Microstructural and Mechanical Properties in Traditional Ceramics as a Function of Quartzofeldspathic Sand Incorporation

Abstract

We intend to study the influence of addition of quartzo-feldspathic sand on the mechanical properties and the microstructure of Tunisian illite-kaolinite clay ceramics. The fired characteristics of the clay and quartzo-feldspathic sand mixtures have been studied separately at soaking temperatures reaching respectively 850°, 950° and 1050°C during a firing profile of ∼7–8 h. Investigation of phase transformations of the mixed samples shows that albeit the proportion of the quartz has been increased, its peak intensity remains constant. Such stability may be explained by quartz dissolution in the glassy phase. The mechanical strength of the mixed samples has been examined in terms of flexural strength. In the studied case, the latter increases from 13.5 to 23.3 N.mm−2 as the sample becomes denser in the mixture M2. It may also be noticed that an overdose of quartz reduces the mechanical strength. Hence, a moderate addition of well-sorted fine quartzofeldspathic sand ameliorates the mechanical properties and the microstructure. The latter is analysed by scanning electron microscope (SEM).