The Jwaneng Kalahari Sand-Asphalt LTPP Experiment: Performance Over 14 Years and Derivation of Pavement Designs

Abstract

The Jwaneng long-term Kalahari base course experiment on the Kanye-Jwaneng road in Botswana was opened to traffic early in 1980. It consisted of 12 sections of Kalahari fine sand- asphalt using various tars and bitumens and 11 sections of calcrete with two control sections of gravel base and subbase, all under a double surface treatment and most over an untreated Kalahari fine sand as subbase and lower layers. The purpose of the experiment was to evaluate various alternative base material and thickness designs for roads in the Kalahari where good quality gravels are scarce. However, only the sand-asphalts and their performance are described here as the calcretes have been reported elsewhere. After about 0,4 ME80 in 13 years when the experiment was terminated an analysis of the data available enabled conservative designs to be derived for pavements with Kalahari sand-asphalt bases on untreated sand lower layers to carry traffic in five categories ranging from 0,1 to an extrapolated 1,0 ME80. The experiment also showed that it is not necessary to import a gravel subbase as sand compacted to 97-100% MAASHO performed well and, if confined, could even be considered as untreated base course for a lightly trafficked road.