Compression curve analysis and compressive strength measurement of brittle granule beds in lieu of individual granule measurements

Powders in granulated form are used in various processes to facilitate convenient usage. The durability ofthe formed granules is a crucial parameter, typically evaluated by the compressive strength of the gran-ules. However, especially for granules with a diameter in the order of tens of microns, statistically relevanttesting of individual granules is not a feasible alternative, and in such cases uniaxial bed compression isrequired.There has not been consensus on whether uniaxial compression of a granule bed can be used to studythe fracture of micron size or brittle granules. In our case study of a bed of sintered kaolinite granuleswith diameters under 100 m, we show how the compressive strength of individual granules can beobtained from the compressive measurement of the entire bed by plotting the relative density versus thelogarithmic pressure scale.We compressed the kaolinite powder with different loads; microscopy confirmed that below the ana-lyzed strength the granules are intact, though the granules start to fracture in the curved region on thecompression curve. We found that angle-fitting can be used to locate the average compressive strengthon the compression curve and to follow the evolution of strength with sintering temperature. The experi-ments in unison demonstrate that compression curve analysis is applicable for strength analysis of brittlegranules.