Date of Award
Doctor of Philosophy
Civil, Construction, and Environmental Engineering
R C. Williams
Polymer modified asphalt binders have been widely used in the construction of flexible pavement over the past few decades. Due to the economic and environmental concerns of using the traditional petroleum-derived polymers, there is a demand for developing sustainable alternatives that can replace the petroleum-derived polymers for use in asphalt pavements. Triglyceride molecules from vegetable oils have been considered as important renewable resources, which can be used as biomonomers and be polymerized into bioadvantaged polymers with similar properties to petroleum-derived monomers and polymers. In this research, non-food soybean oil is selected as a starting point to produce bioadvantaged polymers because it is the most affordable and abundant locally produced vegetable oil in the United States. The polymerized soybean oil has rubbery properties and can be used as an alternative to petroleum-derived butadiene in the styrenic block copolymers. In the laboratory, the bioadvantaged polymer poly(styrene-block-acrylated epoxidized soybean oil) (PS-PAESO) with various polystyrene molecular weights and contents are successfully produced through reversible addition-fragmentation chain transfer (RAFT) polymerization. Their modification effects in asphalt binders are investigated and evaluated via laboratory testing. The testing results are used in the response surface modeling (RSM) for the development of prediction models with the intent to optimize the formulation of the biopolymer for asphalt pavement applications in warm climate regions. The testing results show the great potential of using biopolymers as sustainable alternatives to commercial styrene-butadiene polymers as it improves the neat asphalt binder’s stiffness, elasticity, and rutting resistance at the same polymer dosage levels. The study on economic and environmental implications of biopolymers demonstrate that they are more cost-effective, environmentally friendly, and safer to produce than petroleum-derived styrenic polymers. Using biopolymers in asphalt modification has shown great success, however, there has been no literature so far discussing the use of acrylated epoxidized soybean oil (AESO) alone as an additive in asphalt binders, while many relevant researchers have conducted studies of using bio-based oil in asphalt binders. To study the modification effects of AESO in asphalt binders, laboratory produced AESO and commercially available AESO are used at various concentration levels in the neat asphalt binder, and their performances are evaluated through a comprehensive binder investigations including rotational viscosity, performance grading, rheological, aging susceptibility, high temperature storage stability testing, etc. The results reveal that AESO is able to be used as a modifier in asphalt performance modifications by softening the asphalt binder and reducing the binder’s stiffness. Furthermore, laboratory produced AESO performs superior to commercial AESO in terms of low temperature properties and fatigue life at the same dosage level without showing any separation problems. The findings also show that sufficient high dosage level of laboratory produced AESO can dramatically change the rheological properties of the neat asphalt binder with significant improvements on the resistance to fatigue damage and thermal cracking. Overall, the preliminary laboratory investigations on using soybean-derived polymers and additives in asphalt modifications have shown the feasibility of turning non-food soybean oil into more useful and valuable new materials. The results presented in this work may provide insights into the asphalt modifications using soybean-derived modifiers.
Chen, Conglin, "Performance evaluation of polymer modified asphalt binders utilizing soybean-derived materials" (2018). Graduate Theses and Dissertations. 16797.