Séchage des matériaux de chaussée traités à l’émulsion de bitume

Abstract : The preparation of cold mix asphalts, composed of aggregates and bitumen emulsion, represent a substantial economic and environmental potential but the presence of water delays the strengthening of the material. Our objective is to understand how the mix dries and how this affects its properties. The drying of pure liquids in simple porous media has been extensively studied : a constant drying rate period as well as a homogeneous distribution of water are observed until 90% of the water has been extracted; afterwards the drying rate decreases. Studies have shown that the drying of complex fluids (ionic solutions, suspensions, gels) is very different due to the transport and/or accumulation of the fluid’s non-vaporizable elements. We chose to study first the drying of the complex fluid i.e. the bitumen emulsion as well as silicone oil emulsions to understand better the drying mechanisms, then the drying of the complex fluid in a porous media. We used Magnetic Resonance Imaging (MRI) to monitor the internal characteristics of our systems. This allowed us to show that water is extracted uniformly over the drying emulsion’s entire thickness ($approx$cm), leading to the progressive droplet compaction and deformation. However, a water concentration gradient forms near the free surface, which ultimately slows the drying as droplets coalesce. We then show that the drying rate of a porous medium initially saturated with emulsion decreases from the beginning of drying. The rapid formation and progression of a dry area in the porous medium and the absence of bitumen transport partly explain this but it is very likely that the bitumen emulsion’s drying characteristics contribute to the decreasing drying rate
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Marie Goavec. Séchage des matériaux de chaussée traités à l’émulsion de bitume. Matériaux. Université Paris-Est, 2018. Français. ⟨NNT : 2018PESC1048⟩. ⟨tel-02067302⟩

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