Bearsley S, Forbes A, Haverkamp R G
Higgins Contractors Ltd., Private Bag 11411, Palmerston North, New Zealand.
J Microsc. 2004 Aug;215(Pt 2):149-55. doi: 10.1111/j.0022-2720.2004.01373.x.
The structure of the asphaltene phase in the bitumen is believed to have a significant effect on its rheological properties. It has traditionally been difficult to observe the asphaltene phase in unaltered samples of bitumen. The maltenes are thought to form a continuous phase in which the asphaltenes are 'dispersed'. In this study, confocal laser-scanning microscopy (CLSM) operating in fluorescence mode was used to examine the structure of paving-grade Safaniya and San Joaquin bitumen. The asphaltene fraction fluoresces in the 515-545 nm wavelength range when irradiated with light with a wavelength of 488 nm. The major advantages of CLSM are that the bitumen sample requires little pretreatment or preparation that may affect the original dispersion of asphaltenes and the bitumen is observed at ambient temperature and pressure. This reduces the possibility of producing images that are not representative of the original material. CLSM was able to show the distribution of maltene and asphaltene components in bitumen. The asphaltene aggregates in the bitumen were observed to be 2-7 micro m in size and formed a dispersed 'sol' structure in the continuous maltene matrix rather than a network 'gel' structure. Surprisingly, the structure and fluorescence of the asphaltene phase does not appear to alter radically upon oxidative ageing. The structure of the asphaltene phase of an AR4000 San Joaquin bitumen was found to be more homogeneous than that of Safaniya bitumen, illustrating the range of structures that can be observed in bitumens by this method.
人们认为，沥青中沥青质相的结构对其流变特性有重大影响。传统上，很难在未改变的沥青样品中观察到沥青质相。人们认为，软沥青质形成一个连续相，沥青质则“分散”于其中。在本研究中，使用以荧光模式运行的共聚焦激光扫描显微镜（CLSM）来研究铺路级别的萨法尼亚和圣华金沥青的结构。当用波长为488 nm的光照射时，沥青质馏分在515 - 545 nm波长范围内会发出荧光。CLSM的主要优点是，沥青样品几乎不需要可能影响沥青质原始分散状态的预处理或制备过程，并且在常温常压下观察沥青。这降低了生成不能代表原始材料的图像的可能性。CLSM能够显示沥青中软沥青质和沥青质成分的分布。观察到沥青中的沥青质聚集体尺寸为2 - 7微米，并且在连续的软沥青质基质中形成分散的“溶胶”结构，而非网络“凝胶”结构。令人惊讶的是，在氧化老化后，沥青质相的结构和荧光似乎并未发生根本性改变。研究发现，AR4000圣华金沥青的沥青质相结构比萨法尼亚沥青的更均匀，这说明了通过该方法可以观察到沥青中存在的多种结构类型。
