Anti-crack self-repairing mass concrete and application thereof

Abstract

The application discloses anti-cracking self-repairing mass concrete and application thereof, and belongs to the technical field of concrete. The anti-cracking self-repairing mass concrete provided by the application comprises a steel reinforcement cage and concrete for pouring the steel reinforcement cage, the outer surface of the steel reinforcement cage is bound with an anti-cracking self-repairing fiber net, the anti-cracking self-repairing fiber net takes a grid-shaped fiber as a core, and the outer surface of the fiber net is loaded with a microbial repairing agent hydrogel layer, a polymer layer, a nutrient substance hydrogel layer and a polymer outer layer in sequence, the polymer layer and the polymer outer layer are a combination of polylactic acid and polystyrene, and the thickness of the polymer outer layer is greater than or equal to 900 micrometers. The anti-cracking self-repairing fiber net is added into the mass concrete, so that the crack situation of the mass concrete is reduced, the microbial repairing agent is released in response when cracks are generated, the cracks of the concrete are automatically filled, the self-repairing of the concrete structure damage is realized, and the service life of the concrete structure is prolonged.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a crack-resistant, self-healing mass concrete and its application. Background Technology

[0002] Mass concrete refers to large-volume concrete structures with a minimum dimension of 1 meter. It is commonly found in the foundations of large bridge piers, hydraulic spillways in water conservancy projects, dock walls and floor slabs in shipyards, and wharves in marine engineering. Due to the massive volume of concrete and the large amount of cement used, the cement releases a significant amount of heat during hydration, causing the internal temperature of the concrete to rise and creating a large temperature difference with the external environment, making it prone to temperature cracks. Besides cracks caused by temperature stress, cracks can also occur due to the concrete's own shrinkage (such as drying shrinkage and autogenous shrinkage) and external constraints, thus affecting the structure's integrity, durability, and waterproofing. Therefore, controlling concrete cracking is of paramount importance in the pouring of mass concrete.

[0003] Currently, crack repair methods mainly rely on regular structural inspections and manual filling. These methods not only increase the number of rework operations and costs, but also, if the repair material has poor compatibility with the concrete, the crack and the repair material are prone to breakage, affecting the repair effect. Therefore, self-healing technology that can actively detect and repair concrete cracks has become a research hotspot in the concrete field. There are many principles of self-healing concrete, one of which is the use of microbial repair agents. By adding mineralizing microorganisms to the concrete, a self-healing effect is achieved when cracks appear. However, directly adding microorganisms to the concrete can affect the lifespan and effectiveness of the microorganisms. To improve the mineralization self-healing efficacy of microorganisms, existing technologies have disclosed various methods of encapsulating microorganisms in spherical polymers or silica-based materials. However, these spherical self-healing agents are very small, with particle sizes often only a few hundred micrometers to a few millimeters. Large quantities are often required to achieve the self-healing effect, which in turn leads to a decrease in the compressive strength of the concrete. Moreover, without crack control measures for the concrete, when the self-healing agent is depleted, the cracks can only be repaired manually. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a crack-resistant, self-healing mass concrete. By incorporating a crack-resistant, self-healing fiber mesh, the crack-resistant mesh reduces the cracking and fissure formation in the mass concrete. When cracks occur, it can promptly release a microbial repair agent. Under conditions of nutrients and water, the microorganisms are activated, metabolize to produce calcium carbonate, and fill the cracks in the concrete, achieving self-repair of the concrete structure and extending the service life of the concrete structure.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] A crack-resistant, self-healing large-volume concrete includes a reinforcing cage and concrete for casting the reinforcing cage. The outer surface of the reinforcing cage is bound with a crack-resistant, self-healing fiber mesh. The crack-resistant, self-healing fiber mesh has a mesh-like fiber core, and its outer surface is sequentially loaded with a microbial repair agent hydrogel layer, a polymer layer, a nutrient hydrogel layer, and a polymer outer layer. The polymer layer and the polymer outer layer are a combination of polylactic acid and polystyrene, and the thickness of the polymer outer layer is ≥900μm.

[0007] Preferably, the thickness of the polymer outer layer is 920–1300 μm.

[0008] In one specific embodiment, the method for preparing the crack-resistant self-healing fiber mesh includes the following steps:

[0009] S1. Soak the mesh-like fibers in sodium alginate and spore suspension, then immediately soak them in calcium cross-linking agent solution, remove and dry them, repeat the above operation 0 to 3 times to form a microbial repair agent hydrogel layer;

[0010] S2. Immerse the mesh-like fibers with the microbial repair agent hydrogel layer obtained in step S1 in a polymer material solution, remove and dry them, and repeat the above operation 0 to 3 times to form a polymer layer;

[0011] S3. The mesh-like fibers with a two-layer structure obtained in step S2 are soaked in nutrients and sodium alginate suspension, and then immediately soaked in calcium crosslinking agent solution. They are then removed and dried. The above operation is repeated 0 to 3 times to form a nutrient hydrogel layer.

[0012] S4. Immerse the three-layer mesh fiber obtained in step S3 in a polymer material solution, remove and dry it, repeat the above operation 0 to 3 times to form a polymer outer layer and obtain a crack-resistant self-healing fiber mesh.

[0013] Crack-resistant self-healing fiber mesh is laid on the surface of the reinforcing cage of large-volume concrete. Its crack-resistant mesh can improve the tensile strength of concrete and reduce cracking and the generation of harmful cracks in large-volume concrete. When concrete cracks due to deformation caused by drying shrinkage or temperature shrinkage, water and oxygen can penetrate from the surrounding environment through micro-cracks. At this time, the polymer layer and polymer outer layer of the crack-resistant self-healing fiber mesh are responsively damaged due to cracks. The hydrogel carrying spores is exposed to nutrients. The spores germinate and generate the final self-healing product, namely microbial-induced calcium carbonate precipitation, thereby repairing the exposed cracks.

[0014] In one specific embodiment, the method for preparing the sodium alginate and spore suspension is as follows: bacteria with the ability to induce the formation of CaCO3 are cultured in a culture medium, the strain is extracted, washed with PBS buffer solution, and then inoculated into a basic salt culture medium. The strain is treated in a boiling water bath and an ice water bath for a period of time to form spores. The spores and sodium alginate are then mixed to obtain sodium alginate and spore suspension.

[0015] Studies have shown that endophytic spores produced by bacteria capable of inducing CaCO3 formation through the above-mentioned boiling water bath and ice water bath treatments can germinate under harsh alkaline conditions (pH 12), high salinity environments (up to 100 g / L), and freeze-thaw cycles (temperatures from -10°C to 60°C), enabling the spores to germinate in the high-alkaline environment of concrete and the high-salinity environment of marine engineering structures.

[0016] In another specific embodiment, bacteria capable of inducing the formation of CaCO3 can also be adapted to a highly alkaline chemical environment through alkali tolerance training by gradually increasing the pH concentration.

[0017] Preferably, the concentration of sodium alginate is 6-18 g / L. When the concentration of sodium alginate is within the preferred range, it can improve the adhesion of sodium alginate and spore suspension to the mesh fibers.

[0018] In one specific embodiment, the calcium crosslinking agent solution is at least one of calcium chloride and calcium acetate; preferably, the calcium crosslinking agent solution is a mixed solution of calcium chloride and calcium acetate, wherein the mass ratio of calcium chloride to calcium acetate is 1:1.

[0019] In one specific embodiment, the mass ratio of polystyrene to polylactic acid is (1-3):1. Polylactic acid has good compatibility with hydrogel and can form a uniform protective shell on the outer layer of hydrogel. However, polylactic acid is relatively brittle and its impact resistance is generally poor. Polystyrene has poor compatibility with hydrogel, and when used alone, the polymer layer is uneven and a small amount of bubbling occurs, but its waterproof and impact-resistant effects are good. Using a mixture of polylactic acid and polystyrene as the outer protective layer of the crack-resistant self-healing fiber mesh is beneficial for forming a uniform polymer layer and provides the best waterproof and impact-resistant effect.

[0020] Preferably, the polymer layer is formed by evaporating a polymer material solution with a concentration of 12 g / L to 20 g / L, and is prepared by dissolving polystyrene and polylactic acid in chloroform. When the polymer material concentration is 12 to 16 g / L, at least two or more polymer layers are required to effectively form a waterproof and impact-resistant polymer layer. When the polymer material concentration is 16 to 20 g / L, a single polymer layer can also achieve effective waterproofing and impact resistance.

[0021] In one specific embodiment, the mesh is at least one of basalt fiber mesh and glass fiber mesh.

[0022] In one specific embodiment, the nutrients in the nutrient hydrogel layer are yeast extract, calcium source and urea, and the hydrogel is sodium alginate hydrogel; preferably, the calcium source is calcium acetate.

[0023] In one specific embodiment, the concrete mix proportion is: coarse aggregate 1100-1300 kg / m³ 3 Fine aggregate 600-800 kg / m³ 3 Cement 200-400 kg / m³ 3 Silica fume 40-60 kg / m³ 3 40-60 kg / m³ of fly ash 3 Water-reducing agent 1-10 kg / m³ 3 Water 80-150 kg / m 3 .

[0024] In one specific embodiment, the fine aggregate is natural river sand or manufactured sand; the coarse aggregate is crushed stone or pebbles; and the cement is ordinary silicate cement, low-heat silicate cement, or medium-heat silicate cement.

[0025] In one specific embodiment, the coarse aggregate has a particle size of 5-80 mm. Preferably, the coarse aggregate is obtained by three-gradation of crushed stone or pebbles with particle sizes of 5-20 mm, 20-40 mm, and 40-80 mm.

[0026] In one specific embodiment, the cement is at least one of ordinary silicate cement, low-heat silicate cement, or medium-heat silicate cement.

[0027] Another object of the present invention is to protect the method for preparing the large-volume concrete, comprising the following steps:

[0028] After the reinforcing cage is tied, a layer of crack-resistant self-healing fiber mesh is tied to the outer surface of the reinforcing cage. Coarse aggregate, fine aggregate, cement, silica fume and fly ash are put into the mixing plant and mixed for 1 to 2 minutes. Then, ice water mixture is added and mixed for 2 to 5 minutes. Water-reducing agent is added and mixing is continued until the ice is fully melted. Concrete is poured in layers in the reinforcing formwork, with each layer being 30 to 50 cm evenly distributed. The concrete is vibrated until the surface of the concrete shows cement paste and no longer settles and the surface basically does not bubble. The vibrated and leveled concrete surface is covered with plastic film. After hardening, the formwork is removed and the standard curing is at least 28 days.

[0029] Another object of the present invention is to protect the application of the crack-resistant self-healing mass concrete in hydraulic or marine structures.

[0030] Beneficial effects

[0031] This invention provides a crack-resistant, self-healing mass concrete. By incorporating a crack-resistant, self-healing fiber mesh, harmful cracks in mass concrete can be effectively reduced. Furthermore, upon crack formation, a microbial repair agent is released in response. Microorganisms are activated and, under the influence of nutrients and a calcium source, metabolize to produce calcium carbonate, filling the cracks in the concrete and achieving self-repair of the concrete structure, thus extending its service life. The crack-resistant, self-healing fiber mesh provided by this invention differs from the spherical structure of traditional self-healing materials. The crack-resistant effect of the mesh-like fibers not only effectively reduces cracking in mass concrete, but also allows the self-healing agent loaded on the surface of the mesh-like fibers to respond promptly upon cracking, improving the reliability of the self-healing concrete. Detailed Implementation

[0032] 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.

[0033] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0034] The raw materials used in the examples and comparative examples are described below:

[0035] Cement: Ordinary Portland cement, P·O 42.5, purchased from Dengzhou Zhonglian Cement Co., Ltd.;

[0036] Iron ore powder: purchased from Angang Group Xinyang Iron & Steel Co., Ltd.;

[0037] Fly ash: purchased from Nanyang Tianfu Industrial Co., Ltd.;

[0038] Fine aggregate: natural river sand, sourced from Tanghe River, Henan Province;

[0039] Coarse aggregate: limestone crushed stone, purchased from Dengzhou Zhonglian Cement Co., Ltd., with a particle size of 5-20mm and 20-40mm, two-dimensional mix;

[0040] Water-reducing agent: GK-3000 polycarboxylate high-performance water-reducing agent (retarded setting type), purchased from Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.;

[0041] Ice-water mixture: The raw material is tap water, which meets the requirements of the standard "Mixing Water for Concrete" (JGJ 63-2006);

[0042] Basalt fiber mesh: Basalt fiber geogrid, BFG1*1 (60*60), Zhejiang Shijin Basalt Fiber Co., Ltd.;

[0043] Basalt chopped fiber: Basalt fiber chopped yarn, monofilament diameter 17μm, length 6mm, Zhejiang Shijin Basalt Fiber Co., Ltd.;

[0044] Fiberglass mesh: HH40805YJUJ0, Dezhou Hongtai Geotechnical Materials Co., Ltd.;

[0045] Wire mesh: 30mm aperture, Hebei Hanlian Metal Wire Mesh Products Co., Ltd.

[0046] Bacteria capable of inducing CaCO3 formation: Bacillus spheroides strain MB284, international number: ATCC13805, purchased from Beijing Bio-Bio Biotechnology Co., Ltd.

[0047] Yeast extract: CAS: 8013-01-2, Product No.: Y1625, purchased from Sigma-Aldrich;

[0048] Urea: CAS: 57-13-6, Nanjing Chemical Reagent Co., Ltd.;

[0049] PBS buffer solution: 0.1 mmol, pH 7.0, Guangzhou Hewei Pharmaceutical Technology Co., Ltd.;

[0050] Basic salt culture medium: Weigh 3.5g Na2HPO4·2H2O, 1.0g KH2PO4, 0.5g (NH4)2SO4, 0.1g MgCl2·6H2O and 0.05g Ca(NO3)2·4H2O and dissolve them in 1000ml distilled water. Add 1.0ml trace element solution SL-4, adjust the pH to 7.25, and sterilize by steaming at 121℃ for 15min. The preparation method of trace element solution SL-4 is as follows: Weigh 0.5g EDTA, 0.2g FeSO4·7H2O and 100ml trace element solution SL-6 and dissolve them in 900ml distilled water. Trace element solution SL-6 was purchased from Beijing Putian Tongchuang Biotechnology Co., Ltd.

[0051] Sodium alginate: CAS: 9005-38-3, purchased from Sigma-Aldrich;

[0052] Calcium chloride: Calcium chloride dihydrate, purchased from Anaiji Chemical;

[0053] Calcium acetate: Calcium acetate monohydrate, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.;

[0054] Polystyrene: GPPS525, Guangzhou Petrochemical;

[0055] Polylactic acid: REVODE210, Zhejiang Hisun Biomaterials Co., Ltd.;

[0056] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0057] Preparation Example

[0058] Preparation Example 1

[0059] Crack-resistant self-healing fiber mesh 1: Self-made, preparation method as follows:

[0060] S1. Preparation of sodium alginate and spore suspension: Spherical Bacillus lysine strain MB284 was cultured for 24 hours in a medium containing 20 g / L yeast extract and 20 g / L urea. The strain was extracted, washed three times with PBS buffer, and then inoculated into basal salt medium. The medium was treated in a boiling water bath for 30 min, followed by an ice-water bath for 30 min, and finally transferred to a 45°C shaker incubator for 2 days to form spores. 10 9 Mix spores at cell / ml and sodium alginate at 8g / L, stir slowly for 1 hour, and set aside.

[0061] Preparation of nutrients and sodium alginate suspension: Mix 20 g / L yeast extract, 20 g / L urea, 20 g / L calcium acetate and 8 g / L sodium alginate in deionized water.

[0062] Preparation of calcium crosslinking agent solution: Dissolve calcium chloride and calcium acetate in deionized water at a molar ratio of 1:1 to prepare a solution with a calcium ion concentration of 0.26 mol / L. The pH value of the solution is controlled at around 7 by adding acetic acid or sodium hydroxide.

[0063] Preparation of polymer material solution: Polystyrene and polylactic acid in a mass ratio of 1:1 are dissolved in chloroform at a total concentration of 12 g / L;

[0064] Basalt fiber mesh was soaked in sodium alginate and spore suspension, and then immediately soaked in calcium crosslinking agent solution. After drying for 2 hours, the above operation was repeated once to form a microbial repair agent hydrogel layer.

[0065] S2. Immerse the basalt fiber mesh with the microbial repair agent hydrogel layer obtained in step S1 in the polymer material solution, take it out and dry it for 30 minutes, repeat the above operation once to form a polymer layer;

[0066] S3. The basalt fiber mesh with a two-layer structure obtained in step S2 is soaked in nutrients and sodium alginate suspension, and then immediately soaked in calcium crosslinking agent solution. It is then removed and dried for 2 hours. The above operation is repeated once to form a nutrient hydrogel layer.

[0067] S4. The basalt fiber mesh with a three-layer structure obtained in step S3 is immersed in a polymer material solution, taken out and dried for 30 minutes. The above operation is repeated once to form a polymer layer and obtain crack-resistant self-healing fiber mesh 1.

[0068] Preparation Example 2

[0069] Crack-resistant self-healing fiber mesh 2: The preparation method is different from that of crack-resistant self-healing fiber mesh 1 in that the total number of polymer outer layers is 4, that is, the total number of soaking and drying in step S4 is changed to 4 times.

[0070] Preparation Example 3

[0071] Crack-resistant self-healing fiber mesh 3: The preparation method is different from that of crack-resistant self-healing fiber mesh 1 in that the polymer material solution is a mixture of polystyrene and polylactic acid with a concentration of 18g / L, and the mass ratio of polystyrene to polylactic acid is 1:1.

[0072] Preparation Example 4

[0073] Crack-resistant self-healing fiber mesh 4: The preparation method is different from that of crack-resistant self-healing fiber mesh 1 in that the basalt fiber mesh is replaced with glass fiber mesh.

[0074] Preparation Example 5

[0075] Crack-resistant self-healing fiber mesh 5: The preparation method is the same as that of crack-resistant self-healing fiber mesh 1, except that the basalt fiber mesh is replaced with iron wire mesh.

[0076] Preparation Example 6

[0077] Crack-resistant self-healing fiber mesh 6: The preparation method is the same as that of crack-resistant self-healing fiber mesh 1, except that the polymer layer is polystyrene, and polylactic acid is replaced with polystyrene in the preparation of the polymer material solution, while the concentration remains unchanged.

[0078] Preparation Example 7

[0079] Crack-resistant self-healing fiber mesh 7: The preparation method is the same as that of crack-resistant self-healing fiber mesh 1, except that the polymer layer is polylactic acid, and polystyrene is replaced with polylactic acid in the preparation of the polymer material solution, while the concentration remains unchanged.

[0080] Preparation Example 8

[0081] Crack-resistant self-healing fiber mesh 8: The preparation method is different from that of crack-resistant self-healing fiber mesh 1 in that the total number of polymer outer layers is 1, that is, the total number of soaking and drying in step S4 is changed to 1.

[0082] Preparation Example 9

[0083] Self-healing fiber: The preparation method is different from that of crack-resistant self-healing fiber mesh 1, except that the basalt fiber mesh is replaced with basalt short-cut fibers;

[0084] The following performance tests were conducted on the crack-resistant self-healing fiber mesh, and the results are shown in Table 1:

[0085] (1) Impermeability test: The impermeability test was conducted to investigate whether the outer layer of the polymer could protect the hydrogel carrying spores and nutrients from the intrusion of water and / or aqueous solution during the concrete hydration stage. The test method was as follows: In the preparation stage, phenolphthalein was added to the nutrient solution at a concentration of 0.1 g / L. Other preparation steps were the same as in Preparation Examples 1 to 8. Then, the crack-resistant self-healing fiber mesh was retained in a highly alkaline solution for 1 hour. The inner layer of hydrogel was observed under an optical microscope to see if it turned pink / purple, and the observed color was recorded.

[0086] (2) Impact resistance test: The impact resistance test is conducted to ensure that the outer load material of the crack-resistant self-healing fiber mesh is not damaged during the concrete pouring and vibration stages. The test method is as follows: In the preparation stage, phenolphthalein is added to the nutrient solution at a concentration of 0.1 g / L. Other preparation steps are the same as those in preparation examples 1 to 8. The crack-resistant self-healing fiber mesh containing phenolphthalein is fixed on the fixture. The fixture material is selected with moderate hardness to prevent additional damage to the sample. The weight of the drop hammer is 1 kg and the drop height is 0.3 m. After the drop hammer is released, the crack-resistant self-healing fiber mesh is kept in a highly alkaline solution for 1 hour. The inner hydrogel is observed through an optical microscope to see if pink / purple appears and the observed color is recorded.

[0087] (3) Thickness of the polymer outer layer: The thickness of the polymer outer layer of the crack-resistant self-healing fiber network was observed under an optical microscope, and the arithmetic mean was calculated from 10 locations.

[0088] Table 1. Test results of crack-resistant self-healing fiber webs prepared in Examples 1-8

[0089]

[0090] Example 1

[0091] A crack-resistant, self-healing large-volume concrete

[0092] The invention includes a reinforcing cage and concrete for pouring the reinforcing cage, wherein the outer surface of the reinforcing cage is bound with a crack-resistant self-healing fiber mesh, and the crack-resistant self-healing fiber mesh is crack-resistant self-healing fiber mesh 1.

[0093] The concrete mix proportion is: 1250 kg / m³ of coarse aggregate. 3 Fine aggregate 748kg / m 3 Cement 310kg / m 3 Silica fume 56kg / m 3 56 kg / m³ of fly ash 3 Water-reducing agent 9.1 kg / m 3 150kg / m 3 ;

[0094] The preparation method of the crack-resistant self-healing large-volume concrete is as follows: After the reinforcing cage is tied, a layer of crack-resistant self-healing fiber mesh 1 is tied to the outer surface of the reinforcing cage. Coarse aggregate, fine aggregate, cement, silica fume and fly ash are put into the mixing plant and mixed for 1 to 2 minutes. Then, ice water mixture is added and mixed for 2 to 5 minutes. Water-reducing agent is added and mixing is continued until the ice is fully melted. Concrete is poured in layers in the reinforcing formwork, with each layer being 30 to 50 cm evenly distributed. The concrete is vibrated until the surface of the concrete shows cement paste and no longer settles and the surface basically does not bubble. The concrete surface after vibration and leveling is covered with plastic film. After hardening, the formwork is removed and the standard curing is carried out for at least 28 days.

[0095] Examples 2-4

[0096] Compared with Example 1, the difference is that the crack-resistant self-healing fiber mesh 1 replaces the crack-resistant self-healing fiber meshes 2 to 4 respectively;

[0097] Comparative Examples 1-4

[0098] Compared with Example 1, the difference is that the crack-resistant self-healing fiber mesh 1 replaces the crack-resistant self-healing fiber meshes 5 to 8 respectively;

[0099] Comparative Example 5

[0100] Compared with Example 1, the difference lies in the preparation method of the crack-resistant self-healing large-volume concrete as follows: After the reinforcing cage is tied, coarse aggregate, fine aggregate, cement, silica fume, fly ash, and self-healing fiber are put into the mixing plant and mixed for 1-2 minutes. Then, an ice-water mixture is added and mixed for 2-5 minutes. Water-reducing agent is added and mixing continues until the ice is fully melted. Concrete is poured in layers in the reinforcing steel formwork, with each layer being 30-50cm evenly distributed. The concrete is vibrated until the surface of the concrete shows cement paste and no longer settles and the surface is basically free of bubbles. The vibrated and leveled concrete surface is covered with plastic film. After hardening, the formwork is removed and the standard curing time is at least 28 days.

[0101] Comparative Example 6

[0102] Compared with Example 1, the difference is that no crack-resistant self-healing fiber mesh is added;

[0103] Performance testing

[0104] The following tests were performed on the concrete, and the results are shown in Table 2.

[0105] (1) 28d compressive strength: The compressive strength of concrete cubes was tested in accordance with "4.2 Compressive strength test of concrete cubes" in DL / T 5150—2017 "Test Procedure for Hydraulic Concrete";

[0106] (2) Crack condition: The crack condition on day 7 was measured by comparing the standard point line gauge film ruler with the card and feeler gauge, and the total length of the crack, the average length of the crack and the maximum width of the crack were recorded.

[0107] (3) Self-healing effect: A portion of the concrete from the example and the comparative example were used to form 10 circular specimens with a diameter of φ100*50mm. After 7 days of curing, a through crack with a width of 0.2-0.5mm was pressed into the center of the circular specimen using a pressure method. The initial water seepage through the through crack was then tested using an anti-seepage device. After water curing, the water seepage of the crack was tested after 10 days, 20 days, and 40 days of water curing. Finally, the degree of repair of the concrete crack was evaluated by the ratio of the water seepage after curing to the initial water seepage. The lower the ratio, the better the crack repair. When the result is 0, it means that the crack has been repaired. The water seepage of each test was the average value of all specimens.

[0108] Table 2 Performance Tests of Crack-Resistant and Self-Healing Mass Concrete

[0109]

[0110]

[0111] As can be seen from Example 1 and Comparative Example 5, when the mesh fiber is replaced with short-cut fiber, the crack resistance effect is not achieved. At the same time, the self-healing function of concrete is also affected because the short-cut fiber has poor dispersion effect.

[0112] As can be seen from Examples 1, 4 and Comparative Example 1, both basalt fiber mesh and glass fiber mesh have good crack resistance and self-healing effects when the mesh fiber is selected. However, due to the smooth surface of the wire mesh, the adhesion of sodium alginate to the wire surface is insufficient, resulting in less self-healing agent loaded and a lower thickness of the polymer layer, thus resulting in poor self-healing effect.

[0113] As can be seen from Examples 1-3 and Comparative Examples 3 and 4, the polymer outer layer needs to have a thickness of ≥900μm and a certain impact resistance to resist the impact of concrete pouring. Otherwise, the polymer outer layer will crack prematurely, causing the hydrogel of the nutrient layer to absorb water and expand during the mixing period. After dehydration in the later stage, it will leave pores. Furthermore, the diffusion of nutrients will also affect the compressive strength of the concrete and cause harmful cracks with a large width.

[0114] As can be seen from Example 1 and Comparative Example 2, when polystyrene is used alone, the polymer layer formed is not uniform enough, and the thinner parts are prone to cracking, which affects the self-healing performance of the concrete.

[0115] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A crack resistant self-repairing mass concrete comprising a reinforcement cage and a concrete cast to the reinforcement cage, characterized in that, The outer surface of the reinforcement cage is bound with the anti-cracking self-repairing fiber net, the anti-cracking self-repairing fiber net takes the grid-shaped fiber as the core, and the outer surface is sequentially loaded with the microbial repairing agent hydrogel layer, the polymer layer, the nutrient substance hydrogel layer and the polymer outer layer, the polymer layer and the polymer outer layer are the composition of polylactic acid and polystyrene, and the thickness of the polymer outer layer is ≥900 μm.

2. The anti-cracking self-healing mass concrete according to claim 1, wherein, The preparation method of the anti-cracking self-repairing fiber net comprises the following steps: S1. The grid-shaped fiber is soaked in a sodium alginate and spore suspension, and then immediately soaked in a calcium crosslinking agent solution, taken out and dried, and the above operation is repeated 0-3 times to form a microbial repairing agent hydrogel layer; S2. The grid-shaped fiber with the microbial repairing agent hydrogel layer obtained in the step S1 is soaked in a polymer material solution, taken out and dried, and the above operation is repeated 0-3 times to form a polymer layer; S3. The grid-shaped fiber with the two-layer structure obtained in the step S2 is soaked in a nutrient substance and sodium alginate suspension, and then immediately soaked in a calcium crosslinking agent solution, taken out and dried, and the above operation is repeated 0-3 times to form a nutrient substance hydrogel layer; S4. The grid-shaped fiber with the three-layer structure obtained in the step S3 is soaked in a polymer material solution, taken out and dried, and the above operation is repeated 0-3 times to form a polymer outer layer, and the anti-cracking self-repairing fiber net is prepared.

3. The anti-cracking self-healing mass concrete according to claim 2, wherein, The preparation method of the sodium alginate and spore suspension is that bacteria with the ability of inducing CaCO3 formation are cultured in a culture medium, the strain is extracted, washed with a PBS buffer solution, then inoculated into a basic salt culture medium, and treated in a boiling water bath and an ice water bath for a period of time to form spores, and the spores and sodium alginate are mixed to prepare the sodium alginate and spore suspension.

4. The anti-cracking self-healing mass concrete according to claim 2, wherein, The calcium crosslinking agent solution is at least one of calcium chloride and calcium acetate.

5. The anti-cracking self-healing mass concrete according to claim 1, wherein, The mass ratio of the polystyrene to the polylactic acid is (1-3):

1.

6. The anti-cracking self-healing mass concrete according to claim 1, wherein, The grid-shaped fiber is at least one of a basalt fiber net and a glass fiber net.

7. The crack-resistant, self-healing mass concrete as described in claim 1, characterized in that, The nutrient substance in the nutrient substance hydrogel layer is yeast extract, a calcium source and urea, and the hydrogel is a sodium alginate hydrogel.

8. The anti-cracking self-healing mass concrete according to claim 1, wherein, The mix proportion of the concrete is: coarse aggregate 1100-1300 kg / m 3 , fine aggregate 600-800 kg / m 3 , cement 200-400 kg / m 3 , silica fume 40-60 kg / m 3 , fly ash 40-60 kg / m 3 , water reducing agent 1-10 kg / m 3 , water 80-150 kg / m 3 .

9. The method for preparing anti-cracking self-repairing mass concrete according to any one of claims 1-8, characterized in that, The method comprises the following steps: After the reinforcement cage is bound, a layer of anti-cracking self-repairing fiber net is bound on the outer surface of the reinforcement cage, coarse aggregate, fine aggregate, cement, silica fume and fly ash are put into a mixing station, stirred for 1-2 min, then an ice water mixture is added, stirred for 2-5 min, then a water reducing agent is added, and the stirring is continued until the ice blocks are fully melted; the concrete is poured in layers in the reinforcement formwork, each layer is 30-50 cm, the material is evenly distributed, and the concrete surface is vibrated until the surface presents a cement paste and there is basically no bubbling on the surface; the surface of the vibrated and leveled concrete is covered with a plastic film, and the formwork is removed after hardening, and the standard curing is at least 28 d.

10. The anti-cracking self-repairing mass concrete according to any one of claims 1-8 is applied in hydraulic structures or marine structures.

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