Self-repairing special concrete and preparation method thereof

Abstract

The invention relates to the field of building materials, and particularly discloses a self-repairing special concrete and a preparation method thereof, the self-repairing special concrete comprises the following raw materials by weight: 40-80 parts of cement, 60-100 parts of gravel, 70-90 parts of machine-made sand, 15-25 parts of an admixture, 20-30 parts of a self-repairing material, 2-6 parts of an auxiliary agent, and 20-45 parts of water; the self-repairing material is prepared by the following steps: uniformly dispersing a repairing material in a water-soluble coating material, adding a wetting agent, shearing, emulsifying and homogenizing to form a stable emulsion, and spray-drying to form microcapsules; adding the microcapsules into a polylactic acid solution, carrying out ultrasonic oscillation and mixing, and emulsifying, curing and centrifuging the mixed solution to obtain the self-repairing material. The preparation method of the self-repairing special concrete comprises the following step: uniformly stirring and mixing the cement, the broken stones, the machine-made sand, the admixture, the self-repairing material, the auxiliary agent and the water to obtain the self-repairing special concrete. The obtained concrete can automatically repair cracks and cracks, and the repair effect is good.

Description

Technical Field

[0001] The present application relates to the field of building materials, and more specifically, to a self-repairing special concrete and a preparation method thereof. Background Art

[0002] Concrete cracking is the most common form of concrete structural failure. Failure to promptly repair cracks can lead to extensive damage to the concrete, severely impacting its lifespan. Therefore, employing high-performance repair materials is crucial for improving the safety and extending the service life of concrete projects. While concrete cracks are inevitable, their microscopic nature is determined by the concrete's physical and mechanical properties, their harmfulness can be controlled.

[0003] Concrete, the world's most widely used and most versatile building material, is prone to various cracks during use. Shrinkage cracks, caused by uneven humidity levels and evaporation, are particularly common, affecting not only the exterior appearance of the project but also the durability of the concrete. Controlling concrete cracks in construction projects typically involves post-repair and scheduled maintenance. This passive approach is not only labor-intensive and resource-intensive, but may also be ineffective for repairing fine cracks. In recent years, the research and development of intelligent concrete repair materials capable of autonomously repairing damaged concrete and extending the service life of concrete structures has become a trend in concrete repair materials.

[0004] Currently, there are three main types of materials used to repair concrete cracks: inorganic repair materials, primarily cement-based repair materials formulated with specialized cements. However, these materials suffer from significant shortcomings, including large shrinkage, poor impermeability, inability of the slurry to reach the intended repair area, and susceptibility to salt and alkali. Organic polymer materials, such as epoxy resins, polyurethanes, and acrylic acid, also lack the ability to repair microcracks due to the high viscosity of epoxy resins. Therefore, developing self-healing concrete is crucial. Summary of the Invention

[0005] The present application provides a self-repairing special concrete and a preparation method thereof, which can automatically repair cracks and fissures under the action of humidity difference when cracks occur in the concrete.

[0006] In the first aspect, the present application provides a self-repairing special concrete adopting the following technical solutions: A self-repairing special concrete comprises the following raw materials in parts by weight: 40-80 parts of cement, 60-100 parts of crushed stone, 70-90 parts of machine-made sand, 15-25 parts of admixture, 20-30 parts of self-repairing material, 2-6 parts of additive, and 20-45 parts of water; The self-repairing material is prepared by the following steps: uniformly dispersing the repairing material in the water-soluble coating material, adding a wetting agent, shearing and emulsifying to form a stable emulsion, and spray drying to form microcapsules; The microcapsules are added into the polylactic acid solution, ultrasonically shaken and mixed, and the mixture is emulsified, solidified and centrifuged to obtain the self-repairing material.

[0007] By adopting the above technical solution, cement provides the main gelling effect, crushed stone and machine-made sand are used as basic aggregates, and admixtures are used to fill pores and participate in the volcanic ash reaction, thereby improving the density of the concrete, the mechanical properties of the material, and the self-healing function of cracks.

[0008] Water-soluble microcapsules with uniform particle size are formed through an emulsification-spraying process. The microcapsules are used as the core, and a hydrophobic shell is formed after solidification with a polylactic acid solution, so as to protect the core microcapsules during the mixing process with water and cement. When cracks appear, the shell breaks after being subjected to micro-stress. The water-soluble microcapsules dissolve in water during humidity changes, releasing repair materials to fill the cracks, thereby achieving self-repair.

[0009] Preferably, the amounts of raw materials used in the self-repairing material are as follows, in parts by weight: 4-9 parts of repairing material, 3-10 parts of water-soluble coating material, 0.5-1 part of wetting agent, and 3-8 parts of polylactic acid solution.

[0010] By adopting the above technical solution, the ratio of the repair material, water-soluble coating material, wetting agent, and polylactic acid solution is optimized, making the preparation process of the self-healing material more stable and the resulting dual structure uniform, improving the material's encapsulation efficiency and stability. This allows the formed microcapsules to effectively coat the repair material, ensuring effective encapsulation while avoiding excessive wall thickness that affects release efficiency, ensuring a balance between the strength and toughness of the microcapsules, and facilitating the formation of a stable and uniform core that can both rupture and release the repair material in the event of damage and maintain structural integrity when intact. The wetting agent further improves the dispersibility of the repair material and enhances the emulsification and homogenization effect. The use of polylactic acid prevents the polylactic acid shell from prematurely rupturing the microcapsule core during concrete mixing and hardening, ensuring the self-healing material's repair effect.

[0011] Preferably, the water-soluble coating material is water-soluble polyvinyl alcohol.

[0012] By adopting the above technical solution, water-soluble polyvinyl alcohol is used as the coating material, which has good film-forming properties and compatibility, can enhance the mechanical strength of the microcapsules, and at the same time ensure the release of the repair material when it comes into contact with water.

[0013] Preferably, the wetting agent is one of Tween 80, sodium alkylbenzene sulfonate, and nonylphenol polyoxyethylene ether.

[0014] Furthermore, the wetting agent is preferably Tween 80.

[0015] By adopting the above technical solution, the wetting agent can effectively reduce the interfacial tension, form a uniform emulsion, prevent particle agglomeration, and at the same time enhance the stability of the microcapsules, further improving the self-healing effect.

[0016] Preferably, the repair material includes at least two of silicon dioxide, calcium oxide, calcium sulfoaluminate, and magnesium oxide.

[0017] Preferably, the repair material is a mixture of silicon dioxide, calcium oxide, calcium sulfoaluminate and magnesium oxide in a mass ratio of 0.8:(0.5-1):(1-2):(0.8-1.5).

[0018] By adopting the above technical solution, calcium oxide reacts with water to form calcium hydroxide, which squeezes cracks and closes them. The pozzolanic reaction of silica consumes calcium hydroxide to produce a gelling hydration product, enhancing density over the long term. Calcium sulfoaluminate reacts with water to quickly form ettringite, which fills cracks. The hydration reaction of magnesium oxide produces a certain amount of expansion, compensating for shrinkage stress and preventing secondary cracking. The various reaction products interweave to form a denser repair structure, achieving rapid hardening, short- to medium-term expansion, and long-term stability. Further optimizing the ratios between the repair material components will maximize the synergistic effect between the various repair materials, achieve better repair results, and enhance the self-healing ability of concrete.

[0019] Preferably, the auxiliary agent includes one or both of polycarboxylate water reducer and sodium lignin sulfonate.

[0020] By adopting the above technical solution and using polycarboxylate water reducer or sodium lignin sulfonate as an additive, the water consumption of the concrete mixture can be effectively reduced, the fluidity can be improved, and the anti-segregation performance of the concrete can be enhanced, ensuring the uniformity and stability of the mixture during the construction process. This not only helps to improve the workability of the concrete, but also improves the density and strength of the final hardened concrete.

[0021] Preferably, the admixture includes one or more of fly ash, silica fume, and slag powder.

[0022] Furthermore, the admixtures are preferably fly ash and silica fume.

[0023] By adopting the above technical solution, the addition of admixtures not only reduces the amount of cement used, but also further enhances the density of concrete, thereby improving the crack resistance and later strength development of concrete.

[0024] In the second aspect, the present application provides a method for preparing self-repairing special concrete, which adopts the following technical solution: a method for preparing self-repairing special concrete, comprising the following steps: mixing cement, machine-made sand, gravel, admixtures, self-repairing materials, additives and water and stirring them evenly.

[0025] By adopting the above technical solution, the prepared concrete has excellent self-repairing ability, automatically repairs when micro cracks appear, and the service life of the concrete is long.

[0026] In summary, this application has the following beneficial effects: This application uses water-soluble polyvinyl alcohol as the coating material. The repair material is encapsulated through microcapsules and combined with polylactic acid solution to form a stable shell to ensure the uniform dispersion of the self-repairing material in the concrete matrix. When cracks appear in the concrete, the cracks and cracks are automatically and accurately repaired under the action of humidity difference. DETAILED DESCRIPTION

[0027] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0028] Preparation of self-healing materials Preparation Example 1 The self-healing material was prepared by the following steps: 4 kg of the repair material was uniformly dispersed in 3 kg of water-soluble polyvinyl alcohol, 0.5 kg of a wetting agent was added, shear emulsification and homogenization were performed to form a stable emulsion, and then spray-dried to form microcapsules; the repair material was silicon dioxide and calcium oxide in a mass ratio of 0.8:1, and the wetting agent was sodium alkylbenzene sulfonate; The microcapsules were added to 3 kg of a polylactic acid solution with a mass concentration of 8%, and the mixture was evenly mixed under ultrasonic oscillation at 100 W to obtain a mixed solution. The mixed solution was sheared and emulsified at a speed of 2000 rpm, heated to 70°C for curing, and then centrifuged to obtain a self-healing material.

[0029] Preparation Example 2 The self-healing material was prepared by the following steps: 9 kg of the repair material was evenly dispersed in 10 kg of water-soluble polyvinyl alcohol, 1 kg of a wetting agent was added, shear emulsification was homogenized to form a stable emulsion, and then spray-dried to form microcapsules; the repair material was composed of calcium sulfoaluminate, magnesium oxide, and nonylphenol polyoxyethylene ether in a mass ratio of 1:1.5; The microcapsules were added to 8 kg of a 5% polylactic acid solution, and the mixture was evenly mixed by ultrasonic oscillation at 150W to obtain a mixed solution. The mixed solution was sheared and emulsified at a speed of 1500 rpm, heated to 80°C for curing, and then centrifuged to obtain a self-healing material.

[0030] Preparation Example 3 The difference from Preparation Example 1 is that 8 kg of repair material, 7.5 kg of water-soluble polyvinyl alcohol, 0.6 kg of wetting agent, and 7 kg of polylactic acid solution are used. The rest are the same as Preparation Example 1.

[0031] Preparation Example 4 The difference from Preparation Example 3 is that the repair material is a mixture of silicon dioxide, calcium oxide, calcium sulfoaluminate, and magnesium oxide in a mass ratio of 0.8:0.5-1:2:0.8, the wetting agent is Tween 80, and the rest is the same as Preparation Example 3.

[0032] Preparation Example 5 The difference from Preparation Example 3 is that the repair material is a mixture of silicon dioxide, calcium oxide, calcium sulfoaluminate, and magnesium oxide in a mass ratio of 1:0.3:3:0.4, and the rest is the same as Preparation Example 3. Example

[0033] Example 1 The self-repairing special concrete includes the following raw materials: 40 kg of cement, 60 kg of continuously graded crushed stone with a particle size of 5-20 mm, 70 kg of machine-made sand with a fineness modulus of 2.6-2.9, 15 kg of admixture, 20 kg of the self-repairing material prepared in Preparation Example 1, 2 kg of additives, and 20 kg of water; the admixture is micron-grade fly ash, and the additive is a polycarboxylate water reducer.

[0034] The preparation method of the self-repairing special concrete is: cement, crushed stone, machine-made sand, admixture, self-repairing material, additive and water are stirred and mixed uniformly.

[0035] Example 2 The self-repairing special concrete includes the following raw materials: 80 kg of cement, 100 kg of continuously graded crushed stone with a particle size of 5-20 mm, 90 kg of machine-made sand with a fineness modulus of 2.6-2.9, 25 kg of admixture, 30 kg of the self-repairing material prepared in Preparation Example 1, 6 kg of additives, and 45 kg of water; the admixture is micron-graded slag powder, and the additive is sodium lignin sulfonate.

[0036] The preparation method is the same as that in Example 2.

[0037] Example 3 The self-repairing special concrete includes the following raw materials: 65 kg of cement, 90 kg of continuously graded crushed stone with a particle size of 5-20 mm, 85 kg of machine-made sand with a fineness modulus of 2.6-2.9, 20 kg of admixture, 25 kg of the self-repairing material prepared in Preparation Example 1, 4 kg of additives, and 38 kg of water; the admixtures are 15 kg of silica fume and 5 kg of slag powder, and the additive is sodium lignin sulfonate.

[0038] The preparation method is the same as that in Example 2.

[0039] Example 4 The difference from Example 3 is that the self-repairing material prepared in Preparation Example 2 is selected, and the rest is the same as Example 3.

[0040] Example 5 The difference from Example 3 is that the self-repairing material prepared in Preparation Example 3 is selected, and the rest is the same as Example 3.

[0041] Example 6 The difference from Example 3 is that the self-repairing material prepared in Preparation Example 4 is selected, and the rest is the same as Example 3.

[0042] Example 7 The difference from Example 3 is that the self-repairing material prepared in Preparation Example 5 is selected, and the rest is the same as Example 3.

[0043] Example 8 The difference from Example 5 is that the admixtures are 10 kg of silica fume and 10 kg of fly ash, and the rest are the same as Example 5.

[0044] Comparative Example Comparative Example 1 The difference from Example 8 is that the self-repairing material is prepared by the following steps: uniformly dispersing the repair material in the water-soluble coating material, adding a wetting agent, shearing and emulsifying to form a stable emulsion, and spray drying to form a microcapsule repair material; the rest is the same as Example 8.

[0045] Comparative Example 2 The difference from Example 8 is that the repair material is silicon dioxide, and the rest is the same as Example 8.

[0046] Comparative Example 3 The difference from Example 8 is that the admixtures are 5 kg of slag powder and 5 kg of self-repairing material, and the rest are the same as Example 8.

[0047] Performance testing Concrete specimens were prepared using the concrete prepared in Examples 1-8 and Comparative Examples 1-3, as well as a blank control group, where the blank control group did not contain the self-healing material. During the preparation of the concrete specimens, a 0.3 mm diameter string was placed in the test mold and removed after initial setting to form pre-cracks. Curing conditions were: 25±2°C, 95% humidity. After 56 days of curing, the specimens were observed for cracks throughout. Cracks were observed using a standard magnifying glass with an accuracy of 0.05 mm. Crack widths were measured using a crack width gauge, and the number of cracks and the maximum crack width were recorded.

[0048] Table 1 Number of cracks Maximum crack width Example 1 2 0.1 Example 2 3 0.08 Example 3 2 0.06 Example 4 2 0.07 Example 5 1 0.07 Example 6 2 0.08 Example 7 3 0.1 Example 8 1 0.05 Comparative Example 1 12 0.26 Comparative Example 2 16 0.37 Comparative Example 3 9 0.12 Blank control group 18 0.5 From Examples 1-8 and Table 1, it can be seen that the concrete prepared using the specific raw material components of the present application can effectively and automatically repair cracks and fissures, so that the concrete has good crack resistance and self-repairing capabilities.

[0049] Through Example 8 and Comparative Example 1 and in combination with Table 1, it can be seen that when microcapsules are directly used as self-repairing materials, since the microcapsules begin to dissolve when they come into contact with water, the repair material begins to be released, and instead participates in the hardening process of the concrete rather than the subsequent crack repair process. Since the repair material can participate in reactions such as cement hydration, the density of the concrete is increased, but it is inevitable that cracks will appear on the concrete itself after curing, and the pre-cracks formed cannot be repaired well. Through Example 8 and Comparative Example 2 and in combination with Table 1, it can be seen that only silica is used as a repairing material, and a single silica cannot independently achieve efficient self-repair, so that the number of concrete cracks and cracks is large, and the maximum width of the cracks is wide. Through Example 8 and Comparative Example 3 and in combination with Table 1, it can be seen that there are too few admixtures and self-repairing materials in Comparative Example 3, so that the density of the concrete itself is poor, and the repair effect on pre-cracks and cracks formed by itself is poor. It can be seen that this application uses cement to provide the main gelling effect, crushed stone and machine-made sand as basic aggregates, and admixtures to fill pores and participate in volcanic ash reactions, thereby increasing the density inside the concrete, improving the mechanical properties of the material, and realizing the self-healing function of cracks through self-repairing materials.

[0050] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A self-repairing special concrete, characterized in that: The raw materials include the following parts by weight: 40-80 parts of cement, 60-100 parts of crushed stone, 70-90 parts of machine-made sand, 15-25 parts of admixture, 20-30 parts of self-repairing material, 2-6 parts of additives, and 20-45 parts of water; The self-repairing material is prepared by the following steps: uniformly dispersing the repairing material in the water-soluble coating material, adding a wetting agent, shearing and emulsifying to form a stable emulsion, and spray drying to form microcapsules; The microcapsules are added into the polylactic acid solution, ultrasonically shaken and mixed, and the mixture is emulsified, solidified and centrifuged to obtain the self-repairing material.

2. The self-repairing special concrete according to claim 1, characterized in that: The raw materials used in the self-repairing material are used in the following amounts by weight: 4-9 parts of repairing material, 3-10 parts of water-soluble coating material, 0.5-1 part of wetting agent, and 3-8 parts of polylactic acid solution.

3. The self-repairing special concrete according to claim 2, characterized in that: The water-soluble coating material is water-soluble polyvinyl alcohol.

4. The self-repairing special concrete according to claim 3, characterized in that: The wetting agent is one of Tween 80, sodium alkylbenzene sulfonate and nonylphenol polyoxyethylene ether.

5. The self-repairing special concrete according to claim 1, characterized in that: The repairing material includes at least two of silicon dioxide, calcium oxide, calcium sulfoaluminate, and magnesium oxide.

6. The self-repairing special concrete according to claim 5, characterized in that: The repair material is a mixture of silicon dioxide, calcium oxide, calcium sulfoaluminate and magnesium oxide in a mass ratio of 0.8:(0.5-1):(1-2):(0.8-1.5).

7. The self-repairing special concrete according to claim 1, characterized in that: The auxiliary agent includes one or both of polycarboxylic acid water reducer and sodium lignin sulfonate.

8. The self-repairing special concrete according to claim 1, characterized in that: The admixture includes one or more of fly ash, silica fume and slag powder.

9. The method for preparing the self-repairing special concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: The cement, machine-made sand, crushed stone, admixture, self-repairing material, additive and water are mixed and stirred uniformly.