Rheological Characterisation of Modified Bitumens with Biodiesel-Derived Biobinders

Growing environmental concerns and scarcity issues of petroleum-derived bitumen have motivated the search for alternative and renewable sources to be used in asphalt mixtures. The concept of biobinders (binders manufactured from biomass) are becoming more popular in the field as a potential solution. In particular, waste biomass products are of interest due to their availability and impact on sustainability. Biobinders have shown great potential to reduce bitumen demand and have exhibited good performance in terms of resisting common distresses affecting roads. However, they are still relatively unknown and detailed characterisation in terms of their engineering properties is needed before they can be used in practice. This paper describes the bio-modification of two penetration grade bitumens with a vegetal-derived biodiesel residue. Three modified bitumens were produced and the rheological characteristics were analysed using a dynamic shear rheometer (DSR). The results indicate that the addition of biobinder ‘softens’ the bitumens by decreasing the complex modulus and increasing the viscous response, except for the higher content modified blend which at high temperatures exhibits a more elastic behaviour. Similar to aged conventional binders, laboratory ageing of the blends increases the elastic response and stiffness.