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The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.

Title:

Use of Ground-penetrating Radar for Detecting Voids Underneath a Jointed Concrete Pavement
Authors:
Clemeña, G. G.
Long, R. R.
Michael M. Sprinkel
Michael M. Sprinkel
Year: 1986
VTRC No.: 86-R36
Abstract: A survey of a jointed, reinforced concrete pavement with ground-penetrating radar indicated that the equipment provides a nondestructive inspection technique that can be used at a minimum rate of 5 lane miles of pavement per hour and with only minimal interference with traffic. The coring of some slabs and subsequent use of a devised water test revealed that the radar was very effective in detecting voids deeper than 1/8 in but considerably less .effective in spotting shallow voids. The overall accuracy was approximately 68%, which indicates that the sensitivity of the equipment needs to be improved. The location component used with the radar unit showed insufficient accuracy. A regression analysis of the recorded quantities of grout used daily in subsealing portions of the pavement versus the total linear feet of vbids detected underneath the slabs grouted each day yielded only a 51% correlation. However, the regression was found to be significant at a 95% probability level. It is believed that if the width and depth of each void can be conveniently estimated so that the extent of voids can be expressed in terms of volume instead of length only, an even more successful method of estimating grout quantities would be available. It has been shown that information derived from a radar survey can be very useful in developing a sound and cost-effective slab stabilization operation through the proper placement of grout holes.