Petrological features of volcanic scoriae from the southern part of the Cameroon Volcanic Line and their supplementary cementations application

Abstract

Volcanic scoriae from the southern part of the Cameroon Volcanic Line (Limbé, Loum-Tombel, Yamba, Doupé, Njinkouo, Foumbot, Manjo-manengollé, Galim and Djoungo) were investigated in order to determine their chemical and mineralogical composition, to deduce their origin and to identify their natural characteristics which may be useful to the cement industry. The mineralogical composition was determined by X-ray Diffractometer (XRD); X-ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) instruments provided geochemical data. In order to establish the relationship between the natural characteristics of volcanic scoriae and the properties of cements, the amount of amorphous phases was determined by dissolution using sodium hydroxide solution and the pozzolanic activity by thermogravimetric analysis. Field observations show that these rocks are basalts, basanites, hawaiites and picrobasalts. Their mineralogical composition includes augite, olivine, plagioclase, enstatite, feldspars, ettringite, portlandite and Fe–Ti minerals. Overall, they are characterized by high MgO, Fe2O3, CaO, and TiO2 contents. The behavior of major and trace elements suggests that volcanic scoriae have an evolution dominated by partial melting. Besides, high chondrite normalized La/Yb (8–22), Tb/Yb (>1.9) and Dy/Yb (>2) values suggest that the melting corresponds to the garnet lherzolite stability field. The scoriae exhibit good pozzolanic reactivity after 28 days according to their considerable amount of amorphous phases, low CaO contents and their large specific surface area. According to ASTM C618 standard, the sum of SiO2, Al2O3 and Fe2O3 (SAI = 65.96–76.34 wt.%); LOI (-0.1–16.99 wt.%), and of CaO, Fe2O3 and MgO (CIM = 23.43–34.06 wt.%) suggest that those less weathered materials seem appropriate as an additive in cement manufacture. The suitable use of volcanic scoriae in the cement industry closely depends on the petrological features of amorphous phases.