盐冻融条件下环氧沥青混凝土多尺度疲劳开裂特性

Multi-scale Fatigue Cracking Characteristics of Epoxy Asphalt Concrete under Salt Freeze-Thaw Conditions

摘要:

为获得积雪冰冻地区环氧沥青混凝土（EAC）疲劳开裂特性，以EAC及对照组——SBS改性沥青混凝土（SBSMAC）为试验对象，采用小梁三点弯曲重复加载试验、数字图像相关技术（DIC）及扫描电镜（SEM），从宏观、细观、微观3个尺度，对冻融循环和盐冻融循环条件下，EAC和SBSMAC试件疲劳加载全寿命周期内裂纹的萌生、扩展和加速破坏进行分析. 结果表明：基于EAC和SBSMAC损伤因子拟合函数的导数曲线，得到疲劳损伤的关键分界点，据此划分沥青混凝土的疲劳损伤阶段，是一种正确可行的新方法；EAC的宏观裂纹起裂点及微裂纹扩展点出现时间均晚于SBSMAC，EAC具有更好的抵抗材料损伤的能力；在积雪冰冻地区使用乙酸钾（CH₃COOK）替代常用的氯盐类融雪剂，可减轻路面疲劳损伤程度；EAC断裂面处的微观形貌优于SBSMAC.

Abstract:

To investigate the fatigue cracking characteristics of epoxy asphalt concrete （EAC） in snowy and frozen regions， EAC and a control group， SBS modified asphalt concrete （SBSMAC）， were subjected to testing. Using the small beam three-point bending repeated loading test， digital image correlation （DIC）， and scanning electron microscopy （SEM）， the initiation， propagation， and accelerated failure of cracks in EAC and SBSMAC specimens were analyzed during their entire fatigue life cycles under freeze-thaw cycles and salt-freeze-thaw cycles from macro， meso， and micro scales. The results indicate that determining the fatigue damage stages of asphalt concrete based on the cut-off points obtained from the derivative curves of the fitting functions for the damage factors of EAC and SBSMAC is a correct and feasible new method. Both the macroscopic crack initiation point and the microcrack propagation point of EAC are superior to those of SBSMAC， suggesting that EAC has better resistance to material damage compared to SBSMAC. The use of potassium acetate （CH₃COOK） as an alternative to commonly used chloride-based deicing agents in snowy and frozen regions can reduce the degree of pavement fatigue damage. Additionally， the microscopic morphology at the fracture surface of EAC is better than that of SBSMAC.