Here's an abstract of a wonderful abstract found here: written by Van Stephan Burroughs in fulfilment of the requirements for the Degree of Doctor of Philosophy in the Faculty of the Built Environment, University of New South Wales.
"The results show that over 90% of the variation in stabilised strength and density of the samples is due to variation in soil properties, with differences in stabiliser type or stabiliser quantity being relatively minor."
"The most important soil properties explaining stabilized strength are linear shrinkage (linear shrinkage) and plasticity index"
say what now?
"These results stress the importance of selecting a soil favourably predisposed to stabilisation. Field techniques to search for such soils could be refined on the basis of the new soil criteria presented. Use of the criteria should also minimise unnecessary laboratory testing of the density and strength of soils that subsequently prove unsuitable for stabilisation. A flow chart is presented to guide practitioners through the different stages of soil testing, assessment, and rammed earth stabilisation."