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1.1 This test method covers the equipment, field procedures, and interpretation methods for the assessment of Portland Cement Concrete Pavement dowel bar alignment using Magnetic Pulse Induction (MPI), also referred to as magnetic imaging tomography or eddy current tomography. Magnetic Pulse Induction (MPI) devices induce a weak pulsed magnetic field that causes the induction of eddy currents in metal objects disturbing the field. When metal (dowel bar) enters into the field an electrical signal is produced and processed through algorithms to detect and produce quantitative values for the depth, alignment and side shift locations of each dowel and tie bar present in the pavement joint.

1.2 MPI equipment includes the following systems scanning device that induces the magnetic field and collects the electrical signal, orientation system such as a rail system, field data collection device that collects the signal data from the scanner, performs field analysis, and stores data, analysis software package that calculates the dowel bar positions, allows data adjustments to account for detected anomalies and produces reports.

1.3 MPI field procedures describe the steps and processes required to collect reliable, repeatable and accurate results from the scanner operation and orientation system. Critical to the accuracy is the absence of any metal items except for the dowel bars in the vicinity of the joints being tested. Metal in the scanner and orientation system should be minimized. The scanner operation procedures cover the collecting of the data, reviewing the results on the field data collector, and determining if the data collection test was successful.

1.4 MPI interpretation methods describe how to analyze data collected in the field procedure, steps taken to address interferences, and anomalies discovered during the data analysis to provide accurate results for the dowel bar positions. Also minimum report content is prescribed for the production of meaningful test information substantiating the results.

1.5 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

5.1 Joints in concrete pavements of highways, airfields, and other facilities are exposed to stresses and strains due to traffic and temperature variation. Examining concrete pavement dowel bars (see Specifications A615/A615M and A1078/A1078M) in joints is important to insure that load transfer at joints between concrete slabs occur efficiently in order to prevent damage to the pavement and thus shortening its service life. Using Magnetic Pulse Induction (MPI) to examine dowel bars provides owners and contractors a non-destructive testing method to determine that the bars are installed correctly. MPI examination can be performed on existing joints and can support forensic investigations into pavement failures.

5.2 The use of MPI methods and equipment provides a Quality Control process for installers to use to document that dowel bars are installed correctly in new pavements. Owners use the same device to perform Quality Assurance activities and accept installed facilities from contractors.

5.3 MPI devices provide reliable quantitative results that are repeatable with not only the same device but also with other calibrated MPI devices.