Crack control self-repairing intelligent super-high durability concrete, preparation method and application thereof

Abstract

The application relates to a crack-controlling self-repairing intelligent super-high durability concrete, a preparation method thereof and application, and belongs to the technical field of intelligent concrete materials. Through the adoption of a modified red mud-based conductive aggregate and a stainless steel-PE fiber synergistic reinforcing structure, the crack width is accurately controlled within 150 microns (the lowest actual measurement can reach 128 microns), and the crack is monitored in real time by using the resistance change rate; meanwhile, the application innovatively proposes a double-zone self-repairing mechanism of "sodium silicate in the aggregate zone + nano self-repairing additive in the non-aggregate zone", and after the crack is formed, the repair reaction is triggered by a high-humidity environment, and the repair efficiency reaches 98% within 180 days, which is significantly better than that of a single repair system. The prepared concrete has a compressive strength of 150 MPa, a chloride ion diffusion coefficient as low as 0.28*10 ‑12 m 2 / s (the impermeability is 1 / 1000 of that of ordinary concrete), and the conductive aggregate is prepared from industrial waste red mud, so that the advantages of resource recycling and high cost performance are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intelligent concrete materials, in particular to a crack control and self-repairing type intelligent ultra-high durability concrete, a preparation method and application thereof. BACKGROUND

[0002] As one of the most widely used building materials, concrete plays a crucial role in infrastructure construction. However, traditional concrete has problems such as insufficient durability, easy cracking, and poor impermeability. In particular, during long-term service, the generation and development of cracks can greatly reduce the overall performance of the structure, and even lead to early failure of the structure. Therefore, improving the durability and self-repairing ability of concrete has become a key direction in the field of current concrete materials research.

[0003] In recent years, intelligent concrete materials have received widespread attention. So-called intelligent concrete generally refers to functional concrete that can perceive environmental changes, stress states, or has crack self-healing function, based on basic mechanical properties. Self-repairing concrete, as an important component of intelligent concrete, mainly uses physical, chemical or biological means to actively seal cracks after they form, thereby improving the service life of the structure. Existing self-repairing concrete systems mainly include microcapsule type, pipe packaging type and mineral expansion type, etc. However, most of these methods have limited repair efficiency, harsh repair triggering conditions, high material cost or incompatibility with ordinary preparation processes, making it difficult to be widely applied.

[0004] In addition, in view of the problem that reinforced concrete is easily eroded by chloride ions in marine or saline environments, the academic community is also actively developing high-performance concrete with strong impermeability and low chloride ion diffusion rate. For example, adding nano materials (such as nano silicon), active mineral admixtures (such as metakaolin), and using polycarboxylate high-performance water reducing agent to optimize the pore structure, all of which can help improve the density and corrosion resistance of concrete. However, a single method often cannot balance strength, durability and functionality. Electrically conductive concrete is a new type of functional concrete developed in recent years. By introducing electrically conductive aggregates or electrically conductive fibers, the material has certain electrical properties, providing a basis for subsequent structure health monitoring or self-heating deicing functions. However, ordinary conductive aggregates (such as graphite, carbon black, etc.) have poor compatibility with ordinary concrete systems, and the dosage control is difficult. Therefore, there is an urgent need to develop a new type of concrete material that integrates high strength, high durability, crack control and intelligent self-repairing functions. Such materials should have good workability, be suitable for existing construction processes, and have economic feasibility and sustainability.

[0005] CN118724497A discloses a kind of in-situ curing microcapsule for concrete self-repair, which separates repair agent and curing agent by composite capsule wall, and realizes in-situ bonding to repair cracks after rupture. However, the preparation of microcapsule requires multiple-step prepolymerization (synthesis of inner wall / outer wall prepolymer, emulsification, pH adjustment), which is complex. The contact efficiency of repair agent and curing agent is limited by the degree of capsule wall rupture, and the stability of large-scale production is insufficient. CN113912318A discloses a kind of mineral precipitation type self-repairing material, which uses water-absorbing resin to control moisture to promote calcium carbonate / magnesium precipitation. However, the repair speed is slow (28 days healing efficiency is only 44.26%), and it is highly dependent on environmental humidity, and the repair efficiency is significantly reduced under dry conditions. CN115745497A discloses a kind of hollow glass tube packaging repair liquid technology, which relies on glass tube rupture to release adhesive. However, the glass tube has poor compatibility with the concrete interface. When the molecular weight of the repair liquid is too low (<5000), the strength is insufficient. When the molecular weight is too high (>8000), the flowability is poor, and the repair uniformity is difficult to guarantee. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a crack control and self-repairing type intelligent ultra-high durability concrete, its preparation method and application. The prepared concrete not only has excellent strength and impermeability, but also has intelligent crack detection and self-repairing ability, which can significantly prolong the service life of concrete structure and effectively meet the engineering application requirements under complex environment.

[0007] Based on the above purpose, the present application discloses a kind of crack control and self-repairing type intelligent ultra-high durability concrete, the crack control and self-repairing type intelligent ultra-high durability concrete has electric conduction-self-perception-self-repairing mechanism, raw material contains electric conduction aggregate, self-repairing additive and fiber, the self-repairing additive is nano self-repairing additive, the nano self-repairing additive uses high belite sulphate cement as main body material, also adds nano zinc oxide, nano silicon dioxide and nano magnesium oxide, the fiber includes stainless steel fiber.

[0008] In the present application, electric conduction-self-perception is formed by stainless steel fiber and electric conduction aggregate in raw material to form an electric conduction network, and crack is identified by monitoring resistance change; stainless steel fiber and PE fiber cooperate to control crack width within 150 μm. Self-repairing mechanism forms double-zone self-repairing mechanism through "aggregate area sodium silicate + non-aggregate area nano self-repairing additive": after crack appears, sodium silicate exposed in aggregate area forms calcium silicate precipitation to close crack; nano self-repairing additive exposed in non-aggregate area generates various precipitates (ettringite, magnesium carbonate, C-S-H gel, etc.) and compensates shrinkage to jointly and efficiently close crack, especially suitable for self-repairing demand under high humidity environment.

[0009] Preferably, the crack control self-repairing type intelligent super-high durability concrete comprises the following components in percentage by mass: cementitious material 35%-45%, conductive aggregate 38%-45%, self-repairing additive 1.05%-1.35%, water reducing agent 0.5%-1%, water 5%-10%, and the balance is fiber; wherein the fiber volume content is 1.5%, and the water-binder ratio is 0.15-0.25.

[0010] Preferably, the conductive aggregate is modified red mud-based aggregate, has a particle size of 2-4 mm, and has good electrical conductivity and pore structure.

[0011] Preferably, in the nano self-repairing additive, the mass of nano zinc oxide is 0.3%-0.6% of the mass of the main material, the mass of nano silicon dioxide is 1.5%-2% of the mass of the main material, and the mass of nano magnesium oxide is 1.0%-1.8% of the mass of the main material.

[0012] During service, when the concrete cracks, the aggregate area cracks: sodium silicate is exposed to air, reacts with water to form calcium silicate precipitation to seal the cracks; the non-aggregate area cracks: the nano self-repairing additive is exposed to air, reacts with water to form needle-shaped ettringite and magnesium carbonate precipitation; nano zinc oxide can prevent the self-repairing additive from reacting too early; nano MgO acts as an expansive agent, compensates for dry shrinkage, and inhibits the generation of new cracks. Both work together to achieve the purpose of self-repairing.

[0013] Preferably, the addition amount of the self-repairing additive is 3% of the addition mass of the cementitious material.

[0014] Preferably, the fiber further comprises PE fiber, and the mass ratio of the stainless steel fiber to the PE fiber is (5-7):(3-5), the length of the stainless steel fiber is 10-15 mm, and the diameter is 0.2-0.3 mm, the length of the PE fiber is 12-18 mm, and the diameter is 0.02-0.04 mm. The synergistic effect of the two kinds of fibers significantly enhances the crack resistance and tensile toughness of the material, and realizes the crack width control within 150 μm.

[0015] Preferably, the cementitious material contains the following components in percentage by mass: cement 77%-82%, silica fume 8%-15%, and metakaolin 8%-15%; and the water reducing agent is a polycarboxylate-based high-efficiency water reducing agent. Wherein, due to the filling effect and the pozzolanic filling effect of the silica fume, the microstructure of the concrete is more compact, and the strength of the concrete is improved; the metakaolin as a high-activity mineral admixture can further improve the durability and chemical corrosion resistance of the concrete.

[0016] The application further provides a preparation method of the crack control self-repairing type intelligent super-high durability concrete.

[0017] (1) The bayer process red mud is activated by acid, and is granulated with graphite and biomass powder according to the mass ratio of 100: (15-25): (8-12); sintering at 1100-1250 DEG C for 30-60 minutes to form porous conductive aggregate; then the conductive aggregate is soaked in a 2% sodium silicate solution, and the sodium silicate solution is adsorbed in the pores of the conductive aggregate under vacuum conditions, and after drying, the sodium silicate becomes a solid adhering to the inner wall of the conductive aggregate;

[0018] (2) The cementitious material, nano repair additive and conductive aggregate with adhered sodium silicate are dry mixed for 2-5 minutes;

[0019] (3) The water reducing agent and water are added and stirred for 3-6 minutes;

[0020] (4) The fiber is added and stirred at low speed for 2-4 minutes;

[0021] (5) After pouring and forming, the concrete is cured under the conditions of temperature 20±2 DEG C and humidity ≥95% for at least 28 days.

[0022] Preferably, in steps (2) and (3), the dry mixing speed is 40-60 rpm, and in step (4), the low speed stirring speed is 20-30 rpm.

[0023] The crack control and self-repairing type intelligent ultra-high durability concrete provided by the application has the advantages of ultra-high strength, extremely low chloride ion permeability and high impermeability, and is applied to major infrastructures in harsh environments requiring absolute safety and ultra-long service life, such as marine engineering and offshore infrastructure, engineering in saline soil areas, transportation facilities, energy and nuclear energy engineering, etc.

[0024] Therefore, the crack control and self-repairing type intelligent ultra-high durability concrete, the preparation method and the application thereof have the following advantages:

[0025] (1) The intelligent concrete provided by the application has the ability of automatic crack identification and crack width control, and the core principle is that a three-dimensional conductive network formed by stainless steel fibers and conductive aggregate is constructed inside the concrete. The current data is collected by an external current collection module, the voltage is a fixed value, the current change is monitored, and the resistance is calculated; the crack of the concrete can be detected according to the resistance change value, and the network presents stable resistance characteristics when the concrete is intact; once the concrete cracks due to stress, the conductive path will be cut off or the path tortuosity will increase, thereby causing a significant change in the macroscopic resistance value, and the crack initiation and development can be realized by monitoring the resistance change. In terms of crack control, the stainless steel fiber and the PE fiber improve the crack resistance of the concrete through a synergistic toughening mechanism. After the crack appears, the fiber spans across both sides of the crack, plays a bridging role, effectively constrains the further opening and expansion of the crack, and thus the crack width is automatically controlled within 150 microns.

[0026] (2) It has the ability of self-repairing, and its core repair mechanism lies in the unique double-zone self-repairing mechanism: when cracks occur in the concrete, the stress at the cracks exposes the self-repairing additive pre-loaded in the interior. In the aggregate zone, the sodium silicate pre-stored in the pores of the conductive aggregate by the solution immersion method can react with the environmental substances to form a precipitate after being exposed by the cracks, thereby repairing the region; in the matrix part of the non-aggregate zone, the dispersed nano self-repairing additive is simultaneously exposed and rapidly reacts to generate various insoluble products to efficiently seal the cracks, thereby realizing more comprehensive repair of the cracks through partition control.

[0027] (3) The structure performance is excellent, the compressive strength is as high as 100 MPa or more, and the structure is dense, and the chloride ion permeability is 1 / 1000 of that of ordinary concrete, and the impermeability is improved to 1%. DETAILED DESCRIPTION

[0028] The technical solutions of the present application are further described below through examples.

[0029] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those skilled in the art to which the present application belongs.

[0030] In addition, it should be understood that although the present specification is described in terms of embodiments, each embodiment does not contain only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each example can also be appropriately combined to form other embodiments that those skilled in the art can understand. These other embodiments are also covered by the protection scope of the present application.

[0031] Example 1

[0032] The present embodiment provides a crack control self-repairing type intelligent ultra-high durability concrete, which comprises the following components by mass percentage (except for special marking, the whole is calculated based on the crack control self-repairing type intelligent ultra-high durability concrete):

[0033] The cementitious material is 42%, which comprises cement 33.6% (80% of the cementitious material), silica fume 3.36% (8% of the cementitious material), and metakaolin 5.04% (12% of the cementitious material).

[0034] The modified red mud-based aggregate with a particle size of 2-4 mm is 38%.

[0035] The nano self-repairing additive is 1.26%, wherein the high belite sulfate cement is used as the main material, and the nano zinc oxide with a mass of 0.3% of the main material, the nano silicon dioxide with a mass of 2% of the main material and the nano magnesium oxide with a mass of 1.8% of the main material are further added.

[0036] The polycarboxylic acid high-efficiency water reducing agent (water reducing rate ≥ 35%) is 0.8%.

[0037] The water is 7.2%, so that the overall water-binder ratio is 0.17.

[0038] The volume content of the fiber is 1.5%, accounting for 10.74% of the mass of the concrete, wherein the mass ratio of the stainless steel fiber and the PE fiber is 6:4, the length of the stainless steel fiber is 12mm, the diameter is 0.25mm, the length of the PE fiber is 15mm, and the diameter is 0.03mm.

[0039] The embodiment also provides a preparation method of the concrete, including the following steps:

[0040] (1) electrically conductive aggregate pretreatment: after the bayer red mud is activated by acid, the bayer red mud is granulated with graphite and biomass powder at a mass ratio of 100:20:10; the porous electrically conductive aggregate is formed by sintering at 1200℃ for 60 minutes, is placed in a reactor and is exhausted under negative pressure for 10 minutes, then sodium silicate solution is poured into the reactor, so that the electrically conductive aggregate is completely soaked in 2% sodium silicate solution, and then vacuum adsorption is performed for 30 minutes; the pretreated electrically conductive aggregate is taken out and is placed in a 60℃ oven to dry the sodium silicate to a solid state to obtain the pretreated electrically conductive aggregate;

[0041] (2) dry mixing: the cement, silica fume, metakaolin, nano self-repairing additive and pretreated electrically conductive aggregate are put into a stirrer, and dry mixing is performed at 50rpm for 3 minutes;

[0042] (3) wet mixing: water and water reducing agent are added, and stirring is performed at 50rpm for 5 minutes;

[0043] (4) fiber dispersion: two kinds of fibers are added, and low-speed stirring is performed at 25rpm for 3 minutes;

[0044] (5) forming and curing: the test piece is poured, and curing is performed at 20℃ and a humidity of ≥95% for at least 28 days.

[0045] In the embodiment, the length of the stainless steel fiber can also be 10mm or 15mm, the diameter is 0.2mm or 0.3mm, the length of the PE fiber is 12mm or 18mm, and the diameter is 0.02mm or 0.04mm, and the performance is basically the same as that of the embodiment.

[0046] In the preparation method of the embodiment, in step (1), the acid-activated Bayer process red mud can also be granulated with graphite and biomass powder at a mass ratio of 100:15:8 or 100:25:12, and can also be sintered at 1100 or 1250℃ for 30 or 50 minutes; in step (2), dry mixing can be performed at 40rpm or 60rpm for 2 or 5 minutes; in step (3), stirring can be performed at 40rpm or 60rpm for 3 or 6 minutes; in step (4), low-speed stirring can be performed at 20rpm or 30rpm for 2 or 4 minutes, and the performance is basically the same as that of the embodiment.

[0047] Embodiment 2

[0048] The embodiment provides a crack control and self-repairing type intelligent super-high durability concrete, which comprises the following components in percentage by mass (except for special indications, the whole is calculated based on the crack control and self-repairing type intelligent super-high durability concrete):

[0049] The cementitious material is 35%, which comprises cement 26.95% (accounting for 77% of the cementitious material), silica fume 2.8% (accounting for 8% of the cementitious material) and metakaolin 5.25% (accounting for 15% of the cementitious material).

[0050] The modified red mud-based aggregate with a particle size of 2-4mm is 38%.

[0051] The nano self-repairing additive powder (3% of the mass of the cementitious material) is 1.05%, which comprises high belite sulfate cement as the main material, and further comprises nano zinc oxide with a mass of 0.4% of the main material, nano silicon dioxide with a mass of 1.75% of the main material and nano magnesium oxide with a mass of 1.25% of the main material.

[0052] The polycarboxylate-based high-efficiency water reducing agent (water reducing rate ≥ 35%) is 0.5%.

[0053] Water is 10%, so that the water-binder ratio is 0.25.

[0054] The fiber volume content is 1.5%, accounting for 12.45% of the total mass of the concrete, which comprises stainless steel fibers and PE fibers at a mass ratio of 7:3, and the sizes of the stainless steel fibers and the PE fibers are the same as those in embodiment 1.

[0055] The preparation method of the embodiment is the same as that of embodiment 1.

[0056] Embodiment 3

[0057] The embodiment provides a crack control and self-repairing type intelligent super-high durability concrete, which comprises the following components in percentage by mass (except for special indications, the whole is calculated based on the crack control and self-repairing type intelligent super-high durability concrete):

[0058] Cementitious material 42%, which contains cement 34.44% (accounting for 82% of cementitious material), silica fume 4.2% (accounting for 10% of cementitious material) and metakaolin 3.36% (accounting for 8% of cementitious material).

[0059] Modified red mud-based aggregate with particle size of 2-4 mm 42%;

[0060] Nano self-repairing additive powder (3% of the mass of cementitious material) 1.26%, which takes high belite portland cement as the main material, and further adds nano zinc oxide with a mass of 0.3% of the main material, nano silicon dioxide with a mass of 2% of the main material and nano magnesium oxide with a mass of 1.8% of the main material.

[0061] Water reducing agent 1%; water 5% to make the water-binder ratio 0.15; the volume content of fiber is 1.5%, accounting for 8.74% of the total mass of concrete, which contains stainless steel fiber and PE fiber with a mass ratio of 5:5, and the size of the stainless steel fiber and the PE fiber is the same as that of example 1.

[0062] The preparation method of this example is the same as that of example 1.

[0063] Example 4

[0064] This example provides a crack control and self-repairing type intelligent super-high durability concrete, which contains the following components with a mass percentage (except for special marking, the whole is calculated based on the crack control and self-repairing type intelligent super-high durability concrete):

[0065] Cementitious material 42%, which contains cement 33.6% (accounting for 80% of cementitious material), silica fume 3.36% (accounting for 8% of cementitious material) and metakaolin 5.04% (accounting for 12% of cementitious material).

[0066] Modified red mud-based aggregate with particle size of 2-4 mm 38%.

[0067] Nano self-repairing additive (3% of the mass of cementitious material) 1.26%, which takes high belite portland cement as the main material, and further adds nano zinc oxide with a mass of 0.3% of the main material, nano silicon dioxide with a mass of 2% of the main material and nano magnesium oxide with a mass of 1.8% of the main material.

[0068] Polycarboxylic acid type high efficiency water reducing agent (water reducing rate ≥ 35%) 0.8%.

[0069] Water 7.2% to make the water-binder ratio 0.17.

[0070] The volume content of fiber is 1.5%, accounting for 10.74% of the total mass of concrete, which contains stainless steel fiber and PE fiber with a mass ratio of 6:4, and the size of the stainless steel fiber and the PE fiber is the same as that of example 1.

[0071] Therefore, the difference between the present embodiment and the components of embodiment 1 is that the present embodiment does not have a sodium silicate solution.

[0072] The present embodiment also provides a preparation method of the above concrete, comprising the following steps:

[0073] (1) Preparation of conductive aggregate: after the Bayer process red mud is acid-activated, granulation is performed with graphite and biomass powder at a mass ratio of 100:20:10; sintering is performed at 1200°C for 60 minutes to form a porous conductive aggregate, which is placed in a reactor for 10 minutes of negative pressure exhaust, and the sodium silicate is dried to solid state in a 60°C oven to obtain the conductive aggregate;

[0074] (2) Dry mixing: cement, silica fume, metakaolin, nano self-repairing additive, and conductive aggregate are put into a mixer, and dry mixing is performed at 50 rpm for 3 minutes;

[0075] (3) Wet mixing: water and water reducing agent are added, and stirring is performed at 50 rpm for 5 minutes;

[0076] (4) Fiber dispersion: two kinds of fibers are added, and low-speed stirring is performed at 25 rpm for 3 minutes;

[0077] (5) Molding and curing: the test piece is poured, and curing is performed at 20°C and a humidity of ≥95% for at least 28 days.

[0078] Therefore, the difference between the preparation method provided by the present embodiment and the preparation method of embodiment 1 is only that the present embodiment does not have the related steps of pre-treatment of the conductive aggregate.

[0079] Embodiment 5

[0080] The present embodiment provides a crack control and self-repairing type intelligent ultra-high durability concrete, which comprises the following components (except for special annotations, the whole is calculated based on the crack control and self-repairing type intelligent ultra-high durability concrete) in mass percentage:

[0081] Gelled material 45%, which comprises cement 34.65% (77% of the gelled material), silica fume 6.75% (15% of the gelled material), and metakaolin 3.6% (8% of the gelled material).

[0082] Modified red mud-based aggregate with a particle size of 2-4 mm 38%;

[0083] Nano self-repairing additive powder (3% of the gelled material) 1.35%, wherein high belite sulfate cement is used as the main material, and 0.3% of nano zinc oxide, 2% of nano silicon dioxide, and 1.8% of nano magnesium oxide of the mass of the main material are added.

[0084] Water reducing agent 1%; water 5%, so that the water-binder ratio is 0.15; the fiber volume content is 1.5%, accounting for 9.65% of the total mass of the concrete, which contains stainless steel fiber and PE fiber in a mass ratio of 5:5, and the sizes of the stainless steel fiber and the PE fiber are the same as those in Example 1.

[0085] The preparation method of this example is the same as that of Example 1.

[0086] Example 6

[0087] This example provides a crack control and self-repairing type intelligent super-high durability concrete, which comprises the following components in mass percentage (except for special marking, the whole is calculated based on the crack control and self-repairing type intelligent super-high durability concrete):

[0088] Cementitious material 35%, which contains cement 26.95% (accounting for 77% of the cementitious material), silica fume 2.8% (accounting for 8% of the cementitious material), and metakaolin 5.25% (accounting for 15% of the cementitious material).

[0089] Modified red mud-based aggregate with a particle size of 2-4 mm 45%;

[0090] Nano self-repairing additive powder (3% of the mass of the cementitious material) 1.05%, which contains high belite sulfate cement as the main material, and further contains nano zinc oxide with a mass of 0.3% of the main material, nano silicon dioxide with a mass of 2% of the main material, and nano magnesium oxide with a mass of 1.8% of the main material.

[0091] Water reducing agent 1%; water 5%, so that the water-binder ratio is 0.15; the fiber volume content is 1.5%, accounting for 12.95% of the total mass of the concrete, which contains stainless steel fiber and PE fiber in a mass ratio of 5:5, and the sizes of the stainless steel fiber and the PE fiber are the same as those in Example 1.

[0092] The preparation method of this example is the same as that of Example 1.

[0093] The performance detection process is as follows:

[0094] 1. Concrete compressive strength test: the concrete prepared in Examples 1-4 is tested for compressive strength after 28 days of curing according to the national standard GB / T500812019 "Standard for Testing Methods of Physical and Mechanical Properties of Concrete", and the test results are shown in Table 1.

[0095] 2. Concrete durability test: the concrete prepared in Examples 1-4 is tested for water permeability and chloride ion permeability after 28 days of curing according to the national standard GB / T50082-2024 "Standard for Testing Methods of Long-term Performance and Durability of Concrete", and the test results are shown in Table 1.

[0096] 3. Concrete self-repairing test: the concrete prepared in Examples 1-4 was loaded to a pre-crack of 0.1 mm after curing for 28 days, and the loaded test piece was then placed in a high-humidity environment of 20±2℃ and ≥95% humidity for self-repairing for 180 days, and then taken out, and the crack repair was observed, and the test results are shown in Table 1.

[0097] Concrete crack self-monitoring test: the test piece was polished and cleaned with alcohol, and electrodes were arranged using an external electrode method. When the test piece was preloaded, a current acquisition module was used to collect current data, the voltage was a fixed value, the current change was monitored, and the resistance was calculated. Specifically, a four-electrode method was used for resistivity testing. Four copper mesh electrodes with a spacing of 40 mm were embedded in the mold during test piece preparation. The outer two electrodes served as current electrodes, and the inner two electrodes served as voltage electrodes. A PLD-6005 direct current power supply was used to provide a constant current during testing, and a TDS-530 data acquisition instrument was used to collect data. The test results are shown in Table 1.

[0098] Table 1 is the performance test results of the samples prepared in Examples 1-6,

[0099]

[0100] As shown in Table 1, the concrete samples provided in Examples 1-6 have high strength, intelligent monitoring and self-repairing functions in one. By using modified red mud-based conductive aggregate and stainless steel-PE fiber synergistic reinforcement structure, the crack width is precisely controlled within 150 μm (actually measured to be 128-142 μm), and the crack can be monitored in real time according to the resistance change rate. Because of the presence of conductive aggregate inside, the initial resistance is low; after cracking, pores appear inside the concrete, the resistance increases; after healing, the pores are filled and the resistance returns to a certain level.

[0101] Meanwhile, the "aggregate area sodium silicate + non-aggregate area nano self-repairing additive" dual-zone self-repairing mechanism is innovatively proposed. The repair reaction is triggered by a high-humidity environment after the crack forms. The repair efficiency of the sample of Example 1 is as high as 98% within 180 days, which is significantly better than that of the single repair system (Example 4). The compressive strength reaches 150 MPa, and the chloride ion diffusion coefficient is as low as 0.28×10 -12 m 2 / s (the impermeability is one thousandth of that of ordinary concrete), and the conductive aggregate is prepared from industrial waste red mud, which has the advantages of resource recycling and high cost performance.

[0102] The above detailed description of the specific embodiments of the present application has been given to illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and does not limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A crack-controlled, self-healing, intelligent ultra-high durability concrete, characterized in that, The crack-controlled self-healing intelligent ultra-high durability concrete has a conductive-self-sensing-self-healing mechanism. The raw materials contain conductive aggregate, self-healing admixture, and fiber. The production process of the conductive aggregate is as follows: Bayer red mud is activated by acid and then granulated with graphite and biomass powder at a mass ratio of 100:(15-25):(8-12); sintered at 1100-1250℃ for 30-60 minutes to form porous conductive aggregate; then the conductive aggregate is soaked in a 2% sodium silicate solution, and under vacuum conditions, the sodium silicate solution is adsorbed into the pores of the conductive aggregate. After drying, pretreated conductive aggregate is obtained. The self-healing admixture is a nano self-healing admixture, which uses high-belite sulfate cement as the main material and also adds nano zinc oxide, nano silicon dioxide and nano magnesium oxide. The fibers include stainless steel fibers and PE fibers.

2. The crack-controlled self-healing intelligent ultra-high durability concrete according to claim 1, characterized in that, The crack-controlled self-healing intelligent ultra-high durability concrete comprises the following components by mass percentage: 35%-45% cementitious materials, 38%-45% conductive aggregates, 1.05%-1.35% self-healing admixtures, 0.5%-1% water-reducing agent, 5%-10% water, and the balance being fibers; wherein the fiber volume content is 1.5%, and the water-cement ratio is 0.15-0.

25.

3. The crack-controlled self-healing intelligent ultra-high durability concrete according to claim 1, characterized in that, The conductive aggregate is a modified red mud-based aggregate with a particle size of 2-4 mm.

4. The crack-controlled self-healing intelligent ultra-high durability concrete according to claim 1, characterized in that, In the aforementioned nano self-healing additive, nano zinc oxide accounts for 0.3%-0.6% of the main material mass, nano silicon dioxide accounts for 1.5%-2% of the main material mass, and nano magnesium oxide accounts for 1.0%-1.8% of the main material mass.

5. The crack-controlled self-healing intelligent ultra-high durability concrete according to claim 2, characterized in that, The amount of the self-healing admixture added is 3% of the mass of the cementitious material.

6. The crack-controlled self-healing intelligent ultra-high durability concrete according to claim 1, characterized in that, The mass ratio of the stainless steel fiber to the PE fiber is (5-7):(3-5). The stainless steel fiber has a length of 10-15 mm and a diameter of 0.2-0.3 mm. The PE fiber has a length of 12-18 mm and a diameter of 0.02-0.04 mm.

7. The crack-controlled self-healing intelligent ultra-high durability concrete according to claim 2, characterized in that, The cementitious material contains the following components by mass percentage: 77%-82% cement, 8%-15% silica fume, and 8%-15% metakaolin; the water-reducing agent is a polycarboxylate-based high-efficiency water-reducing agent.

8. A method for preparing crack-controlled self-healing intelligent ultra-high durability concrete as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Bayer red mud is activated by acid and then granulated with graphite and biomass powder at a mass ratio of 100:(15-25):(8-12). It is sintered at 1100-1250℃ for 30-60 minutes to form porous conductive aggregate. The conductive aggregate is then soaked in a 2% sodium silicate solution. Under vacuum conditions, the sodium silicate solution is adsorbed into the pores of the conductive aggregate. After drying, the sodium silicate becomes a solid and adheres to the inner wall of the conductive aggregate. (2) Dry mix the cementitious material, nano-repair additive, and conductive aggregate with adhering sodium silicate for 2-5 minutes; (3) Add water-reducing agent and water, and stir for 3-6 minutes; (4) Add fiber and stir at medium-low speed for 2-4 minutes; (5) After casting, it shall be cured for at least 28 days at a temperature of 20±2℃ and a humidity of ≥95%.

9. The method for preparing crack-controlled self-healing intelligent ultra-high durability concrete according to claim 8, characterized in that, In step (2), the dry mixing speed is 40-60 rpm; in step (3), the stirring speed is 40-60 rpm; and in step (4), the medium-low speed stirring speed is 20-30 rpm.

10. The application of the crack-controlled self-healing intelligent ultra-high durability concrete as described in any one of claims 1-7, characterized in that, It is applied in marine engineering and offshore infrastructure, engineering in saline-alkali land areas, transportation facilities, and energy and nuclear power engineering.

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