This UNITECR 2022 paper is an open access article under the terms of the Creative Commons Attribution License, CC-BY 4.0, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited. DIRECT OBSERVATION OF DRYING BY NEUTRON AND X-RAY TOMOGRAPHY ANALYSIS M. H. Moreira(1)*, S. Dal Pont(2), A. Tengattini(3), A. P. Luz(1), T. M. Cunha(1), R. F. Ausas(4), V. C. Pandolfelli(1) (1) Federal University of Sao Carlos, Graduate Program in Materials Science and Engineering, Sao Carlos, SP, Brazil. (2) 3SR, Université Grenoble Alpes, Grenoble, France. (3) Large Scale Structures, Institut Laue-Langevin, Grenoble, France. (4) Institute of Mathematical and Computer Sciences, University of São Paulo, São Carlos, Brazil. ABSTRACT The drying of refractory monolithics is one of the main drawbacks of this class of materials due to its implication on the production halt of many industrial equipment. This is especially true for calcium aluminate cement (CAC)-bonded castables, where the vapor derived from the unreacted water and dehydration reactions can pressurize yielding cracks and explosions of the ceramic lining. Numerous advances on additives have been made to increase these materials' resistance to explosive spalling, however, the fundamentals of the physical phenomena that yields such a problem remain an open issue. For years, the techniques used to study this process were limited to indirect tests, such as the thermogravimetric analysis or the pressure and temperature measurements of samples being unidirectionally heated. Recently, direct techniques such as nuclear magnetic resonance and X-ray tomography were applied in the context of regular concrete on fire scenarios. The current work presents preliminary results of neutron tomography applied to monitoring the drying of refractory castables. The overall behavior of the castable was qualitatively similar to those observed for regular concrete, and the results provide information that can be successfully applied on numerical simulations of larger pieces with dimensions closer to the industrial ones, overcoming the main drawback of such techniques, their small sample dimensions. INTRODUCTION Drying consists in the removal of water from a material via a gradient on the concentration, temperature or pressure distribution inside a porous medium1. Several mechanisms can act as a direct consequence of these inhomogeneities. The most notable examples are the convection mechanism due to the temperature gradient and the mass flux, which is related to a pressure difference (i.e., following the Darcy law). Even though several studies were done1,2, the highly dynamic nature of the drying stage, as well as the large sizes and masses of refractory pieces applied in industrial processes, still offer several challenges for the comprehension and, ultimately, the optimization of the drying performance of monolithics. Studies using thermogravimetric analysis provided important advances on the understanding of the dehydration reactions that take place during the initial heating of castables1, 3, 4 . These tests, however, do not provide any information on the moisture distribution inside the material, or the pressure values which are developed in their pores.