Characteristic properties of elastomer-modified bitumen

The addition of elastomer to bitumen alters its characteristic properties, and the final product - the modified bitumen - becomes more elastic and less susceptible to temperature variations. Additionally, the modified bitumen with elastomers has better cohesion properties and higher resistance to ageing compared with the unmodified paving grade bitumen. 

In particular, the elastic recovery of the bitumen has remarkably improved when modified with elastomers. Typical values of 25% to 35%, at 25°C, for conventional bitumen can be increased, so as to reach elastic recovery values higher than 95%. As a consequence, the strain developed when bitumen is loaded is recovered to a large extent and plastic (permanent) deformation is minimised. 

By adding an elastomer to the bitumen, the penetration value decreases, the softening point increases and the penetration index increases. These changes indicate that the bitumen becomes harder and less susceptible to temperature variations. 

The addition of elastomer also lowers the Fraass breaking point. As a result, the modified bitumen is expected to crack at lower subzero temperatures compared to unmodified paving grade bitumen. 

Finally, modification with elastomers increases bitumen s viscosity. This implies that an increase of working temperatures is required in order to achieve the same viscosity values as the unmodified bitumen, to carry out mixing, laying and compaction. 

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