Seven-layer gradient function composite repair construction method for concrete freeze-thaw damage

Abstract

The application discloses a seven-layer gradient function composite repairing construction method for concrete freeze-thaw damage, and the method comprises the following steps: investigating a freeze-thaw damage area, determining damage depth and range, removing all loose, peeled and cracked concrete by using mechanical tools until the base surface is exposed, carrying out rust removal and corrosion prevention treatment on the exposed steel bars, cleaning the interface by using high-pressure water jet, removing dust and debris, and coating, in sequence, a primer, anti-freezing repair mortar, nano-enhanced coating, cement-based anti-freezing, waterproof and corrosion-proof protective coating, alkali-resistant sealing primer and protective coating on the base surface, wherein the protective coating is coated in two layers, the damaged base body is reconstructed in a gradient mode, the structural integrity is restored, a long-acting protection system with the functions of active protection and passive barrier is constructed from inside to outside and with gradient transition of material properties, and the service life of the repaired structure in an extreme environment is significantly prolonged.

Description

Technical Field

[0001] This invention relates to the field of concrete repair technology, specifically to a seven-layer gradient functional composite repair construction method for concrete freeze-thaw damage. Background Technology

[0002] In frigid regions, concrete structures are subjected to severe freeze-thaw cycles, salt erosion, and large temperature differences, posing a serious challenge to their durability. Freeze-thaw damage is one of the primary factors leading to the deterioration of concrete performance and a sharp reduction in its lifespan. Repeated freezing and expansion of moisture in the capillary pores of concrete generates internal stress, causing surface spalling, mortar loss, and aggregate exposure. In severe cases, this can lead to structural cracking and a decrease in load-bearing capacity. Simultaneously, corrosive media such as chloride ions in de-icing salt exacerbate steel corrosion, resulting in synergistic salt-freeze damage, the effects of which are far greater than the effects of freeze-thaw alone.

[0003] Currently, the repair techniques for freeze-thaw damage to concrete have the following limitations: The repair concept is one-sided: most technologies focus on the restoration of a single performance, such as only crack injection (epoxy resin) or surface sealing, lacking a systematic design from the base layer to the surface layer, from structural repair to long-term protection, and failing to cut off the chain damage path of freeze-thaw-leakage-salt corrosion.

[0004] Material performance mismatch: Traditional repair materials (such as ordinary mortar) have significant differences in linear expansion coefficient, elastic modulus, and frost resistance compared to the damaged substrate, making them prone to interfacial delamination under temperature stress, forming new weak layers. Existing high frost-resistant materials (such as F300 grade concrete) are mostly used in new construction projects, with few material systems specifically designed for repair conditions.

[0005] Insufficient long-term protection: Conventional protective coatings are mostly physical covers with limited adhesion and durability, and are prone to powdering and peeling under extreme freeze-thaw cycles and ultraviolet radiation. Once microcracks appear in the coating, corrosive media can penetrate deeply, rendering any repairs ineffective.

[0006] Lack of synergistic solutions for salt and frost resistance: Many technologies have failed to effectively address the problem of salt intrusion. For example, while methods such as carbon fiber reinforcement can improve load-bearing capacity, they have little effect on preventing salt ion penetration and preventing continuous corrosion of internal steel bars.

[0007] Therefore, there is an urgent need for an innovative construction method that starts from the mechanism, integrates multiple materials and processes, and can systematically and fundamentally solve the combined damage of concrete caused by freeze-thaw and salt corrosion in frigid regions. Summary of the Invention

[0008] The purpose of this invention is to provide a seven-layer gradient functional composite repair method for concrete freeze-thaw damage, solving the problem of poor waterproofing and salt resistance after repair of freeze-thaw damaged concrete at present.

[0009] The objective of this invention can be achieved through the following technical solutions: A seven-layer gradient functional composite repair method for concrete freeze-thaw damage includes the following steps: Step S1: Investigate the freeze-thaw damage area to determine the depth and extent of the damage. Use mechanical tools to remove all loose, peeling and cracked concrete until the base surface is exposed. Perform rust removal and anti-corrosion treatment on the exposed reinforcement. Use high-pressure water jet (pressure not less than 20MPa) to clean the interface and remove dust and debris. Step S2: Weigh the following raw materials by weight: 80-90 parts water-based epoxy resin, 15-25 parts nano silica, 1-2 parts defoamer, 0.1-0.5 parts rheology modifier, 3-8 parts adhesion promoter, 15-25 parts curing agent and 20-30 parts water. Mix the raw materials evenly to obtain a primer. Apply the primer to the substrate surface and cure until surface dry. Step S3: Weigh the following raw materials by weight: 100-120 parts cement, 85-150 parts coarse sand, 65-100 parts fine sand, 8-15 parts EVA latex powder, 5-10 parts silica fume, 0.01-0.05 parts air-entraining agent and 0.1-0.3 parts basalt fiber. Mix the raw materials evenly to prepare the antifreeze repair mortar. Apply the antifreeze repair mortar to the primer surface and cure until surface dry. Step S4: Weigh the following raw materials by weight: 60-80 parts water-based silicone emulsion, 15-25 parts nano silica sol, 5-8 parts silicone water-repellent agent, 0.1-0.3 parts leveling agent, 0.1-0.3 parts defoamer and 20-30 parts water. Mix the raw materials evenly to obtain a nano-reinforced coating. Apply the nano-reinforced coating to the surface of the antifreeze repair mortar and cure until the surface is dry. Step S5: Mix component A and component B at a mass ratio of 1:1-1.5 to prepare a cement-based antifreeze, waterproof, and anticorrosive protective coating. Component A includes the following raw materials by weight: 40-60 parts polyacrylate emulsion, 10-20 parts ethylene-vinyl acetate copolymer emulsion, 2-5 parts dodecyl alcohol ester, 0.5-2 parts trimethylolpropane, 0.1-0.3 parts tributyl phosphate, and 20-30 parts water. Component B includes the following raw materials by weight: 70-80 parts pozzolanic silicate cement, 15-25 parts quartz powder, 5-10 parts silica fume, and 0.3-0.8 parts polycarboxylate superplasticizer. Apply the cement-based antifreeze, waterproof, and anticorrosive protective coating to the surface of the nano-reinforced coating and cure until surface dry. Step S6: Mix component C and component D at a mass ratio of 1:1.2 to prepare an alkali-resistant sealing primer. Component C includes the following raw materials by weight: 80-100 parts epoxy resin, 5-15 parts softening resin, 5-15 parts glycidyl butyl ether, 0.5-1 part defoamer, and 0.1-0.5 parts leveling agent. Component D includes the following raw materials by weight: 80-100 parts modified amine curing agent and 1-5 parts silane coupling agent. Apply the alkali-resistant sealing primer to the surface of the cement-based antifreeze, waterproof, and anticorrosion protective coating and cure until surface dry. Step S7: Mix component E and component F in a mass ratio of 1:1 to obtain a protective coating. Component E includes the following raw materials by weight: 100-120 parts modified epoxy resin and 40-60 parts propylene glycol methyl ether acetate. Component F includes the following raw materials by weight: 15-25 parts diaminocage-type silsesquioxane, 5-15 parts KH550 and 10-20 parts n-butanol. Apply two layers of protective coating to the surface of the alkali-resistant sealing primer and cure until surface dry.

[0010] Furthermore, the modified epoxy resin is prepared by the following steps: Step A1: Mix octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and deionized water, purge with nitrogen, and react for 10-15 h at a rotation speed of 120-150 r / min and a temperature of 90-95℃. Then raise the temperature to 105-110℃ and continue the reaction for 2-3 h to obtain epoxy polysiloxane. Step A2: Dissolve lithium dimethylvinylsilane in tetrahydrofuran, purge with nitrogen, stir and add trifluoropropylmethylcyclotrisiloxane at 150-200 r / min and 0℃, heat to 25-30℃ and react for 20-24 h, then add trichlorosilane and continue the reaction for 1-1.5 h to obtain branched polysiloxane; Step A3: Mix branched polysiloxane, 3-mercaptopropyltrimethoxysilane, benzophenone and xylene, purge nitrogen, and react for 20-30 minutes under the conditions of 150-200 r / min, 20-25℃ and 365nm ultraviolet light irradiation to obtain modified branched polysiloxane. Step A4: Mix the modified branched polysiloxane, epoxy polysiloxane, caster catalyst and xylene, purge with nitrogen, and react for 6-8 hours at a rotation speed of 200-300 r / min and a temperature of 50-60℃ to obtain the modified epoxy resin.

[0011] Furthermore, the ratio of octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxanetetramethylammonium hydroxide and deionized water in step A1 is 1 mol: 0.4 mol: 1 mol: 1.5 mol: 20 mL.

[0012] Furthermore, the molar ratio of Si-Cl bonds on lithium dimethylvinylsilanolate, trifluoropropylmethylcyclotrisiloxane, and trichlorosilane in step A2 is 1:4:1.

[0013] Furthermore, the molar ratio of branched polysiloxane and 3-mercaptopropyltrimethoxysilane in step A3 is 1:3, and the amount of benzophenone used is 0.03% of the mass of branched polysiloxane.

[0014] Furthermore, the molar ratio of the modified branched polysiloxane and the epoxy polysiloxane described in step A4 is 1:2, and the amount of the cassiterite catalyst is 0.01% of the mass of the epoxy polysiloxane.

[0015] Furthermore, the diaminocage-type silsesquioxane is prepared by the following steps: A mixture of aminopropylheptaisobutylsilsesquioxane and tetrahydrofuran was prepared under nitrogen protection. The mixture was stirred and tetramethylammonium hydroxide was added at a speed of 150-200 r / min and a temperature of 10-15 °C. The mixture was then heated to 68-70 °C and reacted for 10-12 h to obtain an intermediate. The intermediate was then mixed with toluene and stirred at a speed of 200-300 r / min and a temperature of 115-120 °C. A mixture of aminopropyltriethoxysilane and triethylamine was added and the mixture was refluxed for 20-24 h to obtain diaminocage-type silsesquioxane.

[0016] Furthermore, the molar ratio of aminopropylheptaisobutylsilsesquioxane to tetramethylammonium hydroxide is 1:1.2, the amount of intermediate and aminopropyltriethoxysilane is 1:2.5, and the amount of triethylamine is 0.01% of the mass of the intermediate.

[0017] The beneficial effects of this invention: This application discloses a seven-layer gradient functional composite repair construction method for freeze-thaw damage of concrete. The method involves surveying the freeze-thaw damaged area to determine the depth and extent of the damage, using mechanical tools to remove all loose, spalled, and cracked concrete until the base surface is exposed, performing rust removal and anti-corrosion treatment on the exposed reinforcement, and using high-pressure water jet cleaning to remove dust and debris. A primer is then applied to the base surface. The primer comprises the following raw materials: water-based epoxy resin, nano-silica, defoamer, rheology modifier, adhesion promoter, curing agent, and water. The nano-silica is smaller than the capillary pore size of the concrete, allowing it to penetrate deeply into the substrate through capillary action of water. The nano-silica accumulates on the pore walls, forming hydrophobic micro-plugs and networks, significantly reducing the water absorption of the substrate. By reducing the water absorption rate and capillary water absorption coefficient, the content of freezeable water is fundamentally reduced. An antifreeze repair mortar is applied to the primer surface. This mortar comprises cement, coarse sand, fine sand, EVA latex powder, silica fume, air-entraining agent, and basalt fiber. The addition of the air-entraining agent introduces a large number of uniform, stable micron-sized closed air bubbles, serving as a buffer space for ice crystal expansion. The addition of EVA latex powder and silica fume enhances the mortar's flexibility, bonding strength, and density. A nano-reinforced coating is then applied to the surface of the antifreeze repair mortar. This coating comprises water-based silicone emulsion, nano-silica sol, silicone water-repellent agent, leveling agent, defoamer, and water. The nano-silica sol penetrates into the micropores of the mortar surface, undergoing a pozzolanic reaction to generate CSH gel, significantly improving… The surface layer exhibits high density and hardness. Simultaneously, the organosilicon component imparts excellent hydrophobicity, effectively preventing the retention and absorption of liquid water and water-soluble salts on the surface. A cement-based antifreeze, waterproof, and anticorrosive protective coating is applied to the surface of the nano-reinforced coating. This coating comprises component A and component B. Component A includes the following raw materials: polyacrylate emulsion, ethylene-vinyl acetate copolymer emulsion, dodecyl alcohol ester, trimethylolpropane, tributyl phosphate, and water. Component B includes the following raw materials: pozzolanic silicate cement, quartz powder, silica fume, and polycarboxylate superplasticizer. This coating provides a macroscopic waterproof barrier and resistance to physical freeze-thaw impacts. An alkali-resistant sealing primer is then applied to the surface of the cement-based antifreeze, waterproof, and anticorrosive protective coating. The alkali-resistant sealing primer comprises component... Components C and D are used. Component C includes the following raw materials: epoxy resin, softening resin, glycidyl ether, defoamer, and leveling agent. Component D includes the following raw materials: modified amine curing agent and silane coupling agent. The alkali-resistant sealing primer can seal the micropores and alkaline substances present in the preceding cement-based material, providing a completely inert, smooth, and highly adhesive interface, and effectively isolating it from the chemical erosion of various acid, alkali, and salt media. Two protective coatings are applied to the surface of the alkali-resistant sealing primer. The protective coatings include components E and F. Component E includes the following raw materials: modified epoxy resin and propylene glycol methyl ether acetate. Component F includes the following raw materials: diaminocage-type silsesquioxane, KH550, and n-butanol. The two protective coatings can bond together, increasing the protective performance of the coatings.The addition of diaminocage-type silsesquioxane also gives the protective coating a waterproof and breathable effect.

[0018] Modified epoxy resin is prepared by ring-opening with octamethylcyclotetrasiloxane as a raw material, followed by hydrolytic condensation with 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, and then end-capping with tetramethyldivinyldisiloxane to obtain epoxy polysiloxane. Using lithium dimethylvinylsilanolate as an initiator and trifluoropropylmethylcyclotrisiloxane as a polymerization monomer, a polysiloxane with lithium silanolate at one end and a double bond at the other end is prepared. Trichlorosilane is then added to achieve a further polymerization reaction. The Si-Cl bond on silane reacts with lithium silanolate to prepare branched polysiloxane. The branched polysiloxane is then reacted with 3-mercaptopropyltrimethoxysilane, causing the double bond on the branched polysiloxane to react with the mercapto group of 3-mercaptopropyltrimethoxysilane, thus preparing modified polysiloxane. The modified polysiloxane is then reacted with epoxy polysiloxane, causing the Si-H bond on the modified polysiloxane to react with the double bond on the epoxy polysiloxane, thus preparing modified epoxy resin.

[0019] Diaminocage-type silsesquioxane is prepared by using aminopropylheptaisobutylsilsesquioxane as a raw material and catalyzing with tetramethylammonium hydroxide to selectively break the Si-O-Si bond at the para position, generating three Si-OH bonds to obtain an intermediate. The intermediate is then subjected to a apex-cap reaction with aminopropyltriethoxysilane to obtain diaminocage-type silsesquioxane. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0021] Example 1: A seven-layer gradient functional composite repair method for concrete freeze-thaw damage, specifically including the following steps: Step S1: Investigate the freeze-thaw damage area to determine the depth and extent of the damage. Use mechanical tools to remove all loose, peeling and cracked concrete until the base surface is exposed. Perform rust removal and anti-corrosion treatment on the exposed reinforcement. Use 20MPa high-pressure water jet to clean the interface and remove dust and debris. Step S2: Apply primer to the substrate surface and cure until surface dry; Step S3: Apply antifreeze repair mortar to the primer surface and cure until surface dry; Step S4: Apply nano-reinforced coating to the surface of the antifreeze repair mortar and cure until surface dry; Step S5: Apply a cement-based antifreeze, waterproof, and anticorrosive protective coating to the surface of the nano-reinforced coating and cure until surface dry; Step S6: Apply an alkali-resistant sealing primer to the surface of the cement-based antifreeze, waterproof, and anticorrosion protective coating, and cure until surface dry; Step S7: Apply two layers of protective coating to the surface of the alkali-resistant sealing primer and cure until surface dry.

[0022] The primer described in step S2 comprises the following raw materials in parts by weight: 80 parts waterborne epoxy resin, 15 parts nano silica, 1 part defoamer, 0.1 part rheology modifier, 3 parts adhesion promoter, 15 parts curing agent, and 20 parts water. The waterborne epoxy resin is model 3EE102W, the defoamer is model BYK-025, the rheology modifier is model Bentone LT, the adhesion promoter is model KH550, and the curing agent is model AQUAEPO-3126.

[0023] The antifreeze repair mortar described in step S3 comprises the following raw materials by weight: 100 parts cement, 85 parts coarse sand, 100 parts fine sand, 8 parts EVA latex powder, 5 parts silica fume, 0.01 parts air-entraining agent, and 0.1 parts basalt fiber. The cement type is P·O42.5, the EVA latex powder type is 5010N, the silica fume type is SF90, the air-entraining agent type is TEGO XP 22066, and the basalt fiber has a length of 12mm and a diameter of 15μm.

[0024] The nano-reinforced coating described in step S4 comprises the following raw materials in parts by weight: 60 parts of water-based silicone emulsion, 15 parts of nano-silica sol, 5 parts of silicone water-repellent agent, 0.1 parts of leveling agent, 0.1 parts of defoamer, and 20 parts of water. The water-based silicone emulsion is model IOAT6864, the nano-silica sol is model CY-S01B, the silicone water-repellent agent is model SHP50, the leveling agent is model BYK333, and the defoamer is model BYK028.

[0025] The cement-based antifreeze, waterproof, and anticorrosive protective coating described in step S5 is prepared by mixing component A and component B in a mass ratio of 1:1. Component A includes the following raw materials in parts by weight: 40 parts polyacrylate emulsion, 10 parts ethylene-vinyl acetate copolymer emulsion, 2 parts dodecyl alcohol ester, 0.5 parts trimethylolpropane, 0.1 parts tributyl phosphate, and 20 parts water. The polyacrylate emulsion is model DC-2051, and the ethylene-vinyl acetate copolymer emulsion is model Celvolit 1318. Component B includes the following raw materials in parts by weight: 70 parts pozzolanic silicate cement, 15 parts quartz powder, 5 parts silica fume, and 0.3 parts polycarboxylate superplasticizer. The pozzolanic silicate cement is P·P42.5, the quartz powder is 300 mesh, the silica fume is model SF90, and the polycarboxylate superplasticizer is model TH-928.

[0026] The alkali-resistant sealing primer described in step S6 is prepared by mixing component C and component D in a mass ratio of 1:1.2. Component C includes the following raw materials in parts by weight: 80 parts epoxy resin, 5 parts flexible resin, 5 parts glycidyl ether, 0.5 parts defoamer and 0.1 parts leveling agent. The epoxy resin is EPON 828, the flexible resin is EPU-300A, the defoamer is BYK-A 530 and the leveling agent is BYK333. Component D includes the following raw materials in parts by weight: 80 parts modified amine curing agent and 1 part silane coupling agent. The modified amine curing agent is FXR-1081 and the silane coupling agent is KH550.

[0027] The protective coating described in step S7 is prepared by mixing component E and component F in a mass ratio of 1:1. Component E includes the following raw materials in parts by weight: 100 parts modified epoxy resin and 40 parts propylene glycol methyl ether acetate. Component F includes the following raw materials in parts by weight: 15 parts diaminocage-type silsesquioxane, 5 parts KH550 and 10 parts n-butanol.

[0028] The modified epoxy resin is prepared by the following steps: Step A1: Octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and deionized water were mixed and purged with nitrogen. The mixture was reacted at 120 r / min and 90 °C for 10 h. The temperature was then raised to 105 °C and the reaction was continued for 2 h to obtain epoxy polysiloxane. Step A2: Lithium dimethylvinylsilane was dissolved in tetrahydrofuran and protected by nitrogen. Trifluoropropylmethylcyclotrisiloxane was added while stirring at 150 r / min and 0 °C. The temperature was raised to 25 °C and the reaction was carried out for 20 h. Trichlorosilane was added and the reaction was continued for 1 h to obtain branched polysiloxane. Step A3: The branched polysiloxane, 3-mercaptopropyltrimethoxysilane, benzophenone and xylene are mixed and purged with nitrogen. The mixture is then reacted for 20 minutes at a rotation speed of 150 r / min, a temperature of 20℃ and irradiation with 365 nm ultraviolet light to obtain the modified branched polysiloxane. Step A4: Mix the modified branched polysiloxane, epoxy polysiloxane, caster catalyst and xylene, purge with nitrogen, and react for 6 hours at a speed of 200 r / min and a temperature of 50℃ to obtain the modified epoxy resin.

[0029] The ratio of octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxanetetramethylammonium hydroxide and deionized water in step A1 is 1 mol: 0.4 mol: 1 mol: 1.5 mol: 20 mL.

[0030] The molar ratio of Si-Cl bonds on lithium dimethylvinylsilane, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step A2 is 1:4:1.

[0031] The molar ratio of branched polysiloxane and 3-mercaptopropyltrimethoxysilane in step A3 is 1:3, and the amount of benzophenone used is 0.03% of the mass of branched polysiloxane.

[0032] The molar ratio of the modified branched polysiloxane and the epoxy polysiloxane described in step A4 is 1:2, and the amount of the cassiterite catalyst is 0.01% of the mass of the epoxy polysiloxane.

[0033] The diaminocage-type silsesquioxane is prepared by the following steps: A mixture of aminopropylheptaisobutylsilsesquioxane and tetrahydrofuran was purged with nitrogen and stirred at 150 r / min and 10 °C. Tetramethylammonium hydroxide was added, and the mixture was heated to 68 °C and reacted for 10 h to obtain an intermediate. The intermediate was then mixed with toluene and stirred at 200 r / min and 115 °C. A mixture of aminopropyltriethoxysilane and triethylamine was added, and the mixture was refluxed for 20 h to obtain diaminocage-type silsesquioxane.

[0034] The molar ratio of aminopropylheptaisobutylsilsesquioxane to tetramethylammonium hydroxide is 1:1.2, the amount of intermediate and aminopropyltriethoxysilane is 1:2.5, and the amount of triethylamine is 0.01% of the mass of the intermediate.

[0035] Example 2: A seven-layer gradient functional composite repair method for concrete freeze-thaw damage, specifically including the following steps: Step S1: Investigate the freeze-thaw damage area to determine the depth and extent of the damage. Use mechanical tools to remove all loose, peeling and cracked concrete until the base surface is exposed. Perform rust removal and anti-corrosion treatment on the exposed reinforcement. Use 30MPa high-pressure water jet to clean the interface and remove dust and debris. Step S2: Apply primer to the substrate surface and cure until surface dry; Step S3: Apply antifreeze repair mortar to the primer surface and cure until surface dry; Step S4: Apply nano-reinforced coating to the surface of the antifreeze repair mortar and cure until surface dry; Step S5: Apply a cement-based antifreeze, waterproof, and anticorrosive protective coating to the surface of the nano-reinforced coating and cure until surface dry; Step S6: Apply an alkali-resistant sealing primer to the surface of the cement-based antifreeze, waterproof, and anticorrosion protective coating, and cure until surface dry; Step S7: Apply two layers of protective coating to the surface of the alkali-resistant sealing primer and cure until surface dry.

[0036] The primer described in step S2 comprises the following raw materials in parts by weight: 85 parts waterborne epoxy resin, 20 parts nano silica, 1.5 parts defoamer, 0.3 parts rheology modifier, 5 parts adhesion promoter, 20 parts curing agent, and 25 parts water. The waterborne epoxy resin is model 3EE102W, the defoamer is model BYK-025, the rheology modifier is model DeuRheo WT-102, the adhesion promoter is model KH550, and the curing agent is model AQUAEPO-3126.

[0037] The antifreeze repair mortar described in step S3 comprises the following raw materials by weight: 110 parts cement, 110 parts coarse sand, 80 parts fine sand, 11 parts EVA latex powder, 8 parts silica fume, 0.03 parts air-entraining agent, and 0.2 parts basalt fiber. The cement type is P·O42.5, the EVA latex powder type is 5010N, the silica fume type is SF95, the air-entraining agent type is TEGO XP 22066, and the basalt fiber has a length of 12mm and a diameter of 15μm.

[0038] The nano-reinforced coating described in step S4 comprises the following raw materials in parts by weight: 70 parts of water-based silicone emulsion, 20 parts of nano-silica sol, 6 parts of silicone water-repellent agent, 0.2 parts of leveling agent, 0.2 parts of defoamer, and 25 parts of water. The water-based silicone emulsion is model IOAT6864, the nano-silica sol is model CY-S01B, the silicone water-repellent agent is model SHP50, the leveling agent is model BYK333, and the defoamer is model BYK028.

[0039] The cement-based antifreeze, waterproof, and anticorrosive protective coating described in step S5 is prepared by mixing component A and component B in a mass ratio of 1:1.3. Component A includes the following raw materials in parts by weight: 50 parts polyacrylate emulsion, 15 parts ethylene-vinyl acetate copolymer emulsion, 3.5 parts dodecyl alcohol ester, 0.12 parts trimethylolpropane, 0.2 parts tributyl phosphate, and 25 parts water. The polyacrylate emulsion is model DC-2051, and the ethylene-vinyl acetate copolymer emulsion is model Celvolit 1318. Component B includes the following raw materials in parts by weight: 75 parts pozzolanic silicate cement, 20 parts quartz powder, 8 parts silica fume, and 0.5 parts polycarboxylate superplasticizer. The pozzolanic silicate cement is P·P42.5, the quartz powder is 350 mesh, the silica fume is model SF90, and the polycarboxylate superplasticizer is model TH-928.

[0040] The alkali-resistant sealing primer described in step S6 is prepared by mixing component C and component D in a mass ratio of 1:1.2. Component C includes the following raw materials in parts by weight: 90 parts epoxy resin, 10 parts flexible resin, 10 parts glycidyl ether, 0.8 parts defoamer, and 0.3 parts leveling agent. The epoxy resin is EPON 828, the flexible resin is EPU-300A, the defoamer is BYK-A 530, and the leveling agent is BYK333. Component D includes the following raw materials in parts by weight: 90 parts modified amine curing agent and 3 parts silane coupling agent. The modified amine curing agent is FXR-1081, and the silane coupling agent is KH550.

[0041] The protective coating described in step S7 is prepared by mixing component E and component F in a mass ratio of 1:1. Component E includes the following raw materials in parts by weight: 110 parts modified epoxy resin and 50 parts propylene glycol methyl ether acetate. Component F includes the following raw materials in parts by weight: 20 parts diaminocage-type silsesquioxane, 10 parts KH550 and 15 parts n-butanol.

[0042] The modified epoxy resin is prepared by the following steps: Step A1: Octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and deionized water were mixed and purged with nitrogen. The mixture was reacted at 120 r / min and 95 °C for 10 h. The temperature was then raised to 110 °C and the reaction was continued for 2 h to obtain epoxy polysiloxane. Step A2: Lithium dimethylvinylsilane was dissolved in tetrahydrofuran and protected with nitrogen. Under the conditions of 200 r / min and 0℃, trifluoropropylmethylcyclotrisiloxane was added while stirring. The temperature was raised to 25℃ and the reaction was carried out for 22 h. Then, trichlorosilane was added and the reaction was continued for 1.3 h to obtain branched polysiloxane. Step A3: The branched polysiloxane, 3-mercaptopropyltrimethoxysilane, benzophenone and xylene are mixed and purged with nitrogen. The mixture is then reacted for 25 minutes at a rotation speed of 150 r / min, a temperature of 25℃ and irradiation with 365 nm ultraviolet light to obtain the modified branched polysiloxane. Step A4: Mix the modified branched polysiloxane, epoxy polysiloxane, caster catalyst and xylene, purge with nitrogen, and react for 7 hours at a speed of 200 r / min and a temperature of 55℃ to obtain the modified epoxy resin.

[0043] The ratio of octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxanetetramethylammonium hydroxide and deionized water in step A1 is 1 mol: 0.4 mol: 1 mol: 1.5 mol: 20 mL.

[0044] The molar ratio of Si-Cl bonds on lithium dimethylvinylsilane, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step A2 is 1:4:1.

[0045] The molar ratio of branched polysiloxane and 3-mercaptopropyltrimethoxysilane in step A3 is 1:3, and the amount of benzophenone used is 0.03% of the mass of branched polysiloxane.

[0046] The molar ratio of the modified branched polysiloxane and the epoxy polysiloxane described in step A4 is 1:2, and the amount of the cassiterite catalyst is 0.01% of the mass of the epoxy polysiloxane.

[0047] The diaminocage-type silsesquioxane is prepared by the following steps: A mixture of aminopropylheptaisobutylsilsesquioxane and tetrahydrofuran was purged with nitrogen and stirred at 150 r / min and 15 °C. Tetramethylammonium hydroxide was added, and the mixture was heated to 69 °C and reacted for 11 h to obtain an intermediate. The intermediate was then mixed with toluene and stirred at 300 r / min and 120 °C. A mixture of aminopropyltriethoxysilane and triethylamine was added, and the mixture was refluxed for 22 h to obtain diaminocage-type silsesquioxane.

[0048] The molar ratio of aminopropylheptaisobutylsilsesquioxane to tetramethylammonium hydroxide is 1:1.2, the amount of intermediate and aminopropyltriethoxysilane is 1:2.5, and the amount of triethylamine is 0.01% of the mass of the intermediate.

[0049] Example 3: A seven-layer gradient functional composite repair method for concrete freeze-thaw damage, specifically including the following steps: Step S1: Investigate the freeze-thaw damage area to determine the depth and extent of the damage. Use mechanical tools to remove all loose, peeling and cracked concrete until the base surface is exposed. Perform rust removal and anti-corrosion treatment on the exposed reinforcement. Use 40MPa high-pressure water jet to clean the interface and remove dust and debris. Step S2: Apply primer to the substrate surface and cure until surface dry; Step S3: Apply antifreeze repair mortar to the primer surface and cure until surface dry; Step S4: Apply nano-reinforced coating to the surface of the antifreeze repair mortar and cure until surface dry; Step S5: Apply a cement-based antifreeze, waterproof, and anticorrosive protective coating to the surface of the nano-reinforced coating and cure until surface dry; Step S6: Apply an alkali-resistant sealing primer to the surface of the cement-based antifreeze, waterproof, and anticorrosion protective coating, and cure until surface dry; Step S7: Apply two layers of protective coating to the surface of the alkali-resistant sealing primer and cure until surface dry.

[0050] The primer described in step S2 comprises the following raw materials in parts by weight: 90 parts waterborne epoxy resin, 25 parts nano silica, 2 parts defoamer, 0.5 parts rheology modifier, 8 parts adhesion promoter, 25 parts curing agent, and 30 parts water. The waterborne epoxy resin is model 3EE102W, the defoamer is model Foamaster MO 2134 AG, the rheology modifier is model DeuRheo WT-102, the adhesion promoter is model KH560, and the curing agent is model AQUAEPO-3126.

[0051] The antifreeze repair mortar described in step S3 comprises the following raw materials by weight: 120 parts cement, 150 parts coarse sand, 65 parts fine sand, 15 parts EVA latex powder, 10 parts silica fume, 0.05 parts air-entraining agent, and 0.3 parts basalt fiber. The cement type is P·O42.5, the EVA latex powder type is 5044N, the silica fume type is SF95, the air-entraining agent type is TEGO XP 22066, and the basalt fiber has a length of 12mm and a diameter of 15μm.

[0052] The nano-reinforced coating described in step S4 comprises the following raw materials in parts by weight: 80 parts of water-based silicone emulsion, 25 parts of nano-silica sol, 8 parts of silicone water-repellent agent, 0.3 parts of leveling agent, 0.3 parts of defoamer, and 30 parts of water. The water-based silicone emulsion is model IOAT6864, the nano-silica sol is model CY-S01B, the silicone water-repellent agent is model SHP50, the leveling agent is model BYK333, and the defoamer is model BYK028.

[0053] The cement-based antifreeze, waterproof, and anticorrosive protective coating described in step S5 is prepared by mixing component A and component B in a mass ratio of 1:1.5. Component A includes the following raw materials in parts by weight: 60 parts polyacrylate emulsion, 20 parts ethylene-vinyl acetate copolymer emulsion, 5 parts dodecyl alcohol ester, 2 parts trimethylolpropane, 0.3 parts tributyl phosphate, and 30 parts water. The polyacrylate emulsion is model DC-2051, and the ethylene-vinyl acetate copolymer emulsion is model Celvolit 1318. Component B includes the following raw materials in parts by weight: 80 parts pozzolanic silicate cement, 25 parts quartz powder, 10 parts silica fume, and 0.8 parts polycarboxylate superplasticizer. The pozzolanic silicate cement is P·P42.5, the quartz powder is 400 mesh, the silica fume is model SF95, and the polycarboxylate superplasticizer is model TH-928.

[0054] The alkali-resistant sealing primer described in step S6 is prepared by mixing component C and component D in a mass ratio of 1:1.2. Component C includes the following raw materials in parts by weight: 100 parts epoxy resin, 15 parts flexible resin, 15 parts glycidyl butyl ether, 1 part defoamer and 0.5 parts leveling agent. The epoxy resin is EPON 828, the flexible resin is EPU-300A, the defoamer is BYK-A 530 and the leveling agent is BYK333. Component D includes the following raw materials in parts by weight: 100 parts modified amine curing agent and 5 parts silane coupling agent. The modified amine curing agent is FXR-1081 and the silane coupling agent is KH560.

[0055] The protective coating described in step S7 is prepared by mixing component E and component F in a mass ratio of 1:1. Component E includes the following raw materials in parts by weight: 120 parts modified epoxy resin and 60 parts propylene glycol methyl ether acetate. Component F includes the following raw materials in parts by weight: 25 parts diaminocage-type silsesquioxane, 15 parts KH550 and 20 parts n-butanol.

[0056] The modified epoxy resin is prepared by the following steps: Step A1: Octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and deionized water were mixed and purged with nitrogen. The mixture was reacted at 150 r / min and 95 °C for 15 h. The temperature was then raised to 110 °C and the reaction was continued for 3 h to obtain epoxy polysiloxane. Step A2: Lithium dimethylvinylsilane was dissolved in tetrahydrofuran and protected with nitrogen. Trifluoropropylmethylcyclotrisiloxane was added while stirring at 200 r / min and 0 °C. The temperature was raised to 30 °C and the reaction was carried out for 24 h. Trichlorosilane was then added and the reaction was continued for 1.5 h to obtain branched polysiloxane. Step A3: The branched polysiloxane, 3-mercaptopropyltrimethoxysilane, benzophenone and xylene are mixed and purged with nitrogen. The mixture is then reacted for 30 minutes at a rotation speed of 200 r / min, a temperature of 25℃ and irradiation with 365 nm ultraviolet light to obtain the modified branched polysiloxane. Step A4: Mix modified branched polysiloxane, epoxy polysiloxane, caster catalyst and xylene, purge with nitrogen, and react for 8 hours at a speed of 300 r / min and a temperature of 60℃ to obtain modified epoxy resin.

[0057] The ratio of octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxanetetramethylammonium hydroxide and deionized water in step A1 is 1 mol: 0.4 mol: 1 mol: 1.5 mol: 20 mL.

[0058] The molar ratio of Si-Cl bonds on lithium dimethylvinylsilane, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step A2 is 1:4:1.

[0059] The molar ratio of branched polysiloxane and 3-mercaptopropyltrimethoxysilane in step A3 is 1:3, and the amount of benzophenone used is 0.03% of the mass of branched polysiloxane.

[0060] The molar ratio of the modified branched polysiloxane and the epoxy polysiloxane described in step A4 is 1:2, and the amount of the cassiterite catalyst is 0.01% of the mass of the epoxy polysiloxane.

[0061] The diaminocage-type silsesquioxane is prepared by the following steps: A mixture of aminopropylheptaisobutylsilsesquioxane and tetrahydrofuran was purged with nitrogen and stirred at 200 r / min and 15 °C. Tetramethylammonium hydroxide was added, and the mixture was heated to 70 °C and reacted for 12 h to obtain an intermediate. The intermediate was then mixed with toluene and stirred at 300 r / min and 110 °C. A mixture of aminopropyltriethoxysilane and triethylamine was added, and the mixture was refluxed for 24 h to obtain diaminocage-type silsesquioxane.

[0062] The molar ratio of aminopropylheptaisobutylsilsesquioxane to tetramethylammonium hydroxide is 1:1.2, the amount of intermediate and aminopropyltriethoxysilane is 1:2.5, and the amount of triethylamine is 0.01% of the mass of the intermediate.

[0063] Comparative Example 1: Compared with Example 1, this comparative example uses triethylenetetramine instead of diaminocage-type silsesquioxane, and the other steps are the same.

[0064] Comparative Example 2: Compared with Example 1, this comparative example uses octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, under nitrogen protection, and reacts at 120 r / min and 90°C for 10 h. Then the temperature is raised to 105°C and the reaction continues for 2 h. The product obtained replaces the modified epoxy resin, and the remaining steps are the same.

[0065] Comparative Example 3: Compared with Example 1, this comparative example uses hexamethylcyclotrisiloxane instead of trifluoropropylmethylcyclotrisiloxane, and the other steps are the same.

[0066] Standard concrete samples were prepared according to GB / T50082-2009 and treated using the methods of Examples 1-3 and Comparative Examples 1-3 to obtain experimental samples. Waterproofing tests were conducted by immersing the samples in a 6M sodium chloride solution and applying a 60V DC voltage to both sides of the sample block. The amount of charge passing through the sample block was continuously monitored for 6 hours. The resistance of concrete to chloride ion penetration was evaluated based on the amount of charge. The amount of charge is positively correlated with the chloride ion penetration coefficient. The penetration coefficient was calculated using a formula. The test results are shown in Table 1 below.

[0067] Table 1 As shown in Table 1, this application has excellent waterproof and salt-proof effects.

[0068] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A seven-layer gradient functional composite repair method for concrete freeze-thaw damage, characterized by: Specifically, the steps include the following: Step S1: Investigate the freeze-thaw damage area to determine the depth and extent of the damage. Use mechanical tools to remove all loose, peeling and cracked concrete until the base surface is exposed. Perform rust removal and anti-corrosion treatment on the exposed reinforcement. Use high-pressure water jet to clean the interface and remove dust and debris. Step S2: Weigh the following raw materials by weight: 80-90 parts water-based epoxy resin, 15-25 parts nano silica, 1-2 parts defoamer, 0.1-0.5 parts rheology modifier, 3-8 parts adhesion promoter, 15-25 parts curing agent and 20-30 parts water. Mix the raw materials evenly to obtain a primer. Apply the primer to the substrate surface and cure until surface dry. Step S3: Weigh the following raw materials by weight: 100-120 parts cement, 85-150 parts coarse sand, 65-100 parts fine sand, 8-15 parts EVA latex powder, 5-10 parts silica fume, 0.01-0.05 parts air-entraining agent and 0.1-0.3 parts basalt fiber. Mix the raw materials evenly to prepare the antifreeze repair mortar. Apply the antifreeze repair mortar to the primer surface and cure until surface dry. Step S4: Weigh the following raw materials by weight: 60-80 parts water-based silicone emulsion, 15-25 parts nano silica sol, 5-8 parts silicone water-repellent agent, 0.1-0.3 parts leveling agent, 0.1-0.3 parts defoamer and 20-30 parts water. Mix the raw materials evenly to obtain a nano-reinforced coating. Apply the nano-reinforced coating to the surface of the antifreeze repair mortar and cure until the surface is dry. Step S5: Mix component A and component B at a mass ratio of 1:1-1.5 to prepare a cement-based antifreeze, waterproof, and anticorrosive protective coating. Component A includes the following raw materials by weight: 40-60 parts polyacrylate emulsion, 10-20 parts ethylene-vinyl acetate copolymer emulsion, 2-5 parts dodecyl alcohol ester, 0.5-2 parts trimethylolpropane, 0.1-0.3 parts tributyl phosphate, and 20-30 parts water. Component B includes the following raw materials by weight: 70-80 parts pozzolanic silicate cement, 15-25 parts quartz powder, 5-10 parts silica fume, and 0.3-0.8 parts polycarboxylate superplasticizer. Apply the cement-based antifreeze, waterproof, and anticorrosive protective coating to the surface of the nano-reinforced coating and cure until surface dry. Step S6: Mix component C and component D at a mass ratio of 1:1.2 to prepare an alkali-resistant sealing primer. Component C includes the following raw materials by weight: 80-100 parts epoxy resin, 5-15 parts softening resin, 5-15 parts glycidyl butyl ether, 0.5-1 part defoamer, and 0.1-0.5 parts leveling agent. Component D includes the following raw materials by weight: 80-100 parts modified amine curing agent and 1-5 parts silane coupling agent. Apply the alkali-resistant sealing primer to the surface of the cement-based antifreeze, waterproof, and anticorrosion protective coating and cure until surface dry. Step S7: Mix component E and component F in a mass ratio of 1:1 to obtain a protective coating. Component E includes the following raw materials by weight: 100-120 parts modified epoxy resin and 40-60 parts propylene glycol methyl ether acetate. Component F includes the following raw materials by weight: 15-25 parts diaminocage-type silsesquioxane, 5-15 parts KH550 and 10-20 parts n-butanol. Apply two layers of protective coating to the surface of the alkali-resistant sealing primer and cure until surface dry.

2. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 1, characterized in that: The modified epoxy resin is prepared by the following steps: Step A1: Mix octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and deionized water, and purge with nitrogen to carry out the reaction to obtain epoxy polysiloxane. Step A2: Dissolve lithium dimethylvinylsilane in tetrahydrofuran, purge with nitrogen for protection, stir and add trifluoropropylmethylcyclotrisiloxane, heat and react, then add trichlorosilane and continue the reaction to obtain branched polysiloxane. Step A3: Mix branched polysiloxane, 3-mercaptopropyltrimethoxysilane, benzophenone and xylene, purify with nitrogen, and react under ultraviolet light to obtain modified branched polysiloxane. Step A4: Mix the modified branched polysiloxane, epoxy polysiloxane, caster catalyst and xylene, purge with nitrogen gas for protection, and react to obtain the modified epoxy resin.

3. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 2, characterized in that: The ratio of octamethylcyclotetrasiloxane, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, tetramethyldivinyldisiloxane, tetramethylammonium hydroxide and deionized water in step A1 is 1 mol: 0.4 mol: 1 mol: 1.5 mol: 20 mL.

4. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 2, characterized in that: The molar ratio of Si-Cl bonds on lithium dimethylvinylsilane, trifluoropropylmethylcyclotrisiloxane and trichlorosilane in step A2 is 1:4:

1.

5. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 2, characterized in that: The molar ratio of branched polysiloxane and 3-mercaptopropyltrimethoxysilane in step A3 is 1:

3.

6. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 2, characterized in that: The molar ratio of the modified branched polysiloxane and epoxy polysiloxane mentioned in step A4 is 1:

2.

7. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 1, characterized in that: The diaminocage-type silsesquioxane is prepared by the following steps: A mixture of aminopropylheptaisobutylsilsesquioxane and tetrahydrofuran was purged with nitrogen for protection, stirred, and tetramethylammonium hydroxide was added. The mixture was heated to obtain an intermediate. The intermediate was then mixed with toluene and stirred, and aminopropyltriethoxysilane and triethylamine were added. The mixture was refluxed to obtain diaminocage-type silsesquioxane.

8. The construction method for seven-layer gradient functional composite repair of concrete freeze-thaw damage according to claim 7, characterized in that: The molar ratio of aminopropylheptaisobutylsilsesquioxane to tetramethylammonium hydroxide is 1:1.2, and the amounts of the intermediate and aminopropyltriethoxysilane are 1:2.5.

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