Bitumen modification is the process of adjusting bitumen properties by mixing it with polymer additives or using modern production techniques.
To achieve good properties of this construction material, increase its temperature and deformation resistance, the dispersion phase must be influenced. Three approaches currently exist:
- Compounding of peroxidized bitumen containing large amounts of asphaltene with deasphaltation asphalt, tower bottoms or selective oil purification extract. Oil products with significant content of low molecular aromatic oils, with low viscosity and a relatively low settling temperature, can be used in the process.
- Catalytic oxidation. This approach is used relatively rarely. Some of the catalysts used are phosphorus oxide or iron chloride. Bitumen, obtained in this manner, features higher penetration and lower brittle temperature than bitumen made by regular oxidation process.
- Modification of bitumen with highly elastic materials. This approach is the most promising. Most often, polymers are used as modifiers. Researchers have tested practically every material of this nature, but the best performance was demonstrated by carbon chain polymers with direct or branched chain, which contain no heteroatoms: rubbers of various structure, polyethene and polypropylene.
Introduction of even a small amount of polymer into bitumen improces its quality: increases softening temperature and reduces penetration.
Besides, polymer modifiers reduce bitumen brittle temperature and increase heat resistance. Many years of observing roads constructed with modified bitumen indicate that using these materials extends the durability of the road top.
When polymer swells, the dispersed structure of bitumen is transformer. The weight part of oil fraction and redistribution of oils associated by asphaltenes is observed. Removing them from the surface of asphaltenes leads to restructuring of dispersion system, with the end result of asphaltenes coagulation into a solid phase.
The amount of polymer added is defined by future application of the material. It should be noted that the presence of 1-3% of polymer by weight, the interval of plasticity expands mostly in the low temperature range, while with 5% and above, the heat resistance of the material is significantly increased.