Abstract:
Construction of a new road may require the daily use of upwards of 1 000 m3 of water –
usually fresh – sufficient for 20 000 people at the Cape Town drought ration of
50 litres/day. The Swartklip experiment was therefore constructed in 1975 in a moderate
macroclimatic area near Cape Town and the Lambert’s Bay experiment in a dry area of
the Western Cape Province, South Africa, in order to ascertain how to use seawater for
the compaction of graded crushed stone bases without incurring damage to the base
during construction or compromising its long-term performance. After completion, the
seawater crushed stone bases had salinities as determined by the saturated paste
electrolytic conductivity test of 0,5 S/m in comparison with the freshwater controls of 0,06
and 0,08 S/m respectively, and the maximum of 0,15 S/m later normally permitted. After
up to 30 years of monitoring both during and after construction, it is concluded that
seawater can successfully be used in all layers of a flexible pavement with a graded
crushed stone base under a 13 or 19 mm Cape seal for at least a 20-year design life,
provided that certain precautions are taken in the design and during construction
