Organic-inorganic supramolecular composite early strength agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of building materials, in particular to an organic-inorganic supramolecular composite early strength agent as well as a preparation method and application thereof. The early strength agent is formed by carrying out random free radical copolymerization on a monomer A, a monomer B, a monomer C and modified nano halloysite and then carrying out electrostatic interaction with polyoxometallate, wherein the monomer A is at least one of unsaturated carboxylic acid and unsaturated carboxylate; the monomer B is isopentenol polyoxyethylene ether, and the monomer C is at least one of methacryloyl propyl trimethyl ammonium chloride and acryloyl propyl trimethyl ammonium chloride; the polyoxometallate is at least one of phosphomolybdic acid and silicomolybdic acid; the modified nano halloysite is nano halloysite of which the surface is sequentially subjected to amination modification and maleic anhydride functionalization. The early strength agent provided by the invention synchronously realizes double improvement of water reducing and early strength functions through multi-stage effects of charge synergy, nanometer enhancement, space stabilization and ion regulation and control.

Description

Technical Field

[0001] This application relates to the field of building materials technology, and more specifically, to an organic-inorganic supramolecular composite early strength agent, its preparation method, and its application. Background Technology

[0002] Over the past decade, with the increasing demands for construction efficiency and resource conservation in the construction industry, early-strength technology for cement-based materials and products has made significant progress in both theoretical research and engineering practice. Based on the hydration reaction mechanism of cement-based materials, the core technologies for accelerating the hydration process currently fall into three categories: First, molecular design-driven polymer dispersion technology—early-strength polycarboxylate admixtures. By precisely controlling the main chain charge density, side chain length, and functional group type (such as carboxyl groups and sulfonic acid groups), multi-level synergistic effects are achieved: the anionic main chain adsorbs onto the surface of cement particles, inducing electrostatic repulsion to inhibit agglomeration; the long polyether side chains form a steric barrier to hinder flocculation; and specific functional groups accelerate the dissolution of calcium ions and promote the early dissolution of the C3S phase, thereby significantly improving the early strength development rate. Second, nanoscale-induced heterogeneous nucleation technology—functional nanomaterials (such as nano-SiO2 / CaCO3 / TiO2, etc.). Their nanoscale characteristics (matching the CSH gel scale) endow them with ultra-high specific surface area and surface unsaturated bond states (such as Si-OH), selectively enriching Ca through hydrogen bonds and ion-dipole interactions. 2+ / [SiO4] 4- Plasma forms locally supersaturated micro-regions, reducing the CSH nucleation activation energy by 30–50%, inducing the formation of high cross-linking density gels and optimizing the interfacial transition zone, thus improving early strength; the third is nano-supramolecular hybrid technology—supramolecular dispersants based on nanotemplates, which composite nanounits on a polycarboxylic acid backbone, simultaneously exerting the polymer dispersion effect and nanotemplate function: the polycarboxylic acid chains ensure particle dispersion and increase the hydration interface, while the nanocomponents directionally induce rapid nucleation and growth of CSH, achieving early strength improvement and forming a synergistic early strength control system.

[0003] Compared to early-strength polycarboxylate admixtures, nanomaterials can achieve significant early-strength effects with extremely low dosages without affecting later strength growth, showing broad application prospects. However, the performance advantages of nanomaterials are essentially due to their nanoscale effect, which is easily degraded by particle agglomeration in cement-based strong alkaline and high-salt environments, resulting in a significant reduction in practical application effects.

[0004] For example, patent document CN 104944824 B, "An Early Strength Agent and an Early Strength Water-Reducing Agent for Cement Concrete," discloses an early strength agent component containing nano-calcium carbonate, calcium salt, and a water-reducing agent. That is, by combining nano-calcium carbonate and light calcium carbonate powder with calcium formate or calcium nitrate, the cement concrete early strength agent formed solves the problems of corrosion and alkali-aggregate reaction of early strength agents in the prior art, significantly improves the early and late strength of concrete, shortens the setting time, and improves construction efficiency.

[0005] Patent document CN 112979204B, "A magnesium-doped calcium silicate nucleation early strength agent with long-term stability and its preparation method," discloses a magnesium-doped calcium silicate nucleation early strength agent with long-term stability and its preparation method. By introducing magnesium ions into the structure of silicate polymers, a stable calcium silicate nucleation early strength agent is obtained, which can improve the early strength of cement.

[0006] It can be seen that the aforementioned patents mostly involve using polycarboxylate superplasticizers to disperse nanomaterials; however, there are few reports on the composite hybridization of superplasticizers and nanomaterials. Furthermore, the performance and stability of additives doped with nanomaterials are also among the challenges that existing technologies need to address. Summary of the Invention

[0007] This application provides an organic-inorganic supramolecular composite early strength agent, its preparation method, and its application. The early strength agent of this application achieves a dual improvement in water reduction and early strength through multi-level effects of charge synergy, nano-reinforcement, spatial stabilization, and ion regulation. Moreover, the preparation process of the early strength agent of this application is relatively simple, and it can also give full play to the activity of nano halloysite, solve the dispersion and stability problem of HNTs, and thus significantly promote the development of early mechanical properties of cement-based materials.

[0008] In the first aspect, this application provides an organic-inorganic supramolecular composite early strength agent, which adopts the following technical solution: An organic-inorganic supramolecular composite early strength agent is formed by random free radical copolymerization of monomers A, B, C and modified nano-haloite, followed by electrostatic interaction with polyoxometalates. Wherein, monomer A is at least one of unsaturated carboxylic acid and unsaturated carboxylic acid salt; monomer B is isopentenyl alcohol polyoxyethylene ether; monomer C is at least one of methacryloylpropyltrimethylammonium chloride and acryloylpropyltrimethylammonium chloride; the polyoxometalate is at least one of phosphomolybdic acid and silicomolybdic acid; and the modified nano halloysite is nano halloysite whose surface has been successively modified by amylation and functionalized with maleic anhydride.

[0009] By adopting the above technical solutions, the core mechanism of current mainstream early-strength agents lies in the targeted regulation of cement hydration process: by intervening in the evolution of concrete's chemical composition, microstructure formation, and setting kinetics, they significantly promote the early development of the cement matrix and the hydration reaction rate. Essentially, they accelerate the dissolution kinetics of key mineral phases such as tricalcium silicate (C3S), dicalcium silicate (C2S), tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF), simultaneously driving the nucleation and growth of products such as ettringite (AFt) and hydrated calcium silicate (CSH) gel, ultimately achieving a synergistic acceleration of the cement setting-hardening process, thereby endowing concrete with excellent early-strength properties.

[0010] Halloysite nanotubes (HNTs) are a natural aluminosilicate clay mineral with a unique hollow, multi-layered tubular structure (outer diameter approximately 50 nm, inner diameter 15–20 nm, length 0.5–2 μm). They are abundant, inexpensive, and environmentally friendly. Studies have shown that HNTs enhance the performance of cement-based materials in two ways: physically, the tubular morphology forms a microfiber network scaffold in the slurry, refining the porosity of the interfacial transition zone and increasing density; chemically, surface silanol and aluminol hydroxyl groups continuously release active silicon / aluminum components in an alkaline environment, stimulating the pozzolanic reaction and promoting the formation of secondary CSH gels. However, nano-haloysite often faces the problem of poor dispersion stability.

[0011] Therefore, in the technical solution of this application, a stable "ionic cross-linking network" is formed through the strong electrostatic complexation of cationic monomer C and anionic polyoxometalates, which can significantly improve the dispersion efficiency and active release of halloysite nanotubes, as well as enhance the rigidity of the molecular structure and improve adsorption stability. Furthermore, HNTs containing double bonds are covalently anchored to the molecular backbone through copolymerization, and combined with excellent dispersion efficiency and activity, fully utilize their nanocrystal nucleation effect. On the one hand, they act as nuclei to accelerate the heterogeneous nucleation of cement hydration products (CSH gel), improving early strength; on the other hand, they compact the microstructure of cement stone through nanofilling effect. Moreover, the introduction of HNTs increases the molecular chain length and relative molecular weight of the early strength agent, thereby enhancing the steric hindrance effect of the early strength agent molecules on cement particles and improving the dispersion ability of the early strength agent on cement particles. In addition, cationic monomer C can be adsorbed onto the surface of cement particles through electrostatic interaction, replacing low-valent cations (such as Ca). 2+ This disrupts the double-layer compression and promotes cement dispersion. The polyoxometalate introduced in this application, with its multi-charge properties, can further chelate calcium ions and regulate the crystallization kinetics of hydration products.

[0012] In addition, the long polyether side chains of the grafted isopentenyl alcohol polyoxyethylene ether fully extend in the hydration medium, and synergistically construct a "spatial-nano dual network" with the nanotube structure of HNTs to form a high-thickness adsorption layer, giving the system excellent steric hindrance effect, greatly improving the dispersibility of cement particles, stabilizing the dispersion system and inhibiting the aggregation of HNTs; the carboxyl groups provided by the carboxylic acid unit enhance the anchoring effect on cement minerals through chemical adsorption, form chemical adsorption with cement minerals, synergistically enhance dispersibility and optimize water-reducing performance.

[0013] Ultimately, this application not only significantly improves the dispersion efficiency and activity release of halloysite nanotubes, but also achieves a dual enhancement of water reduction and early strength functions through multi-level effects of charge synergy, nano-reinforcement, spatial stabilization and ion regulation, thus significantly promoting the development of early mechanical properties of cement-based materials.

[0014] Furthermore, the mass ratio of monomer A, monomer B, monomer C and modified nano halloysite is (4~12): (1~3):1:(0.2~0.4).

[0015] Furthermore, the molar ratio of the polyoxometalate to the monomer C is (1.1~1.4):1.

[0016] Furthermore, the preparation method of the modified nano-haloysite includes the following steps: (1) Aminoation modification reaction on the surface of nano halloysite First, γ-aminopropyltriethoxysilane (KH-550) was added to deionized water at room temperature, and ammonia was added dropwise to adjust the pH to 8-10, resulting in a hydrolysate. Then, nano-haloite powder was dispersed in anhydrous ethanol and stirred to obtain a dispersion. The dispersion was then mixed with the hydrolysate and fully dispersed. The mixture was reacted and stirred at 70-80℃ for 5-10 hours. After centrifugation and washing of the reaction mixture, it was finally freeze-dried to obtain aminated nano-haloite. (2) Maleic anhydride functionalization of nano-haloysite reaction The aminated nano-haloite obtained in step (1) was dispersed in deionized water at room temperature; then the system temperature was raised to 50~60℃, maleic anhydride was added, and the mixture was stirred at this temperature for 3~6h; after the reaction was completed, the system was cooled to room temperature, the reaction mixture was centrifuged and washed, and then vacuum dried to obtain modified nano-haloite.

[0017] Furthermore, in the step of the amylation modification reaction of the nano halloysite surface, the mass fraction of γ-aminopropyltriethoxysilane in water is 0.5-1%, the mass fraction of the nano halloysite in anhydrous ethanol is 1-2%, and the mass ratio of γ-aminopropyltriethoxysilane to nano halloysite is 1:(2-3).

[0018] Furthermore, in the step of the maleic anhydride functionalization of nano-halolite reaction, the mass fraction of aminated nano-halolite in water is 3-6%, and the mass ratio of maleic anhydride to aminated nano-halolite is (2-3):1.

[0019] Furthermore, the early strength agent has a polymer weight-average molecular weight of 40–80 kDa and a PDI of 1.8–3.

[0020] Secondly, this application provides a method for preparing an organic-inorganic supramolecular composite early strength agent, employing the following technical solution: A method for preparing an organic-inorganic supramolecular composite early strength agent includes the following steps: Copolymerization reaction: Mix monomer A, monomer B, monomer C, modified nano-HNTs, oxidant and reducing agent, and react at 35-45℃ for 6-8 hours to carry out free radical copolymerization reaction; Electrostatic assembly reaction: Polyoxometalate is added to the copolymer system after copolymerization and stirred. The reaction is carried out at room temperature for 5-10 hours to obtain an early strength agent.

[0021] Furthermore, the oxidant is any one of ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount of the oxidant used is 0.3 to 0.6% of the total mass of the monomer.

[0022] Furthermore, the reducing agent is one or two of sodium metabisulfite, sodium sulfite, sodium bisulfite, and ferrous sulfate in any proportion, and the mass ratio of the original agent to the oxidizing agent is 1:1.

[0023] Furthermore, the free radical copolymerization reaction is an aqueous free radical copolymerization reaction, and the polymerization concentration of the free radical copolymerization reaction is 25-30%.

[0024] Thirdly, this application provides an application of an organic-inorganic supramolecular composite early strength agent, wherein the organic-inorganic supramolecular composite early strength agent is used in cement-based materials, and its dosage is 0.1% to 0.4% of the amount of gel material in the cement-based materials.

[0025] In summary, this application has the following beneficial effects: 1. The early strength agent of this application achieves a dual improvement in water reduction and early strength functions through multi-level effects of charge synergy, nano-reinforcement, spatial stabilization and ion regulation, which significantly promotes the development of early mechanical properties of cement-based materials.

[0026] 2. In this application, a stable "ionic cross-linking network" is formed through the strong electrostatic complexation of cationic monomer C and anionic polyoxometalate, which can significantly improve the dispersion efficiency and activity release of halloysite nanotubes. Furthermore, isopentenyl polyoxyethylene ether is synergistically constructed with the nanotube structure of HNTs to form a "spatial-nano dual network," creating a high-thickness adsorption layer. This stabilizes the dispersion system and inhibits HNT aggregation through steric hindrance. Detailed Implementation

[0027] The present application will be further described in detail below with reference to the embodiments.

[0028] This application provides an organic-inorganic supramolecular composite early strength agent, which is formed by random free radical copolymerization of monomers A, B, C and modified nano-haloite, and then electrostatic interaction with polyoxometalates. Wherein, monomer A is at least one of unsaturated carboxylic acids and unsaturated carboxylates; further, monomer A is selected from any one or a mixture of more than one of acrylic acid, alkali metal salts of acrylic acid, methacrylic acid, and alkali metal salts of methacrylic acid in any proportion. The structural formula of monomer A is shown in formula (Ⅰ) below: (I) In formula (Ⅰ), R1 is H or CH3, and R2 is H or an alkali metal ion.

[0029] Monomer B is isopentenyl alcohol polyoxyethylene ether, and the structural formula of monomer B is shown in formula (II) below: (II) Monomer C is at least one of methacryloylpropyltrimethylammonium chloride and acryloylpropyltrimethylammonium chloride; the structural formula of monomer C is shown in formula (Ⅲ) below: (III) In formula (Ⅲ), R3 is H or CH3.

[0030] The polyoxometalate is at least one of phosphomolybdic acid and silicomolybdic acid; the modified nano-haloite is nano-haloite whose surface has been successively modified by amylation and functionalized with maleic anhydride.

[0031] The preparation method of modified nano-haloysite includes the following steps: (1) Amination modification reaction on the surface of nano HNTs First, γ-aminopropyltriethoxysilane (KH-550) was added to deionized water (0.5-1% by mass) at room temperature and stirred (at a rate of 800-1200 r / min). An appropriate amount of ammonia water (analytical grade, 25%-28%) was then added dropwise, and the pH was adjusted to 8-10. Next, the nano-HNTs powder was dispersed in anhydrous ethanol (1-2% by mass) and stirred (at a rate of 800-1200 r / min for 1 h). The dispersion was then mixed with the hydrolyzed KH-550 solution. The mixture was sonicated for 30 min to disperse it fully, and then stirred at 70-80℃ (at a rate of 800-1200 r / min for 5-10 h). The reaction mixture was centrifuged and washed three times with deionized water (8000 rpm for 10 min) to remove unreacted KH-550. Finally, the mixture was freeze-dried for 24 h to obtain modified nano-HNTs. The stirring rate remained constant throughout the entire reaction.

[0032] Furthermore, both the nano-HNTs powder and γ-aminopropyltriethoxysilane (KH-550) are commercially available products, and the mass ratio of KH-550 to nano-HNTs is 1:(2~3). The stirring rate remains constant throughout the entire reaction process.

[0033] (2) Reaction of maleic anhydride functionalized nano-HNTs First, the amination-modified nano-HNTs obtained in step (1) were added to deionized water (mass fraction 3-6%) at room temperature and ultrasonically dispersed for 0.5-1 h. Next, the system temperature was raised to 50-60℃, maleic anhydride was added, and the mixture was stirred at this temperature (rate 800-1200 r / min, 3-6 h). After the reaction was completed, the system was cooled to room temperature, and the reaction mixture was centrifuged and washed three times with deionized water (8000 rpm, 10 min). Finally, the mixture was vacuum dried for 24 h to obtain the modified nano-HNTs.

[0034] Furthermore, maleic anhydride is a commercially available product, and the mass ratio of maleic anhydride to aminated nano-HNTs is (2~3):1. The nano-HNTs powder used in the embodiments of this application, namely nano-haloysite powder, is commercially available, specifically purchased from Xianfeng Nano, with a diameter of 50-300nm.

[0035] This application also provides a method for preparing an organic-inorganic supramolecular composite early strength agent, comprising the following steps: (1) Copolymerization reaction: Monomer A, monomer B, monomer C, modified nano-HNTs, oxidant and reducing agent are mixed and added, and reacted at 35-45℃ for 6-8 hours to carry out free radical copolymerization reaction. The free radical copolymerization reaction is an aqueous free radical copolymerization reaction, and the polymerization concentration of the free radical copolymerization reaction is 25-30%.

[0036] The mass ratio of monomer A, monomer B, monomer C and modified nano HNTs is (4~12): (1~3):1:(0.2~0.4).

[0037] The oxidant consists of a single oxidant selected from any one of water-soluble ammonium persulfate, sodium persulfate, and potassium persulfate, with the amount of oxidant being 0.3-0.6% of the total mass of the single oxidant. The reducing agent is one or two of sodium metabisulfite, sodium sulfite, sodium bisulfite, and ferrous sulfate, combined in any proportion, with the mass ratio of reducing agent to oxidant being 1:1.

[0038] (2) Electrostatic assembly reaction: Polyoxometalate (POM) was added to the copolymer system obtained in step (1). The molar ratio of POM to monomer C was (1.1~1.4):1. A conventional magnetic stirring reaction was carried out at room temperature for 5~10 h. The stirring rate was 600~1000 r / min. An early strength agent was obtained. The aforementioned organic-inorganic supramolecular composite early strength agent can be used for early reinforcement of cement-based materials, and its dosage (converted to solids) is 0.1~0.4% of the amount of cementitious material.

[0039] It should be noted that the weight-average molecular weight of the organic-inorganic supramolecular composite early-strength agent described in the examples was determined using a Shimadzu LC-20A high-performance gel permeation chromatography (GPC) system. The chromatographic column used was a TSK G4000PWXL series, the column temperature was 25℃, the eluent was 0.1M sodium acetate aqueous solution, the flow rate was 0.5ml / min, the injection volume was 15μl of 1‰ aqueous solution of the sample, and the standard curve was prepared using dextran standard (Sigma-Aldrich).

[0040] The following explanation is provided through specific examples.

[0041] Examples 1-8 The differences between Examples 1 to 8 lie in the types and amounts of raw materials and the process parameters, as detailed in Tables 1 and 2. In Table 1, the feed ratio is the mass ratio of monomer A, monomer B, monomer C, and modified nano-HNTs.

[0042] Table 1. Raw material ratio table for the embodiment.

[0043] Table 2 Process parameters for the embodiments (oxidant and reducing agent dosages are percentages of the total monomer mass).

[0044] In Examples 1-4 and 6-8, both the nano-HNTs powder and γ-aminopropyltriethoxysilane (KH-550) were commercially available products, and the mass ratio of KH-550 to nano-HNTs was 1:3; the mass ratio of maleic anhydride to aminated nano-HNTs was 3:1. In Examples 5-6, both the nano-HNTs powder and γ-aminopropyltriethoxysilane (KH-550) were commercially available products, and the mass ratio of KH-550 to nano-HNTs was 1:2; the mass ratio of maleic anhydride to aminated nano-HNTs was 2:1.

[0045] Comparative Example The difference between Comparative Examples 1-3 and the Examples lies in the different raw materials and preparation process conditions of the early strength agent, as detailed in Tables 3 and 4. The feeding ratio in Table 3 is the mass ratio of monomer A, monomer B, monomer C, and modified nano-HNTs.

[0046] Table 3. Raw material ratio table for the comparative example

[0047] Table 4. Process parameters for the comparative examples (oxidant dosage is a percentage of the total monomer mass).

[0048] In Comparative Examples 1-2 and 5-7, both nano-HNTs powder and γ-aminopropyltriethoxysilane (KH-550) were commercially available products, and the mass ratio of KH-550 to nano-HNTs was 1:3; the mass ratio of maleic anhydride to aminated nano-HNTs was 3:1.

[0049] Performance testing The strength testing method for cement mortar was based on the test methods in GB / T 17671-2021 (ISO method). The early-strength agents in the application examples and comparative application examples were evaluated. The basic mix proportions of the test mortar are shown in Table 7. The cement used in the test was P.II 52.5 cement, and the sand used was ISO standard sand. The performance test results of the comparative group, examples, and comparative examples are shown in Table 8. A comparative group was also set up, with the admixture being commercially available Sika 530P early-strength water-reducing agent. The dosage of the early-strength agent in comparative group 1 was 0.2%, and the dosage in comparative group 2 was 0.4%. Application examples 1-8 correspond to examples 1-8, application examples 9-11 correspond to example 3, and comparative application examples 1-5 correspond to comparative examples 1-5. Table 7. Experimental proportions for examples and comparative examples

[0050] Table 8 Performance test results of the examples and comparative samples (under standard maintenance conditions)

[0051] Analysis of the above test results shows that, comparing the performance of Examples 1-8 with that of Comparative Group 1, under the same accelerator dosage of 0.2%, Examples 1-8 significantly promote the early strength growth of cement-based materials. The 12-hour compressive strength and 1-day compressive strength of the prepared cement-based materials are significantly improved and are higher than those of Comparative Group 1. However, even when the accelerator dosage in the Comparative Group is increased to 0.4%, its performance is still lower than that of Examples 1-8. Therefore, compared with traditional accelerators, the accelerator of this patent application has the characteristics of low dosage and excellent early strength performance.

[0052] In addition, we found that under the same dosage conditions, among the early-strength agents in Application Examples 1-4, Application Example 3 showed the best performance in terms of dispersion effect. This is because the polyether long chain and the nanotube structure of HNTs synergistically construct a "spatial-nano dual network," forming a high-thickness adsorption layer, which endows the system with excellent steric hindrance effect, significantly improving the dispersibility of cement particles. The molecular weight of the early-strength agent plays an important role; it should not be too high or too low. The reason is that when the molecular weight of the early-strength agent is too high, the main chain structure will cause a cage effect on the carboxylic acid groups. When the molecular weight is too low, the low content of carboxylic acid groups will cause the early-strength agent to fail to adhere to the surface of cement particles, and too few HNT components will not be able to exert their nanocrystal nucleation effect, making it difficult to improve the early strength of concrete.

[0053] Furthermore, it can be seen from the working performance of Application Examples 5-6 that when the number of repeating units of monomer A is small, the adsorption sites, i.e., carboxylic acid groups, in the early strength agent will be too few, resulting in low dispersion performance. Therefore, the working performance of Application Example 5 is better than that of Application Example 6. It can be seen from Application Examples 7-8 that the working performance of Application Example 7 is better than that of Application Example 8. This is because the number of polyether units in the structure of monomer B should not be too high. If it is too high, it will cause the early strength agent to entangle and agglomerate, and it will not be able to form an effective dispersion on the cement-based material system.

[0054] Compared with Examples 1-8, the working performance of Comparative Application Example 1 is significantly lower than that of the early strength agent of this application, confirming that the lack of carboxylic acid groups prevents effective dispersion of cement-based materials, thus affecting the water-reducing performance of the early strength agent; the poor working performance of Comparative Application Example 2 is due to the lack of corresponding polyether units, i.e., the inability to achieve a spatial network structure, which makes it difficult to improve the early strength of cement-based materials; and the worst working performance of Comparative Application Example 3 is the lack of corresponding nano-HNTs structure, confirming that the lack of corresponding nano-HNTs structure prevents the HNTs from exerting their activity, fails to improve the degree of cement hydration reaction, and thus makes it difficult to achieve the purpose of improving compressive strength. Similarly, in Comparative Application Example 4, the structure contains only unmodified nano-HNTs, making it difficult to synergistically construct a "spatial-nano dual network" with isopentenyl alcohol polyoxyethylene ether. This results in ineffective dispersion of nano-HNTs and difficulty in improving early strength. The poor performance of Comparative Application Examples 5-6 is likely due to the lack of or insufficient amount of the corresponding anionic POM, which prevents the formation of a stable "ionic cross-linking network." This reduces the dispersion efficiency of HNTs, hindering their activity release and ultimately preventing a significant improvement in the early strength of cement-based materials. Furthermore, Comparative Application Example 7 also demonstrates that excessively high levels of the corresponding anionic POM cause the polymer chains of the early-strength agent to become entangled, making effective dispersion difficult. This indicates that the early-strength agent of this application achieves a dual improvement in water reduction and early-strength function through multi-level effects of charge synergy, nano-reinforcement, spatial stabilization, and ion regulation, significantly promoting the development of early mechanical properties of cement-based materials.

[0055] Meanwhile, from application examples 3, 9-11, it is not difficult to find that when the dosage of the early strength agent increases (0.1%→0.4%), the working strength of the test sample will increase slowly. However, if the dosage continues to increase, the working strength of the test sample shows a significant decreasing trend. This confirms that when the dosage of the organic-inorganic supramolecular composite early strength agent is too high, it may enter an adsorption supersaturation state. At this time, the nano HNTs may undergo secondary agglomeration due to the adsorption bridging effect caused by the adsorption groups on the early strength agent. This may lead to the polymer chain parts in the early strength agent becoming entangled with each other, reducing the dispersion performance of cement, and ultimately resulting in a lower working strength of the obtained cement-based material.

[0056] This application utilizes the structural characteristics of organic-inorganic supramolecular composite early-strength agents. Through the strong electrostatic complexation of cationic units (APTAC / MAPTAC) and anionic POM, a stable "ionic cross-linking network" is formed, significantly improving the dispersion efficiency of HNTs and the adsorption and dispersion effect of active release charges, thus significantly enhancing the active release of nano HNTs. Simultaneously, HNTs containing double bonds are covalently anchored to the molecular backbone through copolymerization, fully leveraging their nanocrystal nucleation effect to accelerate the heterogeneous nucleation of cement hydration products. Furthermore, they synergistically construct a "spatial-nano dual network" with long-chain polyether units, forming a high-thickness adsorption layer that endows the system with excellent steric hindrance effect, greatly improving the dispersibility of cement particles. The multi-charge characteristics of POM further chelate calcium ions, regulating the crystallization kinetics of hydration products, significantly improving the problem of low early strength in cement-based materials, ultimately achieving the goals of shortening construction time and improving the environment.

[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An organic-inorganic supramolecular composite early-strength agent, characterized in that, It is formed by random free radical copolymerization of monomers A, B, C and modified nano halloysite, followed by electrostatic interaction with polyoxometalates. Wherein, monomer A is at least one of unsaturated carboxylic acid and unsaturated carboxylic acid salt; monomer B is isopentenyl alcohol polyoxyethylene ether; monomer C is at least one of methacryloylpropyltrimethylammonium chloride and acryloylpropyltrimethylammonium chloride; the polyoxometalate is at least one of phosphomolybdic acid and silicomolybdic acid; and the modified nano halloysite is nano halloysite whose surface has been successively modified by amylation and functionalized with maleic anhydride.

2. The organic-inorganic supramolecular composite early strength agent according to claim 1, characterized in that, The mass ratio of monomer A, monomer B, monomer C and modified nano halloysite is (4~12): (1~3):1:(0.2~0.4).

3. The organic-inorganic supramolecular composite early-strength agent according to claim 1, characterized in that, The molar ratio of the polyoxometalate to the monomer C is (1.1~1.4):

1.

4. The organic-inorganic supramolecular composite early-strength agent according to claim 1, characterized in that, The preparation method of the modified nano-haloysite includes the following steps: (1) Aminoation modification reaction on the surface of nano halloysite First, γ-aminopropyltriethoxysilane (KH-550) was added to deionized water at room temperature, and ammonia was added dropwise to adjust the pH to 8-10, resulting in a hydrolysate. Then, nano-haloite powder was dispersed in anhydrous ethanol and stirred to obtain a dispersion. The dispersion was then mixed with the hydrolysate and fully dispersed. The mixture was reacted and stirred at 70-80℃ for 5-10 hours. After centrifugation and washing of the reaction mixture, it was finally freeze-dried to obtain aminated nano-haloite. (2) Maleic anhydride functionalization of nano-haloysite reaction The aminated nano-haloite obtained in step (1) was dispersed in deionized water at room temperature; then the system temperature was raised to 50~60℃, maleic anhydride was added, and the mixture was stirred at this temperature for 3~6h; after the reaction was completed, the system was cooled to room temperature, the reaction mixture was centrifuged and washed, and then vacuum dried to obtain modified nano-haloite.

5. The organic-inorganic supramolecular composite early strength agent according to claim 4, characterized in that, In the step of the amylation modification reaction of the nano halloysite surface, the mass fraction of γ-aminopropyltriethoxysilane in water is 0.5~1%, the mass fraction of the nano halloysite in anhydrous ethanol is 1~2%, and the mass ratio of γ-aminopropyltriethoxysilane to nano halloysite is 1:(2~3).

6. The organic-inorganic supramolecular composite early strength agent according to claim 4, characterized in that, In the step of the maleic anhydride functionalization of nano-halolite reaction, the mass fraction of aminated nano-halolite in water is 3~6%, and the mass ratio of maleic anhydride to aminated nano-halolite is (2~3):

1.

7. A method for preparing an organic-inorganic supramolecular composite early-strength agent as described in any one of claims 1-6, characterized in that, Includes the following steps: Copolymerization reaction: Mix monomer A, monomer B, monomer C, modified nano-HNTs, oxidant and reducing agent, and react at 35-45℃ for 6-8 hours to carry out free radical copolymerization reaction; Electrostatic assembly reaction: Polyoxometalate is added to the copolymer system after copolymerization and stirred. The reaction is carried out at room temperature for 5-10 hours to obtain an early strength agent.

8. The method for preparing an organic-inorganic supramolecular composite early-strength agent according to claim 7, characterized in that, The oxidant is any one of ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount of the oxidant is 0.3-0.6% of the total mass of the monomers; the reducing agent is one or two of sodium metabisulfite, sodium sulfite, sodium bisulfite, and ferrous sulfate in any proportion.

9. The method for preparing an organic-inorganic supramolecular composite early strength agent according to claim 7, characterized in that, The free radical copolymerization reaction is an aqueous free radical copolymerization reaction, and the polymerization concentration of the free radical copolymerization reaction is 25-30%.

10. An application of an organic-inorganic supramolecular composite early-strength agent as described in any one of claims 1-6, characterized in that, The organic-inorganic supramolecular composite early strength agent is used in cement-based materials, and its dosage is 0.1% to 0.4% of the amount of gel material in the cement-based materials.

Images