Pozzolanas: Mineral additives also called supplementary cementing materials or pozzolana are fine grained siliceous materials or pozzolana are fine grained siliceous inorganic materials which as such, do not possess cementing properties in themselves, but react chemically with calcium hydroxide Ca(OH)₂ released from the hydration of portland cement at normal temperature to form compounds of low solubility having cementing properties. The action is termed as pozzolanic action.