A comprehensive laboratory investigation on the workability

compressibility and hydraulic conductivity of fine-grained zeolite-amended clayey soil-bentonite backfills is conducted via a series of slump and oedometer compression tests. Kaolin is used as the control clayey soil

and it is amended with various contents of bentonite and zeolite to prepare zeolite-amended kaolin-bentonite (ZKB) backfills. The study results are compared with those of zeolite-amended sandy soil/Na-bentonite backfills as well as compacted zeolite-bentonite liners reported in previous studies to clarify the effects of zeolite content and zeolite grain-size on the compressibility and hydraulic conductivity. The results indicate that the water content required to achieve a target slump (100-150 mm) increases with increasing zeolite content

and is approximately in the range of 0.96 to 1.18 times the liquid limit. The results reveal that the hydraulic conductivity of the zeolite-amended clayey soil-bentonite backfills is generally lower than the typical regulatory limit (10-9 m/s). The addition of fine-grained zeolite has little influence on the compressibility and hydraulic conductivity of clayey soil-bentonite and sandy soil/Na-bentonite backfills. In contrast

the addition of coarse-grained zeolite is likely to considerably increase the hydraulic conductivity of soil-bentonite backfill. Finally

a proposed empirical method is examined for predicting the hydraulic conductivity of the backfills in this study. The predicted hydraulic conductivity values are found to fall in the range of 1/3 to 3 times those obtained from the oedometer tests.