Cementitious backfill with high sulfur content - Physical, chemical, and mineralogical characterization

Use of cemented backfill in underground mining is common practice. The major economical benefits include increased recovery of ore and a reduction in the volume of waste requiring surface disposal. This paper presents new studies into the behavior of cemented backfill, namely, the chemical and mineralogical changes (weathering) with time that affect the mechanical strength of the fill. The weathering mechanism typically consists of sulfate attack. This process can occur rapidly during curing and depends on the binding agents used. The reaction involves dissolution of hydrated calcium phases followed by formation of expansive phases resulting in the degradation of the backfill's mechanical properties, The use of fly ash, which is resistant to sulfate attack, generally reduces any strength deterioration. These phenomena are illustrated with a case study that demonstrates the influence of these alteration on the long-term mechanical properties of a cemented paste backfill sampled in situ. (C) 1999 Elsevier Science Ltd. All rights reserved.