High-fluidity sustained-release in-situ polymerized gelling material for fissure repair and preparation method thereof

Abstract

This invention discloses a high-flowability, slow-release, in-situ polymeric cementitious material for crack repair and its preparation method. The high-flowability, slow-release, in-situ polymeric cementitious material for crack repair of this invention comprises, by mass percentage: silicate cement: 80-85%, monomer: 2-4%, crosslinking agent: 0.5-1%, slow-release initiator capsule: 1-3%, polycarboxylate superplasticizer: 0.1-0.3%, with the balance being water. This invention prepares a core-shell coated slow-release initiator capsule, achieving in-situ polymerization of the monomer in the cementitious material through slow release. This results in a slow-release, in-situ polymeric cementitious material with good workability, a flowability of 220-280 mm, and a 120-150% increase in bond strength compared to traditional cement. This invention provides a new method for crack grouting repair.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-flowability slow-release in-situ polymeric cementitious material for crack repair and its preparation method. Background Technology

[0002] Cement concrete, due to its high mechanical properties and excellent durability, is widely used in construction, bridge, and road engineering. However, under harsh external environments and human factors, concrete can crack to varying degrees. If not repaired promptly, the concrete structure will deteriorate rapidly under the influence of internal and external stresses and environmental media, leading to surface crack propagation, concrete spalling, and even interface fracture. Therefore, to prevent further deterioration of concrete due to years of neglect, crack repair technology is an effective method to restore the integrity of the concrete structure, improve its performance, reduce safety risks, and prevent larger-scale damage, thereby reducing more expensive repair or reconstruction costs.

[0003] Currently, crack repair materials include microbial repair, epoxy resins, cement-based materials, and polymers. Epoxy resins offer good corrosion resistance, adhesion, and waterproofing, but suffer from low-temperature brittleness. Polymers provide good adhesion but exhibit poor aging performance. Cement-based materials offer excellent durability but suffer from low adhesion and high brittleness. Polymer-modified cement is an excellent cementitious material with good adhesion and impermeability; however, traditional polymers such as redispersible polymer powders and polymer emulsions have high viscosity, leading to reduced workability and hindering the repair of cracks. Furthermore, the performance of traditional polymer modifications is limited and cannot adequately meet engineering requirements. In-situ polymerization is a novel approach with advantages such as simple operation, high polymer dispersibility, and good toughness, showing promising application prospects in crack repair. However, the rapid polymerization reaction can lead to a rapid loss of slurry fluidity, which is detrimental to crack repair. Therefore, overcoming the disadvantage of excessively rapid polymerization rates and achieving controllable reaction processes is crucial for the application of in-situ polymerization in crack repair. Summary of the Invention

[0004] In view of this, the present invention aims to provide a high-flowability slow-release in-situ polymerized cementitious material for crack repair. It improves the repair performance through in-situ polymerization of monomers and prevents the monomers from rapidly polymerizing under the action of an initiator by using slow-release capsules, thus ensuring the high flowability of the repair cementitious material in the early stage. This makes it suitable for crack repair projects and has good repair performance, thereby effectively solving the problems of poor adhesion and low permeability of traditional repair methods, while the fast reaction rate of in-situ polymerization reaction easily leads to rapid loss of slurry flowability, which is not conducive to crack repair.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A high-flowability, slow-release, in-situ polymeric cementitious material for crack repair comprises, by mass percentage, the following raw materials: silicate cement: 80-85%, monomer: 2-4%, crosslinking agent: 0.5-1%, slow-release initiator capsule: 1-3%, polycarboxylate superplasticizer: 0.1-0.3%, with the balance being water.

[0007] Optionally, the sustained-release initiator capsule is composed of a core material and a wall material, wherein the core material is ammonium persulfate and sodium bisulfite, and the wall material is ethyl cellulose, and the mass ratio of the core material to the wall material is 1:(1-2).

[0008] Optionally, the sustained-release initiator capsule is prepared by the following method:

[0009] Ammonium persulfate and sodium bisulfite were added to a dichloromethane organic solution at a molar ratio of 1:(0.5-1) and dispersed evenly. Then, the mixture was slowly added dropwise to a 3-5% gelatin protective solution. The mixture was stirred in a water bath at 30-35°C at a speed of 600-1000 r / min for 6-8 hours to solidify the capsules. Finally, the capsules were filtered, washed, and dried to obtain sustained-release initiator capsules.

[0010] Optionally, the sustained-release initiator capsule has a particle size of 100-200 μm.

[0011] Optionally, the monomer is sodium acrylate monomer obtained by neutralization reaction of sodium hydroxide and acrylic acid.

[0012] Optionally, the crosslinking agent is methylenebisacrylamide.

[0013] Optionally, the silicate cement is ordinary silicate cement with a strength grade of not less than P·O42.5.

[0014] A second objective of this invention is to provide a method for preparing the above-mentioned high-flowability slow-release in-situ polymeric cementitious material for crack repair, the method comprising the following steps:

[0015] 1) Dissolve the monomer, the crosslinking agent, and the polycarboxylate superplasticizer in water to obtain solution A;

[0016] 2) Add the sustained-release initiator capsule to solution A, stir and disperse to obtain solution B;

[0017] 3) Mix the solution B with the silicate cement and stir evenly to obtain a high-flowability slow-release in-situ polymeric cementitious material for crack repair.

[0018] The reaction mechanism of this invention:

[0019] This invention utilizes soluble monomers to enhance interfacial penetration in old concrete, reacting to generate a polymer network. The polymer and cement hydration products in the repair matrix cross-link, forming a double-penetrating network structure, thereby improving repair capabilities. Furthermore, this invention encapsulates the initiator in a "core-shell" structure. Even before the initiator contacts the monomer, the slurry maintains high workability, allowing for early pouring into cracks and penetrating downwards and to the left and right interfaces of the old concrete. This effectively solves the problem of rapid monomer polymerization leading to a loss of cement workability within minutes, resulting in a decline in pourability. Simultaneously, under the influence of a concentration gradient, the initiator in the capsule slowly releases free radical ions into the liquid phase. The monomer polymerizes under the action of these free radicals, forming a polymer structure that causes the slurry to harden and solidify without excessive settling or segregation, significantly improving repair capabilities.

[0020] Compared with existing technologies, the high-flowability slow-release in-situ polymeric cementitious material for crack repair described in this invention has the following advantages:

[0021] 1. This invention achieves in-situ polymerization of monomers in cementitious materials through in-situ slow-release, preparing a high-fluidity, high-performance crack repair material. The resulting slow-release in-situ polymerized cementitious material has good workability, with a flowability of 220-280 mm. The repaired bond strength is 120-150% higher than that of traditional cement. It effectively solves the problem that the particle size of polymer-modified cement such as redispersible polymer powder, which is most commonly used in the engineering field, is too large, making it difficult to penetrate deeper into the old concrete interface and resulting in limited repair efficiency. It also solves the problem that cement, as a commonly used cementitious material for crack grouting repair, has poor adhesion to the old interface, leading to the risk of re-cracking.

[0022] 2. The slow-release in-situ polymerized gelling material of this invention has a simple preparation process, low polymer usage, and compared with traditional polymer repair materials, it has low carbon emissions and high polymer repair efficiency. Attached Figure Description

[0023] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 The appearance morphology of the sustained-release initiator capsule of the present invention is shown. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions and effects of the present invention, several embodiments will be provided below. Obviously, the following description is only an embodiment and does not limit the scope of protection of the present invention.

[0026] The specific raw material ratios and preparation process parameters of the sustained-release initiator capsules in the high-flowability sustained-release in-situ polymerized gelling materials used for crack repair in Examples 1-5 of this invention are shown in Table 1.

[0027] The sustained-release initiator capsules of Examples 1-5 of this invention were prepared by the following method:

[0028] According to the raw material ratios and process parameters in Table 1, ammonium persulfate and sodium bisulfite were added to a dichloromethane organic solution and dispersed evenly. Then, they were slowly added dropwise to a gelatin protective solution. The mixture was stirred at a certain speed in a water bath at a specific temperature for a period of time to achieve capsule solidification. Finally, the capsules were filtered, washed, and dried to obtain sustained-release initiator capsules. The particle sizes of the sustained-release initiator capsules obtained in each embodiment are shown in Table 1, and their appearance morphology is as follows: Figure 1 As shown.

[0029] Table 1

[0030]

[0031] The specific raw material formulations of the high-flowability, slow-release, in-situ polymeric cementitious materials used for crack repair in Examples 1-5 of this invention are shown in Table 2. Among them, the silicate cement is P·O42.5 ordinary silicate cement.

[0032] The high-flowability, slow-release, in-situ polymeric cementitious materials used for crack repair in Examples 1-5 of this invention are specifically prepared by the following methods:

[0033] 1) According to the raw material ratio in Table 2, dissolve the monomer, crosslinking agent and polycarboxylate superplasticizer in water to obtain solution A;

[0034] 2) According to the raw material ratio in Table 2, add the sustained-release initiator capsules to solution A, stir and disperse to obtain solution B;

[0035] 3) According to the raw material ratio in Table 2, mix solution B with silicate cement and stir evenly to obtain a high-flowability slow-release in-situ polymerized cementitious material for crack repair.

[0036] To evaluate the repair performance of the high-flowability slow-release in-situ polymeric cementitious materials used for crack repair in Examples 1-5 of this invention, firstly, cement blocks of 40×40×160mm (Comparative Example 1) were formed. After standard curing for 28 days, the blocks were split into two segments of equal length to form old cement blocks. The high-flowability slow-release in-situ polymeric cementitious material slurry used for crack repair in Examples 1-5 was then bonded to the old cement blocks. Finally, after curing, the bonding performance was evaluated by testing the flexural strength. The flexural strength was tested according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar" (ISO method). The test results are shown in Table 2.

[0037] As shown in Table 2, the high-flowability slow-release in-situ polymeric cementitious materials used for crack repair in Examples 1-5 of the present invention have good workability, with an initial flowability of 220-280 mm, and the repaired bond strength is 120-150% higher than that of traditional cement.

[0038] Table 2

[0039]

[0040] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-flowability, slow-release, in-situ polymeric cementitious material for crack repair, characterized in that, By mass percentage, it includes the following raw materials: silicate cement: 80-85%, monomer: 2-4%, crosslinking agent: 0.5-1%, slow-release initiator capsules: 1-3%, polycarboxylate superplasticizer: 0.1-0.3%, and the balance is water; The sustained-release initiator capsule is composed of a core material and a wall material. The core material is ammonium persulfate and sodium bisulfite, and the wall material is ethyl cellulose. The mass ratio of the core material to the wall material is 1:(1-2). The monomer is sodium acrylate monomer obtained by neutralization reaction of sodium hydroxide and acrylic acid; The crosslinking agent is methylenebisacrylamide.

2. The high-flowability, slow-release, in-situ polymeric cementitious material for crack repair according to claim 1, characterized in that, The sustained-release initiator capsules have a particle size of 100-200 µm.

3. The high-flowability, slow-release, in-situ polymeric cementitious material for crack repair according to claim 1, characterized in that, The silicate cement is ordinary silicate cement with a strength grade of not less than P·O42.

5.

4. A method for preparing the high-flowability, slow-release, in-situ polymeric cementitious material for crack repair as described in any one of claims 1 to 3, characterized in that, Includes the following steps: 1) Dissolve the monomer, the crosslinking agent, and the polycarboxylate superplasticizer in water to obtain solution A; 2) Add the sustained-release initiator capsule to solution A, stir and disperse to obtain solution B; 3) Mix the solution B with the silicate cement and stir evenly to obtain a high-flowability slow-release in-situ polymeric cementitious material for crack repair.

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