EFFECT OF THE PARTICLE SIZE DISTRIBUTION ON THE HEAT TRANSFER MECHANISMS AND THE HEAT STORAGE CAPACITY IN CERAMIC INSERTS MADE BY ALKALINE ACTIVATION

Geopolymerization and alkaline activation constitute credible alternatives to conventional ceramic processes for the development of improved stoves with low environmental impact.This work analyses the influence of the particle size distribution on the heat transfer mechanisms, the heat storage capacity and the mechanical strength of ceramic inserts made by alkaline activation. Formulations integrating different particle size classes and alkaline solutions of 2 moles and 6 moles were studied through particle size analyses, thermal tests and combustion tests. The results show that the particle size controls the density of the matrix, the residual porosity and the continuity of the binder network, directly influencing the thermal conductivity, the thermal inertia and the mechanical strength. An optimized particle size distribution favours a homogeneous microstructure, a better thermomechanical stability and a progressive restitution of heat, leading to a significant improvement in the energy efficiency of the fireplaces. These performances, superior to those of conventional ceramic inserts fired at high temperature, confirm the potential of alkalinally activated materials as a sustainable and energy efficient solution.