This study was aimed at developing and demonstrating the application of bio-renewable polymers for use in asphalt pavements by utilizing soybean oil through chemical synthesis. Triglyceride molecules from vegetable oils have been considered as important renewable resources, which can be used as biomonomers and be polymerized into biopolymers with properties similar to petroleum-derived monomers and polymers. Biopolymers with various polymer formulations were synthesized to investigate their effects in asphalt modification. Chemical and rheological characterization of biopolymers and biopolymer modified asphalt binders were conducted to better understand the materials properties. The chemical characterizations were studied by conducting the hydrogen nuclear magnetic resonance (H-NMR), high temperature gel chromatography (HT-GPC), and other tests. The rheological properties of biopolymer modified binders were evaluated through a comprehensive asphalt binder testing program according to the AASHTO/ASTM test methods. The biopolymer modified asphalt binder testing results were subsequently used for statistical analysis and modelling to identify the significant polymer formulation parameters that affected the modification results and allowed researchers to optimize the biopolymer formulation for use in asphalt binders. A cost comparisons between the biopolymer and the styrene-butadiene (SB) polymer were made to evaluate the economic benefits of biopolymer in the polymer production and the hot mix asphalt (HMA). The biopolymer formulation that performed best was selected and produced in the laboratory and the grading results confirmed its effectiveness in asphalt modification. The cost comparisons indicated that the biopolymer was able to save about $2,800 per lane mile in the HMA than that of SB polymer. A newly constructed biopolymer pilot plant in Iowa was able to produce more than 600 gallons of the biopolymer for paving a National Center for Asphalt Technology (NCAT) Test Track section. Production of the biopolymer at the pilot plant demonstrated the biopolymer polymerization reaction could be scaled up from the laboratory to the pilot plant level. The success of the biopolymer asphalt mixture paving construction proved that the biopolymer could be blended at existing asphalt blending and production facilities and the mixture can be mixed and compacted as easily as other commercial polymer modified binders in mixtures, working at the same dosage level and delivering similar or even better modification effects. These biopolymers are also sustainable, cost effective, and environmentally friendly. The overall research effort demonstrated the feasibility of implementing the biopolymer into construction practices.
