I VARIATION IN CHEMICAL AND RHEOLOGICAL PROPERTIES OF BITUMEN DUE TO AGEING ACTION

Performances in service and expected life of flexible road pavements are strongly affected by characteristics and durability of bituminous binder. It is chiefly important the sensitivity of bitumen to ageing, namely its capacity of changing chemical, physical and rheological properties in different service stages (heating extraction, bitumen storage, mixture with aggregates at high temperature, transportation and placement of mixture, air and solar exposure during service life). During these stages, ageing, which can generally be detected by the increase of consistency of bitumen, can be attributed to the loss of volatilous fractions, to the oxidation process accelerated by high temperatures and to moleculare aggregation. In the present paper the results of a study on laboratory ageing processes in bitumen, trought different laboratory methods (Rolling Thin Film Oven Test, Pressure Ageing Vessel, UV-Ageing), are presented. The experimental investigation is based on Thin-Layer Chromatographic analysis of both natural bitumen and artificially aged in order to observe changes of chemical group characteristics of bitumen. The variation of rheological properties with respect to ageing has been studied through a complete rheological analysis with the Dynamic Shear Rheometer