Effect of graphite additions on the intumescent behaviour of alkali-activated materials based on glass waste

Alkali-activated materials, were synthesized from glass waste powder (cullet from window-type sheets) with NaOH solution. In order to get a high porous microstructure, the hardened pastes were subjected for thermal treatment at temperatures of 400, 500, 600, 700, and 800 degrees C for 60 min. An important increase in the specimen's volume and porosity appeared during the thermal treatment; this is due to the foaming/intumescent phenomenon specific to this type of material. For the specimen's pastes based on the partial replacement of glass waste powder with graphite (1, 3 and 5 wt.%), it was determined that the increase of compressive strength assessed after thermally treated. The increase of graphite amount also resulted in the decrease of the initial temperature of the intumescent process (i.e., at 500 degrees C). The microstructure with high porosity after thermal treatment of these materials, with various sizes of closed pores, makes them suitable for use as both thermal and acoustical insulation materials. (C) 2020 The Author(s). Published by Elsevier B.V.