- [Narrator] The Texas Department of Transportation
allows the use of reclaimed asphalt pavement,
known as RAP, in pavement surfaces
to conserve natural resources and save costs.
A big unknown has been the contribution of RAP
to pavement and wet weather skid resistance,
which is critical for public safety.
Researchers at the Texas A&M Transportation Institute
have developed guidelines on how to identify good RAP
and use it in a mixed design
that has adequate skid resistance.
- TxDOT needed to know
how this use impacts the skid resistance
of the pavement surface.
- The SAC is the,
the full name is Service Aggregate Classification.
That's in TxDOT, a specification.
They use this to divide the aggregate
into different categories.
SAC A aggregate is more crushed faces,
is not as smooth as like round stones.
So these stones,
usually, we will use high skid-resistant pavement.
SAC B is smoother and more round,
and maybe even more soft.
So, this cannot use directly in the payment
with high traffic volume or high traffic speed
because the skid resistance maybe not that high.
- [Emmanuel] Considering the increased use
of SAC A aggregates in Texas in recent years,
using RAP promotes sustainability.
By reusing aggregates that would help conserve
the limited supply of virgin SAC A aggregates in Texas.
- [Sheng] We fabricated the aggregate ring specimens.
The specimens was arranged like a ring, like a circle shape
and then we can use dynamic friction test
to measure the skid resistance of this aggregate.
Second task.
We identify test sections and connect all the information
like pixel design information, the skid number information,
and then we also measure the skid resistance
and the texture using the Dyna Friction Tester
and the laser equipment.
Also, we duplicate the mixture in the lab
based on the mixer information.
We can make mixture slab in the lab
and also perform all these tests
like the skid resistant tests and the texture test.
For the third task, we designed more than 20 mixtures.
These mixtures have different RAP types,
different RAP percentages
and different aggregate quotations.
Then we evaluate all the aggregates
and all the mixture slabs
in terms of skid resistant and texture.
Based on that, we develop the relationship
between the aggregate and the mixture
and then we propose the thresholds and the criteria.
- Guidelines were developed that would be useful
in identifying good SAC A RAP.
By using RAP, we would promote sustainability
because we would be basically reusing aggregates
and conserve the state's limited supply
of virgin SAC A aggregates.
And, you know, we show ourselves as being a good steward
of the state's natural resources.
- [Narrator] For more information
and to find the publications for this project,
please visit the TxDOT research library
at the link shown below.