Influence of Curing on the Mechanical Properties of Cement-Bitumen Treated Materials Using Foamed Bitumen: An Interlaboratory Test Program

The use of reclaimed asphalt (RA) in road pavements is continuously gaining interest thanks to the technical, economic and environmental advantages guaranteed by such sustainable practice. Cold recycling techniques compared to traditional asphalt mixes allow a significant reduction of energy, fume emissions, use of natural resources, etc. In this perspective, the Task Group 1 on “Cold Recycling” of the RILEM Technical Committee on “Asphalt Pavement Recycling” (TC 264-RAP) launched an interlaboratory test program (ITP) aimed at ensuring a better understanding for cold recycled mixtures. The paper presents the results collected by a restricted group of the participating laboratories testing cement-bitumen treated materials that included a single RA source and prepared with foamed bitumen. Gyratory compacted specimens were used to evaluate the influence of curing (free, partial or restricted-surface drying for 14 days at 40 °C at a relative humidity of 55 ± 5%). Stiffness was evaluated as a function of the curing stage and the corresponding water loss; strength was tested after 14 days of curing testing specimens in both dry and wet conditions to also determine the water sensitivity. As expected, the different curing conditions clearly influenced the rate of water loss of tested samples with clear effects on mechanical properties and durability.