The recent AASHTO Guide for the structural design of flexible pavement uses resilient modulus
as the input property for different pavement layers. Different aggregate sources as well as the
relatively wide range of gradation (as set by specifications of the Saudi Ministry of Transportation)
of aggregates to be used for base layer make it necessary to study the effect of these two factors on
the resilient behavior of these aggregates. Two models were used to describe the resilient behavior
of tested aggregates. The main regression constants (K1 and K3) of both models were found to be
significantly affected by aggregate type but not by aggregate gradation. Regression models were
also developed to relate these constants to aggregates' physical properties.