Effects of Fillers on the Rheological/Mechanical Performance of Mastics/Asphalt Mixes

Resumé

This paper summarises the effects of four different fillers on the rheological properties of mastics and mechanical properties of asphalt mixtures produced with these four different types of added fillers. The main aim of the study is to evaluate rheological properties of the mastic that control the asphalt performance (i.e. rutting, fatigue cracking and thermal cracking). The second objective of the study is to evaluate some of the mechanical properties of the asphalt mixtures produced with the studied fillers as well as the optimum bitumen content for a certain aggregates, grading curve and filler content.
Therefore, in addition to a preliminary characterization of the fillers based on the evaluation of the Specific Surface Area (SSA) and Rigden voids, the study is divided in two main sections. Firstly four different mastics have been prepared in order to conduct Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests and therefore obtain information about the rheological behaviour of the lab prepared mastics. In addition, the performance grade (PG) of the mastics with regards to the main distresses above has been performed. Secondly asphalt mixtures have been produced using the studied fillers to conduct the Marshall method of mix design and thus analyse the volumetric of the mixture as well as its mechanical properties (i.e. Marshall stability and flow) in order to determine the effect of fillers on the mechanical performance of the asphalt mixtures.
The Marshall results revealed a relatively strong correlation between the Marshall stability and the SSA of the fillers that might be attributed not only to the different stiffnesses obtained with fillers of different SSA but also to the ease of a crack path to travel through a mastic produced with lower SSA fillers with regards to those produced with fillers with a higher SSA value. As a result of the DSR test on the lab-produced mastics another important correlation was observed between the SSA and the failure temperature at high test temperatures which depends on the rutting parameter, observing that higher failure temperatures are obtained when fillers with higher SSA values are used.