Investigations on the caking behaviour of bulk solids-macroscale experiments

Mechanisms that induce caking are, for example, liquid bridge formation, sintering, cohesion, adsorption, crystallisation, and/or deformation. The caking of bulk solids is mainly influenced by storage conditions like humidity, temperature, storage time, and the stress that acts on the bulk solid during storage. The influence of these storage conditions can be investigated in macroscale experiments, among others, either with a Schulze ring shear tester or a uniaxial test. In this paper, a uniaxial consolidation test is used for measuring the unconfined failure strength. To simulate real storage conditions, the material is placed in a climatic chamber at different-but constant-humidity, temperature, and stress levels during different consolidation times. The porous material of the cylindrical container ensures a homogenous humidity and temperature level in the whole sample. After this consolidation, the unconfined failure strength of the caked sample is determined with a material testing machine. The results for ammonium chloride are presented.