Improvement of rheological characteristics of bitumen and elimination of problems in flexible pavement material formation by additives

Bituminous materials which are widespreadly used in engineering are prefered for their rheological properties and thermal resistances. Flexible pavements are expected to be qualified in performance and stability, cost efficient in upkeeprepairing. Hence, the bitumen which is one of the main compounds of flexible pavements has been modified to increase the performances of flexible pavements. Flexible pavements that are used in the top layer of the roads are formed from bituminous binders and aggregates. It is the material properties of the bituminous binders and the aggregates that determine the quality of the flexible pavements. Problems related to the deformations such as adhesion in the top layers of the roads, formation of rutting, crackings and peelings are common in the recent years. Thus modified bitumen usage is spreading in order to eliminate the defects in flexible pavements. In this study, the modification of the bitumen with additives and the effects of the additives on the rheologic characteristics of the bitumen was studied. Epoxy resin which is a thermosetting group polymer, phenolformaldehyde, vii polytetrafluoroethylene which is a thermoplastic group polymer and known as teflon commercially and Mg abietate were used as additives. The effects of these additives on the rheology of the bitumens were tested by viscosity, penetration, softening point, dynamic shear rheometer (DSR), differential scanning calorimeter (DSC), rolling thin film oven test (RTFOT), pressure ageing vessel (PAV), bending beam rheometer (BBR) and surface energy test. Adhesion performances of the uncompacted modified bitumens and aggregate mixture were tested by Nicholson peeling test. In addition original and modified bitumens and mixtures made with Marshall method were tested for stability. It is found from the tests that the additives improve the rheologic characteristics of the bitumen. 2% of epoxy resin by mass had increased the viscosity of the bitumen, had improved the adhesion characteristics, had decreased the rutting and fatique cracks and increased the stripping resistivity and stability. In the similar method, 2% of phenolformaldehyde resin by mass had increased the viscosity of the bitumen, had improved the adhesion characteristics, had decreased the rutting and fatique cracks and increased the stripping resistivity and stability. 3% of PTFE by mass had increased the viscosity and the resistance to fatique cracks and rutting of the bitumen. Synthesized Mg abietate mixture had increased the stripping resistivty of the bitumen by increasing the adhesion. Key Words :Modification of the bitumen, asphalt, magnesium abietate, phenolformaldehyde, PTFE, epoxy resin