The potential benefits related to a reduction in energy costs, of risks to the environment as well as to improved safety for workers lead to an increasing interest for the use of paving materials bound with bituminous emulsions. Up to now, the mechanical properties achieved with this kind of technology remain however lower than those reached by hot mixes. This has restricted its use to roadbase materials (gravel-emulsion) or to maintenance works (micro-surfacing) on light or medium traffic roads. The design of true cold bituminous concrete wearing course mixes, which may be laid in lifts of several centimetres, is confronted to rather challenging technical issues, especially with regard to the manufacturing and laying conditions allowing to reach sufficiently high mechanical properties. This communication presents the systematic approach which has been undertaken by the EUROVIA company so as to develop cold bituminous concrete. This effort has particularly benefited from the outcome of the European OPTEL project. This project, which has been run with several industrial partners and research organisations, has especially contributed to a better fundamental understanding of the product. Our practical experience as a road building contractor further leads us to the statement that the optimisation of cold mixes call for a change in our traditional way of thinking, stemming from the formulation methods for hot mixes. These thoughts have allowed us : - to develop specific laboratory tools for a better appraisal of the behaviour of these materials at the different manufacturing and laying stages, - to elaborate the general frame of a mix design method suitable for cold mixtures, - to adapt our manufacturing (mixing plant) and laying equipment. The paper also presents the state of the validation studies which have been conducted so far in the frame of various full-scale experiments. For the covering abstract see ITRD E135448.
Abstract