Evaluation of nano-titanium dioxide additive on asphalt binder aging properties

Photocatalysis compounds such as titanium dioxide (TiO2) can trap and degrade organic and inorganic particles in the air and thus remove harmful air pollutants such as nitrogen oxides (NOx) and volatile organic compounds in the presence of ultraviolet light (sunlight). Despite the rapid development of this technology, current applications are limited to concrete pavement surfaces, which represent only 6% of the national road network in the United States. About 94% of the road network in the United States is surfaced with hot-mix asphalt, a percentage that supports directing future research toward the use of TiO2 coating in flexible pavements. Before this technology is integrated into asphalt pavements, the effects of integrating the additives on the rheological properties of the binder should be investigated. To address this objective, a commercial crystallized anatase-based TiO2 powder was blended with a conventional asphalt binder classified as PG 64-16 at three modification rates (3%, 5%, and 7%). Prepared blends were characterized with the use of fundamental rheological tests and with measurements of the environmental efficiency of the binder in removing part of the NOx pollutants from the air stream. Results of the experimental program indicated that the use of TiO2 as a modifier to asphalt binder was effective in removing part of the NOx pollutants from the air stream. Rheological test results indicated that the addition of TiO 2 did not affect the physical properties of the conventional binder. Exposing the binder to ultraviolet light did not appear to accelerate the aging mechanisms in the binder