ICT researchers explore energy use associated with in-place recycling paving methods

In-place recycling methods have become popular with transportation agencies who want to focus on the use of sustainable, cost-effective, and environmentally conscious construction practices. These methods could offer a viable alternative to the more traditional rehabilitation techniques used on asphalt-surfaced pavements because practice has shown them to provide good product value for relatively low construction costs. In-place recycling generally involves milling existing pavements, mixing the milled material, adding heat and/or rejuvenators or additives, and immediately repaving using the processed recycled material. 

In a new study sponsored by the Federal Highway Administration (FHWA), Illinois Center for Transportation (ICT) researchers, in collaboration with researchers from the University of California–Davis and Rutgers University, will assess total energy use involved in the primary two in-place recycling techniques: hot-in-place recycling (HIPR) and cold-in-place recycling (CIPR). A number of factors will be taken into consideration in the assessment, including equipment operation, fuel consumption, transportation, materials production and handling, and reusability of reclaimed aggregates. The same information will also be gathered for conventional paving for the purpose of quantifying any differences between the two approaches.

A life-cycle assessment methodology and framework will be developed to help guide agencies in making rational decisions when identifying the environmental determinants associated with in-place recycling methods and when comparing these methods with conventional rehabilitation methods. The environmental burdens of pavements rehabilitated using HIPR and CIPR will be analyzed throughout their life cycles.

“We will gather, analyze, and distill data to determine the total energy use of various in-place paving methods and compare that to conventional paving,” says  Hasan Ozer, research assistant professor in the Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign. “Data will be collected from states and contractors, a life-cycle inventory will be developed, and a user-friendly tool will be created for development of a generalized methodology for in-place recycling techniques,” adds ICT director Imad Al-Qadi, Founder Professor of Engineering in the Department of Civil and Environmental Engineering at Illinois, who serves as principal investigator for this study.

In spite of the demonstrated success of these techniques, the researchers expect to face quite a few challenges during the course of the project—namely, the variability of life expectancy and performance of applied in-place techniques, the lack of regional life-cycle inventory databases, and the uncertainty and variability of data associated with in-place recycled pavement.

In addition to Al-Qadi and Ozer, participating in this research effort are Marshall Thompson, professor emeritus in the Department of Civil and Environmental Engineering at Illinois; John Harvey, chair of the Transportation Technology and Policy Graduate Group at UC Davis and the Institute of Transportation Studies; and Hao Wang, assistant professor at Rutgers School of Engineering.

“As more technologies and their advocates are recognizing the importance of sustainability, it is imperative that we have good analyses to properly evaluate them,” says Harvey.

The study, titled “A Life-Cycle Methodology for Energy Use by In-Place Pavement Recycle Techniques,” is expected to be completed by the end of 2016.