Thermal Aging of Bitumen and Biorejuvenator Blends: Triglyceride versus Free Fatty Acids

Abstract

When added to aged bitumen, oil-based rejuvenators are expected to restore its original properties to some degree. The extent of the rejuvenation depends on the composition of the oils. In this study, the effect of individual components of vegetable oils on blends with bitumen was investigated. First, 5% and 10% by weight of two free fatty acids, namely oleic acid and linoleic acid, and one triglyceride, triolein, were blended with bitumen, and thereafter, the blends underwent thermal aging at high temperatures under air in a ventilated oven. The fatty acids and triglyceride are referred to as rejuvenators in this context. Upon thermal aging, the free fatty acids did not produce any effect or were much less effective in decreasing the complex shear modulus (stiffness) of bitumen compared with the triglyceride. One reason for this result may be the favorable chemical changes of the triglyceride at high temperatures compared with the free fatty acids. Above all, this study provides basic knowledge to demonstrate the importance of the chemical composition of vegetable oils that are selected as bitumen rejuvenators, specifically when targeting long-term stability of the blends.