Effect of Mineral Fillers on Oxidative Aging of Epoxy Bitumen

This research involving two binders, a neat 70/100 paving grade bitumen and an epoxy-diluted bitumen, evaluated the effect of hydrated lime and limestone filler on the oxidative age hardening of binders. A pressure aging vessel (PAV) unit was used to mimic long-term oxidative aging, and the rheological properties of binders containing fillers were measured using a dynamic shear rheometer. The active nature of hydrated lime with binders was further verified by conducting elongation-to-fracture tensile tests. Results indicate that the effect of the filler reactivity is much more pronounced in epoxy bitumen than in neat bitumen, with the pure limestone filler showing the highest stiffening effect. The epoxy bitumen containing limestone filler was also tougher, showing higher elongation-to-break than the mastics generated with hydrated lime. Even though the epoxy bitumen containing limestone was the strongest and toughest material, it exhibited higher susceptibility to fracture after 80 h in PAV than of the same binder with hydrated lime. This research verifies earlier studies that hydrated lime could improve the low-temperature properties, resulting in the reduction of the deleterious effects of oxidative age hardening in bituminous binders.