English Version of a publication in the German magazine BITUMEN (ISSN 0006-3916) issue 1/2001

Results of ARBIT test programme 1998/99 involving 36 unmodified and modified bituminous binders on the German market

Rolf GUERICKE
Hans-E. HOEPPEL

Prof. Dr.-Ing. R. Guericke, Dr. rer. nat. H.-E. Hoeppel, ARBIT (German Ass. of Bitumen Suppliers, Hamburg) E-Mail: info@arbit.de

ABSTRACT

Local rutting problems occurred in the mid nineties led to uncertainty of the future competitiveness of asphalt pavements for heavy duty trafficked highways in Germany. In response to this, the asphalt and bitumen industry launched activities and programmes to identify the specific sources of failures and to generally improve the resistance to rutting. Among them the performance of the respective segment of bituminous binders came into the focus. Additionally to the conventional binder tests, 36 unmodified and modified binders in the range of harder grades were subjected to a large scale test programme including various new binder test methods using Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Force Ductilometer as well as two methods of long term aging. The results of the binder test were correlated to asphalt mix test results, i.e. Rutting: Hamburg Rutting (immersion) Test, Cold cracking: Arand Restrained & Direct Tension Test, Adhesion / Stripping: Loss of Indirect Tensile Strength after storage in water. The main results are (a) Valuation of new binder test methods: Zero Shear Viscosity using DSR in oscillation mode was found as most valid to reflect the partial binder contribution to rutting resistance of an asphalt mix for the whole spectrum of the tested binders; BBR-results showed clearly a better correlation to cold cracking behaviour of asphalt mix samples than Fraass test results; Force Ductility breaking energy led at all three applied test temperatures, at 7, 13 and 19°C to a clear discrimination of unmodified binders in comparison to PMBs, (a similar trend in this ranking was found by Zero Shear Viscosity results). (b) Selection of bituminous binders for Asphalt layers: The results of Hamburg Rutting (immersion) Test - as a combination of moisture and mechanical stresses to be found also under practice conditions - indicate the advantage of even harder unmodified binders and more evident the advantage of PMBs in regard of resistance to rutting in combination on with stripping.