In the first year we will focus on developing treatment methods for increasing oxidative stability of the crude and high oleic soybean oil. The research team will conduct a literature review to summarize the effects of chemical species in recycling agents on asphalt binder and mixture properties and performance. In addition, any possible solutions and modifications reported in the literature will be reviewed. We will evaluate crude soybean oil instead of refined/purified edible soybean oil which results in significant savings in materials cost. Using chemical and physical techniques (see Figure 1), undesirable species in the soybean oil that may negatively affect asphalt binders and asphalt mixtures will be identified. We will also consider and examine high oleic soybean oil as an available option in this phase. Then, possible modifications will be performed for increasing the oxidative stability and improving the performance of soybean oil as recycling agent. Removal of free fatty acids, non-oil materials such as proteins and phospholipids from the crude oil by refining process is important since it increases quality and oxidative stability of the oil. However, bleaching and deodorization may not be needed as they are more important for edible oils. Oxidative stability of soybean oil can be increased by a simple chemical/physical process such as activated carbon adsorption. If the crude oil shows desirable properties after such process based on the chemical analysis, the study will continue and rely on this oil. If not, the crude oil will be subjected to refining process that includes degumming and/or alkali treatment.
Since soybean oil is highly unsaturated oil, it is highly susceptible to lipid oxidation. Inhibition from the oxidation of
unsaturated acids in the soybean oil and increasing their stability to thermal degradation will be achieved by addition of asphalt binder modifiers such as a synthetic antioxidant or antioxidant mixtures such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) in different concentrations. The PI and Co-PIs will update the NSB Technical Advisory Committee (TAC) members on the progress of the proposed tasks on a quarterly basis and a final report will be delivered at the end of this phase. We expect to find a procedure to modify soybean oil to be used as a satisfying recycling agent. The outcomes of this phase will be used as an input for the next phase.