Abstract:
As freshwater is extremely scarce along the desert coast of Namibia ten experimental
sections of graded crushed stone base compacted with either seawater or freshwater as
controls were constructed in 1976 at Lüderitz. These sections included sections with
seawater only up to subbase level and seawater in all layers, with and without 5% added
gypsum in the base in order to simulate a gypseous binder, using freshwater base
sections with and without 0,5% added NaCl as control sections, as well as certain
compaction and construction time constraints. The mean salinity of the bases after
compaction and slushing with sea or freshwater as measured by the paste electrolytic
conductivity test were 0,4 – 0,5 S/m in the seawater sections in comparison with 0,15 S/m
in the freshwater section with seawater only in the subbase and lower layers and 0,09 S/m
in the section with freshwater in all layers, and the maximum of 0,15 S/m usually permitted
No significant salt damage occurred to the primed base or to the surfacing during or after
construction and after 35 years of monitoring it was concluded that at any time of the year
under conditions similar to those at Lüderitz seawater can be used in all layers including a
G3 base under a 19 mm Cape seal provided that certain precautions are taken.
