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10632699 
Technical Report 
Evaluation of infrared ignition furnace for determination of asphalt content 
Prowell, BD 
2002 
National Center for Asphalt Technology, Auburn University 
Auburn, AL 
NCAT Report 02-05 
20 
English 
This study evaluated the Troxler Model 4730 infrared ignition furnace as compared to a standard Thermolyne ignition furnace. Comparisons were based on correction factor for aggregate loss during ignition, accuracy and variability of the measured asphalt content and aggregate degradation during ignition. Forty-eight samples, representing two nominal maximum aggregate sizes (9.5 and 19.0 mm), four aggregate types (granite, crushed gravel, limestone and dolomite) and two asphalt contents (optimum and optimum plus 0.5 percent asphalt content) were tested in each furnace.

The results indicated that the correction factors for aggregate loss during ignition were significantly different for each type of furnace, thus requiring a separate calibration for each type of furnace. Practically, the differences for all but the 9.5 mm NMAS limestone and both dolomite mixtures are less than 0.1 percent. The samples at optimum plus 0.5 percent asphalt content were tested using the calibration factors developed for a particular mix/furnace combination. The results were analyzed in terms of accuracy (bias) and variability (standard deviation). Neither the measured bias’ nor standard deviations for the two types of furnaces were significantly different. Results from four sieve sizes (NMAS, 4.75, 2.36 and 0.075 mm) were evaluated for aggregate breakdown. A comparison of the recovered aggregate gradations from both furnaces indicated no significant difference in the degree of aggregate degradation during the ignition test. Therefore, based on the comparison of a single unit each of the standard and infrared furnaces, properly calibrated, they both should produce statistically similar asphalt contents and recovered aggregate gradations.