Rheological characterization of bituminous mastics containing waste bleaching clays

Bleaching clays are mostly used in food industries to clarify vegetal oils. After use they are generally dumped as waste (stage 1) or used in green innovative plants to feed biogas reactors (stage 2). In latter stage the initial residual oil content (ap-prox. 25% by mass) is reduced to less than 1% by the biological process. In this study the bleaching clays effects on bituminous mastics of a traditional binder course Hot Mix Asphalt have been investigated. The physical characteristics of the two bleaching clays and of a traditional limestone filler were also studied. DSR rheological tests at high and low temperatures were performed on mastics samples containing different amounts of fillers (limestone, stage 1 or stage 2). The addition of the different waste bleaching clays significantly affects the rheological behav-ior of the mastics: the filler from stage 2 increases the mastic stiffness improving the resistance to permanent deformations as shown by repeated creep tests, while the filler from stage 1 strongly interacts with the bitumen reducing the mechanical characteristics of the mastics at all temperatures.