Round-Robin Study of Asphalt-Concrete Content by Ignition

Abstract

The National Center for Asphalt Technology (NCAT) has developed a test method to determine the asphalt content of hot-mix asphalt (HMA) mixtures by ignition. In the ignition method, an HMA sample is subjected to heat of 538°C (1,000°F) in a furnace to ignite and burn the asphalt cement (AC) from the aggregate. The difference in weight of the sample before and after is used to determine the asphalt content of the mixture. The aggregate recovered after ignition testing may then be used for gradation analysis. A round-robin study was completed by NCAT to determine the accuracy and precision of the ignition method. The round-robin test program is discussed, as well as the accuracy and precision values determined for the measured AC content and gradation using the ignition method. The results of the round-robin study indicate that the ignition method can measure the AC content of HMA mixtures with greater precision than solvent-extraction methods, without significantly affecting the gradation of the aggregate. This test method has shown excellent potential for replacing existing test methods for measuring asphalt content.