Evaluation of Dowel Bar Inserter Practices in PCC Pavements with Magnetic Tomography Technology

Dowel bars used in jointed concrete pavements (JCP) are significant in preventing pumping, faulting, and cracking and in providing efficient load transfer between slabs. Therefore, dowel bars need to be properly aligned and positioned; improper placement may reduce the effectiveness of the dowel bars, which will lead to spalling and cracking. Proper positioning of dowel bars enables free, uninhibited opening and closing of the joints resulting from expansion or contraction of the pavement slabs in response to temperature changes, as well as initial shrinkage. Dowel bars should also be centered on the joint to ensure adequate embedment in both approach and leave slabs for proper load transfer. Any deviations from the ideal dowel bar position may be defined as misplacement or misalignment. Typically, dowel bars are placed either before Portland cement concrete (PCC) placement by using dowel baskets, or after PCC placement by using an automatic dowel bar inserter (DBI). The DBI offers an advantage in construction cost and speed; however, concerns have been raised over the dowel alignment quality. To determine the effectiveness of DBI practices in the state, the Nebraska Department of Roads (NDOR) has used a nondestructive testing device, MIT Scan-2 which is based on magnetic tomography technology for measuring the position and alignment of dowel bars. MIT Scan-2 consists of three main components: (a) a sensor unit (the rectangular box) that emits electromagnetic pulses and detects the induced magnetic field; (b) an onboard computer that runs the test, collects, and stores the test data; and (c) a glass-fiber reinforced plastic rail system that guides the sensor unit along the joint. The device is easy to use, the dowel alignment can be checked within a few hours of concrete placement, and the results can be printed using the onboard printer immediately after scanning. MIT Scan-2 allows the entire joint to be scanned in one pass, providing results for all dowel bars in the joint.

    Language

    • English

    Project

    • Status: Active
    • Funding: $98602.00
    • Contract Numbers:

      SPR-P1(16) M036

    • Sponsor Organizations:

      Federal Highway Administration

      1200 New Jersey Avenue, SE
      Washington, DC  United States  20590

      Nebraska Department of Roads

      1500 Highway 2
      Lincoln, NE  United States  68502
    • Performing Organizations:

      University of Nebraska, Lincoln

      527 Nebraska Hall
      Lincoln, NE  United States  68588-0529
    • Principal Investigators:

      Kim, Yong-Rak

    • Start Date: 20150701
    • Expected Completion Date: 0
    • Actual Completion Date: 20161231
    • Source Data: RiP Project 39669

    Subject/Index Terms

    Filing Info

    • Accession Number: 01569415
    • Record Type: Research project
    • Source Agency: Nebraska Department of Roads
    • Contract Numbers: SPR-P1(16) M036
    • Files: RiP, STATEDOT
    • Created Date: Jul 11 2015 1:00AM