Open graded friction course (OGFC) is highly susceptible to environmental impacts such as load and clogging, due to its rich void structure and exposure to environments. Especially in cold regions, freeze–thaw (F-T) damage is inevitable for OGFC. While the existing analysis methods cannot specifically describe the material's micro-response to load or environment. Therefore, the digital image correlation (DIC) in combination with computed tomography (CT) was applied to closely examine the intricate process of F-T damage of OGFC in this research. Principal strain and strain energy were used to describe the F-T damage process and distribution. In addition, the effects of initial void content and immersion conditions on the temporal and spatial distribution of damage were discussed. The data demonstrated that the spatial distribution of F-T damage strain was uneven. During F-T cycles, the principal strain inside the OGFC during F-T cycles was generally increased, and the deformation of the sample gradually accumulated. According to the strain energy growth rate variation, the F-T damage could be divided into two stages during the 18 F-T cycles, namely, the development stage and the deceleration stage. Moreover, the crucial parts of F-T damage were determined to be at the end of the voids connected with the outside or the void interface between the aggregates and asphalt mortar. The larger initial void content would increase the strain of OGFC during F-T cycles, as well as the inhomogeneity of the strain. Furthermore, the strain energy increased considerably, and the development of F-T damage of OGFC accelerated. Under partial immersion conditions, the immersed part has large strain and strain energy due to the direct effect of F-T, and the increase in immersion depth aggravates the F-T damage.

中文翻译：

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DIC结合CT探索沥青混合料冻融损伤分布


由于其丰富的空隙结构和暴露于环境中，开放分级摩擦层 (OGFC) 极易受到负载和堵塞等环境影响。特别是在寒冷地区，冻融（F-T）对OGFC的损害是不可避免的。而现有的分析方法无法具体描述材料对载荷或环境的微观响应。因此，本研究采用数字图像相关（DIC）结合计算机断层扫描（CT）来仔细检查OGFC F-T损伤的复杂过程。主应变和应变能用来描述F-T损伤过程和分布。此外，还讨论了初始空隙含量和浸没条件对损伤时空分布的影响。数据表明F-T损伤应变的空间分布不均匀。在F-T循环过程中，OGFC内部的主应变普遍增加，样品的变形逐渐积累。根据应变能增长速率的变化，在18个F-T循环中，F-T损伤可分为两个阶段，即发展阶段和减速阶段。此外，确定F-T损伤的关键部位位于与外部相连的空隙末端或集料与沥青砂浆之间的空隙界面。较大的初始空隙含量会增加 OGFC 在 F-T 循环过程中的应变，以及应变的不均匀性。此外，应变能大幅增加，OGFC F-T损伤加速发展。 在部分浸没条件下，由于F-T的直接作用，浸入部分具有较大的应变和应变能，并且浸入深度的增加加剧了F-T损伤。