Investigation of effect to bitumen and stone mastic asphalt pavement of graphite

Bitumen in hot mix asphalt (HMA), is viscoelastic material having suitable mechanical and rheological characteristics for road paving applications. Moreover, hot mix asphalt need to be developed to resist particular permanent deformations like rutting and thermal cracking due to increased traffic volumes and vehicle loads. Additives such as carbon black, graphite, carbon fibers are added to mixture or bitumen in order to transfer heat by increasing thermal conductivity. In this study, the effect of graphite used for improving the thermal properties of bituminous mixtures on rheological and conventional properties of bitumen has been investigated. Penetration, softening point, rotational viscosity and dynamic shear rheometer tests were applied to binders modified by four different proportions of graphite by weight of bitumen. Stone mastic asphalt mixtures which were manufactured with pure and modified bitumen were aged in different time intervals in oven. They have been applied to Marshall stability and flow, indirect tensile stiffness modulus and indirect tensile fatigue tests. In conclusion, it was determined that penetration values decreased while softening point values increased with the increasing of graphite content. While the graphite induced 8oC increases in mixing-compacting temperature by increasing the viscosity values, on the other hand it caused an increase in rutting parameter. In low temperature, the deformation and stiffness values changed significantly with the increase of the graphite content, but the property hold on the stiffness of the bitumen did not change significantly. It has been determined that there is no significant difference in the time-dependent deformation behavior of the original and aged samples in pure and different graphite content despite the stiffness values and load repetition number of the samples increased with rise of the aging time.