Polycarboxylate-type organic-inorganic hybrid admixture, preparation method thereof and application of admixture in calcined clay-limestone low-carbon cement

Abstract

The invention discloses a polycarboxylic acid organic-inorganic hybrid admixture, a preparation method thereof and application of the polycarboxylic acid organic-inorganic hybrid admixture in calcined clay-limestone low-carbon cement. The polycarboxylic acid organic-inorganic hybrid admixture is prepared by the following steps: copolymerizing a monomer A, a monomer B and a monomer C, grafting amino crown ether through amidation reaction, and then performing electrostatic interaction with polyoxometallate. The monomer A is unsaturated carboxylic acid or unsaturated carboxylate, the monomer B is acrylic acid-N-succinimide ester, and the monomer C is methacryloyl propyl trimethyl ammonium chloride or acryloyl propyl trimethyl ammonium chloride. According to the invention, a rigid benzene ring structure of crown ether is utilized to generate strong steric hindrance, and the crown ether and POM nanoparticles form a compact cross-linked network structure together, such a spatial cross double network physically obstructs intercalation adsorption of clay, intercalation adsorption of the admixture between clay layers is doubly obstructed, and the adaptability of the admixture is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a polycarboxylate-based organic-inorganic hybrid admixture, its preparation method, and its application in calcined clay-limestone low-carbon cement. Background Technology

[0002] In recent years, the widespread adoption of new dry-process cement technology has promoted energy efficiency improvements and environmental enhancements in the industry. In particular, the increased use of alternative materials such as slag and fly ash has effectively reduced the clinker requirement per unit of cement, significantly decreasing CO2 generation. Domestic and international scholars have been researching novel low-carbon cementitious systems for a long time. Among them, Limestone Calcined Clay Cement (LC3), developed by the Swiss Federal Institute of Technology in Lausanne, comprises limestone, calcined clay, gypsum, and clinker. The core reaction mechanism of this material lies in the interaction between limestone and calcined clay to form aluminocarbonate hydrates, a process that significantly accelerates the hydration of the cementitious system. With the increase in the proportion of calcined clay, the hydration products increase simultaneously, allowing LC3 to maintain excellent mechanical properties even at high clinker substitution rates. In the LC3-X naming system, X represents the mass percentage of clinker in the total cementitious materials. The typical formulation LC3-50 achieves a 50% clinker substitution rate, and its comprehensive performance indicators are comparable to those of ordinary Portland cement.

[0003] However, studies have shown that conventional polycarboxylate superplasticizers (PCEs) applied to LC3 systems exhibit poorer concrete workability than ordinary silicate cement concrete. This is due to the physical properties of clay minerals (such as montmorillonite and illite), namely their layered structure and surface electrical properties. The failure mechanism of PCE in clay-containing systems mainly stems from two aspects: First, PCE molecular chains easily embed into the interlayer structure of clay minerals, triggering a significant steric hindrance effect, resulting in a sharp decrease in dispersion ability and affecting concrete workability. Second, although calcined clay particles carry a negative surface charge, in the liquid phase environment of cement paste, calcium ions promote electrostatic complexation and anchoring of negatively charged PCE molecules at the clay interface through charge bridging, blocking their continuous dispersion function. These dual effects make conventional PCE difficult to adapt to the LC3 cementitious system. Therefore, directional modification of admixture structure through molecular design strategies has become a key research direction for improving the workability of LC3 concrete.

[0004] Patent No. CN 117964318 A discloses a high-strength, high-ductility, low-carbon cement-based composite material for marine engineering. By weight, it comprises: 350-800 parts cement, 200 parts silica fume, 0-300 parts calcined clay, 0-150 parts limestone powder, 0-360 parts fine aggregate, 200 parts PE fiber, 30 parts water-reducing agent, and 180 parts water. The cement-based composite material prepared by this invention solves the problems of excessive brittleness and insufficient toughness in traditional concrete. However, the patent does not specify the structure of the high-efficiency water-reducing agent, nor does it report its impact on workability.

[0005] Patent No. CN115959870 A discloses a crack-resistant, low-carbon, high-performance concrete and its preparation method. The crack-resistant, low-carbon, high-performance concrete includes the following raw materials and their dosages: LC3 cementitious material 390-410 kg / m³. 3 Sand 640~660kg / m 3 Stone 1000~1100kg / m 3 Water 150-170 kg / m 3 Water-reducing agent 8.0~8.5kg / m³ 3 Activated carbon fiber: 0.1–0.3 kg / m 3 Graphene oxide 0.1~0.3kg / m 3 The LC3 cementitious material is mainly composed of cement, calcined clay, limestone powder, and gypsum; the water is a mixture of wastewater from the mixing plant and clean water. The water-reducing agent is a polycarboxylate-based water-reducing agent with a solid content of 20% and a water reduction rate of 19%. The above PCE structure does not mention whether it contains anti-clay groups, resulting in the system not having a significant advantage in slump and spread. Summary of the Invention

[0006] In order to solve the technical problems existing in the above-mentioned prior art, the existing research mainly improves its anti-mud properties through the following technical approaches: (1) adopting amphoteric functional group design to avoid interaction with clay and intercalation; (2) using monomers with significant steric hindrance to prevent intercalation adsorption and enhance dispersion; (3) removing the -CH2-CH2-O- structure in the side chain; In view of the limitations of the above technical routes, the present invention provides a polycarboxylic acid organic-inorganic hybrid admixture and its preparation method and its application in calcined clay-limestone low-carbon cement (LC3). The admixture modifies the molecular structure of polycarboxylic acid and introduces anti-clay functional monomers for modification, thereby improving its anti-clay properties while ensuring its good workability, thus solving the problem of large-scale application of low-carbon cementitious systems in the concrete and construction industries.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A polycarboxylic acid-based organic-inorganic hybrid admixture is prepared by copolymerizing monomers A, B, and C, grafting amino crown ethers via amidation, and finally reacting with a polyoxometalate via electrostatic interaction. Wherein, monomer A is an unsaturated carboxylic acid or an unsaturated carboxylic acid salt, specifically selected from any one or a mixture of one or more of acrylic acid, alkali metal salts of acrylic acid, methacrylic acid, and alkali metal salts of methacrylic acid in any proportion; The monomer B is N-succinimide acrylate (NHS). The monomer C is methacryloylpropyltrimethylammonium chloride (MAPTAC) or acryloylpropyltrimethylammonium chloride (APTAC). Furthermore, the amino crown ether is 4'-aminobenzo18-crown-6 (AmBC).

[0008] Crown ethers are a class of macrocyclic polydentate ligands composed of multiple repeating ether bonds (-CH2-CH2-O-). The numerical prefix in their names (e.g., 18-crown-6) indicates the total number of atoms and oxygen atoms within the ring. Taking the typical component 18-crown-6 as an example, its molecular cavity diameter is approximately 0.26–0.32 nm, which is highly compatible with potassium ions (K+, diameter 0.266 nm), forming a stable "crown ether-K+" supramolecular complex (binding constant reaches 106 M⁻¹). After modifying the polycarboxylic acid backbone with crown ethers, their hydrophobic cyclic structure can selectively capture K+ / Na+ between clay layers (e.g., montmorillonite), compressing the interlayer spacing of the clay through an ion extraction effect (from 12 Å to 9.5 Å), while simultaneously blocking the adsorption pathway of the negative charge on the clay surface to the polycarboxyl group (-COO-), forming a dynamic ion barrier. The crown ether structure can reduce the ineffective adsorption rate of polycarboxylic acid in clay-containing systems by >85%, and the reversible ionic response characteristics of the crown ether can adaptively regulate the changes in ion concentration in concrete pore liquid, thereby achieving long-term anti-clay stability.

[0009] Furthermore, the molar ratio of monomer A, monomer B, monomer C, amino crown ether, and polyoxometalate is (6~8):1:2:(1.2~1.5):(2.2~2.8).

[0010] Furthermore, the polycarboxylate-based organic-inorganic hybrid admixture has a weight-average molecular weight of 60-100 kDa and a PDI of 2-3.

[0011] Furthermore, the polyoxometalate is phosphomolybdic acid H3[PMo] 12 O 40 or molybdenum silicate H4 [SiMo] 12 O 40 Both of these polyoxometalates are commercially available, with [SiMo] being the most readily available. 12 O40 ] 4- and [PMo 12 O 40 ] 3- Anionic groups can undergo charge assembly with the cationic tertiary amine groups of MAPTAC or APTAC. Polyoxometalates (POMs) are nanoscale polyoxometalate clusters formed by coordination bonds between transition metals (such as tungsten and molybdenum) and oxygen atoms. Their typical Keggin structure consists of 12 metal-oxygen octahedra surrounding a central heteroatom (such as phosphorus or silicon) tetrahedron, forming a cage-like spherical structure with a diameter of approximately 1.2 nm. The surface is covered with numerous terminal and bridging oxygen atoms, giving it both strong acidity (proton-donating ability) and high negative charge density. Introducing POM units into the polycarboxylic acid molecule structure allows the dense negative charge on its surface to effectively shield the positive charge sites at the edges of clay particles, blocking their adsorption to polycarboxylic acid molecules, thereby significantly improving the workability and mechanical properties of clay-containing concrete.

[0012] Furthermore, the preparation method of the polycarboxylate-based organic-inorganic hybrid admixture of the present invention includes the following steps: (1) Copolymerization reaction: Monomer A, monomer B, monomer C, initiator and chain transfer agent are mixed to carry out free radical copolymerization reaction. This free radical copolymerization reaction is a conventional aqueous free radical copolymerization reaction. The resulting copolymer system is then cooled to room temperature and the pH is adjusted to neutral. (2) Amide reaction: Add amino crown ether to the copolymer system of step (1) and stir for 3 hours in the dark under ice-water bath conditions; (3) Electrostatic assembly reaction: Add polyoxometalate to the product system of step (2) and stir at room temperature to obtain the polycarboxylic acid organic-inorganic hybrid additive of the present invention.

[0013] In step (1) above, the polymerization concentration in the copolymerization reaction is 15~20%, the polymerization temperature is 35~45℃, and the reaction time is 4~6h; Step (3) above involves magnetic stirring at a speed of 600-1000 r / min for a reaction time of 5-10 h.

[0014] In step (1) above, the initiator is selected from any one of water-soluble azo oxidants, ammonium persulfate, sodium persulfate, and potassium persulfate, and the amount of initiator is 0.3 to 0.8 wt% of the total mass of monomers A, B, and C; the chain transfer agent is selected from any one of mercaptoacetic acid, mercaptopropionic acid, and sodium hypophosphite, and the amount of chain transfer agent is 0.1 to 0.3 wt% of the total mass of monomers A, B, and C.

[0015] Furthermore, in step (1), the pH of the copolymerization system is adjusted to 7.0 using a 0.4~0.6 mol / L NaOH aqueous solution.

[0016] Furthermore, the temperature of the ice water bath in step (2) is 0~4℃.

[0017] This invention addresses the problems in the prior art by synthesizing polycarboxylate-based organic-inorganic hybrid admixtures, based on the structural characteristics and reactivity of commonly used clay-resistant admixtures, crown ethers, and POM groups. This approach aims to improve the workability of calcined clay-limestone low-carbon cement (LC3) concrete. When used in calcined clay-limestone low-carbon cement, the polycarboxylate-based organic-inorganic hybrid admixture is added at a dosage of 0.1-0.2% of the cementitious material mass. This enhances the polycarboxylate admixture's resistance to clay in the LC3 system and significantly improves the workability of the concrete.

[0018] The polycarboxylate-based organic-inorganic hybrid admixture used in the calcined clay-limestone low-carbon cement (LC3) system of this invention has carboxyl groups and quaternary ammonium cationic groups distributed on the main chain of its molecular structure, forming dual adsorption sites. This preferentially anchors the cement particle surface, fully realizing the high water-reducing function. Furthermore, the rigid cavity (diameter ≈ 0.32 nm) of the 4'-aminobenzo-18-crown-6 side chain in the polycarboxylate-based organic-inorganic hybrid admixture can selectively complex and extract K+ from the clay interlayer. + / Na + This process compresses the interlayer spacing of montmorillonite from 12 Å to 9.5 Å, blocking its intercalation channels. Furthermore, the rigid benzene ring structure of the crown ether generates strong steric hindrance, forming a dense cross-linked network structure with POM nanoparticles. This "spatial cross-linked double network" physically blocks clay intercalation and adsorption. In addition, the admixture structure does not contain long polyether side chains, avoiding matching with the interlayer structure of clay from the source and completely blocking the intercalation and adsorption pathway. Finally, the inorganic nano-properties of POM further increase the polymer interface area, reducing the adsorption capacity of clay, ultimately achieving efficient enrichment and improved utilization of the admixture in cement particles.

[0019] Compared with the prior art, the present invention has the following advantages: This invention utilizes the structural characteristics of organic-inorganic hybrid admixtures. Specifically, the rigid benzene ring structure of the crown ether in the organic-inorganic hybrid admixture generates strong steric hindrance, which together with POM nanoparticles forms a dense cross-linked network structure. This "spatial cross-linked double network" physically blocks clay intercalation and adsorption, thus doubly hindering the intercalation and adsorption of the admixture between clay layers and significantly improving the adaptability of the admixture. This invention utilizes the carboxyl groups and quaternary ammonium cationic groups distributed on the main chain of the organic-inorganic hybrid admixture molecule to form dual adsorption sites, preferentially anchoring to the surface of cement particles and fully exerting the water-reducing effect; This invention utilizes the POM unit in the organic-inorganic hybrid admixture. The small size effect of the inorganic nanoparticles in the POM unit leads to a sharp increase in the interfacial area between the admixture and the polymer matrix, resulting in less adsorption of the admixture on clay and further improving the high efficiency of admixture utilization in concrete. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0022] The weight-average molecular weight was determined using a Shimadzu LC-20A high-performance gel permeation chromatography (GPC) system. The chromatographic column used was a TSKG4000PWXL series, the column temperature was 25℃, the eluent was 0.1M sodium acetate aqueous solution, the flow rate was 0.5ml / min, and the injection volume was 15μl of 1‰ aqueous solution of the sample. The standard curve was prepared using dextran standard (Sigma-Aldrich).

[0023] The types and proportions of monomers A, B, C, amino crown ethers, and polyoxometalates in the admixtures of each embodiment and comparative example are shown in Table 1 below: Table 1. Types and amounts of raw materials used in each embodiment and comparative example. The reaction conditions during the preparation of the additives in each embodiment and comparative example are shown in Table 2 below.

[0024] Table 2. Preparation reaction conditions in each example and comparative example. Application Examples The calcined clay-limestone low-carbon cement system used in this invention is composed of the following substances: 30 parts by weight of calcined clay (CC), 15 parts by weight of limestone (L), 55 parts by weight of Portland cement (P), and polycarboxylate-based organic-inorganic hybrid admixture.

[0025] The composition, particle size, and loss on ignition (LOI) analysis of the calcined clay-limestone low-carbon cement systems described in the various embodiments and comparative examples are shown in Tables 3-5. The composition was determined using a Thermo Fisher Scientific ADVANT XP X-ray fluorescence spectrometer, and the particle size distribution was determined using an Anton Paar PSA 1190LD laser particle size analyzer. The calcined clay, limestone, and Portland cement were all commercially available products, and their composition is shown in Table 3, particle size analysis in Table 4, and loss on ignition data in Table 5. Table 3. Composition of the calcined clay-limestone low-carbon cement system described in each embodiment and comparative example. Table 4. Particle size distribution of each component in the calcined clay-limestone low-carbon cement system described in each embodiment and comparative example. Table 5. Firing vectors of each component in the calcined clay-limestone low-carbon cement system described in each embodiment and comparative example. The admixtures in each embodiment and the comparative example were applied to the above-mentioned calcined clay-limestone low-carbon cement system. The sources and dosages of the polycarboxylate-based organic-inorganic hybrid admixtures were different, as shown in Table 6.

[0026] Table 6. Dosage of admixtures in calcined clay-limestone low-carbon cement systems for each example and comparative case. Performance testing The test methods were followed according to GB / T 8077-2023 "Test Method for Homogeneity of Concrete Admixtures". The effects of the admixtures in the application examples and comparative application examples on the fluidity and time-dependent loss of the neat paste in freshly mixed calcined clay-limestone low-carbon cement system (LC3) were evaluated, with a fixed water-cement ratio of 0.30. A comparative group was also set up, using commercially available Klon KL-1397 polyether anti-sludge admixture. The admixture dosage in comparative group 1 was 0.15%, and in comparative group 2 it was 0.17%. The experimental results are shown in Table 7.

[0027] Table 7 Performance Tests for Each Application Example As can be seen from the experimental results in Table 7, when applied to the calcined clay-limestone low-carbon cement system (LC3), based on the performance comparison between Application Examples 1-7 and Comparative Group 1, it is evident that, under the same admixture dosage, the initial clean slurry flowability and 1-hour slurry flowability of Application Examples 1-7 are higher than those of Comparative Group 1. Therefore, compared to traditional comb-type cement dispersants, the polycarboxylate-based organic-inorganic hybrid admixture of this application exhibits characteristics such as low dosage, high water reduction rate, and excellent slump retention, even when applied to calcined clay-limestone low-carbon cement systems with high clay content.

[0028] In addition, under the same dosage conditions, the dispersion effects of the admixtures in Application Examples 1-3 were also different. Ultimately, it was found that the performance of Application Example 2 was superior to that of the other application examples. This is because both large and small molecular weights are not conducive to the admixture's performance. This is because the carboxyl groups and quaternary ammonium cation groups in the admixture structure form dual adsorption sites, thus enabling the admixture to be fixed on the surface of cement particles. The crown ether structure and the nanostructure of POM form a spatially cross-linked double network structure. When the admixture has a high molecular weight, the solution conformation of the molecular structure is too large, and the main chain structure will cause a cage effect on the adsorption sites, namely the carboxylic acid and quaternary ammonium cation groups. When the molecular weight is too low, the content of adsorption sites is too low, which will cause the admixture to fail to be fixed on the surface of cement particles and fail to form an effective network structure. Consequently, it cannot effectively hinder the adsorption of the admixture on the clay, making it difficult to improve the initial fluidity and the fluidity over time of the LC3 system.

[0029] By comparing application examples 4 and 5, it can be seen that when the number of repeating units of monomer A is small, the adsorption sites, i.e., carboxylic acid groups, in the admixture will be too few, resulting in low dispersion performance. Therefore, the working performance of application example 5 is better than that of application example 4. From application examples 6 and 7, it can be seen that the working performance of application example 6 is better than that of application example 7. This is because the number of crown ether structures, i.e., AmBC units, should not be too high. If it is too high, the admixture itself will become entangled and agglomerated, and it will not be able to form an effective dispersion for the calcined clay-limestone low-carbon cement system (LC3).

[0030] Meanwhile, it is not difficult to find from application examples 8 to 11 that when the dosage of polycarboxylate-based organic-inorganic hybrid admixture increases (0.1%→0.2%), the initial fluidity and the fluidity over time of the fresh cement paste in the LC3 system will show a trend of first slowly increasing and then decreasing. This is because when the dosage is too high, the dual adsorption sites of the admixture will cause bridging and secondary agglomeration, which will lead to the entanglement of the chain segments in the admixture, thereby reducing the initial dispersion performance of the LC3 system and ultimately reducing the overall working performance of the system.

[0031] Compared with Examples 1-7, the performance of Comparative Application Example 1 was significantly lower than that of the polycarboxylate-based organic-inorganic hybrid admixture of the present invention applied to the LC3 system. This confirms that the lack of acrylate-N-succinimidyl ester and crown ether structures means that the POM structure alone cannot effectively block clay intercalation adsorption. Similarly, the performance of Comparative Application Example 2 was also lower than that of the polycarboxylate-based organic-inorganic hybrid admixture of the present invention applied to the LC3 system. This confirms that the presence of only acrylate-N-succinimidyl ester units and the lack of crown ether structures still cannot effectively block clay intercalation adsorption and makes it difficult to form a spatially intersecting double-grid structure.

[0032] Comparative application example 3 showed the worst performance among all application examples, confirming that the lack of corresponding quaternary ammonium cation groups and POM structure will prevent the realization of dual adsorption sites and spatially cross-network structure. Relying solely on the crown ether structure cannot form an "effective isolation zone" between clay and cement-based materials, thus making it difficult to fully realize the high dispersion function.

[0033] Further analysis and comparison of the performance of application examples 4-5 revealed that the final application performance was poor regardless of whether there was too much or too little POM structure. This indicates that the amount of monomer C and POM structure will affect the double network structure formed by them and crown ether units, thereby affecting the overall working performance of the admixture.

[0034] This invention utilizes the structural characteristics of organic-inorganic hybrid admixtures. Specifically, the rigid benzene ring structure of the crown ether in the structure generates strong steric hindrance, which, together with POM nanoparticles, forms a dense cross-linked network structure. This "spatially cross-linked double network" physically blocks clay intercalation adsorption, thus doubly hindering the intercalation adsorption of admixtures between clay layers. At the same time, the carboxyl groups and quaternary ammonium cation groups distributed on the main chain form dual adsorption sites, preferentially anchoring to the surface of cement particles, further enhancing the dispersion ability of admixtures in the LC3 system, and ultimately achieving efficient enrichment and improved utilization of admixtures in cement particles.

[0035] The technical solution of the present invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of the present invention, including the best mode, and also to enable any person skilled in the art to practice the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims. For those skilled in the art, it is understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polycarboxylate-based organic-inorganic hybrid admixture, characterized in that, It is prepared by copolymerizing monomers A, B, and C, grafting amino crown ethers through amidation, and finally reacting with polyoxometalates via electrostatic interaction. Wherein, monomer A is an unsaturated carboxylic acid or an unsaturated carboxylic acid salt; The monomer B is N-succinimide acrylate; The monomer C is methacryloylpropyltrimethylammonium chloride or acryloylpropyltrimethylammonium chloride; The polyoxometalate is a nanoscale polyoxometalate cluster compound formed by coordination bonds between a transition metal and oxygen atoms, wherein the transition metal is tungsten or molybdenum.

2. The polycarboxylate-based organic-inorganic hybrid admixture according to claim 1, characterized in that, The monomer A is selected from any one or a mixture of one or more of acrylic acid, alkali metal salts of acrylic acid, methacrylic acid, and alkali metal salts of methacrylic acid in any proportion.

3. The polycarboxylate-based organic-inorganic hybrid admixture according to claim 1, characterized in that, The amino crown ether is 4'-aminobenzo18-crown-6 (AmBC). The polyoxometalate is phosphomolybdic acid H3[PMo] 12 O 40 or molybdenum silicate H4 [SiMo] 12 O 40 ].

4. The polycarboxylate-based organic-inorganic hybrid admixture according to claim 1, characterized in that, The molar ratio of monomer A, monomer B, monomer C, amino crown ether, and polyoxometalate is (6~8):1:2:(1.2~1.5):(2.2~2.8).

5. The polycarboxylate-based organic-inorganic hybrid admixture according to claim 1, characterized in that, The polycarboxylic acid-based organic-inorganic hybrid admixture has a weight-average molecular weight of 60-100 kDa and a PDI of 2-3.

6. A method for preparing a polycarboxylate-based organic-inorganic hybrid admixture according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Copolymerization reaction: Monomer A, monomer B, monomer C, initiator and chain transfer agent are mixed to carry out free radical copolymerization reaction, and then the obtained copolymer system is cooled to room temperature and the pH is adjusted to neutral; (2) Amide reaction: Add amino crown ether to the copolymer system of step (1) and stir for 3 hours in the dark under ice-water bath conditions; (3) Electrostatic assembly reaction: Add polyoxometalate to the product system of step (2) and stir at room temperature to obtain the polycarboxylic acid organic-inorganic hybrid additive.

7. The preparation method according to claim 6, characterized in that, The free radical copolymerization reaction in step (1) is a conventional aqueous free radical copolymerization reaction, and the polymerization concentration in the copolymerization reaction is 15~20%, the polymerization temperature is 35~45℃, and the reaction time is 4~6h; In step (1), the pH of the copolymerization system is adjusted to 7.0 using a 0.4~0.6 mol / L NaOH aqueous solution; The temperature of the ice water bath in step (2) is 0~4℃; Step (3) involves magnetic stirring at a speed of 600-1000 r / min for a reaction time of 5-10 h.

8. The preparation method according to claim 6, characterized in that, The initiator used in step (1) is selected from any one of water-soluble azo oxidants, ammonium persulfate, sodium persulfate, and potassium persulfate. The amount of initiator used is 0.3~0.8 wt% of the total mass of monomers A, B, and C. The chain transfer agent is selected from any one of mercaptoacetic acid, mercaptopropionic acid, and sodium hypophosphite, and the amount of chain transfer agent used is 0.1~0.3 wt% of the total mass of monomers A, B, and C.

9. The application of the polycarboxylate-based organic-inorganic hybrid admixture according to any one of claims 1 to 5 in calcined clay-limestone low-carbon cement.

10. The application according to claim 9, characterized in that, The amount of the polycarboxylate-based organic-inorganic hybrid admixture in calcined clay-limestone low-carbon cement is 0.1~0.2% of the mass of the cementitious material.

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