(air whooshing)
- [Narrator] Hot-mix cold-laid asphalt mixes
are used in maintenance applications
in many TxDOT districts across Texas.
Until now, these mixes were designed and tested
using a Texas Gyratory Compactor, or TGC.
The Texas Department of Transportation
and the Texas A&M Transportation Institute
are looking to phase out the use of the TGC
as well as update and streamline
the hot-mix cold-laid design procedure.
- [Travis] This research was predominantly looking
at switching our hot-mix cold-laid,
which is a maintenance style material,
from being designed on the Texas Gyratory Press
over to the Superpave Gyratory Press.
The TGC, the Texas Gyratory, has been around
since the late thirties.
In the early 2000s,
the Superpave was created based on the TGC,
and so we've had an effort for probably the past 20 years
to try to get all of our mixtures off of the TGC
and use the more automated SGC.
The hot-mix cold-laid is the last key to this puzzle
and 100% getting away from the TGC.
- When you change to Gyratory Compactor
from Texas Gyratory Compactor to Superpave,
and the performance test has to be changed as well.
So we have to find other performance tests
to replace the HVEEM Stability Test.
- [Travis] Typically with hot-mix cold-laid,
you have to run what we call a HVEEM Stabilometer.
And that's a four-inch diameter specimen, which is the TGC.
So when we go to the SGC, which is six-inch across,
what performance test do we run?
And so this was not only can we design it
on a different press,
but what test do we run instead of the HVEEM
since we now have a larger specimen
that wouldn't work with that older device?
- In the lab, we mold compacted tons of samples
in order to come up, you know,
the equivalent number of gyrations
for Superpave Gyratory Compactor,
and to give the similar aspect content
as usually they do through Texas Gyratory Compactor.
Again, we have to ensure the good performance.
That's why we identify the Cantabro Test
and IDEAL RT Test to ensure they are good
and better performance in the field.
- [Travis] So we have a mock specification
and test procedure for the design
on the Superpave Gyratory
and we have the IDEAL RT Test procedure.
I've actually already sent that
to our level two design committee,
so that represents all of the contractors in the state
that do hot-mix designs.
It's gonna be safer, it's gonna be less upkeep.
We're gonna be able to utilize equipment
that we're using on other hot-mix projects.
So really, we're just gonna be able to cut
half of our equipment inventory, from compactors, in half,
and then we're gonna get better, more repeatable results
between individuals.
- [Narrator] For more information
and to find the publications for this project,
please visit the TxDOT Research Library
at the link shown below.