Wearing courses for unpaved roads in southern Africa: a review

The requirements of and some specifications for wearing courses for unpaved roads are reviewed. It is concluded that further development of specifications is required, and that there is probably great scope for improvement of South Africa's unpaved roads through better materials selection and proper compaction. Whereas it may often be relatively easy to select a satisfactory coarse grained material visually, it appears that there is only a 50:50 chance of satisfactory material being placed on the road when it is fine-grained. In such cases testing must be carried out. More use of the CBR test for materials selection seems to be indicated, as well as simple field and laboratory control tests. For improved materials selection to be successful more attention will probably also have to be paid to improved materials location.