Thin bonded concrete overlay of asphalt (BCOA), formerly known as thin whitetopping, can be defined as a rehabilitation alternative consisting of a 100 to 175 mm thick concrete overlay on an existing flexible or composite pavement. Thin BCOA has been used as a 20-year design life rehabilitation alternative for asphalt pavements in fair to good condition under low and intermediate traffic levels. While the technology for thin BCOA has been common on highways and conventional roads in several US states and other countries, its use has been very limited in California. As with any pavement rehabilitation, the materials and construction stages of thin BCOA result in significant environmental impacts, in terms of energy use, material resource consumption, waste generation, and emissions during the life of the BCOA pavement. This paper presents a life cycle assessment (LCA) that quantifies the potential environmental impacts due to the material and construction stages of a BCOA pilot project that has been implemented in Woodland, California. The scope of the study is from cradle-to-laid, including material and construction stages and transportation of the materials. However, sensitivity analysis has been performed in this paper to compare different BCOA design alternatives. The scope of the comparison selected is from cradle-to-gate. The impact categories included in this study are primary energy demand (fuel and non-fuel), greenhouse gas emissions, particulate matter, and smog formation. HVS PCC Type III mix had the highest energy consumption and environmental impacts followed by PCC Type II/V mix designs.
Key words: asphalt, life cycle assessment, sensitivity analysis