A high-ductility, high-interfacial-permeability cement-based remediation material and its preparation method

Abstract

This invention discloses a high-interface-permeability, high-ductility cement-based repair material and its preparation method. The high-interface-permeability, high-ductility cement-based repair material of this invention comprises, by mass percentage: silicate cement: 80-90%, monomer: 2-4%, initiator: 0.1-0.3%, crosslinking agent: 0.05-0.1%, graphene oxide: 0.05-0.1%, defoamer: 0.5-1.5%, and the balance being water. This invention uses monomers as precursors for polymerization, and through initiation, they are uniformly dispersed in the cement-based cementitious material, forming a tough three-dimensional network structure. The high-interface-permeability, high-ductility cement-based cementitious material exhibits good bonding performance. Compared with traditional redispersible polymer powder modified cement, the 28-day flexural strength is increased by 110-120%, the 28-day tensile strength is increased by 150-200%, and the bond strength is increased by 100-150%. This invention provides a new method for improving the toughness and high interface-permeability of cement.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-ductility, high-interfacial-penetration cement-based repair material and its preparation method. Background Technology

[0002] Cement concrete, due to its high compressive strength, high durability, and high impermeability, is currently the most widely used building material, in fields such as traditional buildings, bridges, and roads. However, traditional cement concrete has inherent defects. Concrete itself is brittle, has low toughness, and low tensile strength, making it prone to cracking under external environmental loads, thus reducing its service life. Therefore, improving the brittleness, low toughness, and low tensile properties of concrete is key to extending its long-term service life.

[0003] Currently, the most common method for improving the brittleness of concrete is to add fibers during the concrete mixing process. The fibers, through their bonding effect with the concrete matrix, inhibit the formation and unsteady propagation of microcracks, thus achieving a toughening and crack-resistant effect. However, fibers are difficult to disperse in cement and are expensive. Adding polymers, such as epoxy resins, emulsions, and redispersible polymer powders, can also improve the brittleness of cement materials. However, the distribution of polymers in cement is uneven, and polymer adsorption on the surface of cement particles affects cement hydration, leading to a decrease in mechanical properties. Although traditional polymers can effectively improve the toughness of cement, the improvement is limited. For example, redispersible polymer powders generally only improve the toughness of cement by 20-50%, are not easy to penetrate at the interface, resulting in weak interfacial bonding, and have low polymer utilization efficiency, leading to high carbon emissions from the system. Summary of the Invention

[0004] In view of this, the present invention aims to provide a high-ductility cement-based repair material with high interfacial penetration, which can improve the high brittleness, low toughness and low tensile properties of cement through in-situ polymerization, thereby extending the service life of cement. This effectively solves the problems of existing cement concrete having high brittleness, low toughness and low tensile strength, and being prone to cracking under external environmental loads, thus reducing its service life.

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

[0006] A highly ductile cement-based repair material with high interfacial permeability comprises the following raw materials by mass percentage: silicate cement: 80-90%, monomer: 2-4%, initiator: 0.1-0.3%, crosslinking agent: 0.05-0.1%, graphene oxide: 0.05-0.1%, defoamer: 0.5-1.5%, and the balance being water.

[0007] Optionally, the monomer is a mixture of sodium acrylate and acrylamide, wherein the mass ratio of sodium acrylate to acrylamide is (7-9):(1-3).

[0008] Optionally, the initiator is a mixture of potassium persulfate and sodium bisulfite, wherein the mass ratio of potassium persulfate to sodium bisulfite is (1-2):1.

[0009] Optionally, the crosslinking agent is methylenebisacrylamide.

[0010] Optionally, the graphene oxide has a sheet-like structure, a content greater than 99%, a sheet diameter of 0.5-5 μm, and a thickness of 0.8-1.2 nm.

[0011] Optionally, the defoamer is one of tributyl phosphate or an organosilicone defoamer.

[0012] Optionally, the silicate cement is ordinary silicate cement with a strength grade of not less than P·O42.5.

[0013] A second objective of this invention is to provide a method for preparing the above-mentioned high-interfacial-permeability, high-ductility cement-based repair material, the method comprising the following steps:

[0014] The silicate cement, the monomer, the initiator, the crosslinking agent, the graphene oxide, the defoamer, and the water are mixed evenly, molded, and cured to the specified age to obtain a high-ductility cement-based repair material with high interfacial penetration.

[0015] The reaction mechanism of this invention:

[0016] This invention utilizes soluble monomers to achieve uniform polymer distribution through in-situ polymerization, avoiding the aggregation of long-chain polymers and realizing polymer dispersion and good penetration at the interface, thereby improving the adhesion between the slurry and the matrix. Furthermore, in terms of monomer selection, this invention uses a mixture of sodium acrylate and acrylamide, which can improve the toughness of the formed polymer. The polymerization of the monomers can chemically combine with cement hydration products such as CSH gel and calcium hydroxide to form a double-network structure, improving the high ductility of the cement. In-situ polymerization introduces surface-active polymers that drastically reduce the surface tension of the system by altering the adsorption rate and the rate of molecular diffusion to the interface. This can introduce air bubbles into the cement paste, leading to a decrease in mechanical properties. In this invention, graphene oxide, a derivative of graphene, is a two-dimensional material with high specific surface area (700-1500 m² / g), excellent elastic modulus (2-232 GPa), and high tensile strength (~130 GPa). Its interaction with the polymer disrupts the air bubbles, eliminating them and effectively improving the microstructure of the cement, increasing its toughness, and mitigating the negative impact of reduced mechanical properties caused by polymer introduction. Furthermore, this invention directly mixes graphene oxide with the monomers in a solution before the monomers form the polymer. Because the monomers are acrylic acid-based substances, they adsorb onto the surface of graphene oxide, providing additional electrostatic repulsion and steric hindrance, effectively improving the dispersion of graphene oxide and further enhancing the toughness of the cement material.

[0017] Compared with existing technologies, the high interfacial permeability and high ductility cement-based repair material of the present invention has the following advantages:

[0018] 1. This invention achieves polymer dispersion and interfacial penetration by adding monomers, initiators, and crosslinking agents to freshly mixed cement, and enables in-situ polymerization reaction in the cement to achieve high interfacial adhesion. Then, it is compounded with graphene oxide to achieve the preparation of cement materials with high toughness. The cement-based cementitious material has good bonding performance, with 28-day flexural strength increased by 110-120%, 28-day tensile strength increased by 150-200%, and bond strength increased by 100-150%.

[0019] 2. The preparation method of the present invention is simple and has low production cost. Compared with traditional polymer-modified cement, the polymer has a higher utilization efficiency and better modification effect.

[0020] 3. This invention provides a new method for improving the toughness and interfacial permeability of cement. Detailed Implementation

[0021] 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.

[0022] The specific raw material formulations of the high-interfacial-permeability, high-ductility cement-based repair materials in Examples 1-6 of this invention are shown in Table 1. The cement used is P·O42.5 ordinary Portland cement.

[0023] The specific preparation steps of the high interfacial permeability and high ductility cement-based repair materials in Examples 1-6 of this invention are as follows: According to the proportions in Table 1, silicate cement, monomer, initiator, crosslinking agent, graphene oxide, defoamer and water are stirred evenly, molded, and cured under standard conditions for 28 days to obtain high interfacial permeability and high ductility cement-based repair materials.

[0024] The flexural strength and tensile strength of the high-ductility cement-based repair materials with high interfacial penetration in Examples 1-6 of this invention were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" to evaluate their ductility. The bond strength of the high-ductility cement-based repair materials with high interfacial penetration in Examples 1-6 of this invention was tested according to JGJ / T 70-2009 "Standard for Test Methods of Basic Properties of Building Mortar" to evaluate their interfacial permeability. The results were compared with those of a cement-based repair material with only redispersible adhesive powder added (Comparative Example 1). The test results are shown in Table 2.

[0025] As can be seen from the results in Tables 1 and 2, the high interfacial penetration and high ductility cement-based repair materials of Examples 1 to 6 of the present invention have good toughness, with 28-day flexural strength increased by 110-120%, 28-day tensile strength increased by 150-200%, and bond strength increased by 100-150%.

[0026] Table 1

[0027]

[0028] Table 2

[0029]

[0030] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-ductility, high-interfacial-permeability cement-based repair material, characterized in that, By mass percentage, it includes the following raw materials: silicate cement: 80-90%, monomer: 2-4%, initiator: 0.1-0.3%, crosslinking agent: 0.05-0.1%, graphene oxide: 0.05-0.1%, defoamer: 0.5-1.5%, and the balance is water; The monomer is a mixture of sodium acrylate and acrylamide, wherein the mass ratio of sodium acrylate to acrylamide is (7-9):(1-3). The initiator is a mixture of potassium persulfate and sodium bisulfite, wherein the mass ratio of potassium persulfate to sodium bisulfite is (1-2):1; The crosslinking agent is methylenebisacrylamide.

2. The high interfacial permeability, high ductility cement-based repair material according to claim 1, characterized in that, The graphene oxide has a sheet-like structure, a content greater than 99%, a sheet diameter of 0.5-5 μm, and a thickness of 0.8-1.2 nm.

3. The high interfacial permeability, high ductility cement-based repair material according to claim 1, characterized in that, The defoamer is one of tributyl phosphate or organosilicon defoamer.

4. The high interfacial permeability, high ductility cement-based repair material 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.

5. A method for preparing the high interfacial permeability, high ductility cement-based repair material according to any one of claims 1 to 4, characterized in that, Includes the following steps: The silicate cement, the monomer, the initiator, the crosslinking agent, the graphene oxide, the defoamer, and the water are mixed evenly, molded, and cured to the specified age to obtain a high-ductility cement-based repair material with high interfacial penetration.

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