Ellie Fini

Abstract:

This paper introduces a newly developed bio-oil and bio-modifier produced from thermochemical conversion of animal waste. It further discusses the chemical profile and key active compounds in bio-modifier as well as their characteristic behavior in an attempt to tailor bio-oil production to yield the optimum chemistry. Bio-chemicals and additives have long been used to improve the performance of asphalt pavement. This study investigates intermolecular interactions between bio-molecules derived from swine manure and their effect on bitumen interfaces in an attempt to enhance moisture resistance of bitumen to be used as sealants in construction applications. In fact, use of chemicals and additives for specific purposes such as adhesion promotion of bitumen is a common practice. Bio-oils derived from industrial or agricultural waste streams are attractive candidates as low-cost modifiers that would also improve waste management practices and generate new commercial opportunities. A major component of the swine manure-derived bio-oil is hexadecanamide, a saturated hydrocarbon terminated with a primary amide. Both H-bonding and dispersion interactions are important in the self-assembly of hexadecanamide, but their relative impacts may differ in the context of bitumen or bio-oil. To understand bio-oil’s effect on enhancing bitumen moisture resistance, this paper examines the intermolecular interactions among aforementioned prominent bio-oil’s molecules and their effect on bitumen interfaces. Accordingly, it is hypothesized that both the amide and acid compounds found in bio-oil could play an important role in modifying the chemistry and morphology of bitumen interfaces with aggregate, air, and water. The study results showed that amide- and acid-terminated surfactant modifiers have very different effects on the surface morphology of bitumen and its interaction with a silica surface. The amide compound in pure form did not mix well with the bitumen. This behavior is attributed to the tendency of the amide to form multiple, strong H-bonds with other amide molecules, effectively hiding its polar head and limiting its function as a surfactant. Calculations based on density functional theory confirm that formation of extensive chains of amide dimers are energetically more favored than that of adsorption complexes of amide-asphaltene or amide-wax. In contrast, the acid appeared to mix well into the bitumen and did not affect the morphology of the bitumen-air interface but severely altered the morphology of the bitumen-glass interface with significant impacts on wetting behavior. Organization of the amide molecules in crystalline layers is influenced by both van der Waals forces and H-bonding interactions, such that almost 49% of stability of the hexadecanamide dimers, in side-to-side arrangement, is due to van der Waals interaction between the aliphatic chains. It was shown that solubilizing agents could reduce the amide intermolecular interactions and its affinity for forming extended chains, increasing its effectiveness as a surfactant promoting anti-stripping properties of bitumen.