United States Department of Transportation
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Evaluation of flexible pavement performance using LTPP data.
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2002-07-01
[PDF-3.75 MB]
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Abstract:Pavements are complicated physical structures responding in a complex way to
the influence of many variables. Understanding how the long-term performance of
pavement: relates to the factors such as environmental and traffic loads is key to
building and maintaining a cost-effectiv~ highway system. For this purpose, SHRPL
TPP, a comprehensive20-year study, was designed to evaluate the performance of
in-service pavemen~.
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In this research, pavement performance related data available in DataPave3.0
were extracted and synthesized to cauy out a systematic study of the variables
affecting performance of pavements.,
Firstly, GPS-land GPS-2 test sections from Alabama were analyzed to
evaluate the performance predictive capability of the 1993 AASHTO flexible
pavement design model. Research, showed that, statistically. speaking, the 1993
AASHTO flexible pavement design model provides biased prediction of the
performance of flexible pavements with granular bases and unbiased prediction of
the performance of pavements with bound bases when using subgrade resilient
moduli from laboratory testin~. Research revealed serviceability degradation and
subgrade resilient modulus are the key parameters for t~e 1993 AASHTO design
model.
Secondly, 48 SPS-I sections in Alabama, Arizona, Arkansas, and Iowa were
used to evaluate the effects of specific design feature on pavement performance.
Research revealed that fatigue cracking was a serious distress manifestation for pavements with granular bases. 44Full-depth" AC pavements performed better than
other structural designs. Open graded drainable base layers improved the
performance of pavements over fine-grained subgrades but pavements with dense
graded black bases over coarse-grained subgrades performed better.
Thirdly, 40 SPS-5 sections in Alabama,. Alberta, California, Miss~ssippi and
Texas were chosen to evaluate strategies for rehabilitation of existing pavements.
Research indicated that milling of existing pavement surfaces before overlay
provided some benefits for thin overlay but no benefits for thick overlay. Virgin AC
mixes performed consistently better than AC mixes with 30% RAP. Increased
overlay thickness (thus total thickness) improved performance, especially in
preventing fatigue and transverse cracking.
Data in the SHRP-LTPP database provided a good platform for conducting this
research. But, it has deficiencies such as incompleteness of certain data, and
inconsistencies of some data elements which certainly diminishes confidence in the
evaluations performed.
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