In this study, we show the results of reactivity testing for a large variety of supplementary cementitious materials (SCMs) and fillers. The reactivity test is performed by measuring the heat release (using isothermal calorimetry) and calcium hydroxide consumption (using thermogravimetric analysis) of SCMs mixed with calcium hydroxide (3:1 ratio of calcium hydroxide and SCM) at 50Â °C in a 0.5Â M KOH environment. Based on the response in the test, SCMs may be classified into inert, pozzolanic, and latent hydraulic; the pozzolanic and latent hydraulic materials may be further classified into less reactive and more reactive materials. Reactivity test results are compared with isothermal calorimetry and compressive strength measurements on cementitious pastes made with a subset of SCMs. Good correlations are obtained between isothermal calorimetry and compressive strength. Clear correlations between reactivity test results and compressive strength were not seen.