Full-scale monitoring of cold mix asphalt during curing

Abstract

Cold mix asphalts (CMA) could be an answer to the need to use road materials with a lower carbon footprint. They are implemented at room temperature without drying aggregates, allowing significant energy savings for the pavement industry. However, their behavior in road pavements is still little known. This paper investigates the structural evolution and damaging of monitored test sections containing CMAs and their link to mix and binder variations with time. The behavior of the pavement was assessed in regards to the mix composition, surface layer, number of loading cycles using accelerated pavement testing and weather conditions. Full-scale experimentations showed that structures containing CMAs as base course have a very distinctive behavior in response to loading. Firstly, they undergo high strain amplitudes, compared to structures containing hot mix asphalts (HMAs), and these amplitudes increase with the number of loading cycles without apparent structural damage. It was also demonstrated that a HMA surface layer shields the CMA course. Full-scale and in-lab tests demonstrated that CMA curing (after 36 months) is not influenced by a surface layer and that the performances of CMAs can be reduced by a lower binder content. Moreover an overloaded section displayed only transverse cracking. Permanent deformation was visible on this sacrificial section, from the CMA surface to the unbound granular material course. Generally, this work also gives more insight on structural behavior of pavements containing CMAs under loading. The testing procedures and equipment suitable for structures with HMAs are not always adapted to structures with CMAs.