Use of metakaolins from Eseka and Dibamba-Cameroon as an optimization additive of CEM I Portland cement mortar

Abstract

The present study deals with two kaolins from Eseka and Dibamba-Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low-carbon cement. X-ray diffractometry was used to establish the mineralogical composition of two kaolins. X-ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO₂/Al₂O₃ is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.