Nearly all highway, airport, dock and industrial pavements contain large quantities of untreated aggregate in the form of unbound pavement layers. In many pavements, which are lightly or moderately trafficked, crushed rock or gravel derived aggregates comprise the majority of the construction or, in the case of unsealed pavements, all of the structure. This book provides studies of the performance and description of this material that will help the reader to better understand its characteristics and behaviour both alone and as part of the pavement structure it forms. This work will be useful to practitioners, policy makers, researchers and students. It forms a sequel to the earlier book "Unbound Aggregates in Road Construction" also published by Balkema.