CN111863144A - Asphalt and modifier compatibility evaluation method based on interface interaction - Google Patents

Abstract

The invention discloses an evaluation method for compatibility of asphalt and a modifier based on interfacial interaction, belongs to the technical field of modified asphalt, and solves the problem that no evaluation method capable of showing a dynamic process when a styrene-butadiene-styrene (SBS) modifier is compatible with matrix asphalt is provided at present. The invention constructs a matrix asphalt model, an SBS modifier model and an SBS and matrix asphalt interface model respectively through molecular dynamics simulation software. And (2) performing molecular dynamics simulation on the SBS and matrix asphalt interface model at different temperatures, calculating to obtain interface energy, comparing the values, and analyzing the interaction between the SBS and the matrix at the interface to evaluate the compatibility of the matrix asphalt and the SBS. The evaluation method is based on numerical simulation, is simple to operate, has intuitive results, provides help for the research of the blending mechanism of SBS and the matrix asphalt, provides an idea for establishing a compatibility evaluation system of the modified asphalt, and provides a theoretical basis for the development of the SBS modified asphalt and the improvement of the modification effect.

Description

Asphalt and modifier compatibility evaluation method based on interface interaction

Technical Field

The invention discloses an asphalt and modifier compatibility evaluation method based on interface interaction, and belongs to the technical field of modified asphalt.

Background

Asphalt as a complex high molecular hydrocarbon shows typical elasticity-viscosity-plasticity under the action of a certain temperature and load, and the temperature sensitivity of the asphalt directly influences the performance of an asphalt pavement. In recent years, with the rapid increase of the traffic flow of expressways and the increase of overloaded and heavy-duty vehicles, the common base asphalt is difficult to adapt to the higher requirements of modern traffic on asphalt materials. The addition of the modifier can improve the road performance of the mixture at high temperature, and improve the performances of the mixture in the aspects of rutting resistance, fatigue resistance, ageing resistance, low-temperature cracking resistance and the like.

Generally, the key to the asphalt modification effect is the compatibility of the modifier with the asphalt. Compatibility is defined thermodynamically as the ability of two or more substances to form a homogeneous system in any proportion. The compatibility in road engineering means that the polymer modifier reacts with the base asphalt in fine particles or is uniformly and stably dispersed in the base asphalt without layering, agglomeration and segregation.

The compatibility of the modifier with the matrix asphalt is mainly determined by the interaction between the two interfaces, the so-called interface, not just a line between the polymer phase and the asphalt phase, but rather a broad area from the surface of the polymer phase to the surface of the asphalt phase. For polymer modified asphalt, the interface is formed by molecular adsorption with similar solubility parameters, and the property of the interface can influence the stability and compatibility of high-performance polymer modified asphalt and the development of modified asphalt. The polarity and molecular structure of the general polymer are closer to that of the asphalt, the stronger the interaction between the general polymer and the matrix asphalt is, the better the compatibility between the general polymer and the matrix asphalt is, and the corresponding modification effect is also better.

Styrene-butadiene-styrene (SBS) is widely applied in modifier, but SBS and base asphalt have difference in molecular weight, physical density and chemical structure, and belong to a thermodynamically incompatible system, and when the SBS and the base asphalt are blended, it is difficult to obtain a blending system with a relatively uniform and stable phase structure. In the current practical application, the current situation that the modified asphalt is poor in compatibility and storage stability becomes a problem existing in road construction in China, and the modified asphalt can be guaranteed to have excellent performance only when the modifier is good in compatibility with the asphalt. Therefore, the research on the compatibility of SBS and asphalt is of great significance.

At present, people mostly analyze the change of components before and after asphalt modification to analyze the action mechanism of modified asphalt, or utilize the interaction between different asphalt components and a modifier to judge the contribution effect of each component in the asphalt on the modified asphalt, so as to research the interaction between the asphalt components and the modifier, and compare and analyze the compositions and structures of the asphalt and the modifier by means of testing means such as a Scanning Electron Microscope (SEM), an infrared spectrum (IR), a Nuclear Magnetic Resonance (NMR) and the like, and explain the blending mechanism of a mixture from the perspective of interface binding capacity. Meanwhile, the research from molecular and atomic level is very rare, so that the research depth and precision are not enough.

With the rapid development of the scientific and technological era, the molecular simulation method is gradually applied to the field of roads and is also an important method for researching the interface properties of road materials, and the method can track the dynamic evolution process of a complex system along with time; different types of layer structures can be established in a molecular system, so that the interface behavior is simulated from the molecular angle, the adsorption and aggregation behavior is evaluated from the micro scale, and the interaction among different interfaces is evaluated, thereby providing an idea for researching the compatibility of SBS modified asphalt.

Therefore, the invention researches the stability of the SBS modified asphalt by a molecular simulation technology and a molecular dynamics method. The method mainly comprises the steps of respectively constructing a matrix asphalt model, an SBS block copolymer molecular structure model and an SBS and matrix asphalt interface model through molecular dynamics simulation software, calculating to obtain interface energy, analyzing corresponding adsorption conditions, and using the interface energy as an evaluation compatibility index to represent the compatibility of an SBS modifier and asphalt.

Disclosure of Invention

(1) Technical problem

The invention provides an asphalt and modifier compatibility evaluation method based on interface interaction, which evaluates the compatibility of SBS and matrix asphalt from the molecular angle, and has intuitive and reliable result, thereby solving the problem that an SBS and matrix asphalt interface model is not directly constructed at present; the interaction of the SBS modifier with the matrix asphalt interface is not quantitatively given; the problem of dynamic change of an internal molecular structure when SBS is compatible with the matrix asphalt is not provided, and the problems of low test analysis precision and high cost are solved.

(2) Technical scheme

In view of the problem that the interaction between the modifier and the interface of the matrix asphalt is not directly and quantitatively given at present, the invention mainly obtains the interaction energy at the interface, namely the interface energy, by calculating through a molecular simulation technology, thereby providing the asphalt and modifier compatibility evaluation method based on the interface interaction. Firstly, determining the content of each component through an asphalt four-component test, constructing a matrix asphalt model through molecular software, and verifying the rationality of the matrix asphalt model. Drawing a molecular structure model of the SBS block copolymer, constructing an SBS modifier model according to the mixing amount of the SBS modifier, adding the SBS modifier model into a software module to serve as a first layer interface, and using a matrix asphalt model as a second layer, so as to construct an SBS and matrix asphalt interface model, and performing energy minimization and annealing treatment on the interface model. And finally, selecting an interface model with the lowest energy to perform molecular dynamics simulation at different temperatures to sequentially obtain potential energy, calculating the interface energy according to a formula, comparing the interface energy, and analyzing the adsorption condition between the SBS and the matrix asphalt interface to evaluate the compatibility between the matrix asphalt and the SBS modifier.

(3) Advantageous effects

With the wide application of modified asphalt, people are pursuing better modification effect. The modifying effect of modified asphalt is often determined by the compatibility between the modifier and the asphalt, while the compatibility between the modifier and the base asphalt is mainly determined by the interaction between the two interfaces. However, it is difficult to form a relatively stable phase structure when blending because of the difference in structure and physical and chemical properties between SBS and asphalt. Therefore, the method for evaluating the compatibility of SBS and the base asphalt is provided, which is helpful for the research of the blending mechanism of the SBS and the base asphalt. The invention provides an evaluation method for the compatibility of asphalt and a modifier based on interface interaction, which is an evaluation method with simple operation and high precision, and can construct an SBS and matrix asphalt interface model from the molecular angle, quantitatively predict the interface energy of SBS and asphalt, and evaluate the interaction of the SBS and the asphalt at the interface, thereby evaluating the compatibility of SBS and asphalt. By means of molecular dynamics simulation, the evaluation method of the compatibility of SBS and asphalt is specifically provided, an idea is provided for researching the compatibility mechanism of SBS and asphalt, a basis is provided for the development of SBS modified asphalt, and the evaluation method has very important significance for effectively solving the problem of asphalt segregation and improving the stability of modified asphalt.

Detailed Description

The invention provides an asphalt and modifier compatibility evaluation method based on interface interaction, which comprises the following specific implementation steps of:

(1) testing the content of saturates, aromatics, gums and asphaltenes in the four components of matrix asphalt according to petroleum asphalt four-component assay method (NB/SH/T0509-2010);

(2) respectively drawing matrix asphalt four-component typical representative molecular structure models through a Sketch function of molecular dynamics simulation software, respectively determining the number of the four-component molecular structure models according to the measured content of the four components of the matrix asphalt and the molecular weight of the molecular structure, constructing the matrix asphalt model by using an Amorphous Cell module, carrying out simulation operation on the matrix asphalt molecular dynamics model at normal temperature, and calculating a simulation density value to compare the simulation density value with a density value measured by a matrix asphalt test so as to verify the rationality of the matrix asphalt molecular dynamics model;

(3) drawing monomer repeating units of styrene and 1, 3-butadiene in a styrene-butadiene-styrene (SBS) modifier by using a Build module in molecular dynamics simulation software, determining the degree of polymerization of SBS, constructing an SBS Block Copolymer molecular structure model by using a Block Copolymer module, determining the number of the SBS Block Copolymer molecular structure models according to the doping amount of the SBS modifier in modified asphalt, and constructing an SBS modifier model in an Amorphous Cell;

(4) constructing an interface model of SBS and matrix asphalt in Build Layers function, adding an SBS modifier model as a first layer interface, taking a matrix asphalt model as a second layer interface, performing energy minimization and annealing treatment on the interface model, and selecting the interface model of SBS and matrix asphalt with the lowest energy as an initial model for molecular dynamics simulation;

(5) molecular dynamics simulation is carried out on the SBS and matrix asphalt interface model with the lowest energy at different temperatures, potential energy calculation is carried out on each interface model at different temperatures in sequence by adopting an Analysis module of Forcite, then the interface energy is calculated according to a formula I,

ΔE＝E_interaction＝E_total-(E_surface-E_emulsifier) ①

in the formula, E_interactionRepresenting the interfacial energy between SBS and base bitumen, E_totalIs the total energy of the SBS and matrix asphalt model interface model, E_surfaceIs the total energy of the first layer interface SBS modifier model, E_emulsifierThe total energy of the second layer interface matrix asphalt model is compared with the interface energy value to analyze the aggregation and adsorption conditions between the matrix asphalt and the SBS modifier and evaluate the compatibility of the matrix asphalt and the SBS modifier.

Claims (1)

1. A method for evaluating compatibility of asphalt and a modifier based on interfacial interaction is characterized by comprising the following specific steps:

(1) testing the content of saturates, aromatics, gums and asphaltenes in the four components of matrix asphalt according to petroleum asphalt four-component assay method (NB/SH/T0509-2010);

(2) respectively drawing matrix asphalt four-component typical representative molecular structure models through a Sketch function of molecular dynamics simulation software, respectively determining the number of the four-component molecular structure models according to the measured content of the four components of the matrix asphalt and the molecular weight of the molecular structure, constructing the matrix asphalt model by using an Amorphous Cell module, carrying out simulation operation on the matrix asphalt molecular dynamics model at normal temperature, and calculating a simulation density value to compare the simulation density value with a density value measured by a matrix asphalt test so as to verify the rationality of the matrix asphalt molecular dynamics model;

(3) drawing monomer repeating units of styrene and 1, 3-butadiene in a styrene-butadiene-styrene (SBS) modifier by using a Build module in molecular dynamics simulation software, determining the degree of polymerization of SBS, constructing an SBS Block Copolymer molecular structure model by using a Block Copolymer module, determining the number of the SBS Block Copolymer molecular structure models according to the doping amount of the SBS modifier in modified asphalt, and constructing an SBS modifier model in an Amorphous Cell;

(4) constructing an interface model of SBS and matrix asphalt in Build Layers function, adding an SBS modifier model as a first layer interface, taking a matrix asphalt model as a second layer interface, performing energy minimization and annealing treatment on the interface model, and selecting the interface model of SBS and matrix asphalt with the lowest energy as an initial model for molecular dynamics simulation;

(5) molecular dynamics simulation is carried out on the SBS and matrix asphalt interface model with the lowest energy at different temperatures, potential energy calculation is carried out on each interface model at different temperatures in sequence by adopting an Analysis module of Forcite, then the interface energy is calculated according to a formula I,

ΔE＝E_interaction＝E_total-(E_surface-E_emulsifier) ①

in the formula, E_interactionRepresenting the interfacial energy between SBS and base bitumen, E_totalIs the total energy of the SBS and matrix asphalt model interface model, E_surfaceIs the total energy of the first layer interface SBS modifier model, E_emulsifierThe total energy of the second layer interface matrix asphalt model is compared with the interface energy value to analyze the aggregation and adsorption conditions between the matrix asphalt and the SBS modifier and evaluate the compatibility of the matrix asphalt and the SBS modifier.