Steady-state Deformation Behaviour of Bitumen

The deformation behaviour of bitumen has a significant influence on the deformation behaviour of the asphaltic mixtures. This paper describes the steady-state deformation behaviour of a 70/100 penetration grade bitumen. Constant stress shear creep tests over a range of stress levels and temperatures were conducted on the bitumen before and after short term aging. In order to investigate the effect of the aging experienced by the bitumen during mixing operation, the bitumen specimens were aged by the RTFOT (Rolling Thin Film Oven Test) equipment. The tests were performed using a Bohlin Gemini200 Dynamic Shear Rheometer (DSR). It is found that the steady-state deformation behaviour of the pure bitumen can be characterised by power law creep with the creep exponent of 1 at low stress levels (<100kPa), indicating linear behaviour, and the creep exponent of approximately 2.6 at high stress levels (>500 kPa), indicating nonlinear viscous behaviour. At the intermediate stress levels (100 kPa> and <500 kPa) the behaviour is transition from linear to non-linear behaviour. It is also found that the ageing of bitumen during the mixing operation has no effect on the steady-state deformation behaviour of the bitumen.