Project Report on the Continued Development and Analysis of the Flexible Pavements Database Page: 4
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o HMA surface on top of untreated granular base (flexbase)
o Two course surface treatment on top of untreated granular base (flexbase)
* Traffic levels (2 levels)
o Heavier traffic
o Lighter traffic
* Environmental conditions (5 levels)
o Wet No Freeze
o Wet Freeze
o Dry No Freeze
o Dry Freeze
o Mixed
* Age and Section replicates (2+1 levels)
o The target was set for two new sections and one old section to capture the effect of
age as well as the in-section variability.
Whenever replicate sections are available, there were going to be included. In most cases,
this was achieved by selecting more than one experimental section in the same road project with
a typical spacing between I or 2 miles so that both the test sections are exposed to identical
conditions.
Thus, the complete main factorial consisted of 60 sections (3 x 2 x 5 x 2). In order to
include a limited number of other variables, the originally proposed number of sections was 64.
TxDOT research has demonstrated the importance of aging the HMA on flexible pavement
performance, so the database has to include aged and un-aged sections. Therefore, a much larger
number of sections were also considered to account for aging (old and new sections) and other
variables not explicitly accounted for. It was decided that 67% of the total number of sections
would be constituted of "new" pavement sections while the remaining 33% coming from the
existing TFPD would be deemed the "old" sections. Thus, a mix of old and new sections will
provide the opportunity to monitor performance trends against aging of asphalt mixes. For this
reason the third replicate was added so as to result in 90 sections.
One of the main shortcomings, already identified during 0-5513, was the reduced number
of sections in the wet-warm and dry-cold areas and the abundance of sections in Central Texas.
Thus, the new, more balanced experimental design incorporated sections in Beaumont, Lubbock,
and Wichita Falls, and other Districts that are closer to Austin (Central Texas). In addition, 10
sections outside the experimental design were also identified at the discretion of the Project
Monitoring Committee (PMC) to include unconventional materials like warm-mix asphalt
(WMA), crack attenuating mixes (CAM), and crumb rubber mixes into the performance
monitoring as well as material testing program.
During this project (0-6275), the researchers started upgrading the 41 new TxDOT-
recommended sections by collecting and testing site-specific materials. In addition, some 20
sections, on average, were to be added each year to reach the total of 100 new sections. The
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Banerjee, Ambarish; Aguiar-Moya, José Pablo; Sivaram, Prasad; Smit, Andre de F. & Prozzi, Jorge Alberto. Project Report on the Continued Development and Analysis of the Flexible Pavements Database, report, February 2011; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth281719/m1/18/?rotate=90: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.