Volume 32, Issue 4 (July 2004)
An Alternate Method to Determine Asphalt Content of Hot Mix Asphalt Using Volumetric Properties
Accurate determination of asphalt content (AC) in hot mix asphalt (HMA) is essential to evaluate the performance characteristics of HMA pavements. The standard test methods for determining the AC, currently used by the Oklahoma Department of Transportation (ODOT) and other DOTs and asphalt industries, are time-consuming, environmentally unsuitable, and not applicable to several absorptive and dolomitic aggregates. This study has developed a systematic method for the determination of AC using volumetric properties of aggregate, asphalt, and HMA mix. The developed method employed the theoretical maximum specific gravity (Gmm) of an HMA mix, the bulk and apparent specific gravity of the aggregate (Gsb and Gsa), and the specific gravity of the asphalt binder (Gb). The CoreLok™ device is used to determine the volumetric properties of the aggregate and HMA mix. This developed method is easy to use, environmentally safe, time efficient, and accurate. Three different aggregates were selected for the study based on varying gradation, absorption, and ignition oven correction (IOC) factor. HMA mixes were prepared with each of these aggregates using 5.0 %, 5.5 %, and 6.0 % AC. For each of the mixes, AC was calculated using the proposed method and compared with the actual AC value. The predicted AC values were compared with AC values from the ignition oven method (AASHTO T 308) and the solvent extraction method (AASHTO T 164). Results showed that the proposed method predicted the AC of HMA mix accurately. The method introduces a correction factor (Cv), which needs to be determined during the design stage and specified on the mix design information. The Cv value is used to calculate AC by the proposed method during quality assurance and quality control at the production and service life of HMA.