We study the kinetics of bitumen emulsion destabilization after the addition of sodium hydroxide (NaOH) using macroscopic observations and rheology. Destabilization occurs in a two-step process: first, emulsion flocculates, forming a percolated network of contacting drops, and then coalescence provokes the irreversible connection of bitumen drops, leading to a bitumen continuous network that further relaxes the shape. We show that the destabilization kinetics exhibits a rheological easily identifiable signature allowing reproducible and accurate measurement of the connection/coalescence time t_rc (which corresponds to the time, determined by rheology, required to form the network made of drops connected by nonrelaxed coalescence). Using this powerful tool, we show that, even if viscosity is thought to govern the shape relaxation of the connected network it does not determine the connection kinetics. Indeed, emulsions with similar rheological behaviors exhibit very different destabilization times. Instead, we evidence a good correlation between the bitumen crystallized wax content and t_rc. From these experimental results, we discuss the stabilizing effect against coalescence of crystals in bitumen emulsions.

中文翻译：

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沥青乳液失稳动力学：结晶蜡含量的重要性

我们使用肉眼观察和流变学研究了添加氢氧化钠（NaOH）后沥青乳液失稳的动力学。失稳过程分两步进行：首先，乳液絮凝，形成接触液滴的渗透网络，然后聚结引起沥青液滴不可逆转的连接，从而导致沥青连续网络进一步使形状松弛。我们表明，去稳定动力学表现出流变学易于识别的特征，从而允许对连接/聚结时间t _rc进行可重复和准确的测量（它对应于由流变学确定的，形成由通过非松弛聚结连接的液滴组成的网络所需的时间）。使用此功能强大的工具，我们表明，即使认为粘度决定着所连接网络的形状松弛，它也无法确定连接动力学。实际上，具有相似流变行为的乳液表现出非常不同的去稳定时间。相反，我们证明了沥青结晶蜡含量与t _rc之间存在良好的相关性。从这些实验结果，我们讨论了对沥青乳状液中晶体聚结的稳定作用。