CN115417618B - Anionic curing expansion microcapsule and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of material science and engineering, and particularly relates to an anion curing expansion microcapsule and a preparation method and application thereof. The anion curing expansion microcapsule comprises a wall material and a core material; wherein the wall material is calcium alginate, and the core material is an anionic curing agent. The anion curing expansion microcapsule has high mechanical property and high anion curing efficiency, and can be rapidly expanded and plugged to play a role in repairing when the salt solution invades; the microcapsule shell can be used as a self-curing material of concrete, can reduce the shrinkage of a matrix, improve the freeze thawing resistance and cracking resistance, and effectively improve the strength of a cement stone matrix; the three-dimensional network structure of the microcapsule shell greatly increases the contact area between the microcapsule shell and the anionic curing agent, increases the anionic curing efficiency, prolongs the curing period, improves the sulfate erosion resistance and chloride ion permeation resistance of the concrete, and improves the durability of the concrete.

Description

Anion-cured expanded microcapsules, preparation method and application thereof

technical field

The invention belongs to the technical field of material science and engineering, and in particular relates to an anion-cured expansion microcapsule and its preparation method and application.

Background technique

Concrete structures are widely used in various civil engineering projects, and are usually obtained by mixing cement with sand and gravel as aggregate, adding water and other admixtures. The embedding of steel bars can further enhance the mechanical properties of concrete such as tensile strength, ductility and crack resistance. However, with the rise of my country's marine industry and the development of marine engineering, the demand for high-performance reinforced concrete structures has increased significantly. Corrosion of steel bars in the marine environment is serious, leading to a decrease in the safety and durability of concrete structures, causing serious economic losses, environmental pollution, and waste of resources.

The pore solution remains highly alkaline in the unpolluted concrete environment, and there is a stable passivation film on the surface of the steel bar, and the corrosion rate is lower than 0.1μAcm ^-2 . However, the concentration of corrosive chloride ions in the marine environment increases, and the chloride ions penetrate into the concrete through various functions such as capillary action, diffusion, and electrochemical migration, thereby reducing the resistivity of the concrete, affecting the pH of the local environment, and changing the semiconducting properties of the passivation film, resulting in Reinforcement passivation occurs and corrosion rates increase, ultimately deteriorating the entire reinforced concrete structure.

Concrete sulphate attack is a kind of erosive medium damage with great harm, and it is one of the important factors affecting the durability of concrete. It is also an environmental water erosion with the most complicated influencing factors and the most harmful. The generation of ettringite, gypsum and wollastonite in the process of sulfate attack will cause expansion and damage to concrete, which is the main cause of concrete corrosion damage. The salt minerals produced by the reaction can dissolve or decompose components such as CH and C-S-H in the hardened cement stone, resulting in the loss of cement stone strength and bonding performance. Its erosion forms can be divided into chemical erosion (ettringite, gypsum, molarite crystallization), physical erosion (alkali metal sulfate crystallization) and physical chemical erosion (magnesium sulfate dissolution-crystallization). This results in the destruction of the internal mechanism, which ultimately leads to a reduction in the durability of the concrete.

Corrosion inhibitors are specially used to prevent or delay the corrosion of reinforced concrete to improve the durability of structures. The corrosion inhibitor mainly has the following basic properties: 1. It can inhibit the occurrence and development of corrosion; 2. It does not change the basic properties of concrete; 3. It can maintain long-term effectiveness under alkaline or neutral conditions; 4. It is basically harmless to people. . Inorganic steel rust inhibitors mainly include nitrite, nitrate, chromate, dichromate, phosphate, polyphosphate, silicate, molybdate, borate, etc. Its role is to form a precipitated protective film on the surface of the steel bar to inhibit the corrosion of the steel bar caused by chloride ions. Organic rust inhibitors are mainly amines, aldehydes, acetylenic alcohols, organophosphorus compounds, organosulfur compounds, carboxylic acids and their salts, sulfonic acids and their salts, heterocyclic compounds, etc. The substance enters the interior of the concrete, prolongs the time when the concentration of chloride ions on the surface of the steel bar reaches a critical value, and improves the service life of the concrete. However, the existing corrosion inhibitors react slowly with anions, and cannot quickly block the anion-transmitting medium, so it is difficult to fundamentally solve the problem of steel bar corrosion.

Contents of the invention

Aiming at the defects existing in the prior art, the present invention provides an anion-cured expanded microcapsule and its preparation method and application. The use of the anion-cured expansion microcapsules in concrete can significantly improve the concrete's resistance to sulfate attack and chloride ion penetration, fundamentally solve or alleviate the corrosion problem of steel bars, and greatly extend the structural durability of concrete.

For achieving above object, the technical scheme that the present invention takes is:

An anion-cured expanded microcapsule, which includes a wall material and a core material;

Wherein, the wall material is calcium alginate, and the core material is an anionic curing agent.

In the present invention, the anion curing agent refers to a material having strong adsorption capacity for corrosive ions such as chloride ions and sulfate ions, such as barium carbonate, interlayer hydrotalcite, and the like.

The cured and expanded microcapsules of the present invention use the water-absorbing polymer calcium alginate as the wall material and the anionic curing agent as the core material, which is applied to concrete. When harmful fluids such as seawater invade along tiny cracks, they quickly absorb water and expand to realize short-term leakage repair. , Inhibit harmful fluids from continuously intruding into the concrete interior. When calcium alginate releases water, the anion curing agent embedded in the three-dimensional network structure of calcium alginate begins to absorb harmful anions in the environmental solution. The large contact area and slow water release speed ensure that the anion curing agent and anion The full response of the concrete realizes the "blocking first and then absorbing" of the anion and its transmission medium in the special application scene, fundamentally solves or alleviates the corrosion problem of the steel bar, and greatly prolongs the structural durability of the concrete.

The present invention also finds that by using calcium alginate as the wall material, the mechanical strength of the obtained anion-cured expanded microcapsules is >1N, and after absorbing water, it has elasticity, and is rarely broken during the stirring process of concrete or mortar, while if it is made of urea-formaldehyde, styrene or Phenolic resin and the like are used as wall materials, and the obtained microcapsules are brittle and easily broken during the stirring process, resulting in early release of the core material and failure of the microcapsules.

In addition, calcium alginate is used as the wall material, and the calcium alginate can also be used as a concrete internal maintenance material, which can reduce matrix shrinkage and improve freeze-thaw resistance and crack resistance during the natural maintenance process of concrete, and effectively increase the strength of cement stone matrix.

Preferably, based on the weight of the anion-cured expanded microcapsules, the content of the core material is 30%-55%. The present invention finds that controlling the content of the core material within the above-mentioned range locks the water-absorbing resin, namely calcium alginate, through the core material, causing it to be unable to expand freely, thus avoiding the excessive water-absorbing and swelling of the anion-curing expansion microcapsules of the present invention to form pores and cause concrete mechanical problems. Decreased intensity.

Preferably, the anionic curing agent is selected from one or both of barium carbonate and corrosion-inhibiting hydrotalcite. The present invention finds that compared with other anion curing agents, barium carbonate and corrosion-inhibiting hydrotalcite are used, and the obtained anion-curing expanded microcapsules have better anion-curing performance and lower production cost. Hydrotalcite is an interlayer compound composed of positively charged metal hydroxides and negatively charged anions filled between the layers. Using interlayer ion exchangeability, the anions with anti-corrosion ability are chemically synthesized and inserted into the Corrosion-inhibiting hydrotalcite is prepared between the hydrotalcite layers.

Further preferably, the corrosion-inhibiting hydrotalcite is selected from one or both of aluminum-magnesium-barium hydrotalcite and aluminum-zinc-molybdenum hydrotalcite.

Most preferably, the anionic curing agent is a mixture of barium carbonate and corrosion-inhibiting hydrotalcite in a mass ratio of 2:1 to 5:1. Experiments have found that the compounding of the above two can obtain the best performance of the obtained microcapsules in resistance to sulfate attack and chloride ion penetration.

The corrosion-inhibiting hydrotalcite is preferably prepared by co-precipitation.

The present invention also provides a method for preparing the above-mentioned anion-cured expanded microcapsules, comprising the following steps:

(1) Mix anionic curing agent, dispersant and deionized water, and mix uniformly by ball milling to obtain a mixed solution;

(2) Sodium alginate is dissolved in deionized water to obtain an aqueous wall material solution;

(3) mixing the mixed solution with the wall material aqueous solution to obtain a mixture;

(4) Mix the mixture obtained in step (3) with calcium salt solution, filter, wash, and dry to obtain the anion-cured expanded microcapsules.

Preferably, in step (1), the mass ratio of the anionic curing agent to deionized water is 1:1˜1:2.

As a preference, in the step (1), the amount of the dispersant is 2wt% of the amount of the anion curing agent.

Preferably, in step (1), the dispersant is ammonium polyacrylate and/or sodium hexametaphosphate, and the present invention finds that the anion-cured microcapsules prepared by using the above-mentioned dispersant have the most uniform shape.

Preferably, in step (1), the ball milling method is drum milling, the ball-to-material ratio is 2:1, and the ball milling time is 12 to 36 hours.

Preferably, the step (2) specifically includes: heating the deionized water to 55-70° C., slowly adding sodium alginate powder under stirring, and continuously stirring to obtain an aqueous wall material solution.

Further preferably, in step (2), the mass ratio of the sodium alginate powder to the deionized water is 1:50-1:125, and the continuous stirring time is 30-90 minutes.

Preferably, the step (3) specifically includes: ultrasonically dispersing the mixed solution for a period of time, and then slowly adding the ultrasonically mixed solution into the wall material aqueous solution, and continuously stirring for a period of time.

Further preferably, in step (3), the power of the ultrasonic dispersion is 250W, and the ultrasonic dispersion time is 5-10 minutes.

Further preferably, in step (3), the mass ratio of the anionic curing agent in the mixed solution to the sodium alginate in the wall material aqueous solution is 3.0-6.0:1, and the continuous stirring time is 30-90 minute.

Preferably, the step (4) specifically includes: dropping the mixture obtained in the step (3) into the calcium salt solution, filtering, washing, and drying to obtain anion-cured expanded microcapsules.

As preferably, in step (4), the calcium salt solution is one or both of calcium nitrate solution and calcium lactate solution, the concentration of the calcium salt solution is 1-2%, and the drying temperature is 30 ~40°C.

To sum up, the present invention preferably prepares the mixed liquid by ball milling-ultrasonic technology, mixes the mixed liquid with the wall material aqueous solution evenly, and prepares the anion-cured expanded microcapsules by the orifice forming coagulation bath method. The microcapsule prepared by the method has high content of core material, high mechanical strength of the microcapsule and simple preparation process.

The present invention also provides the application of the above-mentioned anion-cured expansion microcapsules, or the anion-cured expansion microcapsules prepared by the above-mentioned preparation method in the field of concrete, especially the application in reinforced concrete structures for preventing seawater corrosion.

The beneficial effects of the present invention are at least:

1) The anion-cured expansion microcapsules provided by the present invention, the anion-curing agent is coated in the water-absorbing polymer calcium alginate, exerts the function of "blocking first and then absorbing", and improves the resistance of concrete to sulfate erosion and chloride ion penetration, and is Provide strong technical support for special environment applications such as marine engineering.

2) The anion-cured expanded microcapsules provided by the present invention have mechanical strength>1N, and have elasticity after absorbing water, and reduce cracking during the mixing process of concrete or mortar;

3) The anion-cured expansion microcapsules provided by the present invention can be used as an internal curing material in concrete, which has certain anti-cracking and anti-shrinkage effects, thereby improving the durability of concrete;

4) The water absorption rate of the anion-cured expansion microcapsules provided by the present invention is controlled at 40% to 90%, so as to avoid the reduction of the mechanical strength of concrete caused by excessive water absorption and swelling to form pores.

Description of drawings

Fig. 1 is the anion-cured microcapsule (single grain) that embodiment 1 prepares;

Fig. 2 is the anion-cured microcapsule (multiple grain) that embodiment 1 prepares;

Fig. 3 is the sieving result of the anion-cured microcapsules that embodiment 1 prepares;

Figure 4 is the anion-cured microcapsule (single grain) prepared in Comparative Example 1.

Detailed ways

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Without departing from the spirit and essence of the present invention, any modifications or substitutions made to the methods, steps or conditions of the present invention fall within the scope of the present invention.

If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field, or according to the product specification. All reagents or instruments that do not indicate the manufacturer are conventional products that can be purchased through regular channels.

In the following examples,

The preparation method of the magnesium aluminum barium hydrotalcite used: dissolve the aluminum material, barium material and magnesium material with a mass ratio of 20:5:3 in water, adjust the pH to 9, react at 65°C, and then heat at 250°C Roasting to obtain aluminum magnesium barium hydrotalcite; the aluminum material is aluminum nitrate, the magnesium material is magnesium nitrate, and the barium material is barium nitrate.

The preparation method of the aluminum-zinc-molybdenum hydrotalcite used: dissolve the aluminum material, zinc material and molybdenum material with a mass ratio of 20:4.5:6 in water, adjust the pH to 9, react at 65°C, and then heat at 250°C roasting to obtain aluminum-zinc-molybdenum hydrotalcite; the aluminum material is aluminum nitrate, the zinc material is zinc nitrate, and the molybdenum material is molybdenum nitrate.

The dispersant is sodium hexametaphosphate.

Example 1

Weigh 60 parts of barium carbonate and magnesium-aluminum-barium hydrotalcite powder, 90 parts of deionized water, 1.2 parts of dispersant, and 120 parts of agate balls in a mass ratio of 2:1, put them into a ball mill jar and roll and mill for 36 hours. An anion curing agent mixed solution is obtained. Weigh 500 parts of deionized water into the reaction kettle, heat the reaction kettle to 60°C and keep the constant temperature, at a stirring speed of 670r/min, slowly add 8 parts of sodium alginate powder and continue stirring for 90 minutes to obtain sodium alginate solution . Pour the anion curing agent solution into a beaker, and keep it under 250W ultrasonic vibration for 10 minutes to obtain a uniformly dispersed anion curing agent mixture. According to the mass ratio of the anionic curing agent to sodium alginate being 5.5, 110 parts of the anionic curing agent mixed solution were added and stirred continuously for 60 minutes to obtain a milky white mixed solution. Prepare a calcium nitrate solution with a sufficient concentration of 2%, drop the milky white mixed solution into the calcium nitrate solution, filter, wash with water, wash with alcohol and dry at 30°C to obtain anion-cured expanded microcapsules ACM-50. Its anionic curing agent content is 52.37wt%, and its strength is 2.3N (micromechanical testing machine).

Figure 1 shows the anion-cured microcapsules (single grain) prepared in Example 1. The microcapsules are uniform milky white and spherical in shape.

Figure 2 shows the anion-cured microcapsules (multiple particles) prepared in Example 1.

Figure 3 shows the sieving results of the anion-cured microcapsules prepared in Example 1. It can be seen from the figure that the microcapsules with a size of 0-1.18mm account for 1.4% of the total mass ratio, and the microcapsules with a size of 1.18-2.36mm account for the total mass ratio The microcapsules with a size of 2.36-4mm accounted for 28.9% of the total mass ratio.

Example 2

Weigh 60 parts of barium carbonate and aluminum-zinc-molybdenum hydrotalcite powder, 60 parts of deionized water, 1.2 parts of dispersant, and 120 parts of agate balls in a mass ratio of 5:1, put them into a ball mill jar and roll and mill for 12 hours. An anion curing agent mixed solution is obtained. Weigh 400 parts of deionized water into the reactor, heat the reactor to 70°C and keep the temperature constant, slowly add 8 parts of sodium alginate powder at a stirring speed of 670r/min and continue stirring for 90 minutes to obtain a sodium alginate solution . Pour the anionic curing agent solution into a beaker, and keep it under 250W ultrasonic vibration for 5 minutes to obtain a uniformly dispersed anionic curing agent mixed solution. According to the mass ratio of the anionic curing agent to sodium alginate being 3.2, 52 parts of the anionic curing agent mixed solution were added and stirred continuously for 90 minutes to obtain a milky white mixed solution. Prepare a calcium nitrate solution with a sufficient concentration of 1%, drop the milky white mixed solution into the calcium nitrate solution, filter, wash with water, wash with alcohol and dry at 30°C to obtain anion-cured expanded microcapsules ACZ-30. Its anionic curing agent content is 30.4wt%, and its strength is 1.9N.

Example 3

Weigh 60 parts of barium carbonate, magnesium aluminum barium hydrotalcite, aluminum zinc molybdenum hydrotalcite powder, 120 parts of deionized water, 1.2 parts of dispersant, and 120 parts of agate balls according to the mass ratio of 2:0.5:0.5, and put them into the ball mill After mixing for 12 hours by roller ball milling in a tank, an anion curing agent mixed solution was obtained. Weigh 1,000 parts of deionized water into the reactor, heat the reactor to 55°C and keep the temperature constant, slowly add 8 parts of sodium alginate powder at a stirring speed of 670r/min and continue stirring for 90 minutes to obtain a sodium alginate solution . Pour the anionic curing agent solution into a beaker, and keep it under 250W ultrasonic vibration for 5 minutes to obtain a uniformly dispersed anionic curing agent mixed solution. According to the mass ratio of the anionic curing agent to sodium alginate being 4.5, 108 parts of the anionic curing agent mixed solution were added and stirred continuously for 30 minutes to obtain a milky white mixed solution. Prepare a calcium lactate solution with a sufficient concentration of 1%, drop the milky white mixed solution into the calcium nitrate solution, filter, wash with water, wash with alcohol and dry at 30°C to obtain anion-cured expanded microcapsules ACC-40. Its anionic curing agent content is 42.55wt%, and its strength is 2.9N.

Example 4

The only difference with Example 1 is that the anion curing agent raw material used is 60 parts of barium carbonate.

Anion-cured expanded microcapsules AB-50 were obtained after treatment. Its barium carbonate content is 52.87wt%.

Example 5

The only difference from Example 1 is that the raw material of the anion curing agent used is 60 parts of magnesium aluminum barium hydrotalcite powder.

Anion-cured expanded microcapsules AM-50 were obtained after treatment. Its magnesium aluminum barium hydrotalcite content is 51.36wt%.

Comparative example 1

According to the mass ratio of 2:1, weigh 60 parts of barium carbonate and magnesium aluminum barium hydrotalcite powder, 90 parts of deionized water, no dispersant, and 120 parts of agate balls, put them into a ball mill jar and roll and ball mill them for 36 hours to obtain Anionic curing agent mixed solution. Weigh 500 parts of deionized water into the reaction kettle, heat the reaction kettle to 60°C and keep the constant temperature, at a stirring speed of 670r/min, slowly add 8 parts of sodium alginate powder and continue stirring for 90 minutes to obtain sodium alginate solution . Pour the anion curing agent solution into a beaker, and keep it under 250W ultrasonic vibration for 10 minutes to obtain a uniformly dispersed anion curing agent mixture. According to the mass ratio of anion curing agent to sodium alginate being 4.5, 108 parts of anion curing agent mixed solution were added and stirred continuously for 30 minutes to obtain a mixed solution. Prepare a calcium chloride solution with a sufficient concentration of 2%, drop the mixed solution into the calcium chloride solution, filter, wash with water, wash with alcohol and dry at 30°C to obtain anion-cured expanded microcapsules DBL-50.

Figure 4 shows the anion-cured microcapsules (single grain) prepared in Comparative Example 1. Different from the uniform milky white microcapsules prepared in Example 1, the microcapsules prepared in Comparative Example 1 are uneven in color and unstable in shape. It shows that the uneven dispersion of anionic curing agent will greatly affect the effect of anionic curing, and at the same time cause adverse effects on the performance of concrete. In addition, the use of calcium chloride solution in Comparative Example 1 to solidify the microcapsules will also lead to the failure of the anion curing agent in the microcapsules.

Experimental Example 1 (Marine Concrete Performance Test)

The raw materials of the marine concrete used in the test are as follows:

Raw materials used: P.I 42.5 cement, river sand fineness modulus 2.8, limestone aggregate (5-10mm and 10-20mm two-stage gradation, i.e. pebbles and big pebbles), polycarboxylate water reducer, anion curing expansion of the present invention Agents ACM-50, ACZ-30, ACC-40, AB-50, AM-50 and DBL-50. The formulation of the marine concrete is shown in Table 1 below.

Table 1 Marine concrete mix ratio (kg/m ³ )

cement sand Pebbles Dashizi water Superplasticizer Anionically Cured Microcapsules 420 745 447 670 168 2.8 12.6

The formula of the blank marine concrete is shown in Table 2 below.

Table 2 Mixing ratio of marine concrete blank sample (kg/m ³ )

cement sand Pebbles Dashizi water Superplasticizer 420 745 447 670 168 2.8

According to GB50082-2016, the sulfate corrosion resistance coefficient of concrete after 120 wet and dry cycles and the chloride ion permeability coefficient were tested by RMC method. The results are shown in Table 3.

Table 3 Application effect of anion-cured microcapsules in marine concrete

It can be seen from Table 3 that compared with the blank sample, the sulfuric acid corrosion resistance coefficients of Examples 1 to 4 are all improved, indicating that the content of anionic curing agent in microcapsules has a positive impact on the corrosion resistance of concrete, and through microcapsules The coefficient of sulfuric acid corrosion resistance of concrete has been greatly improved due to the synergistic effect of expansion plugging cracks and anion curing function. The chloride ion permeability coefficients of Example 1, Example 2, Example 3 and Example 5 all decreased, indicating that the microcapsules loaded with hydrotalcite anion curing agent had obvious adsorption to chloride ions. By comparing Example 1, Example 4 and Example 5, it can be known that the sulfate curing ability of barium carbonate is better than hydrotalcite, and the chloride ion curing ability is inferior to hydrotalcite. By compounding it into microcapsules, it can comprehensively improve the resistance of concrete Corrosion ability. During the concrete mixing process, the microcapsules will absorb a certain amount of water and expand, resulting in a decrease in the actual water-binder ratio of the concrete to a certain extent, resulting in a decrease in slump, but the effect is not significant. In addition, the self-curing effect of microcapsules can improve the compressive strength of concrete. However, the DBL-50 microcapsules in Comparative Example 1 did not add dispersant, resulting in non-standard shape and uneven distribution of anionic curing agent, resulting in a certain decrease in the compressive strength and corrosion resistance coefficient of concrete.

The above embodiments are only descriptions of preferred implementations of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, ordinary engineers and technicians in the field may make various modifications to the technical solutions of the present invention. and improvements, all should fall within the scope of protection determined by the claims of the present invention.

Claims (11)

1. An anionically solidified expanded microcapsule comprising a wall material and a core material;

wherein the wall material is calcium alginate, and the core material is an anionic curing agent;

the anionic curing agent is a mixture of barium carbonate and corrosion inhibition hydrotalcite in a mass ratio of 2:1-5:1;

the corrosion inhibition hydrotalcite is one or two selected from aluminum-magnesium-barium hydrotalcite and aluminum-zinc-molybdenum hydrotalcite.

2. The anionically cured expanded microcapsule according to claim 1, wherein the core material is present in an amount of 30% to 55% by weight of the anionically cured expanded microcapsule.

3. A process for preparing an anionically solidified expanded microcapsule according to claim 1 or 2, comprising the steps of:

(1) Mixing an anionic curing agent, a dispersing agent and deionized water, and uniformly mixing by adopting a ball milling method to obtain a mixed solution;

(2) Dissolving sodium alginate in deionized water to obtain a wall material aqueous solution;

(3) Mixing the mixed solution with the wall material aqueous solution to obtain a mixture;

(4) And (3) mixing the mixture obtained in the step (3) with a calcium salt solution, filtering, washing and drying to obtain the anion curing expansion microcapsule.

4. The method according to claim 3, wherein in the step (1), the mass ratio of the anionic curing agent to deionized water is 1:1-1:2;

and/or the dispersant is used in an amount of 2wt% of the amount of the anionic curing agent;

and/or the ball milling method is roller type ball milling, the ball-material ratio is 2:1, and the ball milling time is 12-36 hours.

5. The method according to claim 3 or 4, wherein step (2) comprises: and heating the deionized water to 55-70 ℃, slowly adding sodium alginate powder under stirring, and continuously stirring to obtain a wall material aqueous solution.

6. The preparation method of claim 5, wherein the mass ratio of the sodium alginate powder to the deionized water is 1:50-1:125, and the continuous stirring time is 30-90 minutes.

7. The method according to claim 3 or 4, wherein step (3) comprises: performing ultrasonic dispersion on the mixed solution for a period of time, slowly adding the mixed solution after ultrasonic treatment into the wall material aqueous solution, and continuously stirring for a period of time;

and/or the mass ratio of the anionic curing agent in the mixed solution to the sodium alginate in the wall material aqueous solution is 3.0-6.0: and 1, continuously stirring for 30-90 minutes.

8. The method according to claim 7, wherein the power of the ultrasonic dispersion is 250W and the time of the ultrasonic dispersion is 5 to 10 minutes.

9. The method according to claim 3 or 4, wherein step (4) comprises: dripping the mixture obtained in the step (3) into a calcium salt solution, and filtering, washing and drying to obtain the anion curing expansion microcapsule;

and/or in the step (4), the calcium salt solution is one or two of a calcium nitrate solution and a calcium lactate solution, the concentration of the calcium salt solution is 1-2%, and the drying temperature is 30-40 ℃.

10. Use of an anionically cured expandable microcapsule according to claim 1 or 2, or prepared by a method according to any of claims 3-9, in the field of concrete.

11. Use of an anionically cured expanded microcapsule according to claim 1 or 2, or prepared by a method according to any one of claims 3-9, in reinforced concrete structures that are resistant to seawater corrosion.

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