The project developed a method for assessing the condition of pavement layers based on falling weight deflectometer (FWD) deflection measurements.
The use of nondestructive deflection testing has become an integral part of the structural evaluation and rehabilitation process of pavements in recent years. Various types of equipment are used by state highway agencies to apply patterns of loading and record deflection data along the pavement. When pavements experience some form of distress, variations in pavement deflections and shape of deflection basin along a project will occur because of the differences in the condition of pavement layers. Currently available procedures for the analysis of deflection data do not identify the presence, location, and extent of distress within the pavement structure. Therefore, there is a need to develop a means for assessing pavement layer condition based on surface deflection data and thus reduce the need for destructive testing.
The research developed a methodology for assessing pavement layer condition based on surface deflection data. The method, applicable to all layers of rigid and flexible pavements that include an asphalt concrete (AC) surface layer, incorporates artificial neural network models and regression equations for estimating layer condition indicators from surface deflection data. The method also incorporates criteria, for assessing layer condition, that were developed on the basis of limited field data. The method assesses layer condition by comparing the estimated values of specific condition indicators to those for layers in good condition; it does not relate the difference to specific types of distress or other reasons. Methods for evaluating full-depth AC pavements and AC pavements with granular bases were incorporated into software designated APLCAP (Asphalt Pavement Layer Condition Analysis Program). Because this research involved limited evaluation of the method's applicability, further calibration and collection of specific data may be required to enhance interpretation of the method's outputs and ensure their validity. The agency's final report , including the software, has been distributed to all state highway agencies. The report is summarized in NCHRP Research Results Digest 254.
The unedited final report and appendices, as submitted by the research agency, are available below: