Pavement Preservation Journal - Spring 2015 - (Page 35)
Thin Overlays Can Preserve
Pavements as Well as
Reduce Surface Noise
T
hin overlays are
non-structural preventive
maintenance HMA mixes
used for the routine
maintenance and rehabilitation of
existing pavements.
These overlays are commonly
placed in thin lifts of about 1 in. thick,
and are mainly used to preserve
pavements exhibiting surface
distresses such as raveling, aging,
bleeding, minor cracking, minor
disintegration, texture loss, and skid
resistance loss.
Thin HMA overlays enhance
pavement performance and extend
pavement service life, including
functional characteristics such as
improved user serviceability (i.e.,
smoothness, comfort, and quiet ride),
skid resistance, splash and spray
reduction, and noise reduction.
IMAGE CREDIT: TREVINO, UTA
STUDYING NOISE MITIGATION
The noise mitigating properties
of some of these mixes have been
studied in the field in Austin, Tex.,
by The University of Texas Center
Detail of thin overlay mix on I-35, north of
Austin; measured sound on a par with, or better
than, conventional porous friction courses
for Transportation Research, and the
results show that these surfaces are
even quieter than some permeable [or
open-graded] friction courses, which
are commonly regarded as the quietest
asphalt mixes.
Research has shown some of the
advantages of using thin lift asphalt
mixtures include:
* Improved ride quality
* Reduced noise levels
* Reduced life cycle costs
* No loose stones, and
* No curing time required.
Most asphalt maintenance is needed
to address functional issues, and not
structural issues. Therefore, increasing
the thickness of the pavement is not
always necessary, and thin overlays
are often sufficient to improve the
surface smoothness and quality.
If placed and compacted properly,
good performance should be obtained.
The application of thin overlays is not
always viable, but may be appropriate
for rehabilitating low-volume roads
and for pavement preservation of all
asphalt roads.
For pavement preservation, thin
overlays are capable of providing
long-lasting surfaces that are also
economical and provide good
performance; for the case of interest of
this article, these surfaces also provide
the important benefit of reducing tire/
pavement noise.
FIELD MEASUREMENTS
For the case of the overlays studied
in Austin, some thin overlay mixes
recently have recently been tested for
noise, on both high- and low-volume
roads. The On-Board Sound Intensity
IMAGE CREDIT: TREVINO, UTA
By Manuel Trevino, Ph.D.
On-Board Sound Intensity (OBSI) equipment
and vehicle
(OBSI) method for close-proximity
tire/pavement noise measurement
[AASHTO] was utilized.
Some examples of these surfaces
that have been studied are:
* I-35 main lanes, from the Bell/
Williamson county line to
Lakeway Drive
* RM 12, one mile south of U.S. 290 to
Wimberley city limits, and
* RM 3238, just north of U.S. 290,
between Bee Cave and Dripping
Springs. These three thin overlay
mixes have proved to be very quiet
in recent tests.
The preliminary noise test
results from these surfaces are
very promising.
For the I-35 pavement the average
noise level was 97.5 dBA, for RM 12 it
was also 97.5 dBA, and for RM 3238,
it was 99.8 dBA, all of which can be
considered very quiet, quieter than
many other porous friction courses.
Further testing will be done to
follow the sections' performance
over time.
Dr. Trevino is affiliated with the Center
for Transportation Research, University of
Texas at Austin
Spring 2015
pavement preservation journal
35
Table of Contents for the Digital Edition of Pavement Preservation Journal - Spring 2015
President’s Message
Hot, Cold In-Place Recycling Gets Boost at Western States Conference
Fort Collins HIR Project Provides Delegates with Up-Close Look
NCAT Reports 2012 Cycle Results, 2015 Preservation Activities
New Congress Means New Push Toward Reauthorization
FP² at TRB
Pavement Preservation in Spotlight at World of Asphalt 2015 in March
Control Potholes by Sealing Cracks, Joints in Advance
‘Thinlay’ Asphalt Overlays Next Word in Pavement Preservation
Texas Considers Ultra-Thin HMA Alternatives to Seal Coats
Thin Overlays Can Preserve Pavements as Well as Reduce Surface Noise
In California, Scrub Seals Gain Favor for Cost, Crack Sealing
IGGA Recognizes Leaders in Grooving, Grinding
Index of Advertisers
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