A compatibility evaluation method for SBS modified asphalt based on equilibrium swelling theory

Abstract

The present invention discloses a method for evaluating the compatibility of SBS-modified asphalt based on equilibrium swelling theory. First, the molecular structure of the SBS modifier is determined based on nuclear magnetic resonance spectroscopy. Second, the molecular structure and composition ratio of each molecule in the base asphalt are determined by combining a four-component 20-molecule model of the base asphalt, component separation, and elemental analysis. Then, an SBS-modified asphalt model and an SBS single-molecule model are established, and molecular dynamics simulations are performed. Third, the solvent-accessible surface area of SBS after reaching swelling equilibrium in asphalt and the solvent-accessible surface area of an SBS single molecule are calculated. Finally, the equilibrium swelling ratio of SBS is calculated based on the determined solvent-accessible surface area, and the compatibility of SBS and asphalt is evaluated using the equilibrium swelling ratio. This method facilitates accurate evaluation of the compatibility of SBS-modified asphalt at the microscale and can provide technical support for raw material selection, formulation design, and process optimization of modified asphalt.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the compatibility of modified asphalt, and in particular to a method for evaluating the compatibility of SBS modified asphalt based on the equilibrium swelling theory. Background Art

[0002] SBS-modified asphalt is widely used in road construction due to its excellent road performance. However, the poor compatibility between asphalt and SBS modifiers can lead to segregation during storage and transportation, severely impacting the modified asphalt's performance. Research on the compatibility of asphalt with SBS modifiers is crucial for optimizing raw materials, formulation design, and process development for modified asphalt.

[0003] The compatibility of SBS-modified asphalt is primarily evaluated through the modification effects of mechanical or thermodynamic properties and the micromorphology of SBS. Evaluation methods based on modification effects are significantly affected by test conditions and have difficulty explaining the microscopic mechanism of compatibility. Evaluation methods based on micromorphology are significantly influenced by subjective factors and cannot be quantitatively evaluated. Molecular dynamics simulation can provide atomic-scale structural and interaction information and is an effective means of evaluating compatibility. Currently, researchers have proposed methods for evaluating the compatibility of asphalt based on the interaction between asphalt and SBS. However, the interaction between asphalt and SBS is only one of the factors affecting their compatibility; the swelling effect of SBS in asphalt also has a significant impact on compatibility. Summary of the Invention

[0004] To address the aforementioned issues in the background art, the present invention provides a method for evaluating the compatibility of SBS-modified asphalt based on equilibrium swelling theory. This method facilitates accurate microscopic evaluation of the compatibility of SBS-modified asphalt, providing technical support for raw material selection, formulation design, and process optimization.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A compatibility evaluation method for SBS modified asphalt based on equilibrium swelling theory includes the following steps:

[0007] Step 1: Using nuclear magnetic resonance spectroscopy to test the content of different structural units of the SBS modifier, determine the molecular structure of the SBS modifier, and use the BuildPolymers command of Materials Studio software to construct an SBS molecular model, wherein: the nuclear magnetic resonance spectroscopy test uses a Varian INOVA-400 instrument and deuterated chloroform is used as a solvent to dissolve the SBS modifier;

[0008] Step 2: Use MaterialsStudio software to generate a four-component 20-molecule model of the matrix asphalt, and use elemental analysis and component separation tests to determine the composition ratio of each molecule in the matrix asphalt;

[0009] Step 3: Determine the number of molecules in the SBS modified asphalt based on the SBS dosage and the composition ratio of each molecule in the matrix asphalt. Use GROMACS software to mix the SBS and matrix asphalt molecules according to the quantity, establish an SBS modified asphalt model, and perform molecular dynamics simulation. The specific steps of the molecular dynamics simulation are as follows:

[0010] (1) Perform geometry optimization to optimize the initial configuration of the molecule and ensure that the energy of the simulation system is minimized;

[0011] (2) Annealing simulation under NVT ensemble was performed with a simulation time step of 1 fs, a simulation time of 6 ns, and three cycles of simulation temperature from 0 K to 500 K;

[0012] (3) Annealing simulation was performed under the NPT ensemble, with a simulation time step of 1 fs, a simulation time of 6 ns, a simulation temperature of 0 K to 500 K for 3 cycles, and a simulation pressure of 10 bar;

[0013] (4) Perform NPT ensemble simulation with a simulation time step of 1 fs, a simulation time of 20 ns, a simulation temperature of 298 K, and a simulation pressure of 1 bar;

[0014] Step 4: Use GROMACS software to build an SBS single molecule model and perform molecular dynamics simulation. The method of molecular dynamics simulation is the same as step 3.

[0015] Step 5: Using the simulation results from step 3, calculate the solvent accessible surface area SASA after SBS reaches swelling equilibrium in asphalt S , use the simulation results of step 4 to calculate the solvent accessible surface area SASA of SBS single molecule U , the accessible surface areas of the two solvents are taken as the average value after no significant change with the increase of simulation time;

[0016] Step 6: Calculate the equilibrium swelling ratio SR of SBS. SR is used to characterize the compatibility of SBS and matrix asphalt. The larger the equilibrium swelling ratio, the better the compatibility between SBS and asphalt. The calculation formula of SR is as follows:

[0017]

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. In order to reflect the influence of the swelling effect of SBS on the compatibility, the present invention adopts the swelling ratio of SBS when it reaches swelling equilibrium in asphalt as the evaluation index of compatibility.

[0020] 2. The method of the present invention complements the interaction-based compatibility evaluation method and can evaluate the compatibility of SBS modified asphalt more comprehensively and accurately.

[0021] 3. The present invention achieves the purpose of quantitatively evaluating the compatibility of SBS modified asphalt at the microscopic scale, enriches the compatibility evaluation method of SBS modified asphalt, and provides technical support for raw material optimization, formula design and process optimization of modified asphalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The molecular structure of the SBS modifier determined by the present invention.

[0023] Figure 2 This is the SBS modified asphalt structure simulated by the present invention.

[0024] Figure 3 This is the SBS single molecule structure simulated by the present invention.

[0025] Figure 4 It is the equilibrium swelling ratio of SBS determined in the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0027] Example:

[0028] This embodiment provides a compatibility evaluation method for SBS modified asphalt based on equilibrium swelling theory. First, the molecular structure of the SBS modifier is determined based on nuclear magnetic resonance spectroscopy experiments. Second, the molecular structure and composition ratio of each molecule in the matrix asphalt are determined by combining the four-component 20-molecule model of the matrix asphalt, component separation, and elemental analysis experiments. Then, an SBS modified asphalt model and an SBS single molecule model are established, and molecular dynamics simulations are performed. Third, the solvent accessible surface area of SBS after reaching swelling equilibrium in asphalt and the solvent accessible surface area of SBS single molecule are calculated. Finally, the equilibrium swelling ratio of SBS is calculated based on the determined solvent accessible surface area, and the equilibrium swelling ratio is used to evaluate the compatibility of SBS and asphalt. The specific steps are as follows:

[0029] Step 1: Prepare three types of SBS, namely linear SBS with a block ratio of 3:7 (SBS-L37), linear SBS with a block ratio of 4:6 (SBS-L46) and star SBS with a block ratio of 3:7 (SBS-S37), dissolve the three types of SBS in deuterated chloroform as solvent, and use Varian INOVA-400 instrument to measure the nuclear magnetic resonance hydrogen spectrum of the three types of SBS to determine the molecular structure of SBS (such as Figure 1 As shown), the SBS molecular model was constructed using the BuildPolymers command of MaterialsStudio software.

[0030] Step 2: Use MaterialsStudio software to generate a four-component 20-molecule model of asphalt. Use elemental analysis and component separation tests to test the C, H, N, S, and O element contents and the contents of saturated, aromatic, colloid, and asphaltene components in No. 70 asphalt. Use the multiple regression method to determine the composition ratio of each molecule in the matrix asphalt.

[0031] Step 3: Determine the number of molecules in the SBS modified asphalt based on the SBS dosage and the composition ratio of each molecule in the base asphalt. Use GROMACS software to mix the SBS and base asphalt molecules according to the quantity, establish five modified asphalt models, and perform molecular dynamics simulations, where:

[0032] The specific steps of molecular dynamics simulation are as follows:

[0033] (1) Perform geometry optimization to optimize the initial configuration of the molecule and ensure that the energy of the simulation system is minimized;

[0034] (2) Annealing simulation under NVT ensemble was performed with a simulation time step of 1 fs and a simulation time of 6 ns. The simulation temperature was cycled from 0 K to 500 K for 3 cycles. In each cycle, the temperature was first increased from 0 K to 500 K and then decreased from 500 K to 0 K. The heating rate and cooling rate were both 500 K / ns.

[0035] (3) Annealing simulation was performed under the NPT ensemble, with a simulation time step of 1 fs, a simulation time of 6 ns, a simulation temperature of 0 K to 500 K for 3 cycles, and a simulation pressure of 10 bar;

[0036] (4) Perform NPT ensemble simulation with a simulation time step of 1 fs, a simulation time of 20 ns, a simulation temperature of 298 K, and a simulation pressure of 1 bar.

[0037] The five types of modified asphalt are: SBSMA-L37-3%, SBSMA-L37-5% and SBSMA-L37-7% with SBS-L37 as the modifier and the dosage of 3%, 5% and 7% respectively; SBSMA-L46-5% with SBS-L46 as the modifier and the dosage of 5%; SBSMA-S37-5% with SBS-S37 as the modifier and the dosage of 5%.

[0038] Step 4: Use GROMACS software to establish single-molecule models of the three SBSs respectively, and use the same simulation method as in step 3 to perform molecular dynamics simulations on them.

[0039] Step 5: Use the simulation results of step 3 (such as Figure 2 Calculate the solvent accessible surface area SASA of SBS swollen in matrix asphalt S , using the simulation results of step 4 (such as Figure 3 Calculate the solvent accessible surface area SASA of SBS not swollen in the matrix asphalt U , calculate the equilibrium swelling ratio of SBS in asphalt (such as Figure 4 The final value of the solvent-accessible surface area for both modifiers is the average value after 19 ns of simulation. Among the three modifiers, linear SBS (SBS-L46) with an S / B block ratio of 4:6 has the best compatibility with asphalt, followed by linear SBS (SBS-L37) with an S / B block ratio of 3:7. Star-shaped SBS (SBS-L46) with an S / B block ratio of 3:7 has the worst compatibility with asphalt. For the modifier SBS-L37, compatibility with asphalt is good at 3% and 5% additions, but compatibility with asphalt decreases significantly at 7%.

Claims

1. A compatibility evaluation method for SBS modified asphalt based on equilibrium swelling theory, characterized in that The method comprises the following steps: Step 1: Use nuclear magnetic resonance spectroscopy to test the content of different structural units of the SBS modifier, determine the molecular structure of the SBS modifier, and use the Build Polymers command of Materials Studio software to construct the SBS molecular model; Step 2: Use Materials Studio software to generate a four-component 20-molecule model of the matrix asphalt, and use elemental analysis and component separation tests to determine the composition ratio of each molecule in the matrix asphalt; Step 3: Determine the number of molecules in the SBS-modified asphalt based on the SBS dosage and the composition ratio of each molecule in the base asphalt. Use GROMACS software to mix the SBS and base asphalt molecules in the appropriate quantities, establish an SBS-modified asphalt model, and perform molecular dynamics simulations. Step 4: Use GROMACS software to build a SBS single molecule model and perform molecular dynamics simulation; Step 5: Using the simulation results from step 3, calculate the solvent accessible surface area of SBS after it reaches swelling equilibrium in asphalt. SASA S , use the simulation results of step 4 to calculate the solvent accessible surface area of SBS single molecule SASA U , the accessible surface areas of the two solvents are taken as the average value after no significant change with the increase of simulation time; Step 6: Calculate the equilibrium swelling ratio of SBS SR ,use SR Characterize the compatibility of SBS and matrix asphalt. The larger the equilibrium swelling rate, the better the compatibility of SBS and asphalt. SR The calculation formula is as follows: 。 2. The compatibility evaluation method of SBS modified asphalt based on equilibrium swelling theory according to claim 1, characterized in that In the step 1, the nuclear magnetic resonance spectroscopy experiment was performed using a Varian INOVA-400 instrument.

3. The compatibility evaluation method of SBS modified asphalt based on equilibrium swelling theory according to claim 1, characterized in that In the step 1, deuterated chloroform is used as a solvent to dissolve the SBS modifier.

4. The compatibility evaluation method of SBS modified asphalt based on equilibrium swelling theory according to claim 1, characterized in that In step 3 and step 4, the specific steps of molecular dynamics simulation are as follows: (1) Perform geometric optimization operations to optimize the initial configuration of the molecule and ensure that the energy of the simulation system is minimized; (2) Perform annealing simulation under NVT ensemble, with a simulation time step of 1 fs, a simulation time of 6 ns, and three cycles of simulation temperature from 0 K to 500 K; (3) Annealing simulation was performed under the NPT ensemble, with a simulation time step of 1 fs, a simulation time of 6 ns, a simulation temperature of 0 K to 500 K for 3 cycles, and a simulation pressure of 10 bar; (4) Perform NPT ensemble simulation with a simulation time step of 1 fs, a simulation time of 20 ns, a simulation temperature of 298 K, and a simulation pressure of 1 bar.

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