Effect of carbonation on properties of blended and non-blended cement solidified waste forms

Five types of cement and two pozzolans were used to investigate the influence of carbonation on the properties of solidified waste forms. The waste chosen was a commercially blended product which was mixed with cement and then cured in three different environments: nitrogen, air and carbon dioxide for 28 days. Samples were examined for strength development, setting time, microstructural development and leachate metal fixation. Samples cured in a carbon dioxide rich environment showed distinct changes in mechanical properties, microstructure and fixation of metal species. Carbonation was also found to play an important role in the hydration of the binder waste form mix. Carbonated solidified products were characterised by enhanced calcite contents, higher strength values and a significant reduction in leachable metals concentration for all the cement types examined when compared with samples cured in nitrogen. It is also shown that the type of cement or cement-blended system can be optimised to obtain maximum improvement in fixation of waste species in a carbonated product. (C) 1997 Elsevier Science B.V.