Pavement Preservation Journal - Summer 2017 - 32
IMAGE CREDIT: FP 2 INC.
he old saying that bituminous
pavements start out black,
and portland cement concrete
pavements start out white, but
both turn gray in the long run has merit
because it's true. Asphalt pavements lose
essential bituminous components as they
age, turning black to gray, while concrete
That loss of essential components is more
than a cosmetic issue; the characteristics
of an aged pavement are cracking, brittleness and loss of aggregate and oxidation,
which together will compromise service life
and pavement condition index number. For
pavements that are in fair but not deteriorating condition, maltene-based rejuvenators applied as an emulsion can constitute
the "right treatment, for the right road, at
the right time."
"When asphalt binder is exposed to
oxygen and the sun's ultraviolet rays, it
begins to age and oxidize," say Richard
Willis, Ph.D., and Nam H. Tran, Ph.D., P.E.,
National Center for Asphalt Technology,
in their article Rejuvenators Bring Back
Life to Aging Asphalt Pavements (Asphalt
Delegates examine absorption of
maltene-petroleum based rejuvenator
application at 2016 National Pavement
Preservation Conference demonstration
Pavement, July/August 2015). "The changes
that occur to asphalt binders are primarily due to the chemical composition of
These changes take place in both shortand long-term stages, they say. Short-term
aging is due mostly to the evaporation of
volatile hydrocarbon compounds from the
binder, oxidation or absorption of what they
call "oily" components during the heat of
production. Long-term aging takes place
once the pavement is in the field, and is
due to the reaction of asphalt components
and oxygen in the atmosphere.
"These aging processes leave binders
stiffer, less ductile, and with lower temperature susceptibility than conventional
paving grade asphalts," Willis and Tran say.
"The aging process reduces the ratio of oily
maltenes in the binder, leaving a greater
ratio of stiffer asphaltenes, which cause
the asphalt binder to become less ductile.
These viscosity and elasticity changes
result in a hardened, brittle asphalt binder."
MALTENES AND ASPHALTENES
The key to understanding how maltenebased rejuvenator emulsions work is knowledge of what maltenes and asphaltenes are.
"What's left after refining and distillation of crude oil are the heavy resins at
the bottom of the crude barrel, or asphalt,"
says Colin Durante, president, Pavement
Technology, Inc., Westlake, Ohio. "Asphalt
is sold and supplied based on its penetration or PG grading. In our industry we emulsify asphalt with water to make various
products that can be sprayed on pavements
to coat and protect them [fog or chip seals],
or blended with aggregates and placed as
[slurry and micro surfacings]."
True maltene-based rejuvenators are
different. "Consider asphalt binder,"
Durante says. "The binder (pen or PG
grade) will have heavy and black materials in it, called asphaltenes, and light oils
and resins called maltenes. The maltenebased rejuvenator, which is the only true
type of rejuvenator, is a blend of four
IMAGE CREDIT: METROPOLITAN GOVERNMENT
OF NASHVILLE-DAVIDSON COUNTY
Fountain of Youth: Asphalt Maltene
Rejuvenators Add Life to Pavements
Nashville has adopted the use of pavement
rejuvenators like Reclamite to protect
pavement that is three to five years old;
pink color typical until emulsion breaks
maltene fractions with no black color to
them, because it does not contain asphalt.
Unlike asphalt emulsions, which protect
and add binder to the surface, the maltene
emulsion rejuvenator penetrates into the
surface and combines with the weathered and oxidized asphalt binder holding
the aggregate. It softens it, or changes its
viscosity and durability."
Thus, the rejuvenator asphalt maltenebased emulsion penetrates and combines
with the asphalt binder in-depth, making
it sticky again so it can keep the aggregate
matrix together-the result of the rebalancing of the maltene distribution ratio.
"If you spray WD-40 on a rusted bolt,
it will break the surface tension and go
inside and loosen it," Durante said. "The
surfactant and wetting agents we put in
the rejuvenator/water mixture do the same
thing; they make the emulsion wetter,
so it can break the surface tension of a
pavement and get into the voids of the
"Once the rejuvenating oils are down
where you want them in the pavement," he
added, "the water evaporates, leaving the
maltene oils in the pavement. It's similar
to how an asphalt emulsion spreads the
asphalt on the surface, where the water
evaporates, leaving the asphalt film where
you want it."
Petroleum- or maltene-based rejuvenators aren't the only product being sold as
rejuvenators. "Recently, some proprietary
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