurnal temperature variations, frequent freeze-thaw cycles, and severe salt-frost erosion. Concrete structures in such environments are highly susceptible to surface spalling, matrix cracking, crumbling and powdering, and steel reinforcement corrosion, significantly shortening their service life and posing serious structural safety hazards. Repairing concrete structures in extremely cold environments places extremely high demands on the low-temperature curing performance, early mechanical properties, freeze-thaw resistance, interfacial bonding performance, and low-temperature toughness of repair materials, representing a core technical challenge that urgently needs to be addressed in the construction and operation and maintenance of projects in cold regions.

[0003] Magnesium phosphate cement, as a novel inorganic cementitious material, possesses advantages such as rapid hardening and early strength, good bonding performance, and the ability to harden at low temperatures, attracting widespread attention in the field of rapid concrete repair. For example, Chinese patent application CN112321322A discloses an interface agent for repairing frost-damaged concrete, its preparation, and repair method. This interface agent, prepared from recalcined magnesium oxide, phosphate, borax, and other raw materials, exhibits characteristics such as early strength, high bond strength, and low-temperature hydration, making it suitable for interface treatment and rapid repair of frost-damaged concrete in low-temperature regions. Another example is Chinese patent application CN119041258A, which discloses a rapid concrete repair construction method suitable for extremely cold environments. By applying an interface agent with phase change heat storage function to the surface of the concrete substrate to be repaired, the temperature at the interface between the magnesium phosphate cement repair material and the concrete substrate can be maintained above 0℃ in the early stages. While magnesium phosphate cement can still hydrate normally in sub-zero temperatures, its hydration reaction rate significantly decreases and strength development slows down in extremely cold environments below -20℃. Existing technologies also propose using crushed ice or snow to mix the mixture, utilizing the heat of hydration of magnesium phosphate cement itself to melt the ice and snow to achieve a hydration reaction at low temperatures.

[0004] However, the existing technologies still have the following shortcomings: First, most existing technologies are designed for low-temperature environments of -5℃ to -15℃. For extremely cold environments below -30℃, the heat of hydration of magnesium phosphate cement itself is insufficient to maintain an effective hydration temperature. Moreover, relying solely on the heat of hydration for temperature rise results in rapid heat loss and uneven temperature distribution, leading to uncontrollable curing rates, slow early strength development, or even failure to cure. Second, the phase change heat storage solutions in existing technologies are limited to the interface agent level, only ensuring temperature at the interface between the repair material and the concrete substrate, without modifying the repair material itself. This fails to address the curing and performance issues of the repair material in extremely cold environments. Third, existing phosphate repair materials exhibit high brittleness after curing, insufficient flexural and impact resistance, high strength loss after multiple freeze-thaw cycles, and insufficient interfacial adhesion with the concrete matrix at low temperatures. These shortcomings cannot meet the engineering requirements for rapid repair and long-term stable service of concrete structures in extremely cold environments. Therefore, there is an urgent need to develop a phosphate composite material that can achieve controllable low-temperature curing in extremely cold environments, while also possessing high toughness and excellent freeze-thaw resistance. Summary of the Invention

[0005] The purpose of this invention is to provide a phosphate composite material for concrete repair in extremely cold environments and its preparation method. Through the multiple effects of dual-network gel anchoring, temperature-responsive release of slow-release components, temperature-sensitive deformation antifreeze and latent heat release low-temperature curing, it solves the technical problems of uncontrollable curing rate, slow early strength development, insufficient toughness and poor freeze-thaw resistance of phosphate repair materials in extremely cold environments.

[0006] To address the aforementioned challenges, the present invention provides the following technical solution: A phosphate composite material for concrete repair in extremely cold environments, comprising the following components by weight: 40-65 parts of phosphate gelling material, 15-30 parts of double-network gel carrier, 2-8 parts of latent heat release type low temperature accelerator, 5-15 parts of nano-reinforcing component, 0.5-3 parts of coagulation regulator, and 5-12 parts of water; The dual-network gel carrier is a polysaccharide-polymer dual-network gel structure loaded with a sustained-release phosphate component and a temperature-sensitive deformable microsphere-carbon layer composite; the sustained-release phosphate component is obtained by coating an aluminum dihydrogen phosphate solution with a natural polysaccharide-calcium ion crosslinking system; the temperature-sensitive deformable microsphere-carbon layer composite is obtained by grafting temperature-sensitive deformable microspheres onto the surface of carbonaceous sheets using a coupling agent. The dual-network gel carrier uses a natural polysaccharide solution as the gel matrix, an organic acid calcium solution as the crosslinking agent, and a synthetic polymer as the film-forming aid. Through the crosslinking reaction between the natural polysaccharide molecular chains and calcium ions during the calcium ion crosslinking and curing process, the entanglement between the synthetic polymer chains and the natural polysaccharide network, and the physical embedding effect during the gel three-dimensional network formation process, the slow-release phosphate component and the temperature-sensitive deformable microsphere-carbon layer composite are in situ anchored within the polysaccharide-polymer dual-network gel three-dimensional network structure. Preferably, the phosphate cementitious material is composed of calcined magnesium oxide and ammonium dihydrogen phosphate in a mass ratio of (1-5):1; the particle size of the calcined magnesium oxide is 200-300 mesh. Preferably, the natural polysaccharide is one or more of sodium alginate, carrageenan, and pectin; the sodium alginate has a purity of 90-95%; the carrageenan is selected from k-type carrageenan; and the pectin is pectin extracted from one of the following fruits: orange, bayberry, red dragon fruit, blueberry, watermelon, banana, and green grape. Preferably, the organic acid calcium is one or more selected from L-calcium lactate, calcium gluconate, and calcium citrate; Preferably, the synthetic polymer is polyvinyl alcohol, with a weight-average molecular weight of 30,000-120,000.

[0007] Preferably, the preparation method of the dual-network gel carrier is as follows: A pore-forming agent, a 4-5% (w / w) natural polysaccharide solution, a sustained-release phosphate component, a temperature-sensitive deformable microsphere-carbon layer composite, and a 10-12% (w / w) synthetic polymer solution are added to a reaction vessel and stirred for 20-30 minutes at 40-50°C and 500-600 r / min. Then, a 10-12% (w / w) organic acid calcium solution is added, and the mixture is poured into a mold and cured for 20-30 minutes to obtain a gel carrier loaded with a sustained-release phosphate component and temperature-sensitive deformable microspheres. The carbon layer composite dual-network gel carrier: During the above-mentioned curing process, calcium ions provided by organic acid calcium undergo cross-linking reaction with the active groups on the natural polysaccharide molecular chains to construct a three-dimensional gel network framework. The synthesized polymer chains and the natural polysaccharide network interweave and entangle to form a dual-network structure. The slow-release phosphate component and the temperature-sensitive deformable microsphere-carbon layer composite are physically embedded in the network pores during the gel network forming process, and are in-situ anchored in the dual-network gel structure through the chemical fixation of the calcium ion cross-linking network and the entanglement and locking effect of the polymer chains.

[0008] Preferably, the pore-forming aid is obtained by mixing an amphoteric surfactant and a sulfonate surfactant in a mass ratio of (5-6):(3-4); the amphoteric surfactant is one or more of lauramidopropyl betaine, cocamidopropyl betaine, and oleamidopropyl dimethyl betaine; the sulfonate surfactant is sodium C14-16 olefin sulfonate; the synthetic polymer solution is a 10-12% (w / w) polyvinyl alcohol aqueous solution, obtained by adding polyvinyl alcohol to water, heating to 70-95°C and stirring until completely dissolved; Preferably, the ratio of the amount of the pore-forming aid, natural polysaccharide solution, slow-release phosphate component, temperature-sensitive deformable microsphere-carbon layer composite, synthetic polymer solution and organic acid calcium solution is 8-10g:50-70mL:16-18g:20-30g:250-260mL:20-30mL.

[0009] Preferably, the preparation method of the sustained-release phosphate component is as follows: 40-60% aluminum dihydrogen phosphate solution, natural polysaccharide, deionized water, and anhydrous ethanol are added to a reaction vessel and stirred for 10-30 minutes at 20-25°C and 500-600 r / min. Then, a calcium salt solution with a mass fraction of 0.4-0.6% is added, and stirring continues for 1-2 hours. The mixture is filtered, and the product is washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product is then vacuum dried at 60-70°C and -0.08 MPa to -0.1 MPa for 1-2 hours to obtain the sustained-release phosphate component. Preferably, the calcium salt is one or more of calcium chloride and calcium formate; Preferably, the ratio of aluminum dihydrogen phosphate solution, natural polysaccharide, deionized water, anhydrous ethanol and calcium salt solution is 30-36 mL: 1.5-1.8 g: 80-100 mL: 190-200 mL: 30-40 mL.

[0010] Preferably, the preparation method of the temperature-sensitive deformation microsphere-carbon layer composite is as follows: anhydrous ethanol and deionized water are added to a reaction vessel, an alkali solution is added to adjust the pH value to 9-10, modified temperature-sensitive deformation microspheres are added, and the mixture is stirred for 30-50 min at 30-40℃ and 500-600 r / min. Then, carbonaceous sheet material is added, and the mixture is stirred for 2-3 h. The mixture is filtered, and the product is washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product is then vacuum dried at 60-70℃ and -0.08 MPa to -0.1 MPa for 1-2 h to obtain the temperature-sensitive deformation microsphere-carbon layer composite. Preferably, the alkaline solution is a sodium hydroxide solution and / or a potassium hydroxide solution with a mass fraction of 1-10%; Preferably, the carbonaceous sheet material is graphene and / or expanded graphite; the graphene sheet diameter is 1-15 μm and the number of layers is 2-10; the expanded graphite particle size is 50-200 mesh and the expansion ratio is 150-350 times. Preferably, the ratio of anhydrous ethanol, deionized water, modified temperature-sensitive deformable microspheres, and carbonaceous sheet material is 900-1000mL:100-120mL:5-8g:50-60g.

[0011] Preferably, the modified temperature-sensitive deformation microspheres are prepared as follows: temperature-sensitive deformation microspheres and anhydrous ethanol are added to a reaction vessel, and then stirred for 30-50 min at 30-40℃ and 500-600 r / min. Then, an organic base and a condensation reagent are added, and stirring is continued for 30-40 min. A silane coupling agent is added, and stirring is continued for 3-5 h. The mixture is then filtered, and the product is washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product is then vacuum dried at 60-70℃ and -0.08 MPa to -0.1 MPa for 1-2 h to obtain the modified temperature-sensitive deformation microspheres. Preferably, the organic base is one or more selected from N,N-diisopropylethylamine, triethylamine, tributylamine, 4-dimethylaminopyridine, 1,8-diazabicycloundec-7-ene, and tetramethylammonium hydroxide; Preferably, the condensing agent is one or more of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate, N,N'-diisopropylcarbodiimide, 1-hydroxybenzotriazole, 1-propylphosphonic anhydride, dicyclohexylcarbodiimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; Preferably, the silane coupling agent is one or more selected from γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane; Preferably, the ratio of the amount of the temperature-sensitive deformation microspheres, anhydrous ethanol, organic base, condensation reagent and silane coupling agent is 45-48g:800-900mL:15-17g:10-13g:6-8g. The present invention also provides a method for preparing the temperature-sensitive deformation microspheres: S1. Add 80-90g sodium chloride, 25-30g magnesium hydroxide, and 5-10g magnesium chloride to 800-900mL of deionized water, and stir for 30-50min at 30-40℃ and 500-600r / min to obtain an aqueous mixture. S2. Mix 150-160g acrylonitrile, 60-62g methacrylonitrile, 20-22g isopentane, 50-52g isooctane, 1-2g ethylene glycol dimethacrylate, 1-2g diallyl carbonate, 9-12g naphthenic oil and 1-2g azobisisobutyronitrile until homogeneous to obtain an oil phase mixture; S3. The aqueous phase mixture and the oil phase mixture are mixed in a sealed pressure-resistant reactor at a mass ratio of 10:1 and dispersed at high speed at 1500-1600 r / min for 10-12 min. Then, under inert gas protection, the mixture is stirred and polymerized at 60-70℃, 80-90 r / min and 0.5-0.8 MPa for 20-25 h.

[0012] After the polymerization reaction in step S4 and S3 is completed, the reaction solution is filtered, and the filter cake is washed 2-4 times with deionized water and anhydrous ethanol, respectively. It is then dried under vacuum at 60-70℃ and -0.08MPa to -0.1MPa for 1-2 hours to obtain temperature-sensitive deformation microspheres. Preferably, the inert gas is at least one of nitrogen, argon, and helium.

[0013] Preferably, the latent heat release type low temperature promoter is a phase change energy storage microcapsule with alkane as core material and amino resin as wall material, the phase change temperature is -30 to -20℃, the core-to-wall ratio is (2-4):1, and the average particle size of the microcapsule is 4-10μm. Preferably, the alkane is one or more selected from n-decane and n-undecane; Preferably, the amino resin is one or more of melamine-formaldehyde resin, butylated urea-formaldehyde resin, methylated urea-formaldehyde resin, hexamethoxymethyl melamine resin, and polymerizable high-imino high-methylated melamine resin.

[0014] Preferably, the nano-reinforcing component is one or more of nano-silica, nano-aluminum hydroxide, and nano-zinc oxide, with a particle size of 30-80 nm; preferably, the coagulation regulator is borax and / or boric acid.

[0015] This invention also provides a method for preparing the phosphate composite material for repairing concrete in extremely cold environments, comprising the following steps: A dual-network gel carrier and nano-reinforcing components were added to a phosphate gelling material and sheared and dispersed at 400-600 r / min for 15-30 min to obtain a mixed powder. The dual-network gel carrier was vacuum dried to constant weight before being added, and the phosphate gelling material was a dry powder. The above mixing process was carried out in a closed, dry environment. After mixing, the resulting mixed powder was stored in a moisture-proof, sealed package. The vacuum drying was performed at 60-70℃ and -0.08 MPa to -0.1 MPa. A latent heat release type low temperature promoter and a coagulation regulator are added to water. The latent heat release type low temperature promoter is stirred and dispersed at 300-500 r / min for 10-20 min, and the coagulation regulator is stirred and dissolved at 300-500 r / min for 10-20 min to obtain a mixture. The mixture is added to the powder mixture and stirred at 200-400 r / min for 3-5 min to obtain a phosphate composite material for repairing concrete in extremely cold environments.

[0016] The nano-reinforcing component is ultrasonically dispersed in anhydrous ethanol for 15-30 minutes before use.

[0017] Beneficial technical effects of the present invention: (1) In this invention, a slow-release phosphate component and a temperature-sensitive deformable microsphere-carbon layer composite are anchored in a natural polysaccharide-synthetic polymer three-dimensional network through a dual-network gel carrier. The natural polysaccharide molecular chains in this three-dimensional network structure contain a large number of active functional groups such as hydroxyl and carboxyl groups, which can chemically bond and hydrogen bond with silanol groups, calcium ions and other substances on the surface of the concrete matrix. At the same time, the porous structure of the gel network is conducive to the mechanical interlocking between the repair material and the matrix, thereby significantly improving the interfacial bonding performance between the repair material and the concrete matrix, so that the bonding strength of the composite material reaches 2.5-3.2 MPa after curing at -30℃ for 28 days. (2) The aluminum dihydrogen phosphate solution was coated by the natural polysaccharide-calcium ion cross-linking system. Under extremely cold conditions, the natural polysaccharide-calcium ion cross-linking network produced microcracks due to low temperature contraction. At the same time, the volume expansion caused by water molecules freezing at low temperature further destroyed the compactness of the cross-linking network, so that the coated aluminum dihydrogen phosphate could be released in a temperature-responsive manner. The released aluminum dihydrogen phosphate not only provides additional phosphate ions, promoting the hydration of unreacted magnesium oxide and increasing the formation of hydration products (such as struvite), but also participates in independent hydration reactions, generating Al(OH)3 gel and Al(PO4)·2H2O gel. This helps to form a denser microstructure, enabling the composite material to still cure normally at -60℃ (initial setting 18-22 min, final setting 32-40 min), with a 28-day compressive strength of 58.5-66.5 MPa and a flexural strength of 12.2-14.0 MPa. Furthermore, at -30℃, the 28-day compressive strength can reach 68.5-76.5 MPa and the flexural strength can reach 14.5-16.2 MPa, achieving excellent mechanical properties over a wide temperature range from -60℃ to -30℃. (3) This invention covalently grafts temperature-sensitive deformation microspheres onto the surface of carbonaceous sheets via a coupling agent-mediated amidation reaction, constructing a composite system with reversible volume shrinkage-expansion characteristics. The low-boiling-point foaming agents such as isopentane and isooctane in the temperature-sensitive deformation microspheres shrink in volume at low temperatures and expand in volume when the temperature rises. This reversible volume change can effectively buffer the internal stress generated by the expansion of ice crystals during freeze-thaw cycles. At the same time, the high thermal conductivity of the carbonaceous sheets helps to uniformly disperse thermal stress. The synergistic effect of the two significantly improves the freeze-thaw resistance of the material. After 300 freeze-thaw cycles, the mass loss rate is only 1.2-1.8%, the relative dynamic elastic modulus remains at 92.5-95.2%, and the fracture toughness KIC reaches 2.78-3.12 MPa·m. 1 / 2 ; (4) The present invention introduces phase change energy storage microcapsules with a phase change temperature of -30℃ to -20℃, which matches the temperature of extremely cold environments. In service environments of -30℃ to -60℃, the phase change exothermic reaction provides in-situ local thermal protection for the hydration reaction of phosphate cementitious materials, ensuring the controllable curing of the repair material at extremely low temperatures. Moreover, the early compressive strength can reach 12.5-15.8MPa in 2 hours, meeting the engineering requirements for rapid repair in extremely cold environments. The composite material of the present invention has a storage stability of 8.5-10.1 months. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To enable those skilled in the art to better understand the present application, the technical solution of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0020] It should be noted that the term "comprising" in the specification and claims of this application is intended to cover a non-exclusive inclusion. For example, a method comprising a series of steps is not necessarily limited to those explicitly listed, but may include other steps not explicitly listed or inherent to these methods. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. The present application will now be described in detail with reference to embodiments.

[0021] Unless otherwise specified, all materials and reagents used in the embodiments and comparative examples of this invention are commercially available.

[0022] Example 1

[0023] This embodiment provides a phosphate composite material for concrete repair in extremely cold environments, comprising the following components by weight: 45 parts of phosphate gelling material, 18 parts of double-network gel carrier (the carrier is loaded with slow-release phosphate components and temperature-sensitive deformation microsphere-carbon layer composite), 3 parts of latent heat release low temperature accelerator, 8 parts of nano silica reinforcing component, 1.2 parts of borax coagulation regulator, and 8 parts of water.

[0024] In this embodiment, the phosphate cementitious material is composed of calcined magnesium oxide and ammonium dihydrogen phosphate in a mass ratio of 2.5:1.

[0025] The preparation method of phosphate composite material for concrete repair in extremely cold environments in this embodiment includes the following steps: S1: Preparation of temperature-sensitive deformation microspheres. 85g sodium chloride, 27.5g magnesium hydroxide, 7.5g magnesium chloride, and 850mL deionized water were added to a reaction vessel and stirred for 40min at 35℃ and 550r / min to obtain an aqueous phase mixture. 155g acrylonitrile, 61g methacrylonitrile, 21g isopentane, 51g isooctane, 1.5g ethylene glycol dimethacrylate, 1.5g diallyl carbonate, 10.5g naphthenic oil, and 1.5g azobisisobutyronitrile were added to the reaction vessel and stirred until homogeneous to obtain an oil phase mixture. The aqueous phase mixture and the oil phase mixture were added to the reactor at a mass ratio of 10:1 and stirred evenly. The mixture was dispersed at a high speed of 1550 r / min for 11 min. Under nitrogen protection, the mixture was stirred and polymerized for 22.5 h at a temperature of 65 °C, a rotation speed of 85 r / min, and a pressure of 0.65 MPa. The mixture was filtered, and the filter cake was washed three times with deionized water and three times with anhydrous ethanol. The mixture was then vacuum dried at 65 °C for 1.5 h to obtain temperature-sensitive deformation microspheres.

[0026] S2: Preparation of modified temperature-sensitive deformation microspheres. 46.5 g of temperature-sensitive deformation microspheres and 850 mL of anhydrous ethanol were added to a reaction vessel and stirred for 40 min at 35 °C and 550 r / min. Then, 16 g of N,N-diisopropylethylamine and 11.5 g of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate were added, and stirring continued for 35 min. Next, 7 g of γ-aminopropyltriethoxysilane was added, and stirring continued for 4 h. The mixture was filtered, and the product was washed three times each with deionized water and anhydrous ethanol, and then dried under vacuum at 65 °C for 1.5 h to obtain the modified temperature-sensitive deformation microspheres.

[0027] S3: Preparation of temperature-sensitive deformation microsphere-carbon layer composite. 950 mL of anhydrous ethanol and 110 mL of deionized water were added to a sealed, pressure-resistant reactor. A 3% sodium hydroxide solution was added to adjust the pH to 9.5. Then, 6.5 g of modified temperature-sensitive deformation microspheres were added, and the mixture was stirred at 35 °C and 550 r / min for 40 min. Next, 55 g of carbonaceous sheet material (graphene, 8 μm in diameter, 6 layers) was added, and stirring continued for 2.5 h. The mixture was filtered, and the product was washed three times each with deionized water and anhydrous ethanol, and then vacuum dried at 65 °C for 1.5 h to obtain the temperature-sensitive deformation microsphere-carbon layer composite.

[0028] S4: Preparation of sustained-release phosphate component. 33 mL of 50% aluminum dihydrogen phosphate solution, 1.65 g of natural polysaccharide (sodium alginate), 90 mL of deionized water, and 195 mL of anhydrous ethanol were added to a reaction vessel and stirred for 20 min at 22.5 °C and 550 r / min. Then, 35 mL of 0.5% calcium chloride solution was added, and stirring continued for 1.5 h. After filtration, the product was washed three times each with deionized water and anhydrous ethanol, and dried under vacuum (-0.09 MPa) at 65 °C for 1.5 h to obtain the sustained-release phosphate component.

[0029] S5: Preparation of a dual-network gel carrier. 5.5 g of lauramidopropyl betaine and 3.5 g of C16 olefin sodium sulfonate were stirred until homogeneous to obtain a pore-forming agent. 9 g of the pore-forming agent, 60 mL of a 4.5% sodium alginate solution, 17 g of a sustained-release phosphate component, 25 g of a temperature-sensitive deformable microsphere-carbon layer composite, and 255 mL of an 11% synthetic polymer (polyvinyl alcohol, weight average molecular weight 80,000) solution were added to a reaction vessel and stirred for 25 min at 45℃ and 550 r / min. Then, 25 mL of an 11% L-calcium lactate solution was added, and the mixture was poured into a mold and cured for 25 min to obtain a dual-network gel carrier loaded with a sustained-release phosphate component and a temperature-sensitive deformable microsphere-carbon layer composite.

[0030] S6: Preparation of composite materials. 18 parts of the above-mentioned dual-network gel carrier and 8 parts of nano-silica reinforcement components with a particle size of 50 nm (the nano-silica was ultrasonically dispersed in anhydrous ethanol for 20 min before use) were added to 45 parts of phosphate cementitious material. The mixture was sheared and dispersed at 500 r / min for 20 min in a sealed environment to obtain a mixed powder. The obtained mixed powder was stored in a moisture-proof sealed package. 3 parts of a latent heat release type low-temperature accelerator (n-decane@melamine-formaldehyde resin phase change energy storage microcapsules, phase change temperature -25℃, core-to-wall ratio 3:1, average particle size 5 μm) and 1.2 parts of borax were added to 8 parts of water. The latent heat release type low-temperature accelerator was stirred and dispersed at 400 r / min for 15 min, and the borax was stirred and dissolved at 400 r / min for 15 min to obtain a mixture. The mixture was added to the mixed powder and stirred at 300 r / min for 4 min to obtain a phosphate composite material for concrete repair in extremely cold environments.

[0031] Example 2

[0032] This embodiment provides a phosphate composite material for concrete repair in extremely cold environments, comprising the following components by weight: The mixture consisted of 55 parts of phosphate gelling material, 22 parts of dual-network gel carrier (loaded with slow-release phosphate components and temperature-sensitive deformation microsphere-carbon layer composite), 5 parts of latent heat release low-temperature accelerator, 10 parts of nano-silica reinforcing component, 1.8 parts of borax coagulation regulator, and 10 parts of water.

[0033] In this embodiment, the phosphate cementitious material is composed of calcined magnesium oxide and ammonium dihydrogen phosphate in a mass ratio of 3:1.

[0034] The preparation method of this embodiment is basically the same as that of Example 1. The difference is that the weight of each component is adjusted according to the ratio of this embodiment, and the amount of raw materials used in each step is adjusted accordingly.

[0035] Example 3

[0036] This embodiment provides a phosphate composite material for concrete repair in extremely cold environments, comprising the following components by weight: The mixture consisted of 62 parts of phosphate gelling material, 28 parts of dual-network gel carrier (loaded with slow-release phosphate components and temperature-sensitive deformation microsphere-carbon layer composite), 7 parts of latent heat release low-temperature accelerator, 14 parts of nano-silica reinforcing component, 2.8 parts of borax coagulation regulator, and 12 parts of water.

[0037] In this embodiment, the phosphate cementitious material is composed of calcined magnesium oxide and ammonium dihydrogen phosphate in a mass ratio of 3.8:1.

[0038] The preparation method of this embodiment is basically the same as that of Example 1. The difference is that the weight of each component is adjusted according to the ratio of this embodiment, and the amount of raw materials used in each step is adjusted accordingly.

[0039] Comparative Example 1 Based on Example 1, the temperature-sensitive deformation microsphere-carbon layer composite in step S5 was replaced with the temperature-sensitive deformation microspheres prepared in step S1, that is, no carbon sheet material was added, and the remaining steps were the same as in Example 1, to prepare a phosphate composite material.

[0040] Comparative Example 2 Based on Example 1, the temperature-sensitive deformation microsphere-carbon layer composite in step S5 was replaced with the raw material carbon sheet material (graphene) in step S3, that is, the temperature-sensitive deformation microspheres were not added, and the remaining steps were the same as in Example 1, to prepare a phosphate composite material.

[0041] Comparative Example 3 Based on Example 1, the dual-network gel carrier in step S6 was replaced with a physical mixture of slow-release phosphate component and temperature-sensitive deformable microsphere-carbon layer composite in step S5 at a mass ratio of 17:25. That is, the dual-network gel structure formed by natural polysaccharides and synthetic polymers was not added. The remaining steps were the same as in Example 1 to prepare the phosphate composite material.

[0042] Comparative Example 4 Based on Example 1, the slow-release phosphate component prepared in step S4 was replaced with the same mass of uncoated aluminum dihydrogen phosphate solution (i.e., the aluminum dihydrogen phosphate solution was not coated with the natural polysaccharide-calcium ion crosslinking system). The remaining steps were consistent with Example 1 to prepare a phosphate composite material. Uncoated aluminum dihydrogen phosphate dissolves directly in the mixing water, and its release rate is not temperature-controlled. At low temperatures, the release is too rapid, leading to an overly vigorous hydration reaction, significantly shortened setting time, and concentrated early hydration heat release, which is detrimental to the controllable adjustment of the curing rate under extremely cold conditions.

[0043] Comparative Example 5 Based on Example 1, without adding the latent heat release type low temperature accelerator in step S6, the remaining steps are consistent with Example 1 to prepare a phosphate composite material.

[0044] Performance testing Performance tests were conducted on Examples 1-3 and Comparative Examples 1-5 according to the following standards and methods: Setting time test: The setting time was determined according to GB / T1346-2024 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". Tests were conducted at low temperatures of -30℃, -45℃, and -60℃, using a Vicat apparatus to determine the initial and final setting times. The low-temperature environment was controlled using a programmable temperature and humidity chamber. Before the test, all raw materials and testing equipment were placed at a constant temperature in the corresponding low-temperature environment for 24 hours to ensure that the material temperature was consistent with the test environment. The results are shown in Table 1.

[0045] Compressive and flexural strength tests were conducted according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The specimens were 40mm × 40mm × 160mm in size and cured at -30℃, -45℃, and -60℃ for 2h, 12h, 24h, 3d, 7d, and 28d respectively before measuring compressive and flexural strength. Low-temperature curing was controlled using a programmable constant temperature and humidity chamber. Compressive strength testing was performed using a computer-controlled electro-hydraulic servo pressure testing machine with a loading rate of 2400N / s; flexural strength testing was performed using an electric flexural testing machine with a loading rate of 50N / s. The results are shown in Table 2-7.

[0046] Bond strength testing: The bond strength was tested according to the method specified in JC / T336-2011 "Polymer Cement Mortar for Repair of Concrete Structures". Using a C50 concrete substrate (300mm×300mm×50mm), a 5mm thick layer of repair material (40mm×40mm×10mm) was applied to the surface of the concrete substrate. After curing at -30℃ for 28 days, the tensile bond strength was measured using a digital bond strength tester. Six specimens were prepared for each example and comparative example, and the average value was taken. The results are shown in Table 8.

[0047] Freeze-thaw resistance test: The test was conducted according to the rapid freezing method in GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The specimen size was 100mm × 100mm × 400mm. After 300 freeze-thaw cycles from -30℃ to +10℃, the mass loss rate and relative dynamic modulus of elasticity were measured. The freeze-thaw cycle test was performed using a rapid freeze-thaw testing machine for concrete. Each freeze-thaw cycle lasted 2-4 hours, and the thawing time was not less than 1 / 4 of the total freeze-thaw cycle time. The mass loss rate was calculated using an electronic balance (accuracy 0.01g), and the relative dynamic modulus of elasticity was measured using a resonance method concrete dynamic modulus of elasticity measuring instrument. The results are shown in Table 9.

[0048] Low-temperature toughness testing: The test was conducted according to ASTM D5045-14, "Standard Test Methods for Plane-Strain Fracture Toughness and Strain Energy Release Rate of Plastic Materials." The fracture toughness (KIC) of the repair material was tested using the three-point bending method at -30°C. The specimen dimensions were 40mm × 80mm × 160mm, with a span of 120mm and a pre-crack depth of 16mm. The test was performed using a computer-controlled electronic universal testing machine with a loading rate of 1mm / min. Six specimens were prepared for each example and comparative example, and the average value was taken. The results are shown in Table 10.

[0049] Storage stability test: The composite materials prepared in Examples 1-3 and Comparative Examples 1-5 were sealed and stored at room temperature for 6 months. The stratification and sedimentation of the system were observed and recorded monthly. Storage stability was recorded in monthly units until obvious stratification or sedimentation occurred. The results are shown in Table 7.

[0050] Table 1. Condensation times (in minutes) of each embodiment and comparative example at different temperatures.

[0051] Note: "-" indicates that it cannot be cured at -60℃.

[0052] Table 1 shows that at -30℃, the initial setting time for Examples 1-3 was 11-14 min, the final setting time was 22-26 min, and the initial-to-final setting interval was 11-12 min; at -45℃, the initial setting time was 14-18 min, the final setting time was 28-32 min, and the initial-to-final setting interval was 14 min; and at -60℃, the initial setting time was 18-22 min, the final setting time was 34-40 min, and the initial-to-final setting interval was 16-18 min. These data indicate that the composite material of the present invention exhibits faster and more controllable setting and hardening characteristics in extremely cold environments. Comparative Example 5 failed to solidify at -60℃, demonstrating that the phase change energy storage microcapsules, as a latent heat release type low-temperature promoter, are crucial in providing local thermal protection for the hydration reaction of phosphate through phase change exothermic reactions in extremely cold environments. The setting time of Comparative Example 4 at low temperature was significantly shorter than that of Example 1. This is because the uncoated aluminum dihydrogen phosphate was released too quickly at low temperatures, leading to an overly vigorous hydration reaction. This indicates that the temperature-responsive release mechanism of the slow-release phosphate component is essential for achieving controllable adjustment of the curing rate in extremely cold environments. The setting time of Comparative Example 3 was significantly longer than that of Example 1, indicating that the dual-network gel carrier plays an important role in maintaining the reactivity and uniformity of the system.

[0053] Table 2 Compressive strength of each embodiment and comparative example under curing conditions at -30℃ (unit: MPa)

[0054] Table 3 Compressive strength of each embodiment and comparative example under curing conditions at -45℃ (unit: MPa)

[0055] Note: "-" indicates that the specimen cannot develop effective strength at this temperature and cannot be tested.

[0056] Table 4 Compressive strength of each embodiment and comparative example under curing conditions of -60℃ (unit: MPa)

[0057] Note: "-" indicates that the specimen cannot develop effective strength at this temperature and cannot be tested.

[0058] Table 5. Flexural strength of each embodiment and comparative example under curing conditions at -30℃ (unit: MPa)

[0059] Table 6. Flexural strength of each embodiment and comparative example under curing conditions at -45℃ (unit: MPa)

[0060] Note: "-" indicates that the specimen cannot develop effective strength at this temperature and cannot be tested.

[0061] Table 7. Flexural strength of each embodiment and comparative example under curing conditions at -60℃ (unit: MPa)

[0062] Note: "-" indicates that the specimen cannot develop effective strength at this temperature and cannot be tested.

[0063] As shown in Tables 2-7, under extremely cold curing conditions of -30℃, -45℃, and -60℃, the compressive and flexural strengths of Examples 1-3 at each age were significantly superior to those of the comparative examples. Taking 28 days of curing at -30℃ as an example, the compressive strength of Examples 1-3 reached 68.5-76.5 MPa, and the flexural strength reached 14.5-16.2 MPa. Even in the ultra-low temperature environment of -60℃, the 28-day compressive strength of Examples 1-3 still reached 58.5-66.5 MPa, and the flexural strength reached 12.2-14.0 MPa, demonstrating the excellent mechanical properties of the composite material of this invention over an extremely wide temperature range. In terms of early strength at the hourly level, the compressive strength of Examples 1-3 after 2 hours of curing at -30℃ reached 12.5-15.8 MPa, and the flexural strength reached 2.8-3.5 MPa, exhibiting an extremely rapid early strength development rate, meeting the engineering requirements for rapid repair in extremely cold environments.

[0064] The compressive and flexural strengths of Comparative Examples 1 and 2 at various temperatures were significantly lower than those of Example 1, indicating that the combination of temperature-sensitive deformation microspheres and carbonaceous sheets has a significant synergistic effect on improving mechanical properties. Neither the temperature-sensitive deformation microspheres nor the carbonaceous sheets alone can achieve the same reinforcing effect as the composite combination. Comparative Example 3 exhibited the lowest mechanical properties among all comparative examples, demonstrating that the dual-network gel structure is irreplaceable in strengthening the phosphate matrix. Comparative Example 5 failed to develop effective strength at -45°C and could not solidify at -60°C, further illustrating that the in-situ thermal protection provided by the phase change energy storage microcapsules plays a decisive role in the formation of mechanical strength under extremely cold environments.

[0065] Table 8. Bond strength of each embodiment and comparative example after curing at -30℃ for 28 days (unit: MPa)

[0066] As shown in Table 8, the bond strength of Examples 1-3 after curing at -30℃ for 28 days reached 2.5-3.2 MPa, which meets the requirement of tensile bond strength (28 days) ≥ 2.0 MPa in JG / T 336-2011 standard. Comparative Example 3 showed the lowest bond strength (1.3 MPa), indicating that the chemical bonding between the active functional groups of natural polysaccharides and synthetic polymers in the dual-network gel structure and the concrete matrix surface is the key factor in improving the interfacial bond strength.

[0067] Table 9. Freeze-thaw resistance of each embodiment and comparative example after 300 freeze-thaw cycles.

[0068] As shown in Table 9, after 300 freeze-thaw cycles, the mass loss rate of Examples 1-3 was only 1.2-1.8%, and the relative dynamic elastic modulus remained at 92.5-95.2%, far superior to the comparative examples. The mass loss rate and relative dynamic elastic modulus of Comparative Examples 1 and 2 were worse than those of Example 1, indicating that the composite system of temperature-sensitive deformation microspheres and carbonaceous sheets buffered the ice crystal expansion stress through reversible volume changes during freeze-thaw cycles, and the two synergistically played a crucial role in enhancing freeze-thaw resistance. Comparative Examples 3 and 5 exhibited the worst freeze-thaw resistance, further verifying the anchoring and stabilizing effect of the dual-network gel structure and the low-temperature protection effect of the phase change energy storage microcapsules.

[0069] Table 10 Fracture toughness KIC of each embodiment and comparative example at -30°C (unit: MPa·m) 1 / 2 )

[0070] As shown in Table 10, the fracture toughness KIC of Examples 1-3 reached 2.78-3.12 MPa·m. 1 / 2 The fracture toughness was significantly higher than that of the comparative examples. Comparative example 3 had the lowest fracture toughness (1.62 MPa·m). 1 / 2 This indicates that the dual-network gel structure dissipates impact energy through the stretching, slippage, and deformation of the three-dimensional network, which is key to achieving low-temperature toughness.

[0071] Table 11 Storage stability of each embodiment and comparative example (unit: months)

[0072] As shown in Table 11, the storage stability of Examples 1-3 reached 8.5-10.1 months, which is far superior to that of the comparative examples. The poor storage stability of Comparative Examples 3 and 4 indicates that the dual-network gel structure plays an irreplaceable role in uniformly anchoring the sustained-release phosphate component and the temperature-sensitive deformable microsphere-carbon layer composite within it, and in preventing sedimentation and stratification during long-term storage.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A phosphate composite material for concrete repair in extremely cold environments, characterized in that, By weight, it includes the following components: 40-65 parts of phosphate gelling material, 15-30 parts of double-network gel carrier, 2-8 parts of latent heat release type low temperature accelerator, 5-15 parts of nano-reinforcing component, 0.5-3 parts of coagulation regulator, and 5-12 parts of water; The dual-network gel carrier is a polysaccharide-polymer dual-network gel structure loaded with a sustained-release phosphate component and a temperature-sensitive deformable microsphere-carbon layer composite. The sustained-release phosphate component is obtained by coating an aluminum dihydrogen phosphate solution with a natural polysaccharide-calcium ion crosslinking system. The temperature-sensitive deformable microsphere-carbon layer composite is obtained by grafting temperature-sensitive deformable microspheres onto the surface of carbonaceous sheets using a coupling agent.

2. The phosphate composite material for concrete repair in extremely cold environments according to claim 1, characterized in that: The phosphate cementitious material is composed of calcined magnesium oxide and ammonium dihydrogen phosphate in a mass ratio of (1-5):1; the particle size of the calcined magnesium oxide is 200-300 mesh. The natural polysaccharide is one or more of sodium alginate, carrageenan, and pectin; the sodium alginate has a purity of 90-95%; the carrageenan is selected from k-type carrageenan; the pectin is extracted from one of the following fruits: orange, bayberry, red dragon fruit, blueberry, watermelon, banana, and green grape. The organic acid calcium is one or more of L-calcium lactate, calcium gluconate, and calcium citrate; The synthetic polymer is polyvinyl alcohol, with a weight-average molecular weight of 30,000-120,000.

3. The phosphate composite material for concrete repair in extremely cold environments according to claim 1, characterized in that, The preparation method of the dual-network gel carrier is as follows: pore-forming agent, 4-5% by mass of natural polysaccharide solution, slow-release phosphate component, temperature-sensitive deformable microsphere-carbon layer composite and 10-12% by mass of synthetic polymer solution are added to a reaction vessel and stirred for 20-30 min at 40-50℃ and 500-600 r / min. Then, 10-12% by mass of organic acid calcium solution is added, and the mixture is poured into a mold and cured for 20-30 min to obtain the dual-network gel carrier. The pore-forming aid is obtained by mixing an amphoteric surfactant and a sulfonate surfactant in a mass ratio of (5-6):(3-4); the amphoteric surfactant is one or more of lauramidopropyl betaine, cocamidopropyl betaine, and oleamidopropyl dimethyl betaine; the sulfonate surfactant is sodium C14-16 olefin sulfonate; the synthetic polymer solution is an aqueous solution of polyvinyl alcohol, prepared by dissolving polyvinyl alcohol in water and heating it to 70-95℃. The ratio of the pore-forming aid, natural polysaccharide solution, slow-release phosphate component, temperature-sensitive deformable microsphere-carbon layer composite, synthetic polymer solution and organic acid calcium solution is 8-10g:50-70mL:16-18g:20-30g:250-260mL:20-30mL.

4. The phosphate composite material for concrete repair in extremely cold environments according to claim 1, characterized in that, The preparation method of the sustained-release phosphate component is as follows: 40-50% aluminum dihydrogen phosphate solution, natural polysaccharide, deionized water, and anhydrous ethanol are added to a reaction vessel and stirred for 10-30 minutes at 20-25℃ and 500-600 r / min. Then, a calcium salt solution with a mass fraction of 0.4-0.6% is added, and stirring continues for 1-2 hours. After filtration, the product is washed 2-4 times with deionized water and anhydrous ethanol, respectively, and then vacuum dried at 60-70℃ and -0.08 MPa to -0.1 MPa for 1-2 hours to obtain the sustained-release phosphate component. The calcium salt is one or more of calcium chloride and calcium formate; The ratio of aluminum dihydrogen phosphate solution, natural polysaccharide, deionized water, anhydrous ethanol and calcium salt solution is 30-36 mL: 1.5-1.8 g: 80-100 mL: 190-200 mL: 30-40 mL.

5. The phosphate composite material for concrete repair in extremely cold environments according to claim 1, characterized in that, The preparation method of the temperature-sensitive deformation microsphere-carbon layer composite is as follows: anhydrous ethanol and deionized water are added to a reaction vessel, and an alkaline solution is added to adjust the pH value to 9-10. Modified temperature-sensitive deformation microspheres are added, and the mixture is stirred for 30-50 min at 30-40℃ and 500-600 r / min. Then, carbonaceous sheet material is added, and the mixture is stirred for 2-3 h. The mixture is filtered, and the product is washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product is then vacuum dried at 60-70℃ and -0.08 MPa to -0.1 MPa for 1-2 h to obtain the temperature-sensitive deformation microsphere-carbon layer composite. The alkaline solution is a sodium hydroxide solution and / or a potassium hydroxide solution with a mass fraction of 1-10%. The carbonaceous sheet material is graphene and / or expanded graphite; the graphene sheet diameter is 1-15 μm and the number of layers is 2-10; the expanded graphite particle size is 50-200 mesh and the expansion ratio is 150-350 times. The ratio of anhydrous ethanol, deionized water, modified temperature-sensitive deformable microspheres, and carbonaceous sheet material is 900-1000mL:100-120mL:5-8g:50-60g.

6. The phosphate composite material for concrete repair in extremely cold environments according to claim 5, characterized in that, The modified temperature-sensitive deformation microspheres are prepared as follows: temperature-sensitive deformation microspheres and anhydrous ethanol are added to a reaction vessel and stirred for 30-50 min at 30-40℃ and 500-600 r / min. Then, an organic base and a condensation reagent are added, and stirring is continued for 30-40 min. Then, a silane coupling agent is added, and stirring is continued for 3-5 h. The mixture is filtered, and the product is washed 2-4 times with deionized water and anhydrous ethanol, respectively. The product is then vacuum dried at 60-70℃ and -0.08 MPa to -0.1 MPa for 1-2 h to obtain the modified temperature-sensitive deformation microspheres. The organic base is one or more selected from N,N-diisopropylethylamine, triethylamine, tributylamine, 4-dimethylaminopyridine, 1,8-diazabicycloundec-7-ene, and tetramethylammonium hydroxide; The condensing agent is one or more of 2-(7-azabenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate, N,N'-diisopropylcarbodiimide, 1-hydroxybenzotriazole, 1-propylphosphoric anhydride, dicyclohexylcarbodiimide, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. The ratio of the amount of temperature-sensitive deformable microspheres, anhydrous ethanol, organic base, condensation reagent and silane coupling agent is 45-48g:800-900mL:15-17g:10-13g:6-8g. The method for preparing the temperature-sensitive deformation microspheres is as follows: S1. Add 80-90g sodium chloride, 25-30g magnesium hydroxide, and 5-10g magnesium chloride to 800-900mL of deionized water, and stir for 30-50min at 30-40℃ and 500-600r / min to obtain an aqueous mixture. S2. Mix 150-160g acrylonitrile, 60-62g methacrylonitrile, 20-22g isopentane, 50-52g isooctane, 1-2g ethylene glycol dimethacrylate, 1-2g diallyl carbonate, 9-12g naphthenic oil and 1-2g azobisisobutyronitrile until homogeneous to obtain an oil phase mixture; S3. The aqueous phase mixture and the oil phase mixture are mixed in a sealed pressure-resistant reactor at a mass ratio of 10:1 and dispersed at high speed at 1500-1600 r / min for 10-12 min. Then, under inert gas protection, the mixture is stirred and polymerized at 60-70℃, 80-90 r / min and 0.5-0.8 MPa for 20-25 h. After the polymerization reaction in step S4 and S3 is completed, the reaction solution is filtered, and the filter cake is washed 2-4 times with deionized water and anhydrous ethanol, respectively. It is then dried under vacuum at 60-70℃ and -0.08MPa to -0.1MPa for 1-2 hours to obtain temperature-sensitive deformation microspheres. The inert gas is at least one of nitrogen, argon, and helium.

7. The phosphate composite material for repairing concrete in extremely cold environments according to claim 1, characterized in that: The latent heat release type low temperature promoter is a phase change energy storage microcapsule with alkane as core material and amino resin as wall material, with a phase change temperature of -30 to -20℃, a core-to-wall ratio of (2-4):1, and an average microcapsule particle size of 4-10μm. The alkane is one or more of n-decane and n-undecane; The amino resin is one or a combination of several of the following: melamine-formaldehyde resin, butylated urea-formaldehyde resin, methylated urea-formaldehyde resin, hexamethoxymethyl melamine resin, and polymerizable high-imino high-methylated melamine resin.

8. The phosphate composite material for concrete repair in extremely cold environments according to claim 1, characterized in that: The nano-reinforcing component is one or more of nano-silica, nano-aluminum hydroxide, and nano-zinc oxide, with a particle size of 30-80 nm; the coagulation regulator is borax and / or boric acid.

9. A method for preparing a phosphate composite material for repairing concrete in extremely cold environments as described in any one of claims 1-8, characterized in that, Includes the following steps: The dual-network gel carrier and nano-reinforcing components were added to the phosphate gelling material and sheared and dispersed at 400-600 r / min for 15-30 min to obtain a mixed powder. The dual-network gel carrier was vacuum dried to constant weight before being added, and the phosphate gelling material was a dry powder. The above mixing process was carried out in a closed and dry environment. After mixing, the resulting mixed powder was stored in a moisture-proof and sealed package. A latent heat release type low temperature promoter and a coagulation regulator are added to water. The latent heat release type low temperature promoter is stirred and dispersed at 300-500 r / min for 10-20 min, and the coagulation regulator is stirred and dissolved at 300-500 r / min for 10-20 min to obtain a mixture. The mixture is added to the powder mixture and stirred at 200-400 r / min for 3-5 min to obtain a phosphate composite material for repairing concrete in extremely cold environments.

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