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Because the freeze-thaw cycle damages the stones, Soliman notes that in
order to create a well-performing asphalt mix, there needs to be solid interlock
between the largest stones and the asphalt binder.
He says the larger stones break or crack into smaller pieces, which forms
loose gravel on the surface and deteriorates the strength of roads.
Is there a perfect mix of asphalt that can hold up to the ever-fluctuating
weather on the prairies?
Soliman and Alawneh are using the Canadian Light Source (CLS) synchrotron
as part of their study. The CLS is a source of light that scientists
use to gather information about the structural and chemical properties of
materials at the molecular level. It’s similar to a CT scan, though on a much
higher scale and with a significantly stronger resolution.
By testing asphalt core samples, Soliman and Alawneh can find what
happens inside the asphalt during a freeze-thaw period. They’re able to
see aggregate particles cracking or breaking during freezing, as well as
the separation between materials and aggregate particles due to freezing
and thawing.
Another factor in this study is water – precipitation, melted snow and ice
– and how it impacts asphalt mixes. When water creeps inside the asphalt
and freezes, it stresses the mix and can accelerate damage.
“By using this facility here, we’ll be able to understand what happened
inside the mix, how this mix will change, or how the internal structural will
change after exposing that material to freezing conditions,” said Soliman.
Soliman and Alawneh also are studying whether incorporating more recycled
materials to the asphalt mix would help or hinder the strength of the
road. Recycled material from old roads has been repurposed in new road
construction projects, but they are also looking at material like used asphalt
shingles and plastic waste.
This study is already two years in the making and once it’s completed,
Soliman and Alawneh plan to share their findings with anyone associated
with road building in Canada.
“If (Saskatchewan Heavy Construction Association) members want to
investigate using a new mix or new design or new product, we can help
them assess it before they move forward and use it on the road,” said
Soliman. “Pavement projects are large investments – multimillion-dollar
projects – so you don’t want to take a risk and do something new without
understanding or without having good information on what could happen
to it in the future.”
FEATURE
“The main idea of this
research is to understand the
mechanism of the freezethaw
damage. We need to
know which components of
the mix contribute more to
the freeze-thaw damage to
be able to modify our mixes
to have better performance
in those conditions.”
– Haithem Soliman, University of
Saskatchewan Engineering
20 | Quarter 2 2020 | saskheavy.ca
/Asphalt
/saskheavy.ca
