characterization of marls suitability for ceramic

INTRODUCTION
Large tonnages of clay materials are used in ceramic industry such as common bricks, structural bricks, refractories, pottery products, stonewares, sanitary wares, and roofing tiles (Murray, 1994; Harvey & Lagaly, 2006; Reeves et al., 2006; Murray, 2007; Keith & Murray, 2009; Petrick et al., 2011; Mukherjee, 2013). Mineralogical, chemical, and grain-size distributions of clays determine their engineering properties (Harvey & Lagaly, 2006; Keith & Murray, 2009). Due to their plastic behavior, clay materials could be worked in many desired shapes, dried, and fired to produce products with high hardness (Murray, 1994).
Morocco is one of the most producers and consumers of clayey building materials. In particular, the Rif area (Northern Morocco) is mostly filled with clays of Neogene age (El Ouahabi, 2013; Mesrar et al., 2013; El Ouahabi et al., 2014a; El Ouahabi et al., 2014b). These clayey materials have particularly drawn attention since few years ago.
In the Northwest of Morocco (Tetouan area), sandy marls of Late Pliocene age showed high content of illite/muscovite (43-57 %) and clay minerals (30 %). The clay fraction consists mostly of illite (88 %). These Pliocene clays are silty clay (92 % of 2-20 μm fraction), with low to medium plasticity and are suitable for structural clay products (El Ouahabi et al., 2014a; El Ouahabi et al., 2014b).