Non-Invasive In-Situ Monitoring of Cpb Hydration Using Combined Ultrasonics and Low-Field Nmr

Abstract

For the wider adoption of CPB as a passive support material, further understanding of the undisturbed microstructural evolution of CPB materials during early hydration is important. Here we demonstrate the combined use of ultrasonics and NMR T2 relaxation measurements to monitor early hydration (< 14 days), allowing simultaneous in-situ monitoring of micro- and macro-structural evolution of CPB materials. The Vp and Vs measurements show constant longitudinal wave velocity due to saturation and increasing shear wave velocity (> 2days) due to enhancing skeletal stiffness. The NMR relaxometry detects micro-structural evolution during the slurry (< 2 days) prior to change in ultrasonic response. Providing complementary information to ultrasonic measurements at longer hydration times (> 2 days). The concurrent monitoring shows that there is strong correlation between T2 and skeletal shear modulus. The capacity of T2 NMR measurements to non-invasisely monitor the initial slurry phase is particularly important for scheduling of mine-site operations.

Keywords: cemented paste backfill, Ultrasonics P and S- waves, nuclear magnetic resonance, microstructure, Tailings management