Raw materials for the heavy-clay industry in Emilia-Romagna and Marche (central-northern Italy)

Within a research program concerning raw materials and products of the Italian heavy-clay industry, 75 clays used by producers in the regions of Emilia-Romagna and Marche (central-northern Italy) were characterized by chemical, mineralogical and grain size analyses to relate them to their utilization in the various brick and tile productions. From a geological point of view, the clays considered are mainly belonging to Quaternary alluvial deposits and to Pliocene-Pleistocene marine sediments. Raw materials show distinct chemical and mineralogical compositions, with the most significant variations due to the content of carbonates. As regards the grain size distribution, all the samples can be classified as silty clays or clayey silts. Moving on to the technological field. Roofing tiles and paving bricks are produced through complex: bodies which are mainly constituted of non-carbonatic clays, while carbonate-free clays are never employed for the hollow products. As for soft-mud bricks, grain size distribution of the clays is the most important feature