STATEMENT (Posted June 20, 2001):
A construction technique,
known commonly as "Ultra-Thin Whitetopping" (UTW), can be used
for the rehabilitation of flexible pavement. The rehabilitation
is accomplished by the placement of a thin portland cement concrete
overlay (2" to 4" thickness) on existing roads, streets or, in
the most common form, intersections. UTW is not, however an approved
FAA standard for pavement rehabilitation within the Airport Improvement
Program (AIP) guidelines. One of the aviation community concerns
is the durability of the bond between the asphalt pavement and
the concrete overlay. Unlike conventional whitetopping, UTW relies
upon the bond of the concrete to the asphalt for the load capacity.
The UTW design has been validated by simulating truck traffic
using accelerated load testing. But, the effects of the environment
on the bond between the concrete and the asphalt have not been
validated for the long term.
This project will
involve doing field studies and performing laboratory testing
to determine how the environmental factors affect the bond. Laboratory
evaluations will simulate the long term by accelerating the time
scale. The degradation of bond of the concrete to the asphalt
will be determined and compared to the cyclic temperature extremes
and exposure to numerous freeze thaw cycles. The goal of the project
is to determine if there is a loss of the bond between UTW and
existing asphalt surfaces and if the degradation is significant
enough to limit use of the rehabilitation technique for pavement
trafficked by light load aircraft (gross weights of 30,000 pounds
The project will be
accomplished along two Tracks.
Track 1 is to be a
field study of in-service UTW projects. The field study will concentrate
on documenting the in-service performance of the asphalt-PCC bond.
There will not be any destructive testing in Track 1. A list of
UTW projects from the Midwest, Florida and Tennessee will be provided
to the contractor by the IPRF. The list is not intended for general
distribution and will be given to the team selected to do the
work. The project list is intended to assist the research team
in locating and documenting projects. The research team is expected
to determine if there are other projects that should be included
in the field study. The research team will coordinate with the
IPRF to review the applicability of highway-based UTW research
to the airport environment. The field study should quantify the
method of asphalt pavement surface preparation for each of the
projects included in the study. Results of the field study, including
the research team's conclusion about the effectiveness of the
bond, will be presented in a stand-alone report. The Track 1 team
will comment on the test plan prepared under Track 2 and include
specific recommendations for the accelerated environmental studies.
Track 1 investigation will include a review of the background
engineering documents and related studies for the UTW paving at
the Savannah-Hardin County Airport, Savannah, TN. The pavement
includes a runway, 2 taxiways, and a GA apron. The Track 1 team
will accomplish a visual survey of the pavement to validate the
background documents. The Track 1 team will identify the parameters
that are considered critical to the evaluation of long-term performance
of the pavement. The Track 1 team will make recommendations concerning
the long-term observations. The IPRF will distribute documents
relevant to the pavement systems at Savannah-Hardin County Airport
as a part of the award of the contract. Questions about the contents
of the documents that are available shall be directed to the IPRF
Project Director or the IPRF Principal Investigator.
Track 2 will begin
with the preparation of a test plan for evaluating environmental
effects on the long-term bond between asphalt concrete and the
UTW. The minimum environmental extremes that will be considered
will be wet/dry, freeze/thaw, and temperature. The test plan should
attempt to simulate the extremes found in different regions of
the continental U.S. The test plan will not be submitted for IPRF
review until comments from the Track 1 group are included in the
plan. The Track 2 team will not be required to include all the
comments of the Track 1 study but reasons for not including Track
1 recommendations will be required. The test plan will be completed
before the Track 1 report is presented in final form. The test
plan will be implemented only after submittal to and review by
the IPRF. For planning purposes, the IPRF review period will not
exceed thirty days.
for Track 2:
- The success of Track 2 will
depend in large part on the laboratory equipment used in the
research. Therefore proposals must include a description of
the laboratory equipment. Special instructions for including
the equipment description in the proposal are provided in the
Instructions for Preparing Proposals for Project FAA 01-G-002-3.
- The technical panel that will
review the proposal will expect to see in the proposal viewpoints,
based upon the experience of the research team, for two issues.
- Age of asphalt -UTW overlays
are not placed on new asphalt. UTW is a rehabilitation technique.
The test plan must include a description about how the research
will include aged asphalt pavement as a test specimen.
- Edge restraint - UTW panels
are typically interior panels. The proposal must include
a discussion about the necessity to include edge restraint
in the environmental test for bond.
Proposals will be
accepted for Track 1 only, Track 2 only or both Track 1 and Track
2. Proposals must clearly state if they are for Track 1, Track
2 or both. The IPRF retains the right to award separate contracts
for Track 1 and Track 2 to different research groups, agencies
or individuals. The IPRF will coordinate activities if separate
contracts are awarded.
Track 1 Team will make recommendations to the Track 2 Team concerning
any testing recommended to be included intended to aid in the
evaluation of performance of the pavement at the Savannah-Hardin
County Airport. The Track 1 Team shall provide a report to the
IPRF that documents the baseline conditions of the pavement and
include recommendations for the IPRF to accomplish the long term
observation of pavement performance.
The final products
will be two (2) research reports that document the expected bond
retention of UTW for a variety of environmental conditions (separate
reports for Tracks 1 and 2.) The IPRF will specify the report
format. The investigator will provide two originals and 25 copies
of each manuscript including any artwork or photos. The publications
will also be submitted in an electronic format compatible with
industry recognized desktop computer publication software.
The investigator will
be responsible for the preparing and submitting quarterly reports
that describe the progress of the research effort. Reports will
be due in the offices of the IPRF on the last day of the fiscal
year quarter (i.e., last day of March, last day of June, last
day of September, and the last day of December). The reports will
be two pages maximum in a format that will be specified.
DIRECTOR: Lawrence W. Cole, P.E., (847)
Jim Lafrenz, Cooperative
Agreement Programs Manager