The δ-method has been developed to estimate molecular weight distributions of bitumens from phase-angle master curves. The method uses a correlation between the cross-over frequency(ω_C) and the molecular weight (MW) that was developed from average MW measured by vapour pressure osmometry. This study proposes a revised correlation whose parameters have been calculated from Gel Permeation Chromatography (GPC), which can be conducted at a low level of dilution preserving the interactions in the bitumen bulk. Furthermore, data from the GPC allow the optimisation of the parameters considering the entire MW distribution (MWD), thus improving the predictive capability of the method. Three unmodified petroleum bitumens at different levels of ageing and three rheological models were used in the optimisation. Two groups of parameters were identified; one for hard (e.g. Pen 35-50) and another one for soft-medium bitumens (e.g. Pen 50–70 or Pen 70-100). The apparent-MWDs (A-MWDs) calculated with the new parameters show improved correlation with the respective distributions and average molecular weight from GPC.

已经开发了 δ 方法来从相角主曲线估计沥青的分子量分布。该方法使用交叉频率（ω _C) 和分子量 (MW)，该分子量 (MW) 是从通过蒸汽压渗透法测量的平均 MW 得出的。本研究提出了一种修正的相关性，其参数是通过凝胶渗透色谱 (GPC) 计算得出的，该相关性可以在低稀释度下进行，从而保持沥青体积中的相互作用。此外，来自 GPC 的数据允许在考虑整个 MW 分布 (MWD) 的情况下优化参数，从而提高该方法的预测能力。在优化过程中使用了三种不同老化程度的未改性石油沥青和三种流变模型。确定了两组参数；一种用于硬质（例如 Pen 35-50），另一种用于软介质沥青（例如 Pen 50-70 或 Pen 70-100）。