The drying behavior for various calcium aluminate cement and hydratable alumina‐bonded refractory castables was investigated in the first‐drying temperature range (100°C‐300°C). Using a specialized high‐temperature Nuclear Magnetic Resonance setup, we were able to directly and nondestructively measure the spatially and temporally resolved moisture distribution, while simultaneously measuring the temperature distribution as well. These measurements show that the drying front position is a linear function of time, which can be explained on the basis of a simplified model where only vapor transport is considered. Based on the measurements and the model, one can directly determine the permeability at high temperatures. Moreover, the results demonstrate that the drying front speed and temperature strongly correlates with the control of key material parameters (eg, water demand, binder content, etc). In particular, microsilica fume‐containing low‐cement castables displayed the highest vapor pressures, while regular castables generated the lowest vapor pressures reflecting the permeability of these materials.

In this study a specialized high-temperature nuclear magnetic resonance (NMR) setup is presented for measuring free moisture in monolithic refractory castables during one-sided heating (100–300 °C). This setup makes use of a high thermal-stability Birdcage-coil for measuring the quantitative moisture content at high-temperatures, while also utilizing a mini-coil for calibrating transverse relaxation changes, as a function of temperature and hydration state, taking place in the sample throughout a drying experiment. We employ a high-temperature correction scheme that calibrates the effects of rising temperatures on the NMR signal. With this configuration, we can non-destructively measure moisture and temperature profiles continuously and achieve a spatial resolution of 2–3 mm for samples as long as 74 mm. After applying the NMR correction, we can extract information about the physical and chemical components of water as they are released from the porous matrix during first heat up. As a model material, we demonstrate the capability of our setup with a conventional castable after it has been cast and cured for 48 h.

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