A concrete crack self-healing functional material and a preparation method thereof

Abstract

This invention relates to the field of building materials technology, specifically to a self-healing functional material for concrete cracks and its preparation method, comprising the following components by mass percentage: 0.3%–0.7% nonionic surfactant AEO-9, 0.5%–0.9% sodium silicate, 0–0.4% potassium silicate, 0–0.3% sodium carbonate, 0.2%–0.4% sodium citrate, 0–0.2% sodium gluconate, 45%–55% fly ash, 3%–5% nano-SiO2, 0.2%–0.4% basalt fiber, 0.3%–0.5% superabsorbent polymer (SAP), 0.05%–0.1% ammonium persulfate, 0.02%–0.05% cerium ammonium nitrate, with the balance being deionized water. The method includes the following steps: S1: preparing carrier D; S2: preparing solution I; S3: preparing solution II; S4: preparing composite powder P; S5: preparing mixture M; S6: preparing the self-healing functional material. This self-healing concrete crack material, after 200 freeze-thaw cycles in a 5% Na2SO4 solution at -10℃, retains a relative dynamic modulus of elasticity of ≥85% and a flexural strength recovery rate of ≥110%, showing broad prospects for promotion.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a self-healing functional material for concrete cracks and its preparation method. Background Technology

[0002] Cement concrete has become the most widely used structural material for infrastructure such as bridges, tunnels, high-grade highways and urban buildings due to its outstanding advantages such as high compressive strength, abundant raw materials and good construction adaptability. With the advancement of national strategies such as "building a strong transportation nation" and "building a strong maritime nation", concrete structures are gradually being extended to extreme environments such as high cold, high salinity and large temperature difference, and the design life has been increased from 30 years to 100 years, which puts forward higher requirements for its durability and crack control.

[0003] However, concrete inherently has low tensile strength and large shrinkage deformation. Under the combined effects of temperature gradient, drying shrinkage, freeze-thaw cycles, chloride / sulfate corrosion, and fatigue load, it is prone to microcracks. Cracks wider than 0.1 mm can become rapid channels for water, oxygen, and corrosive ions, accelerating the depassivation of steel bars, corrosion expansion, and peeling of the protective layer. This eventually leads to a vicious cycle of "cracks - penetration - corrosion - more cracks." Domestic and international surveys show that steel corrosion caused by crack penetration accounts for more than 60% of premature failures of concrete structures. In salt-frost regions, the crack propagation rate can be increased by 2 to 3 times, and large-area spalling and network cracking can occur in structures after 20 years of service. Maintenance costs account for more than 40% of the total life cycle cost.

[0004] To delay or avoid the degradation of durability caused by cracks, researchers have successively proposed technical routes such as expansion agent to compensate for shrinkage, steel fiber / polymer fiber toughening, surface coating with penetrating crystallizing waterproofing agent, microbial induced mineralization deposition (MICP), and microcapsule / microchannel self-repair. The above methods can all achieve the healing of cracks of 0.2 to 0.5 mm under laboratory conditions, with a strength recovery rate of 50% to 90%. However, there are still obvious shortcomings in engineering applications: (1) The single mechanism depends on specific environmental conditions (humidity, temperature, pH, calcium ion concentration). In drought, low temperature (<5℃) conditions, the healing rate is not high. (1) The reaction stops under high alkalinity (pH>12.5); (2) The repair agent cannot be activated multiple times after one release, making it difficult to meet the "cracks repeatedly open and close - heal" requirement during the service life; (3) The capsule is brittle, the fibers are easy to agglomerate, and the microbial activity is suppressed, resulting in discrete healing efficiency and insufficient long-term reliability. Therefore, developing a concrete self-healing material that takes into account "low temperature triggering - multiple healing - environmental tolerance" has become a key technical bottleneck that long-life concrete in extreme environments urgently needs to overcome. Therefore, a concrete crack self-healing functional material and its preparation method are urgently needed to improve the above problems. Summary of the Invention

[0005] The purpose of this invention is to at least address one of the aforementioned technical deficiencies.

[0006] Therefore, one objective of this invention is to provide a self-healing functional material for concrete cracks and its preparation method, so as to solve the problems mentioned in the background art and overcome the shortcomings of the prior art.

[0007] To achieve the above objectives, one embodiment of the present invention provides a self-healing material for concrete cracks, comprising the following components by mass percentage: 0.3%–0.7% nonionic surfactant AEO-9, 0.5%–0.9% sodium silicate, 0–0.4% potassium silicate, 0–0.3% sodium carbonate, 0.2%–0.4% sodium citrate, 0–0.2% sodium gluconate, 45%–55% fly ash, 3%–5% nano-SiO2, 0.2%–0.4% basalt fiber, 0.3%–0.5% superabsorbent polymer (SAP), 0.05%–0.1% ammonium persulfate, 0.02%–0.05% cerium ammonium nitrate, with the balance being deionized water;

[0008] The preparation method of self-healing functional material for concrete cracks includes the following steps:

[0009] S1: Preparation of carrier D: fly ash and nano-SiO2 are mixed in a high-speed mixer to obtain carrier D;

[0010] S2: To prepare solution I, AEO-9 is dissolved in water, and crystallization components (sodium silicate, potassium silicate, sodium carbonate) are added. The solution is then dispersed by ultrasonication to obtain solution I.

[0011] S3: Prepare solution II by dissolving the complexing components (sodium citrate, sodium gluconate) in water and adjusting the pH of the solution.

[0012] S4: To prepare composite powder P, solutions I and II are sequentially atomized and sprayed onto the surface of carrier D, and then mixed to obtain composite powder P;

[0013] S5: Prepare mixture M by adding basalt fiber and SAP together to P and then mixing them to obtain mixture M;

[0014] S6: To prepare a self-healing functional material, ammonium persulfate and cerium ammonium nitrate were mixed to form a 1wt% aqueous solution, M was sprayed in, granulated, and vacuum dried at 60℃ until the moisture content was <2% to obtain a self-healing functional material with a particle size of 0.1–0.3 mm.

[0015] The present invention is further configured such that: the basalt fiber length is 3-6 mm, the SAP particle size is 100-300 μm, the fly ash is Class I ash, the specific surface area of ​​nano SiO2 is ≥200 m² / g, and the purity is ≥99%.

[0016] The present invention is further configured such that: in step S1, fly ash and nano-SiO2 are dry-mixed in a high-speed mixer for 10 minutes.

[0017] The present invention is further configured such that: in step S2, AEO-9 is dissolved in water at a temperature of 40°C, and the ultrasonic power is 300W, the frequency is 40kHz, and the time is 20min.

[0018] The present invention is further configured such that the pH value of the solution in S3 is adjusted to 9.0±0.2.

[0019] The present invention is further configured such that: the atomization pressure in S4 is 0.2 MPa, the spraying speed is 10 mL / min, and the mixing time is 15 min.

[0020] The present invention is further configured such that: the mixing in S5 is carried out at a low speed for 5 minutes.

[0021] The present invention is further configured such that: in step S6, granulation is performed using a high-speed centrifugal granulator with a rotation speed of 3000 r / min and a drying time of 12 h.

[0022] In summary, the beneficial technical effects of the present invention are as follows:

[0023] 1. The self-healing functional material for concrete cracks and its preparation method: the self-healing microspheres formed can automatically absorb water and be activated after crack formation; the crystalline component and the complexing component react synergistically to rapidly generate CSH gel and CaCO3 crystals, achieving a closure rate of ≥90% for 0.4mm cracks within 28 days;

[0024] 2. The self-healing functional material for concrete cracks and its preparation method: basalt fibers form a three-dimensional bridging network at the crack interface, inhibiting crack propagation and improving fracture toughness; SAP continuously releases water, maintaining local humidity >90%, promoting secondary hydration and crystal growth, and achieving multiple healing processes;

[0025] 3. The self-healing functional material for concrete cracks and its preparation method: fly ash-nano SiO2 carrier provides high specific surface area and active sites, which improves the crystallization reaction rate, while refining the pore structure, resulting in a reduction of chloride ion migration coefficient by more than 60%;

[0026] 4. The self-healing functional material for concrete cracks and its preparation method: The preparation process of this invention is simple, does not require high temperature and high pressure, uses conventional equipment, is suitable for large-scale production and direct addition on engineering sites, and does not affect the workability and strength development of concrete;

[0027] 5. The self-healing functional material for concrete cracks and its preparation method: The self-healing functional material provided by this invention maintains a relative dynamic elastic modulus of ≥85% and a flexural strength recovery rate of ≥110% after 200 freeze-thaw cycles in a 5% Na2SO4 solution at -10℃. It is suitable for bridge, tunnel, and pavement concrete projects in harsh environments such as plateaus, coastal areas, and saline-alkali lands, and has broad prospects for promotion.

[0028] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0030] Figure 1 These are images of the crack healing process in Embodiment 7 of the present invention (0d, 3d, 7d, 28d).

[0031] Figure 2 It is the crystallized product of the crack in Example 7 of the present invention after 28 days. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] This invention discloses a self-healing functional material for concrete cracks, comprising the following raw materials: nonionic surfactant AEO-9, crystalline components (sodium silicate, potassium silicate, sodium carbonate), complexing components (sodium citrate, sodium gluconate), fly ash, nano-SiO2, basalt fiber, superabsorbent resin SAP, initiation system (ammonium persulfate, cerium ammonium nitrate), and deionized water.

[0034] Specifically, by weight fraction, it consists of the following raw materials: 0.3%–0.7% AEO-9, 0.5%–0.9% sodium silicate, 0–0.4% potassium silicate, 0–0.3% sodium carbonate, 0.2%–0.4% sodium citrate, 0–0.2% sodium gluconate, 45%–55% fly ash, 3%–5% nano-SiO2, 0.2%–0.4% basalt fiber, 0.3%–0.5% SAP, 0.05%–0.1% ammonium persulfate, 0.02%–0.05% cerium ammonium nitrate, with the balance being deionized water;

[0035] The basalt fibers are 3-6 mm in length and the SAP particles are 100-300 μm in size; the fly ash is Class I ash with a nano-SiO2 specific surface area ≥200 m² / g and a purity ≥99%.

[0036] AEO-9 is a nonionic fatty alcohol polyoxyethylene ether surfactant that can significantly reduce the surface tension of the matrix and increase the penetration depth of the repair solution in the cracks. Sodium silicate / potassium silicate / sodium carbonate are inorganic crystalline components that can react with the hydration product Ca(OH)2 to generate CSH gel and CaCO3 crystals, achieving physical filling and chemical bonding of the cracks. Sodium citrate and sodium gluconate are environmentally friendly organic complexing agents that can reduce the nucleation energy barrier and accelerate crystal deposition. The fly ash-nano SiO2 composite carrier provides a high specific surface area and active sites, promoting crystal nucleation and refining the pore structure. Basalt fibers form a three-dimensional bridging network in the crack area, inhibiting crack propagation and improving fracture toughness. SAP has a high water absorption and retention capacity, forming a "micro-reservoir" in the crack area to continuously provide the water required for crystallization and achieve multiple healing. Ammonium persulfate-cerium ammonium nitrate constitute an oxidation-reduction initiation system that can trigger graft polymerization at room temperature, ensuring that the functional components are stably anchored on the carrier surface.

[0037] The preparation method of self-healing functional material for concrete cracks includes the following steps:

[0038] S1: Prepare carrier D by weighing fly ash and nano-SiO2 by mass and dry mixing them in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0039] S2: To prepare solution I, AEO-9 was dissolved in deionized water at 40℃, and the crystallization components (sodium silicate, potassium silicate, sodium carbonate) were added. The solution was then ultrasonically dispersed at 300W and 40kHz for 20min to obtain solution I.

[0040] S3: To prepare solution II, dissolve the complexing components (sodium citrate and sodium gluconate) in deionized water and adjust the pH to 9.0 ± 0.2 with 0.1 mol / L NaOH to obtain solution II;

[0041] S4: To prepare composite powder P, solutions I and II are sequentially atomized and sprayed onto the surface of composite carrier D at a spraying rate of 10 mL / min and an atomization pressure of 0.2 MPa. After spraying, the mixture is mixed for 15 min to obtain composite powder P.

[0042] S5: Prepare mixture M by adding basalt fiber and SAP together into composite powder P and mixing at a low speed of 200 r / min for 5 min to obtain mixture M;

[0043] S6: To prepare self-healing functional materials, ammonium persulfate and cerium ammonium nitrate were mixed to form a 1wt% aqueous solution, which was sprayed into the mixture M at 5mL / min. The mixture was then fed into a high-speed centrifugal granulator and granulated at 3000r / min. The mixture was then vacuum dried at 60℃ for 12h until the moisture content was <2%. The self-healing functional materials with a particle size of 0.1–0.3mm were obtained by sieving.

[0044] In S2, the ultrasonic dispersion temperature is controlled at 40±2℃ to prevent premature hydrolysis of the crystalline components; in S4, the atomizing spray uses a two-fluid nozzle with a gas-liquid ratio of 10:1 to ensure that the average droplet size is <50μm; in S6, the vacuum drying vacuum degree is -0.09MPa to prevent high-temperature oxidation and decomposition of organic components; anhydrous ethanol and deionized water are used only as solvents or dispersion media and do not participate in chemical reactions. They can be recycled after condensation.

[0045] The self-healing concrete crack functional material and its preparation method of the present invention will be further described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The following detailed descriptions are all based on embodiments and are intended to provide more comprehensive support for the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by those skilled in the art; the terminology used in this invention is only used to describe specific embodiments and is not intended to limit the exemplary embodiments of the present invention. Unless otherwise specified, the materials, equipment, and testing methods used in the embodiments are all conventional means in the art; all values ​​are the average of three parallel tests.

[0046] Example 1

[0047] A self-healing concrete crack material is composed of the following components by weight percentage:

[0048] The composition is as follows: AEO-9 0.3%, sodium silicate 0.7%, sodium citrate 0.3%, fly ash 50%, nano-SiO2 3%, basalt fiber 0.2%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.02%, and the balance is deionized water.

[0049] The basalt fiber has a length of 4 mm and the SAP particle size is 200 μm; the fly ash is Class I ash, the specific surface area of ​​nano SiO2 is ≥200 m² / g, and the purity is ≥99%.

[0050] A method for preparing a self-healing material for concrete cracks, comprising the following specific steps:

[0051] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0052] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0053] S3. Dissolve sodium citrate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0054] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0055] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0056] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0057] Example 2

[0058] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0059] The composition is as follows: AEO-9 0.5%, sodium silicate 0.9%, potassium silicate 0.2%, sodium citrate 0.2%, sodium gluconate 0.1%, fly ash 55%, nano-SiO2 5%, basalt fiber 0.3%, SAP 0.3%, ammonium persulfate 0.1%, cerium ammonium nitrate 0.03%, with the balance being deionized water.

[0060] The basalt fiber has a length of 4 mm and the SAP particle size is 200 μm; the fly ash is Class I ash, the specific surface area of ​​nano SiO2 is ≥200 m² / g, and the purity is ≥99%.

[0061] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0062] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0063] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate and potassium silicate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0064] S3. Dissolve sodium citrate and sodium gluconate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0065] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0066] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0067] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0068] Example 3

[0069] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0070] The composition is as follows: AEO-9 0.7%, sodium silicate 0.5%, sodium citrate 0.3%, sodium gluconate 0.2%, fly ash 45%, nano-SiO2 4%, basalt fiber 0.4%, SAP 0.5%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.05%, and the balance is deionized water.

[0071] The basalt fiber has a length of 4 mm and the SAP particle size is 200 μm; the fly ash is Class I ash, the specific surface area of ​​nano SiO2 is ≥200 m² / g, and the purity is ≥99%.

[0072] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0073] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0074] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0075] S3. Dissolve sodium citrate and sodium gluconate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0076] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0077] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0078] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0079] Example 4

[0080] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0081] The composition is as follows: AEO-9 0.5%, sodium silicate 0.7%, sodium gluconate 0.2%, fly ash 50%, nano-SiO2 4%, basalt fiber 0.3%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.03%, and the balance is deionized water.

[0082] The basalt fiber has a length of 6 mm and the SAP particle size is 200 μm; the fly ash is Class I ash, the nano SiO2 has a specific surface area ≥200 m² / g, and a purity ≥99%.

[0083] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0084] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0085] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0086] S3. Dissolve sodium gluconate in deionized water and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0087] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0088] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0089] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0090] Example 5

[0091] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0092] The composition is as follows: AEO-9 0.5%, sodium silicate 0.5%, sodium citrate 0.3%, fly ash 50%, nano-SiO2 4%, basalt fiber 0.3%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.03%, and the balance is deionized water.

[0093] The basalt fiber has a length of 4 mm and the SAP particle size is 300 μm; the fly ash is Class I ash, the nano SiO2 has a specific surface area ≥200 m² / g, and a purity ≥99%.

[0094] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0095] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0096] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0097] S3. Dissolve sodium citrate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0098] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0099] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0100] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0101] Example 6

[0102] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0103] The composition is as follows: AEO-9 0.5%, sodium silicate 0.6%, potassium silicate 0.4%, sodium citrate 0.4%, sodium carbonate 0.3%, fly ash 50%, nano-SiO2 4%, basalt fiber 0.3%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.03%, with the balance being deionized water.

[0104] The basalt fiber has a length of 4 mm and the SAP particle size is 150 μm; the fly ash is Class I ash, the nano SiO2 has a specific surface area ≥200 m² / g, and a purity ≥99%.

[0105] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0106] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0107] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, potassium silicate and sodium carbonate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0108] S3. Dissolve sodium citrate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0109] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0110] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0111] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0112] Example 7

[0113] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0114] The composition of AEO-9 is 0.5%, sodium silicate 0.8%, potassium silicate 0.2%, sodium citrate 0.4%, sodium carbonate 0.1%, fly ash 50%, nano-SiO2 4%, basalt fiber 0.3%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.03%, and the balance is deionized water.

[0115] The basalt fiber has a length of 4 mm and the SAP particle size is 200 μm; the fly ash is Class I ash, the specific surface area of ​​nano SiO2 is ≥200 m² / g, and the purity is ≥99%.

[0116] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0117] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0118] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, potassium silicate and sodium carbonate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0119] S3. Dissolve sodium citrate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0120] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0121] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0122] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0123] Example 8

[0124] The difference from Example 1 lies in the specific dosage of each component of the self-healing concrete crack material, as detailed below:

[0125] The composition is as follows: AEO-9 0.5%, sodium silicate 0.7%, sodium citrate 0.3%, fly ash 50%, nano-SiO2 4%, basalt fiber 0.3%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.03%, and the balance is deionized water.

[0126] The composition is as follows: AEO-9 0.5%, sodium silicate 0.7%, potassium silicate 0.4%, sodium citrate 0.3%, sodium carbonate 0.2%, fly ash 50%, nano-SiO2 4%, basalt fiber 0.3%, SAP 0.4%, ammonium persulfate 0.05%, cerium ammonium nitrate 0.03%, with the balance being deionized water.

[0127] The basalt fiber is 4 mm in length and the SAP particle size is 200 μm; the fly ash is Class I ash, the nano SiO2 has a specific surface area ≥200 m² / g and a purity ≥99%.

[0128] A method for preparing a self-healing material for cracks in cement concrete, comprising the following specific steps:

[0129] S1. Fly ash and nano-SiO2 are dry-mixed in a high-speed mixer at 800 r / min for 10 min to obtain composite carrier D;

[0130] S2. Dissolve AEO-9 in deionized water at 40℃, add sodium silicate, and ultrasonically disperse at 300W and 40kHz for 20min to obtain solution I.

[0131] S3. Dissolve sodium citrate in deionized water, and adjust the pH to 9.0 with 0.1 mol / L NaOH to obtain solution II;

[0132] S4. Spray solutions I and II sequentially onto the surface of carrier D at a spraying rate of 10 mL / min and a spraying pressure of 0.2 MPa. After spraying, continue mixing for 15 min to obtain composite powder P.

[0133] S5. Add basalt fiber and SAP together to P, and mix at a low speed of 200 r / min for 5 min to obtain mixture M;

[0134] S6. Prepare a 1wt% aqueous solution of ammonium persulfate and cerium ammonium nitrate, spray M into the solution, granulate by centrifugation at 3000 r / min, vacuum dry at 60℃ for 12 h until the moisture content is <2%, and obtain a self-healing functional material with a particle size of 0.1–0.3 mm by sieving.

[0135] Comparative Example 1

[0136] The difference between this comparative example and Example 1 is that sodium citrate and sodium gluconate are not added to the self-healing concrete crack material, while the other components and preparation steps are the same.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that basalt fiber is not added to the self-healing concrete crack material, while the other components and preparation steps are the same.

[0139] Comparative Example 3

[0140] The difference between this comparative example and Example 1 is that SAP is not added to the self-healing functional material for cement concrete cracks, while the other components and preparation steps are the same.

[0141] Comparative Example 4

[0142] The difference between this comparative example and Example 1 is that the AEO-9 surfactant is not added to the self-healing concrete crack material, while the other components and preparation steps are the same.

[0143] Comparative Example 5

[0144] The difference between this comparative example and Example 1 is that fly ash and nano-SiO2 carrier components are not added to the self-healing concrete crack functional material, while the other components and preparation steps are the same.

[0145] Comparative Example 6

[0146] This comparative example uses a commercially available sodium silicate-based self-healing agent (Na2O·nSiO2, n=3.2) at a dosage of 0.3 wt% of the cementitious material as a control.

[0147] Comparative Example 7

[0148] This comparative example is a baseline concrete specimen without any self-healing materials added.

[0149] Performance testing

[0150] According to JC / T2553-2019 and GB / T50082-2009, mortar specimens of 40mm×40mm×160mm were formed with a water-cement ratio of 0.40 and a functional material content of 0.3wt% of cementitious material. After standard curing for 28 days, 0.4mm cracks were pre-formed and subjected to freeze-thaw cycles in a -10℃, 5% Na2SO4 solution. Crack healing rate, flexural strength recovery rate, relative dynamic modulus of elasticity, and chloride ion migration coefficient were measured every 25 cycles. Specific performance indicators are shown in the table below:

[0151]

[0152]

[0153] The results are analyzed as follows:

[0154] (1) After 50 salt-freezing cycles, the cracks in the specimens of Examples 1 to 8 were basically closed, with a healing rate of 90%–97%; the flexural strength recovery rate after 28 days was 108%–118%, the relative dynamic elastic modulus remained above 95%, and the chloride ion migration coefficient decreased by 58%–68% compared with the baseline group, indicating that the material has excellent self-healing properties and durability.

[0155] (2) Due to the lack of key functional components, the healing rate of Comparative Examples 1 to 4 was only 42%–73%, the flexural strength recovery rate was 82%–96%, the relative dynamic elastic modulus did not exceed 85%, and the chloride ion migration coefficient decreased by only 18%–35%, with overall performance significantly lower than that of the Examples.

[0156] (3) In Comparative Example 5, the component without a carrier lacked the active sites and nucleation effect of fly ash-nano SiO2 carrier, resulting in a healing rate of 60%, a strength recovery rate of 80%, and a chloride ion migration coefficient that decreased by only 26%, indicating that the carrier has a key influence on the reaction rate and density.

[0157] (4) Comparative Example 6 (commercially available sodium silicate-based repair agent) relies on a single crystallization mechanism, with a healing rate of only 45%, a strength recovery rate of 79%, and a chloride ion migration coefficient reduction of only 20%, indicating that the multi-mechanism synergistic system is more advantageous in extreme environments.

[0158] (5) Comparative Example 7 did not add any self-healing material, the cracks did not heal, the strength recovery rate was only 75%, and the chloride ion migration coefficient did not decrease, further verifying the necessity of the material of the present invention.

[0159] (6) Example 7 showed the best performance, with a healing rate of 97%, a flexural strength recovery rate of 118%, a chloride ion migration coefficient decrease of 68%, and no peeling occurred when the freeze-thaw cycle reached F225. Figure 1 and Figure 2 It is known that this self-healing functional material can generate a large number of repair product crystals at the cracks in concrete and adhere to the cracks, enabling cracks of about 0.4 mm to self-heal after 28 days of curing, thus greatly restoring the performance of concrete.

[0160] All embodiments demonstrated excellent crack repair and durability improvement effects under extreme conditions such as saline freezing, high alkali, and drought. The flexural strength recovery rate was higher than 108%, the healing rate remained stable above 92%, the relative dynamic elastic modulus was ≥96%, and the chloride ion migration coefficient decreased by more than 60%. Compared with the comparative examples, the embodiments showed improvements of 20%~39%, 55%, and over 50% in strength recovery rate, healing rate, and impermeability, respectively, fully demonstrating the key role of the synergistic effect of each functional component in achieving the comprehensive performance of "rapid sealing—long-term densification—multiple healing." This material is suitable for concrete structures in harsh environments such as bridges, tunnels, and pavements in saline freezing areas, and has significant engineering application prospects.

[0161] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A self-healing material for concrete cracks, characterized in that: The product comprises the following components by weight percentage: 0.3%–0.7% nonionic surfactant AEO-9, 0.5%–0.9% sodium silicate, 0%–0.4% potassium silicate, 0%–0.3% sodium carbonate, 0.2%–0.4% sodium citrate, 0%–0.2% sodium gluconate, 45%–55% fly ash, 3%–5% nano-SiO2, 0.2%–0.4% basalt fiber, 0.3%–0.5% superabsorbent polymer (SAP), 0.05%–0.1% ammonium persulfate, 0.02%–0.05% cerium ammonium nitrate, with the balance being deionized water. The preparation method of self-healing functional material for concrete cracks includes the following steps: S1: Preparation of carrier D: fly ash and nano-SiO2 are mixed in a high-speed mixer to obtain carrier D; S2: To prepare solution I, AEO-9 is dissolved in water, and crystallization components (sodium silicate, potassium silicate, sodium carbonate) are added. The solution is then dispersed by ultrasonication to obtain solution I. S3: Prepare solution II by dissolving the complexing components (sodium citrate, sodium gluconate) in water and adjusting the pH of the solution. S4: To prepare composite powder P, solutions I and II are sequentially atomized and sprayed onto the surface of carrier D, and then mixed to obtain composite powder P; S5: Prepare mixture M by adding basalt fiber and SAP together to P and then mixing them to obtain mixture M; S6: To prepare a self-healing functional material, ammonium persulfate and cerium ammonium nitrate were mixed to form a 1wt% aqueous solution, M was sprayed in, granulated, and vacuum dried at 60℃ until the moisture content was <2% to obtain a self-healing functional material with a particle size of 0.1–0.3 mm.

2. The self-healing concrete crack material according to claim 1, characterized in that: The basalt fiber has a length of 3-6 mm, the SAP particle size is 100-300 μm, the fly ash is Class I ash, the nano SiO2 has a specific surface area ≥200 m² / g, and a purity ≥99%.

3. The self-healing concrete crack material according to claim 1, characterized in that: In step S1, fly ash and nano-SiO2 are dry-mixed in a high-speed mixer for 10 minutes.

4. The self-healing concrete crack material according to claim 1, characterized in that: In step S2, AEO-9 is dissolved in water at a temperature of 40°C, and the ultrasonic power is 300W, the frequency is 40kHz, and the time is 20min.

5. The self-healing concrete crack material according to claim 1, characterized in that: The pH value of the solution in S3 is adjusted to 9.0±0.

2.

6. The self-healing concrete crack material according to claim 1, characterized in that: The atomization pressure in S4 is 0.2 MPa, the spraying speed is 10 mL / min, and the mixing time is 15 min.

7. The self-healing concrete crack material according to claim 1, characterized in that: The S5 mixture is mixed at a low speed for 5 minutes.

8. The self-healing concrete crack material according to claim 1, characterized in that: In the S6 process, granulation is performed using a high-speed centrifugal granulator with a rotation speed of 3000 r / min and a drying time of 12 h.

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