Geochemical suitability of Lower Eocene extra-siliceous limestone for cement making (Bizerte deposit-Extreme North of Tunisia)

Abstract

The extra siliceous limestone sample of the Lower Eocene from the abandoned cement quarry part of the limestone deposit from the area of Bizerte (Extreme North East of Tunisia) has been investigated for its suitability for cement making. Petrological as well as X-ray diffraction pattern studies indicated that the limestone sample was crystalline and dominantly composed of calcite and quartz. They have variable silica and lime contents. Geochemical analysis results of 25 samples indicated that the limestone from the Bizerte deposit shows a wide range of variation in LOI (33–39 wt%), SiO2 (7–6 wt%), CaO (4–49 wt%) Al2O3 (2–4 wt%), and Fe2O3 (0.74–1.45 wt%). MgO, K2O, Na2O, and TiO2 are present in traces. CaO shows a strong positive correlation with LOI, whereas CaO and SiO2 show a negative correlation. The chemical composition of limestone confirms the mineralogical composition. The aim of this paper is to show the influence of high siliceous limestone component from Bizerte deposit on clinker parameters (silica modulus and lime saturation factor) in order to highlight their effect for the cement process making. In addition, to establish a predictionnal geochemical model in order to integrate and optimize this raw material estimated at 81,78,000 tons in cement manufacturing. The geochemical analysis by XRF of the limestone samples taken at different levels from the quarry proves their affluence in carbonate with a lime content of 46 wt% and the abundance of silica with a content of 12 wt%. Mineralogical analysis shows the predominance of calcite and quartz at the XRD diffraction patterns. The obtained results are used subsequently to establish geochemical maps of lime and silica allowing the orientation of the operational plan according to the geochemical quarry composition. The geochemical as well as mineralogical analyses show that the integration of the extra siliceous limestone in the raw powder composition permits the filling in of the defect of silica in limestone exploitation by preserving the quality of the produced cement in accordance with the Tunisian and European standard requirements. This study explains then the importance of geochemical assessment of limestone for cement manufacturing.