Evaluation of Pozzolanic activity of some clays in Ghana

Abstract

A study of pozzolanic activity of four Ghanaian clays is presented. The moisture content, particle size distribution, and the chemical composition of clays were determined. X-ray diffractometric and thermal analysis were also performed to determine the mineralogical composition. Calcinations of the clays were carried out at different temperatures between 600-1000°C and the pozzolanas produced used to replace 20% Portland cement by mass in mortars. Compressive strengths of 1:3 pozzolana cement mortar cubes at 28 days were determined. The values obtained showed that Asokwa (AS) and Mankesim (MN) clay samples become highly pozzolanic at 800°C whilst Hwereso (HW) and Nkonsia (NK) clays had their optimum calcination at 900°C and 600°C respectively. The compressive strengths were higher than the 24.1 N/mm2 minimum standard set for concrete and general construction.