Influence of soft bitumens on the chemical and rheological properties of reclaimed polymer-modified binders from the “old” surface-layer asphalt

• Residual characteristics of the polymer modification are found in the reclaimed binders.
• The soft bitumen influences the chemistry and rheology of reclaimed binder significantly.
• Mixing with soft PMB binder makes it possible to restore the rheological properties of the reclaimed PMB binder.

Reclaimed asphalt (RA) that contains polymer-modified bitumen (PMB) offers a potential premium material contribution for recycling. This study investigated the influence of soft virgin bitumens on the chemical and rheological properties of three reclaimed PMBs from different “old” surface-layer asphalt mixtures in Europe. Although the PMB degrades during the service life of the asphalt pavement, residual characteristics of the polymer modification are found in the reclaimed binder and can be manifested when blending with virgin paving grade bitumen or with virgin PMB binder. The soft bitumen influences the chemistry and rheology of reclaimed binder significantly, but these chemical and rheological changes are not consistent. Mixing with soft PMB binder makes it possible to restore the rheological properties of the reclaimed PMB binder. It means that the polymer from the reclaimed binder can function in a new mixture when recycled.