Special Section: Hot and Cold
Asphalt Recycling Section
by Daniel Brown, Contributing Editor
Cold in L.A.
CIR plus microsurfacing get the job done
C
area. It turned out that Pavement Recycling Systems (PRS)
old-in-place recycling (CIR) followed by microwas doing some cold-in-place recycling work on the
surfacing was not only a cost-effective treatment
nearby Angeles Forest Highway.
for Los Angeles County when it encountered un“That got us thinking, ‘What if we used cold-instable pavement conditions in one of its roads, but CIR
place recycling to fix this problem on Upper Big T?’”
was the perfect green solution.
recalls Diaz. “We wouldn’t have to haul in new materiAt issue is Upper Big Tujunga Road, a 9.5-mile, twoals, and if we could recycle what is there, that’s more
lane mountain road in a remote location in the Angeles
viable than trying to remove everything and replace it
National Forest. The CIR treatment, going 3 inches deep,
with hot mix. Because most CIR treatments require a
followed by microsurfacing, cost the county approxiwearing surface, microsurfacing seemed like the best
mately $750,000.
alternative.”
The LA County Department of Public Works encounSo the county consulted with Pavement Recycling
tered problems with the road when it applied a chip seal
in October 2010. The U.S. Forest Service required that the Systems and with Doug Ford, President of Pavement
Coatings (PCC), a Jurupa Valley, Calif., company that perpreservation work be done late in the year. “With cooler
forms microsurfacing. The CIR work was then performed
weather, it was not an optimal time to apply the cationic
by PRS and the mihigh-float emulsion with
crosurfacing was per5/16-inch chips,” says
formed by PCC as subImelda Diaz, Civil Engineer
contractors to Torres
with the County. Upon iniConstruction.
tial placement of the chip
- Imelda Diaz, LA County DPW
Only about half of
seal, some of the chips ravUpper Big Tujunga required CIR work – 9 lane miles to
eled off, so the County raised the amount of emulsion,
be exact. The CIR was only needed on the half with exapplying up to double the amount specified at first. That
cess asphalt on the road. “The high asphalt content on the
seemed to have solved the problem.
road was initially a danger, and then it became an asset,”
Then in April 2011, the Los Angeles area encountered
said Doug Ford. “With the cold-in-place recycling we ran
a period of hot weather. “The pavement started moving;
1.6 percent emulsion, but without that additional asphalt
it became soft and gummy,” says Diaz. “The emulsion in
we would have run 2.5 percent or more of emulsion.”
the chip seal may not have fully reacted when it was first
placed in the cooler months of October and November,
and remained dormant through the winter. Then in April
The CIR Train
when we got that hot spell, the heat seemed to have ac“Leading off the CIR train was a Caterpillar PR 1000 milltivated the emulsion in the chip seal. So essentially it was
ing machine, working 3 inches deep and 12.5 feet wide.
like rock floating in the emulsion.”
The mill conveyed the material back to a recycler, which
Now the road was unsafe, especially for motorcycles.
has screens and a crusher to reduce all recycled asphalt
So the County closed Upper Big Tujunga Road for a time, to 1-inch-minus,” says Chris Rogers, Superintendent for
and sought answers from contractors and suppliers in the Pavement Recycling Systems. “When the material has
“So essentially it was like rock
floating in the emulsion”
28 July 2012 Better Roads