PS-53 - Texas State University

Form ProjStat
(Rev. 5/2013)
Research Project Statement 16-53
FY 2016 Annual Program
Assess Deflection-Based Field Testing for Project Acceptance
The Problem:
Currently, TxDOT measures the quality of flexible base and sub-base layers with localized nuclear
density measurements. This testing provides specification verification at very limited locations and
gives minimal confidence that the roadway section is going to provide uniform support. Consequently,
weak areas can easily be missed, and these weak areas result in premature pavement failures well
before the pavement’s intended design life. For current design-build pavements, the contractors are
also requested to mold soil samples taken from the field to measure resilient modulus in the
laboratory. This testing is also conducted at very limited locations and perceived to be of little value.
On recently constructed segments of SH 130, the contractor opted for layer-specific deflection based
testing with the Falling Weight Deflectometer (FWD). FWD testing was conducted on top of both the
lime-stabilized subgrade and the flexible base layers prior to placing the HMA base and surface layers.
Deflection measurements were made at 50 feet intervals in all lanes, simple acceptance criteria were
developed based on the structural design assumptions, and a recommended course of action was
defined in case the measured deflections were substantially higher than the computed target value.
In addition to the use of the FWD on SH 130, on one segment of the current Grand Parkway
construction project in Houston, QC/QA testing with the FWD is being conducted on top of the bond
breaker layer prior to the placement of the CRCP slab.
Other internal TxDOT studies by the Construction Division have shown that Intelligent Compaction (IC)
with instrumented rollers has great potential if properly targeted and well understood to provide 100%
coverage of the section under construction so that the acceptance based testing can be focused on
the suspect areas only.
TxDOT’s current acceptance approaches have not changed in the past 20 years. The current
approaches do not have the ability to detect weak areas or to even assure that structural design
assumptions are being met. Adopting full-coverage testing will eliminate costly failures and improve
long term pavement life. The technologies described in this proposal are available and can be
implemented at little cost to TxDOT or the contractors. They will greatly reduce the risk of premature
This research will assess practices in deflection-based field testing flexible base and sub-base layers
for project acceptance. The researchers will conduct the following steps in successful completion of
this project:
1. Review all of the projects constructed in Texas where either the FWD and or the lightweight FWD
(LFWD) deflectometers were used for acceptance of all flexible base and sub-base layers.
2. Conduct ruggedness and repeatability testing on both the FWD and LFWD on a range of different
materials types.
3. Develop draft procedures for FWD and IC acceptance of pavement layers.
4. Develop protocols for what to do when sections fail to meet the proposed acceptance criteria. This
will include testing with DCP and moisture sensors, and criteria to define what actions to take based
on those results.
5. Conduct pilot studies on a minimum of six TxDOT construction projects. Evaluate the potential for
testing on top of the lime stabilized layer, flex base layers, and top of bond breaker layers.
6. Pilot test the proposed acceptance test with contractors on two design/build projects. Obtain the
contractor’s input on the strengths and weaknesses of the proposed system.
7. Conduct a webinar on study findings and identify future directions.
1. Value of Research (VoR) that includes both qualitative and economic benefits.
2. Research report describing data collected and conclusions for all projects tested in Texas.
Project Statement 16-53
Form ProjStat
(Rev. 5/2013)
3. Testing protocols for collecting data with the FWD, LFWD, and IC systems during construction.
4. Recommended procedures for using deflection based testing and IC on future projects.
5. Statewide webinar presenting results and recommendations.
1. Proposals will be considered non-responsive and will not be accepted for technical evaluation if
they are not received by the deadline or do not meet the requirements stated in RTI’s University
2. Proposals should be submitted in PDF format, 1 PDF file per proposal. File name should include
project name and university abbreviation.
Friday, September 11, 2015 9:00 – 12:00
Austin Riverside Campus
118 E. Riverside Dr.
ENV Conference Room, 1st Floor, 1B1A
Webex Information:
Join the online meeting:
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Meeting number: 737 294 354
Meeting password: 1234
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Call-in toll-free number: 1-866-6371408 (US)
Conference Code: 199 125 9183
Proposals are due to RTI by 4:00 p.m. Central Time, October 12, 2015. Email submissions should be
sent to [email protected]
Project Statement 16-53