Containing 13 papers from the December 2000 conference in Orlando, Florida, this book covers the use of the PURWheel laboratory tracking device, the Asphalt Pavement Analyzer, the identification of aggregate role, the evaluation of sensitivity, fine aggregate angularity, guidelines for the selection

Introduction and research approach -- Findings -- Interpretation, appraisal, and application -- Conclusions and suggested research -- References -- Abbreviations used without definitions in TRB publications.

The performance of hot mix asphalt, Portland cement concrete, unbound base, and subbase layers in a pavement are significantly affected by aggregate shape characteristics. Classification of coarse and fine aggregate shape properties such as shape (form), angularity, and texture, are important in predicting the performance of pavements. Consequently, there is a need to implement a system that can characterize aggregates without the limitations of the current aggregate classification standards. The Aggregate Image Measurement System (AIMS) was developed as a comprehensive and capable means of measuring aggregate shape properties. A new design of AIMS will be introduced with several modifications to improve the operational and physical components. The sensitivity, repeatability, and reproducibility are analyzed to evaluate the quality of AIMS measurements. The sensitivity of AIMS is evaluated and found to be good for several operational and aggregate parameters. Important operational and environmental factors that could affect the AIMS results are identified and appropriate limits are recommended. AIMS is able to control normal variations in the system without affecting the results. A comprehensive analysis is conducted to determine the repeatability and reproducibility of AIMS for multiple users and laboratories. Single-operator and multi-laboratory precision statements are developed for the test method in order to be implemented into test standards.

The Superpave mix design system includes four consensus aggregate properties to ensure aggregate quality: coarse aggregate angularity, flat and elongated particles, fine aggregate angularity, and sand equivalent. In addition to determining these consensus aggregate properties, ascertaining aggregate gradations and specific gravities are also required to complete an optimal mix design. A method of extracting the asphalt from recycled asphalt pavement (or from quality control/quality assurance samples) that would produce a clean aggregate sample for analysis was needed. VDOT has used the ignition method for determining asphalt content and for the recovery of aggregates for gradation analysis since 1995. This study evaluated the effect on aggregate properties of samples extracted using the ignition furnace. For the purposes of the study, recycled asphalt pavement was artificially produced by mixing virgin aggregates with asphalt and aging the mixture prior to extraction in the ignition furnace. Consensus aggregate properties, specific gravity tests, and gradation analysis were performed on three replicates each of the virgin and recovered aggregates. Only the sand equivalent test and aggregate-specific gravities showed regular significant differences. It was found that the specific gravity values measured for aggregates recovered using the ignition furnace were closer to the measured values for the virgin aggregates than the effective specific gravity method which has been traditionally used for estimating a bulk gravity for recycled asphalt pavement. As a result of this study, recommendations were made to the Virginia Department of Transportation to change testing requirements on recycled asphalt pavement.