Slag as a supplementary cementitious material is known for its latent hydraulic properties. Thus, constant efforts are being directed towards improving its reactivity. This mostly involves the use of alkali salts. The authors present the results of alkali activation of a slag from Hamilton, Ontario, Canada, by means of water glass (Na2SiO3). Distinct improvement in early and late age strength was noted when water glass was used in combination with CH. The microstructure of this activated slag paste at 28 days is described. The microanalytical techniques used included SEM/EDXA, and XRDA.