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When you drive down the road, you probably aren't thinking about the process of creating
that road and making sure it stays smooth and safe, but Stacy Williams is. She's conducting
research at the University of Arkansas that will help set a standard for warm mix asphalt,
a sustainably type of pavement that is more energy efficient and cost less than traditional
asphalt. Stacy Williams - Traditional hot mix asphalt
is produced at temperatures in the range of 330 to 350 degrees Fahrenheit. Where warm
mix asphalts can be produced at temperatures of 30, 50, even 100 degrees cooler and still
have the same compaction properties. Warm mix asphalt is produced using two methods:
additives, which are added to the binder to make it more workable at lower temperatures,
and a process called foaming, which mixes tiny bubbles into the binder to act as a lubricant.
Williams and her students test these methods to make sure that warm mix asphalt can save
money and energy and still perform as well as or better than traditional asphalt. To
compare the performance of warm mix and traditional asphalt, Williams and her students use machines
that simulate different road conditions. John Ryan - The highway department for Arkansas
needs regulations to tell contractors what is a good foamed warm mix design and what's
not. And so our research out here is really trying to figure out how we can make lab samples
mimic the effects of real life foamed asphalt and so we can correlate doing a lab to what
happens in real life. Stacey Williams - We can't, you know, obviously
bring in a giant, 10-ton roller into the lab even though that would be fun. We need to
have something on a smaller scale so test we can test it in the lab before we spend
our tax dollars to build twenty miles of it in the field and then find out later that
it didn't work. And so the compaction machines have a lot to do with the level of compaction
not only that happens during construction but also what will be seen over time.
We also have a wheel tracking test that tests for rutting and we sometimes refer to it as
the torture test. Worst case in our laboratory test is 50 degree Celsius, which is about
122 Fahrenheit, submerged in water, and then a steel wheel rolling back and forth on it,
so it has to endure a lot. But what we're really looking for here is what happens if
we soak a sample in hot water and we put it through a freeze-thaw cycle how well does
it hold up after that type of torture. So what we're looking at here is not so much
the traffic torture but the environmental torture that that mix will see when we go
from hot summers to cold winters. And I'd really like to see the connection of here's
an idea, here's what we can do with it in a lab, and now I get to see it on the roadway
out in the real world.