A Miniature Cone for Measuring the Slump of Soil-Bentonite Cutoff Wall Backfill

Measurement of slump for soil-bentonite (SB) cutoff wall backfill using a standard ASTM C143-00 slump cone is widely employed to design SB backfill for workability and to evaluate field backfill quality during cutoff wall construction. The standard cone is particularly suitable for field testing, where large backfill quantities are available, but is less practical for laboratory testing of backfills during design. This paper describes the development and evaluation of a miniature slump cone that requires only ∼16 % of the backfill volume required for the standard cone. Results of slump tests performed on three model SB backfills with different solid compositions indicate that the miniature cone provides reproducibility similar to that given by the standard cone when the backfills are prepared to a standard slump of 100 mm to 200 mm. The empirical relationship between standard slump (SS) and miniature slump (SM) for all three model backfills is represented accurately by a single linear expression (i.e., SS=60+1.8SM, where SS and SM are in millimetres) that is nearly identical to the predicted correlation given by an analytical slump cone model (i.e., SS=64+1.8SM) for the range 100⩽SS⩽200 mm.