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Use of Magnetic Tomography Technology to Evaluate Dowel Placement

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Use of Magnetic Tomography Technology to Evaluate Dowel Placement cover

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List of Figures

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Technical Report Documentation Page

1. Report No.
FHWA-IF-06-006
2. Government Accession No.
 
3. Recipient's Catalog No.
 
4. Title and Subtitle
Use of Magnetic Tomography Technology to Evaluate Dowel Placement
5. Report Date
November 2005
6. Performing Organization Code
 
7. Author(s)
H. Thomas Yu and L. Khazanovich
8. Performing Organization Report No.
9. Performing Organization Name and Address
ERES Consultants
505 West University Ave
Champaign, IL 61820
10. Work Unit No.
 
11. Contract or Grant No.
DTFH61-03-C-00120
12. Sponsoring Agency Name and Address
Federal Highway Administration
Office of Pavement Technology
1200 New Jersey Avenue SE
Washington, DC 20590
13. Type of Report and Period Covered
Final Report
14. Sponsoring Agency Code
 
15. Supplementary Notes
Samuel S. Tyson, P.E., Contracting Officer's Technical Representative
Mail Code: HIPT-20
E-mail: sam.tyson@fhwa.dot.gov
16. Abstract
Extensive laboratory and field evaluations were conducted under this project to evaluate the effectiveness and limitations of the MIT Scan-2 device, which uses magnetic tomography technology to evaluate the placement of metal dowel bars in concrete pavements. The laboratory testing results confirm that the MIT Scan-2 device provides accuracy that is both reasonable and useful for horizontal and vertical misalignments within the following limits:
  • Depth - 100 to 190 mm (3.9 to 7.5 in.)
  • Side shift - +100 mm (+4 in.)
  • Horizontal misalignment - +40 (+1.6 in.) plus a uniform rotation of +80 mm (+3.1 in.)
  • Vertical misalignment - +40 mm (+1.6 in.)
The estimated overall standard deviation of measurement error is 3.0 mm (0.12 in.), which means that the device can provide measurement accuracy of +5 mm (0.20 in.) with 95% reliability. With proper calibration to account for dowel baskets, the device can provide similar levels of accuracy for dowel bars placed either in dowel baskets or by a dowel bar inserter. This assumes that the dowels are insulated (epoxy coated or painted) and that the transport ties are cut. Field experience with the MIT Scan-2 showed that the device is reliable and easy to use. Up to 400 or more joints can be tested in an 8-hour period using a single charge of the battery. An exception is that testing during cold weather greatly reduces the battery life.

The ability to assess MIT Scan-2 results and focus, in real time, on potentially needed adjustments both in the paving equipment and hardware and in the portland cement concrete mixture proportions make the MIT Scan-2 a unique and valuable tool.

The principal limitation of MIT Scan-2 is that the presence of other metal objects (such as tie bars, nails in the joint, coins, pieces of wire, or any other metal item) near the measurement region can introduce significant errors, effectively invalidating the results.

17. Key Words
concrete pavement, dowel bar alignment, joints, load transfer, magnetic tomography, MIT Scan-2, non-destructive testing.
18. Distribution Statement
 
19. Security Classif. (of this report)
 
20. Security Classif. (of this page)
 
21. No of Pages
80
22. Price
 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

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Updated: 04/07/2011
 

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