Abstract: The factors affecting the expansion properties of slurry backfill material was investigated based on the analysis of the expansion mechanism of liquid and solid phase, and on the measuring of the expansion rate. It was proved that the liquid expansion is caused by admixtures and solid expansion is caused by the growth of ettringite. By testing the structure of the backfill body, it was found that the admixture does not affect the micro-structure and the phase of backfill body, it only makes the distribution of pore structure and the strength of the backfill body changed.

Key words: Backfill material, Expansion mechanism, Structure