基于自由体积理论的再生剂扩散系数量化分析OA

The diffusion coefficient is a core quantitative indicator for evaluating the diffusion behavior of rejuvenator agents in aged asphalt.By accurately calculating the diffusion coefficient,the penetration process of the rejuvenator agent and its restoration effect on the performance of aged asphalt can be effectively predicted.Based on the Vrentas-Duda free volume theory,a diffusion coefficient prediction model suitable for characterizing the rejuvenator-aged asphalt system was constructed,and systematic numerical analysis and sensitivity discussion were conducted on various parameters involved in the model.Research indicates that the Vrentas-Duda model can effectively quantify the diffusion behavior of rejuvenator agents in aged asphalt.The parameters included in the model,such as the molecular volume of the rejuvenator agent,glass transition temperature,system temperature,and free volume parameter,directly determine the magnitude of the diffusion coefficient.This parameter is closely related to the viscosity-temperature characteristics and rheological behavior of the rejuvenator and aged asphalt,reflecting the essential influence of the material's inherent properties on the diffusion process. The main factors affecting the diffusion coefficient,including system temperature,degree of asphalt aging,and initial concentration of rejuvenator,were further revealed through factor analysis.The results indicate that the diffusion coefficient increases significantly with rising temperature,indicating that temperature elevation helps to enhance molecular kinetic energy and increase free volume,thereby facilitating the diffusion of the rejuvenator.The intensified aging of asphalt leads to an increase in polar components and a decrease in aromatic components in the system,with the overall structure becoming more rigid and the free volume shrinking,thereby inhibiting diffusion efficiency.The relative concentration of rejuvenator determines the driving force of diffusion,with higher concentrations resulting in faster diffusion rates,exhibiting typical concentration gradient-driven characteristics. In the process of further quantification,numerical simulation and analysis of the diffusion coefficient were conducted under multiple operating conditions,taking into account the actual regeneration process conditions.The results indicate that the diffusion coefficient exhibits a good cubic polynomial distribution relationship with the temperature variation,suggesting a stable mathematical pattern across a wide temperature range.Especially around 100℃+Tg2,there is a significant mutation point in the diffusion coefficient,indicating the transition of asphalt from a glassy state to a viscous flow state.The free volume of the system increases rapidly,and the diffusion ability of the rejuvenator is significantly enhanced.This result has important guiding significance for the temperature control in actual thermal regeneration processes. In summary,increasing the initial dosage of rejuvenator,appropriately elevating the mixing temperature,and reducing the degree of asphalt aging can effectively promote the diffusion behavior of the rejuvenator,thereby enhancing the regeneration effect of aged asphalt.There is a synergistic effect between temperature and rejuvenator content,and the joint optimization of the two foctors can achieve better diffusion effects.However,the intensification of asphalt aging will inhibit diffusion behavior.Therefore,in the process of hot in-plant recycling,it is necessary to comprehensively consider these factors such as the degree of asphalt aging,the amount of rejuvenator added,and the heating temperature,and set reasonable process parameters to enhance diffusion efficiency and ensure the quality of regeneration.The diffusion coefficient model constructed in this study possesses high theoretical reliability and practical application value,and can provide a scientific basis for the optimization of regeneration processes and the design of rejuvenator formulations.