Foamed asphalt is a "natural" for rural Ulster
County, N.Y., where the local economy depends on unimpeded tourist traffic to
Ulster's scenic Catskill Mountains north of New York City.
This process--now gaining popularity across North
America--lets Ulster County keep its roads open to local and tourist traffic
while they undergo complete recycling and stabilization as base material prior
to overlay.
Excessive, weeks-long truck traffic, demolition material and
virgin aggregate hauling, noise, dust and commotion are eliminated, and a
virtually new, high-performance road base is created at a fraction of the cost
of new base materials and deep lifts of asphalt pavements.
In-place recycling of rural roads with foamed asphalt lets
Ulster County reconstruct far more roads each season than would otherwise be
possible, letting precious road dollars go further. This is even more important
as Ulster is undergoing a residential boomlet as urbanites bypass New York
City's suburbs to build year-round homes there to escape the hectic urban life.
And the minimal environmental impact of in-place recycling
means less disruption to tourists and outdoorsmen who come to Ulster County for
its quiet peaks, deep woods and cold lakes and streams.
Keep the roads open
"Our policy is to try not to close the road under
construction," said John Lukaszewski, field operations manager, County of
Ulster Public Works, Department of Highways & Bridges, Kingston, N.Y.
"It's a public safety issue. Sometimes we have to temporarily close a
road, but the notification procedure is involved and we'd rather keep it
open."
Foamed asphalt gives Ulster County that option. "All
traffic can continue as normal, with a little bit of delay, that's all,"
Lukaszewski said. "Citizens stay happy, and when taxpayers are happy, that
makes us happy and helps us do our job better and faster."
"In the long run this process saves tax dollars,"
said Ulster County Commissioner of Highways & Bridges James Donahue.
"It provides a great sub-base, and anything we'll put on top will last
that much longer, with much longer-term savings over the years. And the road
stays open for residents, deliveries and emergency vehicles."
Ulster County has been using foamed asphalt for at least
five years, but has been doing road reclamation and recycling for about 16
years. "We've had a nice outcome with foamed asphalt," Lukaszewski said.
"Instead of having to put an asphalt binder down, it gives us our binder
in-place, and we just have to come back and top with a clean 1-in. top-size
blacktop, 3 in. deep."
That first foamed asphalt job has held up well, he said. "It's
a fairly high-volume road for us, about 5,000 vpd. It's done very well and
we're really happy with it."
Foam = lightweight cost
Being a rural county, Ulster lacks a strong tax base. Road
and bridge expenditures come from the county's general fund--with some federal
assistance--and thus compete with other worthy needs. The county maintains
about 900 lane miles of roads, for a population of 140,000. The county needs to
save money without cutting corners wherever it can, and foamed asphalt does the
trick.
"The savings with foamed asphalt are enormous,"
Lukaszewski said. "We'd have to dig up and get rid of the material and
truck material back in. On a project like this one, we're saving hundreds of
thousands of dollars. Economically it fits the bill. Money is the big issue. If
you don't have the money, you can't do the work. So we work with what we
have."
The county now reclaims and foams in excess of 20 miles each
year.
"We've tried liquid calcium chloride stabilization, and
it does a good job, but it's kind of a mess," Lukaszewski said. "It's
good for dust and stabilizes clay somewhat, but people don't like to hear
you're using calcium chloride in rural areas where they depend on wells."
Expanding on asphalt
Foamed, or expanded, asphalt offers new options for
contractors and state and local road agencies to undertake economical base
stabilization.
Low-cost foamed asphalt technology stabilizes and improves
the performance of existing road materials, producing high-quality base courses
and cold mixes at the lowest possible cost.
The expanded asphalt has a resulting high surface area
available for bonding with the aggregate, leading to a stable road base using
100% of the existing in-place materials.
Foamed asphalt--the product of the injection of a predetermined
amount of cold water into hot penetration-grade asphalt in a series of
individual expansion chambers--replaces costly asphalt emulsions in base
stabilization.
Unlike asphalt emulsions, foamed asphalt does not require a
three- or four-day "break" period before it can be mixed.
And foamed asphalt technology is completely compatible with
in-place recycling or crushing of degraded asphalt or gravel road wearing
courses. After grading and compaction, this surface can support traffic
immediately, but often is soon overlaid with a fresh, virgin wearing course.
This in-situ base recycling and stabilization is the most common application of
foamed asphalt throughout the world and North America.
Other benefits include:
* The recycled lift is more resistant to penetration of
water;
* Foamed
asphalt-stabilized bases are usually less expensive than a bituminous emulsion
or a combination of emulsion and cement;
* Additional water is not added to the recycled material, as
is necessary when emulsion is used; and
* The rapid strength gain from use of foamed emulsion means
that traffic may be introduced onto the recycled road as soon as compaction is
complete.
Cover the bleeding
Due to the abundance of glacial-deposited clays, Ulster
County's roads suffer from major expansion of clay road bases. "The clay
causes excessive heaving," Lukaszewski said. "Because of that, on a
lot of roads we won't use blacktop, instead using a cold mix material we call
Motorpave, which is very flexible and won't break down. If it heaves, traffic
puts it back in its place as soon as the frost is gone."
Motorpave is a cold stone mix blended with hot CMS-2
medium-set emulsion mixed in a traveling pugmill on site and placed through a
screed. It's an update of the old "mix-in-place" method, Lukaszewski
said, of stone placed on-grade and windrowed down the middle by motor graders.
The windrow would be shot with oil, mixed back and forth
with the graders, then laid out, wet-rolled, chipped with fine stone and rolled
again. "That was the pavement," Lukaszewski said. "Instead of
mixing in place, now it's done in a machine. Traffic continues to flow and it
works well for us."
In summer 2003, Ulster was using contractor Reclamation
Inc., West Hurley, N.Y., to foam-stabilize cracked and potholed Blue Mountain
Road (County Road 35), a two-mile project. The road also suffered from
excessive bleeding, the result of decades' worth of band-aid, chip-seal surface
treatments.
Like other county rebuilds, the 22-ft-wide road was being reclaimed
to a depth of 8 in., with 4 in. of foam stabilization, bladed, compacted and
topped with the 3-in. Motorpave thin lift. For the foam, liquid asphalt was
being injected at a rate of 2.5% and no fines, cement or lime was being added.
Shoulders were to be placed in some sections. The Motorpave mix was to be
placed by contractor Peckham Materials, Kingston, N.Y.
"Reclaiming is saving municipalities thousands of
dollars in removal costs," said Michael B. Haggerty, marketing director,
Reclamation Inc. "By our recycling the existing pavement, and then
stabilizing it and creating a structure that is close to a new hot-mix asphalt
pavement we only have to put a minimal structure on top, saving our customers
money in the long run."
Foamed asphalt has become a significant market for
reclamation, Haggerty said. "Foamed asphalt has really come to light in
the last five years. This year [2003] is our eighth season doing foamed and
it's become a big market for us. It's a quick-curing product and we can pave on
it the next day. It's more weather-resilient than other stabilization
processes. It fits the bill for us."
