February 16, 2009
www.acppubs.com
An Associated Construction Publication serving California and Hawaii since 1893
Death Valley California
Chip Seal Test
L.A.’s Miracle Mile
Construction
FOCUS:
Asphalt
Death Valley
California Chip
Seal Test
Chip sealing a narrow, winding road in Death Valley, CA, contributes info to
Federal Highway Administration study of polymer-modified asphalt emulsions
By Paul Fournier
t’s a safe bet the drivers of the stonefilled semis were not thinking about
the engineering significance of
the job as they focused on not letting their trailers jackknife and
become airborne over the edge of the
steep mountain pass.
“I told the drivers they needed good
Jake Brakes, and that whatever gear
they went up the hill with, to drop
a gear on the way down,” said Jeff
Wilmot, chief operations officer of
Hardrives Construction Inc. Wilmot
was overseeing the chip sealing of
some 21 miles of Badwater Road in
Death Valley National Park under a
contract with Federal Lands Highway
(FLH) Division, the road-building
arm of the Federal Highway Administration (FWHA).
Hardrives’ contract is one of four
pavement preservation surface treatment projects in California and Utah
that FLH is gathering data from as part
of a federal “White Paper” study on the
use of polymer-modified asphalt emulsions (PME).
Filling A Knowledge Gap
Results of the study, which is being
conducted by the National Center for
Pavement Preservation (NCPP) under a
contract with FHWA and the FLH division, are expected to help transportation
officials choose appropriate pavement
surface treatments. Although PME are
increasingly being used to boost the effectiveness of such treatments as chip
sealing and micro surfacing, until now
little information has been collected in
one place on the proper use, application techniques and benefits of PME in
thin surface treatments. The study aims
to rectify this, with one objective being
the preparation of an FHWA-FLH Division manual that will include current
best practices, model test methods and
specifications, and recommendations
for PME use application.
According to Michael Voth, pavement
and materials technical leader for FLH,
the jobs – located in California’s Death
Valley National Park, Dinosaur National Park in Colorado/Utah, and four additional national parks in Utah – were
selected because they provided a broad
An Etnyre asphalt distributor climbs
a hill while applying a generous amount of
polymer-modified asphalt emulsion
to the road. (Photo: Barchfeld Photography)
The chip spreader closely follows the asphalt
emulsion distributor, spreading stone at
the rate of 22 pounds per square yard.
(Photo: Barchfeld Photography)
range of conditions: varying climate,
different aggregate suppliers, diverse
emulsion suppliers, different contractors, and even varying levels of traffic.
Stepping Up To The Plate
An important role in the study has
been assumed by industry, said Voth.
“Private industry has been a very good
partner with us in this effort,” Voth
said, referring to both pro bono and atcost laboratory work provided by the
private sector.
He explained that samples of aggregate and emulsions from the projects
have been sent to three laboratories –
BASF Corporation, PRI Asphalt Technologies Inc., and Paragon Technical
Services Inc. – for testing and analyses. BASF Corporation is funding the
material testing, in conjunction with
NCPP. Chris Lubbers, senior technical
service engineer for BASF, is conducting tests at the company’s laboratory in
Charlotte, NC.
“The labs are running conventional
tests plus some proposed new tests for
the study,” said Lubbers. “We’re trying
to get away from strictly relying on the
old tests and methods. For example,
we’ll be trying to validate low temperature recovery of asphalt emulsion
residue.” Currently, standard methods
used to recover asphalt residue require
heating samples to much higher temperatures than those experienced in the
field. Lubbers said it would be preferable to be able to test polymer-modified
emulsion residue that had been recovered at temperatures typically experienced by surface treatment systems.
Target: Performance Specs
FLH’s Voth pointed out that one of
the objectives is to see if testing of the
same materials by independent labs
will produce similar, reproducible
and predictable results. Furthermore,
the agency will monitor project pavements for a couple of years following
completion, checking such characteristics as roughness, cracking and rutting,
among others.
Voth said results of lab tests on materials would be compared with observations of actual field performance of
pavement preservation treatments over a
period of time. Hopefully this will help
engineers to predict field performance
based on the use of specific types and
quantities of materials for given application methods. This could lead to the
establishment of performance specifications for pavement preservation surface treatments involving PME.
Perilous Passage
While data collected from selected
projects for the study is expected to
have major ramifications for those planning and designing pavement preservation treatments, the immediate concern
of Hardrives’ truckers and equipment
operators on the Death Valley project
was safely negotiating Badwater Road
as they performed their work.
Sometimes broad and level, sometimes steep, narrow and winding, Badwater Road stretches from the southeast
corner of Death Valley National Park
about 50 miles northward to the intersection with Route 190 near the Furnace Creek Visitor Center. The section
being chip sealed began at Mormon
Point, one of the lowest points in the
U.S. at 260 feet below sea level, not
far from the lowest, Badwater Basin,
which boasts an elevation of -282 feet.
From this low-lying beginning, the
project climbed arduously southward
to a few miles past Jubilee Pass, stopping at elevation 1,735 feet.
But this wasn’t actually the end of
the challenge for the project’s truckers.
“The stone chips were hauled from
Nevada, and the only place large
enough for a stockpile was near Salsberry Pass,” Wilmot said. According to
the Park’s official map, Salsberry Pass
is located approximately five miles beyond the project limit at a point on Badwater Road about 3,300 feet above sea
level, or 3,600 feet above the job’s starting point. And this significant difference in elevation led to white-knuckle
trips for truck drivers heading down the
precipitous 20-foot-wide mountain pass
towing 30 tons of stone chips.
Many of the roads in Death Valley
and other national parks were built in
the 1930s and essentially followed the
existing terrain. Wilmot said Hardrives
has worked in at least 50 national parks
and national monuments for Federal
Lands, and they have found that the
agency likes to keep the roads as natural as possible, which means many of
them are very steep. “That’s why we
use an all-wheel-drive Etnyre QUAD
chip spreader for the jobs,” he added.
Not A Summertime Job
Chip sealing got under way on
November 11 during Death Valley’s winter, a period running from
Death Valley Chip Seal Test
November through March with daytime temperatures mostly between 65
and 80 degrees Fahrenheit. Trying to
perform road work during summer can
be perilous in Death Valley, which has
the hottest and driest climate in North
America. In summer, daytime highs
average 120 degrees, and the highest
temperature ever recorded in the Western Hemisphere occurred there in July
1913 when it soared to 134 degrees.
What’s more, the highest ground temperature was recorded there in July
1972 when it soared to 201 degrees
Fahrenheit – hot enough to cook an egg
on the pavement.
Large Chips, Generous PME
Wilmot fielded a crew of 24 to do
the job, which totaled about 253,000
square yards. The crew labored under
a tight schedule, limited by contract
to working days between 9 a.m. and
4 p.m. In addition to chip sealing the
road, they had to sweep it and haul
A Roscoe 15-ton pneumatic roller provides
compaction. (Photo: Barchfeld Photography)
away the stone sweepings, and then
follow up with an asphalt fog seal.
Workers applied about 425 tons of
CRS-2 latex-modified asphalt emulsion, supplied by Western Emulsions’
Irwindale, CA, plant, at the rate of
0.4 gallons per square yard. The latex
was a styrene-butadiene-rubber (SBR)
product. An even higher rate, about
0.42 gallons per square yard, was used
where existing pavement was more
oxidized or had recently undergone
patching or overlay.
Application rates were generous
according to Wilmot. “Federal Lands
likes large chips – in this case up to
30 percent retained on a 3/8 sieve, so
it takes more emulsion,” he said. The
contractor spread stone chips, supplied by Wulfenstein Construction of
Pahrump, NV, at an average rate of
22 pounds per square yard. For compaction they used two Roscoe 15ton pneumatic rollers and a Dynapac
pneumatic roller.
Preserved Road
And Useful Data
Despite the challenges of steep
grades, narrow roadway and restricted
working hours, Hardrives completed
the project in just five days.
Not only does this project ensure
that the pavement, which was showing
signs of distress, will be preserved for
an estimated eight years before requiring another treatment, it is providing
valuable information that will lead to
long-term improvements in the planning and design of pavement preservation treatments utilizing PME. ■
Editor’s Note: Freelance writer Paul
Fournier is former editor of New England Construction, an Associated Construction Publications (ACP) magazine
– [email protected].
Reprinted from the
February 16, 2009 issue of
CALIFORNIA BUILDER & ENGINEER