Cemented Paste Backfill (CPB) is a relatively new backfilling technology for which a better understanding of binder hydration is required. This research uses electromagnetic (EM) wave-based techniques to non-destructively study a CPB consisting of tailings, sand, process water and binder (90% blast-furnace slag; 10% Portland cement). EM experiments were performed using a broadband network analyzer (20 MHz to 1.3 GHz) in the lab and capacitance probes (70 MHz) in the lab and field. Results showed that the EM properties are sensitive to curing time, operating frequency and specimen composition including binder content. The volumetric water content interpreted from dielectric permittivity varied little with curing. Temporal variations in electrical conductivity reflected the different stages of hydration. Laboratory results aided interpretation of field data and showed that a reduction in binder content from 4.5% to 2.2% delays setting of CPB from 0.5 days to over 2 days, which has important implications for mine design.

Cemented Paste Backfill (CPB) is a relatively new backfilling technology for which a better understanding of binder hydration is required. This research uses electromagnetic (EM) wave-based techniques to non-destructively study a CPB consisting of tailings, sand, process water and binder (90% blast-furnace slag; 10% Portland cement). EM experiments were performed using a broadband network analyzer (20 MHz to 1.3 GHz) in the lab and capacitance probes (70 MHz) in the lab and field. Results showed that the EM properties are sensitive to curing time, operating frequency and specimen composition including binder content. The volumetric water content interpreted from dielectric permittivity varied little with curing. Temporal variations in electrical conductivity reflected the different stages of hydration. Laboratory results aided interpretation of field data and showed that a reduction in binder content from 4.5% to 2.2% delays setting of CPB from 0.5 days to over 2 days, which has important implications for mine design.