Bitumen aging has long been recognised as one of the primary factors that affect pavement’s durability. The amount of rheology-based indexes proposed to track the evolution of bitumen aging level underlines their potential for this purpose. Among these phase angle is a powerful tool since it is highly sensitive to changes that occur in bitumen. Hence, this work aims to estimate the aging level of 23 neat bitumens based solely on the evaluation of their phase angle master curve through the application of two multivariate statistical approaches: Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). PCA score plot displays correctly the studied bitumens according to their aging level, going from left to right, where a marked inflection point is detected along the path taken by the studied bitumens when they age. The groups of bitumens located on each side of this inflection point coincide with the two major clusters obtained through HCA. All the bitumens classified as being in the imminence of the cracking zone through the well-known Glover Rowe (G-R) cracking indicator integrate the HCA cluster after the inflection point. The originality of this study lies in the possibility of indicating the aging state and also cracking susceptibility of bitumen based exclusively on the assessment of the phase angle master curve.

HIGHLIGHTS

• Using solely phase angle master curves, PCA score plot projects correctly the studied bitumens according to their aging level, where a marked inflection point is detected.

• The bitumens projected at each side of the inflection point coincide with the two major clusters obtained through HCA.

• All the bitumens classified as being in the damage onset or cracking zone according to the G-R method belong to the HCA cluster after the inflection point.

• The inflection point observed on the PCA score plot appears to be a transition from which the studied bitumens are more susceptible to cracking.

长期以来，沥青老化被认为是影响路面耐久性的主要因素之一。为跟踪沥青老化程度的发展而提出的基于流变学的指标数量突显了其在此目的的潜力。在这些相位角中，有一个强大的工具，因为它对沥青中发生的变化高度敏感。因此，这项工作旨在仅通过使用两种多元统计方法：主成分分析（PCA）和层次聚类分析（HCA）对相角主曲线进行评估，来估计23种纯沥青的老化水平。PCA分数图根据其老化程度从左到右正确显示了被研究的沥青，在该沥青中，沿着被研究的沥青老化时所沿着的路径检测到了明显的拐点。位于此拐点两侧的沥青组与通过HCA获得的两个主要簇重合。通过著名的格洛弗罗（Grover Rowe）裂化指示剂归类为在裂化区附近的所有沥青均在拐点之后整合了HCA团簇。这项研究的独创性在于，仅根据相角主曲线的评估就可以表明沥青的老化状态和开裂敏感性。

强调

• 仅使用相角主曲线，PCA分数图可根据研究的沥青的老化水平正确投影它们，并在其中检测到明显的拐点。

• 投影在拐点两侧的沥青与通过HCA获得的两个主要簇重合。

• 根据GR方法归类在破坏开始或破裂区域中的所有沥青都在拐点之后属于HCA簇。

• 在PCA分数图上观察到的拐点似乎是一个过渡，从该过渡中，所研究的沥青更容易破裂。