ABSTRACT
ABSTRACT: In recent times, fundamental durability properties of bitumen stabilized materials (BSMs), in-terms of age hardening and moisture damage, have been a concern for practitioners. It is known from hot-mix asphalt (HMA) that age hardening occurs during in-plant mixing, construction and long-term in-service conditions in the pavement. The same principle has been used to investigate the age hardening behaviour of BSMs, but looking at in-plant production and in-service condition, which are critical for BSMs. This paper discusses the results on the behaviour of bitumen age hardening in the foamed bitumen and bitumen emulsion mixes. The study shows that short term age hardening can occur in foamed bitumen due to long hours of circulation of the binder at high temperature (between 170° to 180ºC) before mixing. However, it has been shown that the foaming process itself does not alter the physical properties of the bitumen significantly. For bitumen emulsion, the rheological properties (penetration, viscosity, and softening point) of residual emulsified bitumen after evaporation of the water found to be consistent with the base bitumen. During long-term in-service conditions, however, foamed bitumen and bitumen emulsion mixes yield significant age hardening of the binders. At the same time, age hardening behaviour differs for the foamed bitumen and bitumen emulsion, with the formed bitumen having higher age hardening potential.
