New Mixture Additives for Sustainable Bituminous Pavements

Recently, most engineering disciplines have pursued paradigm shifts from traditional practices, and this trend is particularly apparent in the field of materials engineering including civil infrastructure materials. Development of new materials and mixture systems that are more engineered, economic, and better performing in infrastructure systems has been sought toward sustainable performance. Asphaltic roadway is one of primary infrastructure assets in the United States. About 95% of the roads are constructed using asphalt mixtures. Compared to recent advancements of other infrastructure materials such as cement concrete, polymers, and metallic materials, asphalt mixtures have not been actively studied to achieve advanced material properties and/or multifunctional performance characteristics in pavement structures. Toward that end, this research project, as a pilot study, seeks exploratory (innovative) mixture additives for more sustainable bituminous roadways/pavements in Nebraska. Among several potential additives, in this particular research, we will investigate physical and mechanical properties of asphalt mixtures that are transformed with two different additives: bio-fiber and graphene nanoplatelet. Bio-fiber is selected because it is locally available from abundant and inexpensive agricultural crop residues, and fibers have been reported as effective materials in many different engineering materials by improving reinforcing effects and stabilizing mechanisms within mixtures. In fact, our preliminary test results indicate that corn-fiber reinforcement can improve fracture toughness of asphalt concrete mixtures. Graphene nanoplatelets have not been attempted to improve the properties of asphalt mixtures, while they have already been used to advance mechanical properties of various engineering materials and composites including cement concrete. Graphene nanoplatelets are expected to provide significant impact on asphalt mixture performance in terms of enhancing strength and durability at very low concentrations (less than 1% by weight of binder) due to chemical compatibility with carbonaceous nature of asphalt binder. The two foreign additives will be evaluated mostly with experimental measurements such as stiffness, strength, cracking behavior, and durability by varying their concentrations and geometries.