Texas Asphalt - Fall 2017 - 27

Interchange after reconstruction
(circa 2001).

All this combined to cause concerns
about the initial plan to put down
a two  inch concrete overlay as the
road surface.
"I got to worrying that, with this much
flexing and movement, if you put a concrete overlay on there, it's not going to
bond," Kight said. "And with that flexing
and bending, the concrete surface overlay
is going to crack up. Then in the winter,
when rains gets into cracks and freezes, the
surface disintegrates. Unless these decks
were surgically clean, it's not going to bond
to start with."
He said tests on a cross section also
showed the thickness of the concrete
overlay did not match the planned design
specifications and varied from as thin as
one inch toward one edge to around four
inches on the opposite edge.
So the decision was made to go instead
with a flexible, yet tough hot asphalt mix.
This mix would feature a high-stiffness

AC 40 binder, instead of the standard AC
20, for better strength and durability.
In another move intended to produce a
stronger road with a longer life cycle,
TxDOT opted for a heavier trap rock aggregate in the mix, instead of the limestone
aggregate typically used on road projects
in the San Antonio area. Transporting the
heavier trap rock would add costs to the
project, but the harder aggregate would
make the riding surface more resistant
to wear and skidding and provide for a
longer life cycle.
Before the asphalt was put down, a seal
coat consisting of a rubber modified asphalt
and Grade 3 aggregate was applied to aid
in the bond between the bridge and the
hot mix surfacing. In the late 1980s, Frank
Jaster had just started as an engineer in the
TxDOT district lab. One of his first tasks in
that job was to go into the lab and design
the asphalt mix with the strength and durability Kight wanted.
"This was definitely a unique mix,"
Jaster said. "They put some thought into
it. It was specialized and they decided to
use a better aggregate and a better quality binder to hold everything together.
They wanted something that would be
flexible and tough. Those were basically
our instructions at the district lab, 'we're
going to use these products right here
and we need to make this thing get the

optimal gradation of the aggregate and
the optimal asphalt content.'"
David Fuller oversaw the original
paving project for contractor Austin
Bridge & Road.
Fuller recalled that the "unique" segmental design led to a more unique approach
to the resurfacing, including the decision
to use a trap rock aggregate not as readily
available in that part of the state. Twentyfive to 30 years later, Fuller noted that the
pavement on the "Downtown Y" is "still
holding up and doing pretty good."
Jaster pointed out that asphalt mix "performed for decades" before the IH 35 leg of
it needed resurfacing. He said IH 10 still
has not required a milling and overlay project. When you drive along that stretch, the
trap rock aggregate still looks "black like it
was when it was originally placed."
"That's one of the good things about
this," Kight said. Not only has that lowered
the overall life span costs of operations, but
it also has helped with safety, not being
out there in traffic trying to do milling or
overlays. Because we have such high volumes of traffic on these roadways, safety
is of prime importance and this asphalt mix
has contributed to long-term safety and
has proven to be very cost effective. ✪
Photos were provided by Brian Purcell (Texas
Highway Man) of http://texashighwayman.com

Bane Machinery is proud to offer comfort,
visibility and uptime with Dynapac
road construction equipment.


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Texas Asphalt Magazine FALL 2017
31/07/17 27
10:38 pm

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Table of Contents for the Digital Edition of Texas Asphalt - Fall 2017

President’s Message
Associate Member Forum
The Major’s Perspective
TXAPA Scholarship Program Changes Produce Big Results
Partnering Opportunities for Quality
San Antonio Downtown Y Stands the Test of Time
The Pros and Cons of Expectations
U.S. Polyco
HMA Labs
Calendar of Events
New Members
Products & Services Marketplace
Advertisers Index
Texas Asphalt - Fall 2017 - Intro
Texas Asphalt - Fall 2017 - cover1
Texas Asphalt - Fall 2017 - cover2
Texas Asphalt - Fall 2017 - 3
Texas Asphalt - Fall 2017 - 4
Texas Asphalt - Fall 2017 - 5
Texas Asphalt - Fall 2017 - 6
Texas Asphalt - Fall 2017 - President’s Message
Texas Asphalt - Fall 2017 - 8
Texas Asphalt - Fall 2017 - NAPA
Texas Asphalt - Fall 2017 - 10
Texas Asphalt - Fall 2017 - Associate Member Forum
Texas Asphalt - Fall 2017 - 12
Texas Asphalt - Fall 2017 - The Major’s Perspective
Texas Asphalt - Fall 2017 - 14
Texas Asphalt - Fall 2017 - TXAPA Scholarship Program Changes Produce Big Results
Texas Asphalt - Fall 2017 - 16
Texas Asphalt - Fall 2017 - 17
Texas Asphalt - Fall 2017 - 18
Texas Asphalt - Fall 2017 - 19
Texas Asphalt - Fall 2017 - 20
Texas Asphalt - Fall 2017 - Partnering Opportunities for Quality
Texas Asphalt - Fall 2017 - 22
Texas Asphalt - Fall 2017 - 23
Texas Asphalt - Fall 2017 - 24
Texas Asphalt - Fall 2017 - 25
Texas Asphalt - Fall 2017 - San Antonio Downtown Y Stands the Test of Time
Texas Asphalt - Fall 2017 - 27
Texas Asphalt - Fall 2017 - The Pros and Cons of Expectations
Texas Asphalt - Fall 2017 - 29
Texas Asphalt - Fall 2017 - 30
Texas Asphalt - Fall 2017 - 31
Texas Asphalt - Fall 2017 - 32
Texas Asphalt - Fall 2017 - U.S. Polyco
Texas Asphalt - Fall 2017 - 34
Texas Asphalt - Fall 2017 - HMA Labs
Texas Asphalt - Fall 2017 - 36
Texas Asphalt - Fall 2017 - Calendar of Events
Texas Asphalt - Fall 2017 - 38
Texas Asphalt - Fall 2017 - New Members
Texas Asphalt - Fall 2017 - Products & Services Marketplace
Texas Asphalt - Fall 2017 - 41
Texas Asphalt - Fall 2017 - 42
Texas Asphalt - Fall 2017 - Advertisers Index
Texas Asphalt - Fall 2017 - 44
Texas Asphalt - Fall 2017 - 45
Texas Asphalt - Fall 2017 - 46
Texas Asphalt - Fall 2017 - cover3
Texas Asphalt - Fall 2017 - cover4