Bitumen, commonly obtained from oil refinery processes, are at ambient temperature solid materials, from black to dark brown in colour, with thermoplastic behaviour and good characteristics of adhesion and waterproofing.
The production processes used are mainly fractional distillation, production for de-asphalting with solvent in lubricant cycle refineries, thermal treatment of residuals.
From a chemical-physical view point, bitumen are complex mixtures consisting of hydrocarbons and other organic compounds containing different atoms besides carbon, such sulphur, nitrogen, oxygen. Through fractionation processes it is possible to identify some chemical homogenous fractions with a specific characteristics, to which ascribe certain properties of bitumen:
Asphaltenes, macromolecules with high molecular weight, responsible for the high viscosity of bitumen, they represent the specific component,
Resins, which perform a dispersing action in the asphalts in the oily body of bitumen and therefore, give it stability and elastic properties;
Maltenic oils, subdivided into compounds of an aromatic nature or saturates, responsible for the ability of bitumen to flow and wet the surfaces to be covered.
Bitumen were the first oil product used by man thanks to its high adhesive and waterproofing power. Bitumen, in fact, are used as powerful binders, endowed with adhesive and cohesive characteristics; in addition to high impermeability, they offer the ability to resist the majority of acids, alkali and salts, while solid at ambient temperature they are used for heating and emulsifying with water and when necessary can be recycled.
Thanks to this property, they are widely used materials in the building and maintenance of road pavement and in a wide variety of industrial applications where waterproofing and adhesion characteristics are requested. First among these is the preparation of waterproof membranes.