3.7.2 Maximum Size
It is usual to limit the maximum particle size so that the material can be laid by machine and a smooth finish, suitable for traffic or for sealing, achieved. For high quality crushed rock base materials, a maximum nominal size of 20 mm is considered suitable to provide for ease of compaction, minimisation of particle segregation and a smooth surface finish. However, larger maximum size (e.g. 30 mm and 40 mm) natural materials can be handled satisfactorily.