High stiffness underlayers with high percentage of re- use as developed in the NR2C-project

New Road Construction Concepts (NR2C) is a FEHRL- project supported by the European Commission under the Sixth Framework Programme. NR2C aims at developing perspectives and specific innovations in different areas. One of the ideas concerns the development of high performance underlayers with high percentage of reclaimed asphalt. Three different mixes were designed, optimized and compared, namely with 0 %, 25 % and 40 % reclaimed asphalt. After an extensive laboratory study, the selected solutions have been further studied in a full- scale ALT facility. The structure tested has been instrumented with strain gauges, deflection and temperature sensors in order to analyse the performances. In a first step, fatigue behaviour was evaluated by applying 100'000 12-tons axle loads at 15 ° C. Then, low temperature behaviour was investigated by load applications during a number of temperature cycles where the air temperature varied between +2 °C and -7 ° C. In addition to the ALT, tests on large slabs with extreme temperature and other laboratory tests on mixes and binders have been performed. Finally, no negative effect using a high percentage of reclaimed asphalt has been found within this study. However key parameters as for instance the mix design and RA properties require special attention.