Asphalt Pavement Magazine - March/April 2018 - 8

President's Perspective

Stone Matrix Asphalt: The "Balanced" Mix
Fifteen years ago, I was a keynote speaker at
a conference on Stone Matrix Asphalt (SMA).
SMA was introduced to the U.S. following
the 1990 FHWA/AASHTO/NAPA European
asphalt study tour, and by 2002, the year
of the conference, several DOTs became
lead states in the use of this technology.
There was considerable activity and energy
focused on evaluating the product and its
implementation, including field trials and
completion of numerous research initiatives.
It seemed SMA was off and running.
The expectation expressed at that
time by FHWA, state DOTs, NCAT, and
NAPA was that SMA would become the
preferred premium surface for heavy duty,
high-traffic volume pavements such as
interstates. For example, Larry Michael,
who was with the Maryland State Highway
Administration, said: "It is without a doubt
the most tenacious mix I have seen. It is
almost impossible to make it rut, and will
outlast any other mix." Larry was not alone
in his support of this technology. The
promise of SMA - a longer lasting, durable
high-performance surface - is exactly what
the customer wants, and SMA is specifically
designed to maximize rut resistance and
durability - a truly "balanced" mixture.

SMA definition
Stone Matrix Asphalt (SMA) is a tough,
stable, rut-resistant mixture. The SMA
design concept relies on stone-on-stone
contact to provide strength and a rich
mortar binder to provide durability.
These objectives are usually achieved with
a gap-graded aggregate coupled with fiber
and/or polymer-modified, high asphalt
content matrix.
Over 25 years have passed since that
1990 study and, apart from a handful of
states that have successfully implemented
SMA, SMA has not become the widespread,
national surface mix of choice for hightraffic volume applications. So what may
have stalled the nationwide use of SMA? Did
we lose interest in SMA, or did the high cost
of liquid AC and polymer in 2008/2009 and
shrinking highway budgets relegate SMA to
an expensive tool in the tool box? Perhaps

the introduction of warm mix technology
into U.S. markets in 2004 shifted the focus
away from SMA? And what about those key
states that use and have used SMA for over
a quarter of a century? What lessons can
we learn from states that have successfully
adopted the technology? They report SMA
pavement service lives greater than 25 years.
And, how about our partners in Europe,
especially Germany? Does it continue to be
the material of choice for the autobahns, and
has the technology changed?
The answer to these and many other
questions will be presented at NAPA's
1st International Conference on SMA,
co-sponsored by the Transportation
Research Board, in Atlanta, Ga., Nov. 5-7.
Agencies and industry will share case
studies and best practices that highlight
producing and constructing a mixture with
high value and performance capabilities.
SMA is not only a premium asphalt
pavement, but it is an engineered mixture
worthy of a fresh look and an intensive
discourse, especially given that dedicated
freight corridors, i.e. Critical Commerce
Corridors, are a fast approaching reality.
Academia will provide insight into how
SMA can continue to evolve through
material choices such as reclaimed asphalt
pavement, polymer modifiers, recycled
tire rubber, fibers, and careful aggregate
selection. Specifiers and producers will
discover enhanced mixture characteristics
in terms of life-cycle cost, performance, and
sustainability. Those who have never used
SMA will gain a new understanding of what
it means to specify, produce, and construct
SMA using today's technology.
NAPA, in partnership with FHWA, has
not hosted an international conference since
the International WMA conference of 2011.
Thus, this is a rare instance where agencies,
industries, and academia from around the
world have the opportunity to come together
for two-and-a-half days and focus their
efforts on a singular product such as SMA.
Please plan to join us at this conference.
I am excited to see what unfolds and am
confident that we will discover new ways
to deliver a truly balanced mix that exceeds
expectations. AP

8 * View past issues online at www.naylornetwork.com/nap-nxt

By Mike Acott,
NAPA President

SMA is not only a
premium asphalt
pavement, but it
is an engineered
mixture worthy
of a fresh look
and an intensive
discourse,
especially given
that dedicated
freight corridors,
i.e. Critical
Commerce
Corridors, are a
fast-approaching
reality


http://www.naylornetwork.com/nap-nxt

Table of Contents for the Digital Edition of Asphalt Pavement Magazine - March/April 2018

President’s Perspective
Industry News
Tools for the Trade
Meet the Chairman: Craig Parker
How to Host an Effective Congressional Site Tour
Quality in Construction: The Sheldon G. Hayes Award
Quality in Construction: The Larry H. Lemon Awards
Quality in Construction: The Ray Brown Airport Award
NAPA Quality in Construction Awards
Industry Calendar
Index of Advertisers / Advertisers.com
Perspectives
Asphalt Pavement Magazine - March/April 2018 - Intro
Asphalt Pavement Magazine - March/April 2018 - cover1
Asphalt Pavement Magazine - March/April 2018 - cover2
Asphalt Pavement Magazine - March/April 2018 - 3
Asphalt Pavement Magazine - March/April 2018 - 4
Asphalt Pavement Magazine - March/April 2018 - 5
Asphalt Pavement Magazine - March/April 2018 - 6
Asphalt Pavement Magazine - March/April 2018 - 7
Asphalt Pavement Magazine - March/April 2018 - President’s Perspective
Asphalt Pavement Magazine - March/April 2018 - 9
Asphalt Pavement Magazine - March/April 2018 - 10
Asphalt Pavement Magazine - March/April 2018 - Industry News
Asphalt Pavement Magazine - March/April 2018 - 12
Asphalt Pavement Magazine - March/April 2018 - 13
Asphalt Pavement Magazine - March/April 2018 - 14
Asphalt Pavement Magazine - March/April 2018 - 15
Asphalt Pavement Magazine - March/April 2018 - Tools for the Trade
Asphalt Pavement Magazine - March/April 2018 - 17
Asphalt Pavement Magazine - March/April 2018 - Meet the Chairman: Craig Parker
Asphalt Pavement Magazine - March/April 2018 - 19
Asphalt Pavement Magazine - March/April 2018 - 20
Asphalt Pavement Magazine - March/April 2018 - 21
Asphalt Pavement Magazine - March/April 2018 - How to Host an Effective Congressional Site Tour
Asphalt Pavement Magazine - March/April 2018 - 23
Asphalt Pavement Magazine - March/April 2018 - 24
Asphalt Pavement Magazine - March/April 2018 - 25
Asphalt Pavement Magazine - March/April 2018 - Quality in Construction: The Sheldon G. Hayes Award
Asphalt Pavement Magazine - March/April 2018 - 27
Asphalt Pavement Magazine - March/April 2018 - 28
Asphalt Pavement Magazine - March/April 2018 - 29
Asphalt Pavement Magazine - March/April 2018 - 30
Asphalt Pavement Magazine - March/April 2018 - 31
Asphalt Pavement Magazine - March/April 2018 - 32
Asphalt Pavement Magazine - March/April 2018 - 33
Asphalt Pavement Magazine - March/April 2018 - 34
Asphalt Pavement Magazine - March/April 2018 - 35
Asphalt Pavement Magazine - March/April 2018 - 36
Asphalt Pavement Magazine - March/April 2018 - 37
Asphalt Pavement Magazine - March/April 2018 - 38
Asphalt Pavement Magazine - March/April 2018 - 39
Asphalt Pavement Magazine - March/April 2018 - Quality in Construction: The Larry H. Lemon Awards
Asphalt Pavement Magazine - March/April 2018 - 41
Asphalt Pavement Magazine - March/April 2018 - 42
Asphalt Pavement Magazine - March/April 2018 - 43
Asphalt Pavement Magazine - March/April 2018 - 44
Asphalt Pavement Magazine - March/April 2018 - 45
Asphalt Pavement Magazine - March/April 2018 - 46
Asphalt Pavement Magazine - March/April 2018 - 47
Asphalt Pavement Magazine - March/April 2018 - 48
Asphalt Pavement Magazine - March/April 2018 - 49
Asphalt Pavement Magazine - March/April 2018 - 50
Asphalt Pavement Magazine - March/April 2018 - 51
Asphalt Pavement Magazine - March/April 2018 - 52
Asphalt Pavement Magazine - March/April 2018 - 53
Asphalt Pavement Magazine - March/April 2018 - Quality in Construction: The Ray Brown Airport Award
Asphalt Pavement Magazine - March/April 2018 - 55
Asphalt Pavement Magazine - March/April 2018 - 56
Asphalt Pavement Magazine - March/April 2018 - 57
Asphalt Pavement Magazine - March/April 2018 - 58
Asphalt Pavement Magazine - March/April 2018 - 59
Asphalt Pavement Magazine - March/April 2018 - 60
Asphalt Pavement Magazine - March/April 2018 - 61
Asphalt Pavement Magazine - March/April 2018 - NAPA Quality in Construction Awards
Asphalt Pavement Magazine - March/April 2018 - 63
Asphalt Pavement Magazine - March/April 2018 - 64
Asphalt Pavement Magazine - March/April 2018 - 65
Asphalt Pavement Magazine - March/April 2018 - 66
Asphalt Pavement Magazine - March/April 2018 - Industry Calendar
Asphalt Pavement Magazine - March/April 2018 - Index of Advertisers / Advertisers.com
Asphalt Pavement Magazine - March/April 2018 - 69
Asphalt Pavement Magazine - March/April 2018 - Perspectives
Asphalt Pavement Magazine - March/April 2018 - cover3
Asphalt Pavement Magazine - March/April 2018 - cover4
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