Pavement Preservation Journal - Fall 2017 - 37

without tracking bond or tack coat onto
streets, sidewalks, parking lots and eventually into stores and offices.
Unrestricted traffic can often be
returned to the fresh surface within one
half hour, says spray jet paver manufacturer Roadtec Inc., adding these surface
treatments are effective on high-level
interstate highway pavements, as well as
neighborhood streets.
Commercial spray pavers include the
Roadtec SP-200e and the Vögele Super
1800-3i SprayJet. Like all spray pavers, the
SP-200e sprays tack and applies hot mix
asphalt seconds later. "Combining spraying and laydown produces a high-quality
mat with a strong bond between layers,"
the manufacturer says. "A spray bar just in
front of the paver's auger distributes the
liquid through computer-controlled, selfcleaning valves. An onboard microprocessor precisely controls the rate of flow.
Valves can also be controlled manually."
The SP-200e is used for thin-lift applications, but it can serve as a conventional
paver as well.
Because keeping forward movement is
important to mat quality and contractor
productivity, to cut down on refill stops, the
SP-200e is equipped with a 2,100 gallon
emulsion tank, the largest tank available
on the market today, Roadtec says.

IMAGE CREDIT: ROADTEC INC.

SPRAY PAVING IN NAPA
Via a polymer modified emulsion bond coat
and ultrathin bonded wearing course, an
SP-200 spray paver preserved the Silverado
Trail, a scenic two-lane road that runs for

29 miles along the eastern edge of the Napa
Valley in northern California.
In the city of Napa, a 10-year-old asphalt
overlay on the road was showing signs of
wear over a 2.9-mile section. There was
minor cracking, some raveling, and a few
areas required full-depth asphalt patching.
But for the most part the road was in good
shape; it was structurally sound.
To preserve the road and extend its life,
and having good previous experience with
the process, Caltrans placed an ultrathin
bonded wearing course. Minimal milling
was required.
On the Silverado Trail, the Construction
Division of Telfer Oil, Martinez, Calif., used
the spray paver to place a heavily polymer modified emulsion at a rate of 0.17 to
0.20 gallon per square yard. "The emulsion
is similar to a PMCRS-2H emulsion, which
is a standard chip sealing emulsion," said
Karl Meyers, vice president and general
manager of Telfer Pavement Technologies
Construction Division, McClellan, Calif.
Immediately after the sprayed bond coat,
the paver placed a 7/8-in.-deep of opengraded hot mix made with PG 64-16 liquid
asphalt that was modified with crumb rubber. The target value for binder content was
8.5 percent, and the top-size aggregate in
the mix was 3/8-inch. It also contained a
small amount of sand.
Static compaction with two double-drum
rollers followed the paver. "You have to run
two rollers because you need to hit the
temperature range on compaction, which
is 180 to 280 degrees Fahrenheit," Meyers
said. "That thin lift behind the screed is

On Silverado Trail in Napa, Calif., asphalt emulsion bond coat is sprayed by Roadtec SP 200 spray
paver immediately in advance of screed placing asphalt rubber modified UTBWC

cooling fast, and you want to release the
road to traffic quickly. Plus, the paver is
moving at 70 to 100 feet per minute, so you
need to run two rollers behind."
The process has a number of advantages,
Meyers said. "You are not getting any tack
coat dragged around the city, you get an
outstanding bond with the hot mix, you
are forming a waterproof membrane, and
you can release the road quickly to traffic," he said.
"The open-graded mixture really reduces
the water splash in traffic," Meyers added.
"Another advantage is that when the emulsion wicks up into the hot mix asphalt,
it cools the pavement down right away.
So even though our Silverado Trail project
was done at night in high traffic, we were
able to release intersections to the public
in 15 minutes."
In addition to cost savings versus conventional mill-and-fill, the process saved
the time and traffic disruption that milland-fill would have required.
UTACS IN LAS VEGAS
In the Far West, the similar ultrathin
asphalt concrete surfacings (UTACS) are
gap-graded wearing courses, bonded to
the surface by a warm polymer modified
asphalt emulsion, followed immediately
by the hot, gap-graded, ultra-thin asphalt
concrete friction layer.
In Nevada, using a Vögele Super 1800-2
SJ spray paver, Las Vegas Paving Corp.
placed a 1 in.-deep UTACS, with almost
100 percent passing 1/2-in. with some
fines. For this project, warm polymer modified asphalt emulsion was being sprayed
directly ahead of the screed via spray bars
on each side of a spray jet paver at a rate
of 0.13 gal. per square yard.
"The emulsion is not unlike a prime or
tack coat, but it provides much more coverage," said Clark Webster, general superintendent, Las Vegas Paving. "And no one
can run on it. The spray paver places the
coat behind the wheels but ahead of the
material, so cars or our haul vehicles can't
drive over it and pick up the sticky, polymer
modified emulsion. It gives us the best of
both worlds; we are able to use a polymer
modified emulsion without having the mess
of tires tracking it everywhere."
The placement of emulsion spray is automated, and the system regulates percentages of emulsion applied, making it easy
Fall 2017 | PAVEMENT PRESERVATION JOURNAL

37



Table of Contents for the Digital Edition of Pavement Preservation Journal - Fall 2017

President's Message
FP2 Marks Silver Anniversary
ARRA, FP2 Preservation Proponents Assault Capitol Hill
Neglected Rural Roads Drag on Economy
Early NCAT Results Favor Preservation
Perservation Partnerships: Southeast PPP Ponders Early Treatment Failures; Midwest PPP Meets in Michigan
Texas Contractor Upgrades Performance
Asphalt Emulsion Bond Coats Optimize UTBO, Thinlay Performance
Student Studies Sustainable Chip Seals
Pavement Preservation Journal - Fall 2017 - Intro
Pavement Preservation Journal - Fall 2017 - cover1
Pavement Preservation Journal - Fall 2017 - cover2
Pavement Preservation Journal - Fall 2017 - 3
Pavement Preservation Journal - Fall 2017 - 4
Pavement Preservation Journal - Fall 2017 - 5
Pavement Preservation Journal - Fall 2017 - 6
Pavement Preservation Journal - Fall 2017 - 7
Pavement Preservation Journal - Fall 2017 - 8
Pavement Preservation Journal - Fall 2017 - President's Message
Pavement Preservation Journal - Fall 2017 - FP2 Marks Silver Anniversary
Pavement Preservation Journal - Fall 2017 - 11
Pavement Preservation Journal - Fall 2017 - 12
Pavement Preservation Journal - Fall 2017 - 13
Pavement Preservation Journal - Fall 2017 - 14
Pavement Preservation Journal - Fall 2017 - 15
Pavement Preservation Journal - Fall 2017 - 16
Pavement Preservation Journal - Fall 2017 - ARRA, FP2 Preservation Proponents Assault Capitol Hill
Pavement Preservation Journal - Fall 2017 - 18
Pavement Preservation Journal - Fall 2017 - 19
Pavement Preservation Journal - Fall 2017 - 20
Pavement Preservation Journal - Fall 2017 - 21
Pavement Preservation Journal - Fall 2017 - 22
Pavement Preservation Journal - Fall 2017 - Neglected Rural Roads Drag on Economy
Pavement Preservation Journal - Fall 2017 - 24
Pavement Preservation Journal - Fall 2017 - 25
Pavement Preservation Journal - Fall 2017 - 26
Pavement Preservation Journal - Fall 2017 - Early NCAT Results Favor Preservation
Pavement Preservation Journal - Fall 2017 - 28
Pavement Preservation Journal - Fall 2017 - Perservation Partnerships: Southeast PPP Ponders Early Treatment Failures; Midwest PPP Meets in Michigan
Pavement Preservation Journal - Fall 2017 - 30
Pavement Preservation Journal - Fall 2017 - 31
Pavement Preservation Journal - Fall 2017 - 32
Pavement Preservation Journal - Fall 2017 - Texas Contractor Upgrades Performance
Pavement Preservation Journal - Fall 2017 - Asphalt Emulsion Bond Coats Optimize UTBO, Thinlay Performance
Pavement Preservation Journal - Fall 2017 - 35
Pavement Preservation Journal - Fall 2017 - 36
Pavement Preservation Journal - Fall 2017 - 37
Pavement Preservation Journal - Fall 2017 - 38
Pavement Preservation Journal - Fall 2017 - 39
Pavement Preservation Journal - Fall 2017 - 40
Pavement Preservation Journal - Fall 2017 - 41
Pavement Preservation Journal - Fall 2017 - 42
Pavement Preservation Journal - Fall 2017 - Student Studies Sustainable Chip Seals
Pavement Preservation Journal - Fall 2017 - 44
Pavement Preservation Journal - Fall 2017 - 45
Pavement Preservation Journal - Fall 2017 - 46
Pavement Preservation Journal - Fall 2017 - cover3
Pavement Preservation Journal - Fall 2017 - cover4
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