Ground calcium carbonate (GCC) from the Barre de Ghomrassene in Southeast Tunisia: a suitable raw material for paint industry

The main scope of the present work is to investigate the potential of using ground calcium carbonate (GCC) from the Barre de Ghomrassene (BDG) in Southeast Tunisia in paint industry. In order to evaluate the performance of the material and the formulated paint films, representative raw specimens of main deposits of naturel GCCs in the Mediterranean basin and Middle East countries such as extra-white limestone from the Abiod Formation (Feriana region in West-Central Tunisia), A??gedi?i Formation (Ni?de Group, South Central Turkey), and Samalut Formation (Elminea, South Cairo, Egypt) were considered. Samples were ground to specific surface of about 3000 cm²/g and were subjected to detailed characterization including chemical and mineral composition, physical, and chromaticity characteristics. Results show that the GCC from the lower part of the Barre de Ghomrassene is, in most, dark and grainstone in texture, which limit its use in paint and coating application. Elsewhere, it is marked by high purity degree (generally more than 97% calcite); high lightness (more than 86.5, 95.2 in average) with relatively low chromaticity (a*?<?3.3, b*?<?9.1); low oil intake (17.4 g/100 GCC); very low electrolyte levels; good pH buffering (close to 9); accepted ranges of density and abrasion (2.65–2.7 and 10–18, respectively); good grindability; low levels of harmful components such as MgO, SiO₂, Fe₂O₃, and acid insoluble residue (less than 0.1% each); and improved rheological properties. The BDG seems to be a suitable filler for paint when mixed with water, styrene acrylic, and common additives. The formulated paint films meet all standard requirements, in that they have very good opacity, matt visual dualgloss 20/60°, high luminescence (L*?=?96.4), suitable hardness (145 s), good adhesion (B5), and sufficient impact resistance (1.5 kg m). The performances of these films are analogous to those based on Abiod and Samalut formations (natural carbonate), but they are slightly less lighter than those based on A??gedi?i Formation (metamorphic carbonate). Hence, the studied GCC can be used to substitute them in particular for local GCCs from the Abiod Formation, which are limited and over exploited.