Referring to Figure 4, at all mixing water contents as low as LL of the soil, cement content
decreased with increased W/C ratio dramatically up till W/C ≈ 6. The solidification effect
will increase with decreasing W/C ratio. Indeed, it has been reported that specimens with
identical W/C ratios demonstrate the same stress-strain behaviour as well as strength
characteristics in unconfined compressive strength tests (Miura et al., 2001). At higher water
contents, the plot’s gradient takes a gentler turn, indicating lesser dependency of W/C ratio on
the cement dosage. With increased water content, the effect of fabric diminishes, particularly
if the cement percentage added is comparatively low. It was further elaborated by Miura et al.
(2001) that W/C up to 10 is considered in the low range, where the fabric of the clay-cement
mixtures plays a negligible role in the shearing resistance or load-bearing. Mixing was carried
out using a small spatula in scooping motions, mimicking field shallow mixing with a
backhoe. The mixing frequency was fixed at 5, 50 and 100 cycles, to simulate a poor to
adequate agitation of the soil-cement mixture for attaining uniformity. The mould containing
the mixture was finally tapped 50 times to avoid formation of large voids, excessive
adherence of materials on the interior wall and an overly undulating top surface. Both the
number of cement layers and mixing cycles were considered primary factors affecting the
mixing quality, while the mixing water contents as well as cement dosages served as the
initial conditions of mixing environment. All specimens were cured in an airtight container at
controlled room temperature of 20oC and relative humidity of 70 %. At the age of 28 days,
unconfined compressive strength test was performed on the specimens following the standard
procedure of JIS A 1216-1993. The test was considered suitable for the purpose of gauging
the effect of uniformity as it measures the representative strength of a specimen, which is
indeed a measurement of the average compression resistance. Complementary observations
of the specimens’ internal composition and structure were also carried out using X-ray CT
(computerised tomography) scans. The scanner employed for the purpose had an X-ray
irradiation angle of 60o in cone shape, and was equipped with micro-focus function
(minimum focus size 4m) for capturing high resolution images of very small parts in a
specimen