Civil Engineering Today

  Classification of Pozzolanas Pozzolanas are classified as natural and artificial : 1. Natural pozzolanas -  All pozzolanas are rich in silica and alumina and contain only a small quantity of alkalis .  The following are some of the naturally occurring pozzolanas: ·  Clays and shales which must be calcined to become active. ·   Diatomaceous earth and opaline cherts and shales which may or may not need calcination ·  Volcanic tuffs and pumicites. Fine grained ashes form better pozzolana. However, tuffs solidified volcanic ash-may be ground to desired fineness for use. ·  Rhenish and Bavarian trass.   2.  Artificial Pozzolanas - Artificial pozzolanas is a man-made material that is a byproduct of industrial processes, such as burning organic materials like coal in furnaces to reclaim ash.  Some of the examples of artificial pozzolanas are: 1 . Fly ash 2.  Surkhi (burnt clay pozzolana) 3 . Rice husk ash 4 . Ground...