Characterization and Valorization of Clay Deposits from the Region of Beni Mellal-Khenifra in the Ceramic Industry (Morocco)

The state of the clay reserves of the exploited or potentially exploitable sites is diagnosed, integrating the geological, physico-chemical and mechanical aspects in order to better valorize these resources. This study focused on 15 representative samples collected in different geological contexts. The particle size distribution, Atterberg limits, X-ray diffraction (XRD), X-ray fluorescence (XRF), total organic content and calcimetry were determined. The mechanical characteristics were revealed by studying the shrinkage after drying/firing process, loss on ignition (LOI), the bending test and water absorption capacity (WAC). The studied clays presented a silty to sandy-silty composition with a clay fraction not exceeding 12.5% and a plasticity index (PI) between 20 and 30%. The carbonate and organic matter contents are low (CaCO3T < 12.5%, OM < 2.5%). The bulk mineralogy is dominated by quartz (5–36%), K-feldspar (3.3–19.7%) and goethite (8.8–25%). The clay mineral content is between 12 and 25.2%. It is dominated by illite (5–90%), kaolinite (0–70%) and chlorite (0–45%). Smectite, vermiculite and mixed-layer clays are rarely identified. The chemical composition is dominated by SiO2 (44.9–62.2%) and Al2O3 (10.5–19.6%). Technological and mechanical tests show a high bending strength (BS) (5.01–13.02 N/mm2) which is positively correlated with the quartz content but inversely proportional to the calcium carbonate content. The LOI (8.69–29.78%) and the WAC (7.88–35.72%) are tolerable. The drying shrinkage (DS) (0.31–14.43%) and firing shrinkage (FS) (0.24–5.59%) coefficients are low. The suitability of clays from the Beni Mellal-Khenifra region to be used in ceramic manufacturing is constrained by pretreatments (crushing, grinding, sieving) and formulation to balance the composition and/or the particle size curve or to correct the plasticity.