Statistical analysis of the fracture behaviour of porous ceramic Raschig rings

Microstructural control during processing is necessary to assure uniform performance of random packed columns filled with ceramic Raschig rings. In this work, the statistical analysis of the fracture strength of three series of Raschig rings fabricated using three different green processes, uniaxial pressing, extrusion and slip casting, is proposed as a method of comparing the reliability of the three processes. The rings were prepared from industrial and urban wastes and contained hydroxyapatite as agent for the ionic exchange that leads to the immobilisation of heavy metals. Strength values were determined by the diametric compression of ring test and results were analysed using Weibull statistics. Results were correlated with scanning microscope observations of fracture surfaces. Simple monomodal two parameter Weibull statistics have been demonstrated to be suitable to analyse the fracture behaviour of the rings. From the stand point of strength reliability, extrusion is proposed as the most adequate green forming method.