Author(s): Ineta Rozentrauha, Sergejs Survila, Linda Kre, Modris Drille, Gaida Maruta Sedmale, Inese Pastare
The sewage sludge from a water purification plant was analysed for recycling to the dense glass-ceramic materials. The sewage sludge containing aluminium compounds and ca 50 % of organic matter was used as a filler, but as the matrix of glass-ceramic was examined an illitic clay from Liepa deposit (Latvia). The raw materials were investigated by differential-thermal (DTA) and X-ray diffraction analysis (XRD). The dense glass-ceramic was produced from the water purification sewage sludge and limeless clay in ratio 10-40 : 90-60. The optimal values of bulk density (2.28 g/cm3) and thermal shrinkage (29 %) for novel materials were observed for glass-ceramic with the sludge additive at amount of 20 wt %, obtained by sintering at temperature 1140 oC. The relationship between thermal treatment conditions and maximal treatment temperature was established. The following crystalline phases for novel materials were detected by XRD analysis: microcline (KAlSi3O8), hematite (Fe2O3), quartz (SiO2) and corundum (Al2O3). The physical-chemical properties of novel materials correspond to the dense glass-ceramics composite while the material itself could be applied as building material.