Preferred method for rubber-cement composite surface modification based on molecular simulation

Abstract

The application discloses a rubber-cement composite material surface modifier optimization method based on molecular simulation, which comprises the following steps: based on molecular dynamics simulation, a full-atom numerical model for characterizing the physicochemical properties of cement matrix, rubber and modifier material is constructed by using Materials Studio software; based on the full-atom numerical model, the Gibbs free energy of the material system is calculated by using a quantum mechanics method to predict whether chemical reaction or physical adsorption behavior occurs between the selected modifier and the two types of materials of rubber and cement, and finally a rubber-cement-based composite material system model before and after the treatment of the modifier is constructed; the free volume fraction and atomic concentration of the composite material system model before and after the modification are analyzed on a microscale to quantitatively evaluate the effect of the modifier on the material performance, and then the optimal surface modifier is determined. The application can construct a numerical model accurately reflecting the material properties and analyze and optimize the material surface / interface modifier.

Description

Technical Field

[0001] This invention relates to the interdisciplinary field of computational materials science and surface modification technology, specifically to a method for selecting the optimal surface modifier for rubber-cement composite materials based on molecular simulation. Background Technology

[0002] With the deepening of the concepts of environmental protection and resource recycling, the efficient utilization of waste rubber, as a typical non-degradable polymer solid waste, has become an important issue for green and low-carbon development.

[0003] Cement, as an important engineering material, is widely used in infrastructure construction such as civil engineering and transportation. However, its poor impact resistance and toughness limit its performance in certain scenarios.

[0004] Replacing some aggregate with waste rubber particles in the cement matrix to prepare novel composite materials not only provides a feasible solution to the problem of waste rubber disposal, but also explores a valuable technical approach to improve the impact resistance and shock absorption performance of traditional cement-based materials.

[0005] However, due to the strong chemical inertness and significant structural heterogeneity of waste rubber, its interfacial compatibility with the cement matrix is ​​poor, resulting in weak interfacial bonding, which seriously restricts the overall mechanical properties and long-term service reliability of rubber-cement composite materials.

[0006] Currently, improving the rubber-cement interface still mainly relies on surface treatment with modifiers. However, traditional modifier screening methods often depend on experimental trial and error, which consumes a lot of time and resources. Especially for waste rubber raw materials with complex sources and varied surface properties, it is difficult to explain the interaction mechanism and interfacial behavior between modifiers and rubber and cement at the microscopic level, which significantly restricts the precise design and targeted selection of modifiers.

[0007] Molecular simulation methods (such as molecular dynamics and quantum mechanics) provide important tools for exploring the mechanisms of microscopic interface behavior. Among them, molecular dynamics, as a microscopic simulation method based on classical mechanics and statistical mechanics, can construct numerical models of material systems at the atomic and molecular scale, analyze the evolution of the microscopic structure of the interface, and make up for the shortcomings of traditional experimental methods in the study of microscopic mechanisms. Quantum mechanics, on the other hand, starts from the electronic scale and judges the spontaneity and feasibility of interactions between substances by calculating the Gibbs free energy of the system, providing key information parameters for molecular dynamics simulation, thereby providing more comprehensive guidance for the optimal design of surface modifiers for rubber-cement composite materials.

[0008] Therefore, this application proposes a method for selecting surface modifiers for rubber-cement composite materials based on molecular simulation. By constructing a numerical model that accurately reflects the physical properties of the material system and conducting computer experiments, this method provides an important means to scientifically guide the selection of surface modifiers at the microscale and to realize the high-value utilization of waste rubber in cement materials. Summary of the Invention

[0009] The main objective of this invention is to provide a molecular simulation-based method for selecting surface modifiers for rubber-cement composite materials by combining quantum mechanics and molecular dynamics methods. This provides a reliable numerical analysis tool for the surface modification design and interfacial compatibility mechanism research of rubber-cement composite materials, thereby solving the technical problems mentioned in the background art.

[0010] The present invention solves the above-mentioned technical problems by adopting the following technical solutions: A method for selecting the optimal surface modifier for rubber-cement composite materials based on molecular simulation specifically includes the following steps: Using Materials Studio software, based on molecular dynamics simulations, an all-atom numerical model was constructed to characterize the physicochemical properties of cement matrix, rubber, and modifier materials. Then, based on the all-atom numerical model, the Gibbs free energy of the material system was calculated using quantum mechanical methods to predict the spontaneous reaction behavior and interfacial affinity between the selected modifier and rubber and cement. Based on the prediction results, a model of the rubber-cement composite material system before and after the modifier treatment was constructed. By analyzing the free volume fraction and atomic concentration of the composite material system model before and after modification at the microscale, the enhancement effect of the modifier on the material properties can be quantitatively evaluated, and the optimal surface modifier can be determined (evaluation criteria: the smaller the free volume fraction, the fewer the pores, and the better the composite material performance; the higher and more uniform the interface atomic concentration, the better the interface performance of the composite material and the better the overall performance).

[0011] Preferably, the construction process of the all-atom numerical model of the cement matrix includes: An initial Tobermorite model was constructed, and its structure was optimized using the Forcite module of Materials Studio software. The optimization method combined the steepest descent method and the conjugate gradient method. A crosslinking program was written in Perl language to designate silicon and oxygen atoms in the initial Tobermorite model after structural optimization as crosslinking bonding sites Link1 and Link2, with bonding radii of 3 to 10 Å. After each bonding, geometric optimization was performed, and dynamic relaxation was performed under the NPT ensemble. During the relaxation process, the interatomic interactions were described based on the Dreiding force field. Through a chemical cross-linking reaction, the initial Tobermorite model with optimized structure is transformed from a branched silicon-oxygen tetrahedral structure into a three-dimensional network structure, ultimately forming a cement-based model.

[0012] Preferably, the process for constructing the all-atom numerical model of the rubber includes: Three monomer molecular models of natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR), the main components of rubber, were established. The model was generated by simulating the vulcanization reaction of rubber using Materials Studio software. Based on the Amorphous Cell module of Materials Studio software, the three monomer molecules of rubber and sulfur molecules are stacked to form an amorphous unit cell structure, and the interaction between atoms is described by COMPASS III force field. A rubber vulcanization reaction program was written using the Perl language, specifying the carbon and sulfur atoms in the rubber monomer molecules as the main bonding sites. After bonding, the model is geometrically optimized and kineticly relaxed under the NPT ensemble, ultimately forming a vulcanized rubber model with a three-dimensional network structure.

[0013] Preferably, the modifier model is an organic acid containing hydroxyl, phenolic hydroxyl, or carboxyl groups.

[0014] Preferably, the specific calculation process for calculating the Gibbs free energy of a material system using the quantum mechanical method includes: Representative monomer molecules of modifiers, rubber, and cement-based materials were constructed as reactant models; Based on the reactant model, models of potential products formed by the interaction of the modifier with rubber and cement-based materials were constructed respectively. DMol based on Materials Studio software 3 The module performs structural optimization and energy calculation on the constructed reactant and potential product models. In the calculation, the generalized gradient approximation (meta-GGA) in the form of SCAN is used to handle the exchange correlation energy, the atomic nuclei and inner-shell electrons are treated as all-electrons, and the basis set is selected as the dual numerical orbital basis set (DND). Gibbs free energy (i.e., Gibbs free energy = electron energy + zero-point energy + enthalpy - entropy × temperature) is calculated by statistically analyzing the electron energy, zero-point energy corrected enthalpy, and entropy of potential products and reactants. By comparing the difference in Gibbs free energy between potential products and reactants, it is determined whether the reaction is spontaneous and the mode of action of the modifier.

[0015] Preferably, the specific criterion for determining whether the selected modifier undergoes a chemical reaction or physical adsorption behavior with rubber and cement materials based on the Gibbs free energy prediction is as follows: If the difference in Gibbs free energy between the potential products and reactants treated with the modifier is greater than 0, it is considered that the two cannot react spontaneously, and the modifier mainly acts on the surface of the corresponding material through physical adsorption. If the difference in Gibbs free energy between the potential products and reactants treated with the modifier is less than 0, it is considered that the two can react spontaneously, and the modifier mainly acts on the surface of the corresponding material through chemical reaction.

[0016] Preferably, a model of the rubber-cement composite material after modification is constructed based on the action mode obtained from Gibbs free energy analysis.

[0017] Preferably, the procedure for quantitatively analyzing and evaluating the free volume fraction and atomic concentration of the composite material system model before and after modification includes: Based on the Forcite module of Materials Studio software, static geometry optimization was performed on the composite material system model before and after modification. Then, dynamic relaxation was performed in the NPT ensemble and NVT ensemble, respectively. The interaction between atoms was described by COMPASS III force field. The free volume fraction (i.e., the ratio of free volume to total volume) of the composite material system model before and after modification was calculated to assess the material's microporosity. The total volume of the model was the constructed unit cell volume, and the free volume was identified and quantified using a Connolly probe to identify and quantify the volume of unoccupied "voids" between material molecules. The Connolly probe radius was 0.1 Å. The atomic concentration of the composite material system model before and after modification is calculated and analyzed. The relative concentration of atoms is mainly calculated in the direction perpendicular to the interface, and an atomic distribution profile in this direction is generated to analyze the influence and effect of the modifier treatment on the atomic distribution at the model interface (evaluating the interface structure and modification effect).

[0018] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0019] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0020] As can be seen from the above technical solution, the present invention provides a method for selecting the optimal surface modifier for rubber-cement composite materials based on molecular simulation. Compared with the prior art, the present invention has the following advantages: 1. The all-atom numerical model of this invention is constructed based on molecular dynamics methods, which can effectively characterize the physicochemical properties of rubber-modifier-cement-based composite systems. It enables researchers to clearly understand the microstructure and interface properties of materials at the molecular scale, thus providing a reliable model basis for the selection of modifiers and the study of interface compatibility mechanisms.

[0021] 2. This invention uses quantum mechanics to calculate the Gibbs free energy of a material system, which can accurately predict the interaction between the modifier and the rubber and cement matrix, thus providing strong support for the rapid screening of modifiers and the analysis of interfacial interaction mechanisms.

[0022] 3. This invention, by calculating and analyzing the free volume fraction and atomic concentration of the composite system before and after modification agent treatment at the microscale, can quantitatively evaluate the effect of the modifier on the microstructure and properties of the material, thereby achieving the scientific selection of surface modifiers, reducing experimental trial and error, and lowering the R&D cycle and cost.

[0023] 4. This invention utilizes molecular-scale methods combining molecular dynamics and quantum mechanics to conduct computer experiments, enabling the explanation of the interfacial behavior and interaction mechanisms between modifiers and rubber and cement at the microscopic level. This guides the precise design and targeted selection of modifiers, ultimately achieving the high-value utilization of waste rubber in cement materials.

[0024] It should be understood that the descriptions in this section are not intended to identify key or essential features of embodiments of the invention, nor are they intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Of course, implementing any product of the invention does not necessarily require achieving all of the advantages described above simultaneously. Attached Figure Description

[0025] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the overall method flow of the present invention; Figure 2 This is a schematic diagram of the cement-based modeling method of the present invention; Figure 3 This is a schematic diagram of the modeling method for vulcanized rubber models of the present invention; Figure 4 This is a molecular model diagram of the reactants and potential products of the present invention; Figure 5This is a model diagram of the rubber-cement matrix composite material before and after treatment with the modifier of the present invention; Figure 6 This is a cloud map showing the free volume fraction of the rubber-cement based model before and after treatment with the modifier of the present invention. Figure 7 This is an atomic concentration diagram of the rubber-cement based model before and after treatment with the modifier of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. 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.

[0027] For details in the embodiments, please refer to Figures 1 to 7 .

[0028] like Figure 1 As shown in the embodiments of the present invention, the method for selecting surface modifiers for rubber-cement composite materials based on molecular simulation constructs a full-atomic model that accurately describes the physical properties of cement, rubber, and modifier monomers using the Materials Studio software platform. Furthermore, the Gibbs free energy of the system is calculated using quantum mechanics to determine the type of interaction (chemical reaction or physical adsorption) between the modifier and the cement and rubber materials. Based on this result, rubber-cement composite material models before and after modifier treatment are constructed. Finally, the influence of the modifier on performance is evaluated by analyzing the free volume fraction and atomic concentration at the microscale, thereby achieving the selection of the surface modifier. Specific steps include: Step S1. Molecular dynamics simulations were performed using Materials Studio software to construct an all-atom numerical model for characterizing the physicochemical properties of the cement matrix, rubber, and modifier materials.

[0029] Specifically, this includes: using the Tobermorite model, processing it with a crosslinking program written in Perl language to ultimately form a three-dimensional crosslinked network cement matrix model; and using the amorphous cell structure composed of three rubber components, writing a rubber vulcanization reaction program to ultimately form a vulcanized rubber model.

[0030] For cement-based model construction, such as Figure 2As shown, a numerical model of cement with a three-dimensional cross-linked network structure was established using Materials Studio software based on the tobermorite configuration. This model can more accurately characterize cement hydration products. The specific process is as follows: First, a Tobermorite model was constructed and its structure optimized using the Forcite module, combining the steepest descent method with the conjugate gradient algorithm. Second, a crosslinking program was written in Perl. In the program, silicon and oxygen atoms in the Tobermorite model were designated as crosslinking bonding site 1 (Link1) and crosslinking bonding site 2 (Link2), respectively. The bond cutoff distance ranged from 3 Å to 10 Å. Geometric optimization was performed after each bonding, followed by dynamic relaxation under the NPT ensemble. During relaxation, interatomic interactions were described using the Dreiding force field. Finally, through a chemical crosslinking reaction, the initial Tobermorite model transformed from a branched silicon-oxygen tetrahedral structure into a three-dimensional network structure, ultimately forming a cement-based model.

[0031] For rubber model construction, such as Figure 3 As shown, the process of generating rubber by simulating the vulcanization reaction of rubber using Materials Studio software is as follows: First, molecular models of the three main components of rubber—natural rubber (NR), butadiene rubber (BR), and styrene-butadiene rubber (SBR)—were established. Second, based on the Amorphous Cell module, the three rubber monomer molecules and sulfur molecules were stacked to form an amorphous unit cell structure, with an initial packing density of 0.9 g / cm³. 3 The interaction between atoms was described using the COMPASS III force field. Finally, a rubber vulcanization reaction program was written in Perl, specifying carbon and sulfur atoms in the rubber monomer molecules as the main bonding sites, with bonding radii ranging from 3 to 10 Å. After bonding, the model was geometrically optimized and kineticly relaxed under the NPT ensemble, ultimately forming a vulcanized rubber model with a three-dimensional network structure.

[0032] Gallic acid (GA) is used as an example modifier to illustrate the application of the method, not to limit it. Those skilled in the art will understand that the proposed technique is equally applicable to other types of modifiers.

[0033] Step S2. Based on the all-atom numerical model, the Gibbs free energy change of the material system is calculated using quantum mechanics methods to predict whether the selected modifier will react chemically or physically with rubber and cement. Finally, a model of the rubber-cement based composite material system before and after the modifier treatment is constructed.

[0034] The specific steps are as follows: First, representative monomer molecules of the modifier, rubber, and cement-based materials are constructed as reactant models. Based on this, potential product models are constructed for the interaction of the modifier with rubber and cement-based materials, respectively. For example, the molecular configurations of potential products SBR-GA-1 or SBR-GA-2 that may form from the interaction of GA and SBR are shown. Other related models include... Figure 4 As shown.

[0035] Secondly, based on DMol 3 This module performs structural optimization and energy calculations on the constructed reactant and potential product models. In the calculations, the generalized gradient approximation (meta-GGA) of the SCAN form is used to handle exchange correlation energies. All-electron treatment is applied to atomic nuclei and inner-shell electrons; pseudopotential approximations are not used for inner-shell electrons. The basis set is a dual-orbital (DND) basis set. The electron energies, zero-point energy-corrected enthalpies, and entropies of the potential products and reactants are statistically analyzed at room temperature (298K) to calculate the Gibbs free energy. G = Electron energy + Zero-point energy + Enthalpy - Entropy × Temperature).

[0036] By comparing the Gibbs free energy difference (Δ) between potential products and reactants G To determine whether a reaction is spontaneous and the mode of action of the modifier, the relevant calculation formulas are as follows:

[0037]

[0038] in, For the Gibbs free energy of the products, The Gibbs free energy of the reactants; The Gibbs free energy of the reactants of the modifier. The Gibbs free energy of rubber or cement-based reactants. The Gibbs free energy is the product formed after the modifier interacts with rubber or cement-based materials. If the difference in Gibbs free energy between the potential products and reactants treated with the modifier is Δ G If the value is greater than 0, it is considered that the two cannot react spontaneously, and the modifier mainly acts on the surface of the corresponding material through physical adsorption. If the difference in Gibbs free energy between the potential products and reactants treated with the modifier is Δ G If the value is less than 0, it is considered that the two can react spontaneously, and the modifier mainly acts on the surface of the corresponding material through chemical reaction.

[0039] Table 1 below shows the Gibbs free energy changes of the reactants and potential products involved in the construction of rubber-cement based composites. Based on this, and according to the modifier's mode of action, models of rubber-cement based composites before and after modifier treatment are constructed, as follows. Figure 5 As shown.

[0040] Table 1

[0041] Step S3. Analyze the free volume fraction and atomic concentration of the composite material system model before and after modification at the microscale to quantitatively evaluate the effect of the modifier on the material properties, and then determine the optimal surface modifier (evaluation criteria: the smaller the free volume fraction, the fewer the pores, and the better the composite material performance; the higher and more uniform the interface atomic concentration, the better the interface performance of the composite material and the better the overall performance).

[0042] The specific steps are as follows: First, static geometric optimization and kinetic relaxation were performed on the rubber-cement composite system models before and after modifier treatment. Specifically, the geometric optimization of the constructed model was performed based on the Forcite module, followed by kinetic relaxation under the NPT and NVT ensembles, respectively. The interatomic interactions were described using COMPASS III force fields.

[0043] Secondly, the free volume fraction of the composite material system model before and after modifier treatment was calculated to evaluate the micropore distribution of the material. The free volume fraction is the ratio of the free volume to the total volume of the model. The free volume is defined by a Connolly probe to identify and quantify the volume of "voids" between material molecules that are not occupied by atoms; the Connolly probe radius is 0.1 Å. The relevant calculation results are as follows: Figure 6 As shown, the free volume fraction of the model before modification was 0.092, and the free volume fraction of the model after modification was 0.087. This indicates that the GA modifier treatment can reduce the micropores of the rubber-cement composite system, making the structure more compact. Therefore, the free volume fraction can be used as one of the important parameters for evaluating the effect of the modifier.

[0044] Finally, the atomic concentration of the composite material system model before and after the modifier treatment was calculated and analyzed; At this point, the relative concentration of atoms is statistically analyzed along the direction perpendicular to the interface, and an atomic distribution profile is generated in this direction to analyze the influence and effect of the modifier treatment on the atomic distribution at the model interface. The relevant calculation results are as follows: Figure 7As shown, the atomic concentration at the interface of the modified composite model is higher than that of the unmodified model. This indicates that the modifier molecules penetrate and fill the initial defects and micropores in the interface region, acting as a bridge between the rubber and cement matrix, enhancing their compatibility, and thus improving the macroscopic mechanical properties of the rubber-cement composite material.

[0045] Finally, by comparing the effects of modification before and after modification or different modifiers, the modifier with the atomic concentration and free volume fraction closest to the ideal conditions was selected as the optimal modifier.

[0046] In summary, the above methods construct a reliable all-atom model for characterizing the physicochemical properties of rubber-cement composite materials based on molecular dynamics, and combine this with quantum mechanical methods to calculate the Gibbs free energy to predict the interaction mechanism between the modifier and the matrix. Through index analysis and calculation at the microscale, this provides an important method for rapidly screening modifiers, significantly reducing the trial-and-error costs of traditional experiments and effectively shortening the research and development cycle.

[0047] In another aspect, the present invention also discloses a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the method described above.

[0048] In another aspect, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of the method described above.

[0049] In another embodiment provided in this application, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to execute any of the molecular simulation-based preferred methods for surface modifiers of rubber-cement composite materials in the above embodiments.

[0050] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, an optical medium, or a semiconductor medium, etc.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0052] Furthermore, it should be noted that if any directional indication (such as up, down, left, right, front, back, etc.) is involved in the embodiments of the present invention, the directional indication is only used to explain the relative positional relationship and movement of each component in a specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0053] Furthermore, those skilled in the art should understand that in the actual use of the embodiments of this application, there may be preset thresholds used as the basis for judging the corresponding technical solutions. These thresholds are conventional technical means commonly used in the field to implement functions such as state judgment, condition recognition, and control logic switching. The specific values, setting basis, value selection methods, determination methods, and adjustment rules of the thresholds involved in this technical solution are all conventional technical choices that can be reasonably determined by those skilled in the art based on conventional technical factors such as actual application scenarios, system working states, characteristics of the detection object, hardware performance parameters, and functional requirements, through conventional experiments, calibrations, and debugging. The specific setting and adjustment of the aforementioned thresholds will not cause this technical solution to be unimplementable as a whole, nor will it affect the realization of the core concept and the achievement of the technical effects of this technical solution.

[0054] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, in the embodiments of this invention, "multiple" refers to two or more. Moreover, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

Claims

1. A method for selecting the optimal surface modifier for rubber-cement composite materials based on molecular simulation, characterized in that, include: Molecular dynamics simulations were performed using Materials Studio software to construct an all-atom numerical model for characterizing the physicochemical properties of cement matrix, rubber, and modifier materials. Based on the all-atom numerical model, the Gibbs free energy of the material system is calculated using quantum mechanical methods to predict the spontaneous reaction behavior and interfacial affinity between the selected modifier and rubber and cement. Based on the prediction results, a model of the rubber-cement based composite material system before and after the modifier treatment is constructed. The free volume fraction and atomic concentration of the composite material model before and after modification are analyzed at the microscale to quantitatively evaluate the effect of the modifier on the material properties and thus determine the optimal surface modifier.

2. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 1, characterized in that, The process for constructing the all-atom numerical model of the cement matrix includes: An initial Tobermorite model was constructed, and its structure was optimized using the Forcite module of Materials Studio software. The optimization method combined the steepest descent method and the conjugate gradient method. A crosslinking program was written in Perl language to designate silicon and oxygen atoms in the initial Tobermorite model after structural optimization as crosslinking bonding sites Link1 and Link2, with bonding radii of 3 to 10 Å. After each bonding, geometric optimization was performed, and dynamic relaxation was performed under the NPT ensemble. During the relaxation process, the interatomic interactions were described based on the Dreiding force field. Through a chemical cross-linking reaction, the initial Tobermorite model with optimized structure is transformed from a branched silicon-oxygen tetrahedral structure into a three-dimensional network structure, ultimately forming a cement-based model.

3. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 2, characterized in that, The process of constructing the all-atom numerical model of the rubber includes: Three monomer models of natural rubber, butadiene rubber and styrene-butadiene rubber, the main components of rubber, were established. The model was generated by simulating the vulcanization reaction of rubber using Materials Studio software. Based on the Amorphous Cell module of Materials Studio software, the three monomer molecules of rubber and sulfur molecules are stacked to form an amorphous unit cell structure, and the interaction between atoms is described by COMPASS III force field. A rubber vulcanization reaction program was written using the Perl language, specifying the carbon and sulfur atoms in the rubber monomer molecules as the main bonding sites. After bonding, the model is geometrically optimized and kineticly relaxed under the NPT ensemble, ultimately forming a vulcanized rubber model with a three-dimensional network structure.

4. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 3, characterized in that, The modifier model uses organic acids containing hydroxyl, phenolic hydroxyl, or carboxyl groups.

5. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 1, characterized in that, The specific calculation process for calculating the Gibbs free energy of a material system using the quantum mechanical method includes: Representative monomer molecules of modifiers, rubber, and cement-based materials were constructed as reactant models; Based on the reactant model, models of potential products formed by the interaction of the modifier with rubber and cement-based materials were constructed respectively. DMol based on Materials Studio software 3 The module performs structural optimization and energy calculation on the constructed reactant and potential product models. In the calculation, the exchange correlation energy is handled by the generalized gradient approximation in the form of SCAN, the atomic nuclei and inner-shell electrons are treated as all-electrons, and the basis set is selected as a dual-numerical-orbital basis set. Gibbs free energy is calculated by statistically analyzing the electronic energies, zero-point energy-corrected enthalpy, and entropy of potential products and reactants. By comparing the difference in Gibbs free energy between potential products and reactants, it is determined whether the reaction is spontaneous and the mode of action of the modifier.

6. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 5, characterized in that, The specific criteria for determining whether the selected modifier undergoes a chemical reaction or physical adsorption behavior with rubber and cement materials, as predicted by the Gibbs free energy, are as follows: If the difference in Gibbs free energy between the potential products and reactants treated with the modifier is greater than 0, it is considered that the two cannot react spontaneously, and the modifier mainly acts on the surface of the corresponding material through physical adsorption. If the difference in Gibbs free energy between the potential products and reactants treated with the modifier is less than 0, it is considered that the two can react spontaneously, and the modifier mainly acts on the surface of the corresponding material through chemical reaction.

7. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 6, characterized in that, The model of the rubber-cement composite material treated with the modifier was constructed based on the action mode obtained from Gibbs free energy analysis.

8. The preferred method for surface modifiers of rubber-cement composite materials based on molecular simulation as described in claim 1, characterized in that, The procedure for quantitatively analyzing and evaluating the free volume fraction and atomic concentration of the composite material system model before and after modification includes: Based on the Forcite module of Materials Studio software, static geometry optimization was performed on the composite material system model before and after modification. Then, dynamic relaxation was performed in the NPT ensemble and NVT ensemble, respectively. The interaction between atoms was described by COMPASS III force field. Calculate the free volume fraction of the composite material system model before and after modification to assess the microporosity of the material; The atomic concentration of the composite material system model before and after modification was calculated and analyzed to evaluate the interface structure and modification effect.

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