Leaching and microstructural analysis of cement-based solidified wastes

Leach tests alone cannot determine the actual performance and long-term env ironmental impacts of solidified/ stabilized waste because they do not prov ide information on the physical and chemical changes between waste and addi tives. This research study utilized a combined approach to investigate the leaching behaviors and binding chemistry of a solidified/stabilized industr ial waste. The combined approach included leach tests and microstructural a nalysis. The OPC system showed more satisfactory results in TCLP and DLT th an the OPC/PFA system. Because no identifiable hydration products were obse rved, SEMI EDS images and XRD of solidified waste suggest that the presence of zinc retards the hydration of OPC and PFA. However, a new crystalline c ompound, ZnO, is detected by XRD in samples A01 and B02. These are believed to be a result of the addition of cement to zinc sludge, which may cause z inc to change from its amorphous to crystalline form. In addition, a certai n amount of zinc was found on the surface of solidified waste by XPS. The u se of microstructural analysis has been proved to be essential in providing useful information on the physical and chemical changes within the cement matrix.