Influence of TiO2 and Na2O additives on properties of synthetic rock of fly ash from municipal waste incinerator

Influence of additives and hot-pressing temperature on properties of the synthetic rock was investigated, which was developed for preparing a harmless and stabilized crystalline solid of fly ash from municipal waste incinerator. Upon sintering at 1200degreesC for 16 h, it was revealed that the addition of 20 mass% TiO2 and 1.5 mass% Na2O was necessary for the preparation of dense rock products. X-ray diffractometry showed that these additives promoted the formation of perovskite (CaTiO3) and gehlenite (Ca2Al2SiO7) minerals. During hot pressing, bulk density of the synthetic rock increased steeply with temperature between 1000 and 1100degreesC. On the other hand, its open porosity decreased rapidly with temperature between 1050 and 1150degreesC. These facts imply that a temperature of 1100-1150degreesC is suitable for the hot pressing of fly ash.