The conclusions from this study are based upon the research results obtained during two phases of research. The first phase of work was conducted to identify test conditions within the Asphalt Pavement Analyzer (APA) that produced results most related to field rutting performance. The results were used to recommend a tentative APA test method. Based on this phase of work, cylindrical samples compacted to 4-percent air voids and beam samples compacted to 5-percent air voids resulted in APA laboratory test results that were more closely related to field rutting performance than were cylindrical and beam samples compacted to 7-percent air voids. Samples tested in the APA at a test temperature corresponding to the high temperature of the standard performance grade for a project location better predicted field rutting performance than did samples tested at 6°C higher than the high temperature of the standard performance grade. Samples tested with both the standard and large-diameter hoses predicted field rutting performance about equally; however, samples tested with the standard hose produced less variability. Beam and cylindrical samples predicted field rutting performance about equally. The second phase of the study was conducted to validate the proposed APA test http://gulliver.trb.org/publications/nchrp/nchrp_rpt_508.pdf This report may be accessed by Internet users at method. Laboratory rut depths measured by the APA had good correlations on individual project basis; however, it is generally not possible to predict field rut depths from APA testing on a specific project using relationships developed from other projects with different geographical locations and traffic. (Author/publisher)
Abstract