Phosphate Transport in Illite Due to Consolidation

The conditions were studied under which consolidation loading caused the release of phosphate from a saturated illite clay. P 32 tracer techniques were employed to follow the movement of phosphate in composite samples composed of tagged and untagged portions. The samples, initially consolidated to 1·0 kgcm −2 stress were reconsolidated to 0·1, 0·5, 2, 4 and 8 kg cm −2 stress and the transport of phosphate was monitored by counting the radioactivity of 0·01-in. thick sections sliced parallel to the major principal plane. Corrections were applied for P 32 -P 31 self-diffusion. It was found that: (1) for low phosphate concentrations there was no observable transport due to consolidation type flow: (2) for high phosphate concentrations and for stresses less than or equal to the preconsolidation load there was no observable transport due to consolidation type flow; and (3) for high phosphate concentrations and for loads above the preconsolidation load there was detectable transport of phosphate, presumably due to the consolidation flow. A mechanism based on self-diffusion plus uniform flow was able to semi-quantatively explain the test results.