<scp>TEM</scp> and <scp>SAED</scp> Characterization of Metakaolin. Pozzolanic Activity

Abstract

The present study deals with a characterization of metakaolin pozzolanic activity and its chemical character exhibited in the O rdinary P ortland C ement ( OPC ) blends by means of Transmission Electron Microscopy (TEM) and S elected‐ A rea E lectron D iffraction (SAED) techniques principally. Metakaolin sample was prepared by calcination of kaolin rock ( G uadalajara, S pain) at 780°C. Two OPC of different chemical composition from the tricalcium aluminate content point of view were chosen and P ortland cement blends series elaborated and then submitted to the pozzolanic activity test ( EN 196‐5 or F rattini test ). The main mineralogical components of the metakaolin are determined qualitatively: χ‐alumina and quartz. The chemical character of the metakaolin is described because of its final composition as well as due to its A l atoms possible coordination. The crystalline order of the material is found to be of both amorphous and polycrystalline, being an intimate amorphous mixture of alumina and silica. Finally, all the alumina capable of reacting chemically is denominated and classified as reactive alumina component, Al 2 O 3 r− , of pozzolans, as well as the aluminic chemical character of metakaolin in OPC blends is once again proved and exhibited by means of F riedel's salt formation studied already at 4 h‐age.