Foam bitumen is highly efficient in wetting and coating the surface of mineral aggregate at lower temperature. The residual water content in the decaying foam bitumen was determined by thermogravimetric analysis. In order to improve understanding and characterization of the bitumen foam, X-ray radiography was used to study the formation and decay of bitumen foam in 2D representation. Influence of the water content in combination with compaction temperature has been investigated using gyratory compaction method. Image segmentation analysis was used to determine the foam bubble size distribution as a function of time. The results demonstrate that the morphology of bubble formation depends on the types of bitumen used. In this thesis, new experimental tools were developed and applied for characterizing the foam bitumen during the hot foaming process.
University of Stellenbosch, South Africa.
It may include eg previous versions that are now no longer available. An exponential function has been implemented to represent the bubble area distribution. Moreover, theoretical investigation based on the 3D X-ray computed tomography scan dataset of bubble merging showed that the disjoining pressure increased as the gap between the bubbles in the surface layer foam film decreased with time and finally was ruptured. Moreover, increasing the water content helps in coating large aggregates when the mixture is produced at low temperature, nevertheless using high water content reduces the Marshall stability to certain extent. Moreover the morphology of bubble formation depends on the types of bitumen used. Moreover the influence of viscosity and surface tension on bubble shape and rise velocity of the bubbles using level-set method was implemented in finite element method. The results demonstrate the influence of the water content on morphology and expansion of foam bitumen bubbles.