Several years ago, a research programme started to develop a family of plant-based binders that might ultimately provide an alternative to the different grades of road bitumen. In April 2003, it resulted in the first construction project for a wearing course, in close partnership with the General Council of the Departement of Cotes d'Armor in the framework of its innovation project "The Road of the Future". With assistance from the French Energy Conservation Agency (ADEME) in-depth laboratory studies resulted inthe development of a range of plant-based binders. They are manufactured from renewable raw materials and fit in with the ideas of sustainable development. They may be used for maintenance mixes, or for surfacings which must blend harmoniously with the environment. This is because they are transparent in thin films and therefore take on the natural colour of the aggregate. They have specific rheological properties, in particular viscosity which means mixes can be manufactured at about 110degreesC, or even below.They also help to reduce greenhouse gas emissions. They give the mixes the physical and mechanical performance required for wearing courses. However, the mix design method must be adapted in view of the binder's changing properties. Three sets of works, using a very thin layer of mix made with 0/6 mm aggregate, have been conducted on county roads in the framework of an innovation charter signed with the respective Departement General Councils and the Setra. Monitoring of the surface characteristics of these projects has shown that their skid resistance is still very satisfactory afterbetween 20 and 30 months of service. The mechanical performance is also satisfactory, without rutting or deterioration even in areas where the climate requires potentially damaging winter maintenance. The development of these plant-based binders is ongoing, involving the creation of aesthetically pleasing mixes, and several examples are described. For the covering abstract see ITRD E139491.
Abstract