Self-healing cementitious composite material and method of making

Abstract

The application relates to the technical field of building materials, in particular to a self-repairing cement-based composite material and a preparation method thereof; the self-repairing cement-based composite material is prepared from the following raw materials in parts by weight: 1000-1200 parts of coarse aggregate, 600-850 parts of fine aggregate, 300-450 parts of Portland cement, 40-60 parts of fly ash, 150-200 parts of mineral powder, 4-6 parts of a water reducing agent, 5-8 parts of a retarder, 60-120 parts of a self-repairing agent and 150-200 parts of water; the coarse aggregate is selected from gravel with a particle size of 5-20 mm, and the fine aggregate is selected from medium sand with a particle size of 0.5-0.8 mm; the cement is selected from P.O52.5 Portland cement, the mineral powder is S95 grade, and the fly ash is grade II; the self-repairing cement-based composite material prepared by the application can not only efficiently repair concrete cracks but also has a long repair time and can effectively improve the waterproof performance of the repaired concrete, effectively guarantees the quality of the concrete, and prolongs the service life of the concrete to a certain extent.

Description

Technical Field

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

[0002] Cement-based composite materials are the most widely used materials in modern construction, but their inherent brittleness makes them prone to microcracks during service. These microcracks not only reduce the mechanical properties of the material, but also provide a convenient channel for the intrusion of harmful substances (such as chloride ions, sulfate ions, carbon dioxide, etc.), accelerating steel corrosion and material deterioration, seriously threatening the safety and durability of the structure and shortening its service life. To solve these technical problems, self-healing technologies have emerged. Among them, microbial-induced calcium carbonate precipitation technology has attracted much attention due to its environmental friendliness and the good compatibility of the repair products with the concrete matrix. This technology utilizes specific microorganisms to decompose urea or other organic calcium sources during metabolism, producing carbonate ions, which combine with calcium ions in the environment to form calcium carbonate precipitates, thereby sealing the cracks.

[0003] Existing self-healing cement-based materials based on microorganisms still face the following technical challenges:

[0004] 1. The high alkalinity and high pore pressure during the cement hydration process pose a serious threat to the survival of microorganisms, causing the repair agent to be largely deactivated in the early stages of its introduction.

[0005] 2. The single microbial repair mechanism often lacks a continuous and stable supply of nutrients and a suitable reaction environment after cracks are formed, resulting in limited repair efficiency and difficulty in effectively repairing wider cracks.

[0006] 3. Traditional coating materials (such as urea-formaldehyde resin) are either too fragile and crack prematurely during concrete mixing, or too tough and cannot respond in time when cracks occur.

[0007] 4. The introduction of repair agents should not significantly affect the initial workability and mechanical properties of concrete.

[0008] Based on the above, the present invention provides a self-healing cement-based composite material and its preparation method to solve the technical problems mentioned above. Summary of the Invention

[0009] This invention provides a self-healing cement-based composite material and its preparation method. The prepared self-healing cement-based composite material can not only efficiently repair cracks in concrete with a long-lasting and durable repair effect, but also effectively improve the waterproof performance of the repaired concrete, effectively ensuring its quality and extending the service life of concrete to a certain extent.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A self-repairing cement-based composite material is prepared from the following raw materials by weight: 1000-1200 parts of coarse aggregate, 600-850 parts of fine aggregate, 300-450 parts of Portland cement, 40-60 parts of fly ash, 150-200 parts of slag, 4-6 parts of water reducing agent, 5-8 parts of retarder, 60-120 parts of self-repairing agent and 150-200 parts of water.

[0012] Further, the preparation method of the self-repairing agent is as follows:

[0013] Step one, uniformly spray 3-8 wt% polybutylene succinate solution in chloroform on the surface of the composite powder to form a polybutylene succinate film layer with a thickness of 30-50 nm, then vacuum dry and recover chloroform to obtain the composite microspheres; the composite powder is prepared by mixing calcium peroxide and sodium stearate at a mass ratio of 1:1-2, and the average particle size of both is 100-200 mesh;

[0014] Step two, uniformly disperse the core material in a 2-5 times mass sodium alginate aqueous solution with a concentration of 3-6 wt%, then slowly drop the obtained dispersion into a 3-6 times mass calcium chloride aqueous solution with a concentration of 8-15 wt%, and then filter, wash with water and dry at 40-50°C overnight after stirring and solidification to obtain the modified core material with a particle size;

[0015] Step three, put the modified core material, composite microspheres and water-absorbing resin into a roller at a mass ratio of 1:0.1-0.3:0.05-0.08, and spray the coating liquid to the surface of the modified core material and composite microspheres through a spray gun during the rotation of the roller; after the spraying is completed, the roller is dried while rotating, and the self-repairing agent with an average particle size of 0.8-1.5 mm is obtained.

[0016] Further, the coating liquid is prepared by uniformly mixing ethyl cellulose powder and a complex solvent at a solid-liquid ratio of 1:8-12; wherein the complex solvent is prepared by compounding dimethylbenzene with 25-35% volume of ethanol.

[0017] The preparation method of the core material is as follows: add 2×10 9 -6×10 10 CFU / mL of alkaliphilic Bacillus suspension to a porous substrate with a mass of 20-50% of the suspension, soak for 2-3 days, filter out the porous substrate, and dry at 40-50°C overnight to obtain the core material.

[0018] Further, the preparation method of the porous substrate is: uniformly mixing hydroxyapatite with an average particle size of 0.5-1mm and tetraethyl orthosilicate with a mass of 5-8% of that of the hydroxyapatite, then adding ammonia solution with a mass of 0.8-1.2 times of that of the tetraethyl orthosilicate and a pH of 9-10, stirring and reacting at 65-75 DEG C for 3-5h, and then sequentially performing filtration, washing and drying treatment on the reaction solution to obtain the porous substrate.

[0019] Further, the cement is P.O52.5 Portland cement, the mineral powder is S95 grade, and the fly ash is grade II.

[0020] Further, the coarse aggregate is selected from gravel with a particle size of 5-20mm, and the fine aggregate is selected from medium sand with a particle size of 0.5-0.8mm.

[0021] Further, the retarder is selected from any one of calcium lignosulfonate, hydroxymethyl cellulose and hydroxyethyl cellulose.

[0022] Further, the water reducing agent is selected from any one of polycarboxylic acid water reducing agent, aminosulfonate water reducing agent and naphthalenesulfonate water reducing agent.

[0023] A preparation method of a self-repairing cement-based composite material comprises the following steps: accurately weighing each raw material, and sequentially adding coarse aggregate, fine aggregate, Portland cement, fly ash and mineral powder into a stirring device, adding the remaining raw materials after mixing and stirring for 100-120s, and mixing and stirring for 100-150s to obtain the self-repairing cement-based composite material.

[0024] Compared with the prior art, the self-repairing cement-based composite material has the following beneficial effects:

[0025] 1. The multi-layer protection structure ensures long-term survival rate of the alkaliphilic Bacillus in a harsh cement environment. 2. The innermost porous hydroxyapatite substrate is modified by tetraethyl orthosilicate, and the microporous structure can not only adhere a large amount of alkaliphilic Bacillus, but also protect the alkaliphilic Bacillus. 3. The intermediate sodium alginate / calcium chloride gel can provide a mild microenvironment for the alkaliphilic Bacillus and buffer the damage of external alkaline substances. 4. The outermost ethyl cellulose film is dense and hydrophobic, which can effectively block water and high-alkali ions in the cement paste from entering the inside during the concrete curing stage, so that the alkaliphilic Bacillus is in a "dormant" state. 5. Only when cracks occur and the repair agent is broken, the alkaliphilic Bacillus is activated, thereby ensuring long-term effectiveness and intelligent responsiveness of the repair agent.

[0026] 2、The self-repairing agent prepared in the application is first encountered with water and expands rapidly after breaking at the crack, and the physical plugging is realized to the crack to achieve the preliminary repair function. The exposed calcium peroxide reacts with water to generate oxygen after the polybutylene succinate is broken or decomposed, which can provide the necessary oxygen for the activation and activation of alkaliphilic Bacillus, and accelerate its reproduction and growth. On the other hand, the generated calcium hydroxide can locally increase the pH value to create the most suitable alkaline environment for alkaliphilic Bacillus. In addition, sodium stearate can not only be used as an organic carbon source for bacterial metabolism and be utilized by alkaliphilic Bacillus, but also dissolve after encountering water and combine with calcium ions to generate calcium stearate with certain hydrophobic properties, which can not only effectively repair the crack, but also improve the hydrophobic properties of the repaired part, and finally under the synergistic cooperation of calcium stearate and water-absorbing resin, not only the crack can be repaired, but also the waterproof performance can be effectively improved. In addition, the activated alkaliphilic Bacillus on the porous hydroxyapatite substrate induces the generation of calcium carbonate crystals through metabolic action to realize long-term and stable biomineralization repair of the crack. This multiple synergistic mechanism of "physical plugging-chemical plugging-biomineralization" overcomes the limitations of single repair mechanism, and significantly improves the repair efficiency and durability of cracks of different widths.

[0027] 3、The outer coating and overall design of the self-repairing agent in the application avoid its premature dissolution or breakage during stirring. In addition, it can be uniformly dispersed in the cement matrix to ensure that it does not break under normal stress and is only activated when the microcrack expands. The pre-prepared composite microspheres of calcium peroxide and sodium stearate are coated with the core material and water-absorbing resin to realize the integrated preparation of the repair function components, ensure that each component is released at the same time and works synergistically at the crack, and avoid the repair failure problem caused by uneven distribution of components. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all embodiments. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the application.

[0029] In the following examples, the production of Bacillus alkalophilus spores is carried out in two stages, wherein the first stage of cultivation uses medium A and the second stage of cultivation uses medium B. Medium A comprises: 5 g / L of proteose peptone, 3 g / L of beef extract, 0.42 g / L of sodium bicarbonate, and 0.53 g / L of sodium carbonate (pH 9.7); and medium B comprises: 0.2 g / L of ammonium chloride, 0.02 g / L of potassium dihydrogen phosphate, 0.225 g / L of calcium chloride, 0.2 g / L of potassium chloride, 0.2 g / L of magnesium chloride hexahydrate, 0.01 g / L of manganese sulfate monohydrate, 0.1 g / L of yeast extract, 5.16 g / L of sodium citrate, 4.2 g / L of sodium bicarbonate, 5.3 g / L of sodium carbonate, and 1 mL of trace element solution SL12B (pH 10).

[0030] The water-absorbing resin is a polyacrylate water-absorbing resin produced by Shandong Linchuan Water Technology Co., Ltd.; and the polycarboxylate superplasticizer is JG-2H polycarboxylate superplasticizer produced by Tianjin Zhongye Building Material Co., Ltd.

[0031] Example 1

[0032] A self-repairing cement-based composite material is composed of the following raw materials by weight: 1000 parts of coarse aggregate, 600 parts of fine aggregate, 300 parts of Portland cement, 40 parts of fly ash, 150 parts of mineral powder, 4 parts of polycarboxylate superplasticizer, 5 parts of calcium lignosulfonate, 60 parts of self-repairing agent, and 150 parts of water; wherein the coarse aggregate is selected from crushed stone with a particle size of 10 mm, and the fine aggregate is selected from medium sand with a particle size of 0.6 mm; the cement is selected from P.O52.5 Portland cement, the mineral powder is S95 grade, and the fly ash is grade II.

[0033] The preparation method of the self-repairing agent is as follows:

[0034] Step one: uniformly spray a 3wt% polybutylene succinate solution in chloroform onto the surface of the composite powder to form a polybutylene succinate film layer with a thickness of 30 nm, and then vacuum dry and recover chloroform to obtain the composite microspheres; the composite powder is prepared by mixing calcium peroxide and sodium stearate at a mass ratio of 1:1, and the average particle size of both is 100 mesh;

[0035] Step two: uniformly disperse the core material in a 3wt% sodium alginate aqueous solution with a mass of 2 times that of the core material, and then slowly drop the obtained dispersion into an 8wt% calcium chloride aqueous solution with a mass of 3 times that of the core material, and then stir and solidify, and then sequentially filter, wash with water, and dry at 40°C overnight to obtain the modified core material with a particle size;

[0036] The preparation method of the core material is as follows: add 2×10 9The porous substrate with a mass of 20% of the alkaliphilic bacillus suspension is added, the porous substrate is filtered out after being soaked for 2 days, and the core material is obtained by drying at 50℃ overnight;

[0037] The preparation method of the porous substrate is as follows: hydroxyapatite with an average particle size of 0.5 mm is uniformly mixed with tetraethyl orthosilicate with a mass of 5% of the hydroxyapatite, then an ammonia solution with a mass of 0.8 times of the tetraethyl orthosilicate and a pH of 9 is added, the reaction liquid is filtered, washed and dried in sequence after being stirred at 65℃ for 5 h, and the porous substrate is obtained.

[0038] Step three, the modified core material, composite microspheres and water absorbing resin are put into the roller according to a mass ratio of 1:0.1:0.05, the coating liquid is sprayed onto the surface of the modified core material and the composite microspheres by the spray gun during the rotation of the roller, and the self-repairing agent with an average particle size of 0.8 mm is obtained by drying after the spraying is completed.

[0039] The coating liquid is uniformly mixed by ethyl cellulose powder and a compounded solvent according to a solid-liquid ratio of 1:8; the compounded solvent is compounded by dimethylbenzene and ethanol with a volume of 25% of the dimethylbenzene.

[0040] A preparation method of a self-repairing cement-based composite material, comprising the following steps: accurately weighing each raw material, and sequentially adding coarse aggregate, fine aggregate, Portland cement, fly ash and mineral powder into a stirring device, adding the remaining raw materials after mixing and stirring for 100 s, and obtaining the self-repairing cement-based composite material after mixing and stirring for 100 s.

[0041] Example 2

[0042] A self-repairing cement-based composite material is composed of the following raw materials in weight parts: 1100 parts of coarse aggregate, 750 parts of fine aggregate, 400 parts of Portland cement, 50 parts of fly ash, 180 parts of mineral powder, 5 parts of polycarboxylate superplasticizer, 6 parts of calcium lignosulfonate, 100 parts of self-repairing agent and 180 parts of water; wherein the coarse aggregate is selected from crushed stone with a particle size of 10 mm, the fine aggregate is selected from medium sand with a particle size of 0.6 mm, the cement is selected from P.O52.5 Portland cement, the mineral powder is S95 grade, and the fly ash is grade II.

[0043] The preparation method of the self-repairing agent is as follows:

[0044] Step one, a 5wt% polybutylene succinate solution in chloroform is uniformly sprayed on the surface of the composite powder to form a polybutylene succinate film layer with a polythickness of 40 nm, and the composite microspheres are obtained after vacuum drying and recovering chloroform; the composite powder is prepared by mixing calcium peroxide and sodium stearate according to a mass ratio of 1:1.5, and the average particle size of both is 150 mesh;

[0045] Step two, uniformly disperse the core material in a 3 times mass, 5wt% concentration sodium alginate aqueous solution, then slowly drop the obtained dispersion into a 5 times mass, 12wt% concentration calcium chloride aqueous solution, after stirring and solidification, filter, wash with water and dry at 45℃ overnight to obtain a modified core material with a particle size of;

[0046] The preparation method of the core material is as follows: add 40% of the porous substrate by mass to the alkaliphilic Bacillus suspension with a concentration of 4x10 10 CFU / mL, soak for 3 days, filter out the porous substrate, and dry at 45℃ overnight to obtain the core material;

[0047] The preparation method of the porous substrate is as follows: uniformly mix hydroxyapatite with an average particle size of 0.8mm and tetraethyl orthosilicate with a mass of 6% of the hydroxyapatite, then add an ammonia solution with the same mass as the tetraethyl orthosilicate and a pH of 9.5, stir and react at 70℃ for 4h, and then filter, wash and dry the reaction solution in sequence to obtain the porous substrate;

[0048] Step three, put the modified core material, composite microspheres and water absorbing resin into a roller according to a mass ratio of 1:0.2:0.06, spray the coating liquid onto the surface of the modified core material and the composite microspheres through a spray gun during the rotation of the roller, and dry the roller while rotating after the spraying is completed to obtain a self-repairing agent with an average particle size of 1.2mm;

[0049] The coating liquid is uniformly mixed by ethyl cellulose powder and a complex solvent according to a solid-liquid ratio of 1:10; the complex solvent is compounded by dimethylbenzene and ethanol with a volume of 30% of the dimethylbenzene.

[0050] A preparation method of a self-repairing cement-based composite material, comprising the following steps: accurately weigh each raw material, and then add the coarse aggregate, fine aggregate, Portland cement, fly ash and mineral powder into a stirring device in sequence, add the remaining raw materials after mixing and stirring for 110s, and then mix and stir for 130s to obtain the self-repairing cement-based composite material.

[0051] Example 3

[0052] A self-repairing cement-based composite material, which is composed of the following raw materials in parts by weight: 1200 parts of coarse aggregate, 850 parts of fine aggregate, 450 parts of Portland cement, 60 parts of fly ash, 200 parts of mineral powder, 6 parts of polycarboxylic acid water reducer, 8 parts of calcium lignosulfonate, 120 parts of self-repairing agent and 200 parts of water; wherein the coarse aggregate is selected from crushed stone with a particle size of 10mm, and the fine aggregate is selected from medium sand with a particle size of 0.6mm; the cement is selected from P.O52.5 Portland cement, the mineral powder is S95 grade, and the fly ash is grade II.

[0053] The preparation method of the self-repairing agent is as follows:

[0054] Step one, uniformly spray 8wt% polybutylene succinate solution in chloroform on the surface of the composite powder to form a polybutylene succinate film layer with a thickness of 50nm, then vacuum drying and recovering chloroform to prepare the composite microspheres; the composite powder is prepared by mixing calcium peroxide and sodium stearate in a mass ratio of 1:2, and the average particle size of both is 200 mesh;

[0055] Step two, uniformly disperse the core material in a 6wt% sodium alginate aqueous solution with a mass of 5 times that of the core material, then slowly drop the obtained dispersion into a 15wt% calcium chloride aqueous solution with a mass of 6 times that of the core material, stir and solidify, then filter, wash with water and dry at 50℃ overnight to obtain the modified core material with a particle size of;

[0056] The preparation method of the core material is as follows: add 50% porous substrate by mass to a suspension of alkaliphilic Bacillus with a concentration of 6×10 10 CFU / mL, soak for 3 days, filter out the porous substrate, and dry at 50℃ overnight to obtain the core material;

[0057] The preparation method of the porous substrate is as follows: uniformly mix hydroxyapatite with an average particle size of 1mm and tetraethyl orthosilicate with a mass of 8% of the hydroxyapatite, then add an ammonia solution with a mass of 1.2 times that of the tetraethyl orthosilicate and a pH of 10, stir and react at 75℃ for 3h, then filter, wash and dry the reaction solution in sequence to obtain the porous substrate;

[0058] Step three, put the modified core material, composite microspheres and water absorbing resin into a roller in a mass ratio of 1:0.3:0.08, and spray the coating liquid onto the surface of the modified core material and composite microspheres through a spray gun during the rotation of the roller; after spraying, dry the roller while it is rotating to obtain the self-repairing agent with an average particle size of 1.5mm;

[0059] The coating liquid is prepared by uniformly mixing ethyl cellulose powder and a complex solvent in a solid-liquid ratio of 1:12; the complex solvent is prepared by compounding dimethylbenzene and ethanol with a volume of 35% of the dimethylbenzene.

[0060] A preparation method of a self-repairing cement-based composite material, comprising the following steps: accurately weighing each raw material, and sequentially adding coarse aggregate, fine aggregate, Portland cement, fly ash and mineral powder into a stirring device, mixing and stirring for 120s, then adding the remaining raw materials, and mixing and stirring for 150s to obtain the self-repairing cement-based composite material.

[0061] Comparative example 1: the difference between this comparative example and example 1 is that equal amount of calcium peroxide is used instead of the composite powder in this comparative example.

[0062] Comparative example 2: the difference between this comparative example and example 1 is that equal amount of sodium stearate is used instead of the composite powder in this comparative example.

[0063] Comparative Example 3: The difference between this comparative example and Example 1 is that no water-absorbing resin is used in the self-repairing agent in this comparative example.

[0064] Performance test: the self-repairing cement-based composite material provided by Examples 1-3 and Comparative Examples 1-3 is respectively tested for impermeability, mechanical property and mechanical property after crack repair. The concrete mechanical property test is in accordance with the standard GB / T50081-2002 ordinary concrete mechanical property test method, and the durability test is in accordance with the standard GB / T50082-2009 ordinary concrete long-term performance and durability test method. Among them, the mechanical property test is to determine the compressive strength of the concrete after curing for 7d and 28d, and the mechanical property test after crack repair is to determine the compressive strength of the concrete after curing for 7d and 28d again after the concrete has a crack width of 0.2-0.4mm through the splitting tensile test. The test data obtained are recorded in the following table:

[0065]

[0066] By comparing and analyzing the related data in the table, it can be seen that the self-repairing cement-based composite material prepared by the application can not only efficiently repair the cracks of the concrete, but also has a long-term and lasting repair effect, and can effectively improve the waterproof performance of the repaired concrete, effectively ensure the quality, and prolong the service life of the concrete to a certain extent. Therefore, the self-repairing cement-based composite material and the preparation method thereof provided by the application have a broader market prospect and are more suitable for promotion.

[0067] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0068] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their entire scope and equivalents.

Claims

1. A self-healing cement-based composite material, characterized in that, Composed of the following raw materials in parts by weight: 1000-1200 parts coarse aggregate, 600-850 parts fine aggregate, 300-450 parts silicate cement, 40-60 parts fly ash, 150-200 parts mineral powder, 4-6 parts water-reducing agent, 5-8 parts retarder, 60-120 parts self-healing agent, and 150-200 parts water; The preparation method of the self-healing agent is as follows: Step 1: A 3-8 wt% polybutylene succinate solution in chloroform is uniformly sprayed onto the surface of the composite powder to form a polybutylene succinate film with a thickness of 30-50 nm. After vacuum drying and chloroform recovery, composite microspheres are obtained. The composite powder is made by mixing calcium peroxide and sodium stearate in a mass ratio of 1:1-2, and the average particle size of both is 100-200 mesh. Step 2: Disperse the core material uniformly in a sodium alginate aqueous solution with a concentration of 3-6 wt% and a mass of 2-5 times that of the core material. Then, slowly drop the resulting dispersion into a calcium chloride aqueous solution with a concentration of 8-15 wt% and a mass of 3-6 times that of the core material. After stirring and solidification, filter, wash with water, and dry overnight at 40-50℃ to obtain the modified core material with the specified particle size. Step 3: Add the modified core material, composite microspheres, and water-absorbing resin into the drum at a mass ratio of 1:0.1-0.3:0.05-0.

08. While the drum is rotating, spray the coating liquid onto the surface of the modified core material and composite microspheres using a spray gun. After spraying, dry the drum while it is rotating to obtain a self-healing agent with an average particle size of 0.8-1.5mm. The coating solution is prepared by uniformly mixing ethyl cellulose powder and a compound solvent at a solid-liquid ratio of 1:8-12; wherein the compound solvent is prepared by mixing xylene with ethanol at a volume of 25-35%; The preparation method of the core material is as follows: 2×10 9 -6×10 10 Add 20-50% of the porous substrate to a CFU / mL suspension of Bacillus alkaliphilus, soak for 2-3 days, filter out the porous substrate, and dry it overnight at 40-50℃ to obtain the core material. The porous substrate is prepared by uniformly mixing hydroxyapatite with an average particle size of 0.5-1 mm with 5-8% of its mass in tetraethyl orthosilicate, then adding an ammonia solution with a mass of 0.8-1.2 times that of tetraethyl orthosilicate and a pH of 9-10, stirring and reacting at 65-75°C for 3-5 hours, and then filtering, washing and drying the reaction solution sequentially to obtain the substrate.

2. The self-healing cement-based composite material according to claim 1, characterized in that: The cement used is P.O52.5 silicate cement, the mineral powder is grade S95, and the fly ash is grade II.

3. The self-healing cement-based composite material according to claim 1, characterized in that: The coarse aggregate is selected from crushed stone with a particle size of 5-20mm, and the fine aggregate is selected from medium sand with a particle size of 0.5-0.8mm.

4. The self-healing cement-based composite material according to claim 1, characterized in that: The retarder is selected from any one of calcium lignosulfonate, hydroxymethyl cellulose, and hydroxyethyl cellulose.

5. The self-healing cement-based composite material according to claim 1, characterized in that: The water-reducing agent is selected from any one of polycarboxylate water-reducing agents, aminosulfonate water-reducing agents, and naphthalenesulfonate water-reducing agents.

6. A method for preparing a self-healing cement-based composite material according to any one of claims 1-5, characterized in that, The process includes the following steps: accurately weigh each raw material, and add coarse aggregate, fine aggregate, silicate cement, fly ash and mineral powder into the mixing equipment in sequence. After mixing for 100-120 seconds, add the remaining raw materials and mix for 100-150 seconds to obtain the self-healing cement-based composite material.

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