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(suspenseful music)
(screen whooshing)

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- [Narrator] Seal coats on roadways

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cost the Texas Department
of Transportation

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over $250 million annually.

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Researchers with the Texas
A&M Transportation Institute

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worked with TxDOT

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to develop guidelines
for selecting projects

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with multiple seal coat layers

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for better performing pavement sections

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and to improve costs over
the lifecycle of the coats.

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- So seal coats are preventive
maintenance treatment

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that TxDOT tends to use
about every seven years

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on roads that are structurally sound.

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And so over time on roads that are good,

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as you maintain them,

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you continue to add layers of seal coat.

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And we've seen some problems with shoving,

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in intersections, mainly,

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that's where you start to see it first,

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in curves, you'll see some shoving.

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And the question becomes,

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when does these multiple layers

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of seal coat become unstable,

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and how many layers can you have?

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- Yeah, so the key finding
in this project is that

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we think that there is a
maximum number of seal coats.

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It's not a magic number of three or four.

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There's a lot of factors
that play into this

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based on traffic loading.

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And so what we determined

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was we were trying to find some testing

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that could help us determine

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when we're reaching that threshold.

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The contributing factor in this research

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was to help us identify

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what testing was available to narrow down

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that max number.

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- We did a

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visual inspection of the roadway.

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We did a video.

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We collected texture measurements.

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That's what we did in
the field and in the lab.

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We actually made samples

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with multiple layers of seal
coat with different materials,

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and then we tested those
with different tests

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to look for stability.

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- The next step in this
project is implementation.

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It would be using the tools
developed in the research

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as a toolbox to determine

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when we're reaching that max level

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as accumulation of seal coats

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and what the next step should be,

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whether that is doing a seal
coat, a rehab, or an overlay.

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- A lot of what we do when
we build a seal coat, right,

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we're building a road in the weather.

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We're not manufacturing it,

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and so we don't have as tight of controls.

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So when you have to build
something in the weather

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and under traffic in the roadway,

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there's always a risk

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of having a lot of things influence

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the quality of the construction.

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That's why we wanna look
at the best practices

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on ways to mitigate or
minimize these problems.

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- [Narrator] For more information

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and to find the publication
for this project,

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please visit the TxDOT research library

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at the link shown below.