Experimental and numerical investigation of the first heat-up of refractory concrete

The first heat-up of furnaces consisting of wet refractory concrete is a challenge due to the pore pressure build-up which can exceed the strength of the concrete. To extend understanding of the complex heat and mass transfer phenomena taking place during the first heat-up, two reproducible heat-up experiments are carried out. These are performed by using a new developed pore pressure sensor. The experiments exhibit an intense change of concrete's thermal conductivity during the process. Further, even in case of one sided heating, two drying fronts are found to occur. In addition to the experimental investigation the first heat-up is simulated using a physical model, based on the coupled balances of energy and the masses of liquid water, water vapour and air as well. By the aid of numerical simulation the first heat-up is further investigated and mass flow behaviour of air, vapour and liquid water is discussed. Within the scope of a sensitivity study the concrete's thermal conductivity and it's permeability are obtained as it's most important material properties and they are used for calibration of the model aiming well representation of the experimental data. The adjusted material properties are found to be in good agreement with refractory concrete properties reported in literature.