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- [Narrator] In several TxDOT districts,
asphalt binders used in chip seal construction
are required to contain a specific percentage
of tire rubber.
Testing for tire rubber content can be done
in the materials and test division lab
using x-ray fluorescence technology,
but the Texas Department of Transportation
and researchers with the Center for Transportation Research
want to bring XRF testing to the job site.
- The current process requires the district to take a sample
and send it to MTD.
MTD can run the test,
the x-ray fluorescence test
and then give the district the results.
That requires a time lag.
- We've been measuring it here at MTD
for quality assurance samples,
quality that those are supplier samples
and for project samples.
However, by the time we get the sample
and get the testing done, in some cases,
if it's a seal coat project, the project is done.
So that was the intent is to give the district the tools
to be able to run the test as soon as possible.
- These x-ray fluorescence guns are portable,
so you can either have them in the district lab
or if you want to, you can take it out on the job site
on the side of the road and get a sample
from the distributor or the tanker truck
and then in a couple of minutes, you can run the gun
and get the answer.
You get on the side of the road
before anybody actually even sprayed
any of the asphalt on the ground
to ensure that you had the right tire rubber content.
- First, we purchased three different,
new equipment
to distribute the three district labs
and a lot of training happened
in the district facilities,
trained them how to use the equipment
and it also included looking into
using the equipment in the field.
- We created a spreadsheet.
It's a global spreadsheet for all of the guns
that we bought, so a person doesn't have
to generate calibration curves.
They're all in the spreadsheet already.
All a person has to do is perform the analysis,
take the results from the gun and plug it into a spreadsheet
where they have chosen their specific gun
and their specific supplier and binder
and it tells 'em what the tire rubber content is.
- Asphalts with tire rubber are typically charged
at a premium, so they are a little bit more expensive
'cause they're modified versus unmodified asphalts
and this gives us the tool to make sure,
if we're asking for 5%, are we getting 5%?
The bottom line is that we are able to apply the spec.
We're able to make sure that we're meeting the spec
and we're getting what we're asking for.
- [Narrator] For more information
and to find the publications for this project,
please visit the TxDOT research library
at the link shown below.