Abstract The overall characteristics and fracture behavior of asphalt pavements and overlays is significantly controlled by the mechanical behavior of bitumen used in the mixture of asphalt concrete. The bitumen behaves like a dominantly brittle and elastic medium under subzero temperatures. In practice, cracked asphalt pavements experience mixed mode tensile-shear deformations due to moving traffic loads or cyclic thermal gradients. On the other hand, aging phenomenon can affect significantly the overall strength and load bearing capacity of pavements and bituminous asphalt mixtures. Different binders with different penetration grades and performance characteristic are often used for paving the roads. In order to investigate the effect of binder type and aging condition on the mixed mode I/II cracking response of bitumen materials, an experimental and theoretical study is performed in this research. Three binders: namely 30/40 bitumen, 60/70 bitumen and modified bitumen with SBS polymer (i.e. polymeric binder) are used to conduct a full set of mixed mode I/II fracture toughness experiments using an inclined edge notched bend beam specimen. The experimental results showed significant influence of mode mixity, bitumen type and aging on the fracture toughness data. The fracture toughness is reduced for the whole tested binders by moving from pure mode I to pure mode II. While aging has negative effect on the crack growth resistance of 30/40 and 60/70 binders, the mixed mode I/II fracture toughness of polymeric modified bitumen was increased after aging. The morphology of fracture surface and direction of fracture was studied for the tested binders under different environmental and loading conditions. The mixed mode I/II fracture toughness data were also predicted using two generalized tangential stress/strain based fracture criteria.

中文翻译：

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沥青类型、温度和老化对沥青结合料混合 I/II 断裂韧性的影响-实验和理论评估

摘要 沥青路面和覆盖层的整体特性和断裂行为受沥青混凝土混合料中使用的沥青的力学行为的显着控制。沥青在零度以下的温度下表现得像一种主要的脆性和弹性介质。在实践中，由于移动的交通荷载或循环热梯度，开裂的沥青路面会经历混合模式的拉伸-剪切变形。另一方面，老化现象会显着影响路面和沥青混合料的整体强度和承载能力。不同渗透等级和性能特征的不同粘合剂常用于铺路。为了研究粘合剂类型和老化条件对沥青材料混合模式 I/II 开裂响应的影响，在这项研究中进行了实验和理论研究。三种粘合剂：即 30/40 沥青、60/70 沥青和含 SBS 聚合物的改性沥青（即聚合物粘合剂）用于使用倾斜边缘缺口弯曲梁试样进行全套混合模式 I/II 断裂韧性实验。实验结果表明，模式混合、沥青类型和时效对断裂韧性数据有显着影响。通过从纯模式 I 移动到纯模式 II，整个测试粘合剂的断裂韧性降低。虽然老化对 30/40 和 60/70 粘合剂的抗裂纹扩展性有负面影响，但聚合改性沥青的混合模式 I/II 断裂韧性在老化后增加。研究了不同环境和载荷条件下测试结合剂的断裂面形貌和断裂方向。还使用两个基于广义切向应力/应变的断裂标准来预测混合模式 I/II 断裂韧性数据。