This paper deals with the alkaline activation of fly ashes for the production of a novel cementitious material and with the effect of curing conditions on the nature of the reaction products. Curing procedures favouring carbonation process negatively affects the development of mechanical strength of this new alkaline cement. Carbonation of the system involves its pH modification and consequently the modification of the nature of the reaction products and the kinetics of reactions. (c) 2005 Elsevier Ltd. All rights reserved.