Recycling techniques and environmental issues relating to the widening of an high traffic volume italian motorway

On the last few decades, the use of recycled materials has become important because of the limited availability of good aggregates and the difficulties and excessive disposal costs for milled materials. In particular, cold in-place recycling (CIPR) has become an attractive alternative to other methods of repairing and upgrading roads. CIPR appears to be the most cost-effective method, and due to innovations relating to the technical equipment, CIPR provides for the production of high-performance materials for the base, subbase and foundation layers. One of the main advantages of CIPR is that the existing damaged road is simultaneously recycled (milled) and mixed with binders in a single-pass operation, enabling a high production rate to be achieved. The binders, which can include cement, cement slurry, lime, bituminous emulsion or foamed bitumen, are injected directly into the recycler mixing chamber while the milling operation is being carried out. This study provides an environmental evaluation of a specific rehabilitation project involving several recycling techniques on the A14 motorway. The A14 motorway is one of the main Italian motorways, and it links Bologna and Taranto over about 750 km. A selected section in the Marche region of about 42 km has been up-graded to a six-lane dual carriageway facility. In this study, three rehabilitation options are evaluated and compared in terms of their environmental impact, with particular emphasis on the construction of the sub-base course. In the end, the definitive design involved different recycling techniques, including CIPR with bituminous emulsion and cement for the subbase layer, stabilization of the soil with lime for the embankment, the use of reclaimed asphalt in the production of hot mix asphalt, and the use of crushed cement concrete for the cement treated layers. All of these recycling methods allow the saving of the virgin aggregates, and a reduction in materials transportation and pollutant emissions coming from both the production plant and the means of transport.