Stone Matrix Asphalt is a gap-graded hot-mix asphalt mixture composed of a coarse aggregate skeleton and a binder-rich mortar. The mixture type was first introduced to the United States in 1991, with one of the first test sections placed on I-70 near Richmond, Indiana. To help control the selection of coarse aggregate, the Indiana Department of Transportation specified a maximum Los Angeles Abrasion loss value of 30 percent. An investigation into the coarse aggregate specifications for use in Stone Matrix Asphalt was completed in this study. Emphasis was placed on evaluating various tests that may be useful is specifying coarse aggregates, and to develop a test or set of tests and specifications. Finally, the validity of the current 30 percent Los Angeles Abrasion loss value as requirement for coarse aggregate selection was determined. A survey of state agencies revealed a large variation in the Los Angeles Abrasion values currently specified. Laboratory testing revealed that the Micro-Deval test is a good compliment to the Los Angeles Abrasion test. The Micro- Deval test presents an added benefit as it includes the presence of water. Of the four tests investigated, aggregate degradation during compaction was the most accurate method for predicting coarse aggregate performance of the four tests. A combination of the Los Angeles Abrasion, Micro-Deval, and aggregate degradation tests was even more accurate in predicting coarse aggregate performance.

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Stone Matrix Asphalt, aggregate strength, Micro-Deval, Los Angeles Abrasion, SPR-2865

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, IN

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