沥青胶结料低温物理硬化及结晶动力学分析

Physical Hardening Test and Crystallization Kinetics Analysis of Pavement Asphalt Binder

为了准确模拟沥青胶结料的物理硬化过程及评估其物理硬化趋势,采用常规弯曲梁流变(BBR)试验设备对10种常用道路沥青进行了改进弯曲梁流变(EBBR)试验,并根据试验结果计算了低温等级损失指标;此外,在设计不同的低温恒温养护时间的基础上,测试了沥青蠕变劲度与蠕变劲度变化率,并采用Avrami等温结晶动力学理论对试验结果进行了拟合分析.结果表明:EBBR法较BBR法对沥青的低温性能区分精度更高;采用Avrami等温结晶动力学理论可较好地模拟沥青胶结料的物理硬化过程,拟合分析得到的Avrami指数与EBBR试验得到的低温等级损失值变化规律具有一致性;沥青胶结料低温物理硬化与结晶性能为评价沥青在实际工程中的低温抗开裂能力提供了更准确的信息.

Low temperature cracking and damage of asphalt pavement is very common,the asphalt bending beam rheometer(BBR)test proposed by SHRP to evaluate the phenomenon of low temperature cracking is still widely used.In order to better evaluate the asphalt physical hardening of one of the main factors of early cracking of asphalt pavement,extended bending beam rheometer(EBBR)test was used to evaluate ten kinds of commonly used road asphalt,and the low temperature grade loss index was calculated from the test results.Asphalt creep stiffness and creep rate at different low temperature conditioning period were measured,and Avrami isothermal crystallization dynamics theory was used to do fitting analysis,so the asphalt binder physical hardening mechanism can be studied.The results show that the EBBR method is more accurate than the BBR method for evaluating the low temperature performance of the asphalt,and the changes of Avrami index obtained by the fitting analysis of isothermal crystallization data can distinguish the low temperature physical hardening of the different asphalt from the same low temperature grade loss value obtained by the EBBR test,and the performance of asphalt physical hardening and crystallization can provide more accurate information about the anti-cracking ability of pavement asphalt.