Mineralogy and lithogeochemistry of lower Cretaceous kaolin deposits in the Malha Formation, Southwestern Sinai, Egypt: Implications for the building and construction industry

Abstract

This study analyses the exposed outcrops of the Lower Cretaceous (Aptian-Albian) kaolin deposits of the Malha Formation, and characterizes them in terms of lithological, mineralogical, and chemical composition. In addition, the effect of thermal treatment on kaolinite mineral behavior is evaluated. The Malha Formation comprises kaolin deposits, which were sampled at the Rewekna, Ras Watta, Abu El-Nomerat, Essela, and Mosaba Salama sections. The studied samples are composed of kaolinite and quartz as the main constituents, followed by anatase and hematite as accessory (coloring) minerals. X-ray fluorescence (XRF) analysis reveals high Al₂O₃, SiO₂, and LOI, low CaO, MgO, Cl, SO₃, and P₂O₅ contents as well as alkali metals (e.g., K₂O and Na₂O). An increase in aluminum and silicon oxides is observed along with the presence of high kaolinite content in these samples. Calcination of the studied kaolinite, by thermal treatment, leads to dehydroxylation and/or transformation to High Reactive Metakaolinite (HRM). The partial replacement of cement by different ratios (3, 5, 10, 15, and 20%) of the produced Metakaolinite (MK) was completed to enhance the physical and mechanical properties. These procedures make the concrete more flexible and workable, increase durability, and are stronger. Besides, reduce the temperature produced from the hydration, as well as decreasing permeability and water absorption of the concrete. This work concludes that the cement substitution and mineral admixtures using Metakaolinite (MK) between 10 and 15% by weight of cement gave rise in compressive strength by 20% if compared by the control mix.