Bitumen refers to the black sticky binder essentially used to glue mineral aggregate for making road pavements, in a final black paving material called asphalt mixtures. The binder is called “bitumen” in Europe when it is obtained from petroleum as described below. In the USA, it is rather called “asphalt cement” or sometimes simply “asphalt”, which can sometimes create a confusion with Europeans who reserve the term “asphalt” for mixtures. It is therefore important to clearly identify the source of information when dealing with asphaltic materials, because asphalt might refer to the binder (USA) or the mixture (Europe, USA). Bitumen always refers to the binder, but the word is barely used in the USA. To avoid any confusion, in this note, we stick to the European habits and therefore use “bitumen” for the binder and prefer “asphalt” for the mixture.

In any case, bitumen must not be confused with coal tar, another black sticky binder that was used long ago for the same application. It however came from the pyrolysis of coal and its use was discontinued in the road industry in the second half of the 20^th century, initially for economical reasons (bitumen became generally cheaper due to the fast development of the modern refining business that paralleled the rapid development of internal combustion engines for transportation) and then for health reasons, given that coal tar was found to be carcinogenic, unlike bitumen.