IS-CambridgeCompressibility, grain breakage and time-dependent behavior of gap-graded aggregates of sugar cubes

The results of a simple and alternative, yet powerful, procedure to experimentally investigate particle breakage behavior are presented in this paper. One-dimensional compression tests on a crushable granular and gap-graded material (aggregates of sugar cubes) are described and discussed. Sugar parallelepipedic (27.4×17.6×12.2 mm) cubes are compacted aggregations of welded sugar crystals having a mean size of 0.45 mm. Two different geometric arrangements, having widely different initial void ratios (0.2 and 0.8) were tested. The lower void ratio corresponded to ordered piling arrangements, while the higher ratio corresponded to disordered piling arrangements. Vertical stresses up to a maximum of 640 kPa were applied and grain size distributions (gsd) were obtained after the loading process. Identical gsd shapes of two S-shaped curves were obtained at the maximum vertical stresses for both ordered and disordered arrangements, underlying the gsd attractor concept associated with highly stressed aggregates irrespective of the initial state. Two breakage mechanisms were identified in the loading process, namely, comminution and splitting crushing. The time-dependent behavior was also studied based on creep tests lasting a maximum of 157.5 days. It was found that creeping could be explained by a delayed grain breakage process.