Reduced rutting in unbound granular pavement layers through improved grading design

Experiments to quantify the resistance of compacted granular materials to wheel track rutting revealed the importance of aggregate grading and the need for correct procedures for simulation tests. Selection of an optimum grading to maximize compacted density produced a material with significantly improved resistance to rutting and a slight increase in load spreading capability. These performance characteristics were demonstrated through experiments with two types of wheel tracking and the use of repeated load triaxial tests. Repeated plate loading tests caused much smaller permanent deformations than moving wheel loads, while bidirectional wheel loading proved to be more damaging than unidirectional loading, The main practical conclusion from the research was that improved performance from granular materials can be achieved by proper aggregate grading design.