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A platform for research: civil engineering, architecture and urbanism
Foamed Bitumens: Foamability and Foam Stability
Foamed bitumens were obtained by injecting water into hot bitumen using the Foamlab apparatus from SAE (Fayat Group). Three bitumens were studied and the volume of foam obtained under fixed conditions of bitumen temperature and water content, was quantified through the maximum expansion ratio ERm. This parameter reached a maximum value ERmax(T) versus water content, that increased with temperature and varied to a lesser extent depending on bitumen origin. The optimal water content to obtain ERmax(T) increased linearly with temperature. In all cases, the ratio of ERmax(T) to the optimal water content, called “coefficient of foamability” M, was independent of temperature for a given bitumen, and ranged between 2 and 3. ERm below the optimum water content were directly proportional to the coefficient of foamability and the water content. This is in agreement with simple thermal arguments. Thus, foam formation is controlled by the quantity of water vaporized in contact with the hot bitumen, and the yield and kinetics of this heat transfer, which is a function of the nozzle. The foam half-lives first decreased with increasing water content and were then almost constant at a given temperature once the water content exceeded half of the optimal water content. Moreover, half-life was found to be proportional to bitumen viscosity, in agreement with current theories of foam stability. Lastly, a slight ageing was observed on some of the bitumens after foaming, but it remained much less severe compared to current specifications on RTFOT ageing.
Foamed Bitumens: Foamability and Foam Stability
Foamed bitumens were obtained by injecting water into hot bitumen using the Foamlab apparatus from SAE (Fayat Group). Three bitumens were studied and the volume of foam obtained under fixed conditions of bitumen temperature and water content, was quantified through the maximum expansion ratio ERm. This parameter reached a maximum value ERmax(T) versus water content, that increased with temperature and varied to a lesser extent depending on bitumen origin. The optimal water content to obtain ERmax(T) increased linearly with temperature. In all cases, the ratio of ERmax(T) to the optimal water content, called “coefficient of foamability” M, was independent of temperature for a given bitumen, and ranged between 2 and 3. ERm below the optimum water content were directly proportional to the coefficient of foamability and the water content. This is in agreement with simple thermal arguments. Thus, foam formation is controlled by the quantity of water vaporized in contact with the hot bitumen, and the yield and kinetics of this heat transfer, which is a function of the nozzle. The foam half-lives first decreased with increasing water content and were then almost constant at a given temperature once the water content exceeded half of the optimal water content. Moreover, half-life was found to be proportional to bitumen viscosity, in agreement with current theories of foam stability. Lastly, a slight ageing was observed on some of the bitumens after foaming, but it remained much less severe compared to current specifications on RTFOT ageing.
Foamed Bitumens: Foamability and Foam Stability
Lesueur, Didier (author) / Clech, Hélène (author) / Brosseaud, Aline (author) / Such, Christian (author) / Cazacliu, Bogdan (author) / Koenders, Burgard (author) / Cérino, Pierre-Jean (author) / Bonvallet, Jacques (author)
Road Materials and Pavement Design ; 5 ; 277-302
2004-01-01
26 pages
Article (Journal)
Electronic Resource
English
Foam , Bitumen , Cold Mixes , Foam Stability , Foamability
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