Investigation of Cement–Bentonite Slurry Samples Containing PFA in the UCS and Triaxial Apparatus

Three mixtures of cement–bentonite
slurry containing 28, 36 and 44 % PFA (as a proportion
of cementitious materials) were tested using the
unconfined compressive strength and triaxial apparatus
to determine the stress–strain and shear strength
relationships for samples cured for various periods.
The samples were batched using 4 % bentonite and
20 % cementitious materials (by mass of water) and
allowed to cure underwater once extruded from sealed
moulds. Curing periods of 14, 28 and 90 days were
selected to investigate the changes in behaviour at
durations commonly specified (28 and 90 days) as
well as providing insight into changing behaviour with
curing (additional curing periods of 7 and 60 days
were investigated on a smaller number of samples to
increase understanding). Two rates of displacement
were used (1.0 and 1.3 mm/min) and four confining
pressures (0, 50, 100 and 200 kPa). Shear strength and
strain at peak deviator stress of the samples do not
appear to vary considerably with confining pressure.
For samples containing 28 % PFA, the majority of
physical properties exhibited by the cement–bentonite
samples change with curing period up to 60 days,
where after the properties become similar to those
cured for 90 days.