In situ cold retreatment of wearing courses - Example of works reducing emissions of greenhouse gas and the use of virgin aggregates

Maintenance of surface courses is a daily problem for road managers and it has become even more complicated considering the increasing demand for the preservation of natural resources and environmentally friendly techniques. This context has been the driver for the development and implementation of a cold in-place retread technique using either bituminous emulsions or foamed bitumen. The process targets the rehabilitation of the surfacing of flexible or semi-flexible pavements, up to about 150mm thick. All the functions needed to complete the process are dealt with by a single and powerful specific equipment (cold recycling machine). The technique is thus a clever alternative to usual techniques of rehabilitation/reinforcement by planning and laying of new materials. Its main advantages are economic and ecological, in particular with regard to the saving of virgin aggregate resources and the reduction of the emissions related to hot mix manufacturing and transportation. The paper presents an overview of the research activities which have supported this development and discusses the outcome of the monitoring of several job sites. The magnitude of the environmental benefits which are achievable with the process are illustrated by two case histories.