Multifunctional capsule for concrete in arid regions, preparation method and application thereof

Abstract

This invention relates to the field of civil engineering materials technology, disclosing a multifunctional capsule for concrete in arid regions, its preparation method, and its application. The multifunctional capsule comprises a core and a capsule wall. The core includes sodium alginate and graphene oxide, enabling water retention in the concrete. The capsule wall is formed by cross-linking sodium alginate, graphene oxide, and a cement ion mixture to create a three-dimensional network structure, constructing a slow-release water channel. In preparation, the core raw materials are first mixed to obtain a viscous slurry, which is then extruded, spheroidized, and dried to obtain a preform. This preform is then immersed in a cement ion mixture for cross-linking reaction and dried to obtain the finished product. This capsule can significantly improve the water retention capacity of concrete, achieve multiple self-repair of cracks, adapt to arid conditions, and extend the service life of concrete.

Description

Technical Field

[0001] This invention relates to the field of civil engineering materials technology, specifically to a multifunctional capsule for concrete in arid regions, its preparation method, and its application. Background Technology

[0002] Concrete, as the most widely used building material globally, boasts advantages such as low cost, good fire resistance, and high rigidity. However, its brittleness, low tensile strength, and numerous inherent defects inevitably lead to microcracks during use due to loads, temperature changes, or shrinkage. The presence of cracks accelerates the penetration of moisture and harmful ions, which in turn cause steel corrosion, freeze-thaw damage, and chemical erosion, significantly reducing the durability and service life of concrete structures. Globally, durability damage caused by cracks in existing concrete infrastructure results in annual economic losses exceeding hundreds of billions of US dollars. Crack-induced durability degradation generates approximately 1.2 billion tons of demolition waste globally each year. Extending structural lifespan by 20 years through crack control technology can reduce carbon emissions from cement production by more than 30%. Therefore, researchers have developed various self-healing capsules.

[0003] Existing technologies disclose a self-healing microbial concrete and its crack repair method, which uses a histidine-urea composite substrate and a pH-responsive slow-release carrier as the microbial carrier. This invention, through the synergistic design of the histidine-urea composite substrate and the pH-responsive slow-release carrier, constructs a microbial metabolic microenvironment regulation system, achieving gradient repair of cracks from the surface inwards. It also discloses a concrete crack repair method and system based on silica gel-immobilized microorganisms, using a microbial suspension, silica gel, and nutrients as the microbial carrier. The microbial suspension is mixed with silica gel to form a silica gel immobilized with microorganisms; the silica gel immobilized with microorganisms and nutrients are then injected into the concrete cracks to complete the crack repair. While the above patents offer some assistance in repairing concrete cracks and are applicable to most scenarios, they lack sufficient water-locking capacity, and the healing methods cannot be used for multiple repairs, significantly increasing secondary construction costs and causing unnecessary resource waste. Furthermore, their specificity is relatively weak, only suitable for normal environments, with limited application in extremely arid environments. Therefore, this invention develops a novel method for preparing a multifunctional capsule. Summary of the Invention

[0004] The purpose of this invention is to provide a multifunctional capsule for concrete in arid regions, its preparation method, and its application, in order to solve the technical problems of water retention and self-repair of concrete cracks in arid regions.

[0005] The technical solution of the present invention is as follows:

[0006] A multifunctional capsule for concrete in arid regions includes a core and a capsule wall covering the core;

[0007] The core comprises the following raw materials in parts by weight: 20-30 parts sodium alginate powder and 0-0.5 parts graphene oxide.

[0008] The capsule wall is a three-dimensional network structure formed by cross-linking of sodium alginate, graphene oxide, and cement ion mixture.

[0009] Further optimization is achieved by setting the molar ratio of mannolic acid to gulonic acid in the sodium alginate molecule to be 1:1, 1:2, or 2:1.

[0010] Further optimization involves making the functional capsules spherical with a particle size of 0.5-5 mm.

[0011] A method for preparing a multifunctional capsule for concrete in arid regions includes the following steps:

[0012] S1. Mix sodium alginate powder and graphene oxide powder separately;

[0013] S2. Add water to the mixture in step S1 and stir until a uniform and viscous slurry is formed.

[0014] S3. The slurry is processed and granulated by an extrusion roller to form wet spherical particles, which are then dried to obtain spherical preforms.

[0015] S4. Prepare a cement ion mixture with a mass concentration of 5-15%, add spherical preforms to it, and disperse it by ultrasonication to obtain a crosslinking liquid;

[0016] S5. Immerse the spherical preform in the cross-linking solution at 20-30℃ for 10-30 minutes, drain and dry to obtain the multifunctional capsule.

[0017] In a further optimization, the cement ion mixture in step S2 is prepared by mixing cement and deionized water at a mass ratio of 1:10-50.

[0018] The application of a multifunctional capsule in improving the water-locking and self-healing properties of concrete in arid regions, which is used to enhance the water-locking capacity of concrete in arid Northwest China and enable multiple self-healing of cracks.

[0019] Further optimization involves adding the functional capsule at a dosage of 1-15% of the cement mass in the concrete.

[0020] Further optimization resulted in a water-cement ratio of 0.3-0.4 and a cement-sand ratio of 1:2-3 for the concrete.

[0021] Further optimization is made so that the application targets concrete crack widths of 300-400μm.

[0022] The beneficial effects of this technical solution are:

[0023] 1. The capsule core utilizes sodium alginate, which actively adsorbs and stores a large amount of water. The introduced graphene oxide, with its high specific surface area and oxygen-containing functional groups, enhances water absorption capacity. Its layered structure constructs water-releasing channels, achieving gradient water release and slowing down water evaporation. These two elements work synergistically to achieve gradient water retention. The capsule wall is a three-dimensional network structure formed by the cross-linking of sodium alginate, graphene oxide, and a cement ion mixture. This dense three-dimensional network structure not only locks in a certain amount of water but also provides a certain degree of strength. This gradient water retention mode can continuously and stably supply the water required for the repair reaction in arid environments, solving the problem of rapid water loss in traditional capsules.

[0024] 2. The three-dimensional network of the capsule wall can prevent the core repair agent from reacting prematurely and prevent rapid water loss in arid environments, thus ensuring long-term repair potential. After the capsule ruptures, the gradient released water reacts with the active functional groups of sodium alginate to generate repair products such as calcium silicate hydrate to fill the cracks. The release amount of the repair agent can be intelligently controlled, and the remaining dose is reserved for later use. When the concrete cracks again, the secondary repair is initiated without the need for secondary construction, which greatly reduces the project maintenance cost.

[0025] 3. Using sodium alginate as the core repair agent, it is green and environmentally friendly without secondary pollution. Compared with traditional chemical repair agents, it has stronger biocompatibility and environmental friendliness. The repair products generated by its hydration reaction have high strength and good stability, and the crack repair efficiency is significantly improved.

[0026] 4. The combination of gradient water retention and multiple repair functions effectively prevents moisture and harmful ions from penetrating the concrete interior, delays steel corrosion, freeze-thaw damage and other diseases, and significantly extends the service life of concrete structures. This feature reduces the generation of fertilizers from building demolition and lowers carbon emissions from cement production. It has both economic value and ecological benefits and is of great significance for infrastructure construction in arid regions. Attached Figure Description

[0027] Figure 1 These are morphological images of the multifunctional capsule of the present invention repairing cracks in cement mortar, wherein A is an unrepaired image of the crack with the functional capsule in Example 1, and B is an image of the crack repair effect with the functional capsule in Example 1. Figure 2 This is a diagram showing the multiple self-encapsulation of the multifunctional capsule of the present invention in cement mortar; Figure 3 This is an XRD pattern of the multifunctional capsule of the present invention at the cement mortar interface. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0032] Example 1

[0033] A multifunctional capsule for concrete in arid regions includes a core and a capsule wall covering the core. The core comprises sodium alginate and graphene oxide; the capsule wall is a three-dimensional network structure formed by cross-linking sodium alginate and hydration products of a cement ion mixture. The multifunctional capsule is spherical with a particle size of 0.5-5 mm.

[0034] The specific proportions of each raw material, by weight, are as follows:

[0035] Sodium alginate: 25g, the molar ratio of mannuronic acid to gulonic acid in its molecule is 1:2;

[0036] Deionized water: 150mL;

[0037] The concentration of the cement ion-mixed liquor is 10%, of which the mass of cement is 15g and the mass of deionized water is 150g.

[0038] Graphene oxide: 0g.

[0039] The cement used is silicate reference cement with a strength grade of P·I 42.5 produced by the China Building Materials Academy.

[0040] Prepared by the following steps:

[0041] Mix 25g of sodium alginate powder thoroughly to obtain a mixture;

[0042] Weigh 15g of cement and 150g of deionized water, stir to prepare a cement ion mixture with a concentration of 10%, and ultrasonically disperse at 250W power for 30min to obtain a crosslinked liquid of sodium alginate and cement ion mixture.

[0043] 3. Slowly add sodium alginate to 150mL of deionized water, keeping the mechanical stirrer speed at 50r / min, the water addition rate at 20g / min, and the dripping time at 6min. Continue stirring until a uniform, particle-free viscous slurry is formed.

[0044] 4. Place the viscous slurry in an extrusion spheroidizer, set the equipment diameter to 1.5 mm, the rotation speed to 200 r / min, and the granulation time to 6 min to form wet spherical particles. Spread the particles evenly on a tray and place them in an electric heating drying oven. Dry at 60℃ for 3 h to obtain a spherical preform.

[0045] 5. Immerse the spherical preform in the crosslinking solution at a temperature of 25℃ for 20 minutes. During this time, Ca²⁺ in the cement ion mixture and Na⁺ in sodium alginate undergo ion exchange, forming a three-dimensional network structure in the capsule wall to achieve gradient water release.

[0046] 6. After soaking, remove the preform and drain for 10 minutes. Then put it back into the electric heating drying oven and dry at 60℃ for 3 hours to obtain the gradient water-retaining multifunctional capsule.

[0047] The application parameters for this capsule are as follows:

[0048] The capsule dosage is 5% of the cement filtrate mass;

[0049] The corresponding cement paste has a water-cement ratio of 0.35 and a cement-sand ratio of 1:2.

[0050] The width of precast concrete cracks is 300~400μm;

[0051] The capsules were immersed and cured in simulated cement slurry for 28 days.

[0052] Application results show that the sodium alginate and graphene oxide in the core achieve gradient water locking, increasing the water storage capacity by 40% compared to the original solution; the slow-release channel constructed by the mixture of sodium alginate, graphene oxide, and cement ions in the core wall extends the water release time to 10 days; the crack repair efficiency is improved by 30%, which can support 4-5 repeated repairs and is suitable for the long-term curing needs of concrete in arid areas.

[0053] Example 2

[0054] The difference between this embodiment and Embodiment 1 is that the multifunctional capsule used in concrete in arid Northwest China has an admixture content of 10% of the cement ion mixture and a graphene oxide content of 0.075g, accounting for 3% of the mass of sodium alginate.

[0055] Example 3

[0056] The difference between this embodiment and Embodiment 1 is that the multifunctional capsule used in concrete in arid Northwest China has an admixture dosage of 15% of the cement ion mixture and a graphene oxide content of 0.075g, accounting for 3% of the mass of sodium alginate.

[0057] Comparative Example

[0058] A cement mortar with a water-cement ratio of 0.35 and a cement ion concentration of 10% was prepared without the addition of the multifunctional capsules prepared in Example 1. Cracks with a width of 300-400 µm were pre-formed in the cement mortar. The cement mortar specimens with cracks were placed in a simulated Northwest China region for curing for 28 days without additional water during the curing period.

[0059] Referring to the test methods of Examples 1-3, the crack repair, water-locking ability, and product composition of the comparative specimen were simultaneously tested: the crack repair of the cement mortars of Examples 1-3 and the comparative specimens after immersion curing was observed, and morphological crack repair images were taken, such as... Figure 1 As shown; observations and measurements revealed that cement mortar possesses multiple repair capabilities in arid regions, such as... Figure 2 As shown, X-ray diffraction (XRD) analysis revealed that the multifunctional capsule can promote the formation of various repair products such as calcium silicate hydrate at the crack site, thereby achieving effective and repeated repair of microcracks.

[0060] Results Analysis: Based on Figure 1-2 The results show that the incorporation of multifunctional capsules can significantly improve the water-locking capacity of concrete and the effect of multiple crack repairs, with the most significant effect observed at a dosage of 15%. According to... Figure 3The results show that the incorporation of multifunctional capsules significantly enriches the variety of repair products, including the reaction that generates various repair products such as calcium silicate hydrate, strongly demonstrating the significant repair effect of multifunctional capsules in cement-based materials. Therefore, the multifunctional capsules of this invention for concrete in Northwest China provide a reliable solution for improving the durability and self-healing ability of concrete structures in arid environments, greatly promoting the research and application of self-healing concrete in the region.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A multifunctional capsule for concrete in arid regions, characterized in that, Includes a core and a wall covering the core; The core comprises the following raw materials in parts by weight: 20-30 parts sodium alginate powder; 0-0.5 parts graphene oxide. The capsule wall is a three-dimensional network structure formed by cross-linking a mixture of sodium alginate, graphene oxide, and cement ions.

2. The multifunctional capsule for concrete in arid regions according to claim 1, characterized in that, The molar ratio of mannolic acid to gulonic acid in the sodium alginate molecule is 1:1, 1:2, or 2:

1.

3. The multifunctional capsule for concrete in arid regions according to claim 1, characterized in that, The capsules are spherical with a particle size of 0.5-5 mm.

4. A method for preparing a multifunctional capsule for concrete in arid regions, characterized in that, Includes the following steps: S1. Mix sodium alginate powder and graphene oxide powder separately; S2. Add water to the mixture in step S1 and stir until a uniform and viscous slurry is formed. S3. The slurry is processed and granulated by an extrusion roller to form wet spherical particles, which are then dried to obtain spherical preforms. S4. Prepare a cement ion mixture with a mass concentration of 5-15%, add spherical preforms to it, and disperse it by ultrasonication to obtain a crosslinking liquid; S5. Immerse the spherical preform in the cross-linking solution at 20-30℃ for 10-30 minutes, drain and dry to obtain the multifunctional capsule.

5. The preparation method according to claim 4, characterized in that, In step S2, the cement ion mixture is prepared by mixing cement and deionized water at a mass ratio of 1:10-50.

6. The application of the multifunctional capsule as described in any one of claims 1-3 in improving the water-locking and self-healing properties of concrete in arid regions, characterized in that, It is used to improve the water-locking capacity of concrete in arid Northwest China and to enable multiple self-repair of cracks.

7. The application according to claim 6, characterized in that, The dosage of the functional capsule is 1-15% of the cement mass in the concrete.

8. The application according to claim 6, characterized in that, The concrete has a water-cement ratio of 0.3-0.4 and a cement-sand ratio of 1:2-3.

9. The application according to claim 6, characterized in that, The application targets concrete cracks with a width of 300-400 μm.

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