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Rheological Investigations on Foamed Bitumen
The increased workability of the mixture of foamed bitumen with aggregate particles is largely influenced by the rheological properties of the foamed binder during mixing and subsequent compaction. Because foamed bitumen is a two-constituent system of air bubbles entrapped in the binder, a complex behavior is expected as the temperature reduces during mixing and foam decay. In this investigation, a VG10 grade bitumen as per Indian specification was used for foaming at 180 and 160 °C at two water contents, 4 and 6%. Five minutes after the foams were produced, two sets of samples were collected. The first set was subjected to a shear rate sweep test in a rotational viscometer at 100, 120, and 140 °C. The second set of samples was vacuumed in a degassing oven to remove the entrapped air and was subjected to identical shear rate sweep testing in the viscometer. At a given temperature, it was seen that that the foamed bitumen exhibited higher viscosity when compared with an unaged bitumen. However, what was interesting was the rapid reduction in apparent viscosity as the material was sheared. It is postulated that this occurred not only due to the inherent shear-thinning characteristics of the binder but also due to the collapse of air entrained in the foam. It was also observed that the apparent viscosity of vacuum-foamed bitumen was almost identical to the unaged bitumen at the testing temperatures. The rheological behavior at the tested temperature did not depend strongly on the foamed binder production parameters.
Rheological Investigations on Foamed Bitumen
The increased workability of the mixture of foamed bitumen with aggregate particles is largely influenced by the rheological properties of the foamed binder during mixing and subsequent compaction. Because foamed bitumen is a two-constituent system of air bubbles entrapped in the binder, a complex behavior is expected as the temperature reduces during mixing and foam decay. In this investigation, a VG10 grade bitumen as per Indian specification was used for foaming at 180 and 160 °C at two water contents, 4 and 6%. Five minutes after the foams were produced, two sets of samples were collected. The first set was subjected to a shear rate sweep test in a rotational viscometer at 100, 120, and 140 °C. The second set of samples was vacuumed in a degassing oven to remove the entrapped air and was subjected to identical shear rate sweep testing in the viscometer. At a given temperature, it was seen that that the foamed bitumen exhibited higher viscosity when compared with an unaged bitumen. However, what was interesting was the rapid reduction in apparent viscosity as the material was sheared. It is postulated that this occurred not only due to the inherent shear-thinning characteristics of the binder but also due to the collapse of air entrained in the foam. It was also observed that the apparent viscosity of vacuum-foamed bitumen was almost identical to the unaged bitumen at the testing temperatures. The rheological behavior at the tested temperature did not depend strongly on the foamed binder production parameters.
Rheological Investigations on Foamed Bitumen
Nivedya, M. K. (author) / Roja, K. Lakshmi (author) / Veeraragavan, A. (author) / Krishnan, J. Murali (author)
2013 Airfield & Highway Pavement Conference ; 2013 ; Los Angeles, California, United States
Airfield and Highway Pavement 2013 ; 967-976
2013-06-18
Conference paper
Electronic Resource
English
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