(gentle music)
- [Narrator] High performance concrete, or HPC,
has many applications in Texas,
including its use in bridge decks.
The durability of HPCs offers extra protection to bridges,
especially in areas where corrosion
from deicing salts can be an issue.
The Texas Department of Transportation
and researchers with the Texas A&M Transportation Institute
are working to develop new performance-based specifications
for high performance concrete
that will help ensure its long-term durability.
- TEX DOT use the mix design option one to five
and eight in item 421,
as in high performance concrete in bridge deck.
However, these mixes are originally developed
for alkali silica reaction mitigation,
and primarily focused on maintaining high strength
and with low water-cement ratio.
So high strength is the main criteria,
but that doesn't really define high performance concrete.
- So currently, TEX DOT requires prescriptive specifications
when we talk about high performance concrete requirements,
so there has been a move through industry nationwide
to go more of a performance-based type of specification,
and so this research was the attempt to develop
what those performance limits would be,
what tests we need to have the contractor focus on
to determine whether that mix design
is going to be considered a high performance concrete
with these new criteria limits.
- In the major durability issues,
like alkali silicon reaction in concrete,
shrinkage in concrete, transport property,
the chloride durability, and freeze-thaw durability
are not addressed in the current options,
so we actually address these four major durability aspects
in this project.
The transport property, so what we did is a rapid
and reliable way to measure the concrete transport property.
We introduce resistivity, we improve that test,
we improve a better procedure to do formation factor
from resistivity, better transport property,
which leads to better way to do the chloride prediction
and increase the durability prediction.
And we also develop a Excel-based TEX DOT tool.
That tool allow you
to do the very rapid way of performance evaluation
during mixed design and trial batch stages.
- We're trying to help the contractor out as well,
so we're trying to help him to say
if you know some basic information about your materials,
you could input 'em into the tool and then it would tell you
we think these are going to meet,
so you could kind of selectively pick your mix designs
that you're gonna go send for testing.
- So basically, TEX DOT tool that we developed
as a performance specification,
it's going to help to test the common mix design practice
and see whether it is qualified as an HPC or not.
And if it is not, then the fine tuning
and improving recommendation will be provided.
- Those deicing salts do tend to corrode
or distress our bridges, so the idea
of making sure we have high performance concrete
in those regions is going to save us
in terms of a maintenance budget
and then delays for the traveling public as well,
and the life of the structure should extend as well, right?
So we're not gonna be replacing decks
because they're corroding or doing deck overlays.
We can now push maybe that activity out 10, 20 years further
because we have a better concrete
that was used to construct those.
- [Narrator] For more information
and to find the publications for this project,
please visit the TEX DOT Research library
at the link shown below.