Clayey materials from the Sierra de la Demanda Range (Spain): their potential as raw materials for the building ceramics industry

Abstract

This work describes the possible use of thick Early Cretaceous clay deposits, which occur in the southern sector of the Sierra de la Demanda range, as raw materials in the manufacture of ceramic articles. The global mineralogical composition is characterized by high proportions of phyllosilicates and quartz with variable quantities of feldspars, carbonates and hematite. The clay mineralogy differentiates two types of raw materials: illitic clay and kaolinitic-illitic clay. A granulometric distribution in the 2ÿ60 mm fraction, good behaviour during the drying stage and acceptable results in firing tests confirmed that most samples can be utilized as raw material in the building ceramics industry. The range of suitable firing temperatures for these materials is 950ÿ1000ëC, a temperature which needs to be raised for samples with a high percentage of kaolinite and quartz. Moreover, other materials with abundant calcite (20ÿ30%) are suitable for use as modifiers of some properties or colour