Clay raw materials from the Triassic Red Beds (Northern Jaen, Spain) for making ceramic construction materials

Abstract

The suitability of Triassic Red Beds from northern Jaén in the production of structural clay products has been evaluated. These materials have high phyllosilicate contents (36-69%), although some samples are enriched in quartz (<8-54%) and feldspars (<5-2I%). Dolomite (<5-20%) and calcite (< 7%) are present. Illite is the main phyllosilicate (96-74%), kaolinite values are rather low (<17%) and chlorite is present in low content (<14%). The studied samples have high silica (39.2-74.8%) and alumina (6.9-18.3%) content. K4ost of the samples have low CaO and MgO concentrations (<6%). <2 pm (64-36%) and 2-20 pm (68-36%) are the predominant grain size fraction of the studied samples. Low plasticity for extrusion process of the Triassic Red Beds is not appropriated for making bricks and roofing tiles by themselves. However, water absorption and linear shrinkage values are often suitable for manufacturing bricks. A small number of samples are appropriated for making roofing tiles, due to the its high firing shrinkage. Mixing of these materials with different proportions of complementary raw materials would allow to make porous bodies.