A polymer cement-based repair material and a method of making the same

Abstract

The application discloses a polymer cement-based repairing material and a preparation method thereof, and relates to the technical field of building materials. In the preparation of the polymer cement-based repairing material, modified silicon dioxide is prepared by reacting pre-modified silicon dioxide with cysteine; carboxyl styrene-butadiene emulsion is prepared by polymerizing and emulsifying styrene, acrylic acid and 1,3-butadiene; modified styrene-butadiene emulsion is prepared by reacting the modified silicon dioxide with the carboxyl styrene-butadiene emulsion; modified basalt fiber is prepared by hydrolyzing gamma-aminopropyl triethoxysilane and grafting the gamma-aminopropyl triethoxysilane on the surface of pretreated basalt fiber; and the polymer cement-based repairing material is prepared by mixing cement, quartz sand, limestone powder, a water reducing agent, a defoaming agent, a water retaining agent, sodium gluconate, modified basalt fiber and dilute emulsion. The polymer cement-based repairing material prepared by the application has excellent anti-drying shrinkage performance, interfacial bonding performance and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a polymer cement-based repair material and its preparation method. Background Technology

[0002] Styrene-butadiene emulsion modified sulfoaluminate cement mortar repair material has advantages such as ultra-early strength and low-temperature construction capability. Combined with the excellent toughness and interfacial bonding performance of polymers, it can meet the engineering needs of emergency rapid repair and rapid commissioning of concrete, and has become the mainstream material in the field of rapid concrete repair.

[0003] However, most commercially available styrene-butadiene emulsions on the market have random inert structures, lack controllable active crosslinking sites and sufficient polar functional groups, have poor calcium ion stability, and are prone to flocculation and demulsification in high-calcium and high-aluminum sulfoaluminate systems. This not only damages workability but also significantly reduces the density and impermeability and freeze-thaw resistance of the hardened body. Furthermore, they rely solely on physical adsorption to achieve interfacial bonding, resulting in weak interfacial bonding between the organic phase and inorganic fillers and cement hydration products. After repair, problems such as interfacial debonding, secondary cracking, and surface peeling are likely to occur, leading to insufficient long-term service durability.

[0004] Therefore, developing a polymer-based cement repair material with a stable covalent hybrid cross-linked structure and excellent interfacial bonding performance is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a polymer cement-based repair material and its preparation method to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following solution: A polymer cement-based repair material is prepared by reacting pre-modified silica with cysteine ​​to obtain modified silica; by polymerizing and emulsifying styrene, acrylic acid, and 1,3-butadiene to obtain a carboxylated styrene-butadiene emulsion; by reacting modified silica with the carboxylated styrene-butadiene emulsion to obtain a modified styrene-butadiene emulsion; by hydrolyzing γ-aminopropyltriethoxysilane and grafting it onto the surface of pretreated basalt fibers to obtain modified basalt fibers; and by mixing cement, quartz sand, limestone powder, water-reducing agent, defoamer, water-retaining agent, sodium gluconate, modified basalt fibers, and diluted emulsion. The pre-modified silica is prepared by hydrolyzing 3-chloropropyltriethoxysilane and grafting it onto the surface of silica. The pretreated basalt fiber is obtained by degreasing and pretreating basalt fiber; The diluted emulsion is prepared by mixing modified styrene-butadiene emulsion and deionized water.

[0007] A method for preparing a polymer cement-based repair material, the method comprising the following preparation steps: (1) Mix pre-modified silica, cysteine, anhydrous ethanol, deionized water, potassium iodide, and anhydrous potassium carbonate in a mass ratio of 1:(0.1~0.12):(11~13):(1.2~1.4):(0.006~0.008):(0.12~0.14) until homogeneous. Stir ultrasonically at room temperature for 20~40 min. Under nitrogen protection, heat to 75~85℃ and stir for 23~25 h. Cool to room temperature, filter, add 9~11 times the mass of ethanol of pre-modified silica, add 0.4~0.6 mol / L dilute hydrochloric acid at 0~4℃ to adjust the pH of the system to 5~6, stir for 3~5 min, filter, wash with anhydrous ethanol 2~4 times, and vacuum dry at 35~45℃ for 11~13 h to obtain modified silica; (2) By mass, 60-65 parts of styrene, 1.5-3.5 parts of acrylic acid, 0.11-0.13 parts of tert-dodecyl mercaptan, 3.2-3.4 parts of emulsifier, 0.2-0.4 parts of sodium bicarbonate, and 150-170 parts of deionized water are mixed evenly and stirred at room temperature for 4-6 minutes. Then, 35-40 parts of 1,3-butadiene are introduced and stirred for another 20-40 minutes to obtain a pre-emulsion. The pre-emulsion is mixed evenly with ammonium persulfate solution and heated to 70-80°C under nitrogen protection. The mixture is stirred for 7-8 hours and cooled to 35-45°C. 25 vol% dilute ammonia is added to adjust the pH to 8.8-9.0 to obtain a carboxylated styrene-butadiene emulsion. (3) Take 100 parts by mass of carboxylated styrene-butadiene emulsion, add modified silica dispersion under nitrogen protection, stir at room temperature for 10-20 min, add initiator solution under light protection, continue stirring for 5-15 min, and irradiate under 365nm ultraviolet lamp for 40-50 min to obtain modified styrene-butadiene emulsion. (4) Mix anhydrous ethanol and deionized water at a volume ratio of 9:1, add glacial acetic acid to adjust the pH of the system to 4~4.4, add γ-aminopropyltriethoxysilane at 0.3~0.5 times the mass of deionized water, stir at 55~65℃ for 25~35 min, cool to 45~55℃, add pretreated basalt fiber at 1~1.2 times the mass of deionized water, continue stirring and reacting for 50~70 min, filter, wash with anhydrous ethanol 2~4 times, dry at 100~110℃ for 50~70 min, cool naturally to room temperature, and obtain modified basalt fiber; (5) By mass, 60-70 parts of modified styrene-butadiene emulsion and 28-30 parts of deionized water are mixed evenly and stirred at room temperature for 1-3 minutes to obtain a diluted emulsion; 220-240 parts of cement, 550-600 parts of quartz sand, 25-35 parts of limestone powder, 0.6-0.8 parts of water-reducing agent, 0.44-0.48 parts of defoamer, 0.11-0.13 parts of water-retaining agent, and 0.07-0.09 parts of sodium gluconate are mixed evenly and stirred at room temperature for 4-6 minutes. 1.4-1.6 parts of modified basalt fiber are added in three portions and stirred for 1-3 minutes. The diluted emulsion is added and stirred for 3-5 minutes to obtain a polymer cement-based repair material.

[0008] As an optimization, the preparation process of the pre-modified silica in step (1) is as follows: anhydrous ethanol and deionized water are mixed evenly at a volume ratio of 9:1, 0.4 to 0.6 times the mass of deionized water is added to silica, ultrasonically dispersed at room temperature for 20 to 40 minutes, pH is adjusted to 4 to 5 with glacial acetic acid, 0.3 to 0.4 times the mass of silica is added to 3-chloropropyltriethoxysilane, the temperature is raised to 50 to 60°C, the reaction is continued to be stirred for 5 to 6 hours, cooled to room temperature, filtered, washed 2 to 4 times with anhydrous ethanol, and vacuum dried at 40 to 50°C for 11 to 13 hours to obtain pre-modified silica.

[0009] As an optimization, the emulsifier in step (2) is prepared by mixing sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 2:1.

[0010] As an optimization, the preparation process of the ammonium persulfate solution in step (2) is as follows: 0.5~0.7 parts of ammonium persulfate and deionized water are mixed evenly at a mass ratio of 1:(18~22), and stirred at room temperature for 5~15 minutes to obtain the ammonium persulfate solution.

[0011] As an optimization, the preparation process of the modified silica dispersion in step (3) is as follows: 4-6 parts of modified silica are mixed with deionized water and anhydrous ethanol at a mass ratio of 1:(1.5-2.5):(0.75-1.25) and ultrasonically dispersed at 0-4℃ for 20-30 min. Then, 0.003-0.005 times the mass of the modified silica is added to tris(2-carboxyethyl)phosphine and stirred at room temperature for 4-6 min to obtain the modified silica dispersion.

[0012] As an optimization, the preparation process of the initiator solution in step (4) is as follows: 0.17~0.19 parts of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, triethanolamine, and deionized water are mixed evenly at a mass ratio of 1:(1.9~2.1):(12~14) and stirred for 4~6 minutes under light-protected conditions to obtain the initiator solution.

[0013] As an optimization, the preparation process of the pretreated basalt fiber in step (4) is as follows: basalt fiber and acetone are mixed evenly at a mass ratio of 1:(4~6), soaked at room temperature for 1.5~2.5h, filtered, washed with deionized water 2~4 times, and dried at 75~85℃ for 1.5~2.5h to obtain pretreated basalt fiber.

[0014] As an optimization, the basalt fiber has a length of 12 mm, a tensile strength >1050 MPa, and an elastic strength >35 GPa, and was purchased from Taian Haoda New Materials Co., Ltd.

[0015] As an optimization, the cement used in step (5) is 42.5 sulfoaluminate cement, with an initial setting time of 30 min and a final setting time of 150 min, purchased from Wuhan Jiyesheng Chemical Co., Ltd.; the quartz sand has a particle size of 40-80 mesh with continuous gradation and a density of 2.65 g / cm³. 3 The limestone powder was purchased from Wanzhu Mineral Products Co., Ltd. in Lingshou County; the particle size of the limestone powder was 400 mesh, and the density was 2.6 g / cm³. 3 The water-reducing agent was purchased from Shijiazhuang Baijiang Mineral Products Co., Ltd.; the water-reducing agent was polycarboxylate superplasticizer, purchased from Shandong Xinhongyue Chemical Co., Ltd.; the defoamer was modified polyether powder defoamer, purchased from Nanjing Chuhai New Material Technology Co., Ltd.; and the water-retaining agent was hydroxypropyl methylcellulose water-retaining agent with a viscosity of 100,000 mPa·s, purchased from Guangzhou Yehusheng Chemical Co., Ltd.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are: First, 3-chloropropyltriethoxysilane is hydrolyzed and grafted onto the surface of silica to prepare pre-modified silica. The pre-modified silica is then reacted with cysteine ​​to prepare modified silica. The multi-functional groups on the silica surface undergo click addition and hydrogen bonding reactions with the C=C of the carboxylated styrene-butadiene emulsion and cement hydration products, building a cross-linking bridge between inorganic nanoparticles, organic polymers, and the cement matrix. This strengthens the organic-inorganic interfacial bonding force, eliminates interfacial pores and defects, and thus endows the polymer cement-based repair material with excellent mechanical strength and interfacial adhesion properties.

[0017] Secondly, a carboxyl-based styrene-butadiene emulsion is prepared by polymerizing and emulsifying styrene, acrylic acid, and 1,3-butadiene. After the polymer forms a film, it creates a continuous flexible organic network that interweaves and interlocks with the rigid inorganic skeleton formed by cement hydration. This effectively buffers stress concentration, inhibits microcrack propagation, and significantly improves the defects of cement-based materials, such as high brittleness and easy cracking. At the same time, the carboxyl groups on the surface of the styrene-butadiene emulsion can form hydrogen bonds and chemical bonds with cement hydration products, greatly improving the interfacial bonding performance and overall flexibility of new and old concrete, thereby effectively improving the interfacial bonding performance and mechanical properties of polymer cement-based repair materials. Furthermore, after the carboxyl-based styrene-butadiene emulsion is incorporated into the slurry, it can be uniformly dispersed and fill the capillary pores and micropores of the cement hydration system, reducing water evaporation channels, lowering the rate of free water loss inside the hardened body, and alleviating the volume shrinkage caused by drying and water loss, thereby significantly improving the resistance to drying shrinkage cracking of polymer cement-based repair materials.

[0018] Finally, basalt fibers were pretreated by degreasing to obtain pretreated basalt fibers; γ-aminopropyltriethoxysilane was hydrolyzed and grafted onto the surface of the pretreated basalt fibers to obtain modified basalt fibers; highly active amino functional groups were introduced into the surface of the basalt fibers. The amino groups can form stable hydrogen bonds and amide bonds with cement hydration products and carboxyl groups of carboxylated styrene-butadiene emulsion, which greatly enhances the interfacial bonding strength between the modified basalt fibers and the organic-inorganic composite matrix. At the same time, the core functions of basalt fibers in bridging, crack prevention, stress dispersion and bidirectional bonding are brought into play, giving the polymer cement-based repair material resistance to drying shrinkage cracking and excellent mechanical properties. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: A method for preparing a polymer cement-based repair material, the method comprising the following steps: (1) Anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1. Silica with a mass of 0.4 times that of deionized water was added. The mixture was ultrasonically dispersed at room temperature for 40 min. The pH was adjusted to 4 with glacial acetic acid. 3-chloropropyltriethoxysilane with a mass of 0.3 times that of silica was added. The mixture was heated to 50 °C and stirred for 6 h. After cooling to room temperature, the mixture was filtered, washed twice with anhydrous ethanol, and vacuum dried at 40 °C for 13 h to obtain pre-modified silica. The pre-modified silica, cysteine, anhydrous ethanol, and deionized water were then mixed. Water, potassium iodide, and anhydrous potassium carbonate were mixed evenly in a mass ratio of 1:0.1:11:1.2:0.006:0.12. The mixture was ultrasonically stirred at room temperature for 40 min. Under nitrogen protection, the temperature was raised to 75℃ and stirred for 25 h. After cooling to room temperature, the mixture was filtered. Ethanol with a mass of 9 times that of the pre-modified silica was added. 0.4 mol / L dilute hydrochloric acid was added at 0℃ to adjust the pH of the system to 5. The mixture was stirred for 5 min, filtered, washed twice with anhydrous ethanol, and vacuum dried at 35℃ for 13 h to obtain modified silica. (2) By mass, 60 parts of styrene, 1.5 parts of acrylic acid, 0.11 parts of tert-dodecyl mercaptan, 3.2 parts of emulsifier, 0.2 parts of sodium bicarbonate and 150 parts of deionized water are mixed evenly and stirred at room temperature for 6 min. Then, 35 parts of 1,3-butadiene are introduced and stirred for another 40 min to obtain a pre-emulsion. 0.5 parts of ammonium persulfate and deionized water are mixed evenly at a mass ratio of 1:18 and stirred at room temperature for 15 min to obtain an ammonium persulfate solution. The pre-emulsion and the ammonium persulfate solution are mixed evenly and heated to 70°C under nitrogen protection. The mixture is stirred for 8 h and cooled to 35°C. 25 vol% dilute ammonia is added to adjust the pH to 8.8 to obtain a carboxylated styrene-butadiene emulsion. (3) By mass fraction, 5 parts of modified silica were mixed with deionized water and anhydrous ethanol at a mass ratio of 1:1.5:0.75 and ultrasonically dispersed at 0℃ for 30 min. Tris(2-carboxyethyl)phosphine at a mass ratio of 0.003 times that of modified silica was added and stirred at room temperature for 6 min to obtain modified silica dispersion. 0.17 parts of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone were mixed with triethanolamine and deionized water at a mass ratio of 1:1.9:12 and stirred at light-protected conditions for 6 min to obtain initiator solution. 100 parts of carboxylated styrene-butadiene emulsion were taken, and modified silica dispersion was added under nitrogen protection. Stirred at room temperature for 20 min. Initiator solution was added under light-protected conditions, and stirring was continued for 15 min. The emulsion was irradiated under a 365nm ultraviolet lamp for 50 min to obtain modified styrene-butadiene emulsion. (4) Basalt fiber and acetone were mixed evenly at a mass ratio of 1:4, soaked at room temperature for 2.5 h, filtered, washed twice with deionized water, and dried at 75 °C for 2.5 h to obtain pretreated basalt fiber; anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1, glacial acetic acid was added to adjust the pH of the system to 4, γ-aminopropyltriethoxysilane was added at 0.3 times the mass of deionized water, stirred at 55 °C for 35 min, cooled to 45 °C, pretreated basalt fiber at 1 times the mass of deionized water was added, and the reaction was continued to be stirred for 70 min, filtered, washed twice with anhydrous ethanol, dried at 100 °C for 70 min, and naturally cooled to room temperature to obtain modified basalt fiber; (5) By mass, 65 parts of modified styrene-butadiene emulsion and 29 parts of deionized water are mixed evenly and stirred at room temperature for 1 min to obtain a diluted emulsion; 220 parts of cement, 550 parts of quartz sand, 25 parts of limestone powder, 0.6 parts of water-reducing agent, 0.44 parts of defoamer, 0.11 parts of water-retaining agent and 0.07 parts of sodium gluconate are mixed evenly and stirred at room temperature for 6 min; 1.5 parts of modified basalt fiber are added in three portions and stirred for 3 min; the diluted emulsion is added and stirred for 5 min to obtain a polymer cement-based repair material.

[0021] Example 2: A method for preparing a polymer cement-based repair material, the method comprising the following steps: (1) Mix anhydrous ethanol and deionized water at a volume ratio of 9:1, add silica at a mass of 0.5 times that of deionized water, sonicate for 30 min at room temperature, adjust pH to 4.5 with glacial acetic acid, add 3-chloropropyltriethoxysilane at a mass of 0.35 times that of silica, heat to 55°C, continue stirring for 5.5 h, cool to room temperature, filter, wash 3 times with anhydrous ethanol, and vacuum dry at 45°C for 12 h to obtain pre-modified silica; combine pre-modified silica, cysteine, anhydrous ethanol, and deionized water. Water, potassium iodide, and anhydrous potassium carbonate were mixed evenly in a mass ratio of 1:0.11:12:1.3:0.007:0.13. The mixture was ultrasonically stirred at room temperature for 30 min. Under nitrogen protection, the temperature was raised to 80℃ and stirred for 24 h. After cooling to room temperature, the mixture was filtered. Ethanol with a mass of 10 times that of the pre-modified silica was added. 0.5 mol / L dilute hydrochloric acid was added at 2℃ to adjust the pH of the system to 5.5. The mixture was stirred for 4 min, filtered, washed three times with anhydrous ethanol, and vacuum dried at 40℃ for 12 h to obtain modified silica. (2) By mass, 62.5 parts styrene, 2.5 parts acrylic acid, 0.12 parts tert-dodecyl mercaptan, 3.3 parts emulsifier, 0.3 parts sodium bicarbonate and 16 parts deionized water are mixed evenly and stirred at room temperature for 5 min. Then, 37.5 parts 1,3-butadiene are introduced and stirred for another 30 min to obtain a pre-emulsion. 0.6 parts ammonium persulfate and deionized water are mixed evenly at a mass ratio of 1:20 and stirred at room temperature for 10 min to obtain an ammonium persulfate solution. The pre-emulsion and the ammonium persulfate solution are mixed evenly and heated to 75°C under nitrogen protection. The mixture is stirred for 7.5 h and cooled to 40°C. 25 vol% dilute ammonia is added to adjust the pH to 8.9 to obtain a carboxylated styrene-butadiene emulsion. (3) By mass, 5 parts of modified silica were mixed with deionized water and anhydrous ethanol at a mass ratio of 1:2:1 and ultrasonically dispersed at 2°C for 25 min. Tris(2-carboxyethyl)phosphine at a mass ratio of 0.004 times that of modified silica was added and stirred at room temperature for 5 min to obtain modified silica dispersion. 0.18 parts of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone were mixed with triethanolamine and deionized water at a mass ratio of 1:2:13 and stirred at light-protected conditions for 5 min to obtain initiator solution. 100 parts of carboxylated styrene-butadiene emulsion were taken, and modified silica dispersion was added under nitrogen protection. Stirred at room temperature for 15 min. Initiator solution was added under light-protected conditions, and stirring was continued for 10 min. The emulsion was irradiated under a 365 nm ultraviolet lamp for 45 min to obtain modified styrene-butadiene emulsion. (4) Basalt fiber and acetone were mixed evenly at a mass ratio of 1:5, soaked at room temperature for 2 hours, filtered, washed three times with deionized water, and dried at 80℃ for 2 hours to obtain pretreated basalt fiber; anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1, glacial acetic acid was added to adjust the pH of the system to 4.2, γ-aminopropyltriethoxysilane with a mass of 0.4 times that of deionized water was added, stirred at 60℃ for 30 minutes, cooled to 50℃, pretreated basalt fiber with a mass of 1.1 times that of deionized water was added, and the reaction was continued to be stirred for 60 minutes, filtered, washed three times with anhydrous ethanol, dried at 105℃ for 60 minutes, and naturally cooled to room temperature to obtain modified basalt fiber; (5) By mass, 65 parts of modified styrene-butadiene emulsion and 29 parts of deionized water are mixed evenly and stirred at room temperature for 2 minutes to obtain a diluted emulsion; 230 parts of cement, 575 parts of quartz sand, 30 parts of limestone powder, 0.7 parts of water-reducing agent, 0.46 parts of defoamer, 0.12 parts of water-retaining agent and 0.08 parts of sodium gluconate are mixed evenly and stirred at room temperature for 5 minutes. 1.5 parts of modified basalt fiber are added in three portions and stirred for 2 minutes. The diluted emulsion is added and stirred for 4 minutes to obtain a polymer cement-based repair material.

[0022] Example 3: A method for preparing a polymer cement-based repair material, the method comprising the following steps: (1) Anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1. Silica with a mass of 0.6 times that of deionized water was added. The mixture was ultrasonically dispersed at room temperature for 20 min. The pH was adjusted to 5 with glacial acetic acid. 3-chloropropyltriethoxysilane with a mass of 0.4 times that of silica was added. The mixture was heated to 60 °C and stirred for 5 h. After cooling to room temperature, the mixture was filtered, washed four times with anhydrous ethanol, and dried under vacuum at 50 °C for 11 h to obtain pre-modified silica. The pre-modified silica, cysteine, anhydrous ethanol, and deionized water were then mixed. Potassium iodide and anhydrous potassium carbonate were mixed evenly in a mass ratio of 1:0.12:13:1.4:0.008:0.14. The mixture was ultrasonically stirred at room temperature for 20 min. Under nitrogen protection, the temperature was raised to 85℃ and stirred for 23 h. After cooling to room temperature, the mixture was filtered. Ethanol with a mass of 11 times that of the pre-modified silica was added. 0.6 mol / L dilute hydrochloric acid was added at 4℃ to adjust the pH of the system to 6. The mixture was stirred for 3 min, filtered, washed 4 times with anhydrous ethanol, and vacuum dried at 45℃ for 11 h to obtain modified silica. (2) By mass, 65 parts of styrene, 3.5 parts of acrylic acid, 0.13 parts of tert-dodecyl mercaptan, 3.4 parts of emulsifier, 0.4 parts of sodium bicarbonate and 170 parts of deionized water are mixed evenly and stirred at room temperature for 4 min. Then, 40 parts of 1,3-butadiene are introduced and stirred for another 20 min to obtain a pre-emulsion. 0.7 parts of ammonium persulfate and deionized water are mixed evenly at a mass ratio of 1:22 and stirred at room temperature for 5 min to obtain an ammonium persulfate solution. The pre-emulsion and the ammonium persulfate solution are mixed evenly and heated to 80°C under nitrogen protection. The mixture is stirred for 7 h and cooled to 45°C. 25 vol% dilute ammonia is added to adjust the pH to 9.0 to obtain a carboxylated styrene-butadiene emulsion. (3) By mass fraction, 5 parts of modified silica were mixed with deionized water and anhydrous ethanol at a mass ratio of 1:2.5:1.25 and ultrasonically dispersed at 4°C for 20 min. Tris(2-carboxyethyl)phosphine at a mass ratio of 0.005 times that of modified silica was added and stirred at room temperature for 4 min to obtain a modified silica dispersion. 0.19 parts of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone were mixed with triethanolamine and deionized water at a mass ratio of 1:2.1:14 and stirred at light-protected conditions for 4 min to obtain an initiator solution. 100 parts of carboxylated styrene-butadiene emulsion were taken, and the modified silica dispersion was added under nitrogen protection. The mixture was stirred at room temperature for 10 min. The initiator solution was added at light-protected conditions, and the mixture was stirred for another 5 min. The mixture was then irradiated under a 365 nm ultraviolet lamp for 40 min to obtain a modified styrene-butadiene emulsion. (4) Basalt fiber and acetone were mixed evenly at a mass ratio of 1:6, soaked at room temperature for 1.5h, filtered, washed 4 times with deionized water, and dried at 85℃ for 1.5h to obtain pretreated basalt fiber; anhydrous ethanol and deionized water were mixed evenly at a volume ratio of 9:1, glacial acetic acid was added to adjust the pH of the system to 4.4, γ-aminopropyltriethoxysilane was added at 0.5 times the mass of deionized water, stirred at 65℃ for 25min, cooled to 55℃, pretreated basalt fiber at 1.2 times the mass of deionized water was added, and the reaction was continued to be stirred for 50min, filtered, washed 4 times with anhydrous ethanol, dried at 110℃ for 50min, and naturally cooled to room temperature to obtain modified basalt fiber; (5) By mass, 65 parts of modified styrene-butadiene emulsion and 29 parts of deionized water are mixed evenly and stirred at room temperature for 1 min to obtain a diluted emulsion; 240 parts of cement, 600 parts of quartz sand, 35 parts of limestone powder, 0.8 parts of water-reducing agent, 0.48 parts of defoamer, 0.13 parts of water-retaining agent and 0.09 parts of sodium gluconate are mixed evenly and stirred at room temperature for 4 min; 1.5 parts of modified basalt fiber are added in three portions and stirred for 1 min; the diluted emulsion is added and stirred for 3 min to obtain a polymer cement-based repair material.

[0023] Comparative Example 1: The preparation method of the polymer cement-based repair material in Comparative Example 1 differs from that in Example 2 in that the amount of modified silica added in step (3) is changed to 0 parts. The remaining steps are the same as in Example 2.

[0024] Comparative Example 2: The preparation method of the polymer cement-based repair material in Comparative Example 2 differs from that in Example 2 in that the amount of modified silica added in step (3) is changed to 2 parts. The remaining steps are the same as in Example 2.

[0025] Comparative Example 3: The preparation method of the polymer cement-based repair material in Comparative Example 3 differs from that in Example 2 in that the amount of modified silica added in step (3) is changed to 4 parts. The remaining steps are the same as in Example 2.

[0026] Comparative Example 4: The preparation method of the polymer cement-based repair material in Comparative Example 4 differs from that in Example 2 in that the amount of modified silica added in step (3) is changed to 6 parts. The remaining steps are the same as in Example 2.

[0027] Comparative Example 5: The preparation method of the polymer cement-based repair material in Comparative Example 5 differs from that in Example 2 in that "62.5 parts styrene and 2.5 parts acrylic acid" in step (2) is changed to "65 parts styrene". The remaining steps are the same as in Example 2.

[0028] Comparative Example 6: The preparation method of the polymer cement-based repair material in Comparative Example 6 differs from that in Example 2 in that steps (1) to (3) are omitted, and the modified styrene-butadiene emulsion in step (5) is replaced with styrene-acrylic emulsion. The remaining steps are the same as in Example 2.

[0029] Comparative Example 7: The preparation method of the polymer cement-based repair material in Comparative Example 7 differs from that in Example 2 in that steps (1) to (3) are omitted, and the modified styrene-butadiene emulsion in step (5) is replaced with polyvinyl acetate emulsion. The remaining steps are the same as in Example 2.

[0030] Comparative Example 8: The preparation method of the polymer cement-based repair material in Comparative Example 8 differs from that in Example 2 in that the amount of modified styrene-butadiene emulsion added in step (5) is changed to 50 parts. The remaining steps are the same as in Example 2.

[0031] Comparative Example 9: The preparation method of the polymer cement-based repair material in Comparative Example 9 differs from that in Example 2 in that the amount of modified styrene-butadiene emulsion added in step (5) is changed to 60 parts. The remaining steps are the same as in Example 2.

[0032] Comparative Example 10: The preparation method of the polymer cement-based repair material in Comparative Example 10 differs from that in Example 2 in that the amount of modified styrene-butadiene emulsion added in step (5) is changed to 70 parts. The remaining steps are the same as in Example 2.

[0033] Comparative Example 11: The preparation method of the polymer cement-based repair material in Comparative Example 11 differs from that in Example 2 in that the amount of modified styrene-butadiene emulsion added in step (5) is changed to 75 parts. The remaining steps are the same as in Example 2.

[0034] Comparative Example 12: The preparation method of the polymer cement-based repair material in Comparative Example 12 differs from that in Example 2 in that step (4) is omitted, and the modified basalt fiber in step (5) is replaced with polypropylene fiber. The remaining steps are the same as in Example 2.

[0035] Comparative Example 13: The preparation method of the polymer cement-based repair material in Comparative Example 13 differs from that in Example 2 in that step (4) is omitted, and the modified basalt fiber in step (5) is replaced with carbon fiber. The remaining steps are the same as in Example 2.

[0036] Comparative Example 14: The preparation method of the polymer cement-based repair material in Comparative Example 14 differs from that in Example 2 in that γ-aminopropyltriethoxysilane in step (4) is replaced with 3-mercaptopropyltriethoxysilane. The remaining steps are the same as in Example 2.

[0037] Comparative Example 15: The preparation method of the polymer cement-based repair material in Comparative Example 15 differs from that in Example 2 in that γ-aminopropyltriethoxysilane in step (4) is replaced with 5,6-epoxyhexyltriethoxysilane. The remaining steps are the same as in Example 2.

[0038] Comparative Example 16: The preparation method of the polymer cement-based repair material in Comparative Example 16 differs from that in Example 2 in that step (4) is omitted, and modified basalt fibers are not added in step (5). The remaining steps are the same as in Example 2.

[0039] Comparative Example 17: The preparation method of the polymer cement-based repair material in Comparative Example 17 differs from that in Example 2 in that the amount of modified basalt fiber added in step (5) is changed to 0.5 parts. The remaining steps are the same as in Example 2.

[0040] Comparative Example 18: The preparation method of the polymer cement-based repair material in Comparative Example 18 differs from that in Example 2 in that the amount of modified basalt fiber added in step (5) is changed to 1 part. The remaining steps are the same as in Example 2.

[0041] Comparative Example 19: The preparation method of the polymer cement-based repair material in Comparative Example 19 differs from that in Example 2 in that the amount of modified basalt fiber added in step (5) is changed to 2 parts. The remaining steps are the same as in Example 2.

[0042] Comparative Example 20: The preparation method of the polymer cement-based repair material in Comparative Example 20 differs from that in Example 2 in that the amount of modified basalt fiber added in step (5) is changed to 2.5 parts. The remaining steps are the same as in Example 2.

[0043] Test Example 1 Test of the optimal addition amount of modified silica Test method: Mechanical property testing: According to GB / T 17671-2021, the polymer cement-based repair materials of the examples and comparative examples were mixed evenly, cast into 40mm×40mm×160mm molds, cured in a standard curing chamber for 1 day, demolded, and cured in an environment of 20℃ and 60% humidity for 28 days. The flexural strength and compressive strength of the mortar were tested using a fully automatic cement mortar testing machine. The results are shown in Table 1.

[0044] Interfacial bond performance test: Ordinary cement mortar specimens were prepared with a cement-sand ratio of 1:3 and a water-cement ratio of 0.42. After curing for 28 days, the specimens were cut in half from the middle, the cut surfaces were cleaned, and one half of the specimen was placed into a mold. The other half was filled with the polymer cement-based repair material from the examples and comparative examples, reshaped, and then cured to the specified age for interfacial bond strength testing, characterized by flexural strength. The results are shown in Table 1.

[0045] Table 1 Example 1 5 8.13 48.81 2.26 Example 2 5 8.26 49.36 2.38 Example 3 5 8.21 48.97 2.31 Comparative Example 1 0 6.94 45.86 1.45 Comparative Example 2 2 7.23 46.92 1.59 Comparative Example 3 4 7.67 47.31 1.98 Comparative Example 4 6 7.34 49.43 1.92 By comparing the flexural strength, compressive strength, and bond strength of Examples 1-3 and Comparative Examples 1-4, it was demonstrated that the multi-functional groups on the silica surface undergo click addition and hydrogen bonding reactions with the C=C of the carboxylated styrene-butadiene emulsion and cement hydration products, establishing a cross-linking bridge between inorganic nanoparticles, organic polymers, and the cement matrix. This strengthens the organic-inorganic interfacial bonding force, eliminates interfacial porosity and defects, and thus endows the polymer cement-based repair material with excellent mechanical strength and interfacial bonding properties. The preferred amount of modified silica added in this system is 5 parts.

[0046] Test Example 2 Test on the optimal type and dosage of polymer emulsion Test method: Mechanical property testing: Same as test example 1. Results are shown in Tables 2 and 3.

[0047] Interfacial adhesion performance test: Same as test example 1. The results are shown in Tables 2 and 3.

[0048] Drying shrinkage test: According to JC / T 603-2004, the polymer cement-based repair materials of the examples and comparative examples were mixed evenly and cast into 25mm×25mm×280mm molds. After curing in a standard curing chamber for 1 day, the specimens were demolded, and the dirt on the copper heads was removed. The specimens were then transferred to a constant temperature and humidity chamber at 20℃ and 50% humidity. The initial length was measured using a vertical length comparator. Then, the length of the mortar was measured on days 7, 14, and 28, and the drying shrinkage rate was calculated. The results are shown in Table 3.

[0049] Table 2 Example 1 Carboxyl-modified styrene-butadiene emulsion 8.13 48.81 2.26 Example 2 Carboxyl-modified styrene-butadiene emulsion 8.26 49.36 2.38 Example 3 Carboxyl-modified styrene-butadiene emulsion 8.21 48.97 2.31 Comparative Example 5 Styrene-butadiene emulsion 7.83 36.1 1.71 Comparative Example 6 Styrene-acrylic emulsion 7.62 29.1 1.68 Comparative Example 7 polyvinyl acetate emulsion 7.11 33.00 1.37 By comparing Examples 1-3 and Comparative Examples 5-7, it is demonstrated that the styrene-butadiene emulsion (SBR) can form a continuous flexible organic network after film formation, which interweaves and interlocks with the rigid inorganic skeleton formed by cement hydration. This effectively buffers stress concentration, inhibits microcrack propagation, and significantly improves the brittleness and cracking defects of cement-based materials. Simultaneously, the carboxyl groups on the surface of the SBR can form hydrogen bonds and chemical bonds with cement hydration products, greatly enhancing the interfacial bonding performance and overall flexibility of new and old concrete, thereby effectively improving the interfacial bonding performance and mechanical properties of polymer cement-based repair materials. The preferred polymer emulsion in this system is a carboxyl-modified SBR emulsion.

[0050] Table 3 Polymer emulsion addition amount / part 65 50 60 70 75 Compressive strength / MPa 8.26 7.12 7.85 8.27 7.38 Flexural strength / MPa 49.36 38.40 42.51 46.18 43.74 Interfacial bond flexural strength / MPa 2.38 1.85 2.05 2.13 2.06 7-day shrinkage rate / % 0.21 0.29 0.26 0.21 0.20 14-day shrinkage rate / % 0.28 0.38 0.34 0.27 0.26 28-day shrinkage rate / % 0.29 0.42 0.37 0.29 0.28 By comparing Example 2 and Comparative Examples 8-11, it was demonstrated that the carboxyl-modified styrene-butadiene emulsion, after being incorporated into the slurry, can be uniformly dispersed and fill the capillary and micropores of the cement hydration system, reducing water evaporation channels, decreasing the rate of free water loss within the hardened body, and alleviating volume shrinkage caused by drying water loss, thereby significantly improving the anti-drying shrinkage cracking performance of polymer cement-based repair materials. The preferred addition amount of carboxyl-modified styrene-butadiene emulsion in this system is 65 parts.

[0051] Test Example 3 Optimal fiber type, modification method and addition amount test Test method: Mechanical property testing: Same as test example 1. Results are shown in Tables 4 and 5.

[0052] Interfacial adhesion performance test: Same as test example 1. The results are shown in Table 5.

[0053] Drying shrinkage test: Same as test example 2. Results are shown in Table 4.

[0054] Table 4

[0055] By comparing Example 2 and Comparative Examples 12-13, it is demonstrated that basalt fiber can play a core role in bridging and crack prevention, stress dispersion, and bidirectional bonding, giving polymer cement-based repair materials resistance to drying shrinkage cracking and excellent mechanical properties. Carbon fiber also has excellent performance but is more expensive. Basalt fiber performs better in terms of engineering practicality and performance balance. Therefore, the preferred type of added fiber in this system is basalt fiber.

[0056] Table 5 Example 2 Amino-modified 1.5 8.26 49.36 2.38 Comparative Example 14 mercapto modification 1.5 7.85 46.80 2.14 Comparative Example 15 Epoxy group modification 1.5 8.20 48.93 2.34 Comparative Example 16 Amino-modified 0 5.20 39.50 2.12 Comparative Example 17 Amino-modified 0.5 6.15 42.81 2.25 Comparative Example 18 Amino-modified 1 7.32 46.55 2.32 Comparative Example 19 Amino-modified 2 8.05 47.82 2.35 Comparative Example 20 Amino-modified 2.5 7.68 45.24 2.29 By comparing Example 2 and Comparative Examples 14-20, it was demonstrated that introducing highly active amino functional groups on the surface of basalt fibers can form stable hydrogen bonds and amide bonds with cement hydration products and carboxyl groups of carboxylated styrene-butadiene emulsions, which greatly enhances the interfacial bonding strength between the modified basalt fibers and the organic-inorganic composite matrix. Although the introduction of epoxy groups has a similar effect, it is not economically advantageous. Therefore, the preferred basalt fiber modification method in this system is γ-aminopropyltriethoxysilane grafting, and the optimal addition amount is 1.5 parts.

[0057] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polymer cement-based repair material, characterized in that, Modified silica was prepared by reacting pre-modified silica with cysteine; carboxylated styrene-butadiene emulsion was prepared by polymerizing and emulsifying styrene, acrylic acid, and 1,3-butadiene; modified styrene-butadiene emulsion was prepared by reacting modified silica with carboxylated styrene-butadiene emulsion; modified basalt fiber was prepared by hydrolyzing γ-aminopropyltriethoxysilane and grafting it onto the surface of pretreated basalt fiber; and modified basalt fiber was prepared by mixing cement, quartz sand, limestone powder, water-reducing agent, defoamer, water-retaining agent, sodium gluconate, modified basalt fiber, and diluted emulsion. The pre-modified silica is prepared by hydrolyzing 3-chloropropyltriethoxysilane and grafting it onto the surface of silica. The pretreated basalt fiber is obtained by degreasing and pretreating basalt fiber; The diluted emulsion is prepared by mixing modified styrene-butadiene emulsion and deionized water.

2. A method for preparing a polymer cement-based repair material, characterized in that, The preparation method of the polymer cement-based repair material includes the following preparation steps: (1) Mix pre-modified silica, cysteine, anhydrous ethanol, deionized water, potassium iodide, and anhydrous potassium carbonate in a mass ratio of 1:(0.1~0.12):(11~13):(1.2~1.4):(0.006~0.008):(0.12~0.14) until homogeneous. Stir ultrasonically at room temperature for 20~40 min. Under nitrogen protection, heat to 75~85℃ and stir for 23~25 h. Cool to room temperature, filter, add 9~11 times the mass of ethanol of pre-modified silica, add 0.4~0.6 mol / L dilute hydrochloric acid at 0~4℃ to adjust the pH of the system to 5~6, stir for 3~5 min, filter, wash with anhydrous ethanol 2~4 times, and vacuum dry at 35~45℃ for 11~13 h to obtain modified silica; (2) By mass, 60-65 parts of styrene, 1.5-3.5 parts of acrylic acid, 0.11-0.13 parts of tert-dodecyl mercaptan, 3.2-3.4 parts of emulsifier, 0.2-0.4 parts of sodium bicarbonate, and 150-170 parts of deionized water are mixed evenly and stirred at room temperature for 4-6 minutes. Then, 35-40 parts of 1,3-butadiene are introduced and stirred for another 20-40 minutes to obtain a pre-emulsion. The pre-emulsion is mixed evenly with ammonium persulfate solution and heated to 70-80°C under nitrogen protection. The mixture is stirred for 7-8 hours and cooled to 35-45°C. 25 vol% dilute ammonia is added to adjust the pH to 8.8-9.0 to obtain a carboxylated styrene-butadiene emulsion. (3) Take 100 parts by mass of carboxylated styrene-butadiene emulsion, add modified silica dispersion under nitrogen protection, stir at room temperature for 10-20 min, add initiator solution under light protection, continue stirring for 5-15 min, and irradiate under 365nm ultraviolet lamp for 40-50 min to obtain modified styrene-butadiene emulsion. (4) Mix anhydrous ethanol and deionized water at a volume ratio of 9:1, add glacial acetic acid to adjust the pH of the system to 4~4.4, add γ-aminopropyltriethoxysilane at 0.3~0.5 times the mass of deionized water, stir at 55~65℃ for 25~35 min, cool to 45~55℃, add pretreated basalt fiber at 1~1.2 times the mass of deionized water, continue stirring and reacting for 50~70 min, filter, wash with anhydrous ethanol 2~4 times, dry at 100~110℃ for 50~70 min, cool naturally to room temperature, and obtain modified basalt fiber; (5) By mass, 60-70 parts of modified styrene-butadiene emulsion and 28-30 parts of deionized water are mixed evenly and stirred at room temperature for 1-3 minutes to obtain a diluted emulsion; 220-240 parts of cement, 550-600 parts of quartz sand, 25-35 parts of limestone powder, 0.6-0.8 parts of water-reducing agent, 0.44-0.48 parts of defoamer, 0.11-0.13 parts of water-retaining agent, and 0.07-0.09 parts of sodium gluconate are mixed evenly and stirred at room temperature for 4-6 minutes. 1.4-1.6 parts of modified basalt fiber are added in three portions and stirred for 1-3 minutes. The diluted emulsion is added and stirred for 3-5 minutes to obtain a polymer cement-based repair material.

3. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The preparation process of the pre-modified silica in step (1) is as follows: Anhydrous ethanol and deionized water are mixed evenly at a volume ratio of 9:1, and 0.4 to 0.6 times the mass of deionized water is added to silica. The mixture is ultrasonically dispersed at room temperature for 20 to 40 minutes. The pH is adjusted to 4 to 5 with glacial acetic acid. 0.3 to 0.4 times the mass of silica is added to 3-chloropropyltriethoxysilane. The temperature is raised to 50 to 60°C, and the mixture is stirred and reacted for 5 to 6 hours. The mixture is cooled to room temperature, filtered, washed 2 to 4 times with anhydrous ethanol, and vacuum dried at 40 to 50°C for 11 to 13 hours to obtain pre-modified silica.

4. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The emulsifier in step (2) is prepared by mixing sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 2:

1.

5. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The preparation process of the ammonium persulfate solution in step (2) is as follows: 0.5~0.7 parts of ammonium persulfate and deionized water are mixed evenly at a mass ratio of 1:(18~22), and stirred at room temperature for 5~15 minutes to obtain the ammonium persulfate solution.

6. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The preparation process of the modified silica dispersion in step (3) is as follows: 4-6 parts of modified silica are mixed with deionized water and anhydrous ethanol at a mass ratio of 1:(1.5-2.5):(0.75-1.25) and ultrasonically dispersed at 0-4℃ for 20-30 min. Tris(2-carboxyethyl)phosphine is added at 0.003-0.005 times the mass of the modified silica and stirred at room temperature for 4-6 min to obtain the modified silica dispersion.

7. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The preparation process of the initiator solution in step (4) is as follows: 0.17~0.19 parts of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, triethanolamine, and deionized water are mixed evenly in a mass ratio of 1:(1.9~2.1):(12~14) and stirred for 4~6 minutes under light-protected conditions to obtain the initiator solution.

8. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The preparation process of the pretreated basalt fiber in step (4) is as follows: Basalt fiber and acetone are mixed evenly at a mass ratio of 1:(4~6), soaked at room temperature for 1.5~2.5h, filtered, washed with deionized water 2~4 times, and dried at 75~85℃ for 1.5~2.5h to obtain pretreated basalt fiber.

9. The method for preparing the polymer cement-based repair material according to claim 8, characterized in that, The basalt fiber has a length of 12 mm, a tensile strength >1050 MPa, and an elastic strength >35 GPa.

10. The method for preparing the polymer cement-based repair material according to claim 2, characterized in that, The cement used in step (5) is 42.5 sulfoaluminate cement, with an initial setting time of 30 min and a final setting time of 150 min; the quartz sand has a particle size of 40-80 mesh with continuous gradation and a density of 2.65 g / cm³. 3 The limestone powder has a particle size of 400 mesh and a density of 2.6 g / cm³. 3 The water-reducing agent is a polycarboxylate water-reducing agent; the defoamer is a modified polyether powder defoamer; and the water-retaining agent is a hydroxypropyl methylcellulose water-retaining agent with a viscosity of 100,000 mPa·s.

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