Quick-hardening concrete crack repairing agent and preparation method thereof

Abstract

The invention relates to the technical field of concrete crack repairing, and particularly discloses a quick-hardening concrete crack repairing agent and a preparation method thereof. The invention relates to a quick-hardening concrete crack repairing agent, which is prepared from the following raw materials: 45 to 55 parts of sulphoaluminate cement; 10 to 15 parts of silica fume; 12 to 18 parts of metakaolin; 5-8 parts of a bimetallic composite seed crystal; 10 to 15 parts of double-layer shell nano anhydrite; 2-4 parts of magnesium oxide; 0.5 to 1 part of polypropylene fiber; 0.5 to 0.8 part of a water reducing agent; 15 to 20 parts of water; the bimetallic composite seed crystal is a zirconium and strontium element co-doped composite crystal nucleus; the double-shell nano anhydrite is composed of an inner core nano anhydrite, a middle aluminum sulfate early strength phase and an outer mesoporous SiO2 shell. The quick-hardening concrete crack repairing agent has the advantages of being short in setting time, high in early strength and excellent in interface bonding performance.

Description

Technical Field

[0001] The present application relates to the technical field of concrete crack repair, and more specifically, to a fast-hardening concrete crack repair agent and a preparation method thereof. Background Art

[0002] In the field of civil engineering, concrete structures are prone to cracking due to long-term loads, environmental erosion, temperature changes and other factors. These cracks not only reduce the integrity and durability of the structure, but can also lead to problems such as steel corrosion and leakage, seriously threatening the safety and service life of the project. Therefore, concrete crack repair technology has become a key link in ensuring structural safety, and crack repair agents, as the core material of this technology, their performance directly determines the quality of the repair effect. Currently, crack repair agents have been widely used in the maintenance and reinforcement of various concrete projects such as buildings, bridges, tunnels, and water conservancy projects. They restore the mechanical properties and usability of concrete structures through filling, bonding, and reinforcement.

[0003] Related technologies, such as patent application CN118167075A, disclose a method for repairing concrete. This method includes crack detection and marking, cleaning the crack interior and surface, preparing and preparing repair materials, repairing and applying the cracks, and treating the crack surface. The repair materials include cement, sand, a special gel, additives, and a binder. By adding a gel material to the repair material, the material imparts excellent adhesion and durability, allowing the repaired concrete to achieve an appearance and performance matching the original concrete. The repair material has a simple formulation and is easy to mix, reducing complexity and difficulty during operation. However, the above-mentioned repair materials still have obvious defects in practical applications: the repair materials in the related art use ordinary cement as the main cementitious material, and its hydration reaction depends on the slow reaction of cement clinker minerals and water. The initial setting time at room temperature often exceeds 5 hours, and the final setting time is as long as more than 12 hours. In addition, the formula lacks targeted early strength stimulating components, and the additives have limited promoting effect on the hydration process, and cannot accelerate the rapid generation and coagulation and hardening of hydration products in the cementitious system. This makes it difficult for the repaired cracks to form effective strength in a short period of time, and it is impossible to meet the demand for rapid load-bearing in emergency repair scenarios, which seriously prolongs the project recovery period. Therefore, how to develop a fast-hardening concrete crack repair agent with a short setting time, high early strength and excellent interface bonding performance has become a key technical problem that needs to be solved in this field. Summary of the Invention

[0004] In order to provide a fast-hardening concrete crack repair agent with short setting time, high early strength and excellent interface bonding performance, the present application provides a fast-hardening concrete crack repair agent and a preparation method thereof.

[0005] The present application provides a fast-hardening concrete crack repair agent that adopts the following technical solution: A fast-hardening concrete crack repair agent comprising the following raw materials in parts by weight: 45-55 parts of sulphoaluminate cement; 10-15 parts of silica fume; 12-18 parts of metakaolin; 5-8 parts of bimetallic composite seed crystals; 10-15 parts of double-shell nano-anhydrite; 2-4 parts of magnesium oxide; Polypropylene fiber 0.5-1 part; Water reducing agent 0.5-0.8 parts; 15-20 parts water; The bimetallic composite crystal seed is a composite crystal core co-doped with zirconium and strontium elements; The double-layer shell nano anhydrite is composed of an inner core of nano anhydrite, a middle layer of aluminum sulfate early strength phase, and an outer layer of mesoporous SiO2 shell.

[0006] By adopting the above technical solution, sulfoaluminate cement is used as the main cementitious material, and its fast hydration reaction provides a basis for the rapid setting and hardening of the repair agent. Silica fume and metakaolin are highly active and can fill pores and enhance density. Bimetallic composite seed (zirconium and strontium co-doped) is used as the fast hardening core, Zr 4+ Reduce the nucleation barrier of ettringite and increase the early generation rate of AFt; Sr 2+ The Sr-AFt crystals are made more stable, solving the problem of traditional ettringite being easily decomposed in the later stage. The synergistic effect of the two ions makes the initial setting time of the repair agent exceed 2 hours, while ensuring the continuous growth of strength. The double-shell nano-anhydrite has a unique structure, which releases aluminum sulfate in the early stage and reacts quickly with C3A to form ettringite. Later, the core anhydrite continuously releases SO4 2- , ensuring continuous strength growth. Magnesium oxide regulates the heat of hydration, polypropylene fiber enhances crack resistance, a water reducer improves workability, and water provides a reaction medium. These components work synergistically to effectively address the long setting time and low early strength issues of existing repair materials, achieving a shorter setting time, higher early strength, and superior interfacial bonding.

[0007] Optionally, the bimetallic composite seed crystal is prepared by the following method: Zirconium nitrate and strontium nitrate are dissolved in deionized water, ammonia water is added dropwise to adjust the pH to 10, and the mixture is reacted at 160-180°C for 8-10 hours. The product is centrifugally washed and vacuum dried at 50-60°C, and then ball-milled to obtain bimetallic composite seed crystals.

[0008] By adopting the above technical solution, zirconium nitrate and strontium nitrate are dissolved in deionized water, and ammonia water is added dropwise to adjust the pH to 10.5 before a hydrothermal reaction is carried out. Under these conditions, zirconium and strontium elements can fully react to form co-doped composite crystal nuclei. The high temperature and high pressure environment provided by the hydrothermal reaction is conducive to the growth of crystals and the improvement of the crystal form, so that the generated seed crystals have better activity and stability. After centrifugal washing to remove impurities, vacuum drying to prevent oxidation and agglomeration, ball milling is performed to obtain bimetallic composite seed crystals with uniform particle size. This preparation method ensures the quality and performance of the bimetallic composite seed crystals, so that they can better play the role of reducing the nucleation barrier of ettringite, increasing the early generation rate, and forming stable Sr-AFt crystals in the repair agent, thereby helping to shorten the setting time of the repair agent and improve the early strength.

[0009] Optionally, the mass ratio of the zirconium nitrate, strontium nitrate and deionized water is 1:(0.1-0.3):(5-8).

[0010] By adopting the above technical solution, the above mass ratio can ensure that the zirconium and strontium elements are evenly dispersed in the solution, fully react in the hydrothermal reaction, and generate bimetallic composite crystal seeds with excellent performance, thereby enabling the repair agent to achieve the best effect in setting time and strength development, meeting the requirements of rapid repair and long-term stability.

[0011] Optionally, the double-shell nano-anhydrite is prepared by the following method: Nano-anhydrite is dispersed in aluminum sulfate solution, ultrasonically treated for 30-50 minutes, then a mixture of hexadecyltrimethylammonium bromide-ethanol-ammonia water is added, and then ethyl silicate is added. The mixture is stirred for 10-12 hours under nitrogen protection, and calcined at 500-550° C. for 2-4 hours to obtain double-shell nano-anhydrite.

[0012] By adopting the above technical solution, the double-shell structure formed by the above preparation method has unique advantages. The outer mesoporous SiO2 is initially blocked from dissolving too quickly, and the middle aluminum sulfate is preferentially released early to react with C3A to form ettringite, solving the problem of early SO4 2— Insufficient release problem, the core anhydrite continues to release SO4 slowly in the later stage 2— , ensuring continuous growth in strength and effectively improving the performance of the repair agent.

[0013] Optionally, the concentration of the aluminum sulfate solution is 0.1-0.3 mol / L, and the mass ratio of the nano-anhydrite to the aluminum sulfate solution is 1:(5-7).

[0014] Optionally, in the hexadecyltrimethylammonium bromide-ethanol-ammonia aqueous solution mixture, the mass ratio of hexadecyltrimethylammonium bromide, ethanol and ammonia aqueous solution is 1:(6-10):(0.5-1.5); the amount of the hexadecyltrimethylammonium bromide-ethanol-ammonia aqueous solution added is 8-12 times the mass of the nano-anhydrite.

[0015] Optionally, the added amount of the ethyl silicate is 30%-50% of the mass of the nano-anhydrite.

[0016] Optionally, the heating rate during the calcination process is 5-10°C / min, and after calcination, the product is naturally cooled to room temperature and passed through a 300-400 mesh sieve for later use.

[0017] By adopting the above technical solution, the above heating rate can ensure that the structure of the double-shell nano-hard gypsum gradually stabilizes during the calcination process, avoiding structural damage caused by excessively rapid heating. Natural cooling to room temperature can evenly release the internal stress of the material, preventing defects such as cracks caused by rapid cooling. Passing through a 300-400 mesh sieve can remove large particles of impurities and agglomerates, resulting in double-shell nano-hard gypsum with uniform particle size. These conditions work together to ensure the quality and performance of the double-shell nano-hard gypsum, enabling it to better play its role in regulating SO4 in the repair agent. 2— It can release and promote the formation of calcium aluminate, thereby improving the setting time and strength development performance of the repair agent, meeting the needs of rapid repair of concrete cracks.

[0018] Optionally, the polypropylene fiber has a length of 6-12 mm and a diameter of 20-30 μm.

[0019] The present application also provides a method for preparing a fast-hardening concrete crack repair agent, which adopts the following technical solution: A method for preparing a fast-hardening concrete crack repair agent comprises the following steps: S1. Add sulphoaluminate cement, silica fume, metakaolin, bimetallic composite seed crystals, double-shell nano-anhydrite, magnesium oxide, and polypropylene fiber to a blender in sequence, and stir at 1000-1200 rpm for 8-12 minutes to obtain a dry mix; S2. Add water reducing agent and water to the dry mix, adjust the speed to 600-800 rpm and stir for 3-5 minutes to obtain the fast-hardening concrete crack repair agent.

[0020] The components of the repair agent prepared by the above method can fully play their roles, achieving the effects of short setting time, high early strength and excellent interface bonding performance, and meeting the technical requirements for rapid repair of concrete cracks.

[0021] In summary, this application has the following beneficial effects: 1. This application fundamentally solves the problems of slow setting and insufficient early strength of traditional repair agents through the innovative design of a synergistic system of bimetallic composite crystal seeds and double-shell nano-hard gypsum. The zirconium element in the bimetallic composite crystal seeds can accelerate the nucleation process of ettringite crystals and significantly shorten the setting time; the strontium element enhances the stability of the crystal structure and avoids the later strength decay. The double-shell nano-hard gypsum has a unique layered structure and quickly releases sulfate ions in the early stage to promote the formation of ettringite and achieve rapid hardening; it continuously releases sulfate ions in the later stage to ensure long-term and stable strength growth. Sulphoaluminate cement as a base material provides a fast-hardening foundation, the dense structure of silica fume and metakaolin enhances strength, magnesium oxide compensates for shrinkage, and polypropylene fibers inhibit cracks. Under the synergistic effect of multiple components, the repair agent can form sufficient strength in a short time, solving the problem of traditional materials extending the engineering cycle due to slow setting, and is especially suitable for emergency repair scenarios.

[0022] 2. This application significantly improves the interfacial bonding between the repair agent and the concrete matrix by precisely controlling the structure and properties of key components. Bimetallic composite seeds promote the preferential growth of calcium aluminoferrite at the interface to form a tight anchoring structure; the sulfate ions released by the double-shell nano-hard gypsum react with the matrix components to enhance the chemical bonding. Silica fume and metakaolin react with volcanic ash to form a gel, which penetrates and fills the pores of the matrix, forming a "nano-bridging" effect; polypropylene fibers span the micro-cracks at the interface to enhance mechanical bite. These designs together improve the integrity of the interface between the repair layer and the original concrete, avoiding problems such as interface peeling and hollowing that are common with traditional repair agents. At the same time, the hydration products of magnesium oxide form a dense protective layer, which delays the penetration of corrosive ions and significantly improves the long-term durability of the repair structure. DETAILED DESCRIPTION

[0023] The present application is further described in detail below with reference to the embodiments.

[0024] Preparation example of bimetallic composite seed Preparation Example 1 The bimetallic composite seed crystal is prepared by the following method: 1 kg of zirconium nitrate and 0.1 kg of strontium nitrate were dissolved in 5 kg of water, and ammonia water was added dropwise to adjust the pH to 10. The mixture was reacted at 160° C. for 8 h. The product was centrifugally washed and vacuum dried at 50° C., and then ball milled to obtain bimetallic composite seed crystals.

[0025] Preparation Example 2 The bimetallic composite seed crystal is prepared by the following method: 1 kg of zirconium nitrate and 0.2 kg of strontium nitrate were dissolved in 6.5 kg of water, and ammonia water was added dropwise to adjust the pH to 10. The mixture was reacted at 170° C. for 9 h. The product was centrifugally washed and vacuum dried at 55° C., and then ball milled to obtain bimetallic composite seed crystals.

[0026] Preparation Example 3 The bimetallic composite seed crystal is prepared by the following method: 1 kg of zirconium nitrate and 0.3 kg of strontium nitrate were dissolved in 8 kg of water, and ammonia water was added dropwise to adjust the pH to 10. The mixture was reacted at 180° C. for 10 h. The product was centrifugally washed and vacuum dried at 60° C., and then ball-milled to obtain bimetallic composite seed crystals.

[0027] Preparation example of double-shell nano-anhydrite Preparation Example 4 Double-shell nano-hard gypsum is prepared by the following method: 1 kg of nano-hard gypsum was dispersed in 5 kg of 0.1 mol / L aluminum sulfate solution and ultrasonically treated for 30 minutes. Then, 8 kg of a mixture of hexadecyltrimethylammonium bromide-ethanol-ammonia water was added. In the mixture of hexadecyltrimethylammonium bromide-ethanol-ammonia water, the mass ratio of hexadecyltrimethylammonium bromide, ethanol and ammonia water was 1:6:0.5. Then, 0.3 kg of ethyl silicate was added. The mixture was stirred for 10 hours under nitrogen protection and calcined at 500°C for 4 hours with a heating rate of 5°C / min during the calcination process. After calcination, the mixture was naturally cooled to room temperature and passed through a 300-mesh sieve to obtain a double-shell nano-hard gypsum.

[0028] Preparation Example 5 Double-shell nano-anhydrite is prepared by the following method: 1 kg of nano-hard gypsum was dispersed in 6 kg of 0.2 mol / L aluminum sulfate solution, ultrasonically treated for 40 minutes, and then 10 kg of hexadecyltrimethylammonium bromide-ethanol-ammonia aqueous solution was added. In the hexadecyltrimethylammonium bromide-ethanol-ammonia aqueous solution, the mass ratio of hexadecyltrimethylammonium bromide, ethanol and ammonia aqueous solution was 1:8:1. Then 0.4 kg of ethyl silicate was added, stirred for 11 hours under nitrogen protection, calcined at 530°C for 3 hours, with a heating rate of 8°C / min during the calcination process, and naturally cooled to room temperature after calcination. The mixture was passed through a 300-mesh sieve to obtain double-shell nano-hard gypsum.

[0029] Preparation Example 6 Double-shell nano-hard gypsum is prepared by the following method: 1 kg of nano-hard gypsum was dispersed in 7 kg of aluminum sulfate solution with a concentration of 0.3 mol / L, ultrasonically treated for 50 minutes, and then 12 kg of a mixture of hexadecyltrimethylammonium bromide-ethanol-ammonia water was added. In the mixture of hexadecyltrimethylammonium bromide-ethanol-ammonia water, the mass ratio of hexadecyltrimethylammonium bromide, ethanol and ammonia water was 1:10:1.5. Then 0.5 kg of ethyl silicate was added, stirred for 12 hours under nitrogen protection, calcined at 550°C for 2 hours, with a heating rate of 10°C / min during the calcination process, and naturally cooled to room temperature after calcination. The mixture was passed through a 400-mesh sieve to obtain a double-shell nano-hard gypsum.

[0030] Preparation Example 7 Silica-coated nano-anhydrite is prepared by the following method: 1 kg of nano-hard gypsum was dispersed in 12 kg of a mixture of cetyltrimethylammonium bromide-ethanol-ammonia water, wherein the mass ratio of cetyltrimethylammonium bromide, ethanol and ammonia water in the mixture was 1:10:1.5. Then 0.5 kg of ethyl silicate was added, stirred for 12 h under nitrogen protection, and calcined at 550 ° C for 2 h with a heating rate of 10 ° C / min during the calcination process. After calcination, the mixture was naturally cooled to room temperature and passed through a 400-mesh sieve to obtain silica-coated nano-hard gypsum.

[0031] Example Example 1 A fast-hardening concrete crack repair agent, the raw material components and amounts of which are shown in Table 1, wherein the bimetallic composite crystal seeds are the bimetallic composite crystal seeds prepared in Preparation Example 1, the double-shell nano-hard gypsum is the bimetallic composite crystal seeds prepared in Preparation Example 4, the polypropylene fiber has an average length of 6 mm and an average diameter of 20 μm, and the water reducer is a polycarboxylic acid-based ultra-early strength water reducer.

[0032] A fast-hardening concrete crack repair agent is prepared by the following method: S1. Add sulphoaluminate cement, silica fume, metakaolin, bimetallic composite seed crystals, double-shell nano-anhydrite, magnesium oxide, and polypropylene fiber to a blender in sequence, and stir at 1000 rpm for 12 min to obtain a dry mix; S2. Add water reducing agent and water to the dry mix, adjust the speed to 600 rpm and stir for 3 minutes to obtain a fast-hardening concrete crack repair agent.

[0033] Example 2 A fast-hardening concrete crack repair agent, the raw material components and amounts of which are shown in Table 1, wherein the bimetallic composite crystal seeds are the bimetallic composite crystal seeds prepared in Preparation Example 2, the double-shell nano-hard gypsum is the bimetallic composite crystal seeds prepared in Preparation Example 5, the polypropylene fiber has an average length of 10 mm and an average diameter of 25 μm, and the water reducer is a polycarboxylic acid-based ultra-early strength water reducer.

[0034] A fast-hardening concrete crack repair agent is prepared by the following method: S1. Add sulphoaluminate cement, silica fume, metakaolin, bimetallic composite seed crystals, double-shell nano-anhydrite, magnesium oxide, and polypropylene fiber to a blender in sequence, and stir at 1100 rpm for 10 min to obtain a dry mix; S2. Add water reducing agent and water to the dry mix, adjust the speed to 700 rpm and stir for 4 minutes to obtain a fast-hardening concrete crack repair agent.

[0035] Example 3 A fast-hardening concrete crack repair agent, the raw material components and amounts of which are shown in Table 1, wherein the bimetallic composite crystal seeds are the bimetallic composite crystal seeds prepared in Preparation Example 3, the double-shell nano-hard gypsum is the bimetallic composite crystal seeds prepared in Preparation Example 6, the polypropylene fiber has an average length of 12 mm and an average diameter of 30 μm, and the water reducer is a polycarboxylic acid-based ultra-early strength water reducer.

[0036] A fast-hardening concrete crack repair agent is prepared by the following method: S1. Add sulphoaluminate cement, silica fume, metakaolin, bimetallic composite seed crystals, double-shell nano-anhydrite, magnesium oxide, and polypropylene fiber to a blender in sequence, and stir at 1200 rpm for 8 min to obtain a dry mix; S2. Add water reducing agent and water to the dry mix, adjust the speed to 800 rpm and stir for 5 minutes to obtain a fast-hardening concrete crack repair agent.

[0037] Table 1 Raw material components and dosage of the repair agent in Examples 1-3 (kg)

[0038] Example 4 A fast-hardening concrete crack repair agent is different from Example 1 in that the polypropylene fiber in this embodiment has a length of 20 mm and an average diameter of 30 μm.

[0039] Comparative Example Comparative Example 1 A rapid-hardening concrete crack repair agent is provided. The difference from Example 1 is that an equal amount of Portland cement is used instead of sulphoaluminate cement in this comparative example.

[0040] Comparative Example 2 A fast-hardening concrete crack repair agent is different from Example 1 in that no bimetallic composite crystal seeds and double-shell nano-hard gypsum are added in this comparative example, and the difference is supplemented by sulphoaluminate cement and silica fume.

[0041] Comparative Example 3 A fast-hardening concrete crack repair agent is different from Example 1 in that no bimetallic composite crystal seeds are added in this comparative example, and the difference is supplemented by double-shell nano-hard gypsum.

[0042] Comparative Example 4 A fast-hardening concrete crack repair agent is provided. The difference from Example 1 is that no double-shell nano-hard gypsum is added in this comparative example, and the difference is supplemented by 3 kg of bimetallic composite crystal seeds and 7 kg of sulphoaluminate cement.

[0043] Comparative Example 5 A fast-hardening concrete crack repair agent is provided. The difference from Example 1 is that in this comparative example, an equal amount of the silica-coated nano-anhydrite prepared in Preparation Example 7 is used to replace the double-shell nano-anhydrite.

[0044] Comparative Example 6 A rapid-hardening concrete crack repair agent is provided. The difference from Example 1 is that magnesium oxide is not added in this comparative example, and the difference is supplemented by sulphoaluminate cement.

[0045] Performance testing 1. Refer to the Test Method for Setting of Cement Concrete Mixtures (T0527-2005) to test the initial setting time and final setting time of the above-mentioned repair agent. The test results are shown in Table 2.

[0046] 2. The early strength of the above-mentioned patching agent was tested by using a cube compression test, with reference to the "Test Method for Strength of Cement Mortar" (GB / T17671). The test results are shown in Table 2.

[0047] 3. The bonding performance between the repair agent and the concrete matrix was tested by a pull-out test, with reference to GB / T50728-2011 "Technical Specifications for Safety Appraisal of Engineering Structure Reinforcement Materials". The test results are shown in Table 2.

[0048] Table 2 Test results

[0049] The initial setting time of the repair agents in Examples 1-4 was 660-730 seconds, and the final setting time was 32-35 minutes. This was due to the synergistic effect of the bimetallic composite seeds and the double-shell nano-anhydrite. The bimetallic composite seeds accelerated the nucleation of ettringite crystals, the double-shell nano-anhydrite rapidly released sulfate ions early on to promote ettringite formation, and the sulfoaluminate cement provided a rapid hardening foundation, which together shortened the setting time.

[0050] Compared Example 1 replaces the sulfoaluminate cement with Portland cement, the initial setting time is prolonged to 1080s, and the final setting time is prolonged to 46min. Because the hydration reaction of ordinary Portland cement is slow, the setting time is prolonged. Compared Example 2 does not add the bimetallic composite seed crystal and the double-shell nano-hard gypsum, the initial setting time is greatly prolonged to 1440s, and the final setting time is prolonged to 58min. Without the key early-strength-activating component, the generation of hydration products and the setting and hardening of the cementitious system cannot be accelerated. Compared Examples 3-5 respectively lack the bimetallic composite seed crystal, the double-shell nano-hard gypsum, or replace the nano-hard gypsum coated with silicon dioxide, and the initial setting and final setting times are all longer than those of the examples. It is shown that the bimetallic composite seed crystal and the double-shell nano-hard gypsum are indispensable for shortening the setting time, and the double-shell structure has unique advantages. Compared Example 6 does not add magnesium oxide, the initial setting time is prolonged to 760s, and the final setting time is prolonged to 36min. Magnesium oxide can adjust the hydration heat, and also has a certain influence on the setting time.

[0051] The compressive strengths of Examples 1-4 are in the range of 36.8-42.5MPa. The multi-component synergistic effect, the strontium element in the bimetallic composite seed crystal enhances the stability of the crystal structure, the double-shell nano-hard gypsum continuously releases sulfate ions in the later stage to ensure the strength growth, the dense structure of silica fume and metakaolin improves the strength, and the magnesium oxide compensates for the shrinkage, etc.

[0052] The adhesive strengths of Examples 1-4 are in the range of 2.5-2.9MPa. The bimetallic composite seed crystal promotes the preferential growth of ettringite at the interface to form an anchoring structure, the sulfate ions released by the double-shell nano-hard gypsum enhance the chemical bonding force, the “nano-bridging” effect of silica fume and metakaolin, and the polypropylene fiber strengthens the mechanical interlocking effect. Therefore, the repair agent provided in the application has strong interfacial adhesion performance and can be better applied to concrete repair construction.

[0053] The specific embodiments are merely an explanation of the application, and are not a limitation of the application. Those skilled in the art can make modifications to the embodiments without creative contributions after reading the specification, as long as the modifications are within the scope of the claims of the application and are protected by the Patent Law.

Claims

1. A fast-hardening concrete crack repair agent, characterized in that: The invention comprises the following raw materials in parts by weight: 45-55 parts of sulphoaluminate cement; 10-15 parts of silica fume; 12-18 parts of metakaolin; 5-8 parts of bimetallic composite seed crystals; 10-15 parts of double-shell nano-anhydrite; 2-4 parts of magnesium oxide; Polypropylene fiber 0.5-1 part; Water reducing agent 0.5-0.8 parts; 15-20 parts water; The bimetallic composite crystal seed is a composite crystal core co-doped with zirconium and strontium elements; The double-layer shell nano anhydrite is composed of an inner core of nano anhydrite, a middle layer of aluminum sulfate early strength phase, and an outer layer of mesoporous SiO2 shell.

2. The rapid-hardening concrete crack repair agent according to claim 1, characterized in that: The bimetallic composite seed crystal is prepared by the following method: Zirconium nitrate and strontium nitrate are dissolved in deionized water, ammonia water is added dropwise to adjust the pH to 10, and the mixture is reacted at 160-180°C for 8-10 hours. The product is centrifugally washed and vacuum dried at 50-60°C, and then ball-milled to obtain bimetallic composite seed crystals.

3. The rapid hardening concrete crack repair agent according to claim 2, characterized in that: The mass ratio of the zirconium nitrate, strontium nitrate and deionized water is 1: (0.1-0.3): (5-8).

4. The rapid hardening concrete crack repair agent according to claim 1, characterized in that: The double-shell nano-anhydrite is prepared by the following method: Nano-anhydrite is dispersed in aluminum sulfate solution, ultrasonically treated for 30-50 minutes, then a mixture of hexadecyltrimethylammonium bromide-ethanol-ammonia water is added, and then ethyl silicate is added. The mixture is stirred for 10-12 hours under nitrogen protection, and calcined at 500-550° C. for 2-4 hours to obtain double-shell nano-anhydrite.

5. The rapid hardening concrete crack repair agent according to claim 4, characterized in that: The concentration of the aluminum sulfate solution is 0.1-0.3 mol / L, and the mass ratio of the nano-anhydrite to the aluminum sulfate solution is 1:(5-7).

6. The rapid hardening concrete crack repair agent according to claim 4, characterized in that: In the hexadecyltrimethylammonium bromide-ethanol-ammonia aqueous solution mixture, the mass ratio of hexadecyltrimethylammonium bromide, ethanol and ammonia aqueous solution is 1:(6-10):(0.5-1.5); the added amount of the hexadecyltrimethylammonium bromide-ethanol-ammonia aqueous solution is 8-12 times the mass of the nano-anhydrite.

7. The rapid-hardening concrete crack repair agent according to claim 4, characterized in that: The added amount of the ethyl silicate is 30%-50% of the mass of the nano-anhydrite.

8. The rapid-hardening concrete crack repair agent according to claim 4, characterized in that: The heating rate during the calcination process is 5-10°C / min, and the product is naturally cooled to room temperature after calcination, and then passed through a 300-400 mesh sieve for later use.

9. The rapid-hardening concrete crack repair agent according to claim 4, characterized in that: The polypropylene fiber has a length of 6-12 mm and a diameter of 20-30 μm.

10. The method for preparing the rapid hardening concrete crack mending agent according to any one of claims 1 to 9, characterized in that: The steps include: S1. Add sulphoaluminate cement, silica fume, metakaolin, bimetallic composite seed crystals, double-shell nano-anhydrite, magnesium oxide, and polypropylene fiber to a blender in sequence, and stir at 1000-1200 rpm for 8-12 minutes to obtain a dry mix; S2. Add water reducing agent and water to the dry mix, adjust the speed to 600-800 rpm and stir for 3-5 minutes to obtain the fast-hardening concrete crack repair agent.

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