A sustainability evaluation of hot-in-place asphalt recycling technique

The sustainability of hot-in-place asphalt recycling (HIR) was evaluated through performance evaluation and environmental impact assessment. Two HIR repaving projects were chosen, located in Galesburg and Machesney Park, Illinois, USA. The HIR pavement performance constructed at these sites included both field evaluation (i.e., condition rating system, falling weight deflectometer, and smoothness measurements) and laboratory characterization at the mixture and binder level (i.e., dynamic shear rheometer, bending beam rheometer, Illinois Flexibility Index Test, and Hamburg wheel track test). Using the balanced mixture design approach to optimize rutting and cracking resistance of recycle mixes, better performance was predicted for the Galesburg site compared to the Machesney Park site. In addition, an environmental analysis was conducted by comparing the energy and greenhouse gases (GHGs) from the initial construction of HIR and a conventional mill and fill design. The HIR approach was seen to have energy savings of 3.9-17.6% and GHG savings of 1.3-19.2% depending whether a hauling distance of 40 km or 160 km was assumed for on and off-site transportation. To incorporate the effect of pavement performance, a scenario analysis was conducted using annualized energy consumption over the expected treatment life. The minimum required expected life was then determined under which the HIR treatment would offset environmental savings due to poor performance. Thus, the paper provided a holistic sustainability approach considering both environmental impacts and expected performance of HIR.