Life cycle assessment on using recycled materials for rehabilitating asphalt pavements

This research performed life cycle inventory using proposed recycled material formulas and service records and incorporating the database provided by Eco-indicator 99 in order to study the eco-burden presented by using recycled materials to rehabilitate asphalt pavements. Three recycled materials (recycled hot mix asphalt, asphalt rubber, and Glassphalt) and the traditional hot-mixed asphalt are compared. Assuming that the thickness of the asphalt is 5 cm and the service life is 6 years, the eco-burden presented by the traditional hot-mixed asphalt is 3.45 kPt. per lane-kilometer. Using recycled hot mixed asphalt can reduce the eco-burden by 23% under the same conditions. Using asphalt rubber increases the eco-burden by 16%, while the eco-burden remains essentially the same (reduced by less than 1%) using Glassphalt. Taking into account the difference in service life between different materials, this research also uses a 40-year time span to evaluate the eco-burden for each material. The results show that the traditional hot mixed asphalt has an eco-burden of 23.03 kPt. for that time span. Both recycled hot mixed asphalt and asphalt rubber can reduce the eco-burden by 23% in the same period. On the contrary, Glassphalt increases the eco-burden by 19%. This research also identified the sources of the eco-burden for these asphalts. The results show that a large percentage of the eco-burden comes from two sources, the asphalt binder used (39-48%) and the heat sources required to process these paving materials (42-50%). This suggests that the most effective way to lower the eco-burden may be to reduce the heat requirement during the manufacturing process. (C) 2007 Elsevier B.V. All rights reserved.