The present work aims to investigate a new composite used in building construction. The starting products are an industrial plaster, mica, vermiculite and water. The chemical characterization of the matrix reveals the presence of dihydrate (5 wt%) in plaster which modifies the setting time of the hydration process. This phenomenon is not observed with a pure plaster suggesting that another parameter modifies the kinetics: the particle size. Indeed, the setting time decreases of 30 min when the plaster is sieved from 150 to 10 mu m. The evolution of the thermal properties versus the nature and the quantity of additives is also studied. Vermiculite proves to be well suited to decrease the thermal conductivity of the panel (0.58-0.27 W m(-1) K-1) whereas mica tends to increase it. The analytical model of Hashin and Strikman well describe the evolution of the thermal conductivity until a porosity of 40%. (C) 2013 Elsevier B.V. All rights reserved.