Gypsum products

Gypsum produced as a by-product of flue gas

• desulfurization

• decalcification

• saphonification

• dechlorinatiom

The resulting particle is a fibrous aggregate of fine crystals with capillary pores known as

• plaster of Paris

• Dental stone

• Die stone

• all

When gypsum is heated in a kettle, vat, or rotary kiln that maintains a wet environment; a crystalline hemihydrate called

• dental stone

• dental plaster

• plaster of paris

• Die stone

α-hemihydrate β-hemihydrate • Formed when dihydrate is heated under

• compressed air

• steam pressure

• Vaccum

• free oxygen

Set gypsum products probably never attain 100% conversion unless they are exposed to

• low humidity

• high humidity

• no humidity

• room temperature

The colloidal theory proposes that, when mixed with water, hemihydrate enters into the colloidal state through a ________mechanism.

• sol-gel

• gel-gel

• sol-sol

• all

The hydration theory suggests that rehydrated plaster particles unite through ___________ bonding with sulfate groups to form the set material.

• Covalent

• hydrogen

• oxygen

• double

The tests done for setting of gypsum products are listed as below EXCEPT

• Loss of gloss test.

• Gillmore’s test

• Vicat test

• Meltons test

Increasing or decreasing the rate of crystal growth will accelerate or retard the

• mixing time

• setting time

• working time

• curing time

The most commonly used accelerator is

• potassium nitrate

• potassium oxide

• potassium sulfate

• zinc