Microstructural characterisation of alkali-activated PFA matrices for waste immobilisation

A variety of natural and industrial waste product materials rich in SiO2 and Al2O3 may be activated with alkalis to produce cementitious systems which when cured under mild temperature conditions, set and harden to give a very compact paste. When fly ash is the activated material, fast setting and rapid strength development have been reported. In addition to their application in construction, they may have a role in the immobilisation of toxic waste. Alkali-activated fly ash matrices containing arsenic were studied by a combination of scanning and transmission electron microscopy along with energy-dispersive X-ray analysis of argon-milled sections. Little arsenic was incorporated in the matrix of hydration product but it was apparently associated with iron derived from the hydration of the fly ash. There was no association of As with added Fe2O3. (C) 2004 Elsever Ltd. All rights reserved.