Abstract

This paper investigates the suitability of the Campanian-Maastrichtian reef limestones from Merfeg Formation in Central Tunisia for a potential of use in the painting industry. Samples were milled to a specific surface area of approximately 3500 ± 250 cm2/g. Physical and mechanical behavior, including (chemical-mineralogical composition, particle size distribution, optical performance, thermal behavior, density, Los Angeles abrasion tests and Micro-Deval and oil absorption) for raw material and the physical and mechanical behavior including (pH, viscosity, density and dry extract, visual glossiness wet film thickness and Wet abrasion resistance) for the paint films were carried these tests meet all standard requirements. The results show that the middle (second class) limestone of the Merfeg formation is marked by a high degree of purity, low levels of harmful oxides such as Fe₂O₃, MgO and SiO₂, brightness high (more than 86.5, 95.2 on average) with relatively low chromaticity (a*<3.3, b*<9.1), low oil consumption (18 ml/100 g of limestone on average), good grindability and acceptable abrasion range (10-17) and improved rheological properties. The calcium from the Merfeg formation appears to be suitable filler for the paint when mixed with water. On average, the formulated emulsion paint was composed of 58.8% calcium carbonate as filler, 28.9% water, 6% acrylic styrene, 4.5% TiO₂ as pigment and additives currents (1.8% in total). The formulated paint films meet all standard requirements, in that they have very good opacity, high luminescence (L*=96.4), good pH buffering (close to 9), appearance and washability (wet abrasion resistance less than 5 μm). The performances of the films are similar to those based on the Barre de Ghoumrassene Member and El Garia Formation in Southeast and Northeast Tunisia respectively; however, they are slightly lower than the Abiod Formation (a lateral equivalent of Merfeg Formation) from the Feriana Hill in West-Central Tunisia and the Aşıgediği Formation in South Central Turkey. Henceforth, the studied carbonate, calcium might be valorized in paint industry, which are eco-friendly and easy to apply.

Keywords: Limestones; Merfeg formation; Raw material; Physicochemical characterization; Valorization; Paint film