Cement-based composite material with organic-inorganic interpenetrating structure and preparation method of cement-based composite material

Abstract

The invention belongs to the technical field of building materials, and provides a cement-based composite material with an organic-inorganic interpenetrating structure and a preparation method of the cement-based composite material. According to the preparation method disclosed by the invention, the monomer and the polymer containing the active group are introduced, the in-situ polymer formed by the monomer through in-situ polymerization and the polymer containing the active group form a double-network polymer, a single-network structure is refined, and the single-network structure and a cement hydration reaction product which is synchronously performed form an organic-inorganic interpenetrating structure; the interaction between double networks and the cement-based material is enhanced, meanwhile, the microstructure is optimized, the mechanical property of the single polymer modified cement-based material can be improved, the compressive strength is improved, and the breaking strength is further enhanced; the prepared cement-based composite material with the organic-inorganic interpenetrating structure has excellent breaking strength and compressive strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and particularly relates to a cement-based composite material with an organic-inorganic interpenetrating structure and a preparation method thereof. BACKGROUND

[0002] As the core cementitious material of building engineering, cement-based materials have advantages such as high compressive strength and easy construction, but their inherent defects limit their more extensive application, such as brittleness, low tensile strength, easy cracking, poor durability and the like.

[0003] Polymer materials are widely used in the field of functional design of composite materials due to their high elastic modulus, excellent interfacial adhesion and anti-chemical corrosion properties.

[0004] In the modification research of cement-based materials, the polymer component often realizes the core functions such as matrix sealing protection, fracture toughness improvement and multi-phase interface strengthening through a physical-chemical coupling mechanism, and the toughening regulation of the brittleness defects of cement-based materials is particularly significant. Through the construction of an organic-inorganic composite system, the polymer can effectively fill the micro-nano pores of the hydration products of the cement-based material, and rely on the molecular chain entanglement and chemical bond cooperation to form a multi-scale interface transition zone, so as to realize the performance complementation of rigid skeleton and flexible network at the molecular dynamics level. Such synergistic effect not only significantly improves the fracture ability and energy dissipation ability of the cement-based material, but also provides a theoretical and technical path for the development of advanced civil engineering materials with high durability and environmental adaptability.

[0005] The prior art often adopts a physical mixing method to mix the polymer and the cement-based material, such as pre-dispersing a polymer emulsion (such as a water-based epoxy resin, a polyvinyl alcohol solution) or dry mixing. Although the physical mixing method can improve the impermeability and the bending strength, it has problems such as uneven dispersion, insufficient compatibility, complex process and the like; and the polymer is easy to aggregate in the cement-based material, resulting in weakened interfacial bonding. The physical mixing method is difficult to form chemical bonding, has poor long-term stability, and has a small increase in the bending strength, so the improvement effect is limited.

[0006] In recent years, in-situ polymerization technology has shown great potential for improving the mechanical properties of cement-based materials by directly reacting monomers into the cementitious materials to form polymer networks. The organic polymer network formed by in-situ polymerization interweaves with the inorganic cement hydration product network, improving the dispersion of polymers in cement-based materials, enhancing the mechanical bonding force between polymers and cement, increasing interfacial bonding strength, and improving pore structure. The resulting organic-inorganic dual-network structure significantly enhances the flexural strength of cement-based materials. However, due to the inherently low compressive strength and modulus of polymers, isolated polymer phases become a vulnerability in composite materials. While modifying cement-based materials with a single polymer can effectively improve the problem of brittleness and cracking, the relatively weak interfacial strength between the polymer and cement leads to interfacial slippage or fracture. Furthermore, the slowing of the hydration rate significantly reduces the early-stage compressive strength of cement, negatively impacting later-stage compressive strength. In other words, while in-situ polymerization technology can mitigate the adverse effects of polymers on the flexural strength of cement-based materials, it cannot overcome the inherent properties of polymers and the reduction in compressive strength caused by their delayed cement hydration. The preparation of a cement composite material that possesses both flexural and compressive strength is crucial for the development of cement composite materials. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a cement-based composite material with an organic-inorganic interpenetrating structure and a method for preparing the same. The cement-based composite material with an organic-inorganic interpenetrating structure prepared by the method provided by this invention possesses both excellent flexural strength and compressive strength.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] This invention provides a method for preparing a cement-based composite material with an organic-inorganic interpenetrating structure, comprising the following steps:

[0010] The aqueous dispersion of the polymer was pretreated to obtain a pretreated polymer system;

[0011] The pretreated polymer system, monomers, and additives are mixed to obtain an organic system;

[0012] The organic system and cement-based material are mixed, and then molded and cured sequentially to obtain the cement-based composite material with the organic-inorganic interpenetrating structure.

[0013] The polymer is a substance containing active groups;

[0014] The monomer is either a first monomer or a second monomer;

[0015] The first monomer is a monomer containing unsaturated carbon-carbon double bonds that can undergo free radical polymerization; when the monomer is the first monomer, the auxiliary agent includes an initiator and a crosslinking agent;

[0016] The second monomer is a monomer or oligomer unit containing an epoxy group that can be polymerized by ring-opening polymerization; when the monomer is the second monomer, the auxiliary agent is a curing agent;

[0017] The cement-based material includes cement.

[0018] Preferably, the polymer includes one or more of natural polymers and their derivatives, synthetic polymers, supramolecular systems, and covalent organic framework materials;

[0019] The natural polymers and their derivatives include one or more of the following: starch, oxidized starch, carboxymethyl starch, carboxylated oxidized starch, microcrystalline cellulose, nanocellulose, oxidized cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, oxidized sodium alginate, potassium alginate, sulfonated lignin, carrageenan, κ-carrageenan, hyaluronic acid, sodium hyaluronate, oxidized hyaluronic acid, xanthan gum, pectin, low-methoxyl pectin, chitosan, oxidized chitosan, carboxymethyl chitosan, gelatin, methacrylamide gelatin, collagen, glycogen, dextrin, cyclodextrin, dextran, and pullulan.

[0020] The synthetic polymer includes one or more of sodium polyacrylate, polyvinyl alcohol, sodium polystyrene sulfonate, polyethylene glycol and its derivatives, polyethylene glycol diacrylate, polyhydroxyethyl methacrylate, polymaleic anhydride copolymer, polyacrylamide, polyacrylic acid and polyglutamic acid;

[0021] The supramolecular system includes one or more of the following: phenylboronic acid-diol complex, hydroxypropyl-β-cyclodextrin, metal-organic gel, cyclodextrin inclusion complex, amphiphilic peptides, ureidinone derivatives, and ureidinone dimers;

[0022] The covalent organic framework material includes one or more of the following: imine bond covalent organic framework materials, hydrazone bond covalent organic framework materials, sulfonated covalent organic framework materials, and borate ester covalent organic framework materials;

[0023] The polymer has a mass of 0.1% to 5% of the cement mass.

[0024] Preferably, the pretreatment is heating and stirring or ultrasonic dispersion and stirring;

[0025] The heating and stirring temperature is 60–100°C, and the time is 0.5–3 hours.

[0026] The ultrasonic dispersion and stirring frequency is 15–200 kHz, and the time is 5–30 min.

[0027] Preferably, the first monomer includes one or more of acrylamide monomers, acrylic monomers, and acrylate monomers;

[0028] The acrylamide monomers include acrylamide and / or hydroxymethylacrylamide;

[0029] The acrylic monomers include sodium acrylate and / or acrylic acid;

[0030] The acrylate monomers include one or more of acrylates, butyl acrylate, butyl methacrylate, ethylene glycol dimethacrylate, and hydroxyethyl methacrylate;

[0031] The second monomer comprises an epoxy monomer and / or an oligomer unit formed from an epoxy monomer;

[0032] The epoxy monomers include glycidyl epoxide monomers and / or non-glycidyl epoxide monomers;

[0033] The oligomer units formed by the epoxy compound monomers include oligomer units formed by glycidyl epoxy monomers and / or oligomer units formed by non-glycidyl epoxy monomers.

[0034] The mass of the monomer is 0.1% to 15% of the mass of the cement.

[0035] Preferably, the initiator includes one or more of inorganic peroxide initiators, organic peroxide initiators, azo initiators, and redox system initiators;

[0036] The inorganic peroxide initiator includes one or more of ammonium persulfate, potassium persulfate, and sodium persulfate;

[0037] The organic peroxide initiator includes one or more of benzoyl peroxide, di-tert-butyl peroxide, methyl ethyl ketone peroxide, tert-butyl peroxide, and cumene hydroperoxide.

[0038] The azo initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile;

[0039] The initiator of the redox system includes one or more of potassium permanganate, bromate, chlorate, sodium bisulfite, sodium sulfite, sodium metabisulfite, and sodium thiosulfate;

[0040] The mass of the initiator is 0.2% to 5% of the mass of the first monomer;

[0041] The crosslinking agent is a compound containing at least two amino groups; the crosslinking agent includes one or more of N,N'-methylenebisacrylamide, hexamethylenetetramine, hydroquinone, polyethyleneimine, p-phenylenediamine, and dimethylaminoethyl methacrylate.

[0042] The mass of the crosslinking agent is 0 to 4% of the total mass of the first monomer and the polymer.

[0043] Preferably, the curing agent includes one or more of amine curing agents, acid anhydride curing agents, and latent curing agents;

[0044] The amine curing agent includes one or more of polyamide curing agents, aromatic amine curing agents, aliphatic primary amine curing agents, and phenolic amine curing agents;

[0045] The anhydride curing agents include alicyclic anhydride curing agents and / or aromatic anhydride curing agents;

[0046] The latent curing agent includes a microencapsulated amine curing agent;

[0047] The mass of the curing agent is 5-30% of the mass of the second monomer.

[0048] Preferably, the cement-based material further includes a water-reducing agent, which includes one or more of polycarboxylate-based water-reducing agents, lignin sulfonate-based water-reducing agents, and naphthalene-based water-reducing agents; the mass of the water-reducing agent is 0 to 1% of the cement mass.

[0049] Preferably, the cement-based material includes one or more of cement paste, cement mortar, and concrete.

[0050] Preferably, the molding environment temperature is 0–40°C, and the molding time is 2–60 hours.

[0051] The ambient temperature for the curing process is 0–40℃, and the humidity is ≥80%.

[0052] The present invention also provides a cement-based composite material with an organic-inorganic interpenetrating structure prepared by the preparation method described in the above technical solution.

[0053] This invention provides a method for preparing a cement-based composite material with an organic-inorganic interpenetrating structure.

[0054] The inventors analyzed the reasons for the reduced compressive strength of polymer-modified cementitious materials and concluded that strengthening the interaction between the polymer and cement to enhance interfacial strength is crucial to mitigating the adverse effects of polymers on the compressive strength of cementitious materials. The interaction between polymers and cementitious materials is the core of composite material performance optimization, and its mechanism can be improved from three aspects: physical, chemical, and microstructure. Refining the polymer network structure enhances the mechanical bonding force between the polymer network and cement, thereby improving their physical interaction. Introducing functional groups such as carboxyl groups into the polymer, which can form chemical bonds with cement products, effectively strengthens the chemical interaction between cementitious materials and polymers. The dispersibility of the polymer promotes the uniform distribution of cement particles and strengthens the interfacial transition zone between aggregates and the cement matrix. By constructing a dual-network polymer, refining the single-network structure, and forming an organic-inorganic interpenetrating structure with the simultaneously occurring cement hydration reaction products, the interaction between the dual network and cementitious materials is enhanced. Simultaneously, optimizing the microstructure improves the mechanical properties of single-polymer modified cementitious materials, increasing compressive strength and further enhancing flexural strength. The preparation method provided by this invention has the following specific advantages:

[0055] 1. By constructing a polymer dual network in cement-based materials, forming an organic-inorganic interpenetrating network with the cement matrix, the toughness of cement-based materials is improved. The high brittleness, low tensile strength, and susceptibility to cracking of cement-based materials limit their wider application. Adding polymers to modify cement-based materials, leveraging their flexibility and good bonding properties, can effectively enhance the toughness and flexural strength of cement-based materials. Through direct addition or in-situ polymerization, polymers form an organic network structure in cement-based materials, effectively filling the pores in the cement matrix, reducing porosity, optimizing the microstructure, increasing the density of the cement structure, and forming an organic-inorganic interpenetrating structure with cement hydration products. This structure, through stress dispersion, crack bridging, hindering crack propagation paths, and withstanding larger deformations, gives cement-based materials greater toughness.

[0056] 2. By constructing a dual-network polymer, the mechanical properties of the polymer network are enhanced, further improving the flexural strength of cement-based materials. Initial bonding between monomers and polymers is achieved through uniform dispersion of monomers within the polymer, constructing a dual-network structure in the cement-based material with size differences and physical and chemical interactions (the dual network structure consists of a polymer network containing active groups and a polymer network formed by in-situ polymerization of monomers). The refined polymer network structure and the interactions between the dual networks enhance the polymer network strength, resulting in stronger mechanical properties of the polymer in cement. This leads to a stronger stress dispersion effect on the cement-based material, reducing stress concentration-induced damage and achieving a greater improvement in the flexural strength of the cement-based material.

[0057] 3. By introducing active functional groups and constructing a dual-network polymer to modify cement-based materials, the polymer network structure is refined, the interfacial strength between the polymer and the cement matrix is ​​strengthened, and the compressive strength of the cement-based composite material is improved. Cement-based materials modified by ordinary polymers or by in-situ polymerization of monomers may have weak interfacial interactions between the polymer and the cement matrix, leading to a decrease in the compressive strength of the cement-based material with increasing polymer content. The refined polymer network after dual-network modification forms a denser organic-inorganic interpenetrating network structure with the cement-based material, enhancing the physical entanglement between the polymer network and cement hydration products. Furthermore, the numerous active functional groups present in the polymer network generate chemical cross-linking effects with the cement-based material, reducing the adverse effects of the polymer on the compressive strength of the cement.

[0058] 4. By inducing nucleation sites in cement through polymers, the nucleation and growth of cement hydration products are promoted, resulting in a more uniform distribution of hydration products. Polar groups on the polymer surface (such as -OH and -COOH) can serve as heterogeneous nucleation sites. For example, oxidized starch, after heat pretreatment, gelatinizes and exposes a large number of hydroxyl and carboxyl groups, promoting the nucleation and growth of CSH gel. The dense distribution of nucleation sites promotes the uniform precipitation of hydration products, improves the microstructure of cement, makes the distribution of hydration products more uniform, and macroscopically enhances the mechanical properties of cement. Attached Figure Description

[0059] Figure 1 The diagram shows the flexural strength of different cement-based composite materials (reference group, 0.5% OS) in Comparative Example 1.

[0060] Figure 2 The compressive strength diagrams for different cement-based composite materials (reference group, 0.5% OS) in Comparative Example 1 are shown.

[0061] Figure 3 SEM image of cement-based composite material (0.5% OS) with added oxidized starch in Comparative Example 1;

[0062] Figure 4 and Figure 5 SEM images of the cement-based composite material (0.5% OS) with added oxidized starch in Comparative Example 1 after being etched with hydrochloric acid at different magnifications.

[0063] Figure 6 The diagram shows the flexural strength of different cement-based composite materials (baseline group, 1% AM / 0.3% OS, 3% AM / 0.3% OS, 7% AM / 0.3% OS) in Example 1.

[0064] Figure 7 The compressive strength diagrams for different cement-based composite materials (baseline group, 1% AM / 0.3% OS, 3% AM / 0.3% OS, 7% AM / 0.3% OS) in Example 1 are shown.

[0065] Figure 8 The diagram shows the flexural strength of different cement-based composite materials (baseline group, 3% AM / 0.5% OS, 7% AM / 0.5% OS) in Example 2.

[0066] Figure 9 The compressive strength diagrams for different cement-based composite materials (baseline group, 3% AM / 0.5% OS, 7% AM / 0.5% OS) in Example 2 are shown.

[0067] Figure 10 The diagram shows the flexural strength of different cement-based composite materials (baseline group, 5% AM / 0.3% OS, 5% AM / 1.5% OS) in Example 3.

[0068] Figure 11 The compressive strength diagrams for different cement-based composite materials (baseline group, 5% AM / 0.3% OS, 5% AM / 1.5% OS) in Example 3 are shown.

[0069] Figure 12 The diagram shows the flexural strength of different cement-based composite materials (baseline group, 5% AM, 0.5% OS, and 5% AM / 0.5% OS) in Example 4.

[0070] Figure 13 The compressive strength diagrams for different cement-based composite materials (baseline group, 5% AM, 0.5% OS, and 5% AM / 0.5% OS) in Example 4 are shown.

[0071] Figure 14 FTIR plots of different cement-based composite materials (baseline group, 5% AM / 0.5% OS) in Example 4;

[0072] Figure 15 This is a SEM image of the cement-based composite material with 5% AM in Example 4 after being etched with hydrochloric acid;

[0073] Figure 16 This is a SEM image of the cement-based composite material 5% AM / 0.5% OS in Example 4 after being etched with hydrochloric acid;

[0074] Figure 17 The diagram shows the flexural strength of different cement-based composite materials (baseline group, ungelatinized 0.3% OS, gelatinized 0.3% OS) in Comparative Example 2.

[0075] Figure 18 Compressive strength diagrams of different cement-based composite materials (baseline group, ungelatinized 0.3% OS, gelatinized 0.3% OS) in Comparative Example 2;

[0076] Figure 19The diagram shows the flexural strength of different cement-based composite materials (2% AM, 2% AM / 0.5% OS) in Comparative Example 3.

[0077] Figure 20 Compressive strength diagrams for different cement-based composite materials (2% AM, 2% AM / 0.5% OS) in Comparative Example 3;

[0078] Figure 21 This is a schematic diagram of the formation process of the acrylamide and oxidized starch dual-network structure in cement. Detailed Implementation

[0079] This invention provides a method for preparing a cement-based composite material with an organic-inorganic interpenetrating structure, comprising the following steps:

[0080] The aqueous dispersion of the polymer was pretreated to obtain a pretreated polymer system;

[0081] The pretreated polymer system, monomers, and additives are mixed to obtain an organic system;

[0082] The organic system and cement-based material are mixed, and then molded and cured sequentially to obtain the cement-based composite material with the organic-inorganic interpenetrating structure.

[0083] The polymer is a substance containing active groups;

[0084] The monomer is either a first monomer or a second monomer;

[0085] The first monomer is a monomer containing unsaturated carbon-carbon double bonds that can undergo free radical polymerization; when the monomer is the first monomer, the auxiliary agent includes an initiator and a crosslinking agent;

[0086] The second monomer is a monomer or oligomer unit containing an epoxy group that can be polymerized by ring-opening polymerization; when the monomer is the second monomer, the auxiliary agent is a curing agent;

[0087] The cement-based material includes cement.

[0088] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0089] The present invention pretreats the aqueous dispersion of a polymer to obtain a pretreated polymer system.

[0090] In this invention, the polymer is a substance containing active groups; the active groups include hydroxyl and carboxyl groups; the mass content of the active groups in the polymer is preferably greater than or equal to 10%, more preferably greater than or equal to 15%. In this invention, the molecular weight of the polymer is preferably greater than or equal to 100, more preferably 1 × 10⁻⁶. 4 ~3×10 6In this invention, the polymer preferably includes one or more of natural polymers and their derivatives, synthetic polymers, supramolecular systems, and covalent organic framework materials, and is more preferably natural polymers and their derivatives. In this invention, the natural polymers and their derivatives preferably include one or more of starch, oxidized starch, carboxymethyl starch, carboxylated oxidized starch, microcrystalline cellulose, nanocellulose, oxidized cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, oxidized sodium alginate, potassium alginate, sulfonated lignin, carrageenan, κ-carrageenan, hyaluronic acid, sodium hyaluronate, oxidized hyaluronic acid, xanthan gum, pectin, low-methoxyl pectin, chitosan, oxidized chitosan, carboxymethyl chitosan, gelatin, methacrylamide gelatin, collagen, glycogen, dextrin, cyclodextrin, dextran, and pullulan, and is more preferably oxidized starch (OS). In this invention, the synthesized polymer preferably includes one or more of sodium polyacrylate, polyvinyl alcohol, sodium polystyrene sulfonate, polyethylene glycol and its derivatives, polyethylene glycol diacrylate, polyhydroxyethyl methacrylate, polymaleic anhydride copolymer, polyacrylamide, polyacrylic acid, and polyglutamic acid. In this invention, the supramolecular system preferably includes one or more of phenylboronic acid-diol complex, hydroxypropyl-β-cyclodextrin, metal-organic gel, cyclodextrin inclusion complex, amphiphilic peptides, ureidopyrimidinone derivatives, and ureidopyrimidinone dimers; the metal-organic gel is specifically preferably Fe... 3+ -Carboxylate; the amphiphilic peptide is preferably a MAX8 self-assembled peptide. In this invention, the covalent organic framework material preferably includes one or more of imine-bonded covalent organic framework materials, hydrazone-bonded covalent organic framework materials, sulfonated covalent organic framework materials, and borate ester covalent organic framework materials. In this invention, the mass of the polymer is preferably 0.1% to 5% of the cement mass, more preferably 0.1% to 3%, more preferably 0.3% to 1%, specifically preferably 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. In this invention, the mass ratio of polymer to water in the aqueous dispersion of the polymer is preferably 1 to 75:300, more preferably 1 to 25:300. Specifically, it is preferably 4.5:300, 7.5:300, or 22.5:300.

[0091] In this invention, the pretreatment is preferably performed by heating and stirring or by ultrasonic dispersion and stirring.

[0092] In this invention, the heating and stirring temperature is preferably 60–100°C, more preferably 70–90°C, and specifically preferably 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C; the time is 0.5–3 hours, more preferably 1–2 hours, and specifically preferably 0.5 hours, 1 hour, 1.5 hours, 2 hours, or 3 hours. After heating and stirring, this invention preferably further includes cooling to 0–50°C, more preferably to 10–30°C, and even more preferably to 15–25°C.

[0093] In this invention, the frequency of the ultrasonic dispersion stirring is preferably 15-200 kHz, more preferably 20-100 kHz, and more preferably 24 kHz. The time is preferably 5-30 min, and more preferably 5 min, 10 min, 15 min, 20 min, 25 min or 30 min.

[0094] In this invention, the mass content of reactive functional groups in the pretreated polymer system is preferably greater than or equal to 8%, and more preferably greater than or equal to 20%.

[0095] In this invention, the pretreatment causes the polymer to break down, the molecular chains to extend, and they to entangle and overlap in water, exposing more active groups, such as hydroxyl groups, which form a network structure through hydrogen bonds and van der Waals forces. Specifically, taking oxidized starch as an example: the hydrogen bond network within the oxidized starch granules breaks during the heating pretreatment, i.e., gelatinization, exposing a large number of hydroxyl and carboxyl groups, significantly increasing hydrophilicity, and allowing it to form hydrogen bonds or physical entanglement with water and other polar molecules. It also allows for interaction with metal ions (such as Ca). 2+ Fe 3+ The enhanced complexing ability of starch makes it suitable as an ion adsorption carrier. Through molecular chain hydration and steric hindrance, gelatinized oxidized starch can increase the viscosity of the system and inhibit particle sedimentation. In cement-based materials, it can refine the network structure of the monomer in-situ polymerization network and strengthen the interfacial strength between the polymer and the cement matrix, thus contributing to the enhancement of the compressive strength of cement-based materials.

[0096] After obtaining the pretreated polymer system, the present invention mixes the pretreated polymer system, monomers and auxiliaries to obtain an organic system.

[0097] In this invention, the monomer is either a first monomer or a second monomer. In this invention, the first monomer is a monomer containing unsaturated carbon-carbon double bonds and capable of free radical polymerization. In this invention, the second monomer is a monomer containing epoxy groups and capable of ring-opening polymerization, or an oligomer unit thereof.

[0098] In this invention, the first monomer preferably comprises one or more of acrylamide monomers, acrylic monomers, and acrylate monomers, more preferably acrylamide monomers. In this invention, the acrylamide monomer preferably comprises acrylamide (AM) and / or hydroxymethylacrylamide, more preferably acrylamide. In this invention, the acrylic monomer preferably comprises sodium acrylate and / or acrylic acid. In this invention, the acrylate monomer preferably comprises one or more of acrylates, butyl acrylate, butyl methacrylate, ethylene glycol dimethacrylate, and hydroxyethyl methacrylate.

[0099] In this invention, the second monomer preferably comprises an epoxy compound monomer and / or an oligomer unit formed from an epoxy compound monomer. In this invention, the epoxy compound monomer preferably comprises a glycidyl epoxide monomer and / or a non-glycidyl epoxide monomer. In this invention, the oligomer unit formed from the epoxy compound monomer preferably comprises an oligomer unit formed from a glycidyl epoxide monomer and / or an oligomer unit formed from a non-glycidyl epoxide monomer.

[0100] In this invention, the mass of the monomer is preferably 0.1% to 15% of the cement mass, more preferably 1% to 7%, and even more preferably 3% to 5%, specifically preferably 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. In this invention, controlling the mass of the monomer to 0.1% to 15% of the cement mass results in a cement-based composite material with an organic-inorganic interpenetrating structure that exhibits excellent flexural strength, economic benefits, and practical application value.

[0101] In this invention, the mass ratio of the polymer to the monomer is preferably 1:30 to 1:1, more preferably 1:10 to 1:2, and even more preferably 1:6 to 1:2. Specifically, it is preferably 1:1, 1:2, 1:3, 1:3.3, 1:5, 1:6, 1:8, 1:10, 1:14, 1:15, 1:16.67, 1:20, 1:23.3, 1:25, or 1:30. In this invention, controlling the mass ratio of the polymer to the monomer to be 1:30 to 1:1 ensures the integrity of the single network in the dual-network structure.

[0102] In this invention, when the monomer is a first monomer, the auxiliary agent includes an initiator and a crosslinking agent.

[0103] In this invention, the initiator preferably includes one or more of inorganic peroxide initiators, organic peroxide initiators, azo initiators, and redox system initiators, and more preferably inorganic peroxide initiators. In this invention, the inorganic peroxide initiator preferably includes one or more of ammonium persulfate, potassium persulfate, and sodium persulfate. In this invention, the organic peroxide initiator preferably includes one or more of benzoyl peroxide, di-tert-butyl peroxide, methyl ethyl ketone peroxide, tert-butyl peroxide, and cumene hydroperoxide. In this invention, the azo initiator preferably includes azobisisobutyronitrile and / or azobisisoheptanenitrile. In this invention, the redox system initiator preferably includes one or more of potassium permanganate, bromate, chlorate, sodium bisulfite, sodium sulfite, sodium metabisulfite, and sodium thiosulfate.

[0104] In this invention, the mass of the initiator is preferably 0.2% to 5% of the mass of the first monomer; more preferably 0.5% to 3%, and specifically preferably 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0105] In this invention, the crosslinking agent is preferably a compound containing at least two amino groups; specifically, the crosslinking agent preferably includes one or more of N,N'-methylenebisacrylamide, hexamethylenetetramine, hydroquinone, polyethyleneimine, p-phenylenediamine, and dimethylaminoethyl methacrylate.

[0106] In this invention, the mass of the crosslinking agent is preferably 0-4% of the total mass of the first monomer and the polymer, more preferably 0.3-2%, and specifically preferably 0.1%, 0.5%, 0.6%, 0.7%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or 4%. In this invention, the crosslinking agent plays a crosslinking role between the first monomer and the polymer. The amount of crosslinking agent affects the degree of in-situ crosslinking polymerization, which in turn affects the density of the network structure. By controlling the amount of crosslinking agent to 0-4% of the total mass of the monomer and the polymer, this invention can regulate the monomer polymerization network structure to have a suitable size, enabling the in-situ polymerization network and the macromolecular polymer network to form an interpenetrating and dense network structure, avoiding excessively high or low crosslinking density from affecting the formation of an interpenetrating structure between the two networks.

[0107] In this invention, when the monomer is a second monomer, the auxiliary agent is a curing agent.

[0108] In this invention, the curing agent preferably comprises one or more of amine curing agents, acid anhydride curing agents, and latent curing agents. In this invention, the amine curing agent preferably comprises one or more of polyamide curing agents, aromatic amine curing agents, aliphatic primary amine curing agents, and phenolic amine curing agents. In this invention, the acid anhydride curing agent preferably comprises alicyclic acid anhydride curing agents and / or aromatic acid anhydride curing agents. In this invention, the latent curing agent preferably comprises microencapsulated amine curing agents.

[0109] In this invention, the mass of the curing agent is preferably 5% to 30% of the mass of the second monomer, specifically preferably 5%, 10%, 15%, 20%, 25%, or 30%.

[0110] In this invention, the degree of in-situ crosslinking polymerization affects the density of the network structure. By controlling the mass of the auxiliaries relative to the monomers, the size of the monomer polymerization network structure is adjusted, so that the in-situ polymerization network and the macromolecular polymer network can form an interpenetrating and dense network structure, avoiding the crosslinking density being too high or too low, which would affect the formation of the interpenetrating structure of the two networks.

[0111] In this invention, the mixing temperature of the pretreated polymer system, monomers and additives is preferably 0 to 50°C, more preferably 5 to 30°C, and even more preferably 15 to 25°C.

[0112] In this invention, the mixing of the pretreated polymer system, monomer, and additive preferably includes the following steps: mixing the monomer and water to obtain a monomer solution; mixing the monomer solution and the pretreated polymer system, and then adding the additive. In this invention, the mixing time of the monomer and water is preferably greater than or equal to 5 minutes, more preferably 15 to 40 minutes. In this invention, during the mixing process of the monomer and water, the mass ratio of monomer to water is preferably 1 to 30:60, more preferably 5 to 15:60. In this invention, the mixing of the monomer solution and the pretreated polymer system preferably includes sequential stirring and ultrasonic mixing; the stirring time is preferably greater than or equal to 1 minute, more preferably 5 to 20 minutes; the ultrasonic mixing time is preferably 1 to 30 minutes, more preferably 5 to 15 minutes. In this invention, after the additive is added, the invention preferably further includes stirring for 1 to 30 minutes, more preferably 5 to 15 minutes.

[0113] In this invention, mixing the pretreated polymer system, monomers, and additives enables the monomers to form uniformly dispersed connection sites in the solution through preliminary chemical cross-linking or physical adsorption with polymers having active groups, so that the monomers can be uniformly connected to the polymer network after polymerization in cement.

[0114] After obtaining the organic system, the present invention mixes the organic system with cement-based materials, and then performs molding and curing in sequence to obtain the cement-based composite material with the organic-inorganic interpenetrating structure.

[0115] In this invention, the cement-based material includes cement. Preferably, the cement includes one or more of silicate cement, ordinary silicate cement, composite silicate cement, aluminate cement, and sulfoaluminate cement. Specifically, the cement is preferably PI52.5 silicate cement.

[0116] In this invention, the cement-based material preferably further includes a water-reducing agent, which preferably includes one or more of polycarboxylate-based water-reducing agents, lignin sulfonate-based water-reducing agents, and naphthalene-based water-reducing agents; the mass of the water-reducing agent is preferably 0-1% of the cement mass, more preferably 0-0.5%, and specifically preferably 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0117] In this invention, the cement-based material preferably further includes aggregates and / or admixtures. In this invention, the aggregates preferably include sand and / or stone. In this invention, the mass of the aggregates is preferably 150-600% of the cement mass, more preferably 300-500%, and specifically preferably 150%, 200%, 250%, 300%, 350%, 400%, 450%, 500%, 550%, or 600%. In this invention, the admixtures preferably include silica fume and / or fly ash. In this invention, the mass of the admixtures is preferably 5-40% of the cement mass, more preferably 10-30%, and specifically preferably 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40%.

[0118] In this invention, the cement-based material is preferably cement paste, cement mortar, or concrete.

[0119] The present invention does not specifically limit the preparation method of the cement-based material.

[0120] In one specific embodiment of the present invention, when the cement-based material preferably includes cement, aggregate and admixture, the preparation method of the cement-based material preferably includes the following steps: mixing cement, aggregate and admixture to obtain the cement-based material; the mixing time is preferably 1 to 20 minutes, more preferably 1 to 5 minutes.

[0121] In this invention, when the cement-based material is cement paste or cement mortar, the mixing of the organic system and the cement-based material preferably includes slow mixing and rapid mixing in sequence.

[0122] In this invention, when the cement-based material is cement paste, the revolution speed of the slow mixing is preferably ≥50 rpm, more preferably 57-67 rpm, and the rotation speed is preferably ≥100 rpm, more preferably 130-150 rpm. In this invention, when the cement-based material is cement mortar, the revolution speed of the slow mixing is preferably ≥120 rpm, more preferably 135-145 rpm, and the rotation speed is preferably ≥240 rpm, more preferably 275-295 rpm. In this invention, the slow mixing time is preferably 1-10 minutes, more preferably 2-5 minutes.

[0123] In this invention, when the cement-based material is cement paste, the revolution speed of the rapid mixing is preferably ≥100 rpm, more preferably 120-130 rpm, and the rotation speed is preferably ≥200 rpm, more preferably 275-295 rpm. In this invention, when the cement-based material is cement mortar, the revolution speed of the rapid mixing is preferably ≥240 rpm, more preferably 280-290 rpm, and the rotation speed is preferably ≥480 rpm, more preferably 560-580 rpm. In this invention, the rapid mixing time is preferably 30-180 s, more preferably 90-150 s.

[0124] In this invention, when the cement-based material is concrete, the mixing of the organic system and the cement-based material is preferably by stirring. The stirring speed is preferably ≥10 rpm, more preferably 10-20 rpm, and the stirring time is preferably 60s-30min.

[0125] In this invention, the solid content of the slurry obtained by mixing the organic system and the cement-based material is preferably 60-80%, specifically preferably 60%, 65%, 70%, 75% or 80%.

[0126] In this invention, the molding is preferably carried out in a mold. The ambient temperature for molding is preferably 0–40°C, more preferably 15–25°C, and the molding time is preferably 2–60 hours, more preferably 24 hours. In the initial stage of molding, vibration is preferably performed, with the vibration frequency preferably 5–100 times, more preferably 50–75 times. The purpose of the vibration is to remove air bubbles from the slurry. In this invention, molding is preferably carried out under a covering film, the purpose of which is to retain moisture and humidity.

[0127] In this invention, the ambient temperature for the curing is preferably 0-40℃, more preferably 18-22℃, the humidity is preferably ≥80%, more preferably ≥95%, and the time is preferably 3-90 days.

[0128] The present invention also provides a cement-based composite material with an organic-inorganic interpenetrating structure prepared by the preparation method described in the above technical solution.

[0129] In this invention, the organic-inorganic interpenetrating cement-based composite material has a more refined dual-network polymer structure, forming an organic-inorganic network structure with cement hydration products. In this invention, the organic-inorganic interpenetrating cement-based composite material exhibits both excellent flexural strength and compressive strength.

[0130] The following detailed description, in conjunction with embodiments, illustrates the organic-inorganic interpenetrating structure cement-based composite material and its preparation method provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0131] Comparative Example 1

[0132] Preparation of reference group samples: Weigh 1500g of P.I.52.5 silicate cement and add it to the mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water, stir for 5 minutes, and then pour it into the mold.

[0133] Preparation of cement-based composite material samples with added oxidized starch (denoted as 0.5% OS): Weigh 0.5% of the cement mass of oxidized starch (OS), add it to 300g of water, heat and stir in an 85℃ water bath for 1.5h, then remove it, add water to the total volume of 600g, and cool to room temperature (20℃); weigh 1500g of P.I.52.5 silicate cement and add it to a mixing pot, and stir with a cement mixer for 2min; add the gelatinized oxidized starch solution, stir for 3min at a revolution speed of 62±5rpm and a rotation speed of 140±10rpm, then stir for 2min at a revolution speed of 125±5rpm and a rotation speed of 285±10rpm, and pour into a mold.

[0134] Curing process: The slurry in the mold was agitated 60 times, then covered with plastic wrap and left to stand for 24 hours before demolding. Standard curing (ambient temperature 18–22℃, humidity ≥95%) was performed for 7 and 28 days. Compressive strength and flexural strength were then tested. The test method for compressive strength was GB / T 17671-2021, and the test method for flexural strength was GB / T 17671-2021. The results are as follows: Figure 1 and Figure 2 As shown, from Figure 1 and Figure 2As shown, the composite material with added oxidized starch (corresponding to 0.5% OS in the figure) has a 7-day flexural strength of 7.7 MPa and a 28-day flexural strength of 8.4 MPa, which are higher than the baseline group's 7-day flexural strength of 4.9 MPa and 28-day flexural strength of 6 MPa. The composite material with added oxidized starch (corresponding to 0.5% OS in the figure) has a 7-day compressive strength of 54.2 MPa and a 28-day compressive strength of 70.7 MPa, which are higher than the baseline group's 7-day compressive strength of 50.1 MPa and 28-day compressive strength of 59.5 MPa.

[0135] Take 0.5% OS samples after 7 days, soak them in anhydrous ethanol for 7 days to stop hydration, dry them, and then perform SEM testing. The results are as follows. Figure 3 As shown. From Figure 3 It can be seen that the addition of oxidized starch makes the cement hydration products tend to nucleate and grow. This multi-site nucleation and growth mechanism promotes the uniform distribution of cement hydration products, thereby producing a denser microstructure and lower porosity, which is beneficial to the improvement of cement mechanical properties.

[0136] Take a 0.5% OS sample after 7 days, etch it with 5wt% hydrochloric acid, immerse it in anhydrous ethanol for 7 days to stop hydration, dry it, and then perform SEM testing. The results are as follows. Figure 4 and Figure 5 As shown, from Figure 4 and Figure 5 It can be seen that the polymer network formed by OS is embedded in the cement hydration products, exhibiting filamentous networks and film-like morphologies of different sizes. This structure establishes an interpenetrating network architecture with the cement hydration products, which is beneficial for enhancing the connection between hydration products, filling pores, and improving the mechanical properties of cement.

[0137] Example 1

[0138] Preparation of reference group samples: Weigh 1500g of P.I.52.5 silicate cement and add it to the mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water, stir for 5 minutes, and then pour it into the mold.

[0139] Cement-based composite material samples with added acrylamide and oxidized starch (denoted as 1%AM / 0.3%OS, 3%AM / 0.3%OS, and 7%AM / 0.3%OS, respectively) were prepared as follows: 0.3% of oxidized starch by mass of cement was weighed, added to 300g of water, heated and stirred in an 85℃ water bath for 1.5h, then removed and cooled to room temperature (20℃); 1%, 3%, and 7% of acrylamide monomer by mass of cement were weighed, added to 300g of water and stirred until dissolved; the acrylamide solution and oxidized starch solution were mixed, water was added to a total volume of 600g, stirred evenly, and ultrasonically mixed for 10min; ammonium persulfate and N,N'-methylenebisacrylamide were weighed according to a mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12, added to the acrylamide and oxidized starch mixed solution, stirred evenly, and ultrasonically dispersed for 10min; 1500g of PI52.5 silicate cement was weighed and added to a mixing pot, and stirred with a cement mixer for 2min. Add different amounts of acrylamide and oxidized starch mixed solution, stir for 3 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm, then stir for 2 minutes at a revolution speed of 125±5 rpm and a rotation speed of 285±10 rpm, and then pour into a mold.

[0140] After the slurry was poured into the mold, it was shaken 60 times. It was then covered with plastic wrap and allowed to stand for 24 hours before demolding. After standard curing for 7 days and 28 days, compressive strength and flexural strength tests were conducted. The results are as follows: Figure 6 and Figure 7 As shown.

[0141] from Figure 6 and Figure 7 It can be seen that the flexural strength of cement increases with the increase of acrylamide content at a content of 0.3% oxidized starch. At the same time, the compressive strength of cement increases slightly compared with the control group at a low content of acrylamide. At a high content of acrylamide, the cement hydration is delayed and the stiffness is reduced due to the introduction of excessive polymer, and the compressive strength of cement decreases significantly at 7 days. The compressive strength recovers at 28 days.

[0142] Example 2

[0143] Preparation of reference group samples: Weigh 1500g of P.I.52.5 silicate cement and add it to the mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water, stir for 5 minutes, and then pour it into the mold.

[0144] Preparation of cement-based composite samples with added acrylamide and oxidized starch (denoted as 3% AM / 0.5% OS and 7% AM / 0.5% OS, respectively): 0.5% of oxidized starch by mass of cement was weighed and added to 300g of water. The mixture was heated and stirred in an 85℃ water bath for 1.5h, then removed and cooled to room temperature (20℃). 3% and 7% of acrylamide monomers by mass of cement were weighed and added to 300g of water, stirring until dissolved. The acrylamide solution and oxidized starch solution were mixed, and water was added to a total volume of 600g. After stirring evenly, the mixture was ultrasonically mixed for 10min. Ammonium persulfate and N,N'-methylenebisacrylamide were weighed according to a mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12, and added to the acrylamide and oxidized starch mixture. The mixture was stirred evenly and ultrasonically dispersed for 10min. 1500g of… Add PI52.5 silicate cement to a mixing pot and mix for 2 minutes using a cement mixer; add a mixture of acrylamide and oxidized starch with different dosages, and mix for 3 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm, then mix for 2 minutes at a revolution speed of 125±5 rpm and a rotation speed of 285±10 rpm before pouring into a mold.

[0145] After the slurry was poured into the mold, it was shaken 60 times. It was then covered with plastic wrap and allowed to stand for 24 hours before demolding. After standard curing for 7 and 28 days, compressive strength and flexural strength tests were conducted. The results are as follows: Figure 8 and Figure 9 As shown.

[0146] from Figure 8 and Figure 9 It can be seen that: with a 0.5% oxidized starch content, the flexural strength of cement increases with the increase of acrylamide content; at the same time, the compressive strength of cement increases slightly with low acrylamide content, and decreases with high acrylamide content.

[0147] Example 3

[0148] Preparation of reference group samples: Weigh 1500g of P.I.52.5 silicate cement and add it to the mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water, stir for 5 minutes, and then pour it into the mold.

[0149] Cement-based composite material samples with added acrylamide and oxidized starch (denoted as 5% AM / 0.3% OS and 5% AM / 1.5% OS, respectively) were prepared as follows: Oxidized starch at 0.3% and 1.5% of the cement mass was weighed and added to 300g of water. The mixture was heated and stirred in an 85℃ water bath for 1.5h, then removed and cooled to room temperature (20℃). Acrylamide monomer at 5% of the cement mass was weighed and added to 300g of water and stirred until dissolved. The acrylamide solution and oxidized starch solution were mixed, and water was added to a total volume of 600g. After stirring evenly, the mixture was ultrasonically mixed for 10min. Ammonium persulfate and N,N'-methylenebisacrylamide were weighed according to a mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12 and added to the acrylamide and oxidized starch mixture. The mixture was stirred evenly and ultrasonically dispersed for 10min. 1500g of... Add PI52.5 silicate cement to a mixing pot and mix for 2 minutes using a cement mixer; add a mixture of acrylamide and oxidized starch with different dosages, and mix for 3 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm, then mix for 2 minutes at a revolution speed of 125±5 rpm and a rotation speed of 285±10 rpm before pouring into a mold.

[0150] After the slurry was poured into the mold, it was agitated 60 times. It was then covered with plastic wrap and allowed to stand for 24 hours before demolding. After standard curing for 7 and 28 days, compressive strength and flexural strength tests were conducted. The results are as follows: Figure 10 and Figure 11 As shown, from Figure 10 and Figure 11 It can be seen that excessive oxidized starch affects the fluidity of cement, occupies a large amount of water and space, and affects the density of cement. As the amount of oxidized starch increases, the effect on improving flexural strength gradually decreases, while the effect on compressive strength is relatively small.

[0151] Example 4

[0152] Preparation of reference group samples: Weigh 1500g of P.I.52.5 silicate cement and add it to the mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water, stir for 5 minutes, and then pour it into the mold.

[0153] Preparation of cement-based composite material with added acrylamide (denoted as 5% AM): Weigh 5% acrylamide monomer by mass of cement, add to 600g of water and stir until dissolved. Weigh ammonium persulfate and N,N'-methylenebisacrylamide according to the mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12, add to the acrylamide solution and stir for 5min. Weigh 1500g of P.I.52.5 silicate cement and add to the mixing pot, stir with a cement mixer for 2min. Add acrylamide solution, stir for 5min and pour into a mold.

[0154] Preparation of cement-based composite material samples with added oxidized starch (denoted as 0.5% OS): Weigh 0.5% of the oxidized starch by mass of cement, add it to 300g of water, heat and stir in an 85℃ water bath for 1.5h, then remove it, add water to the total volume of 600g, and cool to room temperature (20℃); Weigh 1500g of P.I.52.5 silicate cement and add it to a mixing pot, and stir for 2min using a cement mixer; Add the gelatinized oxidized starch solution, stir for 3min at a revolution speed of 62±5rpm and a rotation speed of 140±10rpm, then stir for 2min at a revolution speed of 125±5rpm and a rotation speed of 285±10rpm, and pour into a mold.

[0155] Preparation of cement-based composite material samples with added acrylamide and oxidized starch (denoted as 5% AM / 0.5% OS): Weigh 0.5% of oxidized starch by mass of cement, add to 300g of water, heat and stir in an 85℃ water bath for 1.5h, then remove and cool to room temperature (20℃); weigh 5% of acrylamide monomer by mass of cement, add to 300g of water and stir until dissolved; mix the acrylamide solution and oxidized starch solution, add water to a total volume of 600g, stir evenly, and ultrasonically mix for 10min; weigh ammonium persulfate and N,N'-methylenebisacrylamide according to the mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12, add to the acrylamide and oxidized starch mixture, stir evenly, and ultrasonically disperse for 10min; weigh 1500g of P.I.52.5 silicate cement and add to a mixing pot, stir using a cement mixer for 2min; add the acrylamide and oxidized starch mixture, stir for 5min, and pour into a mold.

[0156] After the slurry was poured into the mold, it was shaken 60 times. It was then covered with plastic wrap and allowed to stand for 24 hours before demolding. After standard curing for 7 and 28 days, compressive strength and flexural strength tests were conducted. The results are as follows: Figure 12 and Figure 13 As shown, from Figure 12 and Figure 13It can be seen that introducing acrylamide into the cement system can improve the flexural strength of cement, but acrylamide will have an adverse effect on the compressive strength of cement. Oxidized starch can not only improve the flexural strength of cement, but also has a certain effect on improving the compressive strength of cement, but its effect on improving the flexural strength of cement is relatively smaller than that of acrylamide. When acrylamide and oxidized starch are introduced at the same time, the flexural strength of cement is further improved compared with acrylamide or oxidized starch alone, and the effect of acrylamide on the low compressive strength of cement is alleviated.

[0157] The above-mentioned 7-day test samples were soaked in anhydrous ethanol for 7 days to stop hydration, dried, and then subjected to SEM and FTIR tests. The results are as follows: Figures 14-16 As shown.

[0158] from Figure 14 It can be seen that the absorption peak of the -NH2 plane rocking vibration starts from 1129 cm⁻¹. -1 Moved to 1113cm -1 This reflects changes in the chemical environment of the amino group, which are due to the interaction between the amino group and metal ions, as well as the hydrogen bonds formed between the amino group and hydroxyl groups in the hydration products, thus leading to changes in the vibrational properties of the amino group. The polymer-modified sample exhibits a change in the Si-O-Si bending vibration peak from 456 cm⁻¹. -1 up to 518cm -1 The characteristic shift indicates an interaction between polyacrylamide and the hydrated calcium silicate phase; the observation of characteristic peaks for carbon-carbon double bonds suggests that the in-situ polymerization of acrylamide was not complete; at 1625 cm⁻¹ -1 The absorption peak appearing at 1632 cm⁻¹ mainly originates from the intermolecular hydrogen bond interaction between acrylamide and oxidized starch. This specific hydrogen bond interaction causes the bending vibration absorption peak of -OH to rise from 1632 cm⁻¹. -1 The shift to lower wavenumbers confirmed the hydrogen bonding between acrylamide and oxidized starch.

[0159] from Figure 15 and Figure 16 It can be seen that the hydration products of the acrylamide and oxidized starch synergistically modified samples are covered with a polymer film, and the hydration products are bridged through a polymer network. After hydrochloric acid etching, it can be seen that the polymer network constructed in situ successfully forms an interpenetrating structure with the oxidized starch network. The synergistic effect of polyacrylamide and oxidized starch refines the polymer network structure. At the same time, amino, hydroxyl, and carboxyl groups bond with metal ions and cement hydration products in cement, which is beneficial to strengthening the connection between cement and polymer.

[0160] Comparative Example 2

[0161] Preparation of reference group samples: Weigh 1500g of PO42.5 silicate cement and add it to a mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water and stir for 5 minutes before pouring it into a mold.

[0162] Preparation of cement-based composite material samples with added oxidized starch and gelatinized (denoted as gelatinized 0.3% OS): Weigh 0.3% oxidized starch by mass of cement, add it to 300g of water, heat and stir in an 85℃ water bath for 1.5h, then remove it, add water to the total water volume to 600g, and cool to room temperature (20℃); Weigh 1500g of PO42.5 silicate cement, add silicate cement to a mixing pot, and stir with a cement mixer for 2min; Add gelatinized oxidized starch solution, stir for 5min, and pour into a mold.

[0163] Preparation of cement-based composite material samples with added oxidized starch (denoted as ungelatinized 0.3% OS): Weigh 0.3% of the cement mass of oxidized starch and add it to water and stir evenly; weigh 1500g of cement and add it to a mixing pot, and stir with a cement mixer for 2 minutes; add the oxidized starch solution, and stir for 3 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm, then stir for 2 minutes at a revolution speed of 125±5 rpm and a rotation speed of 285±10 rpm, and then pour it into a mold.

[0164] After the slurry was poured into the mold, it was agitated 60 times. It was then covered with plastic wrap and allowed to stand for 24 hours before demolding. After 7 days of standard curing, compressive strength and flexural strength tests were conducted, and the results are as follows: Figure 17 and Figure 18 As shown, from Figure 17 and Figure 18 It can be seen that gelatinized oxidized starch forms a more uniform polymer network, exposing more hydroxyl and carboxyl groups, resulting in a better enhancement effect on the mechanical properties of cement.

[0165] Comparative Example 3

[0166] Preparation of reference group samples: Weigh 1500g of P.I.52.5 silicate cement and add it to the mixing pot. Use a cement mixer to stir for 2 minutes at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Slowly add 600g of water, stir for 5 minutes, and then pour it into the mold.

[0167] Preparation of cement-based composite material samples with added acrylamide (denoted as 2% AM): Weigh 2% acrylamide monomer (by mass of cement) and add it to 600g of water, stirring until dissolved. Weigh ammonium persulfate and N,N'-methylenebisacrylamide according to a mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12, add them to the acrylamide solution, and stir for 5 min. Weigh 1500g of PI52.5 silicate cement and add it to a mixing pot, stirring slowly for 2 min using a cement mixer. Add the acrylamide solution, and stir for 3 min at a revolution speed of 62±5 rpm and a rotation speed of 140±10 rpm. Then stir for 2 min at a revolution speed of 125±5 rpm and a rotation speed of 285±10 rpm before pouring into a mold.

[0168] Preparation of cement-based composite material samples with added acrylamide and oxidized starch (2% AM / 0.5% OS): Weigh 0.5% of oxidized starch by mass of cement, add to 300g of water, heat and stir in an 85℃ water bath for 1.5h, then remove and cool to room temperature (20℃); weigh 2% of acrylamide monomer by mass of cement, add to 300g of water and stir until dissolved; mix the acrylamide solution and oxidized starch solution, add water to a total volume of 600g, stir evenly, and ultrasonically mix for 10min; weigh ammonium persulfate and N,N'-methylenebisacrylamide according to the mass ratio of acrylamide:ammonium persulfate:N,N'-methylenebisacrylamide = 15:0.3:0.12, add to the acrylamide and oxidized starch mixture, stir evenly, and ultrasonically disperse for 10min; weigh 1500g of PI52.5 silicate cement and add to a mixing pot, stir with a cement mixer for 2min; add the acrylamide and oxidized starch mixture, stir for 5min, and pour into a mold.

[0169] After the slurry was poured into the mold, it was shaken 60 times. It was then covered with plastic wrap and allowed to stand for 24 hours before demolding. After standard curing for 7 and 28 days, compressive strength and flexural strength tests were conducted. The results are as follows: Figure 19 and Figure 20 As shown, from Figure 19 and Figure 20 It can be seen that the samples modified by in-situ polymerization of acrylamide monomer and synergistic modification of oxidized starch have stronger flexural strength and compressive strength than the samples modified by acrylamide alone.

[0170] Figure 21 This diagram illustrates the formation process of a dual-network structure of acrylamide and oxidized starch in cement, where AM represents acrylamide monomer, CH represents calcium hydroxide, CSH represents hydrated calcium silicate, PAM represents polyacrylamide, and OS represents oxidized starch. Figure 21It can be seen that after the polymer network of oxidized starch is uniformly dispersed in the cement matrix, it forms a three-dimensional network structure and interacts with cement particles through physical entanglement and chemical bonding. Acrylamide monomers adsorbed on the oxidized starch network and free in water interact with cement particles, ultimately adsorbing onto both cement particles and oxidized starch. During cement hydration, acrylamide monomers undergo in-situ polymerization, gradually forming a polyacrylamide network, which forms a cross-linked interpenetrating organic double network structure with oxidized starch, enhancing the strength of the organic network. Simultaneously, the polymer and cement hydration products form an organic-inorganic interpenetrating network structure. This organic double network structure is more compact, strengthening the physical entanglement between the polymer and cement hydration products. Furthermore, relying on the numerous active functional groups of oxidized starch, the interaction between the polymer network and cement hydration products is further enhanced, thus strengthening the stress dispersion effect of the polymer network in the cement matrix.

[0171] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a cement-based composite material with an organic-inorganic interpenetrating structure, characterized in that, Includes the following steps: The aqueous dispersion of the polymer was pretreated to obtain a pretreated polymer system; The pretreated polymer system, monomers, and additives are mixed to obtain an organic system; The organic system and cement-based material are mixed, and then molded and cured sequentially to obtain the cement-based composite material with the organic-inorganic interpenetrating structure. The polymer is a substance containing active groups; The monomer is either a first monomer or a second monomer; The first monomer is a monomer containing unsaturated carbon-carbon double bonds that can undergo free radical polymerization; when the monomer is the first monomer, the auxiliary agent includes an initiator and a crosslinking agent; The second monomer is a monomer or oligomer unit containing an epoxy group that can be polymerized by ring-opening polymerization; when the monomer is the second monomer, the auxiliary agent is a curing agent; The cement-based material includes cement.

2. The preparation method according to claim 1, characterized in that, The polymers include one or more of the following: natural polymers and their derivatives, synthetic polymers, supramolecular systems, and covalent organic framework materials; The natural polymers and their derivatives include one or more of the following: starch, oxidized starch, carboxymethyl starch, carboxylated oxidized starch, microcrystalline cellulose, nanocellulose, oxidized cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, oxidized sodium alginate, potassium alginate, sulfonated lignin, carrageenan, κ-carrageenan, hyaluronic acid, sodium hyaluronate, oxidized hyaluronic acid, xanthan gum, pectin, low-methoxyl pectin, chitosan, oxidized chitosan, carboxymethyl chitosan, gelatin, methacrylamide gelatin, collagen, glycogen, dextrin, cyclodextrin, dextran, and pullulan. The synthetic polymer includes one or more of sodium polyacrylate, polyvinyl alcohol, sodium polystyrene sulfonate, polyethylene glycol and its derivatives, polyethylene glycol diacrylate, polyhydroxyethyl methacrylate, polymaleic anhydride copolymer, polyacrylamide, polyacrylic acid and polyglutamic acid; The supramolecular system includes one or more of the following: phenylboronic acid-diol complex, hydroxypropyl-β-cyclodextrin, metal-organic gel, cyclodextrin inclusion complex, amphiphilic peptides, ureidinone derivatives, and ureidinone dimers; The covalent organic framework material includes one or more of the following: imine bond covalent organic framework materials, hydrazone bond covalent organic framework materials, sulfonated covalent organic framework materials, and borate ester covalent organic framework materials; The polymer has a mass of 0.1% to 5% of the cement mass.

3. The preparation method according to claim 1, characterized in that, The pretreatment is either heating and stirring or ultrasonic dispersion and stirring; The heating and stirring temperature is 60–100°C, and the time is 0.5–3 hours. The ultrasonic dispersion and stirring frequency is 15–200 kHz, and the time is 5–30 min.

4. The preparation method according to claim 1, characterized in that, The first monomer includes one or more of acrylamide monomers, acrylic monomers, and acrylate monomers; The acrylamide monomers include acrylamide and / or hydroxymethylacrylamide; The acrylic monomers include sodium acrylate and / or acrylic acid; The acrylate monomers include one or more of acrylates, butyl acrylate, butyl methacrylate, ethylene glycol dimethacrylate, and hydroxyethyl methacrylate; The second monomer comprises an epoxy monomer and / or an oligomer unit formed from an epoxy monomer; The epoxy monomers include glycidyl epoxide monomers and / or non-glycidyl epoxide monomers; The oligomer units formed by the epoxy compound monomers include oligomer units formed by glycidyl epoxy monomers and / or oligomer units formed by non-glycidyl epoxy monomers. The mass of the monomer is 0.1% to 15% of the mass of the cement.

5. The preparation method according to claim 1, characterized in that, The initiator includes one or more of the following: inorganic peroxide initiators, organic peroxide initiators, azo initiators, and redox system initiators; The inorganic peroxide initiator includes one or more of ammonium persulfate, potassium persulfate, and sodium persulfate; The organic peroxide initiator includes one or more of benzoyl peroxide, di-tert-butyl peroxide, methyl ethyl ketone peroxide, tert-butyl peroxide, and cumene hydroperoxide. The azo initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile; The initiator of the redox system includes one or more of potassium permanganate, bromate, chlorate, sodium bisulfite, sodium sulfite, sodium metabisulfite, and sodium thiosulfate; The mass of the initiator is 0.2% to 5% of the mass of the first monomer; The crosslinking agent is a compound containing at least two amino groups; the crosslinking agent includes one or more of N,N'-methylenebisacrylamide, hexamethylenetetramine, hydroquinone, polyethyleneimine, p-phenylenediamine, and dimethylaminoethyl methacrylate. The mass of the crosslinking agent is 0 to 4% of the total mass of the first monomer and the polymer.

6. The preparation method according to claim 1, characterized in that, The curing agent includes one or more of amine curing agents, acid anhydride curing agents, and latent curing agents; The amine curing agent includes one or more of polyamide curing agents, aromatic amine curing agents, aliphatic primary amine curing agents, and phenolic amine curing agents; The anhydride curing agents include alicyclic anhydride curing agents and / or aromatic anhydride curing agents; The latent curing agent includes a microencapsulated amine curing agent; The mass of the curing agent is 5-30% of the mass of the second monomer.

7. The preparation method according to claim 1, characterized in that, The cement-based material also includes a water-reducing agent, which includes one or more of polycarboxylate water-reducing agents, lignin sulfonate water-reducing agents, and naphthalene-based water-reducing agents; the mass of the water-reducing agent is 0 to 1% of the cement mass.

8. The preparation method according to claim 1 or 7, characterized in that, The cement-based material includes one or more of cement paste, cement mortar, and concrete.

9. The preparation method according to claim 1, characterized in that, The molding environment temperature is 0–40°C, and the time is 2–60 hours. The ambient temperature for the curing process is 0–40℃, and the humidity is ≥80%.

10. The organic-inorganic interpenetrating cement-based composite material obtained by the preparation method according to any one of claims 1 to 9.

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