Current and Proposed Practices for
Nondestructive Highway Pavement Testing
MAUREEN A. KESTLER
eight states replied, indicating a response rate of
OVERVIEW
76%. Of the 38 responding states, 21 states own
In September 1994 the U.S. Army Cold Regions
(Dynatest) FWDs. Further investigation (Dynatest
Research and Engineering Laboratory (CRREL)
1993) beyond survey results showed that, as of
distributed a short survey on nondestructive test-
November 1993, six of the nonresponding states
ing practices to each of the 50 state Departments
also owned Dynatest FWDs. Two states contract
of Transportation (DOTs). The following report
FWD work, six states own KUABs, one state owns
briefly summarizes state responses to questions
a Mechanics Foundation JILS, three states own
regarding nondestructive testing (NDT) equip-
Road Raters, and four states continue to use Dyna-
ment used or owned, number of lane-miles tested
flects. Several states own combinations of the
annually, software and analytical tools utilized,
above devices, e.g., one state owns two Dynatest
and NDT test point spacing and configuration.
FWDs and one KUAB, another state owns one
Compilation of survey results constituted Phase
Dynatest FWD and two Dynaflects, etc. Each of
I of a multiphase effort leading toward develop-
the NDT devices reported in this survey are briefly
ment of a method for optimizing falling weight
discussed in Appendix A (Smith and Lytton 1984).
deflectometer (FWD) test point spacing. Long-
range objectives are to assess national expendi-
NDT equipment uses and
tures on NDT and to work in cooperation with
software/analytical tools used
selected state DOTs to determine whether present
Predominant uses for NDT equipment are pave-
costs for overlay design and pavement evaluation
ment overlay design, pavement evaluation, net-
could be reduced by the development of a com-
work/inventory, research, void detection, and load
puter program that continually assesses and up-
transfer for portland cement concrete (PCC) pave-
dates in-situ variability, and recommends an
ments. Table 1 summarizes NDT software and
optimal distance to the next FWD test point as
analytical tools most commonly used by state
data are collected in the field. This interim re-
DOTs. Figures 1a and 1b graphically show the
port* includes neither an analysis nor a final prod-
breakdown in methods/software for overlay de-
uct, but rather summarizes survey results and
sign, evaluation, network, and project level us-
outlines the theory and planned approach for com-
age. American Association of State Highway and
puter program development.
Transportation Officials (AASHTO) guidelines and
DARWIN, a computer-aided design method that
uses AASHTO methods, provide the most fre-
quently used overlay design technique of those
SURVEY RESULTS
reported. "In-house overlay design programs,"
ranging from sophisticated internally developed
NDT equipment
The NDT Practices Survey was distributed to
software to more simplistic spreadsheets, are also
the 50 state DOTs during the fall of 1994. Thirty-
often used. (Note that weighted averages were
assigned for figure development, i.e., states using
only one software program were assigned a weight
*This report was written in response to numerous requests
of one whereas states that specified three overlay
for a copy of the paper associated with a presentation titled
design methods were assigned three weights of
"What Do DOTs Do with FWDs?", given at the FWD User's
1/3 each.)
Group Meeting in Raleigh, North Carolina, in October 1995.
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