Abstract
In road applications, the current challenge is to develop more ecological products while maintainingasphalt mixture performance and durability. This sustainable development politics in civil engineeringleads to promote techniques saving both energy and raw materials like combining the use of warmmix asphalt concretes (WMA) with the use of reclaimed asphalt pavement (RA). However, one of the cur-rent problematic when combining WMA and RA is to assess the quality adhesion of the ‘‘asphalt/aggregate” couple that is a fundamental parameter for the good mixture properties at short time and therebydurability of this composite structure. Indeed, the reduction of the manufacture temperature and the useof an aged binder may also have consequences on adhesion quality between asphalt and aggregates. It isthe reason why it is crucial to identify the most impacting factors of wetting phenomena at the interface‘‘asphalt/aggregate”. So, in this paper, the role of asphalt characteristics (viscosity, ageing, composition)as well as the one of substrate was investigated.The substrate heterogeneity degree determines asphalt wetting behavior. For a model glass substrate,only asphalt characteristics have an impact: asphalt viscosity, polarity and saturates content are influentfactors. On the mineral heterogeneous substrate, asphalt viscosity and asphaltenes content have animpact on wetting indicators. Substrate heterogeneities also appear as a very important factor whichimproves considerably wetting quality. The tested mineral substrate has been revealed as a biphasic com-posite material for which the wetting regime was modeled by a Cassie-Baxter model. A comprehensiveapproach has been proposed to explain asphalt wetting on heterogeneous substrates in correlation withScanning Electron Microscopy observations. This Cassie-Baxter model is essential to understand adhesionphenomena on heterogeneous road materials. It seems also to be a promising way to evaluate qualityadhesion of ‘‘asphalt/RA” mixtures.