The relation between the strength of the remolded and field samples of cement clay column

Abstract

The addition of stabilizer i.e. cements or lime changes the clay particles in the clayey soils. Instead of plate-like or flaky shape of particles, the formation of CSH or CAH cluster which has spider or hairy cluster shaped (under scanning electron microscope) has created bonding which increased the shear strength of the stabilized soils significantly. According to BS 1924, in preparing the soils samples for unconfined compression, the stabilized soils need to be compacted to a certain degree of compaction by means of dynamic compaction. Author suggested that this dynamic compaction, without any measurement regarding what was the energy amount being imposed on the stabilized soil samples, might damage the CSH clusters or CSH matrix gel thus resulting non-reliable result on the strength of the laboratory prepared specimens. This result also does not resemble the strength developed in cement column or lime column in the field. The study divided into three major stages. Firstly was the preparation of samples for UCT based on BS 1924. The samples were compacted using static packing pressure and the required pressure was recorded as standard packing pressure (SPp). Secondly is the development of small scale physical model to study the undrained shear strength of the stabilized kaolinite. Finally is the preparation of UCT samples compacted to a pre-determined packing pressure (PPp). Pre-determined packing pressure is 50% of the standard packing pressure. It was found that, reducing 50% of the static packing pressure has reduced the strength of samples significantly. It was also found that the strength of samples compacted to SPp is approximately ten times higher than that of cement column model at 56-days curing for samples of 6% to 18% cement. Electric or ionic conductivity trend shows that as the strength increase, the conductivity value would decrease. This finding has led author to conclude that electric or ionic conductivity test can be applied as supporting test in predicting the strength development in cement stabilized kaolinite. © 2008 ejge.