Effect of Placement Configurations on Strength Behaviour of Cemented Paste Backfill

This paper presents the effects of placement conditions on strength properties of cemented paste backfill CPB cast in different size moulds (D x H = 10 x 20 cm, 7.5 x 15 cm, and 5 x 10 cm) and prepared at binder contents of 3 wt%, 4.5 wt%, and 7 wt%. CPB samples were subjected to four placement conditions: capped-drained C-D; uncapped-drained U-D; capped-undrained C-U; and uncapped-undrained U-U. Results show that the highest strengths were obtained from C-D samples, followed by U-D, C-U and U-U samples, respectively. This may be explained by the drainage of free water within CPB at early ages, which offers higher strengths. The CPB's strength increased with a decrease in mould size in all cases for all the samples. The moulds 5 x 10 cm gave the best strengths due to a more homogenous matrix and the decreased number of micro-cracks in grains.