This contribution reviews the geopolymeric potential of Ca-rich oil shale processing residues and aims at the characterization of the effects of different alkaline activator solutions on the polymerization of oil shale processing residues experimentally tested in recent-case studies. The analysis shows that the alkali activation of Estonian oil shale solid wastes is controlled by the presence and dissolution of reactive Ca-bearing phases. However, the geopolymeric potential of oil shale ashes is limited by the amount of available reactive Si and Al in the source material. Excess Ca in activated samples is precipitated as Ca-hydroxide showing Si deficiency in the system. To induce a substantial polymer formation, additional sources of readily available Si and Al must be introduced in the mix design. In addition, for industrial applications, further optimization of the mix design and curing conditions, including thermal curing, is needed to reduce dry shrinkage and microstructural cracking.