How Top-Size Affects The Resilient Modulus Of Roadway Base Materials

Abstract

The American Association of State Highway and Transportation Officials (AASHTO) uses resilient modulus values as the load-carrying capacity parameter for all pavement materials. However, the maximum sample diameter in standard resilient modulus test specifications is only 150 mm (6 inches). With that limitation, large-sized aggregates can not be tested at their full gradation because if top-size-to-sample diameter ratios exceed 1:5, arching effects occur during sample preparation which adversely affect the results. Thus, little work has been performed on the resilient modulus of large top sized aggregates. In this study, 305 mm (12 inch) diameter samples of two different aggregates were tested for resilient modulus. The materials were tested at top sizes of 63 mm (2.5 inches), 38 mm (1.5 inches), and 19 mm (0.75 inches). Results indicate that the tests bec~me less repeatable as top size increases, and that resilient modulus does not increase as top size increases. The second result is contrary to the conventional belief that load carrying capacity of aggregates increases with increasing top size.