This paper utilizes electrical methods to follow the early hydration characteristics of a range of materials activated with calcium hydroxide at room temperature (20 degrees C). The electrical response is measured in terms of the in-phase (i.e. resistance) and quadrature (i.e. capacitance) components of the sample admittance. A number of presentation formalisms are exploited in identifying the stages of hydration and studying reaction kinetics in alkali-activated systems. It is also shown that the electrical response of the material displays a frequency dependence, which is particularly evident in the measure capacitance. The work highlights the applicability of the electrical method as a non-invasive, non-destructive technique in evaluating the reactivity of supplementary materials.