Soil compaction and strength indicators were assessed
on prepared samples (<4.75 mm) using the standard
Proctor test explained in detail by [19]. Compaction was
done in three layers at different water contents (ranging
from 5% - 65% by wt) using 25 blows from a standard
Proctor hammer (mass—2.5 kg; drop height—305 mm)
in a cylindrical mould of diameter 102.05 mm. Moisture
contents for compacting each soil were chosen based on
the consistency limits. The soils were left to equilibrate
over night prior to compaction. Compacted soils were
oven dried at 105˚C for 24 hrs and weighed to determine
dry bulk density. For soils containing expanding clay
minerals, volume measurements were made directly on
the soil to cater for shrinkage during drying. Additionally,
replicate cores were used to determine PR and SH, using
a spring type cone penetrometer (Eijkelkamp; 06.01.SA)
and the CIT (Simon Deakin Instruments; CIST/882) respectively. Five readings with a 1 cm2
cone, (cone angle
of 60˚), inserted to 2 cm were averaged to obtain the
mean surface PR, whilst the reading corresponding to the
forth drop of the hammer (mass—2.25 kg; drop height—
457 mm) was recorded as the Cmax [20]. Moisture contents of the compacted soils were determined gravimetrically
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