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 The I-19
pictured before the AR OGFC in 1988, is a major trucking route
from Mexico to the U.S. The existing jointed, non-doweled 9"
concrete pavement originally constructed in 1965 was in extremely
poor condition, faced with an expensive remove and replace situation,
ADOT opted to try a 1" thick OGFC with a 10% Asphalt-Rubber
binder to get a few more years service. They expected 5 to 8
years and ended up with a pavement lasting for 15 years. See
photo.
The pavement was a part of an Arizona Department
of Transportation review of all AR pavements ten years or older
in 2000. The review was conducted by Gene Morris, P.E., former
research engineer for ADOT and myself. In reviewing all the ADOT
records on the project, we found the pavement had not had any
maintenance in its first 12 years.
According to Ken Damgaard of the ADOT
Tucson District, about half of the section was damaged by construction
equipment during work on an exit in 2002. In the late fall, ADOT
milled off about half of the thickness and replaced it with a
3/4" overlay of AR ACFC. However, a small portion remained
unscathed as depicted in the photo taken in March 2003. The table
below is from the project review, which can be viewed on the
Arizona DOT website at:
http://www.dot.state.az.us/ABOUT/materials/pavedsgn/index.htm
Not only did they get a pavement
that exceeded the anticipated service life, an extra bonus was
realized in a 78% reduction in noise. A sound level survey was
conducted by Western Technologies, Inc of Phoenix in 1990 between
Valencia and Irvington Roads just south of Tucson.
The measurements were taken on the Asphalt-Rubber
Concrete Road Surface at the center of the median, approximately
35 feet from the shoulder of the north and south bound inner
lanes just north of Valencia. The measurements were taken between
11:45 AM and 1:40 PM. The average sound level was 73.7 dB.
The measurement on the existing concrete
pavement was also taken 35 feet from the shoulder in the inner
lanes just south of Irvington Road. The average noise levels
recorded was 80.4 dB.
The difference for both sound levels
resulted in a 6.7 dBA reduction. This can be correlated to the
sound intensity being reduced by 4 times, which would translate
into a 78% reduction. Many asphaltrubber mixes like this have
been quietly at work reducing noise and saving maintenance dollars
in Arizona. The proof is in the pavement.
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