Influence of graphite on the physical and rheological properties of bituminous binder before and after short-term ageing

Abstract

Bitumen is commonly used as a binder in the surface course of the flexible pavement. Failures in flexible pavement are mainly due to rutting and cracking distresses that occurs during the service life of the pavement at high and low temperature respectively. To minimize these distresses, there is a need to improve the quality of the bitumen binder. In this study, graphite is considered as potential modifier of the bitumen. The objective of this paper is to investigate the effect of graphite powder on the physical and rheological properties of the bitumen binder before and after being subjected to short-term ageing. Graphite powder was blended in the bitumen in variegated percentages from 5 to 20% with an increment of 5% by weight of bitumen. The samples were simulated to short-term ageing using rolling thin film oven test. Penetration, softening point, rotational viscosity and dynamic shear rheometer tests were performed on these unaged and short-term aged samples. The result indicates an improvement in physical and rheological properties of the bitumen binder as illustrated through decrease in penetration value along with increase in softening point, viscosity and rutting resistance parameter with increase of additive content for both unaged as well as short-term aged samples. The temperature susceptibility and stripping properties of the modified binder also gets improved. However, the addition of graphite resulted in an increase in mixing and compaction temperature. Also, the addition of graphite reduced the degree of ageing of the bitumen binder as indicated through lower penetration ageing ratio, lower softening point increment, lower viscosity ageing index, lower ageing index of rutting factor and an increase in ageing index of loss tangent with increased additive content. The recommended content of graphite as modifier is 8%.