Construction and Performance of a Stone Matrix Asphalt Mix Test Section in Virginia

About the report:

SMA is a gap-graded mix filled with a rich asphalt-fines mastic developed in Europe. In 1991 five states constructed trial sections to determine if satisfactory mixes could be produced in the United States with current materials and high rates of production. This report discusses Virginia's first section, placed in 1992 near Lynchburg. During construction, better equipment was necessary to control the amount of fines contained in SMA mixes. Lack of control in the mix gradation caused variability on the roadway and on routine mix tests conducted during construction. The mix containing the cellulose fiber, Arbocel, has rotted more at stoplights than the mix containing the polymer, Vestoplast, or the high-stability control mix. However, all mixes continue to perform well. Laboratory creep tests and gyratory shear tests predicted that the control mix and Vestoplast mix would be more resistant to rutting and consolidation under traffic. This investigation and work in other states have improved the current Virginia specification for SMA. The gradation was coarsened, a stiffer asphalt cement was required, and plant equipment that can adequately handle the aggregates was used. With these changes, future installations will perform better than the current dense graded mixes.

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