ASPHALTopics | Summer 2014 | VOL 27 | NO3

For approximately 30 years, Vacuum Tower
Asphalt Extenders (VTAEs) have been blended
as part of asphalt binders and, until recently,
no adverse effects on pavement performance
have been reported. Also known as Re-fined
Vacuum Tower Bottoms (RVTBs), Re-fined
Engine Oil Bottoms (REOB), Waste Engine
Oil Residue (WEOR), and asphalt flux, the
asphalt additive has recently come under fire. Some
research has suggested that binders have been mixed
with 15% to 30% VTAE, while the industry standard
is generally to incorporate less than 10% of VTAE.
Conflicting research has led to confusion and misinformation
about the use of this additive in HMA mixes
and the performance in the field.
“In the last six months, the use of VTAE has become
a very hot topic and there is a lot of poor information
circulating in the industry,” says Gerald Huber, Associate
Director of Research for Heritage Research Group in
Indianapolis. “There’s an impression that used motor
oil is being poured into mixes, and that it’s a waste
product, which isn’t accurate. Some researchers are
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conducting tests and saying that it performs fine; while
others are doing non-standard tests and saying that the
additive creates problems. A lot of rumours are flying
around, with many people not really knowing that VTAE is.”
VTAE is what remains from the distillation of used
motor oil. The used oil is recycled at refineries, where
it undergoes a multiple-stage distillation process to
return the material to a base oil. VTAE, a co-product
of the refining process, is a thick hydrocarbon substance
with properties that have been shown to improve the
performance of asphalt binder. VTAE contains iron and
other metals from a vehicle’s engine. The material also
contains phosphorous and zinc from viscosity enhancers
and anti-friction polymers, which are present in the engine
oil. Elevated levels of zinc in an asphalt binder, which
do not occur naturally in crude oil, is used as one of the
markers to reveal that VTAE is present.
In response to conflicting research results on VTAE,
Heritage Research Group conducted a study for the
Illinois Department of Transportation last spring and
presented a paper on the research at CTAA in November.
The study compared the properties of a Superpave
binder grade of PG 58-28 that was
formulated with nine per cent of
VTAE, as well as another PG 58-28
formulated without VTAE. A thorough
set of binder testing, including
Superpave PG Binder Testing, X-Ray
Fluorescence, Polycyclic Aromatic
Compound (PAC) content, gel
permeation chromatography (GPC)
and thermogravimetric analysis (TGA)
was performed to compare the effects
of blending VTAE on binder grading,
chemical composition, environmental
impact, and compatibility of VTAE
with asphalt binder.
A second portion of the study,
comparing the mixture performance
of HMA both with neat PG 58-28 and
PG 58-28 containing VTAE, provided
volumetric analysis and examined
resistance to moisture damage,
resistance to rutting, mixture stiffness
and fatigue resistance. The mixtures
also underwent an environmental
assessment using leachate testing.
The results of the study show that
asphalt binders, with and without
VTAE, age at a similar rate and ››