Development of a life-cycle assessment tool for flexible pavement in-place recycling techniques and conventional methods

The worldwide interest in using recycled materials in flexible pavements as an alternative to virgin materials has increased significantly over the past few decades. Therefore, recycling has been utilized in the pavement maintenance and rehabilitation activities. Three types of in-place recycling technologies have been introduced since the late 70’s: hot-in-place recycling (HIR), cold-in-place recycling (CIR), and full-depth reclamation (FDR). The use of in-place recycling (IPR) have been evolving using new equipment trains, mix design specifications, and use of additives (e.g., engineered emulsion, lime, and cement). The advantages of using these evolving techniques include conservation of virgin materials, reduction of energy use and environmental impacts, reduction of construction time and traffic flow disruptions, reduction of number of hauling trucks, and improvement of pavement condition. The main objectives of this thesis are to develop a framework and a life-cycle assessment (LCA) methodology to evaluate maintenance and rehabilitation treatments, specifically in-place recycling and conventional paving methods; provide a fuel usage analysis of in-place recycling techniques during the construction stage; and develop a LCA tool utilizing Visual Basic for Applications (VBA) to help local and state highway agencies to evaluate environmental benefits and tradeoffs of in-place recycling techniques as compared to conventional rehabilitation methods at each life-cycle stage from the material extraction and production to the end of life. The ultimate outcome of this study is the development of a framework and a user-friendly LCA tool assesses the environmental impact of a wide range of pavement treatments, including in-place recycling, conventional methods, and surface treatments. The tool utilizes data, simulation, and models through all the stages of the IPR stages for the pavement LCA, including materials, construction, maintenance/rehabilitation, use, and end of life stages. The developed tool provides pavement industry practitioners, consultants and agencies the opportunity to complement their projects economic and social assessment with the environmental impacts quantification. In addition, the tool presents the main factors that impact produced emissions and energy consumed at every stage of the pavement life cycle due to pavement treatment. The tool provides detailed information such as fuel usage analysis of in-place recycling techniques based on field data. It shows that fuel usage is affected by pavement hardness, pavement width, air temperature, and horsepower of the equipment used