Bentonite/cement grouts and slurries are used in the civil engineering industry
in various ground engineering processes. The specifications usually require
a minimum compressive strength or shear strength at 28 days age. The
interaction between the materials namely bentonite, cement and water is
complex; both the bentonite content and the cement content of the grout affect
the development of shear strength. An investigation of the development of shear strength has been made for a
range of grouts with bentonite contents from 5% to 20% by weight of water
and water/cement ratios from 4 to 12. The shear strength was measured at
various ages up to 336 days age using a Pilcon hand held shear vane tester,
for many grout mixes the shear strength was still increasing at 336 days age.
Two mixes were placed in vertical plastic pipes in order to investigate how
shear strength may vary with depth in a ground borehole.
A mathematical model has been developed to predict the shear strength of any
grout mix at any age within the range studied, the model comprises a simple
equation with two coefficients A and B which can be obtained from contour
plots depending on the mix proportions. The model has been tested using four
mixes different from those use to derive the model; statistically there is no
significant difference between the actual and predicted results and the model
can be used with reasonable confidence.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.