Experiments with Cold Mixes on Laboratoire Central des Ponts et Chaussées Fatigue Test Track: Behavior under Traffic Loads,Mechanical Characteristics,and Modeling

Abstract

A joint experiment has been set up by Laboratoire Central des Ponts et Chaussées and SCREG using the Nantes circular test track. Four pavement structures have been constructed, each consisting of a layer of graded crushed aggregate and 10 cm of bituminous material. The bituminous mixes are made up of a reference base hot mix, a reference conventional emulsion-bound granular material, a double-coated cold mix, and an experimental special emulsion-bound granular material. Sub-grade low bearing capacity and limited pavement thicknesses resulted in high deflections. The structures were submitted to 1,900,000 loadings of 6.5 t dual wheels. Loading was carried out in two phases: consolidation, then fatigue. Monitoring of the structures' behavior showed that deflections remained high and rutting occurred in subjacent untreated materials, but not in the bituminous mixes. High strains were recorded in the cold mixes. Cracks became visible fairly early in the four structures. They nevertheless withstood the loadings without requiring any maintenance. Besides, numerous laboratory tests were carried out on laboratory mixes and samples taken from in situ layers: compressive strength, resistance to water, compactability with gyratory shear compactor, and static and dynamic moduli. The results enabled a more complete characterization of cold mixes. They also validated the concept of the innovative cold mixes tested. Finally, theoretical analysis was conducted, resulting in a fairly satisfactory structure modeling, using materials nonlinearity.