THE STRESS RELAXATION OF MODIFIED BITUMENS

摘要

The Asphalt pavements in Central and Eastern Europe have to be resistant to high and very low temperatures and climatic changes. Especially emphasize influence of low temperatures seems to be critical parameter. That is why the modified bitumens with low temperature susceptibility and with high resistance to low temperature cracking are searched for. Dynamic Shear Rheometer (DSR) can be used as a quick method that can evaluate the modification system of bituminous binders. The advantage of DSR testing is also related to possibility of comparison of unaged and aged bitumen. The relaxations of shear stress of several asphalt rubber binders (containing 11%, 13 %, 15 % and 17 % of crumb rubber) and paving bitumen were determined in DSR at the temperature of 0 ℃ and -10℃. Relaxation tests were performed in the controlled strain regime. Total shear strain (rotation of upper geometry) was set to 1 % of the sample thickness and stress was applied for 60 s. Relaxation time was set to a period of 15 minutes. The shear stress relaxation behaviour of unaged bitumens and bitumens aged after 75 minutes and 225 minutes in Rolling Thin Film Oven Test (RTFOT) is presented and discussed.