(suspenseful music) (screen whooshing)
- [Narrator] Seal coats on roadways
cost the Texas Department of Transportation
over $250 million annually.
Researchers with the Texas A&M Transportation Institute
worked with TxDOT
to develop guidelines for selecting projects
with multiple seal coat layers
for better performing pavement sections
and to improve costs over the lifecycle of the coats.
- So seal coats are preventive maintenance treatment
that TxDOT tends to use about every seven years
on roads that are structurally sound.
And so over time on roads that are good,
as you maintain them,
you continue to add layers of seal coat.
And we've seen some problems with shoving,
in intersections, mainly,
that's where you start to see it first,
in curves, you'll see some shoving.
And the question becomes,
when does these multiple layers
of seal coat become unstable,
and how many layers can you have?
- Yeah, so the key finding in this project is that
we think that there is a maximum number of seal coats.
It's not a magic number of three or four.
There's a lot of factors that play into this
based on traffic loading.
And so what we determined
was we were trying to find some testing
that could help us determine
when we're reaching that threshold.
The contributing factor in this research
was to help us identify
what testing was available to narrow down
that max number.
- We did a
visual inspection of the roadway.
We did a video.
We collected texture measurements.
That's what we did in the field and in the lab.
We actually made samples
with multiple layers of seal coat with different materials,
and then we tested those with different tests
to look for stability.
- The next step in this project is implementation.
It would be using the tools developed in the research
as a toolbox to determine
when we're reaching that max level
as accumulation of seal coats
and what the next step should be,
whether that is doing a seal coat, a rehab, or an overlay.
- A lot of what we do when we build a seal coat, right,
we're building a road in the weather.
We're not manufacturing it,
and so we don't have as tight of controls.
So when you have to build something in the weather
and under traffic in the roadway,
there's always a risk
of having a lot of things influence
the quality of the construction.
That's why we wanna look at the best practices
on ways to mitigate or minimize these problems.
- [Narrator] For more information
and to find the publication for this project,
please visit the TxDOT research library
at the link shown below.