沥青胶结料应变延迟恢复特性的动态剪切流变试验表征

Delayed Strain Recovery Characterization of Asphalt Binder Based on Dynamic Shear Rheology Test

沥青胶结料在中、高温条件下的变形恢复特性直接影响沥青混合料的抗车辙性能。传统的经验指标(针入度、软化点等)以及一些基于复数模量的力学性能指标在表征沥青的应变延迟恢复特性方面存在不足。本工作基于串联Maxwell模型和并联Kelvin模型所描述的力学行为差异及粘弹性力学参数的频率响应特征,提出了采用相位角频域曲线的斜率来表征沥青胶结料应变延迟恢复特性的方法。本研究综合分析了三种不同针入度水平的基质沥青和两种SBS改性沥青在30~70℃下的复数模量和相位角参数,发现相位角频域主曲线相比复数模量主曲线可以更清晰地反映不同类型沥青胶结料的粘弹力学特性差异。试验结果表明,SBS改性沥青的相位角并非如基质沥青随角频率增加单调降低,而是会在特定的温度、频率区间呈现增长趋势。此规律可用于表征沥青胶结料的应变延迟恢复特性,并用于评价材料在特定温度范围的抗车辙性能。

The characteristics of deformation recovery of asphalt binder in medium to high temperature conditions affect the rutting resistance of asphalt mixture directly.The traditional empirical indexes(i.e.,penetration,softening point,etc.)and certain mechanical performance indexes based on complex modulus have apparent drawbacks in characterizing the delayed strain recovery properties of asphalt.This work proposed a characterization method using the slope of phase angle curves in frequency domain based on the difference of mechanical behavior described by series Maxwell model and parallel Kelvin model and the frequency response characteristics of viscoelastic mechanical parameters.This study comprehensively analyzed the complex moduli and phase angles of three penetration levels of base asphalt and two types of SBS modified asphalt at 30—70℃.It was found that the difference in viscoelastic properties of the different types of asphalt binders can be reflected by the master curve of phase angle in frequency domain more clearly than the master curve of complex modulus.The experiment results showed that the phase angle of SBS modified asphalt presents an increase trend in specific temperature and frequency domains,rather than the monotonically decrease trend with the increase of phase angle presented by the base asphalt.This rule can be used to characterize the delayed strain recovery characte-ristics of asphalt binder and to evaluate the rutting resistance of the material in a specific temperature range.