C-s-h-polymer nanocomposite, preparation method and application thereof

Abstract

The application belongs to the technical field of building materials, and particularly relates to a C-S-H polymer nanocomposite material, a preparation method and application thereof. The method comprises the following steps: adding a polymer emulsion into a sodium silicate solution, adjusting the pH value of the solution, and then stirring and mixing under water bath conditions to form a mixed solution; the polymer chains in the polymer emulsion contain carboxylate groups; a calcium chloride solution is slowly dropped into the mixed solution for reaction; after the reaction is completed, washing and drying are performed to obtain the C-S-H polymer nanocomposite material. Compared with the prior art, the application solves the problems of high porosity and poor mechanical properties of C-S-H materials in the prior art, and the problems of complex process and weak interface bonding of the existing organic-inorganic composite method. In the scheme, the coordination effect of the active functional groups on the polymer chains and calcium ions is utilized to control the growth of C-S-H from the nucleation stage, and in-situ filling of the polymer to the pores of the C-S-H gel is realized.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a C–S–H polymer nanocomposite material, its preparation method, and its application. Background Technology

[0002] Calcium silicate hydrate (C–S–H) gel is the main hydration product of silicate cement, accounting for more than 50% of the solid phase volume and being the primary source of strength in silicate cement-based materials. However, the inherent brittleness and high porosity of the native C–S–H structure limit its further application in high-performance concrete. To improve the mechanical properties and durability of cement-based materials, polymers are typically introduced to form organic-inorganic composite materials.

[0003] Existing research has shown that the molecular structure of C–S–H gel directly affects its mechanical properties, and thus determines the macroscopic mechanical properties of cement-based materials. Therefore, using polymers to regulate the molecular configuration of C–S–H gel, thereby directly improving its mechanical properties, has become an innovative approach to enhance the macroscopic properties of cement-based materials. In existing technologies, research on polymer-modified C–S–H composites mainly focuses on the physical blending or simple doping of polymers. For example, patent CN114315221B discloses a method for preparing a high-ductility hydrated calcium silicate-based composite material, using polyvinyl alcohol or sodium carboxymethyl cellulose to bond synthesized C–S–H together, forming a simple organic-inorganic composite material. However, the incorporation of polymers in this scheme does not fundamentally change the molecular structure of C–S–H, and therefore fails to significantly improve the intrinsic mechanical properties of C–S–H. Patent CN117024016B discloses an ultra-high toughness multifunctional self-assembled C–S–H gel material and its preparation method, using polymers such as acrylic acid and acrylamide to bond synthesized C–S–H together. While these published patents achieve organic-inorganic composites, in these schemes, the polymer only acts as a "binder": binding multiple C–S–H gels together, without precisely controlling the molecular structure of the C–S–H gel or reducing its porosity to improve performance.

[0004] Therefore, there is currently a lack of an effective method to simultaneously achieve C–S–H structure regulation and pore filling at the nanoscale, thereby obtaining C–S–H composite materials with both low porosity and high elastic modulus. Summary of the Invention

[0005] The purpose of this invention is to provide a C–S–H polymer nanocomposite material, its preparation method, and its application to solve at least one of the aforementioned problems. This addresses the issues of high porosity and poor mechanical properties in existing C–S–H materials, as well as the complex processes and weak interfacial bonding in existing organic-inorganic composite methods. This solution utilizes the coordination between active functional groups on the polymer chain and calcium ions to regulate the growth of C–S–H from the nucleation stage, achieving in-situ filling of the pores in the C–S–H gel by the polymer.

[0006] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a method for preparing C–S–H-polymer nanocomposites, comprising the following steps: S1: The polymer emulsion is added to the sodium silicate solution, the pH value of the solution is adjusted, and then the mixture is stirred under water bath conditions to form a mixed solution; wherein, the polymer chain in the polymer emulsion contains carboxylate groups; S2: Under a nitrogen atmosphere, calcium chloride solution is slowly added dropwise to the mixed solution in step S1 while stirring continuously to allow the reaction to occur; S3: After the calcium chloride solution is added dropwise in step S2, the mixture is stirred and the reaction continues under nitrogen atmosphere and water bath conditions. S4: After the reaction in step S3 is completed, the mixture is washed and dried to obtain the C–S–H-polymer nanocomposite material.

[0007] Preferred, including: The polymer solids in the polymer emulsion include styrene-acrylate copolymer and butadiene-styrene-acrylate copolymer; The sodium silicate solution was prepared by dissolving sodium metasilicate pentahydrate in deionized water, with a concentration of 0.10~0.20 mol / L; The calcium chloride solution was prepared by dissolving anhydrous calcium chloride in deionized water, with a concentration of 0.20~0.40 mol / L; The amount of polymer emulsion incorporated is 10% to 40%, based on the mass ratio of polymer solids to sodium metasilicate pentahydrate in the polymer emulsion. The volume ratio of the sodium silicate solution to the calcium chloride solution is 1:1 to 1:2.

[0008] Preferably, step S1 includes: The pH of the solution was adjusted to 13.0-13.5 using sodium hydroxide solution. The temperature of the water bath is 35~45℃.

[0009] Preferably, step S2 includes: The titration rate of the slow dripping is 5~15 mL / min.

[0010] Preferably, step S3 includes: The temperature of the water bath is 35~45℃; The duration of the sustained reaction is 10 to 15 days.

[0011] Preferably, step S4 includes: The precipitate formed during the reaction was washed with anhydrous ethanol. The drying process is vacuum drying at 35~45℃.

[0012] The second aspect of the present invention discloses a C–S–H-polymer nanocomposite material, which is prepared by the preparation method described in any of the preceding claims.

[0013] Preferred, including: The Ca / Si ratio of the C–S–H polymer nanocomposite is 1.0~2.0; In the C–S–H polymer nanocomposite material, the polymer accounts for 5% to 20% of the total mass.

[0014] Preferably, in the C–S–H polymer nanocomposite material, the polymer is adsorbed on the surface of C–S–H particles, and the C–S–H particles are adhered to form an accumulation.

[0015] A third aspect of the present invention discloses the application of a C–S–H-polymer nanocomposite material as described in any of the preceding claims in building materials.

[0016] The working principle of this invention is as follows: Unlike existing technologies where polymers act as physical "binders" only after C–S–H formation, this invention introduces the polymer into the sodium silicate solution before C–S–H nucleation. The polymer chains interact with subsequently introduced calcium ions through coordination between the carboxyl groups, thus intervening in the C–S–H formation process from the outset. This coordination interaction forms a dynamic polymer-Ca... 2+The complex reduces the concentration of free calcium ions, inhibits the disordered nucleation of silicate ions, and provides a controllable chemical environment for C–S–H growth. On the other hand, C–S–H requires calcium ions to be extracted from the complex during growth, thus precisely controlling the calcium content entering C–S–H at the molecular level. This achieves directional regulation of the calcium-silicon ratio of C–S–H, promoting the growth of low-calcium-silicon ratio C–S–H structures with superior mechanical properties. Simultaneously, the carboxyl groups on the polymer chains, through complexation with interlayer and surface calcium ions, embed themselves within the C–S–H nanosheets, filling the nanopores of the C–S–H gel in an organic-inorganic manner, forming a dense stacked structure. Therefore, through the synergistic effect of nucleation regulation, in-situ growth, and structural filling, the nanocomposite material obtained in this invention significantly reduces porosity while substantially increasing the elastic modulus, breaking through the bottleneck of limited performance improvement in traditional physical blending modification.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Simple process, in-situ composite: This invention employs a one-step co-precipitation method, introducing the polymer into the silicon source solution before C–S–H nucleation. This method eliminates the need for complex initiators, crosslinking agents, or ultraviolet irradiation, utilizing the inherent active functional groups on the polymer chain (such as carboxylate groups -COO). - Spontaneous reaction of Ca in solution 2+ Coordination occurs, enabling in-situ composite formation of the polymer during the growth of C–S–H nanoparticles.

[0018] 2. Strong interfacial bonding and dense microstructure: Fourier transform infrared spectroscopy (FTIR) reveals that the -COO groups in the polymer... - The isopolar groups can form strong coordination bonds (Ca-O) with Ca atoms on the C–S–H surface. This chemical bonding allows the polymer to tightly coat the surface of C–S–H particles and bridge adjacent particles, thereby significantly reducing the porosity of the material. BET surface area analysis shows that the cumulative pore volume of the resulting composite material can be as low as 0.19 cm³. 3 / g, far lower than that of unmodified C–S–H (0.45 cm⁻¹). 3 / g), which means that the synthesized C–S–H-polymer nanocomposite has a denser microstructure.

[0019] 3. Superior Mechanical Properties: This invention modifies the C–S–H molecular structure by controlling the nucleation process. Utilizing polymer complexation, the calcium-to-silicon ratio (Ca / Si) of C–S–H can be effectively reduced from 1.7 to approximately 1.5. A lower Ca / Si ratio promotes the formation of a more stable C–S–H structure, which is beneficial to the long-term durability of the material. The increased density of the C–S–H gel and the altered Ca / Si ratio significantly improve the Young's modulus of the composite material. Specifically, the Young's modulus of the C–S–H-SAE nanocomposite reaches 26.7 GPa, approximately 70% higher than that of the unmodified C–S–H gel (15.7 GPa), exhibiting both high density and superior mechanical properties, outperforming traditional low-density C–S–H.

[0020] In summary, the present invention has a simple process and is easy to industrialize. It can reduce the amount of cementitious materials while maintaining mechanical properties and improve the durability of cement-based materials, providing a new technical path for achieving high-performance, low-carbon building materials. Attached Figure Description

[0021] Figure 1 Here is a SEM image of the sample in Example 1 of this invention, wherein: Figure 1 (a) Observed at 10K magnification Figure 1 (b) Observed at 30K magnification.

[0022] Figure 2 Here is a SEM image of the sample in Example 2 of this invention, wherein: Figure 2 (a) Observed at 10K magnification Figure 2 (b) Observed at 30K magnification.

[0023] Figure 3 Here is a SEM image of the sample in Comparative Example 1 of this invention, wherein: Figure 3 (a) Observed at 10K magnification Figure 3 (b) Observed at 30K magnification.

[0024] Figure 4 Here is a SEM image of the sample in Comparative Example 2 of this invention, wherein: Figure 4 (a) Observed at 10K magnification Figure 4 (b) Observed at 30K magnification.

[0025] Figure 5 Fourier transform infrared spectra of the C–S–H-polymer nanocomposites prepared in Examples 1, 2, 1, and 2. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] Unless otherwise specified in the following description, the reagents used are conventional commercial products, the methods used are well-known in the art, and any other matters not covered herein may be handled using existing technologies.

[0028] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-performance C–S–H polymer nanocomposite material and its preparation method. This method aims to solve the problems of high porosity and poor mechanical properties in existing C–S–H materials, as well as the complex processes and weak interfacial bonding of existing organic-inorganic composite methods. By utilizing the coordination interaction between active functional groups on the polymer chains and calcium ions, the growth of C–S–H is regulated from the nucleation stage, achieving in-situ filling of the pores of the C–S–H gel by the polymer.

[0029] The preparation process includes the following steps: Step 1, prepare sodium silicate solution: Dissolve sodium metasilicate pentahydrate (Na2SiO3·5H2O) in deionized water to prepare a sodium silicate solution with a concentration of 0.10~0.20 mol / L; add polymer to sodium silicate solution and stir for 15 min to obtain mixed solution.

[0030] Step 2, adjust the pH value: add sodium hydroxide (NaOH) to the sodium silicate-polymer mixed solution to adjust the pH value of the mixed solution to 13.0~13.5; place the prepared mixed solution in a three-necked flask and stir continuously for 15 min in a water bath at a temperature of 35~45℃, and continuously introduce nitrogen gas into the reaction system to prevent carbonization.

[0031] Step 3, Preparation and addition of calcium source: Dissolve anhydrous calcium chloride (CaCl2) in deionized water to prepare a calcium chloride solution with a concentration of 0.20~0.40 mol / L; use a peristaltic pump to slowly add the prepared calcium chloride solution dropwise into the mixed solution obtained in step 2, controlling the titration rate at 5~15 mL / min, so that calcium and silicon source can undergo a co-precipitation reaction. Nitrogen gas is purged throughout the reaction to prevent carbonization.

[0032] Step 4, Reaction and Washing: After titration, continue stirring at 35~45℃ for 10~15 days, during which time the mixture is continuously stirred slowly with a stirrer and nitrogen gas is continuously purged to prevent carbonization; after the reaction is completed, the precipitate is washed with anhydrous ethanol to remove adsorbed byproducts and other ions.

[0033] Step 5, Drying: Dry the washed precipitate in a vacuum drying oven at 35~45℃ to constant weight, and then grind it to obtain a high-performance C–S–H-polymer nanocomposite material.

[0034] In step 1, the polymer emulsion is selected from at least one of styrene-acrylate copolymer (SAE) emulsion or butadiene-styrene-acrylate copolymer (SB) emulsion. The amount of polymer added is 10% to 40% of the mass of sodium silicate pentahydrate (based on solid content). Since the polymer is in emulsion form, the actual amount of water used to prepare the sodium silicate solution should be the sum of the amount of deionized water added and the water content in the emulsion (i.e., the amount of water introduced into the polymer emulsion needs to be deducted when preparing the sodium silicate solution).

[0035] In step 3, the volume ratio of sodium silicate solution to calcium chloride solution is 1:1 to 1:2, and the Ca / Si ratio of the synthesized C–S–H gel is between 1.0 and 2.0, which is within the common Ca / Si ratio range in silicate cement. Ultimately, in the high-performance C–S–H polymer nanocomposite material, the polymer accounts for 5% to 20% of the total mass of the C–S–H gel material.

[0036] This invention introduces a polymer into a sodium silicate solution before C–S–H nucleation. By utilizing the coordination between the carboxyl groups on the polymer chains and calcium ions, the calcium-silicon ratio of C–S–H is controlled at the molecular level, forming a dense stacked structure (molecular configuration), thereby directly improving its mechanical properties. Based on a simple co-precipitation method, this invention achieves simultaneous C–S–H structure control (reducing the calcium-silicon ratio) and pore filling at the nanoscale through the chemical coordination of specific functional groups (such as carboxylate groups) with the C–S–H precursor. The resulting C–S–H-SAE nanocomposite material exhibits an elastic modulus approximately 70% higher than unmodified C–S–H, possessing both high density (low porosity) and high mechanical properties (high elastic modulus).

[0037] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings, specific embodiments, and comparative examples. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] Example 1 A high-performance C–S–H-SAE nanocomposite material is prepared by the following steps: (1) Dissolve 9.546 g of sodium metasilicate pentahydrate in 298.560 g of deionized water to prepare a sodium silicate solution in a volumetric flask; then add 3.350 g of SAE emulsion (the solid content of the polymer emulsion is 57.0%) to the sodium silicate solution; at this time, the concentration of sodium silicate solution in the composite solution is 0.15 mol / L.

[0039] (2) Dissolve 8.989 g of anhydrous calcium chloride (CaCl2) in 270.000 g of deionized water and prepare a calcium chloride solution with a concentration of 0.3 mol / L in a volumetric flask.

[0040] (3) Place the prepared sodium silicate-polymer composite solution as the base solution in a three-necked round-bottom flask, add an appropriate amount of NaOH to the composite solution, and adjust the pH value of the composite solution to 13.2.

[0041] (4) Place the flask in a 40℃ water bath, weigh 270 mL of calcium chloride solution, and slowly add the calcium chloride solution dropwise into the sodium silicate solution using a peristaltic pump. Maintain a stirring speed of 100 rpm and purge with nitrogen throughout the process to prevent carbonization. At this point, the Ca / Si atomic ratio in the composite solution is 1.8. SEM-EDS testing showed that the Ca / Si ratio of the C–S–H gel in the silicate cement paste with a water-cement ratio of 0.45 was 1.8. Therefore, the Ca / Si atomic ratio in Example 1 is consistent with the actual situation.

[0042] (5) After the calcium chloride solution is added dropwise, seal the flask and continue to react in a 40°C water bath for 14 days, stirring slowly with a magnetic stirrer during the period.

[0043] (6) After the reaction was completed, the precipitate was washed with anhydrous ethanol to remove other ions adsorbed on the surface of the C–S–H-SAE composite material. Then the precipitate was dried in a vacuum drying oven at 40°C to obtain the C–S–H-SAE composite material.

[0044] Example 2 A high-performance C–S–H-SB nanocomposite material is prepared by the following steps: The basic steps are the same as in Example 1, except that in step (1), 9.546 g of sodium metasilicate pentahydrate is dissolved in 298.166 g of deionized water to prepare a sodium silicate solution in a volumetric flask; then, 3.744 g of SB emulsion (the solid content of the polymer emulsion is 51.0%) is added to the sodium silicate solution, at which point the concentration of sodium silicate is 0.15 mol / L. Finally, C–S–H-SB nanocomposite material is obtained.

[0045] Comparative Example 1 A high-performance C–S–H nanocomposite material is prepared by the following steps: The basic steps are the same as in Example 1, except that no polymer emulsion is added in step (1). At this time, 9.546 g of sodium metasilicate pentahydrate is dissolved in 300.000 g of deionized water and a sodium silicate solution with a concentration of 0.15 mol / L is prepared in a volumetric flask; finally, C–S–H nanocomposite material is obtained.

[0046] Comparative Example 2 A high-performance C–S–H-EVA nanocomposite material is prepared by the following steps: The basic steps are the same as in Example 1, except that in step (1), 9.546 g of sodium metasilicate pentahydrate is dissolved in 298.463 g of deionized water to prepare a sodium silicate solution in a volumetric flask; then, 3.446 g of EVA emulsion (the solid content of the polymer emulsion is 55.4%) is added to the sodium silicate solution, at which point the concentration of sodium silicate is 0.15 mol / L. Finally, C–S–H-EVA nanocomposite material is obtained.

[0047] The Ca / Si ratio of the C–S–H polymer composite was analyzed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). All powder samples were ground and then passed through a 250-mesh sieve. The powder surface was sputter-coated with gold before testing. A surface scan was performed on each sample to obtain more information on the Ca and Si content at various points. The average of three valid data points for each group was taken. The final Ca / Si values ​​for each sample are shown in Table 1.

[0048] The mechanical properties of C–S–H polymer nanocomposites were characterized using nanoindentation (NI) technology. All powder samples were ground and passed through a 250-mesh sieve. Then, 1 g of powder sample was placed in a 10 mm diameter stainless steel mold and pressed into a block using a universal testing machine. A load was applied at a rate of 75 N / s and held at maximum load for 4 min. Finally, C–S–H disks were prepared using a pressure of 95 MPa. Before testing, the compacted C–S–H disks were placed in a silicone mold, and then epoxy resin was poured into the mold. The entire impregnation process was maintained in a vacuum environment to eliminate air bubbles in the epoxy resin. After the epoxy resin cured, the samples were removed from the silicone mold. The C–S–H nanocomposites were polished using SiC sandpaper with grits of 400, 800, and 1200 mesh. Subsequently, they were polished stepwise with 9 μm, 3 μm, and 1 μm diamond polishing slurries to obtain a surface roughness that met the testing requirements. The experiment used a Berkovich indenter, and 100 indentations (10×10 lattice) were collected for each sample. The distance between adjacent indentations was 20 μm. The final elastic modulus of each sample is shown in Table 1. According to the Oliver-Pharr principle, the elastic modulus of the sample is... E It can be obtained from the following formula (1): (1); Where, ᝜� is the Poisson's ratio of C–S–H in the sample, which is taken as 0.3 in this experiment; ᝜� i The Poisson's ratio of the indenter head is taken as 0.07;E i The elastic modulus of the indenter is taken as 1140 GPa; E r The reduced modulus was obtained experimentally.

[0049] The pore structure parameters and specific surface area of ​​C–S–H were obtained through BET specific surface area analysis. The test samples were first degassed at 40℃ for 16 h to remove the gas adsorbed on their surface. The final pore volume and specific surface area results are shown in Table 1.

[0050] Table 1 Mechanical properties and pore structure of high-performance C–S–H polymer nanocomposites For the C–S–H-SAE and C–S–H-SB nanocomposites in the examples, their Ca / Si ratios were significantly lower than those of the comparative examples C–S–H and C–S–H-EVA (Table 1). Specifically, the Ca / Si ratios of C–S–H-SAE and C–S–H-SB were reduced by 10.3% and 11.3% respectively compared to C–S–H.

[0051] For the C–S–H-SAE and C–S–H-SB nanocomposites in Examples, their pore volume and specific surface area are significantly smaller than those of the comparative examples C–S–H and C–S–H-EVA (Table 1).

[0052] SEM observations revealed that the C–S–H-polymer nanocomposites synthesized in Examples 1 and 2 and Comparative Examples 1 and 2 were composed of plate-like crystals. Figure 1 (b) Figure 2 (b) Figure 3 (b) and Figure 4 (b) These crystals intersect each other. The polymer adsorbs onto the C–S–H surface, which closes the pores of the C–S–H surface. Figure 1 (b) Figure 2 (b) and Figure 4 (b) This leads to a decrease in nitrogen adsorption capacity and a reduction in pore volume. C–S–H-SAE has the lowest specific surface area, which is 26.5% lower than that of the comparative C–S–H, indicating that the incorporation of SAE makes C–S–H exhibit a more compact microstructure.

[0053] A strong chemical reaction was also observed in the examples. FTIR analysis revealed that C–S–H-SAE and C–S–H-SB were concentrated in the 1730–1732 cm⁻¹ region. -1 There is a stretching vibration peak of the carboxyl group at this location. Figure 5 In pure SAE, the position of this carboxyl vibration peak is at 1728 cm⁻¹. -1This indicates a shift in the absorption peak, primarily due to the formation of a Ca-O bond between the O atom in the carboxyl group and the Ca atom in C–S–H. This suggests a strong chemical interaction between SAE / SB and C–S–H, enabling SAE / SB to effectively adsorb onto the C–S–H surface, resulting in a more compact microstructure.

[0054] The average elastic modulus of the examples (C–S–H-SAE and C–S–H-SB) was significantly higher than that of the comparative examples, increasing by approximately 70.2% and 41.1% respectively compared to the comparative C–S–H. This indicates that SAE and SB are highly beneficial to improving the mechanical properties of C–S–H. The main reasons for this can be attributed to two aspects: First, the incorporation of SAE and SB leads to a decrease in the Ca / Si ratio during C–S–H formation (see Table 1). Previous studies have shown that the elastic modulus of C–S–H with a high Ca / Si ratio is lower than that of C–S–H with a low Ca / Si ratio. Therefore, SAE and SB, through the coordination of their carboxyl groups with calcium ions, reduce the Ca / Si ratio of C–S–H at the molecular structure level, thereby improving the mechanical properties of C–S–H. This coordination effect has been demonstrated by the shift of the C=O absorption peak in the FTIR spectrum (see Table 1). Figure 4 , from 1728 cm -1 Drifting to 1730~1732 cm -1 This was confirmed. Secondly, SEM observation showed that the polymer incorporation resulted in finer C–S–H particles. The diameter of the C–S–H particles in Comparative Example 1 was 1.0 μm. Figure 3 (a)), while the particle size of C–S–H decreased to 0.6 μm, 0.7 μm and 0.7 μm respectively after incorporation of SAE, SB and EVA. Figure 1 (a) Figure 2 (a) and Figure 4 (a)). Fine particles are more likely to achieve close packing during subsequent growth and stacking, significantly reducing large-sized pores between particles, thus transforming the C–S–H gel from a loosely packed structure to a densely packed structure. Figure 1 (a) Figure 2 (a) and Figure 4 (a)). This structure effectively fills the C–S–H nanopores, which was quantitatively verified in nitrogen adsorption tests. The synergistic effect of the densely packed structure and the low calcium-to-silicon ratio ultimately endows the composite material of the example with a significantly improved elastic modulus.

[0055] The innovation of this invention lies in its approach. Unlike traditional physical blending or post-polymer doping methods, this invention introduces the polymer (SAE or SB) into a sodium silicate solution before C–S–H nucleation, achieving in-situ composite of the polymer and C–S–H through a one-step co-precipitation method. In this invention, the polymer not only acts as a "binder" but, more importantly, as a structure modifier, can regulate the molecular structure of C–S–H, thereby enhancing its intrinsic mechanical properties. FTIR confirms that the carboxyl groups in the polymer form Ca-O coordination bonds with calcium atoms on the C–S–H surface, achieving strong adsorption and bridging of the polymer on the C–S–H particle surface. This chemical action significantly reduces the porosity of the material (cumulative pore volume as low as 0.19 cm³). 3 The prepared C–S–H-SAE nanocomposite material exhibits a more compact packing structure, with an elastic modulus approximately 70% higher than that of unmodified C–S–H, reaching 26.7 GPa, significantly higher than that of traditional low-density C–S–H. This performance improvement stems from the synergistic effect of the polymer's regulation of molecular structure and effective pore filling.

[0056] In the field of building materials applications, this invention offers significant practical benefits: on the one hand, the high elastic modulus and high density of the composite material can effectively reduce the amount of cementitious components in cement-based materials while maintaining the same mechanical properties, achieving material reduction and resource conservation; on the other hand, its low porosity and strong interfacial bonding characteristics help improve the durability of cement-based materials, extend their service life, and reduce the maintenance costs throughout their entire life cycle. Furthermore, this in-situ co-precipitation method is simple, requires no complex equipment, and has good prospects for industrial application, providing a new technical path for achieving high-performance, low-carbon-emission cement-based materials.

[0057] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a C–S–H polymer nanocomposite material, characterized in that, Includes the following steps: S1: The polymer emulsion is added to the sodium silicate solution, the pH value of the solution is adjusted, and then the mixture is stirred under water bath conditions to form a mixed solution; wherein, the polymer chain in the polymer emulsion contains carboxylate groups; S2: Under a nitrogen atmosphere, calcium chloride solution is slowly added dropwise to the mixed solution in step S1 while stirring continuously to allow the reaction to occur; S3: After the calcium chloride solution is added dropwise in step S2, the mixture is stirred and the reaction continues under nitrogen atmosphere and water bath conditions. S4: After the reaction in step S3 is completed, the mixture is washed and dried to obtain the C–S–H-polymer nanocomposite material.

2. The method for preparing a C–S–H polymer nanocomposite material according to claim 1, characterized in that, include: The polymer solids in the polymer emulsion include styrene-acrylate copolymer and butadiene-styrene-acrylate copolymer; The sodium silicate solution was prepared by dissolving sodium metasilicate pentahydrate in deionized water, with a concentration of 0.10~0.20 mol / L; The calcium chloride solution was prepared by dissolving anhydrous calcium chloride in deionized water, with a concentration of 0.20~0.40 mol / L; The amount of polymer emulsion incorporated is 10% to 40%, based on the mass ratio of polymer solids to sodium metasilicate pentahydrate in the polymer emulsion. The volume ratio of the sodium silicate solution to the calcium chloride solution is 1:1 to 1:

2.

3. The method for preparing a C–S–H polymer nanocomposite material according to claim 1, characterized in that, Step S1 includes: The pH of the solution was adjusted to 13.0-13.5 using sodium hydroxide solution. The temperature of the water bath is 35~45℃.

4. The method for preparing a C–S–H polymer nanocomposite material according to claim 1, characterized in that, Step S2 includes: The titration rate of the slow dripping is 5~15 mL / min.

5. The method for preparing a C–S–H polymer nanocomposite material according to claim 1, characterized in that, Step S3 includes: The temperature of the water bath is 35~45℃; The duration of the sustained reaction is 10 to 15 days.

6. The method for preparing a C–S–H polymer nanocomposite material according to claim 1, characterized in that, Step S4 includes: The precipitate formed during the reaction was washed with anhydrous ethanol. The drying process is vacuum drying at 35~45℃.

7. A C–S–H polymer nanocomposite material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

8. The C–S–H polymer nanocomposite material according to claim 7, characterized in that, include: The Ca / Si ratio of the C–S–H polymer nanocomposite is 1.0~2.0; In the C–S–H polymer nanocomposite material, the polymer accounts for 5% to 20% of the total mass.

9. The C–S–H polymer nanocomposite material according to claim 7, characterized in that, In the C–S–H polymer nanocomposite material, the polymer is adsorbed on the surface of C–S–H particles, which adhere to form an accumulation of C–S–H particles.

10. The application of the C–S–H-polymer nanocomposite material as described in any one of claims 7 to 9 in building materials.

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