Nuclear method for determination of asphalt content corrected for moisture in bituminous mixture. Final report, March 1988-February 1989

This report presents results of research on the development of a method for determination of asphalt content corrected for moisture using the nuclear-gauge method. The researchers selected an approach that involved rapid drying of the asphalt concrete samples in a microwave oven prior to the determination of asphalt content using a Troxler Model 3241-C nuclear asphalt-content gauge. As a reference, asphalt contents were also measured using quantitative extraction. In general, good agreement was found between asphalt contents measured by the Troxler Model 3241-C nuclear gauge and asphalt contents measured by quantitative extraction. In extended sampling for Plant 1, no significant increase in nuclear gauge error was seen over a 10-day sampling period, which indicates that daily calibration of the nuclear gauge is probably unnecessary to maintain satisfactory performance. The field demonstration of the procedure of drying the bituminous mixture in a microwave oven and then determining its asphalt content by the nuclear method indicated asphalt-content results were obtained approximately 1 hour faster than results obtained by quantitative extraction