Comparison of Moisture Damage in Hot-Mix Asphalt Using Ultrasonic Accelerated Moisture Conditioning and Tensile Strength Test Results (05-1692)
Martin McCann, USDA Forest Service
Richard Anderson-Sprecher, University of Wyoming
Kenneth P. Thomas, Western Research Institute
Shin-Che Huang, Western Research Institute

Ultrasonic accelerated moisture conditioning (UAMC) has been demonstrated to be a quantitative analysis to evaluate the moisture sensitivity of a hot mix asphalt mixture. Data from the UAMC test procedure was evaluated for repeatability and statistically compared to tensile strength test results after one and multiple cycles of freeze-thaw conditioning. UAMC is accomplished by containing a loose sample of hot mix asphalt on a sieve in a 60oC waterbath while subjecting the sample to ultrasonic energy. As the asphalt recedes from the surface of the aggregate, small particles of the mix are released and drop through the sieve. The percent of material lost from the sample is recorded for five hours and plotted with respect to conditioning time. The slope of a linear regression function that is fit to the data represents the rate at which the small particles are released as the asphalt recedes along the surface of the aggregate. The value of the slope has been demonstrated to be a quantifiable representation of the moisture sensitivity for a HMA mixture, and the greater the value the more susceptible the mixture is to moisture damage. Seven mixes were subjected to UAMC. Replicate samples were used to define the UAMC slope of the linear regression function and evaluate the repeatability of the UAMC one-day test procedure. Repeatability was confirmed in six of the seven mixes, and the average UAMC slope for all mixes had a significant relationship to tensile strength test results after one and multiple cycles of freeze-thaw conditioning.