A review has been made of literature describing the results of research into the properties and performance of unbound mineral aggregate used in the construction of road pavements. This review highlights the different approach taken in New Zealand to the design and construction of highway pavements, compared to that used in the United Kingdom, the United States, Australia and Europe. In New Zealand, unbound aggregate is used as a structural layer immediately under a thin bituman seal.
The geological characteristics of an aggregate determine the way it will perform as a roading material. Petrographic analysis, combined with some mechanical tests, can provide a good guide of durability.
Structural properties are related to density which is a function of particle-size distrubution, particle shape, compactive effort and water content.
Recent research into the theory of shakedown and in the use of the laboratory shear-box has provided a much clearer appreciation of the factors which influence the performance of an unbound aggregate pavement.
Keywords: Aggregates, pavements, roads