ASPHALTopics | Fall 2015 | VOL 28 | NO 3

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Since 1995, Louisiana has been monitoring the performance history of
pavements using their pavement management system measures for rating
the performance of pavement. In a comparison of roads in 2013 with those
in 2003 using IRI (international roughness index) and rut measurement on
the state highway system, there is less rutting and smoother roads thanks
to these changes in the specifications (above). Fatigue cracking between
2003 and 2013 is a slightly different trend; however, the early trend on new
pavement projects is that fatigue cracking has decreased (below).
Another innovation was the introduction of a new mix – open graded
friction course (OGFC). OGFC improved safety because of reduced splash
and glare in a high rainfall environment. This improved safety is born out
ALGCRK (sq9/mi)
Avg IRI (in/mi)
Avg Rut (in)
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
18 OHMPA | ASPHALTOPICS
IRI – now vs 10 yrs ago
State HS IRI
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25000
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rut – now vs 10 yrs ago
State HS Rut
2013 ASP
2003 ASP
Linear (2013 ASP)
Linear (2003 ASP)
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0 5 10 15 20 25
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2013 ASP
2003 ASP
Linear (2013 ASP)
Linear (2003 ASP)
Fatigue Cracking – now vs 10 yrs ago
State HS fa;gue crack
2013 ASP
2003 ASP
Linear (2013 ASP)
Linear (2003 ASP)
by a drastic reduction in wet weather
crashes; for example, I-20 District 5 from
Britton Road to Vancil Road (right). They
also looked into rubberized overlay for
both composite and asphalt sections
with good success at reducing rutting
and cracking and thus improving ride.
How do you get to better performance
from what you used to do before?
Specify new tests that are technically
supportable and practical and then
make sure that everyone performs them
the same way. Although a laboratory
test does nothing to actually improve
the road itself, it provides an indicator
from which to measure consistency,
and a measure which brings the agency
confidence that the product meets the
intended design.
To specify and monitor performance,
Louisiana has adopted a number of
performance tests as part of the mix
design procedure. One of the tests is
the loaded wheel test (Hamburg) used
to measure resistance to rutting and
moisture sensitivity.
Another key test is the SCB (semi-circular
bend) test which measures resistance to
crack propagation and looks at fracture
resistance with three different notch
depths. The data indicate that resistance
to cracking gets better as more polymer
is added to mix. To get a mix with low
rutting and high crack resistance, you
need a polymer modified asphalt.
Another key to getting better
performance is the adoption of
a lab accreditation program for
both contractor and agency labs
to ensure that everyone gets similar
and repeatable testing results.
The state of Louisiana and its
contractors have partnered over the
last 20 years to improve pavement
performance by implementing
scientifically validated and technically
feasible testing and specifications.
This partnership has resulted in saving
construction time, improving pavement
quality, saving money, improving the
environment and saving lives. And it’s
not over.