Degree of Cure and Stress Development in Cold Recycling Layers

Abstract: Characterization and modeling of cure evolution in cold recycled mixtures have been limited to the loss of moisture content during the curing process or some other mechanical properties that don't take the mixture's time and temperature dependence into account. As a result, there is a very limited understanding of how the layer responds to loads during the curing phase. This hinders the ability to determine the optimal time for opening traffic after compaction, deciding when to pave an asphalt overlay on top of the CR-E layer, and addressing potential complications that could happen in the field while the layer is still curing. In this study, a phenomenological approach is used for modeling the curing kinetics of cold recycled mixtures and a generalized rheokinetic viscoelastic model is developed to capture the relaxation modulus evolution with degree of cure and integrated into finite element simulations. This approach allows for the assessment of stress development across varying degrees of cure. Additionally, the models were used to evaluate the effects of overlay thickness, vehicle speed and tire loading on stress development within the layer throughout the curing process. The models could be used to set degree of cure thresholds for allowing traffic after compacting CR or required degree of cure before overlaying the layer.