Evaluation of the Effect on Aggregate Properties of Samples Extracted Using the Ignition Furnace

About the report:

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.

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