基于耗散伪应变能的沥青疲劳动力学表征

Pseudo Energy-based Kinetic Characterization of Fatigue in Asphalt Binders

沥青的开裂和塑性变形是疲劳损伤过程中的2个耦合子进程。为了分离沥青在疲劳损伤阶段的开裂子进程及塑性变形子进程及寻求疲劳损伤进程与2个子进程的关联特征指标,基于能量力学法及动力学理论研究沥青的疲劳损伤进程、开裂子进程及塑性变形子进程。首先采用能量力学法从沥青疲劳损伤阶段不同温度下的累积总耗散伪应变能(DPSE)分离出开裂导致的累积耗散伪应变能(DPSEc)及塑性变形引起的累积耗散伪应变能(DPSEp);然后采用三参数模型来匹配沥青疲劳损伤进程、开裂及塑性变形子进程的耗散伪应变能,获得了能够定量描述能量耗散演变快慢的特征能量变化率;最后基于动力学理论建立沥青疲劳损伤阶段的特征能量变化率与温度的关系,并确定表征沥青疲劳损伤进程的动力学指标。结果表明:基质沥青及SBS改性沥青的DPSE,DPSEc,DPSEp的特征能量变化率与绝对温度倒数呈线性关系,DPSEp的特征能量变化率随温度的增加而增加,而DPSEc的特征能量变化率随温度的增加而减小,其原因是随着温度的升高,沥青塑性变形发展变快,而开裂则减缓;SBS改性沥青疲劳损伤进程、开裂子进程及塑性变形子进程的活化能(163.9,70.1,91.6kJ·mol^-1)均大于基质沥青相应进程的活化能(94.0,47.0,45.8kJ·mol^-1),这表明SBS改性沥青抗开裂性能及抗永久变形性能均好于基质沥青;此外,SBS改性沥青及基质沥青疲劳损伤进程的总活化能等于开裂子进程及塑性变形子进程的活化能之和。因此,可通过活化能这一动力学指标将沥青疲劳损伤进程、开裂子进程与塑性变形子进程进行关联。

Cracking and plastic deformation of asphalt binders are two coupled sub-processes in the process of fatigue damage.To separate the two sub-processes,a characteristic indicator was developed to indicate the correlation between the fatigue damage process and the two subprocesses.In this study,an energy-based mechanistic approach and kinetics theory were adapted to model the fatigue damage process as well as,the cracking,and plastic deformation sub-process of the asphalt binder.First,based on the energy-based mechanistic approach,the total cumulative dissipated pseudo strain energy(DPSE)was separated into cumulative DPSE for cracking(DPSEc)and that for plastic deformation(DPSEp),and they were determined at different temperatures.Then,a three-parameter model was used to model the DPSE of the fatigue damage process,cracking sub-process,and plastic deformation sub-process of the asphalt binder,and representative energy change rates were obtained to describe the evolution of the energy dissipations quantitatively for each process.Finally,the relationship between the representative energy change rate and temperature was established based on the kinetic theory.Kinetic indicators for characterizing the damage process of asphalt binders were determined.The results show a linear relationship between the characteristic energy change rates of DPSE,DPSEc,and DPSEpand the reciprocal of absolute temperature.In addition,while the characteristic energy change rate of DPSEpincreases,the representative energy change rate of DPSEcdecreases with the increase in temperature.This is because the plastic deformation of the asphalt binder evolves rapidly but the cracks develop slowly when the temperature increases.The activation energies of the fatigue damage process,cracking sub-process,and plastic deformation sub-process of styrene-butadiene-styrene(SBS)modified asphalt binders(163.9,70.1,and 91.6 kJ·mol^-1,respectively)are greater than those of the corresponding processes of virgin asphalt binders(94.0,47.0,and 45.8 kJ·mol^-1,respectively).This indicates that SBS modified asphalt binders exhibit better resistance to cracking and permanent deformation in comparison with virgin asphalt binders.Moreover,the total activation energies of the fatigue damage process are equal to the sum of the activation energies of the cracking sub-process and the plastic deformation sub-process for both binders.Therefore,the kinetic indicators of activation energies can be used to analyze the fatigue damage process,cracking sub-process,and plastic deformation sub-process of asphalt binders.