text: what is the plaster composition for pools?   there is disclosed a cement plaster composition wherein an additive having from about 10% to about 75% of a silicone treated powder and from about 90% to about 25% of a pozzalanic filler is combined with a type i portland cement and a crushed aggregate to form a water repellent coating for plastering a swimming pool surface. the additive may also include rheology modifiers, water reducing agents, or set time modifiers.