[MUSIC] Hello, everybody. My name is Virginie Mouillet. I am the senior researcher working in the field of bitumen physical chemistry research for the CEREMA for more than 15 years. Now, that you are more familiar with bitumen, we are going to look together at the schematic chemical structure and its link with rheological behavior. Bitumen is a nitrogen compound showing a highly complex constitution. This complexity of bitumen chemistry lies in the fact that many different chemicals are present, as shown on this table. To resume bitumen, many consist in carbon and hydrogen atoms. In addition, atoms, such as sulfur, nitrogen and oxygen are generally present. Traces of metal are also found. The most numerous being vanadium and nickel. However, approaching bitumen chemistry on a global basis is not sufficient when one tries to understand the properties of bitumen, in particular it's biology. Thus, the molecules are generally chemically separated into different chemical families depending on their size and solubility in solvent. Science to asphaltene precipitation followed by your chromotographic separation of maltenes in solution. The composition of bitumen is usually given in terms of the relative quantity of its so called SARA fractions. For saturate, aromatics, resins, and asphaltenes, as shown on this figure. It has to be noted that the percent of each SARA fractions depends on the crude origin, manufacturing process, and grade of analyzed bitumen. As shown on this picture, maltenes in solutions are separated into three different fractions that are saturates, aromatics and resins. Saturates from colloid liquid at room temperature. Aromatics are the most abundant constituent of a bitumen. They form a yellow to red liquid at room temperature and are somewhat than to saturate at the same temperature. Resins, very viscous at room temperature play a crucial role in the stability of bitumen since they act as a stabilizer for the asphaltene as would be detailed in the next slides. Asphaltene are defined as the soluble part of a bitumen in any. They form a black powder at room temperature as visualized in this figure and are actually responsible for the black color of bitumen. The contents fuse automatic rings with the most probable structure corresponding to 4 to 10 fuse to rings, together with some pending [INAUDIBLE] chance. In comparison [INAUDIBLE] molecules asphaltene contain more condense aromatic rings and more [INAUDIBLE] group. They are by far the most [INAUDIBLE] fractions because of their viscosity building wall. Because of the many condensed wings, asphatenes from almost planar molecules then can associate full bi-pide bonding to form graphite-like stacks as this described on this figure. The graphite-like crystals of asphaltene are very small. Their size is of order of two to five nanometers, and they contain an average of five unit sheets. When put in a solvent, the asphaltene still associate and the aggregation process leads to what it's generally called micelles, as seen on this figure. Their size depends on the solvent nature, on the asphaltene content and on temperature. The aggregation process persists inside the bitumen and forms the basis of the colloidal structure of bitumen. As seen on this figure, the bitumen structure can be described as a colloidal dispersion as asphaltenes muscles in the [INAUDIBLE], even if asphaltene are known to be insoluble in oils. This is linked to the resins [INAUDIBLE] Component into [INAUDIBLE] and act as stabilizer for the asphaltene cells in the bitumen component. However, according to the relative percent of the different component, especially asphaltene and resin, three different types of bitumen colloidal structure can be obtained as shown on this table. A gel bitumen, showing the higher content of asphaltenes, contrary to soft bitumen. As a consequence, colloidal index has been defined [INAUDIBLE] asphaltenes and saturate content on resins and aromatics content. The colloidal model was [INAUDIBLE] to explain the differences in rheological properties between bitumen. A sol bitumen is thought to occur when the asphaltene are fully dispersed and non-interacting, leading to a newtonian behavior. At the inverse, a gel structure is due to fully interconnecting asphaltene. Licers showing highly, no new behavior. According to the gel of sol character the property differ. The sole bitumen exhibit an excellent resistance to fast solicitation but are more sensible than gel bitumen to slow solicitation as well as to temperature variation. Also, due to the well stabilized asphaltene, the sol bitumen show lower viscosity than gel bitumen at constant temperature. Between these two extremes, majority of bitumen display an intermediate behavior due to a mixes sol gel structure. And represents a majority of paving grade bitumen. In conclusion, once can see that the complexity of bitumen chemistry usually given in terms of the relative content of SARA fraction, is at the origin of material, particular rheological behavior. This lies in the fact that asphaltene associate inside bitumen to lead to micelles that are dispersed in maltene, with resin acting as stabilizer of asphaltene. This internal organization is described as a colloidal structure. And the majority of paving grade bitumen display a mixed sol-gel structure with viscoelastic behavior that would be detained later. I thank you very much for your attentions. [MUSIC]
