PROPOSED HEALING AND CONSOLIDATION MECHANISMS OF ROCK-SALT REVEALED BY ESEM

The grain boundary healing behavior of crushed rock salt was mainly st udied by employing the environmental scanning electron microscope (ESE M) to study the consolidation mechanism of rock salt backfill. Dedicat ed miniature round rock salt specimens were prepared for observation o f the water trapping effect by using a cold stage in the ESEM to reach saturation conditions. Comparable high pressure pellets were prepared for measuring the crystal growth. Consolidation tests using materials made at different pressures and containing different moisture levels were conducted in order to construct the proposed mechanism. Direct ob servation of specimens in the ESEM resulted in viewing water trapped o n the surface and the formation of a water meniscus between two partic les. The concentration of brine at the grain boundary was observed as contributing to the amount of recrystallization. From aforementioned o bservations, a schematic drawing of the dissolution and recrystallizat ion process may be redrawn. The amount of water therefore has a great effect on the consolidation of rock salt and is possibly due to the sl iding, rotation, or crushing of the contact zone of the granular mater ial. From such a study, tentative healing and consolidation mechanisms can be deduced. (C) 1993 Wiley-Liss, Inc.