Anti-crack self-repairing mass concrete and application thereof

Abstract

The invention discloses anti-crack self-repairing mass concrete and application thereof, and belongs to the technical field of concrete.The anti-crack self-repairing mass concrete comprises a reinforcement cage and concrete for pouring the reinforcement cage, and an anti-crack self-repairing fiber net is bound to the outer surface of the reinforcement cage; the anti-cracking self-repairing fiber net takes latticed fiber as a core, a microbial repairing agent hydrogel layer, a polymer layer, a nutrient substance hydrogel layer and a polymer outer layer are sequentially loaded on the outer surface of the anti-cracking self-repairing fiber net, the polymer layer and the polymer outer layer are compositions of polylactic acid and polystyrene, and the thickness of the polymer outer layer is larger than or equal to 900 micrometers. The anti-crack self-repairing fiber net is added into the mass concrete, the crack condition of the mass concrete is reduced, the microbial repairing agent is released in a response mode when the crack is generated, the crack of the concrete is automatically filled, self-repairing of damage of the concrete structure is achieved, and the service life of the concrete structure is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and particularly to a crack-resistant self-repairing mass concrete and its application. Background Art

[0002] Mass concrete refers to the large-volume concrete with the minimum size of the concrete structure entity not less than 1 m, which is commonly found in the pier foundations of large bridges, hydraulic discharge structures in water conservancy projects, dock walls and dock floor slabs in dock projects, and wharves in marine engineering projects, etc. Due to the huge volume of concrete in mass concrete and the large amount of cement used, a large amount of heat will be released during the hydration process of cement, resulting in an increase in the internal temperature of the concrete, a large temperature difference with the external environment, and it is easy to generate temperature cracks. In addition to the cracks caused by temperature stress, cracks may also occur in the structure due to the combined action of various factors such as the self-shrinkage of concrete (such as drying shrinkage, autogenous shrinkage, etc.) and external constraints, which will affect the integrity, durability, waterproofness and other properties of the structure. Therefore, in the pouring of mass concrete, the control of concrete cracks is of utmost importance.

[0003] At present, the crack repair methods mainly rely on regular inspection of the structure and manual filling to repair cracks. These repair methods not only increase the number of repeated construction and the cost, but also if the repair material has poor compatibility with the concrete, it is very easy to break between the crack and the repair material, affecting the repair effect. Therefore, the self-repair technology that can actively sense and repair concrete cracks has become a research hotspot in the concrete field. There are many principles of self-repairing concrete. One method is to use a microbial repair agent. By adding microorganisms that can produce mineralization to the concrete, the self-repair effect can be achieved when cracks occur. However, directly adding microorganisms to the concrete will affect the lifespan and efficacy of the microorganisms. In order to improve the mineralization self-repair efficacy of microorganisms, various methods of coating microorganisms have been disclosed in the prior art, and the microorganisms are encapsulated in spherical polymers or silica-based materials. However, the volume of this spherical self-repair agent is relatively small, and the particle size is often only a few hundred micrometers to a few millimeters. A large amount of addition is often required to achieve the crack self-repair effect, but this will lead to a decrease in the compressive strength of the concrete. Moreover, if the crack resistance of the concrete is not controlled, when the self-repair agent is consumed, the cracks can only be repaired manually. Summary of the Invention

[0004] To solve the above problems, the present invention provides a crack-resistant self-healing mass concrete. By adding a crack-resistant self-healing fiber mesh, the crack-resistant grid reduces the cracking and generation of cracks in the mass concrete. When cracks occur, it can promptly respond to release the microbial repair agent. The microorganisms are activated under the conditions of nutrients and water, and metabolize to generate calcium carbonate to fill the cracks in the concrete, achieving self-repair of the damage to the concrete structure and extending the service life of the concrete structure.

[0005] The technical solutions to achieve the object of the present invention are as follows:

[0006] A crack-resistant self-healing mass concrete, comprising a steel reinforcement cage and the concrete for casting the steel reinforcement cage. An anti-cracking self-healing fiber mesh is tied to the outer surface of the steel reinforcement cage. The anti-cracking self-healing fiber mesh has a grid-shaped fiber as the core, and the outer surface is successively 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 composition of polylactic acid and polystyrene, and the thickness of the polymer outer layer ≥ 900 μm.

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

[0008] In a specific embodiment, the preparation method of the anti-cracking self-healing fiber mesh comprises the following steps:

[0009] S1. Immerse the grid-shaped fiber in sodium alginate and spore suspension, and then immediately immerse it in a calcium cross-linking agent solution, take it out and dry it. Repeat the above operations 0 - 3 times to form a microbial repair agent hydrogel layer;

[0010] S2. Immerse the grid-shaped fiber with the microbial repair agent hydrogel layer obtained in step S1 in a polymer material solution, take it out and dry it. Repeat the above operations 0 - 3 times to form a polymer layer;

[0011] S3. Immerse the grid-shaped fiber with the two-layer structure obtained in step S2 in a nutrient and sodium alginate suspension, and then immediately immerse it in a calcium cross-linking agent solution, take it out and dry it. Repeat the above operations 0 - 3 times to form a nutrient hydrogel layer;

[0012] S4. Immerse the grid-shaped fiber with the three-layer structure obtained in step S3 in a polymer material solution, take it out and dry it. Repeat the above operations 0 - 3 times to form a polymer outer layer, and obtain the anti-cracking self-healing fiber mesh.

[0013] The crack-resistant self-repairing fiber mesh is laid on the surface layer of the steel reinforcement cage of mass concrete. Its crack-resistant grid can improve the tensile strength of the concrete, reduce the cracking of mass concrete and the generation of harmful cracks. When cracks are generated in the concrete due to drying shrinkage or temperature shrinkage, water and oxygen penetrate through the micro-cracks from the surrounding environment. At this time, the polymer layer and the polymer outer layer of the crack-resistant self-repairing fiber mesh are destructed in response to the cracks, and the hydrogel carrying spores is exposed to nutrients. The spores germinate and generate self-repairing end products, namely microbially induced calcium carbonate precipitation, so as to repair the exposed cracks.

[0014] In a specific embodiment, the preparation method of the sodium alginate and spore suspension is as follows: bacteria with the ability to induce the formation of CaCO 3 are cultured in a culture medium, the strains are extracted, washed with PBS buffer solution, and then inoculated into a basal salt medium. They are 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 obtain the sodium alginate and spore suspension.

[0015] Studies have shown that the endospores produced by bacteria with the ability to induce the formation of CaCO 3 through the above-mentioned boiling water bath and ice water bath treatments can germinate under harsh alkaline conditions (pH value of 12), high salinity environments (up to 100 g / L), and freeze-thaw cycles (temperature of -10°C to 60°C), so that the spores can germinate in the high-alkali environment of concrete and the high-salinity environment of marine engineering buildings.

[0016] In another specific embodiment, bacteria with the ability to induce the formation of CaCO 3 can also be adapted to the highly alkaline chemical environment through the means of alkaline tolerance training by gradually increasing the pH concentration.

[0017] Preferably, the concentration of the sodium alginate is 6 - 18 g / L. When the concentration of the sodium alginate is within the preferred range, the adhesion force between the sodium alginate and spore suspension and the grid-shaped fiber can be improved.

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

[0019] In a specific embodiment, the mass ratio of the polystyrene to the polylactic acid is (1 to 3):1; the polylactic acid has good compatibility with the hydrogel and can form a uniform protective shell on the outer layer of the hydrogel. However, the polylactic acid is relatively brittle and the impact resistance effect is average. The compatibility of the polystyrene with the hydrogel is not as good as that of the polylactic acid. When used alone, the polymer layer is uneven and there are a small number of bubbles. However, its waterproof and impact resistance effects are good. Mixing the polylactic acid and the polystyrene for use as the outer protective layer of the crack-resistant self-repairing fiber mesh is beneficial to forming a uniform polymer layer and has the best waterproof and impact resistance effects.

[0020] Preferably, the polymer layer is formed after the evaporation of the polymer material solution. The concentration of the polymer material solution is 12 g / L to 20 g / L, and it is prepared by dissolving the polystyrene and the polylactic acid in chloroform. When the polymer material is 12 to 16 g / L, at least 2 layers or more of the polymer layer are required to effectively form a water-impermeable and impact-resistant polymer layer. When the concentration of the polymer material is 16 to 20 g / L, a single-layer polymer can also achieve effective waterproof and impact resistance effects.

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

[0022] In a 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 a specific embodiment, the mix proportion of the concrete is as follows: coarse aggregate 1100 to 1300 kg / m 3 、fine aggregate 600 to 800 kg / m 3 、cement 200 to 400 kg / m 3 、silica fume 40 to 60 kg / m 3 、fly ash 40 to 60 kg / m 3 、water reducing agent 1 to 10 kg / m 3 、water 80 to 150 kg / m 3 .

[0024] In a specific embodiment, the fine aggregate is natural river sand or manufactured sand; the coarse aggregate is crushed stone or pebble; the cement is ordinary Portland cement, low heat Portland cement, or medium heat Portland cement.

[0025] In a specific embodiment, the particle size of the coarse aggregate is 5 to 80 mm. Preferably, the coarse aggregate is obtained by grading three levels of crushed stone or pebble with particle sizes of 5 to 20 mm, 20 to 40 mm, and 40 to 80 mm.

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

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

[0028] After the steel cage is tied up, a layer of crack-resistant self-repairing fiber mesh is tied on the outer surface of the steel cage. The coarse aggregate, fine aggregate, cement, silica fume and fly ash are put into the mixing station and stirred for 1 - 2 minutes, then the ice-water mixture is added, and after stirring for 2 - 5 minutes, the water reducing agent is added and stirring continues until the ice cubes are fully melted; the concrete is poured in layers in the steel formwork, with a uniform cloth of 30 - 50 cm for each layer, and vibrated until the surface of the concrete presents cement paste and no longer sinks and basically does not bubble; the surface of the vibrated and leveled concrete is covered with a plastic film, and after hardening, the formwork is removed, and standard curing is carried out for at least 28 days.

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

[0030] Beneficial effects

[0031] The present invention provides a crack-resistant self-repairing mass concrete. By adding a crack-resistant self-repairing fiber mesh, harmful cracks in the mass concrete can be effectively reduced, and when cracks occur, the microbial repair agent is released in a responsive manner, the microorganisms are activated, and under the action of nutrients and calcium sources, calcium carbonate is metabolized and generated to fill the cracks in the concrete, realizing the self-repair of the damage to the concrete structure and prolonging the service life of the concrete structure. The crack-resistant self-repairing fiber mesh provided by the present invention is different from the spherical structure of traditional self-repairing materials. The crack-resistant effect of the grid-shaped fiber not only effectively reduces the cracking of the mass concrete, but also when cracking occurs, the self-repairing agent loaded on the surface of the grid-shaped fiber can respond in a timely manner, improving the reliability of the self-repairing concrete. Specific embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] In the embodiments, the experimental methods used are all conventional methods without special instructions, and the materials, reagents, etc. used can be obtained from commercial channels without special instructions.

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

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

[0036] Mineral powder: Purchased from Anyang Iron and Steel Group Xinyang Iron and Steel Co., Ltd.;

[0037] Fly ash: Purchased from Nanyang Tianfu Industry Co., Ltd.;

[0038] Fine aggregate: Natural river sand, from Tanghe, Henan;

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

[0040] Water - reducing agent: GK - 3000 polycarboxylate superplasticizer (retarding type), purchased from Chang'an Yucai Building Materials Co., Ltd., Shijiazhuang City;

[0041] Ice - water mixture: The raw material is tap water, meeting 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, with a single - filament diameter of 17μm and a length of 6mm, Zhejiang Shijin Basalt Fiber Co., Ltd.;

[0044] Glass fiber mesh: HH40805YJUJ0, Dezhou Hongtai Geosynthetic Materials Co., Ltd.;

[0045] Wire mesh: With a pore size of 30mm, Hebei Hanlian Metal Mesh Products Co., Ltd.;

[0046] Bacteria with the ability to induce the formation of CaCO 3 Bacteria: Lysinibacillus sphaericus strain MB284, international number: ATCC13805, purchased from Beijing Bio - Win Biotechnology Co., Ltd.;

[0047] Yeast extract: CAS: 8013 - 01 - 2, product number: Y1625, purchased from Sigma - Aldrich;

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

[0049] PBS buffer solution: 0.1mmol, PH = 7.0, Guangzhou Hewei Medical Technology Co., Ltd.;

[0050] Basal salt medium: Weigh 3.5g of Na 2 HPO 4·2H 2 O, 1.0 g KH 2 PO 4 , 0.5 g (NH 4 ) 2 SO 4 , 0.1 g MgCl 2 ·6H 2 O and 0.05 g Ca(NO 3 ) 2 ·4H 2 O were dissolved in 1000 ml of distilled water, 1.0 ml of trace element solution SL-4 was added, the pH was adjusted to 7.25, and autoclaved at 121 °C for 15 min; the preparation method of trace element solution SL-4 was: weigh 0.5 g of EDTA, 0.2 g of FeSO4·7H 2 O, 100 ml of trace element solution SL-6 were dissolved in 900 ml of 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 Anychem Chemical;

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

[0054] Polystyrene: gpps525, Guangzhou Petrochemical;

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

[0056] Unless otherwise specified, the component raw materials used in each example and comparative example of the present invention are all commercially available raw materials, and the component raw materials used in each parallel experiment are the same kind.

[0057] Preparation Example

[0058] Preparation Example 1

[0059] Anti-cracking self-healing fiber mesh 1: Self-made, the preparation method is as follows:

[0060] S1. Preparation of sodium alginate and spore suspension: The spherical Lysinibacillus sphaericus strain MB284 was cultured in a medium containing 20 g / L of yeast extract and 20 g / L of urea for 24 hours, the strain was extracted, washed 3 times with PBS buffer solution, then inoculated into the basal salt medium, treated in a boiling water bath for 30 min, then treated in an ice water bath for 30 min, and finally transferred to a shaking incubator at 45 °C for 2 days to form spores; 10 9Mix the spores at a concentration of

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

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

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

[0064] Immerse the basalt fiber mesh in the sodium alginate and spore suspension, then immediately immerse it in the calcium crosslinking agent solution, take it out and dry for 2 h, repeat the above operation 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 for 30 min, repeat the above operation once to form a polymer layer;

[0066] S3. Immerse the basalt fiber mesh with the two-layer structure obtained in step S2 in the nutrient and sodium alginate suspension, then immediately immerse it in the calcium crosslinking agent solution, take it out and dry for 2 h, repeat the above operation once to form a nutrient hydrogel layer;

[0067] S4. Immerse the basalt fiber mesh with the three-layer structure obtained in step S3 in the polymer material solution, take it out and dry for 30 min, repeat the above operation once to form a polymer layer, and obtain the crack-resistant self-repairing fiber mesh 1.

[0068] Preparation Example 2

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

[0070] Preparation Example 3

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

[0072] Preparation Example 4

[0073] Anti-cracking and self-healing fiber mesh 4: The preparation method is different from that of the anti-cracking and self-healing fiber mesh 1 in that the basalt fiber mesh is replaced by a glass fiber mesh.

[0074] Preparation Example 5

[0075] Anti-cracking and self-healing fiber mesh 5: The preparation method is different from that of the anti-cracking and self-healing fiber mesh 1 in that the basalt fiber mesh is replaced by a wire mesh.

[0076] Preparation Example 6

[0077] Anti-cracking and self-healing fiber mesh 6: The preparation method is different from that of the anti-cracking and self-healing fiber mesh 1 in that the polymer layer is polystyrene, and polylactic acid is replaced by polystyrene in the preparation of the polymer material solution, with the concentration remaining unchanged.

[0078] Preparation Example 7

[0079] Anti-cracking and self-healing fiber mesh 7: The preparation method is different from that of the anti-cracking and self-healing fiber mesh 1 in that the polymer layer is polylactic acid, and polystyrene is replaced by polylactic acid in the preparation of the polymer material solution, with the concentration remaining unchanged.

[0080] Preparation Example 8

[0081] Anti-cracking and self-healing fiber mesh 8: The preparation method is different from that of the anti-cracking and self-healing fiber mesh 1 in that the total number of layers of the polymer outer layer is 1 layer, that is, the total number of soaking and drying times in step S4 is changed to 1 time.

[0082] Preparation Example 9

[0083] Self-healing fiber: The preparation method is different from that of the anti-cracking and self-healing fiber mesh 1 in that the basalt fiber mesh is replaced by basalt chopped fibers;

[0084] The following performance tests were carried out on the anti-cracking and self-healing fiber mesh, and the results are shown in Table 1:

[0085] (1) Anti-seepage test: The anti-seepage test was carried out to study whether the polymer outer layer can protect the hydrogel carrying spores and nutrients from the intrusion of water and / or aqueous solutions during the concrete hydration stage. The test method is as follows: At the preparation example stage, phenolphthalein was added to the nutrient solution at a concentration of 0.1 g / L, and the other preparation steps were the same as those in Preparation Examples 1-8. Then, the anti-cracking and self-healing fiber mesh was retained in a highly alkaline solution for 1 hour, and whether the inner hydrogel showed pink / purple was observed through an optical microscope, and the observed color was recorded.

[0086] (2) Impact resistance test: The impact resistance test is conducted to ensure that the outer load-bearing 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 example 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 1-8. The crack-resistant self-healing fiber mesh containing phenolphthalein inside is fixed on a fixture. The fixture material is selected with moderate hardness to prevent additional damage to the specimen. The weight of the drop hammer is 1 kg, and the dropping height is 0.3 m. Release the drop hammer, and then keep the crack-resistant self-healing fiber mesh in a highly alkaline solution for 1 hour. Observe whether the inner hydrogel appears pink / purple through an optical microscope and record the observed color.

[0087] (3) Thickness of the polymer outer layer: Observe the thickness of the polymer outer layer of the crack-resistant self-healing fiber mesh under an optical microscope, and take the arithmetic mean of 10 measurements.

[0088] Table 1 Performance test results of the crack-resistant self-healing fiber meshes in Preparation Examples 1-8

[0089]

[0090] Example 1

[0091] A crack-resistant self-healing mass concrete

[0092] It includes a steel reinforcement cage and the concrete for casting the steel reinforcement cage. The outer surface of the steel reinforcement cage is tied with a crack-resistant self-healing fiber mesh, and the crack-resistant self-healing fiber mesh is the crack-resistant self-healing fiber mesh 1.

[0093] The mix proportion of the concrete is as follows: coarse aggregate 1250 kg / m 3 , fine aggregate 748 kg / m 3 , cement 310 kg / m 3 , silica fume 56 kg / m 3 , fly ash 56 kg / m 3 , water reducing agent 9.1 kg / m 3 , water 150 kg / m 3 ;

[0094] The preparation method of the crack-resistant self-healing mass concrete is as follows: After the steel reinforcement cage is tied, a layer of crack-resistant self-healing fiber mesh 1 is tied on the outer surface of the steel reinforcement cage. Put the coarse aggregate, fine aggregate, cement, silica fume, and fly ash into the mixing station, stir for 1-2 minutes, then add the ice-water mixture, stir for 2-5 minutes, and then add the water reducing agent and continue stirring until the ice cubes are fully melted. Pour the concrete in layers in the steel formwork, with a uniform distribution of 30-50 cm for each layer, and vibrate until the concrete surface shows cement paste and no longer sinks and there are basically no bubbles on the surface. Cover the vibrated and leveled concrete surface with a plastic film, remove the formwork after hardening, and cure under standard conditions for at least 28 days.

[0095] Examples 2 to 4

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

[0097] Comparative Examples 1 to 4

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

[0099] Comparative Example 5

[0100] Compared with Example 1, the difference is that the preparation method of the crack-resistant self-healing mass concrete is as follows: after the steel cage is bound, the coarse aggregate, fine aggregate, cement, silica fume, fly ash, and self-healing fiber are put into the mixing station, and after stirring for 1 to 2 minutes, then the ice-water mixture is added, and after stirring for 2 to 5 minutes, the water reducing agent is added, and stirring is continued until the ice cubes are fully melted; the concrete is poured in layers in the steel formwork, with uniform cloth laying of 30 to 50 cm for each layer, and vibrating until the surface of the concrete shows cement slurry and no longer sinks and the surface basically does not bubble; the surface of the vibrated and leveled concrete is covered with a plastic film, and the formwork is removed after hardening, and standard curing is carried out for 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 Test

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

[0105] (1) 28-day compressive strength: The compressive strength at 28 days is tested in accordance with "4.2 Concrete Cube Compressive Strength Test" in DL / T 5150—2017 "Test Code for Hydraulic Concrete";

[0106] (2) Crack condition: The crack condition at the 7th day is measured by using a standard dot-line gauge, a film ruler comparison card and a feeler gauge, and the total length, average length and maximum width of the cracks are recorded.

[0107] (3) Self-healing effect: Take a part of the concrete in the example and the concrete in the comparative example, and respectively form 10 round cake specimens with a diameter of φ100 * 50 mm. After reaching the age of 7 days, use a pressing method to press through cracks with a width of 0.2 - 0.5 mm in the middle of the round cake. Then, test the initial water seepage through the through cracks using an anti-seepage device, and then carry out soaking maintenance. Test the crack water seepage after soaking for 10 days, 20 days, and 40 days respectively. Finally, evaluate the repair degree of the concrete cracks by the ratio of the water seepage after maintenance to the initial water seepage. The lower the ratio, the better the crack repair. When the result is 0, it means the cracks have been repaired. The water seepage of each test is the average value of all specimens.

[0108] Table 2 Performance Test of Crack-resistant Self-healing Mass Concrete

[0109]

[0110]

[0111] It can be seen from Example 1 and Comparative Example 5 that if the grid-shaped fibers are replaced with chopped fibers, the crack-resistant effect cannot be achieved, and at the same time, because the dispersion effect of the chopped fibers is not good, the self-healing function of the concrete is also affected.

[0112] It can be seen from Example 1, 4 and Comparative Example 1 that when the grid-shaped fibers are selected as basalt fiber mesh and glass fiber mesh, they both have good crack-resistant and self-healing effects. However, due to the smooth surface of the iron wire mesh, the adhesion of sodium alginate on the iron wire surface is insufficient, resulting in less self-healing agent loaded and a lower thickness of the polymer layer, and the self-healing effect is poor.

[0113] It can be seen from Example 1 - 3 and Comparative Examples 3 and 4 that the polymer outer layer needs to meet a thickness of ≥900 μm and a certain impact resistance to resist the impact force during concrete pouring. Otherwise, the polymer outer layer will rupture in advance, resulting in the hydrogel of the nutrient layer absorbing water and swelling during the mixing period, and instead leaving holes after dehydration in the later stage. And the diffusion of nutrients also affects the compressive performance of the concrete, and at the same time causes harmful cracks with a larger width.

[0114] It can be seen from Example 1 and Comparative Example 2 that when polystyrene is used alone, since the formed polymer layer is not uniform enough and the thickness of the lower part is relatively low, it is easy to rupture, resulting in an impact on the self-healing performance of the concrete.

[0115] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A crack-resistant self-repairing mass concrete, comprising a steel cage and concrete cast in the steel cage, characterized in that: The outer surface of the steel cage is tied with an anti-cracking self-repairing fiber mesh, which has a grid-like fiber as the core, and the outer surface is loaded with a microbial repair agent hydrogel layer, a polymer layer, a nutrient hydrogel layer and a polymer outer layer in sequence. The polymer layer and the polymer outer layer are a composition of polylactic acid and polystyrene, and the thickness of the polymer outer layer is ≥900μm.

2. The crack-resistant self-repairing mass concrete according to claim 1, characterized in that: The method for preparing the crack-resistant self-repairing fiber mesh comprises the following steps: S1. Soak the mesh fiber in sodium alginate and spore suspension, and then immediately soak it in a calcium crosslinker solution, take it out and dry it, and repeat the above operation 0 to 3 times to form a microbial repair agent hydrogel layer; S2. Soaking the mesh-like fibers with the microbial repair agent hydrogel layer obtained in step S1 in a polymer material solution, taking them out and drying them, and repeating the above operation 0 to 3 times to form a polymer layer; S3. The grid-like fibers loaded with the two-layer structure obtained in step S2 are immersed in a nutrient and a sodium alginate suspension, and then immediately immersed in a calcium crosslinker solution, taken out and dried, and the above operation is repeated 0 to 3 times to form a nutrient hydrogel layer; S4. Soak the grid-like fibers loaded with the three-layer structure obtained in step S3 in a polymer material solution, take them out and dry them, and repeat the above operation 0 to 3 times to form a polymer outer layer to obtain a crack-resistant self-repairing fiber mesh.

3. The crack-resistant self-repairing mass concrete according to claim 2, characterized in that: The preparation method of 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 a PBS buffer solution, and then inoculated into a basic salt culture medium, respectively 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 obtain the sodium alginate and spore suspension.

4. The crack-resistant self-repairing mass concrete according to claim 2, characterized in that: The calcium cross-linking agent solution is at least one of calcium chloride and calcium acetate.

5. The crack-resistant self-repairing mass concrete according to claim 1, characterized in that: The mass ratio of the polystyrene to the polylactic acid is (1-3):

1.

6. The crack-resistant self-repairing mass concrete according to claim 1, characterized in that: The mesh-like fibers are at least one of basalt fiber mesh and glass fiber mesh.

7. The crack-resistant self-repairing mass concrete according to claim 1, characterized in that: The nutrients in the nutrient hydrogel layer are yeast extract, calcium source and urea, and the hydrogel is sodium alginate hydrogel.

8. The crack-resistant self-repairing mass concrete according to claim 1, characterized in that: The mix ratio of the concrete is: coarse aggregate 1100-1300 kg / m 3 , Fine aggregate 600~800kg / m 3 , cement 200~400kg / m 3 , silica fume 40~60kg / m 3 、Fly ash 40~60kg / m 3 , water reducing agent 1~10kg / m 3 , water 80~150kg / m 3 .

9. The method for preparing crack-resistant self-repairing mass concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: After the steel cage is tied, a layer of anti-cracking self-repairing fiber mesh is tied on the outer surface of the steel cage. Coarse aggregate, fine aggregate, cement, silica fume and fly ash are put into the mixing station and stirred for 1 to 2 minutes. Then add the ice-water mixture and stir for 2 to 5 minutes before adding the water reducer. Continue stirring until the ice is fully melted. Pour the concrete in layers in the steel formwork, evenly distribute each layer of 30 to 50 cm, and vibrate until the concrete surface shows cement slurry and no longer sinks and there is basically no bubbling on the surface. Cover the vibrated and leveled concrete surface with plastic film, remove the formwork after hardening, and maintain standard maintenance for at least 28 days.

10. Use of the crack-resistant self-repairing large-volume concrete according to any one of claims 1 to 8 in hydraulic structures or marine structures.

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