Chemical and thermodynamic properties of palm oil-based materials and their impact on recycled binder blends

Abstract

• We characterised chemical and thermodynamic properties of palm oil-based materials. • We assessed the impact of adding these agents to binder blends of an HMA with high RAP. • Surface free energy was used to assess the adhesion quality and durability of the bonds between aggregates and recycled binder blends with these agents. • Key chemical compounds present in the palm oil materials contributed to the rejuvenation effectiveness. • Palm oil-based materials are promising candidates to be used as rejuvenators in HMA with high RAP. Rejuvenators are agents added during the production of hot mix asphalts with high contents of reclaimed asphalt pavement (RAP) to restore some properties of the aged RAP binder. These materials can be obtained from numerous sources; hence, their chemical composition and physical properties vary greatly, which can have an impact on the final mixtures’ properties. This work assesses key chemical properties of crude palm oil and two of its solid by-products to understand their rejuvenation effect on a blend of a virgin and an aged RAP asphalt binder. The evaluation included thermogravimetry analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and chromatography analysis. Besides, surface free energy measurements (SFE) on the recycled binder blends (i.e., virgin asphalt binder, RAP asphalt binder and rejuvenator) and of two aggregate sources were used to evaluate the impact of the palm oils in the adhesive bonds’ quality and moisture sensitivity of the recycled binder blends-aggregates systems. Results indicate that the palm oil materials have good thermal stability and contain several large molecular size (LMS) compounds that contribute to the rejuvenation effect. Besides, recycled binder blends produced with the palm oil materials developed strong adhesive bonds in dry and wet conditions. Overall, results highlight the potential of palm oil and its solid by-products as rejuvenators for high RAP content asphalt mixtures.