Field validation of recycled cold mixes viscoelastic properties

Abstract

Visco-elastic properties of recycled cold mixes are analyzed in this paper by tests carried out in laboratory; the aim of the paper is to evaluate how reliable are these properties to be used for the prediction of visco-elastic response of pavement layers containing recycled cold mixes.The paper focuses on both bitumen emulsion and foam bitumen recycled cold mixes; two different mixtures were designed in laboratory to achieve specific mechanical properties and used to build two instrumented test sections. Visco-elastic properties and fatigue resistance of these mixtures were determined on cores extracted from the test sections and compared with those determined on a conventional hot asphalt mixture for base layer. This comparison allowed to highlight the reduced thermo-sensitive and time-dependant behavior of these mixtures.Visco-elastic properties of the recycled cold mixtures determined in laboratory, then were used to predict strains in the base layer of the test pavements by using the ViscoRoute 2.0 software. The comparison between measured and predicted strain pulses allowed to evaluate the reliability of visco-elastic parameters determined in laboratory to predict response of layers composed of recycled cold mixes. The obtained results show that visco-elastic parameters of bitumen emulsion recycled cold layers exhibit a satisfactorily capacity to accurately reproduce the pavement response; the same reliability cannot be found for foam bitumen recycled cold layers, whose behavior diverges significantly from that of a continuum.