Abstract.

The proceedings of June 1993 international symposium held in Atlanta, Georgia, called specifically to develop and standardized evaluation procedures for non-destructive methods of testing pavements. The 29 papers discuss analytical models and techniques, measurement and calculation techniques in the field and laboratory, problems and errors associated with backcalculation methods and design parameters, and testing for other pavement uses. Also includes a history of the quest for a standard and the status of that effort. Reproduced from typescripts. Annotation copyright by Book News, Inc., Portland, OR

An evaluation of NDT equipment and acquisition of a Falling Weight Deflectometer (FWD) for the Illinois Department of Transportation was accomplished. This was followed by an extensive testing program using the FWD to evaluate concrete pavements in Illinois. Test results were evaluated and procedures developed for testing and evaluation of jointed and continuously reinforced concrete pavements. Results show that some causes of incipient distresses can be detected using the FWD device including subgrade strength, loss of load transfer and development of voids. Recommendations for rehabilitations are presented in the final report.

FWD testing was completed on three urban arterial sections and six residential streets prior to and after rehabilitation to select the appropriate layout for FWD testing, establish joint performance threshold values, optimize FWD testing time and cost, and evaluate the effect of asphalt overlays on joint performance parameters. Moreover, the performance of full-depth repairs (FDR) and the incorporation of joint performance at the design stage were studied. Residential streets joint and basin FWD testing was completed to evaluate the structural capacity of residential streets and compare their performance to arterial regional roads. Comparisons between two widely used FWD geophones layouts allowed for the selection of a layout that represents the more critical loading condition on joints. Peak deflections and differential deflections were correlated with load transfer efficiencies to select threshold values for LTEs, peak deflections and differential deflections to trigger rehabilitation at the appropriate time. Statistical testing was used to optimize FWD testing to two load levels instead of four. The study found that asphalt overlays reduce recorded deflections and overestimate computed joints performance parameters. The effect of asphalt overlays was evaluated to establish correction factors, Fasphalt, for each load level to estimate deflections on the concrete surface using deflections obtained from testing on the overlay surface of Pembina Highway. The correction was found to improve the reliability of joint condition evaluation for that site. The study also found that FDRs generally restore the load transfer capacity of joints with good support and mechanical load transfer achieved. Moreover, it was demonstrated that joint performance information can be used at the design stage in the decision-making process to select the location and type of joint repairs. Lastly, residential streets were found to have less load transfer capacity than arterial regional roads and weaker pavement structure. The findings from this study indicated that NDT can be used to evaluate pavement condition, determine layer stiffness for use in rehabilitation design and to improve planning of rehabilitation through timely determination of rehabilitation needs and improvement of the reliability of load transfer efficiency estimate and void detection of PCC joints.