| Summary: | Concrete asphalt is a hydrocarbon material that includes a mix of mineral components along with a bituminous
binder. Prior to mixing, its production protocol requires drying and heating the aggregates. Generally performed in a
rotary drum, these drying and heating steps within mix asphalt processes have never been studied from a physical
perspective. We are thus proposing in the present paper to analyze the drying and heating mechanisms when granular
materials and hot gases are involved in a co-current flow. This process step accounts for a large proportion of the
overall energy consumed during hot-mix asphalt manufacturing. In the present context, the high energy cost
associated with this step has encouraged developing new strategies specifically for the drying process. Applying new
asphalt techniques so that an amount of moisture can be preserved in the asphalt concrete appears fundamental to
such new strategies. This low-energy asphalt, also referred to as the "warm technique", depends heavily on a relevant
prediction of the actual moisture content inside asphalt concrete during the mixing step. The purpose of this paper is
to present a physical model dedicated to the evolution in temperature and moisture of granular solids throughout the
drying and heating steps carried out inside a rotary drum. An initial experimental campaign to visualize inside a drum
at the pilot scale (i.e. 1/3 scale) has been carried out in order to describe the granular flow and establish the necessary
physical assumptions for the drying and heating model. Energy and mass balance equations are solved by
implementing an adequate heat and mass transfer coupling, yielding a 1D model from several parameters that in turn
drives the physical modeling steps. Moreover, model results will be analyzed and compared to several measurements
performed in an actual asphalt mix plant at the industrial scale (i.e. full scale).
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