基于Arrhenius方程的老化沥青流变特性

Rheological properties of aged asphalt based on Arrhenius equation

为了研究沥青老化过程中的流变特性,选择5种沥青分别进行不同时间的旋转薄膜烘箱老化试验(RTFOT),分别采用Brookfield黏度计和低温弯曲梁流变仪(BBR),对不同老化状态的沥青样品进行旋转黏度和低温流变参数测定。根据不同温度下的黏度试验,提出采用Arrhenius方程计算沥青黏流活化能Eη的方法,讨论沥青老化过程中Eη的变化规律;并分析低温劲度模量及其随时间的变化率m与RTFOT老化时间的关系,讨论老化沥青的黏流活化能与m的关系。研究结果表明:通过Arrhenius方程可以计算得到不同老化状态沥青的黏流活化能Eη,用以表征沥青的流变性能和感温性;随着老化程度的加深,Eη不断增大,即老化对沥青的流变行为有显著影响,沥青老化后分子结构变化引起流动能量增加,柔韧性减弱;虽然老化后沥青的黏度值和黏流活化能都不断增加,但二者大小没有必然联系,黏度随温度的变化才是沥青流变性能的反映;不同沥青在RTFOT老化0~85、85~180、180~360min不同阶段的黏流活化能增大速率存在较大差别,反映了其抗老化性能和老化机理的差异;沥青抵抗短期老化和长期老化的能力并不一致,SK(韩国SK-110)和ZHH(中海-90)具有优良的抗短期老化性能,而ESSO(埃索-90)和SK抗长期老化性能最好;随着老化程度的加深,沥青样品的黏流活化能与低温蠕变劲度变化率呈较好的负相关性,即沥青的黏流特性与低温蠕变行为密切相关。

To analyze rheological properties of asphalt in the process of aging, a series of aging tests were conducted on five regular asphalt samples for different time by rolling thin film oven test （RTFOT） in the laboratory, and then Brookfield viscosimeter and low temperature bending beam rheometer （BBR） were carried out on asphalt samples with different aging states to measure rational viscosity and low temperature rheologieal parameters, respectively. The parameter visco- flow activation energy Eη of asphalt was calculated by using Arrhenius equation according to the viscosity values at different temperatures. The changing regularity of Eη during the aging process, the change of low-temperature stiffness modulus, the change rate of stiffness with time m and the RTFOT aging time were analyzed. And the relationship between the visco-flow activation energy Eη and m was discussed. The results show that the parameter visco-flow activation energy Eη for different aging state can be obtained by means of Arrhenius equation, which reflects the rheological properties and temperature sensibility of asphalt. With the deepening of aging, Eη of asphalt increases continuously. There is significant influence of aging on rheological behavior of asphalt. After aging of asphalt, the change of molecular structure leads to the increase of flow energy and the decrease of flexibility. There is no inevitable relationship between Ev and the viscosity value of asphalt although they both increase after aging. The viscosity changes with the actual reflection of rheological properties of asphalt. The increase rate of viscous-flow activation energy of different asphalt at different stages of RTFOT aging, such as 0 to 85, 85 to 180 and 180 to 360 min is different, which reflects the difference of aging resistance and aging mechanism. The resistance to short-term aging capacity is not same to long-term aging capacity, SK and ZHH asphalts have good resistance to short-term aging performance, but ESSO and SK asphalts have the best resistance to long-term aging performance. With the deepening of aging time, it shows a better negative correlation between Eη and the rate of low temperature creep stiffness, that is, the viscous flow characteristics are closely related to the low temperature creep behavior of asphalt. 3 tabs, 7 figs, 26 refs.