FHWA Resource Center
RC Success Stories
VOLUME 1, ISSUE 4
Your Link To Successful Solutions For Today's Transportation
DECEMBER, 2001
KDOT's Successful Program May Fit Your Needs
Spending for state highway construction programs has increased dramatically in recent years. At the same time, agency downsizing has reduced the number of inspection personnel responsible for overseeing highway construction projects. To cope with the increased demand on limited resources, states have either developed or are investigating alternative means of delivering their program. The use of contractor test results as part of the project acceptance decision for asphalt concrete pavement projects is one area that states are considering.
Recently, Federal Highway Administration (FHWA) sponsored a field best practice review to document successful state experience in the use of contractor test results. These reviews will be shared with states considering similar programs. Field reviews have been completed in Kentucky, Kansas and Idaho in the summer of 2001 (additional reviews are planned for 2002). Detailed information was collected for over 100 guide questions and is available upon request. This report summarizes the findings from the Kansas review conducted May 29-31, 2001. The review team consisted of pavement engineers with diverse backgrounds. Team participants were from the Alabama, Florida, Kansas, Kentucky and Texas Divisions, Arizona State Highway Agency, Southern Resource Center (SRC) and Washington HQ Office. During this review, the team met with Kansas Department of Transportation (KDOT) agency--including those responsible for developing the program. They also met with several contractors and visited construction projects to observe program implementation.
In essence, the contractor's data is used to accept asphalt pavement utilizing pay factors for air voids and roadway density. KDOT began with an absolute average deviation form of specification and is transitioning to the Percent Within Limits (PWL) type of specification. KDOT utilizes the F and t test to verify the contractor's results for air void content, theoretical maximum density (Gmm), and roadway density. The contractor determines the density at two locations per sublot and KDOT verifies the contractor's results utilizing five samples, one from each sublot.
Kansas has over five years of experience using contractor's quality control tests in the acceptance decision. The Superpave mix design system was implemented concurrently with the specification incorporating the contractors test results in the acceptance decision.
KDOT compares the contractor's quality control results with their verifications results using the F and t test with alpha of 0.01. For density, the comparison is completed on each day's production and for air voids and Gmm, the first two lots are accepted based on QC results--if verified by KDOT. The QC results for these lots are considered verified if the verification test is within three standard deviations or 1% of the QC mean. KDOT and their FHWA Division office developed an Excel spreadsheet to implement the statistical verification system shown at left.
KDOT is proud of their system and believes their success is due to the commitment, support and cooperation of all parties involved. In addition, there is a core team consisting of champions continuously troubleshooting, improving and refining the system. The continued success of the program is due to an integrated system that includes the laboratory and technician certification programs, the Independent Assurance Program, and the statewide use of the F and t statistical evaluation procedures. KDOT welcomes the opportunity to share their experience with anyone wishing to learn more about their system.
For more information contact:
Greg Schiess, Florida Division,
850-942-9650 x 3023 or greg.schiess@fhwa.dot.gov
Michael Smith, Materials Engineer,
404-562-3694 or michael.smith@fhwa.dot.gov
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