AASHTO T 308, “Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method,” requires determination of asphalt and aggregate correction factors for asphalt mix designs for each ignition furnace used to test a design. In some cases where there are numerous asphalt mix designs or numerous ignition furnaces testing a particular mix design, correction factors are shared between ignition furnaces, though this practice is not permitted by AASHTO T 308 without supporting evidence.
There is a lack of knowledge of (1) how ignition furnace installation, operation, and maintenance influence correction factors and (2) ways to minimize differences that arise between ignition furnaces. Moreover, there is a lack of a statistically valid verification procedure to identify causes for non-comparing, statistically different, or biased test results from ignition furnaces. A verification procedure will promote consistency in results and assist in dispute resolution.
The objectives of this research are to (1) determine the significant influences that affect the variability of asphalt and aggregate correction factors for ignition furnaces; (2) develop guidelines for the installation, operation, and maintenance of ignition furnaces to minimize the variability in correction factors between furnaces; and (3) develop and document a statistically valid correction factor verification procedure to identify and troubleshoot causes for non-comparing, statistically different, or biased results of AASHTO T 308.This research shall focus on the influence of the installation, operation, and maintenance of current commercial ignition furnaces on correction factors. However, the potential interactions of mix components may also be considered, if judged relevant. As used herein, the term “ignition furnace(s)” encompasses (1) convection and direct infrared units; (2) units with internal and external weighing; (3) commercially available units; and (4) units located in the same or different laboratories.