Results of surface hot-in place recycling (remix) of modified and alternative asphalt mixtures in Finland. Part II: bitumen scale

Surface hot-in place recycling of asphalt mixtures has been conducted on Finnish roads for several years. The procedure is performed either in full-lane('remix') or shorter widths ('rut-remix'). In a 2020-2021 project, different mixture types were subjected to both kinds of recycling; reference mixtures, and mixtures modified with aramid fibres, FEP elastomer pellets, polymer, Storelastic rubber additive, recycled asphalt shingles, steel slag, and soft bitumen. This paper (Part II) presents the results of an extensive laboratory test plan at the bitumen scale. Asphalt mixture cores were recovered from four roads, and the bitumen was extracted fortesting. Various tests were performed on the bitumens in original state (aged, before recycling) and after recycling (remix or rut-remix), including FT-IR, DSR, MSCR, as well as bitumen content, penetration, and softening point. The master curves were constructed for all bitumens. Gradations are also presented herein. The effect of remix/rut-remix is evaluated via changes in all measured properties (including Glover-Rowe) before and after recycling, over a wide range of temperatures. The results complement the mixture-scale data and provide a comprehensive database of bitumen performance for an extended group of materials. Data appendices are accessible from the link at the bottom of the page.