In the development and optimization of supplementary cementitious materials (SCMs), it is of high importance to have relatively fast and simple methods to evaluate their reactivity in cement-like systems.A common approach is the Chapelles test which probes the pozzolanic reactivity by measuring the amount of consumed Ca(OH)2 in Ca(OH)2-SCM suspensions, cured at fixed temperature (20-80 ℃) and for a fixed time (2-14days).For these experiments, additional information can be achieved by studying the solid residues by 29Si and 27A1 MAS NMR, which allows identification of the formed hydration products and the remains of SCM in a semi-quantitative manner.In addition to this approach, the present work employs a combination of chemical methods and solid-state NMR to identify the reactive species in kaolinite heat treated at different temperatures.