Physical Assessment of Pozzolanic Activity of Saudi Kaolinitic Clays for Use in Sustainable Cement-based Materials [ ]

Presently, there is a growing concern in calcined clays as supplementary cementitious materials SCM, because of their relatively great geographic distribution and their demonstrated pozzolanic properties once calcined under specific conditions. In this study, two different Saudi kaolinitic clays (from KHUSHAYM RADI DEPOSIT) were calcined at three different temperatures 650, 700 and 750 °C, the influence of calcination temperature on the mineralogical compositions and micro-morphologies were investigated by X-ray diffraction spectrometer XRD and the scanning electron microscope SEM respectively. The pozzolanic activities were studied using hydrated lime as an activator. 80% clay – 20% hydrated lime pastes were prepared using water/solid ratio = 1 (on basis of mass) and hydrated for 3 and 7 days. The phase composition/decomposition of the hydrated pastes was identified by using differential scanning calaorimetry (DSC) and XRD. The microstructure characteristics and x-ray microanalysis were examined by SEM equipped with energy dispersive analytical x-ray unit (EDAX). Significant modifications in the micro-morphologies have been observed due to calcination. The investigated clay samples showed different pozzolanic activities.