Rheological study of bituminous mastics for the sealing of cracks of flexible and semi-rigid pavements

The cracking phenomenon is connected mainly to fatigue mechanisms and to thermal actions, which induce high tensile stresses inside the pavement which provoke the arise of cracks, especially in areas with lower resistance. This process, if not faced at early stage, can develop very quickly up to the case of a complete unserviceable road superstructure. In order to avoid this limit condition, it is necessary to intervene quickly with the sealing of the cracks, by adopting reliable techniques and materials with high performances. The contribution of this paper is on the execution of a detailed analysis of the rheological properties of different bituminous mastics which can be used to seal the cracks, referring to traditional characterization (penetration, softening point) and rheological tests, such as creep-recovery with DSR at medium temperatures (30°C) and flexural creep tests with BBR at low temperatures (-10, -15 and -20°C), before and after PAV ageing. In order to investigate on the activity of the fillers, the experimental phase was firstly focused on mastics prepared with plain 70/100 bitumen and with two different percentages (33 and 50%) of different kinds of filler (silica, limestone, lime, mortar, cement, ladle slag, blast furnace slag). Only afterwards, once discovered the fillers with the best performances, the plain bitumen was changes with the modified one, getting at the end to a merit rheological classification useful for the applicative scopes on site.