The development of mechanical strength and the mineral and microstructural characteristics of the alkali activated fly ash (AAFA), reveal the importance of the role played by the curing conditions prevailing during setting and hardening process: curing in a covered mould (CCM) at 95 degrees C- dry curing (DC) at 150 degrees C, or steam curing (ST) at 95 degrees C. CCM yields the highest compressive strength (up to 102 MPa after 8 h of curing) and can be readily used in any AAFA system. DC is only recommended for NaOH-based systems (low SiO2/Al2O3 ratio), since waterglass-based mixes tend to retard reaction kinetics. SC, in turn, has an intermediate effect on strength development, between CCM and DC. (c) 2006 Elsevier Ltd. All rights reserved.