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This paper aims to investigate the viability of using swine waste binder to improve the rheological properties of bituminous asphalt binder. Due to rising bituminous asphalt binder costs, diminishing reserves of crude oil from which asphalt binder is derived, and the gradual paradigm shift toward more environmentally friendly and energy efficient hot-mix asphalt (HMA) mixtures, the asphalt pavement industry is exploring different sustainable alternative binders. Biobinder has the potential to partially or fully replace typical crude-based asphalt. In this paper, biobinder from swine manure is produced by thermochemical liquefaction process at 380°C and 40 MPa (approximately 400 atm) pressure in the absence of oxygen. A Superpave PG 64-22 is then modified with 5% biobinder by total weight of asphalt binder to produce the biobinder. Samples of the base asphalt binder (nonmodified PG 64-22) and samples of asphalt modified with biobinder are characterized by running the Superpave rotational viscosity (RV), dynamic shear rheometer (DSR), and the bending beam rheometer (BBR) tests. Furthermore, Fourier transform infrared (FTIR) spectroscopy investigations were used to validate the chemical bond initiations that caused changes in stiffness and viscosity of the asphalt modified with 5% biobinder from those of base asphalt binder (PG 64-22). The modification resulted in 27% decrease in viscosity of the base binder. The rolling thin film (RTFO)-aged samples of modified binder experienced a 28.9% decrease in average viscosity change when compared with the RTFO-aged samples from the base binder. Additionally, the pressure aging vessel (PAV)-aged samples of modified binder experienced a 62.9% decrease in average viscosity change when compared with the PAV-aged samples of base binder. The rotational viscosity results proved that the addition of biobinder (swine waste asphalt binder) can reduce the viscosity of the asphalt binder. Furthermore, the modified binder had lower complex moduli and phase angles compared with the base binder (based on DSR results). The BBR results indicated that biobinder had the potential to improve the thermal cracking performance of conventional asphalt binders by reducing the creep stiffness and increasing m-value. The BBR results proved that the modification of the PG 64-22 induces a one grade jump on the lower temperature side. The functional groups in typical petroleum-based asphalt binders remained unchanged after the addition of the biobinder to the PG 64-22 binder. Additionally, the FTIR spectra showed that addition of biobinder decreased the stiffness of the PG 64-22 binder through the reduction in molecular carbonyl and sulphoxide bond chains at high temperature. This research investigation provides useful rheological and morphological guidance on the use of swine waste binder as an asphalt binder and mixture modifier.

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