Vocabulaire engins de chantier (anglais)

Disponible uniquement sur Etudier
  • Pages : 19 (4681 mots )
  • Téléchargement(s) : 0
  • Publié le : 1 avril 2011
Lire le document complet
Aperçu du document
| | |
| ||
| | |
|Asphalt |Asphalt is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some |
| |natural deposits.Asphalt is composed almost entirely of bitumen. There is some disagreement amongst chemists regarding the |
| |structure of asphalt, however it is most commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes|
| |as the continuous phase.|
| | |
| |Asphalt is sometimes confused with tar, which is an artificial material produced by the destructive distillation of organic |
||matter. Tar is also predominantly composed of bitumen, however the bitumen content of tar is typically lower than that of |
| |asphalt. Tar and asphalt have very different engineering properties. |
| ||
| |Asphalt can be separated from the other components in crude oil (such as naphtha, gasoline and diesel) by the process of |
| |fractional distillation, usually under vacuum conditions. A better separation can be achieved by further processingof the |
| |heavier fractions of the crude oil in a de-asphalting unit which uses either propane or butane in a supercritical phase to |
| |dissolve the lighter molecules which are then separated. Further processing is possible by "blowing" the product: namely |
| |reacting itwith oxygen. This makes the product harder and more viscous. |
| | |
| |Natural deposits of asphalt include Lake Asphalts (primarily from the PitchLake in Trinidad and Tobago and Bermudez Lake in |
| |Venezuela), Gilsonite, the Dead Sea in Israel, and Tar Sands. |
| | |
||Asphalt is rather hard to transport in bulk (it hardens unless kept very hot) so it is sometimes mixed with diesel oil or |
| |kerosene before shipping. Upon delivery, these lighter materials are separated out of the mixture. This mixture is often |
| |called bitumen feedstock, or BFS....