Understanding the Limitations of Modifying Bitumen with Re-Refined Engine Oil Bottom (REOB)

Area of Science:

• Materials Science
• Chemical Engineering
• Pavement Engineering

Background:

• The bitumen market faces complexity from diverse crude sources and refining changes, impacting bitumen properties.
• Traditional testing methods like PEN grade may not detect modifications from additives such as Re-refined Engine Oil Bottoms (REOB).
• REOB, a byproduct of engine oil refining, is a potential modifier for bitumen, but its inconsistent nature poses challenges.

Purpose of the Study:

• To comprehensively compare European and North American REOB sources.
• To assess the effects of REOB on bitumen binder performance within a unified framework.
• To evaluate identification, stability, compatibility, ageing susceptibility, and low-temperature properties of REOB-modified bitumen.

Main Methods:

• Preparation of two REOB-modified bitumen series by blending 5, 10, and 15 wt.% REOB into hard grade bitumen.
• Assessment of REOB-modified binders through chemical identification, stability, compatibility, ageing, and low-temperature property tests.
• Rheological analysis to evaluate binder performance changes.

Main Results:

• Increased carbonyl formations and phase instability (saturates exudation) observed in REOB-modified bitumen.
• REOB softens bitumen, but ageing leads to significant stiffness increase.
• Low-temperature tests indicate REOB-modified bitumen is prone to brittle fracture, losing relaxation properties.

Conclusions:

• REOB is an inconsistent material with complex interactions with bitumen's molecular groups.
• REOB incorporation increases bitumen's susceptibility to ageing and phase instability.
• REOB-modified bitumen exhibits increased brittle fracture tendency, compromising low-temperature performance.