A rapid self-repairing agent for marine reinforced concrete and a preparation method thereof

Abstract

The application discloses a kind of marine reinforced concrete crack fast self-repairing agent and preparation method thereof, the self-repairing agent includes the following components by mass fraction: polyacrylic acid hydrogel 20-30%, microorganism 5-10%, betaine 20-30%, calcium salt 15-25%, aluminum salt 20-30%.Its preparation method is: acrylic acid monomer is mixed with crosslinking agent, initiator, auxiliary crosslinking agent;Aluminum salt, acrylic acid are mixed to obtain aluminum acrylate;The two are mixed with microorganism and betaine, stirring and heating, and microorganism-polyacrylic acid hydrogel is prepared;After drying, it is broken, and calcium salt powder is wrapped, then immersed in polymer emulsion, dried, and prepared.The application can quickly block cracks by forming organic-inorganic composite repair products, solidify harmful media, release beneficial ions, achieve the dual goal of crack self-repairing and reinforcement corrosion inhibition.

Description

Technical Field

[0001] This invention relates to a self-healing crack agent and its preparation method, and more particularly to a rapid self-healing crack agent for marine reinforced concrete and its preparation method. Background Technology

[0002] Reinforced concrete, as the most widely used engineering material, is extensively applied in marine engineering construction. However, seawater is rich in corrosive ions such as chloride and sulfate ions, posing a significant threat to the durability of reinforced concrete. Long-term exposure to the natural environment and the coupled damage from multiple factors lead to uneven volume deformation and the formation of micro-cracks. Corrosive ions in seawater penetrate the concrete, destroying hydration products, corroding the reinforcing steel, and causing rapid crack propagation. Once the cracks reach a certain width, they negatively impact the load-bearing capacity of the concrete structure, resulting in a decline in its service performance. By incorporating specific admixtures into concrete, giving it self-healing crack repair capabilities and self-inhibiting corrosion resistance, the durability of reinforced concrete in marine corrosive environments can be better guaranteed, extending its service life. This significantly reduces the need for arduous manual repair work and lowers engineering operation and maintenance costs. Crack self-healing technology is particularly advantageous for underwater, enclosed spaces, and other areas where manual repairs are difficult.

[0003] The requirements for crack prevention in reinforced concrete in marine environments are high. This includes not only timely repair of cracks in their early stages but also corrosion inhibition of exposed reinforcing steel. Due to the strong corrosiveness of seawater, the self-healing mechanism of marine concrete cracks must have a faster response speed compared to conventional aquatic environments. It should quickly seal the cracks' water transport function to reduce the damage caused by continuous seawater intrusion. In summary, the self-healing mechanism for reinforced concrete cracks in marine environments must meet multiple requirements, including rapid response, efficient crack filling, and corrosion protection of reinforcing steel.

[0004] Current self-healing agents for marine concrete cracks primarily work by filling crack spaces and sealing seepage channels. However, this method typically takes a long time and cannot quickly stop leaks. Furthermore, it cannot inhibit the corrosive damage caused by seawater ions penetrating the concrete, accelerating concrete deterioration and causing the repaired area to crack again. Simultaneously, these self-healing agents fail to protect exposed reinforcing steel, leading to rapid corrosion. The accumulation and expansion of corrosion products further contribute to concrete cracking and damage. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a rapid self-healing agent for marine reinforced concrete cracks that can quickly seal cracks and inhibit concrete corrosion;

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned rapid self-healing agent for cracks in marine reinforced concrete.

[0007] Technical solution: The rapid self-healing agent for cracks in marine reinforced concrete described in this invention comprises the following components by mass fraction: 20-30% polyacrylic acid hydrogel, 5-10% microorganisms, 20-30% betaine, 15-25% calcium salt, and 20-30% aluminum salt.

[0008] The molar ratio of the calcium salt to the aluminum salt is 1:2.0-3.0.

[0009] The microorganisms mentioned are acetic acid oxidizing bacteria.

[0010] The calcium salt is at least one of calcium acetate, calcium formate, or calcium lactate.

[0011] Wherein, the aluminum salt is replaced by sodium aluminate and / or aluminum hydroxide.

[0012] The preparation method of the above-mentioned rapid self-healing agent for cracks in marine reinforced concrete includes the following steps:

[0013] (1) A mixture of acrylic monomer, crosslinking agent, initiator, auxiliary crosslinking agent and solvent is prepared; aluminum salt and acrylic acid are mixed and reacted to produce aluminum acrylate;

[0014] (2) Mix the mixture, aluminum acrylate, microorganisms and betaine, and heat under stirring conditions to obtain polyacrylic acid hydrogel containing microorganisms;

[0015] (3) After drying the polyacrylic acid hydrogel containing microorganisms, it is broken into particles and then coated with calcium salt powder to obtain solid spherical particles.

[0016] (4) The solid sphere particles are immersed in the polymer emulsion and then dried to obtain the self-healing agent.

[0017] In step (1), the crosslinking agent is N,N'-methylenebisacrylamide and / or hydroxymethylacrylamide; the initiator is at least one of potassium persulfate, potassium peroxymonosulfate, ammonium persulfate or sodium persulfate; the auxiliary crosslinking agent is at least one of anhydrous methanol, sodium bisulfite or tetramethylethylenediamine; and the solvent is water.

[0018] In step (1), the mass ratio of acrylic monomer to crosslinking agent, initiator, auxiliary crosslinking agent, and solvent is 10:1-2:0.2-0.25:20-40:200-300. The molar ratio of aluminum salt to acrylic acid is 1.0:2.0-3.0.

[0019] In step (2), the mass ratio of the mixture, aluminum acrylate, microorganisms and betaine is 30-50:10-19:0.5-1.0:2.0-3.0.

[0020] In step (2), the mixture, aluminum acrylate, microorganisms and betaine are mixed in the reactor and then sealed and placed in a constant temperature water bath for reaction; the temperature of the constant temperature water bath is 50℃-70℃; the process will react rapidly; the preferred time is 1-2 minutes.

[0021] In step (3), the mass ratio of polyacrylic acid hydrogel to calcium salt in the solid sphere particles is 1:0.2-0.5.

[0022] In step (3), the drying temperature is 50-60℃ and the time is 24-48h; the polyacrylic acid hydrogel containing microorganisms is dried and broken into fine particles, and calcium salt powder is coated on the outer surface of the particles using a sugar coating machine; the specific coating method can be achieved by existing technology; the solid sphere particles are particles with a continuous particle size of 0.15mm-4.75mm.

[0023] In step (4), the mass ratio of the solid sphere particles to the polymer emulsion is 100:2.0-5.0.

[0024] In step (4), the polymer emulsion is at least one of styrene-butadiene emulsion, styrene-acrylic emulsion, or acetostyrene-acetylated emulsion; the drying temperature is 60-70°C and the drying time is 5-10 min.

[0025] The repair agent is added by replacing fine aggregate of equal weight.

[0026] Invention Principle: The acrylic acid in this invention crosslinks to form a polyacrylic acid hydrogel, which has excellent pH response. After the gel enters the crack space, it has good water absorption and swelling capacity under highly alkaline conditions (pH > 12). Water entering the gel causes it to expand tens of times in volume, quickly sealing the crack space and directly reducing the crack's water seepage capacity.

[0027] Calcium and aluminum ions react under alkaline conditions to form calcium-aluminum bimetallic hydroxides. Simultaneously, they combine with a large number of water molecules, causing volume expansion that fills the gaps in the hydrogel, enhancing its leak-sealing ability. The resulting calcium-aluminum bimetallic hydroxides possess a unique interlayer structure that adsorbs and fixes chloride and sulfate ions that penetrate cracks, preventing their corrosive and destructive effects.

[0028] After the polyacrylic acid hydrogel absorbs water, the spores of acetic acid-oxidizing bacteria within the gel are reactivated and will grow using betaine as a substrate. Betaine decomposes to release carbonate and nitrite ions. The acetic acid-oxidizing bacteria can also use acetic acid as a substrate, decomposing it into carbonate ions. The carbonate ions released from the microbial decomposition of the substrate react with free calcium ions to form calcium carbonate precipitates that accumulate in the pores of the hydrogel, while the released nitrite ions provide a protective effect on the reinforcing steel.

[0029] Beneficial Effects: Compared with existing technologies, this invention achieves the following significant effects: The repair agent of this invention forms an organic-inorganic composite product of hydrogel, bio-calcium carbonate, and bimetallic hydroxide within the crack space. The hydrogel initially absorbs water and expands in volume, isolating the crack's water transport capacity and providing a suitable environment for microorganisms. The calcium-aluminum bimetallic hydroxide forms in situ, solidifying corrosion ions that have penetrated the crack, while simultaneously filling the pores of the hydrogel, providing support and bonding. Microorganisms decompose the substrate, releasing nitrite ions to protect the reinforcing steel. Simultaneously, biominerals are formed to further fill the pores of the gel particles, enhancing the crack repair effect. Attached Figure Description

[0030] Figure 1 Microscopic observation image of organic-inorganic composite remediation products;

[0031] Figure 2 The crack water penetration resistance repair rate of the repair agent in Example 1;

[0032] Figure 3 The crack repair capabilities of the repair agents in Examples 1-3;

[0033] Figure 4 To simulate the changes in pH and microbial abundance in the solution of marine concrete cracks;

[0034] Figure 5 The variation patterns of betaine and acetate ion concentrations in a simulated solution for cracks in marine concrete were investigated.

[0035] Figure 6 To simulate the variation of nitrite ion concentration in a solution for cracks in marine concrete;

[0036] Figure 7 The study simulated the changes in chloride and sulfate ion concentrations in a solution for marine concrete cracks. Detailed Implementation

[0037] The present invention will now be described in further detail.

[0038] Example 1

[0039] Prepare repair agent 1 according to the following steps:

[0040] Step 1: In the reactor, add 9.0 ml of distilled water, 4.0 ml of anhydrous methanol, 1.0 g of acrylic acid, and 0.20 g of N,N'-methylenebisacrylamide, mix well, and then add 8.0 ml of 0.5% sodium bisulfite, 8.0 ml of 0.5% potassium persulfate, and 0.20 mL of tetramethylethylenediamine.

[0041] Step 2: Dissolve 0.5g of microbial spore powder, 3.0g of betaine, 3.0g of sodium aluminate, and 1.0g of acrylic acid in 15.0ml of distilled water, and then add it to the reactor from Step 1;

[0042] Step 3: Seal the reaction vessel and place it in a 50°C constant temperature water bath for reaction, stirring continuously to obtain microbial-polyacrylic acid hydrogel;

[0043] Step 4: Dry the hydrogel at 50℃ for 48 hours, and break the dried hydrogel into fine particles of 0.05mm-4.6mm;

[0044] Step 5: Using a sugar coating machine, coat the fine particles from Step 4 with 1.5g of calcium acetate powder to obtain solid spheres of 0.15mm-4.75mm.

[0045] Step Six: Immerse the solid spheres from Step Five in styrene-butadiene emulsion, and then dry them at 60°C for 10 minutes to obtain Repair Agent 1.

[0046] Prepare self-healing concrete according to Table 1, and mold the specimen into a φ100mm×100mm cylinder.

[0047] Table 1. Mix proportions of self-healing concrete

[0048]

[0049] The prepared self-healing concrete was cured for 28 days under standard conditions. After curing, cracks approximately 1.0 mm wide were prepared in the specimens using the splitting crack method, and the crack width was fixed. The cracked specimens were then cured under simulated seawater conditions to test the crack repair effect; the simulated seawater conditions were: NaCl2 4.53 g / L, MgCl2 5.20 g / L, Na2SO4 4.09 g / L, CaCl2 1.16 g / L, and KCl 0.695 g / L.

[0050] Figure 1 The image shows a microscopic observation of the repair product of the repair agent. It can be seen that the surface of the hydrogel particles is relatively smooth, while the surface of the inorganic minerals is relatively rough. The product is a composite structure of inorganic minerals and gel interpenetrating and coating each other. This indicates that the gel's swelling after absorbing water provides a suitable environment for microbial mineralization, promoting the formation of inorganic minerals on the gel surface and causing the dispersed gel particles to cement together as a whole, thus ensuring the stability of the repair effect.

[0051] like Figure 2 As shown, the water penetration resistance repair rate of the cracks reached 80% in 6 hours, and after 12 hours, the water penetration resistance repair rate of the cracks reached more than 95%, and the cracks almost stopped seeping water.

[0052] Example 2

[0053] Prepare repair agent 2 according to the following steps:

[0054] Step 1: In the reactor, add 12.0 ml of distilled water, 12.0 ml of anhydrous methanol, 2.0 g of acrylic acid, and 0.15 g of N,N'-methylenebisacrylamide in sequence, mix well, and then add 12.0 ml of 0.5% sodium bisulfite, 12.0 ml of 0.5% sodium persulfate, and 0.2 mL of tetramethylethylenediamine.

[0055] Step 2: Dissolve 1.0g of microbial spore powder, 2.0g of betaine, 2.5g of aluminum hydroxide, and 1.0g of acrylic acid in 18ml of distilled water, and add the mixture to the reactor from Step 1;

[0056] Step 3: Seal the reaction vessel and place it in a 70℃ constant temperature water bath for reaction, stirring continuously to obtain microbial-polyacrylic acid hydrogel;

[0057] Step 4: Dry the hydrogel at 60℃ for 24 hours, and then break the dried hydrogel into finely graded particles with a diameter of less than 0.05mm-4.5mm.

[0058] Step 5: Using a sugar coating machine, coat the fine particles from Step 4 with 1.5g of calcium formate powder to obtain solid spherical particles with a continuous diameter of 0.15mm-4.75mm.

[0059] Step Six: Impregnate the solid spheres from Step Five with styrene-butadiene emulsion. After impregnation, dry at 70°C for 5 minutes to obtain Repair Agent 2.

[0060] Prepare self-healing concrete according to Table 1, and mold the specimen into a φ100mm×100mm cylinder.

[0061] The prepared self-healing concrete was cured for 28 days under standard conditions. After curing, cracks approximately 1.0 mm wide were prepared in the specimens using the splitting crack method, and the crack width was fixed. The cracked specimens were then cured under simulated seawater conditions to test the crack repair effect.

[0062] Example 3

[0063] Prepare repair agent 3 according to the following steps:

[0064] Step 1: In the reactor, add 14.5 ml of distilled water, 8 ml of anhydrous methanol, 1.5 g of acrylic acid, and 0.20 g of N,N'-methylenebisacrylamide in sequence, mix well, and then add 8.0 ml of 0.5% sodium bisulfite, 8.0 ml of 0.5% potassium persulfate, and 0.2 ml of tetramethylethylenediamine.

[0065] Step 2: Dissolve 0.50g of microbial spore powder, 2.0g of betaine, 2.0g of sodium aluminate, and 0.5g of acrylic acid in 9.5ml of distilled water, and add the mixture to the reactor in Step 1;

[0066] Step 3: Seal the reaction vessel and place it in a 50°C constant temperature water bath for reaction, stirring continuously to obtain microbial-polyacrylic acid hydrogel;

[0067] Step 4: Dry the hydrogel at 50℃ for 48 hours, and then break the dried hydrogel into finely graded particles with a diameter of less than 4.0 mm.

[0068] Step 5: Using a sugar coating machine, coat the fine particles from Step 4 with 2.5g of calcium lactate powder to obtain solid spherical particles with a continuous particle size of 0.15mm-4.75mm.

[0069] Step Six: Impregnate the solid spheres from Step Five with styrene-butadiene emulsion. After impregnation, dry at 70°C for 5 minutes to obtain Repair Agent 3.

[0070] Prepare self-healing concrete according to Table 1, and mold the specimen into a φ100mm×100mm cylinder.

[0071] The prepared self-healing concrete was cured for 28 days under standard conditions. After curing, cracks approximately 1.0 mm wide were prepared in the specimens using the splitting crack method, and the crack width was fixed. The cracked specimens were then cured under simulated seawater conditions to test the crack repair effect.

[0072] like Figure 3 As shown, the repair agents prepared in Examples 1-3 all achieved a 28-day crack repair rate of over 95% in concrete, indicating that the repair agents of the present invention have a good crack repair effect.

[0073] Simulated seawater was prepared, and the pH, microbial population changes, and acetate ion concentration in the crack solution were tested.

[0074] Ordinary silicate cement was mixed with simulated seawater at a ratio of 1:10, and after standing for 24 hours, the supernatant was collected to prepare a simulated solution for marine concrete cracks. The repair agent 1 prepared in Example 1 was ground and crushed, and the repair agent fragments were mixed with the marine concrete crack solution at a ratio of 1:7. The pH, changes in the number of microorganisms, and the concentration of acetate ions in the crack solution were tested.

[0075] like Figure 4 As shown, after the remediation agent was added, the pH of the solution gradually decreased and stabilized at around 10.2. With the solution pH stable at a low alkalinity, the number of microorganisms in the solution began to gradually increase, indicating a rise in OD... 600 The curve gradually increases to around 1.8, indicating the presence of a large number of microorganisms in the solution. For example... Figure 5As shown, the betaine concentration gradually decreases with the increase of the microbial population, indicating that betaine is consumed. Simultaneously, acetate ions are also gradually consumed to exhaustion, indicating that the microorganisms are increasingly using acetate ions as a substrate for metabolic activities, resulting in mineralization. Figure 6 As shown, the concentration of nitrite ions in the solution gradually increases with the enhancement of microbial metabolic activity, which can provide good protection for the reinforcing steel. Figure 7 As shown, in the early stage of the reaction, the concentrations of chloride and sulfate ions rapidly decreased to a stable level, indicating that chloride and sulfate ions were adsorbed and fixed, and that their potential harm to concrete was limited.

Claims

1. A rapid self-healing agent for cracks in marine reinforced concrete, characterized in that, It contains the following components by mass fraction: 20-30% polyacrylic acid hydrogel, 5-10% microorganisms, 20-30% betaine, 15-25% calcium salt, and 20-30% aluminum salt; The preparation method of the aforementioned rapid self-healing agent for cracks in marine reinforced concrete includes the following steps: (1) A mixture is prepared by mixing acrylic monomer with crosslinking agent, initiator, auxiliary crosslinking agent and solvent; aluminum salt and acrylic acid are mixed to obtain aluminum acrylate; (2) Mix the mixture, aluminum acrylate, microorganisms and betaine, and heat under stirring conditions to obtain polyacrylic acid hydrogel containing microorganisms; (3) After drying the polyacrylic acid hydrogel containing microorganisms, it is crushed into particles and calcium salt powder is coated on the outer surface of the particles to obtain solid sphere particles. (4) The solid sphere particles are immersed in the polymer emulsion and then dried to obtain the self-healing agent.

2. The rapid self-healing agent for cracks in marine reinforced concrete according to claim 1, characterized in that, The molar ratio of the calcium salt to the aluminum salt is 1:2-3.

3. The rapid self-healing agent for cracks in marine reinforced concrete according to claim 1, characterized in that, The microorganisms mentioned are acetic acid oxidizing bacteria.

4. The rapid self-healing agent for cracks in marine reinforced concrete according to claim 1, characterized in that, The calcium salt is at least one of calcium acetate, calcium formate, or calcium lactate.

5. The rapid self-healing agent for cracks in marine reinforced concrete according to claim 1, characterized in that, The aluminum salt is replaced by sodium aluminate and / or aluminum hydroxide.

6. A method for preparing the rapid self-healing agent for cracks in marine reinforced concrete as described in claim 1, characterized in that, Includes the following steps: (1) A mixture is prepared by mixing acrylic monomer with crosslinking agent, initiator, auxiliary crosslinking agent and solvent; aluminum salt and acrylic acid are mixed to obtain aluminum acrylate; (2) Mix the mixture, aluminum acrylate, microorganisms and betaine, and heat under stirring conditions to obtain polyacrylic acid hydrogel containing microorganisms; (3) After drying the polyacrylic acid hydrogel containing microorganisms, it is crushed into particles and calcium salt powder is coated on the outer surface of the particles to obtain solid sphere particles. (4) The solid sphere particles are immersed in the polymer emulsion and then dried to obtain the self-healing agent.

7. The preparation method of the rapid self-healing agent for cracks in marine reinforced concrete according to claim 6, characterized in that, In step (2), the heating is constant temperature water bath heating, and the heating temperature is 50℃-70℃.

8. The preparation method of the rapid self-healing agent for cracks in marine reinforced concrete according to claim 6, characterized in that, In step (1), the crosslinking agent is N,N'-methylenebisacrylamide and / or hydroxymethylacrylamide; the initiator is at least one of potassium persulfate, potassium bisulfate, ammonium persulfate or sodium persulfate; and the auxiliary crosslinking agent is at least one of anhydrous methanol, sodium bisulfite or tetramethylethylenediamine.

9. The preparation method of the rapid self-healing agent for cracks in marine reinforced concrete according to claim 6, characterized in that, In step (3), the solid sphere particles are particles with a continuous particle size of 0.15mm-4.75mm.

10. The preparation method of the rapid self-healing agent for cracks in marine reinforced concrete according to claim 6, characterized in that, In step (4), the polymer emulsion is at least one of styrene-butadiene emulsion, styrene-acrylic emulsion, or acetostyrene-acetylated emulsion.

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