Polylysine-based composite cementitious material, method of making and use thereof

Abstract

The application discloses a polylysine-based composite cement material and a preparation method and application thereof. The polylysine-based composite cement material comprises the following raw materials in percentage by weight: white cement, polyvinyl alcohol, tannic acid and polylysine are 100:10:0.5:(2-10), and the rest is water, and the water-cement ratio is (0.5-0.8):1. The material can control surface biological adhesion and promote the spreading growth of corals, and the coral growth rate of the 10% polylysine group is increased by 61.02% compared with that of the pure white cement group.

Description

Technical Field

[0001] This invention relates to a polylysine-based composite cement material, its preparation method, and its application in coral attachment, growth promotion, and coral reef ecological restoration. Background Technology

[0002] Artificial reefs, coral transplant substrates, and marine ecological restoration components are typically made of cement-based materials. While traditional cement materials have advantages such as wide availability, low cost, ease of molding, and good durability, they still have certain limitations in marine ecological restoration applications. For example, traditional cement materials have limited biocompatibility, making it difficult to effectively control the early bioattachment process and easily forming a surface attachment layer that is detrimental to the attachment and subsequent growth of target corals, thus limiting their effectiveness in coral reef restoration.

[0003] In existing technologies, polymer or functional additive modification schemes have been used to improve the performance of cement-based materials. However, while single polymer modification enhances interfacial interactions, it may also affect the normal hydration process due to the coating effect on cement particles, leading to increased porosity, loose structure, and decreased mechanical properties. Meanwhile, composite cement materials specifically designed for coral attachment, growth promotion, and marine ecological restoration are still relatively scarce, especially cement-based materials that combine synergistic effects between organic and inorganic interfaces, bio-attachment regulation capabilities, and coral growth promotion effects. Therefore, it is necessary to provide a novel composite cement material that, through rational design of the interfacial interaction relationship between organic components and the inorganic cement system, improves its surface biocompatibility, regulates the attachment process, and promotes coral attachment and growth while ensuring material formability, thereby meeting the practical needs of coral reef ecological restoration and marine habitat construction. Summary of the Invention

[0004] Objectives of the Invention: To address the shortcomings of existing cement-based marine ecological restoration materials in terms of biocompatibility, which makes it difficult to simultaneously address coral attachment, growth promotion, surface bio-attachment regulation, and material structural stability, one objective of this invention is to provide a polylysine-based composite cement material that combines synergistic effects of the organic-inorganic interface, bio-attachment regulation capabilities, and coral growth promotion effects. Another objective is to provide a method for preparing this polylysine-based composite cement material by introducing polyvinyl alcohol, tannic acid, and polylysine into a white cement system to construct an organic-inorganic synergistic interface structure, thereby regulating the bio-attachment process on the material surface and promoting coral attachment and spreading growth. A final objective is to provide the application of this polylysine-based composite cement material in coral attachment substrates or in promoting coral spreading growth, marine ecological restoration, coral reef habitat restoration, or regulating primary producer attachment on sample surfaces.

[0005] Technical solution: The present invention discloses a polylysine-based composite cement material, which comprises the following raw materials by weight: white cement: polyvinyl alcohol (PVA): tannic acid (TA): polylysine (EPL) in a ratio of 100:10:(0.1~0.5):(2~10), with the remainder being water, and the water-cement ratio being (0.5-0.8):1.

[0006] Preferably, the raw materials include the following by weight: white cement: polyvinyl alcohol: tannic acid: polylysine in a ratio of 100:10:0.5:(2-10), with the remainder being water, and a water-cement ratio of 0.6:1. Preferably, when the primary objective is to improve the overall structure and mechanical properties of the material, the weight ratio of white cement, polyvinyl alcohol, tannic acid, and polylysine is 100:10:0.5:2; when the primary objective is to promote coral attachment and spreading growth, the weight ratio of white cement, polyvinyl alcohol, tannic acid, and polylysine is 100:10:0.5:10.

[0007] The preparation method of the polylysine-based composite cement material of the present invention is characterized by comprising the following steps:

[0008] S1. Mix white cement, polyvinyl alcohol, tannic acid and polylysine, add water and stir to form a uniform slurry;

[0009] S2. Pour the slurry into the mold to form the sample, perform freeze-thaw cycle treatment on the formed sample, demold and cure.

[0010] In step S2, the freeze-thaw cycle treatment includes: at -25°C ±5 Freeze at ℃ for more than 48 hours, then at 25℃ ± 5 Melt at ℃ for more than 24 hours, repeating the freezing and thawing process at least twice. The mold is cylindrical, with a diameter of 7.5 cm and a height of 1.5 cm. After the freeze-thaw cycle is completed, the sample is demolded and stored at 25℃. ±2 Allow to cure naturally at ℃ for more than 24 hours.

[0011] The present invention also includes the application of the polylysine-based composite cement material in coral attachment substrates or in promoting coral spreading and growth.

[0012] The present invention also includes the application of the polylysine-based composite cement material in marine ecological restoration or coral reef habitat restoration.

[0013] Among them, the coral is the beautiful staghorn coral (Acropora formosa).

[0014] The present invention also includes the application of the polylysine-based composite cement material in the control of primary producer adhesion on the surface of sample blocks.

[0015] Among them, by adjusting the amount of EPL, the overall structure and mechanical properties can be adjusted and optimized, or the ability to promote coral attachment and spreading growth can be controlled.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The polylysine-based composite cement material of the present invention can regulate the bio-attachment process on the sample surface. Experimental results show that the chlorophyll a concentration on the surface of the composite cement sample containing 10% EPL is significantly lower than that of the pure white cement group and the control group with only PVA added, indicating that it can effectively reduce the biomass of unfavorable attachment on the sample surface. (2) The polylysine-based composite cement material of the present invention can significantly promote coral attachment and spreading growth. The coral spreading area on the surface of the composite cement sample containing EPL is significantly larger than that of the pure white cement group and the group with only PVA added, and the coral spreading area shows an upward trend with the increase of EPL addition, among which the 10% EPL group has the best effect. (3) The polylysine-based composite cement material of the present invention can significantly improve the coral growth rate. On the 90th day, the coral growth rate of the 10% EPL group reached 784.66±0.10%, which is 61.02% higher than that of the pure white cement group, indicating that EPL has a significant effect on promoting coral growth. (4) The polylysine-based composite cement system of this invention can form a stable organic-inorganic interfacial network. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) results show that the hydroxyl groups in PVA, the amino and amide groups in EPL, and the phenolic hydroxyl groups in TA can undergo hydrogen bonding, ionic bonding, and complexation with cement hydration products, thereby improving the structure of the interfacial transition zone. (5) The composite system prepared by this invention is adjustable. By adjusting the addition ratio of EPL, different emphases can be achieved between optimizing comprehensive mechanical properties and promoting coral growth, making it suitable for different marine ecological restoration scenarios. Attached Figure Description

[0017] Figure 1 This diagram illustrates the preparation of pure white cement, PVA-infused reef materials, and EPL-modified materials of different concentrations as described in this invention.

[0018] Figure 2 A graph showing the changes in chlorophyll concentration per unit area for each treatment group at different time points;

[0019] Figure 3 Figure showing the change in coral spreading area over culture time for different treatment groups;

[0020] Figure 4 Statistical graph of coral growth rate in different treatment groups;

[0021] Figure 5The FTIR spectra of TA, CEM, PVA, CEM, PVA / CEM, and PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL in Example 10 are shown below.

[0022] Figure 6 The images show the SEM morphology of CEM, PVA / CEM, PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL in Example 10.

[0023] Figure 7 This is a comparison chart of the flexural strength of CEM, PVA / CEM, PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL in Example 10;

[0024] Figure 8 This is a comparison chart of the compressive strength of CEM, PVA / CEM, PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL in Example 10. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] In the following experiments, the number of replicates for each group of the bioattachment and coral culture test was n=4, and the number of replicates for each group of the mechanical property test was n=6. All data are expressed as mean ± standard deviation.

[0027] Example 1: Preparation of a pure white cement control sample block

[0028] Yinshan brand white cement was selected as the basic inorganic binder. Water was added at a water-cement ratio of 0.6:1 to prepare pure white cement slurry. The slurry was poured into a cylindrical mold with an inner diameter of 7.5 cm and a height of 1.5 cm to form a sample. The molded sample was then frozen at -30℃ for 48 h, and then transferred to 25℃ to thaw for 24 h. The freezing and thawing cycle was repeated twice. After demolding, the sample was naturally cured at 25 ± 2℃ for 24 h to obtain a cylindrical pure white cement sample with a diameter of 7.5 cm and a height of 1.5 cm, which was designated as CEM and served as a control group.

[0029] Example 2: Preparation of composite sample with added PVA

[0030] The experimental procedure was the same as in Example 1, except that PVA was added at 10% of the mass of white cement, and the other conditions were the same as in Example 1, to obtain PVA / CEM composite cement blocks.

[0031] Example 3: Preliminary preparation and screening of polylysine composite cement samples

[0032] To investigate the molding stability of EPL directly introduced into the PVA / white cement system, the experimental procedure was the same as in Example 1. Based on the mass of white cement, 10% PVA and different mass fractions of EPL were added to the system, with EPL addition amounts of 2%, 5%, and 10%, respectively. After adding water and stirring evenly, the mixture was poured into molds and molded. The mixture was then treated with the freeze-thaw process described in Example 1 to obtain composite cement blocks with different EPL contents.

[0033] The results showed that during the freeze-thaw process, varying degrees of EPL component exudation occurred at the bottom of the EPL composite cement samples (2%, 5%, and 10%) in contact with the mold. The exudation became more pronounced with increasing EPL content. This indicates that when PVA and EPL are blended alone, the fixation effect of EPL in the composite cement system is insufficient, potentially affecting the stability of the sample composition and the repeatability of subsequent bioattachment, coral cultivation, and mechanical property tests. Therefore, it is necessary to further introduce a linker component that can interact with EPL and cement hydration products to improve the retention stability of EPL in the composite cement system.

[0034] Example 4: Optimization of Tannic Acid Addition Amount

[0035] To improve the fixation effect of EPL in the composite cement system, TA was further introduced as a connecting and complexing component. Since Example 3 showed that different degrees of EPL exudation occurred under different EPL dosage conditions, and the 10% EPL group performed best in promoting subsequent coral attachment and growth, and this dosage was also more conducive to characterizing the fixation stability of EPL in the system, 10% EPL was selected as the representative system for TA addition optimization. The experimental procedure was the same as in Example 1. Based on the mass of white cement, 10% PVA, 10% EPL, and different mass fractions of TA were added to the system, with TA addition amounts of 0.1%, 0.3%, 0.5%, and 0.7%, respectively. After adding water and stirring evenly, the mixture was poured into molds and shaped, and then treated using the freeze-thaw process described in Example 1 to obtain EPL composite cement samples with different TA dosages.

[0036] During the preparation of the precursor solution and freeze-thaw molding process, it was observed that the exudation of EPL solution gradually decreased with the increase of TA addition. When the TA addition was 0.5%, almost no EPL exudation was observed in the composite cement sample during the freeze-thaw process, indicating that TA at this addition level could effectively improve the fixation effect of EPL in the composite cement system. When the TA addition was further increased to 0.7%, the precursor mixture formed by PVA, EPL, and TA showed obvious agglomeration, making it difficult to blend uniformly with white cement, which was detrimental to the preparation and molding of the composite cement slurry.

[0037] Therefore, TA not only reduces the migration and exudation of EPL during freeze-thaw cycles, but its addition amount also needs to be controlled within a range (below 0.7%) to avoid precursor liquid agglomeration. In the system of this invention, the preferred addition amount of TA is 0.5% of the mass of white cement. Subsequent composite cement samples with different EPL admixtures were prepared using 10% PVA, 0.5% TA, and the corresponding proportion of EPL.

[0038] Example 5: Preparation of 2% EPL Composite Cement Samples

[0039] The experimental procedure was the same as in Example 4. Based on the mass of white cement, 10% PVA, 0.5% TA and 2% EPL of the white cement were added to the system. After adding water and stirring evenly, the mixture was poured into a mold and shaped. The mixture was then treated with the freeze-thaw process described in Example 4 to obtain a 2% EPL composite cement sample block, denoted as PVA / CEM-2% EPL.

[0040] Example 6: Preparation of 5% EPL Composite Cement Samples

[0041] The experimental procedure was the same as in Example 4. Based on the mass of white cement, 10% PVA, 0.5% TA and 5% EPL of the white cement were added to the system. The remaining steps were the same as in Example 4, and a 5% EPL composite cement sample was obtained, which was denoted as PVA / CEM-5% EPL.

[0042] Example 7 Preparation of 10% EPL Composite Cement Sample Blocks

[0043] The experimental procedure was the same as in Example 4. Based on the mass of white cement, 10% PVA, 0.5% TA and 10% EPL of the white cement were added to the system. The remaining steps were the same as in Example 4, and a 10% EPL composite cement sample was obtained, which was denoted as PVA / CEM-10% EPL.

[0044] The above preparation methods are as follows: pure white cement CEM, PVA-modified composite cement materials (PVA / CEM), and EPL modified with different concentrations (PVA / CEM-EPL). Figure 1 As shown.

[0045] Example 8: Method for Monitoring Bioattachment

[0046] The composite cement samples prepared in Examples 1, 2, and 5-7 were cured under the same conditions and then uniformly placed in a semi-outdoor greenhouse experimental tank at the Hainan Tropical Marine Biology Experimental Station of the Chinese Academy of Sciences on Luhuitou Peninsula in the Sanya National Coral Reef Nature Reserve, Hainan Province, for subsequent bioattachment and coral cultivation experiments from October 16, 2024 to January 10, 2025. Bioattachment on the surface of the composite cement samples was sampled and analyzed on days 10, 30, 60, and 90 after placement. The number of replicates for each group was n=4, and the data are expressed as mean ± standard deviation. The specific method was as follows: sediment was scraped from the surface of the composite cement samples, placed in a mortar, ground for 5 min with a small amount of quartz sand and acetone, rinsed, transferred to a light-protected centrifuge tube, and brought to a final volume of 5 mL. Extraction was carried out at 4°C in the dark for 24 h. The sample was then centrifuged at 4000 r / min for 10 min, and the supernatant was filtered through a syringe filter to obtain the chlorophyll a acetone extract. The absorbance of the extract was measured at wavelengths of 750 nm, 664 nm, 647 nm, and 630 nm using an enzyme-linked immunosorbent assay (ELISA) reader. The chlorophyll a concentration was calculated according to HJ 897—2017 "Determination of Chlorophyll a in Water Quality—Spectrophotometric Method". The biofilm deposition was characterized by the chlorophyll concentration per unit area of ​​the sample surface. The results are as follows: Figure 2 As shown in the figure. The test results show that the chlorophyll a concentration on the surface of composite cement blocks with EPL content of 2-10% is lower than that of CEM in Comparative Example 1 and PVA / CEM in Comparative Example 2. In particular, the chlorophyll a concentration on the surface of composite cement blocks containing 10% EPL is significantly lower than that of CEM in Comparative Example 1 and PVA / CEM in Comparative Example 2, indicating that it can effectively regulate the surface bioattachment process.

[0047] Example 9

[0048] 1. Coral attachment and growth culture experiment

[0049] Acropora formosa was selected as the experimental subject. It was fixed onto the surfaces of pure white cement blocks (CEM) obtained in Example 1, PVA / CEM composite cement blocks with added PVA in Example 2, and composite cement blocks with different EPL content (PVA / CEM-2% EPL, PVA / CEM-5% EPL, PVA / CEM-10% EPL) prepared in Examples 5-7 using GEL-10 aquascaping adhesive from Alonfa. The corals were cultured in a semi-outdoor greenhouse at the Hainan Tropical Marine Biology Experimental Station of the Chinese Academy of Sciences on Luhuitou Peninsula, Sanya, for 0–90 days from October 16, 2024 to January 10, 2025. Each group had n=4 replicates, and data are expressed as mean ± standard deviation. During the culture period, the planar spread of the corals on the sample surfaces was recorded by regular photography, and the change in the coral spread projection area over time was statistically analyzed using ImageJ software. The results are shown below. Figure 3 As shown in the figure. The test results indicate that, during the 90-day observation period, the coral spreading area on the surface of the composite cement containing 2-10% EPL was significantly larger than that of the pure white cement CEM obtained in Example 1 and the PVA / CEM in Example 2. Furthermore, the coral spreading area gradually increased with increasing EPL concentration, with the 10% EPL group exhibiting the largest coral spreading area, demonstrating the promoting effect of EPL on coral growth.

[0050] 2. Coral growth rate calculation

[0051] Based on image data, the relative growth rate of corals is calculated using the following formula: Coral growth rate = 100 × (coral spreading area) n - Coral spreading area (0) / Coral spreading area 0. Where, coral spreading area n is the projected area of ​​the coral spreading as photographed on days 30, 60, and 90, and coral spreading area 0 is the projected area of ​​the coral in contact with the sample surface on day 0. Each group has n=4 replicates. Data are expressed as mean ± standard deviation, and results are as follows: Figure 4As shown in the figure. Statistical results indicate that, over time, except for a slight decrease in the growth rate of PVA / CEM-2% EPL compared to CEM on day 30, the growth rate of composite cement blocks with different EPL dosages was consistently significantly higher than that of CEM and PVA / CEM. In particular, PVA / CEM-10% EPL was significantly higher than all other treatment groups. On day 90, the coral growth rate of the pure white cement CEM group was 487.31±0.39%, PVA / CEM-2% EPL group was 310.43±0.41%, PVA / CEM-2% EPL group was 508.34±0.36%, PVA / CEM-5% EPL group was 600.69±0.24%, and PVA / CEM-10% EPL group was 784.66±0.10%. Compared to pure white cement CEM, the growth rate of PVA / CEM-10% EPL increased by 61.02%, and the difference was statistically significant (p<0.05).

[0052] Example 10

[0053] 1. FTIR characterization analysis

[0054] To further reveal the interfacial interaction mechanism between the organic phase and inorganic hydration products in the composite cement system, and to elucidate the effects of different EPL dosages on cement hydration behavior and microstructure, FTIR spectroscopic characterization was performed on TA, PVA, EPL, pure white cement CEM, PVA / CEM, and PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL. The results are as follows: Figure 5 As shown. Test results indicate that within the range of 3600–3200 cm... -1 In the high wavenumber region, the CEM of pure white cement is only 3640 cm⁻¹. -1 A distinct absorption peak appears nearby, which is attributed to the OH stretching vibration of Ca(OH)₂, a cement hydration product, indicating the formation of typical calcium hydroxide crystals in the pure white cement system. Compared to the pure white cement CEM, the PVA / CEM system exhibits a higher absorption peak in the 3200–3500 cm⁻¹ range. -1 The presence of a broadened absorption peak in the region indicates that intermolecular hydrogen bonds have formed between the hydroxyl groups in PVA molecules and the hydroxyl groups, aluminol groups, and adsorbed water molecules on the surface of cement hydration products. As the EPL content increases from 2% to 10% (PVA / CEM-2% EPL, PVA / CEM-5% EPL, PVA / CEM-10% EPL), this broad peak further shifts towards lower wavenumbers, and the peak intensity gradually increases, indicating that the hydrogen bonding in the system continues to strengthen. The amino and amide groups in the EPL molecules further participate in multiple hydrogen and ionic bonding interactions with PVA and cement hydration products. At 2900 cm⁻¹... -1Near the vicinity, absorption peaks of CH stretching vibrations in organic segments were observed in PVA / CEM and the composite systems incorporating EPL, namely PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL, indicating that PVA and EPL have been successfully introduced into the cement-based system. At 1600–1700 cm⁻¹... -1 In the region, the composite systems PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL, after incorporating EPL, exhibited characteristic peaks of amide I and amide II bands, indicating that the amide structure of EPL maintains good stability in the alkaline cement environment and exists as an important active site for the interface between the organic and inorganic phases. In the 1200–800 cm⁻¹ region... -1 Fingerprint area, 970 cm -1 The value at 1120 cm⁻¹ belongs to the Si-O stretching vibration in the CSH gel. -1 The location is the SO stretching vibration in ettringite, 875 cm. -1 and 1420 cm -1 CO3 in the corresponding carbonate 2- CO vibration, 728 cm -1 The peak at 1084 cm⁻¹ can be attributed to C4AF-related characteristic peaks. With increasing EPL doping, the peak at 1084 cm⁻¹... -1 With 970 cm -1 The peak intensities were all enhanced, indicating that EPL and PVA have a synergistic effect, which can promote the formation of CSH gel and enhance the formation of aluminate-related cross-linked structures.

[0055] 2. SEM microstructure analysis

[0056] Scanning electron microscopy (SEM) was used to observe the morphology of pure white cement CEM, PVA / CEM, and composites with different EPL content (PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL). Representative fields of view were selected for morphology analysis. The results are as follows: Figure 6 As shown. Figure 6Test results show that typical lamellar and layered crystals are visible in the pure white cement CEM, along with a small amount of flocculent and network matrix, indicating that calcium hydroxide crystals are well-developed in this group, and the system is dominated by traditional inorganic hydration products. In the PVA / CEM, numerous large-sized interconnected pores and film-like / filamentous structures are observed, with thin pore walls and obvious localized tearing morphology. This suggests that while the introduction of PVA alone enhances interfacial hydroxyl interactions, it may also inhibit the normal hydration of some cement particles due to the polymer coating effect, resulting in a system with more flexible film-like structures rather than a continuous and dense inorganic cementitious skeleton. When 2% EPL is introduced, a more continuous flocculent / network matrix, fewer large pores, and a certain number of needle-like crystals are observed in the PVA / CEM-2% EPL sample, indicating that a relatively stable synergistic structure is formed between the organic and inorganic phases at this dosage. When the EPL doping was further increased to 5% and 10%, the PVA / CEM-5% EPL and PVA / CEM-10% EPL samples gradually exhibited stronger surface coating, more blurred crystal boundaries, and local agglomeration, especially in the PVA / CEM-10% EPL, where blocky aggregates and structural inhomogeneity were observed. This indicates that while higher EPL doping can enhance organic-inorganic association, it can also cause excessive particle coating, local enrichment, or agglomeration, thereby inhibiting the effective development of the inorganic rigid framework.

[0057] 3. Mechanical property analysis

[0058] The flexural and compressive strength of the samples from the different treatment groups were tested according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". It should be noted that the sample blocks used for mechanical property testing differ in size from the cylindrical sample blocks used for bioattachment and coral cultivation experiments (different templates can be used during preparation). The flexural test sample blocks were 40 mm × 40 mm × 160 mm in size, and the compressive strength test sample blocks were 40 mm × 40 mm × 40 mm in size. The mechanical property test sample blocks were prepared separately using the same formula and freeze-thaw process, with n=6 replicates per group. Data are expressed as mean ± standard deviation, and the results are as follows: Figure 7-8As shown in the figure. The test results show that compared with pure white cement CEM, the mechanical properties of the PVA / CEM composite system decreased significantly after the introduction of PVA alone. The flexural strength decreased by approximately 56%, and the compressive strength decreased by approximately 74%. This indicates that the polymer coating effect formed by PVA in the cement matrix inhibits the full hydration of cement particles, leading to increased porosity and damage to the continuous inorganic skeleton structure, thereby weakening the overall load-bearing capacity. However, after further introduction of EPL, the mechanical properties of PVA / CEM-2% EPL, PVA / CEM-5% EPL, and PVA / CEM-10% EPL materials were significantly improved. When the EPL content was 2%, the flexural strength of PVA / CEM-2% EPL increased by approximately 106% and the compressive strength increased by approximately 199% compared with PVA / CEM. This indicates that an appropriate amount of EPL can promote the formation of CSH gel and improve the structure of the interfacial transition zone by forming hydrogen bonds and ionic bonds with cement hydration products through its amino and amide groups, thereby enhancing the overall structural continuity and load-bearing capacity of the material. When the EPL content was further increased to 5% and 10%, the mechanical properties of PVA / CEM-5% EPL and PVA / CEM-10% EPL materials decreased again. Compared with PVA / CEM-2% EPL, the flexural strength of PVA / CEM-5% EPL decreased by about 34%, and the compressive strength decreased by about 39%; the flexural strength of PVA / CEM-10% EPL decreased by about 43%, and the compressive strength decreased by about 49%. This indicates that with the increase of EPL content, the proportion of organic phase in the system further increases, leading to excessive coating and local agglomeration of particle surfaces, inhibiting the effective generation of inorganic hydration products and skeleton construction, thereby reducing the mechanical properties of the material. Furthermore, compared with pure white cement CEM, the flexural strength of PVA / CEM-2% EPL decreased by only about 10%, but the compressive strength decreased by about 21%, indicating that under this content condition, the system achieved a synergistic balance between interfacial bonding enhancement and structural optimization while maintaining high structural integrity. Therefore, it can be considered that the mechanical properties of the composite cement system of this invention depend on the synergistic relationship among the organic-inorganic interface interaction, gel continuity, and inorganic crystal framework support. Under the conditions of this invention, a better comprehensive mechanical property can be obtained when the EPL content is 2%, while a higher content is more beneficial for biological function regulation.

[0059] 4. Mechanism of Action Analysis

[0060] Based on the combined results of FTIR, SEM, and mechanical analysis, the synergistic effects of PVA, TA, and EPL in the white cement system are mainly manifested in the following aspects: First, the hydroxyl groups in PVA molecules can form hydrogen bonds with the hydroxyl groups and aluminate sites on the surface of cement hydration products, and to a certain extent, form an interfacial bonding structure, thus providing a basic organic-inorganic network for the composite system. However, when PVA exists alone, its polymer coating effect is more obvious, which easily weakens the direct inorganic bonding between cement particles and hydration products, leading to an increase in macroporous and flexible film phases. Second, the introduction of EPL provides the system with amino and amide groups. These groups can not only form multiple hydrogen bonds with PVA hydroxyl groups, but also with Ca... 2+ Al 3+ Plasma induces electrostatic interactions or complexation, thereby enhancing the bonding strength of the organic-inorganic interface and promoting the formation of CSH gel and aluminate-related cross-linked structures. Appropriate amounts of EPL are particularly beneficial for inducing the formation of more continuous composite deposition layers on the particle surface and pore walls, improving the structure of the interfacial transition zone. Furthermore, the abundant phenolic hydroxyl groups in TA can react with Ca... 2+ Al 3+ Chelation occurs, further regulating the hydration process of the aluminate and silicate phases, affecting the formation and transformation of ettringite, and promoting the formation of a more stable composite interface layer between the organic and inorganic phases. However, when the EPL content is too high, although the interfacial functional group effect is stronger, excessive organic phase leads to over-coating of the particle surface, local aggregation, and hindered ion diffusion, thereby inhibiting the full formation of the inorganic hydration framework. Therefore, under the current formulation conditions of this invention, 2% EPL is more beneficial for optimizing the overall structure and mechanical properties, while 10% EPL is more beneficial for promoting coral attachment and spreading growth.

Claims

1. A polylysine-based composite cement material, characterized in that, The polylysine-based composite cement material comprises the following raw materials by weight: white cement: polyvinyl alcohol: tannic acid: polylysine in a ratio of 100:10: (0.1-0.5): (2-10), with the remainder being water, and a water-cement ratio of (0.5-0.8):

1.

2. The polylysine-based composite cement material according to claim 1, characterized in that, The raw materials, by weight, include the following: white cement: polyvinyl alcohol: tannic acid: polylysine in a ratio of 100:10:0.5:(2-10), with the remainder being water, and a water-cement ratio of 0.6:

1.

3. The method for preparing the polylysine-based composite cement material according to claim 1 or 2, characterized in that, The steps include the following: S1. Mix white cement, polyvinyl alcohol, tannic acid and polylysine, add water and stir to form a uniform slurry; S2. Pour the slurry into the mold to form the sample, perform freeze-thaw cycle treatment on the formed sample, demold and cure.

4. The preparation method according to claim 3, characterized in that, In step S2, the freeze-thaw cycle treatment includes: at -25°C ± Freeze at 5°C or below for more than 48 hours, then at 25°C. ± Melt at 5℃ for more than 24 hours, and repeat the freezing and thawing process more than twice.

5. The preparation method according to claim 3, characterized in that, In step S2, the mold is cylindrical or cubic.

6. The preparation method according to claim 3, characterized in that, In step S2, after the freeze-thaw cycle treatment is completed, the sample block is demolded and naturally cured for more than 24 hours.

7. The application of the polylysine-based composite cement material according to claim 1 or 2 in coral attachment substrates or in promoting coral spreading and growth.

8. The application of the polylysine-based composite cement material according to claim 1 or 2 in marine ecological restoration or coral reef habitat restoration.

9. The application according to claim 7 or 8, characterized in that, The coral is a beautiful staghorn coral.

10. The application of the polylysine-based composite cement material according to claim 1 or 2 in controlling primary producer adhesion on the surface of a sample block.

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