This paper assesses the use of alkali activation technology in the valorization of a spent fluid catalytic cracking (FCC) catalyst, which is a residue derived from the oil-cracking process, to produce 'geopolymer' binders. In particular, the effects of activation conditions on the structural characteristics of the spent catalyst-based geopolymers are determined. The zeolitic phases present in the spent catalyst are the main phases participating in the geopolymerization reaction, which is driven by the conversion of the zeolitic material to a highly Al-substituted aluminosilicate binder gel. Higher alkali content and SiO2/Na2O ratio lead to a denser structure with a higher degree of geopolymer gel formation and increased degree of crosslinking, as identified through Si-29 MAS NMR. These results highlight the feasibility of using spent FCC catalyst as a precursor for geopolymer production. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.