ADVANCES IN GEOPOLYMER SCIENCE & TECHNOLOGY Opc-fly ash cementitious systems: study of gel binders produced during alkaline hydration

Abstract In the present paper, experiments were performed on blended cements containing 30 % Port-land cement clinker and 70 % fly ash. The powdery material was mixed with deionised water for ‘‘normal’’ hydration, and with two different alkaline solutions for ‘‘normal’ ’ alkaline activation. The mechanical strength developed by this highly blended cement differed significantly depending on the hydrating solution used. XRD, FTIR and 29Si MAS-NMR characterisation studies were conducted to obtain information on the complex structural nature of the hardened matrices, which in all cases consisted of a mixture of amorphous gels (C-S-H + N-A-S-H gel). These highly blended cements are able to comply with the specifications defined in the European Standard EN-197-1:2000