In this study, the drying behavior for a variety of calcium alumina- and hydratable alumina-bonded refractory castables was investigated in the temperature regime of first-drying, i.e., up to 300 oC. Using a specialized high-temperature Nuclear Magnetic Resonance (NMR) setup, we were able to directly and non-destructively measure the spatially and temporally resolved moisture distribution, while simultaneously measuring the temperature distribution as well. We employ a high-temperature correction scheme that calibrates the effects of the surface relaxation for rising temperatures. This setup makes use of a high-sensitivity Birdcage-coil for measuring the quantitative moisture content at high-temperatures, while also utilizing a mini-coil for calibrating relaxation changes, as a function of temperature and hydration state, taking place in the sample throughout a drying experiment. These measurements give for the first time a direct insight into the drying behaviour of castables and show that the drying front speed and temperature are strongly correlated with control of key material parameters such a as binder content and water demand. In addition these measurements provide a direct insight into the steam pressures which are generated within the samples and hence in the risk of explosion.
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