Preparation method and application of repair mortar with steel bar rust conversion function

Abstract

The invention discloses a preparation method and application of repair mortar with a reinforcing steel bar rust conversion function, and belongs to the technical field of repair mortar, the preparation method comprises the following steps: 1, dry-mixing rust inhibitor intercalated hydrotalcite, disodium hydrogen phosphate and sodium phytate in proportion, and grinding until the particle size is less than or equal to 50 microns; 2, adding the cement, the mineral admixture, the aggregate and the compound rust conversion agent into a stirrer according to a formula proportion, and carrying out dry mixing for 3-5 minutes to fully and uniformly mix the materials; 3, adding the water reducing agent and the polymer emulsion into water, and uniformly stirring to prepare an additive solution; and 4, under the condition of continuous stirring, slowly adding the admixture solution into the dry-mixed material obtained in the step 2, and stirring for 5-10 minutes until the uniform and non-caking repair mortar is obtained. The repairing mortar disclosed by the invention can be used for effectively filling the corroded part of the reinforced concrete, recovering the integrity of the structure and remarkably improving the durability of the reinforced concrete in a complex and severe environment.

Description

Technical Field

[0001] The present invention relates to the technical field of repair mortar, and in particular to a preparation method and application of a repair mortar with the function of steel bar rust conversion. Background Art

[0002] During the maintenance and repair of concrete structures, the problem of steel bar corrosion is a key factor that cannot be ignored. The steel bars are wrapped by concrete. Once corrosion occurs, its volume will expand due to the oxidation reaction. This expansion will exert a huge pressure on the surrounding concrete, thereby causing damage phenomena such as cracks and spalling. In some extreme cases, this damage may endanger the stability and safety of the structure, and may even lead to the failure of the entire structure. Therefore, it is extremely important to research and develop a repair mortar that can effectively repair cracks and spalling of concrete and can protect the internal steel bars from further corrosion. Such repair mortar can not only extend the service life of concrete structures, but also significantly reduce the maintenance cost, and has significant practical application value and economic benefits.

[0003] Currently, the main methods for dealing with steel bar corrosion are traditional repair methods, such as chiseling the concrete at the corroded part, removing the rust of the steel bars and then re-pouring the concrete or using ordinary repair mortar for repair. However, these methods have many deficiencies. For example, the rust removal process is cumbersome, the labor intensity is high, the cost is high, and ordinary repair mortar does not have the function of converting steel bar rust, and cannot fundamentally solve the problem of steel bar re-corrosion. The durability of the repaired structure is still difficult to be effectively guaranteed. Therefore, there is an urgent need for a new type of repair mortar that can not only efficiently fill cracks, but also effectively convert the rust layer on the surface of steel bars to form a protective barrier to prevent further corrosion of steel bars. At the same time, this repair mortar should simplify the construction process, reduce the damage to the original concrete structure, and reduce the construction difficulty and time cost to better meet the requirements of rapid and efficient modern construction projects. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a repair mortar with the function of steel bar rust conversion, aiming to solve the technical defects of existing repair mortar in steel bar repair, simplify the construction operation process, improve the durability of reinforced concrete in complex and harsh environments, and achieve the efficient repair of concrete structures.

[0005] To achieve the above purpose, the present invention provides a repair mortar with the function of steel bar rust conversion, which comprises the following components by mass parts:

[0006] Cement: 30 - 50 parts, and the cement is ordinary Portland cement with a strength grade not lower than 42.5;

[0007] Mineral admixture: 10 - 20 parts, and the mineral admixture includes one or more of fly ash, slag powder, and silica fume;

[0008] Aggregate: 60 - 150 parts, and the aggregate is quartz sand with a particle size of 0.1 - 2 mm;

[0009] Compound rust converter: 5 - 10 parts, and the compound rust converter is a compound mixture of organic phosphate, phosphate, and inhibitor intercalated hydrotalcite;

[0010] Water reducing agent: 0.2 - 1.5 parts, and the water reducing agent is a polycarboxylate - based high - performance water reducing agent;

[0011] Polymer emulsion: 10 - 15 parts, and the polymer of the polymer emulsion is an acrylate - type or epoxy - resin - type polymer;

[0012] Water: 25 - 35 parts.

[0013] Preferably, in the above - mentioned repair mortar with the function of steel bar rust conversion, the compound rust converter, by mass fraction, includes the following components:

[0014] Inhibitor intercalated hydrotalcite (INT - LDHs): 30 - 50 parts;

[0015] Disodium hydrogen phosphate (Na2HPO4): 20 - 40 parts;

[0016] Sodium phytate: 20 - 30 parts.

[0017] Preferably, in the above - mentioned repair mortar with the function of steel bar rust conversion, the INT - LDHs is prepared by intercalation modification of Mg - Al - CO3 type or Zn - Al - CO3 type hydrotalcite with a small - molecule organic migrating rust inhibitor.

[0018] Preferably, in the above - mentioned repair mortar with the function of steel bar rust conversion, the polymer emulsion is a fast - hardening acrylate - type or epoxy - resin - type polymer emulsion.

[0019] Preferably, the preparation method of the above - mentioned repair mortar with the function of steel bar rust conversion includes the following steps:

[0020] Step 1: Dry - mix INT - LDHs, Na2HPO4, and sodium phytate in proportion and grind them to a particle size of ≤50 μm;

[0021] Step 2: Add cement, mineral admixture, aggregate, and compound rust converter into a mixer according to the formula ratio, and dry - mix for 3 - 5 minutes to make them fully and evenly mixed;

[0022] Step 3: Add the water reducing agent and polymer emulsion into water, stir evenly to make an admixture solution;

[0023] Step 4: Under continuous stirring, slowly add the admixture solution to the dry-mixed material obtained in Step 2, and stir for 5 - 10 minutes until a uniform and lump-free repair mortar is obtained. Control the water-binder ratio at 0.25 - 0.35 during the wet mixing stage.

[0024] Preferably, the application of the repair mortar with the function of steel bar rust conversion as described above includes the following steps:

[0025] Step 1: Clean the surface of the corroded reinforced concrete structure to remove impurities such as loose and spalled concrete and floating rust.

[0026] Step 2: Apply or spray the prepared repair mortar onto the surface of the concrete around and at the corroded part of the steel bars, with a thickness of 10 - 50 mm.

[0027] Step 3: Cure the applied or sprayed repair mortar for at least 7 days, and keep the surface of the repair mortar moist.

[0028] Preferably, the repair mortar is used for repairing existing reinforced concrete structures in chloride ion erosion or carbonation environments.

[0029] Therefore, the preparation method and application of a repair mortar with the function of steel bar rust conversion adopting the above structure in the present invention have the following beneficial effects:

[0030] (1) Synergistic rust inhibition: The repair mortar of the present invention combines INT-LDHs, sodium phytate, and Na2HPO4, giving full play to the characteristics of sodium phytate and Na2HPO4 in promoting the regeneration of the passivation film. At the same time, the adsorption effect of INT-LDHs on free chloride ions on and near the surface of the steel bars is utilized to enhance the stability of the passivation film, effectively preventing further corrosion of the steel bars and improving the durability of the building structure.

[0031] (2) Efficient repair: The repair mortar can effectively fill the corroded parts of the reinforced concrete, restore the integrity of the structure, significantly improve the durability of the reinforced concrete in complex and harsh environments, realize the re-repair function of the steel bars, and fill the gap in the field of steel bar repair in the existing technology.

[0032] (3) Simple process: The preparation method is simple, the operation process is easy to control, the raw materials are widely available, the cost is low, and it is suitable for large-scale industrial production. During the application process, since there is no need to remove rust from the steel bars, the operation process is greatly simplified, the construction time and cost are reduced, which is conducive to promoting its application and popularization.

[0033] Next, through examples, the technical solutions of the present invention will be further described in detail. Specific Embodiments

[0034] To better understand the above technical solutions, the following will provide a detailed description of the above technical solutions in combination with specific implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0035] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0036] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such commodity or device. Without further limitations, the element defined by the statement "including one..." does not exclude the existence of another identical element in the commodity or device including the said element.

[0037] The present invention provides a repair mortar with the function of reinforcing bar rust conversion, which includes the following components by mass parts:

[0038] Cement: 30 - 50 parts, and the cement is ordinary Portland cement with a strength grade not lower than 42.5;

[0039] Mineral admixture: 10 - 20 parts, and the mineral admixture includes one or more of fly ash, slag powder, and silica fume;

[0040] Aggregate: 60 - 150 parts, and the aggregate is quartz sand with a particle size of 0.1 - 2 mm;

[0041] Compound rust converter: 5 - 10 parts, and the compound rust converter is a compound mixture of organic phosphate, phosphate, and inhibitor intercalated hydrotalcite, etc.;

[0042] Water reducing agent: 0.2 - 1.5 parts, and the water reducing agent is a polycarboxylate-based high-performance water reducing agent;

[0043] Polymer emulsion: 10 - 15 parts, and the polymer of the polymer emulsion is an acrylate-based or epoxy resin-based polymer;

[0044] Water: 25 - 35 parts.

[0045] Specifically, cement provides the basic strength and bonding performance of the repair mortar; mineral admixtures improve the workability, durability and microstructure of the repair mortar; aggregates enhance the volume stability and strength of the repair mortar; the compound rust converter is a compound mixture of organic phosphates, phosphates and rust inhibitor intercalated hydrotalcite, etc., which can chemically react with rust to convert rust into a stable complex and prevent further corrosion of steel bars; the water reducer is a polycarboxylate-based high-performance water reducer, which reduces the water consumption while ensuring the fluidity of the repair mortar, and improves the strength and durability. The polymer emulsion is acrylate or epoxy resin polymer, and its active effect, bridging effect and filling effect improve the physical structure and internal stress of the hardened cement paste, reduce the overall elastic modulus, reduce the water consumption, and improve the capillary pores inside the hardened cement paste, etc.

[0046] To further optimize the above technical solution, the compound rust converter, by mass fraction, comprises the following components:

[0047] Rust inhibitor intercalated hydrotalcite (INT-LDHs): 30-50 parts;

[0048] Disodium hydrogen phosphate (Na2HPO4): 20-40 parts;

[0049] Sodium phytate: 20-30 parts.

[0050] It should be noted that when rust inhibitor intercalated hydrotalcite (INT-LDHs) is applied to concrete, it can adsorb and solidify the free chloride ions in the concrete while releasing the rust inhibitor INT, reduce the enrichment of chloride ions on the surface of steel bars, and reduce the corrosion rate of steel bars; disodium hydrogen phosphate (Na2HPO4) can be used for the surface treatment of steel bars and the surface conversion of rust. Fe on the surface of the steel bar 2+ reacts with disodium hydrogen phosphate: 3Fe 2+ +2HPO4 2- →Fe3(PO4)2↓+2H + . The reaction product can be deposited on the surface of the steel bar and form a passivation film to realize the regeneration of the passivation film and effectively inhibit the corrosion of the steel bar; sodium phytate can react with ferric ions on the surface of the steel bar in an alkaline environment to form a chelate of ferric phytate and adsorb on the surface of the steel bar to form a protective film, which helps to realize the re-passivation of the steel bar and inhibit the occurrence of corrosion.

[0051] To further optimize the above technical solution, INT-LDHs is prepared by intercalating and modifying Mg-Al-CO3 type or Zn-Al-CO3 type hydrotalcite with a small molecule organic migrating rust inhibitor.

[0052] To further optimize the above technical solution, the polymer emulsion is a fast-hardening acrylate or epoxy resin polymer emulsion.

[0053] To further optimize the above technical solution, the preparation method of the repair mortar with the function of steel bar rust conversion as described above includes the following steps:

[0054] Step 1: Dry-mix INT-LDHs, Na2HPO4, and sodium phytate in proportion and grind them to a particle size ≤ 50 μm;

[0055] Step 2: Add cement, mineral admixture, aggregate, and compound rust conversion agent into a mixer according to the formula ratio, and dry-mix for 3 - 5 minutes to make them fully and evenly mixed;

[0056] Step 3: Add water reducer and polymer emulsion into water, stir evenly to make an admixture solution;

[0057] Step 4: Under continuous stirring, slowly add the admixture solution to the dry-mixed materials obtained in Step 2, and stir for 5 - 10 minutes until a uniform and lump-free repair mortar is obtained. Control the water-binder ratio at 0.25 - 0.35 during the wet-mixing stage.

[0058] To further optimize the above technical solution, the application of the repair mortar with the function of steel bar rust conversion as described above includes the following steps:

[0059] Step 1: Clean the surface of the corroded reinforced concrete structure to remove impurities such as loose and spalled concrete and floating rust;

[0060] Step 2: Apply or spray the prepared repair mortar onto the surface of the concrete around and at the corroded steel bar part, with a thickness of 10 - 50 mm;

[0061] Step 3: Cure the applied or sprayed repair mortar for at least 7 days, and keep the surface of the repair mortar moist.

[0062] To further optimize the above technical solution, the repair mortar is used for the repair of existing reinforced concrete structures in chloride ion erosion or carbonization environments.

[0063] To introduce the preparation method and application of a repair mortar with the function of steel bar rust conversion provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0064] Example 1

[0065] Preparation of repair mortar: Select 40 parts of cement (ordinary Portland cement with a strength grade of 42.5), 15 parts of mineral admixture (fly ash and silica fume mixed at a ratio of 1:1), 100 parts of quartz sand with a particle size of 0.1 - 2 mm, 8 parts of compound rust converter, 1 part of polycarboxylate-based high-performance water reducer, 12 parts of acrylate polymer emulsion, and 30 parts of water. Among them, the compound rust converter is composed of 40 parts of rust inhibitor intercalated hydrotalcite (INT-LDHs, Mg-Al-CO3 type hydrotalcite modified by intercalation with small molecule organic migrating rust inhibitor), 30 parts of disodium hydrogen phosphate, and 30 parts of sodium phytate. Put INT-LDHs, disodium hydrogen phosphate, and sodium phytate into a grinding equipment and dry mix them until the particle size is ≤50 μm. Add the cement, mineral admixture, quartz sand, and the treated compound rust converter into a mixer and dry mix for 4 minutes to ensure that the materials are fully and evenly mixed. Add the water reducer and polymer emulsion into water and stir evenly to make an admixture solution. While continuously stirring the dry-mixed materials, slowly add the admixture solution into them and stir for 8 minutes until a uniform and lump-free repair mortar is obtained. Control the water-binder ratio to be 0.3 in the wet mixing stage.

[0066] Application in building structure repair:

[0067] Clean the rusted part: Select a concrete structure where the steel bars are rusted due to chloride ion erosion, clean the surface of the rusted reinforced concrete structure, and carefully remove impurities such as loose, peeled concrete and floating rust with tools.

[0068] Apply the repair mortar: Use a spreading tool to evenly spread the prepared repair mortar on the surface of the steel bar rusted part and the surrounding concrete, and control the spreading thickness to be 30 mm.

[0069] Curing: After spreading, cover the surface of the repair mortar with a plastic film and spray water regularly to keep the surface of the repair mortar moist. The curing time is 10 days.

[0070] After curing, the steel bars at the repaired part were tested, and it was found that a dense passivation film had formed on the surface of the steel bars. Through electrochemical testing methods, the corrosion potential and polarization resistance of the steel bars were measured. The results showed that compared with the steel bars without using this repair mortar, the corrosion potential shifted significantly positive, and the polarization resistance increased significantly, indicating that the corrosion rate of the steel bars decreased substantially. This is because INT-LDHs adsorbed on the surface of the steel bars, enhancing the stability of the passivation film. At the same time, sodium phytate and disodium hydrogen phosphate promoted the regeneration of the passivation film, effectively preventing further corrosion of the steel bars, demonstrating a good synergistic rust inhibition effect and improving the durability of the building structure. Observing the repaired concrete structure, the repair mortar was closely combined with the original concrete, without cracks, peeling and other phenomena. The rusted parts of the steel bars were effectively filled, and the integrity of the structure was restored. Conducting a load test on the repaired structure, the results showed that its bearing capacity reached the design requirements, and its durability in complex and harsh environments was significantly improved. The function of re-repairing the steel bars was successfully realized, filling a part of the gap in the field of steel bar repair in the existing technology. From preparation to construction application, the entire process operation flow is simple and easy to control. During the preparation process, the raw materials have good mixing uniformity, and the equipment requirements are not high; during construction, there is no need for complex rust removal treatment of the steel bars, reducing the construction process, saving a large amount of construction time and cost. Compared with traditional repair methods, the construction efficiency has increased by about 30%, and the cost has been reduced by about 20%, which is suitable for large-scale industrial production and popularization and application.

[0071] Example 2

[0072] Preparation of repair mortar: Select 35 parts of cement (ordinary Portland cement with a strength grade of 42.5), 12 parts of mineral admixture (slag powder), 80 parts of quartz sand with a particle size of 0.1 - 2 mm, 6 parts of compound rust converter, 0.5 part of polycarboxylate-based high-performance water reducer, 10 parts of epoxy resin polymer emulsion, and 28 parts of water. The compound rust converter is composed of 35 parts of rust inhibitor intercalated hydrotalcite (INT-LDHs, Zn-Al-CO3 hydrotalcite intercalated and modified with small molecule organic migrating rust inhibitor), 35 parts of disodium hydrogen phosphate, and 30 parts of sodium phytate. Following the preparation steps of Example 1, first dry mix and grind the compound rust converter, and then successively carry out dry mixing of materials, preparation of admixture solution, and wet mixing and forming operations. Control the water-binder ratio to be 0.28 in the wet mixing stage.

[0073] Application in building structure repair:

[0074] Clean the rusted part: For a concrete structure with steel bar corrosion caused by carbonation, clean the loose concrete and floating rust on the surface of the rusted reinforced concrete structure.

[0075] Spray the repair mortar: Use spraying equipment to spray the prepared repair mortar onto the surface of the concrete around and at the rusted part of the steel bars, with a spraying thickness of 20 mm.

[0076] Curing: After spraying is completed, water is sprayed regularly through a spraying device for 7 days of curing.

[0077] The repaired steel bars are tested, and the linear polarization resistance method is used to monitor the corrosion situation of the steel bars. The results show that the corrosion rate of the steel bars has decreased significantly. In the carbonation environment, the components in the repair mortar play a synergistic role, effectively inhibiting the corrosion of the steel bars, protecting the performance of the steel bars, and providing guarantee for the long-term stability of the building structure. The appearance of the repaired concrete structure is flat, and the bonding between the repair mortar and the original concrete is firm. Durability tests are carried out on the repaired structure, such as impermeability tests. It is found that its impermeability performance has been greatly improved compared with that before repair, indicating that the repair mortar can effectively repair the structural damage caused by carbonation and improve the durability of the structure in the carbonation environment. During the preparation process, the raw materials are mixed evenly and the preparation process is stable. In terms of application, the spraying construction method is more efficient, the damage to the original concrete structure during construction is small, and the construction cost is reduced, reflecting the advantages of this technology in practical engineering applications and being conducive to its wide application in the field of building repair.

[0078] Therefore, the present invention adopts a preparation method and application of a repair mortar with a steel bar rust conversion function having the above structure, and has the following beneficial effects:

[0079] (1) Synergistic rust inhibition: The repair mortar of the present invention combines INT-LDHs, sodium phytate and Na2HPO4, gives full play to the characteristics of sodium phytate and Na2HPO4 to promote the regeneration of the passive film, and at the same time utilizes the adsorption effect of INT-LDHs on free chloride ions on and near the surface of the steel bars to enhance the stability of the passive film, effectively preventing further corrosion of the steel bars and improving the durability of the building structure.

[0080] (2) Efficient repair: The repair mortar can effectively fill the corroded parts of the reinforced concrete, restore the integrity of the structure, significantly improve the durability of the reinforced concrete in complex and harsh environments, realize the function of re-repairing the steel bars, and fill the gap in the field of steel bar repair in the existing technology.

[0081] (3) Simple process: The preparation method is simple, the operation process is easy to control, the raw materials are widely sourced and the cost is low, which is suitable for large-scale industrial production. During the application process, since there is no need to remove rust from the steel bars, the operation process is greatly simplified, the construction time and cost are reduced, which is conducive to promoting its application and popularization.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A repair mortar with the function of steel bar rust conversion, characterized in that, By mass parts, it includes the following components: Cement: 30 - 50 parts, and the cement is ordinary Portland cement with a strength grade not lower than 42.5; Mineral admixture: 10 - 20 parts, and the mineral admixture includes one or more of fly ash, slag powder, and silica fume; Aggregate: 60 - 150 parts, and the aggregate is quartz sand with a particle size of 0.1 - 2 mm; Compound rust converter: 5 - 10 parts, and the compound rust converter is a compound mixture of organic phosphate, phosphate, and inhibitor - intercalated hydrotalcite; Water - reducing agent: 0.2 - 1.5 parts, and the water - reducing agent is a polycarboxylate - based high - performance water - reducing agent; Polymer emulsion: 10 - 15 parts, and the polymer of the polymer emulsion is an acrylate - based or epoxy - resin - based polymer; Water: 25 - 35 parts.

2. The repair mortar with the function of steel bar rust conversion according to claim 1, characterized in that, The compound rust converter, by mass parts, includes the following components: Inhibitor - intercalated hydrotalcite: 30 - 50 parts; Disodium hydrogen phosphate: 20 - 40 parts; Sodium phytate: 20 - 30 parts.

3. The repair mortar with the function of steel bar rust conversion according to claim 2, characterized in that, The inhibitor - intercalated hydrotalcite is obtained by intercalation modification of Mg - Al - CO3 type or Zn - Al - CO3 type hydrotalcite with a small - molecule organic migrating rust inhibitor.

4. A repair mortar with a function of converting steel bar rust according to claim 1, characterized in that, The polymer emulsion is a fast - hardening acrylate - based or epoxy - resin - based polymer emulsion.

5. A preparation method of a repair mortar having a function of converting steel bar rust as described in any one of claims 1-4, characterized in that, It includes the following steps: Step 1: Dry - mix the inhibitor - intercalated hydrotalcite, disodium hydrogen phosphate, and sodium phytate in proportion and grind them to a particle size ≤50 μm; Step 2: Add the cement, mineral admixture, aggregate, and compound rust converter into a mixer according to the formula ratio and dry - mix for 3 - 5 minutes to make them fully and evenly mixed; Step 3: Add the water - reducing agent and polymer emulsion into water and stir evenly to make an admixture solution; Step 4: Under continuous stirring, slowly add the admixture solution into the dry - mixed materials obtained in Step 2 and stir for 5 - 10 minutes until a uniform and lump - free repair mortar is obtained. Control the water - binder ratio at 0.25 - 0.35 during the wet - mixing stage.

6. Use of a repair mortar having a function of converting steel bar rust as described in any one of claims 1-4, characterized in that, It includes the following steps: Step 1: Clean the surface of the corroded reinforced concrete structure to remove impurities such as loose and spalled concrete and floating rust; Step 2: Apply or spray the prepared repair mortar onto the surface of the concrete around and at the corroded part of the steel bars, with a thickness of 10 - 50 mm; Step 3: Cure the applied or sprayed repair mortar for no less than 7 days and keep the surface of the repair mortar moist.

7. The application according to claim 6, characterized in that, The repair mortar is used for the repair of existing reinforced concrete structures in chloride - erosion or carbonation environments.