http://orcid.org/0000-0001-7214-6007
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ABSTRACT
Water may be present in clayey materials in different forms (hydration water and structural water), providing different properties to the materials such as reactivity and plasticity, and affecting the industrial processes in which they are involved, resulting in the importance of the determination these types of water. In addition, some clayey materials such as bentonites or sepiolites, present very high avidity for water, which must be considered in the characterization of the materials, and especially in the structural water content determination. In the literature, no rapid and accurate methods for the determination of structural water content in this type of clayey materials are described and validated, so to fill the lack of a methodology for determining structural water, a method by combustion and infrared detection has been established. In the development of the methodology, the sample preparation was the most important step, in which the drying process of the samples had particular relevance. The time and temperature of drying and the maximum time that the samples can be stored in the desiccator before the analysis were evaluated. The development of the measurement method was performed optimizing the conditions and constructing calibration curves. The developed methodology was validated using reference materials. Finally, several clayey materials (sepiolites, bentonites, and kaolin) were analyzed using the developed methodology. The results were compared with those obtained by differential thermal analysis-thermogravimetry (DTA-TG), concluding that the DTA-TG analysis is only useful for the determination of structural water when the materials do not contain carbonates (e.g., calcite, dolomite).