Fundamental Properties of Asphalts and Modified Asphalts, III

SUBTASK 2-6: VALIDATION SITE MONITORING
Statement of Problem
Laboratory tests and/or models to predict the performance of asphalt pavement materials have
always needed a connection between the original materials and actual performance in the field,
especially comparative performance, in order to calibrate or validate the test or model results.
Approach
The approach being used is to construct field sections where different asphalt sources of the
same Performance Grade are used at the same location so that comparative pavement
performance can be directly evaluated and core samples can be obtained as the comparative
pavements age in service. Original materials were collected at the time of construction and are
available for testing. The sites being monitored, using LTPP monitoring protocols, were
constructed during the previous FHWA contract, “Fundamental Properties of Asphalts and
Modified Asphalts II”.
Goal
The goal of this subtask is to provide accurate and documented performance of different asphalt
sources that also includes asphalt-aggregate interactions, to be used to determine the chemical
and physical property differences that are important to pavement performance.
Support of FHWA Strategic Goals
This subtask supports the FHWA Strategic Goal of Optimizing Pavement Performance.
Work Conducted this Quarter
The annual monitoring of the Kansas comparative pavement validation site was conducted in
May 2008. The site is still performing rather well after six years in service; however, there is
some distress being noted. There is a small amount of fatigue cracking and longitudinal cracking
(both non-wheelpath and in the wheelpath) that is occurring in two of the sections. Two core
samples were obtained by KDOT personnel to investigate one of the fatigue cracks. The core
samples revealed that the cracking is top-down cracking and only goes through the 40 mm top
lift. The four comparative asphalt sources are located in the bottom 60 mm of the pavement with
a 60 mm binder course and a 40 mm surface course placed above. There were no apparent
indications in the two core samples that there was any problem with the bottom lift.
Work to be Conducted Next Quarter
It is planned to perform the annual monitoring of the Wyoming Highway 216 sections and the
Nevada I-15 sections in August and September 2008, respectively.
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