ABSTRACT
In 2019 approximately 45 % of RAP was used in new asphalt mixes in Norway. The national objective to implement circular economy, motivates a much higher recycling rate. It is also important that high recycling rates can be made without health and safety, or environmental hazards. The rejuvenated RAP binder in the new mix should not age more than normal for the target bitumen grade.
Norwegian RAPs often consist of relatively modestly aged binder. Quite soft bitumen grades are used, and asphalt wear and tear from studded tyres shortens pavements life. Less use of studded tyres will increase the pavement life, and the use of more deformation resistant pavements do likewise. In the future, RAP-binders will be harder and more aged than today.
A laboratory study simulates 50 % RAP added to fresh asphalt mixture. Recovered bitumen from two RAP-granulates were softened by commercial rejuvenators, to the target penetration grade 160/220. Granulate one was little aged and granulate two were considerable aged. The blends were then blended with an equal amount virgin 160/220 bitumen.
The binder tests on fresh binder; binder after RTFOT-ageing; binder after one and two PAV long term ageing cycles, were: penetration, softening point, Fraass’ breaking point, DSR (G*) and MSCRT (Jnr and R%). The blends were tested for water affinity and water susceptibility with a stripping prone aggregate. The test methods used were the Rolling Bottle Test and the Shaking Abrasion test (Vändskak-test).
A practical approach is proposed on how to calculate the proportion of rejuvenator and RAP-binder in the blend, aiming to achieve same viscosity as target bitumen. The calculations are based on expected hardness and viscosity of RAP-bitumen, and viscosity of rejuvenator. Such calculations can be helpful in estimating the suitable rejuvenator dosage in the asphalt mixture.
