Analogical based approach to forward and inverse problems for asphalt materials characterization at low temperatures

The use of increased proportions of Reclaimed Asphalt Pavement (RAP) in the construction of asphalt pavements has become a top priority due to its economic and environmental benefits. However, the blending process that occurs during mixing between the new virgin binder and the RAP aged binder is not well understood, and the question if total blending occurs has not been answered. A number of models were developed and used to predict composite asphalt mixture properties from properties of the components. This type of approach is generally known as a forward problem. Recently, researchers started to investigate the possibility of predicting binder properties from mixture properties (inverse problem). In this paper the inverse problem of obtaining asphalt binder properties from asphalt mixture properties at low temperature is investigated using experimental asphalt binder and asphalt mixture creep stiffness data obtained with the Bending Beam Rheometer (BBR). First, a literature review of the models available is performed. Then, the forward problem of predicting the asphalt mixture properties from asphalt binder properties is investigated using a semi-empirical model and a transformation derived from analogical models, respectively. The same model and transformation are then applied to obtain binder properties from mixture properties. It is shown that the transformation based on analogical models can be successfully used for both forward and inverse problems.