Tack Coat Technology
Tack coats have remained relatively unchanged for decades, but recent
innovations have put more attention on these asphalt emulsions
By Lisa Kopochinski
Although there haven’t been
great changes in tack coat
technology in the past de-cade,
the introduction of more sophisticated
paving equipment allows for higher pro-duction
rates, advanced paving mixtures,
and much more attention to be paid to tack
coats, their application and their impor-tance
in achieving pavement performance.
Essentially, the purpose of a tack coat is
to glue the new surface to the existing one
(typically asphalt or concrete). This pro-vides
an important bond between the two
layers that is critical in ensuring that the
various layers of pavement will work in uni-son.
It also provides some waterproofing by
sealing the two surfaces together, thus mini-mizing
the chance that water will penetrate
between the layers, which causes delamina-tion,
potholes and other road failures.
“Traditionally, tack coats consisted of hot
applied AC and cutbacks,” said Jeff Janssens,
sales and marketing representative for
McAsphalt Industries Ltd. “Cutbacks con-tain
a high amount of volatile compounds
and are not considered environmentally
friendly, and hot applied AC is more diffi-cult
to store and handle. Asphalt emulsion
tack coats replaced cutback and hot ap-plied
formulas, reducing environmental
impact and improving safety.”
Abdul Elkadri, technical marketing
manager at Colasphalt in Acheson, Alta.,
concurs.
“The most significant change is the shift
away from cutback asphalts, which is as-phalt
that has been cut (diluted) with a
solvent, such as kerosene,” he said. “This
process makes the asphalt liquid at ambi-ent
temperatures and allows you to spray
the product at temperatures far lower than
conventional asphalt. The solvents are then
released into the atmosphere and what is
left on the road is asphalt.”
These products are harmful for the envi-ronment,
so gradually there has been a shift
away from using cutbacks in pavement con-structions.
Recently, Environment Canada
released recommendations that limit the
use of these products even further.
“Surely, it won’t be long before these
types of products are banned completely,”
said Elkadri.
History and uses
Created in the early 1900s – largely for dust
control and pavement preservation proj-ects
– a tack coat is a spray application that
can significantly increase the strength and
fatigue life of pavements for a relatively eco-nomic
cost.
A tack coat can be used for nearly any
type of pavement application, such as pre-ventative
or corrective maintenance on
both asphalt and concrete pavements, sta-bilizing
and reclaiming bases, building
structural pavements and recycling worn
out pavement.
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