Phosphate sludge-based ceramics: Microstructure and effects of processing factors
Résumé
The potential use of clay amended phosphate sludge in lightweight aggregates manufacturing was assessed. For this purpose, the microstructure of heated blends was examined with X-ray diffraction, thermal analysis and scanning electron microscope and impedance spectroscopy, and their physical properties were followed as a function of heating temperature, soaking time and clay content. For the latter study, the full factorial design was used. The results showed that phase neoformation involved the breakdowns of the clay minerals and lime of carbonates. Moreover, the sintering process was significant as the clay content exceeded 5 wt% and 900< T< 1000 degrees C. In such a condition, the sintering was chiefly controlled by melt. The results of the full factorial design showed that the increase of one of the processing factors affected positively water absorption, density and compressive strength. These effects were mainly linked to the conjugate formations of calcaluminosilicate and viscous phase. The results also pointed out that the effects of the interactions between the factors on the measured properties were almost negligible. By using the full factorial design, the optimum values of the physical properties were evaluated.