Evaluations of aggregate size characteristics in stone matrix asphalt (SMA) and Superpave designed mixtures

Stone Matrix Asphalt (SMA) has been used in Europe and Scandinavia for three decades and in the United States since 1991. However, it was not until 1995 that a standard mixture design procedure was developed by the National Center for Asphalt Technology (NCAT) for the Transportation Research Board. The procedure was the product of a study initiated by the National Cooperative Highway Research Program (NCHRP). A major objective of NCHRP Project 9-8, Designing Stone Matrix Asphalt Mixtures, was to develop a simple, straightforward mixture design method for Stone Matrix Asphalt. The emphasis of this research was for SMA having a nominal maximum aggregate size (NMAS) of 19 mm. Further study was warranted to verify that the design procedure was applicable for other nominal maximum aggregate sizes. The results of this study are presented in this dissertation.; The Superpave System is the product of the Strategic Highway Research Program (SHRP), which includes a set of new procedures for the design of hot mix asphalt (HMA) mixtures. Research was needed to objectively assess the role of NMAS and gradation in the overall performance of HMA mixtures. Thus paper also presents an examination of NMAS and gradation of Superpave designed mixtures as well as a comparison of SMA and Superpave designed mixtures having the same NMAS as the basis for comparison.; SMA mix designs were performed for five nominal maximum aggregate sizes (25 mm, 19 mm, 12.5 mm, 9.5 mm and 4.75 mm).; The findings of this study indicate that the SMA mix design procedure developed for NCHRP Project 9-8 is indeed applicable for various NMAS mixtures including 19 mm. APA wheel tracking results indicated that all mixtures tested exhibited good rutting resistance; although, it was observed that the fine graded Superpave mixes generally performed better than the others tested. Permeability test data indicated that SMA mixes were generally 10 to 10,000 times more permeable than the Superpave designed mixtures. An exception was the coarse graded Superpave designed mixture with 25 mm NMAS, which exhibited permeability similar to that of the three SMA mixtures with an NMAS of 25 mm. As a result, these mixtures may require more compaction in the field to achieve lower in-place voids in order to minimize permeability and the susceptibility for water induced damage. (Abstract shortened by UMI.)...