United States Department of Transportation
i
Evaluation of Procedures Used to Predict Moisture Damage in Asphalt Mixtures: Executive Summary
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1986-09-01
[PDF-789.94 KB]
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Abstract:Procedures for evaluating the moisture susceptibility of asphalt mixtures were compared by performing them on mixtures having a known history of susceptibility. Data included the retained ratios, visual stripping, mechanical values (tensile strength, stability, etc.), saturation, and swell. The most promising procedures appeared to be the NCHRP 246 and NCHRP 274. Moisture susceptibility was not effectively predicted by the 1-Minute Boiling Water, 10-Minute Boiling Water, Immersion-Compression, Marshall-Immersion, and Dynamic Tumbling procedures. The NCHRP 246 procedure (often referred to as the Lottman procedure) contained two parts: one for short-term pavement performance, and one for long-term pavement performance. The short-term part was not found to be useful with regards to predicting performance. An 80-percent pass/fail criterion was chosen for both tensile strength ratios in the NCHRP 246 and NCHRP 274 procedures, and 70 percent for the M sub r test. Ten percent or greater visual stripping generally indicated unacceptable damage in all procedures performed on compacted mixtures. The data indicated that a freezing period, or higher air void levels, can be beneficial for evaluating moisture susceptibility. The degree of saturation was found to be important in that sufficient water must enter a specimen; however, saturation was not found to be the dominant factor affecting moisture damage. The effects of saturation were masked by other mechanisms such as the type of mechanical test, air void levels, and freezing. There was no conclusive evidence that high saturations or oversaturation due to vacuum conditioning adversely affected the test results.
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