Effectiveness of cement on hydraulic conductivity of compacted soil-cement mixtures

The paper presents the results of an experimental study on the hydraulic conductivity of compacted soil-cement mixtures. The effectiveness of 5% cement addition is evaluated by the permeability value at 28 days' curing and by the ratio of the hydraulic conductivity of the untreated soil to that of the mixture, both compacted wet of optimum with a Proctor Standard effort. Laboratory compaction and permeability tests were performed on 15 soils of different grain size (sandy to clayey soils) and mineralogy. For all the investigated soil-cement mixtures hydraulic conductivity values lower than 2 X 10(-7) cm/s have been achieved after the cement addition. A statistical analysis was developed in order to evaluate relationships between hydraulic conductivity and soil compositional and compaction variables. Prediction models for all soil types and for fine-grained soils are given. In particular, for fine-grained soils a regression equation is proposed that can be used to reliably predict the hydraulic conductivity of compacted soil-cement mixture as a function of clay fraction, fine fraction and liquid limit. Practical applications of the proposed prediction models and the precautions for using them are discussed.