Self-repairing crack concrete and preparation method thereof

Abstract

The application discloses a kind of self-repairing crack concrete and preparation method thereof, belong to building material technical field, with crack targeting type dynamic self-repairing ability, repair efficiency is high and can be repaired repeatedly, different from the one-time repair limitation of traditional microcapsule self-repairing concrete, the dynamic reversible characteristic of disulfide bond of this scheme can realize multiple self-repairing, especially suitable for the microcrack repeatedly occurred in long-term use of concrete, greatly reduce later maintenance cost;The responsive composite hydrogel of the application has crack targeting response characteristics, when cracks occur in concrete, external moisture penetrates, hydrogel swells rapidly, on the one hand, it provides a reaction environment for disulfide bond recombination by opening the internal space of the crack, on the other hand, it drives the modified nanospheres to migrate and aggregate towards the crack, achieving targeted repair;The responsive hydrogel is modified by dopamine, has very strong adhesion, can tightly combine cement hydration products and aggregate, and improve the strength of the interface transition zone.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically a self-healing cracked concrete and its preparation method. Background Technology

[0002] With the vigorous development of modern concrete, various concrete structures are widely used in high-rise buildings, long-span bridges, and industrial buildings. However, due to the inherent defects of concrete, such as high brittleness and low tensile strength, internal cracks inevitably occur during the preparation and use process, thus reducing strength. At the same time, internal cracks in concrete provide channels for water and other substances in the environment to seep in, exacerbating chemical corrosion and the corrosion of internal steel bars, and shortening the service life of the concrete.

[0003] Concrete, as the most commonly used building material, has advantages such as wide availability, high compressive strength, good fire resistance, and convenient construction, and is therefore widely used in engineering construction. However, concrete is a heterogeneous material with high brittleness. During its service life, it is affected by external loads, temperature and humidity changes, corrosion and carbonation, shrinkage reactions, and bleeding, making crack formation almost inevitable. Cracks in concrete affect the aesthetics and safety of buildings. As the depth of cracks increases, the load-bearing capacity decreases sharply. At the same time, cracks become channels for harmful ions from the environment to penetrate into the concrete, accelerating chemical corrosion and the corrosion of internal steel reinforcement, leading to reduced durability and significantly shortening the service life of the concrete.

[0004] Currently, the main method for repairing cracks in concrete is to inject reinforcing adhesive into the cracks under external pressure, thereby sealing the cracks and repairing them.

[0005] In the existing technology, when reinforcing adhesive is injected into concrete cracks under external pressure, the adhesive cannot fully penetrate the cracks and cannot effectively repair the cracked concrete. Furthermore, the existing repair technology cannot provide timely reinforcement to the cracked concrete, exhibiting a certain degree of lag.

[0006] Furthermore, existing dynamic bond-modified self-healing systems often lack crack-targeted response mechanisms. Functional components are randomly dispersed in the concrete matrix, and when cracks occur, they cannot quickly aggregate towards the crack area. Instead, they rely on random diffusion to participate in the repair reaction, resulting in low repair efficiency. At the same time, some solutions neglect the regulation of the repair reaction environment and the enhancement of interfacial bond strength. Even with the introduction of dynamic bonds and nanofillers, it is difficult to achieve efficient and stable targeted self-healing effects, which cannot meet the requirements of practical engineering for the long-term service performance of concrete. Summary of the Invention

[0007] The purpose of this invention is to provide a self-healing cracked concrete and its preparation method, which has the ability to target cracks and dynamically self-heal, with high repair efficiency and can be repaired multiple times. Unlike the one-time repair limitation of traditional microcapsule self-healing concrete, the dynamic reversible disulfide bond characteristics of this solution can achieve multiple self-repairs. It is especially suitable for microcracks that repeatedly appear in concrete during long-term use, and significantly reduces the cost of later maintenance.

[0008] The objective of this invention can be achieved through the following technical solutions: A method for preparing self-healing cracked concrete includes the following steps: Cement, fly ash, silica fume, ceramsite with a particle size of 5-10mm, disulfide bond modified nanospheres, responsive composite hydrogel, polycarboxylate superplasticizer, and water are mixed and poured into a mold, vibrated to compact, covered with a curing film, and cured for 28-30 days at a temperature of 25℃ and a humidity of 95% to obtain self-healing crack concrete.

[0009] Furthermore, the mass ratio of cement, fly ash, silica fume, ceramsite, disulfide bond modified nanospheres, responsive composite hydrogel, polycarboxylate superplasticizer, and water is 100-120:20-22:5-7:50-60:8-10:3-4:1-2:44-46.

[0010] Furthermore, the specific preparation steps of the responsive composite hydrogel are as follows: A 4-6% sodium carboxymethyl cellulose solution and a 0.2-0.3 mol / L ferric chloride solution were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 40-50 min. After standing for 12-14 h to complete cross-linking, the mixture was cut into gel particles with a particle size of 1 mm. The gel particles were then immersed in a tris(hydroxymethyl)aminomethane buffer solution containing 2-4 mg / mL dopamine hydrochloride, and oxygen was introduced at a flow rate of 0.5 L / min. The mixture was stirred at 20-25℃ in the dark for 24-26 h. The product was washed 2-4 times with deionized water and freeze-dried at -40℃ for 48-50 h to obtain a responsive composite hydrogel.

[0011] Furthermore, the volume ratio of sodium carboxymethyl cellulose solution to ferric chloride solution is 50-60:40-42.

[0012] Furthermore, the specific preparation steps of the disulfide bond modified nanospheres are as follows: Hollow amino-modified phenolic resin nanospheres, deionized water, lipoic acid, and sodium hydroxide were added to a reaction vessel and stirred at 20-25℃ and 600 r / min for 40-50 min. Then, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added, and stirring was continued for another 40-50 min. Anhydrous ethanol was then added as a desiccant, and the reaction was continued for 18 h. The mixture was filtered, and the product was washed 2-4 times with deionized water and freeze-dried at -20℃ for 12-14 h to obtain disulfide bond modified nanospheres.

[0013] Furthermore, the ratio of hollow amino-modified phenolic resin nanospheres, deionized water, lipoic acid, sodium hydroxide, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is 100-120g: 800-900mL: 10-12g: 32-35g: 12-14g: 15-18g: 400-500mL.

[0014] Furthermore, the specific preparation steps of the hollow amino-modified phenolic resin nanospheres are as follows: Aminated phenolic resin and anhydrous ethanol were added to a reaction vessel and stirred for 10 min at 20-25℃ and 500-600 r / min. The mixture was then ultrasonically dispersed for 40-60 min, filtered under reduced pressure, and the product was washed 2-4 times with deionized water and freeze-dried at -20℃ for 12-14 h to obtain hollow aminated phenolic resin nanospheres.

[0015] Furthermore, the ratio of amino-modified phenolic resin to anhydrous ethanol is 200-300g: 2-3L.

[0016] Furthermore, the specific preparation steps of the amino-modified phenolic resin are as follows: Deionized water and 4-aminophenol were added to a reaction vessel and stirred at 12-15℃ and 500-600 r / min for 10-12 min. Then, formaldehyde solution was added and stirring was continued for 10-15 min. Ammonia water with a concentration of 2.6 mmol / L was added, and the mixture was heated to 25-28℃ and stirred for 30-50 min. The mixture was then filtered under reduced pressure, and the product was washed 2-4 times with deionized water and freeze-dried at -20℃ for 12-14 h to obtain aminophenolic resin.

[0017] Furthermore, the ratio of deionized water, 4-aminophenol, formaldehyde solution, and ammonia is 4-6L: 200-300g: 100-120mL: 30-50mL.

[0018] The beneficial effects of this invention are: 1. The self-healing cracked concrete prepared by this invention has the ability to target cracks and dynamically self-heal, with high repair efficiency and multiple repairs. Unlike the one-time repair limitation of traditional microcapsule self-healing concrete, the dynamic reversible disulfide bond characteristics of this scheme can achieve multiple self-repairs. It is especially suitable for microcracks that repeatedly appear in concrete during long-term use, which greatly reduces the cost of later maintenance.

[0019] 2. The disulfide bond-modified nanospheres prepared in this invention are the core functional component for self-healing. Disulfide bonds have dynamic and reversible characteristics, and can undergo a break-recombination reaction in a water environment with seepage in cracks, thereby achieving automatic healing of cracks. The disulfide bond-modified nanospheres are obtained by generating disulfide bonds through hollow amino-modified phenolic resin nanospheres. The hollow amino-modified phenolic resin nanospheres are rigid fillers, and the hollow structure can disperse the internal stress of concrete. Amino-modification enhances the interfacial bonding force between the nanospheres and the cement matrix and reduces internal pore defects.

[0020] 3. The responsive composite hydrogel of the present invention has crack-targeting response characteristics. When cracks occur in concrete, external moisture seeps in, and the hydrogel swells rapidly. On the one hand, it expands the internal space of the crack to provide a reaction environment for disulfide bond recombination. On the other hand, it drives the modified nanospheres to migrate and aggregate towards the crack, thereby achieving targeted repair. After being modified with dopamine, the responsive hydrogel has extremely strong adhesion and can tightly bind cement hydration products and aggregates, thereby improving the strength of the interfacial transition zone. Detailed Implementation

[0021] 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.

[0022] Example 1: A method for preparing self-healing cracked concrete, comprising the following steps: S1: Add 4L of deionized water and 200g of 4-aminophenol to a reaction vessel, stir at 12℃ and 500r / min for 10min, then add 100mL of formaldehyde solution, continue stirring for 10min, then add 30mL of 2.6mmol ammonia water, heat to 25℃, continue stirring for 30min, filter under reduced pressure, wash the product twice with deionized water, and freeze-dry at -20℃ for 12h to obtain aminophenolic resin; Add 200g of aminophenolic resin and 2L of anhydrous ethanol to a reaction vessel, stir at 20℃ and 500r / min for 10min, ultrasonically disperse for 40min, filter under reduced pressure, wash the product twice with deionized water, and freeze-dry at -20℃ for 12h to obtain hollow aminophenolic resin nanospheres.

[0023] S2: 100g of hollow amino-modified phenolic resin nanospheres, 800mL of deionized water, 10g of lipoic acid and 32g of sodium hydroxide were added to a reaction vessel and stirred at 20℃ and 600r / min for 40min. Then, 12g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 15g of N-hydroxysuccinimide were added and stirred for another 40min. Then, 400mL of anhydrous ethanol as a desiccant was added and the reaction was stirred for another 18h. The mixture was filtered and the product was washed twice with deionized water and freeze-dried at -20℃ for 12h to obtain disulfide bond modified nanospheres.

[0024] S3: Add 50 mL of 4% sodium carboxymethyl cellulose solution and 40 mL of 0.2 mol / L ferric chloride solution to the reactor. Stir at 20℃ and 500 r / min for 40 min, and let stand for 12 h to complete cross-linking. Cut into gel particles with a particle size of 1 mm. Immerse the gel particles in a buffer solution containing 2 mg / mL dopamine hydrochloride and tris(hydroxymethyl)aminomethane. Purge with oxygen at a flow rate of 0.5 L / min and stir at 20℃ in the dark for 24 h. Wash the product twice with deionized water and freeze-dry at -40℃ for 48 h to obtain the responsive composite hydrogel.

[0025] S4: Mix 100g cement, 20g fly ash, 5g silica fume, 50g ceramsite with a particle size of 5-10mm, 8g disulfide bond modified nanospheres, 3g responsive composite hydrogel, 1g polycarboxylate superplasticizer, and 44g water. Pour the mixture into a mold, vibrate to compact it, cover with a curing film, and cure for 28 days at a temperature of 25℃ and a humidity of 95% to obtain self-healing crack concrete.

[0026] Example 2: A method for preparing self-healing cracked concrete, comprising the following steps: S1: Add 5L of deionized water and 250g of 4-aminophenol to a reaction vessel, stir at 13.5℃ and 550r / min for 11min, then add 110mL of formaldehyde solution, continue stirring for 12.5min, then add 40mL of 2.6mmol ammonia water, heat to 26.5℃, continue stirring for 40min, filter under reduced pressure, wash the product three times with deionized water, and freeze-dry at -20℃ for 13h to obtain aminophenolic resin; Add 250g of aminophenolic resin and 2.5L of anhydrous ethanol to a reaction vessel, stir at 22.5℃ and 550r / min for 10min, ultrasonically disperse for 50min, filter under reduced pressure, wash the product three times with deionized water, and freeze-dry at -20℃ for 13h to obtain hollow aminophenolic resin nanospheres.

[0027] S2: 110g of hollow amino-modified phenolic resin nanospheres, 850mL of deionized water, 11g of lipoic acid and 33.5g of sodium hydroxide were added to a reaction vessel and stirred for 45min at 22.5℃ and 600r / min. Then, 13g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 16.5g of N-hydroxysuccinimide were added and stirred for another 45min. Then, 450mL of anhydrous ethanol as a desiccant was added and the reaction was stirred for another 18h. The mixture was filtered and the product was washed three times with deionized water and freeze-dried at -20℃ for 13h to obtain disulfide bond modified nanospheres.

[0028] S3: Add 55 mL of 5% sodium carboxymethyl cellulose solution and 41 mL of 0.25 mol / L ferric chloride solution to the reactor. Stir at 22.5℃ and 550 r / min for 45 min, and let stand for 13 h to complete cross-linking. Cut into gel particles with a particle size of 1 mm. Immerse the gel particles in a buffer solution containing 3 mg / mL dopamine hydrochloride and tris(hydroxymethyl)aminomethane. Introduce oxygen at a flow rate of 0.5 L / min and stir at 22.5℃ in the dark for 25 h. Wash the product three times with deionized water and freeze-dry at -40℃ for 49 h to obtain the responsive composite hydrogel.

[0029] S4: Mix 110g cement, 21g fly ash, 6g silica fume, 55g ceramsite with a particle size of 5-10mm, 9g disulfide bond modified nanospheres, 3.5g responsive composite hydrogel, 1.5g polycarboxylate superplasticizer, and 45g water. Pour the mixture into a mold, vibrate to compact it, cover with a curing film, and cure for 29 days at a temperature of 25℃ and a humidity of 95% to obtain self-healing crack concrete.

[0030] Example 3: A method for preparing self-healing cracked concrete, comprising the following steps: S1: Add 6 L of deionized water and 300 g of 4-aminophenol to a reaction vessel, stir at 15 °C and 600 r / min for 12 min, then add 120 mL of formaldehyde solution, continue stirring for 15 min, then add 50 mL of 2.6 mmol ammonia water, heat to 28 °C, continue stirring for 50 min, filter under reduced pressure, wash the product 4 times with deionized water, and freeze-dry at -20 °C for 14 h to obtain aminophenolic resin; Add 300 g of aminophenolic resin and 3 L of anhydrous ethanol to a reaction vessel, stir at 25 °C and 600 r / min for 10 min, ultrasonically disperse for 60 min, filter under reduced pressure, wash the product 4 times with deionized water, and freeze-dry at -20 °C for 14 h to obtain hollow aminophenolic resin nanospheres.

[0031] S2: 120g of hollow amino-modified phenolic resin nanospheres, 900mL of deionized water, 12g of lipoic acid and 35g of sodium hydroxide were added to a reaction vessel and stirred at 25℃ and 600r / min for 50min. Then, 14g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 18g of N-hydroxysuccinimide were added and stirred for another 50min. Then, 500mL of anhydrous ethanol as a desiccant was added and the reaction was stirred for another 18h. The mixture was filtered and the product was washed four times with deionized water and freeze-dried at -20℃ for 14h to obtain disulfide bond modified nanospheres.

[0032] S3: Add 60 mL of 6% sodium carboxymethyl cellulose solution and 42 mL of 0.3 mol / L ferric chloride solution to the reactor. Stir at 25℃ and 600 r / min for 50 min, and let stand for 14 h to complete cross-linking. Cut into gel particles with a particle size of 1 mm. Immerse the gel particles in a buffer solution containing 4 mg / mL dopamine hydrochloride and purge with oxygen at a flow rate of 0.5 L / min. Stir at 25℃ in the dark for 26 h. Wash the product with deionized water 4 times and freeze-dry at -40℃ for 50 h to obtain the responsive composite hydrogel.

[0033] S4: Mix 120g cement, 22g fly ash, 7g silica fume, 60g ceramsite with a particle size of 5-10mm, 10g disulfide bond modified nanospheres, 4g responsive composite hydrogel, 2g polycarboxylate superplasticizer, and 46g water. Pour the mixture into a mold, vibrate to compact it, cover with a curing film, and cure for 30 days at a temperature of 25℃ and a humidity of 95% to obtain self-healing crack concrete.

[0034] Comparative Example 1: Based on Example 3, 4-aminophenol in step S1 was replaced with phenol.

[0035] Comparative Example 2: Based on Example 3, the disulfide bond modified nanospheres in step S4 were replaced with the hollow amino-modified phenolic resin nanospheres prepared in step S1.

[0036] Comparative Example 3: Based on Example 3, the responsive composite hydrogel in step S4 is omitted.

[0037] The performance of the self-healing cracked concrete prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1: Table 1 ; As shown in Table 1, Comparative Example 1 failed to form an effective aminated modified structure, leading to a comprehensive decline in the preparation of subsequent functional components and interfacial bonding capabilities. The core function of 4-aminophenol is to introduce amino groups into the phenolic resin, achieving aminated modification. After being replaced with phenol, the prepared phenolic resin lacked an amino structure. On the one hand, it could not form disulfide bonds through the reaction of amino groups with lipoic acid, resulting in the inability to form disulfide bond-modified nanospheres. The core self-healing function was lost, relying solely on the physical filling effect of the resin itself, leading to a significant decrease in repair efficiency. On the other hand, the interfacial bonding between the unaminated resin nanospheres and the cement matrix was extremely poor, failing to effectively disperse internal stress, increasing internal pore defects in the concrete, significantly weakening its resistance to carbonation, and increasing the average carbonation depth. Furthermore, the non-aminated phenolic resin lacked sufficient hydrophilicity and reactivity, completely losing its subsequent ultrasonic dispersion and synergistic effect with the hydrogel, further exacerbating performance deterioration.

[0038] In Comparative Example 2, the disulfide-modified nanospheres are the core component for self-healing. The disulfide bonds they contain can undergo a breakage-recombination reaction in an aqueous environment, enabling automatic crack healing and repeated repairs. When replaced with unmodified hollow amino-modified phenolic resin nanospheres, they can only rely on the rigid filling effect of the hollow structure to disperse stress and on the amino groups to enhance interfacial bonding, lacking dynamic self-healing activity. When cracks appear in the concrete, the nanospheres cannot heal the cracks through chemical reactions, only providing temporary physical sealing, resulting in decreased repair efficiency and an inability to cope with recurring micro-cracks during long-term use. Furthermore, due to the lack of a dense structure formed by disulfide bond recombination, the concrete's resistance to carbonation decreases, the average carbonation depth increases, and crack propagation and durability degradation are more likely to occur later.

[0039] In Comparative Example 3, the disulfide bond-modified nanospheres lost their crack-targeting response capability and could not function efficiently, resulting in insufficient repair targeting and interfacial strength. The core function of the responsive composite hydrogel is to achieve targeted repair. On the one hand, it swells upon contact with water, expanding the crack space and providing a stable reaction environment for disulfide bond recombination; on the other hand, it drives the modified nanospheres to migrate and aggregate towards the crack, while enhancing interfacial adhesion through dopamine modification. Without the hydrogel, the disulfide bond-modified nanospheres are uniformly dispersed in the concrete matrix. When cracks occur, the nanospheres cannot quickly aggregate towards the crack area and only participate in the reaction through random diffusion, significantly reducing the reaction efficiency and repair efficiency. At the same time, the lack of the hydrogel's bonding and strengthening effect on the interface leads to insufficient strength in the interfacial transition zone between cement hydration products and aggregates, decreased internal structural density, weakened carbonation resistance, increased average carbonation depth, and lower interfacial strength after repair, making it prone to recurrence of cracks.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing self-healing cracked concrete, characterized in that, Includes the following steps: After mixing cement, fly ash, silica fume, ceramsite, disulfide bond modified nanospheres, responsive composite hydrogel, polycarboxylate superplasticizer, and water, the mixture is poured into a mold, vibrated to compact, covered with a curing film, and cured for 28-30 days at 25℃ and 95% humidity to obtain self-healing crack concrete.

2. The method for preparing self-healing cracked concrete according to claim 1, characterized in that, The mass ratio of the cement, fly ash, silica fume, ceramsite, disulfide bond modified nanospheres, responsive composite hydrogel, polycarboxylate superplasticizer, and water is 100-120:20-22:5-7:50-60:8-10:3-4:1-2:44-46.

3. The method for preparing self-healing cracked concrete according to claim 1, characterized in that, The specific preparation steps of the responsive composite hydrogel are as follows: A 4-6% sodium carboxymethyl cellulose solution and a 0.2-0.3 mol / L ferric chloride solution were added to a reaction vessel and stirred at 20-25℃ and 500-600 r / min for 40-50 min. After standing for 12-14 h to complete cross-linking, the mixture was cut into gel particles with a particle size of 1 mm. The gel particles were then immersed in a tris(hydroxymethyl)aminomethane buffer solution containing 2-4 mg / mL dopamine hydrochloride, and oxygen was introduced at a flow rate of 0.5 L / min. The mixture was stirred at 20-25℃ in the dark for 24-26 h. The product was washed 2-4 times with deionized water and freeze-dried at -40℃ for 48-50 h to obtain a responsive composite hydrogel.

4. The method for preparing self-healing cracked concrete according to claim 2, characterized in that, The volume ratio of the sodium carboxymethyl cellulose solution to the ferric chloride solution is 50-60:40-42.

5. The method for preparing self-healing cracked concrete according to claim 1, characterized in that, The specific preparation steps of the disulfide bond modified nanospheres are as follows: Hollow amino-modified phenolic resin nanospheres, deionized water, lipoic acid, and sodium hydroxide were added to a reaction vessel and stirred at 20-25℃ and 600 r / min for 40-50 min. Then, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added, and stirring was continued for another 40-50 min. Anhydrous ethanol was then added as a desiccant, and the reaction was continued for 18 h. The mixture was filtered, and the product was washed 2-4 times with deionized water and freeze-dried at -20℃ for 12-14 h to obtain disulfide bond modified nanospheres.

6. The method for preparing self-healing cracked concrete according to claim 5, characterized in that, The ratio of the hollow amino-modified phenolic resin nanospheres, deionized water, lipoic acid, sodium hydroxide, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide is 100-120g: 800-900mL: 10-12g: 32-35g: 12-14g: 15-18g: 400-500mL.

7. The method for preparing self-healing cracked concrete according to claim 5, characterized in that, The specific preparation steps of the hollow amino-modified phenolic resin nanospheres are as follows: Aminated phenolic resin and anhydrous ethanol were added to a reaction vessel and stirred for 10 min at 20-25℃ and 500-600 r / min. The mixture was then ultrasonically dispersed for 40-60 min, filtered under reduced pressure, and the product was washed 2-4 times with deionized water and freeze-dried at -20℃ for 12-14 h to obtain hollow aminated phenolic resin nanospheres.

8. The method for preparing self-healing cracked concrete according to claim 7, characterized in that, The ratio of the amino-modified phenolic resin to anhydrous ethanol is 200-300g: 2-3L.

9. The method for preparing self-healing cracked concrete according to claim 7, characterized in that, The specific preparation steps of the amino-modified phenolic resin are as follows: Deionized water and 4-aminophenol were added to a reaction vessel and stirred at 12-15℃ and 500-600 r / min for 10-12 min. Then formaldehyde solution was added and stirring was continued for 10-15 min. Ammonia water with a concentration of 2.6 mmol / L was added, and the mixture was heated to 25-28℃ and stirred for 30-50 min. The mixture was then filtered under reduced pressure. The product was washed 2-4 times with deionized water and freeze-dried at -20℃ for 12-14 h to obtain amino-modified phenolic resin. The ratio of deionized water, 4-aminophenol, formaldehyde solution, and ammonia is 4-6L: 200-300g: 100-120mL: 30-50mL.

10. A self-healing cracked concrete, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.