Design of Overlays for Flexible Pavements Based on AASHTO Road Test Data

Report No: 78-R37

Published in 1978

About the report:

The need for a suitable method of designing the thickness of overlays and predicting the performance of the overlaid pavement has recently been recognized. The AASHTO Road Tests included studies on 99 overlays, but they failed to produce conclusive results and hence provided no guidance for overlay designs. In the present investigation the raw data on the 99 overlays tested at the AASHTO Road Tests were evaluated. In the process, the raw data on the pavements that were overlaid also had to be evaluated. A relationship between pavement serviceability, 18-kip equivalents, and the thickness index of the pavements before the overlay was determined. The relationship so developed was found to apply to the overlaid pavements. Based on this relationship, the strength coefficient of the overlay was determined and a method of designing the thickness of an overlay was developed. This design method does not require the use of pavement deflection data by which the thicknesses of overlays are usually designed.

Disclaimer Statement: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.


Other Authors

Nari K. Vaswani

Last updated: January 27, 2024

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