Question

The term _______________ plaster is used to indicate plaster of Paris with retarder.

(a) Hemihydrate Gypsum

(b) Keene’s cement

(c) Parian cement

(d) Sirapite

I have been asked this question in an interview for internship.

The query is from Special Materials for Plastered Surfaces in chapter Pointing and Plastering of Construction & Building Materials

Answer 1

Correct choice is (a) Hemihydrate Gypsum

The best explanation: On heating the hemihydrate gypsum, temperature of about 200°C, the entire water of crystallization is driven off and the resulting product is known as gypsum anhydride or hard burnt plaster. The setting time of the Gypsum anhydride is more and to shorten it,  the accelerators added to it.