ABSTRACT

The National Cooperative Highway Research Program (NCHRP) Project 9-38 developed a method for estimating asphalt fatigue endurance limit (FEL) which employs bending beam fatigue (BBF) lives. Another project, NCHRP 9-44A, used BBF test data to formulate a healing-based FEL prediction model. Both procedures were evaluated in this study by utilising data from the National Center for Asphalt Technology Pavement Test Track. The estimated FELs were used in perpetual pavement design to investigate their impact on asphalt thickness. The NCHRP 9-44A-predicted FELs increased with longer rest periods, but largely stabilised after 8 s, which agreed with the NCHRP 9-44A researchers’ conclusion that no healing occurs after a rest period of 5–10 s. Overall, the NCHRP 9-38 method yielded greater FELs. Without binder modification and/or high binder content, both methods provided similar FELs, if a rest period longer than 5 s was entered in the NCHRP 9-44A model. Generally, the NCHRP 9-44A-predicted FELs produced thicker layers. However, for conventional asphalt mixtures, both sets of FEL yielded similar thicknesses, if the NCHRP 9-44A model applied a rest period exceeding 5 s. The NCHRP 9-44A model’s predictive capability will increase if it is recalibrated with mixtures containing modified binder and/or higher binder contents.

摘要

国家合作公路研究计划 (NCHRP) 项目 9-38 开发了一种估计沥青疲劳耐力极限 (FEL) 的方法，该方法采用弯曲梁疲劳 (BBF) 寿命。另一个项目 NCHRP 9-44A 使用 BBF 测试数据制定了基于愈合的 FEL 预测模型。本研究利用国家沥青技术路面试验场中心的数据对这两种程序进行了评估。估计的 FEL 用于永久路面设计，以研究它们对沥青厚度的影响。NCHRP 9-44A 预测的 FEL 随着休息时间的延长而增加，但在 8 秒后基本稳定，这与 NCHRP 9-44A 研究人员的结论一致，即在 5-10 秒的休息时间后不会发生愈合。总体而言，NCHRP 9-38 方法产生了更大的 FEL。没有粘合剂改性和/或高粘合剂含量，如果在 NCHRP 9-44A 模型中输入超过 5 秒的休息时间，这两种方法都提供了相似的 FEL。通常，NCHRP 9-44A 预测的 FEL 会产生更厚的层。然而，对于传统的沥青混合料，如果 NCHRP 9-44A 模型应用超过 5 秒的休息时间，则两组 FEL 产生相似的厚度。如果用含有改性粘合剂和/或更高粘合剂含量的混合物重新校准 NCHRP 9-44A 模型的预测能力将会提高。