Mixed Recycling with Emulsion and Cement of Asphalt Pavements. Design Procedure and Improvements Achieved

Cold in place recycling, as an alternative to milling and standard replacement, shows a series of technical, economic and environmental advantages, which have done its use to grow in Spain, especially from 1990 onwards. Nevertheless, these actions have revealed certain aspects and limitations that prevent cold recycling from being considered a fully consolidated technique nowadays. The use of vaguely defined criteria for the design of the recycled mix, the lack of criteria for construction control as well as of specifications about the end product, and the ignorance of the evolution of the material performance with time have given cold recycling some technical insecurity. In this article, the problems arising from the standard methodology used for the design of cold recycled mixes have been analysed firstly, as well as the effect that certain variables, compaction and curing especially, have on their properties. Secondly, the effect that the use of both emulsion and cement during recycling has on the mix properties has been studied, comparing the results with those obtained by means of the standard procedures where only emulsion or cement are used. Finally, a new methodology for the design and control of the recycled mix has been suggested.