Untreated aeolian sand base course for low-volume road proven by 50-year old road experiment

Abstract

The Hoopstad long-term pavement performance experiments constructed in 1962 between Hoopstad and Bultfontein in the Free State Province of South Africa included a 90 m section of a fine-grained, nonplastic, A-2-4(0), aeolian, Kalahari-type sand as unstabilised base course. After 50 years and approximately 1.0M E80 all the experimental sections are still carrying traffic, none has been rehabilitated and none appears to have ever failed. The results of a pavement evaluation carried out in 2013 indicate that similar sand can be used unstabilised as base course for a Category C or D low-volume road designed to carry up to at least 0.1M E80/lane over 20 years, provided it is compacted to refusal or at least 100% MAASHO on a good support, is well drained, well sealed with at least the equivalent of a double seal, and that the shoulders also offer good lateral support and drainage. The seal must also be sufficiently wide to accommodate the traffic expected. Such a design offers tremendous potential for the construction of relatively inexpensive, all-weather, low-volume roads in the vast area of arid and semi-arid southern Africa in which similar sands and a scarcity of gravels occur.