SCIENTIFIC OR TECHNICAL NOTE Use of granulated blast furnace slag and lime in cement-bentonite slurry wall construction Davood Talefirouz *1 , Erdal C ¸ okc ¸a 1 and Joshua Omer 2 This paper describes an experimental investigation on the use of ground granulated blast furnace slag (GGBFS) and lime as stabilizers for cement-bentonite (CB) slurry used in constructing vertical barrier walls. The primary objective is to develop a blended material, which can reduce the permeability and also enhance the strength of CB slurry walls with a shortened curing time. Mixtures comprising various proportions of cement, bentonite, GGBFS, and lime were prepared and tested for particle size distribution (PSD), liquid limit, plastic limit, permeability, unconfined compressive strength (UCS), and constrained modulus. For each mixture, the effect of varying curing time on the results of the aforementioned tests was also investigated. The research results demonstrate that blending CB with optimum fractions of GGBFS and lime lead to decreased permeability and increased UCS of the mixture, without any adverse consequences. Thus, subject to satisfaction of other requirements, it is concluded that a potentially superior material for constructing slurry walls can be achieved by using CB-GGBFS-lime blended mixtures. Keywords: Cement-bentonite slurry, Slag, Lime, Constrained modulus, Permeability, Unconfined compressive strength List of symbols CB cement-bentonite c v coefficient of consolidation C-S-L cement-slag-lime E D constrained modulus GGBFS ground granulated blast furnace slag G s specific gravity i hydraulic gradient k con consolidation permeability k fw flexible wall permeability LL liquid limit m v coefficient of volume change PI plasticity index PL plastic limit PSD particle size distribution q u unconfined compressive strength u pore pressure s 3 cell pressure s 9 effective stress Introduction The slurry trench method is used for creating impermeable groundwater barriers and has been used to create cutoff walls in the core or foundation soils beneath dams and dykes of different types and sizes. These subsurface barriers consist of a vertically excavated trench that is filled with slurry. Cement-bentonite (CB) slurry vertical barrier systems are widely used to control groundwater movements. A significant role of the barrier as a ground remediation system is to reduce the rate of groundwater flow. The installation process for a vertical barrier involves excavat- ing a trench to the desired depth while simultaneously pumping in the CB slurry to maintain the stability of the sides of the excavation. Typically, the slurry consists of about 95% water and 4–6% bentonite by dry mass. Cement-bentonite mixtures as slurry wall materials usually have a coefficient of permeability in the range of 10 27 to 10 28 ms 21 ; however, these limits may not be appropriate for certain site conditions. Since conventional plain CB slurry walls may not always achieve the maximum permeability desired, mod- ification of CB with some industrial waste materials such as GGBFS have been attempted and it has been found that this can lower the permeability significantly. As far as strength is concerned, it has been possible to incorporate GGBFS in mixtures to enhance the self-hardening proper- ties of CB slurry walls. 1 Civil Engineering Department, Middle East Technical University, Ankara, Turkey 2 Kingston University, Surrey KT1 2EE, UK *Corresponding author, email talefirouz.davood@metu.edu.tr ß 2014 W. S. Maney & Son Ltd Received 27 October 2014; accepted 13 January 2015 DOI 10.1179/1939787915Y.0000000005 International Journal of Geotechnical Engineering 2014 VOL 0 NO 0 1