Cold mixes, more precisely those made with emulsion, have several specific features (presence of water, aggregate-emulsion, reactivity, properties evolving with time). Their behaviour, in many respects, is different from that of hot mixes. Diverse types of cold mix have now reached a considerable level of development: grave-emulsion, open-graded cold mix asphalt concrete, stockpile mixtures. Others, like dense cold mix asphalt concrete, have not been extensively developed yet; some are still at research stage. The various types of cold mix are described. Until recently, there was only a small number of design methods for cold mix, which are almost totally empirical. The tests comprised in these methods are mainly derived from tests for hot mixes. It is therefore not surprising that the specifications applicable to cold mixes are still limited and, sometimes, not fully adequate. An important research has been conducted recently. It has produced a specific design method for cold mixes. The main steps of this method are presented: coating quality, early cohesion, compactability, accelerated curing, water sensitivity, rutting resistance and stiffness modulus. The tests have been selected in order to support performance - based specifications. On the other hand, several site sections cold mix pavement and/or wearing courses have been monitored. The output of the long term monitoring has been compared to the results of laboratory evaluation. This exercise results in a more precise definition of the field of application for each type of cold mix, in terms of position in the pavement, thickness, allowable traffic, etc. Globally, the knowledge of cold mix properties has been improved. The cold mix behaviour modelling has progressed and more adequate pavement design can be performed. Complete and suitable specifications can be drafted. For the covering abstract see ITRD E135448.
Abstract